Blake

Chapter 1: Introduction to Communication SystemsMULTIPLE CHOICE 1. The theory of radio waves was originated by: a. Marconi b. Bell ANS: C 2. The person who sent the first radio signal across the Atlantic ocean was: a. Marconi c. Maxwell b. Bell d. Hertz ANS: A 3. The transmission of radio waves was first done by: a. Marconi c. Maxwell b. Bell d. Hertz ANS: D 4. A complete communication system must include: a. a transmitter and receiver b. a transmitter, a receiver, and a channel c. a transmitter, a receiver, and a spectrum analyzer d. a multiplexer, a demultiplexer, and a channel ANS: B 5. Radians per second is equal to: a. 2π × f b. f ÷ 2π ANS: A 6. The bandwidth required for a modulated carrier depends on: a. the carrier frequency c. the signal-plus-noise to noise ratio b. the signal-to-noise ratio d. the baseband frequency range ANS: D 7. When two or more signals share a common channel, it is called: a. sub-channeling c. SINAD b. signal switching d. multiplexing ANS: D 8. TDM stands for: a. Time-Division Multiplexing b. Two-level Digital Modulation c. Time Domain Measurement d. none of the above c. the phase angle d. none of the above c. Maxwell d. Hertz ANS: A 9. FDM stands for: a. Fast Digital Modulation b. Frequency Domain Measurement ANS: C 10. The wavelength of a radio signal is: a. equal to f ÷ c b. equal to c ÷ λ c. the distance a wave travels in one period d. how far the signal can travel without distortion ANS: C 11. Distortion is caused by: a. creation of harmonics of baseband frequencies b. baseband frequencies "mixing" with each other c. shift in phase relationships between baseband frequencies d. all of the above ANS: D 12. The collection of sinusoidal frequencies present in a modulated carrier is called its: a. frequency-domain representation c. spectrum b. Fourier series d. all of the above ANS: D 13. The baseband bandwidth for a voice-grade (telephone) signal is: a. approximately 3 kHz c. at least 5 kHz b. 20 Hz to 15,000 Hz d. none of the above ANS: A 14. Noise in a communication system originates in: a. the sender c. the channel b. the receiver d. all of the above ANS: D 15. "Man-made" noise can come from: a. equipment that sparks b. temperature ANS: A 16. Thermal noise is generated in: a. transistors and diodes b. resistors ANS: D c. copper wire d. all of the above c. static d. all of the above c. Frequency-Division Multiplexing d. none of the above 17. Shot noise is generated in: a. transistors and diodes b. resistors ANS: A 18. The power density of "flicker" noise is: a. the same at all frequencies b. greater at high frequencies ANS: C 19. So called "1/f" noise is also called: a. random noise b. pink noise ANS: B 20. "Pink" noise has: a. equal power per Hertz b. equal power per octave ANS: B c. copper wire d. none of the above c. greater at low frequencies d. the same as "white" noise c. white noise d. partition noise c. constant power d. none of the above 21. When two noise voltages, V1 and V2, are combined, the total voltage VT is: a. VT = sqrt(V1 × V1 + V2 × V2) c. VT = sqrt(V1 × V2) d. VT = V1 + V2 b. VT = (V1 + V2)/2 ANS: A 22. Signal-to-Noise ratio is calculated as: a. signal voltage divided by noise voltage b. signal power divided by noise power c. first add the signal power to the noise power, then divide by noise power d. none of the above ANS: B 23. SINAD is calculated as: a. signal voltage divided by noise voltage b. signal power divided by noise power c. first add the signal power to the noise power, then divide by noise power d. none of the above ANS: D 24. Noise Figure is a measure of: a. how much noise is in a communications system b. how much noise is in the channel c. how much noise an amplifier adds to a signal d. signal-to-noise ratio in dB ANS: C The bandwidth of an unmodulated carrier is ____________________. ANS: zero 6. VHF stands for the ____________________ frequency band. its amplitude. ANS: channel 5. ANS: 1901 3. frequency. ANS: base 4. ANS: 1863 2. . multiple signal streams take turns using the channel. The 'B' in Hartley's Law stands for ____________________. frequency. or parts. its amplitude. of a sinusoidal carrier that can be modulated are: a. its amplitude c. In ____________________. and phase angle ANS: D COMPLETION 1. ANS: bandwidth 7. its amplitude and frequency d. The more information per second you send. and direction b. the ____________________ the bandwidth required. ANS: FDM 9. ANS: greater larger wider 8. In ____________________. ANS: TDM 10. Radio signals first were sent across the Atlantic in the year ____________________. The part. The job of the carrier is to get the information through the ____________________.25. you split the bandwidth of a channel into sub-channels to carry multiple signals. The telephone was invented in the year ____________________. The frequency band used to modulate the carrier is called the ____________________ band. A radio signal's ____________________ is the distance it travels in one cycle of the carrier. Mathematically. ANS: wavelength 14. ANS: Source. ____________________ noise can be a serious problem. ANS: 300 13. The equipment used to show signals in the frequency domain is the _________________________. ANS: 300 million 15. Thermal noise is caused by the random motions of ____________________ in a conductor. ANS: solar 19. radio signals travel at approximately ____________________ meters per second. . ANS: electrons SHORT ANSWER 1. ANS: spectrum analyzer 16. ANS: 30 12. Disabling a receiver during a burst of atmospheric noise is called ____________________. Name the five elements in a block diagram of a communications system. Receiver. Destination 2. The VHF band starts at ____________________ MHz.ANS: very high 11. ANS: Fourier 17. a spectrum is represented by a ____________________ series. Transmitter. For satellite communications. Name five types of internal noise. The UHF band starts at ____________________ MHz. In free space. ANS: noise blanking blanking 18. Channel. Calculate the total noise voltage. Why is thermal noise called "white noise"? ANS: White light is composed of equal amounts of light at all visible frequencies. Two cascaded amplifiers each have a noise figure of 5 and a gain of 10. Likewise. Find its noise figure. The equation for the noise current is very similar to the equation for thermal noise voltage. The input to an amplifier has a signal-to-noise ratio of 100 dB and an output signal-to-noise ratio of 80 dB. . ANS: 20 dB. controlling the diode current controls the noise power. Partition. If you have 100 mV of signal and 10 mV of noise. Find NF. A microwave receiver has a noise temperature of 145 K. 4. the output of which is a noise current. Since the power in the shot noise is proportional to the diode current.4 10.ANS: Thermal. Suppose there is 30 µV from one noise source that is combined with 40 µV from another noise source. ANS: 5. Explain why you could use a diode as a noise source with a spectrum close to that of pure thermal noise. What is "pink noise"? ANS: Light is pink when it contains more red than it does other colors.5 9. How would you control the amount of noise generated? ANS: When current flows through a diode. Shot. transit-time 3. 5. ANS: 1. ANS: 50 µV 6. thermal noise has equal power density over a wide range of frequencies. and red is at the low end of the visible spectrum. it generates shot noise that can be represented as a current source. what is the signalto-noise ratio in dB? ANS: 20 dB 7. 1/f. both in dB and as a ratio. Likewise. Find the total NF for the pair. both across the same 100-ohm load. pink noise has higher power density at lower frequencies. NF = 100 8. . capacitance and inductance only ANS: C 3. reduce the bandwidth of an amplifier d.Chapter 2: Radio-Frequency Circuits MULTIPLE CHOICE 1. In a BJT. charge time b. increasing the Q of the tuned circuit d. A resonant circuit is: a. Bypass capacitors are used to: a. capacitance. using a common-base amplifier ANS: B 8. The Miller Effect can be avoided by: a. none of the above c. using a common-emitter amplifier b. and resistance d. inductance of collector lead b. lower the Q of the tuned circuit ANS: B 6. The time it takes a charge carrier to cross from the emitter to the collector is called: a. Miller time ANS: B 2. collector-to-emitter capacitance ANS: D c. base-to-collector capacitance c. have no effect on Q c. both a and b d. cause an amplifier to lose gain ANS: D 7. used in narrowband RF amplifiers ANS: C 5. couple RF around an amplifier ANS: A 4. Loading down a tuned-circuit amplifier will: a. cause an amplifier to oscillate b. inductance. it cannot be avoided c. remove RF from non-RF circuits b. raise the Q of the tuned circuit b. The "Miller Effect" can: a. transit time d. base-to-emitter capacitance d. all of the above c. reactance only . A real capacitor actually contains: a. capacitance and resistance only b. neutralize amplifiers d. reduce the Miller effect c. "multiply" the Q d. base time c. a simple form of bandpass filter b. the Miller Effect is due to: a. a two-capacitor divider ANS: A 15. The Colpitts VFO uses: a. a piezoelectric crystal . a piezoelectric crystal c. loop gain equal to unity b. a two-capacitor divider ANS: B 16. The conditions for sinusoidal oscillation from an amplifier are called: a. the loop-gain criteria c. The Hartley oscillator uses: a. an RC time constant d. a linear amplifier c. the Hartley criteria d. an input signal that is an integer multiple of the desired frequency ANS: A 12. Neutralization cancels unwanted feedback by: a. the Barkhausen criteria ANS: D 14. The Clapp oscillator is: a. RC coupling c. adding feedback out of phase with the unwanted feedback b. A sinusoidal oscillation from an amplifier requires: a. a nonlinear circuit b. transformer coupling d. a type of crystal-controlled oscillator d. only built with FETs c. a modified Hartley oscillator b. In RF amplifiers. an RC time constant d. lumped reactance ANS: B 10. a tapped inductor b. impedance matching is usually done with: a. none of the above ANS: C 13. both a and b. For a "frequency multiplier" to work. a signal containing harmonics d. a modified Colpitts oscillator ANS: B c. the Bode criteria b. but at just one frequency d. bypassing the feedback to the "neutral" or ground plane c. decoupling it d. none of the above ANS: A 11. phase shift around loop equal to 0 degrees c. direct coupling b. it requires: a. a tapped inductor b.9. Variable-Frequency Oscillator ANS: B 22. a voltage-controlled capacitor b. If two signals. Voltage-Fed Oscillator b. Varactor-Frequency Oscillator d. all of the above 18. elements must be considered as ____________________ instead of as being "lumped". the output: a. does not contain the input frequencies d. Va = sin(ωat) and Vb = sin(ωbt). used for a precise frequency b. c. a fixed-frequency RF generator d. In a balanced mixer. is a linear mixture of the input signals ANS: C 21. a diode ANS: D c. contains the input frequencies c. will contain ω1 = ωa + ωb and ω2 = ωa – ωb b. ANS: short 2. a VCO phase-locked to a reference frequency b. used in tuner circuits d. "VFO" stands for: a. same as a mixer ANS: A COMPLETION 1. At UHF frequencies and above. will contain ω = (ωa + ωb ) / 2 d. A varactor is: a. used for very low frequency drift (parts per million) c. a VFO with selectable crystals to change frequency c. conductor lengths in RF circuits should be ____________________. are fed to a mixer. Generally. none of the above ANS: A 20. made by grinding quartz to exact dimensions d. Voltage-Feedback Oscillator . contains equal (balanced) amounts of all input frequencies b. Crystal-Controlled oscillators are: a. will contain ω1 = ωa / ωb and ω2 = ωb / ωa c. all of the above ANS: D 19. A "frequency synthesizer" is: a. the output: a.17. ANS: neutralization 12. ANS: 10 10. ANS: tuned circuit 11. a piezoelectric crystal has both a ____________________ and a ____________________ resonant frequency. When one side of a double-sided pc board is used for ground. the ____________________ extracts one frequency from all the harmonics contained in the device current (e. A value of ____________________ or more for Q is required for the approximate tuned circuit equations to be valid. A Colpitts oscillator uses a ____________________ voltage divider to provide feedback. ANS: series. it is called a ____________________.g. In a class C RF amplifier. ANS: capacitive 13. ANS: Q 9. Using additional feedback to compensate for "stray" feedback is called ____________________. parallel . Electrically. A ____________________ circuit is used to remove RF from the DC voltage bus. Interactions between parts of an RF circuit can be reduced by using ____________________ between them. ANS: components 6. ANS: decoupling 7. The bandwidth of a tuned-circuit amplifier depends on the ____________________ of the tuned circuit. ANS: bypass 8. ANS: ground-plane 4. ANS: shielding 5.ANS: distributed 3. the placement of wires and ____________________ can be critical. collector current). A ____________________ capacitor is used to short unwanted RF to ground. In high-frequency RF circuits. What frequencies would you expect at the output of the mixer? ANS: 15 MHz and 25 MHz . A tuned-circuit amplifier with a gain of 10 is being used to make an oscillator.14. Two sinusoidal signals. What inductance would you use with a 47-pF capacitor to make a tuned circuit for 10 MHz? ANS: 5. a mixer must be a non-____________________ circuit. and a tempco of +10 ppm per degree Celsius. a diode or a transistor can act as a ____________________-law mixer.1 4. To produce sum and difference frequencies. V2 is a 5MHz signal. 5. are fed into an ideal balanced mixer. If a varactor has a capacitance of 90 pF at zero volts. 0. V1 and V2. ANS: linear 15.4 µH 2. What will be the shift in frequency at 70°C? What percentage is that? ANS: 50 kHz. What should be the value of the feedback ratio to satisfy the Barkhausen criteria? ANS: 0. An oscillator has a frequency of 100 MHz at 20°C. ANS: square SHORT ANSWER 1. What is the advantage of a Clapp oscillator compared to a Colpitts oscillator? ANS: It is more stable because it "swamps" the device capacitance with large value capacitors in the feedback divider.05% 7. What value of Q is required for a 10-MHz tuned circuit to have a bandwidth of 100 kHz? ANS: 100 3. At some bias point. V1 is a 20-MHz signal. what will be the capacitance at 4 volts? ANS: 30 pF 6. 8. Suppose the phase-locked-loop frequency synthesizer of Figure 2.39 has a reference frequency of 1 MHz and a fixed-modulus divider of 10. What should be the value of the programmable divider to get an output frequency of 120 MHz? ANS: 12 . then the modulation index. m = Emin / Emax c. Antenna Modulation . The equation for full-carrier AM is: a. The modulation index. Angle Modulation d. v(t) = (Ec + Em) × sin(ωct) b. The "envelope" of an AM signal is due to: a. is: a. the baseband signal b. twice the carrier power d. (ωc + ωa)/2 and (ωc – ωa)/2 d. Audio Modulation b. m = Va / ωa ANS: B 4. the total sideband power is: a. m. none of the above c. equal to the carrier power c. none of the above c. At 100% modulation. the amplitude signal d. m = (Emax + Emin) / (Emax – Emin) ANS: C 7. v(t) = (Ec + Em sin(ωmt)) × sin(ωct) c. splatter ANS: C 6.Chapter 3: Amplitude Modulation MULTIPLE CHOICE 1. the carrier signal ANS: A 3. The peak voltage of an AM signal goes from Emax to Emin. Overmodulation causes: a. it will produce the frequencies: a. m = ωa / ωc c. is: a. m = (Emax – Emin) / (Emax + Emin) b. ωc + ωa and ωc – ωa c. distortion b. none of the above ANS: A 8. 1. ωc + ωa and 2ωc + 2ωa b. v(t) = (Ec × Em) × sin(ωmt) × sin(ωct) d. both a and b d. If the audio Va sin(ωat) modulates the carrier Vc sin(ωct). Amplitude Modulation ANS: B 2. m = Va / Vc d. v(t) = (Ec + Em) × sin(ωmt) + sin(ωct) ANS: D 5. m. m = (Va / Vc)2 b.414 × carrier power c. AM stands for: a. half the carrier power b. m = Emax / Emin d. If Va sin(ωat) amplitude modulates the carrier Vc sin(ωct). the received RF signal to increase d. If an AM radio station increases its modulation index. the bandwidth of the AM signal will be: a. If a 5-kHz signal modulates a 1-MHz carrier. If an SSB transmitter radiates 1000 watts at peak modulation. all of the above ANS: C 13. The SC in SSB SC stands for: a. you would expect: a. 5 kHz c. the audio to get louder at the receiver c. sideband-carrier d. all of the above ANS: D 14.ANS: C 9.005 MHz b. requires too much bandwidth c. Peak Efficiency Power ANS: A 16. the frequency-domain signal ANS: C 12. 250 watts b. Peak Envelope Power b. suppressed-carrier ANS: B 15. both a and b d. is more efficient b. 0 watts ANS: D 17. none of the above . none of the above c. requires less bandwidth d. AM is susceptible to noise c. the signal-to-noise ratio to increase b. Music on AM radio stations is "low-fidelity" because: a. SSB AM: a. As compared to plain AM. requires too much power d. the time-domain signal b. PEP stands for: a. The modulation index can be derived from: a. what will it radiate with no modulation? a. 1000 watts c. incompatibility with ordinary AM radios b. single-carrier b. 1. all of the above ANS: D 11. requires a more complex demodulator circuit c. 500 watts d. 10 kHz d. none of the above ANS: B 10. The main problem in using quadrature AM would be: a. Peak Envelope Product d. none of the above c. sqrt(m1 × m2 + m2 × m1) b. the information in the LSB is ____________________. the power in the LSB is ____________________. video d. digital data b. Compared to the USB.b. modulating with a single audio tone produces ____________________ sidebands. audio c. m1 + m2 c. reinsert the carrier d. Compared to the USB. (m1 + m2) / 2 d. all of the above ANS: C 18. ANS: the same 6. be set to USB mode c. ANS: simple 2. To demodulate a USB SSB signal. The total modulation index is: a. commercial AM stations have a narrow bandwidth d. ANS: two 5. all of the above ANS: D 19. The ____________________ of an AM signal resembles the shape of the baseband signal. One tone causes a modulation index of m1 and the other tone causes a modulation index of m2. An advantage of AM is that the receiver can be very ____________________. The type of information that can be sent using AM is: a. ANS: the same . A disadvantage of AM is its ____________________ use of power. ANS: envelope 4. Two tones modulate an AM carrier. both a and b b. ANS: inefficient 3. commercial AM stations use low power c. sqrt(m1 × m1 + m2 × m2) ANS: D 20. In AM. the receiver must: a. none of the above ANS: C COMPLETION 1. what is the power in the USB at 70. if the LSB extends down to 990 kHz.6 . An AM transmitter generates 100 watts with 0% modulation. ANS: 6000 Hz 11. In AM. What is the modulation index? ANS: 0. In AM. then the USB will extend up to ____________________. it will put out ____________________ watts with 100% modulation. If the modulation indexes for the tones are 0. With a 1-MHz carrier. In AM. ANS: remains constant 9. 0. ANS: one 10. The power in an AM signal is maximum when the modulation index is ____________________.7% modulation? ANS: 125 watts 3.4. a voice-band signal of 300 Hz to 3000 Hz will require a bandwidth of ____________________. and 0. ANS: less 8.7. then what is the total modulation index? ANS: 0. ANS: 1010 kHz 12. How much power will it generate with 20% modulation? ANS: 102 watts 2. total sideband power is always ____________________ than the carrier power. You look at an AM signal with an oscilloscope and see that the maximum Vpp is 100 volts and the minimum Vpp is 25 volts. If the carrier power is 1000 watts. as the modulation index increases. If an AM transmitter puts out 100 watts with no modulation.707 4. A carrier is modulated by three audio tones. ANS: 150 SHORT ANSWER 1.3. the carrier power _________________________.5. A SSB transmitter is connected to a 50-ohm antenna.5. what is the PEP? ANS: 4 watts . If the peak output voltage of the transmitter is 20 volts. it is equal to the frequency deviation c. When FM reception deteriorates abruptly due to noise. The FM modulation index: a. The bandwidth of an FM signal is considered to be limited because: a. it is band-limited at the receiver d. Narrowband FM c. Mathematically. the threshold effect d. fractals ANS: B 5. the calculation of FM bandwidth requires the use of: a. integrate the modulating signal before applying to the PM oscillator b. ordinary trigonometry and algebra c. increases with deviation and decreases with modulation frequency c. differentiate the signal out of the PM oscillator ANS: A 3. Taylor series b. decreases with deviation and increases with modulation frequency d. National Broadcast FM b. differentiate the modulating signal before applying to the PM oscillator d. FM bandwidth can be approximated by: a. One way to derive FM from PM is: a. Carson's Rule d. increases with both deviation and modulation frequency b. the limit effect ANS: B c. integrate the signal out of the PM oscillator c. Bessel functions d. Bessel's Rule ANS: C 6. Near Band FM d. the noise effect b. the capture effect c. the power in the outer sidebands is negligible ANS: D 4. is equal to twice the deviation ANS: B 2. NBFM stands for: a. Non-Broadcast FM ANS: D 7. there can only be a finite number of sidebands b.Chapter 4: Angle Modulation MULTIPLE CHOICE 1. it is called: a. Armstrong's Rule b. none of the above . increase the signal to noise ratio for all audio frequencies d. is not compatible with mono FM .8. the time it takes for the circuit to work b. using measurements at points where J0 equals zero c. is monaural d. only by using Bessel functions ANS: B COMPLETION 1. FM stereo: a. increase the signal to noise ratio for higher audio frequencies b. ANS: data c. A pre-emphasis of 75 µs refers to: a. the capture effect c. allow stereo audio to be carried by FM stations ANS: A 10. is implemented using an SCA signal ANS: A 12. the time delay between the L and R channels d. The modulation index of an FM signal can be determined readily: a. can use amplitude modulation b. uses DSBSC AM modulation b. FM and PM are two forms of ____________________ modulation. the time-constant of the filter circuits used ANS: D 11. PM is extensively used in ____________________ communication. none of the above ANS: A 9. using measurements at points where J0 equals one b. the threshold effect d. increase the signal to noise ratio for lower audio frequencies c. An FM receiver switching suddenly between two stations on nearby frequencies is called: a. using measurements at points where the deviation equals zero d. has a higher S/N than mono FM d. can use FM modulation ANS: D 13. ANS: angle 2. An SCA signal: a. the "dead time" before de-emphasis occurs c. Pre-emphasis is used to: a. all of the above c. the "two-station" effect b. ANS: decreases 14. ANS: stay constant 7. In FM. Mathematically. ANS: infinite 10.3. as the modulating frequency decreases. the value of an FM modulation index can be as high as ____________________. In FM. the signal-to-noise ratio of FM is usually ____________________. the number of significant sidebands ____________________. ANS: increases 13. the frequency deviation is proportional to the instantaneous ____________________ of the modulating signal. ANS: frequency 9. Mathematically. . As the FM modulation index increases. ANS: amplitude 8. Compared to AM. the modulation index ____________________. ANS: wider greater 5. The frequency deviation of an FM signal occurs at a rate equal to the ____________________ of the modulating signal. the bandwidth of FM is usually ____________________. ANS: better 4. the modulation index ____________________. As FM sidebands get farther from the center frequency. ANS: any number 12. FM transmitters can use Class ____________________ amplifiers since amplitude linearity is not important. ANS: decreases 11. Both the power and amplitude of an FM signal ____________________ as modulation is applied. ANS: C 6. In FM. their power ____________________. as the frequency deviation decreases. Compared to AM. the number of sidebands in an FM signal is ____________________. For certain values of mf. What will be the deviation caused by a 3-kHz tone if the modulation index is 3? ANS: 9 kHz 4.ANS: increases 15. 1-kHz audio signal? . Rest frequency is another name for an FM ____________________ frequency. The ____________________ effect is characteristic of FM reception in a noisy environment. ANS: Bessel 18. what will be the modulation index caused by a 1-volt. what is the modulation index? ANS: 2 3. such as 2. The ____________________ effect is seen when an FM receiver is exposed to two FM signals that are close to each other in frequency. The bandwidth of an FM signal can be approximated using ____________________ rule. ANS: Carson's 17. ANS: disappears goes to zero 16. the amplitude of the carrier frequency ____________________.4. If a 2-kHz audio tone causes a frequency deviation of 4 kHz. If a 2-volt instantaneous value of modulating signal amplitude causes a 10-kHz deviation in carrier frequency. ANS: threshold 19. ANS: carrier SHORT ANSWER 1. FM bandwidth can be calculated precisely using ____________________ functions. what is the deviation sensitivity of the modulator? ANS: 5 kHz / volt 2. ANS: capture 20. If the deviation sensitivity of an FM modulator is 2 kHz /V. 1. how much power is in the carrier of a 1000-watt FM transmitter? ANS: 48. At a modulation index of 2. . At a modulation index of 2. how much power is in the fifth pair of sidebands of a 1000-watt FM transmitter? ANS: 200 mW (0.4 watts 6.5. Using the Bessel chart of Figure 4. 5. At a modulation index of 2. Using a spectrum analyzer. how much power is in the first pair of sidebands of a 1000-watt FM transmitter? ANS: 673 watts 7. etc) to measure the frequency deviation of an FM modulator? ANS: Use an audio frequency generator to modulate the FM carrier. adjust the audio frequency until the carrier amplitude vanishes. if fm is measured to be 2 kHz when mf is 5. what is the bandwidth of an FM signal with a modulation index of 2 being modulated by a 5-kHz signal if we ignore sidebands containing less than 1% of the total power? ANS: 30 kHz 10. Then do the calculation: δ = fm × mf where mf will have one of the known values.ANS: 2 5.5. Record the audio frequency. For example. then δ is 11 kHz.2 watt) 8. How would you use the fact that J0 is zero for certain known values of mf (2. Using Carson's rule.4. what is the approximate bandwidth of an FM signal with a modulation index of 2 being modulated by a 5-kHz signal? ANS: 30 kHz 9. the RF amplifiers are typically Class AB c. expansion d. ALC is used to: a. the RF amplifiers must be Class A b. The ability to change operating frequency rapidly without a lot of retuning is called: a. keep the modulation below 100% ANS: D 6. all RF amplifiers can be nonlinear b. the RF amplifiers must be Class B c. a smaller range of amplitude from soft to loud c. is a measure of efficiency c. Amplitude Level Control b. ALC stands for: a. heats the transmitter d. maximize transmitted power d. the RF amplifiers are typically Class C d. the RF amplifiers must be linear d. agility c. The difference between the DC power into a transmitter and the RF power coming out: a. the RF amplifiers are typically Class B ANS: C 8. Baseband compression produces: a. VFO b. all of the above ANS: D 3. a smaller range of frequencies from low to high b. none of the above . all of the above c. may require water cooling b. the RF amplifiers are typically Class A b. With low-level AM: a. With high-level AM: a. In an AM transmitter.Chapter 5: Transmitters MULTIPLE CHOICE 1. a smaller number of signals d. the RF amplifiers must be low-power c. minimum RF power is required d. all of the above c. spread-spectrum ANS: A 2. Automatic Level Control ANS: B 5. minimum modulation power is required ANS: A 7. With high-level AM: a. keep the modulation close to 100% b. none of the above ANS: B 4. Accurate Level Control d. both a and b b. 1% tolerance or better b.ANS: C 9. the carrier ANS: A 12. a bridge circuit ANS: C 15. A Class D amplifier is: a. has variable frequency b. approximately four times the DC supply voltage d. a test load ANS: B 16. has variable amplitude d. Power amplifiers must be linear for any signal that: a. a temporary load b. the driver stage b. the power level of the final RF amplifier d. Practical transmitters are usually designed to drive a load impedance of: a. all of the above ANS: B 10. none of the above ANS: C 13. 50 ohms resistive c. very efficient c. the RF amplifier d. the voltage of the final RF stage will be: a. T network d. 300 ohms resistive b. 600 ohms resistive ANS: A 14. approximately half the DC supply voltage b. the power level of the carrier b. pi network c. approximately twice the DC supply voltage c. none of the above . a dummy load d. the modulating amplifier c. In high-level AM. Which of the following can be used for impedance matching? a. the power level of the modulation ANS: D 11. noninductive d. essentially pulse-duration modulation c. When a transmitter is connected to a resistor instead of an antenna. When a transmitter is connected to a resistor instead of an antenna. In high-level AM. the resistor must be: a. the resistor is called: a. In an AM transmitter with 100% modulation. all of the above ANS: B 17. wire-wound c. is complex c. a heavy load c. the power in the sidebands comes from: a. 75 ohms resistive d. "high-level" refers to: a. essentially pulse-width modulation ANS: D 18. none of the above ANS: C 21. a crystal filter d. essentially mixers d. start with a quadrature signal d. Automatic Frequency Centering ANS: C 24. To generate a SSB signal: a. varies the frequency of the carrier oscillator b. An indirect FM modulator: a. all of the above c. Amplitude to Frequency Conversion b. To remove one AM sideband and leave the other you could use: a.b. the carrier frequency can be changed to any required value c. all of the above c. Frequency multipliers are: a. none of the above c. With mixing: a. Audio Frequency Control . both a and b d. Automatic Frequency Control d. requires a varactor in the carrier oscillator b. both a and b d. A direct FM modulator: a. The carrier is suppressed in: a. a frequency multiplier d. both a and b b. integrates the modulating signal c. none of the above ANS: A 22. a balanced modulator b. the carrier frequency can be raised b. none of the above ANS: B 23. AFC stands for: a. essentially balanced modulators b. none of the above 20. start with full-carrier AM b. a mixer ANS: A d. a mechanical filter c. the carrier frequency can be lowered c. varies the phase of the carrier oscillator c. start with DSBSC ANS: B 19. essentially Class C amplifiers ANS: B 25. Reducing the dynamic range of a modulating signal is called ____________________. . ANS: expansion 8. the deviation is altered ANS: C COMPLETION 1. ANS: compression 9. In Canada.d. ANS: carrier 2. The opposite of compression is called ____________________. High-level modulation allows the RF amplifiers to operate more ____________________. ALC is a form of ____________________. ANS: compression 7. Power output of SSB transmitters is rated by ____________________. ANS: agility 5. a ____________________ stage is used. ANS: linear 11. ANS: FCC 3. the ____________________ sets requirements for accuracy and stability of a transmitter's frequency. ANS: PEP 6. To isolate the oscillator from load changes. The accuracy and stability of a transmitter frequency is fixed by the ____________________ oscillator. ANS: efficiently 10. In the USA. _________________________ sets requirements for accuracy and stability of a transmitter's frequency. Low-level modulation requires the RF amplifiers to be ____________________. ANS: Industry Canada 4. Frequency ____________________ is the ability of a transmitter to change frequency without a lot of retuning. ANS: higher 13. ANS: harmonic 16. ANS: D 21. Transmitters built with transistor RF amplifiers often use a ____________________ network for impedance matching. Transceivers combine a transmitter and a ____________________ into one "box". ____________________ is used to operate at more than one frequency. ANS: DSBSC . To generate a SSB signal. ANS: mixing 22. ANS: receiver 18. ANS: driver 19. Most practical transmitters are designed to operate into a ____________________-ohm load. ANS: T 15. Severe impedance ____________________ can destroy a transmitter's output stage. ANS: mismatch 17. ANS: 50 14. Pulse-width modulation is the same as pulse-____________________ modulation. Matching networks also act as filters to help reduce ____________________ levels. The peak collector voltage in a Class C RF amplifier is ____________________ than the DC supply voltage. it is common to modulate the ____________________ as well as the power amplifier in transistor modulators. it is common to start with a ____________________ signal. To allow a high modulation percentage.ANS: buffer 12. Because the sideband filter in a SSB transmitter is fixed. Switching amplifiers are sometimes called Class ____________________ amplifiers. ANS: duration 20. how much power does the modulation amplifier deliver for 100% modulation? ANS: 50 watts 4.23.8% 3. The modern way to make a stable VFO is to make it part of a ____________________ loop. what is the range of possible frequencies? ANS: 50 MHz ± 500 hertz 2. ANS: phase 24.005 MHz 6. The audio modulation frequency range is 1 kHz to 10 kHz. what is the maximum collector voltage at 100% modulation? ANS: 400 volts 5. ANS: reactance 25. If the final RF amplifier of an AM transmitter is powered by 100 volts DC. The power amplifier of an AM transmitter draws 100 watts from the power supply with no modulation. To pass the USB. Assuming high-level modulation. ANS: phase-locked SHORT ANSWER 1. what should be the center frequency of an ideal crystal filter? ANS: 10. What is the minimum frequency the SSB signal can be mixed with so that the output signal has a nominal carrier frequency of 50 MHz? ANS: 40 MHz . Suppose you have generated a USB SSB signal with a nominal carrier frequency of 10 MHz. Suppose the output of a balanced modulator has a center frequency of 10 MHz. What is the efficiency of a 100-watt mobile transmitter if it draws 11 amps from a 12-volt car battery? ANS: 75. If a 50-MHz oscillator is accurate to within 0. Using a varactor to generate FM is an example of a ____________________ modulator.001%. Indirect FM is derived from ____________________ modulation. Explain how you could use it to get an FM signal at 100 MHz with a deviation of 20 kHz.7. Then mix that signal with an 80-MHz carrier to generate a 100-MHz carrier with 20-kHz deviation. Suppose you have an FM modulator that puts out 1 MHz carrier with a 100-hertz deviation. what will be the new carrier frequency? ANS: 4 MHz 8. ANS: First. put the signal through a frequency doubler to get a 20-MHz carrier with a 20-kHz deviation. Suppose you had an FM signal with a carrier of 10 MHz and a deviation of 10 kHz. If frequency multiplication is used to increase the deviation to 400 hertz. . the RF amplifier ANS: D 6.Chapter 6: Receivers MULTIPLE CHOICE 1. Automatic Gain Control ANS: B 8. "IF" stands for: a. intermediate frequency b. small adjustable resistors ANS: D 4. Trimmers and padders are: a. the increase of wire resistance with frequency d. AGC stands for: a. the tissue-burning effect of a strong RF signal c. The frequency of the local oscillator: a. is above the RF frequency c. small adjustable capacitors . Audio Gain Control b. the mixer d. image frequency c. Armstrong b. the tuner b. none of the above ANS: C 5. Hertz ANS: C 3. all of the above c. "Skin effect" refers to: a. the signal and the noise ANS: A 2. the number of converters and the number of IFs c. the sensitivity and the selectivity b. intermodulation frequency ANS: A 7. two types of adjusting tools b. Foster c. small adjustable inductors d. Seeley d. Active Gain Conversion c. The superheterodyne receiver was invented by: a. The two basic specifications for a receiver are: a. the spurious response and the tracking d. The "front end" of a receiver can include: a. indeterminate frequency d. the way radio signals travel across a flat surface b. Active Gain Control d. all of the above c. is below the RF frequency c. Phase distortion is important in: a. color video receivers ANS: B c. a value of 4 is better than a value of 2 ANS: A 14.707 is ideal ANS: C 13. a value of 1. a value of 2 is better than a value of 4 b. all of the above c.b. none of the above c. how well adjacent frequencies are separated by the demodulator d. a value of 0.414 dB is ideal b. sensitivity measures: a. Basically. the mixer b. the highest-frequency signal that can be usefully received c. the dynamic range of the audio amplifier d. selectivity measures: a. the ability to receive one and reject the other c. Basically. how well the adjacent frequencies are separated in the mixer ANS: B 12. When comparing values for shape factor: a. it gives a greater reduction of spurious responses b. it is cheaper ANS: D 10. typically at 455 kHz. The local oscillator and mixer are combined in one device because: a. it increases selectivity d. ANS: C 9. there is no ideal value . both values are basically equivalent d. a value of 1. monochrome video receivers d.0 is ideal d. is fixed. it increases sensitivity c. the IF amplifiers d. the detector ANS: D 15. none of the above ANS: A 11. When comparing values for shape factor: a. Distortion in a receiver can occur in: a. with two signals close in frequency. can be either above of below the RF frequency d. voice communications systems b. the range of frequencies that the receiver can select b. the weakest signal that can be usefully received b. Image frequency problems would be reduced by: a. a diode ANS: D c. they minimize distortion from nonlinearity d. the dynamic range of the receiver b. prior to IF amplification ANS: A 19. envelope detector ANS: B 21. Image frequencies occur when two signals: a. one below and one above the local oscillator by a difference equal to the IF d. and the difference between the two signals is equal to twice the IF ANS: C 18. none of the above ANS: C 20. a product detector c. the type of detector circuit being used ANS: B 17. ratio detector d. quadrature detector d. images cannot be rejected . A common AM detector is the: a. An image must be rejected: a. enter the mixer. having a narrowband RF amplifier before the mixer d. they are faster than silicon diodes b. ratio detector ANS: D 22. A common SSB detector is: a. noise generated in the receiver d. with one being a reflected signal equal to the IF frequency c. enter the mixer. PLL b. The response of a receiver to weak signals is usually limited by: a. the AGC c. enter the mixer. a BFO d. having a wideband RF amplifier after the mixer c. prior to detection d. all of the above c. are transmitted on the same frequency b. a PLL b. all of the above ANS: C 23. An FM detector is the: a. all of the above c.16. PLL b. they are cheaper than silicon diodes c. having an IF amplifier with the proper shape factor b. prior to mixing b. Germanium diodes are used in AM detectors because: a. match the local oscillator to the received signal c. to limit noise response c. a PLL detector b. Autonomous Frequency Control c. a quadrature detector d. AGC c. Foster-Seeley detector c. Limited-Noise Amplifier b. Audio Frequency Compensator b. Automatic Frequency Control d. Suppressing the audio when no signal is present is called: a. An FM detector that is not sensitive to amplitude variations is: a. coherent detection ANS: B 27. Autodyne Frequency Compensation ANS: C 32. BFO stands for: a. ratio detection . squelch d. Bistable Frequency Oscillator 25. reinject the carrier c. To demodulate both SSB and DSBSC. LNA stands for: a. envelope detection d. Logarithmic Noise Amplification c. The function of AFC is: a. Low-Noise Audio d. to remove amplitude variations b. to limit dynamic range d. all of the above ANS: C 28. use one diode for SSB and two diodes for DSBSC ANS: B 26. The function of a limiter is: a. Which would be best for DSBSC: a.24. limiting ANS: B 30. use double conversion d. Beat Frequency Oscillator b. maintain a constant IF frequency b. to limit spurious responses ANS: A 29. AFC stands for: a. Bipolar Frequency Oscillator d. carrier detection b. you need to: a. Low-Noise Amplifier ANS: B 31. Barrier Frequency Oscillator ANS: A c. AFC b. use a Foster-Seeley discriminator b. it stabilizes the audio in a receiver b. Tuned Receiver Function c. Direct Signal Phase ANS: D 37. Almost all modern receivers use the _________________________ principle. Silicon-Activated Wafer d. Symmetrical Audio Wave b. keep the input to the detector at a constant amplitude d. The first radio receiver of any kind was built in the year ____________________. Signal-plus-Noise and Distortion-to-Noise and Distortion Ratio ANS: D 38. none of the above c. none of the above ANS: B 33. Software-Activated Wave . it allows software radios to be built ANS: C 35. SAW stands for: a. keep the gain of the receiver constant b.c. keep the gain of the IF amplifiers constant c. c. Signal and Noise Amplitude Distortion c. TRF stands for: a. Surface Acoustic Wave ANS: B 34. Transmitted Radio Frequency d. Tracking Radio Frequency ANS: A COMPLETION 1. The main function of the AGC is to: a. Tuned Radio Frequency b. it is a stable bandpass filter d. Digital Signal Processor c. Dynamic Signal Properties b. Distorted Signal Packet d. Signal-plus-Noise-to-Noise Ratio d. all of the above ANS: C 36. lock the discriminator to the IF frequency d. Sinusoidal Amplitude Distortion b. The important property of a SAW is: a. ANS: superheterodyne 2. DSP stands for: a. SINAD stands for: a. ANS: track 4. The ____________________ circuit adjusts the gain of the IF amplifiers in response to signal strength. ANS: Sensitivity . The superhet was invented in the year ____________________. ANS: Selectivity 13. In a receiver. it means that when the frequency of one is adjusted. ANS: 1918 6. ANS: mixer 8. the local oscillator is ____________________ than the received signal frequency. ANS: AGC 10. In low-side injection. the output of the ____________________ goes to the IF amplifiers. When two tuned circuits ____________________ each other. ANS: intermediate IF 9. ANS: skin 5. The ____________________ effect causes the resistance of wire to increase with frequency. the other changes with it. ____________________ is the ability of a receiver to receive and successfully demodulate a very weak signal. ANS: front end 7. ____________________ is the ability of a receiver to separate two signals that are close to each other in frequency. In a superhet. ANS: lower 12. An ____________________ converter uses the same transistor for both the local oscillator and the mixer.ANS: 1887 3. the ____________________ frequency is the difference between the local oscillator frequency and the received signal frequency. ANS: autodyne 11. the ____________________ refers to the input filter and RF stage. In a superhet. A BFO produces a locally generated ____________________. An ____________________ detector uses a diode to half-wave rectify an AM signal. ANS: obsolescent 23. A dual-____________________ MOSFET is useful for AGC. ANS: noisy 26. The IF amplifiers in an AM receiver must be Class ____________________. ANS: carrier 20. A multiple-conversion receiver will have better rejection of ____________________ frequencies. ANS: conversion 15. . ANS: gate 25. ANS: S 22.14. ANS: coherent 21. A DSBSC signal requires a ____________________ detection circuit. Unlike the PLL detector. ANS: detector 17. ANS: product 19. A receiver with two different IF frequencies is called a double-____________________ receiver. ANS: envelope 18. FM detectors have a characteristic ____________________-shaped curve. While still commonly found. ANS: amplitude 24. the Foster-Seeley and ratio detectors are ____________________. A ____________________ detector is used for SSB signals. ANS: image 16. Diode mixers are too ____________________ to be practical in most applications. the quadrature detector is sensitive to changes in ____________________ of the input signal. A demodulator is also called a ____________________. Compared to tuned circuits. Typically. A ____________________ refers to any kind of FM or PM detector. ANS: higher 31. ANS: adjustment 30. ANS: fixed constant 32. the frequency of the first local oscillator is ____________________. ANS: discriminator SHORT ANSWER 1. ANS: IF 33. Suppose the bandwidth of a tuned circuit is 10 kHz at 1 MHz. An ____________________-meter is designed to indicate signal strength in many communications receivers. The effectiveness of FM ____________________ is measured by a receiver’s quieting sensitivity. A double-tuned IF transformer is usually ____________________ coupled for the response to have a flat top and steep sides. ANS: limiting 35. Up-conversion is when the output of the mixer is a ____________________ frequency than the incoming signal. ANS: stagger 29. ANS: S 34. ceramic and crystal IF filters do not require ____________________. Approximately what bandwidth would you expect it to have at 4 MHz? ANS: . In a block converter. ANS: over 28.ANS: A 27. Multiple IF stages can be ____________________-tuned to increase the bandwidth. AGC reduces the gain of the ____________________ amplifiers. 01 .20 kHz 2. What would be the acceptable frequency range of the BFO if the maximum acceptable baseband shift is 100 hertz? ANS: 1. what is the frequency of the local oscillator when the receiver is tuned to 5 MHz? ANS: 6 MHz 3.5 MHz. what would be the image frequency if the receiver was tuned to 50 MHz? ANS: 60 MHz 5. An IF filter has a –60 dB bandwidth of 25 kHz and a –6 dB bandwidth of 20 kHz.25 4. Suppose a receiver uses a 5-MHz IF frequency. What value of kc do you need to achieve optimal coupling? ANS: 0. Suppose a SSB receiver requires an injected frequency of 1.5 MHz ± 100 hertz 6. What is the shape factor value? ANS: 1. Assuming high-side injection. The transformer of a double-tuned IF amplifier has a Q of 25 for both primary and secondary. Using high-side injection for a 1-MHz IF. What value of transformer coupling would a double-tuned 10-MHz IF amplifier with optimal coupling need to get a bandwidth of 100 kHz? ANS: 0.06 7. SR = 2fmax c. C = B log2(1 + S/N) d. I = ktB b. none of the above . C = B log2(1 + S/N) d. C = B log2(1 + S/N) d. C = 2B log2M ANS: D 8. Time-Division Multiplexing b.Chapter 7: Digital Communications MULTIPLE CHOICE 1. ASCII code b. I = ktB b. The Shannon-Hartley theorem is: a. The Nyquist Rate can be expressed as: a. a sample-and-hold circuit b. C = 2B log2M ANS: B 6. Time-Domain Multiplexing ANS: A 4. SR = 2fmax c. In digital transmission. I = ktB b. an analog-to-digital converter c. I = ktB b. Ten-Digital Manchester d. SR = 2fmax c. Ten Dual-Manchester c. an amplifier c. C = B log2(1 + S/N) d. all of the above ANS: C 3. TDM stands for: a. signal degradation can be removed using: a. a fixed sample rate d. SR = 2fmax c. true binary numbers ANS: A c. Natural Sampling does not use: a. Hartley's Law is: a. a filter d. The Shannon Limit is given by: a. C = 2B log2M ANS: A 5. The first digital code was the: a. C = 2B log2M ANS: C 7. Morse code d. Baudot code ANS: C 2. a regenerative repeater b. compress the range of base-band frequencies b. In North America. the µ Law (mu law) c. maximize the useable bandwidth in digital transmission ANS: C 16. the A Law c. They are two types of sampling error. PWM d. all of the above . They are the same thing. reduce dynamic range at higher bit-rates c. decreases as the bits per sample decreases ANS: C 14. too few samples per second d. companding uses: a. Quantizing noise (quantization noise): a. preserve dynamic range while keeping bit-rate low d. d. a sample alias b. c. Aliasing is a technique to prevent foldover distortion. decreases as the bits per sample increases d. Foldover distortion is caused by: a. Which is true about aliasing and foldover distortion? a. but not both. PPS ANS: D 13. b. PDM c. PPM b. PAM ANS: B 12. The immediate result of sampling is: a. the α Law (alpha law) d. PDM c. too many samples per second ANS: C 11. decreases as the sample rate decreases c. the maximum bits per sample to the minimum bits per sample d. the maximum rate of conversion to the minimum rate of conversion c. Which of these is not a pulse-modulation technique: a. the Logarithmic Law b. none of the above ANS: A 15. Companding is used to: a. ANS: D 10. The dynamic range of a system is the ratio of: a. PCM d. the strongest transmittable signal to the weakest discernible signal b.9. decreases as the sample rate increases b. noise b. You can have one or the other. is a biphase code b. Manchester d. 8-bit numbers d. In Europe. Code-Compression d. "granular noise" is produced when: a. with a lower bit rate but reduced quality c. can suffer slope overload d. 4-bit numbers c. companding uses: a. none of the above c. with a lower bit rate but the same quality d. has a level transition in the middle of every bit period c. all of the above c. only if the voice is band-limited ANS: B 23.ANS: D 17. the µ Law (mu law) . the A Law ANS: B 18. the signal changes too rapidly c. only over shorter distances b. Compared to PCM. unipolar NRZ b. A typical codec in a telephone system sends and receives: a. the signal does not change d. 16-bit numbers ANS: B 20. the bit rate is too high b. bipolar RZ ANS: C 24. 12-bit numbers b. Coded-Carrier ANS: A 19. requires a much higher sampling rate ANS: D 21. Coder-Decoder b. Manchester coding: a. In delta modulation. provides strong timing information d. delta modulation: a. adaptive delta modulation can transmit voice: a. the Logarithmic Law b. transmits fewer bits per sample b. AMI c. Compared to PCM. the sample is too large ANS: B 22. the α Law (alpha law) d. all of the above ANS: D 25. Which coding scheme requires DC continuity: a. The number of framing bits in DS-1 is: c. Codec stands for: a. detect errors b. The number of frames in a superframe is: a. 8 k c. 56 kb/s d.a. Manchester coding b. 48 c. bits are transmitted over a T-1 cable at: a. all of the above c. In DS-1. synchronize the transmitter and receiver d.544 × 106 ANS: A 30. A T-1 cable uses: a. 6 b. carry signaling ANS: C 27. all of the above c.544 MB/s c. bipolar RZ AMI coding ANS: B 33. 8 29. 8 c. 56 k d. 2 ANS: D c. pulse-width coding c. So-called "stolen" bits in DS-1 are used to: a. 24 d.544 Mb/s b. 2 ANS: A 26. 64 k b. 8 kb/s . A typical T-1 line uses: c. 1. 1 b. carry signaling ANS: B 28. NRZ coding d. synchronize the transmitter and receiver d. The number of samples per second in DS-1 is: a. 4 d. 8 kb/s ANS: A 32. detect errors b. 64 kb/s d. 12 ANS: B 34. Framing bits in DS-1 are used to: a. 56 kb/s b. 4 d. 1. 1. The number of bits per sample in DS-1 is: a. The bit rate for each channel in DS-1 is: a. 64 kb/s ANS: B 31. 1 b. twisted-pair wire b. ANS: binary . Compared to standard PCM systems. A vocoder implements compression by: a. To send it over an analog channel. finding redundancies in the digitized data d. an analog signal must first be ____________________. "Signaling" is used to indicate: a. coaxial cable ANS: A 35. about the same b. constructing a model of the human vocal system c. constructing a model of the transmission medium b. a digital signal must be ____________________ onto a carrier. somewhat better d. ANS: modulated 3. To send it over a digital channel. ANS: decreases gets worse 5. In analog channels. ANS: digitized 4. much better c. using lossless techniques ANS: B 37. all of the above 36. Digitizing a signal often results in ____________________ transmission quality. on-hook/off-hook condition b. busy signal ANS: D c. The ____________________ value of a pulse is the only information it carries on a digital channel. ANS: improved better 2. fiber-optic cable d. the signal-to-noise ratio of an analog signal gradually ____________________ as the length of the channel increases. the quality of the output of a vocoder is: a. not as good ANS: D COMPLETION 1.a. microwave c. ringing d. ANS: Nyquist 16. The ____________________ limit gives the maximum rate of data transmission for a given bandwidth and a given signal-to-noise ratio. ____________________ Law gives the relationship between time. ANS: Hartley's 12. A ____________________ repeater is used to restore the shape of pulses on a digital cable.6. ____________________ sampling is done without a sample-and-hold circuit. and bandwidth. ANS: Natural 15. information capacity. There are techniques to detect and ____________________ some errors in digital transmission. ANS: Foldover . ANS: regenerative 7. ANS: error noise 9. ____________________ distortion occurs when an analog signal is sampled at too slow a rate. the _________________________ theorem gives the maximum rate of data transmission for a given bandwidth. ANS: correct 8. ANS: Time 10. ANS: limited 11. Ignoring noise. All practical communications channels are band-____________________. Converting an analog signal to digital form is another source of ____________________ in digital transmission systems. The ____________________ Rate is the minimum sampling rate for converting analog signals to digital format. ANS: Shannon-Hartley 13. ____________________-division multiplexing is easily done in digital transmission. ANS: Shannon 14. 17. ANS: 1 one 27. A ____________________ is an IC that converts a voice signal to PCM and vice versa. ANS: µ mu 23. In North America. ANS: 12 26. ANS: amplitude 19. ANS: Pulse-code 20. In Europe. ____________________ is used to preserve dynamic range using a reasonable bandwidth. ____________________ means that higher frequency baseband signals from the transmitter "assume the identity" of low-frequency baseband signals at the receiver when sent digitally. ANS: Aliasing 18. ANS: codec 25. ____________________ noise results from the process of converting an analog signal into digital format. ____________________ modulation is the most commonly used digital modulation scheme. ANS: higher . The number of bits per sample transmitted in delta modulation is ____________________. Delta modulation requires a ____________________ sampling rate than PCM for the same quality of reproduction. ANS: Quantizing 21. In a PCM system. The output of a sample-and-hold circuit is a pulse-____________________ modulated signal. ANS: A 24. compression is done using the ____________________-law equation. compression is done using the ____________________-law equation. the samples of the analog signal are first converted to ____________________ bits before being compressed to 8 bits. ANS: Companding 22. In delta modulation. In DS-1. ____________________ noise is produced by a delta modulator if the analog signal doesn't change. DS-1 uses a ____________________ bit to synchronize the transmitter and receiver. Long strings of ____________________ should be avoided in AMI. Adaptive delta modulation can transmit PCM-quality voice at about ____________________ the bit rate of PCM. The ____________________ size varies in adaptive delta modulation. ANS: half 32. ANS: slope 30. ANS: timing 37. ANS: Granular 29. Manchester code has a level ____________________ in the center of each bit period. ANS: zeros 35. . ANS: 8000 40.28. In AMI. Unipolar NRZ is not practical because most channels do not have ____________________ continuity. Data is carried over a T-1 line at a rate of ____________________ bits per second. ANS: step 31. ANS: DC 33. ANS: 24 38. binary ones are represented by a voltage that alternates in ____________________. ANS: framing 39. Manchester coding provides ____________________ information regardless of the pattern of ones and zeros. ANS: polarity 34. There are ____________________ channels in a DS-1 frame. ANS: transition 36. ____________________ overload can occur if the analog signal changes too fast. each channel is sampled ____________________ times per second. What is the minimum required number of samples per second to digitize an analog signal with frequency components ranging from 300 hertz to 3300 hertz? ANS: 6600 samples/second 5.000 hertz and a channel constant of k = 10. ANS: 2000 hertz 3. signaling bits are "stolen" from every ____________________ frame. What is the approximate data rate for a system using 8 bits per sample and running at 8000 samples per second? . ANS: Lossless SHORT ANSWER 1. Use the Shannon-Hartley theorem to find the bandwidth required to send 12. ANS: 5 seconds 2.ANS: 1.000 bits over a channel with a bandwidth of 2. in dB. From a group of twelve frames. What is the approximate dynamic range. Use Hartley's Law to find how much time it would take to send 100. ANS: superframe 42. ____________________ compression transmits all the data in the original signal but uses fewer bits to do it. of a linear PCM system that uses 12 bits per sample? ANS: 74 dB 6. A group of 12 DS-1 frames is called a ____________________. What is the Shannon Limit of a channel that has a bandwidth of 4000 hertz and a signal-to-noise ratio of 15? ANS: 16 kbps 4. ANS: sixth 43.544 × 106 41.000 bits per second if the number of levels transmitted is 8. ANS: 64 kbps 7.388 volt? ANS: 0. Assuming maximum input and output voltages of 1 volt. what is the output voltage of a µ-law compressor if the input voltage is 0. what would the useable data-rate be for each channel in the frame? ANS: 56 kbps 8.833 volt . If bits were "stolen" from every DS-1 frame. DTMF stands for: a. PSTN stands for: a. Call blocking: a. Primary Operational Test System d. Dual-Tone Multifrequency d. local loops b. a central office d. LATA stands for: a. a type of digital local network ANS: A 6. Local Access Telephone Area ANS: A 5. Plain Old Telephone Service c. A LATA is a: a. POTS stands for: a. occurs when the central office capacity is exceeded c. Private Office Telephone System b. Local loops terminate at: a. Digital Trunk Master Frequency .Chapter 8: The Telephone System MULTIPLE CHOICE 1. a way of accessing a tandem office d. none of the above c. an interexchange office c. both a and b d. a tandem office b. trunk lines ANS: B 7. Public Switched Telephone Network b. occurs only on long-distance cables d. Local Area Transport Access c. a local calling area b. a way of accessing a central office c. Local Area Telephone Access d. Primary Service Telephone Numbers c. Primary Service Telephone Network d. Central offices are connected by: a. Digital Telephony Multiple Frequency b. a toll station ANS: C 8. occurs on the local loop when there is an electrical power failure c. Primary Office Telephone Service ANS: D 4. Private Switched Telephone Network ANS: A 3. cannot occur in the public telephone network b. Dial Tone Master Frequency ANS: C 2. Local Access and Transport Area b. POP stands for: a.ANS: D 9. Power-On Protocol d. Framing In The Loop d. Fiber In the Toll Loop ANS: D 12. increase the speed of the local loop for digital data b. 20 hertz AC ANS: A 17. when it is off hook ANS: B 14. when it is on hook b. FITL stands for: a. only when it is ringing c. Point Of Presence ANS: B 10. shielded twisted-pair copper wire ANS: A 11. The range of DC current that flows through a telephone is: a. Framing Information for Toll Loops b. crossbar control d. as long as it is attached to a local loop d. fiber-optic c. 48 volts DC c. 20 µA to 80 µA c. 90 volts. step-by-step switching control c. Loading coils were used to: a. 20 mA to 80 mA ANS: D 15. Fiber-In-The-Loop c. coaxial cable d. The cable used for local loops is mainly: a. twisted-pair copper wire b. reduce the attenuation of voice signals c. 2 mA to 8 mA b. Post Office Protocol b. provide C-type conditioning to a local loop ANS: B 13. The typical voltage across a telephone when on-hook is: a. 20 hertz AC d. 48 volts. none of the above . In telephony. DC current flows through a telephone: a. The typical voltage needed to "ring" a telephone is: c. reduce crosstalk d. ESS ANS: C 16. common control b. 90 volts DC b. 200 µA to 800 µA d. The separation of control functions from signal switching is known as: a. volume net loss ANS: C 20. prevent "singing" d. allow signals to be multiplexed b.a. 48 volts DC b. Basic FDM groups can be combined into: a. Private Automatic Branch Exchange c. allow lines to be "conditioned" c. 0 dBm ANS: C 22. PCM ANS: A 25. 20 hertz AC 18. 1 mW b. 60 ANS: B 23. eliminate reflections c. improve signal-to-noise ratio b. The reference noise level for telephony is: a. Signal loss is designed into a telephone system to: a. Power Amplification Before Transmission b. In telephone system FDM. Public Automated Branch Exchange d. The bandwidth of voice-grade signals on a telephone system is restricted in order to: a. Public Access Branch Exchange ANS: B c. via net loss d. voice is put on a carrier using: a. 1 pW d. mastergroups ANS: D 24. PDM b. reduce power consumption ANS: B 21. 90 volts. all of the above ANS: C 19. The number of voice channels in a basic FDM group is: a. 6 c. 0 dBr c. supergroups b. 20 hertz AC ANS: D c. 48 volts. SSB c. DSBSC d. VNL stands for: a. prevent oscillation d. 90 volts DC d. 12 d. all of the above c. 24 b. voltage net loss b. voice noise level . jumbogroups d. PABX stands for: a. none of the above ANS: A COMPLETION 1. it has been surpassed by newer technologies d. c. it took to long to develop b.26. rectification ANS: C 29. compensation b. A ____________________ is a local calling area. frame alignment c. Information Services Digital Network ANS: A c. Asymmetrical Digital Subscriber Line ANS: B 32. In DS-1. Subscriber Line Interface Card d. Standard Local Interface Circuit c. ISDN stands for: a. Compared to ISDN. Standard Line Interface Card ANS: C 27. all of the above ANS: D 31. Central offices are connected together by ____________________ lines. much more expensive b. "Bit-stuffing" is more formally called: a. Basic ISDN has not been widely adopted because: a. Access to Data Services Line . about the same speed d. Single-Line Interface Circuit b. cancel echoes d. internet access using ADSL is typically: a. check for errors c. All-Digital Subscriber Line b. ANS: LATA 2. much faster c. carry signaling ANS: B 28. Integrated Services Data Network d. provide synchronization b. Information Systems Digital Network 30. justification d. ADSL stands for: a. bits are "robbed" in order to: a. it is too slow c. SLIC stands for: a. Integrated Services Digital Network b. Allocated Digital Service Line d. a ____________________ network never needs more than one intermediate switch. ANS: digital 7. ____________________ thousand telephones can connect to a central office. New ____________________ switching equipment uses TDM to combine signals. As compared to a hierarchical network. One central office can be connected to another through a ____________________ office. ANS: tip 12. Of the red and green 'phone wires. ANS: seized 14. . ____________________ coils were used to reduce the attenuation of voice frequencies. ANS: tandem 4. the red wire is called ____________________. In a twisted-pair telephone cable. the green wire is called ____________________. ANS: green 13. Most local loops still use ____________________ copper wire. Call ____________________ is when it becomes impossible for a subscriber to place a call due to an overload of lines being used. A telephone is said to have ____________________ the line when the central office sends it dial tone. ANS: ring 11. ANS: blocking 6. In a twisted-pair telephone cable. With 7-digit phone numbers. ANS: flat 9. ANS: twisted-pair 8. ANS: Loading 10.ANS: trunk 3. the ____________________ wire is positive with respect to the other. ANS: ten 5. The ____________________ functions are provided by a SLIC. ANS: large 18. ____________________ bands separate the channels in a group. ANS: SSB SSBSC 24. not all ____________________ can be in use at the same time. ANS: lines 17. ANS: conditioned 20. ANS: hybrid 16. In a crosspoint switch. amplifiers are called ____________________. ANS: C-message 23. The old carbon transmitters generated a relatively ____________________ signal voltage. ANS: repeaters 21. The generic term for Touch-Tone® signaling is ____________________. ANS: guard 25. the modulation is usually ____________________. In the telephone system. ANS: suppressor 22. A ____________________ line provides more bandwidth than a standard line.ANS: BORSCHT 15. ANS: 56 . a channel in a DS-1 frame allows only ____________________ kbps when used to send digital data. In FDM telephony. A ____________________ coil prevents loss of signal energy within a telephone while allowing fullduplex operation over a single pair of wires. Because of "bit robbing". An echo ____________________ converts a long-distance line from full-duplex to half-duplex operation. ____________________ weighting is an attempt to adjust the noise or signal level to the response of a typical telephone receiver. In FDM telephony. ANS: DTMF 19. what is the DC resistance of the local loop? .26. ANS: packet 31. ANS: TE1 34. ANS: common-channel 30. ANS: superframe 27. In ISDN. the ____________________ channel is used for common-channel signaling. the speed from the network to the subscriber is ____________________ than the speed in the opposite direction. ____________________ bits are used to compensate for differences between clock rates. SS7 is a ____________________-switched data network. ANS: D 32. For a certain telephone. ANS: B 33. ANS: greater faster SHORT ANSWER 1. If the loop current is 40 mA. In DS-1C. ANS: in-channel 29. the ____________________ channels are used for voice or data. Busy and dial tone are referred to as ____________________ signals because they use the same pair of wires as the voice signal. In ADSL. Terminal equipment especially designed for ISDN is designated ____________________ equipment. In ISDN. the DC loop voltage is 48 V on hook and 8 V off hook. ANS: stuff 28. SS7 is the current version of _________________________ signaling. ANS: asymmetrical 35. The A in ADSL stands for ____________________. A ____________________ is a group of 12 DS-1 frames with signaling information in the sixth and twelfth frames. what is its level in dBrn? ANS: 90 dBrn 6. ANS: 1 dB 5. Calculate the dB of VNL required for a channel with a 3 ms delay. A telephone test-tone has a level of 80 dBrn at a point where the level is +5dB TLP. If the loop current is 40 mA. For a certain telephone. what is the DC resistance of the telephone? ANS: 200 ohms 3. If a telephone voice signal has a level of 0 dBm.ANS: 1000 ohms 2. If C-weighting produces a 10-dB loss.) ANS: 697 Hz and 1209 Hz 4. Which two DTMF tones correspond to the digit "1"? (Use the table in the text. what would the signal level be in dBrnc0? ANS: 65 dBrnc TLP . the DC loop voltage is 48 V on hook and 8 V off hook. American Standard Code for Information Interchange c. over any distance b. usually over long distances d. Emile Baudot . alphanumeric characters b. FF. none of the above c. the Morkum Company b. Alphanumeric Standard Code for Information Interchange ANS: B 7. binary data d. character codes b. Data codes are also called: a. Western Union d. Character codes include: a. FIGS data c. LF stands for: a. all of the above ANS: B 5. American Standard Character-set 2 b. escape characters ANS: C 8. American Standard Code 2 d. In practical terms. usually over a coaxial cable ANS: A 2. parallel data transmission is sent: a. data link control characters ANS: D 6. they do not have any other name d. The five-level teletype code was invented by: a.Chapter 9: Data Transmission MULTIPLE CHOICE 1. control characters d. the Teletype Company ANS: D 3. nonstandard character codes b. Digital data that is not being used to carry characters is called: a. BS. Line Feed c. graphic control characters d. over short distances only c. all of the above c. Line Forward c. ASCII stands for: a. character sets ANS: C 4. numerical data b. and CR are examples of: a. both a and b c. Link Feed ANS: A d. Universal Automatic Receiver for Text ANS: A 10. the clock circuits must be precisely adjusted d. frame-by-frame synchronized using the start and stop bits d. UART stands for: a. transmission must stop periodically for resynchronization c. no start and stop bits means higher efficiency b. frame-by-frame synchronized using a common clock c.b. not a set length ANS: D 12. the CRC bits b. it is easier to implement than asynchronous d. the data bits d. long strings of 1s and 0s must not be allowed b. In synchronous transmission. In asynchronous transmission. Synchronous transmission is used because: a. the time between consecutive frames is: a. equal to zero c. about the same length as ten asynchronous frames b. the frames are: a. the clock bits c. 128 bytes long d. Universal Asynchronous Receiver-Transmitter b. the receiver "syncs-up" with the transmitter by using: a. In synchronous transmission. 1024 bytes long ANS: B 13. the transmitter and receiver are: a. not synchronized at all. hence the name "asynchronous" ANS: C 11. it is cheaper than asynchronous since no UARTS are required c. Unaltered Received Text d. the channel must be noise-free . all of the above ANS: A 14. To maintain synchronization in synchronous transmission: a. much longer than asynchronous frames c. Unidirectional Asynchronous Receiver-Transmitter c. a separate clock line ANS: B 15. equal to the start and stop bit-times b. frame-by-frame synchronized using the data bits b. equal to one bit-time d. In asynchronous transmission. Link Forward 9. is a bit-oriented protocol ANS: B 18. False Error Condition c. requires the use of DLE d. FEC d. HDLC: a. automatic request for queue c. Huffman codes: a. put data into a temporary buffer d. correct synchronization problems ANS: A 21. allow alphanumeric data to be corrected c. allow errors to be detected and corrected c. Correct Received Character ANS: C 24. parity c. automatic receiver queue d. Forward Error Correction d. automatic request for resynchronization b. none of the above c. LRC d. is an IBM product b. different flags at either end of a frame ANS: A 19. FEC stands for: a. Control Receiver Code b.ANS: A 16. allow errors to be detected but not corrected b. The initials ARQ are used to designate: a. VRC is another name for: a. all of the above c. ARQ c. Cycle Repeat Character c. ARQ ANS: D 23. is identical to SDLC d. ARQ is used to: a. FEC b. "bit-stuffing" b. Cyclic Redundancy Check d. correct bit errors b. is an IBM product b. BISYNC: a. automatic request for retransmission ANS: B 20. Fixed Error Control b. all of the above . is a character-oriented protocol ANS: D 17. The use of flags in SDLC requires: a. Forward Error Control ANS: C 22. CRC stands for: a. Parallel transmission can be used only for ____________________ distances. ANS: character 4. compress data ANS: B 26. ANS: Baudot 3. Data codes are also called ____________________ codes. a bit-oriented protocol b. allows the use of digital signatures b. encrypt data b. SDLC stands for: a. Public-key encryption: a. all of the above c. The term "baud" was named after Emil ____________________. an ISO standard d. The ____________________ code is a 7-bit code commonly used in communication between personal computers. correct data d. The two letters ____________________ designate the code character used to advance a printer to the next page. ANS: FF c. all of the above c. Synchronous Data Line Control ANS: A 28. ANS: ASCII 5. based on SDLC ANS: D COMPLETION 1. Synchronous Data Link Control b. is used to convey symmetric keys ANS: D 27. Synchronous Data Line Character c. Run-length encoding is used to: a. avoids the "password problem" d.d. Synchronous Data Link Character d. HDLC is: a. ANS: short 2. none of the above . allow alphanumeric data to be compressed ANS: D 25. ANS: transitions 13. In the ____________________ protocol. each frame starts with an 8-bit ____________________. ANS: UART 10. ANS: stop 8. ANS: buffers 11. ____________________ are used to hold data until they can be read. An asynchronous frame begins with the ____________________ bit. ANS: data 14. There must be sufficient 1-to-0 ____________________ to maintain synchronization in synchronous transmission. Synchronous communication is more ____________________ than asynchronous since there are fewer "overhead" bits. Clock sync is derived from the stream of ____________________ bits in synchronous transmission. ANS: efficient 12. In HDLC. each frame begins with at least two SYN characters. When receiving digital data. ANS: mark binary 1 9. An integrated circuit called a ____________________ is used in an asynchronous communication system to convert between parallel and serial data. At the end of an asynchronous frame. ANS: start 7. ANS: 01111110 17. The first eight bits of an SDLC frame are ____________________. . An asynchronous frame ends with the ____________________ bit. ANS: BISYNC 15. the line will be at the ____________________ level. BCC stands for ____________________ check character. ANS: flag 16.6. Huffman coding and run-length encoding are examples of data ____________________. FEC stands for ____________________ error correction. An ____________________ scheme corrects errors by requiring the retransmission of bad blocks. ANS: forward 22. ANS: burst 25. ANS: escape 19. Parity fails when an ____________________ number of bits are in error. CRC codes are particularly good at detecting ____________________ errors. private-key encryption can be quite secure. ANS: even 24. ANS: compression 26. public-key encryption can be slow. HDLC uses bit-____________________ to prevent accidental flags. ANS: cipher 27. If the key is ____________________ enough. A ____________________ is an encoding scheme that is not public in order to protect data. ANS: password 28. ANS: stuffing 20. DLE stands for data link ____________________. A ____________________ is often used to generate an encryption key because it is easier to remember. ____________________ errors cause many consecutive bits to be bad. ANS: decrypted 30. ANS: long 29. ANS: ARQ 23. ANS: Burst 21.ANS: block 18. . Messages cannot be ____________________ using a public key. Because it is ____________________-intensive. The frame carries 1024 bytes of actual data. a parity bit. How many different characters could be encoded using a six-bit code? ANS: 64 2. If an asynchronous frame is used to send ASCII characters in the form of bytes (8 bits). what is the shortest time it could take to send 1000 characters if each bit in a frame is 1 msec long? ANS: 10 seconds 5. Calculate the efficiency of the communication system. The ASCII codes for the characters '0' through '9' are what hex numbers? ANS: 30H to 39H 4. ANS: 66. Suppose a synchronous frame has 16 bits of non-data in the front and a 16-bit BCC at the end. What is the numerical difference between ASCII 'a' and ASCII 'A' if you treat them as hexadecimal (hex) numbers? ANS: 20 hex (32 decimal) 3.0% . Calculate the efficiency of the communication system.ANS: computation SHORT ANSWER 1. and two stop bits (it could happen).7% 6. ANS: 97. Suppose an asynchronous frame holds 8 bits of data. Compared to CSMA/CD systems. connection is usually done using a bus topology d.Chapter 10: Local Area Networks MULTIPLE CHOICE 1. in networks that cannot provide central monitoring d. hub b. Carrier Delay ANS: C 3. each channel carries only one data stream c. communication is half-duplex only b. use UTP cable d. The Internet is: a. none of the above ANS: B 6. token ANS: C 8. circuit c. Each computer on a network is called a: a. In a circuit-switched network: a. in networks requiring central monitoring c. Dumb terminals are still used: a. Carrier Sense Multiple Access ANS: B 2. CSMA stands for: a. a very large client-server network ANS: A 4. not really a network at all c. a network of networks b. none of the above . Carrier Detection b. Most LANs: a. use CSMA/CD ANS: D 5. token-passing rings are: a. Collision Delay c. are based on Ethernet b. Client-Server Multi-Access b. Carrier Server Master Application d. a very large CSMA/CD network d. not as widely used c. Collision Detection d. all of the above ANS: B 7. node d. in token-passing networks b. The CD in CSMA/CD stands for: a. slower c. all of the above c. One type of network that never has a collision is: a. a collision c. Multiple Auxiliary Units d. packets c. When two PCs send data over a baseband network cable at the same time. it is called: a. the network goes down b.3 c. tokens ANS: A 11. a central bus d. On networks. the cable overheats d. none of the above c. more expensive ANS: D d. long messages are divided into "chunks" called: a. a node b. users d. data is lost .b. contention d. In an Ethernet-based network. multiple access ANS: B 12. contention d. When two or more PCs try to access a baseband network cable at the same time. collisions ANS: D 15. The key feature of a star network is that individual workstations are connected to: a. Multistation Access Unit b. IEEE 802. a collision c. none of the above ANS: D 10. a central ring c. Multiple Access Unit ANS: A 17. token-passing b. MAU stands for: a. excess traffic b. packets b. carriers b. The standard that describes Ethernet-type networks is: a. The effect of too many collisions is: a. multiple access ANS: A 13. EIA 232 c. Ethernet d. the network slows down ANS: B 16. nodes c. excess traffic b. nodes d. all networks have collisions ANS: C 14. a switch can be used to reduce the number of: a. CSMA c. all of the above 9. it is called: a. fiber-optic cable b. to increase the data rate b. a BNC connector c. none of the above ANS: A 22. to increase the data rate b. RG-58U coaxial cable d. A 100BaseT cable uses: a. it can be used as the base for a backbone cable system d. the cable has a base speed of 10 Mbps c. Network Internal Code c. Network Interface Code d. The reason a CSMA/CD network has a minimum length for packets is: a. Three-Level encoding d. an RJ45 connector c. The word "Base" in 10BaseT means: a. Ethernet was invented by: a. all of the above ANS: C 23.b. NIC stands for: a. NRZ encoding b. CCITT ITU-E c. twisted-pair copper wires ANS: B 21. Xerox d. The reason a CSMA/CD network has a maximum length for cables is: a. Manchester encoding c.1 ANS: C 18. 10BaseT cable typically uses: a. Network Interface Cable ANS: A 25. the cable carries baseband signals b. to make sure all other nodes hear a collision in progress d. all of the above ANS: C 24. AMI encoding ANS: A 20. Network Interface Card b. IEEE 488. Digital Equipment Corporation 19. IBM b. to prevent packets from reaching all other nodes during transmission c. An Ethernet running at 10 Mbits / second uses: a. to prevent packets from reaching all other nodes during transmission c. INTEL ANS: C d. 50-ohm coaxial cable . to make sure all other nodes hear a collision in progress d. it is faster when used in large networks c.b. all of the above ANS: C 31. all of the above ANS: D 32. Using one node in the network to hold all the application software is done in: a. Untwisted-Pair copper wire b. sends incoming packets out to all other terminals connected to it b. sends incoming packets out to all other terminals connected to it b. allow faster bit rates b. are cheaper c. CAT-5 cables: a. Unicode Text Packet 27. none of the above ANS: B . a T connector ANS: C 26. client-server networks d. cannot be used in an Ethernet-type network d. are easier to crimp connectors onto d. an RS11 connector c. it is cheaper when used in large networks b. are provided by cable TV companies for Internet access d. modulate the data onto a carrier b. use coaxial cables c. Compared to twisted-pair telephone cables. are more common in token-passing networks ANS: A 29. cannot be used in an Ethernet-type network d. A switch: a. Broadband LANs: a. An advantage of using a switch instead of a hub is: a. UTP stands for: a. it reduces the number of collisions in large networks d. are more common in token-passing networks ANS: B 30. sends incoming packets out to specific ports c. peer-to-peer networks c. all of the above ANS: C 28. Uninterruptible Terminal Packet d. Unshielded Twisted-Pair copper wire ANS: B d. both a and b b. A hub: a. sends incoming packets out to specific ports c. 33. WINDOWS-based d. A LAN is a ____________________ Area Network. basically. Record locking is used to: a. ANS: token 7. a node that rarely sends data ANS: A COMPLETION 1. UNIX-based c. The software that runs a client-server network must be: a. Novell certified ANS: C 35. In a ____________________-switched network. same as a "dumb" terminal d. multitasking b. In a ____________________ network. prevent one user from reading a record that another user is writing to d. The Internet is a network of ____________________. users have a dedicated channel for the duration of communications. ANS: packet c. prevent multiple users from looking at a document simultaneously c. A "thin" client is: a. ANS: circuit 5. Ring networks often use ____________________-passing. all of the above . ANS: Local 2. all nodes are connected to a central computer. The ____________________ of a network describes how it is physically connected together. store records securely on a server b. ANS: star 4. ANS: topology 6. a PC with no disk drives b. none of the above ANS: C 34. A ____________________ is a short section of a message in digital form. ANS: networks 3. the ____________________ of a cable is limited to ensure that collisions are detected.8. ANS: collision 10. ANS: NIC 17. A ____________________ occurs when two nodes transmit simultaneously on the same baseband cable. ANS: backbone 13. one big hub. Carrier-Sense means that a node "listens" for the cable to be ____________________ before using it. In CSMA/CD. ANS: minimum 15. A switch looks at the ____________________ of each incoming packet. ANS: address . In CSMA/CD. ____________________ is when two nodes try to seize the same cable at the same time. packets must have a ____________________ length to ensure that collisions are detected. A "____________________" cable links clusters of computers together. A 100BaseTX cable is a ____________________ cable. ANS: Contention 9. ANS: 100 mega 14. in effect. ANS: quiet free unused available 12. 100BaseT cables can reliably carry up to ____________________ bits per second. ANS: fiber-optic 18. ANS: length 16. In CSMA/CD networks. ANS: detected 11. Hubs can be ____________________ to form. all collisions must be ____________________. ANS: stacked 19. A unique numerical address is provided to a node by its ____________________. So it doesn't matter how the physical connection is made. it can be disconnected and the network still functions. ANS: contention SHORT ANSWER 1. What is the key difference between a hub and a switch? ANS: A hub sends incoming packets out to all other ports on the hub. What is the advantage of a CSMA/CD network over a basic star network? ANS: If the central computer in a star network fails. If a node fails in a CSMA/CD network. The effect of a switch is to greatly reduce ____________________. Each factory uses a different sequence of numbers. . 5. the entire network is inoperative. A switch sends a packet to a specific port based on the address in the packet. and why is it unique? ANS: The address is a long binary number "burned" into a NIC's memory chip at the factory. so the chances of two NICs on the same network having the same address is extremely small.20. 2. ANS: A token-passing network sends the token from node to node in a prescribed order. 4. The collision would not be detected. What is a NIC address. It still works like a token-passing ring. and get off before the packets travel far enough to collide. send a packet. nodes at either end of a cable could get on. Explain how a network can be a physical bus but a logical ring. 3. Why do CSMA/CD packets have a minimum size limit? ANS: If a packet is too short. real-time delivery d. error-check layer d. is faster than X. SNA stands for: a. A virtual circuit is set up by the: a. link layer c. Multiple Access Network .25 b. Metropolitan-Area Network d. physical layer c. The lowest-level layer in ISO OSI is called the: a. frame layer b. network d. MAN stands for: a. Frame Relay: a. link layer ANS: C 8. Standard Network Access b. 8 c. transport layer ANS: A 6. user b. Small Network Access ANS: D 4. 3 b. Packet switching is based on: a.25 ANS: D c. Systems Network Architecture c. does less error checking than X. 5 ANS: C 5. Multiple-Area Network ANS: C 2. allows for variable length packets d. link layer d. The number of layers in ISO OSI is: a. cable layer b. 7 d. switched circuits ANS: A 3. all of the above c. frame c. Standard Network Architecture d. store-and-forward b. all of the above c. Manchester Access Network b. Bad frames are usually detected by the: a. physical layer ANS: D 7.Chapter 11: Wide-Area Networks and the Internet MULTIPLE CHOICE 1. Asynchronous Transfer Mode b. depends on number of "hops" between nodes d. Asynchronous Transmission Mode ANS: A c. Automatic Test Mode 10. Transfer Connection Protocol d. User Data Protocol ANS: A 17. IP is a: a. an application and a process d. Together. TCP/IP consists of: a. 5 layers b. depends on elapsed time since transmission c. Internet Process b. IP stands for: a. Asynchronous Transmission Model d.9. connectionless protocol d. none of the above c. High-speed Transmission Test Procedure c. The "lifetime" of a packet in an IP network: a. User Data Packet d. A bridge: a. non-robust protocol c. Interconnect Protocol d. virtual circuit ANS: C 15. all of the above ANS: D 11. UDP stands for: a. Interconnect Procedure . 7 layers ANS: A 14. connection-oriented protocol b. Universal Data Packet c. looks at the address of each packet c. TCP stands for: a. datagrams c. is essentially forever b. Internet Protocol ANS: B 12. HTTP stands for: a. User Datagram Protocol b. operate at the data-link level d. separates a network into "collision domains" b. ATM stands for: a. Transmission Control Process b. Transmission Control Protocol ANS: B 13. is approximately 200 milliseconds ANS: C 16. File Transfer Protocol b. ISP stands for: a. Simple Mail Transport Protocol d. transfer files between a server on the network and a user b. a 32-bit binary number b. FTP stands for: a. HTML stands for: a. none of the above ANS: A 23. File Transport Protocol ANS: A 22. Internet Service Provider ANS: B 25. Hypertext Transmission and Transport Procedure d. all of the above c. none of the above c. Hypertext Transport Protocol ANS: D 18. Internet Service Protocol b. Internet Service Procedure d. SMTP stands for: a. Short Message Transport Protocol b. telneting b. Simple Message Transport Protocol ANS: C 24. test files to see if their data has been "corrupted" c. running out of available values d. File Test Procedure d. HTML allows: a. Fast Transport Packet c. browsers d. file transport ANS: C 19. Hypertext Markup Language b. Hypertext Transfer-Mode Level ANS: A 20. High-Level Transfer Test Procedure c. The standard Internet address (or URL) is: a. all of the above c. four groups of base-ten numbers c. dumb terminals b. FTP is used to: a. High-speed Transfer-Mode Language c. web page layout d.b. Hypertext Transfer-Mode Layer d. Secondary Mail Transfer Procedure c. high-speed file transfer ANS: C 21. none of the above . transport packets at maximum speed through the network d. HTTP allows the use of: a. Open Standard Interconnection ANS: A COMPLETION 1. stores all domain addresses d. A ____________________ is a hierarchy of procedures for implementing digital communications. c. A dedicated telephone line can be ____________________ on a monthly basis. A ____________________-Area Network could extend across a nation. describes the Internet address-naming procedure ANS: B 28. Open Systems Interconnection b. Packet switching is done on a store-and-____________________ network. a "firewall" b. ANS: Metropolitan 2. the use of "spoofing" protocols ANS: C 29. A ____________________-Area Network would extend typically across a city. ANS: forward 6. a DNS c. ANS: leased 4. An intranet connected to the Internet is often protected by: a. Domain Numbering System d. a "brick wall" d. none of the above c. DNS stands for: a. Open Systems Internet d. ANS: Wide 3. The use of digital circuit-____________________ lines is cheaper than dedicated lines.ANS: D 26. Domain Name System ANS: A 27. ANS: switched 5. A DNS: a. Domain Name Server b. Domain Naming System . has become obsolete on the Internet b. translates words to numbers c. OSI stands for: a. ANS: protocol 7. Voltage levels on a cable are specified at the ____________________ layer. ANS: physical 8. Bad frames are usually detected at the ____________________ layer. ANS: data-link 9. Setting up a path through the network is done by the ____________________ layer. ANS: network 10. The X.25 protocol was developed by the ____________________. ANS: CCITT 11. In X.25, the data-link layer is called the ____________________ layer. ANS: frame 12. In X.25, the network layer is called the ____________________ layer. ANS: packet 13. The physical route of a ____________________ circuit changes each time it is used. ANS: virtual 14. Frame Relay requires channels with low ____________________ rates. ANS: bit-error 15. Compared to X.25, Frame Relay does ____________________ error checking. ANS: less 16. All ATM frames contain just ____________________ bytes. ANS: 53 17. Small frame size and a high-speed channel allow ____________________-time communications. ANS: real 18. ____________________ simply regenerate and retransmit packets in a network. ANS: Repeaters 19. ____________________ look at the address inside a packet to decide whether or not to retransmit it. ANS: Bridges 20. ____________________ decide the best network path on which to forward a packet. ANS: Routers 21. TCP/IP goes back to the ____________________ of the 1970s. ANS: ARPANET DARPANET 22. Between ISO OSI and TCP/IP, ____________________ was used first. ANS: TCP/IP 23. A ____________________ protocol does not track packets after they are sent. ANS: connectionless 24. HTTP allows the use of ____________________ that jump to other pages on the web. ANS: hyperlinks 25. The Internet "backbone" mostly uses high-speed ____________________ cables. ANS: fiber-optic 26. A ____________________ translates words in an Internet address to numbers. ANS: DNS 27. Intranets usually connect to the Internet through a ____________________ for security. ANS: firewall 28. Voice over ____________________ is telephony done over the Internet. ANS: IP 29. "____________________" is another term for real-time transmission over the Internet. ANS: Streaming 30. Most people gain access to the Internet by subscribing to an ____________________. ANS: ISP SHORT ANSWER 1. Name the three parts of an IP address as used on the Internet. ANS: Network number, Subnet number, Host number 2. Why is a logical channel called a "virtual" circuit? ANS: A logical channel is a way of keeping track of which two nodes on the network have messages for each other. The actual physical path can change while packets are being sent. Virtual means it behaves like direct circuit between 'A' and 'B', but it is not a direct circuit. 3. Why is it faster to send packets of a fixed size compared to packets of variable size? ANS: The processing required to store and forward packets of different lengths is greater than that required for packets of a fixed length. More processing implies more time per packet, which implies fewer packets per second through the network. 4. Why are the tasks involved in digital communications divided into layers in a protocol stack? Why not just have one layer that does it all? ANS: Divide and conquer: it reduces complexity to a manageable job. One big layer could not be adapted to newer media etc as easily as a system of independent layers. Think of subroutines in a computer program. 5. What is a "hop"? ANS: Every time a packet is forwarded on to the next store-and-forward node in the network, it is considered to be one "hop". 6. What does it mean to say a packet has a lifetime measured in hops? ANS: Each packet contains a number representing the maximum number of allowed hops. At each hop, this number is reduced by one. When it gets to zero, the packet is deleted from the network. 7. Why should packets have a lifetime? ANS: If they didn't, then the number of "lost" packets traveling around the network would continuously increase. At some point, there would be no bandwidth left to carry real traffic. maximum number of symbols per second c. I is measured in: a. AFSK d. none of the above . FSK stands for: a. modulation index ANS: C 6. margin of noise b. intermodulation distortion b. the eye alternately opens and closes ANS: A 7. Frequency-Shift Keying ANS: B 2. amperes b. number of possible states per symbol d. FSK c. High-frequency radioteletype systems commonly use: a. M is the: a. none of the above c. bits per second c. Phase-Shift Keying c. amperes per second ANS: C 5. the eye is maximally open c. Quadrature Amplitude Masking ANS: A 4. the eye is maximally closed d. Phase-Signal Keying d. An "eye pattern" shows a good channel when: a. bits d. QAM ANS: A c. Quadrature Amplitude Marking d. too many bits low d. What you see in an eye pattern is the effect of: a. In the equation C = 2Blog2M. intersymbol interference ANS: D 8. the eye is half open b. Pulse-Signal Keying b. too many bits high c. PSK b.Chapter 12: Digital Modulation and Modems MULTIPLE CHOICE 1. PSK stands for: a. QAM stands for: a. Full-Signal Keying d. Pulse-Shift Keying ANS: D 3. Quadrature Amplitude Modulation b. In the equation I = ktB. Full-Shift Keying b. 300 bps. ITU is an abbreviation for: a. 180. and 4π/4 b. IEEE d. 135. the U. a Q-bit ANS: C 10. I-bits and Q-bits ANS: B 13. π/4 DQPSK uses: a. a byte c. all of the above . noise and interference b. uneven phase and frequency response c. International Telecommunications Units c. 3π/4. FSK c. International Telecommunications Union d. and 270 degrees c. a training sequence d.N. a "constellation diagram" shows: a.9. angles of 0. low SNR d. full-duplex. 600 bps. International Telephony Unit b. 1200 bps. frequency and phase angle b. The specs of the old Bell type 103 modem were: a. The bits sent to allow equalization are called: a. The ITU is under the auspices of: a. ANSI c. angles of 45. a random sequence c. full-duplex. CCITT b. 90. Instead of a single bit. For QAM. To reduce the need for linearity. ANS: B 16. double phase-shift angles ANS: B 11. 2π/4. amplitude and frequency c. International Telephony Union ANS: C 15. effects of noise on symbols d. Gaussian bits b. 4 bits d. angles of π/4. 1200 bps. FSK b. full-duplex. location of symbols in "symbol space" b. and 315 degrees d. a dibit b. inconsistent bit rates at either end of channel ANS: B 17. half-duplex. amplitude and phase angle d. FSK ANS: A 14. FSK d. High-speed modems equalize the line to compensate for: a. the two dimensions of its symbol space are: a. 225. a QPSK symbol contains: a. separation of symbols in "symbol space" ANS: D 12. random bits c. For QAM. data-compression schemes b. a DCE d. a DTR b. a DSR ANS: C 24. In RS-232. and MNP10 are all: a. the EIA b.90 standard is issued by: a. none of the above c. a DTE c. The V. both a and b d. a DTE c. On a DB-25 RS-232 connector. On a DB-9 RS-232 connector.ANS: C 18. 7 c. ANSI-232C c. data-compression schemes b. 1 c. both a and b d. The official name for RS-232C is: a. the ISO . both a and b d. the ITU d. RS-232C b. EIA-232D ANS: B 23. signal ground is pin: a. a DCE d. signal ground is pin: a. In RS-232. a personal computer would be: a. a modem would be: a. error-correction protocols ANS: B 20. MNP3. a DSR ANS: D 25. 3 d. 5 b. ISO-232C/D d. flow control is done using: a. MNP4. RTS/CTS handshake b. MNP5 and V. MNP2. none of the above c. 3 d. XON/XOFF characters ANS: C 22. 5 b. error-correction protocols ANS: A 21. 1 c. the TIA ANS: C 19. none of the above c.42 bis are both: a. a DTR b. 7 ANS: C 26. In RS-232. Which voltage represents a binary zero on an RS-232 data pin: a. CMTS stands for: a.ANS: D 27. CTS. all of the above ANS: D 31. none of the above c. Any DSL scheme c. Digital Signal Line ANS: C 32. Hardware flow control uses: a. TD and RD b. In a CATV system. A "splitter" at the subscriber end is not required for: a. In a CATV system. Cable Modem Transmission System ANS: A 35. Double-Speed Loop c. Hybrid Fiber Control c. ADSL stands for: a. and signal ground d. +15 volts c. Asymmetrical DSL ANS: B 33. TD and RD ANS: A 30. The minimum lines required for RS-232 are: a. HFC stands for: a. Asynchronous DSL b. Head Frequency Control b. DSR and DCD c. RD. RTS. TD and RD ANS: C 29. Cable Modem Terminal System d. TD. XON and XOFF b. Analog DSL d. ADSL Lite b. XON and XOFF b. TD. Data Signal Line b. and signal ground . RTS and CTS d. ADSL d. Hybrid Frequency Control ANS: C 34. Hybrid Fiber-Coax d. RD. RD. Digital Subscriber Line d. +9 volts b. and signal ground ANS: B 28. TD. DSR. RTS and CTS d. Cable Modem Transmission Server c. All DSL c. +12 volts d. Software flow control uses: a. DSL stands for: a. Cable Modem Terminal Server b. DSR and DCD c. The QAM amplitude-phase combinations are shown with a ____________________ diagram. ITU stands for International _________________________ Union. The response to RTS is ____________________.ANS: C COMPLETION 1. ANS: dibit 8. The number of symbols per second is called the ____________________ rate. ANS: Data 5. ANS: Delta 10. ____________________ coding adds extra bits to improve performance on a noisy line. The 2 bits of information in a QPSK symbol is called a ____________________. In QAM modems. QPSK uses ____________________ different phase angles. QAM stands for ____________________ Amplitude Modulation. ANS: CTS 3. ANS: Keying 4. ANS: constellation 11. ANS: Send 2. ANS: four 9. ANS: Quadrature 6. FSK stands for Frequency-Shift ____________________. ANS: Telecommunications 12. RTS means Request To ____________________. DSR stands for ____________________ Set Ready. ANS: baud 7. DPSK stands for ____________________ PSK. . a ____________________ is used to put several channels of data onto a fiber-optic backbone. ANS: null 20. ANS: CD DCD RLSD 17. Between hardware flow control and software flow control. . ANS: 3 19. In a CATV system using cable modems.ANS: Trellis 13. ____________________ is used in a high-speed modem to compensate for uneven frequency and phase response on a line. In RS-232. A ____________________ modem cable is used to connect two DTEs via their serial ports. ANS: Asymmetrical 21. ____________________ is the process of synchronizing transmitted data from cable modems to a CMTS. ANS: 20k 16. ____________________ flow control is preferred. A voltage higher than ____________________ volts should be considered a high on an RS-232 receiver. ADSL stands for ____________________ DSL. ANS: 54k 15. A typical CATV system is organized as a ____________________ network. ANS: tree 22. the ____________________ line is asserted when the analog carrier from another modem is being received. ANS: hardware 18. The maximum allowed speed for a modem on a dial-up line is about ____________________ bps. ANS: Equalization 14. ANS: CMTS 23. The nominal maximum speed on an RS-232 cable is ____________________ bps. Approximately how many bins are there? ANS: 230 5. ANS: DMT 27. If half the modems are active at any given time. ANS: ADSL 25. ____________________ modulation divides the line bandwidth into many narrow bands called tones or bins for ADSL.3-kHz bins on a 1-MHz cable. A DSLAM is a DSL Access ____________________.ANS: Ranging 24. ANS: lite 26. A DMT system uses 4. A CATV system has 100 cable-modem customers sharing a single channel with a data rate of 36 Mbps. how many possible states must a symbol have to achieve a data rate of 1200 bps? ANS: . How many points will be on the constellation diagram of a QAM system using 8 phase angles and 2 amplitude levels? ANS: 16 3. ____________________ systems send high-speed data over a POTS line while sharing the line with dialup service. The ____________________ version of ADSL does not require a splitter at the subscriber end. Calculate the bits per second capacity of a system sending 1000 symbols per second with 16 possible states per symbol. what bit rate can a customer expect? ANS: 720 kbps 4. ANS: 4000 2. Assuming a maximum symbol rate of 400 per second. ANS: Multiplexer SHORT ANSWER 1. 8 . every other frame c. Code-Division Multiple Access b. 12 channels b. a bit is "stolen" out of each channel: a. a DS-1 frame contains a: a. 24 channels ANS: B 6.536 Mbps b. Besides data bits. none of the above c. every frame b. 64 kbps c. 256 kbps d. The bit-rate of a DS-1 signal over a T-1 line is: a. TDMA stands for: a. CDMA stands for: a. the type of media used c. all of the above ANS: C 5. the signals come from different sources c. 64 channels c. every sixth frame d. a limiting factor in FDM is: a. TDMA is used instead of TDM when: a. 1. the bandwidth of each signal b. 1. framing bit c.Chapter 13: Multiplexing and Multiple-Access Techniques MULTIPLE CHOICE 1.544 Mbps ANS: D 7. 32 channels d. In DS-1. T-bit ANS: D 8. timing bit b. Carrier Division Multiple Access ANS: A 3. the length of the channel d. all the signals come from the same source b. they mean the same thing ANS: B 4. TDM is used in RF communications d. none of the above . Time Domain Multiple Access b. Tone Division Multiple Access d. Time-Division Multiple Access ANS: B 2. When calculating the maximum number of users. Compact Digital Multiplex Arrangement d. every twelfth frame c. signaling bit d. A DS-1 signal contains: a. computer speed ANS: C 16. the chip size ANS: B 17. the digital data bit rate c. all of the above c. direct-sequence method d. direct-sequence method d. A digital space switch is a: a. time switching c.ANS: C 9. RF gain b. multiplexer b. improved signal-to-noise ratio c. a CDMA receiver c. cross-point switching ANS: B 10. compared to standard RF systems. all of the above c. much less bandwidth b. To calculate processing gain. TDM switch ANS: D 12. space switching d. computer-controlled frequency reuse b. "Processing gain" is another term for: a. line switching b. Moving signals from one line to another is called: a. much more bandwidth d. frequency-hopping ANS: C 14. Spread-spectrum can be done by using: a. computer-controlled frequency reuse b. direct-sequence systems. frequency-hopping ANS: D 13. use: a. spreading gain d. divide the transmitted RF bandwidth by: a. space switching d. bandwidth of original baseband d. crosspoint switching ANS: A 11. computerized Strowger switch d. the S/N ratio b. a wideband receiver d. about the same bandwidth c. The term "chip rate" is used in describing: a. crosspoint switch . Moving PCM samples from one time-slot to another is called: a. a narrowband receiver c. A receiver for frequency-hopping spread-spectrum would be: a. time switching c. For a given data rate. signal switching b. approximately double the bandwidth ANS: B 15. a direct-conversion receiver b. a "chip-rate" receiver ANS: B 19. true-random PN sequences b. cannot be used on an RF channel d. each signal uses all of the bandwidth ____________________ of the time. a direct-conversion receiver b. and ____________________. TDMA. cannot be used with direct-sequence spread-spectrum c. ANS: share 2. Three methods of multiple access are FDMA. CDMA: a. Multiplexing allows many signals to ____________________ a channel. non-orthogonal PN sequences d. ANS: all 6. CDMA requires the use of: a. orthogonal PN sequences c. In TDM. cannot be used with frequency-hopping spread-spectrum b. A receiver for direct-sequence spread-spectrum would be: a. ANS: CDMA 3. ANS: time 7. ANS: all 4. ANS: frequency . DS-1 is an example of ____________________-division multiplexing. For optimal performance. all signals can transmit ____________________ of the time. each signal uses part of the bandwidth ____________________ of the time. In FDM. Using CDMA on a radio channel. ANS: part 5.ANS: A 18. a wideband receiver d. none of the above ANS: A COMPLETION 1. allows many transmitters to use a band simultaneously ANS: D 20. a narrowband receiver c. The AM radio band is an example of ____________________-division multiplexing. .544 Meg 12. ANS: hopping 19. ANS: space 15. Each sample in a DS-1 frame contains ____________________ bits. Each DS-1 frame contains a total of ____________________ bits. The deep fades caused by signal-cancellation due to reflection are called ____________________ fading. One method of spread-spectrum is frequency ____________________. Moving PCM samples from one time slot to another is called ____________________ switching. ANS: 193 11. Switching signals from one line to another is called ____________________ switching.8. ANS: difficult 20. A PN sequence is a ____________________-random noise sequence. ANS: AMI 10. ANS: 1. ANS: 8 13. ANS: 24 9. A DS-1 frame is transmitted at a rate of ____________________ bits per second. It is ____________________ to jam a spread-spectrum signal. ANS: superframe 14. ANS: pseudo 18. ANS: Rayleigh 17. A DS-1 frame contains one sample from each of ____________________ channels. A group of twelve DS-1 frames is called a ____________________. ANS: time 16. T1 uses the ____________________ line code. It is ____________________ to eavesdrop on a spread-spectrum signal. 5. spread out over a very wide bandwidth. jamming can interfere with only a small fraction of the total signal. it is virtually impossible to "de-spread" the signal. ANS: ten 23. And without knowing the exact sequence being used. A chipping-rate of at least ____________________ times the bit rate of the data is common. 2. the signal power at any given frequency in its band is so low that it is virtually indistinguishable from noise. What does Hartley's Law tell us about the relationship between time and bandwidth for digital transmission? ANS: The more bandwidth. In a frequency-hopping CDMA system. ANS: orthogonal SHORT ANSWER 1. Because a spread-spectrum signal is. Why is autocorrelation used to receive direct-sequence spread-spectrum signals? . the less time it takes to send a given amount of information. So the more bandwidth available. An eavesdropper would not know a signal was being sent. The 'C' in CDMA stands for ____________________. ANS: code 24. Why is it difficult to jam a spread-spectrum signal? ANS: Jamming requires an interference signal of sufficient power in the same part of the spectrum the information signal occupies. How many signals could fit into 1 MHz of bandwidth if each signal required 100 kHz of bandwidth and the separation between adjacent channels was 10 kHz? ANS: 9 3. by definition. 4. when no two transmitters use the same frequency at the same time the PN sequences are said to be ____________________. the higher the possible bit rate. The extra bits added to the data in direct-sequence spread-spectrum are called ____________________. ANS: chips 22. Why is it difficult to eavesdrop on a spread-spectrum signal? ANS: In a spread-spectrum transmission.ANS: difficult 21. If the two sets of frequencies. f13. (f11.) and (f21. suppose PN1 would cause a transmission to occupy frequencies f11. At some point in time.. f22. and so forth. What is meant by "orthogonal sequences" in CDMA? ANS: During transmission. Assume you have two PN sequences: PN1 and PN2. 6. Now suppose PN2 would cause the transmission to occupy frequencies f21. .ANS: Autocorrelation allows a signal to be "pulled out of" the noise even when the signal-to-noise ratio is less than one. f12. f13. f23. as it is in spread-spectrum... . f22.. have no frequencies in common. f23. then the two PN sequences are said to be orthogonal. and so forth. .). f12. the PN sequences determine which parts of the available bandwidth the spreadspectrum signal will occupy. the loss in a cable's dielectric: a. ideal elements ANS: B 5. As frequency increases. the inductance per foot and the capacitance per foot c. Transmission Delay Ratio c. stays the same b. Time-Domain Response d. the resistance per foot and the inductance per foot c. Shorted Wire Region d. the resistance per foot of the wire used b. decreases d. Shorted Wave Radiation b. Total Distance of Reflection b. stays the same b. the resistance of a wire: a. there is no such effect ANS: C 7. none of the above . TDR stands for: a. its inductance and capacitance are considered to be: a. increases c. a coaxial cable b.Chapter 14: Transmission Lines MULTIPLE CHOICE 1. When analyzing a transmission line. distributed d. I2R loss c. there is no loss in a dielectric ANS: A 8. The effect of frequency on the resistance of a wire is called: a. As frequency increases. SWR stands for: a. an open-wire-line cable d. the Ohmic effect d. The characteristic impedance of a cable depends on: a. decreases d. Time-Domain Reflectometer ANS: B 3. Sine Wave Response ANS: D 2. changes periodically ANS: A 6. 300-ohm twin-lead TV cable ANS: A 4. lumped c. equal reactances b. all of the above c. increases c. the skin effect b. the resistance per foot and the capacitance per foot d. An example of an unbalanced line is: a. The optimum value for SWR is: a. increases with length b. zero b. would not reflect at all ANS: D 14. The velocity factor of a cable depends mostly on: a. would reflect as a negative pulse c. increases with frequency ANS: D 11. A positive voltage pulse sent down a transmission line terminated with its characteristic impedance: a. there is no optimum value c.ANS: D 9. the wire resistance c. would reflect as a negative pulse c. none of the above . would reflect as a positive pulse followed by a negative pulse d. would reflect as a negative pulse c. the load on a cable should be: a. one ANS: B 16. would reflect as a positive pulse followed by a negative pulse d. equal to Z0 b. 50 ohms ANS: C 10. all of the above c. The characteristic impedance of a cable: a. all of the above ANS: B 12. For best matching. standing waves b. would reflect as a positive pulse followed by a negative pulse d. the inductance per foot b. would reflect as a positive pulse b. would not reflect at all ANS: B 13. lower than Z0 c. A non-optimum value for SWR will cause: a. increases with voltage d. higher than Z0 d. loss of power to load c. would reflect as a positive pulse b. as large as possible d. higher voltage peaks on cable d. the dielectric constant d. A positive voltage pulse sent down a transmission line terminated in a short-circuit: a. A positive voltage-pulse sent down a transmission line terminated in an open-circuit: a. would not reflect at all ANS: A 15. would reflect as a positive pulse b. none of the above ANS: D 24. directly c. assuming it to be zero c. the characteristic impedance b. the loss of a 50-ohm cable carrying the same power: a. On a Smith Chart. dividing it by Z0 ANS: D 23. vacuum SWR ANS: C 18. none of the above ANS: C 25. A TDR is commonly used to: a. cannot be compared ANS: B 21. cannot be connected ANS: C 22. voltage SWR d. The radius of the circle you draw on a Smith Chart represents: a. transmission line impedances b. is the characteristic impedance b. VSWR stands for: a. variable SWR b. is infinite c. find the position of a defect in a cable c. none of the above .ANS: D 17. the impedance b. is zero d. The center of the Smith Chart always represents: a. one d. multiplying it by 2π b. would be more d. 50 ohms ANS: C 19. Compared to a 300-ohm line. the voltage c. by using a "balun" b. would be less c. the current d. zero c. you "normalize" the impedance by: a. A Smith Chart is used to calculate: a. The impedance "looking into" a matched line: a. A balanced load can be connected to an unbalanced cable: a. by using a filter d. dividing it by 2π d. would be the same b. measure the characteristic impedance of a cable b. transmission line losses c. propagation velocity ANS: A 20. optimum length of a transmission line d. c. replace a slotted-line d. all of the above ANS: B COMPLETION 1. A cable that lacks symmetry with respect to ground is called ____________________. ANS: unbalanced 2. Parallel lines are usually operated as ____________________ lines since both wires are symmetrical with respect to ground. ANS: balanced 3. Normally, a transmission line is terminated with a load equal to its ____________________ impedance. ANS: characteristic 4. Twisted-pair cables are transmission lines for relatively ____________________ frequencies. ANS: low 5. To analyze a transmission line, it is necessary to use ____________________ parameters instead of lumped ones. ANS: distributed 6. The increase of a wire's resistance with frequency is called the ____________________ effect. ANS: skin 7. The increase of a wire's resistance with frequency is caused by the ____________________ field inside the wire. ANS: magnetic 8. Dielectrics become more ____________________ as the frequency increases. ANS: lossy 9. The inductance and capacitance of a cable are given per unit ____________________. ANS: length 10. Characteristic impedance is sometimes called ____________________ impedance. ANS: surge 11. A cable that is terminated in its characteristic impedance is called a ____________________ line. ANS: matched 12. A pulse sent down a cable terminated in a short-circuit will reflect with the ____________________ polarity. ANS: opposite 13. The apparently stationary pattern of waves on a mismatched cable is called a ____________________ wave. ANS: standing 14. SWR stands for ____________________-wave ratio. ANS: standing 15. The ideal value for SWR is ____________________. ANS: one 16. Transmission line impedances can be found using a ____________________ chart. ANS: Smith 17. Short transmission-line sections called ____________________ can be used as capacitors or inductors. ANS: stubs 18. Any cable that radiates energy can also ____________________ energy. ANS: absorb 19. A ____________________-dB loss in a cable means only half the power sent reaches the load. ANS: 3 20. It is often best to measure SWR at the ____________________ end of a cable. ANS: load 21. Besides heat from I2R, the power a cable can carry is limited by the ____________________ voltage of its dielectric. ANS: breakdown 22. To normalize an impedance on a Smith Chart, you divide it by ____________________. ANS: Z0 23. The ____________________ of a Smith Chart always represents the characteristic impedance. ANS: center 24. A ____________________ wavelength transmission line can be used a transformer. ANS: one-quarter 25. A slotted line is used to make measurements in the ____________________ domain. ANS: frequency SHORT ANSWER 1. A transmission line has 2.5 pF of capacitance per foot and 100 nH of inductance per foot. Calculate its characteristic impedance. ANS: Z0 = 200 ohms 2. Two wires with air as a dielectric are one inch apart. The diameter of the wire is .04 inch. Calculate, approximately, its characteristic impedance. ANS: 386 ohms 3. If a coaxial cable uses plastic insulation with a dielectric constant ∈r = 2.6 , what is the velocity factor for the cable? ANS: 0.62 4. If a cable has a velocity factor of 0.8, how long would it take a signal to travel 3000 kilometers along the cable? ANS: 12.5 ms 5. If a cable has a velocity factor of 0.8, what length of cable is required for a 90° phase shift at 100 MHz? ANS: 0.6 meters 6. A cable has a VSWR of 10. If the minimum voltage along the cable is 20 volts, what is the maximum voltage along the cable? ANS: 200 volts A lossless line has a characteristic impedance of 50 ohms.7.5.2 transmits 100 watts into the line. How much power is actually absorbed by the load? ANS: 96 watts 10. what would be the normalized value of an impedance equal to 200 + j50 ohms? ANS: 4 + j1 . what will be the absolute value of its voltage coefficient of reflection? ANS: 0. If a cable has an SWR of 1.2 9. but is terminated with a 75-ohm resistive load. A generator matched to a line with a voltage coefficient of reflection equal to 0.5 8. Using a Smith Chart to analyze a 50-ohm cable. What SWR do you expect to measure? ANS: 1. Maxwell b. high-power microwave transmitters b. all of the above ANS: C 5. both a and b b.Chapter 15: Radio-Wave Propagation MULTIPLE CHOICE 1. 300 × 106 miles per second ANS: B c. 300 × 10 meters per second d. perpendicular to each other c. Marconi ANS: B 3. TEM stands for: a. Radio waves were first demonstrated experimentally by: a. Armstrong c. reuse of frequencies b. high antennas d. Marconi ANS: C 2. none of the above ANS: C 7. The technology that made cell phones practical was: a. Transmitted Electromagnetic ANS: A 8. Hertz d. all of the above . 3 × 106 meters per second c. In free space. the microprocessor chip c. high power levels c. light ANS: D 6. radio waves b. 3 × 106 miles per second 6 b. Transverse Electromagnetic b. True Electromagnetic d. perpendicular to the direction of travel d. radio waves travel at a speed of: a. Hertz d. The electric and magnetic fields of a radio wave are: a. none of the above c. Maxwell b. Armstrong c. Radio waves were first predicted mathematically by: a. gamma waves d. Which of the following are electromagnetic: a. all of the above ANS: A 4. the miniature cell-site d. Cell phones reduce much of the problems of mobile communications with: a. a flat insulating surface of the right size b. a ground-wave antenna d. a vertically polarized radiator ANS: A 13. An antenna has "gain" as compared to: a. many ANS: B 12. all of the above ANS: D 10. none of the above . an isotropic radiator b. above about 20 MHz ANS: A 16. Which is a possible polarization for an electromagnetic wave: a. 1 c. the Electric-field Intensity of the Radiated Power ANS: B 14. the decrease in energy per square meter due to expansion of the wavefront d. The number of circular polarization modes (directions) is: a. Ground waves are most effective: a. a flat body of water c. a flat dielectric surface of the right size ANS: C 17. circular b. circular b. the Effective Isotropic Radiated Power c. losses due to absorption in the upper atmosphere c. below about 2 MHz b. The "attenuation of free space" is due to: a. the Effective Internal Reflected Power d. Radio waves would most strongly reflect off: a. a flat metallic surface of the right size d. horizontal d. vertical c. horizontal d. when using horizontally polarized waves c. refraction c. vertical c. 3 b.9. Which polarization can be reasonably well received by a circularly polarized antenna: a. Radio waves sometimes "bend" around a corner because of: a. at microwave frequencies d. EIRP stands for: a. 2 d. all of the above ANS: D 11. the E and I fields of the Radiated Power b. losses in the characteristic impedance of free space b. reflection c. the decrease in energy per square meter due to absorption of the wavefront ANS: C 15. same as sky waves d. diffraction ANS: C 23. spatial diversity ANS: A 22. are radio waves used for satellite communications ANS: B 20. the reuse of frequencies c. diffraction d. "Ghosts" on a TV screen are an example of: a. close to the transmitter b. are line-of-sight b. Sky waves cannot be "heard": a. the cell area is increased c. line-of-sight b. are same as space waves d. in the "skip" zone . send a message multiple times over a channel b. "bounce" off the ionosphere c. send a message over multiple channels at the same time c. Space waves are: a. cancellation due to reflection c. radio waves used for satellite communications ANS: A 19. in the "silent" zone d. A "repeater" is used to: a. cancel the effects of fading ANS: C 24. fading b. Sky waves: a. Cellular phone systems rely on: a. repeaters ANS: D 25. multipath distortion d. diffraction 18. If the number of cell-phone users within a cell increases above some limit: a.b. the power levels are increased c. far from the transmitter ANS: D 21. A 20-dB reduction in the strength of a radio wave due to reflection is called: a. the radio horizon d. diffusion ANS: D d. extend the range of a radio communications system d. fading c. frequency diversity b. reflected off the ionosphere c. high power b. not possible c. nothing occurs ANS: A 27. middle layer of the atmosphere ANS: C 29. used for radio telephony b. ANS: 300 × 106 5. ANS: Hertz 3. The troposphere is the: a. a "sectoring" process occurs d. a CDMA spread-spectrum system uses: a. As a cell-phone user passes from one cell to another: a. both cells will handle the call b. Radio waves were mathematically predicted by ____________________. multiple receivers b. lowest layer of the atmosphere d. a "handoff" process occurs c. also called "ducting" d. the cell area is split ANS: B d. the number of channels is reduced 26. a "funnel" receiver c. Unlike sound or water waves. To receive several data streams at once.b. a "rake" receiver d. ANS: Maxwell 2. radio waves do not need a ____________________ to travel through. ANS: photons 6. highest layer of the atmosphere b. used to send data by radio ANS: B COMPLETION 1. Radio waves were first demonstrated by ____________________. The propagation speed of radio waves in free space is ____________________ m/sec. none of the above ANS: B 28. the most ionized layer of the atmosphere . Meteor-trail propagation is: a. ANS: transverse 4. c. Electromagnetic radiation can be thought of as a stream of particles called ____________________. Radio waves are ____________________ electromagnetic waves. ANS: perpendicular 13. The watts per square meter of a radio wave ____________________ as the wave-front moves through space. An antenna is said to have ____________________ in a certain direction if it radiates more power in that direction than in other directions. At a far distance from the source. ANS: gain 16.ANS: medium 7. The dielectric strength of clean dry air is about ____________________ volts per meter. ANS: sphere 10. ANS: specular . With ____________________ polarization. ANS: electric 12. Waves from an ____________________ source radiate equally in all directions. Both the electric and magnetic fields of a radio wave are ____________________ to its propagation direction. ANS: circular 15. The wavefront of a point source would have the shape of a ____________________. the direction of a radio wave's electric field rotates as it travels through space. a radio wavefront looks like a flat ____________________-wave. ANS: decrease 17. ANS: plane 11. The polarization of a radio wave is the direction of its ____________________ field. ANS: isotropic 9. ANS: 3 × 106 8. ANS: perpendicular 14. Reflection of plane-waves from a smooth surface is called ____________________ reflection. The electric field of a radio wave is ____________________ to its magnetic field. "Ghosts" on a TV screen are an example of ____________________ distortion. Cell phones typically operate at a ____________________ power level. The "fast fading" seen in mobile communications is caused by ____________________ waves interfering with direct waves. ANS: multipath 25. The ____________________ of frequencies allows many cell-phone users to share a geographical area. The use of ____________________ chips makes cell phones a practical technology. ANS: reuse 28. ____________________ waves are vertically polarized radio waves that travel along the earth's surface. ____________________ waves travel from transmitter to receiver in a "line-of-sight" fashion. ANS: Refraction 19. to reduce interference. ANS: Sky 23. ANS: Sectoring 29. ANS: low 27. ____________________ is when a cell-site uses three directional antennas. ANS: reflected 26. ____________________ waves are radio waves that "bounce off" the ionosphere due to refraction. The ____________________ zone is a region where sky waves cannot be received. ANS: Ground 22. ANS: skip 24.18. The process of ____________________ makes radio waves appear to "bend around a corner". each covering a third of the cell area. ANS: microprocessor . ANS: Space 21. ANS: diffraction 20. ____________________ is the "bending" of radio waves as they travel across the boundary between two different dielectrics. how far away from a 1-watt point source will it continue to work? ANS: 8.000 meters from the source? ANS: 796 pW/m2 3. what is the power density 10. What power must a point-source of radio waves transmit so that the power density at 3000 meters from the source is 1 µW/m2? ANS: 113 watts 4. approximately. what is the expected time between fades? ANS: 15 msec . If the car is traveling 36 km/hour. What.9 km 5.3 × 10–10 F/m and the same permeability as free space. If a point source of radio waves transmits 1 watt. A line-of-sight radio link over flat terrain needs to use antenna towers 50 km apart. If a radio receiver needs 1 nW/m2 of power density to function. is the minimum height for the towers assuming all the towers are the same? ANS: 37 meters 6. What is the characteristic impedance of that dielectric? ANS: 45 ohms 2.SHORT ANSWER 1. A mobile radio is being used at 1 GHz in an urban environment with lots of reflecting structures. A certain dielectric has permittivity of 6. 10 dB b. one half-wavelength d. active antenna b. resonance ANS: A 7. The ability of an antenna to radiate more energy in one direction than in other directions is called: a. the reflected signal d. in all directions b. standing wave pattern around the antenna c. from +90° to –90° b. the SWR b. directivity c. none of the above . from front to back c. a Hertz antenna ANS: B 3. SWR along the feed cable d. The end-to-end length of a half-wave dipole antenna is actually: a. I2R loss of the antenna ANS: C 5. 3 dB d. the field strength of a horizontally polarized half-wave dipole antenna is strongest: a. in two directions d. the radiated signal c. depends on the number of elements ANS: B 6. infinite ANS: A 8. slightly shorter than a half-wavelength ANS: D 4. a Yagi antenna d.Chapter 16: Antenna MULTIPLE CHOICE 1. one wavelength c. between half-power points d. all of the above ANS: A 2. a Marconi antenna b. The front-to-back ratio of a half-wave dipole antenna is: a. The radiation of energy from an antenna can be seen in the: a. An antenna's beamwidth is measured: a. radiation resistance of the antenna b. 0 dB c. selectivity d. A half-wave dipole is sometimes called: a. Measured on the ground. The real part of an antenna's input impedance is due to: a. slightly longer than a half-wavelength b. between the minor side-lobes c. in one direction c. ANS: C 9. ERP stands for: a. Equivalent Radiation Pattern b. Effective Radiation Pattern ANS: D 10. "Ground Effects" refers to the effects on an antenna's radiation pattern caused by: a. radio signals reflecting off the ground b. buildings and other structures on the ground c. fading d. faulty connection of the feed cable ground ANS: A 11. A 1-MHz monopole antenna must be: a. mounted vertically b. mounted horizontally ANS: A 12. The typical antenna in an AM radio is a: a. dipole b. folded dipole ANS: C 13. The polarization of plane waves received from a satellite is changed by: a. gamma rays c. helical rotation b. Faraday Rotation d. the distance traveled ANS: B 14. A nonresonant antenna: a. will not transmit b. will not receive ANS: C 15. At resonance, the input impedance to a lossless antenna should be: a. resistive c. capacitive b. inductive d. infinite ANS: A 16. An antenna can be matched to a feed line using: a. a shorted stub c. an LC network b. a loading coil d. all of the above ANS: D 17. As the length of a "long-wire" antenna is increased: a. the number of lobes increases c. efficiency decreases c. will cause SWR on the feed cable d. all of the above c. ferrite "loop-stick" d. none of the above c. at least one half-wavelength long d. at least one wavelength long c. Equivalent Radiated Power d. Effective Radiated Power b. the number of nodes decreases ANS: A 18. Arrays can be: a. phased b. driven ANS: D d. none of the above c. parasitic d. all of the above 19. An array with one driven element, a reflector, and one or more directors is called a: a. Marconi c. Log-Periodic Dipole b. Yagi d. stacked array ANS: B 20. LPDA stands for: a. Low-Power Dipole Array b. Low-Power Directed Array ANS: C 21. The radiated beam from a parabolic "dish" transmitting antenna is: a. collimated c. dispersed b. phased d. none of the above ANS: A 22. The energy picked up by a parabolic antenna is concentrated at the: a. center c. focus b. edges d. horn ANS: C 23. Antennas are often tested in: a. an echo chamber b. an anechoic chamber ANS: B 24. Field strength at a distance from an antenna is measured with: a. a slotted line c. an EIRP meter b. a dipole d. a field-strength meter ANS: D COMPLETION 1. An antenna is the interface between the transmission line and ____________________. ANS: space 2. Hertz antenna is another name for a half-wave ____________________. c. a vacuum chamber d. an RF reflective chamber c. Log-Periodic Dipole Array d. Log Power Dipole Array ANS: dipole 3. The length of a half-wave dipole is about ____________________ % of a half-wave in free space. ANS: 95 4. The ____________________ resistance is the portion of an antenna's input impedance due to transmitted radio waves leaving the antenna. ANS: radiation 5. Input impedance at the center feed point of a resonant half-wave dipole is about ____________________ Ω. ANS: 70 6. Input impedance at the center feed point of a resonant folded dipole is about ____________________ Ω. ANS: 280 – 300 7. The vertical angle of radiation is called the angle of ____________________. ANS: elevation 8. Antenna radiation patterns are typically drawn on graphs with ____________________ coordinates. ANS: polar 9. As compared to a ____________________ source, a half-wave dipole has a gain of about 2 dBi. ANS: point isotropic 10. Antenna gain measured in ____________________ is with reference to a half-wave dipole. ANS: dBd 11. ____________________ is the same as the gain for a lossless antenna. ANS: Directivity 12. The front-to-back ratio of a half-wave dipole is ____________________ dB. ANS: 0 13. The ____________________ of a directional antenna is the angle between its half-power points. ANS: beamwidth ANS: horizontal 18. A monopole antenna is typically mounted in the ____________________ direction. ERP is the power input to the antenna multiplied by the antenna's ____________________. The length of a typical monopole antenna is ____________________ wavelength. A monopole antenna mounted high on a tower typically uses a ____________________ plane. ANS: vertical 20. ANS: ground 22. The number of driven elements in a Yagi antenna is typically ____________________. ANS: gain 16. ANS: one 24. ANS: balun 17.14. ANS: effective 15. ERP stands for ____________________ radiated power. ANS: omnidirectional 23. The reflector on a Yagi antenna is called a ____________________ element. ANS: one-quarter 1/4 21. A vertical antenna has an _________________________ radiation pattern for ground-based receivers. ANS: parasitic 25. A ____________________ is required to connect a coaxial cable to a center-fed dipole antenna. . An LPDA is a ____________________ dipole array. A horizontally mounted dipole will radiate waves with ____________________ polarization. A folded dipole has ____________________ bandwidth than a standard dipole. ANS: wider greater more 19. how much gain does it have compared to a half-wave dipole? ANS: 8 dB 4. What is the ERP of an antenna with 10 dBd of gain and driven by one watt? ANS: 10 watts 5. ANS: five 27.14 dB of gain compared to a point source. A resonant antenna has an input impedance of 100 ohms and is driven by 100 watts. An ____________________ chamber is often used to test microwave antennas. How much power will a 95% efficient antenna radiate if driven with 100 watts? ANS: 95 watts 3. Calculate the physical length of a half-wave dipole for use at 300 MHz. ANS: horn 30. ANS: focus 28. All the waves that hit the surface of a parabolic antenna merge at the ____________________. If an LPDA had five elements. ANS: 475 millimeters 2. ANS: anechoic SHORT ANSWER 1. the number of driven elements it had would be ____________________.ANS: log-periodic 26. A ____________________ beam has all its individual rays parallel to each other. If an antenna has 10. A microwave ____________________ antenna is essentially an extension of a waveguide. ANS: collimated 29. What is the RMS current in the antenna? ANS: 1 ampere . A resonant antenna has an input impedance of 100 ohms and is driven by 100 watts. What is the RMS voltage at the feed-point of the antenna? ANS: 100 volts .6. of its circular symmetry d. TE 10 a. below the microwave range b. TM11 b. it is dominant c. TE 01 c. TM10 ANS: C 5. The dominant mode of a circular waveguide is: a. The UHF range is: a. inside the microwave range ANS: A 3. depends on the frequency it carries c. with a magnetic field probe c. all of the above c. 100 MHz c. it is more efficient ANS: B 7. 10 GHz b. none of the above ANS: A 4. 100 GHz ANS: B 2. the shape of the waveguide c. depends on the longer dimension of its cross section d. TE 01 b. the point of signal injection b. The dominant mode of a rectangular waveguide is: c. TE 11 d. with an electric field probe d. TM 01 d. is fixed b. it is the only mode possible b. TM 01 ANS: C 6. The dominant mode of a waveguide depends on: a. the power level of the signal d. The characteristic impedance of a waveguide: a. Power can be coupled into or out of a waveguide: a. 1 GHz d. The microwave frequency range is considered to start at: a. same as the microwave range .Chapter 17: Microwave Devices MULTIPLE CHOICE 1. Circular waveguides use TM 01 mode because: a. through a hole in the waveguide b. both b and c ANS: D 8. above the microwave range d. none of the above c. defect in a waveguide ANS: A 12. all of the above c. couple components on a circuit board d. separates signals among various ports d. tuned circuit b. Traveling-Wave Transmission c. GaAs stands for: a. A TEE connector used with waveguides is: a. none of the above . A "circulator" is a device that: a. their insertion loss c. Directional couplers for waveguides are characterized by: a. allows a signal to pass in one direction only c. isolates frequencies in a waveguide b. allows a signal to pass in one direction only c. all of the above ANS: D 10. prevents microwaves from leaking out of a waveguide ANS: B 15. a "magic" TEE d. prevents microwaves from being "trapped" in a waveguide ANS: C 16. an E-plane TEE ANS: D 13. their coupling specification d. Striplines and microstrips are used to: a. rotates signal polarity in a waveguide b. gallium astenite d. their directivity b. gallium arsenide b. couple waveguides to antennas ANS: C 11.ANS: D 9. A resonant cavity is a type of: a. an H-plane TEE b. Transverse Wave Transmission b. separates signals among various ports d. Transverse-Wave Tube ANS: C 14. Traveling-Wave Tube d. antenna d. couple sections of waveguide b. An "isolator" is a device that: a. gallium assembly ANS: A c. none of the above c. TWT stands for: a. radio detection and ranging d. YIG ANS: B 23. RADAR uses: a. impact avalanche and transit time b. all of the above c. klystron d.17. The device commonly used in microwave ovens is the: a. remote detection and ranging . none of the above c. magnetron b. A YIG can be tuned by applying: a. pulsed transmission b. magnetron b. IMPATT stands for: a. YIG ANS: A 22. radio depth and ranging ANS: C 25. mechanical pressure d. Fresnel lenses b. slots c. The device commonly used in UHF transmitters is the: a. none of the above c. continuous transmission ANS: D c. an electric field b. klystron d. A microwave phased array is often made using: a. klystron d. implied power at transmission terminal d. an "exciter" signal 20. Yagis d. TWT c. The device commonly used in satellite communications is the: a. YIG stands for: a. magnetron b. a magnetic field ANS: B c. RADAR stands for: a. Yttrium-Iron-Germanium ANS: C 19. Yttrium-Iron-Gallium b. YIG ANS: C 21. induced mobility at transmission time ANS: A 18. Yttrium-Iron-Garnet d. TWT c. the Doppler effect d. TWT c. all of the above ANS: A 24. radio ranging b. ANS: faster 10. In a waveguide. decreases with increasing repetition rate d. is always a tenth of the maximum range b. none of the above ANS: A COMPLETION 1. ANS: Dispersion 2. ANS: high 8. decreases with increasing pulse period b. ANS: dominant 4. decreases with increasing pulse duration d. the ____________________ field peaks in the middle of the waveguide cross section. none of the above ANS: B 27. . ANS: two 6. ANS: TM01 7. The waveguide mode with the lowest cutoff frequency is the ____________________ mode. ANS: zero 3. The minimum effective range for pulsed radar: a. the electric field has ____________________ peaks in the waveguide cross section. ANS: slower 9. phase velocity is always ____________________ than the speed of light. ANS: electric 5. A waveguide acts as a ____________________-pass filter. ____________________ is the effect of a pulse "spreading out" as it travels through a waveguide. In TE20 mode. In a circular waveguide. ____________________ mode is used because of its circular symmetry. group velocity is always ____________________ than the speed of light.26. increases with increasing pulse duration c. The electric field is ____________________ along the walls of a rectangular waveguide. impedance ____________________ as frequency increases. In a waveguide. The maximum effective range for pulsed radar: a. In a waveguide. In TE10 mode. increases with increasing repetition rate c. ANS: resistance 15. A ____________________ antenna is just a waveguide with a hole in it. Both klystrons and TWTs are ____________________-beam tubes. A Gunn device oscillates because of its negative ____________________. A ____________________ TEE is a combination of E-plane and H-plane TEES. Both magnetrons and TWTs are slow ____________________ tubes. ANS: cavity 14. ANS: slot 18. Calculate the TE10 cutoff frequency for a rectangular waveguide if the longer dimension of its cross section is 5 cm. ANS: higher SHORT ANSWER 1. The frequency of the returned signal will be ____________________ than the transmitted signal if the target is moving toward the radar antenna. . ANS: wave 16. ANS: linear 17. ANS: smaller 20.ANS: decreases 11. ANS: hybrid 12. The Q of a resonant cavity is very ____________________ compared to lumped LC circuits. A ____________________ antenna is a flat piece of copper on an insulating substrate with a ground plane on the other side. ANS: high 13. The radar cross section of a target is typically ____________________ than its actual size. ANS: patch 19. A wavemeter is a resonant ____________________ with an adjustable plunger. ANS: 173 millimeters 5.ANS: 3 GHz 2. ANS: 346 × 106 meters per second 4. Calculate the group velocity in a waveguide carrying a signal that is twice its cutoff frequency. Find the maximum unambiguous range for a pulsed radar sending 10k pulses per second. Find the gain in dBi of a 10-GHz horn antenna with dE = dH= 60 mm. ANS: 15 km 7.8 6. ANS: 300 meters . Find the minimum unambiguous range for a pulsed radar sending 2-µsec duration pulses. Calculate the wavelength of a 2-GHz signal in a waveguide with a 1-GHz cutoff frequency. Calculate the phase velocity in a waveguide carrying a signal that is twice its cutoff frequency. ANS: 260 × 106 meters per second 3. ANS: 14. reliability c. a very wide microwave beam ANS: A c.9% b. hop d. additional repeaters increase the: a. Loss Of Skip b. FM b. Line-Of-Sight d. LOS stands for: a. skip b. 99% d. 2 watts c. QAM d. all of the above ANS: B 6. Another term for a single microwave link is a: a. jitter b. jitter b. jump ANS: B 2. The typical reliability of a microwave system is: a. SSB ANS: D 3. jitter c. 90% c. a very narrow microwave beam b. In analog microwave systems. additional repeaters increase the: a. Too much antenna gain causes: a. In digital microwave systems. all of the above .Chapter 18: Terrestrial Microwave Communication Systems MULTIPLE CHOICE 1. noise level d. Loss Of Signal ANS: C 8. 20 watts d. section c. A typical microwave system uses a transmitted power of about: a. all of the above ANS: C 7. 99. excessive noise d. Line-Of-Signal c. reliability c. 99. 200 watts b.99% ANS: D 4. Microwave systems use: a. noise level d. none of the above ANS: A 5. good energy per bit per noise density ratio ANS: D 12. Satisfactory performance of a digital microwave system requires a: a. MMDS stands for: a. Satisfactory performance of an analog microwave system is defined as: a.9. when distance exceeds line-of-sight ANS: B 15. attenuation due to weather ANS: D 13. always b. diversity c. an energy-per-hertz level that exceeds a given value d. baseband type ANS: D 16. above 10 GHz d. 60% of the Faraday zone c. good energy per bit per transmitted Watt ratio d. high-gain antennas b. IF type b. 60% of the height of the antenna tower b. The microwave signal path should clear obstacles by at least: a. regenerative type d. all of the above ANS: B 17. all of the above . 60% of the Fresnel zone d. Microwave repeaters can be: a. low level of transmitted power b. all of the above ANS: A 14. high level of ERP c. none of the above ANS: A 11. power d. The effects of fading due to multipath reception are often reduced using: a. 60% of the highest obstacle height ANS: B 10. An advantage of digital techniques over analog in a microwave system is: a. it requires less power b. less bandwidth is required c. below 10 GHz c. Multichannel Microwave Distribution System c. a carrier-to-noise ratio that exceeds a given value b. an ERP level that exceeds a given value c. all of the above c. multipath reception b. ducting d. Repeaters are used in a microwave system: a. Fading is caused by: a. accumulation of noise is reduced d. Low-power Microwave Distribution System ANS: B 19. Local Multipoint Distribution System c. unidirectional ANS: A COMPLETION 1. In digital microwave systems. bidirectional b. the energy per bit per ____________________ is a key parameter. Multipath reception can cause 20 dB or more of ____________________. ANS: noise density 7. STL stands for ____________________-to-transmitter links. LMDS stands for: a. ANS: temperature 6. Multichannel Multipoint Distribution System d. ANS: hop 2.b. Local Microwave Distribution System b. ANS: jitter 5. Local Multichannel Distribution System d. ANS: year 4. Multipoint Microwave Distribution System c. Adding more links causes ____________________ in a digital microwave system. none of the above . One microwave link is called a ____________________. it is more convenient to use noise ____________________ than noise figure in calculations. A typical microwave system has about one hour per ____________________ or less of downtime. LMDS is: a. ANS: fading c. multidirectional d. Multiple Microwave Distribution Systems ANS: C 18. In microwave systems. ANS: studio 3. ANS: baseband 13. Microwave digital radio techniques reduce the accumulation of ____________________ as a signal goes from link to link. what would it be. Two antennas stacked one above the other on a tower is an example of ____________________ diversity in a microwave system. A line-of-sight microwave link operating at 4 GHz has a separation of 40 km between antennas. approximately. ____________________ are necessary in a microwave system that extends beyond the line-of-sight distance. Analog microwave systems use both IF and ____________________ repeaters. A transmitter and receiver operating at 1 GHz are separated by 10 km. MMDS is unidirectional. ANS: noise 14.4 meters 3. Microwave systems generally use less than ____________________ watts of power. but ____________________ is bidirectional. The ability to use two frequencies simultaneously is an example of ____________________. If the line-of-sight distance for an optical beam is 12 km. ANS: space 9. An obstacle in the path is located midway between the two antennas. ANS: diversity 10. and both the sending and receiving antennas have a gain of 20 dBi? . By how much must the beam clear the obstacle? ANS: 16. ANS: Repeaters 12.8. ANS: LMDS SHORT ANSWER 1. ANS: ten 11. for a microwave beam? ANS: 16 km 2. How many dBm of power gets to the receiver if the transmitter puts out 1 Watt. ANS: 201 K 5.4 dBm 4. A microwave system has a feed-line loss of 2 dB and sees a sky temperature of 150 K. What is the carrier-tonoise power ratio? ANS: 40 dB . A microwave receiver receives –60 dBm of signal. Calculate the noise temperature of the antenna/feed-line system referenced to the receiver input. The noise power is –100 dBm.ANS: –42. 4 : 3 ANS: B 8. Nippon Television Systems Commission ANS: B 2. RGB stands for: a. Luminance refers to: a. 625 : 525 c. 525 c. EIA b. 50 b. National Television Systems Committee c. 30 d. National Television Systems Council d. chroma d. The NTSC specification was drawn up by the: a. 625 d. 60 ANS: D 7. The number of NTSC fields sent per second is: a. National Television Systems Commission b.Chapter 19: Television MULTIPLE CHOICE 1. Red-Green Burst b. raster c. IEEE ANS: C 3. contrast c. 50 b. 25 c. 25 c. Red-Green-Blue . 1250 ANS: A 5. 1024 b. IRE d. 60 ANS: B 6. The number of scan lines in an NTSC signal is: a. The number of NTSC frames sent per second is: a. Red-Green Brightness ANS: D 4. 525 : 625 d. 3 : 4 b. Red-Green Bandwidth d. FCC c. brightness b. The aspect ratio of a standard TV receiver is: a. NTSC stands for: a. 30 d. The smallest picture element is called a: a. in-phase color component. black d. IRE units d. whiter than white b. in-phase video component. peak white ANS: B 11.ANS: A 9. horizontal resolution is not measured in lines ANS: B 15. horizontal resolution: a. all white d. pixel d. composite video signal. quadrature video color component d. blacker than black ANS: B 12. white c. all of the above c. whiter than white b. blacker than black ANS: D 13. Y I Q refers to: a. none of the above c. maintain horizontal sync b. maintain vertical sync ANS: A 14. equalize the DC level d. foot-candles b. max white b. in-phase color component. white c. composite color signal. When measured in lines. quadrature phase color component c. whiter than white c. Luminance is measured in: a. NTSC units . is less than vertical resolution d. The blanking level corresponds to a luminance of: a. dot b. The vertical blanking pulse is serrated to: a. quadrature phase color component b. is about the same as vertical resolution c. a method of demodulating stereo sound ANS: A c. black d. The sync pulse level corresponds to a luminance of: a. is greater than vertical resolution b. In a color TV receiver. luminance signal. pic ANS: C 16. The maximum luminance level is called: a. lumins ANS: C 10. detect the presence of a color video signal b. SSB c. much lower b. suppressed-carrier AM b. sync audio pulse . about the same c. Compared to a monochrome CRT. The modulation used for the video signal in a standard NTSC color TV receiver is: a. the video transformer d.17. regenerate the color sub-carrier c. SSB c. The function of the "color burst" is to: a. SAP stands for: a. suppressed-carrier AM b. FM ANS: D 20. vestigial sideband AM d. much higher d. sync amplitude pulse d. Compared to the luminance signal. about the same d. much less b. suppressed-carrier AM b. magnetically for both vertical and horizontal b. electrostatically for vertical and magnetically for horizontal c. much greater c. the accelerating voltage on a color CRT is: a. vestigial sideband AM d. FM ANS: C 21. separate audio pulse ANS: A 23. to synchronize the color demodulation line by line d. the yoke ANS: C 24. SSB c. the horizontal resolution for color is: a. color CRTs use magnetic acceleration ANS: B 25. FM ANS: B 19. resolution does not apply to color ANS: C 18. The horizontal output transformer is also called: a. electrostatically for both vertical and horizontal c. The modulation used for the chroma signal in a standard NTSC color TV receiver is: a. the flyback transformer b. Deflection in CRTs used in TV receivers is done: a. vestigial sideband AM d. all of the above ANS: D 22. the isolation transformer c. separate audio program b. The modulation used for the audio signal in a standard NTSC color TV receiver is: a. ANS: scanning 4. ANS: porch c. ANS: composite 6. ANS: luma luminance 8. allowed full picture chroma b. Video systems form pictures by a ____________________ process. ANS: chroma chrominance 9. ANS: retraces 5. the electron beam ____________________ from right to left. The NTSC specifies a ____________________ video signal. AFPC stands for: a. ____________________ is a conductive coating on both the inside and outside of the CRT in a TV. The ____________________ standard for TV has been in use since 1953. The blanking period before the sync pulse is called the front ____________________. ANS: NTSC 3.d. Brightness information is called ____________________. Color information is called ____________________. The ____________________ ratio of a CRT screen is the ratio of width to height. automatic frequency and phase control ANS: B COMPLETION 1. magnetically for vertical and electrostatically for horizontal ANS: A 26. During the horizontal blanking interval. ANS: aspect 7. none of the above . ANS: Aquadag 2. automatic frequency and picture control d. ANS: phosphor 22. The maximum number of scan lines under NTSC is ____________________. ANS: 525 16. Each horizontal scan line takes ____________________ microseconds. ANS: position 11. ANS: ultor 20. ANS: 3. The human eye is most sensitive to the color ____________________. Vertical blanking lasts about ____________________ milliseconds. ANS: 62.5 12.58 18.3 14.10. ANS: pixels 15. Odd and even fields are identified by the ____________________ of the vertical sync pulse. Horizontal blanking lasts ____________________ microseconds. ANS: green 17. The accelerating voltage for a color CRT is about ____________________ kV. . ANS: 1. The color sub-carrier frequency is approximately ____________________ MHz. The horizontal output transformer is called the ____________________ transformer. ANS: separate 19. not including blanking. The inside of a CRT's face-plate is coated with ____________________ to generate the picture. SAP stands for ____________________ audio program. The second anode of a CRT is often called the ____________________. ANS: 20 to 30 21. ANS: 10 13. Picture elements are called ____________________. A good way to separate luma from chroma is to use a ____________________ filter. The color ____________________ turns off the color circuitry when a color TV is receiving a monochrome signal. The ____________________ controls in a color TV adjust the electron beams to strike the correct triad of phosphor dots. A ____________________ shows a color-bar signal with predetermined levels and phases. ANS: saturation 29. The ____________________ of the chroma signal represents the color hue. The antenna for a CATV system is located at the ____________________ end. ANS: phase 30. ANS: comb 24. ANS: killer 25. ANS: convergence . Color intensity is called ____________________. ANS: purity 31. Signal levels in cable TV systems are usually measured in ____________________. ANS: head 27.ANS: flyback 23. ANS: vectorscope 28. ANS: dBmV 26. The ____________________ controls in a color TV adjust the electron beams to strike the correct color phosphor dots. The "payload" on a communications satellite consists of: a. footprint b. batteries d. 10 watts d. respectively. 357. apogee and perigee c. transponders c. 50 to 250 watts d. The power level for an earth station to transmit to a satellite is on the order of: a. depends on satellite velocity ANS: B 2. 3. 35. apogee and perigee ANS: A 6. solar cells b. perigee and apogee d.: a. earth station c. all of the above . 103 watts 2 b.Chapter 20: Satellite Communications MULTIPLE CHOICE 1. The velocity required to stay in orbit: a.780 km d.578 km c. An antenna is aimed by adjusting the two "look angles" called: a. downlink and uplink ANS: A 3. The power per transponder of a typical Ku-band satellite is in the range: a. 101 watts c. is constant b. declination and elevation b. 104 watts ANS: C 8. is zero (freefall) c. azimuth and declination d. plate ANS: C 4. downlink d. uplink and downlink b. The high and low points of a satellite's orbit are called. The height of the geosynchronous orbit above the equator is about: a.800 km b. is higher close to the earth than far from the earth ANS: D 5. depends on its orbit ANS: B 7. The area on the earth that is "covered" by a satellite is called its: a. 500 to 2500 watts b. is lower close to the earth than far from the earth d. 5 to 25 watts c. azimuth and elevation c. DBS stands for: a. decibels of signal b. none of the above . very small aperture terminal c. antenna maintenance b. none of the above c.ANS: A 9. television repeater only ANS: A 14. "Station-keeping" refers to: a. low power to a large antenna b. direct-broadcast system d. video signal antenna terminal ANS: D 16. TVRO stands for: a. time-division multiple access d. star b. power-down b. very small antenna terminal d. repeater c. low-noise amplitude d. down-beam signal ANS: D 11. A typical VSAT system is configured as a: a. transponder-directed multiple antennas b. low-noise amplifier b. ring d. VSAT stands for: a. On the uplink from a terminal. LNA stands for: a. TDMA stands for: a. orbital adjustments d. low power to a small antenna d. television remote origin d. mesh c. backoff d. low-noise array c. television distribution master antenna ANS: C 15. television receive only b. A reduction in TWT power for linearity is called: a. EIRP drop ANS: B 13. direct-broadcast satellite c. power-level adjustments ANS: C 10. high power to a small antenna c. backdown c. LEO satellites ANS: B 17. video satellite b. transmit delay minimum aperture c. a VSAT system uses: a. low north angle ANS: A 12. ANS: A 18. LEO stands for: a. long elliptic orbit b. low-earth orbit ANS: B 19. For real-time communication, LEO systems require: a. a constellation of satellites c. very high power b. tracking dish antennas d. all of the above ANS: A 20. The frequency bands used by Ku-band satellites are: a. 4 GHz and 6 GHz c. 20 GHz and 30 GHz b. 12 GHz and 14 GHz d. none of the above ANS: B COMPLETION 1. A satellite in geosynchronous orbit takes ____________________ hours to complete one orbit. ANS: 24 2. The ____________________ is the signal path from the earth station to the satellite. ANS: uplink 3. The ____________________ is the signal path from the satellite to the earth station. ANS: downlink 4. A satellite in a ____________________ orbit appears to stay directly above one spot on the equator. ANS: geostationary 5. Non-geostationary satellites are sometimes called ____________________ satellites. ANS: orbital 6. A geosynchronous orbit is about ____________________ km above the earth. ANS: 35,780 7. A ____________________ is an outline of the area on the earth's surface that a satellite broadcasts to. ANS: footprint 8. All satellite orbits are ____________________ in shape. c. lateral earth orbit d. longitudinal earth orbit ANS: elliptical 9. The ____________________ is the distance of a satellite's closest approach to the earth. ANS: perigee 10. The ____________________ is a satellite's farthest distance from the earth. ANS: apogee 11. An antenna's ____________________ is its angular direction between east and west. ANS: azimuth 12. An antenna's ____________________ is its vertical angle with respect to the earth's surface. ANS: elevation 13. An antenna's ____________________ is the angle by which it is offset from the earth's axis. ANS: declination 14. Satellites using the ____________________ band operate on 12 GHz. ANS: Ku 15. The time for a signal to make a round trip via satellite is about ____________________ milliseconds. ANS: 500 16. A ____________________ is a type of repeater used on communications satellites. ANS: transponder 17. Both the gain and the beamwidth of a dish antenna depend on its ____________________. ANS: diameter 18. VSAT systems commonly use a ____________________ network configuration. ANS: star 19. To date, LEO satellite systems have been a financial ____________________. ANS: failure 20. C-band antennas are ____________________ than Ku-band antennas. ANS: larger SHORT ANSWER 1. A receiving antenna with a gain of 44.4 dBi looks at a sky with a noise temperature of 15 K. The loss between the output of the antenna and the input of the LNA is 0.4 dB, and the LNA has a noise temperature of 40 K. Calculate the G/T. ANS: 25 dB 2. A receiver has a noise figure of 1.7 dB. Find its equivalent noise temperature. ANS: 139 K. 3. A receiving antenna with a G/T of 25 dB is used to receive signals from a satellite 38,000 km away. The satellite has a 100-watt transmitter and an antenna with a gain of 30 dBi. The signal has a bandwidth of 1 MHz at a frequency of 12 GHz. Calculate the C/N at the receiver. ANS: 38 dB RCC stands for: a. MSC stands for: a. Mobile Switching Center b. Personal Communications Service b. Radio Cellular Carrier ANS: A 4. ESN stands for: a. Electronic Serial Number b. Personal Cell phone Service d. Advanced Mobile Phone Service . Mobile Telephone Switching Office d. Mobile Transmission Time-Out c. MTSO stands for: a. Portable Communications Systems c. AMPS stand for: a. Emitted Signal Number ANS: A c. Minimum In-band Noise c. Emission Strength Number d. none of the above c. MIN stands for: a. Numerical Access Mode b. American Mobile Phone System b. Manual Identification Number b. Minimum Transmitted Signal Output b. Number Assignment Module c. Advanced Mobile Phone System d. Mobile Identification Number ANS: B 7. Number Access Module d. Minimum Signal Carrier c. Personal Communications Systems ANS: B 3. PCS stands for: a. Maximum Transmitted Signal Output ANS: C 6.Chapter 21: Cellular Radio MULTIPLE CHOICE 1. Maximum In-band Noise d. Radio Common Carrier b. Maximum Signal Carrier d. Mobile Service Cellular ANS: A 5. Analog Mobile Phone Service ANS: D 2. NAM stands for: a. Regional Cellular Carrier d. none of the above c. Numerical Assignment Mode ANS: D 8. select the transmit channel for the cell phone ANS: C 17. identify the type of system (analog or digital) b. Direct Channel Code . FSK c. The CMAC is used to: a. Signal Intensity Descriptor 12. Control Mobile Access Code ANS: A 16. none of the above c. set the access code of the cell phone c. Signal Class Mark d. recognize that it is "roaming" ANS: D 13. Carrier Mode Attenuation Control c. base-station class ANS: D 11. Station Class Mark ANS: B 10. Service Class Mark b. voice is sent using: a. SCM identifies the: a. signal classification (analog or digital) d. SAT stands for: a. The SID is used by a cell phone to: a.9. Station Antenna Tower b. SID stands for: a. Standard Identification Number ANS: C c. Control Mobile Attenuation Code b. System Identification Number d. Sequential Interrupt Demand b. AM c. Digital Communications Carrier d. DCC stands for: a. set its transmitted power level d. Digital Color Code b. Supervisory Audio Tone ANS: B 15. SCM stands for: a. Supervisory Access Tone d. Serial-Code Mode c. set the transmit power of the cell phone d. Digital Communications Code ANS: A 14. recognize an AMPS system c. CMAC stands for: a. maximum power level of a cell phone c. In an AMPS system. code number of a cell phone b. Central Mobile Access Control d. control access to the cell site b. 4 watts ANS: B 20. none of the above c. Code-Division Packet Data b. 0. increase the number of cells c. number of blocked calls c. The combination of the mobile cell phone and the cell site radio equipment is called the: a. MTSO d. 2 km b. as small as possible d. calls b. Base Signal Controller ANS: A 21. Basic Service Code . Cellular Digital Pulse Data c. between 1 and 2 watts b. erlangs ANS: B 24. c. One way to increase the capacity of a cell phone system is: a. Cellular Digital Packet Data ANS: B COMPLETION c. Phone traffic is measured in: a.b. increase the ERP b. RF interface b. control-channel signals are sent using: a. CDMA ANS: C 19. air interface ANS: D 22. Basic Service Contract d. less than 600 mW. decrease the number of cells d. CDMA 18. FSK b.5 km ANS: D 23. The ERP of a typical handheld AMPS cell phone is: a. Coded Digital Packet Data d. In an AMPS system. BSC c. FM ANS: B d. BSC stands for: a. AM c. FM d. number of users d. CDPD stands for: a. d. Base Station Controller b. decrease the ERP ANS: A 25. less than 600 µW. The optimum cell-site radius is: a. Frequency ____________________ is what makes cellular phone systems complex. ANS: I one 8. ANS: handoff 5.1. ANS: attenuation 12. ____________________ is still the most common cellular phone system in North America. A portable. handheld cell phone would be ERP class ____________________. ANS: 0. The number of ERP classes in AMPS is ____________________. If a cell-site radius drops below ____________________ km. . Mobile transmitter power is controlled by the ____________________. ANS: AMPS 3. ANS: 800 2. A cell phone permanently installed in a car would be ERP class ____________________. ANS: three 7. handoffs will occur too frequently. ANS: III three 10. you should always assume that AMPS transmissions are ____________________. The maximum ERP of class III cell phones is ____________________. For security.5 6. ANS: 600 mW 9. ANS: reuse 4. ANS: land station 11. A ____________________ occurs when an in-use cell-phone moves from one cell site to another. A MAC is a mobile ____________________ code. AMPS uses the ____________________-MHz band. ANS: public 13. ANS: splitting 18. What is the traffic in erlangs? . A cell phone moving into a site with no available frequencies will have a ____________________ call. Very small cells called ____________________ are used for reliable indoor reception. ANS: dropped 17. ANS: less SHORT ANSWER 1. ANS: traffic 15. digital cellular phones require ____________________ bandwidth. The optimum size of a cell site depends on the amount of ____________________. how many words of text would be lost during a 100-msec handoff interruption assuming 10 bits per letter and 5 letters per word? ANS: 57. If a 28. Telephone call traffic is measured in ____________________.6 3. ANS: picocells 20. 2. A ____________________ site is a very small unit that can mount on a streetlight pole. The probability that a given cell phone is being used is 15%. The reduction in cell size to increase traffic is called cell ____________________. ANS: microcell 19. Compared with AMPS. Digital is inherently more secure because of its format. ANS: MTSO 14.8-kbps modem is being used over a cell phone. ANS: erlangs 16. Digitized voice signals are easily encrypted. Give two reasons why digital cell phone systems are more secure than analog cell phone systems. A certain cell site contains 200 cell phones. ANS: 1. 2. A mobile switching center is also called an ____________________. ANS: 30 4. . What is "trunking gain"? ANS: For a given probability of being blocked. the maximum allowable traffic per channel increases as the number of channels increases. 3 d. AMPS was designed for: a. 1. third-generation d. PCS cell sites are: a. Bell Labs d. higher-power c. The "forward" PCS channel is: a. GSM is used in: a. voice ANS: D 6. 12 GHz ANS: C 3. distributed d. many ANS: B 7. from the mobile to the base ANS: A 4. The number of competing PCS systems in North America is: a. 4 b. Qualcomm c. 900 MHz d. The frequency band designated for PCS in North America is: a. from mobile to mobile d. AT&T b. smaller ANS: B 5. Current PCS systems are referred to as: a. Lucent ANS: D 8. North America d. Europe ANS: D c.9 GHz b. digital-generation . CDMA technology was invented by: a. Compared to AMPS. second-generation ANS: B 2. use built into an automobile d. bigger b. Asia b. first-generation b. from the base to the mobile b. all of the above c. 2 c.Chapter 22: Personal Communications Systems MULTIPLE CHOICE 1. POTS b. same as the uplink c. all of the above c. 800 MHz c. frequency hopping b. Subscriber ID Method c. Subscriber ID Module d. battery life in a GSM phone should be: a. greater than in a TDMA phone b. Short Inbound Message b. It is necessary to send control information on traffic channels in: a. TDMA only b. CDMA d. Interim Mobile Subscriber Identification d. both GSM and TDMA ANS: D 13. In GSM. direct-sequence modulation ANS: A 14. Other things being equal. frequency hopping b. Intermodulation System Interference ANS: B 16. CDMA d. all of the above c. no better than in an AMPS phone d. IS-136 uses: a.9. no PCS system c. Integrated Mobile Subscriber Identification b. Subscriber-Initiated Message ANS: C 15. less than in a TDMA phone c. International Mobile Subscriber Identification c. voice channels ANS: A 10. CDMA d. no better than a TDMA phone ANS: C 12. voice channels are called: a. In GSM. all of the above . talking channels c. frequency hopping b. bearer channels d. SIM stands for: a. CDMA b. spread-spectrum d. traffic channels b. TDMA ANS: D c. GSM uses: a. IS-95 uses: a. TDMA c. all of the above c. AMPS uses: a. IMSI stands for: a. none of the above 11. GSM only d. TDMA ANS: C 17. Current PCS systems are called ____________________-generation systems. The spread-spectrum technique used in IS-95 PCS is ____________________. each cell is assigned a frequency by the base d. all frequencies are used in all cells b. ANS: 1900 4. unique ANS: D 20. faster data rates c. orthogonal . The next generation of PCS is expected to have: a. In CDMA: a. ANS: second 3. all of the above ANS: D COMPLETION 1. PCS stands for ____________________ Communications System. CDMA uses a set of PN sequences that are: a. PCS is assigned the ____________________-MHz band. ANS: Personal 2. rotating d. Compared to AMPS. Internet access d. ANS: smaller 5. wider roaming area b. In North America. Besides TDMA and CDMA.ANS: B 18. ____________________ is also used in North America for PCS. ANS: CDMA direct sequence c. ANS: GSM 6. the frequency is selected by the mobile phone ANS: A 19. common b. each cell uses half the available frequencies c. PCS cells are ____________________ in size. Unlike other systems. The orthogonal PN sequences used in CDMA are called a ____________________ code. IMT stands for International ____________________ Telecommunications. ANS: Frequency 13. PN stands for Pseudo-____________________ Noise. ANS: 50 16.7. CDMA allows for a ____________________ handoff. ANS: all 11. RF channel S/N ratios ____________________ than zero are typical in CDMA systems. The spread-spectrum technique used in GSM is _________________________. ANS: Walsh 10. ____________________ diversity is inherent in any spread-spectrum system. ANS: Mobile 19. ANS: Packet 18. ANS: random 12. ANS: frequency hopping 8. A phone user typically talks less than ____________________% of the time during a conversation. Unlike AMPS. GPRS stands for General ____________________ Radio Service. ANS: variable 15. ANS: less 14. ANS: Universal . CDMA requires ____________________-loop power control to work properly. ANS: soft 9. ANS: closed 17. UPT stands for ____________________ Personal Telecommunications. CDMA uses a ____________________-rate vocoder. in CDMA ____________________ frequencies are used in all cells. 2. To demodulate. ANS: Wideband SHORT ANSWER 1. 3.20. What is the "near/far" effect in CDMA. 8. UWT stands for Universal ____________________ Telecommunications. What is the advantage of using offset QPSK over standard QPSK? ANS: With standard QPSK. ANS: Wireless 21. Why was PCS assigned to 1. the receiver uses the PN sequence specific to the channel it wants. 4. the transmitted power repeatedly goes to zero. 7. Linearity requirements are less strict for offset QPSK transmitters. it never goes to zero. and what causes it? . What is the advantage of a "soft" handoff? ANS: No calls are dropped. 5. Why would a battery in a GSM phone be expected to last longer than a battery in a TDMA phone? ANS: A TDMA phone is active during one out of every three time slots. If CDMA receivers hear all frequencies all the time. how do they pick a specific frequency? ANS: Each frequency is modulated using a separate orthogonal PN sequence. A GSM phone is active during one out of every eight. How does GSM achieve frequency diversity? ANS: It uses limited frequency hopping. but CDMA can tolerate a lot of such noise.9 GHz instead of the 800-MHz band used for AMPS? ANS: The 800 MHz band was already overcrowded. With offset QPSK. W-CDMA stands for ____________________ CDMA. What is the effect of cochannel interference in CDMA? ANS: It increases the background noise level. 6. ANS: A stronger station farther away can "drown out" a weaker station that is near. This happens when the power transmitted by mobile units is not well controlled by the base. . In a one-way pager system: a. IEEE Standard Message b. POCSAG stands for: a.12 c. A typical pager system does not: a. the UHF band. Industrial. the UHF band only c. all pages are sent from all transmitters b. Post Office Code Standardization Advisory Group d. and Medical . Scientific. The IEEE specification covering wireless LANs is: a. each transmitting antenna covers a wide area c. Scientific. Industrial. a digital modulation scheme used for pagers ANS: B 4. both the VHF and UHF bands d.Chapter 23: Paging and Wireless Data Networking MULTIPLE CHOICE 1. Pager Operations Common Standards Advisory Group b. and Messaging d. an addressing scheme used for pagers c. an error-detection scheme used for pagers d. 802. the VHF band only b. 802. require "handoffs" b. Pagers use: a. an encryption scheme used for pagers b. CAPCODE is: a. require error detection d. allow "roaming" ANS: A 7. IEEE Secure Message ANS: D 3. transmitters use relatively high power d. all of the above ANS: D 5. the VHF band.10 c. Pager Operations Code Standardization Advisory Group c. Post Office Common Standards Advisory Group ANS: C 6. ISM stands for: a. all of the above c. and the ISM band ANS: C 2. Basic Service System ANS: A 11. Bluetooth uses the: a. 2 to 8 nodes d. A Bluetooth "piconet" has: a. The IEEE 802 spec for wireless LANs uses the: a. VHF band b. Time Delay Difference d. Time-Delayed Duplex ANS: A 14. TDD stands for: a. ISM band b. micronet b. multinet ANS: D 16. Total Distance Delay c. scatternet c. UHF band ANS: C 13. 10 cm to 100 meters c. none of the above . CDMA b. 802. 2 to 4 nodes ANS: C 15. infrared band ANS: C 9. Bluetooth Service System d. The IEEE 802 document for wireless LANs specifies the use of: a. frequency hopping ANS: B 12. CSMA/CD d. The basic range of a Bluetooth device is: a. Time-Division Duplex b. 802. UHF band d.11 ANS: B d. 2 to 16 nodes c. TDD net d. VHF band c. BSS stands for: a. QPSK d. Bluetooth uses: a. CDMA b. 2 nodes b. 10 cm to 1 meter c.13 8. Two or more connected piconets forms a: a. infrared band c. all of the above c. all of the above ANS: A 10. ISM band d. CSMA/CA c. Basic Service Set b.b. Infrared Digital Association ANS: A 18. ANS: D COMPLETION 1. can use diffused infrared beams ANS: D d. Infrared networks: a. IEEE ____________________ covers wireless LANs. ANS: 10 5. The range of an IRDA system is: a. ANS: TDMA 3. Infrared Data Association b. Many pagers can share a frequency using ____________________. Infrared Roaming Data Area c.11 6. . cannot penetrate walls b. 1 foot d. The POCSAG was devised by the British ____________________ Office. Each pager has a unique address called a ____________________. ANS: Post 4. several hundred meters b. ANS: 802. can use reflected infrared beams d. all of the above 20. The maximum range of a typical wireless modem is: a. IRDA stands for: a. The IEEE document specifies a maximum power of ____________________ for wireless LANs. several thousand meters. 10 cm to 10 meters ANS: B 17. Infrared Restricted Data Area d. several meters d.b. ANS: capcode 2. 1 meter b. 10 meters ANS: A 19. 1 meter c. within 10 feet c. 10 feet c. A POCSAG message uses a ____________________-bit error correction code. ANS: ISM 8.ANS: 1 watt 7. Bluetooth uses the ____________________ band. ANS: piconet 9. A network of 2 to 8 Bluetooth devices is called a ____________________. ANS: piconets 10. A Bluetooth scatternet consists of 2 or more ____________________. ANS: 1 meter . An IRDA system is deliberately restricted to a range of ____________________. The loss in single-mode fiber-optic cable due to the glass is about: a. 1 dB c. Fiber-optic cables do not: a. chromatic dispersion ANS: A 6. 4 db per km d. all of the above . all of the above c. doesn't have an index of refraction ANS: C 2. zero loss ANS: C 8. to isolate a medical patient from a shock hazard d. carry current b. loss b. none of the above c. cause crosstalk ANS: D 3. the index of refraction of the cladding must be: a. less b. 0. modal dispersion b. greater d. Fiber-optic cable cannot be used: a. intersymbol interference d. Single-mode fiber is made from: a. A single-mode cable does not suffer from: a. generate EMI d. Scattering causes: a. Compared to the core.02 dB c. in an explosive environment b.4 dB per km b. 0. plastic ANS: A 4. to connect a transmitter to an antenna c. all of the above c. both a and b d. dispersion ANS: A 7. waveguide dispersion d. none of the above ANS: B 5.Chapter 24: Fiber Optics MULTIPLE CHOICE 1. the same c. The loss in single-mode fiber-optic cable due to a splice is about: a. 40 dB per km c. glass b. Light Amplification by Stimulated Emitted Rays ANS: B 13. The quantum of light is called: a. 1 dB b. Light Amplification by Stimulated Emission of Radiation c. an erg b. zero-point current d. Light Amplification by Simulated Emission of Radiation b. ANS: reflection c. Avalanche Photo Detector d. Advanced Photodiode ANS: A 14. E-H current ANS: C 15. APD stands for: a. SMA b. 0. the angle of incidence equals the angle of ____________________. 3 dB 9. all of the above ANS: D 11. mA per joule b.b. µW per amp d. 0. baseline current c. responsivity is measured in: a. 3 dB ANS: B 10. LASER stands for: a. Which of the following is a type of fiber connector: a. a photon d. In a PIN diode. amps per watt c. an e-v ANS: C 12. µsec per µW ANS: A COMPLETION 1. The loss in single-mode fiber-optic cable due to a connector is about: a. For a light detector. Advanced Photo Detector c. SC d. Light Amplification by Simulated Emitted Rays d. ST c. 0. a phonon . In the core.02 dB c.2 db d. dark current b. Avalanche Photodiode b.2 db ANS: A d. leakage current in the absence of light is called: a. Optical fiber relies on total ____________________ reflection. ____________________ index has less dispersion than step index. The ____________________ angle is where refraction changes to reflection. In multimode fiber. ANS: intramodal 8. The numerical aperture is the ____________________ of the angle of acceptance. ANS: time 12. ANS: cladding 3. For laser diodes. ANS: linewidth 11. ANS: infrared 9. ANS: graded 10. With optical fiber. An electron-volt is a measure of ____________________. Dispersion can be expressed in units of ____________________ rather than bandwidth. ANS: critical 4. ANS: internal 7. The optical fiber is free to move around in a ____________________ cable. ____________________ light is more common than visible light. ANS: sine 6. . ANS: Intersymbol 13. ANS: loose-tube 14.2. ANS: energy 5. Chromatic dispersion is also called ____________________ dispersion. the term ____________________ is used instead of bandwidth. ____________________ interference is when one pulse merges with the next pulse. The core is surrounded by the ____________________. The optical fiber is not free to move around in a ____________________ cable. ANS: single 17. A ____________________ diode is the usual light source for single-mode cable. For safety.ANS: tight-buffer 15. A ____________________ is a short length of fiber that carries the light away from the source. ANS: laser 18. ANS: photon 19. The quantum of light is called the ____________________. Good connections are more critical with ____________________-mode fiber. ANS: PIN 20. A ____________________ diode is the usual light detector for single-mode cable. you should never ____________________ at the end of an optical fiber unless you know it is not connected to a light source. ANS: look . ANS: pigtail 16. Fiber Transmission Timing Constraint b. Dense Wavelength-Division Modulation c. gain margin c. Fiber Distribution Delay Interface d. type of particle ANS: C 7. DWDM stands for: a. excess gain c. type of optical network c. SONET stands for: a. Double Wavelength-Division Modulation d. Simple Optical Network b. Frequency-Division Data Interface . A Soliton is a: a. Fiber Input Timing Loss ANS: A 3. FITL stands for: a. Fiber Transmission Technology Committee c. Adding bits to synchronize one digital signal to another is called: a. Dense Wavelength-Division Multiplexing ANS: D 6. Fiber In The Loop b. Fiber Distributed Data Interface ANS: B 2. Fiber Digital Data Interface b. FTTC stands for: a. Fiber To The Curb ANS: D 4. bit-synch d. Synchronous Optical Network d. Fiber Telephone Transmission Cable d. none of the above c. Power above the minimum required by an optical receiver is called: a. defect in the glass b. Digital Wavelength-Division Modulation b. bit stuffing c. SDH b. type of pulse d. FDDI stands for: a. WDM ANS: A 8.Chapter 25: Fiber-Optic Systems MULTIPLE CHOICE 1. Standard Optical Network ANS: C 5. Frequency Input to The Loop d. Fiber Input Timing Loop c. Optical Channel one d. 10 km ANS: C 10. FDDI c. not possible c. gigabit Ethernet b. Synchronous Transmission Signal d. 100 miles d. OTDR stands for: a. all of the above ANS: D 13. FTTC d. experimental ANS: B 14. FITL b. Synchronous Transport System ANS: A 12. FITL stands for Fiber In The ____________________. Optical Carrier level one b. Optical Time-Division Relay c. In SONET. c. overdrive 9. high-speed Ethernet d. system margin ANS: B d. FTTC stands for Fiber To The ____________________. ANS: Curb 2. Optical Time-Delay Response b. Synchronous Transport Signal b. obsolete d. Optical Time-Domain Reflectometer d. FDDI c. repeaters are not required for fiber-optic cable lengths up to: a.b. SONET ANS: B COMPLETION 1. The use of solitons on fiber-optic cables is: a. Optical Cable type 1 . A commonly used fiber-based system for LANs is: a. Optical Coupler unidirectional ANS: A 11. 1000 miles c. In SONET. Optical Timing Delay Requirement ANS: C 15. common b. 100 km b. STS stands for: a. Using fiber-optic cable in a telephone system except for the connection to the subscriber's phone is called: a. Synchronous Transmission System c. OC-1 stands for: a. Typically. ANS: pointer 13. Optical amplifiers use a ____________________ laser. WDM stands for ____________________-division multiplexing. ANS: Hierarchy 4. FDDI stands for Fiber ____________________ Data Interface. SDH stands for Synchronous Data ____________________.84 11. The two rings of an FDDI system carry data in ____________________ directions. SONET stands for ____________________ Optical Network. ANS: WDM 10. SONET does not use bit ____________________ to synchronize two digital signals. The OC-1 line rate is ____________________ Mbps. ANS: Distributed 7. ANS: 51. ANS: erbium 8. ANS: Wavelength 5. ANS: token 14.ANS: Loop 3. Optical amplifiers use ____________________-doped glass. FDDI systems use two ____________________ rings to carry signals. ANS: stuffing 12. SONET uses a ____________________ to denote the starting position of an information frame. ANS: pump 9. Dense ____________________ allows many different wavelengths of light to share a cable. ANS: Synchronous 6. ANS: opposite . ANS: 9 22. What is the bandwidth of a first-order LPF with a rise time of 350 nanoseconds? ANS: . ANS: envelope SHORT ANSWER 1. ANS: overhead 19. ANS: node 16. Each ____________________ in an FDDI system acts as a regenerative repeater. FDDI uses ____________________ mode cables. ANS: 4 23. The number of bytes in a SONET frame is ____________________. The data rate of an FDDI system is ____________________ bps. The number of rows in a SONET frame is ____________________. ANS: transport 25. ANS: multi 17. SPE stands for synchronous payload ____________________. The number of bytes in the payload of a SONET frame is ____________________. ANS: 1 24. SONET frames have considerably more ____________________ than do DS frames for information about signal routing and setup. SONET frame rows contain path overhead and ____________________ overhead. The total number of overhead bytes in a SONET frame row is ____________________. ANS: 100 M 18. ANS: 774 21. In SONET. The number of path overhead bytes in a SONET frame row is ____________________. ANS: 810 20.15. and cable each have a rise time of 50 nanoseconds. ANS: 86. Calculate the total rise time for a fiber-optic system if the transmitter.6 nanoseconds .1 MHz 2. receiver.