CS - Lab

EC57Jawaharlal Nehru COLLEGE OF TECHNOLOGY Department of Electronics and Communication Engineering Prepared by: Prof. Dr.Shivshankar Takhur and Asst Prof (Adhoc) Mijoe Joseph Subject Code: EC57 “Communication Systems Lab” MODEL LABORATORY MANUAL Name : …………………………………… Reg No : …………………………………… Branch : …………………………………… Year & Semester : …………………………………… Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 1 of 86 EC57 INDEX EX.NO. DATE NAME OF THE EXPERIMENTS PAGE NO. MARKS REMARKS 1 Amplitude modulation and Demodulation 2 Frequency modulation and Demodulation 3 Sampling techniques 4 Pulse Modulation-PAM 5 Pulse Modulation-PWM 6 Pulse Code Modulation 7 Time Division Multiplexing 8 Line Coding Techniques 9 Amplitude Shift Keying 10 Phase Shift Keying 11 Frequency Shift Keying 12 Quadrature Phase Shift Keying 13 Delta Modulation 14 Differential PCM 15 Phase Locked Loop 16 Pre-Emphasis/ De-Emphasis 17 Error Control coding using MATLAB 18 Characteristics of AM Receiver-Study Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 2 of 86 EC57 Experiment No : 1 Date : AMPLITUDE MODULATION & DEMODULATION AIM: To construct a Amplitude modulator circuit & demodulate the Amplitude modulated wave. COMPONENTS REQUIRED: S.NO COMPONENTS RANGE 1) Transistor BC 107 2) Diode IN4001 3) Capacitors 0.01µF, 0.1µF,10µF 4) Resistors 22KΩ, 10KΩ,1.2KΩ,1.1KΩ 5) CRO 6) Bread Board,power supply 7) Connecting Wires THEORY : The modulation is simply a method of combining two different signals and is used in the transmitter section of a communication system. The two signals that are used are the information signal and the carrier signal. Amplitude Modulation is the simplest form of signal processing in which the carrier amplitude is simply changed according to the amplitude of the information signal hence the name Amplitude modulation. When the information signals amplitude is increased the carrier signals amplitude is increased and when the information signals amplitude is decreased the carrier signals amplitude is Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 3 of 86 EC57 AMPLITUDE MODULATION CIRCUIT DIAGRAM: DEMODULATION CIRCUIT DIAGRAM: Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 4 of 86 typically a capacitor and resistor in parallel. Using AFO the carrier signal is given to the base of the transistor. 8. The power supply is connected to the collector of the transistor. 7. Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 5 of 86 . PROCEDURE: 1. 6.wave rectifier circuit. So the diode is followed by a filter. From the collector of the transistor. The modulating (message or base band) signal is given to the emitter of the transistor. The simplest way of dealing with an AM signal is to use a simple half. The purpose of any detector or demodulator is to recover the original modulating signal with the minimum of distortion and interference. By varying the amplitude of the modulating signal the values of Emax and Emin are noted down to find the modulation index.EC57 Decreased. the modulated wave is noted down using CRO. If the signal were simply passed through a diode to a resistive load. 2. Circuit connections are given as shown in the circuit diagram. the output would be a series of half-cycle pulses at carrier frequency. 5. 3. 4. The demodulated (message) wave amplitude and frequency is noted down from the CRO. The amplitude modulated wave is now given as the input to the detector circuit. The capacitor is charged by the diode almost to the peak value of the carrier cycles and the output therefore follows the envelope of the amplitude modulation. EC57 MODEL GRAPH: OBSERVATION: Amplitude Time Frequency m Message Signal Carrier signal AM signal Demodulated Signal Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 6 of 86 . Types of Demodulation of AM.Define Modulation index(m). 3.What is the band width for AM? RESULT: Amplitude Modulator and Demodulators are constructed and its waveforms are analyzed by using the above circuits.Applications of AM 4.EC57 VIVA QUESTIONS: 1.What is meant by Modulation? 2. Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 7 of 86 . 5. EC57 FREQUENCY MODULATION CIRCUIT DIAGRAM: FM DEMODULATOR: Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 8 of 86 . IC NE565 9) Resistors 10) Capacitors 11) Function Generator 12) DSO 13) Bread Board 14) Connecting Wires 0 – 1 Mhz THEORY :  Frequency modulation is also called as angle modulation. When the modulating signal has zero amplitude.EC57 Experiment No : 2 Date : FREQUENCY MODULATION & DEMODULATION AIM: To construct & Design Frequency modulator using IC XR2206 & demodulate the Frequency modulated wave by using IC565. similarly. the frequency of the carrier decreases.NO 8) COMPONENTS Integrated Circuits RANGE IC X R2206. The frequency of the carrier increases. Frequency modulation is defined as changing the frequency of the carrier with respect to the message signal amplitude. then the carrier has frequency of Fc as amplitude of the modulating signal increases. COMPONENTS REQUIRED: S. Here the amplitude of the carrier remains fixed & timing parameter frequency is varied. as the amplitude of the modulating signal decreases. Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 9 of 86 . EC57 PIN DIAGRAM (XR-2206): MODEL GRAPH Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 10 of 86 . By Carlson’s rule BW = 2 (F+ Fm(max)) Where F = Maximum frequency deviation Fm(Max) = Maximum modulating frequency MODULATION PROCEDURE:  Connections are given as per the circuit diagram. Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 11 of 86 .  Observe the frequency-modulated signal on DSO.  Measure the carrier signal frequency at the pin2 of IC XR2206.  In demodulated output the original message signal is recovered. The maximum frequency deviation is the shift from center frequency Fc when the amplitude of the modulating signal is maximum.  Apply modulating AF signal at pin7 of IC XR2206.  Modulated signal is given as the input to 565.  Calculate the BW.  Calculate the modulation index.EC57  The modulation index is defined as the ratio of the maximum frequency deviation to the modulating frequency. DEMODULATION PROCEDURE:  Connections are made as per the circuit diagram. What is the band width for FM? RESULT: Frequency Modulator and Demodulators are constructed and its waveforms are analyzed by using CRO.Types of Angle Modulation. Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 12 of 86 . 3.Define Frequency Deviation.Applications of FM 4.What is meant by FM? 2.EC57 OBSERVATION: Amplitude Time Frequency Message Signal Carrier signal FM signal Demodulated Signal VIVA QUESTIONS: 1. 5. EC57 SAMPLING CIRCUIT DIAGRAM PIN DIAGRAM: Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 13 of 86 . EC57 Experiment No : 3 Date : SAMPLING TECHNIQUES AIM: To obtain the sampled version of given analog signal using operational amplifier and draw the spectrum. Sclear will short out the storage cap. We might also use them to hold a given signal value from any particular sensor on a robot. while the input buffer ensures the signal won't be changed by the charging process. Ssample will charge the capacitor to the present signal level. Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 14 of 86 . for analysis and later use. APPARATUS REQUIRED: Apparatus Range IC741 Quantity 2 FET BFW10 2 Capacitor 0. Sample and Hold circuits are used internally in Analog to Digital conversion. which provides cleaner switching and also allows another circuit to control the sample and clearing operations.01µF 1 RPS 1 CRO 1 FG 1 Bread board 1 THEORY: The Sample and Hold circuit uses two buffers to keep a voltage level stored in a capacitor. Excellent Sample and Hold circuits like the LF398 are available on a single chip for cheap and easy use. the switches used are various forms of transistor switch. From there. discharging it and setting the output to 0V. the output buffer will make sure that the voltage level across the storage cap won't decrease over time.In actual practice. The input signal is given to the circuit from the function generator.Define sampling. The next sample available is zero order holding device.What is zero order hold? RESULT: Thus the sample and hold circuit output is obtained using OP.amp. 4. integrate the signal between consequence sampling inputs.What is the need for sampling? 2. Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 15 of 86 . The frequency of the input signal is set to 600 Hz. 3.EC57 PROCEDURE: The sample and hold circuit is assembled with the desired components. VIVA QUESTIONS: 1. The amplitude of the input signal should not exceed 10 volts.What is the usage of capacitor in the circuit diagram? 5.Define Nyquist rate. The frequency of the sample signal is set to 5600 Hz. EC57 PAM CIRCUIT DIAGRAM: MODULATION CIRCUIT: DEMODULATION CIRCUIT: Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 16 of 86 . the amplitudes of regularly spaced rectangular pulses vary with the instantaneous sample values of a continuous message signal in a one to one fashion. Since the width of the pulse approaches zero. The width of the pulse remains fixed. Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 17 of 86 . Thus we get the PAM output. The instantaneous sampling gives train of impulses. If the closing time t of the diode approaches zero. Natural sample method is used here to generate the PAM signal. The diodes are used as a switching element. The carrier under goes amplitude modulation in PAM. APPARATUS REQUIRED: Apparatus Range Quantity Transistor 2N2222 1 Resistor 10Kohm 2 22Kohm 3 0. The area of each sampled section is equal to the instantaneous value of the signal input. The pulse in PAM can be of rectangular or the type that we have arrival in natural sampling.1µF 3 Capacitor CRO 1 FG 2 Bread board 1 THEORY: In pulse amplitude modulation. the output gives only the instantaneous value. This signal is modulated with the message signal.EC57 Experiment No: 4 Date : PULSE MODULATION – PAM AIM: To generate pulse amplitude modulated signals and demodulates it to get the original signal. EC57 MODEL GRAPH: Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 18 of 86 . 4.Define PAM. TABULATION: Amplitude Time Frequency Message Signal Carrier signal PAM signal Demodulated Signal VIVA QUESTIONS: 1.EC57 PROCEDURE: 1. What is the need for speech coding at low bit rates? 5. Make connections as shown in the diagram. Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 19 of 86 . 3. Obtain PAM signal Measure the amplitude and frequency Demodulate the PAM signal. Set the input signal and carrier signal. 2.What is aperture effect? 4. 5.What is frame in PAM? 3. What do you mean by companding? Define compander. 2. RESULT: Thus the PAM signal is obtained and the original signal is demodulated from PAM signal. EC57 PWM CIRCUIT DIAGRAM: MODULATION CIRCUIT: DEMODULATION CIRCUIT: Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 20 of 86 . width of the pulse is proportional to the amplitude of the modulating signal. The width of PWM pulses varies. Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 21 of 86 . The demodulation circuit used is a simple filter circuit that demodulator the PWM signal and gives the original message input. Bandwidth on transmission channel depends on rise time of the pulse. The amplitude is constant. It modulates the time parameter of the pulses. APPARATUS REQUIRED: Apparatus Range Quantity IC 555 1 Resistor 47Kohm 1 10Kohm 1 Capacitor 0.01µF 1 RPS 0-30v 1 CRO 1 FG 1 Bread board 1 THEORY: The PWM is also known as pulse duration modulation.EC57 Experiment No : 5 Date : PULSE MODULATION – PWM AIM: To generate pulse width modulated signals and demodulates it to get the original signal. EC57 MODEL GRAPH: Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 22 of 86 . TABULATION: Amplitude Time Frequency Message Signal Carrier signal PWM signal Demodulated Signal VIVA QUESTIONS: 1.Define PWM.Define deviation ratio 4.Define bandwidth efficiency. 2. 2.What is carrier recovery? 5. What is the disadvantage of uniform quantization over the non-uniform Quantization? 3. Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 23 of 86 . 5. Make connections as shown in the diagram.EC57 PROCEDURE: 1. Set the input signal and carrier signal. 3. Obtain PWM signal Measure the amplitude and frequency Obtain the demodulated output. 4. RESULT: Thus the PWM signal is obtained and the original signal is demodulated from PWM signal. EC57 CIRCUIT DIAGRAM: MODULATION CIRCUIT: DEMODULATION CIRCUIT: Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 24 of 86 . EC57 Experiment No : 6 Date : PULSE CODE MODULATION AIM: To generate pulse code modulated signals and demodulates it to get the original signal. APPARATUS REQUIRED: Apparatus Range Quantity PCM kit VCT07 1 CRO 1 Patch card THEORY: Pulse Code modulation come under digital communication technique. In PCM the message signal is represented by a sequence of coded pulse which accomplished by representing the signal in discrete form in both time and amplitude. PCM consist of a receiver and transmitter part. Transmitter section consists of sampler, quantizer, encoder and parallel to serial converter. Receiver part consists of serial to parallel set converter. Digital to analog converter and LPF are constituted as receiver part. Sampling, Quantizing and Encoding operations are performed in the same circuit which is called as analog to digital converter. PROCEDURE: 1. 2. 3. 4. 5. Make connections as shown in the diagram. Set the start of conversion switch from low to high and high to low. Set the input signal and obtain the PCM signal. Obtain the demodulated output. Measure the data and plot the graph. Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 25 of 86 EC57 TABULATION: Message Signal: Amplitude in Time in Frequency in ON Time in OFF Time in PCM Signal: Amplitude in Frequency in Demodulated Signal: Amplitude in Time in Typesetting : Mijoe Joseph Frequency in ©Einstein College of Engineering Page 26 of 86 EC57 VIVA QUESTION: 1.Write the equation for probability of error 2.Define quadbit 3.Explain M-ary 4.State the concept of PCM 5.PCM is analog or digital modulation ,Explain. RESULT: Thus the PCM signal is obtained and the original signal is demodulated from PCM signal. Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 27 of 86 EC57 BLOCK DIAGRAM: Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 28 of 86 Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 29 of 86 . 4. View the modulated output. 5. In synchronous. 3. Adjust the potentiometer to set the input signal. Synchronous TDM and Asynchronous TDM. the multiplexer allocates exactly the same time slot to each device at all times whether or not a device has anything to transmit. In such a case. PROCEDURE: 1. Obtain the demodulated output. Make connections as shown in the diagram. TDM can be implemented in two ways. multiple transmission can occupy a single link by subdividing them and interleaving the portions. Measure the data and plot the graph. 2.EC57 Experiment No :7 Date : TIME DIVISION MULTIPLEXING AIM: To obtain time division multiplexed signal from different channel and make it to transmit in a single channel. APPARATUS REQUIRED: Apparatus Range Quantity TDM kit VCT02 1 CRO 1 Patch card THEORY: Time Division multiplexing is a digital process that can be applied when the data rate capacity of the transmission medium is greater than the data rate required by the sending and receiving devices. EC57 TABULATION: Message Signal: Amplitude in Time in Frequency in Time in Frequency in Carrier Signal: Amplitude in Modulated Signal: Amplitude in Time in Frequency in Demodulated Signal: Amplitude in Time in Typesetting : Mijoe Joseph Frequency in ©Einstein College of Engineering Page 30 of 86 . What is coding efficiency.What are the 4 primary causes for ISI? 2. 4. Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 31 of 86 .State the concept for TDM.What is Multiplexing? 3. RESULT: Thus the TDM signal is obtained and the original signal is demodulated from TDM signal.Explain the ideal channel noise.EC57 VIVA QUESTIONS: 1. 5. EC57 BLOCK DIAGRAM Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 32 of 86 . The process of converting the original information into a data sequence is referred to as source coding. The line coding is the process of converting source coded signals into standard digital codes for the purpose of transmission over the channel. Simplest form of coding is ONOFF. the electrical waveforms are coded representations of the original information. Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 33 of 86 . If the original information is an analog signal.EC57 Experiment No :8 Date : LINE CODING TECHNIQUES AIM: To obtain the standard digital codes from the source coded signals using various techniques. APPARATUS REQUIRED: Apparatus Range Trainer kit VCT37 CRO Quantity 1 1 Patch card THEORY: In digital systems. Generally the line coding is used in transmitter section while decoding in receiver section. this must be converted to a series of discrete values that can be transmitted digitally. The line decoding is the process of converting standard digital codes into source coded waveforms. where a ‘1’ is transmitted by a pulse and a ‘0’ is transmitted by no pulse. There are many possible ways of assigning the waveforms into the digital data. Connect the PRBS (test point P5) to various line coding formats. 5. 6. Connect coded signal test point to corresponding decoding test point as inputs. 2. 5.EC57 Various line coding formats are 1. 4. 6. Press the switch SW2 once. Display the encoded signal on one channel of CRO and decoded signal on second channel of CRO. Set the SW1 as per the requirement. Set the potentiometer P1 in minimum position. Obtain the coded output as per the requirement. 3. Unipolar RZ Polar RZ Polar NRZ Bipolar NRZ Bipolar RZ Manchester coding PROCEDURE: 1. Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 34 of 86 . Switch ON the power supply. 4. 3. 2. EC57 MODEL GRAPH: Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 35 of 86 . Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 36 of 86 . 4. 3.What are the different types of coding techniques for digital data? 2.State the concept of Manchester coding.Differentiate polar and bipolar. RESULT: Thus the various line encoding and decoding techniques were studied and the corresponding waveforms were drawn by using VCT-37 trainer kit.EC57 TABULATION: No Coding techniques 1 Unipolar RZ 2 Polar RZ 3 Polar NRZ 4 Bipolar NRZ 5 Bipolar RZ 6 Manchester coding ON time OFF time VIVA QUESTIONS: 1.Explain Line coding.What is codec? 5. EC57 CIRCUIT DIAGRAM: MODULATION CIRCUIT: Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 37 of 86 . Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 38 of 86 . In this method there is only one unit energy carrier it is switched ON/OFF depending upon the input binary sequence to transmit symbol 0 & 1. APPARATUS REQUIRED: Apparatus Range Quantity Trainer kit VCT17 CRO 1 1 Patch card THEORY: ASK or ON-OFF key is the simplest digital modulation technique. Obtain ASK signal Measure the amplitude and frequency Obtain the demodulated output. The disadvantage of ASK is the modulated carrier signal is not continuously transmitted. 4. 3. The bit error probability rate is also not required in this technique. PROCEDURE: 1. The peak power requirement is also high. Make connections as shown in the diagram. No pulse is transmitted output contains some complete no of cycle of carrier frequency. 5.EC57 Experiment No :9 Date : AMPLITUDE SHIFT KEYING AIM: To generate ASK modulated and demodulated signal. Set the input signal and carrier signal. 2. Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 39 of 86 .EC57 MODEL GRAPH: . EC57 TABULATION: INPUT DATA: Amplitude in ON Time in OFF Time in CARRIER SIGNAL: Amplitude in Time in Frequency in MODULATED SIGNAL: Amplitude in Time in Frequency in DEMODULATED SIGNAL: Amplitude in ON Time in Typesetting : Mijoe Joseph OFF Time in ©Einstein College of Engineering Page 40 of 86 . EC57 PROGRAM FOR ASK: Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 41 of 86 . Why do we go for Gram-Schmidt Orthogonalization procedure? RESULT: Thus the modulated and demodulated signal was obtained for amplitude shift keying techniques Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 42 of 86 . 2.EC57 VIVA QUESTIONS: 1.Define OOK.Define information capacity 3.What is Digital Transmission? 5.What is the Baud rate for ASK? 4. EC57 BLOCK DIAGRAM Typesetting : Mijoe Joseph ©Einstein College of Engineering Page 43 of 86 . 4. 5. Obtain the demodulated output. PROCEDURE: 1. Typesetting : Mijoe Joseph Page 44 of 86 ©Einstein College of Engineering . APPARATUS REQUIRED: Apparatus Range Quantity PSK Kit VCT21 1 CRO 1 Patch cards THEORY: PSK is a digital modulation scheme which is analogues to phase modulation. In binary phase shift keying two output phases are possible for a single carrier frequency one out of phase represent logic 1 and logic 0. The fundamental frequency of an alternate 1/0 bit sequence is equal to one half of the bit rate.Communication Systems Lab Experiment No : 10 Date : PHASE SHIFT KEYING AIM: To obtain the modulated and demodulated output waveform by using Phase Shift Keying technique. As the input digital binary signal change state the phase of output carrier shift two angles that are 180o out of phase. The input carrier is multiplied by either a positives or negatives consequently the output signal is either +1sinwct or 1sinwct. Make connections as shown in the diagram. Obtain PSK signal Measure the output data and draw the graph. 3. Each time a change in input logic condition will change the output phase consequently for PSK the output rate of change equal to the input rate range and widest output bandwidth occurs when the input binary data are alternating 1/0 sequence. In a PSK modulator the carrier input signal is multiplied by the digital data. 2. Set the input signal and carrier signal. The first represent a signal that is phase with the reference oscillator the latter a signal that is 180o out of phase with the reference oscillator. Communication Systems Lab MODEL GRAPH: . : Typesetting : Mijoe Joseph Page 45 of 86 ©Einstein College of Engineering . Communication Systems Lab TABULATION: INPUT DATA: Amplitude in ON Time in OFF Time in CARRIER SIGNAL: Amplitude in Time in Frequency in MODULATED SIGNAL: Amplitude in Time in Frequency in DEMODULATED SIGNAL: Amplitude in ON Time in Typesetting : Mijoe Joseph OFF Time in Page 46 of 86 ©Einstein College of Engineering . Communication Systems Lab PROGRAM FOR PSK: Typesetting : Mijoe Joseph Page 47 of 86 ©Einstein College of Engineering . Explain Coherent detection 2.What is correlator? RESULT: Thus the modulated and demodulated signal was obtained for phase shift keying techniques. Typesetting : Mijoe Joseph Page 48 of 86 ©Einstein College of Engineering .Communication Systems Lab VIVA QUESTIONS: 1. What is maximum likelihood detector? 5.Difference between PSK and FSK 3.Advantages of PSK 4. Communication Systems Lab FSK CIRCUIT DIAGRAM: Typesetting : Mijoe Joseph Page 49 of 86 ©Einstein College of Engineering . APPARATUS REQUIRED: Apparatus Range Quantity IC 555 1 Transistor BC547 1 47Kohm 1 10Kohm 1 Potentiometer 50Kohm 2 Resistor Capacitor 0. fo=1. When input is HIGH. This type of transmission is called frequency shift keying technique. The standard digital data input frequency is 150Hz.01µF 2 FG 1 RPS 1 CRO 1 THEORY: In digital data communication.Communication Systems Lab Experiment No :11 Date : FREQUENCY SHIFT KEYING AIM: To obtain the modulated and demodulated output waveforms by using hardware kit and in Matlab program for Frequency Shift Keying technique. A 555 timer in astable mode can be used to generate FSK signal. transistor Q is off and 555 timer works in the normal astable mode of operation. binary code is transmitted by shifting a carrier frequency between two preset frequencies.45/(Ra+2Rb)c Typesetting : Mijoe Joseph Page 50 of 86 ©Einstein College of Engineering . Communication Systems Lab MODEL GRAPH: THEORETICAL CALCULATION: Typesetting : Mijoe Joseph Page 51 of 86 ©Einstein College of Engineering . Communication Systems Lab PROGRAM: Typesetting : Mijoe Joseph Page 52 of 86 ©Einstein College of Engineering . of cycle Frequency Symbol 1 Symbol 0 Typesetting : Mijoe Joseph Page 53 of 86 ©Einstein College of Engineering .Communication Systems Lab TABULATION: INPUT DATA: Amplitude in ON Time in OFF Time in CARRIER SIGNAL: Amplitude in Time in Frequency in MODULATED SIGNAL: Symbol Amplitude Time period No. Set the input signal and carrier signal. VIVA QUESTIONS: 1. Justify the obtained output with theoretical calculation. 3. 3. Obtain FSK signal Tabulate the output data and draw the graph. Typesetting : Mijoe Joseph Page 54 of 86 ©Einstein College of Engineering .What is base band signal receiver? 5. 5. 4. Make connections as shown in the circuit diagram.Define h-factor in FSK RESULT: Thus the Frequency Shift Keying modulated output waveform is obtained and it is justified with theoretical calculation.What are the Different types of Digital modulation? 2.Define PSK.Advantage of PSK over ASK&FSK? 4. 2.Communication Systems Lab PROCEDURE: 1.QPSK. Communication Systems Lab BLOCK DIAGRAM: QPSK MODULATOR: QPSK DEMODULATOR Typesetting : Mijoe Joseph Page 55 of 86 ©Einstein College of Engineering . where they are converted from parallel I and Q data channels to a single binary output data stream. Typesetting : Mijoe Joseph Page 56 of 86 ©Einstein College of Engineering . which generate the original I and Q data bits. APPARATUS REQUIRED: Apparatus Range Quantity QPSK Kit VCT29 1 CRO 1 Patch cards THEORY: QPSK is another form of angle-modulated. QPSK modulator is two BPSK modulators combined in parallel. The QPSK signal is demodulated in the I and Q product detectors. It is an M-ary encoding technique where M=4. After both bits have been serially inputted. The input QPSK signal is given to the I and Q product detectors and the carrier recovery circuit. The I bit modulates a carrier that is in phase with the reference oscillator and the Q bit modulates a carrier that is 900 out of phase with the reference carrier. The carrier recovery circuit produces the original transmit carrier oscillator signal. constant-amplitude digital modulation. One bit is directed to the I channel and the other to the Q channel. The output of the product detectors are fed to the bit combining circuit. The recovered carrier must be frequency and phase coherent with the transmit reference carrier. Two bits (a dibit) are clocked into the bit splitter. with QPSK four output phases are possible for a single carrier frequency.Communication Systems Lab Experiment No :12 Date : QUADRATURE PHASE SHIFT KEYING AIM: To obtain the modulated and demodulated output waveforms by using hardware kit and by Matlab program for Quadrature phase Shift Keying technique. they are simultaneously parallel outputted. Communication Systems Lab MODEL GRAPH: Typesetting : Mijoe Joseph Page 57 of 86 ©Einstein College of Engineering . Communication Systems Lab PROGRAM: Typesetting : Mijoe Joseph Page 58 of 86 ©Einstein College of Engineering . Adjust pot1 and pot3 to get bipolar data. 4. Typesetting : Mijoe Joseph Page 59 of 86 ©Einstein College of Engineering . 3.Communication Systems Lab TABULATION: INPUT DATA: Amplitude in ON Time in OFF Time in CARRIER SIGNAL: Amplitude in Time in Frequency in PROCEDURE: 1. 2. Connect the QPSK to input of QPSK demodulator. 7. Switch on the power supply. Connect the sine wave input to balanced modulator (I channel) as a carrier signal and to sine wave input to balanced modulator (Q channel) as a carroer signal. Connect the binary input data to Q-channel. 8. RESULT: Thus the Quadurate Phase shift Keying modulated and demodulated output waveform is obtained. Obtain the demodulated QPSK signal. 5. Adjust gain control pot to set equal amplitude in I and Q channel. Obtain QPSK signal. 6. Display binary input data on CRO. 9. Connect the binary input data to I-channel. Communication Systems Lab BLOCK DIAGRAM: DM MODULATOR: DM DEMODULATOR: Typesetting : Mijoe Joseph Page 60 of 86 ©Einstein College of Engineering . 5. Keep the signal ON/OFF switch in OFF position. Ensure that the following initial condition exits on VCT-32 a. b. PROCEDURE: 1. Obtain the modulated output. 2. If the current sample is smaller than previous sample. Note down the quantizer output. a logic level 0 is transmitted. Vary the sine wave from 150Hz. Obtain the demodulated output. therefore multiple-bit code is required to represent a one sample. Note that the amplitude of sine wave decreases at 2KHz of frequency 4. Switch on the power supply. integrated output and biphase NRZ encoder. only a single bit is transmitted. Set clock frequency as 8KHz. With DM. a logic 1 is transmitted. 6. Set the sine wave by adjusting OFFSET and AMP 3. quantizer and integrator. With conventional PCM. Keep all potentiometer controls in min. APPARATUS REQUIRED: Apparatus Range Quantity QPSK Kit VCT32 1 CRO 1 Patch cards THEORY: Delta modulation transmits only 1 bit per sample. now adjust the offset control signal. If the current sample is larger than the previous sample. rather than transmit a coded representation of the sample. Connect modulator output to demodulator input. each code is a binary representation of both the sign and magnitude of a particular sample. The modulator comprises of comparator.Communication Systems Lab Experiment No :13 Date : DELTA MODULATION AIM: The objective of this equipment is to examine and study the technique of delta modulation and demodulation. which simply indicates whether that the sample is larger or smaller than the previous sample. Typesetting : Mijoe Joseph Page 61 of 86 ©Einstein College of Engineering . Turn ON the left side ON/OFF switch and right side ON/OFF. Communication Systems Lab MODEL GRAPH: Typesetting : Mijoe Joseph Page 62 of 86 ©Einstein College of Engineering . Communication Systems Lab TABULATION: INPUT DATA: Amplitude in ON Time in OFF Time in INTEGRATOR SIGNAL: Amplitude in Time in Frequency in MODULATED SIGNAL: Amplitude in Time in Frequency in DEMODULATED SIGNAL: Amplitude in Time in Typesetting : Mijoe Joseph Frequency in Page 63 of 86 ©Einstein College of Engineering . 4. 5. 2.How the noises are reduced in DM? RESULT: Thus the delta modulated and demodulated waveforms were obtained.Define Granular noise.Define Adaptive DM. Typesetting : Mijoe Joseph Page 64 of 86 ©Einstein College of Engineering .What is slope over load? 3.Communication Systems Lab VIVA QUESTIONS: 1.Define delta modulation. Communication Systems Lab BLOCK DIAGRAM: DPCM MODULATOR: DPCM DEMODULATOR: Typesetting : Mijoe Joseph Page 65 of 86 ©Einstein College of Engineering . Typesetting : Mijoe Joseph Page 66 of 86 ©Einstein College of Engineering . Switch on the power supply. This necessitates transmitting several identical PCM codes. Now vary the DC control POT. there are often successive samples taken in which there is little difference between the amplitudes of the two samples.5v. which is redundant. DPCM is designed specifically to take advantage of the sample to samples redundancies in such waveforms. Fewer bits are required for DPCM than conventional PCM. Now connect modulated output to demodulator input 4. Obtain the modulated output. With DPCM. Now display the output of zeros and ones in the CRO. the ADC coded data ranges which also reflects at the output of the LATCH. Because the range of sample differences is typically less than the range of individual samples.Communication Systems Lab Experiment No : 14 Date : DIFFERENTIAL PULSE CODE MODULATION AIM: The objective of this equipment is to examine and study the technique of differential PCM and demodulation. 3. Connect DC voltage and vary to 1. PROCEDURE: 1. APPARATUS REQUIRED: Apparatus Range Quantity DM Kit VCT34 1 CRO 1 Patch cards THEORY: In a PCM Encoded waveform. the difference in the amplitude of two successive samples s transmitted rather than the actual sample. Keep DC voltage in minimum position 2. Communication Systems Lab TRAINER KIT DIAGRAM: Typesetting : Mijoe Joseph Page 67 of 86 ©Einstein College of Engineering . Communication Systems Lab MODEL GRAPH: Typesetting : Mijoe Joseph Page 68 of 86 ©Einstein College of Engineering . Communication Systems Lab TABULATION: INPUT DATA: Amplitude in ON Time in OFF Time in MODULATED SIGNAL: Amplitude in Time in Frequency in DEMODULATED SIGNAL: Amplitude in Time in Typesetting : Mijoe Joseph Frequency in Page 69 of 86 ©Einstein College of Engineering . RESULT: Thus the differential PCM modulated and demodulated waveforms were obtained.Define Vocoder. 2. 3.Bit rate of DPCM. 4.Communication Systems Lab VIVA QUESTIONS: 1. Define Dibit.Say the difference between PCM and DPCM.Define baseband transmission 5. Typesetting : Mijoe Joseph Page 70 of 86 ©Einstein College of Engineering . 001f 10 8 2 NE565 Vin Input Demodulated output 7 3 Reference Output 6 4 5 9 VCO output (fo) 1 C T =0.001f -6V Typesetting : Mijoe Joseph Fig.8 K C=1f C=0.Communication Systems Lab CIRCUIT DIAGRAM: +6V R T =6.1 Page 71 of 86 ©Einstein College of Engineering . IC7490 supply 7) Typesetting : Mijoe Joseph Connecting Wires Page 72 of 86 ©Einstein College of Engineering .Communication Systems Lab Experiment No :15 Date : PHASE LOCKED LOOP AIM: To study the characteristics of Phase Locked Loop . APPARATUS REQUIRED: S.power RANGE BC 107 NE565.NO COMPONENTS 1) Transistor 2) IC 3) Capacitors 4) Resistors 5) CRO 6) Bread Board. The circuit is then said to be locked.Communication Systems Lab DESIGN: THEORY: If an input signal Vs of frequency fs is applied to the PLL. It the two signals differ in frequency and /or phase. the phase detector compares the phase and frequency of the incoming signal to that of the output Vo of the VCO. The phase detector is basically a multiplier and produces the sum (fs+fo) and difference (fs-fo) components at its output. Typesetting : Mijoe Joseph Page 73 of 86 ©Einstein College of Engineering . The VCO continues to change frequency till its output frequency is exactly the same as the input signal frequency. an error voltage Ve is generated. The signal Vc shifts the VCO frequency in a direction to reduce the frequency difference between fs and fo. The high frequency component (fs+fo) is removed by the low pass filter and the difference frequency component is amplified and then applied as control voltage Vc to VCO. f4=360Hz Typesetting : Mijoe Joseph Page 74 of 86 ©Einstein College of Engineering . f3=1250Hz. f2=1640Hz.Communication Systems Lab PIN DIAGRAM: -Vcc 1 14 NC Input 2 13 NC Input 3 NE 565 12 NC VCO Output 4 11 NC 5 10 +Vcc 6 9 7 8 Phase Comparator VCO Input Reference Output Demodulated Output External Capacitor for VCO External Resistor for VCO OBSERVATION: f1=755Hz. Define Lock range. 2.What is frequency synthesizer? RESULT: Thus the PLL characteristics are studied Theoretical Lock range fL= Theoretical Capture range fC= Practical Lock range fL= Practical Capture range fC= Typesetting : Mijoe Joseph Page 75 of 86 ©Einstein College of Engineering . Keep on decreasing the input frequency till f4 when the loop is unlocked.Define PLL. 4. 3.What is VCO? 2. till PLL tracks the input signal.What are the applications of PLL? 4. 5. 5. Set the input square wave of 1Vp-p at 1KHz. Now gradually decrease the input frequency till f3 when the PLL is again locked. Go on increasing the input frequency to f2 (upper end of the lock range). Increase the input frequency till PLL is locked. This is the lower end of the lock range. 3. 6.Communication Systems Lab PROCEDURE: 1. Compare theoretical and practical values of lock range and capture range. Measure the practical free running frequency of VCO for zero input. VIVA QUESTIONS: 1. This frequency f1 gives the lower end of the capture range. Make the circuit connection as shown in Fig 1.Capture range. This is the upper end of the capture range. Communication Systems Lab CIRCUIT DIAGRAM: PRE-EMPHASIS: DE-EMPHASIS: Typesetting : Mijoe Joseph Page 76 of 86 ©Einstein College of Engineering . 3. Plot a graph of normalized gain Vs frequency. vary the frequency and note down the gain of the circuit. APPARATUS REQUIRED: S. Typesetting : Mijoe Joseph Page 77 of 86 ©Einstein College of Engineering .power RANGE IC741 supply 6) Connecting Wires PROCEDURE: 1. Apply a sine wave of 5Vpp amplitude.Communication Systems Lab Experiment No :16 Date : PRE-EMPHASIS / DE-EMPHASIS AIM: Design and conduct an experiment to test a pre-emphasis and de-emphasis circuit for 75Ps between 2.1KHz to 15KHz and record the results. 2. Connections are made as shown in the circuit diagram.NO COMPONENTS 1) IC 2) Capacitors 3) Resistors 4) CRO 5) Bread Board. 1 KHz.1Pf then r = 820 and R = 100. fC = 1/2SRdCd. Pre-emphasis circuit.Communication Systems Lab DESIGN 1. Given f1 = 2.1KHz Then Rd = 820. De-emphasis circuit. f2 = 15KHz. 2.2K and Rf = 15K. MODEL GRAPH: Typesetting : Mijoe Joseph Page 78 of 86 ©Einstein College of Engineering . Choose Cd = 0. then R1 = 2. f1 = 1/2SrC. Also r/R = Rf/R1.1Pf and fC = f1 = 2. f2 = 1/2SRC Choose C = 0. Communication Systems Lab TABULATION: PRE-EMPHASIS: Vi= Frequency(Hz) VO Gain= VO/ Vi Gain in dB Gain= VO/ Vi Gain in dB DE-EMPHASIS: Vi= Frequency(Hz) Typesetting : Mijoe Joseph VO Page 79 of 86 ©Einstein College of Engineering . Communication Systems Lab VIVA QUESTIONS: 1. 4.What is advantage of FM over Am? 2.Define Pre-emphasis and De-emphasis.Define transmission efficiency.What are the types of FM? 5. RESULT: Thus the Pre-Emphasis and De-Emphasis circuit was designed and analysed using IC741. Typesetting : Mijoe Joseph Page 80 of 86 ©Einstein College of Engineering .Define capture effect. 3. Calculate the redundancy bits once again for the received bits.Calculate the reundancy bits for the corrosponding code. ALGORITHM: 1. 3. 2. Typesetting : Mijoe Joseph Page 81 of 86 ©Einstein College of Engineering .Communication Systems Lab Experiment No :17 Date : ERROR CONTROL CODING USING MATLAB AIM: To write a program in MATLAB for error control coding techniques. 5.Get the input binary sequcence.If the redundancy bits=’0’ then no error in the transmission otherwise some error in the transmission.Transmit the signal that contains message bits+redundancy bits added at the end. 4. Communication Systems Lab PROGRAM: Typesetting : Mijoe Joseph Page 82 of 86 ©Einstein College of Engineering . Typesetting : Mijoe Joseph Page 83 of 86 ©Einstein College of Engineering .Communication Systems Lab RESULT: Thus the error control coding techniques are executed using MATLAB programs. each station’s transmitter is allocated a 10KHz bandwidth. If the pass band is greater than 10KHz. If the pass band of a receiver is less than 10KHz. 2. Typesetting : Mijoe Joseph Page 84 of 86 ©Einstein College of Engineering . c. Selectivity is a receiver parameter that is used to measure the ability of the receiver to accept a given band of frequencies and reject all others. Adjust the gain of the audio amplifier in some position. Initial setup is made as follows. Patch card. THEORY: Heterodyne means to mix two frequencies together in a non-linear device or to translate one frequency to another frequency using non-linear mixing. PROCEDURE: 1. Set audio oscillator frequency as 1KHz and amplitude as 1Vp-p b. with the commercial AM broadcast band. The first section is the RF section which consists of a predictor is a broad tuned BPF with an adjustable centre frequency that is tuned to the desired carrier frequency. Switch ON the trainer kit.Communication Systems Lab Experiment No :18 Date : CHARACTERISTICS OF AM RECEIVER AIM: To study the characteristics of AM receiver. APPARATUS REQUIRED: 1. a portion of the modulating signal information for that channel is rejected or blocked from entering the demodulator and. 2. Therefore. consequently lost. a. For example. more than one channel may be received and demodulated simultaneously. Adjust the carrier frequency of AM transmitter to one position. VCT 06KIT. for a receiver to select only those frequencies assigned to a single channel. the receiver must limit its bandwidth to 10KHz. CRO 3. Communication Systems Lab BLOCK DIAGRAM: Typesetting : Mijoe Joseph Page 85 of 86 ©Einstein College of Engineering . What are the three noises present in the AM reciver? 5. 2. Connect CRO across test point and find out -3db bandwidth of IF amplifier.Define shape factor. 2.Define Selectivity. Also find out -60db bandwidth of IF amplifier 3. such that the output is of maximum amplitude. RESULT : Thus the characteristics of the AM receiver is studied.Communication Systems Lab TABULATION: No dB 1 -3 2 -60 Bandwidth 1. Now tune the gang capacitance in the preselector block. Typesetting : Mijoe Joseph Page 86 of 86 ©Einstein College of Engineering .What is sensitivity? 3. 4.Define Q factor in AM receiver. VIVA QUESTIONS: 1. Calculate Shape factor for various input signal.