ANALOG COMMUNICATION SYSTEMSECE-3001 EMBEDDED LAB LAB TASK-1 Amplitude Modulation using Multisim Name- Saurabh Priyadarshi Reg No- 15BEC0631 Slot – L53 + L54 Aim: Verify the following a. Verify the correctness of the circuit used for envelope detection using Multisim Equipment Required: Function Generator Oscilloscope Power Supply AM Voltage Source Components Required: BC107 transistor Resistors Capacitors 1BH62 diode Circuit Diagram: 1. Verify the correctness of the circuit used for AM modulation using Multisim b. Amplitude Modulation Circuit . Since the envelope of an AM wave has the same shape as the message. The detector circuit is employed to separate the carrier wave and eliminate the side bands. demodulation can be accomplished by extracting envelope. .e. Demodulation is the reverse process of modulation. fc >> fm 2. 2. Amplitude Demodulation The process of detection provides a means of recovering the message Signal from modulated signal. Amplitude modulation is defined as the process in which is the amplitude of the carrier wave is varied about a means values linearly with the base band signal. Envelope Detector Theory: Amplitude Modulation: Modulation is defined as the process by which some characteristics of a carrier signal is varied in accordance with a modulating signal. the carrier wave becomes over modulated. independent of the carrier frequency and phase. The baseband signal is referred to as the modulating signal and the output of the modulation process is called as the modulation signal.The carrier frequency fc must be much greater than the highest frequency components fm of the message signal m (t) i. if the modulation index is greater than unity. The modulation index must be less than unity. The envelope of the modulating wave has the same shape as the base band signal provided the following two requirements are satisfied 1. Use multisim software to construct the Amplitude Modulation circuit as shown in the circuit diagram. Use multisim software to construct the circuit for envelope detector as shown in the circuit diagram. For Amplitude Modulation Circuit 1. Enter appropriate values for the carrier amplitude. Enter the values for Vp-p and frequency in each of the function generators 4. 2. Use an AM generator voltage source to produce the input modulated signal. Observations A. carrier frequency and modulation index in the AM voltage source. Connect the oscilloscope across the capacitor and obtain the output waveform. 4. 3. Connect two Function Generators at the input so that one of them will generate the carrier signal and other will generate the message signal. Connect an oscilloscope to output (across the collector and ground) and obtain the output waveform. 2. B.Procedure A. For Envelope Detector 1. 3. For Amplitude Modulation Circuit Circuit: . Input Values For the carrier signal generated by the function generator XPG2 Frequency -10kHz Amplitude – 8 Vp-p For the message signal generated by the function generator XPG1 Frequency -1kHz Amplitude – 2 Vp-p Output Waveform: . 5 . For Envelope Detector Circuit: Input values Carrier Amplitude – 5V Carrier Frequency – 19 kHz Modulation Index – 0.B. the input was the modulated signal and the output obtained was the original message signal which was sine wave.Output Waveform The output waveform is a sine signal which is the required message signal Result: When the circuit of Amplitude modulator was simulated. . an output modulated waveform was obtained which consisted of the message signal modulated with the carrier signal. When the circuit of the envelope detector was simulated. This sine wave was the obtained output waveform.