To Study the Generation and Detection of Pulse Code Modulation (PCM)

Nov 30 -0001

Objective

To study the generation and detection of PCM

Aim of the Experiment

To Study the generation and detection of Pulse Code Modulation (PCM).

Equipment Required

PCM modulation and demodulation trainer kit
Digital storage oscilloscope (100MHz, 1GSa/S)
Power supply
Probes
Patch cord
Connecting wires

Theory

In Pulse code modulation (PCM) only certain discrete values are allowed for the modulating signals. The modulating signal is sampled, as in other forms of pulse modulation. But any sample falling within a specified range of values is assigned a discrete value. Each value is assigned a pattern of pulses and the signal transmitted by means of this code. The electronic circuit that produces the coded pulse train from the modulating waveform is termed a coder or encoder. A suitable decoder must be used at the receiver in order to extract the original information from the transmitted pulse train.

Procedure

1. Make the connections as per the diagram as shown in the circuit diagram figure below and switch on the power supply of the trainer kit.

2. Clock generator generates a 20 KHz clock .This can be given as input to the timing and control circuit and observe the sampling frequency fs= 2 KHz approximately at the output of timing and control circuit.

3. Apply the signal generator output of 6V(p-p) approximately to the A to D converter input and note down the binary word from LEDs i.e. LED ON represents 1 and OFF represents 0.

4. Feed the PCM waveform to the demodulator circuit and observe the waveform at the output of D/A which is quantized level.