PPM generation:

• The PWM pulses obtained at the comparator output are applied to a monostable multivibrator. The monostable is negative edge is triggered.

• Hence corresponding to each trailing edge of PWM signal, the monostable output goes high. It remains high for a fixed time decided by its own RC components.

• Thus as the trailing edges of the PWM signal keep shifting in proportion with the modulating signal x (t) , the PPM pulses also keep shifting.

• Demodulation/Degeneration of PPM:

Operation:

• The noise corrupted PPM waveform is received by the PPM demodulator circuit.

• The pulse generator develops a pulsed waveform at its output of fixed duration and applies these pulses to the rest pin (R) of a SR flip-flop.

• A fixed period reference pulse is generated from the incoming PPM waveform and the SR flip-flop is set by the reference pulses.

• Due to the set and reset signals applied to the flip-flop, we get a PWM signal at its output. The PWM signal can be demodulated using the PWM modulator.