Pulse Position Modulation And Demodulation 2v475a

PULSE POSITION MODULATION AND DEMODULATION EXP NO:

DATE:

AIM: 1.To study the pulse position modulation and demodulation. 2.To study the effect of variations of sampling frequency on the demodulated output.

EQUIPMENT REQUIRED: 1.Pulse Width Modulation Trainer Kit. 2.Dual channel Oscilloscope of range 20Mhz.

THEORY:

BLOCK DIAGRAM: AF SIGNAL ON CH 1

S AMP LING CIRC UIT

AF SIGNAL GENERATOR

PWM O/P ON CH 2

SAMPLING PULSE GENERATOR

COMPARATOR

MONOSTABLE MULTIVIBRATOR

SAWTOOTH WAVEFORM GENERATOR

PPM I/P

DEMOD O/P PWM O/P

PPM-PWM CONVERTOR

SYNC.CLOCK I/P

PPM O/P ON CH2

LOW FILTER

PROCEDURE: 1.Switch ‘ON’ the supply switch on the trainer kit. 2.Connect the ‘Analog Signal Output’ to ‘Analog Signal input’ of the PPM modulator.Adjust frequency 1KHz and the amplitude by the potentiometer P2 to about 3Vp-p. 3.Connect the ‘Sampling Pulse Output’ to ‘Pulse input’ of the modulator. 4.Adjust the frequency of the sampling signal to 5KHz. 5.Observe the sawtooth generator output at pin No:6 of IC3130 and observe the PWM waveform w.r.s. to the modulating signal. 6.Observe the PWM waveform and then observe the PPM waveform at Pin No:3 of IC555 by varying the following: a.AF Signal frequency b.AF Signal Amplitude c.Sampling frequency and d.Sampling pulse width 7.During demodulation,connect PPM output to the input of the PPM-PWM convertor.And also give the sampling pulse input from the modulator as a synchronizing clock from the transmitter. 8.Output of the low filter is the replica of the AF signal given to the PPM Modulator. 9.Repeat the step 6,while observing the demodulated output. 10.And draw the waveforms (with readings).

WAVEFORMS:

OBSERVATIONS:

1.Modulating Signal: Frequency= Amplitude=

2.Carrier Signal: Frequency= Amplitude=

3.PWM Output: Frequency= Amplitude=

4.PPM Output: Frequency= Amplitude=

5.Demodulated Output: Frequency= Amplitude=

RESULT: The PPM modulated and demodulated waveforms are observed by varying the AF signal frequency and the Sampling pulse signal frequency.