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User Manual for Pulse Position Modulation and Demodulation Trainer

Introduction

PS-DC-PPM is proposed to user friendly to process the experiments and the trainer had all internal features like message signal, carrier signal, power supply etc., and the trainer has online video demonstration on our website.

 

 

Technical Specification

  • Message Signal 1 : Frequency 500 Hz : Amplitude 0 to 5V
  • Message Signal 2 : Frequency 1 KHz : Amplitude 0 to 5V
  • Message Signal 3 : Frequency 2 KHz : Amplitude 0 to 5V
  • Carrier Signal : Frequency 20 KHz : Amplitude 5V
  • Modulator Type : IC 555 Based (Timer)
  • Demodulator : 4th Order LPF
  • Amplifier : Op-Amp Based
  • Supply Voltage (Board) : +12V, +5V / DC
  • Supply current : 100 mA (Minimum)
  • Input Voltage : 230 V/ 50 Hz AC
  • Interface connectors : 2mm socket

 

Features

  • On-board message signal with variable amplitude
  • Three different frequency message signal
  • On Board carrier signal
  • PPM Modulation using Timer IC
  • PAM Demodulation using Low Pass Filter
  • Amplifier using Op-Amp
  • Internal Power Supply +5V , +12V/ 500 mA
  • Number of test point to study the PPM system
  • User friendly front panel block diagram

 

PPM Modulation and Demodulation

In pulse position modulation, the position of the pulses are changed in accordance with the amplitude of the modulating signal, width of the pulses is kept constant in this system, while the position of each pulse varied with reference to the amplitude of the modulating signal. The pulse position modulated signal generated by using NE555 IC.

The 555 IC operated in astable mode for PPM generation. In as table mode of operation, the 555 IC generator digital pulses which is the carrier of the modulator, without input the pin5 of IC, fixed frequency carrier generated at the third pin of the IC. While feed sine wave as a modulating signal to the pin5 of IC, the fixed frequency digital signal width varied with respect to the amplitude of the modulating signal. ON time of the digital pulse is constant and determined by the resistor and capacitor combinations RA, RB and C. OFF time of output digital pulse determined by the amplitude of modulating signal. This OFF time pulse width narrower for increasing voltage at pin5 of IC while OFF time pulse width wider for decreasing voltage at pin5 of 555 IC.

This pulse position modulated signal ensembles the modulating signal and hence easily recovered by a simple low pass filter. For efficient demodulation of PPM signal is needs some higher order filter and a high gain amplifier.

Front Panel Diagram





BLOCK DIAGRAM

PPM Modulation





PPM Demodulation





EXPERIMENTAL SECTION

 

LIST OF EXPERIMENTS

Experiment 1:

To Study the PPM Modulation and Demodulation in 500 Hz Message

Experiment 2:

To Study the PPM Modulation and Demodulation in 1 KHz Message

Experiment 3:

To Study the PPM Modulation and Demodulation in 2 KHz Message

Apparatus Requiered of Experiments

  • PPM Trainer : 1 No
  • Patch chord : 4 No’s
  • Power chord : 1 No
  • Manual : 1 No
  • CRO : 1 No

 

EXPERIMENT 1: Study the PPM Modulation and Demodulation (500Hz)

Aim

To study the PPM Modulation and Demodulation in 500 Hz Message

Apparatus Required

  • PPM Trainer - 01
  • Power Chord - 01
  • Patch Chords - 04
  • CRO - 01

 

Procedure

  • Connect power chord to PPM Trainer and switch ON the Trainer.
  • Note down the waveforms of message signal 500 Hz (P1) using CRO.
  • Without message signal note down the carrier signal waveform at P5 test point.
  • Patch P1 to P4 test point and note down the PPM output at P5 test point.
  • For demodulation, Connect P5 and P6 test point using patch chord.
  • Now we get the LPF signal output at P7 test point.
  • Connect P7 and P8 test point using patch chord.
  • . The final demodulated output is available at test point P9 and varies the pot meter to get amplified output.
  • Note down the all the waveforms.

 

Result

Thus, the PPM Modulation and Demodulation (500 Hz massage) was studied.

EXPERIMENT 2: Study the PPM Modulation and Demodulation (1 KHz)

Aim

To study the PPM Modulation and Demodulation in 1 KHz Message

Apparatus Required

  • PPM Trainer - 01
  • Power Chord - 01
  • Patch Chords - 04
  • CRO - 01

 

Procedure

  • Connect power chord to PPM Trainer and switch ON the Trainer.
  • Note down the waveforms of message signal 1 KHz (P2) using CRO.
  • Without message signal note down the carrier signal waveform at P5 test point.
  • Patch P2 to P4 test point and note down the PPM output at P5 test point.
  • For demodulation, Connect P5 and P6 test point using patch chord.
  • Now we get the LPF signal output at P7 test point.
  • Connect P7 and P8 test point using patch chord.
  • The final demodulated output is available at test point P9 and varies the pot meter to get amplified output.
  • Note down the all the waveforms.

 

Result

Thus, the PPM Modulation and Demodulation (1 KHz massage) was studied.

 

EXPERIMENT 3: Study the PPM Modulation and Demodulation (2 KHz)

Aim

To study the PPM Modulation and Demodulation in 2 KHz Message

Apparatus Required

  • PPM Trainer - 01
  • Power Chord - 01
  • Patch Chords - 04
  • CRO - 01

 

Procedure

  • Connect power chord to PPM Trainer and switch ON the Trainer.
  • Note down the waveforms of message signal 2 KHz (P3) using CRO.
  • Without message signal note down the carrier signal waveform at P5 test point.
  • Patch P3 to P4 test point and note down the PPM output at P5 test point.
  • For demodulation, Connect P5 and P6 test point using patch chord.
  • Now we get the LPF signal output at P7 test point.
  • Connect P7 and P8 test point using patch chord.
  • The final demodulated output is available at test point P9 and varies the pot meter to get amplified output.
  • Note down the all the waveforms.

 

Result

Thus, the PPM modulation and demodulation (2 KHz massage) was studied.