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Pulse Modulation Tutorial

Pulse modulation consists of switching the carrier on and off as required.

Fig.1 shows a continuous wave carrier (CW).

PULSE MODULATION - Continous Wave Carrier - CW Diagram

Fig.2 shows the carrier being switched on for a short time to produce a pulse of R.F.


This is the principle of Radar; a short pulse is transmitted and then an echo listened for.

Fig.3 shows a long pulse and three short ones.

principle of Radar Diagram

This generates the letter B in Morse Code.

Fig.4 shows Pulse Width Modulation (PWM).

Pulse Width Modulation PWM Diagram

The width of the pulse is determined by the amplitude of the modulating signal at that instant.

Fig. 5 shows Pulse Position Modulation (PPM).

Pulse Position Modulation (PPM) Diagram

Here the width and amplitude of the pulse are constant but its position is determined by the amplitude of the modulating signal.

PULSE CODE MODULATION is where the amplitude of the modulation is measured at regular intervals and a binary number generated to represent that amplitude.

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