A.J.Chaudhari

M.J.College,Jalgaon

Modulation

Amplitude Modulation (AM)

Modulation

◦ It is the process in which some characteristic of a carrier (high-frequency) signal is changed according to the instantaneous amplitude of the information signal(low frequency).

Need of Modulation

◦ Suitable for signal transmission at great distance

◦ Multiple signals transmitted on the same channel

◦ Reduced antenna size

◦ Noise rejection

Applications

- Satellite communication- Broadcasting of both audio

and video signals. - Mobile radio communications,

such as cell phone.

• Types

– Amplitude Modulation: changes the amplitude of carrier.

– Frequency Modulation: changes the frequency of carrier..

– Phase Modulation: changes the phase of carrier..

Modulator Demodulator

Input

signal

Noise

Channel

Original Signal

Transmitter Receiver

AM generator using Amplifier/Oscillator

The AM signal is generated using a multiplier.

In frequency domain the AM waveform contains USB and LSB

Modulation Index of AM SignalModulation Index of AM Signal

CSULB May 22, 2006