Theory behind the application

• The general process of embedding an information varying signal into a

second signal is modulation.

• Extracting the information varying signal is known as demodulation.

Modulation methods rely on the concepts of

1. Amplitude modulation

2. Frequency modulation

3. Phase modulation

• Let x(t) be the information varying speech signal and c(t) be the carrier

signal. Then ,the modulated signal y(t) is given by y(t)=x(t)c(t)

A speech signal typically has a low frequency range(200hz to 4khz).

Modulation is the key to transmit a voice signal x(t)at different range of

frequencies.