Amplitude Demodulation

TITLE: Amplitude Demodulation

Introduction:

Amplitude modulation is that in which amplitude of the carrier wave is changed according to modulating signal and frequency remains same. In this lab first we modulated a wave using Amplitude modulation and then we demodulated it with the help of Butterworth filter.

There are three methods to do demodulation.

1.     Synchronous method carrier multiplication.

2.     Square law method.

3.     Hilbert transform method.

S(t)=x(t)*cos( t)* cos( t)

      =x(t)* ( t)

      =1/2* x(t)*2 ( t)

      =1/2* x(t)*(1+ ( t))

      =1/2* x(t)+ 1/2* x(t) ( t)

Parameters and values settings:

1.     for message signal

Frequency	10hz
Phase	0
Amplitude	1

2.     for carrier signal

Frequency	100hz
Phase	0
Amplitude	1

3.     for filter

Lower cut off	0.1250hz
Upper cut off	0.45hz
Sampling frequency	1hz
order	2

CONCLUSION:

In this lab I have learned that demodulation occur. In this demodulation

Process we only place Butterworth filter right after the modulated signal

And we set order signal high so we get more accurate signal

And carrier signal value 10 times greater than message signal.