Hi Guys,

I am doing a project on Software Defined Radio receiver..
I have generated a AM signal which is coming from a microphone and it
goes to a signal mixer. I have a local oscillator and the two signals
are mixed (Superhet). The output from the mixer forms the
IF(Intermediate Frequency).Now what I have to do is to demodulate  the
signal and feed it to the speaker using a AF Amplifier. So I was
wondering if if there is a way to do the Demodulation (I think its like
a modulation) on a computer.
Please help me in this issue.

I was just wondering if it is possible to do the Demodulation part using MATLAB.
First of all, I have doubts that MATLAB can take inputs from the
soundcard in Real Time.
O.K. If it is not able to take in Real time, what I can do is take the
signal, record it in my computer using a Goldwave in (.mat) form. Then
I can link this file into a source in the MATLAB simulink and feed it
into the [DSB AM
Demodulator
Passband] block and take the output and again store it in a (.mat) format.

But I am really not able to use the [DSB AM
Demodulator
Passband] signal block.Can anyone suggest if I am going in the right
direction.I will take the output in the .mat file and then play it
using a speaker.
Thanks
Nitin

There are several ways to digitally demodulate your AM modulated IF
signal. One is to take the absolute value and then low pass filter.
The two easiest implementations of a low pass filter are 1) to simply
average the last N values, where N determines the bandwidth of the
filter; and 2)to build a simple recursive filter by setting the output
equal to x times the input plus (1-x) times the previous output. The
bandwidth is controlled by setting the value of x. With the latter
filter this is the equivalent of an idealized diode rectifier followed
by simple RC low pass filter. Have fun!