AM-DSB vs. AM-SSB: A team project.

Preparation

1. Download 6 different wav files x1.wav, x2.wav, x3.wav, x4.wav, x5.wav, x6.wav

2. Download the ece301conv.m file.

3. Open MATLAB and change the directory to where you have saved the previous files.

4. Enter the following commands:

duration=8;
f_sample=44100;
t=(((0-4)*f_sample+0.5):((duration-4)*f_sample-0.5))/f_sample;

5. Load x1(t) by the commands

[x1, f_sample]=audioread('x1.wav');
x1= x1';

6. Load other x2(t) to x6(t) similarly.

Please go through steps in the prerequisite experiment #1 and prerequisite experiment #2 if you have not tried it before.

Goals:

1. You are allowed to only use frequency band 0-8kHz. The first goal is to squeeze in 3 different signals x1(t) to x3(t) using AM-DSB. Each signal has to be pre-filtered to have a bandwidth 1kHz. You need to design the carrier frequencies of this system.

2. The second goal is to squeeze in 6 different signals x1(t) to x6(t) using AM-SSB. Each signal has to be pre-filtered to have a bandwidth 1kHz. You need to design the carrier frequencies of this system and also decide whether you would like to use the lower side band or the upper side band.

Deliverables:

Each team needs to prepare two files “radio1.wav” and “radio2.wav”, and two corresponding “.m files” that can demodulate each embedded signals. For example, one of your .m file should look like the following.

function [ y ] =AMDSB(ch)
% ch: is an input deciding which signal you would like to tune into.
% ch = 1, 2, 3 for AM-DSB and ch=1,…, 6 for AM-SSB.

duration=8;
f_sample=44100;
t=(((0-4)*f_sample+0.5):((duration-4)*f_sample-0.5))/f_sample;
[radio1, f_sample]=audioread('radio1.wav');
radio1=radio1';

% Fill in your main body here

You can use the following command to save your signal, say “x”.

audiowrite(‘test.wav’, x,44100);

Then you have to demonstrate it in front of the TA/instructor so that he/she can hear different signals successfully by demodulating the AM-DSB and AM-SSB waveforms.

Please set up an appointment with the TA or the instructor for the demo of your team.

If you prefer, you can also replace x1 to x6 with your own .wav files. You just need to make sure that the format is 44100Hz/second, N=16 bits, and the length of your wav file is exactly 8 second.