Please do the questions from 6 10 Create a 1 second long m

Please do the questions from 6 - 10 .

Create a 1 second long message signal. The message signal is a rectangular pulse between 450 and 550 milliseconds with magnitude 1. Create carrier signal of the same duration with frequency f_0 = 400 Hz. You can either use sin or cos waveforms as a carrier with magnitude 1. (i.e. C = cos (2 pi f_0t)) Modulate signal by multiplying the message signal and the carrier. Plot all 3 signals in the time domain and explain what you observe in the modulated signal. In the frequency domain: Take the Fourier transform of the message and carrier and modulated signal and plot the magnitude spectrum of all of the 3 signals. Explain what you see in the spectrum of the modulated signal and how it relates to the spectrum of the message and carrier. Solve this modulation problem by hand (i.e. take the Fourier transform of the modulate signal) Plot the magnitude spectrum of the modulated signal as you computed by hand in part 6. What are the similarities between your hand computed result vs. the MATLAB result from part 4? What are the differences between your hand computed result vs. the MATLAB result from part 4? What causes these differences? Extra credit: In MATLAB, show that by modulation we can have more than one user on the spectrum. For this you can create another message and put in on the different carrier and show that the spectrum of the 2 massage signals do not interfere. Explain how the receiver should be designed.

Solution

clear all;

close all;

%x=[1 2 3 4]

x=input(\'enter the input sequence\');

n=input(\'enter the lenth of DFT\');

subplot(4,1,1);

stem(x);

xlabel(\'time\');

ylabel(\'amplitude\');

title(\'input signal\');

y=fft(x,n);

subplot(4,1,2);

stem(y);

xlabel(\'frequency\');

ylabel(\'amplitude\');

title(\'discrete fourier transform\');

z=abs(y);

subplot(4,1,3);

stem(z);

xlabel(\'frequency\');

ylabel(\'magnitude\');

u=angle(y);

subplot(4,1,4);

stem(u);

xlabel(\'frequency\');

ylabel(\'phase plot\');

gtext(\'kl university\')