MATLAB: How can i see the effect of changing time period in frequency domain, i need to see the bandwidth changing while i am changing time period

bandwidth

clc; clear all
Fs=1000; Ts=1/Fs; t = (-3:Ts:3-Ts)*1e-3;
M=4; K=log2(M);
Bw=10e3;
rect1=rectangularPulse(-1*1e-3,1*1e-3,t); % rect pulse = Tsym symbol duration = 2 msec
rect2=rectangularPulse(-.5*1e-3,.5*1e-3,t);
nfft=length(rect1); nfft2=2^nextpow2(nfft); xfft=Fs*(0:nfft2/2-1)/nfft2;
f1=fft(rect,nfft2); ff=f1(1:nfft2/2);
f2=fft(rect2,nfft2); ff2=f2(1:nfft2/2);
plot(xfft,abs(ff)/3000,'r',xfft,abs(ff2)/3000,'y')

in this code i changed the width of the rect signal. how can i see the bandwidth effect?

Best Answer

It is easier to see the differences if you plot each of them individually in a separate subplot.

Change the plot call to:

figure(1)
subplot(2,1,1)
plot(xfft,abs(ff)/3000,'r')
axis([0  10    0  1])
title('Pulse Width Â±1\cdot10^{-3}')
xlabel('Frequency')
ylabel('Amplitide')
grid
subplot(2,1,2)
plot(xfft,abs(ff2)/3000,'g')
axis([0  10    0  1])
title('Pulse Width Â±5\cdot10^{-4}')
xlabel('Frequency')
ylabel('Amplitide')
grid

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