rectangular.m

经典《信号与系统》教程的matlab例程,对深入理解信号与系统相关概念有很大帮助

% Name:Rectangular.m
clear
L=input('Type in the length N=');
n=0:L-1;
w=u(n)-u(n-L);
x=0.25*sin(0.25*pi*(n-(L-1)/2+eps))./(0.25*pi*(n-(L-1)/2+eps)).*w;
%=================================================
N=1024;
H1=fft(w,N);
H2=fliplr(H1);
H=[H2(1:1023),H1];
F1=fft(x,N);
F2=fliplr(F1);
F=[F2(1:1023),F1];
W=-2*pi+2*pi/N:2*pi/N:2*pi-2*pi/N;
%=======================================================================
figure(1)
subplot(221)
plot(W/pi,abs(F)),title('The magnitude response of FIR filter')
xlabel('Frequency (radians)')
axis([-1,1,0,max(abs(F))])
%=========================================================
subplot(222)
plot(W/pi,abs(H))
axis([-1,1,0,max(abs(H))])
title('The frequency response of the Rectangular window'),
%======================================================
subplot(224)
plot(W/pi,20*log10(abs(H)/abs(H1(1))));
axis([0,1,-100,0])
title('The frequency response in dB'),
xlabel('Frequency (*pi)')
%======================================================
subplot(223)
plot(W/pi,20*log10(abs(F)/abs(F1(1))));
axis([0,1,-100,0])
title('The frequency response in dB'),
xlabel('Frequency (*pi)')
%======================================================
figure(2)
subplot(221)
stem(n,w,'.')
%axis([0,L-1,min(w),max(w)])
title('The Rectangular window')
xlabel('Index n')

%=================================================
subplot(222)
stem(n,x,'.')
title('The truncated impulse response')
xlabel('Index n')
axis([0,L-1,min(x),max(x)])
%==================================================