%Demo done during Session 22 to illustrate
%the FFT's of various windows
%
clf
set(0,'defaultaxesfontsize',16);
clear
Nw=input('window length ');
Nfft=input('FFT length ');
woff=pi/Nw;
coff=(Nw-1)/2;
wrec=ones(1,Nw);
wsin=cos(woff*((0:Nw-1)-coff));
whan=.5*wrec-.5*cos(2*pi/(Nw-1)*(0:Nw-1));
wham=.54*wrec-.46*cos(2*pi/(Nw-1)*(0:Nw-1));
xn=0:Nw-1;
plot(xn,wrec,'y','LineWidth',2);
axis([0 Nw-1 0 1])
xlabel('n')
hold 
plot(xn,wsin,'m','LineWidth',2);
plot(xn,whan,'c','LineWidth',2);
plot(xn,wham,'r','LineWidth',2);
legend('Rect','Sine','Hanning','Hamming');
title('Various Windows')
hold off
pause
omega=linspace(-pi,pi,Nfft);
frec=20*log10(abs(fftshift(fft(wrec,Nfft))));
fsin=20*log10(abs(fftshift(fft(wsin,Nfft))));
fham=20*log10(abs(fftshift(fft(wham,Nfft))));
fhan=20*log10(abs(fftshift(fft(whan,Nfft))));
frec=frec-max(frec);
fsin=fsin-max(fsin);
fhan=fhan-max(fhan);
fham=fham-max(fham);
absmin=min([min(frec) min(fsin) min(fhan) min(fham)]);
plot(omega,frec,'y','LineWidth',2); title('Spectrum of Rectangular Window');
axis([-pi pi -100 0])
xlabel('Omega (rps)')
ylabel('Magnitude (dB)')
hold on
pause
plot(omega,fsin,'m','LineWidth',2); title('Spectrum of Sine Window');
pause
plot(omega,fhan,'c','LineWidth',2); title('Spectrum of Hanning Window');
pause
plot(omega,fham,'r','LineWidth',2);
legend('Rect','Sine','Hanning','Hamming');
title('Spectra of Various Windows')
hold off