wn=kaiser(length(xn),5.658);
hn=xn.*wn';
Hk=fft(hn);
kh=[0:1:length(Hk)-1];
subplot(2,1,1);
stem(n,xn);
title('time domain signal');
subplot(2,1,2);
stem(kh,abs(Hk));
title('kaiser window(n=100)');