N=128;
k=0:N-1;

dr = 100;
alpha = 2*pi;
w = besseli(0,alpha*sqrt(1-(2*k/(N-1) -1).^2))/besseli(0,alpha);

B = N*sum(w.^2)/sum(w)^2    % noise bandwidth (bins)

H = abs(fft([w zeros(1,7*N)]));
H = fftshift(H);
H = H/max(H);
H = 20*log10(H);
H = max(-dr,H);

figure
area(k,w,'FaceColor', [0 .4 .6])
xlim([0 N-1])
set(gca,'XTick', [0 : 1/8 : 1]*(N-1))
set(gca,'XTickLabel','0| | | | | | | |N-1')
grid on
ylabel('amplitude')
xlabel('samples')
title('Window function (Kaiser, \alpha = 2\pi)')

figure
h = stem(([1:(8*N)]-1-4*N)/8,H,'-');
set(h,'BaseValue',-dr)
ylim([-dr 0])
set(findobj('Type','line'),'Marker','none','Color',[.871 .49 0])
xlim([-4*N 4*N]/8)
grid on
ylabel('decibels')
xlabel('DFT bins')
title('Frequency response (Kaiser, \alpha = 2\pi)')