fg_07_14.m

英文书《Digital Signal Processing with Examples in MATLAB》附带的MATLAB实例

% fg_07_14          3 Periodograms
sp_fig(1);
set(gcf,'defaultaxesfontsize',16);

N1=2^16; N2=2^9; M=2^11;
randn('seed',123);
x=randn(1,N1);
x=round((M-1)*x/max(abs(x)));
x=sqrt(100*N1/sum(x.^2))*x;

P=abs(fft(x,N1)).^2/N1;
subplot(3,1,1);
axis([0 .5 0 1000]);
line([0:N1/2]/N1,P(1:N1/2+1),'color','r'); grid on;
ylabel('P(\nu); N=2^{16}');
set(gca,'xticklabel',' ');
title('Power density (v^2/Hz-s)');

P=abs(fft(x,N2)).^2/N2;
subplot(3,1,2);
axis([0 .5 0 1000]);
line([0:N2/2]/N2,P(1:N2/2+1),'color','r'); grid on;
ylabel('P(\nu); N=2^{9}');
set(gca,'xticklabel',' ');

[P,nseg]=pds(x,x,N2,1,0);
subplot(3,1,3);
axis([0 .5 0 200]);
line([0:N2/2]/N2,P(1:N2/2+1),'color','b'); grid on;
ylabel('Avg. P(\nu)');
xlabel('\nu (Hz-s)');
nseg=nseg