fg_07_10.m

来自「英文书《Digital Signal Processing with Examp」· M 代码 · 共 23 行

% fg_07_10          Periodogram (energy)
sp_fig(1); N=100; N2=1000;
set(gcf,'defaultaxesfontsize',16);

subplot(2,1,1);
n=0:N-1;
x=n.*exp(-7*n/N).*cos(2*pi*(7+7*n/N).*n/N);
x=x/(1.1*max(x));
xt=resamp(x,N2);
axis([0 N -1 1]);
line([0:N2-1]*N/N2,xt,'color','k'); grid on;
line(0:N-1,x,'color','k','linestyle','none','marker','x');
xlabel('Time index (n)'); ylabel('x(t),  x_n');

subplot(2,1,2);
P=fftshift(abs(fft(x)).^2/N);
stem(-N/2:N/2-1,P,'k*'); grid on;
axis([-N/2 N/2 0 1.1*max(P)]);
xlabel('Frequency index (m)'); ylabel('         P_m'); 
grid on;

EP=sum(P)
Ex2=sum(x.^2)