fg_07_09.m

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

% fg_07_09          Periodogram (power)
sp_fig(1); N=100; M=50;
set(gcf,'defaultaxesfontsize',16);

subplot(2,1,1);
m=0:M-1; n=0:N-1;
b=exp(-m*4/M).*cos(2*pi*9*m/(2*M));
x=b*sin(2*pi*m'*(n-N/2)/N);
x=x/(1.1*max(x));
% Modification for slide show:
y=[x x x x x];

axis([0 5*N -1 1]); 
line(0:length(y)-1,y,'color','r','marker','x'); grid on;
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,'b*'); grid on;
axis([-M M 0 1.1*max(P)]);
xlabel('Frequency index (m)'); ylabel('         P_m'); 
grid on;

avg_powr_in_eq_7_25=sum(P)/N
mean_squ_value_of_x=sum(x.^2)/N