zhouqitu.m

给出了用MATLAB语言实现功率谱估计的程序

%最简单的周期图法
function y=zhouqi()
%求信号x(n)=sin(2*pi*f1*n)+2cos(2*pi*f2*n)+w(n), n=1,···,N-1的功率谱。其中f1=0.05,f2=0.12,w(n)为白噪声
%N=256或1024
%采用周期图法
clf;
%Case 1: N=256;
N=256;
n=[0:N-1];
f1=0.05;
f2=0.12;
wn=randn(1,N)
xn=sin(2*pi*f1*n)+2*cos(2*pi*f2*n)+wn;
Pxx=10*log10(abs(fft(xn).^2)/(N+1));
f=[0:length(Pxx)-1]/length(Pxx);
figure(1);
plot(f,Pxx);
xlabel('Frequency');
ylabel('Power Spectrum(dB)');
title('Periodogram N=256');
%==========================================
%Case 2: N=1024;
N1=1024;
n=[0:N1-1];
f1=0.05;
f2=0.12;
wn1=randn(1,N1)
xn1=sin(2*pi*f1*n)+2*cos(2*pi*f2*n)+wn1;
Pxx1=10*log10(abs(fft(xn1).^2)/(N1+1));
f=[0:length(Pxx1)-1]/length(Pxx1);
figure(2);
plot(f,Pxx1);
xlabel('Frequency');
ylabel('Power Spectrum(dB)');
title('Periodogram N=1024');