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>-------------------------------------------------------------------------
> exa1100701_pwelch.m, for example 11.7.1 and fig. 11.5.1(d)
> to estimate the PSD of x(n) by Welch average;
>--------------------------------------------------------------------------
clear;
> 调出数据；
load test x;
N=4096;
Fn=-0.5:1/N:0.5-1/N;
> 用 Welch 平均估计试验数据的功率谱；
> xpsd=pwelch(x,N,1,hamming(33),16,'whole'); for MATLAB 5.3
xpsd=pwelch(x,hamming(33),16,N,'whole'); >for MATLAB 6.1
mmax=max(xpsd);
xpsd=xpsd/mmax;
xpsd=10*log10(xpsd+0.000001);
plot(Fn,fftshift(xpsd));grid on;