function [P, W] = periodogram_yuqd(xn, Nfft);
%periodogram_yuqd(xn, Nfft) is a function wirtten by yuqd
%to estimate the PSD(power spectral density) of signal x
%The parameter Nfft used to spesify the number of fft points
%Wn is the normalized frequency(rad/s) at which PSD is estimated
%                                    N-1
%use the function Pxx(exp(jW))= abs( sum x(n)exp(-jWn))^2/N
%                                    n=0
%W = linspace(0,pi,Nfft);
N = length(xn);
H = freqz(xn,1,Nfft);
H = (abs(H)).^2;
P = H/N;
W = linspace(0,pi,Nfft);