%采用Welch法計算正弦信號功率譜,Hamming Window;

figure;
fc = 50e9;
Stx = TRANSMITTER_TR_TH_2PPM;
N = length(Stx);
Li = 100;%Bartlett法的分段數
M = N/Li;%每段數據長度
P = zeros(1,M);

%%%%%%%%%%%窗函數%%%%%%%%%%%%%%
n = 1:1:M;
w = zeros(1,M);
w(n) = 0.54-0.46*cos(2*pi*(n-1)/M);
square = w.^2;
totle = sum(square)/M;
%%%%%%%%%%%%%%%%%%%%%%%%%
L = (N-M/2)/(M/2);%真正分段數
P = zeros(1,M);
s1 = Stx(1:M);
s1_w = s1.*w;
S1_w = fft(s1_w,M);
P = (abs(S1_w)).^2/M/totle;
%計算每段數據功率譜
for i=1:L-1
    si = Stx(i*M/2+1:(i+2)*M/2);%第i段數據功率譜
    si_w = si.*w;
    Si_w = fft(si_w,M);%%%FFT
    Pi = (abs(Si_w)).^2/M/totle;
    P = P+Pi;
end
P = P/L;
%橫坐標，赫茲；縱坐標，dB
t = 0:round(M/2-1);
k = t*fc/M;
P_dB = 10*log10(P(t+1));
plot(k,P_dB);
xlabel('頻率 /Hz'),ylabel('功率譜密度 /dB'),title('TR TH-PPM PSD');