, x, var std:
v = var (x); %
sigma = std (x); %
Signal Processing Toolbox ( ). xcorr . , , . , x, :
R = xcorr(x) / length(x);
, . , , , .
Rplus = R(floor(length(R)/2):end);
length , floor .
, , /, . - :
w = [0:0.1:5];
Sw = [];
for i=1:length(w)
Sw(i) = sum(Rplus.* cos(w(i)*t));
end;
Sw = 2*T*Sw;
t , R plus , T . .* ( ) .
. ,
hamm = 0.54 + 0.46*cos(pi*t/max(t));
Rplus = Rplus.* hamm;
, .
.
N = 512; % ( )
w = 2* pi *[0: N /2] / N / T; %
Fw = T * fft (x, N); % F_X(w)
Sw = Fw.* conj (Fw) / N / T; % S_X(w)
Sw = Sw (1: N /2+1); %
. , , . . nextpow2, , . ( /):
dw = 0.5; %
N = 2* pi / dw / T; %
N = 2^ nextpow 2(N); %
. . ,
hamm = hamming(length(x));
scale = 1 / sqrt(0.54^2 + 0.46^2/2);
hamm = hamm * scale;
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hamming Signal Porcessing Toolbox, .
Fw = T * fft (x.*hamm, N); % F_X(w)
.
[1] , 2 .
[2] , , - .