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power spectrum estimation 有幾種方式,- f" U, t" O1 G
Peroidogram
/ X2 A- ^) B3 N/ r: A' [Modified periodogram* Y, l6 N G" z2 M4 w. ]- |( s- J
Bartlett method% `; x' I8 S2 T: q& ^1 a! _+ W6 z
Welch method9 T* U2 s+ r6 ?; F7 u: [/ ]$ l( P
Blackman-Tukey method' h6 [+ d# z2 E) p+ o, }6 S- j$ O
H6 [ w) Q( R- r0 A* R若用simple Peroidogram m file 方式如下,estimated 跟 actual 會有Bias
# d* ^4 w$ k# H- ?. g9 ]x : input sequence' n3 i3 l! f* g3 Q, f# V
n1 : starting index, x(n1)) r: E; M, |6 k
n2 : ending index, x(n2)/ y! @" ^, `2 s) N9 v9 g2 d/ g
8 O# z, E: I( a* X6 Bfunction Px = per(x,n1,n2)
, \$ i, C2 J: N' l. L) hx = x(;
) K+ i& }5 v1 D5 h. Q& ?if nargin == 1
3 @! Z0 j8 j4 \( `1 X# j1 |* n n1 = 1; n2 = length(x); end;( a x" |/ A( _9 u; [
Px = abs(fft(x(n1:n2),1024)).^2/(n2-n1+1);
0 d# }2 K0 l* ~Px(1) = Px(2); |
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