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power spectrum estimation 有幾種方式,7 a' s% x$ }0 o, O- V" q" l
Peroidogram5 `( f9 j: _- X0 I! i2 L2 K1 S! _
Modified periodogram
& V" h+ m" @9 ]Bartlett method7 k0 t; n0 S! s& ?' B3 I
Welch method
3 H) x5 p. e5 a" g$ `3 }Blackman-Tukey method/ i* w) |+ ]2 z5 y5 O$ |, \( L
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若用simple Peroidogram m file 方式如下,estimated 跟 actual 會有Bias- j9 G; g/ x( j5 r2 o4 ?
x : input sequence) u b w' n5 e. j' {$ d) m
n1 : starting index, x(n1)
& x( s0 B, `2 M2 ]% |* Wn2 : ending index, x(n2)! ?2 Z5 X! `! g j B& E* e
1 \3 F0 m8 a+ y2 X0 w7 u# [
function Px = per(x,n1,n2), i# x2 P: N9 d J" h
x = x(;1 _; p: C+ X$ l" j1 T
if nargin == 18 @! j0 G1 X1 c( M1 Y
n1 = 1; n2 = length(x); end;5 D) |4 y0 o9 u4 B4 R# I8 p
Px = abs(fft(x(n1:n2),1024)).^2/(n2-n1+1);
3 ]5 n/ f1 b3 _' r: P7 EPx(1) = Px(2); |
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