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power spectrum estimation 有幾種方式,
& ?% b2 ?2 W- P. ^6 q- H IPeroidogram
* }8 a: p# h3 k& e) {( R$ dModified periodogram8 l f- d: \# I. r. J' G1 W
Bartlett method4 O2 M9 r: A- N
Welch method
" C- B4 @6 q0 OBlackman-Tukey method
; d7 p7 r5 m$ V4 p! m# }, s! K! `+ M: L+ _# k3 C' U* @# z
若用simple Peroidogram m file 方式如下,estimated 跟 actual 會有Bias* R/ n3 Y8 C' a# e
x : input sequence. C& j7 v& J* [, |2 g2 B; ~0 K, n
n1 : starting index, x(n1)
( I. t# [, D, D0 j# R- j2 ]) v8 Cn2 : ending index, x(n2)
- L+ r) q3 X5 \; X: d
# }) T) i, ~) @0 Hfunction Px = per(x,n1,n2)3 v. p s1 A2 X
x = x(;" G$ ~/ O3 y/ j$ C
if nargin == 1 q. z0 U5 c% E Y4 _7 a
n1 = 1; n2 = length(x); end;7 w" |% y0 P8 P
Px = abs(fft(x(n1:n2),1024)).^2/(n2-n1+1);! g4 a U% z3 A7 K5 A. G e
Px(1) = Px(2); |
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