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power spectrum estimation 有幾種方式,
% n- x4 D+ M- R6 qPeroidogram
; m6 m+ ^' P* ] j' e6 ^% j- XModified periodogram' U ~9 v* T" e p2 f2 V; _2 |$ F
Bartlett method9 ~& y$ `: n; G O" P# N# s
Welch method4 \- v% K ?1 J, E/ s
Blackman-Tukey method5 x9 I$ G9 g7 t, i! {. ?7 D9 i
1 g2 w: j2 s2 A, N6 S ]8 Q
若用simple Peroidogram m file 方式如下,estimated 跟 actual 會有Bias/ ^" q2 ]( i* y+ ^5 q9 j
x : input sequence
0 s7 u3 ^% n1 k8 t3 n% nn1 : starting index, x(n1)4 D4 j: w2 f+ q9 h/ L& j3 A
n2 : ending index, x(n2)
/ x( O- B/ e; H: M8 v0 i. V% Q! _5 W# H! y+ _. W" ~4 z# ]# r
function Px = per(x,n1,n2)
: w; ]9 {) }0 y Bx = x(;
# o: B# `, p' t) m) m( Q# x1 Uif nargin == 1
6 k" W9 ]0 e8 F7 V n1 = 1; n2 = length(x); end;% K/ J* `' r2 ?6 I4 g7 q
Px = abs(fft(x(n1:n2),1024)).^2/(n2-n1+1);+ y! b6 |6 E% ~
Px(1) = Px(2); |
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