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power spectrum estimation 有幾種方式,
1 b# e2 ]) v+ v7 xPeroidogram
; Q8 k. ^+ D z+ v$ v1 sModified periodogram- O9 r- x9 F$ ?5 o2 q
Bartlett method
* Z9 p% l/ c* qWelch method' K) j, ~( u$ j
Blackman-Tukey method
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若用simple Peroidogram m file 方式如下,estimated 跟 actual 會有Bias, X) {( k' V) e7 s$ R0 y, U: Z
x : input sequence; M' U- y9 Y' \! m& K
n1 : starting index, x(n1)' k& b) s! ]7 {, l( H& M1 H7 k) x
n2 : ending index, x(n2)0 d( P' O' R4 b9 g) z( s/ [* G
7 O1 s7 h2 s( l& j q, M0 o4 A) @
function Px = per(x,n1,n2)# } d7 I* c! V$ E* p, w3 ~6 |
x = x(;
/ C2 q# t7 [/ }1 xif nargin == 1
- k k& K- s, _0 ` n1 = 1; n2 = length(x); end;3 |. B) R/ O# B3 ]( a U
Px = abs(fft(x(n1:n2),1024)).^2/(n2-n1+1);4 N) a8 D4 E) T, j" G
Px(1) = Px(2); |
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