BRUEL & KJAER 2032 Instruction Manual page 164

13.2.15. Autocorrelation Ch.A or Ch.B
154
In Spectrum Averaging mode:
Rzaa(n)
=
:T -
1
[
W(k) · GAA (k)]
0 ~ n ~ N -1 , 0 ~ k ~ N -1 , N
=
2048
W(k) is the weighting function applied to the Autospectrum. The Analytical Autocorrela-
tion function is defined as
r--J
Rzaa(n)
=
Raa(n)
+
j Raa(n)
r--J
where R
88
(n) =
~[
R
88
(n)]
The displayed function is the normalised Analytical Autocorrelation Coefficient:
Rzaa(n)
P
(n) - - -
zaa - Raa(O)
1
N-1
where R
88
(0) = -
L:
W(k) · GAA(k)
N
k=O
Pzaa(n) is displayed for 0
~
n
~1
023
In Signal Enhancement mode:
Rzaa(n) = y-
1
[
I
GA(k)
1
2
]
0 ~ n ~ N-1, N
=
4096, a(n)
=
0 for N/2 ~ n ~ N-1
where
GA(k)
is the 1-sided spectrum of the Enhanced Time Function a(n) extended
with zero padding
Pzaa(n) is displayed for 0 ~ n ~ 2048.
Pzaa(n) can be displayed in terms of:
Real part
Imaginary part
Magnitude
Phase
Nyquist plot
Nichols plot