National Instruments NI Spectral Measurements Toolkit - Manual (Page 25)

© National Instruments Corporation 25 NI Spectral Measurements Toolkit User Guide
The averaging VIs require that you enter an FFT spectrum as a complex
array. You can perform spectrum unit conversion before or after averaging.
Averaging Conventions
For Spectral Measurements Toolkit VIs, averaging refers to the average of
several different data sets from the same process. The following list
contains averaging operations that apply independently to each frequency
bin of the Fourier transform.
F
R
+ jF
I
The complex representation of the Fourier transform
of a signal f(t) using real and imaginary values.
< F >
k
= F
R
+ jF
I
For vector averaging, real and imaginary parts of the
Fourier transform are averaged separately using either
linear or exponential weighting over k data records.
| F | The magnitude of the Fourier transform.
X
k
, Y
k
kth instance of input spectrum X and its averaged
output Y.
max(X
k
, Y
k
) Each complex frequency of spectrum X
k
is compared
in magnitude to its counterpart in Y
k
. The larger value
is retained. The result is a real spectrum.
conj( ) Complex conjugate.