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O
PERATOR
’
S
M
ANUAL
Power Density Spectrum
The power density spectrum (V
2
/Hz) is the power spectrum divided by the equivalent
noise bandwidth of the filter, in hertz. The power density spectrum is displayed on the dBm scale, with 0 dBm
corresponding to (V
ref
2
/Hz).
oints is lower than the source number of points, the effective sampling frequency is reduced. The
associated with the picket fence effect.
Window Functions
All available window functions belong to the sum of cosines family with one to three non-zero
cosine terms:
Sampling Frequency
The time-domain records are acquired at sampling frequencies dependent on the selected
time base. Before the FFT computation, the time-domain record may be decimated. If the selected maximum
number of p
effective sampling frequency equals twice the Nyquist frequency.
Scallop Loss
This is loss
where:
M = 3
is the maximum number of terms,
a
are the coefficients of the terms,
N
is the number of points of
m
tric around the point k = N/2.
m
the decimated source waveform, and
k
is the time index.
ents of Window Functions lists the coefficients
a .
The window functions seen in the time
The table of Coeffici
domain are symme
Coefficients of Window Functions
Window Type
a
0
a
1
a
2
Rectangular
1.0 0.0 0.0
von Hann
0.5 -0.5 0.0
Hamming
0.54 -0.46 0.0
Flat Top
0.281 -0.521 0.198
Blackman-Harris
0.423 -0.497 0.079
FFT Setup
Setting Up an FFT
1. In the menu b
Math
, then
dr
.
2. Touch a Math
ce button:
F1
th
Fx
The numbe
ath traces
le depends
ptions loaded on you
illoscope. See Spec
ns.; a pop-up menu appear
lect
FFT
ar touch
function tra
Math Setup...
in the
rough
op-down menu
r of m
availab
on the
software o
r osc
ificatio
s. Se
from the menu.
3. Touch
the
Single
or
Dual
n of a function
(functio
)
button if the FFT is to be of the result of
peration.
ath function if you selected
Dual
function. Then touch inside the
Operator2
field and select
FFT
another math o
4. Touch
inside
the
Source1
field and select a channel, memory, or math trace on which to perform the FFT.
5. Touch
inside
the
Operator1
field: Select
FFT
from the pop-up menu if you selected
Single
function. Select
another m
from the pop-up menu.
6. In the right-hand dialog, touch the
FFT
tab.
WRXi-OM-E Rev C
141