Table of Contents
Advertisement
Its highest point can be lower by 3.92 dB (1.57 times) when the source
frequency is half way between two bin frequencies. This variation of the
spectrum magnitude is called the Picket Fence Effect (the loss is called
the Scallop Loss).
All window functions compensate this loss to some extent but the Flat
Top window provides the best correction (see Table 11.3).
Power Spectrum
The Power Spectrum
(V 2) is
the
square
of the
Magnitude
spectrum.
The 9400A displays
the Powe~ Spectrum
on the dBm scale,
with 0 dBm
corresponding to (0.316 Vpeak)
Pover
Density
spectrum
The Power
Density
Spectrum
(V2/Mz)
is
the
Power
Spectrum
divided
by the
product
of
the
equivalent
noise
bandwidth
of
the
filter
and
the
frequency bin width in Hz.
The 9400A displays the Power Density spectrum on the dBm scale, with
0 dBm corresponding to (0.316 Vpeak)-/Hz.
Sampling
Frequency
In the 9400A
the time
domain
records
are acquired
at sampling
frequencies which depend on the selected time base (consult Table 5.1).
Before FFT, the time domain record may be sub-sampled. If the selected
number of points is lower than the displayed record length (Table 5.1),
the total sampling frequency will be reduced.
The total
sampling
frequency
equals
twice
the Nyquist
frequency
(displayed in the FFT Redefine Menu).
Scallop
Loss
Loss associated with the picket fence effect
windows implemented).
(listed in Table 11.3 for
11-19
Fast Fourier Waveform Processing
Option (WP02, V 2.06FT)
Advertisement
Table of Contents
