Agilent Technologies E4406A, User Manual

Page: 94 / 230

94 Chapter 4
Making Measurements
Making the Spectrum (Frequency Domain) Measurement
• Blackman
• Blackman Harris
• K-B 70dB / 90dB/ 110dB (Kaiser-Bessel) - Allows selection
of Kaiser-Bessel filters with sidelobes of
−
70,
−
90, or
−
110 dBc.
FFT Size - This menu contains the following features:
• Length Ctrl - This feature allows you to set the FFT and
window lengths either automatically or manually.
• Min Pts in RBW - This feature allows you to set the
minimum number of data points that will be used inside the
resolution bandwidth. This adjustment is only available if the
Length Ctrl
key is set to Auto.
• Window Length - This feature allows you to enter the FFT
window length ranging from 8 to 1048576. This length
represents the actual quantity of I/Q samples that are
captured for processing by the FFT. This value can only be
entered if length control is set to Manual.
• FFT Length - This feature allows you to enter the FFT length
in the number of captured samples, ranging from 4096 to
1048576. The FFT length setting is automatically limited so
that it is equal or greater than the FFT window length setting.
Any amount greater than the window length is implemented
by zero-padding. This value can be entered only if length
control is set to Man (manual).
ADC Range - Allows you to access the following selection menu
to define one of the following ADC ranging functions:
• Auto - Select this to set the ADC range automatically. For
most FFT spectrum measurements, the auto feature should
not be selected. An exception is when measuring a signal
which is “bursty”, in which case auto can maximize the time
domain dynamic range, if FFT results are less important to
you than time domain results.
• Auto Peak - Select this to set the ADC range automatically to
the peak signal level. Auto peak is a compromise that works
well for both CW and burst signals.
• AutoPeakLock - Select this to hold the ADC range
automatically at the peak signal level. Auto peak lock is more
stable than auto peak for CW signals, but should not be used
for “bursty” signals.
• Manual - Allows you to access the selection menu:
−
6 dB
,
0 dB
,
+6 dB
,
+12 dB
,
+18 dB
,
+24 dB
, to set the ADC range level. Also
note that manual ranging is best for CW signals.
Data Packing - Allows you to access the following selection
menu to define one of the following data packing methods: