3 Spectrum Analyzer Mode
3.2 Swept SA Measurement
max/min” if these limits are exceeded. Note that for an external source, these limits can be affected by
the settings of Source Numerator, Source Denominator, and Power Sweep
Couplings The four parameters Center Frequency, Start Freq, Stop Freq and Span are interdependent, as
changing one necessarily affects one or more of the others. The couplings between Center Frequency
and Span are detailed under the control descriptions for those controls. These couplings also affect
Start Freq and Stop Freq
Preset On Mode Preset, Span and Center Frequency preset, and Stop Freq is derived. See Center Frequency
Presets in "Center Frequency" on page 281 for the Stop Freq after Preset for various model and option
numbers
On Meas Preset, only Span presets, but Center Frequency does not, so Stop Freq will vary depending
on Center Frequency
When Mode Preset is performed while in External Mixing, the Stop Freq of the current Mode is set to
the nominal Max Freq of the highest harmonic range in the Harmonic Table for the current mixer setup
If the current measurement has a limited Span available to it, and cannot achieve the Span shown in
the table (Span = Stop Freq – Start Freq), the instrument uses the maximum Span the measurement
allows, and sets Center Frequency to the midpoint of the Start Freq and Stop Freq values in the
Harmonic Table. Thus, in this case, Stop Freq presets to a frequency above the preset Center
Frequency by ½ of the maximum Span
When Restore Input/Output Defaults is performed, the mixer presets to the 11970A, whose Stop
frequency is 40 GHz
Therefore, after Restore Input/Output Defaults, if you switch to External Mixing and do Mode Preset
while in the Spectrum Analyzer Mode, the resulting Stop Freq is 40 GHz
State Saved Saved in instrument state
Min -79.999990 MHz, unless Source Mode is set to Tracking, in which case it is limited by the minimum
frequency of the Source
Instrument Types Min Value
VXT models M9421A 55.000010 MHz
VXT models M9410A/11A 330.000010 MHz
VXT models M9410A/11A With Option LFE: 6.510 kHz
Without Option LFE: 330.000010 MHz
VXT models M9415A 330.000010 MHz
M8920A 80.010 kHz
If the knob or step keys are being used, depends on the value of the other three interdependent
parameters
While in External Mixing, the minimum Stop Freq you can set is determined by the external mixing
parameters. It will be close to the minimum LO frequency (3.8 GHz if undoubled, 8.6 GHz if doubled)
times the harmonic number, for the lowest harmonic range in the Harmonic Table for the current
mixer setup. It can be queried with :FREQ:STOP? MIN
Max Depends on instrument maximum frequency. Note that, if Source Mode is set to Tracking, the effective
instrument maximum frequency may be limited by the source maximum frequency
If the knob or step keys are being used, depends on the value of the other three interdependent
Spectrum Analyzer Mode User's &Programmer's Reference 295
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