3 ๎Spectrum Analyzer Mode
3.11 ๎Harmonics Measurement
Auto/Man is remembered and restored when the electronic attenuator is once again disabled. This is
described in more detail in "Elec Atten" on page 1960
See "Attenuator Configurations and Auto/Man" on page 1864 for more information on the Auto/Man
functionality
Couplings If the RF Input Port is the RF Input:
โ
If the USB Preamp is connected to USB, use 0๎dB for Mech Atten
โ
Otherwise compute the auto-selected value of Mech Atten based on Reference Level, Int Preamp,
External Gain, Ref Level Offset, Max Mixer Level, ยตW Path Control and IF Gain settings. Limit this
value to be no less than 6๎dB (total attenuation below 6๎dB can never be chosen by Auto)
โ
In N9041B, if the RF Input Port is RF Input๎2, use the formula above and subtract the value of "Full
Range Atten" on page 1956 from the result to determine the Mech Atten. Limit the value so that it
is never lower than 0๎dB and so that total attenuation, including Full Range Atten, is never less
than 6๎dB (total attenuation, including Full Range Atten below 6๎dB, can never be chosen by Auto)
In External Mixing and BBIQ, where the attenuator is not in the signal path, the attenuator setting
changes as described above when Mech Atten is in Auto, but no changes are made to the actual
attenuator hardware setting until the input is changed back to the RF Input
For CXA-m with Option FSA (Fine-Step Attenuator or 2๎dB steps), the FSA-like behavior is only
available when the frequency setting is <=๎7.5๎GHz. So, when the frequency is changed from below
7.5๎GHz to above 7.5๎GHz, the attenuation setting changes to a multiple of 10๎dB that is no smaller
than the previous setting. For example, 4๎dB attenuation changes to 10๎dB
Preset Auto
The Auto value is 10๎dB
State Saved Saved in instrument state
Min 0๎dB
The attenuation set by this control cannot be decreased below 6๎dB with the knob or step keys. Values
below 6๎dB must be directly entered from the keypad or via SCPI. This protects against setting a
dangerously small attenuation value, which can put the instrument at risk of damage to input circuitry.
If the current mechanical attenuation is below 6๎dB, it can be increased with the knob and step keys,
but not decreased
Max
CXA Option 503 or 507 50๎dB
EXA 60๎dB
All other models 70๎dB
Note that in the Single-Attenuator configuration, the total of ATT and EATT cannot exceed 50๎dB. So, if
the EATT is set to 24๎dB first, the main attenuation cannot be greater than 26๎dB and will be reduced
accordingly; if the main attenuator is set to 40๎dB first, EATT cannot be greater than 10๎dB
Annotation The current value for Total Atten is displayed in the Measurement Bar at the top of the display. A value
appears for Electronic Attenuation only if the Electronic Attenuator is enabled. The annotation appears
as:
Atten: <total>๎dB (e<elec>)
The e letter is in amber in Single-Attenuator configurations
Spectrum Analyzer Mode User's &๎Programmer's Reference 1863
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