Keysight x-series Programmer's Reference

3 VMA Mode
3.4 IQ Waveform Measurement
–
The Elec Atten control is grayed out
–
The Auto/Man state of (Mech) Atten is restored
–
If now in Auto, (Mech) Atten recouples
–
If now in Man, (Mech) Atten is set to the value of total attenuation that existed
before the Elec Atten was disabled. The resulting value is rounded up to the
smallest value possible given the (Mech) Atten Step setting - (That is, 57dB
changes to 58dB when (Mech) Atten Step is 2dB)
Using the Electronic Attenuator: Pros and Cons
The electronic attenuator offers finer steps than the mechanical attenuator, has no
acoustical noise, is faster, and is less subject to wear.
The “finer steps” advantage of the electronic attenuator is beneficial in optimizing
the alignment of the instrument dynamic range to the signal power in the front panel
as well as remote use. Thus, you can achieve improved relative signal measurement
accuracy. Compared to a mechanical attenuator with 2dB steps, the 1dB resolution
of the electronic attenuator only gives better resolution when the odd-decibel steps
are used. Those odd-decibel steps are less accurately calibrated than the even-
decibel steps, so one tradeoff for this superior relative accuracy is reduced absolute
amplitude accuracy.
Another disadvantage of the electronic attenuator is that the spectrum analyzer
loses its “Auto” setting, making operation less convenient.
Also, the relationship between the dynamic range specifications (TOI, SHI,
compression, and noise) and instrument performance are less well-known with the
electrical attenuator. With the mechanical attenuator, TOI, SHI, and compression
threshold levels increase dB-for-dB with increasing attenuation, and the noise floor
does as well. With the electronic attenuator, there is an excess attenuation of about
1 to 3dB between 0 and 3.6GHz, making the effective TOI, SHI, and so forth, less
well known. Excess attenuation is the actual attenuation relative to stated
attenuation. Excess attenuation is accounted for in the instrument calibration.
Adjust Atten for Min Clipping
Sets the combination of mechanical and electronic attenuation and gain based on
the current measured signal level so that clipping will be at a minimum.
This is an immediate action function, that is, it executes once, when the control is
pressed.
The algorithms that are used for the adjustment are documented under "Pre-Adjust
for Min Clipping" on page 1773.
691 Vector Modulation Analyzer Mode User's &Programmer's Reference

Keysight x-series Specifications

General

Analysis Bandwidth	Up to 1 GHz (depending on model)
Real-Time Bandwidth	Up to 1 GHz (depending on model)
Form Factor	Benchtop
Connectivity	LAN, USB, GPIB
Resolution Bandwidth	1 Hz to 10 MHz (depending on model)