Clarification The Property About Downconverter Gain (Vertical) When RFSA Measurement

Updated Nov 3, 2020

Reported In

Hardware

  • PXIe-5840

Driver

  • NI-RFSA

Issue Details

The block diagram for 5840 did not show any gains to clarify:

Block Diagram  - NI RF Vector Signal Transceivers Help  - National Instruments

Check the help document about niRFSA Properties, it just say the Downconverter Gain is the net signal gain:

Vertical: Downconverter Gain (dB) Property  - NI RF Vector Signal Analyzers (NI-RFSA 18.1) Help - National Instruments

When I change reference level of RF IN, the value of "Vertical: Downconverter Gain (dB)" has been changed. There is still no details information about the Clarification about the net gain from RF IN to the ADC (including RF IN and ADC).  

Solution

The DC Gain is the net gain from RF IN to the ADC. The DC Gain was based on the calibration data and temperate impact, and temperature correction after self cal is compensated in digital gain;
DC gain was analog gain and digital gain in the FPGA , analog gain states remain the same.
And the temperature drift is compensated digitally..in the FPGA ;

When I just only change the reference level, the DC gain will change later.
It is because of configuration changing in analog block diagram to re-call the cal data then re-calculate the DC gain.
And for the same reference level, the dc gain may change after self cal as the cal data is updated;