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PNA-X. Pulsed Voltage Measurement (for PAE). Analogue Input (AI) or IF Direct Access

Question asked by sergiodibello on Mar 8, 2020
Latest reply on Mar 19, 2020 by sergiodibello
Hi Keysight forum. 

I have a question regarding the rear panel AI (Analogue Input).


We measure Power Amplifier in a pulsed configuration. During the power sweep we need to measure also the PAE.
In order to perform PAE Measurements, we usually measure voltage (through the AI1) that is proportional to the current (measured with a current probe).
According to the help "Analog Inputs (AI1 and AI2) can be used for measuring from -10V to +10V. These inputs can be considered auxiliary receivers and used in a similar way as S-Parameter receivers."
I know how the pulses works and the theory behind the acquisition time, (https://www.keysight.com/it/en/assets/7018-02951/application-notes/5990-7781.pdf?success=true) . 
Short summary: "When P0 outputs a pulse, the DSP starts data acquisition and continues until it completes the required number of samples per specified IF bandwidth".
My questions is about how this AI works. 
Does it work like any other receiver (R1, A, R2, B)? 
This means:
1) Does it start the acquisition when Pulse0 has the positive edge? 
2) Does the acquisition time of the AI depends on the IFBW?
3) What about the sampling rate. Is it 60 MSa/s for DSP ver.4 and 100MSa/s for DSP ver.5? 
Usually the wire that is going to the AI is going also to an ascilloscope and we have seen similar results, but in some pulse configuration (specific pulse width and duty cyle), we have seen strange results measured by the PNA. 
Anyway, we would like to be sure that AI is measuring only inside the pulse.


I know that in theory it is possible to measure the DC voltage also with the IF direct access. (option 020 that we have)
4) Since for PA measurements we only care about R1, A, and B receiver, I guess we should use the R2 receiver since we do not care about S22 measurement. 
We do not care about R2, because:
- either we perform a scalar (response) calibration (SrcPwrCal, R1 Cal and B Receiver Cal with a Thru).
- or we perform a full 2 port Cal (including SrcPwrCal and Receiver Cal -->SmartCal) and then we "downgrade" the calibration to a "Enhance Response Cal" (also knonw as "2 ports one path").

 

I guess to configure the IF path of the R2 receiver we should use some of these commands.
http://na.support.keysight.com/pna/help/latest/IFAccess/IF_Path_Configuration.htm#elements.
What should be configured?
In my opinion only the following:
5) Set external path. SENSe<ch>:PATH:CONFig:ELEMent[:STATe] <elem>, <setting>
6) Set IF frequency to 0. SENSe<cnum>:IF:FREQuency[:VALue] <value>
7) Anything else?
8) Is there any voltage input limit? 
Thanks in advance

Sergio

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