PXI-5610 to PXI-5600 loopback

[Mister_Rose]

I am an RF dummy. But I need to design a test for some RF amplifiers that we are building. We have some equipment in the lab that needs to be ported to our new PXI test system.

Our existing lab system looks like this...

We have an HP 8656 RF signal generator. We configure it to generate a 300Mhz 1dBm carrier. We then plug this into the unit under test (UUT) input, and plug the UUTs output into an attenuator, which then goes into a Tektronix RSA 3303A RF signal analyzer. When the UUT is powered on, I see a nice peak at the set frequency and I can measure the power being delivered (reading on the analyzer + attenuator value = total gain)

I need to replicate this test on our new PXI test system. We have a PXI-5421 AWG plugged into a PXI-5610 Upconverter. I then wire the output of the 5610 into the input of a PXI-5600 downconverter. The downconverter is then connected to a PXI-5620 digitizer. Normally the UUT and the attenuator will be connected in between the 5610 and 5600, but for now I'd like to do a simple loopback test.

I should be able to set everything up, send a signal out the 5421 and  receive that same signal back on the 5620. I see bits and pieces of code in the sample code, but I cannot seem to put them together to get a simple loopback test. I have installed the NI-RFSG, NI-RFSA, NI-Spectral Measurements toolkit, and the NI Modulation toolkit. I don't recall the order of installation, but I do know that I installed the RFSG and RFSA before the Spectral Measurements and Modulation Toolkit.

Can anyone help me out a little here? Perhaps someone has a simple loopback test that can test this configuration?

Thanks in advance,

[Mister_Rose]

I am running the "MT RFSG Generate FM.vi" to create a signal. It seems to be working insomuchas there is no error reported. I have it configured to deliver a 291.3Mhz signal ( I think).

I am using RFSA Downconverter with External Digitizer.vi" to try to measure the signal that is generated, but I do not see any change in either the Magnitude Response or Phase Response graphs.

I can run "SMT Spectrogram for NI Scope.vi" and see a change on the spectrograph, but I am not sure what Iam looking at. There appears to be a warning about ADC overload. The Actual Spectrogram tab indicates that the center frequency is 16MHz, and this appears to be what I am seeing on the graph. So what happened to my 291.3Mhz signal from the Generate FM.vi?

[Mister_Rose]

I tried running the NI-RFSA Soft Front Panel, but I get the following error message.

"An NI RF Downconverter was detected but it is missing an associated NI Digitizer or LO.  Open Measurement and Automation Explorer (MAX), open the Properties for the NI RF Downconverter, select an NI Digitizer (and LO if applicable) to associate and then click Rescan. Otherwise, click Exit."

I cannot get the system to recognize the PXI-5620 digitizer that I have in the system. I can open up the test panel under Traditional NI-DAQ (Legacy) Devices, so the card appears to function. Ditto for the PXI-5600.

What do I need to do to get the downconverter to recognize the digitizer?

[tbob]

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@mister Rose wrote:

. There appears to be a warning about ADC overload.  

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I don't know about your other problems, but you should put an attenuator in your loopback path.  You can't feed the full power of your output stage into the input stage.  The output is many dBs high (maybe around +10dBm) and the input is expecting something like -90dBm or around that point.  That is why you are getting ADC overload.

As for your digitizer not being recognized, do you see it in MAX?  It should be there.  If not, maybe the software drivers are not installed correctly.

[JÞB]

You need an association in MAX between the AWG and the RF source.

But the 5600 does not conform to the SA TK ideal so you MUST PHYSICALLY place them in adjoining slots and use the 5600 driver to demod the signal. 

<Hint- there is a RF guru at NI tech support that taught me this about a month ago> It was a bit pinful - to me, but , I believe a KB article is soon to be published on this exact application.  OH BRIAN!

[Mister_Rose]

The 5421 AWG and 5610 Upconverter are adjacent and connected as follows.

5421  -  5610

--------------------

Ch0   -  Input

Clk In - To AWG Clk In

The 5610 and 5600 are adjacent and connected as follows.

5610  -  5600

---------------------

Input         -  Output

Ref Clk In  -  10 Mhz Out 1V pp 50Ohms

Here is a snapshot of the MAX configuration. Note that the digitizer does not show up in the drop down box when I try to connect it to the downconverter in software.

[tbob]

I noticed that the symbol to the left of NI 5620 for PXI Digitizer is different from most of the rest of the equipment listed.  Could this be part of the problem?  It may not be defined correctly.  Every other instrument has PXI in its name.  This one don't.

[Mister_Rose]

I noticed that too. I figured that I had installed a driver out of order or something, so I reinstalled a bunch of stuff, but I did not have any luck. I even uninstalled the drivers, shut down, removed the card, reinstalled the drivers, shut down again, and then plugged the card back in.

Nothin.

[tbob]

I'm at a loss to explain.  Call NI Tech Support.

[JÞB]

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@tbob wrote:

I'm at a loss to explain.  Call NI Tech Support.

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I did the same thing last month- you do not need to associate the 5600 with the digitizer

Tech support responded

Hi Jeff,

I just gave you a call back to admit my mental lapse there. Just to re-iterate my phone message, the 5620 and 5600 actually don't get associated in MAX because the 5620 is a legacy device based on our Traditional NI-DAQ driver, which is why using it requires the ni5660 driver and not NI-RFSA.

Setting the digitizer that is used with the 5660 configuration is done using the "Digitizer Resource Name" input of the "ni5660 Initialize.vi"
which should be the first one on the code's block diagram. If that's not there, and we need to look into it a little more, please let me know. You can give me a call back at -redacted- or email me back if my suggestion above doesn't work out. I'll leave this SR open for another few days in case that didn't work out. Let me know how things go. Have a good weekend.

Best Regards,

Chris N White
Applications Engineer
National Instruments