Does the Spectral Measurement Toolkit Support the 5644 VST?

[kral]

I'm currently in process of migrating from a PXI-5660 to PXIe-5644 in .NET.  The current measurement process is as follows:

ConfigureSpectrumForRFSA

CalculateCorrectionForRFSA

NiScope.Read

niSMT.ZoomFFT

niSMT.AveragedPowerSpectrum

niSMT.ApplyCorrection

niSMT.SpectrumUnitConversion

niSMT.SpectrumPeakSearch

I've been mainly able to reproduce this flow with the following:

niSMT.ConfigZoomFFT

niRFSA.ReadPowerSpectrum

niSMT.ZoomFFT

niSMT.AveragedPowerSpectrum

niSMT.SpectrumUnitConversion

niSMT.SpectrumPeakSearch

Of course, when I say reproduce, I really only mean I can call the above methods without getting an exception or error.  It does not mean I return any usable measurement.  I've studied the SMT programming flow, routed the data as best as I can muster, and have gone back to the working 5660 SMT usage for verification, and nothing.

I then look to LabVIEW examples for the SMT, and here I notice that none of the SMT examples say they support any VST.  I look at SMT documentation for supported hardware and again, I don't find a reference to the 5644.  I find a forum response about when to use niSMT/niModT or RFmx and for the VST, the SMT isn't mentioned for any application.

So, am I mistaken to think that I can use the SMT for the VST?  I've already concluded that I can't use niScope as was used in the 5660 application.  I've only begun to start looking at RFmx, but I figured before I spend a lot of time switching gears for something else, I should post my question to the community.  Is RFmx the direction I should be taking or does my problem with SMT have nothing to with adequate hardware support?

Please advise.

Michael Kral

[dbell0971]

Hi Michael,

There are several factors at play here, the first being the SMT itself, then the second being the transition from the 5660 to the VST.  You may have figured out a large part of I'll detail below, but having it spelled out might help bring organization to those thoughts.

The Spectral Measurements Toolkit is a set of software that can help generate waveforms and analyze them.  The SMT is independent of any hardware, I've seen users with SMT/LabVIEW and a 3rd party RF instrument.  With the VST, you should still be able to use all of the SMT functions once you've gathered the data from the VST.  The Zoom FFT, AveragedPowerSpectrum, etc. will all function with the VST.  I have seen a good portion of customers using the VST with the SMT.

On the other hand, the transition from the 5660 to the VST is an interesting and less common issue (5660 is older, VST is much newer).  The 5660 is built on top of an older scope that ran a version of NI-SCOPE based on Traditional DAQ, while our newer scopes run on a version of NI-SCOPE based on DAQmx.  To add more to the complexity of your situation, the VST's internal digitization process does not use NI-SCOPE at all.  Because of this, the functions used with the 5660 (NiScope.Read) don't make sense with the VST and will not be usable.  Instead, you will need to use the RFSA functions as it seems you've already determined.

With these factors at play, it makes sense that you were searching for a different example that showed how to use the VST with RFSA/SMT.  The SMT examples in LabVIEW don't explicitly call out the VST as being compatible, but all of the examples will work correctly since they use RFSA and SMT only.  For LabVIEW, I usually start with SMT IQ Spectrum for niRFSA if I just want a spectrum/FFT.  Your programming flow looks pretty similar to what is in the Spectrum example, I think you're on the right track.  As a last note, RFmx is great option if you're interested in making the complete switch.  I'm assuming that this is the link you found about MT/SMT vs. RFmx; if not, it's worth a read.  You should be able to use either one, it's whatever you feel more comfortable with.

To summarize the above and to directly answer your question: the VST should be usable with both MT/SMT and RFmx.  You mention that you aren't able to return any usable measurement, can you give us more info about the data that you are receiving?

Thanks,

David B.

National Instruments

Applications Engineer

[KittF]

Mike,

I have tested the LabVIEW SMT shipping examples with the 5644R and they all work as expected. However, after the VST released the SMT examples where modified and tested to make sure they worked with all of the VST specific features.   It may be that your SMT code needs similar tweaks.  

You can run the shipping SMT examples "SMT Peak Search for niRFSA".  I've attached the C version for your review. 

If it were me, I would move in the direction of RFmx, but I do not have a full grasp of your timeline and resources to make that change.

RFmx is going to be easier to program for RF measurements, and also provide unique ability for parallel acquistion and measurements, which is going to make it faster than SMT.  Furthermore, for functionality that still requires programming with the underlyign RFSA driver, we provide an RFmx method to get the RFSA handle being used by RFmx, so that you do not have to close the RFmx session while working with RFSA.  

==========

I've had a verbal conversation with you since posting the first part of this message.  You have explained to me that you have started using RFmx SpecAn to perform tests that previously were implemented in SMT, and have been able to do so with relative ease, greatly simplifying some of your existing code.

This is great to hear.    Please let us know if you have questions as you proceed.