Convert IQ data to power vs. frequency

[N2STC]

Hello & thanks for reading!  I have searched forums and tried to solve this myself.  I have a USB spectum analyzer from Tektronix which outputs it's data in I/Q form.  I need to see the data as you would on a standard spectrum analyzer display.  When ever I download an example it seems toolkits and .vis are called for which I don't have.  I am using LabView 2014 full development version only.  I have an example python program, but  am having trouble translating to the proper LV .vis.  I'll attach the example program.  I know I should know this, but its been years since I dealt with complex numbers etc.

Help will be greatly appreciated.

Sincerely,

Stan

[Dennis_Knutson]

Have you installed a LabVIEW driver with Help> Find Instrument Drivers? You would also need NI-VISA installed.

[N2STC]

Thanks for the reply.  Sadly, this model doesn't support SCPI type fetch commands, and LV can't see it with VISA.  I have an open ticket(7436871) on the latter, but never got a resolution.  I have had to rely on imported .dll files, which seem to work. 

[Dennis_Knutson]

It would have helped if you had provided the model number (which you still have not done).

[N2STC]

RSA 306.  (Sorry)

[N2STC]

BUMP!

Still looking for an answer.........

Thanks!

[scotia673]

Hi,

I'm not entirely clear on which functionality you're having trouble replicating in LabVIEW, but you mentioned complex numbers; if you right-click on your block diagram to access the functions palette, and go to Numeric->Complex, you'll find a number of VIs that are built for working with complex numbers.

Here is a link to the help pages for these functions:

Complex Functions

http://zone.ni.com/reference/en-XX/help/371361L-01/glang/complex_functions/

[RMaso]

I know this is a fairly old topic, but I'm looking for a solution too. I did come across the following on the TEK site, but it doesn't satisfy me.

http://www1.tek.com/forum/viewtopic.php?f=8&t=6564

Basically, it says you can use a different model LABVIEW driver as long as you run the SignalVU-PC behind LabVIEW (and install the VISA drivers in a specific order). I don't want to require the SignalVU software to be running just to work with the device. I've seen some other threads that dead-end with the comment that the SignalVU software handles GPIB emulation.

Has anyone figured out how to interface with the RSA306 without running SignalVu in the background?

[ToeCutter]

If you have a spectrum in complex I,Q values vs frequency, to convert to power get the amplitude (=(I^2+q^2)^0.5) (or use re,im to amplitude and phase function in LV and just take the amplitude), then square it. This gives a measure of power vs frequency- you may need to multiply by a constant but that depends on your units and scaling.

[Oligarlicky · Accepted solution]

I believe the function you are looking for is FFT Power Spectrum and PSD: