Zero Span Mode IF Bandwidth not correctly saved in the Record IQ .xml file

Hi,

I use the .xml file saved in zero span mode to retrieve my data and to make reports. It appears that when the IF bandwidth is configured below 50 kHz, the value saved in the .xml file is always 50000: <IFBandwidth>50000</IFBandwidth>.

Please find attached a print-screen of my settings (“Settings.PNG”) and the corresponding saved file (“Settings.xml”).

This issue is annoying because my reports do not reflect the real settings. Could you solve this issue?

Many thanks and regards,

Fabrice

xml file attached as .png (because .xml files are not allowed).

Hi Fabrice,

So, what’s going on here is that the API is limiting the IF bandwidth to 50kHz and the GUI is not showing you the clamped value. If you opened the spectrum plot in zero-span you would notice that as you decrease the bandwidth past 50kHz it is being limited. (IE you wouldn’t notice a difference spectrum at 10 and 50kHz bandwidth)

The proper fix here is to have the GUI report the bandwidth that was clamped. The reason there is IF bandwidth limits here, is due to the filter sizes required to get reasonable rolloff at very narrow bandwidths. There are fixed sized filter passes on the downsampling processing in the BB60C API.

If you are able, a workaround is to simply lower your sample rate to something closer to 10kHz. 50kHz bandwidth is less than 1/10th the sample rate you are using. A good target might be between 1/2 and 1/4.

I realize it may not be a viable option, but we do have a programming interface for the BB60C. If you need a very specific setup, polling the IQ data from the device into your C/Matlab/Python/other program, and then filtering down to 10kHz can be straightforward. Then you can save the data in whatever format is best for your application.

Again, open up the spectrum plot to visualize where the lower IF bandwidth cutoff hits. I can make a note to fix the GUI to show the clamped values.

I apologize for the inconvenience. Let me know if you have further questions or feedback.

Regards,
Andrew

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