Demodulate IQ data on a FlexRIO FPGA

[doug.george]

Hi All,

To provide some context, the aim of what I'm trying to do is summarised as follows

1. Use a PXI 5665 to downconvert FM radio waves using RFSA to create IQ data
2. Use P2P to send the data to a FlexRIO where demodulation of the IQ will take place on the FPGA.
3. Send the demodulated data back to the host where it can be stored as a file.

I would like some pointers in regards to the demodulation on FPGA stage. I am aware that there are VIs to demodulate IQ using MT/RFSA. However, I would like to do this on the FPGA and have not been able to find any examples for such an implementation. Are there any examples that people have floating around that does something like this on FPGA? Alternately even just some mathematical ideas on how to demodulate IQ to produce the baseband waveform would be appreciated. I could then implement the maths using FPGA code.

Cheers,

Doug

[BauerPower]

Hey Doug,

There's an RF Communications libary on the community from back in 2011, have you already taken a look at that? I haven't taken the time to go through the examples but figured I'd post it so you can check it out!

https://decibel.ni.com/content/docs/DOC-4068

[doug.george]

Hi Rob,

Thanks for your reply, I've seen that library but I don't really understand what the FM demodulation example is doing. Could you possibly clarify it's behaviour? I notice that there is a phase(n-2) - phase (n-1) /2 operation occuring but I don't understand how this correspond to FM demodulation.

Cheers,

Doug

[netsirk]

Hi Doug,

It looks like there isn't a ton of information on these examples in particular, but the context help on VIs out of the FPGA palette should be able to offer some guidance.

Best regards,

[shawn.t]

Hi Doug,

Have you seen this example?

https://decibel.ni.com/content/docs/DOC-41154

It's doing FFTs on the FlexRIO so it may not be exactly what you're looking for, but it may help get you going.