FM on 10.7 MHz

[Bulova]

Hello,

I am working with Eco 1.18, because the higher ones I can't get running.

Actually I wanted to generate a 10.7 MHz signal with FM, but I am not sure if this can be done. I want to test a FM decoder.

Best regards

Dieter

[redpitaya]

You can create an Arbitrary signal where you specify one period of your signal. If you implement multiple periods inside (to create a short FM message), you just need to make sure that the whole "period" is generated at an appropriate output frequency.

This is a short situation description:
https://imgur.com/a/dx1M6yG

In the latest 2.00-30 OS we have a new test application, where you can upload a custom waveform from the computer and then Red Pitaya can generate it.

If you have questions, please let me know.

[Bulova]

Hello,

yes I also thought of arbitrary. But in fact the needed frequency is much too high, a real arbitrary needs at least two samples per period longterm, shortterm it would need much more. So it would need about 12 samples for 125 Msps to create a 10 MHz signal, and the FM could form 6 periods in that time, that means, the modulation frequency would be about 1.7 MHz.
No, arbitrary would not do it.

A solution would be to manipulate the hardware by control the clock rate by a varactor. But I won't do that.

I did not think about enough about my question, but now I am sure, it cannot be done with the RP.
Thank you anyway.

Dieter

[Bulova]

Hello RP,

how fast are the samples of the buffer being processed, is it with 120 Msps? And the size of the buffer can be used up to 16k?

Maybe it can be done by generating samples by Excel or so.

Best regards

Dieter

[redpitaya]

Hello Dieter,

The samples are generated at 125 Msps. I know of a use-case, where they were generating a 125 MHz spike with the Red Pitaya's output by utilizing the Arbitrary waveform. From my knowledge, specifying less samples means that the output waveform is generated faster (specifying 8192 samples instead of 16384 results in two times higher output frequency (from what is set with the SOUR:FREQ:SET command or the C/Python API alternative)).

However, as you mentioned before, Red Pitaya might not be the best at this (currently, we do not have the capability to stream data from a file to the outputs). Perhaps you can try to find some ideas on the alternative Red Pitaya software for the SDRlab 122-16 (https://github.com/pavel-demin/red-pitaya-notes)

Best regards.

[Bulova]

Hello RP,

yes, I did not mean streaming from file directly, but first loading into RAM, this should be possible. Am I right?

Dieter

[juretrn]

You will first have to load the samples into the block RAM in the FPGA. Streaming direct from RAM is currently not supported.