Re: Capturing 2 Level FSK with frequency hopping?

[Johannes Demel]

Hi Peter,

since you're looking at a signal with less than 10MHz bandwidth around 
910MHz, you might have hardware available that is able to capture the 
whole bandwidth. This should be a good starting point.

Besides, the best approach to solve your challenge depends on more 
parameters.

Questions that I'd consider first:
Do you need to process all 6 bands in parallel?
Are all signal sources synchronized? Do they come from the same source?
How large are the guard bands?
How large is the time gap between every sequential hop in a subband?
Do the subbands depend on each other in some way?
Is there a preamble to sync to?
Do you intend to change block parameters at runtime?

It might be interesting to use polyphase filters to divide your ~10MHz 
signal into 6 subbands first. Then use a polyphase filter to separate 
your channels. Or use the Xlating FIR for your subbands. I'd play around 
and observe the effects of each approach.
You might want to use a polyphase filter for all your 6 * 60 channels.

Cheers
Johannes

On 10.07.22 12:18, Peter Lambrechtsen wrote:
> Hello,
>
> Excuse my ignorance as I am fairly new to gnuradio but I am trying to 
> figure out how best to capture a data stream that is in the ISM band 
> that also has frequency hopping.
>
> Channel spacing of 25kHz
> It has two data bit rates of 62.5bps and 500bps
> Starting at 910.5Mhz and going up to 919.975 and in there it has 6 sub 
> bands of 60 channels it hops between sequentially between the 
> frequencies in the sub band every 0.4s
>
> I'm wondering what the best approach would be to capture the data and 
> figure out when the timing frame was to determine which was the 
> initial frame as then it should be able to follow the sequential hopping.
>
> Still trying to work on the blocks to capture all the traffic as I 
> haven't figured that out yet as I am just working off the specification 
> and trying to understand the Frequency Xlating FIR Filter to at least 
> capture one FSK stream to make sure it is sane what I should be 
> receiving, then move to the frequency hopping.
>
> Thanks, Peter