Re: [Discuss-gnuradio] Re: FSK4 Demodulation on the FPGA

[Kevin Xu]

Max,

Thanks so much for your quick response. As it turns out, I'm already 
part of the op25 yahoo group, and I've seen the good work the op25 group 
has done. However, like you said, I am looking for an implementation 
that's entirely USRP based. I am only looking to be able to get the 
demodulated symbols on the USRP rather than doing it on the PC. Would I 
need to implement all of the blocks you mentioned -

 - channel selection, downconversion to zero IF
 - decimation
 - FM demod
 - post-demod filtering (i.e., RRC filter)


- to accomplish this?

Kevin


On 12/8/2010 9:11 AM, ikjtel wrote:
> > Hey all,
> > Has anyone attempted to implement a C4FM demodulator on the Altera
> > Cyclone in the USRP1? Right now I'm hoping to do this to read
> > P25 encrypted packets on the FPGA instead of on the CPU, and I
> > wanted to know if it was possible. If so, could anyone could
> > point me to any sort of examples or tutorials I could learn
> > from to accomplish this? It would be greatly appreciated.
> Kevin
>
> We've got this working - although at present the code runs in the PC as a GNU 
> Radio application.
>
> Assuming you want a receiver implementation that's entirely USRP based, you 
> would also need some other blocks in addition to the C4FM demod block -
>   - channel selection, downconversion to zero IF
>   - decimation
>   - FM demod
>   - post-demod filtering (i.e., RRC filter)
>
> No idea if there is sufficient gate array capacity in the FPGA to implement all 
> this, or not.
>
> Anyway, here are a few links to get you started
>   - http://sites.google.com/site/radiorausch/
>   - http://sedition.org.au/op25/
>   - op25-dev yahoogroup
> The RadioRausch pages do not load properly for me.  Nonetheless, you want to go to the 
> "four level FSK" page.
>
> You would be most welcome to join the op25-dev group also.
>
> Best of luck
>
> Max
>
>
>
>
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