Re: [Discuss-gnuradio] Re: "Open-Hardware"

[Marcus D. Leech]

> On 12.01.2011 20:22, Marcus D. Leech wrote:
> If connected to a Xilinx board, FIR and decimation could still be done in the 
> FPGA.
Agreed.

> There's a cheap one here, with USB2 and Spartan3, only 70€ (<$100)
> http://www.ztex.de/usb-fpga-1/usb-fpga-1.2.d.html
> Or this one for 145€?
> http://www.cesys.com/fpga/spartan/efm01_en.html
>
> Do you think the FMC interface can be realized with the 52 Xilinx GPIO pins,
> just with the specific FMC driver software?
Quite possibly, don't actually know that much about FMC, but my 
impression is that it's a fairly-generic way of
  putting expansion "goop" onto a generic FPGA board.


> Is this really a problem? For spectral analysis this is only an axis shift.
> For demodulation you would have to do some kind of adaptive doppler 
> compensation and phase
> tracking anyway. Could all this be done by continuously changing the DDC 
> parameters over the wire?
Maybe, maybe not.  Depends on the applications, but I'm guessing that a 
significant number of applications can
  get away with the fact that their signal of interest isn't exactly at 
DC, and do the DDC in software.

For example, I happen to be interested in signals centered at 
1420.40575Mhz.  But I'd be perfectly happy
  if the "0Hz" in the signals was actually at 1420.400MHz--I could 
compensate in the software side. Resolution
  of 50KHz or better should be achievable with the PLL I've shown on 
the block diagram.  Phase noise improves
  with larger resolutions, however.



--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org