Re: [Discuss-gnuradio] 100 Msps FPGA code for USRP N210 - Gnu Spectrum analyzer

[Moeller]

On 18.03.2011 20:09, Marc Epard wrote:
> We've customized an FPGA image for the N210 that lets us grab batches of 256K 
> complex samples (one SRAM full) at 100 Msps with no decimation, scaling,
> or downconversion. It works by filling the SRAM with samples at full rate, 
> then dribbling them out the Ethernet in the normal fashion. I posted the
> ISE project, Verilog code, and a built image at https://public.me.com/mepard. 
> You'll also find some examples of visualizing the spectrum data there.
> I'm particularly fond of the movie.

Thanks for publishing. This is very impressive, using Gnuradio as a spectrum 
analyzer.
A few questions:
- What about compensating the spectral shape within the measurement bandwidth?
  It does not seem too much dependent on the center frequency.
- Movie: why do you have spectral lines walking in both directions?
  Is one direction caused by real frequency components and the other by
  spurious sine components? Can it be predicted and compensated?
- Can half of your scan speed be achieved by using original FPGA,
  taking snapshots and do all processing on the PC? Or do you need some
  special processing that needs a better timing within the FPGA?

I think it's an interesting instrument for electronics education
in schools that can't afford expensive traditional spectrum analyzers.