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Re: [Discuss-gnuradio] resampler block (DRM ok!)
From: |
Eric Blossom |
Subject: |
Re: [Discuss-gnuradio] resampler block (DRM ok!) |
Date: |
Sat, 8 Oct 2005 18:59:15 -0700 |
User-agent: |
Mutt/1.5.6i |
On Fri, Oct 07, 2005 at 11:44:27PM +0200, Stephane Fillod wrote:
>
> > > In the case of the 512kS/s to 48kS/s ddc, would the gr_rational_resampler
> > > be able to replace gr_freq_xlating_fir_filter ?
>
> Ok no.
>
> IOW, the gr_rational_resampler does not do frequency translation,
> and the USRP cannot decimate above 256. I used a decim rate
> below 128 because I heard there's gain problems above.
Yes. If you need more decimation, just use gr.fir_filter_xxx.
The first argument is the decimation factor.
> So it looks like freq_xlating_fir_filter_ccf must be used.
No, only if you want to decimate AND frequency translate. If you just
want to decimate, use gr.fir_filter_xxx. If you just want to
frequency translate, use a complex sinusoid LO and gr.multiply_cc.
If you want both, use freq_xlating_fir_filter_ccf.
> This is still ok, the whole ddc python script takes less than
> 9% on a 1GHz AMD CPU. Still, I wished it would be less, because
> I hope to eventually have several of them running in parallel,
> plus a point and click waterfall, and some demodulating clients
> around.
> Patchs available on demand, comments welcome!
Cool stuff. Looking forward to getting a chance to play with all of it.
Eric
- Re: [Discuss-gnuradio] resampler block, (continued)