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Re: [Discuss-gnuradio] saturation with multi_fft.py
From: |
Eric Blossom |
Subject: |
Re: [Discuss-gnuradio] saturation with multi_fft.py |
Date: |
Wed, 10 Oct 2007 12:53:39 -0700 |
User-agent: |
Mutt/1.5.9i |
On Wed, Oct 10, 2007 at 03:14:21PM -0400, address@hidden wrote:
> The figures I showed you previously used std_4rx_0tx.rbf.
>
> To test with the standard std_2rxhb_2tx.rbf, I use the usrp_fft.py (with
> -S). I tested two cases, both with decimation 180, 1 kHz input, tuned to
> 0 Hz with 0 db gain. The first is with the voltage level of 1.4 V P-P
> (which cuases the clipping on the std_4rx_0tx.rbf), the second figure is
> at the full scale voltage of 2 V P-P. Neither show clipping. The
> clipping is clearly dependent on which rbf file is used.
>
> www.nd.edu/~ematlis/z.gnuradio/usrp_fft_180dec_1.4V_1khz.jpg
>
> www.nd.edu/~ematlis/z.gnuradio/usrp_fft_180dec_2.0V_1khz.jpg
>
> hope this helps clarify the situation....
>
> thanks,
> eric
OK. So it looks like the non-halfband case needs some adjustment to
reduce the gain so that it matches (more closely) the halfband case.
We don't have any multipliers. What power of 2 would you like?
The fix goes on lines 83 and 102 of rx_chain.v. Just change which
bits of hb_in_i are assigned to i_out and likewise for Q.
Send a patch when you're happy ;)
Eric
>
> On Wed, 10 Oct 2007, Eric Blossom wrote:
>
> >On Wed, Oct 10, 2007 at 12:50:35PM -0400, address@hidden wrote:
> >>Eric-
> >>
> >>using -d 160 the problem goes away with this latest build, but remains for
> >>higher decimation values. For example, at decimation of 180, I can
> >>reproduce the problem. As a picture is worth a thousand words, I've put
> >>two jpg's up online at:
> >>
> >>www.nd.edu/~ematlis/z.gnuradio/multi_scope_180dec_1.3V.jpg
> >>
> >>www.nd.edu/~ematlis/z.gnuradio/multi_scope_180dec_1.4V.jpg
> >>
> >>The input signal is again a 10 kHz sine wave. In the first image, the
> >>voltage level is 1.3 V p-p. In the second, 1.4 V p-p. In both cases I
> >>have zero db of gain and decimation of 180, with the LF_RX tuned to 0 Hz.
> >>As you can see, at 1.3 V P-P the result is perfect. However at 1.4 V P-P,
> >>the signal is seriously corrupted and jagged.
> >
> >
> >The second one is showing clipping. Note how the peaks are folded in
> >on top of themselves.
> >
> >Which rbf are you using for these? std_2rxhb_2tx.rbf (the default),
> >or std_4rx_0tx.rbf (the one without the halfband).
> >
> >Can you run the same experiment using the other rbf and post those
> >pictures too?
> >
> >The graphs are great. Thanks for posting the links.
> >
> >Eric
> >
- Re: [Discuss-gnuradio] saturation with multi_fft.py, (continued)
- Re: [Discuss-gnuradio] saturation with multi_fft.py, ematlis, 2007/10/09
- Re: [Discuss-gnuradio] saturation with multi_fft.py, Eric Blossom, 2007/10/09
- Re: [Discuss-gnuradio] saturation with multi_fft.py, ematlis, 2007/10/09
- Re: [Discuss-gnuradio] saturation with multi_fft.py, Eric Blossom, 2007/10/09
- Re: [Discuss-gnuradio] saturation with multi_fft.py, ematlis, 2007/10/09
- Re: [Discuss-gnuradio] saturation with multi_fft.py, Eric Blossom, 2007/10/09
- Re: [Discuss-gnuradio] saturation with multi_fft.py, ematlis, 2007/10/09
- Re: [Discuss-gnuradio] saturation with multi_fft.py, ematlis, 2007/10/10
- Re: [Discuss-gnuradio] saturation with multi_fft.py, Eric Blossom, 2007/10/10
- Re: [Discuss-gnuradio] saturation with multi_fft.py, ematlis, 2007/10/10
- Re: [Discuss-gnuradio] saturation with multi_fft.py,
Eric Blossom <=
- Re: [Discuss-gnuradio] saturation with multi_fft.py, ematlis, 2007/10/10
- Re: [Discuss-gnuradio] saturation with multi_fft.py, Brian Padalino, 2007/10/10
- Re: [Discuss-gnuradio] saturation with multi_fft.py, Dan Halperin, 2007/10/10
- Re: [Discuss-gnuradio] saturation with multi_fft.py, ematlis, 2007/10/10
- Re: [Discuss-gnuradio] saturation with multi_fft.py, Brian Padalino, 2007/10/10
- Re: [Discuss-gnuradio] saturation with multi_fft.py, Eric Blossom, 2007/10/10
- Re: [Discuss-gnuradio] saturation with multi_fft.py, ematlis, 2007/10/10
- Re: [Discuss-gnuradio] saturation with multi_fft.py, Eric Blossom, 2007/10/10
- Re: [Discuss-gnuradio] saturation with multi_fft.py, ematlis, 2007/10/11
- Re: [Discuss-gnuradio] saturation with multi_fft.py, Martin Dvh, 2007/10/11