On Wed, Oct 10, 2007 at 03:14:21PM -0400, [EMAIL PROTECTED] 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, [EMAIL PROTECTED] 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 > > _______________________________________________ Discuss-gnuradio mailing list [email protected] http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
