I used USRPB100+WBX daughter board to transmit linear modulated frequency (LFM) signals at the center frequency fc (fc=80 or fc=83 MHz). The LFM signal sweeps from fc-16 kHz to fc+16 kHz in 0.05 or 0.5 s. The other USRPB100 +WBX daughter board did the reception. The two devices were placed in a large room, separated by variable distances (20 cm to a couple of meters). I also changed the gain in both the source and the receiver (varying gain from -5 to 20 dB for both). Then I examined the received LFM signals through matched-filtering operations. The part that I do not understand that the calculated impulse responses also had extended multipath. I can see four or five strong multipaths, always with one dominating path. The channel time span was 10 ms. To me, it seems impossible to have such a long mutlipath. Can everyone explain the long delayed multipath? Is it real or due to the device distortion? Any suggestions? Many thanks, Ian

Ian, I think you may be seeing IQ imbalance which will cause fake responses. Have you run the IQ Balance calibration utility? Matt On Thu, Apr 25, 2013 at 8:39 AM, Ian Song <ajsongs@gmail.com> wrote: > I used USRPB100+WBX daughter board to transmit linear modulated frequency > (LFM) signals at the center frequency fc (fc=80 or fc=83 MHz). The LFM > signal sweeps from fc-16 kHz to fc+16 kHz in 0.05 or 0.5 s. The other > USRPB100 +WBX daughter board did the reception. The two devices were placed > in a large room, separated by variable distances (20 cm to a couple of > meters). I also changed the gain in both the source and the receiver > (varying gain from -5 to 20 dB for both). > > Then I examined the received LFM signals through matched-filtering > operations. The part that I do not understand that the calculated impulse > responses also had extended multipath. I can see four or five strong > multipaths, always with one dominating path. The channel time span was 10 > ms. To me, it seems impossible to have such a long mutlipath. Can everyone > explain the long delayed multipath? Is it real or due to the device > distortion? Any suggestions? > > > Many thanks, > > > Ian > > _______________________________________________ > USRP-users mailing list > USRP-users@lists.ettus.com > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com > >