If we transmit a modulated signal (carrier = 2.1GHz) with a baseband signal less than 100 Hz and then receive it with the USRP2/WBX the low frequency baseband signals do not appear at the USRP output. Is there a HPF filtering out all frequencies below 100 Hz on the WBX board?

Sharlene, Have you looked at the spectrum on a spectrum analyzer? There is DC Offset correction on the USRP receive chain, which might be removing your 100Hz signal, but there are other possibilities worth investigating: Is a frequency offset causing your desired signal to appear at an unexpected frequency? A USRP2 may have 10ppm or so frequency errors, which at 2.1GHz are: 2.1e9 * 1e-5 = 21KHz It is fairly typical for radios to have frequency offsets, hence many protocols have methods for estimating and cancelling frequency offset. To mitigate this issue, lock both USRP2s to the same external 10MHz reference. Also, consider using uhd_siggen_gui.py with sine and sweep your offset frequency while watching the fft display from the receiver. An external spectrum analyzer can also be used to determine whether your issue is the WBX receiver or the transmitter. If it really is the WBX receiver DC offset cancellation, you can either tune with an LO offset or you can disable the DC offset cancellation via the UHD software api. Jason On Mon, Jan 30, 2012 at 11:45:16AM -0800, Sharlene Katz wrote: > If we transmit a modulated signal (carrier = 2.1GHz) with a baseband signal less than 100 Hz and then receive it with the USRP2/WBX the low frequency baseband signals do not appear at the USRP output. Is there a HPF filtering out all frequencies below 100 Hz on the WBX board? > > _______________________________________________ > USRP-users mailing list > USRP-users@lists.ettus.com > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com