On Thu, Feb 12, 2009 at 5:43 AM, Bruhtesfa Ebrahim <li...@ruby-forum.com> wrote:
> I syncronized my USRPs(one is v4.3 and the other v4.5) by using the USRP > clocking notes on http://www.gnuradio.org/trac/wiki/USRPClockingNotes, > to make them frequency and phase syncronized. Ok. > ...Then,I run usrp_fft.py on the master USRP.I > see that the master USRP receives the 5GHz transmission from signal > generator without problem, but when i change the center frequency to > 4.96GHz to receive from the slave, I got a weird signal.The signal is > not stable, the noise(whole spectrum) level decreases and increases very > fast and it has only a very small peak at the center frequency.Moreover, > the spectrum changes very much with gain.) It sounds like, since you have perfect synchronization between transmitter and receiver, that what you have after downconversion in the daughterboard is DC + noise. That is, the transmitted carrier (plus noise and multipath from the channel) is being mixed with a synchronized local oscillator, resulting in only the noise components being left in the complex baseband signal GNU Radio is receiving. There will also be a DC component based on the path delay and wavelength causing a phase shift between the transmitted carrier phase and and the receiver LO phase. Johnathan _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
