Dear Marcus Leech, Thanks very much for your response.
I use RFX2400 daughterboards and their TX/RX ports. A attenuator is added between the transmitter and receiver boards now. And to simplify the test, I use a constant source at the transmitter side. Here is my GRC flow graph: http://old.nabble.com/file/p30077180/flow%2Bgraph.jpg And here are the results I've observed from the scope: http://old.nabble.com/file/p30077180/Result.jpg Why do I receive a sine wave when I transmit a constant? Best wishes, Hongliang Marcus D. Leech wrote: > > On 10/27/2010 02:11 PM, Hongliang Zhang wrote: >> Hi everyone, >> >> I made a test for UHD blocks today, and I found a problem as follows: >> >> I take two USRP2 boards for my test. One is used as transmiter and the >> other >> board is set to be receiver.And I use UHD Simple Sink and UHD Simple >> Source >> blocks for transmiting and receiving respectively. >> >> sampling frequency = 195.312K (which is the minimum sampling frequncy of >> the >> system). >> gain=0 >> The transmitted signal is a AM modulated sine signal. >> The frequency of orignal sine wave (the message signal) is 10K Hz. >> The frequency of carrier signal (center frequency for modulation at >> transmitter board) is 2.42 GHz, and I use the same frequency at the >> receiver >> board for demodulation. >> Amplitude of transmitted signal is 0.05. >> >> I connect the two boards together, and I add a scope to observe the >> period >> of the received demodulated signal. The problem is the period is about >> 0.000045, which means the frequency of the signal I received is not 10 >> KHz, >> but about 2.2 KHz. >> >> I have used the same external reference clock and PPS signal for both of >> the >> boards, so I think they are set up correctly. Why do I get a received >> signal >> with different frequency from what I transmit? >> >> Does anyone meet the similar problem before? How may I solve the problem? >> >> Thanks so much for every help and suggestions in advance. >> >> Best regards, >> Hongliang >> >> >> >> > What daughterboards are you using? > > Can you share your (GRC) flow-graphs with us--makes it easier to spot > problems. > > I hope that you're using an attenuator between the transmitter side and > receiver side. > > My guess is that there's a sample-rate issue somewhere on the receive > side, like the scope sink > hasn't been told the correct sample rate, so it's displaying > incorrectly, etc. > > > > > -- > Marcus Leech > Principal Investigator > Shirleys Bay Radio Astronomy Consortium > http://www.sbrac.org > > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > http://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > -- View this message in context: http://old.nabble.com/Problem-of-using-UHD-blocks-as-Tx---Rx-tp30069825p30077180.html Sent from the GnuRadio mailing list archive at Nabble.com. _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio