On 05/21/2012 04:12 PM, Alex Zhang wrote: > Thanks! > > I am trying to set up two channels on RX2 as Nick said. And the subdev is > set as "A:0 A:0". Please see the attachement for the GRC flow graph. > > But my problem is that it seems that both the channels can not receive the > expected signal(I am using an OFDM transmitter for test). > The single channel with frequency of 908M or 928M works well as I can see > the OFDM spectrum from the observing FFT plot window. > >
What did you enter for ch0 and ch1 center frequency? I recommend this: uhd.tune_request(908e6, rf_freq=918e6, rf_freq_policy=uhd.tune_request.POLICY_MANUAL) uhd.tune_request(928e6, rf_freq=918e6, rf_freq_policy=uhd.tune_request.POLICY_MANUAL) Its important the RF frequency be the same for each channel, otherwise, the second tune for channel1 will override the tuning for channel0. -josh > On Mon, May 21, 2012 at 5:37 PM, Josh Blum <j...@ettus.com> wrote: > >> >> >> On 05/21/2012 03:09 PM, Alex Zhang wrote: >>> Hi, >>> >>> What I want to do is try to use the two antennas of SBX simultaneously. >>> >>> The TX/RX is used for duplex communications and the RX2 is for sensing. >> The >>> two antennas are working different frequencies. >>> But this solution seems to be unfeasible, as someone said the receiver >>> chain of SBX is the same. The TX/RX and RX2 can not work simultaneously. >>> As suggested in the community, I am trying to using 3 frequecies on one >>> antenna (TX/RX): f1, f2, f3. >>> >>> f1(tx) and f2(rx) are used for FDD duplex communications,and f3 is for >>> sensing path. And f2 and f3 are within the 40MHz difference. >>> >>> My problem is how to set it in USRP source block for this kind of >>> configuration? Does anybody has such example? And I met the error like >>> below: >>> >>> Runtime error:vector::_M_range_check >>> >>> which seems to be caused by incorrect setting of subdev. However, I don't >>> know what the valid value fo subdev in such kind configuration. >>> >>> >> >> Correct, you can only receive from one antenna at a time. If your RX >> frequencies of interest are reasonably near in frequency, lets say 40 >> MHz, you can use multiple DSPs in the FPGA as a kind of 2 channel >> filterbank. >> >> You can set the subdev/frontend spec to "A:0 A:0", this will map the >> frontend A:0 to both DSP0 and DSP1. If you setup the USRP source for 2 >> channels, DSP0 will be output 0 and DSP1 will be output 1. >> >> Be careful with the tune_request so that you are setting the rf >> frequency to the same setting, but with different target frequencies to >> get the DSPs to shift appropriately. There should be some mention of >> tune request in the docs inside the USRP source block properties dialog >> in GRC. >> >> -josh >> >>> >>> >>> _______________________________________________ >>> Discuss-gnuradio mailing list >>> Discuss-gnuradio@gnu.org >>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >> >> _______________________________________________ >> Discuss-gnuradio mailing list >> Discuss-gnuradio@gnu.org >> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >> > > > _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
