A little confused. I am using the gnuradio-companion to configure the uhd.usrp_resource. What is the difference between the rf_freq and the center_freq? How the tune_request (is it a UHD method?) can be reflected in the gnuradio-companion setting?
On Mon, May 21, 2012 at 6:29 PM, Josh Blum <j...@ettus.com> wrote: > > > 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 > >> > > > > > > > -- Alex, *Dreams can come true – just believe.*
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