On 05/21/2012 06:57 PM, Alex Zhang wrote: > 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
Basically, you have two down conversion chains that share a common RF frontend, but independent DSP chains in the FPGA. See: http://files.ettus.com/uhd_docs/manual/html/general.html#tuning-notes Also see: http://files.ettus.com/uhd_docs/doxygen/html/structuhd_1_1tune__request__t.html > tune_request (is it a UHD method?) can be reflected in the > gnuradio-companion setting? > Just copy and paste the code I sent you into the center frequency parameter. -josh > 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 >>>> >>> >>> >>> >> > > > _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio