On Fri, 26 Aug 2005, sudhindra aithal kota wrote: > Hi, > I am running the usrp_siggen.py program with the > option -m 0x98. The signal transmitted is a SIN wave. > My understanding of this option is, Channel 0's I part > is connected to DAC0 and Channel 0's Q part is > connected to DAC1.
That is correct. > Since for a SIN wave the real part > does not exist, there should not be anything > transmitted via DAC0. Whoa - 'SIN' is just the shape and our signal can have real and imag components. Maybe confusing the real/cosine imag/sin analysis with our real world signal ? In usrp_siggen.py the signal source is complex self.siggen = gr.sig_source_c, and the signal sink is complex self.usrp = usrp_sink_c Actually we were just discussing, due to the digital-upconverters on the 9862 chips, sending a signal to either DAC will result in output from both, even if one channel is all zeros. > Then I connect the TX and RX part of the USRP board > and use the usrp_oscope.py function with the option -m > 0x33333310 to view the signal I have transmitted. This > would mean connect ADC0 to the I part of Interpolator0 > and ADC1 to Q part of Interpolator0. I think you mean digital-downconverter, not Interpolator0, those are in the Tx path - were in the Rx path now. Otherwise yes, ADC0 to the I input of DDC0 and ADC1 to the Q input. Do you have both two cables linking the boards or one? ADC1 gets it's input from J18. > I see 2 signals > with a phase difference of 90. Where is the second > signal coming from, when I am transmitting only one > signal? > the source in usrp_oscope.py is also complex from the usrp u = usrp.source_c and with 1 channel is getting the data from digital-downconverter 0. Interestingly, with these arguments: ./usrp_oscope.py -d 64 -c 1e6 ./usrp_siggen.py -c 1e6 -f 10e3 -i 64 with only one cable from J19 to J48 there's a big 450 unit signal, with another cable from J18 to J49 connected it becomes small with an amplitude of 25 ;) I'm still exploring the possibilities myself. --Chuck _______________________________________________ Discuss-gnuradio mailing list [email protected] http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
