Hi Marcus, > Von: "Marcus D. Leech" <patchvonbr...@gmail.com> > > On 12/09/2019 03:11 PM, Lukas Haase wrote: > > > > No, I only have one RX channel at the moment. > > --> One TX @ f and one RX @ 2f. > > The phase relation between this TX+RX should stay constant/coherent once > > both TX+RX tune to a different f and back. > > > > Let me know if the setup is clear, otherwise I'll try to draw a block > > diagram/equations or I can also send the GRC screenshots. > > > > Thanks, > > Luke > > > > > You code shows two RX channels: > > now = self.uhd_usrp_sink_0.get_time_now() > self.uhd_usrp_sink_0.set_command_time(now + uhd.time_spec(1)) > self.uhd_usrp_source_0.set_command_time(now + uhd.time_spec(1)) > > self.uhd_usrp_source_0.set_center_freq(2*self.fcenter, 0) > self.uhd_usrp_source_0.set_center_freq(2*self.fcenter, 1) > self.uhd_usrp_sink_0.set_center_freq(self.fcenter, 0) > > self.uhd_usrp_source_0.clear_command_time() > self.uhd_usrp_sink_0.clear_command_time()
Sorry for the confusion. You are right, there are 2 RX channels but I only use one of them. > So, you're measuring the phase-offset between the TX side and the RX > side at the 2nd harmonic, and expecting that phase relationship to be > the same across re-tunes? Yes, this is exactly what I want. > I'm not sure that's possible. Why not? Conceptually it must be possible: The phase offset is only defined by the *relative* phase between RX/TX-LO. Let's assume that both RX + TX mixer are driven by the *same* LO but the RX side has an additional frequency doubler. Then the phase relationship is ALWAYS constant. By construction. The USRP just makes things complicated because RX and TX are driven by different PLLs and allow their LO to be retuned separately. But ultimately both PLLs are driven by the same reference (to which phase they lock) so there must be a way to have a constant phase relationship. Thanks, Luke _______________________________________________ USRP-users mailing list USRP-users@lists.ettus.com http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
