Marcus, I agree. Is there a way to tune the sideband suppression so that I can attenuate more of the mirrored signal? With the internal lo, everything seems to just work. Are there extra configuration steps that I need to take to adjust for the external lo?
Thanks, Scott On Wed, Nov 2, 2022 at 2:41 PM Marcus D. Leech <patchvonbr...@gmail.com> wrote: > On 02/11/2022 15:27, Kenneth Burchfield wrote: > > Marcus, > > The sidebands do not change with the LO level. > > I am basically running the tx_waveforms example from UHD 4.2.0.0, and I am > adding the argument tx_lo_source=external. Attached is a picture of the > spectrum. I am generating a SINE with wave-freq input 2e6. The center spike > is some LO leakage. The spike at -2e6 is the mirroring I am seeing. > > Thanks, > Scott > > The LO suppression looks to be about 55dBc, which is not horrific. > > The sideband suppression appears to be only about 30dBc, which is not very > good. > > > > On 02/11/2022 12:09, Scott Burchfield wrote: > > Hi, > > > Are there any updates on this problem. I normally try not to reply to old > threads, but I am seeing the same the same spectral mirroring Rob described > earlier. My setup is also the same as Rob’s.I have tracked some newer > threads that mentioned disabling TX_QEC_INIT, but I am still seeing the > mirroring after disabling QEC. > > https://www.mail-archive.com/usrp-users@lists.ettus.com/msg07489.html > > Thanks, > > Scott > > > It seems to me that if you use an external LO, that LO has to go through the > phase-splitter on the mixer, and that phase-split is subject to errors, > so turning off QEC may not be that desirable--although I think the mixer > on the N310 (using an AD9371) > > is a 2XLO, so the phase error should be very very small. > > Do the unwanted sidebands change with LO level? > > >
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