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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