On Thu, Jan 26, 2023 at 05:14:34PM -0500, Marcus D. Leech wrote: > On 26/01/2023 16:33, Mark-Jan Bastian wrote: > > Hi, > > > > On page 7 of the UBX-160 schematics > > https://files.ettus.com/schematics/ubx/UBX-160_revE.pdf > > there is a LO filter selection with three paths: > > - 800 MHz-2.2 GHz > > - passthrough (no filter) > > - lowpass 400 MHz..800 MHz > > Next to that, there is also a way to measure the LO on J3. > > > > Question: > > - Is this LO filter automatically selected, and where should I look for the > > rules ? > > - Is there some way to control this LO filter selection via UHD, similar to > > a tune request? > > > > - The IQ mixer ADL5371 documentation warns that the LO's 3rd harmonic > > needs to be well suppressed. Is there benefit to be gained > > by using an external, more filtered LO instead of the on-board UBX-160 LO > > plus its filters ? > > > > Mark-Jan > > _______________________________________________ > > USRP-users mailing list -- usrp-users@lists.ettus.com > > To unsubscribe send an email to usrp-users-le...@lists.ettus.com > Is this a "just curious" type of question, or are you seeing issues that you > believe may be due to the UBX > LO and Mixer architecture?
When generating a complex +74 MHz and -73 MHz sinewave signal and adding them, I see 1 MHz spur about -30 dB @ -74 MHz, irrespective of LO frequency. Thus the spur might caused by (remaining) nonlinearity in the mixer or the subsequent stages. I would like to control the -30 dB spur to a lower value, or at least find out what the source of this spur is. Next thing could be the DAC, which supports rates up to 1600 MSPS, but is only used at 200 MSPS. Perhaps there is a way to modify the waveform in this step, similar in the way digital predistortion can help improve spectral output purity? Mark-Jan _______________________________________________ USRP-users mailing list -- usrp-users@lists.ettus.com To unsubscribe send an email to usrp-users-le...@lists.ettus.com
