Hi, is the device configured correctly? External and QEC don't work together:
Apparently it is linked to the quadrature error correction (QEC) and can be solved turning off this calibration. This can be done by setting init_cals=BASIC, where you can add the relevant calibrations but avoid RX_QEC_INIT, see https://files.ettus.com/manual/page_usrp_n3xx.html#n3xx_mg_calibrations. Robert From: USRP-users [mailto:usrp-users-boun...@lists.ettus.com] On Behalf Of Marcus D. Leech via USRP-users Sent: Tuesday, September 24, 2019 4:23 AM To: usrp-users@lists.ettus.com Subject: Re: [USRP-users] USRP N310 Phase Bouncing Issue On 09/23/2019 10:12 PM, Austin Adam via USRP-users wrote: Hi USRP Users, Currently we are taking a signal from a signal generator, splitting it four ways, and connecting it to the receiving ports of the USRP N310. We are using a USRP N210 as an external local oscillator (splitting the output into the RX LO ports on the N310) to help synchronize the four signals. During first observation, using GNU Radio, we noticed that the four signals display about a 180 degree phase shift between the daughter boards, as stated online within the getting started manual of the N310. We expected to see this 180 degrees phase shift however, we are unexpectedly noticing a bouncing of phase shift during our simulations. This can be seen in the video attached. We thought the cause of this was because of insufficient power being input into the external LO (+3dBm-6dBm) however increasing the power to satisfy this, did not solve the problem. Are we correct to assume that there should be an initial 180 degree phase discrepancy that can be fixed using GNU? Or is this bouncing in phase a normal occurrence when using an N210 to drive the external LO? The PPS an MIMO cables are not currently connected. Thank you for any responses! ~Austin [Image removed by sender.] Gain30.75.webm<https://drive.google.com/file/d/1pVEcmdE--pvkEy_6eWWNzWQHlYk1CyUI/view?usp=drive_web>[Image removed by sender.] _______________________________________________ USRP-users mailing list USRP-users@lists.ettus.com<mailto:USRP-users@lists.ettus.com> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com Are you operating very close to DC in the baseband? (That is, the LO is very close to the received signal). You could just be seeing the dynamic nature of DC offset removal. The movie won't play for me (probably my fault), so I'm just guessing here. You'll likely see some aggregate phase noise that is the sum of the phase-noise of the LO splitting electronics, and the phase-noise of the RF channels and mixing, etc. What is the magnitude of the phase noise (after you've accounted for the 180deg phase ambiguity due to the 2XLO scheme).
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