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Phase offset between Tx LO and Rx LO in AD9361 using FMCOMMS3 evaluation board

Question asked by AndresTeleco on Sep 10, 2015
Latest reply on Sep 23, 2015 by tlili



I am performing phase offset measurements between the AD9361 transmitter and receiver by sending pulses modulated using BPSK symbols, the FMCOMMS3 evaluation board, a loop back cable, and Simulink for pushing data.


The surprise comes when the phase offset does not remain constant between different simulations (it does between different pulses in the same simulation, or if I enable the MCS RF Enable bit). As the conditions that would affect phase such as the Tx and Rx signal path don't change, my only thought is that these phase changes come from phase differences between the Tx LO and the Rx LO.


I would want to know where does this phase offset between the Tx LO and the Rx LO come from. I mean, what makes the VCOs from the PLL synthesizers from Tx and Rx have a different phase if they share the same reference clock.


Thank you in advance,