differential interference analysis using HMC 702 and HMC 584


I am conducting differential interference analysis using HMC 702 and HMC 584, but there is a problem.
The sign of the phase is changed by turning on / off the power supply.
My question is
· Which code of the phase is decided is PLL IC or VCO?
· Is it possible to control the sign of the initial phase and phase (Θ or - θ) when the PLL is locked?
· If possible, is it possible by register manipulation or does it require external circuitry?
Waiting for your answer.

Best regerds.

  • 0
    •  Analog Employees 
    on May 4, 2017 8:19 PM over 3 years ago

    For fractional operation the output phase of the HMC702 is controlled by the delta sigma modulator seed (Reg 0x11) however there will always be a 180 degree phase ambiguity after power-on due to the divide-by 2 in the HMC702 RF input. 

    • turn on autoseed (Reg 0x12[7]=1) to insure the seed gets loaded on frequency changes.
    • synchronize LE with the reference clock to insure the seed gets loaded at the same time wrt the reference
    • after power-on write the same value to the fractional register (Reg 0x10) twice.  The first write locks the PLL on frequency and the second write sets the phase as specified by the seed value +-180 degrees.  
  • Dear dyoung1

    Thank you for your reply.

    Immediately , I will go through what I taught.

    I will contact you again after the test is over.

    Thank you very much !

    Best Regards.