PLL ADF5610 Phase Noise query

Hi,

In ADF5610 PLL datasheet phase noise graph showing -104dBc/Hz at 10kHz offset for output freq 14.4GHz but in marker same data was measured as -107dBc/Hz.

So I simulated it using ADISIMPLL tool, here it was showing -99dBc/Hz for 14.4GHz at 10KHz offset. I attached simulation file also.

Kindly clarify which one is correct.

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  • This phase noise is within the loop BW. Do you have the same conditions in the simulation? It means f.PFD=100MHz generated by Wenzel XO. But acc. my experience variation few dB is OK. 

  • +1
    •  Analog Employees 
    on Jul 20, 2020 12:41 PM 7 months ago in reply to Pathu

    Hi,

    The phase noise plot in the datasheet is correct but the values in markers are not. Attached is the original measurement result at 14.4 GHz in which Wenzel OCXO is used as reference. I also attached measurements for 14.4 GHz and 8 GHz in which SMA100B is used as reference. Loop filter is same for all cases and it is also attached. 

    These references have very good phase noise and the ADISIMPLL results may not show such results if the reference is not good enough but it is the correct way to model your reference clock and to use that one in the ADISIMPLL simulation to get results similar with the actual design.

    Regards,

     Original Measurement

     SMA100B Measurement

     SMA100B Measurement

    Kudret

  • We have tested your ADF5610 eval-board using external low phase noise OCXO and observe similar phase noise for Integer mode.

    Whereas when we test using frcational mode like frequencies 13.45GHz, 14.41GHz then output spectrum also looks have more spurious and Phase noise is degraded by around 10dBc at 1, 10 & 100KHz Offsets.

    Can you please check in your test setup and provide phase noise plots like fractional output frequencies 13.45, 14.41GHz using 100MHz Wenzel OCXO?

  •        Hi,

    We tested ADF5610 evaluation board using external low phase noise OCXO and we observed spurious frequencies around 10KHz. I attached the test results & settings done in GUI.

    External Reference: 120MHz,

    RF Output frequency: 13.58GHz

    There is no spur in the phase noise graph provided by you in above reply..

    So We gave External reference (100MHz, 80MHz, & 50MHz) using signal generator and observed more variations in the spurious frequencies while varying external reference (R divider kept constantly =1). I also attached some results.

    Please suggest any method to reduce these spurs.Quote