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LMX2615EVM-CVAL: LMX2615EVM-CVAL Phase Noise Measurements

Part Number: LMX2615EVM-CVAL

Good afternoon,

I'm measuring a fair amount of additional phase noise than I would expect when taking a phase noise measurement on a set LMX2615EVM-CVAL output.

I'm trying to replicate the phase noise measurement shown in the user-guide for the eval board in order to establish a baseline of performance.  My results are consistently about 10 - 14 dB higher between the offset frequencies 100 Hz to 100 kHz.  I have verified that my reference source is a 'clean' enough signal and that it's phase noise should not be contributing significantly to the LMX's.  This could easily be mistake I made in the test setup, but I wanted to rule out how I'm using the LMX via TICS Pro first.

I've included my settings for the LMX below and my own measurements in comparison to the ones provided in the datasheet fore an output of 7 GHz.

Thanks for the help,

Nolan

Measured P.N. - 7 GHz Datasheet P.N. - 7 GHz
Hz Y (dB/Hz) Y (dB/Hz)
100 -77.276 -90.9724
1.00E+03 -88.097 -103.8399
1.00E+04 -95.856 -111.5424
1.00E+05 -99.589 -115.3219
1.00E+06 -118.041 -121.9025
1.00E+07 -144.708 -146.3792
1.00E+08 -148.556

(FCAL_EN was set to 1 prior to measurement)

  • Hi Nolan,

    Do you have the phase noise of your reference clock?

  • Hi Noel,

    Copied the results below.  I understand the Wenzel probably provides a reference, but I thought the measurements shouldn't be contributing too much to the overall phase noise measured on the output?

    Thanks for the help!

    -Nolan

    Offset Hz Y (dB/Hz)
    100 -103.632
    1.00E+03 -115.12
    1.00E+04 -118.137
    1.00E+05 -124.124
    1.00E+06 -142.453
    1.00E+07 -144.707
    1.00E+08 -145.993
  • Hi Nolan,

    If I use your reference clock to do a simulation, I can see that the overall phase noise is dominated by the reference clock.

    FYI, below is the Wenzel clock phase noise.

    100Hz      -128.7
    1kHz        -142.5
    10kHz      -155.6
    100kHz    -166
    1MHz       -170.7
    10MHz     -175.3