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HMC833 High Phase Noise

Question asked by katsu on Jul 8, 2016
Latest reply on Aug 16, 2016 by katsu

Hi,
My customer is seeing high phase noise by HMC833 EVB. Could you please provide any suggestion to register setting?

 

Condition: Reference = 10MHz, PFD = 10MHz, Fractional mode, Output Frequency = 1675MHz

 

Please look into the attachments for detail:
     HMC833_Frac_test_E.txt: Register setting
     1675MHz.PNG: Capture of narrow band phase noise
     HMC833_GUI_REG.pdf: Capture of GUI, capture of wide band phase noise

 

Because default loop filter on EVB is used , Loop BW is 74kHz. Phase Noise characteristic should be similar to "fout 1605MHz, Loop BW 74KHz,rms jitter 130fsec" plot of Figure2 in datasheet.
Comparing measured and Fig.2,
~-85dBc/Hz vs. ~-110dBc/Hz at 100kHz offset,
~-103dBc/hz vs. ~-155dBc/Hz at 5MHz offset

So the customer is seeing much higher phase noise and considering that some of register setting is not appropriate.
Vtune voltage is at 2.2V to 2.3V, so VCO auto cal seems to work correctly.

Please suggest better setting.

 

Best Regards,

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