ADF41513 (PLL) + HMC8364 HMC

Hello, 

I have recently purchased a HMC8364 VCO and a ADF41513 PLL as it is recommended from Analog Devices.

Additionally, for the PLL the required/suggested evaluation board EV-ADF41513SD1Z is used.I successfully connected the VCO with the PLL and using the evaluation board of the PLL, high quality tones in the operetional ferequency range can be generated.

However after capturing the produced tone with a high spectral resolution ESA we observe tha the signal/tone appears a frequency drift of order of 500-700Hz. The produced tones are not locked in a specific frequency but they drift up and down (in the range of: 500-700Hz)from a center frequency. This frequency drifts apears both when the PLL operates on intenger and on fractional mode.

I wanted to ask if this frequency drift is normal or not. Can I eliminate or reduce this drift?

Can this drift be related to the values we set in the EVALUATION BOARD SOFTWARE of the PLL? or in a specific register?

Thank you in advance, 

Best regards

Nikolaos

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  • +1
    •  Analog Employees 
    on Mar 23, 2021 10:23 AM

    Hi Nikolaos,

    Some frequency drift can be normal dependent on the measurement setup. To try to completely eliminate any drift and get a sub-Hertz accurate measurement you would need to setup the ADF41513 eval board to accept an external REFIN (please see UG-1427 page 5). 

    Then ensure the signal generator supplying REFIN and your spectrum analyser share a ~10MHz sync reference and are configured correctly.

    If you are already using an external REFIN then let me know and I can try to replicate behavior in lab.

    Regards,

    Alex

Reply
  • +1
    •  Analog Employees 
    on Mar 23, 2021 10:23 AM

    Hi Nikolaos,

    Some frequency drift can be normal dependent on the measurement setup. To try to completely eliminate any drift and get a sub-Hertz accurate measurement you would need to setup the ADF41513 eval board to accept an external REFIN (please see UG-1427 page 5). 

    Then ensure the signal generator supplying REFIN and your spectrum analyser share a ~10MHz sync reference and are configured correctly.

    If you are already using an external REFIN then let me know and I can try to replicate behavior in lab.

    Regards,

    Alex

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