HMC767/HMC361 Deadband

I am using the HMC767 evaluation board connected to the HMC361 frequency divider evaluation board. The HMC767 seems to be working fine by itself but when connected to the HMC361 I see a dead band between 4.2GHz and 4.35GHz. Outside these frequencies the signal is perfectly fine. I increased the 5V a bit up to 5.3V and the band narrowed to 4.23-4.3GHz. Any help?

Thanks,

  • 0
    •  Analog Employees 
    on Nov 1, 2017 5:06 PM

    Hi there,

    The HMC767 is specified for operation between 8.45GHz and 9.55GHz. I'm assuming the "dead band" frequencies you mention are with respect to the output of the HMC361 which would put 4.2GHz (8.4GHz at input of HMC767) just outside of the specification for what it's worth. You are operating very close to the max input drive level of the HMC361 so you might consider adding a small resistive attenuator but in general I wouldn't expect any of these items to be a problem.

    I believe the problem may be tied to the high sub-harmonic level of the VCO which occurs at the same frequency that you're dividing down to. Please see attached.

    If you really need the phase noise performance, you might consider using the HMC703 PLL and HMC510 VCO to achieve similar performance but this would allow you to couple off the RFout / 2 port on the HMC510 instead of using a divider on the output of the HMC767. An added benefit would be the improved integer boundary spur performance of your synthesizer. The ADF5355 or ADF5356 integrated PLL synthesizers could also work if the noise performance will work for your application.

    Best Regards,

    Marty

  • Hi Marty,

    Thank you for the response. Initially we adjusted voltages to both the divider and PLL and the problem seemed to have subsided. But now the problem is manifesting itself again. So I am taking a second look at your response. Do you think the ~8.6GHz sub harmonic at ~4.3GHz of the HMC767 is cancelling out the divider output at an specific band? I don't see any attachment that you referred to.

    As for the parts you suggested, the HMC703 evaluation board uses the HMC508, so you are suggesting a similar approach but with the HMC510, right? Will I still get 4.2GHz to 4.4GHz at the output with this setup. This is the range I am looking for.

    Thank you,