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Operating HMC507 Below Spec 6.65GHz

I am looking to buy a VCO that is stable between 6.5 and 7.0 GHz. I was looking at the HMC507 and the associated eval kit 110227-HMC507LP5 which shows a tuning of 6.65 to 7.65 GHz; but the datasheet has a plot showing tuning below 6.65 GHz. Will this VCO work and be stable at 6.5 GHz? And, if not, do you have any other recommendations?

Thanks in advance for your help!

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  • Hi there,

    I don't recommend you use the HMC VCO products outside of their specified frequency range.  Additionally, use of an active loop filter with the GaAs VCO's is always recommended despite datasheet indications that show typical operation falls below 5V for the frequency band of interest. The following reasons offer an explanation:

    1) Datasheet specifications per the table are typically restricted to 25°C and generally only include frequency, tune voltage, power and current. Temperature performance is included for information only and is 'typical' so not guaranteed.  

    2) Due to process variation there's no guarantee that all product received will allow operation at your "out of band" frequency, especially once you include the effects of power supply and temperature variation.

    3) Tuning sensitivity (Kv) particularly on these GaAs devices, increases quite rapidly below 2V; as Kv increases, phase noise typically degrades. In synthesizer applications as the tune voltage drops below 1V the charge pump linearity degrades resulting in increased spurs. Furthermore, the increase in the ratio between the max / min tuning sensitivity makes managing loop bandwidth vs frequency more difficult as Icp must be varied over a greater range. Operation at lower charge pump current levels will degrade the FOM and thus the close in phase noise.

    4) As Vtune increases beyond the upper spec (typically 13V for GaAs) the tuning sensitivity continues to drop resulting in less available tune voltage particularly over temperature. This implies that it may not be possible to achieve the necessary tune voltage over temperature. In synthesizer applications this will result in loss of lock over temperature.

    Although the  phase noise isn't quite as good I would recommend use of the RFout / 2 port on the HMC1169 or use of the ADF5355 or ADF5356 integrated VCO / PLL synthesizer.

    Best Regards,

    Marty

Reply
  • Hi there,

    I don't recommend you use the HMC VCO products outside of their specified frequency range.  Additionally, use of an active loop filter with the GaAs VCO's is always recommended despite datasheet indications that show typical operation falls below 5V for the frequency band of interest. The following reasons offer an explanation:

    1) Datasheet specifications per the table are typically restricted to 25°C and generally only include frequency, tune voltage, power and current. Temperature performance is included for information only and is 'typical' so not guaranteed.  

    2) Due to process variation there's no guarantee that all product received will allow operation at your "out of band" frequency, especially once you include the effects of power supply and temperature variation.

    3) Tuning sensitivity (Kv) particularly on these GaAs devices, increases quite rapidly below 2V; as Kv increases, phase noise typically degrades. In synthesizer applications as the tune voltage drops below 1V the charge pump linearity degrades resulting in increased spurs. Furthermore, the increase in the ratio between the max / min tuning sensitivity makes managing loop bandwidth vs frequency more difficult as Icp must be varied over a greater range. Operation at lower charge pump current levels will degrade the FOM and thus the close in phase noise.

    4) As Vtune increases beyond the upper spec (typically 13V for GaAs) the tuning sensitivity continues to drop resulting in less available tune voltage particularly over temperature. This implies that it may not be possible to achieve the necessary tune voltage over temperature. In synthesizer applications this will result in loss of lock over temperature.

    Although the  phase noise isn't quite as good I would recommend use of the RFout / 2 port on the HMC1169 or use of the ADF5355 or ADF5356 integrated VCO / PLL synthesizer.

    Best Regards,

    Marty

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