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HMC566LP4E K-Factor

Category: Hardware
Product Number: HMC566LP4E


I downloaded the S2P parameter for HMC566LP4E and it seems that the amplifier is not very stable at high frequency.

In fact, K<1 when frequency is higher than 38.5 GHz.

I tried to test a circuit with HMC566LP4E followed by a QAT-3+ (3dB attenuator) and HMC1065LP4E.

I get a self-oscillation at 38.5 GHz as well, with the same amplitude and frequency even if I disable the HMC1065LP4E.

This self-oscillation also doesn't change if I install a bandpass filter before HMC566LP4E.


Do you have any workaround for this?

Thank you

Best regards


Parents Reply
  • Hello Eamon,

    thank you for the reply.

    Yes I'll probably use ADL8142 in future, that seems far superior.

    But know I've to fix this, so I don't need to trash three boards and the rest of precious components. Disappointed

    The only difference with the EVB is that I didn't use coplanar traces, but simple microstrips. This shouldn't make so much difference since in 10mil RO4350 the main propagation mode is microstrip either way. But the S2P parameters are from official EVK, so that remains a general point of instability for everyone.

  • Hi Partech,

                       The S-Parameter file on the web has the board de-embedded. S-Parameters of the part without de-embedding evaluation board show the part as stable.

    Th red trace is the web file and blue trace is the part mounted on the evaluation board.

    I think the board really needs to be Grounded Coplanar Waveguide at these frequencies.


    Jim B

  • Hello Jim,

    Thank you very much for the clarification.

    Yes, this basically confirms that the chip itself is prone to instability @39GHz and requires careful trace design. I think that this should be noted in next datasheet rev, since the current version specify the impedance only and the graphs are limited to 38GHz.

    Thank you

    Best regards