Quesetion about HMC681A

Hello professor,

    In the datasheet of HMC681A, there is an index of relative phase vs frequency. Could you please explain, what relative phase is, for me? And the datasheet just list the applications of 50 to 350MHz tuning and 350 to 1000MHz.

If the signal I used is lower than 50MHz, what about the performance of HMC681A, especially its impact on the signal phase? If you can recommend other chips whose  impact on the signal phase relatively small, it would be great.

    Thanks for answering. 

  • 0
    •  Analog Employees 
    on Jul 31, 2017 12:58 PM


    At 0 dB phase shift setting, the part will have some phase error, which means the phase shift value will be something closer to zero degrees but not exactly zero. What is meant by relative phase is that the phase error at 0 degree setting is assumed to be zero to show the phase difference of other phase states wrt. zero degrees phase shift.

    At frequencies below 50 MHz, phase error will increase. This behavior can be improved by increasing the RF choke and DC block values, but there will still be some degradation below 50 MHz.