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Regarding SP simulation for phase shifter (phase interpolator)

Jay815
Dear all,

I would like to ask a question about S-Parameter (SP) simulation for phase shifter (phase interpolator) design. I am designing a 10GHz phase shifter using I/Q interpolation (so called, Cartesian phase shifter or phase rotator). In order to see the phase shift, I ran a transient simulation and it worked as expected.

However, when I ran a SP simulation, here is some simulation information,

  1. There are two phase shifters: One’s output is reference and the other’s output is phase shifted.
  2. The input port (port#1) generates an I signal, and the output ports (port#2 and port#3) are connected to output LC loads of two phase shifters. (Of course, I have one more input port for Q signal generation)
  3. In order to see the phase difference of two phase shifter outputs, I checked the phases of S21 and S31. However, the phase difference between S21 and S31 is almost zero, which is not what I expected.

Hence, I am wondering if I cannot see the phase difference of the phase interpolation circuit with SP simulation or not. If it is possible, I am wondering what I did wrong.

For your information, when I designed a LC passive phase shifter, a SP simulation in the same manner worked fine.

Could you please advise?

Thank you so much!

Regards,

Jay
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  • Jay,

    I don't think there's any way to specify a phase shift on a port for s-parameter analysis. The only parameters on the port you have to control the phase are the phase parameter (which along with the mag parameter specify the size of the AC input - this is only used for ac analysis - there's also pacphase which is used in the pac, hbac and qpac analyses), and the sinephase parameter which is only used in time-varying analyses (e.g. tran).

    So that's why it doesn't work - it's not a bug, but since you're not injecting a signal in sp analysis, I'm not sure it really makes sense.

    Regards,

    Andrew.

Reply

  • Jay,

    I don't think there's any way to specify a phase shift on a port for s-parameter analysis. The only parameters on the port you have to control the phase are the phase parameter (which along with the mag parameter specify the size of the AC input - this is only used for ac analysis - there's also pacphase which is used in the pac, hbac and qpac analyses), and the sinephase parameter which is only used in time-varying analyses (e.g. tran).

    So that's why it doesn't work - it's not a bug, but since you're not injecting a signal in sp analysis, I'm not sure it really makes sense.

    Regards,

    Andrew.

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