4 Replies Latest reply on Apr 14, 2011 12:47 PM by stevenwi

    characteristics of a good s-parameter model


      I'm reading the Mentor Help data on s-parameters and have a couple of questions. There is a help topic that describes the characteristics of a good s-parameter model. One of the characteristics is that model dependencies display proper asymptotic behavior at zero and infinite frequency. The explanation as to why is either not explained very well or else I'm just missing it.

      Here is my attempt to explain it to myself. Am I way off?

      - A passive system model dependency would be suspect if it showed resonances at low frequency to DC.  This is because the impact of the system to any input at very low frequency will be dominated by its resistive characteristics, and not its capacitive or inductive loading(purely real). 

      - Secondly I think the corollary requirement at high frequency is just to ensure that the model completely characterizes the system by capturing all relevant resonances at the high end. (Unfortunately I cannot seem to get hyperlynx to create an s-parameter model that behaves asymptotically at high frequency)


      Lastly there is another characteristic Mentor provides for a good model, and it is that a good model should display proper even and odd behavior. I think this is related to the asymptotic behavior at DC, but it is listed as a separate characteristic. Basically it just means that the real part of the response curve must be flat and the imaginary part must be zero. Can anyone explain why, perhaps qualitatively?