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Harmonic Balance simulators and Spice models??

Discussion in 'CAD' started by billcalley, Jun 29, 2005.

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  1. billcalley

    billcalley Guest

    In looking at MWO and ADS, it seems to me that most of the nonlinear
    transistor models in their libraries are simply Spice models (either as
    ..model or .subckt files). Is this pretty much all harmonic balance
    simulators use; or are there actually some true HB transistor models
    out there?

    Thank You,

  2. What would you expect to be in a 'true HB transistor model' that is
    not also accessible from the code comprising a full spice model?

  3. billcalley

    billcalley Guest

    Yet I always hear how inaccurate Spice models are at microwave
    frequencies; so I guess I just assumed there were actually HB models
    out there so as to more accurately take into account all of the high
    frequency effects of an active device...


  4. Steve

    Steve Guest

    There's some interesting stuff (research) going on with nonlinear
    black-box models, but basically if you want a nonlinear time or
    frequency-domain model, you're going to be using a spice-like model.
    In the frequency domain case the HB simulators just fft and ifft, but
    the equations are often those used in spice.

    This isn't all that bad... For instance, some work under Prof. Mayaram
    at Oregon State showed that the BSIM3 model works pretty good, with
    some extra parasitics, into multiple GHz. There are a number of 'high
    frequency' device models that are basically low-frequency spice models
    with extra parasitics which become important as the frequency rises.

    As far as "true HB transistor models" -- what would that look like?
    Most high frequency models are lumped approximations for the passive
    stuff and spice-like nonlinear models with (apparently kluged-up)
    parasitics added that kinda make the frequency response go the right

    If the spice models are bad... -- I've always wondered how anything
    worked even semi-efficiently before HB. Dropping nonlinear devices
    into a microwave network and modeling it using linear models... ugh.
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