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zvcvs parameters for S&H, in ac, implementation

agaurav

Hi,

I want to make an ac model which has got sample and hold (zero-order). I found the block, zvcvs, for that. Can somebody suggest the suitable parameters' values to implement that.

I tried Polynomial argument = z or inversez

S to Z Transformation = default (I assume it means none)

Specification type = polynomial

And then I tried various polynomails (order 1 or 2) to get sample-and-hold fft output for a simple wideband spectrum signal-input but seems I am doing something somewhere wrong. I am not very good at digital and z and bilinear transforms, so I think the capability is there but somehow I am not able to implement it using zvcvs. Can somebody please help me with it - implementing sample and zero-order hold using zvcvs. 

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  • Andrew Beckett

    You can do an implementation of 1/(1-z^-1) by using:

    //
    vsin (samp 0) vsource type=sine ampl=1 freq=20k
    r1 (samp 0) resistor r=1k
    sh (hold 0 samp 0) zvcvs ts=1u numer=[1] denom=[1 -1]
    r2 (hold 0) resistor r=1k

    tran tran stop=3/20k

    For example. Note that you can't simulate this in an "ac" analysis - this doesn't make any sense. And you can't simulate this with pss/pac (which might make some sense because it has a periodic operating point) because the z-domain controlled sources are not supported in the Shooting Newton method because they have "hidden states". It's not clear to me if that's what you wanted anyway...

    Andrew.

Reply
  • Andrew Beckett

    You can do an implementation of 1/(1-z^-1) by using:

    //
    vsin (samp 0) vsource type=sine ampl=1 freq=20k
    r1 (samp 0) resistor r=1k
    sh (hold 0 samp 0) zvcvs ts=1u numer=[1] denom=[1 -1]
    r2 (hold 0) resistor r=1k

    tran tran stop=3/20k

    For example. Note that you can't simulate this in an "ac" analysis - this doesn't make any sense. And you can't simulate this with pss/pac (which might make some sense because it has a periodic operating point) because the z-domain controlled sources are not supported in the Shooting Newton method because they have "hidden states". It's not clear to me if that's what you wanted anyway...

    Andrew.

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