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Does TransferFunctionModel have to be finite dimensional? Or can we for example use Mathematica to make a BodePlot of a transfer function that is not in rational pole-zero form?

I understand that Mathematica can deal with delays, but I'm thinking of more general infinite-dimensional transfer functions, for example the Laplace transform of a $\operatorname{sinc}$.

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1 Answer 1

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a short answer

 pars=Rationalize[{L-> 6.9,A->0.0133,a0->410,
       c1a->0.003,c2a->0.002,c1p->-2.5 10^-6,c2p->4.3 10^-6}];

With the transfer function

G[s_]=(a0 c1a (A Cosh[(L s)/a0]+a0 c2p Sinh[(L s)/a0]))/
      (A a0 (-c1p+c2p) Cosh[(L s)/a0]+(A^2-a0^2 c1p c2p) Sinh[(L s)/a0]);

Bodeplot:

Grid[{{LogLogPlot[Evaluate[20Log10[Abs[#]]&/@{G[I 2 Pi f]}/.pars],
   {f,1,200},
   ImageSize->Large,GridLines->Automatic,AspectRatio->1/3,
   PlotRange->Full,Frame->True,PlotLegends->{"|G(s)|"}]},
   {LogLinearPlot[Evaluate[Arg[#]180/Pi&/@{G[I 2 Pi f]}/.pars],
   {f,1,200},ImageSize->Large,ExclusionsStyle->Gray,
   GridLines->Automatic,AspectRatio->1/3,PlotRange->Full,
   Frame->True,PlotLegends->{"arg{G(s)}",""}]}}]

enter image description here

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  • $\begingroup$ Thanks! Unfortunately the "code" mode hides the lines, is there a way of fixing? $\endgroup$
    – Pait
    Nov 14, 2017 at 15:07
  • $\begingroup$ What lines do you mean? $\endgroup$ Nov 14, 2017 at 20:59
  • $\begingroup$ pars=Rationalize[{...; G[s_]=(a0 c1a (A...; and Grid[{{LogLogPlot[E; they get cut when the page wraps. $\endgroup$
    – Pait
    Nov 14, 2017 at 23:07
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    $\begingroup$ You can scroll right. At least I can (in Chrome) $\endgroup$ Nov 15, 2017 at 15:33
  • $\begingroup$ I opened in a different computer and it reads beautifully! (Curious bug in one of my systems, probably I'll never find out what's wrong.) Thanks! $\endgroup$
    – Pait
    Nov 19, 2017 at 14:02

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