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Re: bode diagram


On May 11, 2005, at 5:26 AM, GaLoIs wrote:

> hi, like plotting simple bode diagrams of systems. could you give  
> me some
> information about it? i can do it with another program, but i'd  
> like to see
> how mathematica works
> thank you
>

Hello,

Here's some simple code for making a Bode plot:

gain[p_, q_, \[Omega]_] := q/Sqrt[p^2*\[Omega]^2 + (q - \[Omega]^2)^2];

\[Phi][p_, q_, \[Omega]_] :=
   ArcCos[(q - \[Omega]^2)/Sqrt[p^2*\[Omega]^2 + (q - \[Omega]^2)^2]];

gainplot[p_, q_]:= Plot[20 Log[10, gain[p,q,10^x]], {x,-1,1},  
PlotRange->All,
     AxesLabel -> {"\!\(log\_10\)\[Omega]", "Gain (dB)"}];

angleplot[p_, q_] := Plot[\[Phi][p, q, 10^x]/Degree, {x,-1,1},  
PlotRange->All,
     AxesLabel -> {"\!\(log\_10\)\[Omega]", "Phase Angle (deg)"},
     Ticks -> {Automatic, 30 Range[1, 6]}];

<< "Graphics`Graphics`"

BodePlot[p_, q_] := DisplayTogetherArray[{gainplot[p, q], angleplot 
[p, q]},
    PlotLabel->"Bode Plot  ( p="<>ToString[p]<>", q="<>ToString[q] 
<>" )",
    Frame-> True, ImageSize -> 500];

BodePlot[.5, 5]

(See http://library.wolfram.com/infocenter/Books/4855/)

Regards,

Selwyn Hollis
www.appliedsymbols.com
www.math.armstrong.edu/faculty/hollis


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