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MathGroup Archive 2000

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Re: Re: Harmonic Analysis

  • To: mathgroup at smc.vnet.net
  • Subject: [mg25626] Re: [mg25601] Re: [mg25591] Harmonic Analysis
  • From: Roberto Brambilla <rlbrambilla at cesi.it>
  • Date: Mon, 16 Oct 2000 03:04:46 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

My idea is to use Coefficient : given

 expr = a00 + a10 f[t] + a01 g[t] + a11 f[t] g[t]+
        a20 f[t]^2 + a21 f[t]^2 g[t] //Expand;
 f[t] = f1 Exp[+j w t] + f1Star  Exp[-j w t]
 g[t] = g1 Exp[+j w t] + g1Star  Exp[-j w t]

I extract exponential coefficient in this way :
(n=-3,-2,-1,1,2,3)

In[..]    n=1; Coefficient[expr, Exp[n j w t]]
Out[..]   a10 f1 + a01 g1 + 2 a21 f1 f1Star g1 + a21 f1^2 g1Star

In[..]    n=-2; Coefficient[expr, Exp[n j w t]]
Out[..]   a20 f1Star^2 + a11 f1Star g1Star

Unfortunately it does not work for n=0

Bye, Rob
Roberto Brambilla
CESI
Via Rubattino 54
20134 Milano
tel +39.2.2125.5875
fax +39.2.2125.610
rlbrambilla at cesi.it



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