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// Scilab ( http://www.scilab.org/ ) - This file is part of Scilab
// Copyright (C) INRIA - F.D
// Copyright (C) INRIA - 1996 - C. Bunks
//
// This file must be used under the terms of the CeCILL.
// This source file is licensed as described in the file COPYING, which
// you should have received as part of this distribution. The terms
// are also available at
// http://www.cecill.info/licences/Licence_CeCILL_V2.1-en.txt
function [pols,gain]=zpbutt(n,omegac)
//<pols,gain>=zpbutt(n,omegac)
//Computes the poles of a Butterworth analog
//filter of order n and cutoff frequency omegac
//transfer function H(s) is calculated by
// H(s) = gain/real(poly(pols,'s'))
// n :Filter order
// omegac :Cut-off frequency in Hertz rd/s
// pols :Resulting poles of filter
// gain :Resulting gain of filter
//
//!
angles=ones(1,n)*(%pi/2+%pi/(2*n))+(0:n-1)*%pi/n;
pols=omegac*exp(%i*angles);
gain=abs((-omegac)^n);
endfunction
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