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// Copyright (C) 2018 - IIT Bombay - FOSSEE
//
// 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-en.txt
// Author:Sonu Sharma, RGIT Mumbai
// Organization: FOSSEE, IIT Bombay
// Email: toolbox@scilab.in
function [z, p, g] = ellipap (n, Rp, Rs)
//Produces a lowpass analog prototype elliptic filter.
//Calling Sequence
//[z, p, g] = ellipap (n, Rp, Rs)
//Parameters
//n: Filter Order
//Rp: Peak-to-peak passband ripple (in dB)
//Rs: Stopband attenuation (in dB)
//Description
//It gives a lowpass analog elliptic prototype filter of nth order, with a Peak-to-peak passband ripple of Rp dB and a stopband attenuation of Rs dB.
//Examples
//[z, p, g] = ellipap (4, 3,10)
//Output :
// g =
//
// 0.3162
// p =
//
// - 0.2071 - 0.8587i
// - 0.0042 - 0.9990i
// - 0.2071 + 0.8587i
// - 0.0042 + 0.9990i
// z =
//
// - 1.3121i
// - 1.0063i
// 1.3121i
// 1.0063i
funcprot(0);
lhs = argn(1)
rhs = argn(2)
if (rhs < 3 | rhs > 3)
error("Wrong number of input arguments.")
end
Rpf = 10 ^ (-Rp/20); //passband pick to pick ripple in fraction
rp = 1 - Rpf ; //analpf function compitable passband ripple (delta-p)
Rsf = 10 ^ (-Rs/20); //stop band pick to pick ripple in fraction
rs = Rsf ; //analpf function compitable stop band ripple (delta-s)
[hs,p,z,g]=analpf(n,"ellip",[rp rs],1); //cutoff frequency of 1 rad/sec for prototype filter
p = p' ;
z = z' ;
g = abs(g);
endfunction
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