afdqk.m

AFD - Advanced Filter Design using MATLABMiroslav D. Lutovac, Dejan V. Tosicversion 1.00 released 15

function q = afdqk(k)

% afdqk.m  AFD auxiliary function q(k)
%
% 2:20  15/2/99
%
%   Authors: Dejan V. Tosic, Miroslav D. Lutovac, 1999.02.08
%                 [e-mail]
%                 [e-mail]
%
%   Copyright (c) 1999 by Tosic & Lutovac
%   $Revision: 1.0 $  $Date: 1999/02/08 03:07:42 $
%
%   References:
%        Miroslav D. Lutovac, Dejan V. Tosic, Brian L. Evans
%           Advanced Filter Design for Signal Processing
%                   Using MATLAB and Mathematica

 e = [1,5, 9, 13,  17,   21,    25,     29,      33,       37];
 c = [1,2,15,150,1707,20910,268616,3567400,48555069,673458874];

if k <= 1/sqrt(2)
   t = (1/2)*(1 - (1-k^2)^(1/4))/(1 + (1-k^2)^(1/4));
else
   t = (1/2)*(1 - sqrt(k))/(1 + sqrt(k));
end

s = sum(c.*( (ones(size(e))*t).^e));

if k <= 1/sqrt(2)
   q = s;
else
   q = exp(pi^2/log(s));
end