afdhp.m

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

function [numH,denH] = afdhp(n,a,e)

% afdhp.m  AFD normalized lowpass elliptic transfer function
%          Hcal(n,ksi,epsilon) numerator and denominator polynomials
%
% 2:29  16/2/99
%
%   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

%  calls:
%% afdxna.m, afdsnaei.m

X = afdxna(n,a);
nX = length(X);
for ind = 1:nX
 S(ind) = afdsnaei(n,a,e,ind);
end

g = 1;
numH = 1;
denH = 1;
if abs(n-2*fix(n/2)) == 0
  for i=1:n/2
    g = g * ( abs(S(i))^2 ) / ( a^2 / (X(i))^2);
    numH = conv(numH, [1   0           a^2/(X(i))^2]);
    denH = conv(denH, [1 -2*real(S(i)) abs(S(i))^2]);
  end
    g = g / sqrt(1+e^2);
else
  for i=1:(n-1)/2
    g = g * ( abs(S(i))^2 ) / ( a^2 / (X(i))^2);
    numH = conv(numH, [1   0           a^2/(X(i))^2]);
    denH = conv(denH, [1 -2*real(S(i)) abs(S(i))^2]);
  end
    g = - g * S((n+1)/2);
    denH = conv(denH, [1 -S((n+1)/2)]);
end
numH = g*numH;