afdqx.m

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

function Rx = afdqx(c)

% afdqx.m  AFD auxiliary function qx(c)
%
% 2:33  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, afdl.m

global AFD_n_x_Ks_Kp;
nxkskp = AFD_n_x_Ks_Kp;
n  = nxkskp(1);
xs = nxkskp(2);
Ks = nxkskp(3);
Kp = nxkskp(4);

a=xs+c(1)^2;
y=1+c(2)^2;

X = zeros(1,n);
for i =1:n
  X(i) = ellipj( ((2*i-1)/n + 1)*ellipke(1/a^2), 1/a^2);
end

X = afdxna(n,a);
L = afdl(n,a);
e = 1/sqrt(L);

x = y;
r = 1; R = 1;
if abs(n-2*fix(n/2)) == 0
  for i=1:n/2
    r = r * ((1 - X(i)^2))/((1 - a^2/X(i)^2));
    R = R * ((x^2 - X(i)^2))/((x^2 - a^2/X(i)^2));
  end
else
  for i=1:(n-1)/2
    r = r * ((1 - X(i)^2))/((1 - a^2/X(i)^2));
    R = R * ((x^2 - X(i)^2))/((x^2 - a^2/X(i)^2));
  end
    R = x*R;
end
R1 = R/r;

x = y*xs;
r = 1; R = 1;
if abs(n-2*fix(n/2)) == 0
  for i=1:n/2
    r = r * ((1 - X(i)^2))/((1 - a^2/X(i)^2));
    R = R * ((x^2 - X(i)^2))/((x^2 - a^2/X(i)^2));
  end
else
  for i=1:(n-1)/2
    r = r * ((1 - X(i)^2))/((1 - a^2/X(i)^2));
    R = R * ((x^2 - X(i)^2))/((x^2 - a^2/X(i)^2));
  end
    R = x * R;
end
R2 = R/r;

Rx = (e*R1/Kp - 1)^2 + (e*R2/Ks - 1)^2;