dfdl.m

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

function L = dfdl(n,a)

% dfdl.m  dfd L(n,a)
%
%   Authors: Dejan V. Tosic, Miroslav D. Lutovac, 1999.03.08
%                 [e-mail]
%                 [e-mail]
%
%   Copyright (c) 1999 by Tosic & Lutovac
%   $Revision: 1.0 $  $Date: 1999/03/08 03:07:42 $
%
%   References:
%        Miroslav D. Lutovac, Dejan V. Tosic, Brian L. Evans
%           Advanced Filter Design for Signal Processing
%                   Using MATLAB and Mathematica

%  calls:
%% dfdxna.m, 

X = dfdxna(n,a);

if abs(n-2*fix(n/2)) == 0
  L = (1/a^n);
  for i=1:n/2
    L = L * ((a^2 - X(i)^2)^2)/((1 - X(i)^2)^2);
  end
else
  L = (1/a^(n-2));
  for i=1:(n-1)/2
    L =L * ((a^2 - X(i)^2)^2) /((1 - X(i)^2)^2);
  end
end