Liren Large Software Subsidy 10/10.iso/l/l455/8.ddi/SIGNAL.DI$/KRATIO.M

Text File | 1993-03-11 | 639 b | 21 lines

function a = kratio(m)
%KRATIO    Utility function for use with ELLIP.
%    KRATIO is a function used to calculate the zeros of an
%    elliptic filter.  It is used with FMINS to find a
%    parameter m satisfying ellipke(m)/ellipke(1-m) = krat.

global ELLIP_KRAT;
krat = ELLIP_KRAT;
% to ensure we don't call ellipke(1) which is inf on non-ieee machines
% and that we only call with positive m.
m = min(1,max(m,0));
if abs(m) > eps(1) & abs(m)+eps(1) < 1
    k = ellipke([m,1-m]);
    r = k(1)./k(2) - krat;
elseif abs(m) <= eps(1)    % m==0
    r = -krat;
else    % m==1 => r == inf, but can't for non-ieee machines
    r = 1e20;
end
a = abs(r);