1 /* atlc - arbitrary transmission line calculator, for the analysis of
2 transmission lines are directional couplers.
4 Copyright (C) 2002. Dr. David Kirkby, PhD (G8WRB).
6 This program is free software; you can redistribute it and/or
7 modify it under the terms of the GNU General Public License
8 as published by the Free Software Foundation; either package_version 2
9 of the License, or (at your option) any later package_version.
11 This program is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program; if not, write to the Free Software
18 Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
21 Dr. David Kirkby, e-mail drkirkby at ntlworld.com
25 /* The following calculates the odd and even mode impedances between two
26 zero thickness strips of width w, spaced a distance s between two
27 groundplanes of spacing h. */
31 #include "gsl_types.h"
32 #include "gsl_definitions.h"
33 #include "definitions.h"
43 #include "exit_codes.h"
44 /* formuals taken from Matthaei, Young and Jones, Microwave Filters, Impedance Matching
45 Networks and Coupling Structures, Artech House, Dedham, MA., 1980. , but I've substituted
46 29.97924580105028, as its clear 30 is just a close approximation */
48 void calculate_Zodd_and_Zeven(double *Zodd, double *Zeven, double *Zo, double w, double H, double s, double er)
50 double ke, ko, ko_dash, ke_dash;
51 ke=(tanh((M_PI/2)*(w/H)))*tanh((M_PI/2)*(w+s)/H);
52 ko=(tanh((M_PI/2)*(w/H)))/tanh((M_PI/2)*(w+s)/H);
54 ke_dash=sqrt(1-ke*ke);
55 ko_dash=sqrt(1-ko*ko);
57 *Zeven=29.9792458010502837*M_PI*gsl_sf_ellint_Kcomp(ke_dash, GSL_PREC_DOUBLE)/(gsl_sf_ellint_Kcomp(ke,GSL_PREC_DOUBLE)*sqrt(er));
58 *Zodd= 29.9792458010502837*M_PI*gsl_sf_ellint_Kcomp(ko_dash, GSL_PREC_DOUBLE)/(gsl_sf_ellint_Kcomp(ko,GSL_PREC_DOUBLE)*sqrt(er));
59 *Zo=sqrt( (*Zodd)*(*Zeven));