Qucs-core  0.0.19
cpwshort.cpp
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00001 /*
00002  * cpwshort.cpp - coplanar waveguide short class implementation
00003  *
00004  * Copyright (C) 2005, 2008 Stefan Jahn <stefan@lkcc.org>
00005  *
00006  * This is free software; you can redistribute it and/or modify
00007  * it under the terms of the GNU General Public License as published by
00008  * the Free Software Foundation; either version 2, or (at your option)
00009  * any later version.
00010  *
00011  * This software is distributed in the hope that it will be useful,
00012  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00013  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00014  * GNU General Public License for more details.
00015  *
00016  * You should have received a copy of the GNU General Public License
00017  * along with this package; see the file COPYING.  If not, write to
00018  * the Free Software Foundation, Inc., 51 Franklin Street - Fifth Floor,
00019  * Boston, MA 02110-1301, USA.
00020  *
00021  * $Id$
00022  *
00023  */
00024 
00025 #if HAVE_CONFIG_H
00026 # include <config.h>
00027 #endif
00028 
00029 #include "component.h"
00030 #include "substrate.h"
00031 #include "cpwline.h"
00032 #include "cpwshort.h"
00033 
00034 using namespace qucs;
00035 
00036 cpwshort::cpwshort () : circuit (1) {
00037   type = CIR_CPWSHORT;
00038 }
00039 
00040 // Returns the coplanar short inductance.
00041 nr_double_t cpwshort::calcLend (nr_double_t frequency) {
00042 
00043   // get properties of substrate and coplanar open
00044   nr_double_t W =  getPropertyDouble ("W");
00045   nr_double_t s =  getPropertyDouble ("S");
00046   substrate * subst = getSubstrate ();
00047   nr_double_t er = subst->getPropertyDouble ("er");
00048   nr_double_t h  = subst->getPropertyDouble ("h");
00049   nr_double_t t  = subst->getPropertyDouble ("t");
00050   int backMetal  = !strcmp (getPropertyString ("Backside"), "Metal");
00051 
00052   nr_double_t ZlEff, ErEff, ZlEffFreq, ErEffFreq;
00053   cpwline::analyseQuasiStatic (W, s, h, t, er, backMetal, ZlEff, ErEff);
00054   cpwline::analyseDispersion  (W, s, h, er, ZlEff, ErEff, frequency,
00055                                ZlEffFreq, ErEffFreq);
00056   nr_double_t dl = (W / 2 + s) / 4;
00057   return dl * ErEffFreq / C0 * ZlEffFreq;
00058 }
00059 
00060 void cpwshort::initSP (void) {
00061   allocMatrixS ();
00062   checkProperties ();
00063 }
00064 
00065 void cpwshort::calcSP (nr_double_t frequency) {
00066   setS (NODE_1, NODE_1, ztor (calcZ (frequency)));
00067 }
00068 
00069 void cpwshort::checkProperties (void) {
00070   nr_double_t s = getPropertyDouble ("S");
00071   substrate * subst = getSubstrate ();
00072   nr_double_t t = subst->getPropertyDouble ("t");
00073   if (t >= s / 3) {
00074     logprint (LOG_ERROR, "WARNING: Model for coplanar short valid for "
00075               "t < s/3 (s/3 = %g)\n", s / 3);
00076   }
00077 }
00078 
00079 nr_complex_t cpwshort::calcZ (nr_double_t frequency) {
00080   nr_double_t o = 2 * pi * frequency;
00081   nr_double_t l = calcLend (frequency);
00082   return nr_complex_t (0, l * o);
00083 }
00084 
00085 void cpwshort::initDC (void) {
00086   setVoltageSources (1);
00087   setInternalVoltageSource (1);
00088   allocMatrixMNA ();
00089   setY (NODE_1, NODE_1, 0);
00090   setB (NODE_1, VSRC_1, 1);
00091   setC (VSRC_1, NODE_1, 1);
00092   setD (VSRC_1, VSRC_1, 0);
00093   setE (VSRC_1, 0);
00094 }
00095 
00096 void cpwshort::initAC (void) {
00097   setVoltageSources (0);
00098   allocMatrixMNA ();
00099   checkProperties ();
00100 }
00101 
00102 void cpwshort::calcAC (nr_double_t frequency) {
00103   setY (NODE_1, NODE_1, 1.0 / calcZ (frequency));
00104 }
00105 
00106 // properties
00107 PROP_REQ [] = {
00108   { "W", PROP_REAL, { 1e-3, PROP_NO_STR }, PROP_POS_RANGE },
00109   { "S", PROP_REAL, { 1e-3, PROP_NO_STR }, PROP_POS_RANGE },
00110   { "Subst", PROP_STR, { PROP_NO_VAL, "Subst1" }, PROP_NO_RANGE },
00111   PROP_NO_PROP };
00112 PROP_OPT [] = {
00113   { "Backside", PROP_STR, { PROP_NO_VAL, "Metal" },
00114     PROP_RNG_STR2 ("Metal", "Air") },
00115   PROP_NO_PROP };
00116 struct define_t cpwshort::cirdef =
00117   { "CSHORT", 1, PROP_COMPONENT, PROP_NO_SUBSTRATE, PROP_LINEAR, PROP_DEF };