Qucs-core  0.0.19
coaxline.cpp
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00001 /*
00002  * coaxline.cpp - coaxial cable class implementation
00003  *
00004  * Copyright (C) 2006, 2008, 2009, 2011 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 "coaxline.h"
00031 
00032 using namespace qucs;
00033 
00034 coaxline::coaxline () : circuit (2) {
00035   alpha = beta = zl = fc = 0;
00036   type = CIR_COAXLINE;
00037 }
00038 
00039 void coaxline::calcPropagation (nr_double_t frequency) {
00040   nr_double_t er   = getPropertyDouble ("er");
00041   nr_double_t mur  = getPropertyDouble ("mur");
00042   nr_double_t rho  = getPropertyDouble ("rho");
00043   nr_double_t tand = getPropertyDouble ("tand");
00044   nr_double_t d    = getPropertyDouble ("d");
00045   nr_double_t D    = getPropertyDouble ("D");
00046   nr_double_t ad, ac, rs;
00047 
00048   // check cutoff frequency
00049   if (frequency > fc) {
00050     logprint (LOG_ERROR, "WARNING: Operating frequency (%g) beyond "
00051               "cutoff frequency (%g).\n", frequency, fc);
00052   }
00053 
00054   // calculate losses
00055   ad = pi / C0 * frequency * std::sqrt (er) * tand;
00056   rs = std::sqrt (pi * frequency * mur * MU0 * rho);
00057   ac = std::sqrt (er) * (1 / d + 1 / D) / std::log (D / d) * rs / Z0;
00058 
00059   // calculate propagation constants and reference impedance
00060   alpha = ac + ad;
00061   beta  = std::sqrt (er * mur) * 2 * pi * frequency / C0;
00062   zl = Z0 / 2 / pi / std::sqrt (er) * std::log (D / d);
00063 }
00064 
00065 void coaxline::calcNoiseSP (nr_double_t) {
00066   nr_double_t l = getPropertyDouble ("L");
00067   if (l < 0) return;
00068   // calculate noise using Bosma's theorem
00069   nr_double_t T = getPropertyDouble ("Temp");
00070   matrix s = getMatrixS ();
00071   matrix e = eye (getSize ());
00072   setMatrixN (celsius2kelvin (T) / T0 * (e - s * transpose (conj (s))));
00073 }
00074 
00075 void coaxline::initCheck (void) {
00076   nr_double_t d   = getPropertyDouble ("d");
00077   nr_double_t D   = getPropertyDouble ("D");
00078   nr_double_t er  = getPropertyDouble ("er");
00079   nr_double_t mur = getPropertyDouble ("mur");
00080 
00081   // check validity
00082   if (d >= D) {
00083     logprint (LOG_ERROR,
00084               "ERROR: Inner diameter larger than outer diameter.\n");
00085   }
00086   nr_double_t f1, f2, cl;
00087   cl = C0 / std::sqrt (mur * er);
00088   f1 = cl / (pi_over_2 * (D + d)); // TE_11
00089   f2 = cl / (1 * (D - d));      // TM_N1
00090   fc = std::min (f1, f2);
00091 }
00092 
00093 void coaxline::saveCharacteristics (nr_double_t) {
00094   setCharacteristic ("Zl", zl);
00095 }
00096 
00097 void coaxline::initSP (void) {
00098   // allocate S-parameter matrix
00099   allocMatrixS ();
00100   initCheck ();
00101 }
00102 
00103 void coaxline::calcSP (nr_double_t frequency) {
00104   nr_double_t l = getPropertyDouble ("L");
00105 
00106   // calculate propagation constants
00107   calcPropagation (frequency);
00108 
00109   // calculate S-parameters
00110   nr_double_t z = zl / z0;
00111   nr_double_t y = 1 / z;
00112   nr_complex_t g = nr_complex_t (alpha, beta);
00113   nr_complex_t n = 2.0 * cosh (g * l) + (z + y) * sinh (g * l);
00114   nr_complex_t s11 = (z - y) * sinh (g * l) / n;
00115   nr_complex_t s21 = 2.0 / n;
00116   setS (NODE_1, NODE_1, s11); setS (NODE_2, NODE_2, s11);
00117   setS (NODE_1, NODE_2, s21); setS (NODE_2, NODE_1, s21);
00118 }
00119 
00120 void coaxline::initDC (void) {
00121   nr_double_t l   = getPropertyDouble ("L");
00122   nr_double_t d   = getPropertyDouble ("d");
00123   nr_double_t rho = getPropertyDouble ("rho");
00124 
00125   if (d != 0.0 && rho != 0.0 && l != 0.0) {
00126     // a tiny resistance
00127     nr_double_t g = pi * sqr (d / 2) / rho / l;
00128     setVoltageSources (0);
00129     allocMatrixMNA ();
00130     setY (NODE_1, NODE_1, +g); setY (NODE_2, NODE_2, +g);
00131     setY (NODE_1, NODE_2, -g); setY (NODE_2, NODE_1, -g);
00132   }
00133   else {
00134     // a DC short
00135     setVoltageSources (1);
00136     setInternalVoltageSource (1);
00137     allocMatrixMNA ();
00138     voltageSource (VSRC_1, NODE_1, NODE_2);
00139   }
00140 }
00141 
00142 void coaxline::initAC (void) {
00143   setVoltageSources (0);
00144   allocMatrixMNA ();
00145   initCheck ();
00146 }
00147 
00148 void coaxline::calcAC (nr_double_t frequency) {
00149   nr_double_t l = getPropertyDouble ("L");
00150 
00151   // calculate propagation constants
00152   calcPropagation (frequency);
00153 
00154   // calculate Y-parameters
00155   nr_complex_t g = nr_complex_t (alpha, beta);
00156   nr_complex_t y11 = coth (g * l) / zl;
00157   nr_complex_t y21 = -cosech (g * l) / zl;
00158   setY (NODE_1, NODE_1, y11); setY (NODE_2, NODE_2, y11);
00159   setY (NODE_1, NODE_2, y21); setY (NODE_2, NODE_1, y21);
00160 }
00161 
00162 void coaxline::calcNoiseAC (nr_double_t) {
00163   nr_double_t l = getPropertyDouble ("L");
00164   if (l < 0) return;
00165   // calculate noise using Bosma's theorem
00166   nr_double_t T = getPropertyDouble ("Temp");
00167   setMatrixN (4 * celsius2kelvin (T) / T0 * real (getMatrixY ()));
00168 }
00169 
00170 // properties
00171 PROP_REQ [] = {
00172   { "D", PROP_REAL, { 2.95e-3, PROP_NO_STR }, PROP_POS_RANGEX },
00173   { "d", PROP_REAL, { 0.9e-3, PROP_NO_STR }, PROP_POS_RANGEX },
00174   { "L", PROP_REAL, { 1500e-3, PROP_NO_STR }, PROP_NO_RANGE },
00175   { "er", PROP_REAL, { 2.29, PROP_NO_STR }, PROP_RNGII (1, 100) },
00176   { "mur", PROP_REAL, { 1, PROP_NO_STR }, PROP_RNGII (1, 100) },
00177   { "tand", PROP_REAL, { 4e-4, PROP_NO_STR }, PROP_POS_RANGE },
00178   { "rho", PROP_REAL, { 0.022e-6, PROP_NO_STR }, PROP_POS_RANGE },
00179   PROP_NO_PROP };
00180 PROP_OPT [] = {
00181   { "Temp", PROP_REAL, { 26.85, PROP_NO_STR }, PROP_MIN_VAL (K) },
00182   PROP_NO_PROP };
00183 struct define_t coaxline::cirdef =
00184   { "COAX", 2, PROP_COMPONENT, PROP_NO_SUBSTRATE, PROP_LINEAR, PROP_DEF };