msrstub.cpp

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/*
 * msrstub.cpp - microstrip radial stub class implementation
 *
 * Copyright (C) 2009 Stefan Jahn <stefan@lkcc.org>
 *
 * This is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this package; see the file COPYING.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street - Fifth Floor,
 * Boston, MA 02110-1301, USA.
 *
 * $Id: msrstub.cpp 1825 2011-03-11 20:42:14Z ela $
 *
 */

#if HAVE_CONFIG_H
# include <config.h>
#endif

#include "component.h"
#include "substrate.h"
#include "msrstub.h"

msrstub::msrstub () : circuit (1) {
  type = CIR_MSRSTUB;
}

// Returns the microstrip radial stub reactance.
nr_double_t msrstub::calcReactance (nr_double_t r1, nr_double_t r2,
                    nr_double_t alpha, nr_double_t er,
                    nr_double_t h, nr_double_t frequency) {

  nr_double_t l0 = C0 / frequency;
  nr_double_t W = (r1 + (r2 - r1) / 2) * rad (alpha);
  nr_double_t ereff = (er + 1.0) / 2 + (er - 1.0) / 
    (2.0 * sqrt (1 + 10.0 * h / W)); 
  nr_double_t k = 2.0 * M_PI * sqrt (ereff) / l0;
  nr_double_t a = k * r1;
  nr_double_t b = k * r2;
  nr_double_t Z_0 = Z0 / sqrt (ereff) * sqrt (sqr (j0 (a)) + sqr (y0 (a))) /
    sqrt (sqr (j1 (a)) + sqr (y1 (a)));
  nr_double_t theta_1 = atan (y0 (a) / j0 (a));
  //  nr_double_t theta_2 = atan (y0 (b) / j0 (b));
  nr_double_t phi_1 = atan (-j1 (a) / y1 (a));
  nr_double_t phi_2 = atan (-j1 (b) / y1 (b));

  nr_double_t X1 = h * Z_0 / (2.0 * M_PI * r1) * 360.0 / alpha * 
    cos (theta_1 - phi_2) / sin (phi_1 - phi_2);

  return X1;
}

void msrstub::calcSP (nr_double_t frequency) {
  setS (NODE_1, NODE_1, ztor (calcZ (frequency)));
}

nr_complex_t msrstub::calcZ (nr_double_t frequency) {

  /* get properties of this component */
  nr_double_t r1 = getPropertyDouble ("ri");
  nr_double_t r2 = getPropertyDouble ("ro");
  nr_double_t al = getPropertyDouble ("alpha");

  /* get properties of the substrate */
  substrate * subst = getSubstrate ();
  nr_double_t er    = subst->getPropertyDouble ("er");
  nr_double_t h     = subst->getPropertyDouble ("h");

  return rect (0, calcReactance (r1, r2, al, er, h, frequency));
}

void msrstub::initDC (void) {
  allocMatrixMNA ();
  setY (NODE_1, NODE_1, 0);
}

void msrstub::calcAC (nr_double_t frequency) {
  setY (NODE_1, NODE_1, 1.0 / calcZ (frequency));
}

// properties
PROP_REQ [] = {
  { "ri", PROP_REAL, { 1e-3, PROP_NO_STR }, PROP_POS_RANGE },
  { "ro", PROP_REAL, { 10e-3, PROP_NO_STR }, PROP_POS_RANGE },
  { "alpha", PROP_REAL, { 90, PROP_NO_STR }, PROP_RNGII (0, 180) },
  { "Subst", PROP_STR, { PROP_NO_VAL, "Subst1" }, PROP_NO_RANGE },
  PROP_NO_PROP };
PROP_OPT [] = {
  PROP_NO_PROP };
struct define_t msrstub::cirdef =
  { "MRSTUB", 1, PROP_COMPONENT, PROP_NO_SUBSTRATE, PROP_LINEAR, PROP_DEF };