278 lines
7.5 KiB
C++
278 lines
7.5 KiB
C++
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/*
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* coplanar.cpp - coplanar class implementation
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*
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* Copyright (C) 2008 Michael Margraf <michael.margraf@alumni.tu-berlin.de>
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* Copyright (C) 2005, 2006 Stefan Jahn <stefan@lkcc.org>
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* Modified for Kicad: 2011 jean-pierre.charras
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or (at
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* your option) any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this package; see the file COPYING. If not, write to
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* the Free Software Foundation, Inc., 51 Franklin Street - Fifth Floor,
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* Boston, MA 02110-1301, USA.
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*
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*/
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#include <stdlib.h>
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#include <stdio.h>
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#include <string.h>
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#include <math.h>
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#include "units.h"
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#include "transline.h"
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#include "coplanar.h"
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COPLANAR::COPLANAR() : TRANSLINE()
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{
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m_name = "CoPlanar";
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backMetal = false;
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}
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GROUNDEDCOPLANAR::GROUNDEDCOPLANAR() : COPLANAR()
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{
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m_name = "GrCoPlanar";
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backMetal = true;
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}
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// -------------------------------------------------------------------
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void COPLANAR::getProperties()
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{
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f = getProperty( FREQUENCY_PRM );
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w = getProperty( PHYS_WIDTH_PRM );
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s = getProperty( PHYS_S_PRM );
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len = getProperty( PHYS_LEN_PRM );
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h = getProperty( H_PRM );
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t = getProperty( T_PRM );
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er = getProperty( EPSILONR_PRM );
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murC = getProperty( MURC_PRM );
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tand = getProperty( TAND_PRM );
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sigma = 1.0 / getProperty( RHO_PRM );
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Z0 = getProperty( Z0_PRM );
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ang_l = getProperty( ANG_L_PRM );
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}
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// -------------------------------------------------------------------
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void COPLANAR::calc()
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{
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skindepth = skin_depth();
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// other local variables (quasi-static constants)
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double k1, kk1, kpk1, k2, k3, q1, q2, q3 = 0, qz, er0 = 0;
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double zl_factor;
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// compute the necessary quasi-static approx. (K1, K3, er(0) and Z(0))
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k1 = w / (w + s + s);
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kk1 = ellipk( k1 );
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kpk1 = ellipk( sqrt( 1 - k1 * k1 ) );
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q1 = kk1 / kpk1;
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// backside is metal
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if( backMetal )
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{
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k3 = tanh( (M_PI / 4) * (w / h) ) / tanh( (M_PI / 4) * (w + s + s) / h );
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q3 = ellipk( k3 ) / ellipk( sqrt( 1 - k3 * k3 ) );
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qz = 1 / (q1 + q3);
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er0 = 1 + q3 * qz * (er - 1);
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zl_factor = ZF0 / 2 * qz;
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}
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// backside is air
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else
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{
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k2 = sinh( (M_PI / 4) * (w / h) ) / sinh( (M_PI / 4) * (w + s + s) / h );
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q2 = ellipk( k2 ) / ellipk( sqrt( 1 - k2 * k2 ) );
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er0 = 1 + (er - 1) / 2 * q2 / q1;
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zl_factor = ZF0 / 4 / q1;
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}
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// adds effect of strip thickness
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if( t > 0 )
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{
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double d, se, We, ke, qe;
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d = (t * 1.25 / M_PI) * ( 1 + log( 4 * M_PI * w / t ) );
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se = s - d;
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We = w + d;
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// modifies k1 accordingly (k1 = ke)
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ke = We / (We + se + se); // ke = k1 + (1 - k1 * k1) * d / 2 / s;
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qe = ellipk( ke ) / ellipk( sqrt( 1 - ke * ke ) );
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// backside is metal
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if( backMetal )
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{
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qz = 1 / (qe + q3);
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er0 = 1 + q3 * qz * (er - 1);
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zl_factor = ZF0 / 2 * qz;
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}
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// backside is air
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else
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{
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zl_factor = ZF0 / 4 / qe;
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}
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// modifies er0 as well
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er0 = er0 - (0.7 * (er0 - 1) * t / s) / ( q1 + (0.7 * t / s) );
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}
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// pre-compute square roots
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double sr_er = sqrt( er );
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double sr_er0 = sqrt( er0 );
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// cut-off frequency of the TE0 mode
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double fte = (C0 / 4) / ( h * sqrt( er - 1 ) );
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// dispersion factor G
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double p = log( w / h );
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double u = 0.54 - (0.64 - 0.015 * p) * p;
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double v = 0.43 - (0.86 - 0.54 * p) * p;
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double G = exp( u * log( w / s ) + v );
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// loss constant factors (computed only once for efficency sake)
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double ac = 0;
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if( t > 0 )
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{
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// equations by GHIONE
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double n = (1 - k1) * 8 * M_PI / ( t * (1 + k1) );
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double a = w / 2;
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double b = a + s;
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ac = ( M_PI + log( n * a ) ) / a + ( M_PI + log( n * b ) ) / b;
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}
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double ac_factor = ac / ( 4 * ZF0 * kk1 * kpk1 * (1 - k1 * k1) );
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double ad_factor = ( er / (er - 1) ) * tand * M_PI / C0;
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// ....................................................
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double sr_er_f = sr_er0;
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// add the dispersive effects to er0
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sr_er_f += (sr_er - sr_er0) / ( 1 + G * pow( f / fte, -1.8 ) );
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// for now, the loss are limited to strip losses (no radiation
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// losses yet) losses in neper/length
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atten_cond = 20.0 / log( 10.0 ) * len
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* ac_factor * sr_er0 * sqrt( M_PI * MU0 * f / sigma );
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atten_dielectric = 20.0 / log( 10.0 ) * len
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* ad_factor * f * (sr_er_f * sr_er_f - 1) / sr_er_f;
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ang_l = 2.0 * M_PI * len * sr_er_f * f / C0; /* in radians */
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er_eff = sr_er_f * sr_er_f;
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Z0 = zl_factor / sr_er_f;
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}
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// -------------------------------------------------------------------
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void COPLANAR::show_results()
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{
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setProperty( Z0_PRM, Z0 );
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setProperty( ANG_L_PRM, ang_l );
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setResult( 0, er_eff, "" );
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setResult( 1, atten_cond, "dB" );
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setResult( 2, atten_dielectric, "dB" );
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setResult( 3, skindepth / UNIT_MICRON, "<EFBFBD>m" );
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}
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// -------------------------------------------------------------------
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void COPLANAR::analyze()
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{
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getProperties();
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/* compute coplanar parameters */
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calc();
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/* print results in the subwindow */
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show_results();
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}
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#define MAX_ERROR 0.000001
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// -------------------------------------------------------------------
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void COPLANAR::synthesize()
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{
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double Z0_dest, Z0_current, Z0_result, increment, slope, error;
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int iteration;
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getProperties();
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/* required value of Z0 */
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Z0_dest = Z0;
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/* Newton's method */
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iteration = 0;
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/* compute coplanar parameters */
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calc();
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Z0_current = Z0;
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error = fabs( Z0_dest - Z0_current );
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while( error > MAX_ERROR )
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{
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iteration++;
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if( isSelected( PHYS_WIDTH_PRM ) )
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{
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increment = w / 100.0;
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w += increment;
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}
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else
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{
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increment = s / 100.0;
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s += increment;
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}
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/* compute coplanar parameters */
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calc();
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Z0_result = Z0;
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/* f(w(n)) = Z0 - Z0(w(n)) */
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/* f'(w(n)) = -f'(Z0(w(n))) */
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/* f'(Z0(w(n))) = (Z0(w(n)) - Z0(w(n+delw))/delw */
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/* w(n+1) = w(n) - f(w(n))/f'(w(n)) */
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slope = (Z0_result - Z0_current) / increment;
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slope = (Z0_dest - Z0_current) / slope - increment;
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if( isSelected( PHYS_WIDTH_PRM ) )
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w += slope;
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else
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s += slope;
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if( w <= 0.0 )
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w = increment;
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if( s <= 0.0 )
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s = increment;
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/* find new error */
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/* compute coplanar parameters */
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calc();
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Z0_current = Z0;
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error = fabs( Z0_dest - Z0_current );
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if( iteration > 100 )
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break;
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}
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setProperty( PHYS_WIDTH_PRM, w );
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setProperty( PHYS_S_PRM, s );
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/* calculate physical length */
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ang_l = getProperty( ANG_L_PRM );
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len = C0 / f / sqrt( er_eff ) * ang_l / 2.0 / M_PI; /* in m */
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setProperty( PHYS_LEN_PRM, len );
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/* compute coplanar parameters */
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calc();
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/* print results in the subwindow */
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show_results();
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}
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