kicad/pcb_calculator/transline/coax.cpp

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/*
* coax.cpp - coaxial class implementation
*
* Copyright (C) 2001 Gopal Narayanan <gopal@astro.umass.edu>
* Copyright (C) 2002 Claudio Girardi <claudio.girardi@ieee.org>
* Copyright (C) 2005, 2006 Stefan Jahn <stefan@lkcc.org>
*
* This program 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 of the License, or (at
* your option) any later version.
*
* This program 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.
*
*/
/*
* coax.c - Puts up window for microstrip and
* performs the associated calculations
*/
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <cmath>
#include <units.h>
#include <transline.h>
#include <coax.h>
COAX::COAX() : TRANSLINE()
{
m_name = "Coax";
// Initialize these variables mainly to avoid warnings from a static analyzer
mur = 0.0; // magnetic permeability of substrate
din = 0.0; // Inner diameter of cable
dout = 0.0; // Outer diameter of cable
l = 0.0; // Length of cable
Z0 = 0.0; // characteristic impedance
ang_l = 0.0; // Electrical length in angle
atten_dielectric = 0.0; // Loss in dielectric (dB)
atten_cond = 0.0; // Loss in conductors (dB)
fc = 0.0; // Cutoff frequency for higher order modes
}
/*
* get_coax_sub() - get and assign coax substrate parameters into coax
* structure
*/
void COAX::get_coax_sub()
{
er = getProperty( EPSILONR_PRM );
mur = getProperty( MUR_PRM );
murC = getProperty( MURC_PRM );
tand = getProperty( TAND_PRM );
sigma = 1.0 / getProperty( RHO_PRM );
}
/*
* get_coax_comp() - get and assign coax component parameters into
* coax structure
*/
void COAX::get_coax_comp()
{
f = getProperty( FREQUENCY_PRM );
}
/*
* get_coax_elec() - get and assign coax electrical parameters into
* coax structure
*/
void COAX::get_coax_elec()
{
Z0 = getProperty( Z0_PRM );
ang_l = getProperty( ANG_L_PRM );
}
/*
* get_coax_phys() - get and assign coax physical parameters into coax
* structure
*/
void COAX::get_coax_phys()
{
din = getProperty( PHYS_DIAM_IN_PRM );
dout = getProperty( PHYS_DIAM_OUT_PRM );
l = getProperty( PHYS_LEN_PRM );
}
double COAX::alphad_coax()
{
double ad;
ad = (M_PI / C0) * f * sqrt( er ) * tand;
ad = ad * 20.0 / log( 10.0 );
return ad;
}
double COAX::alphac_coax()
{
double ac, Rs;
Rs = sqrt( M_PI * f * murC * MU0 / sigma );
ac = sqrt( er ) * ( ( (1 / din) + (1 / dout) ) / log( dout / din ) ) * (Rs / ZF0);
ac = ac * 20.0 / log( 10.0 );
return ac;
}
/*
* analyze() - analysis function
*/
void COAX::analyze()
{
double lambda_g;
/* Get and assign substrate parameters */
get_coax_sub();
/* Get and assign component parameters */
get_coax_comp();
/* Get and assign physical parameters */
get_coax_phys();
if( din != 0.0 )
{
Z0 = ( ZF0 / 2 / M_PI / sqrt( er ) ) * log( dout / din );
}
lambda_g = ( C0 / (f) ) / sqrt( er * mur );
/* calculate electrical angle */
ang_l = (2.0 * M_PI * l) / lambda_g; /* in radians */
setProperty( Z0_PRM, Z0 );
setProperty( ANG_L_PRM, ang_l );
show_results();
}
/*
* synthesize() - synthesis function
*/
void COAX::synthesize()
{
double lambda_g;
/* Get and assign substrate parameters */
get_coax_sub();
/* Get and assign component parameters */
get_coax_comp();
/* Get and assign electrical parameters */
get_coax_elec();
/* Get and assign physical parameters */
get_coax_phys();
if( isSelected( PHYS_DIAM_IN_PRM ) )
{
/* solve for din */
din = dout / exp( Z0 * sqrt( er ) / ZF0 * 2 * M_PI );
setProperty( PHYS_DIAM_IN_PRM, din );
}
else if( isSelected( PHYS_DIAM_OUT_PRM ) )
{
/* solve for dout */
dout = din * exp( Z0 * sqrt( er ) / ZF0 * 2 * M_PI );
setProperty( PHYS_DIAM_OUT_PRM, dout );
}
lambda_g = ( C0 / (f) ) / sqrt( er * mur );
/* calculate physical length */
l = (lambda_g * ang_l) / (2.0 * M_PI); /* in m */
setProperty( PHYS_LEN_PRM, l );
show_results();
}
/*
* show_results() - show results
*/
void COAX::show_results()
{
int m, n;
char text[256], txt[256];
atten_dielectric = alphad_coax() * l;
atten_cond = alphac_coax() * l;
setResult( 0, er, "" );
setResult( 1, atten_cond, "dB" );
setResult( 2, atten_dielectric, "dB" );
n = 1;
fc = C0 / (M_PI * (dout + din) / (double) n);
if( fc > f )
strcpy( text, "none" );
else
{
strcpy( text, "H(1,1) " );
m = 2;
fc = C0 / ( 2 * (dout - din) / (double) (m - 1) );
while( (fc <= f) && (m<10) )
{
sprintf( txt, "H(n,%d) ", m );
strcat( text, txt );
m++;
fc = C0 / ( 2 * (dout - din) / (double) (m - 1) );
}
}
setResult( 3, text );
m = 1;
fc = C0 / (2 * (dout - din) / (double) m);
if( fc > f )
strcpy( text, "none" );
else
{
strcpy( text, "" );
while( (fc <= f) && (m<10) )
{
sprintf( txt, "E(n,%d) ", m );
strcat( text, txt );
m++;
fc = C0 / (2 * (dout - din) / (double) m);
}
}
setResult( 4, text );
}