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kicad/pcb_calculator/transline/rectwaveguide.cpp

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/*
* rectwaveguide.cpp - rectangular waveguide class implementation
*
* Copyright (C) 2001 Gopal Narayanan <gopal@astro.umass.edu>
* 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.
*
*/
#include <cmath>
#include <cstdio>
#include <cstring>
#include "rectwaveguide.h"
#include "units.h"
RECTWAVEGUIDE::RECTWAVEGUIDE() : TRANSLINE(),
mur( 0.0 ), // magnetic permeability of substrate
a( 0.0 ), // width of waveguide
b( 0.0 ), // height of waveguide
l( 0.0 ), // length of waveguide
Z0( 0.0 ), // characteristic impedance
Z0EH( 0.0 ), // characteristic impedance of field quantities*/
mur_eff( 0.0 ), // Effective mag. permeability
atten_dielectric( 0.0 ), // Loss in dielectric (dB)
atten_cond( 0.0 ), // Loss in conductors (dB)
fc10( 1.0 ) // Cutoff frequency for TE10 mode
{
m_Name = "RectWaveGuide";
Init();
}
/*
* returns square of k
*/
double RECTWAVEGUIDE::kval_square()
{
double kval;
kval = 2.0 * M_PI * m_parameters[FREQUENCY_PRM]
* sqrt( m_parameters[MUR_PRM] * m_parameters[EPSILONR_PRM] ) / C0;
return kval * kval;
}
/*
* given mode numbers m and n
* returns square of cutoff kc value
*/
double RECTWAVEGUIDE::kc_square( int m, int n )
{
return pow( ( m * M_PI / m_parameters[PHYS_A_PRM] ), 2.0 )
+ pow( ( n * M_PI / m_parameters[PHYS_B_PRM] ), 2.0 );
}
/*
* given mode numbers m and n
* returns cutoff fc value
*/
double RECTWAVEGUIDE::fc( int m, int n )
{
return sqrt( kc_square( m, n ) / m_parameters[MUR_PRM] / m_parameters[EPSILONR_PRM] ) * C0 / 2.0
/ M_PI;
}
/*
* alphac - returns attenuation due to conductor losses for all propagating
* modes in the waveguide
*/
double RECTWAVEGUIDE::alphac()
{
double Rs, f_c;
double ac;
short m, n, mmax, nmax;
double* a = &m_parameters[PHYS_A_PRM];
double* b = &m_parameters[PHYS_B_PRM];
double* f = &m_parameters[FREQUENCY_PRM];
double* murc = &m_parameters[MURC_PRM];
double* sigma = &m_parameters[SIGMA_PRM];
Rs = sqrt( M_PI * *f * *murc * MU0 / *sigma );
ac = 0.0;
mmax = (int) floor( *f / fc( 1, 0 ) );
nmax = mmax;
/* below from Ramo, Whinnery & Van Duzer */
/* TE(m,n) modes */
for( n = 0; n <= nmax; n++ )
{
for( m = 1; m <= mmax; m++ )
{
f_c = fc( m, n );
if( *f > f_c )
{
switch( n )
{
case 0:
ac += ( Rs / ( *b * ZF0 * sqrt( 1.0 - pow( ( f_c / *f ), 2.0 ) ) ) )
* ( 1.0 + ( ( 2 * *b / *a ) * pow( ( f_c / *f ), 2.0 ) ) );
break;
default:
ac += ( ( 2. * Rs ) / ( *b * ZF0 * sqrt( 1.0 - pow( ( f_c / *f ), 2.0 ) ) ) )
* ( ( ( 1. + ( *b / *a ) ) * pow( ( f_c / *f ), 2.0 ) )
+ ( ( 1. - pow( ( f_c / *f ), 2.0 ) )
* ( ( ( *b / *a )
* ( ( ( *b / *a ) * pow( m, 2. ) )
+ pow( n, 2. ) ) )
/ ( pow( ( *b * m / *a ), 2.0 )
+ pow( n, 2.0 ) ) ) ) );
break;
}
}
}
}
/* TM(m,n) modes */
for( n = 1; n <= nmax; n++ )
{
for( m = 1; m <= mmax; m++ )
{
f_c = fc( m, n );
if( *f > f_c )
{
ac += ( ( 2. * Rs ) / ( *b * ZF0 * sqrt( 1.0 - pow( ( f_c / *f ), 2.0 ) ) ) )
* ( ( ( pow( m, 2.0 ) * pow( ( *b / *a ), 3.0 ) ) + pow( n, 2. ) )
/ ( ( pow( ( m * *b / *a ), 2. ) ) + pow( n, 2.0 ) ) );
}
}
}
ac = ac * 20.0 * log10( exp( 1. ) ); /* convert from Np/m to db/m */
return ac;
}
/*
* alphac_cutoff - returns attenuation for a cutoff wg
*/
double RECTWAVEGUIDE::alphac_cutoff()
{
double acc;
acc = sqrt( kc_square( 1, 0 ) - kval_square() );
acc = 20 * log10( exp( 1.0 ) ) * acc;
return acc;
}
/*
* returns attenuation due to dielectric losses
*/
double RECTWAVEGUIDE::alphad()
{
double k_square, beta;
double ad;
k_square = kval_square();
beta = sqrt( k_square - kc_square( 1, 0 ) );
ad = ( k_square * m_parameters[TAND_PRM] ) / ( 2.0 * beta );
ad = ad * 20.0 * log10( exp( 1. ) ); /* convert from Np/m to db/m */
return ad;
}
/*
* get_rectwaveguide_sub
* get and assign rectwaveguide substrate parameters
* into rectwaveguide structure
*/
void RECTWAVEGUIDE::get_rectwaveguide_sub()
{
m_parameters[EPSILONR_PRM] = getProperty( EPSILONR_PRM );
m_parameters[MUR_PRM] = getProperty( MUR_PRM );
m_parameters[MURC_PRM] = getProperty( MURC_PRM );
m_parameters[SIGMA_PRM] = 1.0 / getProperty( RHO_PRM );
m_parameters[TAND_PRM] = getProperty( TAND_PRM );
}
/*
* get_rectwaveguide_comp
* get and assign rectwaveguide component parameters
* into rectwaveguide structure
*/
void RECTWAVEGUIDE::get_rectwaveguide_comp()
{
m_parameters[FREQUENCY_PRM] = getProperty( FREQUENCY_PRM );
}
/*
* get_rectwaveguide_elec
* get and assign rectwaveguide electrical parameters
* into rectwaveguide structure
*/
void RECTWAVEGUIDE::get_rectwaveguide_elec()
{
m_parameters[Z0_PRM] = getProperty( Z0_PRM );
m_parameters[ANG_L_PRM] = getProperty( ANG_L_PRM );
}
/*
* get_rectwaveguide_phys
* get and assign rectwaveguide physical parameters
* into rectwaveguide structure
*/
void RECTWAVEGUIDE::get_rectwaveguide_phys()
{
m_parameters[PHYS_A_PRM] = getProperty( PHYS_A_PRM );
m_parameters[PHYS_B_PRM] = getProperty( PHYS_B_PRM );
m_parameters[PHYS_LEN_PRM] = getProperty( PHYS_LEN_PRM );
}
/*
* analyze - analysis function
* source: https://empossible.net/wp-content/uploads/2018/03/Lecture-5c-Rectangular-waveguide.pdf
*/
void RECTWAVEGUIDE::calcAnalyze()
{
double lambda_g;
double k_square;
k_square = kval_square();
if( kc_square( 1, 0 ) <= k_square )
{
/* propagating modes */
// Z0 definition using fictive voltages and currents
m_parameters[Z0_PRM] =
ZF0 * sqrt( m_parameters[MUR_PRM] / m_parameters[EPSILONR_PRM] )
/ sqrt( 1.0 - pow( ( fc( 1, 0 ) / m_parameters[FREQUENCY_PRM] ), 2.0 ) );
/* calculate electrical angle */
lambda_g = 2.0 * M_PI / sqrt( k_square - kc_square( 1, 0 ) );
m_parameters[ANG_L_PRM] =
2.0 * M_PI * m_parameters[PHYS_LEN_PRM] / lambda_g; /* in radians */
m_parameters[LOSS_CONDUCTOR_PRM] = alphac() * m_parameters[PHYS_LEN_PRM];
m_parameters[LOSS_DIELECTRIC_PRM] = alphad() * m_parameters[PHYS_LEN_PRM];
m_parameters[EPSILON_EFF_PRM] =
( 1.0 - pow( fc( 1, 0 ) / m_parameters[FREQUENCY_PRM], 2.0 ) );
}
else
{
/* evanascent modes */
m_parameters[Z0_PRM] = 0;
m_parameters[ANG_L_PRM] = 0;
m_parameters[EPSILON_EFF_PRM] = 0;
m_parameters[LOSS_DIELECTRIC_PRM] = 0.0;
m_parameters[LOSS_CONDUCTOR_PRM] = alphac_cutoff() * m_parameters[PHYS_LEN_PRM];
}
}
/*
* synthesize - synthesis function
* source: re-arrangment of calcAnalyze equation
* TE10 (via fc(1,0) ) results in the b term not influencing the result, as long as
* 1) fc > f
* 2) a > b
*/
void RECTWAVEGUIDE::calcSynthesize()
{
double lambda_g, k_square, beta;
/* solve for a */
m_parameters[PHYS_A_PRM] =
C0
/ ( sqrt( ( m_parameters[MUR_PRM] * m_parameters[EPSILONR_PRM] ) ) * 2
* m_parameters[FREQUENCY_PRM] * sqrt( 1
- pow( ( ZF0 * sqrt( m_parameters[MUR_PRM]
/ m_parameters[EPSILONR_PRM] ) )
/ m_parameters[Z0_PRM]
,2.0 ) ) );
k_square = kval_square();
beta = sqrt( k_square - kc_square( 1, 0 ) );
lambda_g = 2.0 * M_PI / beta;
m_parameters[PHYS_LEN_PRM] = ( m_parameters[ANG_L_PRM] * lambda_g ) / ( 2.0 * M_PI ); /* in m */
if( kc_square( 1, 0 ) <= k_square )
{
/*propagating modes */
beta = sqrt( k_square - kc_square( 1, 0 ) );
lambda_g = 2.0 * M_PI / beta;
m_parameters[LOSS_CONDUCTOR_PRM] = alphac() * m_parameters[PHYS_LEN_PRM];
m_parameters[LOSS_DIELECTRIC_PRM] = alphad() * m_parameters[PHYS_LEN_PRM];
m_parameters[EPSILON_EFF_PRM] =
( 1.0 - pow( ( fc( 1, 0 ) / m_parameters[FREQUENCY_PRM] ), 2.0 ) );
}
else
{
/*evanascent modes */
m_parameters[Z0_PRM] = 0;
m_parameters[ANG_L_PRM] = 0;
m_parameters[EPSILON_EFF_PRM] = 0;
m_parameters[LOSS_DIELECTRIC_PRM] = 0.0;
m_parameters[LOSS_CONDUCTOR_PRM] = alphac_cutoff() * m_parameters[PHYS_LEN_PRM];
}
}
void RECTWAVEGUIDE::showSynthesize()
{
if( isSelected( PHYS_A_PRM ) )
setProperty( PHYS_A_PRM, m_parameters[PHYS_A_PRM] );
if( isSelected( PHYS_B_PRM ) )
setProperty( PHYS_B_PRM, m_parameters[PHYS_B_PRM] );
setProperty( PHYS_LEN_PRM, m_parameters[PHYS_LEN_PRM] );
// Check for errors
if( !std::isfinite( m_parameters[PHYS_A_PRM] ) || m_parameters[PHYS_A_PRM] <= 0 )
setErrorLevel( PHYS_A_PRM, TRANSLINE_ERROR );
if( !std::isfinite( m_parameters[PHYS_B_PRM] ) || m_parameters[PHYS_B_PRM] <= 00 )
setErrorLevel( PHYS_B_PRM, TRANSLINE_ERROR );
// Check for warnings
if( !std::isfinite( m_parameters[Z0_PRM] ) || m_parameters[Z0_PRM] < 0 )
setErrorLevel( Z0_PRM, TRANSLINE_WARNING );
if( !std::isfinite( m_parameters[ANG_L_PRM] ) || m_parameters[ANG_L_PRM] < 0 )
setErrorLevel( ANG_L_PRM, TRANSLINE_WARNING );
}
void RECTWAVEGUIDE::showAnalyze()
{
setProperty( Z0_PRM, m_parameters[Z0_PRM] );
setProperty( ANG_L_PRM, m_parameters[ANG_L_PRM] );
// Check for errors
if( !std::isfinite( m_parameters[Z0_PRM] ) || m_parameters[Z0_PRM] < 0 )
setErrorLevel( Z0_PRM, TRANSLINE_ERROR );
if( !std::isfinite( m_parameters[ANG_L_PRM] ) || m_parameters[ANG_L_PRM] < 0 )
setErrorLevel( ANG_L_PRM, TRANSLINE_ERROR );
// Check for warnings
if( !std::isfinite( m_parameters[PHYS_A_PRM] ) || m_parameters[PHYS_A_PRM] <= 0 )
setErrorLevel( PHYS_A_PRM, TRANSLINE_WARNING );
if( !std::isfinite( m_parameters[PHYS_B_PRM] ) || m_parameters[PHYS_B_PRM] <= 00 )
setErrorLevel( PHYS_B_PRM, TRANSLINE_WARNING );
}
#define MAXSTRLEN 128
void RECTWAVEGUIDE::show_results()
{
int m, n, max = 6;
char text[MAXSTRLEN], txt[32];
// Z0EH = Ey / Hx (definition with field quantities)
Z0EH = ZF0 * sqrt( kval_square() / ( kval_square() - kc_square( 1, 0 ) ) );
setResult( 0, Z0EH, "Ohm" );
setResult( 1, m_parameters[EPSILON_EFF_PRM], "" );
setResult( 2, m_parameters[LOSS_CONDUCTOR_PRM], "dB" );
setResult( 3, m_parameters[LOSS_DIELECTRIC_PRM], "dB" );
// show possible TE modes (H modes)
if( m_parameters[FREQUENCY_PRM] < fc( 1, 0 ) )
{
strcpy( text, "none" );
}
else
{
strcpy( text, "" );
for( m = 0; m <= max; m++ )
{
for( n = 0; n <= max; n++ )
{
if( ( m == 0 ) && ( n == 0 ) )
continue;
if( m_parameters[FREQUENCY_PRM] >= ( fc( m, n ) ) )
{
snprintf( txt, sizeof( txt ), "H(%d,%d) ", m, n );
if( ( strlen( text ) + strlen( txt ) + 5 ) < MAXSTRLEN )
{
strcat( text, txt );
}
else
{
strcat( text, "..." );
m = n = max + 1; // print no more modes
}
}
}
}
}
setResult( 4, text );
// show possible TM modes (E modes)
if( m_parameters[FREQUENCY_PRM] < fc( 1, 1 ) )
{
strcpy( text, "none" );
}
else
{
strcpy( text, "" );
for( m = 1; m <= max; m++ )
{
for( n = 1; n <= max; n++ )
{
if( m_parameters[FREQUENCY_PRM] >= fc( m, n ) )
{
snprintf( txt, sizeof( txt ), "E(%d,%d) ", m, n );
if( ( strlen( text ) + strlen( txt ) + 5 ) < MAXSTRLEN )
{
strcat( text, txt );
}
else
{
strcat( text, "..." );
m = n = max + 1; // print no more modes
}
}
}
}
}
setResult( 5, text );
}
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