208 lines
6.7 KiB
Matlab
208 lines
6.7 KiB
Matlab
%
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% EXAMPLE / microstrip / MSL2
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%
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% This example shows how to use the MSL-port.
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% The MSL is excited at the center of the computational volume. The
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% boundary at xmin is an absorbing boundary (Mur) and at xmax an electric
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% wall. The reflection coefficient at this wall is S11 = -1.
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% Direction of propagation is x.
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%
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% This example demonstrates:
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% - simple microstrip geometry (made of PEC)
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% - MSL port
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% - MSL analysis
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%
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%
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% Tested with
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% - Matlab 2009b
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% - Octave 3.3.52
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% - openEMS v0.0.14
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%
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% (C) 2010 Sebastian Held <sebastian.held@uni-due.de>
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close all
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clear
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clc
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%% switches
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postproc_only = 0;
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%% setup the simulation %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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physical_constants;
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unit = 1e-6; % specify everything in um
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MSL_length = 10000;
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MSL_width = 1000;
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substrate_thickness = 254;
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substrate_epr = 3.66;
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% mesh_res = [200 0 0];
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%% prepare simulation folder
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Sim_Path = 'tmp';
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Sim_CSX = 'msl2.xml';
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if ~postproc_only
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[status, message, messageid] = rmdir( Sim_Path, 's' ); % clear previous directory
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[status, message, messageid] = mkdir( Sim_Path ); % create empty simulation folder
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end
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%% setup FDTD parameters & excitation function %%%%%%%%%%%%%%%%%%%%%%%%%%%%
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max_timesteps = 20000;
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min_decrement = 1e-6;
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f_max = 7e9;
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FDTD = InitFDTD( max_timesteps, min_decrement, 'OverSampling', 10 );
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FDTD = SetGaussExcite( FDTD, f_max/2, f_max/2 );
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BC = {'MUR' 'PEC' 'PEC' 'PEC' 'PEC' 'PMC'};
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FDTD = SetBoundaryCond( FDTD, BC );
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%% setup CSXCAD geometry & mesh %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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CSX = InitCSX();
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resolution = c0/(f_max*sqrt(substrate_epr))/unit /50; % resolution of lambda/50
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mesh.x = SmoothMeshLines( [-MSL_length MSL_length], resolution );
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mesh.y = SmoothMeshLines( [-4*MSL_width -MSL_width/2 MSL_width/2 4*MSL_width], resolution );
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mesh.z = SmoothMeshLines( [linspace(0,substrate_thickness,5) 10*substrate_thickness], resolution );
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CSX = DefineRectGrid( CSX, unit, mesh );
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%% substrate
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CSX = AddMaterial( CSX, 'RO4350B' );
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CSX = SetMaterialProperty( CSX, 'RO4350B', 'Epsilon', substrate_epr );
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start = [mesh.x(1), mesh.y(1), 0];
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stop = [mesh.x(end), mesh.y(end), substrate_thickness];
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CSX = AddBox( CSX, 'RO4350B', 0, start, stop );
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%% MSL port
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CSX = AddMetal( CSX, 'PEC' );
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portstart = [ 0, -MSL_width/2, substrate_thickness];
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portstop = [ MSL_length, MSL_width/2, 0];
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[CSX,portstruct] = AddMSLPort( CSX, 1, 'PEC', portstart, portstop, [1 0 0], [0 0 1], [], 'excite' );
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%% MSL
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start = [-MSL_length, -MSL_width/2, substrate_thickness];
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stop = [ 0, MSL_width/2, substrate_thickness];
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CSX = AddBox( CSX, 'PEC', 999, start, stop ); % priority needs to be higher than
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%% define dump boxes
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start = [mesh.x(1), mesh.y(1), substrate_thickness/2];
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stop = [mesh.x(end), mesh.y(end), substrate_thickness/2];
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CSX = AddDump( CSX, 'Et_', 'DumpType', 0,'DumpMode', 2 ); % cell interpolated
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CSX = AddBox( CSX, 'Et_', 0, start, stop );
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CSX = AddDump( CSX, 'Ht_', 'DumpType', 1,'DumpMode', 2 ); % cell interpolated
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CSX = AddBox( CSX, 'Ht_', 0, start, stop );
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%% write openEMS compatible xml-file
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WriteOpenEMS( [Sim_Path '/' Sim_CSX], FDTD, CSX );
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%% show the structure
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CSXGeomPlot( [Sim_Path '/' Sim_CSX] );
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%% run openEMS
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openEMS_opts = '';
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openEMS_opts = [openEMS_opts ' --engine=fastest'];
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% openEMS_opts = [openEMS_opts ' --debug-material'];
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% openEMS_opts = [openEMS_opts ' --debug-boxes'];
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% openEMS_opts = [openEMS_opts ' --debug-PEC'];
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if ~postproc_only
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RunOpenEMS( Sim_Path, Sim_CSX, openEMS_opts );
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end
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%% postprocess
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f = linspace( 1e6, f_max, 1601 );
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U = ReadUI( {'port_ut1A','port_ut1B','et'}, 'tmp/', f );
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I = ReadUI( {'port_it1A','port_it1B'}, 'tmp/', f );
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% Z = (U.FD{1}.val+U.FD{2}.val)/2 ./ I.FD{1}.val;
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% plot( f*1e-9, [real(Z);imag(Z)],'Linewidth',2);
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% xlabel('frequency (GHz)');
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% ylabel('impedance (Ohm)');
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% grid on;
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% legend( {'real','imaginary'}, 'location', 'northwest' )
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% title( 'line impedance (will fail in case of reflections!)' );
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figure
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ax = plotyy( U.TD{1}.t/1e-6, [U.TD{1}.val;U.TD{2}.val], U.TD{3}.t/1e-6, U.TD{3}.val );
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xlabel( 'time (us)' );
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ylabel( 'amplitude (V)' );
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grid on
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title( 'Time domain voltage probes and excitation signal' );
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legend( {'ut1A','ut1B','excitation'} );
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% now make the y-axis symmetric to y=0 (align zeros of y1 and y2)
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y1 = ylim(ax(1));
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y2 = ylim(ax(2));
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ylim( ax(1), [-max(abs(y1)) max(abs(y1))] );
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ylim( ax(2), [-max(abs(y2)) max(abs(y2))] );
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figure
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plot( I.TD{1}.t/1e-6, [I.TD{1}.val;I.TD{2}.val] );
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xlabel( 'time (us)' );
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ylabel( 'amplitude (A)' );
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grid on
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title( 'Time domain current probes' );
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legend( {'it1A','it1B'} );
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% port analysis
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[S11,beta,ZL] = calcMSLPort( portstruct, Sim_Path, f );
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% attention! the reflection coefficient S11 is normalized to ZL!
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figure
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plot( sin(0:0.01:2*pi), cos(0:0.01:2*pi), 'Color', [.7 .7 .7] );
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hold on
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plot( 0.5+0.5*sin(0:0.01:2*pi), 0.5*cos(0:0.01:2*pi), 'Color', [.7 .7 .7] );
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plot( [-1 1], [0 0], 'Color', [.7 .7 .7] );
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plot( S11, 'k' );
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plot( real(S11(1)), imag(S11(1)), '*r' );
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axis equal
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title( 'Reflection coefficient S11 at the measurement plane' );
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figure
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plot( f/1e9, [real(S11);imag(S11)], 'Linewidth',2 );
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legend( {'Re(S11)', 'Im(S11)'} );
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ylabel( 'amplitude' );
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xlabel( 'frequency (GHz)' );
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title( 'Reflection coefficient S11 at the measurement plane' );
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figure
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plotyy( f/1e9, 20*log10(abs(S11)), f/1e9, angle(S11)/pi*180 );
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legend( {'|S11|', 'angle(S11)'} );
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xlabel( 'frequency (GHz)' );
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ylabel( '|S11| (dB)' );
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title( 'Reflection coefficient S11 at the measurement plane' );
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figure
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plot( f/1e9, [real(beta);imag(beta)], 'Linewidth',2 );
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legend( 'Re(beta)', 'Im(beta)' );
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ylabel( 'propagation constant beta (1/m)' );
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xlabel( 'frequency (GHz)' );
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title( 'Propagation constant of the MSL' );
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figure
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plot( f/1e9, [real(ZL);imag(ZL)], 'Linewidth',2);
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xlabel('frequency (GHz)');
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ylabel('impedance (Ohm)');
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grid on;
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legend( {'real','imaginary'}, 'location', 'northeast' )
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title( 'Characteristic line impedance ZL' );
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% reference plane shift (to the end of the port)
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ref_shift = abs(portstop(1) - portstart(1));
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[S11,beta,ZL] = calcMSLPort( portstruct, Sim_Path, f, ref_shift );
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figure
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plotyy( f/1e9, 20*log10(abs(S11)), f/1e9, angle(S11)/pi*180 );
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legend( {'abs(S11)', 'angle(S11)'} );
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xlabel( 'frequency (GHz)' );
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title( 'Reflection coefficient S11 at the reference plane (at the electric wall)' );
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figure
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plot( sin(0:0.01:2*pi), cos(0:0.01:2*pi), 'Color', [.7 .7 .7] );
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hold on
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plot( 0.5+0.5*sin(0:0.01:2*pi), 0.5*cos(0:0.01:2*pi), 'Color', [.7 .7 .7] );
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plot( [-1 1], [0 0], 'Color', [.7 .7 .7] );
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plot( S11, 'k' );
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plot( real(S11(1)), imag(S11(1)), '*r' );
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axis equal
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title( 'Reflection coefficient S11 at the reference plane (at the electric wall)' );
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%% visualize electric and magnetic fields
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% you will find vtk dump files in the simulation folder (tmp/)
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% use paraview to visualize them
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