92 lines
3.3 KiB
Matlab
92 lines
3.3 KiB
Matlab
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% example demonstrating the use of a stripline terminated by a resistance
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% (c) 2013 Thorsten Liebig
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close all
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clear
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clc
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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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SL_length = 50000;
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SL_width = 520;
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SL_height = 500;
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substrate_thickness = SL_height;
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substrate_epr = 3.66;
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f_max = 7e9;
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Air_Spacer = 20000;
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%% setup FDTD parameters & excitation function %%%%%%%%%%%%%%%%%%%%%%%%%%%%
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FDTD = InitFDTD();
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FDTD = SetGaussExcite( FDTD, f_max/2, f_max/2 );
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BC = {'MUR' 'MUR' 'MUR' 'MUR' 'MUR' 'MUR'};
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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( [-SL_length/2 0 SL_length/2], resolution, 1.5 ,0 );
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mesh.y = SmoothMeshLines( [0 SL_width/2+[-resolution/3 +resolution/3*2]/4], resolution/4 , 1.5 ,0);
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mesh.y = SmoothMeshLines( [-10*SL_width -mesh.y mesh.y 10*SL_width], resolution, 1.3 ,0);
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mesh.z = linspace(0,substrate_thickness,5);
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mesh.z = sort(unique([mesh.z -mesh.z]));
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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), mesh.z(1)];
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stop = [mesh.x(end), mesh.y(end), mesh.z(end)];
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CSX = AddBox( CSX, 'RO4350B', 0, start, stop );
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%% add air spacer
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mesh.x = [mesh.x mesh.x(1)-Air_Spacer mesh.x(end)+Air_Spacer];
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mesh.y = [mesh.y mesh.y(1)-Air_Spacer mesh.y(end)+Air_Spacer];
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mesh.z = [mesh.z mesh.z(1)-Air_Spacer mesh.z(end)+Air_Spacer];
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mesh = SmoothMesh(mesh, c0/f_max/unit/20);
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CSX = DefineRectGrid( CSX, unit, mesh );
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%% SL port
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CSX = AddMetal( CSX, 'PEC' );
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portstart = [ -SL_length/2, -SL_width/2, 0];
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portstop = [ 0, SL_width/2, 0];
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[CSX,port{1}] = AddStripLinePort( CSX, 999, 1, 'PEC', portstart, portstop, SL_height, 'x', [0 0 -1], 'ExcitePort', true, 'Feed_R', 50, 'MeasPlaneShift', SL_length/3);
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portstart = [+SL_length/2, -SL_width/2, 0];
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portstop = [0 , SL_width/2, 0];
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[CSX,port{2}] = AddStripLinePort( CSX, 999, 2, 'PEC', portstart, portstop, SL_height, 'x', [0 0 -1], 'MeasPlaneShift', SL_length/3, 'Feed_R', 50);
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% bottom PEC plane
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CSX = AddBox(CSX, 'PEC', 999, [-SL_length/2 -10*SL_width -SL_height],[+SL_length/2 +10*SL_width -SL_height]);
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% top PEC plane
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CSX = AddBox(CSX, 'PEC', 999, [-SL_length/2 -10*SL_width SL_height],[+SL_length/2 +10*SL_width SL_height]);
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%% write/show/run the openEMS compatible xml-file
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Sim_Path = ['tmp_' mfilename];
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Sim_CSX = 'stripline.xml';
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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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WriteOpenEMS( [Sim_Path '/' Sim_CSX], FDTD, CSX );
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CSXGeomPlot( [Sim_Path '/' Sim_CSX] );
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RunOpenEMS( Sim_Path, Sim_CSX );
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%% post-processing
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close all
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f = linspace( 1e6, f_max, 1601 );
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port = calcPort( port, Sim_Path, f, 'RefImpedance', 50);
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s11 = port{1}.uf.ref./ port{1}.uf.inc;
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s21 = port{2}.uf.ref./ port{1}.uf.inc;
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plot(f/1e9,20*log10(abs(s11)),'k-','LineWidth',2);
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hold on;
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grid on;
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plot(f/1e9,20*log10(abs(s21)),'r--','LineWidth',2);
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legend('S_{11}','S_{21}');
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ylabel('S-Parameter (dB)','FontSize',12);
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xlabel('frequency (GHz) \rightarrow','FontSize',12);
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ylim([-50 2]);
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