matlab examples: cleaned up Patch_Antenna
Sebastian Held
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@ -1,23 +1,29 @@
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%
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% EXAMPLE / antennas / patch antenna
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%
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% This example demonstrates how to:
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% - calculate the reflection coefficient of a patch antenna
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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 Thorsten Liebig <thorsten.liebig@uni-due.de>
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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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% all length in mm
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unit = 1e-3;
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f0 = 2e9;
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fc = 1e9;
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freq = linspace(f0-fc,f0+fc,501);
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%% setup the simulation
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physical_constants;
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max_res = c0 / (f0+fc) / unit / 20;
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unit = 1e-3; % all length in mm
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% width in x-direction
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% length in y-direction
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% main radiation in z-direction
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patch.width = 32.86; %resonant length
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patch.width = 32.86; % resonant length
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patch.length = 41.37;
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substrate.epsR = 3.38;
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@ -28,114 +34,147 @@ substrate.cells = 5;
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feed.pos = -4.5;
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feed.width = 0.5;
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feed.R = 50; %feed resistance
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feed.R = 50; % feed resistance
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%size of the simulation box
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% size of the simulation box
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SimBox = [120 120 32];
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%% define openEMS options %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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openEMS_opts = '';
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openEMS_opts = [openEMS_opts ' --engine=fastest'];
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openEMS_opts = [openEMS_opts ' --numThreads=4'];
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%% prepare simulation folder
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Sim_Path = 'tmp';
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Sim_CSX = 'patch_ant.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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[status, message, messageid] = rmdir(Sim_Path,'s');
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[status, message, messageid] = mkdir(Sim_Path);
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%% setup FDTD parameter & excitation function
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max_timesteps = 30000;
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min_decrement = 1e-5; % equivalent to -50 dB
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f0 = 2e9; % center frequency
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fc = 1e9; % 10 dB corner frequency (in this case 1e9 Hz - 3e9 Hz)
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FDTD = InitFDTD( max_timesteps, min_decrement );
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FDTD = SetGaussExcite( FDTD, f0, fc );
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BC = {'MUR' 'MUR' 'MUR' 'MUR' 'PEC' 'MUR'}; % boundary conditions
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% BC = {'PML_8' 'PML_8' 'PML_8' 'PML_8' 'PEC' 'PML_8'}; % use pml instead of mur
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FDTD = SetBoundaryCond( FDTD, BC );
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%% setup FDTD parameter & excitation function %%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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FDTD = InitFDTD(30000, 1e-5);
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FDTD = SetGaussExcite(FDTD,f0,fc);
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BC = [2 2 2 2 0 2]; %mur ABC
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% BC = [3 3 3 3 0 3]; %use pml instead of mur
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FDTD = SetBoundaryCond(FDTD,BC);
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%% setup CSXCAD geometry & mesh %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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%% setup CSXCAD geometry & mesh
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% currently, openEMS cannot automatically generate a mesh
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max_res = c0 / (f0+fc) / unit / 20; % cell size: lambda/20
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CSX = InitCSX();
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mesh.x = [-SimBox(1)/2-8*max_res SimBox(1)/2+8*max_res -SimBox(1)/2 SimBox(1)/2 -substrate.width/2 substrate.width/2 feed.pos-feed.width/2 feed.pos+feed.width/2];
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%add patch mesh with 2/3 - 1/3 rule
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mesh.x = sort(unique([mesh.x -patch.width/2-max_res*0.66 -patch.width/2+max_res*0.33 patch.width/2+max_res*0.66 patch.width/2-max_res*0.33]));
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mesh.x = SmoothMeshLines(mesh.x,max_res);
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mesh.y = [-SimBox(2)/2-8*max_res SimBox(2)/2+8*max_res -SimBox(2)/2 SimBox(2)/2 -substrate.length/2 substrate.length/2 -feed.width/2 feed.width/2];
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%add patch mesh with 2/3 - 1/3 rule
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mesh.y = sort(unique([mesh.y -patch.length/2-max_res*0.66 -patch.length/2+max_res*0.33 patch.length/2+max_res*0.66 patch.length/2-max_res*0.33]));
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mesh.y = SmoothMeshLines(mesh.y,max_res);
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mesh.z = SmoothMeshLines([linspace(0,substrate.thickness,substrate.cells) SimBox(3) SimBox(3)+8*max_res],max_res);
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CSX = DefineRectGrid(CSX, unit,mesh);
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mesh.x = [-SimBox(1)/2 SimBox(1)/2 -substrate.width/2 substrate.width/2 feed.pos-feed.width/2 feed.pos+feed.width/2];
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% add patch mesh with 2/3 - 1/3 rule
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mesh.x = [mesh.x -patch.width/2-max_res*0.66 -patch.width/2+max_res*0.33 patch.width/2+max_res*0.66 patch.width/2-max_res*0.33];
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mesh.x = SmoothMeshLines( mesh.x, max_res ); % create a smooth mesh between specified mesh lines
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mesh.y = [-SimBox(2)/2 SimBox(2)/2 -substrate.length/2 substrate.length/2 -feed.width/2 feed.width/2];
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% add patch mesh with 2/3 - 1/3 rule
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mesh.y = [mesh.y -patch.length/2-max_res*0.66 -patch.length/2+max_res*0.33 patch.length/2+max_res*0.66 patch.length/2-max_res*0.33];
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mesh.y = SmoothMeshLines( mesh.y, max_res );
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mesh.z = [linspace(0,substrate.thickness,substrate.cells) SimBox(3) SimBox(3)];
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mesh.z = SmoothMeshLines( mesh.z, max_res );
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mesh = AddPML( mesh, [8 8 8 8 0 8] ); % add equidistant cells (air around the structure)
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CSX = DefineRectGrid( CSX, unit, mesh );
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%% patch %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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CSX = AddMetal(CSX,'patch');
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%% create patch
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CSX = AddMetal( CSX, 'patch' ); % create a perfect electric conductor (PEC)
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start = [-patch.width/2 -patch.length/2 substrate.thickness];
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stop = [ patch.width/2 patch.length/2 substrate.thickness];
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CSX = AddBox(CSX,'patch',10,start,stop);
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%% substrate
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CSX = AddMaterial(CSX,'substrate');
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CSX = SetMaterialProperty(CSX,'substrate','Epsilon',substrate.epsR);
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%% create substrate
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CSX = AddMaterial( CSX, 'substrate' );
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CSX = SetMaterialProperty( CSX, 'substrate', 'Epsilon', substrate.epsR );
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start = [-substrate.width/2 -substrate.length/2 0];
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stop = [ substrate.width/2 substrate.length/2 substrate.thickness];
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CSX = AddBox(CSX,'substrate',0,start,stop);
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CSX = AddBox( CSX, 'substrate', 0, start, stop );
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%% apply the excitation & resist as a current source%%%%%%%%%%%%%%%%%%%%%%%
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CSX = AddMaterial(CSX, 'resist');
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%% apply the excitation & resist as a current source
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% this creates a "port"
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CSX = AddMaterial( CSX, 'resist' );
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kappa = substrate.thickness/feed.R/feed.width^2/unit;
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CSX = SetMaterialProperty(CSX, 'resist', 'Kappa', kappa);
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start=[feed.pos-feed.width/2 -feed.width/2 0];
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stop =[feed.pos+feed.width/2 feed.width/2 substrate.thickness];
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CSX = AddBox(CSX, 'resist', 15, start, stop);
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CSX = SetMaterialProperty( CSX, 'resist', 'Kappa', kappa );
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start = [feed.pos-feed.width/2 -feed.width/2 0];
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stop = [feed.pos+feed.width/2 feed.width/2 substrate.thickness];
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CSX = AddBox( CSX, 'resist', 15, start, stop );
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CSX = AddExcitation(CSX, 'excite', 0, [0 0 1]);
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CSX = AddBox(CSX, 'excite', 0, start, stop);
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CSX = AddExcitation( CSX, 'excite', 0, [0 0 1] ); % excitation in z-direction
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CSX = AddBox( CSX, 'excite', 0, start, stop );
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%% define voltage calc boxes %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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%voltage calc
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start=[feed.pos 0 0];
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stop =[feed.pos 0 substrate.thickness];
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CSX = AddProbe(CSX,'ut1',0);
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CSX = AddBox(CSX,'ut1', 0 ,stop,start);
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%% define voltage calc boxes
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CSX = AddProbe( CSX, 'ut1', 0 );
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start = [feed.pos 0 0];
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stop = [feed.pos 0 substrate.thickness];
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CSX = AddBox( CSX, 'ut1', 0 , stop, start );
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%current calc
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CSX = AddProbe(CSX,'it1',1);
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start=[feed.pos-feed.width -feed.width substrate.thickness/2];
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stop =[feed.pos+feed.width feed.width substrate.thickness/2];
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CSX = AddBox(CSX,'it1', 0 ,start,stop);
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%% define current calc boxes
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CSX = AddProbe( CSX, 'it1', 1 );
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start = [feed.pos-feed.width -feed.width substrate.thickness/2];
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stop = [feed.pos+feed.width feed.width substrate.thickness/2];
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CSX = AddBox( CSX, 'it1', 0, start, stop );
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%% dump magnetic field over the patch antenna
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CSX = AddDump(CSX,'Ht_','DumpType',1,'DumpMode',2);
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CSX = AddDump( CSX, 'Ht_', 'DumpType', 1, 'DumpMode', 2 ); % cell interpolated
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start = [-patch.width -patch.length substrate.thickness+1];
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stop = [ patch.width patch.length substrate.thickness+1];
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CSX = AddBox(CSX,'Ht_',0 , start,stop);
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CSX = AddBox( CSX, 'Ht_', 0, start, stop );
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%% Write openEMS compatoble xml-file %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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WriteOpenEMS([Sim_Path '/' Sim_CSX],FDTD,CSX);
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%% write openEMS compatible xml-file
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WriteOpenEMS( [Sim_Path '/' Sim_CSX], FDTD, CSX );
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%% run openEMS %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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RunOpenEMS(Sim_Path, Sim_CSX, openEMS_opts);
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%% show the structure
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CSXGeomPlot( [Sim_Path '/' Sim_CSX] );
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%% postproc & do the plots %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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U = ReadUI('ut1','tmp/',freq);
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I = ReadUI('it1','tmp/',freq);
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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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RunOpenEMS( Sim_Path, Sim_CSX, openEMS_opts );
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close all
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%% postprocessing & do the plots
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freq = linspace( f0-fc, f0+fc, 501 );
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U = ReadUI( {'ut1','et'}, 'tmp/', freq ); % time domain/freq domain voltage
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I = ReadUI( 'it1', 'tmp/', freq ); % time domain/freq domain current (half time step is corrected)
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plot(U.TD{1}.t,U.TD{1}.val,'Linewidth',2);
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grid on;
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% plot time domain voltage
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figure
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[ax,h1,h2] = plotyy( U.TD{1}.t/1e-9, U.TD{1}.val, U.TD{2}.t/1e-9, U.TD{2}.val );
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set( h1, 'Linewidth', 2 );
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set( h1, 'Color', [1 0 0] );
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set( h2, 'Linewidth', 2 );
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set( h2, 'Color', [0 0 0] );
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grid on
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title( 'time domain voltage' );
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xlabel( 'time t / ns' );
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ylabel( ax(1), 'voltage ut1 / V' );
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ylabel( ax(2), 'voltage et / V' );
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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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Zin = U.FD{1}.val./I.FD{1}.val;
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figure()
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plot(freq,real(Zin),'k-','Linewidth',2);
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hold on;
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grid on;
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plot(freq,imag(Zin),'r--','Linewidth',2);
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% plot feed point impedance
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figure
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Zin = U.FD{1}.val ./ I.FD{1}.val;
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plot( freq/1e6, real(Zin), 'k-', 'Linewidth', 2 );
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hold on
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grid on
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plot( freq/1e6, imag(Zin), 'r--', 'Linewidth', 2 );
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title( 'feed point impedance' );
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xlabel( 'frequency f / MHz' );
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ylabel( 'impedance Z_{in} / Ohm' );
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legend( 'real', 'imag' );
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% plot reflection coefficient S11
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figure
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uf_inc = 0.5*(U.FD{1}.val + I.FD{1}.val * 50);
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if_inc = 0.5*(I.FD{1}.val - U.FD{1}.val / 50);
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uf_ref = U.FD{1}.val - uf_inc;
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if_ref = I.FD{1}.val - if_inc;
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s11 = uf_ref ./ uf_inc;
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plot( freq/1e6, 20*log10(abs(s11)), 'k-', 'Linewidth', 2 );
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grid on
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title( 'reflection coefficient S_{11}' );
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xlabel( 'frequency f / MHz' );
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ylabel( 'reflection coefficient |S_{11}|' );
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s11 = uf_ref./uf_inc;
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figure()
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plot(freq,20*log10(abs(s11)),'k-','Linewidth',2);
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grid on;
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%% visualize magnetic fields
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% you will find vtk dump files in the simulation folder (tmp/)
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% use paraview to visulaize them
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