From 52feb7d29913c5c726f0ba64d5f21297da7ca487 Mon Sep 17 00:00:00 2001 From: Sebastian Held Date: Thu, 14 Oct 2010 13:25:03 +0200 Subject: [PATCH] matlab examples: cleaned up Patch_Antenna --- matlab/examples/antennas/Patch_Antenna.m | 211 ++++++++++++++--------- 1 file changed, 125 insertions(+), 86 deletions(-) diff --git a/matlab/examples/antennas/Patch_Antenna.m b/matlab/examples/antennas/Patch_Antenna.m index 4f3c8a7..0fc6fbb 100644 --- a/matlab/examples/antennas/Patch_Antenna.m +++ b/matlab/examples/antennas/Patch_Antenna.m @@ -1,23 +1,29 @@ +% +% EXAMPLE / antennas / patch antenna +% +% This example demonstrates how to: +% - calculate the reflection coefficient of a patch antenna +% +% +% Tested with +% - Matlab 2009b +% - Octave 3.3.52 +% - openEMS v0.0.14 +% +% (C) 2010 Thorsten Liebig + close all clear clc -%% setup the simulation %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -% all length in mm -unit = 1e-3; - -f0 = 2e9; -fc = 1e9; -freq = linspace(f0-fc,f0+fc,501); - +%% setup the simulation physical_constants; - -max_res = c0 / (f0+fc) / unit / 20; +unit = 1e-3; % all length in mm % width in x-direction % length in y-direction % main radiation in z-direction -patch.width = 32.86; %resonant length +patch.width = 32.86; % resonant length patch.length = 41.37; substrate.epsR = 3.38; @@ -28,114 +34,147 @@ substrate.cells = 5; feed.pos = -4.5; feed.width = 0.5; -feed.R = 50; %feed resistance +feed.R = 50; % feed resistance -%size of the simulation box +% size of the simulation box SimBox = [120 120 32]; -%% define openEMS options %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -openEMS_opts = ''; -openEMS_opts = [openEMS_opts ' --engine=fastest']; -openEMS_opts = [openEMS_opts ' --numThreads=4']; - +%% prepare simulation folder Sim_Path = 'tmp'; Sim_CSX = 'patch_ant.xml'; +[status, message, messageid] = rmdir( Sim_Path, 's' ); % clear previous directory +[status, message, messageid] = mkdir( Sim_Path ); % create empty simulation folder -[status, message, messageid] = rmdir(Sim_Path,'s'); -[status, message, messageid] = mkdir(Sim_Path); +%% setup FDTD parameter & excitation function +max_timesteps = 30000; +min_decrement = 1e-5; % equivalent to -50 dB +f0 = 2e9; % center frequency +fc = 1e9; % 10 dB corner frequency (in this case 1e9 Hz - 3e9 Hz) +FDTD = InitFDTD( max_timesteps, min_decrement ); +FDTD = SetGaussExcite( FDTD, f0, fc ); +BC = {'MUR' 'MUR' 'MUR' 'MUR' 'PEC' 'MUR'}; % boundary conditions +% BC = {'PML_8' 'PML_8' 'PML_8' 'PML_8' 'PEC' 'PML_8'}; % use pml instead of mur +FDTD = SetBoundaryCond( FDTD, BC ); -%% setup FDTD parameter & excitation function %%%%%%%%%%%%%%%%%%%%%%%%%%%%% -FDTD = InitFDTD(30000, 1e-5); -FDTD = SetGaussExcite(FDTD,f0,fc); -BC = [2 2 2 2 0 2]; %mur ABC -% BC = [3 3 3 3 0 3]; %use pml instead of mur -FDTD = SetBoundaryCond(FDTD,BC); - -%% setup CSXCAD geometry & mesh %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +%% setup CSXCAD geometry & mesh +% currently, openEMS cannot automatically generate a mesh +max_res = c0 / (f0+fc) / unit / 20; % cell size: lambda/20 CSX = InitCSX(); -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]; -%add patch mesh with 2/3 - 1/3 rule -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])); -mesh.x = SmoothMeshLines(mesh.x,max_res); -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]; -%add patch mesh with 2/3 - 1/3 rule -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])); -mesh.y = SmoothMeshLines(mesh.y,max_res); -mesh.z = SmoothMeshLines([linspace(0,substrate.thickness,substrate.cells) SimBox(3) SimBox(3)+8*max_res],max_res); -CSX = DefineRectGrid(CSX, unit,mesh); +mesh.x = [-SimBox(1)/2 SimBox(1)/2 -substrate.width/2 substrate.width/2 feed.pos-feed.width/2 feed.pos+feed.width/2]; +% add patch mesh with 2/3 - 1/3 rule +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]; +mesh.x = SmoothMeshLines( mesh.x, max_res ); % create a smooth mesh between specified mesh lines +mesh.y = [-SimBox(2)/2 SimBox(2)/2 -substrate.length/2 substrate.length/2 -feed.width/2 feed.width/2]; +% add patch mesh with 2/3 - 1/3 rule +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]; +mesh.y = SmoothMeshLines( mesh.y, max_res ); +mesh.z = [linspace(0,substrate.thickness,substrate.cells) SimBox(3) SimBox(3)]; +mesh.z = SmoothMeshLines( mesh.z, max_res ); +mesh = AddPML( mesh, [8 8 8 8 0 8] ); % add equidistant cells (air around the structure) +CSX = DefineRectGrid( CSX, unit, mesh ); -%% patch %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -CSX = AddMetal(CSX,'patch'); +%% create patch +CSX = AddMetal( CSX, 'patch' ); % create a perfect electric conductor (PEC) start = [-patch.width/2 -patch.length/2 substrate.thickness]; stop = [ patch.width/2 patch.length/2 substrate.thickness]; CSX = AddBox(CSX,'patch',10,start,stop); -%% substrate -CSX = AddMaterial(CSX,'substrate'); -CSX = SetMaterialProperty(CSX,'substrate','Epsilon',substrate.epsR); +%% create substrate +CSX = AddMaterial( CSX, 'substrate' ); +CSX = SetMaterialProperty( CSX, 'substrate', 'Epsilon', substrate.epsR ); start = [-substrate.width/2 -substrate.length/2 0]; stop = [ substrate.width/2 substrate.length/2 substrate.thickness]; -CSX = AddBox(CSX,'substrate',0,start,stop); +CSX = AddBox( CSX, 'substrate', 0, start, stop ); -%% apply the excitation & resist as a current source%%%%%%%%%%%%%%%%%%%%%%% -CSX = AddMaterial(CSX, 'resist'); +%% apply the excitation & resist as a current source +% this creates a "port" +CSX = AddMaterial( CSX, 'resist' ); kappa = substrate.thickness/feed.R/feed.width^2/unit; -CSX = SetMaterialProperty(CSX, 'resist', 'Kappa', kappa); -start=[feed.pos-feed.width/2 -feed.width/2 0]; -stop =[feed.pos+feed.width/2 feed.width/2 substrate.thickness]; -CSX = AddBox(CSX, 'resist', 15, start, stop); +CSX = SetMaterialProperty( CSX, 'resist', 'Kappa', kappa ); +start = [feed.pos-feed.width/2 -feed.width/2 0]; +stop = [feed.pos+feed.width/2 feed.width/2 substrate.thickness]; +CSX = AddBox( CSX, 'resist', 15, start, stop ); -CSX = AddExcitation(CSX, 'excite', 0, [0 0 1]); -CSX = AddBox(CSX, 'excite', 0, start, stop); +CSX = AddExcitation( CSX, 'excite', 0, [0 0 1] ); % excitation in z-direction +CSX = AddBox( CSX, 'excite', 0, start, stop ); -%% define voltage calc boxes %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -%voltage calc -start=[feed.pos 0 0]; -stop =[feed.pos 0 substrate.thickness]; -CSX = AddProbe(CSX,'ut1',0); -CSX = AddBox(CSX,'ut1', 0 ,stop,start); +%% define voltage calc boxes +CSX = AddProbe( CSX, 'ut1', 0 ); +start = [feed.pos 0 0]; +stop = [feed.pos 0 substrate.thickness]; +CSX = AddBox( CSX, 'ut1', 0 , stop, start ); -%current calc -CSX = AddProbe(CSX,'it1',1); -start=[feed.pos-feed.width -feed.width substrate.thickness/2]; -stop =[feed.pos+feed.width feed.width substrate.thickness/2]; -CSX = AddBox(CSX,'it1', 0 ,start,stop); +%% define current calc boxes +CSX = AddProbe( CSX, 'it1', 1 ); +start = [feed.pos-feed.width -feed.width substrate.thickness/2]; +stop = [feed.pos+feed.width feed.width substrate.thickness/2]; +CSX = AddBox( CSX, 'it1', 0, start, stop ); %% dump magnetic field over the patch antenna -CSX = AddDump(CSX,'Ht_','DumpType',1,'DumpMode',2); +CSX = AddDump( CSX, 'Ht_', 'DumpType', 1, 'DumpMode', 2 ); % cell interpolated start = [-patch.width -patch.length substrate.thickness+1]; stop = [ patch.width patch.length substrate.thickness+1]; -CSX = AddBox(CSX,'Ht_',0 , start,stop); +CSX = AddBox( CSX, 'Ht_', 0, start, stop ); -%% Write openEMS compatoble xml-file %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -WriteOpenEMS([Sim_Path '/' Sim_CSX],FDTD,CSX); +%% write openEMS compatible xml-file +WriteOpenEMS( [Sim_Path '/' Sim_CSX], FDTD, CSX ); -%% run openEMS %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -RunOpenEMS(Sim_Path, Sim_CSX, openEMS_opts); +%% show the structure +CSXGeomPlot( [Sim_Path '/' Sim_CSX] ); -%% postproc & do the plots %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -U = ReadUI('ut1','tmp/',freq); -I = ReadUI('it1','tmp/',freq); +%% run openEMS +openEMS_opts = ''; +openEMS_opts = [openEMS_opts ' --engine=fastest']; +RunOpenEMS( Sim_Path, Sim_CSX, openEMS_opts ); -close all +%% postprocessing & do the plots +freq = linspace( f0-fc, f0+fc, 501 ); +U = ReadUI( {'ut1','et'}, 'tmp/', freq ); % time domain/freq domain voltage +I = ReadUI( 'it1', 'tmp/', freq ); % time domain/freq domain current (half time step is corrected) -plot(U.TD{1}.t,U.TD{1}.val,'Linewidth',2); -grid on; +% plot time domain voltage +figure +[ax,h1,h2] = plotyy( U.TD{1}.t/1e-9, U.TD{1}.val, U.TD{2}.t/1e-9, U.TD{2}.val ); +set( h1, 'Linewidth', 2 ); +set( h1, 'Color', [1 0 0] ); +set( h2, 'Linewidth', 2 ); +set( h2, 'Color', [0 0 0] ); +grid on +title( 'time domain voltage' ); +xlabel( 'time t / ns' ); +ylabel( ax(1), 'voltage ut1 / V' ); +ylabel( ax(2), 'voltage et / V' ); +% now make the y-axis symmetric to y=0 (align zeros of y1 and y2) +y1 = ylim(ax(1)); +y2 = ylim(ax(2)); +ylim( ax(1), [-max(abs(y1)) max(abs(y1))] ); +ylim( ax(2), [-max(abs(y2)) max(abs(y2))] ); -Zin = U.FD{1}.val./I.FD{1}.val; -figure() -plot(freq,real(Zin),'k-','Linewidth',2); -hold on; -grid on; -plot(freq,imag(Zin),'r--','Linewidth',2); +% plot feed point impedance +figure +Zin = U.FD{1}.val ./ I.FD{1}.val; +plot( freq/1e6, real(Zin), 'k-', 'Linewidth', 2 ); +hold on +grid on +plot( freq/1e6, imag(Zin), 'r--', 'Linewidth', 2 ); +title( 'feed point impedance' ); +xlabel( 'frequency f / MHz' ); +ylabel( 'impedance Z_{in} / Ohm' ); +legend( 'real', 'imag' ); +% plot reflection coefficient S11 +figure uf_inc = 0.5*(U.FD{1}.val + I.FD{1}.val * 50); if_inc = 0.5*(I.FD{1}.val - U.FD{1}.val / 50); uf_ref = U.FD{1}.val - uf_inc; if_ref = I.FD{1}.val - if_inc; +s11 = uf_ref ./ uf_inc; +plot( freq/1e6, 20*log10(abs(s11)), 'k-', 'Linewidth', 2 ); +grid on +title( 'reflection coefficient S_{11}' ); +xlabel( 'frequency f / MHz' ); +ylabel( 'reflection coefficient |S_{11}|' ); -s11 = uf_ref./uf_inc; -figure() -plot(freq,20*log10(abs(s11)),'k-','Linewidth',2); -grid on; - +%% visualize magnetic fields +% you will find vtk dump files in the simulation folder (tmp/) +% use paraview to visulaize them