From 8d2ad3e0afea280107d91e4754b278c38ff8021d Mon Sep 17 00:00:00 2001 From: Thorsten Liebig Date: Tue, 3 Sep 2013 13:12:34 +0200 Subject: [PATCH] new tutorial: a bent patch antenna in cylindrical coordinates Signed-off-by: Thorsten Liebig --- matlab/Tutorials/Bent_Patch_Antenna.m | 197 ++++++++++++++++++++++++++ 1 file changed, 197 insertions(+) create mode 100644 matlab/Tutorials/Bent_Patch_Antenna.m diff --git a/matlab/Tutorials/Bent_Patch_Antenna.m b/matlab/Tutorials/Bent_Patch_Antenna.m new file mode 100644 index 0000000..7e99c3b --- /dev/null +++ b/matlab/Tutorials/Bent_Patch_Antenna.m @@ -0,0 +1,197 @@ +% +% Tutorials / bent patch antenna +% +% Describtion at: +% http://openems.de/index.php/Tutorial:_Bent_Patch_Antenna +% +% Tested with +% - Matlab 2011a / Octave 3.6.4 +% - openEMS v0.0.31 +% +% (C) 2013 Thorsten Liebig + +close all +clear +clc + +%% setup the simulation +physical_constants; +unit = 1e-3; % all length in mm + +% patch width in alpha-direction +patch.width = 32; % resonant length in alpha-direction +patch.radius = 50; % radius +patch.length = 40; % patch length in z-direction + +%substrate setup +substrate.epsR = 3.38; +substrate.kappa = 1e-3 * 2*pi*2.45e9 * EPS0*substrate.epsR; +substrate.width = 80; +substrate.length = 90; +substrate.thickness = 1.524; +substrate.cells = 4; + +%setup feeding +feed.pos = -5.5; %feeding position in x-direction +feed.width = 2; %feeding port width +feed.R = 50; %feed resistance + +% size of the simulation box +SimBox.rad = 2*100; +SimBox.height = 1.5*200; + +%% setup FDTD parameter & excitation function +FDTD = InitFDTD('CoordSystem', 1); % init a cylindrical FDTD +f0 = 2e9; % center frequency +fc = 1e9; % 20 dB corner frequency +FDTD = SetGaussExcite( FDTD, f0, fc ); +BC = [2 2 2 2 2 2]; % boundary conditions +FDTD = SetBoundaryCond( FDTD, BC ); + +%% setup CSXCAD geometry & mesh +% init a cylindrical mesh +CSX = InitCSX('CoordSystem',1); + +% calculate some width as an angle in radiant +patch_ang_width = patch.width/(patch.radius+substrate.thickness); +substr_ang_width = substrate.width/patch.radius; +feed_angle = feed.pos/patch.radius; + +%% create patch +CSX = AddMetal( CSX, 'patch' ); % create a perfect electric conductor (PEC) +start = [patch.radius+substrate.thickness -patch_ang_width/2 -patch.length/2 ]; +stop = [patch.radius+substrate.thickness patch_ang_width/2 patch.length/2 ]; +CSX = AddBox(CSX,'patch',10,start,stop); % add a box-primitive to the metal property 'patch' + +%% create substrate +CSX = AddMaterial( CSX, 'substrate' ); +CSX = SetMaterialProperty( CSX, 'substrate', 'Epsilon', substrate.epsR, 'Kappa', substrate.kappa ); +start = [patch.radius -substr_ang_width/2 -substrate.length/2]; +stop = [patch.radius+substrate.thickness substr_ang_width/2 substrate.length/2]; +CSX = AddBox( CSX, 'substrate', 0, start, stop); + +%% save current density oon the patch +CSX = AddDump(CSX, 'Jt_patch','DumpType',3,'FileType',1); +start = [patch.radius+substrate.thickness -substr_ang_width/2 -substrate.length/2]; +stop = [patch.radius+substrate.thickness +substr_ang_width/2 substrate.length/2]; +CSX = AddBox( CSX, 'Jt_patch', 0, start, stop ); + +%% create ground (not really necessary, only for esthetic reasons) +CSX = AddMetal( CSX, 'gnd' ); % create a perfect electric conductor (PEC) +start = [patch.radius -substr_ang_width/2 -substrate.length/2]; +stop = [patch.radius +substr_ang_width/2 +substrate.length/2]; +CSX = AddBox(CSX,'gnd',10,start,stop); + +%% apply the excitation & resist as a current source +start = [patch.radius feed_angle 0]; +stop = [patch.radius+substrate.thickness feed_angle 0]; +[CSX port] = AddLumpedPort(CSX, 50 ,1 ,feed.R, start, stop, [1 0 0], true); + + +%% finalize the mesh +% detect all edges +mesh = DetectEdges(CSX); + +% add the simulation domain size +mesh.r = [mesh.r patch.radius+[-20 SimBox.rad]]; +mesh.a = [mesh.a -0.75*pi 0.75*pi]; +mesh.z = [mesh.z -SimBox.height/2 SimBox.height/2]; + +% add some lines for the substrate +mesh.r = [mesh.r patch.radius+linspace(0,substrate.thickness,substrate.cells)]; + +% generate a smooth mesh with max. cell size: lambda_min / 20 +max_res = c0 / (f0+fc) / unit / 20; +max_ang = max_res/(SimBox.rad+patch.radius); % max res in radiant +mesh = SmoothMesh(mesh, [max_res max_ang max_res], 1.4); + +disp(['Num of cells: ' num2str(numel(mesh.r)*numel(mesh.a)*numel(mesh.z))]); +CSX = DefineRectGrid( CSX, unit, mesh ); + +%% create nf2ff, keep some distance to the boundary conditions, e.g. 8 cells pml +start = [mesh.r(4) mesh.a(8) mesh.z(8)]; +stop = [mesh.r(end-9) mesh.a(end-9) mesh.z(end-9)]; +[CSX nf2ff] = CreateNF2FFBox(CSX, 'nf2ff', start, stop, 'Directions',[1 1 1 1 1 1]); + +%% prepare simulation folder & run +Sim_Path = ['tmp_' mfilename]; +Sim_CSX = [mfilename '.xml']; + +[status, message, messageid] = rmdir( Sim_Path, 's' ); % clear previous directory +[status, message, messageid] = mkdir( Sim_Path ); % create empty simulation folder + +% write openEMS compatible xml-file +WriteOpenEMS( [Sim_Path '/' Sim_CSX], FDTD, CSX ); + +% show the structure +CSXGeomPlot( [Sim_Path '/' Sim_CSX] ); + +% run openEMS +RunOpenEMS( Sim_Path, Sim_CSX); + +%% postprocessing & do the plots +freq = linspace( max([1e9,f0-fc]), f0+fc, 501 ); +port = calcPort(port, Sim_Path, freq); + +Zin = port.uf.tot ./ port.if.tot; +s11 = port.uf.ref ./ port.uf.inc; +P_in = 0.5*real(port.uf.tot .* conj(port.if.tot)); % antenna feed power + +% plot feed point impedance +figure +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 +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}|' ); + +drawnow + +%find resonance frequncy from s11 +f_res_ind = find(s11==min(s11)); +f_res = freq(f_res_ind); + +%% +disp('dumping resonant current distribution to vtk file, use Paraview to visualize'); +ConvertHDF5_VTK([Sim_Path '/Jt_patch.h5'],[Sim_Path '/Jf_patch'],'Frequency',f_res,'FieldName','J-Field'); + +%% NFFF contour plots %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +% calculate the far field at phi=0 degree +nf2ff = CalcNF2FF(nf2ff, Sim_Path, f_res, [-180:2:180]*pi/180, 0,'Center',[patch.radius+substrate.thickness 0 0]*unit, 'Outfile','pattern_phi_0.h5'); +% normalized directivity as polar plot +figure +polarFF(nf2ff,'xaxis','theta','param',1,'normalize',1) + +% calculate the far field at phi=0 degree +nf2ff = CalcNF2FF(nf2ff, Sim_Path, f_res, pi/2, (-180:2:180)*pi/180,'Center',[patch.radius+substrate.thickness 0 0]*unit, 'Outfile','pattern_theta_90.h5'); +% normalized directivity as polar plot +figure +polarFF(nf2ff,'xaxis','phi','param',1,'normalize',1) + +% display power and directivity +disp( ['radiated power: Prad = ' num2str(nf2ff.Prad) ' Watt']); +disp( ['directivity: Dmax = ' num2str(nf2ff.Dmax) ' (' num2str(10*log10(nf2ff.Dmax)) ' dBi)'] ); +disp( ['efficiency: nu_rad = ' num2str(100*nf2ff.Prad./real(P_in(f_res_ind))) ' %']); + +drawnow + +%% +disp( 'calculating 3D far field pattern and dumping to vtk (use Paraview to visualize)...' ); +thetaRange = (0:2:180); +phiRange = (0:2:360) - 180; +nf2ff = CalcNF2FF(nf2ff, Sim_Path, f_res, thetaRange*pi/180, phiRange*pi/180,'Verbose',1,'Outfile','3D_Pattern.h5','Center',[patch.radius+substrate.thickness 0 0]*unit); + +figure +plotFF3D(nf2ff,'logscale',-20); +