diff --git a/matlab/examples/antennas/ifa.m b/matlab/examples/antennas/ifa.m new file mode 100644 index 0000000..7a6235c --- /dev/null +++ b/matlab/examples/antennas/ifa.m @@ -0,0 +1,192 @@ +% +close all +clear +clc + +%% setup the simulation +physical_constants; +unit = 1e-3; % all length in mm + +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +% substrate.width +% _______________________________________________ __ substrate. +% | A ifa.l |\ __ thickness +% | |ifa.e __________________________ | | +% | | | ___ _________________| w2 | | +% | | ifa.h | | || | | +% |_V_____________|___|___||______________________| | +% | .w1 .wf\ | | +% | |.fp| \ | | +% | | feed point | | +% | | | | substrate.length +% |<- substrate.width/2 ->| | | +% | | | +% |_______________________________________________| | +% \_______________________________________________\| +% +% Note: It's not checked whether your settings make sense, so check +% graphical output carefully. +% +substrate.width = 80; % width of substrate +substrate.length = 80; % length of substrate +substrate.thickness = 1.5; % thickness of substrate +substrate.cells = 4; % use 4 cells for meshing substrate + +ifa.h = 8; % height of short circuit stub +ifa.l = 22.5; % length of radiating element +ifa.w1 = 4; % width of short circuit stub +ifa.w2 = 2.5; % width of radiating element +ifa.wf = 1; % width of feed element +ifa.fp = 4; % position of feed element relative to short + % circuit stub +ifa.e = 10; % distance to edge + + +% substrate setup +substrate.epsR = 4.3; +substrate.kappa = 1e-3 * 2*pi*2.45e9 * EPS0*substrate.epsR; + +%setup feeding +feed.R = 50; %feed resistance + + +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +% size of the simulation box +SimBox = [substrate.width*2 substrate.length*2 150]; + +%% setup FDTD parameter & excitation function +f0 = 2.5e9; % center frequency +fc = 1e9; % 20 dB corner frequency + +FDTD = InitFDTD('NrTS', 60000 ); +FDTD = SetGaussExcite( FDTD, f0, fc ); +BC = {'MUR' 'MUR' 'MUR' 'MUR' 'MUR' 'MUR'}; % boundary conditions +%BC = {'PML_8' 'PML_8' 'PML_8' 'PML_8' 'PML_8' 'PML_8'}; +FDTD = SetBoundaryCond( FDTD, BC ); + +%% setup CSXCAD geometry & mesh +CSX = InitCSX(); + +%initialize the mesh with the "air-box" dimensions +mesh.x = [-SimBox(1)/2 SimBox(1)/2]; +mesh.y = [-SimBox(2)/2 SimBox(2)/2]; +mesh.z = [-SimBox(3)/2 SimBox(3)/2]; + +%% create substrate +CSX = AddMaterial( CSX, 'substrate'); +CSX = SetMaterialProperty( CSX, 'substrate', 'Epsilon',substrate.epsR, 'Kappa', substrate.kappa); +start = [-substrate.width/2 -substrate.length/2 0]; +stop = [ substrate.width/2 substrate.length/2 substrate.thickness]; +CSX = AddBox( CSX, 'substrate', 1, start, stop ); +% add extra cells to discretize the substrate thickness +mesh.z = [linspace(0,substrate.thickness,substrate.cells+1) mesh.z]; + +%% create ground plane +CSX = AddMetal( CSX, 'groundplane' ); % create a perfect electric conductor (PEC) +start = [-substrate.width/2 -substrate.length/2 substrate.thickness]; +stop = [ substrate.width/2 substrate.length/2-ifa.e substrate.thickness]; +CSX = AddBox(CSX, 'groundplane', 10, start,stop); + +%% create ifa +CSX = AddMetal( CSX, 'ifa' ); % create a perfect electric conductor (PEC) +tl = [0,substrate.length/2-ifa.e,substrate.thickness]; % translate +start = [0 0 0] + tl; +stop = start + [ifa.wf ifa.h 0]; +CSX = AddBox( CSX, 'ifa', 10, start, stop); % feed element +start = [-ifa.fp 0 0] + tl; +stop = start + [-ifa.w1 ifa.h 0]; +CSX = AddBox( CSX, 'ifa', 10, start, stop); % short circuit stub +start = [(-ifa.fp-ifa.w1) ifa.h 0] + tl; +stop = start + [ifa.l -ifa.w2 0]; +CSX = AddBox( CSX, 'ifa', 10, start, stop); % radiating element + +ifa_mesh = DetectEdges(CSX, [], 'SetProperty','ifa'); +mesh.x = [mesh.x SmoothMeshLines(ifa_mesh.x, 0.5)]; +mesh.y = [mesh.y SmoothMeshLines(ifa_mesh.y, 0.5)]; + +%% apply the excitation & resist as a current source +start = [0 0 0] + tl; +stop = start + [ifa.wf 0.5 0]; +[CSX port] = AddLumpedPort(CSX, 5 ,1 ,feed.R, start, stop, [0 1 0], true); + +%% finalize the mesh +% generate a smooth mesh with max. cell size: lambda_min / 20 +mesh = DetectEdges(CSX, mesh); +mesh = SmoothMesh(mesh, c0 / (f0+fc) / unit / 20); +CSX = DefineRectGrid(CSX, unit, mesh); + +%% add a nf2ff calc box; size is 3 cells away from MUR boundary condition +start = [mesh.x(4) mesh.y(4) mesh.z(4)]; +stop = [mesh.x(end-3) mesh.y(end-3) mesh.z(end-3)]; +[CSX nf2ff] = CreateNF2FFBox(CSX, 'nf2ff', start, stop); + +%% prepare simulation folder +Sim_Path = 'tmp_IFA'; +Sim_CSX = 'IFA.xml'; + +try, confirm_recursive_rmdir(false,'local'); end + +[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 +if (show == 1) + CSXGeomPlot( [Sim_Path '/' Sim_CSX] ); +end + + +%% run openEMS +RunOpenEMS( Sim_Path, Sim_CSX, '--debug-PEC -v'); %RunOpenEMS( Sim_Path, Sim_CSX, '--debug-PEC -v'); + +%% 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 * port.uf.inc .* conj( port.if.inc ); % 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 + +%% NFFF contour plots %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +%find resonance frequncy from s11 +f_res_ind = find(s11==min(s11)); +f_res = freq(f_res_ind); + +%% +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'); + +plotFF3D(nf2ff) + +% 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))) ' %']); + +E_far_normalized = nf2ff.E_norm{1} / max(nf2ff.E_norm{1}(:)) * nf2ff.Dmax; +DumpFF2VTK([Sim_Path '/3D_Pattern.vtk'],E_far_normalized,thetaRange,phiRange,1e-3);