206 lines
7.1 KiB
Matlab
206 lines
7.1 KiB
Matlab
%
|
|
% EXAMPLE / antennas / inverted-f antenna (ifa) 2.4GHz
|
|
%
|
|
% This example demonstrates how to:
|
|
% - calculate the reflection coefficient of an ifa
|
|
% - calculate farfield of an ifa
|
|
%
|
|
% Tested with
|
|
% - Octave 3.7.5
|
|
% - openEMS v0.0.30+ (git 10.07.2013)
|
|
%
|
|
% (C) 2013 Stefan Mahr <dac922@gmx.de>
|
|
|
|
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
|
|
|
|
%open AppCSXCAD and show ifa
|
|
show = 1;
|
|
|
|
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
|
% 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
|
|
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); %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);
|