% EXAMPLE / antennas / ) 2.4GHz

%

% This example demonstrates how to:

% - calculate the reflection coefficient of an antenna
% - Give the antenna impedance
% - calculate farfield of an antenna

%

close all

clear

clc

%% setup the simulation

physical_constants;

unit = 1e-3; % all length in mm

substrate.width = 10; % width of substrate

substrate.length = 10; % length of substrate

substrate.thickness = 0.8; % thickness of substrate

substrate.cells = 4; % use 4 cells for meshing substrate

ifa.h = 2.1; % height of short circuit stub

ifa.l = 8.875; % length of radiating element1

ifa.w1 = 0.9; % width of short circuit stub

ifa.w2 = 0.3; % width of radiating element

ifa.wf = 0.3; % width of feed element

ifa.fp = 4; % position of feed element relative to short


% circuit stub

ifa.e = 2.7; % distance to edge

ifa.b = 6.075; %Radiating element 3_5_7 length

ifa.a = 0.9; %Radiating element 2_4_6 length

ifa.c = 0.3; % distance between feeding elementand circuit stub

ifa.d = 0.3; %distance between feeding element and radiating element 2...

ifa.gnd = 0.3; %distance antenna to the ground plane

ifa.Ledge = 0.9; % distance to the left edge 1.1 Previously
ifa.cut = 0 ;  %Cutting element

ifa.sbt= 0.4; %reduce substrate length

length = 125 ;
% 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*6 substrate.length*6 60];

%% setup FDTD parameter & excitation function

f0 = 2.4e9; % center frequency

fc = 1e9; % 20 dB corner frequency

c0 = 3e8; %Speed of light

%FDTD = InitFDTD(90000, 1e-3, 'TimeStep', 5e-13);
%FDTD = InitFDTD('OverSampling', 400) %highly discourage you to change the timestep.
%we either make the simulation slower or unstable.
%openEMS chooses the fastest possible and stable timestep. So change the oversampling


FDTD = InitFDTD('NrTS', 200000, 'EndCriteria', 1e-3);


%FDTD = InitFDTD('NrTS', 100000 );

FDTD = SetGaussExcite( FDTD, f0, fc );

BC = {'MUR' 'MUR' 'MUR' 'MUR' 'MUR' 'MUR'}; % simple absorbing boundary conditions because our antenna being destined to be in open space

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-ifa.sbt substrate.thickness];

CSX = AddBox(CSX, 'groundplane', 10, start,stop);


%% create ifa
CSX = AddMetal( CSX, 'ifa' ); % create a perfect electric conductor (PEC)
tl = [ifa.Ledge,substrate.length/2-ifa.e,substrate.thickness];   % translate

start = [(-substrate.width/2)+ifa.w1+ifa.c (ifa.h-3*ifa.a+2*ifa.w2-0.3) 0] + tl;
stop = start + [ifa.wf ifa.h 0];
CSX = AddBox( CSX, 'ifa', 10,  start, stop);  % feed element

start = [-substrate.width/2  (ifa.h-3*ifa.a+2*ifa.w2)-ifa.sbt 0] + tl;
stop =  start + [ifa.w1 ifa.h+ifa.sbt 0];
CSX = AddBox( CSX, 'ifa', 10,  start, stop);  % short circuit stub

start = [(-substrate.width/2) ifa.h 0] + tl;
stop = start + [ifa.l -ifa.w2 0];
CSX = AddBox( CSX, 'ifa', 10, start, stop);   % radiating element1

start = [(-substrate.width/2+ifa.l) ifa.h 0] + tl;
stop = start + [-ifa.w2 -ifa.a 0];
CSX = AddBox( CSX, 'ifa', 10, start, stop);   % radiating element2

start = [(-substrate.width/2+ifa.l) ifa.h-ifa.a 0] + tl;
stop = start + [-ifa.b ifa.w2 0];
CSX = AddBox( CSX, 'ifa', 10, start, stop);   % radiating element3

start = [(-substrate.width/2+ifa.l-ifa.b+ifa.w2) ifa.h-ifa.a+ifa.w2 0] + tl;
stop = start + [-ifa.w2 -ifa.a 0];
CSX = AddBox( CSX, 'ifa', 10, start, stop);   % radiating element4


start = [(-substrate.width/2+ifa.l) (ifa.h-2*ifa.a+ifa.w2) 0] + tl;
stop = start + [-ifa.b ifa.w2 0];
CSX = AddBox( CSX, 'ifa', 10, start, stop);   % radiating element5

start = [(-substrate.width/2+ifa.l) ifa.h-2*ifa.a+2*ifa.w2 0] + tl;
stop = start + [-ifa.w2 -ifa.a 0];
CSX = AddBox( CSX, 'ifa', 10, start, stop);   % radiating element6

start = [(-substrate.width/2+ifa.l) (ifa.h-3*ifa.a+2*ifa.w2) 0] + tl;
stop = start + [-ifa.b+ifa.cut ifa.w2 0];
CSX = AddBox( CSX, 'ifa', 10, start, stop);   % radiating element7

%% apply the excitation & resist as a current source
start = [ (-substrate.width/2)+ifa.w1+ifa.c (ifa.h-3*ifa.a+2*ifa.w2-0.3) 0] + tl;
stop  = start + [ifa.wf -ifa.sbt+0.3 0];
[CSX port] = AddLumpedPort(CSX, 5 ,1 ,feed.R, start, stop, [0 1 0], true); %


% MESH left
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
mesh.x = [mesh.x linspace(-substrate.width*3,(-substrate.width/2)+ifa.Ledge-1,40.0)]; %tab 15 elements step of 0.4

mesh.y = [mesh.y linspace(-substrate.length*3,(substrate.length/2)-ifa.e-ifa.sbt-1,40.0)];%mesh.z = [mesh.z linspace(-10.0,5,40.0) + 0];
CSX = DefineRectGrid(CSX, 0.001, mesh);  %define the mesh with a drawing unit of 1mm (1e-3)


% MESH left2
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
mesh.x = [mesh.x linspace((-substrate.width/2)+ifa.Ledge-1,(-substrate.width/2)+ifa.Ledge,4.0)]; %tab 15 elements step of 0.4

mesh.y = [mesh.y linspace((substrate.length/2)-ifa.e-ifa.sbt-1,(substrate.length/2)-ifa.e-ifa.sbt,5.0)];%mesh.z = [mesh.z linspace(-10.0,5,40.0) + 0];
CSX = DefineRectGrid(CSX, 0.001, mesh);




%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% MESH right
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
mesh.x = [mesh.x linspace((-substrate.width/2)+ifa.l+ifa.Ledge+1,substrate.width*3,35.0)]; % a=4.97
mesh.y = [mesh.y linspace(substrate.width/2-ifa.e+ifa.h+1,substrate.length*3,35.0) ]; % a=5.4

CSX = DefineRectGrid(CSX, 0.001, mesh);
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% MESH right2
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
mesh.x = [mesh.x linspace((-substrate.width/2)+ifa.l+ifa.Ledge,(-substrate.width/2)+ifa.l+ifa.Ledge+1,4.0)];
mesh.y = [mesh.y linspace(substrate.width/2-ifa.e+ifa.h,substrate.width/2-ifa.e+ifa.h+1,5.0) ];

CSX = DefineRectGrid(CSX, 0.001, mesh);
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


%MESH

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%mesh.x = [mesh.x linspace(-4,4,1.0)];
mesh.x = [mesh.x linspace(-substrate.width/2+ifa.Ledge,-substrate.width/2+ifa.Ledge+ifa.l,35.0) ];  % a-b=4.4; Step=

mesh.y = [mesh.y linspace((substrate.length/2)-ifa.e-ifa.sbt,substrate.width/2-ifa.e+ifa.h,14.0) ]; % a-b=2.5; Step=



mesh.z = [mesh.z linspace(-substrate.width*3,-1,45.0) ];
mesh.z = [mesh.z linspace(-1,0,4) ];
mesh.z = [mesh.z linspace(substrate.thickness,substrate.thickness+1,4.0) ];
mesh.z = [mesh.z linspace(substrate.thickness+1,substrate.width*3,45.0) ];

CSX = DefineRectGrid(CSX, 0.001, mesh);

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%% When third rule does't work, use high resolution meshing


%% finalize the mesh with detec edge DOESN'T WORK Hand meshing is better.

%ifa_mesh = DetectEdges(CSX, [], 'SetProperty','ifa');

%mesh.x = [mesh.x SmoothMeshLines(ifa_mesh.x, 0.5)];

%mesh.y = [mesh.y SmoothMeshLines(ifa_mesh.y, 10)];

% generate a smooth mesh with max. cell size: lambda_min / 20

%mesh = DetectEdges(CSX, mesh);

%mesh = SmoothMesh(mesh, c0 / (f0+fc) / unit / 20);

% Always problem to put smoothmeshing problem error: max_recursion_depth exceeded

%CSX = DefineRectGrid(CSX, unit , mesh); % define the mesh with a drawing unit of 1mm (1e-3)



%% add a nf2ff calc box; size is 3 cells away from MUR boundary condition
%%%%%%%It's implements a near field to far field transformation for near field antenna measurement setups
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_LIGHT';

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



%%%TO START SIMULATION AND FIND S11, IMPEDANCE, GAIN

%% 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 = real(0.5 * port.uf.tot .* conj( port.if.tot )); % antenna feed power

%% NFFF contour plots %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%find resonance frequncy from s11
f_res_ind = find(s11==min(s11));
f_res = freq(f_res_ind);


% plot feed point impedance

figure
plot( freq/1e6, abs(Zin), 'k-', 'Linewidth', 2 );
hold on
plot( freq/1e6, real(Zin), 'g--', 'Linewidth', 2 );
hold on
grid on
plot( freq/1e6, imag(Zin), 'm--', 'Linewidth', 2 );
title( 'feed point impedance' );
xlabel( 'frequency f / MHz' );
ylabel( 'impedance Z_{in} / Ohm' );
legend( 'real', 'imag' );
disp( ['-> Zin @ ', num2str(f_res/1e9), 'GHz = ', num2str(Zin(f_res_ind)), ]);
disp( ['-> |Zin| @ ', num2str(f_res/1e9), 'GHz = ', num2str(abs(Zin(f_res_ind))), ' Ohm' ]);

% 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}|' );
disp( ['-> S11 @ ', num2str(f_res/1e9), 'GHz = ', num2str(20*log10(abs(min(s11)))), ' dB']);


drawnow

%% %%%% 3B dB
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');
%nf2ff = CalcNF2FF(nf2ff, Sim_Path, f_res, [-180:2:180]*pi/180, [0 90]*pi/180, 'Mode', 1, 'Center', [0 0 length])
%nf2ff = CalcNF2FF(nf2ff, Sim_Path, f0, [-180:2:180]*pi/180, [0 90]*pi/180, 'Mode', 1, [0 0 0], [0 0 length*unit]);


figure
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);