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matlab Tutorials: update and new helical antenna tutorial

pull/1/head v0.0.27
Thorsten Liebig 2012-03-01 13:52:15 +01:00
parent 710270f8fa
commit 4690e6a5b9
3 changed files with 211 additions and 68 deletions
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1
matlab/CreateNF2FFBox.m
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@ -21,6 +21,7 @@ function [CSX nf2ff] = CreateNF2FFBox(CSX, name, start, stop, varargin)
% %
% example: % example:
% see Tutorials/Simple_Patch_Antenna.m % see Tutorials/Simple_Patch_Antenna.m
% see Tutorials/Helical_Antenna.m
% %
% See also CalcNF2FF % See also CalcNF2FF
% %

93
matlab/Tutorials/CRLH_LeakyWaveAnt.m
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@ -43,9 +43,9 @@ Air_Spacer = 30000;
f_start = 1e9; f_start = 1e9;
f_stop = 6e9; f_stop = 6e9;
f_rad = (1.9:0.1:4.2)*1e9; % frequencies to calculate the 3D radiation pattern
f_rad = (1.9:0.05:4.2)*1e9;
Plot_3D_Rad_Pattern = 1; %this may take a long time! > 30min nf2ff_resolution = c0/max(f_rad)/unit/15;
%% setup FDTD parameters & excitation function %%%%%%%%%%%%%%%%%%%%%%%%%%%% %% setup FDTD parameters & excitation function %%%%%%%%%%%%%%%%%%%%%%%%%%%%
FDTD = InitFDTD(100000, 1e-3); FDTD = InitFDTD(100000, 1e-3);
@ -101,11 +101,10 @@ portstart = [ feed_length+(N_Cells*CRLH.LL)/2 , -CRLH.LW/2, substratelines(end)]
portstop = [ +(N_Cells*CRLH.LL)/2, CRLH.LW/2, 0]; portstop = [ +(N_Cells*CRLH.LL)/2, CRLH.LW/2, 0];
[CSX,portstruct{2}] = AddMSLPort( CSX, 999, 2, 'PEC', portstart, portstop, 0, [0 0 -1], 'MeasPlaneShift', feed_length/2, 'Feed_R', 50 ); [CSX,portstruct{2}] = AddMSLPort( CSX, 999, 2, 'PEC', portstart, portstop, 0, [0 0 -1], 'MeasPlaneShift', feed_length/2, 'Feed_R', 50 );
%% nf2ff calc %% nf2ff calc
start = [mesh.x(1) mesh.y(1) mesh.z(1) ] + 10*resolution; start = [mesh.x(1) mesh.y(1) mesh.z(1) ] + 10*resolution;
stop = [mesh.x(end) mesh.y(end) mesh.z(end)] - 10*resolution; stop = [mesh.x(end) mesh.y(end) mesh.z(end)] - 10*resolution;
[CSX nf2ff] = CreateNF2FFBox(CSX, 'nf2ff', start, stop); [CSX nf2ff] = CreateNF2FFBox(CSX, 'nf2ff', start, stop, 'OptResolution', nf2ff_resolution);
%% write/show/run the openEMS compatible xml-file %% write/show/run the openEMS compatible xml-file
Sim_Path = 'tmp_CRLH_LeakyWave'; Sim_Path = 'tmp_CRLH_LeakyWave';
@ -139,72 +138,30 @@ ylim([-40 2]);
drawnow drawnow
%% NFFF contour plots %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
theta = (0:3:359) - 180;
phi = [0 90];
disp( 'calculating far field at phi=[0 90] deg...' );
nf2ff = CalcNF2FF(nf2ff, Sim_Path, f_rad, theta*pi/180, phi*pi/180, 'Verbose',1);
%%
% prepare figures
figure(10)
hold on;
grid on;
xlabel( 'theta (deg)' );
ylabel( 'directivity (dBi)');
title('phi = 0°');
ylim([-20 10]);
figure(11)
hold on;
grid on;
xlabel( 'theta (deg)' );
ylabel( 'directivity (dBi)');
title('phi = 90°');
ylim([-20 10]);
line_styles = {'b-','g:','r-.','c--','m-','y:','k-.'};
for n=1:numel(f_rad)
f_res = f_rad(n);
% display power and directivity
disp( ['frequency: f = ' num2str(f_res/1e9) ' GHz']);
disp( ['radiated power: Prad = ' num2str(nf2ff.Prad(n)) ' Watt']);
disp( ['directivity: Dmax = ' num2str(nf2ff.Dmax(n)) ' (' num2str(10*log10(nf2ff.Dmax(n))) ' dBi)'] );
% normalized directivity
D_log = 20*log10(nf2ff.E_norm{n}/max(max(nf2ff.E_norm{n})));
% directivity
D_log = D_log + 10*log10(nf2ff.Dmax(n));
figure(10)
plot( nf2ff.theta, D_log(:,1) ,line_styles{1+mod(n-1,numel(line_styles))});
hold on;
figure(11)
plot( nf2ff.theta, D_log(:,2) ,line_styles{1+mod(n-1,numel(line_styles))} );
hold on;
end
%%
figure()
plot(f_rad,nf2ff.Dmax,'b-*','Linewidth',2)
grid on
xlabel( 'frequency' );
ylabel( 'directivity (dBi)');
%%
if (Plot_3D_Rad_Pattern==0)
return
end
%% calculate 3D pattern %% calculate 3D pattern
phi = 0:3:360; phi = 0:2:360;
theta = 0:3:180; theta = 0:2:180;
disp( 'calculating 3D far field pattern...' ); disp( 'calculating 3D far field pattern...' );
nf2ff = CalcNF2FF(nf2ff, Sim_Path, f_rad, theta*pi/180, phi*pi/180,'Verbose',2, 'Outfile','3D_Pattern.h5'); nf2ff = CalcNF2FF(nf2ff, Sim_Path, f_rad, theta*pi/180, phi*pi/180, 'Outfile','3D_Pattern.h5', 'Mode', 1,'Verbose',1);
%%
P_in = 0.5*port{1}.uf.inc .* conj( port{1}.if.inc ); % accepted antenna feed power
P_in = interp1(f, P_in, f_rad);
figure()
[AX,H1,H2] = plotyy(f_rad/1e9,nf2ff.Dmax',f_rad/1e9,100*nf2ff.Prad'./real(P_in),'plot');
grid on
xlabel( 'frequency (GHz)' );
set(get(AX(1),'Ylabel'),'String','directivity (dBi)')
set(get(AX(2),'Ylabel'),'String','radiation efficiency (%)')
set(H1,'Linewidth',2)
set(H2,'Linewidth',2)
set(H1,'Marker','*')
set(H2,'Marker','s')
drawnow
%% %%
disp( 'dumping 3D far field pattern to vtk, use Paraview to visualize...' ); disp( 'dumping 3D far field pattern to vtk, use Paraview to visualize...' );

185
matlab/Tutorials/Helical_Antenna.m Normal file
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@ -0,0 +1,185 @@
%
% Tutorials / helical antenna
%
% Describtion at:
% http://openems.de/index.php/Tutorial:_Helical_Antenna
%
% Tested with
% - Matlab 2011a / Octave 3.4.3
% - openEMS v0.0.27
%
% (C) 2012 Thorsten Liebig <thorsten.liebig@uni-due.de>
close all
clear
clc
post_proc_only = 0;
close all
%% setup the simulation
physical_constants;
unit = 1e-3; % all length in mm
f0 = 2.4e9; % center frequency, frequency of interest!
lambda0 = round(c0/f0/unit); % wavelength in mm
fc = 0.5e9; % 20 dB corner frequency
Helix.radius = 20; % --> diameter is ~ lambda/pi
Helix.turns = 10; % --> expected gain is G ~ 4 * 10 = 40 (16dBi)
Helix.pitch = 30; % --> pitch is ~ lambda/4
Helix.wire_rad = 1;
gnd.radius = lambda0/2;
% feeding
feed.width = 2; %feeding port width
feed.heigth = 2;
feed.R = 120; %feed impedance
% size of the simulation box
SimBox = [1 1 1.5]*2*lambda0;
%% setup FDTD parameter & excitation function
FDTD = InitFDTD( 30000 );
FDTD = SetGaussExcite( FDTD, f0, fc );
BC = {'MUR' 'MUR' 'MUR' 'MUR' 'MUR' 'PML_8'}; % boundary conditions
FDTD = SetBoundaryCond( FDTD, BC );
%% setup CSXCAD geometry & mesh
max_res = floor(c0 / (f0+fc) / unit / 20); % cell size: lambda/20
CSX = InitCSX();
mesh.x = [-SimBox(1)/2-gnd.radius -Helix.radius:Helix.wire_rad:Helix.radius SimBox(1)/2+gnd.radius];
mesh.x = SmoothMeshLines( mesh.x, max_res, 1.4); % create a smooth mesh between specified fixed mesh lines
mesh.y = mesh.x;
mesh.z = unique([-SimBox(3)/2 0:Helix.wire_rad:(Helix.turns*Helix.pitch+feed.heigth+Helix.wire_rad) (feed.heigth+Helix.wire_rad+Helix.turns*Helix.pitch)+SimBox(3)/2 ]);
mesh.z = SmoothMeshLines( mesh.z, max_res, 1.4 );
CSX = DefineRectGrid( CSX, unit, mesh );
%% create helix using the wire primitive
CSX = AddMetal( CSX, 'helix' ); % create a perfect electric conductor (PEC)
ang = linspace(0,2*pi,21);
coil_x = Helix.radius*cos(ang);
coil_y = Helix.radius*sin(ang);
coil_z = ang/2/pi*Helix.pitch;
helix.x=[];
helix.y=[];
helix.z=[];
zpos = feed.heigth+Helix.wire_rad;
for n=0:Helix.turns-1
helix.x = [helix.x coil_x];
helix.y = [helix.y coil_y];
helix.z = [helix.z coil_z+zpos];
zpos = zpos + Helix.pitch;
end
clear p
p(1,:) = helix.x;
p(2,:) = helix.y;
p(3,:) = helix.z;
CSX = AddWire(CSX, 'helix', 0, p, Helix.wire_rad);
start = [Helix.radius-feed.width/2 -feed.width/2 feed.heigth];
stop = [Helix.radius+feed.width/2 +feed.width/2 feed.heigth+2*Helix.wire_rad];
CSX = AddBox(CSX,'helix',0,start,stop);
%% create ground (same size as substrate)
CSX = AddMetal( CSX, 'gnd' ); % create a perfect electric conductor (PEC)
start = [0 0 -0.1];
stop = [0 0 0.1];
CSX = AddCylinder(CSX,'gnd',10,start,stop,gnd.radius);
%% apply the excitation & resist as a current source
start = [Helix.radius-feed.width/2 -feed.width/2 0];
stop = [Helix.radius+feed.width/2 +feed.width/2 feed.heigth];
[CSX] = AddLumpedPort(CSX, 5 ,1 ,feed.R, start, stop, [0 0 1], 'excite');
%%nf2ff calc
start = [mesh.x(11) mesh.y(11) mesh.z(11)];
stop = [mesh.x(end-10) mesh.y(end-10) mesh.z(end-10)];
[CSX nf2ff] = CreateNF2FFBox(CSX, 'nf2ff', start, stop, 'OptResolution', lambda0/15);
%% prepare simulation folder
Sim_Path = 'tmp_Helical_Ant';
Sim_CSX = 'Helix_Ant.xml';
if (post_proc_only==0)
[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);
end
%% postprocessing & do the plots
freq = linspace( f0-fc, f0+fc, 501 );
U = ReadUI( {'port_ut1','et'}, Sim_Path, freq ); % time domain/freq domain voltage
I = ReadUI( 'port_it1', Sim_Path, freq ); % time domain/freq domain current (half time step is corrected)
% 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 * feed.R);
if_inc = 0.5*(I.FD{1}.val + U.FD{1}.val / feed.R);
uf_ref = U.FD{1}.val - uf_inc;
if_ref = if_inc - I.FD{1}.val;
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}|' );
P_in = 0.5*uf_inc .* conj( if_inc ); % accepted antenna feed power
drawnow
%% NFFF contour plots %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%find resonance frequncy from s11
f_res = f0;
% get accepted antenna power at frequency f0
P_in_0 = interp1(freq, P_in, f0);
% calculate the far field at phi=0 degrees and at phi=90 degrees
thetaRange = unique([0:0.5:90 90:180]);
phiRange = (0:2:360) - 180;
disp( 'calculating far field at phi=[0 90] deg...' );
nf2ff = CalcNF2FF(nf2ff, Sim_Path, f_res, thetaRange*pi/180, phiRange*pi/180,'Mode',1,'Outfile','3D_Pattern.h5','Verbose',1);
theta_HPBW = thetaRange(find(nf2ff.E_norm{1}(:,1)<max(nf2ff.E_norm{1}(:,1))/2,1))*2;
% 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_0)) ' %']);
disp( ['theta_HPBW = ' num2str(theta_HPBW) ' °']);
%%
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);