167 lines
5.3 KiB
Matlab
167 lines
5.3 KiB
Matlab
%
|
||
% Tutorials / Patch Antenna Phased Array
|
||
%
|
||
% Description at:
|
||
%
|
||
% Tested with
|
||
% - Matlab 2011a
|
||
% - Octave 4.0
|
||
% - openEMS v0.0.33
|
||
%
|
||
% References:
|
||
% [1] Y. Yusuf and X. Gong, “A low-cost patch antenna phased array with
|
||
% analog beam steering using mutual coupling and reactive loading,” IEEE
|
||
% Antennas Wireless Propag. Lett., vol. 7, pp. 81–84, 2008.
|
||
% [2] S. Otto, S. Held, A. Rennings, and K. Solbach,
|
||
% "Array and multiport antenna farfield simulation using
|
||
% EMPIRE, MATLAB and ADS," 39th European Microwave Conf. (EuMC 2009),
|
||
% Sept. 29 – Oct. 1, Rome, Italy, pp. 1547-1550, 2009.
|
||
% [3] K. Karlsson, J. Carlsson, I. Belov, G. Nilsson, and P.-S. Kildal,
|
||
% “Optimization of antenna diversity gain by combining full-wave and
|
||
% circuit simulations,” in Proc. Second European Conference on Antennas
|
||
% and Propagation EuCAP 2007, 11–16 Nov. 2007, pp. 1–5.
|
||
%
|
||
% (C) 2013-2015 Thorsten Liebig <thorsten.liebig@gmx.de>
|
||
|
||
|
||
close all
|
||
clear
|
||
clc
|
||
|
||
% we need the "Cuircuit Toolbox"
|
||
addpath('C:\CTB');
|
||
% get the latest version from:
|
||
% using git: https://github.com/thliebig/CTB
|
||
% or zip: https://github.com/thliebig/CTB/archive/master.zip
|
||
|
||
% set this to 0 to NOT run a reference simulation with the given C2 and C3
|
||
% for comparison
|
||
do_reference_simulation = 1;
|
||
|
||
% set to 1 if you want to run AppCSXCAD to see the simulated structure
|
||
show_structure = 1;
|
||
|
||
% set this to 1, to force openEMS to run again even if the data already exist
|
||
force_rerun = 0;
|
||
|
||
% frequency range of interest
|
||
f = linspace( 1e9, 5e9, 1601 );
|
||
|
||
% resonant frequency for far-field calculations
|
||
f0 = 3e9;
|
||
|
||
% capacities for port 2 and 3 to shift the far-field pattern
|
||
C2 = 0.2e-12;
|
||
C3 = 0.2e-12;
|
||
|
||
Sim_Path_Root = ['tmp_' mfilename];
|
||
|
||
%% calculate the full S-parameter set for all 3 patch antennas running 3
|
||
% individual openEMS simulations in which one antenna is active and the
|
||
% other two a passive (50 Ohm load) respectively
|
||
xpos = [0 -41 41]; % x-center position of the 3 antennas
|
||
caps = [0 0 0];
|
||
resist = [50 50 50];
|
||
|
||
spara = [];
|
||
color_code = {'k-','r--','m-.'};
|
||
|
||
for n=1:3
|
||
active = [0 0 0];
|
||
active(n) = 1; % activate antenna n
|
||
Sim_Path = [Sim_Path_Root '_' num2str(n)]; % create an individual path
|
||
[port{n} nf2ff{n}] = Patch_Antenna_Array(Sim_Path, ((exist(Sim_Path,'dir')>0) && (force_rerun==0)), show_structure, xpos, caps, resist, active);
|
||
port{n} = calcPort( port{n}, Sim_Path, f, 'RefImpedance', 50);
|
||
nf2ff{n} = CalcNF2FF(nf2ff{n}, Sim_Path, f0, [-180:2:180]*pi/180, 0);
|
||
|
||
figure
|
||
hold on
|
||
grid on
|
||
for p=1:3
|
||
I(p,n) = interp1(f, port{n}{p}.if.tot,f0);
|
||
P_in(p) = 0.5*interp1(f, port{n}{n}.uf.inc,f0)*conj(interp1(f, port{n}{n}.if.inc,f0));
|
||
spara(p,n,:) = port{n}{p}.uf.ref./ port{n}{n}.uf.inc;
|
||
plot(f, squeeze(20*log10(abs(spara(p,n,:)))),color_code{p},'Linewidth',2);
|
||
end
|
||
end
|
||
|
||
%% export sparameter to touchstone file
|
||
write_touchstone('s',f,spara,[Sim_Path_Root '.s3p']);
|
||
|
||
% instructions for Qucs:
|
||
% load the written touchstone file
|
||
% attach C2 and C3 to port 2 and 3
|
||
% attach a signal port to port 1
|
||
% probe the currents going into port 1 to 3
|
||
|
||
% example currents for ports 1 to 3 for C2 = 0.2pF and C3=0.2pF
|
||
I_qucs(1,1) = 0.00398-0.000465j;
|
||
I_qucs(2,1) = 2.92e-5-0.000914j;
|
||
I_qucs(3,1) = 2.92e-5-0.000914j;
|
||
|
||
disp(['I2/I1: Qucs: ' num2str(I_qucs(2)/I_qucs(1)) ' (defined manually)'])
|
||
disp(['I3/I1: Qucs: ' num2str(I_qucs(3)/I_qucs(1)) ' (defined manually)'])
|
||
|
||
%% Calculate the currents of port 1 to 3 using Matlab [1]
|
||
z = s2z(spara);
|
||
|
||
Z2 = 1/(1j*2*pi*f0*C2);
|
||
Z3 = 1/(1j*2*pi*f0*C3);
|
||
|
||
z23(1,1) = interp1(f,squeeze(z(2,2,:)),f0) + Z2;
|
||
z23(1,2) = interp1(f,squeeze(z(2,3,:)),f0);
|
||
z23(2,1) = interp1(f,squeeze(z(3,2,:)),f0);
|
||
z23(2,2) = interp1(f,squeeze(z(3,3,:)),f0) + Z3;
|
||
|
||
%set input/feeding current of port 1 to 1mA
|
||
I_out(1,1) = 1e-3;
|
||
% calc current for port 2 and 3
|
||
I_out([2 3],1) = z23\[-interp1(f,squeeze(z(2,1,:)),f0);-interp1(f,squeeze(z(3,1,:)),f0)]*I_out(1);
|
||
|
||
disp(['I2/I1: Matlab: ' num2str(I_out(2)/I_out(1))])
|
||
disp(['I3/I1: Matlab: ' num2str(I_out(3)/I_out(1))])
|
||
|
||
|
||
%% do a reference simulation for the given C2/C3 values
|
||
if (do_reference_simulation)
|
||
active = [1 0 0];
|
||
caps = [0 C2 C3];
|
||
resist = [50 inf inf];
|
||
Sim_Path = [Sim_Path_Root '_C2=' num2str(C2*1e12) '_C3=' num2str(C3*1e12)];
|
||
[port_ref nf2ff_ref] = Patch_Antenna_Array(Sim_Path, ((exist(Sim_Path,'dir')>0) && (force_rerun==0)), show_structure, xpos, caps, resist, active);
|
||
port_ref = calcPort( port_ref, Sim_Path, f, 'RefImpedance', 50);
|
||
nf2ff_ref = CalcNF2FF(nf2ff_ref, Sim_Path, f0, [-180:2:180]*pi/180, 0);
|
||
|
||
% extract currents from reference simulation
|
||
for p=1:3
|
||
I_ref(p,1) = interp1(f, port_ref{p}.if.tot,f0);
|
||
end
|
||
|
||
disp(['I2/I1: openEMS: ' num2str(I_ref(2)/I_ref(1))])
|
||
disp(['I3/I1: openEMS: ' num2str(I_ref(3)/I_ref(1))])
|
||
end
|
||
|
||
%% calculate and apply weighting coefficients [3]
|
||
% calculate
|
||
coeff = I\I_out;
|
||
|
||
% apply
|
||
E_ff_phi = 0*nf2ff{1}.E_phi{1};
|
||
E_ff_theta = 0*nf2ff{1}.E_phi{1};
|
||
for n=1:3
|
||
E_ff_phi = E_ff_phi + coeff(n)*nf2ff{n}.E_phi{1};
|
||
E_ff_theta = E_ff_theta + coeff(n)*nf2ff{n}.E_theta{1};
|
||
end
|
||
|
||
%% plot far-field patterns
|
||
figure
|
||
polar([-180:2:180]'*pi/180,abs(E_ff_phi(:))/max(abs(E_ff_phi(:))));
|
||
hold on
|
||
if (do_reference_simulation)
|
||
polar([-180:2:180]'*pi/180,abs(nf2ff_ref.E_norm{1}(:,1))/max(abs(nf2ff_ref.E_norm{1}(:,1))),'r--');
|
||
end
|
||
title('normalized far-field pattern','Interpreter', 'none')
|
||
legend('calculated','reference')
|
||
|
||
|