new tutorial: patch antenna phased array
Signed-off-by: Thorsten Liebig <Thorsten.Liebig@gmx.de>pull/10/head
Thorsten Liebig
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function [port nf2ff] = Patch_Antenna_Array(Sim_Path, postproc_only, show_structure, xpos, caps, resist, active )
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% [port nf2ff] = Patch_Antenna_Array(Sim_Path, postproc_only, show_structure, xpos, caps, resist, active )
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%
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% Script to setup the patch array as described in [1].
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% Run main script in Patch_Antenna_Phased_Array.m instead!
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%
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% Sim_Path: Simulation path
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% postproc_only: set to post process only 0/1
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% show_structure: show the strucuture in AppCSXCAD 0/1
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% xpos: the x-position for each antenna is defined
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% caps: the port capacity (will override active port)
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% resist: port resitance
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% active: switch port active
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%
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% References:
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% [1] Y. Yusuf and X. Gong, “A low-cost patch antenna phased array with
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% analog beam steering using mutual coupling and reactive loading,” IEEE
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% Antennas Wireless Propag. Lett., vol. 7, pp. 81–84, 2008.
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%
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% Tested with
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% - Matlab 2011a
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% - openEMS v0.0.31
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%
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% (C) 2013 Thorsten Liebig <thorsten.liebig@gmx.de>
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% example
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% xpos = [-41 0 41];
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% caps = [0.2e-12 0 0.2e-12];
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% active = [0 1 0];
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% resist = [50 50 50];
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%% setup the simulation
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physical_constants;
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unit = 1e-3; % all length in mm
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% patch geometry setup
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patch.W = 35; % width
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patch.L = 28.3; % length
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patch.Ws = 3.8; % width of feeding stub
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patch.Gs = 1; % width of feeding gab
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patch.l = 6; % length of feeding stub
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patch.y0 = 10; % depth of feeding stub into into patch
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% patch resonance frequency
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f0 = 3e9;
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%substrate setup
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substrate.name = 'Ro3003';
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substrate.epsR = 3;
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substrate.kappa = 0.0013 * 2*pi*f0 * EPS0*substrate.epsR;
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substrate.thickness = 1.524;
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substrate.cells = 4;
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substrate.width = patch.W + range(xpos) + 4*patch.l;
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substrate.length = 3*patch.l + patch.L;
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% size of the simulation box
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AirSpacer = [50 50 30];
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edge_res = [-1/3 2/3]*1;
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%% setup FDTD parameter & excitation function
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fc = 2e9; % 20 dB corner frequency
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FDTD = InitFDTD( 'EndCriteria', 1e-4 );
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FDTD = SetGaussExcite( FDTD, f0, fc );
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BC = [1 1 1 1 1 1]*3;
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FDTD = SetBoundaryCond( FDTD, BC );
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%% setup CSXCAD geometry & mesh
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CSX = InitCSX();
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mesh.x = [];
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mesh.y = [];
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mesh.z = [];
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%% create patch
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CSX = AddMetal( CSX, 'patch' ); % create a perfect electric conductor (PEC)
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for port_nr=1:numel(xpos)
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start = [xpos(port_nr)-patch.W/2 patch.l substrate.thickness];
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stop = [xpos(port_nr)-patch.Ws/2-patch.Gs patch.l+patch.L substrate.thickness];
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CSX = AddBox(CSX,'patch',10, start, stop);
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mesh.x = [mesh.x xpos(port_nr)-patch.W/2-edge_res];
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start = [xpos(port_nr)+patch.W/2 patch.l substrate.thickness];
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stop = [xpos(port_nr)+patch.Ws/2+patch.Gs patch.l+patch.L substrate.thickness];
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CSX = AddBox(CSX,'patch',10, start, stop);
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mesh.x = [mesh.x xpos(port_nr)+patch.W/2+edge_res];
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mesh.y = [mesh.y patch.l-edge_res patch.l+patch.L+edge_res];
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start = [xpos(port_nr)-patch.Ws/2-patch.Gs patch.l+patch.y0 substrate.thickness];
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stop = [xpos(port_nr)+patch.Ws/2+patch.Gs patch.l+patch.L substrate.thickness];
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CSX = AddBox(CSX,'patch',10, start, stop);
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% feed line
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start = [xpos(port_nr)-patch.Ws/2 patch.l+patch.y0 substrate.thickness];
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stop = [xpos(port_nr)+patch.Ws/2 0 substrate.thickness];
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CSX = AddBox(CSX,'patch',10, start, stop);
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mesh.x = [mesh.x xpos(port_nr)+linspace(-patch.Ws/2-patch.Gs,-patch.Ws/2,3) xpos(port_nr)+linspace(patch.Ws/2,patch.Ws/2+patch.Gs,3)];
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start = [xpos(port_nr)-patch.Ws/2 0 0];
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stop = [xpos(port_nr)+patch.Ws/2 0 substrate.thickness];
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if (caps(port_nr)>0)
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CSX = AddLumpedElement(CSX, ['C_' num2str(port_nr)], 2, 'C', caps(port_nr));
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CSX = AddBox(CSX,['C_' num2str(port_nr)],10, start, stop);
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[CSX port{port_nr}] = AddLumpedPort(CSX, 5 ,port_nr ,inf, start, stop, [0 0 1], 0);
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else
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% feed port
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[CSX port{port_nr}] = AddLumpedPort(CSX, 5 ,port_nr, resist(port_nr), start, stop, [0 0 1], active(port_nr));
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end
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end
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%% create substrate
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CSX = AddMaterial( CSX, substrate.name );
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CSX = SetMaterialProperty( CSX, substrate.name, 'Epsilon', substrate.epsR, 'Kappa', substrate.kappa );
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start = [-substrate.width/2 0 0];
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stop = [ substrate.width/2 substrate.length substrate.thickness];
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CSX = AddBox( CSX, substrate.name, 0, start, stop );
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mesh.x = [mesh.x start(1) stop(1)];
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mesh.y = [mesh.y start(2) stop(2)];
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% add extra cells to discretize the substrate thickness
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mesh.z = [linspace(0,substrate.thickness,substrate.cells+1) mesh.z];
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%% create ground (same size as substrate)
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CSX = AddMetal( CSX, 'gnd' ); % create a perfect electric conductor (PEC)
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start(3)=0;
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stop(3) =0;
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CSX = AddBox(CSX,'gnd',10,start,stop);
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%% finalize the mesh
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% generate a smooth mesh with max. cell size: lambda_min / 20
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mesh = SmoothMesh(mesh, 2, 1.3);
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mesh.x = [mesh.x min(mesh.x)-AirSpacer(1) max(mesh.x)+AirSpacer(1)];
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mesh.y = [mesh.y min(mesh.y)-AirSpacer(2) max(mesh.y)+AirSpacer(2)];
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mesh.z = [mesh.z min(mesh.z)-AirSpacer(3) max(mesh.z)+2*AirSpacer(3)];
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mesh = SmoothMesh(mesh, c0 / (f0+fc) / unit / 20, 1.3);
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%% add a nf2ff calc box; size is 3 cells away from MUR boundary condition
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start = [mesh.x(4) mesh.y(4) mesh.z(4)];
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stop = [mesh.x(end-3) mesh.y(end-3) mesh.z(end-3)];
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[CSX nf2ff] = CreateNF2FFBox(CSX, 'nf2ff', start, stop);
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mesh = AddPML(mesh,(BC==3)*8);
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CSX = DefineRectGrid(CSX, unit, mesh);
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%% prepare simulation folder
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Sim_CSX = 'patch_array.xml';
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if (postproc_only==0)
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[status, message, messageid] = rmdir( Sim_Path, 's' ); % clear previous directory
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[status, message, messageid] = mkdir( Sim_Path ); % create empty simulation folder
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%% write openEMS compatible xml-file
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WriteOpenEMS( [Sim_Path '/' Sim_CSX], FDTD, CSX );
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%% show the structure
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if (show_structure>0)
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CSXGeomPlot( [Sim_Path '/' Sim_CSX] );
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end
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%% run openEMS
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RunOpenEMS( Sim_Path, Sim_CSX);
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end
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@ -0,0 +1,165 @@
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%
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% Tutorials / Patch Antenna Phased Array
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%
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% Describtion at:
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%
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% Tested with
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% - Matlab 2011a
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% - openEMS v0.0.31
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%
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% References:
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% [1] Y. Yusuf and X. Gong, “A low-cost patch antenna phased array with
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% analog beam steering using mutual coupling and reactive loading,” IEEE
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% Antennas Wireless Propag. Lett., vol. 7, pp. 81–84, 2008.
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% [2] S. Otto, S. Held, A. Rennings, and K. Solbach,
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% "Array and multiport antenna farfield simulation using
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% EMPIRE, MATLAB and ADS," 39th European Microwave Conf. (EuMC 2009),
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% Sept. 29 – Oct. 1, Rome, Italy, pp. 1547-1550, 2009.
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% [3] K. Karlsson, J. Carlsson, I. Belov, G. Nilsson, and P.-S. Kildal,
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% “Optimization of antenna diversity gain by combining full-wave and
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% circuit simulations,” in Proc. Second European Conference on Antennas
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% and Propagation EuCAP 2007, 11–16 Nov. 2007, pp. 1–5.
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%
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% (C) 2013 Thorsten Liebig <thorsten.liebig@gmx.de>
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close all
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clear
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clc
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% we need the "Cuircuit Toolbox"
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addpath('C:\CTB');
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% get the latest version from:
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% using git: https://github.com/thliebig/CTB
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% or zip: https://github.com/thliebig/CTB/archive/master.zip
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% set this to 0 to NOT run a reference simulation with the given C2 and C3
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% for comparison
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do_reference_simulation = 1;
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% set to 1 if you want to run AppCSXCAD to see the simulated structure
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show_structure = 1;
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% set this to 1, to force openEMS to run again even if the data already exist
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force_rerun = 0;
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% frequency range of interest
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f = linspace( 1e9, 5e9, 1601 );
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% resonant frequency for far-field calculations
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f0 = 3e9;
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% capacities for port 2 and 3 to shift the far-field pattern
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C2 = 0.2e-12;
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C3 = 0.2e-12;
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Sim_Path_Root = ['tmp_' mfilename];
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%% calculate the full S-parameter set for all 3 patch antennas running 3
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% individual openEMS simulations in which one antenna is active and the
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% other two a passive (50 Ohm load) respectively
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xpos = [0 -41 41]; % x-center position of the 3 antennas
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caps = [0 0 0];
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resist = [50 50 50];
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spara = [];
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color_code = {'k-','r--','m-.'};
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for n=1:3
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active = [0 0 0];
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active(n) = 1; % activate antenna n
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Sim_Path = [Sim_Path_Root '_' num2str(n)]; % create an individual path
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[port{n} nf2ff{n}] = Patch_Antenna_Array(Sim_Path, ((exist(Sim_Path,'dir')>0) && (force_rerun==0)), show_structure, xpos, caps, resist, active);
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port{n} = calcPort( port{n}, Sim_Path, f, 'RefImpedance', 50);
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nf2ff{n} = CalcNF2FF(nf2ff{n}, Sim_Path, f0, [-180:2:180]*pi/180, 0);
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figure
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hold on
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grid on
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for p=1:3
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I(p,n) = interp1(f, port{n}{p}.if.tot,f0);
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P_in(p) = 0.5*interp1(f, port{n}{n}.uf.inc,f0)*conj(interp1(f, port{n}{n}.if.inc,f0));
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spara(p,n,:) = port{n}{p}.uf.ref./ port{n}{n}.uf.inc;
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plot(f, squeeze(20*log10(abs(spara(p,n,:)))),color_code{p},'Linewidth',2);
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end
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end
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%% export sparameter to touchstone file
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write_touchstone('s',f,spara,[Sim_Path_Root '.s3p']);
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% instructions for Qucs:
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% load the written touchstone file
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% attach C2 and C3 to port 2 and 3
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% attach a signal port to port 1
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% probe the currents going into port 1 to 3
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% example currents for ports 1 to 3 for C2 = 0.2pF and C3=0.2pF
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I_qucs(1,1) = 0.00398-0.000465j;
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I_qucs(2,1) = 2.92e-5-0.000914j;
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I_qucs(3,1) = 2.92e-5-0.000914j;
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disp(['I2/I1: Qucs: ' num2str(I_qucs(2)/I_qucs(1)) ' (defined manually)'])
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disp(['I3/I1: Qucs: ' num2str(I_qucs(3)/I_qucs(1)) ' (defined manually)'])
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%% Calculate the currents of port 1 to 3 using Matlab [1]
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z = s2z(spara);
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Z2 = 1/(1j*2*pi*f0*C2);
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Z3 = 1/(1j*2*pi*f0*C3);
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z23(1,1) = interp1(f,squeeze(z(2,2,:)),f0) + Z2;
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z23(1,2) = interp1(f,squeeze(z(2,3,:)),f0);
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z23(2,1) = interp1(f,squeeze(z(3,2,:)),f0);
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z23(2,2) = interp1(f,squeeze(z(3,3,:)),f0) + Z3;
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%set input/feeding current of port 1 to 1mA
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I_out(1,1) = 1e-3;
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% calc current for port 2 and 3
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I_out([2 3],1) = z23\[-interp1(f,squeeze(z(2,1,:)),f0);-interp1(f,squeeze(z(3,1,:)),f0)]*I_out(1);
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disp(['I2/I1: Matlab: ' num2str(I_out(2)/I_out(1))])
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disp(['I3/I1: Matlab: ' num2str(I_out(3)/I_out(1))])
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%% do a referenc simulation for the given C2/C3 values
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if (do_reference_simulation)
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active = [1 0 0];
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caps = [0 C2 C3];
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resist = [50 inf inf];
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Sim_Path = [Sim_Path_Root '_C2=' num2str(C2*1e12) '_C3=' num2str(C3*1e12)];
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[port_ref nf2ff_ref] = Patch_Antenna_Array(Sim_Path, ((exist(Sim_Path,'dir')>0) && (force_rerun==0)), show_structure, xpos, caps, resist, active);
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port_ref = calcPort( port_ref, Sim_Path, f, 'RefImpedance', 50);
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nf2ff_ref = CalcNF2FF(nf2ff_ref, Sim_Path, f0, [-180:2:180]*pi/180, 0);
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% extract currents from referenc simulation
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for p=1:3
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I_ref(p,1) = interp1(f, port_ref{p}.if.tot,f0);
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end
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disp(['I2/I1: openEMS: ' num2str(I_ref(2)/I_ref(1))])
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disp(['I3/I1: openEMS: ' num2str(I_ref(3)/I_ref(1))])
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end
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%% calculate and apply weighting cooefficients [3]
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% calculate
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coeff = I\I_out;
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% apply
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E_ff_phi = 0*nf2ff{1}.E_phi{1};
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E_ff_theta = 0*nf2ff{1}.E_phi{1};
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for n=1:3
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E_ff_phi = E_ff_phi + coeff(n)*nf2ff{n}.E_phi{1};
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E_ff_theta = E_ff_theta + coeff(n)*nf2ff{n}.E_theta{1};
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end
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%% plot far-field patterns
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figure
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polar([-180:2:180]'*pi/180,abs(E_ff_phi(:))/max(abs(E_ff_phi(:))));
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hold on
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if (do_reference_simulation)
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polar([-180:2:180]'*pi/180,abs(nf2ff_ref.E_norm{1}(:,1))/max(abs(nf2ff_ref.E_norm{1}(:,1))),'r--');
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end
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title('normalized far-field pattern','Interpreter', 'none')
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legend('calculated','reference')
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