156 lines
4.3 KiB
Matlab
156 lines
4.3 KiB
Matlab
close all
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clear
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clc
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%example for an cylindrical mesh, modeling a coaxial cable
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% this example is using a multi-grid approach
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%% setup %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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Settings = [];
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Settings.LogFile = 'openEMS.log';
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physical_constants
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f0 = 0.5e9;
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epsR = 1; %material filling
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length = 1000;
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port_dist = length/2;
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rad_i = 10; %inner radius
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rad_a = 200; %outer radius
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partial = 0.5; %e.g. 0.5 means only one half of a coax, should be <1 or change boundary cond.
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max_mesh = 10 / sqrt(epsR);
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max_alpha = max_mesh;
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N_alpha = ceil(rad_a * 2*pi * partial / max_alpha);
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%make it even...
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N_alpha = N_alpha + mod(N_alpha,2);
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%make sure it is multiple of 4, needed for 2 multi-grid steps
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N_alpha = ceil((N_alpha)/4) *4 + 1;
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openEMS_opts = '';
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% openEMS_opts = [openEMS_opts ' --disable-dumps'];
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% openEMS_opts = [openEMS_opts ' --debug-material'];
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% openEMS_opts = [openEMS_opts ' --numThreads=1'];
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def_refSimu = 0; % do a reference simulation without the multi-grid
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%% setup done %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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if (def_refSimu>0)
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Sim_Path = 'tmp_ref';
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else
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Sim_Path = 'tmp';
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end
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Sim_CSX = 'coax.xml';
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if (exist(Sim_Path,'dir'))
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rmdir(Sim_Path,'s');
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end
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mkdir(Sim_Path);
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%setup FDTD parameter
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if (def_refSimu>0)
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FDTD = InitCylindricalFDTD(1e5,1e-5,'OverSampling',5 );
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else
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FDTD = InitCylindricalFDTD(1e5,1e-5,'OverSampling',5 ,'MultiGrid','60,120');
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end
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FDTD = SetGaussExcite(FDTD,f0,f0);
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BC = [0 0 1 1 2 2];
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FDTD = SetBoundaryCond(FDTD,BC);
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mesh_res = [max_mesh 2*pi*partial/N_alpha max_mesh];
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%setup CSXCAD geometry
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CSX = InitCSX();
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mesh.x = SmoothMeshLines([rad_i rad_a],mesh_res(1));
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mesh.y = linspace(-pi*partial,pi*partial,N_alpha);
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mesh.z = SmoothMeshLines([0 port_dist length],mesh_res(3));
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CSX = DefineRectGrid(CSX, 1e-3,mesh);
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start = [rad_i mesh.y(1) mesh.z(3)];
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stop = [rad_a mesh.y(end) mesh.z(3)];
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CSX = AddExcitation(CSX,'excite',0,[1 0 0]);
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weight{1} = '1/rho';
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weight{2} = 0;
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weight{3} = 0;
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CSX = SetExcitationWeight(CSX, 'excite', weight );
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CSX = AddBox(CSX,'excite',0 ,start,stop);
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start = [mesh.x(1) mesh.y(1) mesh.z(1)];
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stop = [mesh.x(end) mesh.y(end) mesh.z(end)];
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CSX = AddMaterial(CSX,'material');
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CSX = SetMaterialProperty(CSX,'material','Epsilon',epsR);
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CSX = AddBox(CSX,'material',0 ,start,stop);
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%dump
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CSX = AddDump(CSX,'Et_rz_','DumpMode',0);
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start = [mesh.x(1) 0 mesh.z(1)];
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stop = [mesh.x(end) 0 mesh.z(end)];
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CSX = AddBox(CSX,'Et_rz_',0 , start,stop);
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CSX = AddDump(CSX,'Ht_rz_','DumpType',1,'DumpMode',0);
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CSX = AddBox(CSX,'Ht_rz_',0 , start,stop);
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CSX = AddDump(CSX,'Et_','DumpType',0,'DumpMode',0);
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start = [mesh.x(1) mesh.y(1) length/2];
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stop = [mesh.x(end) mesh.y(end) length/2];
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CSX = AddBox(CSX,'Et_',0,start,stop);
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CSX = AddDump(CSX,'Ht_','DumpType',1,'DumpMode',0);
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start = [mesh.x(1) mesh.y(1) length/2];
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stop = [mesh.x(end) mesh.y(end) length/2];
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CSX = AddBox(CSX,'Ht_',0,start,stop);
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% voltage calc (take a voltage average to be at the same spot as the
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% current calculation)
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CSX = AddProbe(CSX,'ut1_1',0);
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start = [ rad_i 0 port_dist ];stop = [ rad_a 0 port_dist ];
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CSX = AddBox(CSX,'ut1_1', 0 ,start,stop);
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CSX = AddProbe(CSX,'ut1_2',0);
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start = [ rad_i 0 port_dist+mesh_res(3) ];stop = [ rad_a 0 port_dist+mesh_res(3) ];
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CSX = AddBox(CSX,'ut1_2', 0 ,start,stop);
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% current calc
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CSX = AddProbe(CSX,'it1',1);
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mid = 75;
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start = [ 0 mesh.y(1) port_dist+mesh_res(3)/2 ];stop = [ mid mesh.y(end) port_dist+mesh_res(3)/2 ];
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CSX = AddBox(CSX,'it1', 0 ,start,stop);
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%% Write openEMS compatoble xml-file %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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WriteOpenEMS([Sim_Path '/' Sim_CSX],FDTD,CSX);
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RunOpenEMS(Sim_Path, Sim_CSX, openEMS_opts, Settings)
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%%
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close all
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freq = linspace(0,2*f0,201);
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UI = ReadUI({'ut1_1','ut1_2','it1'},Sim_Path,freq);
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u_f = (UI.FD{1}.val + UI.FD{2}.val)/2; %averaging voltages to fit current
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i_f = UI.FD{3}.val / partial;
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% plot(UI.TD{1}.t,UI.TD{1}.val);
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% grid on;
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%
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% figure
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% plot(UI.TD{3}.t,UI.TD{3}.val);
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% grid on;
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%plot Z_L compare
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figure
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ZL = Z0/2/pi/sqrt(epsR)*log(rad_a/rad_i); %analytic line-impedance of a coax
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plot(UI.FD{1}.f,ZL*ones(size(u_f)),'g','Linewidth',3);
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hold on;
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grid on;
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Z = u_f./i_f;
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plot(UI.FD{1}.f,real(Z),'k--','Linewidth',2);
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plot(UI.FD{1}.f,imag(Z),'r-','Linewidth',2);
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xlim([0 2*f0]);
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legend('Z_L - analytic','\Re\{Z\} - FDTD','\Im\{Z\} - FDTD','Location','Best');
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