From ba2b962c4b5dabb170824a0cad08e1f2e361bb50 Mon Sep 17 00:00:00 2001 From: Sebastian Held Date: Mon, 3 Jan 2011 15:34:32 +0100 Subject: [PATCH] new example: directional coupler in stacked microstrip technology --- .../examples/microstrip/directional_coupler.m | 235 ++++++++++++++++++ 1 file changed, 235 insertions(+) create mode 100644 matlab/examples/microstrip/directional_coupler.m diff --git a/matlab/examples/microstrip/directional_coupler.m b/matlab/examples/microstrip/directional_coupler.m new file mode 100644 index 0000000..15e0fb0 --- /dev/null +++ b/matlab/examples/microstrip/directional_coupler.m @@ -0,0 +1,235 @@ +function directional_coupler +% +% EXAMPLE / microstrip / directional_coupler +% +% Stacked directional coupler in microstrip technology. +% +% This example demonstrates: +% - simple microstrip geometry +% - S-parameter calculation using the ypar-method +% - display of coupler parameters +% - display of S11 (smith chart) +% +% +% Tested with +% - Matlab 2010b +% - Octave 3.3.54 +% - openEMS v0.0.17 +% +% (C) 2010 Sebastian Held + +clear +close all +clc + +% sim settings +showStructure = 1; +runSimulation = 1; + +for n=1:4 + if n > 1, showStructure = 0; end + ports{n} = sim( n, showStructure, runSimulation ); +end +postprocess( ports ); + + + + +function ports = sim( simnr, showStructure, runSimulation ) +physical_constants + +% setup the simulation +drawingunit = 1e-6; % specify everything in um +Sim_Path = ['tmp' int2str(simnr)]; +Sim_CSX = 'tmp.xml'; +f_max = 100e6; +lambda = c0/f_max; + +% specify the coupler +pcb1.w = 147000; +pcb1.h = 54500; +pcb1.t = 1524; +pcb1.epr = 3; +msl1.w = 135000; +msl1.h = 2800; +pcb2.w = 107000; +pcb2.h = 14000; +pcb2.t = 1524; +pcb2.epr = 3; +msl2.w = 95000; +msl2.h = 4000; + + +CSX = InitCSX(); + +% create the mesh +mesh.x = [-pcb1.w/2 pcb1.w/2 -pcb2.w/2 pcb2.w/2 -msl1.w/2 msl1.w/2 -msl2.w/2 msl2.w/2]; +mesh.x = [mesh.x linspace(-msl2.w/2,-msl2.w/2+msl2.h, 5) linspace(msl2.w/2,msl2.w/2-msl2.h, 5)]; +mesh.y = [-pcb1.h/2 pcb1.h/2 -pcb2.h/2 pcb2.h/2 -msl1.h/2 msl1.h/2 -msl2.h/2 msl2.h/2]; +mesh.z = [linspace(0,pcb1.t,5) linspace(pcb1.t,pcb1.t+pcb2.t,5)]; +mesh.z = [mesh.z mesh.z(end)+10*(mesh.z(end)-mesh.z(1))]; % add space above pcb +res = lambda/sqrt(max([pcb1.epr,pcb2.epr])) / 20 / drawingunit; +mesh.x = SmoothMeshLines2(mesh.x,res); +mesh.y = SmoothMeshLines2(mesh.y,res); +mesh.z = SmoothMeshLines2(mesh.z,res); +mesh = AddPML( mesh, [8 8 8 8 8 8] ); % add space for PML +CSX = DefineRectGrid( CSX, drawingunit, mesh ); + +%% create the structure + +% microstrip +CSX = AddMetal( CSX, 'PEC' ); +start = [-msl1.w/2, -msl1.h/2, pcb1.t]; +stop = [ msl1.w/2, msl1.h/2, pcb1.t]; +priority = 100; % the geometric priority is set to 100 +CSX = AddBox( CSX, 'PEC', priority, start, stop ); + +% ground plane +CSX = AddMetal( CSX, 'PEC_ground' ); +start = [-pcb1.w/2, -pcb1.h/2, 0]; +stop = [ pcb1.w/2, pcb1.h/2, 0]; +CSX = AddBox( CSX, 'PEC_ground', priority, start, stop ); + +% substrate 1 +start = [-pcb1.w/2, -pcb1.h/2, 0]; +stop = [ pcb1.w/2, pcb1.h/2, pcb1.t]; +priority = 10; +CSX = AddMaterial( CSX, 'substrate1' ); +CSX = SetMaterialProperty( CSX, 'substrate1', 'Epsilon', pcb1.epr ); +CSX = AddBox( CSX, 'substrate1', priority, start, stop ); + +% substrate 2 +start = [-pcb2.w/2, -pcb2.h/2, pcb1.t]; +stop = [ pcb2.w/2, pcb2.h/2, pcb1.t+pcb2.t]; +priority = 10; +CSX = AddMaterial( CSX, 'substrate2' ); +CSX = SetMaterialProperty( CSX, 'substrate2', 'Epsilon', pcb2.epr ); +CSX = AddBox( CSX, 'substrate2', priority, start, stop ); + +% stripline +start = [-msl2.w/2, -msl2.h/2, pcb1.t+pcb2.t]; +stop = [ msl2.w/2, msl2.h/2, pcb1.t+pcb2.t]; +priority = 100; +CSX = AddBox( CSX, 'PEC', priority, start, stop ); + +% connections +start = [-msl2.w/2, -msl2.h/2, pcb1.t+pcb2.t]; +stop = [-msl2.w/2+msl2.h, -pcb2.h/2, pcb1.t+pcb2.t]; +priority = 100; +CSX = AddBox( CSX, 'PEC', priority, start, stop ); +start = [ msl2.w/2, -msl2.h/2, pcb1.t+pcb2.t]; +stop = [ msl2.w/2-msl2.h, -pcb2.h/2, pcb1.t+pcb2.t]; +priority = 100; +CSX = AddBox( CSX, 'PEC', priority, start, stop ); + +%% ports +% this project needs 4 simulations +for n=1:4 + portexcite{n} = []; +end +portexcite{simnr} = 'excite'; + +% port 1: input port +start = [-msl1.w/2, 0, pcb1.t]; +stop = [-msl1.w/2, 0, 0]; +[CSX ports{1}] = AddCurvePort( CSX, 1, 50, start, stop, portexcite{1} ); +% port 2: output port +start = [msl1.w/2, 0, pcb1.t]; +stop = [msl1.w/2, 0, 0]; +[CSX ports{2}] = AddCurvePort( CSX, 2, 50, start, stop, portexcite{2} ); +% port 3: coupled port +start = [-msl2.w/2+msl2.h/2, -pcb2.h/2, pcb1.t+pcb2.t]; +stop = [-msl2.w/2+msl2.h/2, -pcb2.h/2, 0]; +[CSX ports{3}] = AddCurvePort( CSX, 3, 50, start, stop, portexcite{3} ); +% port 4: isolated port +start = [msl2.w/2-msl2.h/2, -pcb2.h/2, pcb1.t+pcb2.t]; +stop = [msl2.w/2-msl2.h/2, -pcb2.h/2, 0]; +[CSX ports{4}] = AddCurvePort( CSX, 4, 50, start, stop, portexcite{4} ); + +%% setup FDTD parameters & excitation function +max_timesteps = 50000; +min_decrement = 1e-6; +FDTD = InitFDTD( max_timesteps, min_decrement ); +FDTD = SetGaussExcite( FDTD, 0, f_max ); +BC = {'PML_8' 'PML_8' 'PML_8' 'PML_8' 'PML_8' 'PML_8'}; +BC = {'MUR' 'MUR' 'MUR' 'MUR' 'MUR' 'MUR'}; % faster +FDTD = SetBoundaryCond( FDTD, BC ); + +%% Write openEMS compatible xml-file +if runSimulation + [~,~,~] = rmdir(Sim_Path,'s'); +end +[~,~,~] = mkdir(Sim_Path); +WriteOpenEMS([Sim_Path '/' Sim_CSX],FDTD,CSX); + +if showStructure + CSXGeomPlot( [Sim_Path '/' Sim_CSX] ); +end + +%% run openEMS +openEMS_opts = ''; +openEMS_opts = [openEMS_opts ' --engine=fastest']; +% openEMS_opts = [openEMS_opts ' --debug-material']; +% openEMS_opts = [openEMS_opts ' --debug-boxes']; +if runSimulation + RunOpenEMS( Sim_Path, Sim_CSX, openEMS_opts ); +end + + + + +function postprocess( ports ) +f = linspace( 0, 100e6, 201 ); +Y = calc_ypar( f, ports{1}, 'tmp' ); +R = 50; +S = y2s(Y,R); + +% insertion loss +IL_dB = -20 * log10(abs(squeeze(S(2,1,:)))); + +% coupling factor +CF_dB = -20 * log10(abs(squeeze(S(3,1,:)))); + +% isolation +I_dB = -20 * log10(abs(squeeze(S(4,1,:)))); + +% directivity +D_dB = -20 * log10(abs(squeeze(S(4,1,:) ./ S(3,1,:)))); + +figure +plot( f, [IL_dB CF_dB I_dB D_dB] ); +legend( {'insertion loss','coupling factor','isolation','directivity'} ); +title( ['performance of the coupler for a termination resistance of R=' num2str(R)] ); +grid on + +smithchart +S11 = squeeze(S(1,1,:)); +plot( real(S11), imag(S11) ); +legend( 'S_{11}' ); +title( ['performance of the coupler for a termination resistance of R=' num2str(R)] ); +axis( [-1 1 -1 1] ); + + + +function smithchart +% smith chart +figure +if exist( 'smith', 'file' ) + % smith chart + % www.ece.rutgers.edu/~orfanidi/ewa + % or cmt toolbox from git.ate.uni-duisburg.de + smith +else + % poor man smith chart + color = [.6 .6 .6]; + h = plot( sin(0:0.01:2*pi), cos(0:0.01:2*pi), 'Color', color ); + hg = hggroup; + set( h,'Parent',hg ); + hold on + plot( hg, 0.25+0.75*sin(0:0.01:2*pi), 0.75*cos(0:0.01:2*pi), 'Color', color ); + plot( hg, 0.5+0.5*sin(0:0.01:2*pi), 0.5*cos(0:0.01:2*pi), 'Color', color ); + plot( hg, 0.75+0.25*sin(0:0.01:2*pi), 0.25*cos(0:0.01:2*pi), 'Color', color ); + plot( hg, [-1 1], [0 0], 'Color', color ); + axis equal + axis off +end