Mode matching probe: fixed an error in HField interpolation

Now also excluding the boundaries from the MM.
Updated waveguide example: Rect_Waveguide.m

Signed-off-by: Thorsten Liebig <Thorsten.Liebig@gmx.de>

FDTD/processmodematch.cpp

@@ -61,6 +61,12 @@ void ProcessModeMatch::InitProcess()
 			stop[n]=help;
 		}
 
+		//exclude boundaries from mode-matching
+		if (start[n]==0)
+			++start[n];
+		if (stop[n]==Op->GetNumberOfLines(n)-1)
+			--stop[n];
+
 		if (stop[n]>start[n])
 			++Dump_Dim;
 
@@ -185,7 +191,7 @@ void ProcessModeMatch::SetFieldType(int type)
 		cerr << "ProcessModeMatch::SetFieldType: Warning, unknown field type..." << endl;
 }
 
-double ProcessModeMatch::GetField(int ny, unsigned int pos[3])
+double ProcessModeMatch::GetField(int ny, const unsigned int pos[3])
 {
 	if (m_ModeFieldType==0)
 		return GetEField(ny,pos);
@@ -194,7 +200,7 @@ double ProcessModeMatch::GetField(int ny, unsigned int pos[3])
 	return 0;
 }
 
-double ProcessModeMatch::GetEField(int ny, unsigned int pos[3])
+double ProcessModeMatch::GetEField(int ny, const unsigned int pos[3])
 {
 	if ((pos[ny]==0) || (pos[ny]==Op->GetNumberOfLines(ny)-1))
 		return 0.0;
@@ -210,7 +216,7 @@ double ProcessModeMatch::GetEField(int ny, unsigned int pos[3])
 	return 0.0;
 }
 
-double ProcessModeMatch::GetHField(int ny, unsigned int pos[3])
+double ProcessModeMatch::GetHField(int ny, const unsigned int pos[3])
 {
 	if ((pos[ny]==0) || (pos[ny]>=Op->GetNumberOfLines(ny)-1))
 		return 0.0;
@@ -218,19 +224,19 @@ double ProcessModeMatch::GetHField(int ny, unsigned int pos[3])
 	unsigned int EngPos[] = {pos[0],pos[1],pos[2]};
 
 	int nyP = (ny+1)%3;
-	if (pos[nyP] >= Op->GetNumberOfLines(nyP)-1)
+	if (pos[nyP] == 0)
 		return 0.0;
 	int nyPP = (ny+2)%3;
-	if (pos[nyPP] >= Op->GetNumberOfLines(nyPP)-1)
+	if (pos[nyPP] == 0)
 		return 0.0;
 
 	double hfield = Eng->GetCurr(ny,EngPos) / Op->GetMeshDelta(ny,EngPos,true);
-	EngPos[nyP]++;
-	hfield += Eng->GetCurr(ny,EngPos) / Op->GetMeshDelta(ny,EngPos,true);
-	EngPos[nyPP]++;
-	hfield += Eng->GetCurr(ny,EngPos) / Op->GetMeshDelta(ny,EngPos,true);
 	EngPos[nyP]--;
 	hfield += Eng->GetCurr(ny,EngPos) / Op->GetMeshDelta(ny,EngPos,true);
+	EngPos[nyPP]--;
+	hfield += Eng->GetCurr(ny,EngPos) / Op->GetMeshDelta(ny,EngPos,true);
+	EngPos[nyP]++;
+	hfield += Eng->GetCurr(ny,EngPos) / Op->GetMeshDelta(ny,EngPos,true);
 	return hfield/4.0;
 }
 

FDTD/processmodematch.h

@@ -43,9 +43,9 @@ protected:
 
 	int m_ModeFieldType;
 
-	double GetField(int ny, unsigned int pos[3]);
+	double GetField(int ny, const unsigned int pos[3]);
-	double GetEField(int ny, unsigned int pos[3]);
+	double GetEField(int ny, const unsigned int pos[3]);
-	double GetHField(int ny, unsigned int pos[3]);
+	double GetHField(int ny, const unsigned int pos[3]);
 
 	string m_ModeFunction[3];
 	CSFunctionParser* m_ModeParser[2];

matlab/examples/waveguide/Rect_Waveguide.m

@@ -3,13 +3,13 @@ clear
 clc
 
 %% setup the simulation %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-length = 8000;
+length = 2000;
 unit = 1e-3;
 a = 1000;
 width = a;
 b = 500;
 height = b;
-mesh_res = [10 10 20];
+mesh_res = [10 10 10];
 
 %define mode
 m = 1;
@@ -18,16 +18,24 @@ n = 0;
 EPS0 = 8.85418781762e-12;
 MUE0 = 1.256637062e-6;
 C0 = 1/sqrt(EPS0*MUE0);
+Z0 = sqrt(MUE0/EPS0);
 
 f0 = 1e9;
+freq = linspace(f0-f0/3,f0+f0/3,201);
 
-k = 2*pi*f0/C0;
+k = 2*pi*freq/C0;
 kc = sqrt((m*pi/a/unit)^2 + (n*pi/b/unit)^2);
 fc = C0*kc/2/pi;
-beta = sqrt(k^2 - kc^2);
+beta = sqrt(k.^2 - kc^2);
 
+ZL_a = k * Z0 ./ beta; 
+
+%% mode functions %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 func_Ex = [num2str( n/b/unit) '*cos(' num2str(m*pi/a) '*x)*sin('  num2str(n*pi/b) '*y)'];
-func_Ey = [num2str(m/a/unit) '*sin(' num2str(m*pi/a) '*x)*cos('  num2str(n*pi/b) '*y)'];
+func_Ey = [num2str(-m/a/unit) '*sin(' num2str(m*pi/a) '*x)*cos('  num2str(n*pi/b) '*y)'];
+
+func_Hx = [num2str(m/a/unit) '*sin(' num2str(m*pi/a) '*x)*cos('  num2str(n*pi/b) '*y)'];
+func_Hy = [num2str(n/b/unit) '*cos(' num2str(m*pi/a) '*x)*sin('  num2str(n*pi/b) '*y)'];
 
 %% define and openEMS options %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 openEMS_opts = '';
@@ -35,6 +43,9 @@ openEMS_opts = '';
 % openEMS_opts = [openEMS_opts ' --debug-material'];
 openEMS_opts = [openEMS_opts ' --engine=fastest'];
 
+Settings = [];
+Settings.LogFile = 'openEMS.log';
+
 Sim_Path = 'tmp';
 Sim_CSX = 'rect_wg.xml';
 
@@ -46,7 +57,7 @@ mkdir(Sim_Path);
 %% setup FDTD parameter & excitation function %%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 FDTD = InitFDTD(50000,1e-5,'OverSampling',6);
 FDTD = SetGaussExcite(FDTD,f0,f0/3);
-BC = [0 0 0 0 2 2];
+BC = [0 0 0 0 0 3];
 FDTD = SetBoundaryCond(FDTD,BC);
 
 %% setup CSXCAD geometry & mesh %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
@@ -57,8 +68,8 @@ mesh.z = 0 : mesh_res(3) : length;
 CSX = DefineRectGrid(CSX, unit,mesh);
 
 %% apply the excitation %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-start=[0     0      mesh.z(3) ];
+start=[0     0      mesh.z(1) ];
-stop =[width height mesh.z(3) ];
+stop =[width height mesh.z(1) ];
 CSX = AddExcitation(CSX,'excite',0,[1 1 0]);
 weight{1} = func_Ex;
 weight{2} = func_Ey;
@@ -66,17 +77,80 @@ weight{3} = 0;
 CSX = SetExcitationWeight(CSX,'excite',weight);
 CSX = AddBox(CSX,'excite',0 ,start,stop);
 
+%% voltage and current definitions using the mode matching probes %%%%%%%%%
+start = [mesh.x(1)   mesh.y(1)   mesh.z(15)];
+stop  = [mesh.x(end) mesh.y(end) mesh.z(15)];
+CSX = AddProbe(CSX, 'ut1', 10, 1, [], 'ModeFunction',{func_Ex,func_Ey,0});
+CSX = AddBox(CSX,  'ut1',  0 ,start,stop);
+CSX = AddProbe(CSX,'it1', 11, 1, [], 'ModeFunction',{func_Hx,func_Hy,0});
+CSX = AddBox(CSX,'it1', 0 ,start,stop);
+
+start = [mesh.x(1)   mesh.y(1)   mesh.z(end-15)];
+stop  = [mesh.x(end) mesh.y(end) mesh.z(end-15)];
+CSX = AddProbe(CSX, 'ut2', 10, 1, [], 'ModeFunction',{func_Ex,func_Ey,0});
+CSX = AddBox(CSX,  'ut2',  0 ,start,stop);
+CSX = AddProbe(CSX,'it2', 11, 1, [], 'ModeFunction',{func_Hx,func_Hy,0});
+CSX = AddBox(CSX,'it2', 0 ,start,stop);
+ 
 %% define dump boxes... %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-CSX = AddDump(CSX,'Et','FileType',0,'SubSampling','4,4,1');
+CSX = AddDump(CSX,'Et','FileType',1,'SubSampling','4,4,2');
 start = [mesh.x(1) , height/2 , mesh.z(1)];
 stop = [mesh.x(end) ,  height/2 , mesh.z(end)];
 CSX = AddBox(CSX,'Et',0 , start,stop);
 
-% CSX = AddDump(CSX,'Ht','DumpType',1,'FileType',1,'SubSampling','4,4,4');
+CSX = AddDump(CSX,'Ht','DumpType',1,'FileType',1,'SubSampling','4,4,2');
-% CSX = AddBox(CSX,'Ht',0,start,stop);
+CSX = AddBox(CSX,'Ht',0,start,stop);
 
 %% Write openEMS compatoble xml-file %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 WriteOpenEMS([Sim_Path '/' Sim_CSX],FDTD,CSX);
 
-RunOpenEMS(Sim_Path, Sim_CSX, openEMS_opts)
+RunOpenEMS(Sim_Path, Sim_CSX, openEMS_opts, Settings)
+
+
+%% postproc %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+U = ReadUI({'ut1','ut2'},[Sim_Path '/'],freq);
+I = ReadUI({'it1','it2'},[Sim_Path '/'],freq);
+Exc = ReadUI('et',Sim_Path,freq);
+
+uf1 = U.FD{1}.val./Exc.FD{1}.val;
+uf2 = U.FD{2}.val./Exc.FD{1}.val;
+if1 = I.FD{1}.val./Exc.FD{1}.val;
+if2 = I.FD{2}.val./Exc.FD{1}.val;
+
+uf1_inc = 0.5 * ( uf1 + if1 .* ZL_a );
+if1_inc = 0.5 * ( if1 + uf1 ./ ZL_a );
+uf2_inc = 0.5 * ( uf2 + if2 .* ZL_a );
+if2_inc = 0.5 * ( if2 + uf2 ./ ZL_a );
+
+uf1_ref = uf1 - uf1_inc;
+if1_ref = if1 - if1_inc;
+uf2_ref = uf2 - uf2_inc;
+if2_ref = if2 - if2_inc;
+
+%% plot s-parameter
+figure
+s11 = uf1_ref./uf1_inc;
+s21 = uf2_inc./uf1_inc;
+plot(freq,20*log10(abs(s11)),'Linewidth',2);
+xlim([freq(1) freq(end)]);
+% ylim([-40 5]);
+grid on;
+hold on;
+plot(freq,20*log10(abs(s21)),'r','Linewidth',2);
+legend('s11','s21','Location','SouthEast');
+ylabel('s-para (dB)');
+xlabel('freq (Hz)');
+
+%% compare analytic and numerical wave-impedance
+ZL = uf1./if1;
+figure()
+plot(freq,real(ZL),'Linewidth',2);
+hold on;
+grid on;
+plot(freq,imag(ZL),'r--','Linewidth',2);
+plot(freq,ZL_a,'g-.','Linewidth',2);
+ylabel('ZL (\Omega)');
+xlabel('freq (Hz)');
+xlim([freq(1) freq(end)]);
+legend('\Re(Z_L)','\Im(Z_L)','Z_L analytic','Location','Best');