updated calcPort.m to return time- and frequency domain currents and voltages
Sebastian Held
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ef5a4ee59f
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aacd0964fb
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@ -1,5 +1,5 @@
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function [S11,beta,ZL] = calcPort( portstruct, SimDir, f, ref_shift )
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%[S11,beta,ZL] = calcMSLPort( portstruct, SimDir, [f], [ref_shift] )
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function [S11,beta,ZL,vi] = calcPort( portstruct, SimDir, f, ref_shift )
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%[S11,beta,ZL,vi] = calcPort( portstruct, SimDir, [f], [ref_shift] )
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%
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% Calculate the reflection coefficient S11, the propagation constant beta
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% of the MSL-port and the characteristic impedance ZL of the MSL-port.
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@ -15,6 +15,9 @@ function [S11,beta,ZL] = calcPort( portstruct, SimDir, f, ref_shift )
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% S11: reflection coefficient (normalized to ZL)
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% beta: propagation constant
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% ZL: characteristic line impedance
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% vi: structure of voltages and currents
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% vi.TD.v.{val,t}; vi.TD.i.{val,t};
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% vi.FD.v.{val,val_shifted,f}; vi.FD.i.{val,val_shifted,f};
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%
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% reference: W. K. Gwarek, "A Differential Method of Reflection Coefficient Extraction From FDTD Simulations",
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% IEEE Microwave and Guided Wave Letters, Vol. 6, No. 5, May 1996
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@ -43,6 +46,16 @@ U = ReadUI( {[filename 'A'],[filename 'B'],[filename 'C']}, SimDir, f );
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filename = ['port_it' num2str(portstruct.nr)];
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I = ReadUI( {[filename 'A'],[filename 'B']}, SimDir, f );
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% store the original time domain waveforms
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vi.TD.v = U.TD{2};
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vi.TD.i.t = I.TD{1}.t;
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vi.TD.i.val = (I.TD{1}.val + I.TD{2}.val) / 2; % shift to same position as v
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% store the original frequency domain waveforms
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vi.FD.v = U.FD{2};
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vi.FD.i = I.FD{1};
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vi.FD.i.val = (I.FD{1}.val + I.FD{2}.val) / 2; % shift to same position as v
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f = U.FD{2}.f;
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Et = U.FD{2}.val;
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dEt = (U.FD{3}.val - U.FD{1}.val) / (sum(abs(portstruct.v_delta(1:2))) * portstruct.drawingunit);
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@ -89,4 +102,9 @@ if (nargin > 3)
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ref_shift = ref_shift * portstruct.drawingunit;
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S11 = S11 .* exp(2i*real(beta)*ref_shift);
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S11_corrected = S11_corrected .* exp(2i*real(beta)*ref_shift);
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% store the shifted frequency domain waveforms
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phase = real(beta)*ref_shift;
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vi.FD.v.val_shifted = vi.FD.v.val .* cos(-phase) + 1i * vi.FD.i.val.*ZL .* sin(-phase);
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vi.FD.i.val_shifted = vi.FD.i.val .* cos(-phase) + 1i * vi.FD.v.val./ZL .* sin(-phase);
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end
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@ -11,7 +11,9 @@
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% - simple microstrip geometry (made of PEC)
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% - MSL port
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% - MSL analysis
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%
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%
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% You may modify the PEC boundary condition at xmax to become a MUR
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% boundary. This resembles a matched microstrip line.
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%
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% Tested with
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% - Matlab 2009b
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@ -92,7 +94,9 @@ CSX = AddBox( CSX, 'Ht_', 0, start, stop );
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WriteOpenEMS( [Sim_Path '/' Sim_CSX], FDTD, CSX );
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%% show the structure
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CSXGeomPlot( [Sim_Path '/' Sim_CSX] );
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if ~postproc_only
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CSXGeomPlot( [Sim_Path '/' Sim_CSX] );
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end
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%% run openEMS
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openEMS_opts = '';
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@ -107,7 +111,7 @@ end
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%% postprocess
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f = linspace( 1e6, f_max, 1601 );
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U = ReadUI( {'port_ut1A','port_ut1B','et'}, 'tmp/', f );
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U = ReadUI( {'port_ut1A','port_ut1B','port_ut1C','et'}, 'tmp/', f );
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I = ReadUI( {'port_it1A','port_it1B'}, 'tmp/', f );
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% Z = (U.FD{1}.val+U.FD{2}.val)/2 ./ I.FD{1}.val;
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@ -119,12 +123,12 @@ I = ReadUI( {'port_it1A','port_it1B'}, 'tmp/', f );
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% title( 'line impedance (will fail in case of reflections!)' );
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figure
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ax = plotyy( U.TD{1}.t/1e-6, [U.TD{1}.val;U.TD{2}.val], U.TD{3}.t/1e-6, U.TD{3}.val );
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ax = plotyy( U.TD{1}.t/1e-6, [U.TD{1}.val;U.TD{2}.val;U.TD{3}.val], U.TD{4}.t/1e-6, U.TD{4}.val );
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xlabel( 'time (us)' );
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ylabel( 'amplitude (V)' );
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grid on
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title( 'Time domain voltage probes and excitation signal' );
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legend( {'ut1A','ut1B','excitation'} );
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legend( {'ut1A','ut1B','ut1C','excitation'} );
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% now make the y-axis symmetric to y=0 (align zeros of y1 and y2)
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y1 = ylim(ax(1));
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y2 = ylim(ax(2));
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@ -139,8 +143,26 @@ grid on
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title( 'Time domain current probes' );
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legend( {'it1A','it1B'} );
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figure
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ax = plotyy( U.FD{1}.f/1e9, abs([U.FD{1}.val;U.FD{2}.val;U.FD{3}.val]), U.FD{1}.f/1e9, angle([U.FD{1}.val;U.FD{2}.val;U.FD{3}.val])/pi*180 );
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xlabel( 'frequency (GHz)' );
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ylabel( ax(1), 'amplitude (A)' );
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ylabel( ax(2), 'phase (deg)' );
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grid on
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title( 'Frequency domain voltage probes' );
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legend( {'abs(uf1A)','abs(uf1B)','abs(uf1C)','angle(uf1A)','angle(uf1B)','angle(uf1C)'} );
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figure
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ax = plotyy( I.FD{1}.f/1e9, abs([I.FD{1}.val;I.FD{2}.val]), I.FD{1}.f/1e9, angle([I.FD{1}.val;I.FD{2}.val])/pi*180 );
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xlabel( 'frequency (GHz)' );
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ylabel( ax(1), 'amplitude (A)' );
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ylabel( ax(2), 'phase (deg)' );
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grid on
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title( 'Frequency domain current probes' );
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legend( {'abs(if1A)','abs(if1B)','angle(if1A)','angle(if1B)'} );
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% port analysis
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[S11,beta,ZL] = calcMSLPort( portstruct, Sim_Path, f );
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[S11,beta,ZL,vi] = calcPort( portstruct, Sim_Path, f );
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% attention! the reflection coefficient S11 is normalized to ZL!
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figure
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@ -153,6 +175,18 @@ plot( real(S11(1)), imag(S11(1)), '*r' );
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axis equal
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title( 'Reflection coefficient S11 at the measurement plane' );
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figure
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plot( sin(0:0.01:2*pi), cos(0:0.01:2*pi), 'Color', [.7 .7 .7] );
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hold on
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plot( 0.5+0.5*sin(0:0.01:2*pi), 0.5*cos(0:0.01:2*pi), 'Color', [.7 .7 .7] );
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plot( [-1 1], [0 0], 'Color', [.7 .7 .7] );
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Z = vi.FD.v.val ./ vi.FD.i.val;
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S11_ = (Z-ZL) ./ (Z+ZL);
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plot( S11_, 'k' );
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plot( real(S11_(1)), imag(S11_(1)), '*r' );
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axis equal
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title( {'Reflection coefficient S11 at the measurement plane' 'calculated from voltages and currents'} );
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figure
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plot( f/1e9, [real(S11);imag(S11)], 'Linewidth',2 );
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legend( {'Re(S11)', 'Im(S11)'} );
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@ -184,7 +218,7 @@ title( 'Characteristic line impedance ZL' );
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% reference plane shift (to the end of the port)
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ref_shift = abs(portstop(1) - portstart(1));
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[S11,beta,ZL] = calcMSLPort( portstruct, Sim_Path, f, ref_shift );
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[S11,beta,ZL,vi] = calcPort( portstruct, Sim_Path, f, ref_shift );
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figure
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plotyy( f/1e9, 20*log10(abs(S11)), f/1e9, angle(S11)/pi*180 );
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@ -202,6 +236,18 @@ plot( real(S11(1)), imag(S11(1)), '*r' );
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axis equal
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title( 'Reflection coefficient S11 at the reference plane (at the electric wall)' );
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figure
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plot( sin(0:0.01:2*pi), cos(0:0.01:2*pi), 'Color', [.7 .7 .7] );
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hold on
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plot( 0.5+0.5*sin(0:0.01:2*pi), 0.5*cos(0:0.01:2*pi), 'Color', [.7 .7 .7] );
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plot( [-1 1], [0 0], 'Color', [.7 .7 .7] );
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Z = vi.FD.v.val_shifted ./ vi.FD.i.val_shifted;
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S11_ = (Z-ZL) ./ (Z+ZL);
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plot( S11_, 'k' );
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plot( real(S11_(1)), imag(S11_(1)), '*r' );
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axis equal
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title( {'Reflection coefficient S11 at the reference plane (at the electric wall)' 'calculated from shifted voltages and currents'} );
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%% visualize electric and magnetic fields
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% you will find vtk dump files in the simulation folder (tmp/)
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% use paraview to visualize them
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