150 lines
4.5 KiB
Matlab
150 lines
4.5 KiB
Matlab
function [port] = calcTLPort( port, SimDir, f, varargin)
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% [port] = calcTLPort( port, SimDir, f, varargin)
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%
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% Calculate voltages and currents, the propagation constant beta
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% and the characteristic impedance ZL of the given transmission line port.
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%
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% The port has to be created by e.g. AddMSLPort().
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%
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% input:
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% port: return value of e.g. AddMSLPort()
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% SimDir: directory, where the simulation files are
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% f: frequency vector for DFT
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%
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% variable input:
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% 'RefImpedance': - use a given reference impedance to calculate inc and
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% ref voltages and currents
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% - default is given port or calculated line impedance
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% 'RefPlaneShift': - use a given reference plane shift from port beginning
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% for a desired phase correction
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% - default is the measurement plane
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% - the plane shift has to be given in drawing units!
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% 'SwitchDirection': 0/1, switch assumed direction of propagation
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%
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% output:
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% port.f the given frequency fector
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% port.uf.tot/inc/ref total, incoming and reflected voltage
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% port.if.tot/inc/ref total, incoming and reflected current
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% port.beta: propagation constant
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% port.ZL: characteristic line impedance
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% port.ZL_ref used refernce impedance
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%
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% example:
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% port{1} = calcTLPort( port{1}, Sim_Path, f, 'RefImpedance', 50);
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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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%
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% openEMS matlab interface
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% -----------------------
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% (C) 2010 Sebastian Held <sebastian.held@uni-due.de>
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%
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% See also AddMSLPort, calcPort
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if (iscell(port))
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for n=1:numel(port)
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port{n}=calcTLPort(port{n}, SimDir, f, varargin{:});
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end
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return;
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end
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if ((strcmpi(port.type,'MSL')~=1) && (strcmpi(port.type,'Coaxial')~=1))
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error('openEMS:calcTLPort','error, type is not a transmission line port');
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end
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% check
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if abs((port.v_delta(1) - port.v_delta(2)) / port.v_delta(1))>1e-6
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warning( 'openEMS:calcPort:mesh', 'mesh is not equidistant; expect degraded accuracy' );
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end
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%% read optional arguments %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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%set defaults
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ref_ZL = -1;
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ref_shift = nan;
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switch_dir = 1;
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UI_args = {};
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for n=1:2:numel(varargin)
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if (strcmp(varargin{n},'RefPlaneShift')==1);
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ref_shift = varargin{n+1};
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elseif (strcmp(varargin{n},'RefImpedance')==1);
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ref_ZL = varargin{n+1};
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elseif (strcmpi(varargin{n},'SwitchDirection')==1);
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if (varargin{n+1})
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switch_dir = -1;
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end
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else
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UI_args(end+1) = varargin(n);
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UI_args(end+1) = varargin(n+1);
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end
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end
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% read time domain data (multiples files)
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U = ReadUI( port.U_filename, SimDir, f, UI_args{:} );
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I = ReadUI( port.I_filename, SimDir, f, UI_args{:} );
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% store the original frequency domain waveforms
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u_f = U.FD{2}.val;
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i_f = switch_dir*(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(port.v_delta(1:2))) * port.drawingunit);
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Ht = (I.FD{1}.val + I.FD{2}.val)/2; % space averaging: Ht is now defined at the same pos as Et
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dHt = (I.FD{2}.val - I.FD{1}.val) / (abs(port.i_delta(1)) * port.drawingunit);
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beta = sqrt( - dEt .* dHt ./ (Ht .* Et) );
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beta(real(beta) < 0) = -beta(real(beta) < 0); % determine correct sign (unlike the paper)
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% determine ZL
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ZL = sqrt(Et .* dEt ./ (Ht .* dHt));
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% if (strcmpi(port.type,'Coaxial'))
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% port.ZL = Z0/2/pi/ref_index*log(port.r_o/port.r_i);
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% end
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% reference plane shift (lossless)
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if ~isnan(ref_shift)
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ref_shift = ref_shift * port.LengthScale;
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% shift to the beginning of MSL
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ref_shift = ref_shift - port.measplanepos;
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ref_shift = ref_shift * port.drawingunit;
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% store the shifted frequency domain waveforms
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phase = real(beta)*ref_shift;
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U.FD{1}.val = u_f .* cos(-phase) + 1i * i_f.*ZL .* sin(-phase);
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I.FD{1}.val = i_f .* cos(-phase) + 1i * u_f./ZL .* sin(-phase);
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u_f = U.FD{1}.val;
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i_f = I.FD{1}.val;
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end
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if (ref_ZL < 0)
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ref_ZL = ZL;
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end
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port.ZL = ZL;
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port.beta = beta;
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port.ZL_ref = ref_ZL;
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port.f = f;
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uf_inc = 0.5 * ( u_f + i_f .* ref_ZL );
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if_inc = 0.5 * ( i_f + u_f ./ ref_ZL );
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uf_ref = u_f - uf_inc;
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if_ref = if_inc - i_f;
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port.uf.tot = u_f;
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port.uf.inc = uf_inc;
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port.uf.ref = uf_ref;
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port.if.tot = i_f;
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port.if.inc = if_inc;
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port.if.ref = if_ref;
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port.raw.U = U;
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port.raw.I = I;
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