134 lines
4.0 KiB
Matlab
134 lines
4.0 KiB
Matlab
function [port] = calcPort( port, SimDir, f, varargin)
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% [port] = calcPort( port, SimDir, f, [ref_ZL], [ref_shift])
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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 port.
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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 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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%
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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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%
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% example:
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% port{1} = calcPort( port{1}, Sim_Path, f, 'RefImpedance', 50);
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% or
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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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% See also AddMSLPort
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%DEBUG
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% save('/tmp/test.mat', 'port', 'SimDir', 'f', 'nargin' )
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% load('/tmp/test.mat')
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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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n_conv_arg = 3; % number of conventional arguments
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%set defaults
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ref_ZL = 0;
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ref_shift = nan;
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if (nargin>n_conv_arg)
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for n=1:2:(nargin-n_conv_arg)
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if (strcmp(varargin{n},'RefPlaneShift')==1);
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ref_shift = varargin{n+1};
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end
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if (strcmp(varargin{n},'RefImpedance')==1);
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ref_ZL = varargin{n+1};
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end
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end
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end
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% read time domain data
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filename = ['port_ut' num2str(port.nr)];
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U = ReadUI( {[filename 'A'],[filename 'B'],[filename 'C']}, SimDir, f );
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filename = ['port_it' num2str(port.nr)];
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I = ReadUI( {[filename 'A'],[filename 'B']}, SimDir, f );
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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 = (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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% reference plane shift (lossless)
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if ~isnan(ref_shift)
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% renormalize the shift to the measurement plane
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ref_shift = ref_shift - port.measplanepos * port.drawingunit;
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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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if isfield(port,'Feed_R')
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ref_ZL = port.Feed_R;
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else
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ref_ZL = ZL;
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end
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end
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port.ZL = ZL;
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port.beta = beta;
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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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