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function [port] = calcWGPort( port, SimDir, f, varargin)
% [port] = calcWGPort( port, SimDir, f, varargin)
%
% Calculate voltages and currents, the propagation constant beta
% and the characteristic impedance ZL of the given waveguide port.
%
% The port has to be created by e.g. AddWaveGuidePort().
%
% input:
% port: return value of e.g. AddWaveGuidePort()
% SimDir: directory, where the simulation files are
% f: frequency vector for DFT
%
% variable input:
% 'RefImpedance': - use a given reference impedance to calculate inc and
% ref voltages and currents
% - default is given port or calculated line impedance
% 'RefPlaneShift': - use a given reference plane shift from port beginning
% for a desired phase correction
% - default is the measurement plane at the end of the
% port
% - the plane shift has to be given in drawing units!
% 'RefractiveIndex': set a material refractive index
% 'SwitchDirection': 0/1, switch assumed direction of propagation
%
% output:
% % output signals/values in time domain (TD):
% port.ut.tot total voltage (time-domain)
% port.ut.time voltage time vector
% port.it.tot total current (time-domain)
% port.it.time current time vector
%
% % output signals/values in frequency domain (FD):
% port.f the given frequency fector
% port.uf.tot/inc/ref total, incoming and reflected voltage
% port.if.tot/inc/ref total, incoming and reflected current
% port.beta: propagation constant
% port.ZL: characteristic line impedance
% port.ZL_ref used reference impedance
%
% example:
% port{1} = calcWGPort( port{1}, Sim_Path, f, 'RefImpedance', 50);
%
% openEMS matlab interface
% -----------------------
% (C) 2013 Thorsten Liebig (thorsten.liebig@gmx.de)
%
% See also AddWaveGuidePort, calcPort
if (iscell(port))
for n=1:numel(port)
port{n}=calcWGPort(port{n}, SimDir, f, varargin{:});
end
return;
end
if (strcmpi(port.type,'WaveGuide')~=1)
error('openEMS:calcWGPort','error, type is not a waveguide port');
end
%set defaults
ref_ZL = -1;
ref_shift = nan;
ref_index = 1;
switch_dir = 1;
UI_args = {};
for n=1:2:numel(varargin)
if (strcmp(varargin{n},'RefPlaneShift')==1);
ref_shift = varargin{n+1};
elseif (strcmp(varargin{n},'RefImpedance')==1);
ref_ZL = varargin{n+1};
elseif (strcmp(varargin{n},'RefractiveIndex')==1);
ref_index = varargin{n+1};
elseif (strcmpi(varargin{n},'SwitchDirection')==1);
if (varargin{n+1})
switch_dir = -1;
end
else
UI_args(end+1) = varargin(n);
UI_args(end+1) = varargin(n+1);
end
end
% read time domain data
U = ReadUI( port.U_filename, SimDir, f, UI_args{:} );
I = ReadUI( port.I_filename, SimDir, f, UI_args{:} );
% store the original frequency domain waveforms
u_f = U.FD{1}.val;
i_f = I.FD{1}.val * switch_dir;
% time domain signal
port.ut.time = U.TD{1}.t;
port.ut.tot = U.TD{1}.val;
port.it.time = I.TD{1}.t;
port.it.tot = switch_dir*I.TD{1}.val;
physical_constants
k = 2*pi*f/C0*ref_index;
fc = C0*port.kc/2/pi/ref_index;
port.beta = sqrt(k.^2 - port.kc^2);
port.ZL = k * Z0 ./ port.beta; %analytic waveguide impedance
% reference plane shift (lossless)
if ~isnan(ref_shift)
% shift relative to the beginning of the waveguide
ref_shift = ref_shift - port.measplanepos;
ref_shift = ref_shift * port.drawingunit;
% store the shifted frequency domain waveforms
phase = real(beta)*ref_shift;
u_f_shift = u_f .* cos(-phase) + 1i * i_f.*port.ZL .* sin(-phase);
i_f_shift = i_f .* cos(-phase) + 1i * u_f./port.ZL .* sin(-phase);
u_f = u_f_shift;
i_f = i_f_shift;
end
if (ref_ZL < 0)
ref_ZL = port.ZL;
end
port.ZL_ref = ref_ZL;
port.f = f;
uf_inc = 0.5 * ( u_f + i_f .* ref_ZL );
if_inc = 0.5 * ( i_f + u_f ./ ref_ZL );
uf_ref = u_f - uf_inc;
if_ref = if_inc - i_f;
port.uf.tot = u_f;
port.uf.inc = uf_inc;
port.uf.ref = uf_ref;
port.if.tot = i_f;
port.if.inc = if_inc;
port.if.ref = if_ref;
port.raw.U = U;
port.raw.I = I;
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