CalcPort

From openEMS

calcPort is a post-simulation function to calculate frequency- and time-domain properties and data for ports.

The port has to be created by, for example, AddMSLPort(), AddLumpedPort(), AddRectWaveGuidePort(), or AddCurvePort().

Function Call for calcPort

[port] = calcPort( port, SimDir, f, varargin)

Input parameters

port: return value of AddMSLPort()
SimDir: directory, where the simulation files are
f: frequency vector for calculation

varargin parameters

RefImpedance: use a given reference impedance to calculate incident and reflected voltages and currents
- default is given port or calculated line impedance
RefPlaneShift: for transmission lines only, See also calcTLPort for more details
SwitchDirection: 0/1, switch assumed direction of propagation
SignalType: 'pulse' (default) or 'periodic'

Output

The output structure port{i}, where {i} is the port number, has the following components:

Output signals/values in time domain (TD)

port{i}.ut.tot: total voltage (time-domain)
port{i}.ut.time: voltage time vector
port{i}.it.tot: total current (time-domain)
port{i}.it.time: current time vector

Output signals/values in frequency domain (TD)

port{i}.f: frequency vector
port{i}.uf.tot/inc/ref: total, incident and reflected voltage
port{i}.if.tot/inc/ref: total, incident and reflected current
port{i}.ZL_ref: reference impedance used

port{i}.P_inc: incident power
port{i}.P_ref: reflected power
port{i}.P_acc: accepted power (incoming minus reflected, may be negative for passive ports)

Transmission line port properties

port{i}.beta: propagation constant
port{i}.ZL: characteristic line impedance
port{i}.ZL_ref: reference characteristic line impedance used

Examples

Create two waveguide ports with port 1 active:

start=[mesh.x(1)   mesh.y(1)   mesh.z(11)];
stop =[mesh.x(end) mesh.y(end) mesh.z(12)];  %% change from mesh.z(15)
[CSX, port{1}] = AddRectWaveGuidePort( CSX, 0, 1, start, stop, 'z', a*unit, b*unit, TE_mode, 1);
 
start=[mesh.x(1)   mesh.y(1)   mesh.z(end-13)];
stop =[mesh.x(end) mesh.y(end) mesh.z(end-14)];
[CSX, port{2}] = AddRectWaveGuidePort( CSX, 0, 2, start, stop, 'z', a*unit, b*unit, TE_mode);

After the FDTD simulation is complete, perform the following calculations to get the s-parameters. The frequency-domain incident and reflected voltages are used.

freq = linspace(f_start,f_stop,201);
port = calcPort(port, Sim_Path, freq);
 
s11 = port{1}.uf.ref./ port{1}.uf.inc;
s21 = port{2}.uf.ref./ port{1}.uf.inc;