5.2.2   Point probe

The point port available in QuickWave will serve as a source or a probe depending whether Source or Probe option will be chosen. Point probe (lumped probe, lumped load) is equivalent to point source (lumped source) with excitation equal zero. For point port checked as Probe, zero exciting amplitude is assumed and the lumped port acts as a lumped resistor. The point probe can serve as the elements probing field in free space or resistive probes between two metal parts.

Similarly as in the case of point source, for lumped probe port the user must define:

• a field component to which the port is connected,

• internal resistance of the port (a value from the 0..+INF range, or self adjusted for good energy coupling between the source and the neighbouring FDTD mesh, in which case an appropriate value of resistance is calculated by the software).

The verification of the position and parameters (resistance and field component) of the lumped probe can be made during the electromagnetic simulation using Effective FDTD mesh grid.

When used as a resistive probe between two metal parts the point probe should be placed in a one-cell gap between two metal elements. If the gap (for example between two metal plates) is larger than one cell, the probe should be connected to the metal elements with additional wire elements.

It is also possible to place a point probe directly on the wire. This feature is convenient since changes in the meshing will not need to be associated with changing the size of the gap, to keep it equal to one FDTD cell. The lumped probe port placed on the wire will “cut” a gap in the wire and work directly in that gap.

The Point probe port can take part in the following post-processing algorithms:

• FD-Probing, which stands for frequency domain probing, and means that Fourier transforms of terminal voltage across the resistor and current through the resistor will be calculated,

• S-Parameters post-processing as port No., which includes the lumped port in the S‑parameters extraction system together with Transmission line ports (template port, modal port).

It is worth noting that if a point probe is included in the S-Parameters post-processing, its resistance R serves as a reference resistance for separating the incident and reflected waves. However, if R=+INF or R=0, then 50 Ω is taken as a reference.

Note that FD-Probing post-processing also produces reflection loss as one of its results. It is denoted by a symbol S_number, where “number” is the value of R (or 50, if R=+INF or R=0, in which case 50 Ω is taken as a reference).