Changes

=== Probe Sources ===

Another way of exciting a planar structure is by placing a gap on the path of a vertical current on a PEC via. This represents a filament source, which is used to model coaxial probe excitation. A probe source can be placed only on a PEC via object. Most planar transmission lines are fed using SMA connectors. The outer conductor of the coaxial line is connected to the ground and its inner conductor is extended across the substrate layer and connected to a metallic line. EM.Cube's [[Planar Module]] models a coaxial probe as an infinitesimal gap discontinuity placed across a thin via, representing an ideal voltage source in series with a lumped impedance. When the impedance is zero, the gap acts like an ideal lumped source and creates a uniform electric field across the via. The source pumps vertical electric current into the probe. If the voltage source is shorted (having a zero amplitude), then the gap acts like a shunt lumped element across the via.

Unlike gap sources, whose offset parameter determines their exact location on their host line, the offset parameter of a probe source is not relevant except for long host vias. In the case of a short via that is discretized using a single prismatic element across its host substrate layer, the probe gap is always placed at the middle of its height. Longer vias may have a mesh that consists of two or more stacked prismatic elements. In this case, the probe source's offset determines which prismatic element will host the probe gap discontinuity at its middle.

=== Defining Source Arrays ===