The calculation of current on thin wires using a differential technique

The calculation of induced current on wires is important if equipment immunity to electromagnetic hazards is to be assessed by numerical modelling. Differential techniques in the time domain are attractive for dealing with EMC calculations over a wide frequency range that involve complex geometries. This paper discusses the "in-cell" inductance and capacitance thin wire model currently used in the transmission line matrix (TLM) and finite difference time domain (FDTD) techniques. The performance of these models is assessed using some simple examples and comparison with method of moments calculations. It is concluded that care needs to be taken when using these models and the accuracy that can be obtained depends upon the proximity of the wires to conducting surfaces and other conductors.