Accurate modelling of an arbitrary placed thin wire in a coarse mesh

A description of offset thin wires in numerical electromagnetic simulations is presented without incurring the use of excessive computational storage and simulation times. The description of such fine features has been a major difficulty due to the simultaneous existence of both small and large dimensions which exert constraints when trying to achieve the required accuracy. Alternative approaches have been proposed which utilise the appropriate modifications and interfaces of coarse numerical meshes to allow the incorporation of a fine feature within a cell. These, however, are mainly based on obtaining approximations for the in-cell inductance and capacitance of the wire which are then used to describe gross electromagnetic behaviour through interfacing to the field model. A hybrid method approach is presented in which an exact analytical description of the electromagnetic fields is first obtained and then modelled numerically. The offset capability is possible through the use of summation theorems which extend the method originally developed for centred thin wires. The alternative formulation is accurate, robust and has the advantage of being non-numerical method specific, although the transmission line modelling (TLM) method is used here for illustration. Significantly, no empirical factors are used as in some presently used methods.