Multi-scale modelling in time-domain electromagnetics

The paper reviews the techniques used to describe efficiently in time-domain electromagnetics the presence of fine physical features in an otherwise coarse numerical mesh. This is a major area of concern in electromagnetic modelling and simulation as it affects crucially modelling capabilities in dealing with complex practical configurations. Two broad classes of modelling methods are identified, those where the basic approach is to distort and/or refine the numerical mesh, or, interface the mesh to local solutions. A typical example of a technique in the former category is multi-gridding and in the latter mesh-to-wire interfaces. The emphasis of the paper is to describe the essence of the different approaches, their strengths and weaknesses and to identify areas of further work.