A GENERAL APPROACH FOR EMBEDDING LOCAL FIELD SOLUTIONS INTO TLM SIMULATIONS

Transmission Line Modelling (TLM) method is an well-established technique for simulating a wide variety of phenomena in electromagnetics[1]. As with any numerical method, the complexity of the problem that can be practically dealt with is determined by the availability of computational resources. A recurrent problem when using simulations to assess complex systems for electromagnetic compatibility (EMC) is the treatment of fine features separated, or surrounded by, a significant volume of empty space. Examples include thin wires and strips, narrow apertures and notches and slots at panel joints. Directly employing a very fine mesh to map the fine feature for the whole system will inevitably result in immense computational requirements which usually far exceed the capabilities of commonly available computer systems. Consequently, significant effort has been made over the years to deal with this problem, employing techniques such as multi-gridding[2], the use of unstructured meshes[3,4] and special fine feature nodes[5,6]. In this work a general technique is presented which builds on the use of special fine feature nodes within an otherwise uniform mesh. The approach proceeds by identifying a set of local analytical solutions for the fields in the vicinity of the fine features and these are interfaced with the fields available from the adjacent TLM nodes in a physically consistent manner. This approach yields an algorithm that is both explicitly stable and conservative as well as onl