Application of finite element methods to the modelling of field ingress to structures

The problem of the ingress of electromagnetic waves to structures is of central importance in the field of electromagnetic compatibility (EMC). British Aerospace (Dynamics) Limited have responsibility for EMC in all company products. Computational electromagnetic (CEM) techniques can be applied to both assessment of problems arising in existing systems, and to good initial EMC design of products. The CEM techniques that can be applied to the problem may be broadly classified on the basis of the method by which they are derived from Maxwell´s equations. Methods based on integral equations often using the method of moments are ideal for solving radiated field problems, particularly for conductors. They can be used to compute the incident field strength at the target equipment, and currents flowing on the outer surface. For problems of field ingress to structures, especially if the interior geometry is complex, differential methods are more suitable. Techniques such as finite difference and finite element methods can be employed. Both have different advantages and drawbacks. The application of the finite element (FE) method for modelling field ingress to a simple structure at VHF and UHF frequencies is described