The modelling of nonlinear effects using time domain integral equations

The authors review techniques for the mathematical modelling of electromagnetic coupling to circuit boards and systems and their experimental validation on a time domain measurement facility based at the Royal Signals and Radar Establishment (RSRE) Pershore. Two key features of this work are the very wide bandwidth signals considered (signals with bandwidths from about 100 MHz up to 2 or 3 GHz) and the presence of nonlinear loads such as transistors and diodes. The modelling problem is handled by combining two areas of work; namely time domain integral equations and nonlinear systems theory. The former combines fast computation of nonlinear problems with a clear physical interpretation of cause and effect. The latter permits analysis of nonlinear coupling problems and complements the direct numerical approach by identifying generic properties of the circuit and predicting thresholds for complex behaviour