Susceptibility modeling analysis of parasitics in unshielded products with long wires attached

Numerical modeling of EMI/EMC problems has become more popular over the past few years, due to the commercial availability of modeling software and the drive to reduce product development cycle times. This paper introduces a technique for using applying numeric modeling to immunity problems. Modeling can be used to simulate the effects of radiated immunity as well as radiated emissions. Second, models eliminate the 'try-it-and-see' approach to immunity problems of guessing at the source of an immunity mechanism and experimentally trying many possible solutions until an effective remedy is found. With modeling, solutions are not considered until the central mechanism of the problem is adequately understood. Once an adequate model is developed inspection of the RF current flows at the frequencies of primary interest is particularly instructive in this regard. Then using well known electromagnetic effects (such as reciprocity), modeling can be made much simpler, and effectively extend the usefulness of existing modeling tools.