A mathematical model of concentrically loaded coaxial structures and its EMC applications

Computer programs have been developed at Bristol University for modelling boxed microstrip lines. Modules from these programs have been modified and extended to produce a program which can model any uniform, symmetric, coaxial system that has multiple concentric dielectrics. The program has also been extended to model losses through the use of complex permeability and permittivity values for the dielectrics. The program can be used to find the distribution of fields and hence energy in the coaxial environment. It is a very useful research and development tool-for example it is hoped that it can be used to analyze the feasibility of making an absorbing device to reduce the common mode noise levels on cables coming out of equipment (a major source of electromagnetic noise)