COMPARISON OF ANALYTIC, NUMERICAL AND APPROXIMATE MODELS FOR SHIELDING EFFECTIVENESS WITH MEASUREMENT

The authors present a comparison between different estimates of the sh ielding effectiveness (SE) of cavities containing apertures and predic tions made using a rigorous variational solution. Although the rigorou s solution is computationally intensive, the method can be used as a s tandard against which more practical approximations, numerical methods and laboratory measurements can be compared. SE predictions from thre e methods are compared to the rigorous solution. These are: electromag netic modelling using the transmission modelling (TLM) method, experim ental measurements in a screened room, and an approximate solution bas ed on the interaction of the lowest order waveguide mode and the apert ure field. These comparisons of shielding effectiveness evaluations we re made for a rectangular cavity with a range of aperture sizes and fo r frequencies in the range 200 MHz to 1.0 GHz. The results show that t he measurements compare well with the rigorous solution, time domain s imulators have a relatively long computation time and may still have n oticeable discrepancies while the approximate solutions are computatio nally very efficient but may be significantly in error in particular f or-observation points close to the aperture.