Prediction of shielding performance via the transmission line matrix method (TLM)

The advent of powerful personal computers with fast processors and large amounts of RAM has enabled the direct numerical electromagnetic assessment of the screening properties of novel materials and technologies to be undertaken on a desktop PC. Such an assessment was previously the domain of either expensive workstations or reliant on costly measurements. This paper describes one such numerical technique, the transmission line matrix method, (TLM) and its application to the prediction of the screening properties of single or multi layer materials, when used as part of a complex structure. The basic principles behind TLM are discussed prior to the application of the technique to the prediction of screening performance. An idealised analytic case is assessed prior to comparison with screening performance measurements of a test material panel in a screened room. The method is then compared with isolation measurements taken from an antenna ground plane comprised of a multi layer composite material