The shielding effectiveness of a planar sample of material is an important metric used to determine the suitability of the material to form a closed electromagnetic shield. While the shielding provide by a metal enclosure is invariably determined by structural features, such as joints and apertures, metalised plastics and composite materials typically have much lower shielding effectiveness and therefore must be properly characterised.
Current standard measurement techniques require a good conducting contact between the sample under test and the test fixture, which can be difficult to achieve reliably for samples with a dielectric outer layer, such as carbon-fibre composites. This project has developed a novel compact measurement system that overcomes the edge contact problems by eliminating its requirement. This is achieved by absorbing the edge-diffracted energy in an assembly fabricated from proprietary carbon loaded polyurethane foam. The results from the new system correlate very well with existing methods and are significantly faster to obtain and much more repeatable.
See our paper for more information: Marvin, A. C.; Dawson, L.; Flintoft, I. D. & Dawson, J. F. , "A Method for the Measurement of Shielding Effectiveness of Planar Samples Requiring No Sample Edge Preparation or Contact" , IEEE Transactions on Electromagnetic Compatibility, vol. 51, no. 2 , 255-262 , May 2009.
We are currently taking part in development of the IEEE Standards association P2715 - Guide for the Characterization of the Shielding Effectiveness of Planar Materials which will incorporate this method.
- EPSRC GR/S71552/01 as part of the FLAVIIR programme