Resonantly inverted microwave transmissivity threshold of metal grids

Open Access journal© Crown copyright 2009. This work is part funded by the Ministry of Defence and is published with the permission of the Defence Science and Technology Laboratory on behalf of the Controller of HMSO.The microwave transmission of arrays of square patches, each rotated by 45 from the axes of the square lattice on which they are positioned, has been experimentally studied as a function of metal occupancy. At low frequencies, the microwave transmissivity drops on passing through the connectivity threshold (50 per cent occupancy), as one would expect. However, quite counter-intuitively, near the onset of diffraction, resonant phenomena induce a complete reversal in the sense of this transmissivity switch, i.e. the transmission is seen to increase as the metal occupancy is increased.DstlEngineering and Physical Sciences Research Council (EPSRC