Miniaturised periodic structures
FSS design relies on the repeating geometry, or unit cell, to be resonant in some way. This leads to unit cells that are typically between a quarter and half a wavelength across. In order to achieve small unit cell sizes designers often use convoluted geometries. In this project a different approach has been adopted using lumped circuit elements to provide the resonant effects with any metallic structure allowing a path for the current only, which results in a bandpass FSS. This method is a significant advancement in FSS design as it allows the possibility of manufacturing FSS to frequencies as low as 100MHz with a reasonable unit cell size and bandwidth. Using lumped components we have measured FSS with cell sizes down to λ/50 and elements with periods half this size are possible.
This study has been extended to active elements where tuning is possible and to metamaterials where they hev been demonstrated as high impedance surfaces with compact antennas.