Passive and active frequency selective surfaces with tunable band

Abstract

Frequency Selective Surface (FSS) is a two dimensional array of patches on a dielectric material or that of apertures within a metallic screen. FSS has filtering properties according to its structure. It has various applications in modern communication fields such as radome technology, aircraft, satellite communication, modern building, household etc [1-3]. FSS acts as a sub reflector and an absorber as per requirement of applications [4, 5]. Mainly two types of FSS i.e. aperture type FSS and patch type FSS are used for obtaining band pass and band stop frequency behavior. The frequency response of FSS generally depends on geometry of the unit cell, width and relative permittivity of the dielectric, angle of incidence (AOI) and polarization of the incidence wave etc [6]. Researchers have worked on passive FSS in consideration of band pass and band stop frequency response [7 10]. An FSS is expected with having stable response for higher angle of incidence and polarization of incident EM power on it. As for passive FSS, there has no option to change its frequency response after its fabrication, so the new trend of the research on FSS demands to make it reconfigurable by controlling the FSS parameter from outside. That s why recently the researchers are showing interests on making reconfigurable frequency selective surfaces (RFSS) to fulfill the demands. In recent time, the antenna characteristics like gain, directivity are being enriched with the help of FSS. To achieve the reconfigurable properties from the antenna, reconfigurable FSS can be used with it [11, 12]. Here in this thesis some passive and active FSSs with tunable frequency behavior have been designed, fabricated and discussed. newline