Active Metamaterial Frequency Selective Surface (FSS) Based Tunable Radar Absorbing Structure (RAS)

Abstract

This book chapter presents a comprehensive review of various active metamaterial frequency selective surface (FSS)-based switchable and tunable radar absorbing structures (RASs). Passive absorbing structures offer limited post-fabrication flexibility and cannot be used for any multifunctional characteristic. In contrast, an active RAS can be exploited for manifold applications by regulating the external control. Further, fabrication and installation error can be compensated by using a tunable structure, unlike a passive design. Therefore, active FSS-based RASs are being widely investigated since the last decade. The reported active RASs can be broadly classified into three categories based on their realization techniques, such as mechanically actuation, magnetically regulation, and electronically control. Among them, electronically reconfigurable absorber designs are often preferred due to their high switching speed, wideband tuning, low cost, and compact size. Electronically regulated active components, viz. varactors, p-i-n diodes are mounted across the gaps etched in the FSS designs and their variable characteristics are precisely regulated by applying required biasing voltages. Based on use of these active components, different types of electronically actuated structures have been realized, such as switchable absorber/reflector, switchable absorber, and tunable absorber, spread across different frequency regime. This book chapter summarizes detailed information about the working principle, design topology, biasing mechanism, and experimental procedure of those developed FSS-based switchable and tunable RAS designs, focusing across microwave frequency range.