Design of a Narrowband and a Wideband Switchable Absorber/Reflector Using an Active Frequency Selective Surface With Embedded Biasing Network

This paper presents the design of an active frequency selective surface (AFSS)-based switchable absorber/reflector with polarization-insensitive characteristics. Initially, a narrowband absorber/reflector is realized. Later, lumped resistors are loaded in the same FSS geometry to obtain a switchable absorber/reflector for broadband frequencies. Both the designs consist of an AFSS layer printed at the uppermost surface of one dielectric substrate and a metal ground at the bottom of another dielectric substrate. The switchability between the absorption and reflection state is realized by regulating the PIN diode's OFF/ON states, respectively, employed at the top AFSS layer. The simulated results show that the proposed narrowband structure resonates at 3.24 GHz with a reflection coefficient lower than -10 dB in absorber mode. It acts as a perfect reflector at the same frequency when switched to the reflector mode. In addition, the same structure acts as an absorber for broadband frequencies ranging from 4.89 GHz to 10.28 GHz with less than -10 dB reflection coefficients and a reflector from 4.89-7.95 GHz with a peak return loss of less than 3 dB after proper loading of lumped resistors and air-spacer. Furthermore, the biasing networks for the PIN diodes used in both the structures are embedded within the geometry, which eliminates the requirement of additional bias lines.