Reconfigurable Bandpass Frequency-Selective Rasorber With Perfect Elliptic Filtering Response

Reconfigurable frequency-selective rasorbers (FSRs) with in-band shielding capabilities have attracted extensive research interest over recent decades. However, the development of dual-polarized reconfigurable FSRs that merge high-order wide passbands with ideal elliptical filtering responses remains a significant challenge. Hence, this article introduces an innovative FSR with wideband transmission and perfect elliptical filtering. The FSR consists of a three-layer configuration: two impedance layers and a switchable frequency-selective surface (FSS). High-order slot resonators positioned at the center of the FSS induce multipath couplings, thus achieving elliptical filtering responses. Bilateral capacitive patches integrated with these resonators form an inductively coupled configuration that facilitates a wide passband. Moreover, stack-ing switchable and nonswitchable impedance layers produces stable wideband low reflection. Note that implementing a polarization-isolation bias network allows the device to realize polarization-independent switching between rasorbing and absorbing states. Finally, a prototype is manufactured and measured to validate the simulations. Comparison analysis with existing designs confirms that the proposed FSR delivers superior performance, including the lowest insertion loss (IL), the widest 1-and 3-dB passbands, considerable absorption bandwidth, improved transmission angle stability up to 45
$^{\circ}$
, and an almost ideal elliptical filtering response (shape factor (SF) is 1.01). To our knowledge, this work represents the state-of-the-art reconfigurable FSR design to date.