Miniaturized Design of Dual Transmission Frequency Selective Rasorber With Wide Angular Stability

In this paper, a miniaturized design of dual transmission frequency selective rasorber (FSR) with absorption-transmission-absorption-transmission (A-T-A-T) feature is proposed. Initially, low-frequency resonators are incorporated on the square ring shaped lossy resistive layer for expanding the broad absorption towards the lower spectrum of frequency. Then the dual bandpass frequency selective surface (FSS) with transmission bands lying within the absorption spectrum is integrated with the resistive layer. Further, a cross-loop resonator is integrated inside the square ring of the resistive layer due to which a dual transmission pole is achieved through the resistive layer aligning with the dual operating frequencies of bandpass FSS. The proposed structure exhibits two broad absorption bands ranging from 3.7–10.5 GHz (95.7%) and 12.6–14.6 GHz (14.70%). The two transmission bands are at 10.7 GHz (8.62%) and 16.0 GHz (8.75%) with minimum insertion loss of 1.0 dB and 0.7 dB, respectively. The proposed FSR is polarization-insensitive and a compact design with an electrical size of 0.015λ2 and a thickness of 0.08λ along with a wide angular stability up to 50o incidence. The working process of the proposed design is illustrated by studying an equivalent circuit model (ECM). Further, a prototype of 23 x 23 array is fabricated and the measurements are carried out for both normal and oblique incidences. The close resemblance observed between the measured and simulated response experimentally validates the proposed FSR design.