Broadband polarization insensitive wide angular stable dual‐split square ring circuit analog absorber for radar cross section and electromagnetic interference shielding applications

Abstract

This work presents a simple broadband polarization-insensitive circuit analog absorber (CAA) with wide angular stability. It comprises of dual-cut square loop resonator loaded with eight lumped resistors as top patch and an inductive grid. The normal incidence reveals a 90% absorption bandwidth of 20.51 GHz (110% fractional bandwidth) covering the entire X to K-band with a minimum flat absorption rate of 92.82%. Equivalent circuit analysis is carried out, and responses are validated with full-wave simulations. The proposed prototype is insensitive to different polarization angles under normal incidence and stable with 45 in transverse electric (TE) and transverse magnetic (TM) incidences. The design's novelty lies in using two resistors on each side of the square ring, which improves the absorptivity performance. The inductive grid enhances TM mode's angular stability. The proposed absorber is fabricated, and the measured results are in good agreement. In-band bistatic radar cross section reduction of 12.97 dBsm is obtained with the absorber using an X-band antenna. The temperature profile of the prototype is illustrated using near-in-lock infrared thermography, and 2.1 F of temperature rise is noticed in the absorption band. The proposed structure possesses a low profile, broad bandwidth, polarization insensitivity, and wide angular stability to the best of the author's knowledge.absorber, broadband, IR imaging, lumped resistor, radar cross section | INTRODUCTIONElectromagnetic (EM) wave absorption has gained significance in applications like RF energy harvesting, photodetectors, micro-bolometers, biological image sensing, EM shielding, and radar cross section (RCS) reduction in stealth technology. 1 Salisbury screen was the first traditional microwave absorber, 2 consisting of a flat resistive sheet coated on a λ g =4 ground dielectric spacer. Dependence of effective impedance on substrate thickness confines Salisbury screen to a narrow band. Jaumann absorber, 3 where stacking of different resistive on λ g =4 spacers was proposed for uniform absorption over a wideband. However, the physical size of the Jaumann screen is limiting its usage. Earlier, the EM wave absorption were also focused on pyramidal foam absorbers, carbon