Design of Compact, Broadband Polarization Insensitive Dual-Circular Circuit Analog Absorber for X, Ku and Ka-Band Applications

This work presents a broadband polarization-insensitive circuit analog absorber from X to Ka-band applications. It consists of two different circular rings loaded with lumped resistors on two sides of the TLY-5 substrate, and the whole structure is terminated with the perfect electric conductor (PEC) through an air-spacer. It demonstrates 90% absorption bandwidth over 18.44 GHz with 116.8% fractional bandwidth. The proposed metasurface is polarization insensitive due to the four-fold (circular) symmetry architecture, and it shows good angular stability for both TE and TM oblique incidences within the acceptable limit. The transmission line based equivalent circuit model shows near agreement with full-wave analysis. The novelty of this design lies in the usage of both sides of the substrate made this structure compact with a periodicity of 0.207λ and thickness 0.09λ, where λ is the free-space wavelength corresponding to the lowest frequency of the absorption band. Results from electromagnetic simulator prove the ability of proposed absorber in applications like electromagnetic shielding and energy harvesting.