Low-Profile and Dual-Polarization Water-Based Frequency Selective Rasorber With Ultrawideband Absorption

Abstract

A low-profile and dual-polarization frequency selective rasorber (FSR) with an ultrawide absorption band is proposed. Based on the Mie resonance theory, water blocks with appropriate height are arranged as the lossy layer. The lossless layer is composed of a bandpass frequency-selective surface with Jerusalem-cross gaps. Utilizing the high loss of water, this rasorber can obtain ultrawideband absorption with a power absorptivity over 90% from 4.63 to 100 GHz, and the fractional bandwidth regarding the absorption band is over 182%. The insertion loss is 0.55 dB at 3 GHz under normal incidence and the thickness λ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">_m</i> (λ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">_m</i> being the free-space wavelength at the middle transmission frequency) is 0.077 λ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">_m</i> . The FSR also shows favorable stability of the frequency response over a relatively broad range of oblique incidence angles of 30° for dual-polarization. Compared with formal water-based FSR, this letter places emphasis on the novelty of elimination of the transition band and extended length of absorption band. Ultimately, a low-cost prototype of the presented design is fabricated, simulated, and measured to verify the feasibility.