Metamaterial-Based Angular Stable Polarization-Insensitive Hepta-Band Microwave Absorber With Salient Features for RCS Reduction and Antenna Radiation Improvement
Shyam Sundar Pati, Swaroop Sahoo
Abstract
This article focuses on the design and characterization of a novel ultrathin polarization-insensitive metamaterial-based microwave absorber, engineered to exhibit resonant behavior across seven consecutive frequencies in <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</i> -, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</i> -, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ku</i> -, and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K</i> -bands with an average absorption rate of 97.73%. The absorber is fabricated on an FR-4 substrate with a periodicity of 0.22 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda _{0}$</tex-math></inline-formula> and a thickness of 0.0277 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda _{0}$</tex-math></inline-formula> , where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda _{0}$</tex-math></inline-formula> is the free space wavelength corresponding to the lowest resonance frequency. The proposed metasurface supercell is composed of four unit cells, each comprising three diagonally slotted nonuniform square resonators with complementary pairs of T-shaped metallic patches and centrally positioned sharp-pointed resonators. The article further illustrates a transmission-line-based equivalent circuit model of the proposed absorber in a circuit simulator, which has good agreement with the full-wave simulation. This absorber has the highest angular stability (i.e., up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text {70}^\circ$</tex-math></inline-formula> transverse magnetic and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$>$</tex-math></inline-formula> 60° transverse electric) with near-unity hepta-band absorption in the microwave regime. In addition, the absorber is evaluated for its capability to enhance the in-band front-to-back ratio (by 18.2 dB) and the minimization of bistatic radar cross section (by 27.1 dBsm) of a monopole antenna at normal incidence. The novelty of this design is its operation across seven consecutive frequency bands, exceptional angular stability, polarization insensitivity, and the individual controllability of each resonance.