Novel multiband Meta material Absorbers for Radar Stealth and EM Shielding

Abstract

Metasurfaces are artificially structured designs that provide extraordinary properties like negative refractive index, negative permittivity, and permeability that cannot be attained in naturally existing materials. Due to these extraordinary properties, these subwavelength designs can be extensively used for various applications and improve the efficiency of existing techniques like solar energy harvesting, EM shielding, beam splitting, and many more. Perfect absorbers of the electromagnetic waves (EM) can be obtained through classical techniques like the Faraday effect and bi-refringence, however, these techniques tend to increase the cost, design complexity, structural non-linearities, and design bulkiness. Metasurface-based perfect absorbers have gained significant attention from the research community over the last two decades and are still under exploration. Perfect absorption comes through the design of a left-handed metamaterial (LHM) which ultimately reduces the losses and provides negative permittivity and permeability. In this context several LHMs have been proposed by authors in the literature, however, most of the designs are less angularly stable up to, 45˚ and less polarization insensitive up to up to 60˚. In this thesis, we propose two metasurface designs first design comprises a tetra-band metasurface absorber for X, Ku, and K band applications designed on the idea of SRRs using FR-4 substrate. The proposed design provides four distinct absorption peaks with polarization-insensitive to 90˚ w angular stability of 70˚. The second design is a deca-band metamaterial absorber (MA) for C, X band, K, Ka, and Ku energy bands applications. The proposed structured MA design is polarization insensitive up to 90˚ and incidence angle insensitive up to 70˚ incidence angle owing to its Cyclic-4 (C4) symmetry design. The proposed design is based on the idea of split-ring resonators (SRRs) and implemented on the most cost-effective lossy FR4 substrate, multi-band absorption peaks have been achieved, each having absorptivity of 99%. Various parametric analyses/ modifications were done for optimization absorption. To understand the methodology governing absorption, surface current and electric field distributions have been examined. Further to this, performance was experimentally determined in free space, on a 20×30 size fabricated MA structure using the FR4 substrate. Under normal incidence, the practical results were found consistent with our simulated results. Our proposed design finds its applications in radar stealth materials, energy harvest, ting, and various other microwave applications. We claim that no previous planer, symmetric, single-layered, and passive-elements-based MA design has obtained such better accuracy of results.