Bi-Functional Antenna Coating for Cloaking and Directivity Enhancement Made of Isotropic Materials

Abstract

In this paper, using quasi-conformal mapping, a bi-functional coating layer is designed with the intention of both cloaking and directivity enhancement of an omnidirectional antenna. For TM external waves coming from a certain direction, the proposed coating layer conceals the inner objects. In addition to the cloaking performance, the designed coating layer plays the role of a metamaterial-based lens that dramatically enhances the directivity level of inner omnidirectional loopfamily antennas. To reach this goal, a proper coordinate transformation is elaborately utilized to transform the cylindrical wavefronts radiated from the antenna into semi-pure plane waves. With appropriate simplifications, the proposed coating layer turns into an isotropic meta-device, which is more suitable to be fabricated. To prove the feasibility of the implementation, an SRR-meander line meta-atom is designed to locally realize the required permittivity and permeability distribution of the bi-functional layer. Full-wave simulations are performed via COMSOL finite element solver to validate the cloaking effect and directivity enhancement of the proposed coating layer, at the same time.

Design of an omnidirectional camouflage device with anisotropic confocal elliptic geometry in thermal-electric field

“…Since the advent of transformation optics ( Pendry et al., 2006 ) and neutral inclusion ( Zhou and Hu, 2006 ; He and Wu, 2013 ), metamaterials have been in the promising field, which have been successfully demonstrated in various communities, such as optics ( Pendry et al., 2006 ), electromagnetic waves ( Schurig et al., 2006 ; Chen and Chan, 2007 ; Rahm et al., 2008 ; Han and Zhang, 2020 ; Berry and Rumpf, 2020 ; Fakheri et al., 2020 ; Asrafali et al., 2021 ), acoustics ( Zhang et al., 2011 ; Popa et al., 2011 ), elastic mechanics ( Brun et al., 2009 ; Farhat et al., 2009 ), direct current (DC) electric fields ( Yang et al., 2012 ; Jiang et al., 2012 ; Han et al., 2014a ; 2019 ; Feng and Ni, 2022a , 2022b ), and thermotics ( Fan et al., 2008 ; Narayana and Sato, 2012 ; Guenneau et al., 2012 ; Narayana et al., 2013 ; Han et al., 2014b , 2018 ; Li et al., 2015 , 2018 , 2019 , 2020 , 2021 , 2022 ; Yang et al., 2017 , 2021 ; Xu et al., 2020a ; Feng and Ni, 2022a , 2022b ). These metamaterials exhibit excellent performances in their certain conditions.…”