Abstract
This paper presents a review of metasurface-based antennas conducted at the Microwave Communication Laboratory (MCL) of Ajou University in the Republic of Korea. In this paper, profile miniaturization, bandwidth enhancement, multiband operation, and radiation pattern control of metasurface-based antennas are considered. The paper first presents metasurface-based antennas implemented by placing various radiators on top of the metasurface. It then presents antennas implemented by placing the radiators below the metasurface with and without the ground plane. Metasurface-based antennas are not only able to achieve high efficiency with a low profile but they are also able to generate extra resonances from the metasurface structures, which significantly enhances the overall performance of the antennas. These additional resonances were utilized in multiband and/or wideband operations. In addition, the design of a planar compact wide-gain-bandwidth metasurface-based antenna and its radiation characteristics are presented at a terahertz (THz) frequency range. The THz antennas were designed with metasurfaces and a planar leaky-wave feeding structure. Finally, the outlook on future research at the MCL for antenna-related work and their applications using metasurfaces is provided.
Highlights
The electromagnetic properties of materials can be classified into four types: double positive (DPS), epsilon negative (ENG), mu negative (MNG), and double negative (DNG) À depending on the values of permittivity and permeability [1]
A compact wideband circularly polarized (CP) antenna array, which is a set of 2 Â 2 metasurface-based, CP patch antennas fed by a sequential-phase (SP) network, was investigated in reference [54]
It was shown that the antenna performed as a Fabry–Pérot cavity antenna at the high thickness substrate range, exhibiting high gain and directivity with narrow gain bandwidths, while in the low thickness substrate range, it performed as a metasurface antenna and showed wide-gain-bandwidth characteristics [68]
Summary
The electromagnetic properties of materials can be classified into four types: double positive (DPS), epsilon negative (ENG), mu negative (MNG), and double negative (DNG) À depending on the values of permittivity and permeability [1]. In 1968, Veselago published the first study on the properties of materials with negative permittivity and permeability simultaneously [3] These materials are called left-handed materials (LHM) because they have the characteristic of electromagnetic waves that the group velocity and the phase velocity are reversed and propagate in the opposite direction. The metasurface structure is realized in two dimensions and requires a small physical space; this is in contrast to general metamaterials, which have a three-dimensional structure These properties open the door to the development of new theory and applications [12], and many excellent review articles on the fundamentals and applications of metasurfaces can be found [13,14,15,16,17,18,19,20,21,22]. Various metasurface-based low-profile antennas that perform much better than conventional antennas were designed and investigated
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