Modeling and Analysis of Wideband Multilayer Metasurface Antenna Array Using Characteristic-Mode Analysis

Conventional single-layer homogeneous impedance-sheet models (ISMs) for single-layer metasurface (MTS) antenna elements cannot handle multi-layer inhomogeneous MTS antenna arrays of local field inhomogeneity caused by loadings and feedings. In this communication, a hybrid ISM is proposed to overcome the above challenge with the aid of characteristic mode analysis (CMA). For proof of concept, a wideband multilayer MTS antenna array (MAA) is designed, where capacitive loading is further proposed to manipulate the frequency interval of desired modes for bandwidth improvement. With an element width of $0.29\lambda _{0}$ and an overall size of $0.70\lambda _{0} \times 0.70\lambda _{0} \times 0.08\lambda _{0}$ ( $\lambda _{0}$ is the wavelength in free space at 3.5 GHz), the proposed four-element MAA achieves a measured impedance bandwidth of 17.8% with $\vert S_{11}\vert < -10$ dB, a gain of 9.1–12 dBi, and a least front-to-back ratio of 25 dB. The proposed method extends the application of CMA from MTS antenna elements (MAEs) to MAAs, by enabling advanced mode manipulation techniques for simultaneous antenna miniaturization and bandwidth enhancement.