A wideband coding reflective metasurface with multiple functionalities

Abstract

A controllable wideband multifunctional reflective metasurface is presented. First of all, a polarization-rotating unit cell is proposed by combing micro-electromechanical system (MEMS) technology with reflective metasurface design. The proposed unit cell is characterized by wideband, low loss and controllable properties. Each unit cell is integrated with two MEMS switches. When the two switches operate in different states, the unit cell shows different responses to plane wave incidence, and the corresponding working states can be denoted by 0 or 1. It is worth noting that a 180 degree reflection phase difference is generated for the two working states. Then, the proposed unit cell is periodically arranged to construct a metasurface. Based on different coding matrixes, multiple functionalities can be obtained by using the proposed metasurface. When all the unit cells are controlled to operate in on- or off-state, polarization-rotating function is obtained. Besides, the agility scattering field performance is also presented by using chessboard and random codings. A series of equations is derived to reveal the relationship between reflection coefficient of the unit cell and radar cross section (RCS) reduction of the chessboard reflective surface, which is also verified by full-wave simulations. Finally, four prototypes consisting of 576-cells, which correspond to the all 0, all 1, chessboard and random coding, are fabricated and measured. The measured results demonstrate that the proposed reflective metasurface shows polarization-rotating performance in a frequency range of 8.9-13.2 GHz when all unit cells operate in 0 or 1 state. The measured results of the chessboard and random coding metasurface manifest remarkable RCS reduction compared with the same size metal plane. Good agreement between simulations and measurements is obtained. Owing to the ability to control polarization and beam shape of the reflected wave dynamically, the proposed reflective metasurface has potential applications in the field of intelligent stealth.