# Bi-Directional Fabry–Perot Cavity Antenna Based on Polarization-Dependent Transmit–Reflect Metasurface

## TL;DR

This paper introduces a new antenna design using metasurfaces that can control radiation in two directions independently.

## Contribution

A novel bi-directional Fabry–Perot cavity antenna is proposed using polarization-dependent transmit-reflect metasurfaces.

## Key findings

- The antenna design enables independent control of forward and backward radiation patterns.
- Two antennas demonstrated bi-directional single-beam and multibeam radiation with measured gains matching simulations.

## Abstract

Metasurfaces (MSs) have been an effective method for the manipulation of electromagnetic (EM) radiation. However, this research mainly focused on controlling single-directional radiation. In this paper, a Fabry–Perot cavity (FPC) antenna based on the MSs technique is proposed, which obtains a bi-directional radiation with independent control of the forward and backward radiation patterns. The antenna is located in an FPC with two MSs forming the top and bottom surfaces. The MSs can partially reflect the x-polarized incident wave, i.e., it is a partially reflective metasurface (PRMS). Meanwhile, it can transform a specific incident component from x-polarization into y-polarization with a transmittance around −9.2 dB. In addition, the phase of the x-polarized reflection and y-polarized transmission can be controlled independently. So, a bi-directional radiation, of which the forward and backward radiation can be independently controlled, is obtained by the FPC antenna by manipulating the transmission phase distribution of the two PRMSs. As validation, two bi-directional radiation FPC antennas are designed based on the proposed method. Antenna 1 achieved a bi-directional single-beam radiation, of which the forward and backward radiation radiate to 2° and 177° with a gain of 13.4 dBi and 12.3 dBi, respectively. Antenna 2 achieved a bi-directional multibeam radiation, which radiates dual beams forward and a single beam backward. The two beams forward fire to 37° and 322° with a gain of 9.53 dBi and 9.3 dBi, while the beam backward fires to 178° with a gain of 7.8 dBi. At last, the first antenna is fabricated and measured for experimental validation, achieving the coincident results as simulation. This research can be potentially applied in research on antennas, communication, and wireless sensors in several practical scenarios, such as multibeam electromagnetic radiation, multi-user communication, multi-target monitoring, and sensor–communication system integration.