Multibeam Transmit-Reflect-Array Antenna with Switchable Bidirectional Radiation for IoT applications

Exploring cost-effective configurations to achieving wide beam scanning in full-spherical direction is an appealing topic for wireless communications and the Internet of Things (IoT), yet realizing it within the scope of conventional multiple feeding sources reflectarray/transmitarray is extremely challenging. This article proposes a bidirectional multibeam transmi-treflect-array (TRA) using a multi-layer passive metasurface, which enables beam steering switchable between hemispherical and full-spherical directions. First, we demonstrate a novel stacked unit cell composed of a circular ring-based structure and a polarization-sensitive patch structure. Based on the designed unit cell, two 24×24-element arrays are placed above and below the feed antenna, respectively. By simply rotating the angle of the metasurface layers and subsequently exciting the feed antennas, the designed TRA is able to scan beams along the +z, −z, or ±z direction. In both unidirectional and bidirectional states, forward and backward beam-scanning is achieved within an angular range of ±55°, with peak aperture efficiencies of 13.9% and 11.6%, respectively. The measured results of the prototype also demonstrate that the proposed TRA can steer in both unidirectional and bidirectional operating modes. The proposed method opens a new avenue for the design of cost-effective, easy-to-fabricate, and wide-angle beam-scanning multifunctional TRAs, making it particularly suitable for next-generation IoT communication systems that require wide angular coverage and full-space connectivity.