Frequency Scanning Dual-Mode Asymmetric Dual-OAM-Wave Generation Base on Broadband PB Metasurface

High-Efficiency Multi-Channel Orbital Angular Momentum Multiplexing Enabled by the Angle-Dispersive Metasurface

Orbital angular momentum (OAM) multiplexing of electromagnetic (EM) waves is of great significance for high-speed wireless communication and remote sensing. To achieve high-efficiency OAM multiplexing for multi-channel incident EM waves, this paper presents a novel angle-dispersive meta-atom structure, which can introduce the required anti-symmetric phase dispersion as well as high transmission efficiency for OAM multiplexing. These meta-atoms are then arranged delicately to form an angle-dispersive metasurface working at the X band, which enables three-channel OAM multiplexing by converting highly directional transverse-magnetic (TM) waves incident from 0 and ±45° to coaxial OAM beams with l = 0 and ±2 modes, respectively. The simulation and experimental results reveal that the proposed metasurface can convert a higher proportion of energy to the required OAM modes compared to the conventional OAM multiplexing metasurfaces, which can significantly improve the coaxial transmission efficiency of multi-channel OAM multiplexing.

Polarization-Dependent Coding Metasurface with Switchable Transmission and RCS Reduction Bands

In this article, a coding metasurface is specifically designed to switch transmission and reflection functionalities between two different frequency bands for linearly polarized waves within wide incidence angles. A metasurface consists of four metallic patterns, where the middle two structures are inserted to ensure effective performance of transmission and reflection, while the top and bottom patterns are designed based on simultaneously controlling the reflection phase for both polarization states. It has been experimentally demonstrated that the proposed metasurface can convert a transmission band into a complete reflection band (meanwhile, the reflection band is translated into a complete transmission band) by changing the incident polarization state. Highly efficient transmission and reflection characteristics have been achieved from 21.1 to 24.5 GHz as well as from 33.3 to 38.3 GHz, whereas more than 10 dB radar cross-section (RCS) reduction has also been obtained for both TE and TM modes in their respective reflection bands. The performance of the proposed metasurface is well sustained up to 40° oblique incidence. This work will help to open a new aspect in metasurfaces to manipulate the electromagnetic waves at preferable frequency bands to achieve desirable functionalities.

Generation of multi-OAM beams using a compact dual-mode source and a 3D-printed Luneburg lens

In this paper, a Luneburg lens-based multi-beam orbital angular momentum (OAM) antenna is proposed to achieve the 2D beam scanning capability of dual-mode OAM beams. The proposed design is composed of nine compact dual-mode antennas as sources, and a 3D-printed Luneburg lens. The sources, i.e., octagonal patch antennas, can radiate both right-handed circularly polarized (RHCP) and left-handed circularly polarized (LHCP) OAM beams with mode number l = ±1 by switching the input ports. Then, the sources are put at multiple focal points of the Luneburg lens to generate the OAM beams in different directions, and the directivities of the OAM beams are also enhanced by the Luneburg lens. The proposed design can realize nine dual-mode OAM beams with ±30° beam scanning range in two orthogonal planes. It should be noted that the proposed design can be expanded to achieve a larger number of beams with a periodic extension of the source antennas, also a wider beam scanning range with a Luneburg lens of a larger radius.