Real-Time Mode Switching and Beam Scanning of High-Gain OAM Waves Using a 1-Bit Reconfigurable Reflectarray Antenna

Shenheng Xu,Maokun Li,Ziyang Wang,Xiaotian Pan,Fan Yang

doi:10.3390/electronics9122181

Abstract

A reconfigurable electromagnetic surface has been studied to realize the adjustable orbital angular momentum (OAM) beams for real-time wireless communication and dynamic target detection in the future. OAM mode switching realized by many previous designs suffers from low gains without OAM beam scanning. In this article, a 1-bit reconfigurable reflectarray antenna is designed, fabricated, and tested for the real-time control of OAM mode switching and large-angle vortex beam scanning in three-dimensional space. The proposed reflectarray surface is composed of 1-bit electronically reconfigurable cells, and the size is 24 λ × 24 λ with 2304 units. The reconfigurable element is designed by using a radiation patch loading a PIN diode with effective control of two states, “ON” and “OFF”, for the demand of 180° phase difference. The reflectarray surface can be assigned to a code sequence of 0 or 1 by the Field-Programmable Gate Array (FPGA) in real time. Henceforth, the coding surface can dynamically control the generation of high-gain OAM beams, where only the optimized phase distributions on the surface need to be changed according to demand. To verify the concept, a large-scale reflectarray surface is fabricated and measured with an oblique feed at 15°. Different OAM-carrying phase distributions for different OAM beam states are calculated and tested. The test results show that the OAM mode switching between l = 1 and l = 2 is realized, and other variable modes such as l = 3 or l = 5 can also be achieved by modifying the phase encoding sequence. Furthermore, the direction of the vortex beams can be accurately controlled with gains over 20 dBi, and the large-angle vortex beam scanning is verified. Therefore, all results demonstrate that the proposed 1-bit reconfigurable reflectarray is efficient for the regulation and control of OAM-carrying beams for the demand of real-time dynamic wireless communications in the future.

Highlights

IntroductionEspecially orbital angular momentum (OAM), is currently a subject of great interest in academic research
Angular momentum, especially orbital angular momentum (OAM), is currently a subject of great interest in academic research
It is satisfactory for the scanning ability of an OAM beam in arbitrary azimuth planes

Summary

Introduction

Especially orbital angular momentum (OAM), is currently a subject of great interest in academic research. Electromagnetic (EM) waves can carry both linear momentum and angular momentum [1]. There are three different values of S corresponding to three different polarization states: when. OAM is determined by the azimuthal phase term exp(iθ) of the helical wave-front, in whichcan take any integer values as −2, −1 and +1, and θ is the azimuthal angle with a range of 0 to 2π. EM waves carrying OAM are called vortex waves and have aroused great interest iny scholars. They first came to the forefront in optical fields [3], and many novel applications [4,5,6,7,8,9,10]

Methods

Discussion

Conclusion