A Bessel Constraint Method for OAM Waves in Short-Range Wireless Communication

Orbital angular momentum (OAM) multiplexing techniques have great potential in high-speed and high-capacity short-range wireless communication. However, the divergence angle of OAM waves changes with mode and frequency, increasing the receiver complexity. This paper proposes a Bessel constraint method for generating OAM waves with the same divergence angle. Specifically, this paper first analyzes the factors affecting the divergence angle by combining two uniform circular arrays (UCAs) as uniform concentric circular arrays (UCCAs). Then, this paper defines the intensity proportion between the two UCAs to analyze constraint conditions. Additionally, two algorithms are designed to generate multimode OAM waves with equal divergence angles, considering scenarios with and without multiple frequency bands. Simulation results demonstrate the effectiveness of these algorithms in generating OAM waves with matching maximum strength ring radii, enabling the receiver to fully receive OAM waves of multiple modes and frequencies with just one UCA. Furthermore, the proposed approach facilitates the adjustment of OAM waves with different modes and frequencies by flexibly modifying the intensity proportion without necessitating alterations to the antenna radius.