A Circular-Polarized Vortex Beams Generation With Orbital Angular Momentum Based on a Leaky-Wave Antenna

A circular-polarized vortex beams generation with orbital angular momentum (OAM) based on a leaky-wave antenna (LWA) with substrate integrated waveguide is proposed in this letter. The loop LWA is designed to transmit vortex beams with various OAM modes controlled by the operating frequency. With the frequency change from 11 to 12 GHz, the OAM modes change accordingly. The OAM antenna realizes a low profile by use of the leaky-wave structure. Meanwhile, two transverse slots and one longitudinal slot are utilized to realize circular polarization to improve the mode purity of OAM. Notably, the measured results demonstrate that the gain reaches 7.18 dBi with vortex beams generated by four OAM modes (+2, +1, 0, −1). The axial ratio is good from 11 to 12 GHz, indicating that circular polarization is achieved.