A low-profile Alford antenna for OAM beam generation with enhanced mode purity

This paper presents the design and experimental validation of a compact, planar Alford antenna capable of generating orbital angular momentum (OAM) beams with enhanced mode purity. The antenna consists of three arc-shaped radiating elements, each fed with equal amplitude and a 120∘ phase shift, forming the phase structure required for OAM mode l = + 1 generation. This controlled phase progression enables the creation of a helical wavefront. Numerical simulations and experimental measurements confirm good impedance matching, with a measured S 11 of −30 dB at 5 GHz. The radiation pattern features a central null with minimal side lobes, consistent with the characteristics of OAM beams. The antenna achieves approximately 90% mode purity, indicating effective suppression of unwanted modes and reduced crosstalk. The peak gain was measured to be 1.8 dBi. The compact structure, stable radiation characteristics, and high mode purity make this antenna suitable for 6G wireless communication systems, and vehicular communication environments.