All Metal Spherical Path-Length Lens Antenna For 360° Beam Steering Applications

This paper proposes an all-metal spherical lens capable of 360° beam steering through feed switching. The proposed lens consists of multiple circular metal plates stacked to form a spherical structure, with uniform air gaps between adjacent plates, effectively creating air-filled parallel-plate waveguides (PPWs). When the feed is incident on the lens, its propagation path is confined by these PPWs. By adjusting the relative angle between the feed and the parallel-plate waveguides within the lens, the relative transmission path error of electromagnetic waves passing through the lens can be controlled. Through theoretical derivation, the relationship between focal length, lens diameter, relative angle, and path error has been established. Once the focal-to-diameter ratio is determined, the relative angle required to achieve minimum path error can be calculated, thereby enabling high-gain radiation beams. The spherical structure of the lens provides rotational symmetry, allowing for 360° beam steering when multiple feeds are implemented. To validate the proposed lens antenna principle, a spherical lens antenna with a focal-to-diameter ratio of 0.5 was fabricated and tested. Experimental results demonstrate that the proposed lens structure achieves a peak gain ranging from 16 to 22.1 dBi within the frequency band of 24-40 GHz. The isolation between ports exceeds 27 dB, and stable beam performance is maintained throughout the entire Ka-band. The proposed lens structure realizes an allmetal spherical lens that offers several advantages, including simplified fabrication, low cost, and broadband beam steering capability, making it particularly suitable for wireless communication applications.