Design of an Ultrabroadband Circularly Polarized 3-D-Printed Millimeter-Wave Lens Antenna

This article presents the design and development of a wideband, circularly polarized lens antenna with high gain for millimeter-wave (MMW) applications. The antenna is composed of dielectric units with varying lengths, engineered to facilitate the conversion of linearly polarized electromagnetic waves into circularly polarized waves. A rigorous theoretical analysis of these dielectric units reveals their ability to achieve a 90 degrees phase difference between the two orthogonal electrical components within a substantial bandwidth. Subsequent empirical measurements corroborate these findings, affirming the antenna's capacity to deliver a prominently wide axial ratio (AR) bandwidth. To achieve circular polarization (CP) and enhancement on gain, the design culminates in the construction of a convex lens, formed using these dielectric units. The proposed antenna demonstrates a remarkable impedance bandwidth spanning from 21.7 to 67 GHz, where the voltage standing wave ratio (VSWR) remains consistently below 2. In addition, the AR bandwidth is over 115.9% from 18 to 67 GHz, ensuring AR below 3 dB. The measured peak gain of the antenna registers at 20.6 dBic. This study extensively explores the intricate relationship between the relative dielectric constant and the dielectric unit. This exploration has yielded a novel and cost-effective solution for achieving ultra broadband CP with high gain, specifically tailored for MMW applications.