Meta-lens-based circularly polarized fixed-beam antenna for high-gain wideband millimeter-wave applications

A planar metamaterial lens-based single-element circularly polarized (CP) antenna for millimeter wave (mm-wave) band applications is presented. The proposed antenna consists of a modified patch excited by a single-point-fed coaxial probe and two displaced layers of a novel meta-lens design. The modified structure allows for the simultaneous excitation of orthogonal components with equal magnitudes. To realize the gain enhancement of the proposed design, a novel meta-lens is designed based on meta-atoms of subwavelength size arranged in a disconnected cross-shape repeated pattern. To effectively focus the outgoing CP wave radiated by the antenna, the focal distance is meticulously optimized. Two layers of the same lens are used to enhance the antenna gain. Following a rigorous numerical analysis and optimization, the proposed design is fabricated and experimentally validated. The comparison of the results with the lens and without the lens illustrates that a 4 dB gain improvement is attained with the compact lens configuration. Furthermore, the antenna features a wide impedance bandwidth (S₁₁) from 24 GHz to 31 GHz and the axial ratio (AR) below 3 dB within the same operating band. The proposed design offers multiple advantages, including a simple geometrical configuration, light in weight, and ease of integration due to the planar lens structure. The proposed antenna is suitable for multiple modern communication systems, including short-range radar systems and other line-of-sight mm-wave applications requiring fixed-beam and high data rates.