Planar CP ME-Dipole Antenna With Surface-Wave Compensation for Symmetric Axial-Ratio Beamwidth in mm-Wave Frontend Systems

A planar embedded magneto-electric (ME) circularly polarized (CP) dipole antenna achieving symmetrical axial-ratio (AR) beamwidth is presented for mm-wave Satcom applications. Although AR beamwidth is a critical parameter governing polarization stability over wide angular coverage, it is often overlooked in favor of impedance and AR bandwidth. While maintaining symmetric AR beamwdith along two principal cutplanes is preferred for certain applications, such issues have rarely been discussed. In conventional air-cavity-based ME dipoles, the absence of dielectric loading results in symmetrical AR beamwidth across both principal planes due to negligible surface-wave (SW) excitation, thereby preserving a stable quadrature condition. In contrast, planar embedded ME dipoles, which are more suitable for compact front-end integration, introduce significant SW modes at mm-wave frequencies. These SWs capture a portion of the radiated power and coherently re-couple to the radiating currents, resulting in amplitude and phase imbalance between orthogonal field components, thereby degrading AR beamwidth symmetry across the principal planes. To address this limitation, the dipole patches are intentionally placed asymmetrically to disrupt the coherent buildup of surface waves, effectively modifying their coupling with the radiating modes. This approach restores symmetric CP radiation without the need for additional structures or multilayer complexity. Based on this principle, two antenna configurations are developed to realize left-hand and right-hand circular polarization, respectively. Both designs demonstrate symmetrical AR beamwidth, stable CP performance, and a fully planar PCB-compatible structure.