Millimeter-Wave Dual-Polarized Luneburg Lens Antenna Based on Hybrid Dual-Mode Unit Cell

This communication introduces a millimeter-wave (MMW) dual-polarized Luneburg lens antenna. The key innovation is a compact three-layer hybrid waveguide that achieves two decoupled orthogonal modes: a metasurface-based TE mode for horizontal polarization (H-pol.) and a pin-loaded parallel-plate TM mode for vertical polarization (V-pol.). Glide-symmetric circular patches and metallic pins enable independent, wide-range tuning of the respective refractive indices, overcoming the mutual coupling problem that limits previous dual-polarized 2-D Luneburg lenses. A modified Luneburg distribution is further introduced to improve the dispersion linearity of the TM mode, ensuring a wider dual-polarized operating bandwidth. A 64 mm-diameter prototype, fabricated by metal 3-D printing with a single dielectric board, produces five pairs of dual-polarized beams within ±45° around 26 GHz. Measured and simulated results demonstrated peak gains of 17.5 dBi (H-pol.) and 18.1 dBi (V-pol.), corresponding aperture efficiencies of 55.5% and 80.6%, radiation efficiencies up to 98.6%. The proposed design offers simultaneously high efficiency, wide bandwidth, multi-beam coverage, and balanced dual-polarized performance, making it highly attractive for 5G MMW communication systems and applications.