Wideband Dual-Polarized Parallel Plate Waveguide Lens Antenna for 5G Applications

This paper proposes a mechanically scanned, broadband, low-cost, dual-polarized parallel-plate lens antenna (PPLA). The dominant TM
₀
mode and the higher-order TE
₁
mode are utilized to achieve dual-polarized radiation. Drawing on the theory of constant refractive index lenses, we initially fill the parallel-plate waveguide with a material of uniform refractive index to ensure beam focusing for vertical polarization (TM
₀
mode). Subsequently, by adjusting the waveguide spacing–a modification that does not affect the effective refractive index for vertical polarization–we align the effective refractive index for horizontal polarization closely with that of vertical polarization, thereby maintaining relative stability and achieving beam focusing for the horizontal polarization. This approach obviates the need for gradient refractive index materials, thus substantially reducing design complexity and manufacturing costs. To validate our proposed concept, we designed, fabricated, and tested a transmission-type circular PPLA and a reflection-type semi-circular PPLA. The test results demonstrate that the impedance bandwidth of the proposed lens antenna can cover the entire Ka-band and potentially extend to even higher frequency bands. Moreover, the peak gain of the antenna increases with frequency within the Ka-band. The proposed antenna offers wideband, dual-polarization, and high-gain radiation characteristics. Additionally, it boasts a simple structure, low cost, and a low profile, rendering it highly suitable for 5G millimeter-wave (mm-wave) communication applications.