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

This article proposes a mechanically scanned, broadband, low-cost, dual-polarized parallel-plate lens antenna (PPLA). The dominant TM0 mode and the higher order TE1 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 (TM0 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 semicircular 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.