A Dual-polarized Aperture-coupled Patch Antenna for n257 Excited by Coplanar Line

Abstract

A dual-polarized patch antenna has been developed for n257 beam-forming application. A lot of 5G millimeter-wave applications require dual-polarized antennas that have broad bandwidth and broad beam-scanning range. Generally, a patch antenna needs thick substrate between the antenna and ground in order to achieve wide bandwidth, but it is difficult to feed such thick antenna by using vias. For example, an aperture coupled patch antenna fed by strip line through slot on ground is used [1] , where the ground is put between the feed line and the antenna. When an aperture coupled antenna is mounted on a radio module on the opposite side of which RF-IC is mounted, it is necessary to sandwich the feed lines by multiple grounds. This results in the increasing of the number of layers used for the antenna. To reduce the number of layers, a coplanar feed line is applied between the antenna and ground in our antenna. Figure 1 shows the design of the proposed antenna. It consists of two patch antenna layers, two coplanar line layers and a ground layer. The antenna size is 3×3 mm 2 that enables the antenna to be aligned at a half wavelength interval. Thickness between the coplanar line and the ground layer is 0.1 mm and that between the coplanar line and the antenna is 0.3 mm. Direction of the upper coplanar line is orthogonal to that of the lower one. In Fig. 1 , the upper layer line generates horizontally polarized radiation and the lower one generates vertically polarized radiation. As the coplanar lines cross slits on the ground, electromagnetic field is excited and coupled to the patch antenna.