I. Introduction
Recently, devices such as millimeter-wave antenna systems have been actively researched for 5G (5th generation mobile networks) communications [1]–[11] and it is expected that highly qualified-more data rates, high resolutions, and etc.-communication techniques will be available using 5G networks. In this paper, dual-polarized patch array antenna operating at 28.5 GHz is designed for SiP (System-in-Package), as well as 5G communications using beamforming techniques. An MMIC (Monolithic Microwave Integrated Circuit) device is placed at the bottom of the antenna package and controls the operation of each patch antenna. The height of dielectric material is increased to achieve wide bandwidth characteristics, and multilayered ground-wall is inserted between patch antennas for mutual coupling reduction as well as a manufacturing stability. Because it has been reported that the dielectric constant of FR4 decreases at higher frequency region, reduced dielectric constants are applied to antenna design [12]–[14].