I. Introduction
In recent years, the 5th generation mobile communication system (5G), which realizes high speed, large capacity, low latency, and multiple terminal connections, has been studied. [1] 5G and Beyond 5G will be indispensable technologies for the future society as they are applied to the Internet of Things (IoT) and vehicle to everything (V2X). Compared to the conventional 4th generation mobile communication system (4G), 5G uses a higher frequency band with a wider bandwidth to realize high-speed and large-capacity communication [2]. As the frequency increases, the propagation loss increases and the straightening of the radio wave also becomes more significant, resulting in degradation of the transmission characteristics. In order to solve these problems, circularly polarized antennas are desired.