A high-gain omnidirectional circularly polarized 2 × 2 array antenna with a sequential-phase feed network

Omnidirectional circularly polarized (OCP) antennas are highly desirable for wireless applications. However, the antennas suffer from limitations, such as low gain and a high profile. This paper presents a 2×2 high-gain OCP array antenna. The antenna element is enhanced for circular polarization (CP) performance by incorporating four shorting pins to enhance gain and is excited by a four-feed with a sequential-phase feed network. The antenna element uses an air dielectric layer to achieve higher gain and wider bandwidth. A 1-to-4 power divider is utilized to provide equal-amplitude and in-phase signals, enabling symmetrical omnidirectional radiation patterns. To validate the design, the antenna is fabricated and measured. The results demonstrate a (−10 dB) bandwidth of 2.39-2.51 GHz (4.9%) and a 3 dB axial ratio (AR) bandwidth of 2.45-2.47 GHz. A peak gain of 9.4 dBic is achieved at 2.45 GHz. The proposed antenna has potential for applications in wireless communication and energy harvesting systems.