A novel approach to design compact, wideband, and high-gain circularly polarized MIMO antenna using dual-polarized elements and hybrid couplers

This paper presents a novel design approach for a compact, circularly polarized (CP) multiple-input multiple-output (MIMO) antenna that achieves wide bandwidth, high gain, and multi-port operation. Unlike conventional MIMO configurations, where each port feeds a single-polarized radiating element and gain enhancement relies on frequency-selective surfaces or T-dividers, the proposed design integrates dual-polarized CP radiating elements with hybrid couplers. Through this configuration, a four-port MIMO array is realized using only two radiating elements, significantly reducing the overall antenna size. The hybrid coupler enables simultaneous excitation of both elements, resulting in enhanced gain and improved radiation characteristics. A prototype is fabricated and experimentally verified. The measured results show that the antenna, with compact dimensions of 1.41λ × 1.06λ × 0.07λ, exhibits an operating bandwidth of 9.5% (5.0-5.5 GHz), port isolation better than 10 dB, and gain ranging from 7.8 to 8.8 dBi. Owing to its compact, wideband, and high-gain CP performance, the proposed antenna is well suited for modern wireless communication systems, including WLAN, Wi-Fi 6, C-band radar, and satellite IoT applications.