Single-Feed Circularly Polarized Super Realized Gain Antenna

TL;DR

This paper introduces a compact, low-profile circularly polarized antenna with superdirective gain at 3.5 GHz, achieved through mutual coupling and reactive loading, suitable for sub-6 GHz wireless applications.

Contribution

It presents a novel single-feed, circularly polarized superdirective antenna design that combines high gain, polarization purity, and compactness in a simple structure.

Findings

Achieves a peak realized gain of 6.1 dB at 3.5 GHz

Provides a 23.75% impedance bandwidth from 3.29 to 4.17 GHz

Demonstrates simultaneous circular polarization and superdirectivity in a low-profile antenna.

Abstract

This paper presents a super realized gain, circularly polarized strip-crossed dipole antenna operating at 3.5 GHz. Superdirective behavior is achieved by leveraging strong inter-element mutual coupling through careful adjustment of the strip dimensions. The antenna features a single driven element, with the other element passively loaded with a reactive impedance. The structure is optimized to maximize left-hand circularly polarized (LHCP) realized gain, ensuring high polarization purity and good impedance matching. The optimized design exhibits a 50 $\Omega$ impedance bandwidth of 3.29 - 4.17 GHz (23.75%) and an axial-ratio bandwidth of 3.43 - 3.57 GHz (4%). At 3.5 GHz, the antenna achieves a peak realized gain of 6.1 dB ($ka \approx 1.65$), with an axial ratio of 1.4 dB. These results demonstrate that circular polarization and superdirectivity can be simultaneously realized in a geometrically simple, low-profile ($0.15\lambda$) antenna, rendering it suitable for integration into compact sub-6~GHz wireless and sensing platforms.