A Miniaturised Circularly Polarised Planar Antenna Utilising a Novel Square Ring Patch Feeding Structure

Abstract

In this article, a miniaturised circularly polarised (CP) metasurface (MTS) antenna excited by a square-ring patch loaded with L-shaped stubs is proposed and developed. A novel MTS antenna is presented, composed of a 3 × 3 patch array integrated with four sets of orthogonal capacitive stubs. In contrast to traditional MTS CP antenna, the capacitive stubs loaded in this design simultaneously control circular polarisation and miniaturisation characteristics, thus requiring a specially designed square-ring feeding structure. Simulated results for the proposed antenna show that an axial ratio (AR) bandwidth of 11.7% in fraction (5.65–6.34 GHz) is achieved with excellent impedance matching. Compared to conventional aperture coupled MTS CP antennas, the proposed structure achieves a size reduction of over 50%. It also exhibits superior axial ratio (AR) bandwidth and a more compact form factor compared to other antennas of similar type. Measured results show a −10 dB impedance bandwidth of 15% (5.66–6.57 GHz), a 3 dB AR bandwidth of 9.5% (5.7–6.25 GHz) and a peak gain over 6.53 dBi in addition to a compact overall size of 0.48λ₀ × 0.48λ₀ × 0.07λ₀.