Single-Feed Broadband Circularly Polarized Sinuous Spiral Crossed-dipole Antenna

A single-feed, crossed-dipole antenna with sinuous spiral structure is proposed in this paper. The primary radiated element of the antenna utilizes two orthogonal sinuous spiral schemes, which are connected by a phase delay ring. Different from four-armed sinuous spiral antennas fed by complicated phase-shifting networks and balun feed-lines, this antenna only has a single coaxial feed port. However, broadband circularly polarized (CP) operation can still be obtained. A circular ring parasitic metal strip is applied to enhance CP performance. The final prototype with an overall size of 50mm $\times 50$ mm $\times 1$ mm ($0.75\lambda 0\times 0.75\lambda 0\times 0.015\lambda 0$ at 4.5 GHz) is simulated using HFSS. The simulation results indicate a $\mathrm{S}_{11}\lt -10\mathrm{d}\mathrm{B}$ bandwidth about 2.6–6.5 GHz (85.7%) and a 3-dB axial ratio (AR) bandwidth of 3.48–5.52 GHz (45.3%).