A Low-Profile Circularly Polarized Microstrip Antenna with Broad Beamwidth Based on Coplanar 3/4 λ Phase-Shifted Sequential Rotation Fed Technique

A novel single-layer coplanar-fed circularly polarized (CP) microstrip antenna is presented. The antenna design uses a novel sequential rotation feed network based on 3/4λ phase-shifted lines and is coplanar with the circular radiating patch. The height of antenna is only 0.08λ and exhibits broad beamwidth for both E-plane and H-plane. Thus low-profile and broad beamwidth characteristics are realized. With eight curved microstrip resonant strips loaded around the circular radiating patch, the CP performance and gain value are improved. The proposed antenna is simulated and optimized. Results show that it has better impedance matching in the 5G millimeter wave frequency band (24.9 - 26.9GHz). The maximum gain is about 7.5 dB in operating bandwidth, and the half-power beamwidth is about 113° (-58° - 55°) in E-plane and about 102° (-52° - 50°) in H-plane.