A low profile circularly polarized antenna with L-shape energy coupling slot and the S-shaped matched transmission line

Abstract

ABSTRACTIn this paper, a novel low profile circularly polarized antenna with L-shape energy coupling slot and the S-shaped matched transmission line (SMTL) is presented. It consists of a monopolar radiator and a hexagonal radiator which will generate vertically and horizontally polarized electric field Eθ and Eφ, respectively. To satisfy the required magnitude/phase relationship between two radiators, the double L-shape energy coupling slot and the SMTL are introduced. Also, 12 circular shape patches are arranged sequentially on the hexagonal radiator to obtain a wide AR beamwidth. The measured results show that the realized antenna has an impedance bandwidth of 2.1% (5.76–5.88 GHz). In particular, the 3 dB Axial Ratio (AR) beamwidth at 5.8 GHz is extended to 212° (φ = 0° plane) and 217° (φ = 90° plane). Stable RHCP omni-directional radiation patterns are obtained over the operating bandwidth with a peak gain of 1.25 dBi. A good agreement between the simulated and measured results is obtained.