Design of omni-directional circularly polarized antennas

Abstract

Two wideband, circularly polarized (CP), planar, monopole, single feed antennas have been proposed and studied.

The Moon-shaped antenna consists of a moon-shaped radiator with a microstrip feed line. A wideband circularly polarized radiation is achieved by optimizing a moon-shaped radiator and ground plane shape. Impedance matching can be improved by gap between the moon shaped radiator and ground plane. The supporting substrate material is used low cost FR4 to design the antenna. The measured performances of the antenna are 1.52 GHz (2.0 -3.52 GHz) for 10-dB return loss bandwidth, 1.4 GHz (2.2-3.6 GHz) for 3-dB axial ratio bandwidth. Good agreement between simulated and measured results is achieved. The proposed antenna overall size is small of 70 mm × 47 mm × 0.8 mm.

The Z-shaped consists of a Z-shaped strip with a microstrip feed line. The antenna is prototyped with support of thin FR4 dielectric substrate. The measured performances of the antenna are 1.28 GHz (2.53 – 3.81 GHz) for 10-dB return loss bandwidth, 1.75 GHz (2.25 – 4.0 GHz) for 3-dB axial ratio bandwidth, and gain around 1.7 dBic over the 3-dB axial ratio bandwidth. Overall antenna volume is 50 mm × 40 mm × 0.8 mm.