A Compact Hollow Dual Circularly Polarized Antenna With Folded Coupled Feed Structure For Distance Detection Application

A wideband and dual circular polarization hollow patch antenna fed by a tapered fold coupled structure is presented for distance detection application. The proposed antenna consists of a gear-shaped ring radiation patch etched on a three-layer dielectric substrate, four tapered folded feedlines, a ring ground plane and a feeding network. To achieve right-handed circular polarization (RHCP) and left-handed circular polarization (LHCP) characteristics, four hybrids are employed. The proposed hollow antenna can be seamlessly integrated and installed under the cover of sharp shaped aerobat without effect on its flight characteristics. As a proof-of-concept, an antenna working at 1.8 GHz is prototyped and tested. The measured and simulated results show that the proposed antenna exhibits a wide impedance bandwidth of 270 MHz (1.695 - 1.965 GHz) and a wide 3-dB axial ratio (AR) beamwidth of 140 degree.