Circularly Polarized Bandwidth-Enhanced Crossed Dipole Antenna With a Simple Single Parasitic Element

A method of using a simple single parasitic element to significantly enhance a 3-dB axial-ratio (AR) bandwidth of a crossed dipole antenna is presented. This approach is verified by introducing one bowtie-shaped parasitic element between two arms of crossed bowtie dipoles to generate additional resonance and thereby significantly broadening AR bandwidth. The final design, with an overall size of 0.79 λ
_o
× 0.79 λ
_o
× 0.27 λ
_o
(λ
_o
is the free-space wavelength of circular polarized center frequency), resulted in very large measured -10-dB impedance and 3-dB AR bandwidths ranging from 1.9 to 3.9 GHz (~68.9%) and from 2.05 to 3.75 GHz (~58.6%), respectively. In addition, the antenna also yielded a right-hand circular polarization with stable far-field radiation patterns and an average broadside gain of approximately 8.2 dBic.