An Improved Design and Implementation of a Broadband Circularly Polarized Antenna

This communication presents an improved design and implementation of a broadband circularly polarized antenna that features a size reduction, good axial-ratio bandwidth and good return loss bandwidth. The circuit comprises one Schiffman phase shifter that is used to obtain a wideband phase difference of 90
$^{\circ}$
, and a pair of orthogonally positioned linearly polarized slot antennas with equal radiation strength that are used to accomplish a circular polarization by combining the horizontally and vertically polarized waves with a Wilkinson power divider. Measured results show that the 3 dB axial-ratio bandwidth of the proposed antenna can reach 81.5% (1.6–3.8 GHz), and the 10 dB return loss bandwidth is 100% (1.48–4.47 GHz).