Wideband Accurate-Out-of-Phase-Fed Circularly Polarized Array Based on Penta-Mode Aperture Antenna Element With Irregular Cavity

This communication presents a wideband circularly polarized (CP) aperture antenna array with a specially designed feeding network. First, an irregular-cavity-backed aperture antenna element is introduced. Due to its penta-mode operation, a 72% CP bandwidth (5.3-11.2 GHz) is obtained, which is much wider than many existing unidirectional aperture-/slot-based CP antennas. In order to solve the element beam tilting problem, a novel four-element array with rotationally symmetric array arrangement and accurate out-of-phase feeding network is then proposed, which has advantages such as compact feeding structure, less gain variation, and symmetric radiation patterns. Measured results indicate that the four-element array achieves a CP bandwidth of 70.6% (5.48-11.46 GHz), a peak gain of 12.8 dBic, a 3 dB gain variation bandwidth of 69%, and averaged front-to-back ratio of 18 dB.