Wideband circularly polarised array antenna with flat-top beam pattern

A wideband circularly polarised array antenna consisting of 10-element bowtie dipole antenna and feed network is presented. A narrow patch connecting the pair of bowtie dipoles as an entity is employed to achieve high gain. To obtain wideband and flat-top beam of radiation patterns, amplitude and phase distribution along the feed are optimised by application of the Self-adaptive Differential Evolution algorithm. Particularly, the feed network with broadband phase shift performance is designed to satisfy bandwidth requirement ranging from 1.1 to 1.6 GHz. The proposed antenna can achieve an excellent impedance matching and Axial Ratio characteristics over the entire operating band. Moreover, the ripple of co-polarisation radiation pattern covering ±12° in the elevation plane is better than 0.92 dB; whereas the gain is also better than 11.8 dB and the side lobes are below -13 dB. Measured results validate the design concept and indicate that the proposed array exhibits good radiation characteristics.