Development of Wideband High‐Selective Circularly Polarised Antenna Based on Filtering Quadrature Phase Feeding Network

ABSTRACT This paper presents a new design of circularly polarised (CP) antenna with wideband and high gain selectivity. To achieve good circular polarisation performance, a wideband quadrature phase feeding network is initially developed with two output signals characterised by equal magnitude and consistent 90‐degree phase difference. Then, to realise high gain selectivity, multi‐mode resonators are introduced into the feeding network. Therefore, a specific filtering quadrature phase feeding network (FQFN) that integrates the functions of power division, frequency selectivity and phase shifting is successfully produced. Afterwards, a three‐order FQFN operating at central frequency of 2.5 GHz is developed and measured for demonstration. As expected, the demonstrator has obtained wide impedance and phase bandwidths of 57.3% and 70.8%, respectively, together with two transmission zeros at about 1.25 and 3.75 GHz. Finally, a pair of crossed magneto‐electric dipole antennas are implemented by adopting the proposed FQFN to achieve wideband CP radiation with high selectivity. Experimental results exhibit that the proposed scheme has achieved both impedance bandwidth of 65.3% and 3‐dB axial ratio bandwidth of 62.4%, simultaneously. Moreover, attributing to the integration of the filtering function within the FQFN, performance of high gain selectivity is accomplished and ensured by three transmission zeros in gain response.