Abstract This study proposes a single feedline technique that results in a wide axial ratio bandwidth (ARBw) of a circularly polarized filtering antenna. The antenna is designed to operate at 4.65 GHz. The design employed a rectangular radiator and two quarter-wavelength resonators. The two components are integrated using a single feedline and proximity coupling. The quarter-wavelength resonators excite the second mode polarization on the coupled rectangular radiator. The combination of width and length of the radiator, as well as the gap between the second resonator and radiator, equalized the two modes' e-fields’ magnitude. The design requires no additional delay circuit, for the gap between the second resonator and radiator provides both selectivity and a 90° phase shift delay. The proposed design has a wide ARBw of 10.10% and an impedance bandwidth of 9.04%. The use of two resonators results in a gain curve resembling a bandpass filter response, with a maximum gain of 7.6 dBic. The antenna is fabricated and measured to validate the proposed method, and the measurement results align well with the simulation results.
Cahyasiwi et al. (Thu,) studied this question.