Novel sequential rotation technique for broadband circularly polarized microstrip ring antennas

A new sequential rotation technique for wideband circularly polarized ring antennas has been investigated. The concept is based on the reconfigurable proximity coupling feeding method proposed by the author recently. Theoretical investigations show that wider axial ratio bandwidth can be obtained. Moreover, it can retain the advantages of the switching between right-handed (RH) and left-handed (LP) circular polarization (CP) easily. The proposed club-shaped microstrip feed line excites the fundamental TM₁₁ mode of the three ring radiating elements through proximity coupling along the semi-annular section of the line. The phase differences between elements are about 120 degree. The induced rotating surface currents on the ring radiators contribute to the circular polarization characteristic of the antennas. Prototypes operate at 2.4 GHz have been designed to show the basic operating principles of the antennas. Simulated return loss, axial ratio, gain and radiation patterns of the antennas have been presented.