Phase‐shifted circularly polarised ring microstrip antenna and application in phased array antennas

Abstract A phase‐shifted circularly polarised ring microstrip antenna (PS‐CP‐RMSA), which can switch between three different phases, is proposed. The phase of a circularly polarised antenna can be shifted by changing the angle of rotation. Taking advantage of this property, the proposed PS‐CP‐RMSA comprises a circularly polarised ring microstrip antenna (CP‐RMSA) with three groups of feed lines and perturbation elements; phase shift can be achieved by switching their groups. Thus, the phase of a circularly polarised antenna can be electronically shifted without phase shifters, which has been difficult in the past. Therefore, the PS‐CP‐RMSA array can perform beam tilt electronically. In this study, PS‐CP‐RMSA and its four‐element array were designed, fabricated, and measured. The maximum circular polarisation gain of the prototype PS‐CP‐RMSA was 6.3 dBic with an axial ratio of 1.1 dB at 5.7 GHz. The maximum gain of the boresight directional beam of the four‐element array was 11.3 dBic with an axial ratio of 0.4 dB at 5.67 GHz. The proposed antenna can be a candidate for a new beam‐control method for array antennas.