Circularly-polarised high gain cavity antenna based on sequentially rotated phase feeding

A Fabry-Pérot cavity (FPC) array antenna providing both very high gain and circularly-polarised (CP) behaviour is proposed. To increase antenna gain and to obtain the CP characteristic, a superstrate is introduced above 2 × 2 feeding microstrip patch antennas (MPAs), which converts linearly-polarised (LP) incident waves to CP waves. Input phase difference between MPAs is designed to be exactly 90° to generate the high-quality CP characteristic in cooperation with the superstrate. By using the FPC, very high gain can be obtained with only a small number of feeders, which also provides another advantage of low mutual coupling among the neighbouring MPAs. Although the proposed antenna is very simple in its structure, it readily provides very high gain, high-quality CP property and very low axial ratio in a wide frequency range, which are great advantages compared with conventional CP antennas.