Risley-Prism-Based Dual-Circularly Polarized 2-D Beam Scanning Antenna With Flat Scanning Gain

Although the two-dimensional (2-D) beam scanning antenna based on the Risley-prism (R-P) principle has been proposed, the previous research mainly used linear phase progression phase-shifting surfaces, which has the problem that the gain decreases rapidly when the beam scans to a large angle in the elevation plane. Here, exponential phase gradient phase-shifting surfaces based on the Risley-prism principle are innovatively proposed, which can realize the flat scanning gain of 2-D beam scanning antenna. In addition, a rotatable polarization control surface is introduced to make the proposed 2-D beam scanning antenna work in dual-circular polarization. The experimental results show that the maximum scanning angle of the antenna is 52° in the elevation plane and 360° in the azimuth plane. In particular, the gain variation of the beam is only 0.6 dB within elevation angle 45°, showing a flat scanning gain characteristic.