A Broadband High-Efficiency Reconfigurable Reflectarray Antenna Using Mechanically Rotational Elements

Design of a circularly polarized reconfigurable reflectarray antenna (RRA) at X band is presented. The RRA element employs concentric dual split rings, and can be mechanically rotated to obtain continuous 360 degrees phase coverage with negligible element loss. A prototype with 15 x 15 manually rotated elements is first computed, simulated, and measured. Full-wave simulations show that the gain of the beam focused in (theta = 20 degrees, phi = 0 degrees) direction is 25.8 dB and the 1-dB gain bandwidth is over 28.6%. The measured results show that the beam at (theta = 20 degrees, phi = 0 degrees) direction achieves the maximum gain of 25.6 dB, corresponding to an aperture efficiency of 51.8%. The beam-steering capability of the RRA is measured within +/- 60 degrees angular range, and well-defined scanned beams are obtained with maximum scan loss of 3.7 dB. The versatile beam-forming capability of the RRA is also verified by synthesizing a square shaped beam and a cosecant shaped beam. Another micromotor-controlled prototype with 756 elements on an octagonal aperture is fabricated and its measured radiation performance validates the feasibility of the proposed design as well.