On the Design of A Reflective RIS for C-Band UAVs Beam-Steering Applications

This paper presents a design for a reflective reconfigurable intelligent surface (RIS) operating in the C-band frequency range. The proposed RIS is specifically intended for beam-steering unmanned aerial vehicle (UAV) applications. The unit cell consists of an impedance surface and a perfect electric conductor (PEC) ground plane. The impedance surface is designed by a square ring on upper side, while the lower side is constructed with a square loop integrated with an inner square patch. The adjustment of the phase of the reflected wave is achieved through the utilization of varactor diodes that are positioned on the underside of the impedance surface. The phase tuning range, which amounts to 3100, is achieved by manipulating the capacitance value of varactor diodes. The construction of the reflective RIS involves the concatenation of these unit cells. The simulation results for the RIS prototype, consisting of $7\times 7$ reflective elements, demonstrate a realized gain of 12.5 dBi at the center frequency of 5 GHz. The beam-steering capability of the reflective RIS spans a range of −40 ⁰ to 40 ⁰ , encompassing a wide angular coverage. The proposed reflective RIS promise as a potential technique for UAV applications.