I. Introduction
Fabry–Perot resonator antennas (FPRAs), also known as EBG resonator antennas, resonant-cavity antennas, and 2-D leaky-wave antennas, have recently attracted significant attention in the electromagnetics field for their highly directive radiation patterns and simple feed mechanism. There are countless applications in modern communication systems for this class of antenna, such as base stations, back-haul networks, and satellite communications [1]–[7]. Antennas of this type could possibly replace array antennas and bulky parabolic antennas in applications where the fabrication cost and the volume of space taken up by the antenna are limitations [8], [9]. Conventional FPRAs are basically composed of a cavity created between a ground plane and a partially reflecting surface (PRS). Constructive wave interference above the cavity, caused by numerous reflections inside the cavity, results in boresight radiation patterns [1]–[10]. Nontransparent fully reflecting surfaces (FRSs) have been recently proposed in [11]–[13] for FPRAs. This new design procedure offers more flexibility in the adjustment of the FPRAs’ aperture field, such as sidelobe levels (SLLs) reduction [12].