Radiation performance of purely metallic waveguide-fed compact Fabry-Perot antennas for space applications

Metallic electromagnetic bandgap resonator antennas are highly attractive to design very efficient primary feeds of focal array fed reflector antennas for space Tx applications. The antennas analayzed in this work consists of purely metallic Fabry-Perot (FP) cavities with a single partially reflecting surface (PRS) and four perfect electrical conductor (PEC) walls on the sides. They are excited by a standard metallic waveguide. In contrast to prior work, we focus our attention on compact FP resonators whose size is in the order of a few wavelengths in free space. Their radiation characteristics (namely, their resonant frequency, maximum directivity, aperture efficiency, and radiation bandwidth) are investigated numerically in X-band with the finite-difference time-domain method. The extensive study of their radiation perfomance as a function of their size and grid reflectivity of the PRS, as well as the comparison with the well-known characteristics of large FP antennas, highlight three main features that must be taken into account for an optimum design for a given grid reflectivity, the resonant frequency increases while reducing the size of the shielded resonator, (2) for a given size of the antenna there exists an optimum reflectivity maximizing the aperture efficiency, (3) at resonance, the beam radiated by a square cavity is not circularly symmetric. In particular, we have shown that, for a 2 X A, cavity, it is possible to reach a high-aperture efficiency (eta(s) = 80%) over a 2.8% (-1 dB radiation) bandwidth. (C) 2007 Wiley Periodicals, Inc.