Analytic Model of a Coax-Fed Planar Cavity-Backed Metasurface Antenna for Pattern Synthesis

We present an analytic model of a coax-fed planar cavity-backed metasurface antenna for radiation pattern synthesis. The metasurface antenna consists of a printed cavity loaded with metamaterial elements which is excited by a coaxial connector. Each metamaterial element radiates a portion of the reverberating fields in the cavity, contributing to an overall beam pattern. To synthesize a desired pattern, the elements need to be arranged in an aperture and radiate with proper weights at their locations. The weight of each element is jointly determined by the geometry of the cavity and the metamaterial element's resonant response. To predict and achieve the required weights, we first provide a full analytic description of the interaction of the cavity and the metamaterial elements. After verifying the analytical model through numerical simulations, we utilize it in an iterative scheme to solve for the metasurface structure that generates a prescribed pattern. Using the outlined procedure, three different antennas are designed, fabricated, and examined in experiments. Excellent agreement between measured and designed patterns is demonstrated, verifying the proposed analysis and synthesis process. Cavity-backed metasurface antennas with either static or dynamically reconfigurable radiation patterns may find application in communications, imaging and sensing.