Analytical and Full-Wave Analysis of Square and Ring Patch Structures for Reflectarray Unit Cells

A theoretical analysis of a square structure, and a ring structure, for use in reflectarray antenna unit cells is presented. We calculate the complex reflection coefficient from the coupling between an incoming wave and the resonant modes of the studied structure. To obtain a more accurate model for both structures, we account for the ratio of resonator to cell size, fringing fields and high frequency effective permittivity. Full-wave simulation using periodic boundary conditions is used to compare the simulation results with the analytical model. The model shows a good agreement for the phase versus patch dimension over a greater range of thickness and dielectric permittivity than previous models. A prototype reflectarray antenna, using these structures, is currently being fabricated.