Review of Wideband Passive Reflectarray Antennas

Abstract

Reflectarray antennas (RAs) combine the high gain and low-loss space feed of reflectors with the per-element phase control of phased arrays, but their resonant, path-length-dependent operation makes bandwidth their principal limitation. The paper presents a comprehensive review of techniques developed to widen the bandwidth of passive reflectarrays, organized around the physical mechanisms that limit it and their dependence on aperture scale. We first analyze the dominant bandwidth-limiting factors—unit-cell dispersion, differential spatial phase delay, phase truncation to a single 360-degree range, and frequency-dependent feed effects—and show how the dominant factor shifts from unit-cell dispersion in small and medium apertures to spatial-delay and feed effects in large and low-F/D apertures. The wideband techniques are then reviewed in two tiers: unit-cell techniques (multi-resonant, multilayer, sub-wavelength, three-dimensional, delay-line/true-time-delay, and hybrid elements) and beyond-unit-cell/structural techniques (feed optimization, folded, frequency-selective-surface integration, phase synthesis, stepped, conformal, and multi-facet architectures). Reported prototypes are compared using a consistent, normalized set of parameters—element phase range, cell period, electrical aperture size, F/D, polarization, and measured gain bandwidth—to expose the trade-offs among bandwidth, aperture efficiency, and fabrication complexity. The review concludes by identifying the key open gaps and outlining a roadmap for advancing wideband reflectarrays in next-generation satellite and space systems.