Design of Broad-Beam Microstrip Reflectarray

The reflectarray’s elements arrangement for generating an arbitrary phase distribution in the antenna aperture and thus a wide beamwidth of the far field pattern is presented. The desired phase delay of reflectarray elements, which duplicated the same radiating aperture as backscatters, is determined on the construction of the curvature of a shaped backscatter surface with the help of Snell's law for beam forming to cover a broad area. The Method of Moments (MoM) and the infinite-array are applied to calculate reflection phase characteristics. The phase and radiation pattern synthesis method for microstrip reflectarray that has to illuminate a predefined circular area are presented by using a variety of discretization of elementary geometrical functions such as, triangular, quadratic, circular, gaussian, cosine, squared cosine, and parabolic distributions. These backscatter functions are discussed in terms of merits and demerits to find appropriate radiation characteristics such as radiation pattern, -3 dB beamwidth, and maximum gain for utilization in Wireless Local Area Network (WLAN) application. The optimized feed distance is calculated from the aperture efficiency by considering feed blockage efficiency and the influence of the feed position on the -3 dB beamwidth and gain performance has been investigated. Having confirmed the validity of this approach, the X-band antenna prototype is designed and developed. This reflectarray is tested experimentally and shows good performance. Key-Words: reflectarray, phase array, broad-beam antenna