An Offset Gregorian Dual-Reflectarray Antenna with Eight Scanned Beams

This article describes the analysis and design of a new beam-scanning dual-reflectarray antenna in an offset Gregorian configuration. The phase distribution on sub-reflectarray is introduced based on a new formulation. In this method, the distances between the real and virtual focal points of the reflectarray and its nth element are taken into account. Introducing a progressive phase-shift term into the basic equation, the produced pencil beam is scanned accordingly. Actually, the large main reflectarray emulates a parabolic reflector, and by introducing phase control into the elements of the small sub-reflectarray, beam scanning is achieved. These elements are based on an ideal reconfigurable element, while a wideband multi-loop element is considered on the main reflectarray. The beam-scanning performance of this dual-reflectarray antenna is investigated in the XZ-plane and also for eight beams around the broadside direction at 12.5 GHz.