Reflectarray Antennas

Foreword

Although the concept of the reflectarray antenna was first introduced in 1963, the vast interest in it did not come about until in the late 1980s with the development of low‐profile microstrip antennas. From the word reflectarray, it can be deduced that this is an antenna that combines the unique features of a parabolic reflector and a phased array. Thus, a low‐profile reflectarray consists of an array of microstrip elements that are provided with a set of pre‐adjusted phases to form a focused beam when illuminated by a feed, in a similar way to a parabolic reflector. The array elements can be printed onto either a flat surface or a slightly curved surface and have been demonstrated to have the ability to produce a high‐gain pencil beam, a contour‐shaped beam, multiple beams, or an electronically scanned beam. Because the array elements in a reflectarray are not physically interconnected, it can produce a high‐gain beam with relatively high efficiency similar to that produced by a parabolic reflector. There were several pioneers that initiated the study of printed reflectarrays during the late 1980s. I thought about the idea of a reflectarray due to my earlier work experiences with microstrip antennas and frequency selective surfaces (FSS). At certain resonant frequencies, the FSS can only reflect as a nearly perfect conductor since all elements are identical. It cannot cause the reflected waves to form a phase‐coherent beam. However, if each FSS element is designed ...