Reflectarray Antennas

10Beam‐Scanning Reflectarray Antennas

In addition to the numerous advantages of reflectarrays over reflectors and arrays for fixed beam applications, the reflectarray antenna also becomes a new paradigm for beam‐scanning applications. High‐gain beam‐scanning architectures impose stringent requirements on the antenna radiation capabilities [1], [2]; as such, very few types of antennas are capable of achieving the required performance. In most high‐gain beam‐scanning applications, the conventional choice is between a reflector (or lens) and a phased array, which is driven by factors relating to scan rate, scan volume, and cost [3]. Reflector antennas are typically more suitable when a very high‐gain aperture is required and a phased array is cost prohibitive [4]. For reflectors, beam‐steering can be accomplished through mechanical scanning, or by using sophisticated feed cluster architectures, where the latter is typically high cost [5]. On the other hand, electronic scanned phased arrays rely on phase shifter technology. For high‐gain beam‐scanning applications where the antenna aperture is large, active phased arrays using transmit/receive (T/R) modules are employed [6]. While the phase shifter and T/R module technology have greatly matured over the years and the cost of active phased arrays have dropped dramatically, they still represent a considerable portion of the overall antenna cost [7]. Typically, the primary disadvantages of phased arrays are the large hardware footprint ...