Reflectarray Antennas

9Multi‐Beam and Shaped‐Beam Reflectarray Antennas

The conventional reflectarray antenna is designed to generate a pencil beam in a certain direction [1], [2]. While pencil beam patterns have numerous applications, for many other applications, such as fixed satellite services where the antenna is mounted on a spacecraft in a geostationary orbit, it is desirable to have a shaped beam (or multiple shaped beams) in order to efficiently illuminate selected geographical areas [3]. The classic choice for these applications has long been the shaped‐beam reflector antenna structure. However, these antennas suffer from mechanical drawbacks such as bulkiness, the need for an expensive custom mold for each coverage specification, thermal problems, and others. As such, the numerous advantages that reflectarray antennas offer, make them a promising choice for these applications. It should be noted that while for wide‐bandwidth applications, the standard parabola will always be the preferred design choice due to its true time‐delay characteristics, for narrow‐band applications (such as a direct broadcast satellite, which requires about 5% bandwidth) or for applications where electrical performance may be traded off for cost or mechanical advantages, a reflectarray antenna can be a good candidate.

The reflectarray allows for an individual control of the phase shift of each element in the array. As a result, the reflectarray can achieve shaped (contoured) beam performance without any additional ...