Principles of Synthesis of Steerable Reflect-array Antennas

The synthesis of steerable reflect-array antennas, as a synthesis of any antenna, should be realized by solving two problems: external antenna problem and internal antenna problem. The first one includes the investigation of the antenna radiation pattern. The second one concerns a design of the structure providing the required amplitude-and-phase distribution along the antenna aperture. The first problem is based on the theory of antenna array. The distance between the small reflectors and geometry of the array are responsible for the directivity, the beam width, and the side lobe level of the antenna. The internal antenna problem consists of finding the phase shift required for each small reflector. Remarkable feature of a tunable reflector made as a microstrip vibrator or a patch in combination with a tunable device is that the almost 360◦ phase shift of the reflected wave can be provided with only one tunable device (varactor diodes or ferroelectric tunable capacitors). Commonly, simulation of the phase shift required is performed with a numerical technique. The design of reflect-array antenna can be sufficiently simplified, if the simulation by the numerical technique is amplified with a correct analytical model.