Substrate Integrated Multibeam Antennas

Abstract

There is an increasing need for antennas with multiple beam capability to satisfy the growing demand for communication systems and multiple target radars. In the millimeter‐wave frequency band, the power budget is usually costly and difficult to satisfy the requirement for long‐distance and wide‐coverage applications. Therefore, high‐gain, high‐efficient multibeam antennas are necessary for millimeter‐wave systems to improve their performances. An antenna array scheme based on the passive beamforming network (BFN) is an efficient way to form multiple beams in different directions from the same aperture. Depending on simple circuitry and cheap cost, this type of multibeam antenna can be a substitution of passive, active, and digital phased arrays. The currently popular substrate integrated waveguide (SIW) techniques, also called as postwall waveguide or laminated waveguide, combine the best and complementary features of both planar transmission lines and nonplanar waveguides. Thus, it is found very appropriate to construct different high‐frequency circuits and antennas that have been validated by several successful examples. This article presents recent achievements in the development of microwave and millimeter‐wave substrate integrated beamforming networks (BFNs) incorporating both lens‐ and circuit‐based types. They include SIW Butler matrix, Blass matrix, Nolen matrix, Rotman lens, R‐KR lens, reflector lens, and multimode lens. Integrated with proper antennas, compact and on‐substrate multibeam antenna arrays are achieved with good performance. Such a series of SIW BFNs and multibeam antennas present excellent candidates for low‐cost and mass‐reproducible applications in space‐ and ground‐based integrated systems with multiple beam capability.