Low-cost Smart Antennas

7Other Types of Low‐cost Smart Antennas

7.1 Introduction

In this chapter, some other types of low‐cost smart antennas are presented. These include the multi‐beam dielectric lens, retrodirective array, pattern‐reconfigurable FP resonant antenna, beam‐switching antennas using the AFR, and multi‐beam antennas based on passive beamforming networks. The dielectric lens, FP resonant antenna, and AFR provide low‐cost solutions to achieving high directivity and multiple beams (or beam‐switching) without resorting to the use of a large number of active radiating elements, thus they are attractive solutions to microwave and mm‐wave smart antennas, such as smart antennas for 5G massive MIMO base stations, mobile satellite communications, and automotive radars. Multibeam or beam‐switching antennas can also be achieved by using antenna arrays integrated with low‐cost passive beamforming networks such as the Butler matrix, Nolen matrix, and Rotman lens. The retrodirective array determines the angle of arrival of the incident signal and re‐transmit the signal back without using any phase shifters, leading to a significant reduction in the cost of the antenna system. In the following sections, the principles and design techniques of these low‐cost smart antennas are explained and examples from recent reported designs are presented.

7.2 Lens Antennas

7.2.1 Lens Antenna Basics

A lens antenna is a microwave antenna in which an antenna or array antenna is placed in front of a dielectric lens. The lens ...