Antennas for communications

The radio spectrum suitable for communications is limited, and even with global allocation and management, the problem of spectrum congestion continues to increase. This has led to more and more being demanded from antennas so that they play their part in minimizing the problem. In the microwave bands used by satellites, the antenna characteristics must now be good enough for frequencies to be reused; at HF, broadband performance is required even from structures of a limited physical size, while in all bands, adaptive antennas are needed to minimize interference from unwanted transmissions. This paper highlights developments in communications antenna technology that are enabling these and other goals to be achieved.