15.1 Introduction

The dramatic increase in satellite communications capacity, capability and flexibility over the last two decades has been made possible by improvements in techniques and in the design of components both in the space and ground segments. A key factor in achieving these improvements has been advances made in antenna technology. The antenna provides the vital link between the ground and the satellite, performing such complex operations as:

• the simultaneous reception and transmission of communication signals;

• the rejection of interference from neighbouring systems, both space and terrestrial;

• the maintaining of accurate pointing between earth station and satellite.

As overall system requirements become more stringent and natural resources such as the geostationary orbit and frequency spectrum more saturated, the antenna rapidly becomes a critical subsystem demanding more sophistication in design and the development of new synthesis techniques. Specifications on both terrestrial and satellite antenna performance, especially as regards copolar isolation, crosspolar discrimination and sidelobe radiation characteristics, reflect these advances and provide a significant challenge to designers.

In this Chapter both earth-station and satellite antenna technology is reviewed. Obviously, it is impossible to cover every aspect of such wide subject matter and the reader is referred to authoritative texts such as References 1 and 2.

15.2 Earth-Station Antennas

Advances in satellite design have led to a reduction in the size of earth-station antennas as used in the fixed satellite service to provide telephony, television uplinking and data dissemination. The original INTELSAT Standard-A antenna of 30 m diameter has been...