TABLE OF CONTENTS Electronic beam steering
Transmitting arrays
Combining radar ouptuts
Improving resolution
Electronic methods of steering beams, communication between radars and advanced processing give modern radar systems considerable flexibility.
In this chapter we look at current radar technology and find out how it is being used. We will try to predict the future of radar in the next chapter.
The antenna has been the subject of some of the most interesting radar developments in recent years. Domestic satellite dishes are representative of the old level of antenna technology because they must be mechanically pointed at their target. Radar versions of these parabolic reflectors are rotated by heavy and expensive (but reliable) turning gear, and a target can only be observed once every few seconds when the dish faces that direction.
At the centre of a reflecting antenna, such as a satellite dish, is the device that illuminates it, called the feed. Feeds can be dipoles, microwave horns or other devices for radiating or receiving electromagnetic waves. The purpose of the reflector is merely to increase the collecting area, and hence the gain, of the antenna. However, a large collecting area can also be achieved in an entirely different way. It is possible to arrange many dipoles on a flat plate and connect them together in a phase-coherent manner to form a phased array. In the UK, one domestic system for receiving satellite broadcasts was constructed in this way.
Phased arrays are often considerably more expensive than reflector antennas...
