3.1 INTRODUCTION

A tracking radar continuously measures the coordinates of a moving target in order to determine its path and to predict where it is going. Tracking can be carried out using range, angle or doppler information, but it is the tracking in angle that forms the characteristic feature of tracking radars.

To some extent, all types of surveillance radar, civil or military, could be considering as tracking systems since they form an estimate of the target position each time the scanner returns to look in that particular direction a process known as track-while-scan. Surveillance radars can keep track of many targets simultaneously but the positional accuracy they provide, especially in angle, is not adequate for some purposes.

In contrast, a tracking radar (often a military system) is dedicated to a target and observes it continuously and with great precision, usually with a view to engaging a weapons system. Some tracking radars have their own search facilities, but the more usual mode of operation is for a main surveillance radar to warn of any targets posing a particular threat and to download the target coordinates to the tracking system, which then searches the immediate area to acquire the target before initiating the tracking process.

The antenna of a tracking radar usually faces the target all the time in order to keep it in the centre of the beam and so maximize the signal-to-noise...