18.1 INTRODUCTION

A typical tracking radar has a pencil beam to receive echoes from a single target and track the target in angle, range, and/or doppler. Its resolution cell defined by its antenna beamwidth, transmitter pulse length, and/or doppler bandwidth is usually small compared with that of a search radar and is used to exclude undesired echoes or signals from other targets, clutter, and countermeasures. Electronic beam-scanning phased array tracking radars may track multiple targets by sequentially dwelling upon and measuring each target while excluding other echo or signal sources.

Because of its narrow beamwidth, typically from a fraction of 1 to 1 or 2 , a tracking radar usually depends upon information from a search radar or other source of target location to acquire the target, i.e., to place its beam on or in the vicinity of the target before initiating a track. Scanning of the beam within a limited angle sector may be needed to fully acquire the target within its beam and center the range-tracking gates on the echo pulse prior to locking on the target or closing the tracking loops.

The primary output of a tracking radar is the target location determined from the pointing angles of the beam and position of its range-tracking gates. The angle location is the data obtained from synchros or encoders on the antenna tracking axes shafts (or data from a beam-positioning computer of an electronic-scan phased array radar). In some cases, tracking...