Target Classification for Air Defence Radars

Radar is evolving rapidly from being a sensor which detects and tracks targets to a high resolution imaging sensor with target classification capabilities. This paper addresses the techniques being developed for air defence radars. The application of target classification functions in fire control radars which support missile systems and multi-function phased array radars is discussed. The main high resolution techniques employed are range profiling, ISAR, frequency/spectral analysis and range-frequency imaging. Typical aircraft images measured are presented. The level of maturity of the hardware and signal processing technology to support these modes is discussed. The key technical, operational and practical issues which drive the design and application of high resolution modes for these types of radars are presented. Factors which determine the type of target classification mode which can be employed include the: operational frequency of the radar, time available for the application of the high resolution waveform, pulse repetition frequency, radar bandwidth available, basic architecture of the radar, and mission of the radar system. The other critical issue for the practical employment of target classification modes is that of the target signature database. Classifier algorithms are used to provide the match between the signature measured by the radar and reference signatures of targets of interest held in a database to provide an estimate of the target class. The assembly and maintenance of the target signature database is discussed and techniques employed are presented