1.1 Background to radar

Radar was first patented in Germany in 1904 by Christian H lsmeyer ^{[1] , [2]}, following pioneering work by James Clerk Maxwell on electromagnetic theory ^{[3] , [4]} in the United Kingdom and by Heinrich Hertz in Germany. Radar has been technically refined continuously, as new innovations have been practically proven, developed and integrated into operational systems. Developments from radar's beginning to advanced techniques are summarised in ^{[5] [8]}. Fundamentally, a radar system sends out pulses of electromagnetic energy, which travel almost unimpeded through the air or space until they encounter an object in their path. The interaction with the object involves some of the energy being reflected from the object, some being absorbed by the object and some being transmitted through the object. The proportion of the incident energy that is reflected is dependent on the wavelength of the radar signal and the size, shape and material composition of the object. The reflected energy can potentially go in any direction, so the energy reflected back to the radar is very small and is detected using a specially designed receiver. Objects of interest, such as aircraft, are called targets, and objects, which can potentially get confused with targets such as reflections from the ground, buildings or the sea, are called clutter . Great efforts are made by radar designers to filter out clutter returns from those of targets.

Technology has become available that can detect targets on the land, on the sea, in the...