Military Avionics Systems

3Basic Radar Systems

3.1 Basic Principles of Radar

The original concept of radar was demonstrated by laboratory experiments carried out by Heinrich Hertz in the 1880s. The term RADAR stands for Radio Aid to Detection And Ranging. Hertz demonstrated that radio waves had the same properties as light (apart from the difference in frequency). He also showed that the radio waves could be reflected from a metal object and could be refracted by a dielectric prism mimicking the behaviour of light.

The concept of radar was known and was being investigated in the 1930s by a number of nations, and the British introduced a ground-based early warning system called Chain Home. In the late 1930s, as part of the world’s first integrated air defence, this system has been credited with the winning of the Battle of Britain in 1940. The invention of the magnetron in 1940 gave the ability to produce power at higher frequencies and allowed radar to be adopted for airborne use. The first application was to airborne interception (AI) radars fitted to fighter aircraft to improve the air defence of Great Britain when used in conjunction with the Chain Home system. By the end of WWII, rudimentary ground-mapping radars had also been introduced under the dubious name of H₂S. Echoes of War (Lovell, 1992) gives a fascinating account of the development of radar during the war. Since that time, radar has evolved to become the primary sensor on military aircraft and is widely used in civil aviation as a weather ...