How radars work – Garth Wilkinson

Garth Wilkinson covered the history of the basic physics of the propagation of electromagnetic waves at the velocity of light as predicted by James Clerk Maxwell & experimentally verified by Heinrich Hertz. The nature of the electromagnetic spectrum was described, and the frequency bands normally used by radars were identified in relationship to atmospheric transmission windows.

The development of the UK “Chain Home” radar air defence system conceived by Robert Watson Watt during WWII was covered, together with parallel developments in Germany & Japan. The design of microwave transmitters ranging from Randall & Boot’s high power magnetron for ground mapping in WWII UK bombing raids, the travelling wave tube amplifier & modern solid state amplifiers was discussed. The basic types of radar antenna, scan patterns & accurate monopulse angle tracking were described in relation to radar function. These ranged from simple lobing techniques to modern advanced active phased array track-while-scan antennas under computer control. The nature of superheterodyne radar receivers was illustrated, together with techniques for eliminating the effects of ground & sea clutter, and identifying moving targets by mean of incoherent (moving target indicator MTI) or coherent (continuous wave or pulse doppler) waveforms. Examples were given of radar types designed to give early warning of ballistic missile launch, and of how radar techniques could be used to search for, track & guide missiles onto their targets. An example was also shown of how a complex network of radars could be integrated with other assets to embody a sophisticated modern air defence system, which was very difficult to defeat. Garth’s talk was followed by an interesting Q&A session, in which the subject of stealth was raised. He said this might be covered in a future talk.

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