patent of A.H.Taylor et al
System for detection objects by radio
Application date 13 June 1933
Granted on 27 November 1934
It was granted to: Albert H. Taylor, Leo C. Young and Lawrence A. Hyland, Washington D.C.
(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 O.G. 757)
This patent claim is very significant, as it concerns velocity detection by means of Doppler modulation, caused by a moving object. MTI or moving target indication is based on the phenomenon of 'Doppler modulation' originating from the 'radial velocity' of a moving object. For quite a long time, was it rather difficult for radar systems, to distinguish between fixed and moving objects. The Doppler modulated 'video signal' looks, at an oscilloscope, like the moving wings of a 'butterfly'. The Germans called these Doppler modulated target patterns 'Laus'. (some versions 'Würzlaus').
Keywords: This invention relates to a method of and means by which moving objects in the air or on the surface of the earth may be detected by the employment of radio receiving and transmitting equipment; The phenomenon upon which this invention operates is based upon the transmission of radio waves which may or may not be directional, the radiation of those waves by an intervening object and the reception of the primary, as well as the reradiated waves by a receiver remotely situated with respect to the transmitter. As will be shown, the detection of intervening objects is accomplished either by properly receiving and and interpreting the interference pattern created by the interaction of the ground waves as sent out from the transmitter and the reradiated waves from the intervening objects, such as an airplane, moving vehicle, or vessel, or by eliminating the said groundwaves and adjusting the receiver to actuation only by the reradiated sky waves ....
Consider also my book on German: Würzburg
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