GB1380040A - Radar systems - Google Patents

Abstract

1380040 Pulse radar TELEFUNKEN PATENTVERWERTUNGS GmbH 31 Aug 1961 [3 Sept 1960] 31316/61 Heading H4D In an M.T.I. radar system, the received echo pulse sequence is arranged in groups of four, at the receiver, to eliminate the fixed target signals. I.F. frequency delay lines, at the receiver, cause each fixed target echo to adopt a quadrature phase displacement relative to the previous pulse such that the resultant of the summation of the amplitude of each group of four is zero. The moving target received signals are not eliminated by this process as they possess phase displacements which are different for each one of the group of four signals and which are a function of the target velocity. The addition of a further 90 degrees phasing between the four moving target signals of the group does not case the resultant of these vectors to be zero. In the embodiments described, those parallel delay circuits are provided which insert respectively, phase rotations of 90, 180 and 270 degrees. The resultant of the M.T.I. echoes is a function of the inserted angle for a given target speed and the largest is fed to the display unit by a selection circuit. A further small phase angle may be added to allow for antenna rotation. In one embodiment, the echo signals are not added vectorially but are represented by their X and Y co-ordinates. Fluctuation signals such as receiver noise and variation of echo signal strength are also reduced by the phase rotations.