GB717794A - Improvements in or relating to radar systems - Google Patents

Abstract

717,794. Radar. WESMTINGHOUSE ELECTRIC INTERNATIONAL CO. July 18, 1952, No. 18278/52. Class 40 (7) In an automatic range tracking radar system comprising a transmitter and a receiver in which early and late gate pulses displaced equally with respect to time on either side of an echo pulse are generated means are provided for preventing the receiver from locking in on pulses directly received from the transmitter. The means include a generator for generating suppressor pulses which cancel out the early gate pulses when these occur at the same time as the directly received transmitted pulses. In one embodiment trigger pulses are fed to square wave generator 10 feeding saw tooth generator 11 whose output is clipped at 12 in accordance with the input form unit 20 to give a variably timed pulse amplified at 13 and supplied to early gate pulse forming circuit. 14. Circuit 14 supplies early gate pulses to early gates coincidence circuit 15 and to late gate pulse generating circuit 16. This supplies late gate pulses to coincidence circuit 17 which together with circuit 15, is fed with the received pulse signals. The outputs of the coincidence circuits 15 and 17 are fed to unit 19 which determines the potential it is necessary to apply through D.C. amplifier 20 to clipping unit 12 to maintain the gate and echo pulses in coincidence. When the echo pulse being followed approaches zero range it will overlap the directly received and much stronger transmitter pulse and lock on to it instead of following the echo when the range of the object giving rise to it once more increases. To prevent this occurring suppressor unit 18 generates a suppressor pulse coinciding with the transmitted pulse in time and of inverse polarity to the early gate pulse. This is applied to the coincidence circuit 15, Fig. 2 (not shown), to cancel out the early gate pulse when this overlaps the transmitted pulse. Circuit 15 then feeds no output to unit 19 and a weak echo appearing from out of the larger transmitted pulse can push the late gate pulse in front of it to a point where the early gate pulse is once more unsuppressed and normal operation resumed.