GB1086874A - Improvements in or relating to radar systems - Google Patents

Abstract

1,086,874. True motion radar. MARCONI CO. Ltd. April 28, 1965 [June 19, 1964], No. 25510/64. Heading H4D. The Specification describes a True Motion P.P.I. radar, similar to that shown in Fig. 1 of Specification 1,023,927, in that the recording tape with one writing and four reproducing heads is replaced with a recording tape 19 having a single writing and/or reproducing head 18, and the four-contact commutator switch feeding the selected reproducer head output to the display tube is replaced by a single contact switch 26 actuating a relay A. The recording tape 19 rotates once in 2 mins., i.e. once per 60 revs. of the antenna 1. Shaft 29, which rotates the wipers of switches 32 and 33, 59 rotates at - revs. per min. such that a wiper 8 2 remains on any contact for - min. Relay A is 59 2 thus actuated for - min., such that contacts 59 A1 and A2 are moved down for the same period. 2 8 Thus for - min. every - min. the echo signals 59 59 from amplifier 17 are recorded on the recording tape, and simultaneously displayed on the 2 display tube. In - min., the antenna 1 rotates 59 1 through 1 - revolution. Fifty-nine such record- 59 ings can thus be recorded on the tape. Since 1 only every fourth of these 1 - revolution scans 59 is recorded, it takes 8 minutes for the tape to be completely filled. During the time that the relay is actuated the wipers of switches 32 and 33 are on earthed contacts, such that the echoes are not displaced, and the " at present " display is shown with the " own craft " echo at the centre of the screen. The wiper of switch 26 then moves off of contact 27 such that relay A is deenergized and contacts A 1 , A 2 and A 3 return to their upper position. The head 18 is now reproducing the echoes on the tape portion next to that which has just been written on, which echoes were written on to the tape portion 6 mins. or three tape revolutions previously. The thus read 6 mins. old echoes are fed to the display tube. The wipers of switches 32 and 33 are on contacts connected to points on the resolvers that give the movement of the craft in the 6 previous minutes. The 6 mins. old echoes are thus displayed with the correct displacement to give the required accelerated true motion display. The next echoes to be reproduced are 4 mins. old, and the switches 32 and 33 accordingly adjust to give the appropriate displacement signals. The display is then repeated for echoes 2 mins. old, and then, with the wiper of switch 26 back on contact 27 and relay A actuated, the present echo position is displayed and recorded. Means are described, Fig. 2 (not shown), whereby additional displacement signals are fed to the display such that the present positions of the " own craft " does not remain in the centre of the display but moves according to its true motion.