GB763805A - Improvements relating to radar aerial assemblies - Google Patents

Abstract

763,805. Aerials. METROPOLITANVICKERS ELECTRICAL CO., Ltd. (Compagnie Francaise Thomson-Houston). Jan. 25, 1955, No. 2222/55. Class 40(7) A radar aerial assembly comprises a fixed primary element radiating energy into a beam producing reflector, the reflector being pivoted about a point on its axis and capable of movement to cause the beam to scan spirally or conically. Preferably balancing means are provided for maintaining the reflector in substantial dynamic equilibrium. As shown schematically in Fig. 3 the reflector 1 may be attached to a shaft 11 pivoted at 3 in the front of a housing 9 by' means of a universal coupling allowing it to oscillate about two axes perpendicular to each other and the shaft 11. To maintain dynamic equilibrium an annular ring carrying adjustable balance weights 4 is provided inside the housing and this is mounted on a second universal coupling at 15. The balance system is coupled to shaft 11 through a sliding ball and socket joint 18 so placed that motion of the shaft causes opposite displacements of the reflector and balance ring. Springs 19 are connected between housing 9 and the reflector 1 and springs 20 between the balance system and the housing. The natural periods of vibration of the two spring systems thus obtained are arranged to be equal and the frequency of the drive is also made to he such that one rotation takes place in this period. This reduces the power required to drive the aerial. A flexible mounting may be introduced between the reflector and the housing to stiffen the system. Alternative ways of obtaining dynamic equilibrium are described with reference to Figs. 4 to 7 (not shown). The drive mechanism for-shaft 11 is described with reference to Fig. 8. Here the spiral scan drive motor 75 drives shaft 48 through gearing and this shaft in turn drives annular gear 44 which engages planet wheel 42 on shaft 62. The shaft 11 is coupled to the planet wheel through ball and socket joint 52. The movement of axis 62 of the planet wheel is also the movement of main shaft 43 which is driven from shaft 48 through pinion 50 and clutch 51. The conical scan is effected by energizing motor 53 which drives gear 44 through gear 60 and operating locking device 55 which causes a notch 63 to engage in socket 54 so that gear 44 and shaft 43 rotate together. Clutch 51 slips under these conditions and the speed and gearing of motor 53 is arranged so that the conical scan is at a higher speed than the spiral scan and wheel 47, which is constructed to " over-run " freely, will disconnect motor 75 even if this is still running. Generator 58 is arranged to provide an alternating reference voltage and switch 66 operated by cam 57 produces a changeover which can be used to resolve ambiguity in the reference signal.