Patent GB-644365-A (GB)
Title: Improvements in or relating to radar scanning apparatus
IPC: H01Q3/18
Filed: 1947-01-28
Abstract: 644,365. Aerials. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. Jan. 28, 1947, No. 2625. Convention date, Nov. 10, 1943. [Classes 40 (v) and 40 (vii)] In radio location apparatus an approximate indication of the location of an object is obtained by rotating a beam of ultra highfrequency electrical energy with a periodically varying eccentricity about a given axis after which a more accurate indication of the location is obtained by rotating the beam at a fixed displacement about said axis. As shown in Fig. 2, a dipole 26, 27 and reflector 31 is carried by rotating coaxial transmission line 24 positioned, when the arrangement is not operating, concentrically with the axis 13 of a parabolic reflector 11, the centre of the dipole coinciding with the focal point 14 of the reflector. The transmission 24 is mechanically and electrically coupled to a further coaxial transmission line 15 which is rotated by the motor 17<SP>1</SP>, by means of the mechanism shown in Fig. 3 which comprises, for mechanical coupling, a universal coupling device formed by an endbell 19 terminating the line portion 15 and provided with two arms 21 carrying set screws 22 in which is supported a second end-bell 23 connected to the transmission line 24, this arrangement allowing the line 24, which carries the dipole, to be rocked over a wide angle in a plane perpendicular to the drawing whilst, at the same time, maintaining a positive drive from the driving line portion 15. Electrical coupling between the two line portions is effected, for the inner conductors, by means of an extension 35 extending from the core 25 into and capacitively coupled with a flared endportion 33 provided on the core 32, the flaring being such that the extension does not come within sparking distance of the portion 33 when the line 24 is rocked through the maximum angle for which the system is to operate and, for the outer conductors, by capacitive coupling between the walls of the end-bell 23 and a turned-lock cuff portion 37 provided on an extension 36 of the outer conductor 15, the spacing between 37 and 23 also permitting maximum rocking of the line portion 24 without spark-over. A flexible rubber diaphragm 38 is clamped to the end-bell 23 by means of a screw cap 40 and to the extension 36 by means of a collar 39 and nut 41. The extension 35 is made to have a length equal to #/4 and the cuff portion 37 is made electrically #/4 long by the addition of insulating material 37<SP>1</SP>. An annular space #/4 long is also provided at the dipole end of line 24 by means of a conducting ring and sleeve 28, 29. The mechanism for effecting the required variation in the eccentricity of the dipole with respect to the axis 13 (Figs. 2, 4 and 5) comprises a drum 47 mounted on ball bearings 48 concentrically with the axis 13 and rotated at a slow rate relative to line portion 15 by means of the gear train 42 ... 45. The drum 47, which extends over part of the end-bell 19, is provided at the end nearest to the dipole with an end face, the plane of which is not perpendicular to the axis 13, against which bears a roller 49 carried by the end-bell 23 and urged into contact with the end face by means of a spring 51 so that as the drum rotates the line portion 24 which is also rotating about its own axis describes a periodic curve about the focus of the reflector, the radius of the curve periodically varying between limits determined by the contour of the end face of the drum. This method of operation is employed to obtain an approximate indication of the location of an object. In order to stop the periodic radial movement and to cause the dipole to rotate in a circle of small diameter about the axis (to obtain a more accurate indication) an annular member 67 supported by means of rollers 65 engaging a slot 66, Figs. 4, 5 and 6, the distance of which from the rim 68 varies with the circumferential distance about the rim, is provided with a ledge 73 lying in a plane normal to the axis 13 and forming an annular path which may be made to move into contact with and be traversed by a second roller 61 carried by the end-bell 23 when the member 67 is caused to move towards the right-hand side of the drawing. This movement is effected by means of a shaft 69 (driven bv motor 74, Fig. 2) and gears 68 and 71 which rotate the member 67 until the rollers 65 engage a portion of the slot which is farthest from the rim gear 68. Reference has been directed by the Comptroller to Specification 635,821.