Patent GB-712019-A (GB)
Title: Angle indication system
IPC: G01S7/22
Filed: 1952-08-08
Abstract: 712,019. Pulse radar; valve gating circuits. BENDIX AVIATION CORPORATION. Aug. 8,1952 [Aug. 20, 1951], No. 20050/52. Classes 40 (6) and 40 (7) Relates to a cathode-ray tube display for a G.C.A. radar of the type disclosed in Specifications 697,631 and 698,909 in which the horizontal and vertical deviations of an aircraft from a landing path are detected by separate aerials scanning in azimuth and elevation respectively, the two aerials being coupled to separate pulse transceivers triggered alternately at a repetition rate of 1200 c/c, the azimuth and elevation signals being applied sequentially to intensity modulate sequentially - produced displaced expanded-sector azimuth and elevation displays on a single cathode-ray tube. and the azimuth position of the elevation aerial and the elevation of the azimuth aerial both being adjustable. According to the present invention range calibration marks 33, Fig. 1, are applied to the azimuth display over a sector corresponding to the azimuthal sector covered by the elevation aerial and range calibration marks 34 are' applied to the elevation display over a sector corresponding to the elevation sector covered by the azimuth aerial, this being achieved in the first instance by gating the calibration pulses by a valve controlled by a triangular azimuthal scan voltage, 61, Fig. 4A, produced by the azimuth aerial and by a negative azimuth position voltage depending on the azimuthal position of the elevation aerial which is produced by a potentiometer ganged to the elevation aerial, Fig. 1 (not shown). As shown in Fig. 2, calibration pulses from a generator 36 are applied to the cathode-ray tube via a gating valve 41 which is blocked when either V44 or V44<SP>1</SP> is conductive, V44 being D.C. coupled to V46. The A Z scan voltage 61 and the A Z position voltage are applied in parallel at 51, 52 to the grids of D.C. coupled valves 49, 46, the anode and grid of V49 being connected to positive and negative potentiometers 54, 56 such that V46 becomes conductive at a point 63 on the curve 62, Fig. 4B, representing the resultant grid potential of V46, and V49 becomes conductive some 'time later in the forward scan period at a point 66 on its grid voltage curve 65, Fig. 4C, thereby cutting off V46. During the reverse A Z scan an inverse cycle of events occurs so that during the complete scan V4 it is conductive during periods 64, 69, Fig. 4B, and at such times V44 is cut off thereby allowing gate valve 41 to pass the calibration pulses. The timing of gating periods 64 69, thus varies with the position voltage and the duration of the periods is adjusted by potentiometers 54, 56 to correspond to the angular horizontal beam width of the EL aerial. The EL scan and position voltages are applied at 51<SP>1</SP>, 52<SP>1</SP> to a similar pair of valves 46<SP>1</SP>, 49' coupled to V44' and when a line of the AZ display is being produced V57 is rendered conductive by the positive portions of an AZ "ON" gating pulse train thereby blocking V44<SP>1</SP>, V44 being similarly blocked during an EL display line by V57 and the EL "ON" gating pulses. In a modification, Figs. 5 and 6, showing the AZ marker control only, the scan and position voltages are both applied in push-pull to V71 and V72 whose cathode potentials are such that V71 and V72 are conductive respectively during non-contiguous periods corresponding to the flat portion of the corresponding grid-voltage curves 84, 85 which vary reciprocally as the position voltage is varied so that the gate valve 41 is varied so that' the gate valve 41 is unblocked during the short intermediate period when V71 and V72 are both blocked, the timing of said period varying with the position voltage and the duration of said period being pre-set by potentiometers 81, 82.