Patent GB-609703-A (GB)
Title: Improvements relating to electrical apparatus for indicating the positions of bodies
IPC: G01S7/12
Filed: 1939-12-05
Abstract: 609,703. Cathode-ray oscillographs. COSSOR, Ltd., A. C., and GODECK, J. E. Dec. 5, 1939, No. 31486. [Class 37] [Also in Group XL (c)] In apparatus for indicating the distance and bearings of bodies from a station at which signals are transmitted and their echoes received, indicating spots are produced on the screen of a cathode-ray tube, which spots represent in polar co-ordinates the distance and direction of reflecting bodies, the screen thus displaying a plan of the environs of the station and of bodies in the vicinity. Aligned transmitting and receiving aerial arrays 1, 2, Fig. 1, each having acute maximum directional properties, are mounted to be rotated together on a shaft 3 by a motor 4, and are connected to transmitter and receiver circuits 7, 8 by feeders 5, 6. The transmitter 7 transmits from aerial 1 a regular succession of pulses of waves of a frequency of about 200 megacycles, the duration of each pulse being about 3 microseconds and the spacing between the pulses about 1000 microseconds. A cathode-ray oscillograph 9 has four deflection plates receiving their deflection potentials from a circuit 10, which produces a deflection of the spot in a circular path at constant angular velocity in response to a sine wave input voltage, and a radial deflection of the spot in proportion to another input voltage. The circuit 10 is shown in Fig. 2. The outputs of hexodes V1, V2 are applied to one pair of deflector plates X1, X2, while the outputs of hexodes V3, V4 are applied to the other pair of deflector plates Y1, Y2. The injection grids are supplied with sine wave potentials from a source 11, equal resistors R5, R6 providing a point for earth connection so that the inputs to the valves V1, V2 are in push-pull. A condenser and resistance bridge 12 provides input potentials for the injection grids of the valves V3, V4 in push-pull with each other and in quadrature with the inputs to the valves V1, V2. If equal amplification is given by the valves V1, V2, V3, V4, the trace of the spot on the screen of the cathode-ray tube is circular. The radial deflector voltages for the control grids of the valves V1, V2, V3, V4 are all applied in parallel from the line 13 through condensers C1, C4 and resistances R7 ... R10. The effect of change of voltage supplied at 13 is to change the slopes of all the valves V1 ... V4 equally and thus to change the radius of the circular trace without varying its circular character. The input sine wave source 11, Fig. 2, is represented by an alternator 14, Fig. 1, driven in synchronism with the rotation of the aerials and having its output passed through a phase adjuster 15 to the deflection control, circuit 10. In order to produce a radial sweep of constant velocity commencing with each transmission of a pulse from the aerial 1, a linear saw-tooth generator 16 is connected to the transmitter 7 so that a fly-back is caused each time a pulse is transmitted. This saw-tooth voltage is injected at 13, Fig. 2. When an echo is received on aerial 2 it is passed through the receiver 8 to the control grid of the cathode-ray tube 9 and beam current is momentarily set up or cut off, producing or suppressing an illuminated spot at the position to which the beam has been deflected by the voltages derived from the circuit 10.