Patent GB-616113-A (GB)
Title: Improvements in or relating to apparatus for indicating on the screen of a cathode ray tube the range and bearing of an object
IPC: G01S7/10
Filed: 1946-08-28
Abstract: 616,113. Radiolocation. COMPAGNIE POUR LA FABRICATION DES COMPTEURS ET MATERIEL D'USINES A GAZ. Aug. 28, 1946, No. 25740. Convention date, Oct. 19, 1939. [Class 40 (vii)] An apparatus for displaying a representation of the range and bearing of a distant object in polar co-ordinates on the screen of a cathoderay tube comprises means for transmitting steep fronted trains of oscillations, which may be electromagnetic, ultra sonic, sonic or infra sonic, having a velocity of propagation large compared with any possible relative speed of said object and the observing apparatus, means for receiving oscillations reflected from said object, either the transmitting or receiving means having a directional characteristic so that a minimum or maximum response to the reflected oscillations is obtained when such means is directed towards the object and means for deflecting the beam of the cathode-ray tube so that the point of impingement of the beam on the screen describes a circular trace of radius determined by the time elapsing between the transmission and reception, after reflection from the object, of the oscillations, and means controlled by the direction of said transmitting or receiving means to vary the trace either in brightness or shape at a point corresponding to said direction. Steep-fronted trains of radio energy radiated from a transmitter 1 and reflected from a distant object 10 are received by a directive receiving system 2. A two-phase generator 3 feeds a modulating device 9 connected to the deflection means of cathode-ray tube 8 to produce a circular trace. The radius of this circular trace is determined by modulator 9 in accordance with the difference in time between the transmission and reception of the pulses; the circuit may comprise a source of constant current, a resistor, and gas triode valve switch, the switch being switched on by transmission and off by reception so that the integral of the potential across the resistor may be used to control the gain of the deflection amplifier which is thus made dependent on range. The two-phase generator is also connected to variable phase shifter 4-set in accordance with the direction of the receiving antenna so that the phase of the output is dependent on bearing. The phase shifter output is applied to a shaping circuit 6 connected to intensity modulating electrode 7, whereby a short bright spot dependent on the bearing direction appears on the circular trace. Alternatively the output of circuit 6 may be applied to deflect the beam to produce a jag or notch in the trace at a position corresponding to the direction of the object. An indicator 5 of received signal amplitude, which may be a cathode-ray oscillograph, is associated with receiving system 2 so that the aerial system may be accurately directed towards the object. If the angle of elevation from which the reflected energy is received is determined as, for example, by the use of a transmitter or receiver directive in both elevation and azimuth, the position in space of the object may be completely determined. The Specification as open to inspection under Sect. 91 comprises also a second display apparatus (Fig. 2, not shown), in which pulses are transmitted under control of a sinusoidal wave generator whose output is also fed to the search coil of a goniometer which is positioned according to the direction of reception of the receiving system. The outputs of the field coils of the goniometer are applied to the deflection elements of a cathode-ray tube to produce a radial line scan in a direction corresponding with the direction of reception. Received signals are used to modulate the scan at a position along it dependent on the time of travel of the oscillations to the object and back. The radial range scale of this apparatus is sinusoidal and may be varied by adjustment of the master generator. This subject-matter does not appear in the Specification as accepted.