GB637642A - Improvements in or relating to radio detection and direction finding with pulse signals - Google Patents

Abstract

637,642. Radiolocation. STANDARD TELEPHONES & CABLES, Ltd. May 5, 1944, No. 8596. Convention date, Feb. 27, 1943. [Class 40 (vii)] In a pulse radar system comprising a cathoderay tube display and a directive aerial having a beam radiation pattern, the aerial beam is cyclically switched into four directions equally inclined and symmetrically disposed with respect to the reference axis of the aerial and the transmitter pulsing and time-base sweep voltage are synchronized with the aerial switching so that a single pulse is transmitted in each switching period and echo pulses received from a particular reflecting object during different switching periods produce separate indications, means being provided for changing the direction of the reference axis until the indications are all of the same quality in order to align the axis with the reflecting object. As shown, the aerial beam is switched by continuously energizing the central dipole unit 10e and successively energizing the outer units 10a, 10b, 10c and 10d by means of the switching unit 51 which is operated by a motor 50 driven by a voltage of switching frequency f (i.e. one quarter of the pulse recurrence frequency) from the oscillator 29 which is synchronized by the transmitter 20, and a harmonic of frequency (4n+1)f where n is any integer is generated at 30 and applied in phase quadrature via valves 32 and 33 to the perpendicular plates of the cathode-ray tube 24 to produce a circular trace which is normally blacked out, echo pulses from the receiver 22 being applied to the grid 68 and/or focusing electrode to give bright spot indications. In each pulse recurrence period the cathode-ray describes (n+“) revolutions so that the echoes received in successive switching periods are displayed on successive quadrants of the trace. The two pairs of alternate beam directions, e.g. those produced by the aerials 10a, 10c and 10b, 10d, respectively, are in mutually perpendicular planes, and the corresponding spot indications 71a, 71c and 71b, 71d are located at the extremities of mutually perpendicular diametrical lines 72 and 73. The aerial system is rotatable about the horizontal and vertical shafts 12 and 16, and is positioned so that all four spots are of equal intensity and/or size, the axis of the aerial systems being then directed towards the obstacle when the elevation and azimuth can be read off the controlling and indicating devices 15 and 19. The range is determined by the position of the spot in the quadrant and may be read off the scale 75. The receptive portion of the system may be used separately to determine the direction of any source of radiated pulses. The aerial system 10 is of the type described in Specification 606,124. Specification 582,521 also is referred to.