Patent GB-601725-A (GB)
Title: Direction and distance indicating system employing electromagnetic waves
IPC: G01S7/12
Filed: 1944-05-31
Abstract: 601,725. Radiolocation. STANDARD TELEPHONES & CABLES, Ltd. May 31, 1944, No. 10491. Convention date, Feb. 28, 1941. [Class 40 (vii)] In a radio detecting system employing reflection of electromagnetic waves modulated by periodic pulses of duration period short relative to the repetition period, the distance and bearing of a distant object are sirriultaneously indicated on the screen of a cathode-rav tube of which the ray is subjected to fields producing radial and rotational motion by means independent of the signal produced by the reflected waves. In the arrangement shown in Fig. 6, the deflecting coils 14 fed with saw-tooth voltages from a generator 17 are rotated by a servomotor 30 in synchronism with the receiving antenna 16 and with the transmitting antenna 32, if the latter is also directional. Impulses are applied to the antenna 32 from a transmitter 31 controlled by a generator 33 which also controls the generator 17, and a blanking oscillator 34 may be included to cut out the receiver 18 during pulse transmission. The signals from the receiver 18 are passed to the control electrode 21 of the cathode-ray tube 13 so that, as indicated in Fig. 5, an arc 7 of luminous points appears on the screen 1 when reflections from the object take place. The determination of distance and bearing is facilitated by a rotatable alidade OCAB, comprising a graduated scale 11, and preferably constructed so that its central portion is more transparent than the outer portions. The coils 14 are preferably orientated so that at any moment the radial line on the screen corresponds to the main directive axis of the antenna 16. The pairs of plates of the cathode-ray tube may be fed with voltages from a modulator which is coupled to a two-phase voltage source linked to the rotating antenna system and which is connected to a generator of saw-tooth voltages, Fig. 7 (not shown). In a modified scanning control, Fig. 8, the saw-tooth voltages are applied to an inner conical electrode 43 and to an outer frusto-conical electrode 42, the voltages for the pairs of plates 27, 28 being derived from a two-phase voltage source 23 controlled by the rotating antenna system. Specification 520,778 is referred to. The Specification as open to inspection under Sect. 91 includes an arrangement in which the transmitted electromagnetic waves are frequency modulated and the received waves mixed to obtain the beat frequency which is fed to a detecting circuit controlling the output voltage of the sweep circuit so that the maximum amplitude of the radial lines on the screen indicates the distance and the position of the peak defines the direction of the reflecting object. In a further modification, the beat frequency fed to a circuit tuned over a prescribed range in a time corresponding to the radial scanning line on the screen produces a corresponding spot or spots which define the distance and bearing of the object. The employment of an omni-directional transmitter near the reflecting object to provide a radio compass system is also referred to. This subject-matter does not appear in the Specification as accepted.