Patent GB-763040-A (GB)
Title: Aerial navigation indicator
IPC: G01S1/02
Filed: 1954-09-24
Abstract: 763,040. Radio navigation. STANDARD TELEPHONES & CABLES, Ltd. Sept. 24, 1954 [Sept. 29, 1953], No. 27665/54. Class 40(7), Relates to a mobile receiver for use in conjunction with a beacon of the type in which three transmitting aerials located at the corners of an equilateral triangle are energized cyclically in pairs (recurrence period one second) to give three bidirectional partiallyoverlapping lobes, Fig. 1 (not shown), the angular spacing between successive lobes being 60 degrees and the three energization periods being preceded by a "silent synchronization period" as shown in Fig. 2 A. According to the present invention the signals received at the mobile receiver are applied to the single input field element of an electro-mechanical resolver having three symmetrically disposed output field elements, the orientation of the input field element relative to the output field elements being adjustable and the three outputs are connected sequentially by a distributer to a storage circuit whose output actuates a left/right indicator such that a null indication is produced when the angular setting of the resolver corresponds to the bearing of the receiver from the beacon; means are also provided for automatically synchronizing the distributer with the beacon keying cycle and for indicating when such synchronism is effected. Altenatively the resolver may comprise three symmetrically disposed input field elements and a single output field element, the receiver output signals being applied sequentially to the input elements and the output element being connected continuously to the storage circuit; in either case the resolver may utilize resistive, inductive or capacitative coupling and either the single element or the spaced elements may be rotatable. As shown in Figs. 2 and 3 the 1500 c/s I.F. output, Fig. 2 B, from receiver 11 is applied through pre-amplifier 13 to a mechanical or electrical vibrator 22 which chops the signal at 230 c/s the chopped signal being applied to a square law detector 23 whose 230 c/s output is applied to the rotor 27 of resolver 28. The three stators of resolver 28 are connected sequentially through the contacts of relays 24; 25; 26 respectively to a synchronous rectifier 29 mechanically' synchronized with chopper 22 and the output from rectifier 29 is applied through a storage circuit 30 and amplifier 31 to the left/right indicator 32 which gives a null indication when the angular position of rotor 27 as set and indicated by the bearing selector 33 corresponds to the bearing of the mobile receiver from the beacon and when the relays 24, 25, 26 are operated cyclically by distributer 21 in synchronism with the beacon keying cycle; alternatively the rotor 27 may' be set automatically by a servomotor controlled by the output from amplifier 31. A second output from pre-amplifier 13 is applied through halfwave detector 17 (output Fig. 2 D) to a filter 18 giving a 4 c/s sine wave, Fig. 2 E, which is squared in shaper 19 and applied through the normally open gate 20 to control distributer 21 and a third output from pre-amplifier 13 is applied through detector 15 (output Fig. 2 C) to a multivibrator 36 controlling gate 20 via the contacts of a further relay in the synchronization checking circuit 16 which is also controlled by an output from distributer 21. If distributer 21 is correctly synchronized, the contacts of the further relay in circuit 16 will make during the " silent synchronization period,". so that no signal is applied to multibrator 36 and gate 20 remains open but if distributer 21 is not correctly synchronized then during the make period of the further relay in circuit 16 a signal is applied to multivibrator 36 thereby closing gate 20 for a quarter of the keying cycle and causing distributer 21 to miss a step, the process being repeated until correct synchronism is achieved; the state of synchronization is indicated by a flag alarm 37 actuated by circuit 16 A. G. C. for receiver 11 is provided by circuit 14 which must be extremely slow acting in order not to disturb the amplitude ratio of the received signals.