Patent GB-1100872-A (GB)
Title: Radio navigation system
IPC: G01S13/78
Filed: 1965-04-15
Abstract: 1,100,872. Radio navigation. INTERNATIONAL STANDARD ELECTRIC CORPORATION. 15 April, 1965 [17 April, 1964], No. 16176/65. Heading H4D. The Specification describes a D.M.E. or TACAN interrogator receiving replies from two or more responder beacons at the same frequency and which tracks only on the responses from the nearest beacon and gives warning when responses are from more than one beacon, either by counting the responses or by determining when the amplitude of the signals from a further beacon is dangerously high compared with that of the signals from the nearest beacon. In the embodiment of Fig. 1, responses are decoded at 6 and fed to contact r 1  of relay R. A rotation control means 1, rotates a resolver 2 and a potentiometer 3 via reduction gears. The outputs of the resolver and potentiometer are fed to a combiner 4 and produce a gating pulse which " walks " with rotation of potentiometer 3 during the search mode and is stationary during the tracking mode. In the tracking mode, when tracking the response from the nearest beacon, a relay K in a circuit 7 fed by a gate 5 receiving the response and gating pulse simultaneously, is energized. Contact k is thus closed, energizing relay A. Control a is thus open, allowing capacitor C to charge. Relay R is energized via contacts r 2  and S. Contact r 1  is closed. Therefore let the tracking mode be lost, whence, relay K is de-energized, opening contact k and de-energizing relay A. Contact a is closed, momentarily energizing relay S from capacitor C. Contact S is momentarily opened de-energizing relay R. Contacts r 1  and r 2  are thus opened such that relay R is locked de-energized and responses from further beacons cannot reach gate 5 via contact r 1 . Potentiometer 3 is now rotating in the search mode until a cam rotating therewith causes contact d to close at a time representing zero range. Relay R is now energized and locked so via contacts r 2  and S, such that the response from the nearest beacon can pass contact r 1  to gate 5. In the response counting arrangement of Fig. 3, each response causes an output pulse from monostable circuit 10. After amplification at 11, these are counted in integrator/counter 12 and when the charge on capacitor 21 reaches a level indicating that responses from more than one beacon are being received, a relay coil 28 in the cathode circuit of follower 13, is energized, whereby horn 32 and light 33 contacts 30 and 31 respectively are closed. In the arrangement of Fig. 4, for comparing the amplitude of responses from the nearest beacon and from the next nearest, two circuits as shown in Fig. 1 are provided, one 37 for the nearest beacon and the other 41 for the other beacon. These circuits are used to supply separating signals to gates 48 and 49 also supplied with all the responses, whereby the responses from the nearest beacon are fed via amplifier 50 to one input of amplitude comparator 52, and the responses from the other beacon are fed via amplifier 51 to the other input of amplitude comparator 52. The amplification of amplifiers 50 and 51 are so adjusted, that comparator 52 gives an output signal energizing alarm 53 when the amplitude of the responses from the further beacon rises too high relative to that of the responses from the nearest beacon.