Patent GB-1234502-A (GB)
IPC: G01S13/91
Filed: 1969-01-13
Abstract: 1,234,502. Radio navigation. P. P. SCHAUFFLER. 13 Jan., 1969, No. 13822/69. Divided out of 1,234,501. Heading H4D. In a channel guidance system a beacon A 1 , Fig. 1, transmits a pulse followed by reflected pulses from all vehicles in the channel and on a vehicle the train of pulses is received, the reflected pulse corresponding to the vehicle is identified and the distance w from the beacon is measured. In an embodiment the beacon also transmits relatively long and sequential pulses on overlapping beams F 1 , F 2  whereby the vehicle can determine its lateral offset x from the relationship x = bw. At the beacon, Figs. 2A, 5A a received synchronizing pulse H 1  triggers a monostable circuit 5, the position of the trailing edge of the output pulse J 1  being selectable. " Distance ",T 1  to T 2 , and " angle ", T 2  to T 3 , intervals of equal duration are defined by monostable circuits 6, 7 which generate respective pulses K 1 , P 1 . The overlapping beams F 1 , F 2  are produced by respective aerials 19a, 19b which are connected by normally closed electronic switches 18a, 18b to a transmitter 15. During the distance interval a pulse L 1  derived from pulse K 1  triggers radar transmitter 10 and the ensuring radar receive video signal M 1  (which includes a radar transmitter leakage pulse as the first one) is transmitted simultaneously by beams F 1 , F 2 . During the angle interval, switches 18a, 18b are controlled by respective pulses S 1 , R 1  from monostable circuits 17, 16 such that beacon pulses V 1a , V 1b  are transmitted sequentially on beams F 1 , F 2 . At the vehicle, Figs. 2B, 5B pulses J 2 , K 2  and P 2  are derived from the synchronizing pulse (the first pulse in trains G 2 , H 2 ) in a manner corresponding to that at the beacon but pulse J 2  terminates shortly before the instant T 1 . During the distance interval, pulse K 2  actuates a sweep generator 56 to apply a vertical timebase L 2  to a cathode-ray tube (C.R.T.) 52, and operates a switch 51 to apply the radar pulse train M 2  of the received signals to (i) intensitymodulate C.R.T. 52 and (ii) a monostable circuit 54 which is accordingly triggered by the first pulse (corresponding to the radar transmitterleakage component at the beacon) of train M 2  to give a variable duration output pulse N 2  which is differentiated to produce a range strobe O 2  applied to intensity-modulate C.R.T. 52. The timing of the strobe is varied by a motor unit 53, adjusted manually at a known position of the vehicle to make strobe O 2  coincident with the echo pulse Ty corresponding to the vehicle, the coincidence condition being thereafter maintained automatically utilizing a discriminator 57. During the angle interval T 2  to T 3  the received beacon pulses B 1 , B 2  are selected by switches 60a, 60b stretched in circuits 61a, 61b the outputs from which are applied to a centrezero angular displacement indicator 62 and to a differential amplifier 70 to afford a voltage proportional to angle b, Fig. 1, and which is multiplied by distance-controlled potentiometer 71 to afford a display of lateral offset x which is also recorded. Modifications.-The angle pulses may be simultaneous and differentiated by different modulation. Visual and/or audible alarms can be incorporated in the offset circuit to warn of departure from the centre-line of the channel and in the distance circuit when transition to the next beacon is necessary. At each beacon the radar transmission may be shifted sequentially on beams similar to beams F 1 , F 2 , the corresponding radar signals relayed to the vehicle being presented on two adjacent sweeps on C.R.T. 52, Fig. 2B. Additions.-A beacon A 2 , Fig. 1, with beams F3, F 4  may be added; additional beams F 5 , F 6  may be provided; and separate beacons A 3 , A 4  may be utilized for inbound and outwardbound traffic lanes.