Patent GB-1178614-A (GB)
Title: Apparatus for use in Identifying an Object
Inventor: KAWAHARA MASAO
IPC: G01S13/75
Filed: 1967-02-27
Abstract: 1,178,614. Track apparatus. TOKYO SHIBAURA ELECTRIC CO. Ltd. 27 Feb., 1967 [2 March, 1966; 25 March, 1966], No. 9201/67. Heading B7N. [Also in Division H4] Apparatus for identifying an object having a response device comprises a transmitter and a receiver, a plurality of angle modulated signals with different carrier frequencies being transmitted and the receiver being responsive to characteristically distorted signals returned by the said response device. As described, signals of differing frequency generated at a transmitter 1, Fig. 1a, by a plurality of oscillators, 4 1 , 4 2 , ... 4 n  are angle modulated in modulators 5 1 , 5 2 , ... 5 n  by signals at a common frequency # m  generated in an oscillator 6. The outputs from the modulators are combined and are transmitted from an aerial 7 to a receiving aerial 8, Fig. lb, in a response device 2 carried by the object to be identified. Switches 11 1 , 11 2 , ... 11 n  are set according to the coding of the object and desired received signals pass through capacitors 9 1 , 9 2 , ... 9 n  and filters 10 1 , 102, . . . 10 n  to a retransmitting aerial 82. The re-transmitted signals are received on an aerial 12, Fig. lc, in a receiver 3, and are separated according to their carrier frequencies by band-pass filters 13 1 , 13 2 , ... 13 n . The angle-modulated signals, which have experienced characteristic distortions during their passage through the capacitor/filter circuits of the response device, are detected by first envelope detectors 14 1 , 14 2 , ... 14 n . Bandpass filters 15 1 , 15 2 , . . . 15 n  following the said first envelope detectors select signals of required frequency (as described, 2# m ) for feeding to second envelope detectors 16 1 , 16 2 , ... 16n and amplitude/timing discriminators 17 1 , 17 2 , ... 17 n . The first envelope detectors in the receiver may be replaced by synchronous detectors (18 1 ), (18 2 ), ... (18 n ), Fig. 5 (not shown), which are connected to the output sides of respective modulators in the transmitter through phaseshifters (19 1 ), (19 2 ), . . . (19 n ). In a second embodiment a clock pulse generator (31), Fig. 7 (not shown), operates gates (32 1 ), (32 2 ), . . . (32 n ) in the modulator circuits of the transmitter, so that their outputs are connected successively to the transmitting aerial. At the receiver a single receiving circuit is provided, and its output is connected successively to utilization circuits, corresponding to the different carrier frequencies, by gates (33 1 ), (33 2 ), ... (33 n ) which are operated successively by the clock pulse generator (31). The system may be used for the identification of railway wagons and in a third embodiment an arrangement is described in which combined transmitting and receiving aerials, which may operate on the induction field, are provided both on the object and for the ground equipment (41), ), Fig. 8 (not shown). The transmitter (42) and the receiver (46) of the equipment (41) may be coupled to a common aerial (44) by a simple capacitor/resistor network (43)/(45) or a bridge circuit may be provided. In a fourth embodiment, two spaced-apart combined transmitting and receiving aerials 44 1 , 44 2 , Fig. 10, are provided for the ground equipment. The two aerials are paralleled on a transmitter 42, but are connected to a receiver 46 through a difference circuit 64. When an aerial 48 of the response device 47 carried by the object traverses the aerials 44 1  44 2 , the receiver 46 receives output first from one and then from the other. Any background noise may be assumed to affect the aerials 44 1 , 44 2  equally, and hence no noise output passes to the receiver 46.