Patent GB-1130050-A (GB)
Title: Improvements in coded identification members
IPC: G01S13/75
Filed: 1966-09-30
Abstract: 1,130,050. Wagon identification. ABEX CORP. 30 Sept., 1966 [20 Oct., 1965], No. 43885/66. Heading B7N. [Also in Division H4] A coded identification member adapted to be scanned by radiant energy from a transmitter comprises a plurality of first code elements each representing one binary value and which reflect back energy in a form which is detectable by a receiver, and one or more second code elements each representing another binary value and from which any energy which is reflected back is not in a form which is detectable by the receiver, all said code elements being adjacent, and the width of each first code element being greater by an integral multiple than the width of each second code element. As described, a coded identification member (14), Fig. 1 (not shown), which may be fixed to a railway truck (12) and be scanned as it passes by a microwave beam from a track side station (11), comprises a frame 200, Fig. 3, in which a number of code elements 201-212 are held side-by-side. Code elements 201, 207, 212 (referred to as type A) are each provided with five vertically arranged depressions constituting V-reflectors, whose apexial axes are at 45 degrees to the horizontal, and code elements 203, 208, 210 (referred to as type B) are similar, but with the apexial axes of their V-reflectors at 135 degrees to the horizontal. The said apexial axes of the type A and type B code elements are arranged on a convex curved surface 236, Fig. 7, which is approximately tangential to a plane normal to the direction 237 of the scanning beam. The code elements of types A and B which comprise V-reflectors are representative of binary ones. The remaining code elements 202, 204, 205, 206, 209, 211 (referred to as type C) have plain surfaces and are representative of binary zeros. Each code element is provided with lugs and depressions on each side which mate with those on adjacent elements, except that it is arranged that a type A or a type B code element cannot be fitted to follow one of the same types. In use, horizontally polarized microwave radiation is focused in a narrow vertically extending band (56), Fig. 2 (not shown), upon a coded identification member (14C) by apparatus at the said trackside station comprising a transmitting aperture at the end of a waveguide (16C), a semicircular zone plate lens (51) and a horizontal polarizing grid (101). Each type A or type B code element in the member (14C) reflects back radiation as it passes by which has its plane of polarization turned by 90 degrees, that is, is vertically polarized. This passes through a vertical polarizing grid (102) and is focused upon a receiving aperture at the end of a waveguide (18C). Type C code elements do not reflect back radiation which is vertically polarized. An earthed conductive plate (62) extends horizontally backwards from the common axis of the lenses (51), (52) and screens the receiving equipment, comprising a detector-amplifier (46) and a decoder (48) fed from the waveguide (180), from the transmitting equipment, comprising a power supply (41) and a klystron oscillator (42) feeding the waveguide (16C). It is stated that by having the widths of the type A and type B code elements twice or another integral multiple value of the width of a type C code element, a simplified parity check may be applied.