Communications: directive radio wave systems and devices (e.g. – Radar reflector
Patent
1993-01-08
1994-08-30
Hellner, Mark
Communications: directive radio wave systems and devices (e.g.,
Radar reflector
342 10, H01Q 1500
Patent
active
053432029
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND TO THE INVENTION
The present invention relates to a radar reflector structure of the type used, for example, to enhance the radar signature of an aircraft, ship or other vehicle.
The present applicant's earlier unpublished application number 8911792.3 and published application GB-A-2216725 disclose reflector structures formed from a number of trihedral re-entrant corner reflectors, each corner reflector comprising three planar elements lying at angles to each other. It has previously been proposed to form such structures either by folding from a single blank or by joining together a number of separate elements with hinges. The use of hinges has the advantage that the structure can be made to fold flat for storage prior to deployment. As described in GB-A-2216725 the structure may be made self-erecting by the use of springs fitted between the elements so as to pull them into the desired shape. Although mechanical hinges may be used these are costly to produce and because of their physical bulk place constraints on the location of the hinge axes. The assembling of the separate reflector elements and the fitting of the hinges also adds considerably to the time taken for manufacture.
SUMMARY OF THE INVENTION
According to the present invention, in a radar reflector structure including a plurality of reflector elements which in use are arranged in a non-planar configuration, the reflector elements include a thin flexible member extending between adjacent reflector elements substantially at or below the surface of the elements, the thin flexible member thereby providing a flexible hinge between the elements.
Preferably the reflector elements are formed as laminates including a rigid layer and the thin flexible member is provided by a layer of the laminates extending integrally across adjacent reflector elements.
By forming the reflector elements with a flexible member which extends between a number of different elements, the present invention provides an integral hinge between the elements. This hinge is considerably less expensive in terms of materials and manufacture by comparison with conventional mechanical hinges and has the further important advantage of a greatly reduced physical bulk. Such a hinge can then be freely formed where required without the constraints on positioning associated with bulky mechanical hinges and without detracting from the ability of the structure to be collapsed into a flat low-volume configuration for storage prior to deployment.
Preferably the thin flexible layer is a polymeric plastics film adhesively bonded to the surface of the reflector elements. More preferably, the thin film is a polyester or polyimide film.
Preferably the reflector elements are formed from printed circuit board (PCB) laminates including a metal layer on at least one surface.
The present inventor has found that the widely available PCB laminates are particularly suitable for forming the reflector elements of the present invention. PCB is available in a wide variety of compositions. Epoxide, polyester, polyimide, and polyether-ether ketone resins are used with many fibre fillers, typically glass which may be in the form of glass cloth, to provide the rigid core. The glass cloth is usually woven, but fibres may be aligned in a single direction, in which case preferably the direction of alignment is substantially normal to the line of the hinge.
Typically one or preferably two surfaces of the PCB laminate are coated with copper. Normally this copper would be etched away to form a circuit, but in the present invention the copper layer is left whole to provide the required reflective properties of the element. PCB laminates have the further advantages of being flat, rigid, tough and heat resistant.
For reflecting radar at substantially 10 GHz, preferably the reflector laminate includes a metal layer having a thickness in the range 0.01 to 1 mm. More preferably the thickness is substantially 0.2 mm.
The preferred thicknesses for the metal layer give highly efficient reflection of radar. Thicker la
REFERENCES:
patent: 2721998 (1955-10-01), Holm
patent: 4028701 (1977-06-01), Parks et al.
patent: 4195298 (1980-03-01), Firth
GEC - Marconi Limited
Hellner Mark
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