Corner reflector

Abstract

A corner reflector has a plurality of trihedral pairs. Each trihedral pair has a rib, a first wing and a second wing to a first side of the rib, the rib. The first wing and the second wing together define a first trihedral of the trihedral pair. Each trihedral pair have a third wing and a fourth wing to a second side of the rib. The rib, the third wing, and the fourth wing together define a second trihedral of the trihedral pair. The corner reflector is operable between a stowed condition and a deployed condition. In the stowed condition the first wing and third wing of each trihedral pair are each stowed against a respective rib of the trihedral pair. In the deployed condition each of the wings of each trihedral pair are angled relative to their respective rib.

Description

CORNER REFLECTORFIELD OF TECHNOLOGY

[0001] The present invention relates to corner reflectors and assemblies and methods of operation of the same, and more particularly but not solely to buoyant flat-pack corner reflectors which are deployable to define a substantially hemispherical corner reflector.BACKGROUND

[0002] Corner reflectors are a form of retroreflector which operate to reflect incident waves back at the source, with a lateral translation.

[0003] Corner detectors may be used in applications such as location-marking and radarguidance interference. Examples of location marking may include search and rescue operations, for example where a vessel or mariner has to be rescued from the sea, or a person rescued from land location.

[0004] It is an object of the disclosure to provide an improved corner reflector which addresses or ameliorates one or more disadvantages or limitations associated with the prior art, or at least to provide the public with a useful choice.SUMMARY

[0005] This international application claims priority to and incorporates by reference in its entirety New Zealand Provisional Patent Application No. 814411 , filed 9 September 2024.

[0006] In a first aspect, the disclosure provides a corner reflector comprising a plurality of trihedral pairs, each trihedral pair having: a rib, a first wing and a second wing to a first side of the rib, the rib, the first wing, and the second wing together defining a first trihedral of the trihedral pair, and a third wing and a fourth wing to a second side of the rib, the rib, third wing, and the fourth wing together defining a second trihedral of the trihedral pair, wherein the corner reflector is operable between: a stowed condition in which the first wing and third wing of each trihedral pair are each stowed against a respective rib of the trihedral pair, and a deployed condition in which each of the wings of each trihedral pair are angled relative to their respective rib.

[0007] In operation from the stowed condition to the deployed condition the trihedral pairs are rotated relative each other about a common axis.

[0008] The first wing and the second wing of each trihedral pair are each pivotably associated with their respective rib.

[0009] The corner reflector of any one of claims 1 -3, wherein in operation from the stowed condition to the deployed condition, the first wing and the second wing of each trihedral pair are each pivoted about their respective rib.

[0010] In each of the plurality of trihedral pairs: a) the first wing and the third wing are each pivotably associated with the rib, b) the second wing and the fourth wing are each pivotably associated with the first wing, and c) the second wing and the fourth wing are pivotably associated with each other.

[0011] The rib and each of the wings of each of the plurality of trihedral pairs are planar.

[0012] The rib and each of the wings of each of the plurality of trihedral pairs have a planar isosceles triangular form, each having two sides of substantially equal length.

[0013] The corner reflector is operable from the stowed condition to the deployed condition by a reconfiguration of each trihedral pair, the reconfiguration of each trihedral pair comprising: a) a pivoting of the first wing and the third wing about the rib, and b) a pivoting of the second wing and the fourth wing about both of i) the respective ones of the first wing and the third wing, and ii) each other.

[0014] In the stowed condition each of the first wing and the third wing of each trihedral pair are oriented to be substantially plane-parallel with their respective rib.

[0015] In the stowed condition each of the first wing and the second wing or the third wing and the fourth wing of each trihedral pair are oriented to be substantially plane-parallel with their respective rib.

[0016] In the deployed condition each of the first wing and the second wing or the third wing and the fourth wing of each trihedral pair are oriented to be non-plane-parallel to their respective rib.

[0017] The corner reflector is operable from the stowed condition to the deployed condition by a user by a single rotational action.

[0018] The corner reflector is operable from the stowed condition to the deployed condition by a pivoting of the trihedral pairs relative to each other about a central axis such that a first face of the corner reflector in the stowed condition abuts a second face of the corner reflector which is, in the stowed condition, opposite to the first face of the corner reflector.

[0019] When operated to the deployed condition from the stowed condition the corner reflector is configured to be retained in the deployed condition.

[0020] The corner reflector comprises a bias towards the deployed condition, and a removable retainer configured to retain the corner reflector in the stowed condition.

[0021] The plurality of trihedral pairs are buoyant in the deployed condition of the corner reflector.

[0022] The corner reflector is buoyant without any structure additional to the plurality of trihedral pairs.

[0023] In the deployed condition a centre of mass of the plurality of trihedral pairs is lower than a centre of buoyancy of the plurality of trihedral pairs.

[0024] The rib and each of the wings of each of the plurality of trihedral pairs are electromagnetically reflective.

[0025] The rib and each of the wings of each of the plurality of trihedral pairs are microwave radar reflective.

[0026] The rib and each of the wings of each of the plurality of trihedral pairs comprise a substrate, the substrate having a radar reflective surface.

[0027] The substrate comprises a buoyant material.

[0028] The substrate comprises a corrugated plastic.

[0029] The surface of the substrate comprises a radar reflective coating.

[0030] The surface of the substrate comprises a laminated film to define the radar reflective surface of the substrate.

[0031] The laminated film comprises a flexible plastic and a micron-thickness aluminium coating.

[0032] The corner reflector in the deployed condition defines a substantially hemispherical corner reflector.

[0033] In the deployed condition the plurality of trihedral pairs of the corner reflector approximate an about 350-degree azimuth and about 180-degree altitude reflector.

[0034] The corner reflector in the deployed condition is buoyant in water.

[0035] The corner reflector in the stowed condition has peripheral dimensions equal to the peripheral dimensions of the first wing and second wing and a portion of the rib of a trihedral pair of the corner reflector.

[0036] The corner reflector is configured to, in the deployed condition, to provide a plurality of radar return vectors oriented for space-based observation.

[0037] The corner reflector is configured to, in the deployed condition, provide radar return vectors oriented for detection by synthetic aperture radar.

[0038] The corner reflector in the deployed condition is configured to provide a plurality of lateral radar return vectors, the plurality of lateral radar return vectors being oriented about an azimuth circle of the corner reflector and located between an altitude of about 20 degrees and about 70 degrees.

[0039] The plurality of lateral radar return vectors are oriented between an altitude of about 30 degrees and about 60 degrees.

[0040] The corner reflector in the deployed condition is configured to provide a plurality of overhead radar return vectors, the plurality of overhead radar return vectors being oriented about an azimuth circle of the corner reflector and between an altitude of about 70 degrees and about 90 degrees.

[0041] The plurality of overhead radar return vectors are oriented between an altitude of about 80 degrees and about 90 degrees.

[0042] In the deployed condition, the corner reflector defines at least two lines of symmetry.

[0043] In the deployed condition, the corner reflector defines four lines of symmetry.

[0044] The lines of symmetry are about a or the central axis of the corner reflector in the deployed condition.

[0045] The corner reflector comprises four trihedral pairs.

[0046] A peak of the corner reflector in the deployed condition is defined at an intersection of the ribs of each of the plurality of trihedral pairs.

[0047] Except for at a first face of the corner reflector in the stowed condition and a second face of the corner reflector in the stowed condition, the second face being opposite the first face, the first wing and the third wing of each adjacent trihedral pair are the same component.

[0048] In the deployed condition, laterally peripheral-most portions of the corner reflector are defined by the second wing, the fourth wing, and the rib of each trihedral pair.

[0049] A base of the corner reflector in the deployed condition is defined at a mutual intersection of the second wing and the fourth wing of each of the plurality of trihedral pairs.

[0050] In the deployed condition, laterally peripheral-most portions of the corner reflector are defined by: a) the first wing, the fourth wing, and the rib of each trihedral pair, and b) the second wing of each trihedral pair and a laterally adjacent first fourth wing of another of the plurality of trihedral pairs.

[0051] The corner reflector has a plurality of bases in the deployed condition, and each base of the plurality of bases is defined at a mutual intersection of the first wing, the second wing, the third wing, and the fourth wing of each of the plurality of trihedral pairs.

[0052] The plurality of bases are radially spaced away from a or the central axis of the corner reflector.

[0053] In another aspect, the disclosure provides a flat-packed deployable corner reflector comprising a plurality of trihedral pairs, each trihedral pair having: a rib,a first wing and a second wing to a first side of the rib, the rib, the first wing, and the second wing together defining a first trihedral of the trihedral pair, and a third wing and a fourth wing to a second side of the rib, the rib, third wing, and the fourth wing together defining a second trihedral of the trihedral pair, wherein the rib and each of the wings of each trihedral pair comprise a buoyant substrate having a surface comprising a radar reflective material, and wherein the corner reflector is operable from a flat-packed condition to a deployed condition in which the corner reflector has a substantially hemispherical form and is buoyant by a pivoting of the trihedral pairs relative to each other about a notional central axis such that a first face of the corner reflector in the flat-packed condition abuts a second face of the corner reflector which is, in the flat-packed condition, opposite to the first face of the corner reflector.

[0054] The plurality of trihedral pairs are buoyant in the deployed condition.

[0055] The corner reflector is buoyant without any structure additional to the plurality of trihedral pairs.

[0056] In the deployed condition the centre of mass of the plurality of trihedral pairs is lower than a centre of buoyancy of the plurality of trihedral pairs.

[0057] In each of the plurality of trihedral pairs: a) the first wing and the third wing are each pivotably associated with the rib, b) the second wing and the fourth wing are each pivotably associated with the first wing, and c) the second wing and the fourth wing are pivotably associated with each other.

[0058] The corner reflector is operable from the flat-packed condition to the deployed condition by a reconfiguration of each trihedral pair, the reconfiguration of each trihedral pair comprising: a) a pivoting of the first wing and the third wing about the rib, and b) a pivoting of the second wing and the third wing about both of i) respective ones of the first wing and the fourth wing, and ii) each other.

[0059] The corner reflector is operable from the flat-packed condition to the deployed condition by a user by a single rotational action.

[0060] The corner reflector is configured to, in the deployed condition, to provide a plurality of radar return vectors oriented for space-based observation.

[0061] In the deployed condition, provide radar return vectors oriented for detection by synthetic aperture radar.

[0062] The corner reflector in the deployed condition is configured to provide a plurality of lateral radar return vectors, the plurality of lateral radar return vectors being oriented about anazimuth circle of the corner reflector and located between an altitude of about 20 degrees and about 70 degrees.

[0063] The plurality of lateral radar return vectors are oriented between an altitude of about 30 degrees and about 60 degrees.

[0064] The corner reflector in the deployed condition is configured to provide a plurality of overhead radar return vectors, the plurality of overhead radar return vectors being oriented about an azimuth circle of the corner reflector and between an altitude of about 70 degrees and about 90 degrees.

[0065] The plurality of overhead radar return vectors are oriented between an altitude of about 80 degrees and about 90 degrees.

[0066] The term "axis" as used in this specification means the axis of revolution about which a line or a plane may be revolved to form a symmetrical shape. For example, a line revolved around an axis of revolution will form a surface, while a plane revolved around an axis of revolution will form a solid.

[0067] As used herein the term "and / or" means "and" or "or", or both.

[0068] As used herein "(s)" following a noun means the plural and / or singular forms of the noun.

[0069] For the purposes of this specification, the term "plastic" shall be construed to mean a general term for a wide range of synthetic or semisynthetic polymerization products, and generally consisting of a hydrocarbon-based polymer.

[0070] For the purpose of this specification, where method steps are described in sequence, the sequence does not necessarily mean that the steps are to be chronologically ordered in that sequence, unless there is no other logical manner of interpreting the sequence.

[0071] The term "comprising" as used in the specification and claims means "consisting at least in part of." When interpreting each statement in this specification that includes the term "comprising," features other than that or those prefaced by the term may also be present. Related terms "comprise" and "comprises" are to be interpreted in the same manner.

[0072] This invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more said parts, elements or features, and where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.

[0073] To those skilled in the art to which the invention relates, many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the scope of the invention as defined in the appended claims.The disclosures and the descriptions herein are purely illustrative and are not intended to be in any sense limiting.

[0074] Other aspects of the invention may become apparent from the following description which is given by way of example only and with reference to the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0075] Preferred embodiments of the invention will be described by way of example only and with reference to the drawings, in which:

[0076] Figure 1 shows a corner reflector in a deployed condition.

[0077] Figure 2 shows a side view of the corner reflector of Figure 1 .

[0078] Figure 3 shows the corner reflector of Figures 1 and 2 in a stowed condition.

[0079] Figure 4 a top view of the corner reflector of Figure 3.

[0080] Figures 5A-C show stages of the deployment of a trihedral pair of a corner reflector.

[0081] Figure 6 shows a trihedral pair of a corner reflector with a reflective layer applied to a substrate of the wings and rib of the trihedral pair.

[0082] Figure 7 shows a corner reflector in a deployed condition.

[0083] Figure 8 shows a lower perspective view of the corner reflector of Figure 7.

[0084] Figure 9 shows a side view of the corner reflector of Figures 7 and 8.

[0085] Figure 10 shows a top view of the corner reflector of Figures 7-9.

[0086] Figure 11 shows a bottom view of the corner reflector of Figures 7-10.

[0087] Figures 12A-D show stages of the deployment of a trihedral pair of a corner reflector.

[0088] Figures 13A-H show plots of the simulated radar response of a corner reflector of the configuration of Figure 1 at different radar frequencies.

[0089] Figures 14A-H show plots of the simulated radar response of a corner reflector of the configuration of Figure 7 at different radar frequencies.DETAILED DESCRIPTION

[0090] The disclosure provides for various configurations of corner reflectors. Corner reflectors are a type of retroreflector which function to reflect incident waves received by the corner reflector from any direction back towards the source, with a lateral translation.

[0091] Figures 1 and 5 show two different example configurations of a corner reflector 100, shown in respective deployed conditions. The corner reflectors of the disclosure may be operable between a stowed condition and a deployed condition in which the corner reflector is configured to reflect incident waves.

[0092] The corner reflectors 100 may be utilised to reflect any form of incoming wave, such as electromagnetic waves.

[0093] In particularly but not solely, the corner reflectors 100 may be utilised for reflecting electromagnetic waves commonly associated with radar. For example, the corner reflectors 100 may be utilised for reflecting microwave radar. The frequency of microwave radars may be, for example, from about 3.5 GHz to about 14 GHz.

[0094] The corner reflectors 100 of the disclosure may be utilised in any range of applications where the generation of a strong radar return signal is desired.

[0095] Examples of such applications may include search and rescue (SAR) operations, where a person or object to be rescued may be more readily located by identification of a strong radar return signal. In such applications the corner reflector may be deployed either on land or at sea.

[0096] Other examples of applications may include marking of locations, such as harbour entrances or hazards such as reefs or bridges in maritime uses, vessel marking to ensure detection by other vessels in maritime uses, or target marking in a military context. The corner reflectors may also have applications in disrupting radar signals, such as to defeat radar homing weapons.

[0097] The outgoing radar signal in such circumstances may be provided by a ground or sea-based radar emitter. In other situations, either additionally or alternatively, the outgoing radar signal may otherwise be provided by an airborne or space-based radar emitter. In particular, the radar emitter may be a synthetic aperture radar, either from and airborne or space-based platform.

[0098] The corner reflectors 100 of the disclosure include a plurality of trihedral pairs.

[0099] As shown in Figure 1 , the corner reflector 100 has four trihedral pairs 110, 120, 130, and 140. Each trihedral pair defines two trihedrals. For example, the trihedral pair 110 of Figure 1 has a first trihedral 110a and a second trihedral 110b. Each trihedral is a set of surfaces having together three vertices which converge to a single point.

[0100] The first trihedral pair 110 has a rib 115. To one side of the rib 115 the first trihedral pair 110 includes a first wing 111 and a second wing 112. At the other side of the rib 115 the first trihedral pair includes a third wing 113 and a fourth wing 114. The wings 111 -114 may be pivotably associated with each other and / or the rib 115 to allow the trihedral 110a to be operated between a stowed state and a deployed state. The deployed state is illustrated in Figure 1 .

[0101] In the configuration of Figure 1 , the first wing 111 is pivotably associated with the rib 115, which is pivotably associated with the second wing 112. The third wing 113 is similarly pivotably associated with the rib 115 and is pivotably associated with the fourth wing 114. The second wing 112 and fourth wing 114 are also pivotably associated with each other.

[0102] In other configurations, the first wing 111 and third wing 113 and / or the second wing 112 and fourth wing 114 of a trihedral pair may be pivotably associated with each other, ratherthan being pivotably associated with the rib 115. However, it may be desirable to configure any such pivoting association such that the rib 115 does not prevent the respective first wing 111 and third wing 113 and / or second wing 112 and fourth wing 114 from becoming substantially plane- parallel with each other when the trihedral pair is stowed.

[0103] In some configurations, each trihedral pair may include its own first wing 111 and third wing 113.

[0104] In other configurations, such as illustrated in Figure 1 , the first wing 111 of a trihedral pair 110 may also define the third wing 113 of an adjacent trihedral pair 120, and the third wing 113 of the trihedral pair 110 may define the first wing 111 of a trihedral pair 140 which is adjacent to it. Where the corner reflector 100 is to be configurable between a stowed condition and a deployed condition each first wing 111 and third wing 113 of each trihedral pair may define the third wing 113 and first wing 111 of respective adjacent trihedral pairs 120 and 140, except for in one instance. One adjacent first wing 111 and third wing 113 of the corner reflector 100 may be separate from each other, so that the corner reflector 100 may be configurable in a stowed condition but also operable to a deployed condition.

[0105] The pivotable associations between the wings and / or rib of each trihedral pair may include one or more hinges. The wings and / or ribs may each define the hinges or respective components of the hinges. For example, a hinge may be provided as a living hinge between two wings or a wing and a rib which are to be pivotably associated. In other arrangements, a hinge may be attached to one or each of the wings or a wings and a rib which are to be pivotably associated.

[0106] While the corner reflector 100 of Figure 1 has four trihedral pairs 110-140, in other configurations the corner reflector may include any plurality of trihedral pairs.Conditions

[0107] The pivotable associations of the wings 111-114 and the rib 115 are operable to allow the corner reflector 100 to be reconfigured between a stowed condition and a deployed condition. In the stowed condition the corner reflector 100 has a relatively reduced size compared to the corner reflector 100 in the deployed condition. In the stowed condition each of the trihedral pairs 110 of the corner reflector may be collapsed.

[0108] Figure 3 shows a perspective view of the corner reflector 100 of Figures 1 and 2 in a stowed condition.

[0109] In the stowed condition the corner reflector may be unsuitable for use as a corner reflector but may be configured for ease of storage or transport due to its reduced size compared to the deployed condition.

[0110] The wings 111-114 and rib 115 of each of the trihedral pairs 110 of the corner reflector 100 may have an at least substantially planar form. In the stowed condition each of the wings of each trihedral pair may be configured to be substantially plane-parallel with theirrespective rib 115. In the stowed condition the respectively adjacent wings 111 -114 and ribs 115 of each trihedral pair 110 may be substantially plane-parallel with each other. In the stowed condition the corner reflector 100 may be said to be flat-packed.

[0111] In the deployed condition the wings 111-114 of each trihedral pair may be nonplane-parallel with their respective rib 115. In the deployed condition the respective adjacent wings 111 -114 and ribs 115 of each trihedral pair 110 may be oriented to be non-plane-parallel with each other.

[0112] Figures 5A-C show the deployment of a trihedral pair 110 of a corner reflector 100. Figure 5A shows the trihedral pair 110 of the corner reflector 100 in a stowed condition. Figure 5B shows the trihedral pair 110 partially operated from the stowed condition towards a deployed condition. In this operation the wings 111 -114 have been pivotably rearranged so that they open away from either side of the rib 115. The first wing 111 and second wing 112 pivot away from an adjacent side of the rib 115 by their pivotable associations. The third wing 113 and fourth wing 114 pivot away from the other side of the rib 115 by their pivotable associations. As the wings 111 and 112, and 113 and 114 expand pivot laterally away from the rib 115, the distal ends 112a and 114a of the second wing 112 and fourth wing 114 are retracted towards a distal end 115a of the rib 115. The trihedral pair 110 may be in its deployed condition when the second wing 112 and fourth wing 114 abut against the distal end 115a of the rib 115, as shown in Figure 5C.

[0113] The rib and each of the wings of each of the trihedral pairs of the corner reflectors 100 of the disclosure may be configured to be electromagnetically reflective, at least at the trihedral faces of each trihedral. In particular, such as where the corner reflectors are for reflecting radar waves, the rib and each of the wings of each trihedral pair of the corner reflector may be microwave radar reflective.

[0114] The rib and each of the wings may be integrally reflective.

[0115] In other configurations, the rib and each of the wings may include a substrate which may or may not be reflective, and a reflective layer over the substrate.

[0116] Figure 6 shows a corner reflector 100 having one trihedral pair 110 in a deployed condition. The wings 111-114 and rib 115 of the trihedral pair 110 may include a substrate 150, as illustrated in Figure 5C. As shown in Figure 6, the substrate is covered in a reflective layer 152.

[0117] Covering the substrate 150 with a reflective layer 152 may allow the wings 111 -114 and rib 115 to have reflective properties without requiring the substrate to have reflective properties. This arrangement may allow for the use of lower-cost substrate materials. It may additionally or alternatively allow for the use of substrate materials which allow the corner reflector 100 to be buoyant.

[0118] Such a reflective layer may for example be a flexible plastic with a metallic coating.The metallic coating may be a micron-thickness metallic coating. For example, the metallic coating may be about 12 microns thick.

[0119] The metallic coating may for example be an aluminium coating.

[0120] The respective pivotable associations between the wings and the rib of the corner reflector may include or may be defined by the reflective layer.

[0121] The dimensions of each of the wings 111-114 and the rib 115 of each trihedral pair 110 may be configured to provide the desired operation of the corner reflector and its operational characteristics. In at least some configurations the wings 111-114 and rib 115 of each trihedral pair 110 may substantially correspond to each other. In some configurations the wings 111 -113 and rib 115 of each trihedral pair may be identical to each other.

[0122] In other configurations one or more of the wings 111 -114 and the rib 115 of each trihedral pair may be of different sizes and / or shapes.

[0123] In at least some configurations, each of the wings 111 -114 and the rib 115 of each trihedral pair may have a substantially planar isosceles triangular form, where each has two sides of substantially equal length. The wings 111-114 and rib 115 of each trihedral pair 110 may correspond in size and shape to the respective wings 111 -114 and rib 115 of one or each of the other trihedral pairs of the corner reflector.

[0124] In some configurations, such as is illustrated in Figure 1 , the wings 111 -114 of the trihedral pair 110 have the same isosceles triangular size and shape.

[0125] In the deployed condition shown in Figure 1 , the trihedral pairs 110, 120, 130, and 140 are arranged about a central axis 118. The central axis 118 may elsewhere herein be described as a notional central axis or a common axis, particularly where a corner reflector 100 is in a stowed condition.

[0126] Figure 2 shows a side view of the corner reflector 100 of Figure 1 . As shown in Figure 1 , the corner reflector 100 defines an uppermost extent 121 and a lowermost extent 122. The uppermost extent 121 of the corner reflector 100 of Figure 2 is defined along the central axis 118 of the corner reflector. Similarly, the lowermost extent 122 of the corner reflector 100 of Figure 2 is defined along the central axis 118.

[0127] In other configurations, a corner reflector 100 may be configured so that only one or neither of an uppermost extent and lowermost extent of the corner reflector is defined along the central axis 118 of the corner reflector in the deployed condition. For example, the corner reflector 100 may be configured as illustrated in Figures 6-8 and particularly with reference to Figure 8, as will be subsequently described in further detail.

[0128] In some configurations the corner reflector 100 may be operable to deploy from the stowed condition to the deployed condition, but not to return from the deployed condition tothe stowed condition. For example, the corner reflector 100 may be configured to become locked in the deployed condition, so that return to the stowed condition is prevented.

[0129] The corner reflector 100 may be configured to become locked in the deployed condition by the pivoting associations of the wings and ribs of the trihedral pairs.

[0130] The corner reflector may be quickly deployed by a user, by grasping both opposite faces of the corner reflector in the stowed condition and rotating them about the common axis 118 so they meet each other. Where the corner reflector is provided with a bias towards the deployed condition, the operation by the user may be minimised. In some such examples, the operation may be limited to removing a retaining assembly from retaining the corner reflector in the stowed condition.

[0131] Figure 4 shows a side view of the corner reflector 100 of Figure 3 in the stowed condition. As illustrated in Figure 4, the respective first wing 111 and second wing 112, and third wing 113 and fourth wing 114, correspond to each other in size and shape. In the stowed condition each of the laterally adjacent ones of the wings together define in their periphery a combined isosceles triangle 116. As shown in Figure 4, angle of the combined triangle 116 at the trihedral apex 117 may be greater than a corresponding angle of each of the ribs 115 extending from the trihedral apex 117. This configuration may allow the opposite corners 116a and 116b of the combined triangle 116 defined by the wings 111 -114 to move towards each other as the wings of each trihedral pair 110 are pivoted away from their respective ribs 115. This allows each trihedral pair to open, so that the each trihedral may have an open mouth into which electromagnetic radiation may be received to be reflected. The relatively lesser angle of each of the ribs 115 from the trihedral apex 117 compared to the combined triangle 116 may also define the limit of opening of each trihedral pair, by interference of the first wing 111 and third wing 113 of each trihedral pair against their respective rib 115.

[0132] As illustrated in Figures 1 -4, the corner reflector 100 is configured so that the deployed condition the rib 115 of each trihedral pair extends to the intersection of the first wing 111 and third wing 113 at a central region of the corner reflector and a distal intersection of the second wing 112 and fourth wing 114 at a peripheral region of the corner reflector 100 in the deployed condition. Such a configuration may maximise the opening size of the reflector defined by each trihedral, thus increasing its potential for reflection. This configuration however may mean that in the stowed condition the ribs 115 may lie outside of the peripheral dimensions of the combined triangle 116 defined by the wings 111 -114, for example as is shown in Figure 4.

[0133] In other configurations, one or more of the ribs 115 may be sized and configured so that they do not extend beyond the periphery of the combined triangle 116 when the corner reflector 100 is in the stowed condition. In such a configuration the corner reflector 100 may have a peripheral size defined by the dimensions of the combined triangle 116. In the deployed conditionof such a configuration of the corner reflector 100 the ribs 115 may not extend to at least one of the intersection of the first wing 111 and third wing 113 and / or second wing 112 and fourth wing 114.

[0134] Another configuration of a corner reflector 100 is shown in Figures 7-11 . The corner reflector 100 has four trihedral pairs 110-140. Each trihedral pair, for example the trihedral pair 110, has a central rib 115, and wings 111 -114.

[0135] Unlike with the corner reflector 100 of Figure 1 , adjacent first wings 111 and third wings 113 of the trihedral pairs 110-114 are not shared. Instead, compared to the corner reflector 100 of Figure 1 , the ribs 115 of the corner reflector 100 of Figure 7 are relatively truncated. As is shown in Figures 8 and 9, instead of defining a single central lowermost extent as in the configuration of Figure 1 , in the configuration of Figures 7-11 each of the trihedral pairs 110-140 define a respective lowermost extents 122 of the corner reflector 100. The lowermost extents 122 are not located along the central axis 118 of the corner reflector, but instead are radially spaced away from it.

[0136] The corner reflector 100 of Figures 7-11 has a single uppermost point 121 , at which each of the trihedral pairs 110-140 meet.

[0137] Figure 10 shows a top view of the corner reflector 100 of Figure 7. Figure 11 shows a bottom view of the corner reflector 100 of Figure 7. The configuration of Figures 7-11 provides for a relatively increased trihedral opening angle compared to the configuration of Figures 1 -6. As shown in Figures 10 and 11 , the corner reflector 100 defines four lines of symmetry.

[0138] Figures 12A-D show stages of the deployment of a trihedral pair 110 of a corner reflector 100 of the form shown in Figures 7-11. In Figure 12A the trihedral pair 110 is shown in a stowed condition, with the wings 111 -114 and rib 115 substantially plane-parallel with each other. To operate towards the deployed condition the wings 111 and 112 ata first side of the rib 115 are folded away from the rib 115, and the wings 113 and 114 at an opposite second side of the rib 115 are also folded away from the rib 115. A first stage of this operation is shown in Figure 12B.

[0139] In Figure 12C the wings 111 , 112, and 113, 114 have been further pivoted away from the rib 115. As the wings pivot outwardly from the rib 115, the distal ends 112a and 114a of the wings 112 and 114 are retracted towards the central axis 118 of the corner reflector 100 and towards the distal end 115a of the rib 115.

[0140] The trihedral pair 110 is fully deployed when the distal ends 112a and 114a of the wings 112 and 114 are retracted so that they abut the distal end 115a of the rib 115, as shown in Figure 12D.

[0141] While the illustrated corner reflectors 100 include four trihedral pairs 110-140, it will be appreciated that the application of the described principles of construction may be utilised to provide a corner reflector having any desired plurality of trihedral pairs.

[0142] The corner reflectors 100 of the disclosure may be configured for floating on a body of water. The corner reflectors 100 may be buoyant in water. In particular, the trihedral pairs of a corner reflector 100 may be configured, when in the deployed condition, so that the trihedral pairs are buoyant in water.

[0143] One or more of the wings 111-114 and the rib 115 of each trihedral pair may include a buoyant material. For example, one or more of the wings 111 -114 and the rib 115 of each trihedral pair may include a plastics material. As will subsequently be described, the wings 111-114 and the rib 115 of each trihedral pair may include a substrate. The substrate may be a plastics material. In particular, but not solely, the substrate may be a corrugated plastic.

[0144] Where the corner reflector 100 is buoyant in the deployed condition, the respective pivotable associations between the wings 111 -114 and the rib 115 of each trihedral pair of the corner reflector may be configured to be substantially water tight. In particular, the pivotable associations of each trihedral pair may be substantially water-tight at the pivotable associations of the first wing 111 and second wing 112, the third wing 113 and fourth wing 114, and the second wing 112 and third wing 113 with each other.

[0145] In other configurations where the corner reflector 100 is buoyant in the deployed condition, one or more of the respective pivotable associations between the wings 111 -114 and the rib 115 of each trihedral pair of the corner reflector may not be configured to be water tight. In particular, one or more of the pivotable associations may be configured to allow water to pass through them, so that water which enters the open mouth of the trihedrals may drain away from the trihedral.

[0146] In other configurations, the trihedral pairs may or may not be buoyant in the deployed condition, and the corner reflector 100 may include one or more buoyancy aids. For example, the corner reflector 100 may be provided within a water-tight inflatable dome to prove for or increase its buoyancy.

[0147] Where the corner reflector 100 is to float on a body of water in the deployed condition, the shape of the corner reflector and particularly the shape of an underside of the corner reflector 100 may influence its floating stability.

[0148] The corner reflectors 100 may be configured so that, in the deployed condition, the centre of mass of the plurality of trihedral pairs is lower than the centre of buoyancy of the plurality of trihedral pairs. Such a configuration may provide floating stability to the corner reflector 100.

[0149] The location and configuration of the lowermost extent or extents 122 of the corner reflector 100 may influence the floating stability of the corner reflector. For example, the corner reflector 100 of Figure 7 may be relatively more stable in waves or chop due to its four radially spaced apart lowermost extents 122 compared to the corner reflector 100 of Figure 1 with its single centrally located lowest extent 122.

[0150] A lowermost extent may also be referred to herein as a base.

[0151] When deployed, as for example shown in Figure 1 and Figure 7, a corner reflector100 may define an at least substantially hemispherical shape.

[0152] Where the corner reflector 100 is deployed from a flat-packed stowed condition, the fact that opposite sides of the corner reflector which are brought together may slightly reduce the effective azimuth of the corner reflector from a full 360 degrees. For example, the corner reflector 100 when deployed may have an effective reflector azimuth of about 350 degrees. Where the corner reflector is described as hemispherical or substantially hemispherical, reflectors having an effective reflector azimuth of at least 350 degrees are contemplated.

[0153] In the deployed condition the corner reflector 100 may provide an about 180- degree altitude reflector.

[0154] In the stowed condition, such as shown in Figure 3, the corner reflector may be operated to the deployed condition by a rotation of the trihedral pairs 110a-d relative to each other about a common axis 118.

[0155] The operation from the stowed condition to the deployed condition may involve a reconfiguration of each trihedral pair 110a-d. The reconfiguration may involve a pivoting of the first wing 111 and third wing 113 relative to the rib 115, a pivoting of the second wing 112 and fourth wing 114 relative respectively to first wing 111 and third wing 113, and a pivoting of the second wing 112 and fourth wing 114 relative to each other.

[0156] In the stowed condition the corner reflector 100 has a first face 123 and an opposite second face 124. From the stowed condition as illustrated in Figure 3, the corner reflector 100 may be operable to the deployed condition by pivoting the first face 123 about the common axis 118 until the first face 123 abuts the second face 124.

[0157] The corner reflector 100 may be configured to be retained in the stowed condition.

[0158] The corner reflector 100 may be biased towards the deployed condition. The pivotable associations of the wings 111 -114 and the rib 115 the trihedral pairs may be biased towards the deployed condition.

[0159] In one example, at least some of the pivotable associations of the wings 111 -114 and rib 115 may be or include living hinges, and the living hinges may be biased such that the trihedral pair that they comprise is biased towards an open shape, corresponding with the deployed condition of the corner reflector.

[0160] Where the corner reflector 100 is biased towards its deployed condition, a retention assembly may be provided to retain the corner reflector 100 in the stowed condition until such a time as the retention assembly is released. Upon release of the retention assembly the corner reflector may under the bias operate to or at least towards the deployed condition.

[0161] Because the corner reflector may at least approximate a hemispherical reflector, the corner reflector may be particularly suited to airborne or space-based detection. By configuration of the opening angles of the trihedral pairs and the orientation of each trihedral pair relative to the central axis of the corner reflector (such as is illustrated and has been described in relation to Figure 1 and Figure 7) the altitude angle of peak reflectivity provided by each corner reflector may be controlled. Similarly, the number of trihedral pairs a corner reflector 100 includes may determine the number of peaks in reflectivity the corner reflector 100 may provide about its azimuth.

[0162] Figures 13A-H show modelling of the radar return values for different altitude (theta) and azimuth (phi) angles for a corner reflector 100 of the configuration of Figure 1. The x-axis shows the altitude (theta) angles between 0 and 90 degrees, the y-axis shows the radar crosssection in m2, and the z-axis shows the azimuth (phi) angles between 0 and -90 degrees.

[0163] Each of Figures 13A-H show the modelled radar cross section for different radar frequencies, ranging from 5.405 GHz in Figure 13A to 10 GHz in Figure 13H. The modelled corner reflector 100 in Figures 13A-H has a diameter of about 1 m2. Figure 13A shows the radar response at 5.405 Ghz. Figure 13B shows the radar response at 6.5 Ghz. Figure 13C shows the radar response at 7.0 Ghz. Figure 13D shows the radar response at 8.0 Ghz. Figure 13E shows the radar response at 9.3 Ghz. Figure 13F shows the radar response at 9.65 Ghz. Figure 13G shows the radar response at 9.8 Ghz. Figure 13H shows the radar response at 10.0 Ghz.

[0164] As shown in Figures 13A-H, the modelled radar cross section increases with the frequency of the incident radar signal.

[0165] As shown in Figures 13A-H, about the 180-degree modelled azimuth the corner reflector 100 provides four distinct peaks 181 in radar cross section at between about 40 and about 50 degrees altitude. Each of these peaks 181 correspond to a reflection by the trihedrals of two adjacent trihedral pairs, for example the trihedral pairs 110 and 120. The magnitude of the radar cross section generated at the peaks 181 varies from about 15-20 sqm for 5.405 GHz radar in Figure 13A to about 60 sqm for 10.0 GHz radar in Figure 13H.

[0166] About the 180-degree azimuth, corner reflector 100 as modelled in Figures 13A-H provide their maximum returns at a plurality of peaks 182, which are found at between about 80 and about 90 degrees altitude. The radar cross section of the peaks 182 is modelled as being of increased variability but of increased size relative to the peaks 181.

[0167] The orientation of the peaks 181 and / or the peaks 182 may be particularly suitable for airborne or space-based reflection of radar.

[0168] Figure 14A-H shows modelling of radar cross section returns at the same frequencies as in Figures 13A-H, but for the corner reflector 100 of Figure 7. Similarly to withFigures 13A-H, the magnitude of the radar cross section returns generally increases with the increasing radar frequency.

[0169] The different configuration of the trihedrals 110-140 of the corner reflector 100 of Figure 7 provides different radar return characteristics compared to with the corner reflector 100 of Figure 1 . The modelled corner reflector 100 has a radius of about 1 m.

[0170] As shown in Figures 14A-H, the corner reflector 100 of Figure 7 has two wide radar return peaks 183 at about 45 and about 135 degrees azimuth and zero degrees elevation azimuth. These return peaks are generated where the incident radar aligns with the ribs 115 of the trihedral pairs 110-140. Compared to the corner reflector 100 of Figure 1 , the corner reflector 100 of Figure 7 may provide for increased radar reflection altitudes at or slightly either side of 0 degrees.

[0171] The greatest radar return signals are provided at the peaks 184. The peaks 184 are located between about 50 and about 60 degrees altitude and are distributed about the azimuth of the corner reflector. The magnitude of the peaks 184 are from about 25 sqm with 5.405 GHz radar in Figure 14A to about 60 sqm in Figure 14H with 10 GHz radar.

[0172] Compared to the peaks 182 of Figures 13A-H, the peaks 184 of Figures 14A-H are located at relatively lesser altitudes, being about 50 to about 60 degrees, rather than about 80 to about 90 degrees altitude.

[0173] From the modelling of Figures 13A-H and 14A-H, it will be appreciated that the geometry of the trihedrals of the corner reflector may be altered to control the peak radar cross sections that the corner reflector may generate and their altitude locations. Similarly, the number of trihedral pairs may be varied to change the number of peak returns that are generated about the effective azimuth of the corner reflector.

[0174] The corner reflector may be optimised for generating peak returns across common observation angles from about 40 degrees altitude to about 80 degrees altitude.

[0175] Because the corner reflectors 100 provide multiple altitudinally inclined peak radar returns about their effective azimuth, they may be configured to be suited to reflect radar from an airborne or space-based emitter. Because of the plurality of radar return signals, for example 16 for a full azimuth of the corner reflectors modelled in Figures 13A-H and 14A-H. These characteristics may provide for increased likelihood of detection of the corner reflector by a radar emitter, particularly an airborne or space-based radar emitter. The likelihood of detection may be further increased where the emitter and corner reflector are moving relative to each other. For example, this may be by movement of an aircraft or the spacecraft relative to the corner reflector. It may additionally or alternatively be by movement of the corner reflector, such as by movement on a vehicle or ship, or by bobbing on the surface of a body of water. This movement may increase the likelihood of the radar emission intersecting with one of the altitude and azimuth angles of the corner reflector at which a peak return may be generated.

[0176] Where bobbing movement of the corner reflector 100 is desired, the single centrally located base point of the corner reflector 100 of Figure 1 may offer improved functionality in at least this regard over the four-based corner reflector 100 of Figure 7.

[0177] Where in the foregoing description reference has been made to elements or integers having known equivalents, then such equivalents are included as if they were individually set forth.

[0178] Although embodiments have been described with reference to a number of illustrative embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the preferred embodiments should be considered in a descriptive sense only and not for purposes of limitation, and also the technical scope of the invention is not limited to the embodiments. Furthermore, the present invention is defined not by the detailed description of the invention but by the appended claims, and all differences within the scope will be construed as being comprised in the present disclosure.

[0179] Many modifications will be apparent to those skilled in the art without departing from the scope of the present invention as herein described with reference to the accompanying drawings.

Claims

CLAIMS1. A corner reflector comprising a plurality of trihedral pairs, each trihedral pair having: a rib, a first wing and a second wing to a first side of the rib, the rib, the first wing, and the second wing together defining a first trihedral of the trihedral pair, and a third wing and a fourth wing to a second side of the rib, the rib, the third wing, and the fourth wing together defining a second trihedral of the trihedral pair, wherein the corner reflector is operable between: a) a stowed condition in which the first wing and the third wing of each trihedral pair are each stowed against a respective rib of the trihedral pair, and b) a deployed condition in which each of the wings of each trihedral pair are angled relative to their respective rib.

2. The corner reflector of claim 1 , wherein in operation from the stowed condition to the deployed condition the trihedral pairs are rotated relative each other about a common axis.

3. The corner reflector of claim 1 or 2, wherein the first wing and the second wing of each trihedral pair are each pivotably associated with their respective rib.

4. The corner reflector of any one of claims 1 -3, wherein in operation from the stowed condition to the deployed condition, the first wing and the second wing of each trihedral pair are each pivoted about their respective rib.

5. The corner reflector of any one of claims 1 -4, wherein in each of the plurality of trihedral pairs: a) the first wing and the third wing are each pivotably associated with the rib, b) the second wing and the fourth wing are each pivotably associated with the first wing, and c) the second wing and the fourth wing are pivotably associated with each other.

6. The corner reflector of any one of claims 1 -5, wherein the rib and each of the wings of each of the plurality of trihedral pairs are planar.

7. The corner reflector of any one of claims 1 -6, wherein the rib and each of the wings of each of the plurality of trihedral pairs have a planar isosceles triangular form, each having two sides of substantially equal length.

8. The corner reflector of any one of claims 1 -7, wherein the corner reflector comprises a bias towards the deployed condition, and a removable retainer configured to retain the corner reflector in the stowed condition.

9. The corner reflector of claim 8, wherein in the deployed condition a centre of mass of the plurality of trihedral pairs is lower than a centre of buoyancy of the plurality of trihedral pairs.

10. The corner reflector of any one of claims 1 -9, wherein the rib and each of the wings of each of the plurality of trihedral pairs are electromagnetically reflective.11 . The corner reflector of any one of claims 1 -10, wherein the corner reflector in the deployed condition defines a substantially hemispherical corner reflector.

12. The corner reflector of any one of claims 1 -11 , wherein in the deployed condition the plurality of trihedral pairs of the corner reflector approximate an about 350-degree azimuth and about 180-degree altitude reflector.

13. The corner reflector of any one of claims 1 -12, wherein the corner reflector in the deployed condition is buoyant in water.

14. The corner reflector of any one of claims 1 -13, wherein the corner reflector in the stowed condition has peripheral dimensions equal to the peripheral dimensions of the first wing and second wing and a portion of the rib of a trihedral pair of the corner reflector.

15. The corner reflector of any one of claims 1 -14, wherein the corner reflector is configured to, in the deployed condition, to provide a plurality of radar return vectors oriented for space-based observation.

16. The corner reflector of any one of claims 1 -15, wherein the corner reflector in the deployed condition is configured to provide a plurality of lateral radar return vectors, the plurality of lateral radar return vectors being oriented about an azimuth circle of the corner reflector and located between an altitude of about 20 degrees and about 70 degrees.

17. A flat-packed deployable corner reflector comprising a plurality of trihedral pairs, each trihedral pair having: a rib, a first wing and a second wing to a first side of the rib, the rib, the first wing, and the second wing together defining a first trihedral of the trihedral pair, and a third wing and a fourth wing to a second side of the rib, the rib, third wing, and the fourth wing together defining a second trihedral of the trihedral pair, wherein the rib and each of the wings of each trihedral pair comprise a buoyant substrate having a surface comprising a radar reflective material, and wherein the corner reflector is operable from a flat-packed condition to a deployed condition in which the corner reflector has a substantially hemispherical form and is buoyant by a pivoting of the trihedral pairs relative to each other about a notional central axis such that a first face of the corner reflector in the flat-packed condition abuts a second face of the corner reflector which is, in the flat-packed condition, opposite to the first face of the corner reflector.

18. The corner reflector of claim 17, wherein the plurality of trihedral pairs are buoyant in the deployed condition.

19. The corner reflector of claim 17 or 18, wherein in each of the plurality of trihedral pairs: a) the first wing and the third wing are each pivotably associated with the rib, b) the second wing and the fourth wing are each pivotably associated with the first wing, and c) the second wing and the fourth wing are pivotably associated with each other.

20. The corner reflector of any one of claims 17-19, wherein the corner reflector is operable from the flat-packed condition to the deployed condition by a reconfiguration of each trihedral pair, the reconfiguration of each trihedral pair comprising: a) a pivoting of the first wing and the third wing about the rib, and b) a pivoting of the second wing and the third wing about both of i) respective ones of the first wing and the fourth wing, and ii) each other.21 . The corner reflector of any one of claims 17-20, wherein the corner reflector is operable from the flat-packed condition to the deployed condition by a user by a single rotational action.

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