EP0000447B1 - Réflecteur radar - Google Patents

Réflecteur radar Download PDF

Info

Publication number
EP0000447B1
EP0000447B1 EP78300151A EP78300151A EP0000447B1 EP 0000447 B1 EP0000447 B1 EP 0000447B1 EP 78300151 A EP78300151 A EP 78300151A EP 78300151 A EP78300151 A EP 78300151A EP 0000447 B1 EP0000447 B1 EP 0000447B1
Authority
EP
European Patent Office
Prior art keywords
strip
sections
edge
radar reflector
radar
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP78300151A
Other languages
German (de)
English (en)
Other versions
EP0000447A1 (fr
Inventor
John Hewitt Firth
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Publication of EP0000447A1 publication Critical patent/EP0000447A1/fr
Application granted granted Critical
Publication of EP0000447B1 publication Critical patent/EP0000447B1/fr
Expired legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
    • H01Q15/14—Reflecting surfaces; Equivalent structures
    • H01Q15/18—Reflecting surfaces; Equivalent structures comprising plurality of mutually inclined plane surfaces, e.g. corner reflector

Definitions

  • the invention relates to radar reflectors comprising at least six corner reflectors directed outwardly of a major axis and more particularly but not solely to such reflectors for use on sea vessels.
  • Radar reflectors are employed to improve the radar echoing properties of objects or land formations with a view to improving the detection of such objects or formation by radar scanning equipment. Radar reflectors of this type to be fully efficient should reflect radar waves back parallel to their initial direction.
  • Known radar reflections such as the standard octahedral provide a polar reflection which exhibits a considerable reduction in response between reflector lobes and which exhibits a particularly poor response when heeled.
  • the reflector is capable of providing reflection of radar signals in any direction and in applications such as in sea vessels it is advantageous if this capability is not badly affected upon heeling of the vessel.
  • Corner reflectors constructed of three sheets of reflective material which are mutually perpendicular, i.e., orthogonal re-entrant trihedrals, are known to provide effective reflection over a range of angles of incidence, with the signal strength decreasing as the obliquity increases, forming a lobe (see also GB-A-681 666).
  • This invention has been arrived at by consideration of the above mentioned requirements and seeks to provide a radar reflector which provides effective reflection of signals received from any direction in a horizontal plane.
  • a radar reflector having a major axis and comprising at least six corner reflectors in the form of orthogonal re-entrant trihedrals directed outwardly of said major axis characterized in that the corner reflectors are disposed along two successive helical paths one of which paths is sinistrorse and the other of which paths is dextrorse and are substantially evenly distributed around an angle of 360 0 .
  • the location of the reflectors along two successive helical paths of opposite hand results in a simple and particularly good response characteristic over a desired azimuth and provides a reflector that is still effective when heeled.
  • corner reflectors are employed.
  • a reflector in accordance with the invention may be formed from a strip of radar reflective sheet material folded in alternate directions along fold axes spaced apart on the strip and extending transversely across the strip with two consecutive ones of the fold axes disposed intermediately being substantially parallel and the remaining folds being alternately convergent and divergent in a direction from one edge to the opposite edge of the strip the folds dividing the strip into sections adjacent sections being disposed at right angles and a separator plate being provided between and at right angles to each pair of adjacent sections to form therewith two corner reflectors.
  • the separator plates may be rectangular but rectangular plates having one point cut off are to be preferred, the plate being positioned such that the edge where the point has been removed is remote from the adjacent sections. This cut away avoids interaction with reflections from other ones of the corner reflectors.
  • the edge of the strip and/or the cut away point of the separator plates can be profiled such that they have an edge profile conforming to part of the internal surface of a cylindrical housing to permit slidable and secure location of the reflector within the housing.
  • FIG. 1 shows a particularly advantageous form of the invention hauled up to the cross tree of a mast.
  • the radar reflector indicated generally at 10 is formed of a strip 10a of radar reflective material e.g. 1.21 mm sheet duraluminium or stainless steel.
  • the strip is folded along axes 11 a, 12a, 12b which extend transversely across the strip in concertina fashion. The folds divide the strip into a series of sections 11, 12 and 13 adjacent ones of which are disposed at right angles.
  • FIG. 2 A flat strip suitable for folding to form in this case triangular divisions is shown in Figure 2.
  • the chain lines indicate axes at which the fold is to be forwards and the dot and chain lines indicate axes at which the fold is to be backwards. It will be apparent from the drawing that the fold axes in this case are all of the same length.
  • the fold axes (12 12b) defining the centre section 12 of the strip are parallel, the centre section being of parallelogram form.
  • the other fold axes (11 a) are alternately convergent in a direction from one edge to the opposite edge of the strip and divide the strip into triangular sections 11 and end sections 13 of basically trapezium form which end sections are cut away to one side of an axis extending at right angles to their adjacent fold axis to leave only the portion with the shorter side at the edge of the strip.
  • the folded strip forms a spine having seven sections adjacent ones of which are disposed at right angles. Each pair of adjacent surfaces of the sections is provided with a sheet metal divider 14 which is affixed thereto by for example rivetting or welding at right angles to both surfaces to form a pair of corner reflectors 14a, 14b in the form of orthogonal re-entrant trihedrals which are capable of acting as elementary reflectors.
  • the radar reflector can be hung from one end from a point adjacent the axis at which the end section is cut away or can be hoisted by a similar connection at each end as shown in Figure 1.
  • the reflector hangs normally by its own weight with the surfaces of the sections inclined, alternately at 45° above and below the horizontal.
  • the maximum reflecting capability of a corner reflector occurs along an axis extending equiangularly between the faces of the corner and this axis may be termed the directional axis of the reflector.
  • the directional axes are inclined above or below the horizontal at a constant angle.
  • FIG. 3 shows only two adjacent sections to facilitate illustration of the twist which occurs. It will be seen that bisectors of the two sections are disposed at horizontal angles 2y o to each other. It has been discovered that if the twist is arranged such that the reflectors on adjacent folds are directed with an azimuthal displacement of about 36° then a most efficient "all round" reflection coverage results.
  • the sections 11 need not be triangular but can be of truncated triangular form that is of trapezium shape.
  • the circle in Figure 4a represents a right section of a cylinder in which are contained the stepped helices of a reflector.
  • the trapezium shown is the projection of an actual trapezium of construction on to the circular plane which is normally horizontal. All intersections, dimensions and angles in this plane with bear a zero suffix.
  • the actual trapezium of construction is at 45 deg to the circular plane. Its plane will be an ellipse. 0, W and W' are in both planes because they are on the axis of rotation.
  • each is defined by the line U o O o Y o' U o is at the apex of the two reflecting corners. (Note however U ⁇ U ° , because both are in the circular and tilted planes).
  • O ° is on the cylinder axis (midway) between the intersections of the axis with adjacent trapezia.
  • Y ° is located arbitrarily on the U ° O ° axis at some point within the cylinder envelope.
  • a hypotenuse length can now be calculated using the smallest of the edges (15) or (18) and multiplying by ⁇ 2.
  • the stepped helix has been constructed of trapezia with sides QP and SN straight and parallel. In fact they could be extended to the wall of the enclosing cylinder when they would assume an elliptical curvature.
  • ⁇ be the angle of tilt of the fold to the horizontal. This is angle described in association with Figure 5b.
  • Each lobe will therefore be inclined at a characteristic elevation, between 0 and E deg, up or down as appropriate, as determined by its azimuth between the face and edge of the corner (see Figure 6a).
  • FIG. 1 and 2 which I call an ambiorse construction, with the sinistrorse folds Nos: 1, 2, and 3 on top, and No: 1 topmost.
  • the spine before folding is shown in Figure 2.
  • Fold No: 3 defines the azimuth datum, 0°, in the horizontal projection shown in Figure 8, where the construction is viewed from above.
  • Each fold is tangential to the circle, radius Xo which is the locus of the corners U.
  • the face of the plate shown in Figure 2 is defined as its 'front' face, and the odd-numbered folds (which are shown as chain lines in Figure 2 and dotted in Figure 8, and which have reference numerals encircled in Figures 2 and 8) are produced by folding the plate forwards for example see fold No: 3, i.e. the front is the face on which the corners 3L and 3R will be situated.
  • the other face is the 'back', and the (even-numbered) backwards folds are shown as dot and chain lines in Figure 2 and as solid lines in Figure 8 and with reference numerals not circled in Figures 2 and 8.
  • Adjacent folds are folded in opposite senses ( Figure 2), i.e. the plate is folded from top to bottom alternately forwards and backwards, with odd-numbered folds forwards (encircled) and even-numbered folds backwards.
  • Fold No: 4 is parallel to Fold No: 3, and is of opposite sense. It is the uppermost of the three (Nos: 4, 5 and 6) dextrorse folds forming the bottom half of the whole construction. Going from Fold No: 4 to Fold No: 5 down the dextrorse helix causes a right-hand turn through the twist angle, and similarly again from Fold No: 5 to Fold No: 6 ("Finish").
  • each pair of corners for each fold is shown in Figure 8 following the construction described above.
  • Table 1 are shown the fold azimuths (left and right, when viewing from behind the reflector, i.e. towards the central axis).
  • the lobe azimuths (left and right) for each fold are given, being K degrees (see Eqn. 22) into each corner from each fold azimuth.
  • the lobe azimuths for the dextrorse helix are exactly at 180° to those for the enantiomorphic sinistrorse helix.
  • the lobe azimuths are shown around Figure 8.
  • the 10 corners are disposed substantially evenly around the azimuth, as indicated in Figure 9.
  • FIG. 10 An altemative collapsible version of a reflector in accordance with the invention is shown in Figure 10.
  • sections 21 and 22 of radar reflective sheet material are hingedly interconnected in edge to edge relationship to form a strip by means of hinges 23.
  • the portions 21 are of similar shaping to the portions 11 and the portion 22 is of similar shaping to the portion 12 of Figure 2.
  • the hinges permit the strip to be folded backwards and forwards in concerting fashion into a small space.
  • the opposite edges of the portion 22 which are hingedly connected to adjacent portions 21 are substantially parallel.
  • the hingedly connected edges of the other portions 21 are alternately divergent and convergent in a direction fron one edge to the other edge of the sectional strip.
  • Each of the portions 21 and 22 except the top portion is provided with a separator plate 24 which are hingedly connected to their respective portion alternately to opposite faces of the plate.
  • the separator plates are shaped and positioned so as to be movable into a position at right angles to their respective portion and to permit the adjacent portion to be hinged into contact therewith at which position the adjacent portions are mutually at right angles.
  • a clip 25 is provided which engages the edge of the separator plate and secures the plate in position.
  • the two adjacent portions and the separator plate form a pair of orthogonal re-entrant trihedrals in the same form as Figure 1.
  • this version of the reflector can be folded down for storage in a confined space yet is quickly reassembled for use.
  • Reflectors employing more than 10 reflective corners in which overlapping of lobes at higher signal strengths occurs may well provide useful constructions and such constructions are at present being analysed as their usefulness is influenced by their response at different heeling angles as well as by several other complex factors.
  • the spine and dividers of the described reflector are formed from a single sheet of material the invention is not restricted to such a construction and any other radar reflective material can be employed.
  • the whole could be moulded in plastics e.g. by injection moulding.
  • Such a moulding could be effected with a moulding material containing particles of radar reflective material so that these particles are embedded in the moulded reflector.
  • Another possibility is the provision of facings of radar reflective material on a plastics moulded construction e.g. by metal plating or metalization.
  • a radar reflector as previously described may be encapsulated or hermetically sealed in a container of for example glass reinforced plastics material.

Landscapes

  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Aerials With Secondary Devices (AREA)
  • Radar Systems Or Details Thereof (AREA)

Claims (9)

1. Réflecteur radar à axe principal, comportant au moins six réflecteurs élémentaires angulaires sous forme de trièdres orthogonaux concaves orientés vers l'extérieur par rapport à cet axe principal, caractérisé en ce que ces réflecteurs élémentaires angulaires sont disposés le long de deux courbes hélicoïdales successives, dont l'une est sinistrorse (enroulée de droite à gauche) et l'autre est dextrorse (enroulée de gauche à droite), et sont pratiquement uniformément répartis sur un angle de 360°.
2. Réflecteur radar selon la revendication 1, caractérisé en ce qu'il se compose d'une bande d'une matière réflectrice d'ondes radar pliée alternativement des deux côtés suivant des axes de pliage transversaux répartis sur la bande à des distances appropriées, dont deux axes de pliage médians consécutifs sont pratiquement parallèles et les autres axes de pliage sont alternativement convergents et divergents d'un à l'autre côté de la bande, et cela de manière que les plis divisent la bande en des sections dont les sections adjacentes sont othogonales, et en ce qu'une plaque de séparation est prévue entre les deux sections de chaque paire de sections adjacentes auxquelles elle est perpendiculaire, de manière à former avec elles deux réflecteurs élémentaires angulaires.
3. Réflecteur radar selon la revendication 1, caractérisé en ce qu'il se compose d'une bande d'une matière réflectrice d'ondes radar, composée d'une pluralité de sections minces, disposées bout à bout suivant des côtés transversaux, de manière que les bords transversaux d'une section intermédiaire sont pratiquement parallèles et que ceux des autres sections sont alternativement convergents et divergents d'un bord à l'autre de la bande, en ce que pour chaque paire de sections adjacentes sont prévues des charnières en guise d'éléments d'accouplement entre les sections, qui permettent le pivotement de ces dernières en une position où elles sont perpendiculaires entre elles, et en ce qu'une plaque de séparation est articulée à l'une desdites sections en vue de son pivotement en une position où elle est perpendiculaire à chacune desdites paires de sections adjacentes pour former avec elles deux réflecteurs élémentaires angulaires.
4. Réflecteur radar selon la revendication 2 ou 3, caractérisé en ce que lesdites plaques de séparation sont rectangulaires.
5. Réflecteur radar selon la revendication 2 ou 3, caractérisé en ce que lesdites plaques de séparation ont la forme d'un rectangle dont un des coins est découpé de manière à former un congé oblique à ce niveau, et sont disposés de manière que ce congé se trouve du côté écarté des sections adjacentes.
6. Réflecteur radar selon l'une ou l'autre des revendications précédentes 2 à 5, caractérisé en ce que la bande ininterrompue ou la- bande composée de parties mutuellement articulées est dûment profilée de manière que son bord extérieur est profilé conformément à une partie de la paroi intérieure d'une enveloppe cylindrique.
7. Réflecteur radar selon la revendication 6, caractérisé en ce que lesdites plaques de séparation sont dûment profilées de manière à présenter un bord profilé conformément à une partie correspondante de la paroi intérieure de ladite enveloppe cylindrique.
8. Réflecteur radar selon l'une ou l'autre des revendications précédentes, caractérisé en ce qu'il est logé dans une enveloppe de forme cylindrique.
9. Réflecteur radar selon l'une ou l'autre des revendications précédentes, caractérisé en ce qu'il comporte dix réflecteurs élémentaires angulaires.
EP78300151A 1977-07-15 1978-07-14 Réflecteur radar Expired EP0000447B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB2992377 1977-07-15
GB29923/77A GB1596841A (en) 1977-07-15 1977-07-15 Radar reflector

Publications (2)

Publication Number Publication Date
EP0000447A1 EP0000447A1 (fr) 1979-01-24
EP0000447B1 true EP0000447B1 (fr) 1981-09-16

Family

ID=10299397

Family Applications (1)

Application Number Title Priority Date Filing Date
EP78300151A Expired EP0000447B1 (fr) 1977-07-15 1978-07-14 Réflecteur radar

Country Status (7)

Country Link
EP (1) EP0000447B1 (fr)
JP (1) JPS5440064A (fr)
CA (1) CA1121035A (fr)
DE (1) DE2861076D1 (fr)
GB (1) GB1596841A (fr)
IT (1) IT1097965B (fr)
NO (1) NO147577C (fr)

Families Citing this family (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0026054B1 (fr) * 1979-09-17 1983-10-26 John Hewitt Firth Réflecteur d'encoignure pour radar
DE3037079A1 (de) * 1980-10-01 1982-04-29 Autoflug Gmbh, 2084 Rellingen Entfaltbares bootsdach mit passiver peilvorrichtung
JPH021937Y2 (fr) * 1981-02-25 1990-01-18
JPS6099409A (ja) * 1983-11-04 1985-06-03 Ishikawajima Harima Heavy Ind Co Ltd ロ−ルベンデイング方法及びその装置
FI86342C (fi) * 1986-07-22 1992-08-10 Bell Stephen W Radarreflektor.
DE3808142A1 (de) * 1988-03-11 1989-09-21 Goebel Gmbh Maschf Lagereinrichtung
GB2216725B (en) * 1988-03-18 1990-11-14 Bell Stephen W Military aircraft
US6742903B2 (en) 2001-07-25 2004-06-01 Francis X. Canning Arrangement of corner reflectors for a nearly omnidirectional return
DE102011010846B4 (de) 2011-02-10 2014-02-06 Audi Ag Verfahren und System zur sichtverbindungsunabhängigen Datenübertragung
CN108776327A (zh) * 2018-06-08 2018-11-09 陕西同华机电有限公司 一种可折叠的悬挂式雷达角反射器

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL77990C (fr) * 1950-05-13
GB1468516A (en) * 1974-09-05 1977-03-30 Secr Defence Reflecters for electromagnetic radiation
US4028701A (en) * 1976-04-05 1977-06-07 Parks Jill J Quasi-corner reflectors for electromagnetic radiation

Also Published As

Publication number Publication date
IT1097965B (it) 1985-08-31
IT7825787A0 (it) 1978-07-17
NO782321L (no) 1979-01-16
JPS6123684B2 (fr) 1986-06-06
EP0000447A1 (fr) 1979-01-24
NO147577B (no) 1983-01-24
GB1596841A (en) 1981-09-03
DE2861076D1 (en) 1981-12-03
JPS5440064A (en) 1979-03-28
CA1121035A (fr) 1982-03-30
NO147577C (no) 1983-05-04

Similar Documents

Publication Publication Date Title
EP0000447B1 (fr) Réflecteur radar
US4387377A (en) Apparatus for converting the polarization of electromagnetic waves
US4352106A (en) Radar reflectors
GB1568132A (en) Omnidirectional antenna
US4195298A (en) Target radar reflector
US3039093A (en) Reflective radar target
US4148033A (en) Radar reflector for buoys and other floating objects
US20030021028A1 (en) Arrangement of corner reflectors for a nearly omnidirectional return
US4823131A (en) Radar reflector
US4996536A (en) Radar reflectors
US5097265A (en) Triangular target boat reflector
US4990918A (en) Radar reflector to enhance radar detection
US3329960A (en) Collapsible parabolic antenna
US3874141A (en) Building panels
JPH08504310A (ja) 特にキャリブレータとして、またはビーコンとして使用するための、偏波測定用のレーダー用反射器
US3015095A (en) Collapsible radar target
US4928130A (en) Staggered arrangement for improving radar reflection
AU655313B2 (en) Radar reflectors
JPS56134802A (en) Radio wave reflector formed with expanded metal
CA1292063C (fr) Reflecteur radar
Gray et al. Double convex lens for marine retro-reflector application
RU222599U1 (ru) Многослойная линзовая антенна с механоэлектрическим сканированием
JPH0352018Y2 (fr)
GB2266191A (en) Radar reflector devices
US3309705A (en) Radar target for circularly polarized radiation

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Designated state(s): BE DE FR NL SE

17P Request for examination filed
GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Designated state(s): BE DE FR NL SE

REF Corresponds to:

Ref document number: 2861076

Country of ref document: DE

Date of ref document: 19811203

DET De: translation of patent claims
PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: FR

Payment date: 19840730

Year of fee payment: 7

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: DE

Payment date: 19840918

Year of fee payment: 7

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: SE

Payment date: 19840930

Year of fee payment: 7

Ref country code: BE

Payment date: 19840930

Year of fee payment: 7

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: NL

Payment date: 19860731

Year of fee payment: 9

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: SE

Effective date: 19870715

BERE Be: lapsed

Owner name: JOHN HEWITT

Effective date: 19870731

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: NL

Effective date: 19880201

NLV4 Nl: lapsed or anulled due to non-payment of the annual fee
PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: FR

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 19880331

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: DE

Effective date: 19880401

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: BE

Effective date: 19890731

EUG Se: european patent has lapsed

Ref document number: 78300151.4

Effective date: 19880713

PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT