Resonant Reflector Assembly and Method

• US 20100328136A1
• Filed: 02/16/2009
• Published: 12/30/2010
• Est. Priority Date: 02/14/2008
• Status: Active Grant

• Current Assignee: Oxford University Innovation Limited (University of Oxford)
• Original Assignee: Isis Innovation Limited
• Inventors: Hao, Tong, Edwards, David John, Burd, Harvey John, Stevens, Christopher John
• Granted Patent: US 8,482,451 B2
• Time in Patent Office: Days
• US Class Current: 342/5
• CPC Class Codes: G01S 13/75 using transponders powered from received waves, e.g. using passive transponders , or using passive reflectors
• CPC Class Codes: G01S 13/885 for ground probing prospecting or detecting using electromagnetic waves G01V3/12
• CPC Class Codes: G01S 2013/9316 combined with communication equipment with other vehicles or with base stations
• CPC Class Codes: G01S 7/025 involving the transmission of linearly polarised waves
• CPC Class Codes: G01V 15/00 Tags attached to, or associated with, an object, in order to enable detection of the object record carriers for use with machines having a detectable tag or marker G06K19/00
• CPC Class Codes: G06K 19/07749 the record carrier being capable of non-contact communication, e.g. constructional details of the antenna of a non-contact smart card
• CPC Class Codes: H01Q 1/04 Adaptation for subterranean or subaqueous use
• CPC Class Codes: H01Q 1/2225 used in active tags, i.e. provided with its own power source or in passive tags, i.e. deriving power from RF signal
• CPC Class Codes: H01Q 1/32 Adaptation for use in or on road or rail vehicles
• CPC Class Codes: H01Q 1/38 formed by a conductive layer on an insulating support patch antennas H01Q9/0407; microstrip dipole antennas H01Q9/065; microstrip slot antennas H01Q13/106; transmission line microstrip antennas H01Q13/206; manufacturing reflecting surfaces using insulating material for supporting the reflecting surface H01Q15/142
• CPC Class Codes: H01Q 21/24 Combinations of antenna units polarised in different directions for transmitting or receiving circularly and elliptically polarised waves or waves linearly polarised in any direction circularly polarised patch antennas H01Q9/0428; circularly polarised horns H01Q13/0241; cross-polarised horns H01Q13/0258; polarisation converters H01Q15/242; cross-polarised rear feeds H01Q19/136; crossed polarisation dual antenna H01Q25/001
• CPC Class Codes: H01Q 25/001 Crossed polarisation dual antennas orthomode horns H01Q13/0258; cross-polarised rear feeds H01Q19/136; orthomode transducers H01P1/161
• CPC Class Codes: H01Q 7/00 Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop
• CPC Class Codes: H01Q 9/16 with feed intermediate between the extremities of the antenna, e.g. centre-fed dipole H01Q9/44 takes precedence

Abstract

A resonant radar reflector assembly comprising first and second reflector members (110A, 110B), the first and second and reflector members each being configured to resonate at their respective resonant frequency when irradiated by radio frequency (RF) radiation of a corresponding frequency, wherein the first member has a portion (114A) responsive to an electric field applied parallel to an electric polarisation axis of the first member, the second member having a corresponding portion (114B) responsive to an electric field applied parallel to a corresponding electric polarisation axis of the second member, the first member also having a portion (112A) responsive to a magnetic field applied parallel to a magnetic polarisation axis of the first member, the second member having a corresponding portion (112B) responsive to a magnetic field applied parallel to a corresponding magnetic polarisation axis of the second member, the first and second members being arranged such that at least one electric or magnetic polarisation axis of the first member is substantially not parallel to the corresponding electric or magnetic polarisation axis of the second member.

Claims

1. A resonant radar reflector assembly comprising first and second reflector members, the first and second reflector members each being configured to resonate at a respective resonant frequency when irradiated by radio frequency (RF) radiation of a corresponding frequency,

wherein the first member has a portion responsive to an electric field applied parallel to an electric polarisation axis of the first member, the second member having a corresponding portion responsive to an electric field applied parallel to a corresponding electric polarisation axis of the second member,

the first member also having a portion responsive to a magnetic field applied parallel to a magnetic polarisation axis of the first member, the second member having a corresponding portion responsive to a magnetic field applied parallel to a corresponding magnetic polarisation axis of the second member,

the first and second members being arranged such that at least one electric or magnetic polarisation axis of the first member is substantially not parallel to the corresponding electric or magnetic polarisation axis of the second member;

and

wherein a resonant frequency of the first member is different to a resonant frequency of the second member, the members being arranged to reflect electromagnetic radiation of different respective prescribed frequencies.

2. An assembly as claimed in claim 1 wherein the electric or magnetic polarisation axis of the first member is substantially orthogonal to the corresponding electric or magnetic polarisation axis of the second member.

5. An assembly as claimed in claim 1 wherein the portion of at least one of the first or second members responsive to an electric field comprises a dipole portion.

7. An assembly as claimed in claim 1 wherein the portion of at least one of the reflector members responsive to a magnetic field applied parallel to a magnetic polarisation axis of the member comprises a conducting portion having a loop portion.

8. An assembly as claimed in claim 7 wherein the loop portion is a discontinuous loop such that the loop does not define a substantially closed conducting path.

11. An assembly as claimed in claim 1 further comprising at least one reflector member having a pair of dipole portions and a loop portion, the dipole portions being electrically coupled to respective opposed ends of the loop portion whereby a substantially continuous conducting path is provided through the loop portion between respective dipole portions.

12. An assembly as claimed in claim 11 wherein each reflector member comprises a capacitive portion.

14. An assembly as claimed in claim 12 wherein the loop portion is coupled to the dipole portions by means of the capacitive portion.

15. An assembly as claimed in claim 1 wherein the reflector members are arranged in use to be spaced apart from a conducting surface.

20. An assembly as claimed in claim 15 wherein the conducting surface is provided by an asset associated with the assembly.

23. An assembly as claimed in claim 1 wherein the portions of the first and second members responsive to an electric field and the portions of the first and second members responsive to a magnetic field comprise substantially flat electrically conducting tracks formed on a substrate.

26. An assembly as claimed in claim 1 further comprising a structure, the structure comprising first and second strings of resonant radar reflector members, the first string having the form of a right-handed helix, the second string having the form of a left-handed helix, the first and second strings intersecting one another at least one intersect position of the structure, the structure providing the reflector assembly one of said at least one intersect positions.

31. An assembly as claimed in claim 26 wherein the first string comprises a plurality of reflector members each having a resonant frequency of a first value and the second string comprises a plurality of reflector members each having a resonant frequency of a second value different from the first value.

32. An assembly as claimed in claim 1 further comprising a structure, the structure comprising a plurality of the reflector assemblies wherein the reflector members are arranged in a spatial configuration whereby an identifier of an asset associated with the structure may be determined based on said spatial configuration.

33. An assembly as claimed in claim 32 wherein a first reflector assembly of the structure comprises a reflector member having a resonant frequency different from a resonant frequency of a reflector member of a second reflector assembly of the structure thereby to provide at least a portion of an identifier of an asset.

34. An assembly as claimed in claim 32 wherein a distance between respective reflector assemblies of the structure is configured to provide at least a portion of an identifier of the asset,

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41. A method of identifying an article comprising the steps of:

providing a resonant radar reflector assembly comprising first and second reflector members, the first and second reflector members each being configured to resonate at their respective resonant frequency when irradiated by radio frequency (RE) radiation of a corresponding frequency,

wherein the first member has a portion responsive to an electric field applied parallel to an electric polarisation axis of the first member, the second member having a corresponding portion responsive to an electric field applied parallel to a corresponding polarisation axis of the second member,

the first member also having a portion responsive to a magnetic field applied parallel to a magnetic polarisation axis of the first member, the second member having a corresponding portion responsive to a magnetic field applied parallel to a corresponding magnetic polarisation axis of the second member,

wherein a resonant frequency of the first reflector member is different from a resonant frequency of the second reflector member;

the first and second members being arranged such that at least one electric or magnetic polarisation axis of the first member is substantially not parallel to the corresponding electric or magnetic polarisation axis of the second member;

irradiating the assembly with RF radiation including radiation of a frequency corresponding to the resonant frequency of the first and second reflector members;

detecting radiation reflected by the assembly; and

measuring the resonant frequency of the first and second reflector members.

43. A method as claimed in claim 41 further comprising measuring a difference between the resonant frequency of the first reflector member and the resonant frequency of the second reflector member.

45. A method as claimed in claim 41 further comprising the step of determining an orientation of a reflector member by changing a plane of polarisation of the plane polarised RF radiation and detecting a signal reflected by said reflector member.

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47. A method of identifying an article comprising the steps of:

providing a resonant radar reflector assembly comprising first and second reflector members, the first and second reflector members being configured to resonate at a resonant frequency when irradiated by radio frequency (RF) radiation of a corresponding frequency, the first and second reflector members each having a dipole portion, at least one of the members further having a loop portion, each member having a polarisation axis, the members being arranged whereby the polarisation axis of the first member is substantially not parallel to the polarisation axis of the second member;

wherein a resonant frequency of the first reflector member is different from a resonant frequency of the second reflector member; and

irradiating the assembly with RF radiation including radiation of a frequency corresponding to the resonant frequency of at least one of the first and second reflector members; and

detecting radiation reflected by the assembly.

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