Resonant assembly, system and method for identification of a buried asset
View Patent ↗A resonant assembly for identification of a buried asset comprising first and second resonant members each configured to resonate at a respective different resonant frequency when excited by an electromagnetic field. The resonant assembly is arranged to cause a near-field coupling of transmit and receive antenna of a detector at the first and second resonant frequencies such that identification of the resonant assembly is performed at least in part according to the frequencies of the coupling.
1. A resonant assembly for identification of a buried asset, comprising first and second resonant members, the first and second resonant members each being configured to resonate at a respective different resonant kHz regime frequency when excited by an electromagnetic field, wherein at least one resonant member comprises a discontinuous loop having at least one inductive element and at least two capacitive elements connected between the free-ends of the loop, such that the assembly is configured to resonate at first and second resonant frequencies in the kHz regime when the loop is excited by the electromagnetic field to thereby cause a near-field coupling of transmit and receive antenna of a detector at the first and second frequencies.
2. The resonant assembly of claim 1 , wherein the at least one inductive element and at least two capacitive elements are arranged such that the first resonant member comprises a first resonant circuit formed by the loop and at least one capacitive element arranged to resonant at the first resonant frequency and the second resonant member comprises a second resonant circuit formed by the inductive element and at least one capacitive element arranged to resonant at the second resonant frequency.
3. The resonant assembly of claim 2 , wherein capacitive values of the at least two capacitive elements and inductive values of the loop and at least one inductive element are selected such that excitation of the loop by the electromagnetic field excites first and second resonant modes of the assembly substantially equally.
4. The resonant assembly of claim 2 , wherein the at least one inductive element and at least two capacitive elements connected between the free-ends of the loop are arranged such that the first and second resonant frequencies have a predetermined relationship.
5. The resonant assembly of claim 4 , wherein the predetermined relationship is in a predetermined ratio.
6. The resonant assembly of claim 2 , wherein the apparatus comprises only one loop for exciting by the electromagnetic field.
7. The resonant assembly of claim 2 , wherein the first resonant frequency is determined according to the equation:
freq
=
1
2
π
1
L
1
×
C
1
wherein L 1 is an inductance of the loop and C 1 is a capacitance of a first capacitive element of the at least two capacitive elements connected to the free-ends of the loop.
8. The resonant assembly of claim 7 , wherein the second resonant frequency is determined according to the equation:
freq
=
1
2
π
(
1
+
2
×
C
3
/
C
1
)
L
1
×
C
1
or
freq
=
1
2
π
1
L
1
×
C
1
(
1
+
2
×
C
3
/
C
1
)
wherein C 3 is a capacitance of a second capacitive element of the at least two capacitive elements connected to the free-ends of the loop.
9. The resonant assembly of claim 1 , wherein the assembly includes a plurality of loops of a conductive material.
10. The resonant assembly of claim 1 arranged within an enclosure for attachment to the buried asset.
11. The resonant assembly of claim 1 , wherein the resonant assembly is for near-field coupling to transmit and receive antennas.
12. The resonant assembly of claim 1 , wherein the loop has a diameter of 15 cm or larger.
13. A system comprising:
a resonant assembly comprising first and second resonant members, the first and second resonant members each being configured to resonate at a respective different resonant frequency when excited by an electromagnetic field, wherein at least one resonant member comprises a discontinuous loop having at least one capacitive element connected between free-ends of the loop; and
a detector apparatus arranged to generate an electromagnetic field, to determine a near-field coupling of the electromagnetic field between a transmit antenna and a receive antenna and to identify a buried asset associated with the resonant assembly at least in part according to a resonant frequency of the first and second members based on the coupling.
14. The system of claim 13 , wherein the transmit and receive antenna of the detector apparatus are generally unequally sized.
15. The system of claim 14 , wherein the receive antenna is substantially larger than the transmit antenna.
16. The system of claim 14 , wherein the receive antenna is approximately twice a size of the transmit antenna.
17. A method of determining an identity of a buried asset, comprising:
generating an electromagnetic field from a transmit antenna to excite first and second resonant members of a resonant assembly associated with a buried asset, the first and second resonant members each being configured to resonate at a respective different resonant kHz regime frequency, wherein at least one resonant member comprises a discontinuous loop having at least one capacitive element connected between free-ends of the loop;
determining a near-field coupling of the electromagnetic field to a receive antenna at a plurality of the kHz regime frequencies of the electromagnetic field; and
identifying the resonant assembly at least in part according to a frequencies of the coupling.
18. The method of claim 17 , comprising comparing the first and second resonant frequencies against a database of resonant frequency information associated with buried assets.
19. The method of claim 17 , further comprising determining geographic location information for a location of the buried asset and identifying the resonant assembly at least in part according to the geographic location information.