Identification and mapping of underground facilities

• US 7,928,892 B2
• Filed: 05/07/2008
• Issued: 04/19/2011
• Est. Priority Date: 05/07/2008
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Greegor, Robert B., Parazzoli, Claudio G., Tanielian, Minas H.
• Primary Examiner(s): Tarcza; Thomas H
• Assistant Examiner(s): Brainard; Timothy A
• Application Number:
  US12/116,540
• Publication Number:
  US 20090278725A1
• Time in Patent Office: 1,077 Days
• Field of Search: 342/22
• US Class Current: 342/22
• CPC Class Codes: G01S 13/003 Bistatic radar systems; Multistatic radar systems
• CPC Class Codes: G01S 13/885 for ground probing prospecting or detecting using electromagnetic waves G01V3/12
• CPC Class Codes: G01V 3/12 operating with electromagnetic waves operating with millimetre waves G01V8/005
• CPC Class Codes: H01Q 15/0086 said selective devices having materials with a synthesized negative refractive index, e.g. metamaterials or left-handed materials

Abstract

A system or method of creating a map of voids in the ground based on a scattered electromagnetic signal includes traversing a receiver/probe in a near field above a target area; generating a signal from a signal transmitter, the signal having a predetermined wavelength λ; receiving a scattered signal with the receiver/probe, the scattered signal including indications of subsurface variations via reflection of the generated signal; and detecting evanescent components of the scattered signal to provide a predetermined resolution. The method includes the use of an electrically small antenna for resolution of subwavelength features. The metamaterial-based antenna is on the order of meters and has an efficient transmit/receive capability. The ESA is 1/10 of the length of the equivalent dipole length, and may be scaled down to 1/10,000. Such an antenna may include phase sensitive current injection in the metamaterial resonant structures for loss-compensation.

Claims

1. A method of creating a map of voids in the ground based on reflected electromagnetic signal, comprising:

traversing a metamaterial electrically small antenna receiver/probe in a near field above a target area;

generating a signal from a signal transmitter located above the target area, the signal having a predetermined wavelength λ

of between 10 kHz to 500 kHz;

receiving a reflected signal with the metamaterial electrically small antenna receiver/probe, the reflected signal including indications of subsurface variations via reflection of the generated signal; and

detecting components of the reflected signal to provide a predetermined resolution.

2. The method of claim 1, wherein the predetermined wavelength is defined by a hypothetical underground facility, the underground facility having a dimension that is characterized by the following equation:

λ

/N;

wherein N is at least 10.

3. The method of claim 1, wherein the step of traversing the metamaterial electrically small antenna receiver/probe in a near field above a target area includes traversing a path in a low altitude that follows a profile of the Earth'"'"'s surface.

4. The method of claim 1, wherein the altitude of the path is in the range of thirty meters to fifty meters.

5. The method of claim 1, wherein the altitude of the path is in the range often meters to one kilometer.

6. The method of claim 1, wherein the signal transmitter is disposed in a far field.

7. The method of claim 1 wherein the signal transmitter in the far field includes an antenna having a length between about ½

and ¼

of the predetermined wavelength λ

.

8. The method of claim 7, wherein an incident wave generated by the signal transmitter is substantially a plane wave.

9. The method of claim 1, wherein the transmitter includes an electrically-small antenna.

10. The method of claim 9, wherein the length of the electrically-small antenna being in the range of λ

/10 to λ

/10,000 of the predetermined wavelength λ

.

11. The method of claim 9, wherein the transmitted signal is a generally conical beam.

12. The method of claim 9, wherein the capability of the metamaterial electrically small antenna receiver/probe to resolve objects compared to a wavelength of interrogation is a function of the fact that the transmitter transmits the signal in the near field of a source and an object.

13. The method of claim 1, wherein the signal transmitter and the metamaterial electrically small antenna receiver/probe are deployed on an aircraft that traverses the flight path in a near field, the flight path approximately conforming to the profile of a surface above a region of interest.

14. The method of claim 1, wherein the altitude of the flight path is approximately λ

/N, wherein λ

is the wavelength and N is an integer value greater than 1.

15. A method of creating a map of voids in the ground based on a reflected electromagnetic signal, comprising:

traversing in an aircraft having a metamaterial electrically small antenna receiver/probe and signal transmitter, in a near field above a target area;

generating a signal from a signal transmitter located above the target area, the signal having a predetermined wavelength λ

of between 10 kHz to 500 kHz;

receiving a reflected signal with the metamaterial electrically small antenna receiver/probe, the reflected signal including indications of subsurface variations via reflection of the generated signal; and

detecting components of the reflected signal to provide a predetermined resolution.

16. The method of claim 15, wherein the predetermined wavelength is defined by a hypothetical underground facility, the underground facility having a dimension that is characterized by the following equation:

λ

/N;

wherein N is at least 10.

17. The method of claim 15, wherein the step of traversing includes traversing a path in a low altitude that follows a profile of the Earth'"'"'s surface.

18. The method of claim 15, wherein the metamaterial electrically small antenna receiver/probe be the altitude of the path is in the range of thirty meters to fifty meters.

19. The method of claim 15, wherein the transmitter includes an electrically-small antenna.

20. The method of claim 19, wherein the electrical length of the electrically-small antenna is in the range of λ

/10 to λ

/10,000 of the predetermined wavelength λ

.

21. The method of claim 15, wherein the flight path approximately conforms to a profile of a surface above a region of interest.

22. The method of claim 15, wherein the altitude of the flight path is approximately between 10 meters and a kilometer.