Method and apparatus for using collimated and linearly polarized millimeter wave beams at Brewster's angle of incidence in ground penetrating radar to detect objects located in the ground

• US 7,893,862 B2
• Filed: 07/03/2008
• Issued: 02/22/2011
• Est. Priority Date: 06/06/2007
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Smith, Robert Alan, Koumvakalis, Nicholas, Holly, Sandor
• Primary Examiner(s): Gregory; Bernarr E
• Application Number:
  US12/167,753
• Publication Number:
  US 20090040093A1
• Time in Patent Office: 964 Days
• Field of Search: 342/21, 342/22, 342/27, 342/28, 342/59, 342/82, 342/89, 342/175, 342188-197, 342/118, 342134-145
• US Class Current: 342/22
• CPC Class Codes: F41H 11/136 Magnetic, electromagnetic, acoustic or radiation systems, e.g. ground penetrating radars or metal-detectors
• CPC Class Codes: G01S 13/04 Systems determining presence of a target based on relative movement of target G01S13/56
• CPC Class Codes: G01S 13/87 Combinations of radar systems, e.g. primary radar and secondary radar
• 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

Abstract

A detection system comprises a transmitter unit, a receiver, and a processor. The transmitter unit is capable of transmitting a first collimated beam having a first frequency and a second collimated beam having a second frequency into a ground, wherein the first collimated beam and the second collimated beam overlap in the ground. The receiver is capable of monitoring for a response radio frequency signal having a frequency equal to a difference between the first frequency and the second frequency. The response radio frequency signal is generated by an object having non-linear conductive characteristics in response to receiving the first collimated beam and the second collimated beam. The processor is capable of controlling an operation of the transmitter unit and the receiver. The processor is connected to the transmitter unit and the receiver. The object is detected when the response radio frequency signal is detected by the receiver.

Claims

1. A detection system for detecting objects having electrical non-linear characteristics located underground, the detection system comprising:

a transmitter unit configured to transmit a first collimated beam having a first radio frequency and a second collimated beam having a second radio frequency into a ground, wherein the first collimated beam and the second collimated beam overlap in the ground;

a receiver configured to monitor for a response radio frequency signal having a frequency equal to a difference between the first frequency and the second frequency, wherein the response radio frequency signal is generated by an object having non-linear conductive characteristics in response to receiving the first collimated beam and the second collimated beam; and

a processor configured to control an operation of the transmitter unit and the receiver, wherein the processor is connected to the transmitter unit and the receiver, and wherein the object is detected when the response radio frequency signal is detected by the receiver.

2. The detection system of claim 1, wherein the first collimated beam and the second collimated beam are linearly polarized.

3. The detection system of claim 2, wherein the first collimated beam and the second collimated beam hit a surface of the ground at a Brewster'"'"'s angle.

4. The detection system of claim 3, wherein the first collimated beam and the second collimated beam overlap each other at the object.

5. The detection system of claim 4, wherein the first collimated beam has a first diameter of at least about 20 times a first wavelength of the first frequency and the second collimated beam has a second diameter of at least about 20 times a second wavelength of the second frequency.

6. The detection system of claim 5, wherein the processor controls the transmitter unit to change the first frequency and the second frequency such that the frequency of the response radio frequency signal changes through a range of frequencies.

7. An apparatus comprising:

a transmitter unit configured to transmit both a first collimated beam, the first collimated beam being linearly polarized and having a first radio frequency, and a second collimated beam, the second collimated beam being linearly polarized and having a second radio frequency, the first and second collimated beam both penetrating into a surface of a ground at an angle of incidence that eliminates reflection of the first collimated beam, and eliminates reflection of the second collimated beam; and

a receiver configured to monitor for a radio frequency signal having a frequency equal to a difference between the first frequency and the second frequency in which the frequency is generated by an object having an electrical non-linear conductive characteristic in response to being exposed to the first collimated beam and the second collimated beam, wherein the object is detected when the radio frequency signal is detected by the receiver.

8. The apparatus of claim 7, wherein the first collimated beam and the second collimated beam overlap in the ground.

9. The apparatus of claim 7 further comprising:

a processor configured to control a selection of the first frequency and the second frequency, wherein the processor is connected to the transmitter unit and the receiver.

10. The apparatus of claim 9, wherein the processor executes instructions to analyze a radio frequency signal received by the receiver to provide an interpretation of the radio frequency signal.

11. The apparatus of claim 7, wherein the first frequency and the second frequency change to change the difference frequency, wherein the difference frequency changes through a range of frequencies.

12. The apparatus of claim 7, wherein the first frequency and the second frequency are selected to cause the first collimated beam and the second collimated beam to penetrate the ground to a selected depth in the ground.

13. The apparatus of claim 7, wherein the object having the electrical non-linear conductive characteristic is a metal with corrosion in portions of the metal.

14. A method of detecting an object with electrical non-linear characteristics, the method comprising:

transmitting a first collimated beam and a second collimated beam that penetrate into a surface of a ground at an angle of incidence that eliminates reflection of the first collimated beam and the second collimated beam, wherein the first collimated beam is linearly polarized and has a first radio frequency;

the second collimated beam is linearly polarized and has a second radio frequency; and

wherein the first collimated beam and the second collimated beam overlap each other in the ground;

monitoring for a radio frequency signal having a frequency equal to a difference between the first frequency and the second frequency, wherein the radio frequency signal is generated by an object in the ground having an electrical non-linear characteristic in response to being exposed to the first collimated beam and the second collimated beam; and

detecting the object having the electrical non-linear characteristic when the radio frequency signal is detected.

15. The method of claim 14, wherein the angle of incidence is a Brewster'"'"'s angle.

16. The method of claim 14, wherein the first collimated beam has a first diameter of at least about 20 times a first wavelength of the first frequency and the second collimated beam has a second diameter of at least about 20 times a second wavelength of the second frequency.

17. The method of claim 14, wherein the first frequency and the second frequency are from around 75 gigahertz to around 100 gigahertz.

18. The method of claim 14, wherein the transmitting step comprises:

transmitting the plurality of radio frequency signals having the first frequency and the second frequency into the ground in which the first frequency and the second frequency change to change the difference frequency through a range of frequencies.

19. The method of claim 14, wherein the object having the electrical non-linear characteristic is a metal with corrosion in portions of the metal.

20. The method of claim 14, wherein the object is one of an improvised explosive device, a detonator with non-linear electronic components, a bunker, an electronic instrument control system, a computer, and communication equipment.