Process for detecting totally or partially hidden non-homogeneities by means of microwave radiation

• US 5,933,014 A
• Filed: 05/24/1996
• Issued: 08/03/1999
• Est. Priority Date: 11/23/1994
• Status: Expired due to Fees

• Current Assignee: Fraunhofer-Gesellschaft ZUR Forderung Der Angewandten Forschung EV
• Original Assignee: Fraunhofer-Gesellschaft ZUR Forderung Der Angewandten Forschung EV
• Inventors: Hartrumpf, Matthias, Munser, Roland
• Primary Examiner(s): Do, Diep N.
• Application Number:
  US08/653,198
• Time in Patent Office: 1,166 Days
• Field of Search: 324/632, 324/637, 324/638, 324/642, 324/643, 324/644, 324/646, 324/67, 342/459, 342/350, 342/359
• US Class Current: 324/642
• CPC Class Codes: G01N 22/02 Investigating the presence of flaws

Abstract

A process for detecting totally or partially hidden faults, such as cracks, and bubbles and the like in an opaque medium, by using microwave radiation. Microwaves from a transmitting antenna are directed against the surface of the medium which is to be inspected, and microwave radiation reflected or back scattered from the medium is detected and analyzed. In order to maximize the signal to noise ratio, minimizing the detection of radiation reflected by the surfaces of the medium itself, at least one of the transmitting antenna and the receiving antenna is oriented at an oblique angle relative to the surface of the medium.

Claims

1. A process for detecting totally or partially hidden faults in an opaque medium by means of microwave radiation, said process comprising the steps of:

directing microwave radiation from at least one directional transmitting antenna onto a surface of said medium; and

detecting microwave radiation returned from said medium, including microwave radiation scattered back by a fault in said medium, by means of at least one directional receiving antenna, said returned radiation having parameters which are indicative of at least an angular position of said fault;

wherein

the transmitting and receiving antennas are oriented on a carrier, with an axis of a directional characteristic of at least one of said antennas oriented at an oblique angle relative to the surface of the medium; and

an axis which bisects an angle between respective axes of directional characteristics of said transmitting and receiving antennas is oriented at an oblique angle relative to the surface of the medium.

2. A process according to claim 1 wherein said at least a directional transmitting antenna and at least a directional receiving antenna comprise a plurality of pairs of transmitting and receiving antennas.

3. A process according to claim 1 wherein the orientations of said transmitting and receiving antennas are adjustable relative to said carrier and relative to each other.

4. A process according to claim 3 further comprising a plurality of additional polygonal arrangements of other transmitting and/or receiving antennas on said carrier device.

5. A process according to claim 4, wherein said step of directing microwave radiation comprises radiating microwaves in the form of one of pulses and modulated, the received radiation being determined based on one of time, frequency and phase.

6. A process according to claim 1, wherein said antennas are one of:

curved and flat patch antennas.

7. A process according to claim 1 wherein said antennas are operated with a fundamental frequency and at least one harmonic frequency thereof.

8. A process according to claim 1 wherein:

the transmitting antennas are configured as an array of antennas, disposed in a first polygon arrangement about an axis of the carrier;

the receiving antennas are configured as an array of antennas, disposed in a second polygon arrangement;

average transmission and reception directions of said antennas projected in a plane perpendicular to said axis of said carrier are at oblique angles relative to one another; and

the polygons are rotated relative to each other on said carrier.

9. A process according to claim 1 wherein said process comprises detecting leaking pipe connections, cracks or other damage in the wall of the pipe or air gaps or water-filled cavities, wet areas, stones, concrete, stoneware or metal objects in the vicinity of the pipes.

10. A process according to claim 1, wherein said carrier comprises an inspection/repair vehicle.

11. The process according to claim 1, wherein axes of directional characteristics of said microwave antennas are oblique to each other.

12. The process according to claim 1, wherein said at least one transmitting antenna and said receiving antenna are oriented relative to said medium such that a propagation axis of radiation transmitted by said at least one transmitting antenna and reflected from a surface of said medium is oblique to an average directional characteristic of the at least one receiving antenna.

13. The process according to claim 1, wherein said at least one transmitting antenna and said receiving antenna are oriented relative to said medium such that a propagation axis of radiation transmitted by said at least one transmitting antenna and reflected from a surface of said medium is skewed relative to an average directional characteristic of the at least one receiving antenna.

14. The process according to claim 1, wherein said propagation axis is skewed relative to an average directional characteristic of the at least one receive antenna.

15. A process for detecting faults in a medium by means of microwave radiation, said process comprising the steps of:

directing microwave radiation from at least one directional transmitting antenna onto a surface of said medium;

detecting microwave radiation returned from said medium, including microwave radiation scattered back by a fault in said medium, by means of a plurality of directional receiving antennas, said returned radiation having parameters which are indicative of at least an angular position of said fault;

wherein the at least one transmitting antenna and the plurality of receiving antennas are oriented on a carrier such that axes of directional characteristics of said receiving antennas are oblique to an axis of a directional characteristics of said at least one transmitting antenna; and

determining an angular position of a fault situated within an angle formed by axes of directional characteristics of pairs of antennas, based on a parameter of the returned radiation detected by said multiplicity of directional receiving antennas.

16. A process according to claim 15 wherein an axis which bisects an angle between respective directional characteristics of said pairs of antennas is oriented at an oblique angle relative to the surface of the medium.

17. A process for detecting totally or partially hidden faults in an opaque medium by means of microwave radiation, said process comprising the steps of:

directing microwave radiation from a plurality of directional transmitting antennas onto a surface of said medium; and

detecting microwave radiation returned from said medium, including microwave radiation scattered back by a fault in said medium, by means of at least one directional receiving antenna, said returned radiation having parameters which are indicative of at least an angular position of said fault;

wherein

said plurality of transmitting antennas and said at least a receiving antenna are oriented on a carrier such that axes of directional characteristics of said transmitting antennas are oblique to an axis of a directional characteristic of said at least one receiving antenna;

said step of directing microwave radiation onto a surface of said medium comprises transmitting microwave signals successively from each of said transmitting antennas; and

an angular position of a detected fault within an angle formed by axes of directional characteristics of pairs of antennas is determined based on a parameter of the signals generated successively by the transmitting antennas and received by the at least one receiving antenna.

18. A process according to claim 17 wherein an axis which bisects an angle between respective directional characteristics of said pairs of antennas is oriented at an oblique angle relative to the surface of the medium.

19. A process for detecting faults in a medium, by means of microwave radiation, said process comprising:

directing microwave radiation from at least one direction transmitting antenna onto said medium;

detecting microwave radiation returned from said medium, including microwave radiation scattered back by a fault in said medium, by means of at least one directional receiving antenna, said returned radiation having parameters which are indicative of at least an angular position of said fault;

wherein said transmitting and receiving antennas are oriented relative to said medium such that a propagation axis of radiation from said at least one transmitting antenna reflected from a surface of said medium is oblique to an average directional characteristic of the at least one receiving antenna.

20. A process for detecting faults in a medium, by means of microwave radiation, said process comprising:

directing microwave radiation from at least one direction transmitting antenna onto said medium;

detecting microwave radiation returned from said medium, including microwave radiation scattered back by a fault in said medium, by means of at least one directional receiving antenna, said returned radiation having parameters which are indicative of at least an angular position of said fault;

wherein said transmitting and receiving antennas are oriented relative to said medium such that a propagation axis of radiation from said at least one transmitting antenna reflected from a surface of said medium is skewed relative to an average directional characteristic of the at least one receiving antenna.