Apparatus and method for detecting and locating hidden objects

• US 7,898,456 B2
• Filed: 02/19/2009
• Issued: 03/01/2011
• Est. Priority Date: 02/19/2008
• Status: Active Grant

• Current Assignee: SubSurface Instruments, Inc. (MDU Resources Group Incorporated)
• Original Assignee: Prairielands Energy Marketing, Inc. (MDU Resources Group Incorporated)
• Inventors: Oehme, Delbert R., Cloutier, Paul A.
• Primary Examiner(s): Sotomayor; John B
• Application Number:
  US12/388,672
• Publication Number:
  US 20090212990A1
• Time in Patent Office: 740 Days
• Field of Search: 342/22, 342/27, 342/126, 342/127, 342/133, 342/139, 342146-147, 342/156, 324/233
• US Class Current: 342/22
• CPC Class Codes: G01S 13/32 using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
• CPC Class Codes: G01S 13/885 for ground probing prospecting or detecting using electromagnetic waves G01V3/12
• CPC Class Codes: G01S 13/887 for detection of concealed objects, e.g. contraband or weapons
• CPC Class Codes: G01S 7/032 Constructional details for solid-state radar subsystems
• CPC Class Codes: H01Q 1/04 Adaptation for subterranean or subaqueous use
• CPC Class Codes: H01Q 11/10 Logperiodic antennas H01Q11/08 takes precedence
• CPC Class Codes: H01Q 21/08 the units being spaced along or adjacent to a rectilinear path waveguide fed H01Q21/0037

Abstract

An apparatus and method for detecting and locating hidden objects employs a symmetrical array of five directional antennas, including a central transmit antenna and a pair of receive antennas at each side of the transmit antenna, respectively. All of the antennas are pointed in the same general direction toward an object field of interest. The transmit antenna radiates a beam of high-frequency electromagnetic energy, and the receive antennas receive high-frequency electromagnetic energy returned by hidden objects. Each pair of receive antennas has an associated phase detector, the output of which represents the phase difference between receive antenna signals corresponding to the received electromagnetic energy. A circuit determines when the outputs of the phase detectors represent predetermined phase differences and operates indicator devices.

Claims

1. Apparatus for detecting and locating hidden objects, comprising:

a symmetrical array of five directional antennas arranged along a common plane with radiation patterns pointing in a same general direction, including a central transmit antenna and a pair of receive antennas at each side of the transmit antenna;

a transmitter that supplies a high-frequency signal to the transmit antenna, whereby the transmit antenna radiates a beam of high-frequency electromagnetic energy, and whereby the pairs of receive antennas receive electromagnetic energy returned by hidden objects;

a phase detector associated with each pair of receive antennas, respectively, for detecting electrical phase differences between receive antenna signals corresponding to the electromagnetic energy received by the associated receive antennas and producing an output dependent upon detected phase differences; and

a circuit that determines when the outputs of the phase detectors represent predetermined phase differences and that operates indicator means.

2. The apparatus of claim 1, wherein the circuit includes a pair of comparators, each of which compares an output from an associated phase detector with a reference and operates an associated indicator device of the indicator means, and wherein each indicator device is activated when the output of the associated phase detector represents a predetermined amount of phase difference.

3. The apparatus of claim 1, further comprising a circuit that indicates that the phase differences are substantially the same.

4. The apparatus of claim 1, wherein the apparatus is a mobile apparatus.

5. The apparatus of claim 1, wherein the high-frequency electromagnetic energy is continuous wave RF.

6. The apparatus of claim 1, wherein the high-frequency electromagnetic energy is in the microwave spectrum.

7. A method of detecting and locating hidden objects that comprises:

providing a symmetrical array of five directional antennas arranged along a common plane with radiation patterns pointing in a same general direction, including a central transmit antenna and a pair of receive antennas at each side of the transmit antenna, respectively;

transmitting a beam of high-frequency electromagnetic energy from the transmit antenna;

receiving at the pairs of receive antennas electromagnetic energy returned by hidden objects;

detecting phase differences between electrical signals corresponding to the electromagnetic energy received by the receive antennas of each pair and producing corresponding outputs; and

determining when the outputs represent predetermined amounts of phase difference and producing an indication.

8. A method of claim 7, further comprising determining when the outputs represent substantially equal amounts of phase difference and producing an indication.

9. The method of claim 7, wherein the high-frequency electromagnetic energy is continuous wave RF radiation.

10. The method of claim 7, wherein the high-frequency electromagnetic energy is in the microwave spectrum.

11. The method of claim 7, wherein the array of antennas is moved over an object field to detect and locate underground objects.

12. The method of claim 11, wherein a laser beam illuminates a point in the object field when a predetermined indication is produced.