Land mine detection system

• US 10,145,660 B1
• Filed: 11/18/2015
• Issued: 12/04/2018
• Est. Priority Date: 11/18/2014
• Status: Active Grant

• Current Assignee: Herbert U. Fluhler, Michael James Guthrie
• Original Assignee: Herbert U. Fluhler, Michael James Guthrie
• Inventors: Fluhler, Herbert U., Guthrie, Michael J.
• Primary Examiner(s): Bythrow, Peter M
• Application Number:
  US14/945,421
• Time in Patent Office: 1,112 Days
• Field of Search: 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 13/86 Combinations of radar systems with non-radar systems, e.g. sonar, direction finder
• CPC Class Codes: G01S 13/885 for ground probing prospecting or detecting using electromagnetic waves G01V3/12
• CPC Class Codes: G01V 3/10 using induction coils
• CPC Class Codes: G01V 3/12 operating with electromagnetic waves operating with millimetre waves G01V8/005
• CPC Class Codes: G01V 3/15 specially adapted for use during transport, e.g. by a person, vehicle or boat
• CPC Class Codes: H01Q 1/04 Adaptation for subterranean or subaqueous use
• CPC Class Codes: H01Q 1/36 Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewithH01Q1/08, H01Q1/14 take precedence
• CPC Class Codes: H01Q 21/064 using horn or slot aerials slotted waveguides arrays H01Q21/005
• CPC Class Codes: H01Q 21/24 Combinations of antenna units polarised in different directions for transmitting or receiving circularly and elliptically polarised waves or waves linearly polarised in any direction circularly polarised patch antennas H01Q9/0428; circularly polarised horns H01Q13/0241; cross-polarised horns H01Q13/0258; polarisation converters H01Q15/242; cross-polarised rear feeds H01Q19/136; crossed polarisation dual antenna H01Q25/001
• CPC Class Codes: H01Q 5/25 Ultra-wideband [UWB] systems, e.g. multiple resonance systems; Pulse systems
• CPC Class Codes: H01Q 7/00 Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop
• CPC Class Codes: H01Q 9/0407 Substantially flat resonant element parallel to ground plane, e.g. patch antenna dipole H01Q9/285; monopole H01Q9/40

Abstract

The present invention discloses a dual-technology sensor head tightly integrating an Electromagnetic Induction (EI) sensor coil for detection, localization and discrimination of metal in mines and Improvised Explosive Devises (IED), and a dual polarized Ultra-Wideband (UWB) radar antenna array for Ground Penetrating Radar for detection, localization and discrimination of same. The core challenge addressed is how to prevent the EI sensor from detecting the metal in the UWB antenna which then desensitizes the EI sensor and degrades its dynamic range. The key characteristic of the new UWB radar antenna design is its very low magnetic induction, thereby imposing very little degradation to the EI coil. Additionally, the UWB antenna array incorporates unique design features to enhances its low frequency performance for better penetration of the ground. Through the design guidelines taught herein the EI sensor has been demonstrated to incur no degradation from the proximate UWB array.

Claims

1. A system for detecting land mines imbedded in a medium comprising:

a detection head further comprising;

at least one EMF detection coil configured for providing a magnetic field that penetrates a volume of said medium to be searched and detecting magnetic metals in a land mine embedded in said medium,

a radar antenna having a first electrically connected array of planar radiating and receiving antenna elements that allow currents to flow across an entire array aperture and

an electronic system for simultaneously operating said detection coil and said radar antenna, for providing indications indicative of a land mine, wherein;

said radar antenna is mounted within said at least one EMF detection coil in an orientation so that said planar radiating and receiving antenna elements are parallel to magnetic flux lines developed by said magnetic field, and

said radar antenna provides signals of a wavelength that penetrates at least said volume of medium to be searched by said magnetic field and detects non-metallic portions of said land mine embedded in said medium.

2. The system of claim 1 wherein said planar radiating and receiving antenna elements are Vivaldi type slot antenna elements.

3. The system of claim 1, wherein said EMF detection coil and said radar antenna emit co-aligned and overlapping sensor detection patterns—

with similar sensitivities for objects expected to provide electromagnetic and radar signatures within said volume of medium to be searched.

4. The system of claim 1 wherein said at least one EMF detection coil further comprises a symmetrical differential figure-8 coil with a symmetrical non-differential transmit mono-coil, and a balanced but anti-symmetrical differential pair of receive coils.

5. The system of claim 3 wherein said co-aligned and overlapping sensor detection patterns wherein said radar antenna is oriented coaxially to a polar axis of said symmetrical non-differential transmit mono-coil, and also symmetrical to said balanced but anti-symmetrical differential pair of receive coils.

6. The system of claim 5 wherein conductors of said radar antenna are configured and oriented to minimize cutting of magnetic field lines from said symmetrical non-differential transmit mono-coil to minimize formation of eddy currents.

7. The system of claim 6 wherein said radar antenna is constructed of a resistive material, for dampening any eddy currents developed by said magnetic field lines.

8. The system of claim 2, wherein said Vivaldi-type slot antenna elements are planar antipodal antenna elements.

9. The system of claim 8, wherein said connected array comprises antenna elements configured as Vivaldi-type slot antenna elements in a linear antipodal arrangement.

10. The system of claim 9 wherein said Vivaldi-type slot antenna elements are connected by a tapering of parallel resistances along a boresight direction of said Vivaldi-type slot antenna elements, said parallel resistances being a Wu-King-like resistive taper, with a highest resistance of about 1000 Ohms per square in throats of slots of the Vivaldi-type slot antenna elements and a lowest resistance being a short at ends of petals of the Vivaldi-type slot antenna elements.

11. The system of claim 1, wherein said radar antenna is a dual polarized connected array antenna.

12. The system of claim 9, wherein the radar antenna comprises gaps between each of the antipodal Vivaldi slotted antenna elements and a conductive material bridging over said gaps.

13. The system of claim 12, wherein said conductive material bridging over said gaps comprises resistors.

14. The system of claim 13, wherein said resistors are arranged in parallel and tapered to provide a highest resistance in throats of slots of the Vivaldi-type slot antenna elements and a lowest resistance at ends of petals of the Vivaldi-type slot antenna elements.

15. The system of claim 14, wherein the lowest resistance at the ends of petals of the Vivaldi-type slot antenna elements is a dead short.

16. The system of claim 9, wherein said radar antenna further comprises a second electrically connected array of planar radiating and receiving antenna elements oriented at 90 degrees to the first and parallel magnetic flux lines developed by said magnetic field, wherein said second electrically connected array comprises substantially the same type of antenna elements so that currents flow across the entire array aperture.

17. The system of claim 1, wherein said radar antenna further comprises a second electrically connected array of planar radiating and receiving antenna elements oriented at 90 degrees to the first and parallel magnetic flux lines developed by said magnetic field, wherein said second electrically connected array comprises substantially the same type of antenna elements so that currents flow across the entire array aperture.