Radar drill guidance system

• US 4,297,699 A
• Filed: 10/24/1979
• Issued: 10/27/1981
• Est. Priority Date: 10/24/1979
• Status: Expired due to Term

• Current Assignee: Xadar Corporation
• Original Assignee: ENSCO, Incorporated (Teris LLC)
• Inventors: Hale, Steven D., Fowler, James C., Moser, Theodore E.
• Primary Examiner(s): Tubbesing, T. H.
• Application Number:
  US06/087,811
• Time in Patent Office: 734 Days
• Field of Search: 343/5 NA, 324/337, 324/338, 175/41
• US Class Current: 342/22
• CPC Class Codes: E21B 47/0228 using electromagnetic energy or detectors therefor
• CPC Class Codes: E21B 7/06 Deflecting the direction of boreholes
• CPC Class Codes: G01S 13/003 Bistatic radar systems; Multistatic radar systems
• CPC Class Codes: G01S 13/10 using transmission of interrupted, pulse modulated waves determination of distance by phase measurement G01S13/32
• CPC Class Codes: G01S 13/88 Radar or analogous systems specially adapted for specific applications electromagnetic prospecting or detecting of objects, e.g. near-field detection, G01V3/00

Abstract

The present invention comprises a short-pulse radar guidance tool which determines borehole-to-roof and borehole-to-floor distances along a coal seam by measuring the travel times of electromagnetic pulses transmitted from the tool and reflected back to a receiving antenna in the tool from the interface at the roof or floor of the coal seam. The tool includes a high frequency electromagnetic pulser, a directional transmitting antenna, a directional receiving antenna, a battery power source, and control circuitry for performing all control and transmitting/receiving functions at the tool location. Placement of the transmitting antenna at a point intermediate the control circuitry and the receiving antenna acts to reduce indirect electromagnetic coupling between the antennas. Circuit isolators are used to further attenuate RF crosstalk occuring between the control circuitry and the receiving antenna.

Claims

1. A radar guidance system for determining subterranean distances comprising a source of electromagnetic pulses, a transmitting means connected to said source of electromagnetic pulses to transmit said electromagnetic pulses into the earth, said transmitting means including a first bow-tie shaped dipole antenna, a receiving means positioned in spaced relationship to said transmitting means to receive electromagnetic energy which returns to the receiving means following the reflection of said electromagnetic pulses from various geological discontinuities in the earth, said receiving means including a second bow-tie shaped dipole antenna, and a control circuit means connected to both said source of electromagnetic pulses and said receiving means for controlling both the transmission of said electromagnetic pulses from said transmitting means and the reception of said electromagnetic energy by said receiving means, said control means being positioned in spaced relationship relative to said transmitting means such that said transmitting means is positioned intermediate said control circuit means and said receiving means to prevent electromagnetic coupling between said control circuit means and said receiving means.

2. A radar guidance system as set forth in claim 1, wherein a first reflecting means positioned below said first bow-tie shaped dipole antenna provides directionality to said transmitting means and a second reflecting means positioned below said second bowtie shaped dipole antenna provides directionality to said receiving means.

3. A radar guidance system as set forth in claim 1, wherein said source of electromagnetic pulses includes an electromagnetic pulser which supplies electromagnetic pulses having a frequency in the range between 100 MHz and 2 GHz.

4. A radar guidance system for determining subterranean distances including a source of electromagnetic pulses, a transmitting means connected to said source of electromagnetic pulses to transmit said electromagnetic pulses into the earth, a receiving means for receiving electromagnetic energy which returns to the receiving means following the reflection of said electromagnetic pulses from various geological discontinuities within the earth, a control circuit means for controlling both the transmission of said electromagnetic pulses from said transmitting means and the reception of said electromagnetic energy by said receiving means, a connecting means for connecting said control circuit means to both said source of electromagnetic pulses and said receiving means, a first RF choke means connected to said connecting means between said control circuit means and said transmitting means to attenuate any common mode RF signals travelling along said connecting means between said control circuit means and said transmitting means, and a second RF choke means connected to said connecting means between said control circuit means and said receiving means to attenuate any common mode RF signals travelling along said connection means between said control circuit means and said receiving means.

5. A radar guidance system as set forth in claim 4, wherein said first RF choke means is formed from a first coiled coaxial cable and said second RF choke means is formed from a second coiled coaxial cable.

6. A radar guidance system as set forth in claim 5, wherein both said first and second coiled coaxial cables are coated with lossy dielectrical material.

7. A radar guidance system as set forth in claim 4, wherein said transmitting means includes a first bow-tie shaped dipole antenna and said receiving means includes a second bow-tie shaped dipole antenna.

8. A radar guidance system as set forth in claim 8, wherein a first reflecting means positioned below said first bow-tie shaped dipole antenna provides directionality to said transmitting means and a second reflecting means positioned below said second bow-tie shaped dipole antenna provides directionality to said receiving means.

9. A radar guidance system for determining subterranean distances including a casing, a source of electromagnetic pulses mounted within said casing, a transmitting means mounted within said casing and connected to said source of electromagnetic pulses to transmit said electromagnetic pulses into the earth, a receiving means mounted within said casing in spaced relationship to said transmitting means to receive electromagnetic energy which returns to the receiving means following the reflection of said electromagnetic pulses from various geological discontinuities within the earth, said receiving means having a receiving antenna structure which intercepts said electromagnetic energy and receiver circuit means connected to said receiving antenna structure for tracking and storing said electromagnetic energy intercepted by said receiving antenna structure, said radar guidance system also including a control means mounted within said casing and connected to both said source of electromagnetic radiation and said receiver circuit means for controlling both the transmission of said electromagnetic pulses from said transmitting means and the reception of said electromagnetic energy by said receiving means, said control circuit means being positioned in spaced relationship relative to said transmitting means such that said transmitting means is positioned within said casing intermediate said control circuit means and both said receiving antenna structure and said receiver circuit means to prevent electromagnetic coupling between said control circuit means and said receiving means.

10. A radar guidance system for determining subterranean distances including a source of electromagnetic pulses, a transmitting means connected to said source of electromagnetic pulses to transmit said electromagnetic pulses into the earth, a receiving means positioned in spaced relationship to said transmitting means to receive electromagnetic energy which returns to said receiving means following the reflection of said electromagnetic pulses from various geological discontinuities within the earth, a control circuit means connected to both said source of electromagnetic pulses and said receiving means for controlling both the transmission of said electromagnetic pulses from said transmitting means and the reception of said electromagnetic energy by said receiving means, said control circuit means being positioned in spaced relationship relative to said transmitting means such that said transmitting means is positioned intermediate said control circuit means and said receiving means, said radar guidance system also including a casing which encloses said source of electromagnetic pulses, said transmitting means, said receiving means and said control circuit means, said casing having a shielding element mounted around the inner surface thereof to prevent direct electromagnetic coupling between said transmitting means and said receiving means.

11. A radar guidance system as set forth in claim 10, wherein said shielding element is formed from metal foil.

12. A radar guidance system as set forth in claim 11, wherein said metal foil is copper.

19. A radar guidance system as set forth in claims 10, 13 or 17, wherein said control circuit means includes a power source.

13. A radar guidance system for determining subterranean distances including a casing, a source of electromagnetic pulses mounted within said casing, a transmitting means mounted within said casing and connected to said source of electromagnetic pulses to transmit said electromagnetic pulses into the earth, a receiving means mounted within said casing in spaced relationship to said transmitting means to receive electromagnetic energy which returns to said receiving means following the reflection of said electromagnetic pulses from various geological discontinuities within the earth, a control circuit means mounted within said casing for controlling both the transmission of said electromagnetic pulses from said transmitting means and the reception of said electromagnetic energy by said receiving means, a connecting means for connecting said control circuit means to both said source of electromagnetic pulses and said receiving means such that said transmitting means is positioned intermediate said control circuit means and said receiving means to prevent electromagnetic coupling between said control circuit means and said receiving means, a first RF choke means mounted within said casing and connected to said connecting means between said control circuit means and said transmitting means to attenuate any common mode RF signals travelling along said connecting means between said control circuit means and said transmitting means, and a second RF choke means mounted within said casing and connected to said connecting means between said control circuit means and said receiving means to attenuate any common mode RF signals travelling along said connecting means between said control circuit means and said receiving means.

14. A radar guidance system as set forth in claim 13, wherein said first RF choke means is formed from a first cylindrically coiled coaxial cable and said second RF choke means is formed from a second cylindrically coiled coaxial cable.

15. A radar guidance system as set forth in claim 14, wherein said casing is cylindrical and the diameters of both said first cylindrically coiled coaxial cable and said second cylindrically coiled coaxial cable are equal to the inner diameter of said cylindrical casing.

16. A radar guidance system as set forth in claim 15, wherein both said first and second cylindrically coiled coaxial cables are coated with lossy dielectrical material.

17. A radar guidance system for determining subterranean distances comprising a casing, a source of electromagnetic pulses mounted within said casing, a transmitting means mounted within said casing and connected to said source of electromagnetic pulses to transmit said electromagnetic pulses into the earth, said transmitting means including a first bow-tie shaped dipole antenna, a receiving means mounted within said casing in spaced relationship to said transmitting means to receive electromagnetic energy which returns to said receiving means following the reflection of said electromagnetic pulses from various geological discontinuities within the earth, said receiving means including a second bow-tie shaped dipole antenna, and a control circuit means mounted within said casing and connected to both said source of electromagnetic pulses and said receiving means for controlling both the transmission of said electromagnetic pulses from said transmitting means and the reception of said electromagnetic energy by said receiving means, said control circuit means being positioned in spaced relationship relative to said transmitting means such that said transmitting means is positioned intermediate said control circuit means and said receiving means to prevent electromagnetic coupling between said control circuit means and said receiving means.

18. A radar guidance system as set forth in claim 17, wherein a first reflecting means positioned below said first bow-tie shaped dipole antenna provides directionality to said transmitting means and a second reflecting means positioned below said second bow-tie shaped dipole antenna provides directionality to said receiving means.