Excitation method and ultra-wide bandwidth antenna for ground penetrating radar systems

• US 6,154,167 A
• Filed: 03/22/1999
• Issued: 11/28/2000
• Est. Priority Date: 03/20/1998
• Status: Expired due to Term

• Current Assignee: Sensors & Software Inc.
• Original Assignee: Sensors & Software Inc.
• Inventors: Annan, Alexander Peter, Leggatt, Charles David
• Primary Examiner(s): Sotomayor, John B.
• Application Number:
  US09/273,462
• Time in Patent Office: 617 Days
• Field of Search: 342/22, 342/190, 342/191, 342/175, 342/198, 342/203
• US Class Current: 342/22
• CPC Class Codes: G01S 13/0209 Systems with very large relative bandwidth, i.e. larger than 10 %, e.g. baseband, pulse, carrier-free, ultrawideband
• 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 11/12 Resonant antennas
• CPC Class Codes: H01Q 11/14 with parts bent, folded, shaped or screened or with phasing impedances, to obtain desired phase relation of radiation from selected sections of the antenna or to obtain desired polarisation effect H01Q11/20 takes precedence

Abstract

A novel method of creating and detecting ultra wide bandwidth signals in a ground penetrating radar context.

Claims

1. An ultra-wide band antenna with predictable polarization and directivity for creating and capturing an electromagnetic field comprising:

(a) a voltage source supplying a current;

(b) a first transmission line embedded in a shielding medium attached to said voltage source for carrying said current;

(c) a second transmission line embedded in a shielding medium attached to said first transmission line for carrying said current;

(d) an electrically conductive radiating member embedded in a potting medium for carrying said current and attached to said first and second transmission lines for carrying said current, said current carried by said electrically conductive radiating member cancelled by said current carried by said second transmission line.

2. An ultra-wide band antenna with predictable polarization and directivity for creating and capturing an electromagnetic field as claimed in claim 1 wherein said shielding medium is an absorbing high electromagnetic impedance medium.

3. An ultra-wide band antenna with predictable polarization and directivity for creating and capturing an electromagnetic field as claimed in claim 2 wherein said absorbing high electromagnetic impedance medium is lossy, high magnetic permeability media.

4. An ultra-wide band antenna with predictable polarization and directivity for creating and capturing an electromagnetic field as claimed in claim 2 wherein said electrically conductive radiating member is an antenna arm.

5. An ultra-wide band antenna with predictable polarization and directivity for creating and capturing an electromagnetic field as claimed in claim 2 wherein said first and second transmission lines are solid shield coaxial transmission lines.

6. An ultra-wide band antenna with predictable polarization and directivity for creating and capturing an electromagnetic field as claimed in claim 5 said first transmission line is impedance matched with a selected impedance element placed in parallel circuit connection with said electrically conductive radiating element and said second transmission line.

7. An ultra-wide band antenna with predictable polarization and directivity for creating and capturing an electromagnetic field as claimed in claim 5 wherein said potting medium is dielectric material whose properties can be selected over a range of values.

8. An ultra-wide band antenna with predictable polarization and directivity for creating and capturing an electromagnetic field as claimed in claim 5 wherein the physical properties of said potting medium are adjusted to modify the electromagnetic impedance of said antenna arm in a prescribed manner.

9. An ultra-wide band antenna with predictable polarization and directivity for creating and capturing an electromagnetic field as claimed in claim 5 wherein the impedance of said antenna arm is varied by adjusting the geometry of said antenna arm.

10. An ultra-wide band antenna with predictable polarization and directivity for creating and capturing an electromagnetic field as claimed in claim 5 wherein said potting compound is varied to modify the electromagnetic velocity of current travelling on said antenna arm.

11. An ultra-wide band antenna with predictable polarization and directivity for creating and capturing an electromagnetic field as claimed in claim 5 wherein the length of said second transmission line and the electromagnetic velocity of said current on said antenna arm are adjustable whereby the travelling time on said second transmission line and said antenna arm are equal.

12. An ultra-wide band antenna with predictable polarization and directivity for creating and capturing an electromagnetic field as claimed in claim 5 wherein said second transmission line further comprises an active circuit element for canceling said current carried by said antenna using time synchronization.

13. An ultra-wide band antenna with predictable polarization and directivity for creating and capturing an electromagnetic field as claimed in claim 6 wherein said potting medium is made of a similar medium as said antenna arm for reducing the impedance of said antenna arm.

14. An ultra-wide band antenna with predictable polarization and directivity for creating and capturing an electromagnetic field as claimed in claim 5 wherein said voltage source is a detection circuit for a receiving sensor.

15. The use of an ultra-wide band antenna with predictable polarization and directivity for creating and capturing an electromagnetic field comprising:

(a) supplying a current from a voltage source;

(b) attaching to said voltage source for carrying said current a first transmission line embedded in a shielding medium;

(c) attaching to said first transmission line a second transmission line embedded in a shielding medium for carrying said current;

(d) attaching to said first and second transmission lines an electrically conductive radiating member embedded in a potting medium for carrying said current;

(e) canceling said current carried by said electrically conductive radiating member by said current carried by said second transmission line.

16. The use of an ultra-wide band antenna with predictable polarization and directivity for creating and capturing an electromagnetic field as claimed in claim 15 wherein said electrically conductive radiating member further comprising an antenna arm for carrying said current.

17. The use of an ultra-wide band antenna with predictable polarization and directivity for creating and capturing an electromagnetic field as claimed in claim 16 further comprising adjusting said second transmission line to the length of said antenna arm whereby said currents along said antenna arm and said second transmission line reach a terminating load at the same time.

18. The use of an ultra-wide band antenna with predictable polarization and directivity for creating and capturing an electromagnetic field as claimed in claim 17 further comprising matching said current carried by said antenna arm with said mismatched impedance of said antenna arm and said second transmission line by selecting said terminating load for said second transmission line.

19. The use of an ultra-wide band antenna with predictable polarization and directivity for creating and capturing an electromagnetic field as claimed in claim 15 selected from the group consisted of agriculture, airports, archeology, biocounting, bridges, building inspection, concrete, conveyor belts, dams, environmental, forensics. police matters, geotechnical, gravelpits, graveyards, groundwater, hydro power, nuclear power, ice detection, snow detection, lakes, rivers, military, mining, pipe inspection, sewer inspection, quarries, milroads, real estate roads, security, immigration, customs, smelters, treasure mapping, trenchless technology, tunnelling, utility works, pipes and wood inspection.

20. The use of an ultra wide band antenna with predictable polarization and directivity for creating and capturing an electromagnetic field as claimed in claim 15 with a multi-transducer configuration to reduce parasitic interference associated with reverberation of said current.