Communications: directive radio wave systems and devices (e.g. – Transmission through media other than air or free space
Reexamination Certificate
2000-12-29
2002-09-03
Gregory, Bernarr E. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Transmission through media other than air or free space
C342S027000, C342S195000
Reexamination Certificate
active
06445334
ABSTRACT:
FIELD OF THE INVENTION
In general, the invention relates to the field of radar systems. More particularly, the invention relates to the field of ground penetrating radar systems.
BACKGROUND OF THE INVENTION
There are numerous applications in which it is useful to view images of underground objects or objects embedded in the ground or in a material such as concrete, that would not otherwise be visible. For example, it is helpful to utility workers to see images of pipes, cables and conduits that are underground where they are about to dig a hole or a trench. It would be even more helpful if the workers could see a three-dimensional image, so that if an imaged object is deep in the ground below the depth they intend to work, they need not be concerned with the object.
Similarly, a system that would allow workers to see images in three dimensions beneath the surface of the ground would be useful in the field of mine detection. This field has become increasingly important as populations have been moving back into previously war-torn areas of the earth. Frequently, when a war ends, civilians move back into a mined area before the authorities can mount a demining operation. Many civilians are injured or killed by such mines even after a war is over. During a war, demining operations help clear a mine field before foot soldiers or vehicles cross it.
In such demining operations, it is useful to know accurately not only the surface coordinates of a buried mine, but also the depth at which the mine is buried. It is also important that the equipment used for demining is mobile and that it is capable of exploring a large amount of territory in a short period of time, while maintaining an accurate and detailed record of the objects detected. Such information allows personnel to make intelligent decisions regarding the methods and equipment that are necessary to remove the detected mines.
SUMMARY OF THE INVENTION
The invention is a ground penetrating radar system mounted on a cart to achieve the desired mobility. The system uses two offset banks of interleaved transmit and receive antennas to achieve the desired accuracy. The receive and transmit antennas are properly oriented with respect to each other to reduce cross coupling and maximize desired subsurface echoes. The system uses nearfield beam forming, which is accomplished through fully coherent signal processing and synthetic aperture reception and processing, to image buried objects in three dimensions. The system displays a plan, or top, view and a side view of the area being scanned to provide a three dimensional perspective on a two dimensional computer screen.
In general, in one aspect, the invention features a ground penetrating radar system which includes a cart configured to be movable along the ground. A computer is mechanically coupled to the cart. A radar electronics module is mechanically coupled to the cart and electrically coupled to the computer. A first antenna array is mechanically coupled to the cart, electrically coupled to the radar electronics module, and oriented to radiate into the ground and receive radiation from the ground. A second antenna array is mechanically coupled to the cart, electrically coupled to the radar electronics module, and oriented to radiate into the ground and receive radiation from the ground. A movement detector, which is configured to detect movement of the cart, is coupled to the computer. The computer is configured to trigger the radar electronics module when the computer detects that the cart has moved a predefined distance.
Implementations of the invention may include one or more of the following. The radar electronics module may include a first radar electronics module electrically coupled to the first antenna array and a second radar electronics module electrically coupled to the second antenna array. The first antenna array may be configured to radiate and receive radiation from a first series of points along a first set of curves parallel to the direction of movement of the cart. The second antenna array may be configured to radiate and receive radiation from a second series of points along a second set of curves parallel to the direction of movement of the cart. The first set of curves may be interleaved with the second set of curves.
In general, in another aspect, the invention features a ground penetrating radar system including a first bank of receive antennas arranged along a first axis, a first bank of transmit antennas arranged along a second axis substantially parallel to the first axis and horizontally displaced from the first axis, a second bank of receive antennas arranged along a third axis substantially parallel to the first axis and horizontally displaced from the first axis, and a second bank of transmit antennas arranged along a fourth axis substantially parallel to the first axis and horizontally displaced from the first axis. A first radar electronics module is coupled to the first bank of transmit antennas and the first bank of receive antennas. A second radar electronics module is coupled to the second bank of transmit antennas and the second bank of receive antennas. The transmit antennas in the first bank of transmit antennas are interleaved with the receive antennas in the first bank of receive antennas and the transmit antennas in the second bank of transmit antennas are interleaved with the receive antennas in the second bank of receive antennas. The receive antennas in the first bank of transmit antennas are offset along the first axis from the receive antennas in the second bank of transmit antennas.
Implementations of the invention may include one or more of the following. The first bank of transmit antennas may be offset along the second axis with respect to the second bank of transmit antennas. The banks of receive antennas may alternate with the banks of transmit antennas. Each transmit antenna may be adjacent to at least one receive antenna. Each transmit antenna may be oriented to minimize electromagnetic coupling to at least one of its adjacent receive antennas. Each transmit antenna may include at least one spiral arm of conductive material. Each receive antenna may include at least one spiral arm of conductive material. A tangent to the inside of the spiral arm at the edge of a transmit antenna may be substantially perpendicular to a tangent to the inside of the spiral arm at the edge of a receive antenna adjacent to the transmit antenna. Each transmit antenna may include two spiral arms of conductive material. Each receive antenna may include two spiral arms of conductive material.
The transmit antennas and the receive antennas may have faces with centers. Two adjacent first bank receive antennas from the first bank of receive antennas and a first bank transmit antenna from the first bank of transmit antennas interleaved between the two adjacent first bank receive antennas may be positioned such that lines between the centers of the faces of the two adjacent first bank receive antennas and the interleaved first bank transmit antenna form a first triangle having sides of approximately the same length. Two adjacent second bank receive antennas from the second bank of receive antennas and a second bank transmit antenna from the second bank of transmit antennas interleaved between the two adjacent second bank receive antennas may be positioned such that lines between the centers of the faces of the two adjacent second bank receive antennas and the interleaved second bank transmit antenna form a second triangle having sides of approximately the same length. A vertex of the first triangle may be displaced in the direction of the first axis relative to a corresponding vertex of the second triangle by an amount substantially equal to one-half the distance from the center of one side of the first triangle to the center of another side of the first triangle.
The third axis may be horizontally displaced from the first axis by an amount substantially equal to eight times the distance from the center of one side of the first triangle to the center of anot
Bradley Marshall R.
Crowe Michael P.
Duncan Michael E.
McCummins, Jr. Robert J.
Baker & Botts L.L.P.
Gregory Bernarr E.
Planning Systems Incorporated
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