Metal detector and ground-penetrating radar hybrid head and manufacturing method thereof
A hybrid ground penetrating radar (GPR)/metal detector (MD) head includes a V-dipole GPR antenna and transmit and receive MD coils. One of the MD coils is arranged in a quadrupole configuration with a crossbar, and the V-dipole antenna is perpendicular to the crossbar. The legs of the V-dipole antenna may straddle the crossbar or may be on one side of the crossbar. The MD coils may be fabricated on a printed circuit board, which may be at a non-normal angle with respect to a central axis of the V-dipole antenna.
1. A ground penetrating radar (“GPR”) and metal detector (“MD”) hybrid head comprising:
an MD sensor including at least one receive coil in a quadrupole configuration including a crossbar, and at least one transmit coil, the crossbar having a first axis parallel to a direction in which current flows in the crossbar; and
at least one GPR V-dipole antenna arranged in a plane perpendicular to the first axis of the crossbar so as to reduce coupling between the coils of the MD sensor and the antenna;
wherein the transmit coil has an outer perimeter, the receive coil has an outer perimeter, and wherein at least a portion of the V-dipole antenna is within a cylinder formed by the projection of one of the outer perimeter of the receive coil or the transmit coil onto a plane perpendicular to a central axis of the V-dipole antenna.
2. The hybrid head of claim 1 , further including at least one electrostatic shield covering the top and bottom portion of the transmit and receive coils so as to stabilize capacitance between the transmit and receive coils and the changing external environment.
3. The hybrid head of claim 1 , wherein the at least one receive coil is concentric with the at least one transmit coil.
4. The hybrid head of claim 3 , wherein each of the at least one transmit coil and the at least one receive coil includes a plurality of turns respectively, the plurality of turns being concentric to each other and offset along an axis of concentricity.
5. The hybrid head of claim 3 , wherein the at least one V-dipole antenna is located within one half of the MD sensor on one side of the crossbar.
6. The hybrid head of claim 3 , where first and second conductors of the at least one V-dipole antenna are placed on opposite sides of the crossbar.
7. The hybrid head of claim 3 , wherein the MD coils are pitched at an angle between 20 and 90 degrees with respect to a central axis of the V-dipole antenna.
8. The hybrid head of claim 1 , wherein the at least one transmit coil and the at least one receive coil are formed on a printed circuit board (“PCB”).
9. The hybrid head of claim 8 , wherein the PCB has at least one layer including at least one turn of the transmit coil and at least one turn of the receive coil.
10. The hybrid head of claim 8 , wherein the PCB includes multiple layers, each of the layers including at least one turn of the transmit coil and at least one turn of the receive coil, wherein the at least one turn of the transmit coil and the at least one turn of the receive coil are approximately concentric and wherein the concentric layers which are arranged in stacked planes which are offset from each other along an axis of concentricity.
11. The hybrid head of claim 8 , wherein the at least one V-dipole antenna is located within one half of the MD receive coil on one side of the crossbar.
12. The hybrid head of claim 8 , where first and second conductors of the at least one V-dipole antenna are placed on opposite sides of the crossbar.
13. The hybrid head of claim 8 , wherein the MD coils are pitched at an angle between 20 and 90 degrees with respect to a central axis of the V-dipole antenna.
14. The hybrid head of claim 1 , further comprising a housing, wherein the MD sensor and the GPR antenna are mechanically connected to the housing.
15. A method for manufacturing an MD/GPR hybrid head, the method comprising the steps of:
forming an MD sensor including at least one receive coil in a quadrupole configuration including a crossbar, and at least one transmit coil, the crossbar having a first axis parallel to a direction in which current flows in the crossbar; and
positioning at least one GPR V-dipole antenna in a plane perpendicular to the first axis of the crossbar so as to reduce coupling between the coils of the MD sensor and the antenna;
wherein the transmit coil has an outer perimeter, the receive coil has an outer perimeter, and wherein at least a portion of the V-dipole antenna positioned within a cylinder formed by the projection of one of the outer perimeter of the receive coil or the transmit coil onto a plane perpendicular to a central axis of the V-dipole antenna.
16. The method of claim 15 , further including the step of covering the top and bottom portion of the transmit and receive coils with at least one electrostatic shield so as to stabilize capacitance between the transmit and receive coils and the changing external environment.
17. The method of claim 15 , wherein the at least one receive coil is concentric with the at least one transmit coil.
18. The method of claim 15 , wherein the at least one V-dipole antenna is positioned within one half of the MD sensor on one side of the crossbar.