Metal detector system having multiple, adjustable transmitter and receiver antennas

Claim 2

A metal detector system comprising: a first planar surface; a second planar surface opposite said first planar surface to define a passage therebetween; a first transmitter antenna adjustably supported on said first planar surface for transmitting a first signal for detecting a metal object in said passage; a first receiver antenna adjustably supported on said second planar surface in a position opposite to a position of said first transmitter antenna for receiving said first signal from said first transmitter antenna and outputting a third signal in response to said first signal and a fourth signal in response to detection of a metal object in said passage; a second transmitter antenna adjustably supported on said second planar surface for transmitting a second signal for detecting a metal object in said passage; a second receiver antenna adjustably supported on said first planar surface in a position opposite to a position of said second transmitter antenna for receiving said second signal from said second transmitter antenna and outputting a fifth signal in response to said second signal and a sixth signal in response to detection of a metal object in said passage; said position of said first receiver antenna relative to said position of said second transmitter antenna on said second planar surface being adjustable to prevent said output signals of said first receiver antenna from being based on said second signal from said second transmitter antenna, and said position of said second receiver antenna relative to said position of said first transmitter antenna on said first planar surface being adjustable to prevent said output signal of said second receiver antenna from being based on said first signal from said first transmitter antenna.

Claim 3

The system as recited in claim 1, wherein said first and second planar surfaces include a first and second vertical side panel, respectively, of a portal.

Claim 4

The system as recited in claim 1, further comprising a conveyor system having oppositely disposed surfaces defining said planar surfaces.

Claim 5

The system as recited in claim 2, wherein said first receiver antenna and said second transmitter antenna are of elongated rectangular shape and are crossed at a predetermined angle, and said second receiver antenna and said first transmitter antenna are of elongated rectangular shape and are crossed at said predetermined angle.

Claim 6

The system as recited in claim 4, further comprising a control unit coupled to outputs of said first and second receiver antennas for processing said third, fourth, fifth and sixth signals and for indicating detection of a metal object in said passage in response thereto.

Claim 7

The system as recited in claim 5, wherein the size of said first receiver antenna coincides with the size of said second transmitter antenna, and the size of said second receiver antenna coincides with the size of said first transmitter antenna.

Claim 8

The system as recited in claim 6, wherein each of said first and second receiver antennas includes two receiver coils wound in opposite direction.

Claim 9

The system as recited in claim 7, wherein a plane containing said first transmitter antenna and said two receiver coils of said second receiver antenna is parallel to a plane containing said second transmitter coil and said two receiver coils of said first receiver antenna.

Claim 10

The system as recited in claim 7, wherein a plane containing said first transmitter antenna and a plane containing said two receiver coils of said second receiver antenna intersect at a second predetermined angle, and a plane containing said second transmitter antenna and a plane containing said two receiver coils of said first receiver antenna intersect at the second predetermined angle.

Claim 11

The system as recited in claim 7, further comprising a first differential amplifier coupled to an output of each of said two coils of said first receiver antenna, and a second differential amplifier coupled to an output of each of said two coils of said second receiver antenna, outputs of said first and second differential amplifiers being coupled to respective inputs of said control unit.

Claim 12

The system as recited in claim 10, wherein the mutual inductances between said first and second transmitter antennas and each of said two coils of said second and first receiver antennas, respectively, are approximately equal.

Claim 13

The system as recited in claim 1, further comprising a piece of conductive metal fixed in close proximity to at least one of said antennas for preventing said output signals of said first receiver antenna from being based on said second signal from said second transmitter antenna and for preventing said output signals of said second receiver antenna from being based on said first signal from said first transmitter antenna.

Claim 14

The system as recited in claim 12, further comprising an amorphous material encapsulating the coils.

Claim 15

The system as recited in claim 13, wherein at least one of said first and second transmitter antennas is split into a plurality of separate transmitter antennas.

Claim 16

The system as recited in claim 13, wherein at least one of said first and second receiver antennas is split into a plurality of separate receiver antennas.

Claim 17

The system as recited in claim 13, further comprising at least one additional transmitter antenna adjustably supported on said second side panel for transmitting an additional signal, and at least one additional receiver antenna adjustably supported on said first side panel in a position opposite to a position of said additional transmitter antenna for receiving said additional signal from said additional transmitter antenna.

Claim 18

The system as recited in claim 13, further comprising a first plurality of first transmitter antennas adjustably supported on said first side panel, a second plurality of second transmitter antennas adjustably supported on said second side panel, a first plurality of first receiver antennas adjustably supported on said second side panel in positions opposite to positions of said first transmitter antennas, and a second plurality of second receiver antennas adjustably supported on said first side panel in positions opposite to positions of said second transmitter antennas.

Claim 19

A metal detector system comprising: a first planar surface; a second planar surface opposite said first planar surface to define a passage therebetween; a first transmitter antenna adjustably supported on said first planar surface for transmitting a first signal for detecting a metal object in said passage; a first receiver antenna adjustably supported on said second planar surface in a position opposite to a position of said first transmitter antenna for receiving said first signal from said first transmitter antenna and outputting a third signal in response to said first signal and a fourth signal in response to detection of a metal object in said passage; a second transmitter antenna adjustably supported on said second planar surface for transmitting a second signal for detecting a metal object in said passage; a second receiver antenna adjustably supported on said first planar surface in a position opposite to a position of said second transmitter antenna for receiving said second signal from said second transmitter antenna and outputting a fifth signal in response to said second signal and a sixth signal in response to detection of a metal object in said passage; and a metal shield adjustably positioned to cover said antennas and to prevent said output signals of said first receiver antenna from being based on said second signal from said second transmitter antenna and to prevent said output signals of said second receiver antenna from being based on said first signal from said first transmitter antenna.

Claim 20

A metal detector system comprising: a first planar surface; a second planar surface opposite said first planar surface to define a passage therebetween; a first transmitter antenna adjustably supported on said first planar surface for transmitting a first signal for detecting a metal object in said passage; a first receiver antenna adjustably supported on said second planar surface in a position opposite to a position of said first transmitter antenna for receiving said first signal from said first transmitter antenna and outputting a third signal in response to said first signal and a fourth signal in response to detection of a metal object in said passage; a second transmitter antenna adjustably supported on said second planar surface for transmitting a second signal for detecting a metal object in said passage; a second receiver antenna adjustably supported on said first planar surface in a position opposite to a position of said second transmitter antenna for receiving said second signal from said second transmitter antenna and outputting a fifth signal in response to said second signal and a sixth signal in response to detection of a metal object in said passage; and a metal shield adjustably positioned to cover said antennas and to prevent said output signals of said first receiver antenna from being based on said second signal from said second transmitter antenna and to prevent said output signals of said second receiver antenna from being based on said first signal from said first transmitter antenna.

Claim 23

The method as recited in claim 19, wherein each antenna is of elongated rectangular shape, and the adjustment of the positions of the antennas includes crossing the first receiver antenna with the second transmitter antenna at a predetermined angle and crossing the second receiver antenna with the first transmitter antenna at the predetermined angle.

Claim 24

The method as recited in claim 19, wherein the adjustment of the positions of the antennas includes changing a distance between the first receiver antenna and the second transmitter antenna, and between the second receiver antenna and the first transmitter antenna.

Claim 25

The method as recited in claim 19, further comprising the step of fixing a piece of conductive metal in close proximity to at least one of the antennas for preventing the output signal of the first receiver antenna from being based on the second signal from the second transmitter antenna and for preventing the output signal of the second receiver antenna from being based on the first signal from the first transmitter antenna.

Claim 28

A metal detector system comprising: a first planar surface; a second planar surface opposite said first planar surface to define a passage therebetween; a first transmitter antenna adjustably supported on said first planar surface for transmitting a first signal for detecting a metal object in said passage; a first receiver antenna adjustably supported on said second planar surface in a position opposite to a position of said first transmitter antenna for receiving said first signal from said first transmitter antenna and outputting a third signal in response to said first signal and a fourth signal in response to detection of a metal object in said passage; a second transmitter antenna adjustably supported on said second planar surface for transmitting a second signal for detecting a metal object in said passage; a second receiver antenna adjustably supported on said first planar surface in a position opposite to a position of said second transmitter antenna for receiving said second signal from said second transmitter antenna and outputting a fifth signal in response to said second signal and a sixth signal in response to detection of a metal object in said passage; said position of said first receiver antenna relative to said position of said second transmitter antenna on said second planar surface being adjustable to prevent said output signals of said first receiver antenna from being based on said second signal from said second transmitter antenna, and said position of said second receiver antenna relative to said position of said first transmitter antenna on said first planar surface being adjustable to prevent said output signal of said second receiver antenna from being based on said first signal from said first transmitter antenna; wherein said first receiver antenna and said second transmitter antenna are of elongated rectangular shape and are crossed at a predetermined angle, and said second receiver antenna and said first transmitter antenna are of elongated rectangular shape and are crossed at said predetermined angle.

Claim 29

A metal detector system comprising: a first planar surface; a second planar surface opposite said first planar surface to define a passage therebetween; a first transmitter antenna adjustably supported on said first planar surface for transmitting a first signal for detecting a metal object in said passage; a first receiver antenna adjustably supported on said second planar surface in a position opposite to a position of said first transmitter antenna for receiving said first signal from said first transmitter antenna and outputting a third signal in response to said first signal and a fourth signal in response to detection of a metal object in said passage; a second transmitter antenna adjustably supported on said second planar surface for transmitting a second signal for detecting a metal object in said passage; a second receiver antenna adjustably supported on said first planar surface in a position opposite to a position of said second transmitter antenna for receiving said second signal from said second transmitter antenna and outputting a fifth signal in response to said second signal and a sixth signal in response to detection of a metal object in said passage; said position of said first receiver antenna relative to said position of said second transmitter antenna on said second planar surface being adjustable to prevent said output signals of said first receiver antenna from being based on said second signal from said second transmitter antenna, and said position of said second receiver antenna relative to said position of said first transmitter antenna on said first planar surface being adjustable to prevent said output signal of said second receiver antenna from being based on said first signal from said first transmitter antenna; wherein said first receiver antenna and said second transmitter antenna are of elongated rectangular shape and are crossed at a predetermined angle, and said second receiver antenna and said first transmitter antenna are of elongated rectangular shape and are crossed at said predetermined angle.