Method and apparatus for metal detection employing digital signal processing
First Claim
1. A metal detector of the continuous wave type including;
- a transmission circuit and a transmitter coil adapted to produce an interrogating magnetic field for detection of a target;
a receiving coil and a receiving circuit adapted to receive and process a receive signal produced by a target and its environment in the interrogating field;
further including at least one digital signal generator adapted to generate at least one pair of reference sinusoidal signals of the same frequency;
wherein there is produced one or more output signals which are a linear combination of selected of said reference signals, said output signals being applied to a transmitter which produces at least one transmission signal said transmission signal being applied to the transmission circuit and transmitter coil combination to produce an interrogating magnetic field for detection of a target.
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Accused Products
Abstract
A metal detector employing digital means for the generation of highly quality reference signals used for transmission and demodulation and capable of continuously monitoring the parameters of the transmitting and receiving coils. Using the monitored signals and calibration of the measurements paths in both amplitude-frequency and phase-frequency, the effects of the targets and magnetic and/or conductive grounds on the transmitting and receiving coils are greatly reduced, leaving the received signals substantially free of instrumental effects. Methods of ground tracking and filtering are described to separate target information from the ground plus-target receive signals. Single-and multi-frequency operation, with or without modulation for both sinusoidal and square wave transmission, is described, as are means to detect abnormal situations and to find and operate at resonance.
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Citations
43 Claims
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1. A metal detector of the continuous wave type including;
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a transmission circuit and a transmitter coil adapted to produce an interrogating magnetic field for detection of a target; a receiving coil and a receiving circuit adapted to receive and process a receive signal produced by a target and its environment in the interrogating field; further including at least one digital signal generator adapted to generate at least one pair of reference sinusoidal signals of the same frequency; wherein there is produced one or more output signals which are a linear combination of selected of said reference signals, said output signals being applied to a transmitter which produces at least one transmission signal said transmission signal being applied to the transmission circuit and transmitter coil combination to produce an interrogating magnetic field for detection of a target. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
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28. A method for detecting metallic targets in a ground including the steps of
providing a transmission circuit and a transmitter coil adapted to produce an interrogating magnetic field for detection of a target; -
providing a receiving coil and a receiving circuit adapted to receive and process a receive signal produced by a target and its environment in the interrogating field; generating by digital means at least one pair of reference sinusoidal signals of the same frequency; producing one or more output signals which are a linear combination of selected of said reference signals; transmitting said output signal to produce the interrogating magnetic field for detection of a target. - View Dependent Claims (29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43)
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Specification