Method and apparatus for distinguishing metal objects employing multiple frequency interrogation
First Claim
1. A method for distinguishing between metal objects, comprising the steps of:
- interrogating a target with at least two frequencies;
receiving respective electrical response signals from said target for at least said two frequencies;
resolving said response signals into respective portions that are at least primarily resistive;
comparing the magnitudes of at least two of said portions;
selecting one response signal from among said response signals based on the results of said step of comparing; and
characterizing said target by use of said one response signal.
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Abstract
A method and apparatus for distinguishing metal objects employing multiple frequency interrogation. In one aspect, the method includes interrogating a target with at least two frequencies, obtaining respective response signals for the two frequencies, resolving the response signals into at least respective resistive component portions, comparing the magnitudes of at least two of the resistive component portions, selecting one response signal from among the response signals based on the comparison, and characterizing the target with the selected response signal. In other aspects, the method includes obtaining response data by interrogating the target at at least two frequencies, normalizing the response data and comparing the normalized response data. A signal is provided indicating the extent of any disagreement in the normalized response data.
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Citations
11 Claims
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1. A method for distinguishing between metal objects, comprising the steps of:
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interrogating a target with at least two frequencies;
receiving respective electrical response signals from said target for at least said two frequencies;
resolving said response signals into respective portions that are at least primarily resistive;
comparing the magnitudes of at least two of said portions;
selecting one response signal from among said response signals based on the results of said step of comparing; and
characterizing said target by use of said one response signal. - View Dependent Claims (2, 3)
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4. An apparatus for distinguishing between metal objects, comprising:
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an interrogating circuit adapted to interrogate a target with at least two frequencies;
a receiving circuit adapted to receive respective electrical response signals from said target for at least said two frequencies;
a demodulating circuit for resolving said response signals into respective portions that are at least primarily resistive;
a comparing circuit for comparing the magnitudes of said portions; and
a selecting circuit for selecting one response signal from among said response signals based on said comparison. - View Dependent Claims (5, 6, 7)
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8. A method for distinguishing between metal objects, comprising the steps of:
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interrogating an actual target with one or more electromagnetic signals at at least first and second frequencies;
receiving respective first and second electrical response signals from said target associated with said first and second frequencies;
obtaining first data from said first electrical response signal data;
normalizing said first data with respect to predetennined reference data at a third frequency; and
comparing the normalized said data corresponding to said first response signal to data corresponding to said second response signal; and
providing a signal responsive to the results of said step of comparing. - View Dependent Claims (9, 10, 11)
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Specification