Electronic article surveillance system with adaptive filtering and digital detection
First Claim
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1. An electronic article surveillance system in which a drive field signal is generated in an interrogation corridor to detect presence of a sensitized tag, comprising:
- means for acquiring a passive snapshot of an environment in the corridor;
means for acquiring an interrogation snapshot of the environment in the corridor; and
an adaptive filter, connected to receive the passive snapshot and to receive the interrogation snapshot, and adapted to adaptively filter the passive snapshot and subtract the filtered passive snapshot from the interrogation snapshot to produce a recovered signal.
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Abstract
An electronic article surveillance (EAS) systems includes an asynchronous noise suppression adaptive filter which removes asynchronous interference from the signal of interest with minimum distortion of the transients emitted when a sensitized tag is interrogated. The system also includes a synchronous noise suppression filter which removes interrogation synchronous noise from the signal of interest. The resulting EAS system increases the likelihood that a sensitized tag will be detected when one is present and reduces the occurrence of false alarms.
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Citations
20 Claims
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1. An electronic article surveillance system in which a drive field signal is generated in an interrogation corridor to detect presence of a sensitized tag, comprising:
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means for acquiring a passive snapshot of an environment in the corridor; means for acquiring an interrogation snapshot of the environment in the corridor; and an adaptive filter, connected to receive the passive snapshot and to receive the interrogation snapshot, and adapted to adaptively filter the passive snapshot and subtract the filtered passive snapshot from the interrogation snapshot to produce a recovered signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. An electronic article surveillance system, comprising:
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at least one interrogation signal generator; at least one signal sense detector; a receiver, connected to receive a signal from the signal sense detector, the receiver further including; synch means for filtering interrogation synchronous interference from the received signal; asynch means for filtering asynchronous interference from the received signal and producing therefrom a recovered signal; and detection means, connected to receive the recovered signal, for identifying whether the recovered signal contains a sensitized tag signal. - View Dependent Claims (18, 19)
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20. A method of detecting presence of a sensitized tag in an interrogation corridor of an electronic article surveillance system, wherein a drive field signal is generated in the interrogation corridor comprising the steps of;
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(a) sampling the environment in the corridor in the absence of the drive field signal to acquire a passive snapshot; (b) sampling the environment in the corridor during presence of the drive field signal to acquire an interrogation snapshot; (c) adaptively filtering the passive snapshot; (d) subtracting the filtered passive snapshot from the interrogation snapshot and producing therefrom a recovered signal; and (e) assessing the recovered signal for presence of a sensitized tag.
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Specification