Electronic article surveillance system with comb filtering by polyphase decomposition and nonlinear filtering of subsequences
AssigneeSensormatic Electronics Corporation
InventorsThomas J. Frederick, Dale R. Bettine
Life of this patent
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Abstract
A signal received in an electronic article surveillance system is subjected to a nonlinear comb filtering function to remove interference. The nonlinear comb filtering is provided by performing a polyphase decomposition of an input digital signal, nonlinear filtering of the resulting subsequences, and then synthesizing the nonlinear-filtered subsequences. A median filter may be used as the subsequence filtering function. A linear comb filtering function may be provided downstream from the nonlinear comb filter to provide additional attenuation of interference.
Claims31
An electronic article surveillance system, comprising:
- means for generating and radiating an interrogation signal which alternates at a predetermined frequency F.sub.0 in an interrogation zone;
- antenna means for receiving a signal present in the interrogation zone;
- A/D conversion means for receiving an analog signal representative of said signal received by said antenna means and converting said analog signal into a sequence of digital samples;
- and
- digital signal processing means for processing said sequence of digital samples to remove interference therefrom, said digital signal processing means processing said sequence of digital samples by:
- forming M subsequences from said sequence of digital samples, M being a positive integer greater than 1;
- applying a respective nonlinear digital filtering function to each of said M subsequences;
- and
- combining the M filtered subsequences to form a processed sequence of digital samples.
A method of removing interference from a signal received by an electronic article surveillance system, comprising the steps of:
- generating and radiating an interrogation signal which alternates at a predetermined frequency F.sub.0 in an interrogation zone;
- receiving an analog signal representative of a signal present in the interrogation zone and converting the received analog signal into a sequence of digital samples;
- and
- processing said sequence of digital samples to remove interference therefrom, said processing step including:
- forming M subsequences from said sequence of
- digital samples, M being a positive integer
- greater than 1;
- applying a respective nonlinear digital filtering function to each of said M subsequences;
- and
- combining the M filtered subsequences to form a processed sequence of digital samples.
An electronic article surveillance system, comprising:
- means for generating and radiating an interrogation signal which alternates at a predetermined frequency in an interrogation zone;
- antenna means for receiving a signal present in the interrogation zone;
- A/D conversion means for receiving an analog signal representative of said signal received by said antenna means and converting said analog signal into a sequence of digital samples;
- and
- digital signal processing means for processing said sequence of digital samples to remove interference therefrom, said digital signal processing means processing said sequence of digital samples by:
- performing a polyphase decomposition to form a plurality of subsequences from said sequence of digital samples;
- applying a respective nonlinear digital filtering function to each of said plurality of subsequences;
- and
- synthesizing the filtered subsequences to form a processed sequence of digital samples.
Dependencies are inferred from the claim text.