System and method for inhibiting detection of deactivated labels using detection filters having an adaptive threshold

1. A method for inhibiting detection of deactivated electronic article surveillance tags, the method comprising:

receiving a signal from at least one tag, the signal including signal detection information and signal deactivation information;

extracting the signal detection information from the received signal, the received signal detection information including a signal detection energy value;

extracting the signal deactivation information from the received signal, the received signal deactivation information including a signal deactivation energy value;

determining a failure to deactivate ratio, the failure to deactivate ratio corresponding to the signal detection energy value divided by the signal deactivation energy value; and

inhibiting generation of an alarm event conditioned upon the failure to deactivate ratio being less than a selectable threshold.

2. The method of claim 1 , further comprising selecting the signal detection energy value having the highest energy value from the output of one or more detection frequency filters.

3. The method of claim 1 , wherein extracting signal deactivation information includes filtering the received signal using a plurality of filters during a tag window portion of a time slot.

4. The method of claim 3 , wherein the plurality of filters are quadrature matched filters.

5. The method of claim 1 , wherein the selectable threshold is dynamically adjustable.

6. The method of claim 5 , further comprising sampling a plurality of received signal data frames to establish a noise factor, the noise factor being used to adjust the dynamically adjustable selectable threshold.

7. The method of claim 6 , wherein establishing the noise factor includes:

averaging a highest detection signal amplitude over the plurality of received signal time slots to generate a weighted average; and

filtering the weighted average using a low pass filter.

8. The method of claim 7 , wherein noise establishing the noise factor is measured during a time slot window.

9. The method of claim 6 , further comprising determining the dynamically adjustable selectable threshold by multiplying the selectable preset threshold by the noise factor.

10. A system for inhibiting detection of deactivated tags, the system comprising:

a receiver, the receiver receiving a signal from at least one tag, the received signal including signal detection information and signal deactivation information;

a detection frequency filter, the detection frequency filter extracting the signal detection information from the received signal, the received signal detection information including a signal detection energy value;

a deactivation frequency filter, the deactivation frequency filter extracting signal deactivation information from the received signal, the received signal deactivation information including a signal deactivation energy value; and

a processor, the processor operating to:

determine a failure to deactivate ratio, the failure to deactivate ratio corresponding to the signal detection energy value divided by the signal deactivation energy value; and

inhibit generation of an alarm event conditioned upon the failure to deactivate ratio being less than a selectable threshold.

11. The system of claim 10 , wherein the processor further operates to select the signal detection energy value having the highest energy value from one or more detection frequency filters.

12. The system of claim 10 , wherein the detection frequency filter and the deactivation frequency filter are comprised of one or more quadrature matched filters.

13. The system of claim 10 , wherein the selectable threshold is dynamically adjustable.

14. The system of claim 13 , wherein the processor further operates to sample a plurality of received signal data frames to establish a noise factor, the noise factor being used to adjust the dynamically adjustable selectable threshold.

15. The system of claim 14 , wherein the processor further operates to establish the noise factor by:

averaging the best detection signal amplitude over the plurality of received signal data frames to generate a weighted average; and

filtering the weighted average using a low pass filter.

16. The system of claim 14 , wherein the processor further operates to determine the dynamically adjustable selectable threshold by multiplying the selectable preset threshold by the noise factor.

17. The system of claim 10 , wherein the detection frequency filter extracts signal detection information at one of a specific frequency and frequency range, and wherein the deactivation frequency filter extracts deactivation signal information at a predetermined frequency.

18. The system of claim 17 , wherein the predetermined deactivation frequency is substantially 59,300 Hz.

19. A computer program product comprising a non-transitory computer usable medium having a computer readable program for a security system which when executed on a computer causes the computer to perform a method comprising:

receiving a signal from at least one tag, the signal including signal detection information and signal deactivation information; extracting the signal detection information from the received signal, the received signal information including a signal detection energy value; extracting signal deactivation information from the received signal, the received deactivation signal information including a signal deactivation energy value; determining a failure to deactivate ratio, the failure to deactivate ratio corresponding to the signal detection energy value divided by the signal deactivation energy value; and inhibiting generation of an alarm event conditioned upon the failure to deactivate ratio being less than a selectable threshold.

20. The method of claim 19 further comprising further comprising selecting the signal detection energy value having the highest energy value from the output of one or more detection frequency filters, wherein the selectable threshold is dynamically adjustable, the dynamic adjustment being based on a noise factor.