Digital detection filters for electronic article surveillance
DCFirst Claim
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1. A digital detector implemented as a quadrature matched filter bank for detecting a response signal from an electronic article surveillance tag, comprising:
- a detection filter pair comprised of h(T0−
t)·
sin(ω
·
t) and h(T0−
t)·
cos(ω
·
t), wherein the envelope h(T0−
t) contains preselected time and frequency domain properties according to the signal to be detected;
means for squaring the output of each of said filters; and
means for summing the squared outputs of each of said filter pairs to provide a test statistic for detection of the tag signal.
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Abstract
Digital implementation of electronic article surveillance (EAS) detection filtering for pulsed EAS systems is provided. Embodiments include direct implementation as a quadrature matched filter bank, as an envelope detector, a correlation receiver, and as a discrete Fourier transform. Pre-detection nonlinear filtering is also provided for impulsive noise environments.
37 Citations
22 Claims
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1. A digital detector implemented as a quadrature matched filter bank for detecting a response signal from an electronic article surveillance tag, comprising:
-
a detection filter pair comprised of h(T0−
t)·
sin(ω
·
t) and h(T0−
t)·
cos(ω
·
t), wherein the envelope h(T0−
t) contains preselected time and frequency domain properties according to the signal to be detected;
means for squaring the output of each of said filters; and
means for summing the squared outputs of each of said filter pairs to provide a test statistic for detection of the tag signal. - View Dependent Claims (2, 3, 4)
a plurality of said filter pairs wherein each pair is at a frequency ω
n for 1≦
n≦
N, where N is selected to cover the range of uncertainty of the signal to be detected; and
,means for summing each of the squared and summed results of each of said filter pairs to provide the test statistic for detection of the tag signal.
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3. The digital detector of claim 2 wherein each of said filter pairs are matched to the response signal from the electronic article surveillance tag wherein the envelope h(T0−
- t) is the time reversed version of the signal to be detected.
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4. The digital detector of claim 3 further comprising means for nonlinear filtering prior to said detection filter pair, wherein the nonlinearity of said means for nonlinear filtering is selected from a hole punch or a clipping nonlinearity.
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5. A digital detector implemented as a quadrature matched filter bank with envelope estimation for detecting a signal from an electronic article surveillance tag, comprising:
-
a detection filter comprised of h(T0−
t)·
sin(ω
·
t) wherein the envelope h(T0−
t) contains preselected time and frequency domain properties according to the signal to be detected;
means for envelope detection of the output of said filter; and
,means for squaring the output of said envelope detection to provide a test statistic for detection of the tag signal. - View Dependent Claims (6, 7, 8)
a plurality of said filters wherein each filter is at a frequency ω
n for 1≦
n≦
N, where N is selected to cover the range of uncertainty of the signal to be detected; and
,means for summing the output of said means for squaring for said plurality of said filters to provide the test statistic for detection of the tag signal.
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7. The digital detector of claim 6 wherein each of said filters are matched to the response signal from the electronic article surveillance tag wherein the envelope h(T0−
- t) is the time reversed version of the signal to be detected.
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8. The digital detector of claim 7 further comprising means for nonlinear filtering prior to said detection filter, wherein the nonlinearity of said means for nonlinear filtering is selected from a hole punch or a clipping nonlinearity.
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9. A digital detector implemented as a bank of correlation receivers for detecting a signal from an electronic article surveillance tag, comprising:
-
a correlation receiver including means for mixing a received signal with an envelope h(t) and a pair of local oscillators cos(ω
·
t) and sin(ω
·
t);
means for integrating the output of said means for mixing over the sampling period T0;
means for squaring the output of said integration means; and
,means for summing the output of said means for squaring for each of the pair of local oscillators to provide a test statistic for detection of the tag signal. - View Dependent Claims (10, 11)
means for summing the output of said plurality of correlation receivers to provide a test statistic for detection of the tag signal.
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11. The digital detector of claim 10 wherein said local oscillators and said means for integration comprise a discrete Fourier transform.
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12. A method, using a quadrature matched filter bank, for digitally detecting a signal from an electronic article surveillance tag, comprising:
-
filtering using a detection filter pair comprised of h(T0−
t)·
sin(ω
·
t) and h(T0−
t)·
cos(ω
·
t), wherein the envelope h(T0−
t) is preselected to contain time and frequency domain properties according to the signal to be detected;
squaring the output of each of said filters;
summing the squared outputs of each of said filter pairs to provide a test statistic for detection of the tag signal. - View Dependent Claims (13, 14, 15)
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16. A method, using a quadrature matched filter bank with envelope estimation, for detecting a signal from an electronic article surveillance tag, comprising:
-
filtering using a detection filter comprised of h(T0−
t)·
sin(ω
·
t) wherein the envelope h(T0−
t) is preselected to contain time and frequency domain properties according to the signal to be detected;
envelope detecting of the output of said filter;
squaring the output of said envelope detection to provide a test statistic for detection of the tag signal. - View Dependent Claims (17, 18, 19)
summing the squared output of said plurality of filters to provide the test statistic for detection of the tag signal.
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18. The method of claim 17 wherein each of said filters are matched to the response signal from the electronic article surveillance tag wherein the envelope h(T0−
- t) is the time reversed version of the signal to be detected.
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19. The method of claim 18 further comprising, prior to said detection filtering, nonlinear filtering using a nonlinearity selected from a hole punch or a clipping nonlinearity.
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20. A method, using a bank of correlation receivers, for detecting a signal from an electronic article surveillance tag, comprising:
-
in a correlation receiver;
mixing a received signal with a matched envelope h(t) and a pair of local oscillators cos(ω
·
t) and sin(ω
·
t);
integrating the mixed signal over the sampling period T0;
squaring the output of said integrated signal;
summing the squared output for each of the pair of local oscillators to provide a test statistic for detection of the tag signal. - View Dependent Claims (21, 22)
summing the output of said plurality of correlation receivers to provide the test statistic for detection of the tag signal.
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22. The method of claim 21 wherein said local oscillators and said integration comprise a discrete Fourier transform.
Specification