US5111186A — LC-type electronic article surveillance tag with …

Claim 1

Independent Claim 54 words

A resonant tag adapted for use in an electronic article surveillance system, said resonant tag having at least a first resonant frequency, the resonant tag comprising: an inductive means: and a voltage dependent capacitance means whose capacitance can be varied with changes in voltage to selectively provide said first resonant frequency for said tag.

Claim 2

Dependent Claim 54 words

A resonant tag adapted for use in an electronic article surveillance system, said resonant tag having at least a first resonant frequency, the resonant tag comprising: an inductive means: and a voltage dependent capacitance means whose capacitance can be varied with changes in voltage to selectively provide said first resonant frequency for said tag.

Claim 3

Dependent Claim 100 words

A resonant tag in accordance with claim 1, wherein: said voltage dependent capacitance means has a first capacitance value when voltages equal or greater than a first threshold voltage are applied to said voltage dependent capacitance means and a second capacitance value when voltages equal to or less than a second threshold voltage are applied to said voltage dependent capacitance means, said second threshold voltage being lower than said first threshold voltage and said first capacitance value resulting in said tag having said first resonant frequency and said second capacitance value resulting in said tag having a second resonant frequency.

Claim 4

Dependent Claim 85 words

A resonant tag in accordance with claim 2, wherein: said voltage dependent capacitance means includes a dielectric whose dielectric constant is at a first dielectric constant value when voltages equal to or greater than said first threshold voltage are applied to said voltage dependent capacitance means and at a second dielectric constant value when voltages equal to or less than said second threshold voltage are applied to said voltage dependent capacitance means, said first and second dielectric constants resulting in said first and second capacitances.

Claim 5

Dependent Claim 108 words

A resonant tag in accordance with claim 3 wherein: said dielectric constant of said dielectric remains at said first dielectric constant value as the voltages applied to said capacitance means decrease from above said first threshold voltage to said second threshold voltage at which said dielectric constant undergoes substantially a step change to said second dielectric constant value; and said dielectric constant of said dielectric remains at said second dielectric constant value as the voltage applied to said capacitance means increases from below said second threshold value to said first threshold value at which said dielectric constant undergoes substantially a step change to said first dielectric constant value.

Claim 6

Dependent Claim 109 words

A resonant tag in accordance with claim 2 wherein: the capacitance of said capacitance means remains at said first capacitance value as the voltage applied to said capacitance means decreases from above said first threshold voltage to said second threshold voltage at which said capacitance of said capacitance means undergoes substantially a step change to said second capacitance value; and the capacitance of said capacitance means remains at said second capacitance value as the voltage applied to said capacitance increases from below said second threshold value to said first threshold value at which said capacitance of said capacitance means undergoes substantially a step change to said first capacitance value.

Claim 7

Dependent Claim 21 words

A resonant tag in accordance with claim 2, wherein: said voltage dependent capacitance means comprises: a capacitor having a ferroelectric dielectric.

Claim 8

Dependent Claim 16 words

A resonant tag in accordance with claim 6, wherein: said ferroelectric dielectric is Lead Zirconium Titanate.

Claim 9

Dependent Claim 30 words

A resonant tag in accordance with claim 2, wherein: said first resonant frequency indicates that said tag is activated and said second resonant frequency indicates that said tag is deactivated.

Claim 10

Dependent Claim 30 words

A resonant tag in accordance with claim 2, wherein: said second resonant frequency indicates that said tag is activated and said first resonant frequency indicates that said tag is deactivated.

Claim 11

Dependent Claim 40 words

A resonant tag in accordance with claim 1 further comprising: one or more further voltage dependent capacitance means having capacitances which can be varied with changes in voltage to selectively provide one or more further resonant frequencies for said tag.

Claim 12

Dependent Claim 75 words

A resonant tag in accordance with claim 10 wherein: each of said voltage dependent capacitance means has a first capacitance value when voltages equal to or greater than a first threshold voltage are applied to that voltage dependent capacitance means and a second capacitance value when voltages equal to or less than a second threshold voltage are applied to that voltage dependent capacitance means, said second threshold voltage being lower than said first threshold voltage.

Claim 13

Dependent Claim 22 words

A resonant tag in accordance with claim 11 wherein: the first threshold voltages associated with said voltage dependent capacitance means are different.

Claim 14

Dependent Claim 22 words

A resonant tag in accordance with claim 12 wherein: the second threshold voltages associated with said voltage dependent capacitance means are different.

Claim 15

Dependent Claim 22 words

A resonant tag in accordance with claim 11 wherein: the second threshold voltages associated with said voltage dependent capacitance means are different.

Claim 16

Dependent Claim 23 words

A resonant tag in accordance with claim 11 wherein: each of said voltage dependent capacitance means comprises a capacitor having a ferroelectric dielectric.

Claim 17

Dependent Claim 16 words

A resonant tag in accordance with claim 15 wherein: said ferroelectric dielectric is lead zirconium titanate.

Claim 18

Dependent Claim 44 words

An article surveillance system, comprising: a resonant tag comprising: an inductive means, and a voltage dependent capacitance means whose capacitance can be varied with changes in voltage to selectively provide a first resonant frequency for said tag; and means for detecting said resonant tag.

Claim 19

Dependent Claim 44 words

An article surveillance system, comprising: a resonant tag comprising: an inductive means, and a voltage dependent capacitance means whose capacitance can be varied with changes in voltage to selectively provide a first resonant frequency for said tag; and means for detecting said resonant tag.

Claim 20

Dependent Claim 29 words

An article surveillance system in accordance with claim 17, wherein: said detecting means is arranged to detect said resonant tag only when said tag exhibits said first resonant frequency.

Claim 21

Dependent Claim 18 words

An article surveillance system in accordance with claim 17 further comprising: an alarm responsive to said detecting means.

Claim 22

Dependent Claim 36 words

An article surveillance system in accordance with claim 17, wherein: said means for detecting comprises: means for transmitting an RF field into a surveillance zone; and means for sensing perturbations to said field in said zone.

Claim 23

Dependent Claim 17 words

An article surveillance system in accordance with claim 20 wherein: said field is an RF swept field.

Claim 24

Dependent Claim 88 words

An article surveillance system in accordance with claim 20 wherein: said voltage dependent capacitance means has a first capacitance value for voltages equal to or greater than a first threshold voltage applied to said voltage dependent capacitance means and a second capacitance value for voltages equal to or less than a second threshold voltage applied to said voltage dependent capacitance means; said first capacitance value resulting in said tag having said first resonant frequency and said second capacitance value resulting in said tag having a second resonant frequency.

Claim 25

Dependent Claim 52 words

An article surveillance system in accordance with claim 22, further comprising: means for applying a voltage equal to or greater than said first threshold voltage to said voltage dependent capacitance means,; and means for applying a voltage equal to or less than said second threshold voltage to said voltage dependent capacitance means.

Claim 26

Dependent Claim 28 words

An article surveillance system in accordance with claim 22, wherein: said means for detecting perturbations to said field detects perturbations at said first and said second resonant frequencies.

Claim 27

Dependent Claim 22 words

An article surveillance system in accordance with claim 22, wherein: said voltage dependent capacitance means comprises: a capacitor having a ferroelectric dielectric.

Claim 28

Dependent Claim 17 words

An article surveillance system in accordance with claim 25, wherein: said ferroelectric dielectric is lead zirconium titanate.

Claim 29

Dependent Claim 46 words

An article surveillance system in accordance with claim 22, wherein: one of said first and second resonant frequencies is indicative of an activated state for said tag and the other of said first and second resonant frequencies is indicative of a deactivated state for said tag.

Claim 30

Dependent Claim 44 words

An article surveillance system in accordance with claim 20; wherein: said tag further comprises: one or more further voltage dependent capacitance means having capacitance which can be varied with changes in voltage to selectively provide one or more further resonant frequencies for said tag.

Claim 31

Dependent Claim 65 words

An article surveillance system in accordance with claim 28, wherein: each of said voltage dependent capacitance means has a first capacitance value when voltages equal to or greater than a first threshold voltage are applied to that voltage dependent capacitance means and a second capacitance value when voltages equal to or less than a second threshold voltage are applied to that voltage dependent capacitance means.

Claim 32

Dependent Claim 23 words

An article surveillance system in accordance with claim 29, wherein: the first threshold voltages associated with said voltage dependent capacitance means are different.

Claim 33

Dependent Claim 23 words

An article surveillance system in accordance with claim 30, wherein: the second threshold voltages associated with said voltage dependent capacitance means are different.

Claim 34

Dependent Claim 23 words

An article surveillance system in accordance with claim 29, wherein the second threshold voltages associated with said voltage dependent capacitance means are different.

Claim 35

Dependent Claim 24 words

An article surveillance system in accordance with claim 29, wherein each of said voltage dependent capacitance means comprises a capacitor having a ferroelectric dielectric.

Claim 36

Dependent Claim 19 words

An article surveillance system in accordance with with claim 29, wherein: the RF field is a swept RF Field.

Claim 37

Dependent Claim 55 words

A resonant tag adapted for use in an electronic article surveillance system, said tag comprising a circuit having at least a first resonant frequency, the circuit comprising: an inductive means: and a voltage dependent capacitance means whose capacitance can be varied with changes in voltage to selectively provide said first resonant frequency for said tag.

Claim 38

Dependent Claim 55 words

A resonant tag adapted for use in an electronic article surveillance system, said tag comprising a circuit having at least a first resonant frequency, the circuit comprising: an inductive means: and a voltage dependent capacitance means whose capacitance can be varied with changes in voltage to selectively provide said first resonant frequency for said tag.

Claim 39

Dependent Claim 99 words

A circuit in accordance with claim 35, wherein: said voltage dependent capacitance means has a first capacitance value when voltages equal or greater than a first threshold voltage are applied to said voltage dependent capacitance means and a second capacitance value when voltages equal to or less than a second threshold voltage are applied to said voltage dependent capacitance means, said second threshold voltage being lower than said first threshold voltage and said first capacitance value resulting in said circuit having said first resonant frequency and said second capacitance value resulting in said circuit having a second resonant frequency.

Claim 40

Dependent Claim 84 words

A circuit in accordance with claim 36, wherein: said voltage dependent capacitance means includes a dielectric whose dielectric constant is at a first dielectric constant value when voltages equal to or greater than said first threshold voltage are applied to said voltage dependent capacitance means and at a second dielectric constant value when voltages equal to or less than said second threshold voltages are applied to said voltage dependent capacitance means, said first and second dielectric constants resulting in said first and second capacitances.

Claim 41

Dependent Claim 107 words

A circuit in accordance with claim 37 wherein: said dielectric constant of said dielectric remains at said first dielectric constant value as the voltages applied to said capacitance means decrease from above said first threshold voltage to said second threshold voltage at which said dielectric constant undergoes substantially a step change to said second dielectric constant value; and said dielectric constant of said dielectric remains at said second dielectric constant value as the voltage applied to said capacitance means increases from below said second threshold value to said first threshold value at which said dielectric constant undergoes substantially a step change to said first dielectric constant value.

Claim 42

Dependent Claim 108 words

A circuit in accordance with claim 36 wherein: the capacitance of said capacitance means remains at said first capacitance value as the voltage applied to said capacitance means decreases from above said first threshold voltage to said second threshold voltage at which said capacitance of said capacitance means undergoes substantially a step change to said second capacitance value; and the capacitance of said capacitance means remains at said second capacitance value as the voltage applied to said capacitance increases from below said second threshold value to said first threshold value at which said capacitance of said capacitance means undergoes substantially a step change to said first capacitance value.

Claim 43

Dependent Claim 20 words

A circuit in accordance with claim 36, wherein: said voltage dependent capacitance means comprises: a capacitor having a ferroelectric dielectric.

Claim 44

Dependent Claim 15 words

A circuit in accordance with claim 40, wherein: said ferroelectric dielectric is lead zirconimum titanate.

Claim 45

Dependent Claim 29 words

A circuit in accordance with claim 36, wherein: said first resonant frequency indicates that said circuit is activated and said second resonant frequency indicates that said circuit is deactivated.

Claim 46

Dependent Claim 29 words

A circuit in accordance with claim 36, wherein: said second resonant frequency indicates that said circuit is activated and said first resonant frequency indicates that said tag is deactivated.

Claim 47

Dependent Claim 39 words

A circuit in accordance with claim 35 further comprising: one or more further voltage dependent capacitance means having capacitances which can be varied with changes in voltage to selectively provide one or more further resonant frequencies for said circuit.

Claim 48

Dependent Claim 74 words

A circuit in accordance with claim 44 wherein: each of said voltage dependent capacitance means has a first capacitance value when voltages equal to or greater than a first threshold voltage are applied to that voltage dependent capacitance means and a second capacitance value when voltages equal to or less than a second threshold voltage are applied to that voltage dependent capacitance means, said second threshold voltage being lower than said first threshold voltage.

Claim 49

Dependent Claim 21 words

A circuit in accordance with claim 45 wherein: the first threshold voltages associated with said voltage dependent capacitance means are different.

Claim 50

Dependent Claim 21 words

A circuit in accordance with claim 46 wherein: the second threshold voltages associated with said voltage dependent capacitance means are different.

Claim 51

Dependent Claim 20 words

A circuit in accordance with claim 45 wherein: the second threshold voltages associated with said dependent capacitance means are different.

Claim 52

Dependent Claim 22 words

A circuit in accordance with claim 45 wherein: each of said voltage dependent capacitance means comprises a capacitor having a ferroelectric dielectric.

Claim 53

Dependent Claim 15 words

A circuit in accordance with claim 49 wherein: said ferroelectric dielectric is lead zirconium titanate.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1995-05-05	1995-11-04	1996-05-05	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1999-05-05	1999-11-04	2000-05-05	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2003-05-05	2003-11-04	2004-05-05	$7700.00	Window Closed / Lapsed

LC-type electronic article surveillance tag with voltage dependent capacitor

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