EP0142380A2
Expired / Lapsed
EP
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Electronic article surveillance system using marker containing a distributed capacitance lc resonant circuit
Assignee: 3M Co
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Filing: 1984-11-15
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Granted: —
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Expires: 2004-11-15
Abstract
Abstract An electronic article surveillance system and a marker for use therein, which marker comprises a tuned resonant circuit including inductive and capacitive components formed of a laminate of a dielectric and conductive-multiturn spirals on opposing surfaces of the dielectric, wherein the capacitive component is formed as a result of distributed capacitance between the opposed spirals, and wherein the circuit thereby resonates at at least two predetermined frequencies which are subsequently received to create an output signal. An electrical connection is desirably provided between predetermined portions of the opposing spirals to lower the resonant frequencies.
Inventors
- 👤 William C. C/O Minnesota Mining And Tait
- 👤 Philip W. C/O Minnesota Mining And O'brien
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 19:30
CPC Classifications
G; G08; G08B; G08B13/00; G08B13/22; G08B13/24; G08B13/2402; G08B13/2405; G08B13/2414; G06; G06K; G06K19/00; G06K19/06; G06K19/067; G06K19/0672; G06K19/07; G06K19/077; G06K19/07749; G06K19/07773; G06K19/07777; G06K19/07779; G06K19/07783; G06K19/07784; G08B13/2428; G08B13/2437; G08B13/244; G08B13/2442; H; H03; H03H; H03H5/00; H03H5/02; H10; H10D; H10D86/00; H10D86/80; H10D86/85
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
202 words
A marker (174) for use in an electronic article surveillance system (170), said marker comprising a tuned resonant circuit (10, 15, 74) including a dielectric sheet (11, 17, 80 and 82) having on each surface thereof a conductive spiral pattern (12 and 13, 16 and 18, 76 and 78) in substantial registry with the spiral pattern on the opposite surface to thereby form a series of closed loops having both inductive and distributed capacitive components, characterized by each of said spiral patterns (12 and 13, 16 and 18 and 76 and 78) having multiple turns and being substantially identical to the spiral pattern on the opposite surface, each turn (68, 70, 72) of said spiral patterns forming a substantially closed loop positioned in substantial registry with a like turn of the opposite spiral pattern, each of said multi-turn spiral patterns further being oppositely wound with respect to the other when both are viewed from the same side of the sheet, and having one predetermined portion (64) in direct electrical contact (19, 84) with an opposing portion (66) of the opposite spiral whereby the resultant circuit resonates at at least one predetermined frequency at which eddy currents are minimized and Q-factor is high.
Claim 2
Dependent Claim
202 words
A marker (174) for use in an electronic article surveillance system (170), said marker comprising a tuned resonant circuit (10, 15, 74) including a dielectric sheet (11, 17, 80 and 82) having on each surface thereof a conductive spiral pattern (12 and 13, 16 and 18, 76 and 78) in substantial registry with the spiral pattern on the opposite surface to thereby form a series of closed loops having both inductive and distributed capacitive components, characterized by each of said spiral patterns (12 and 13, 16 and 18 and 76 and 78) having multiple turns and being substantially identical to the spiral pattern on the opposite surface, each turn (68, 70, 72) of said spiral patterns forming a substantially closed loop positioned in substantial registry with a like turn of the opposite spiral pattern, each of said multi-turn spiral patterns further being oppositely wound with respect to the other when both are viewed from the same side of the sheet, and having one predetermined portion (64) in direct electrical contact (19, 84) with an opposing portion (66) of the opposite spiral whereby the resultant circuit resonates at at least one predetermined frequency at which eddy currents are minimized and Q-factor is high.
Claim 3
Dependent Claim
24 words
A marker according to claim 1, further characterized by conductive means (19, 84) extending through said dielectric sheet for electrically contacting said spiral patterns.
Claim 4
Dependent Claim
20 words
A marker according to claim 1, characterized by the innermost portion of said spiral patterns being in direct electrical contact.
Claim 5
Dependent Claim
20 words
A marker according to claim 1, characterized by the outermost portion of said spiral patterns being in direct electrical contact.
Claim 6
Dependent Claim
31 words
A marker according to claim 4, further characterized by an electrical path around at least one edge of said dielectric sheet for electrically contacting said outermost portion of said spiral patterns.
Claim 7
Dependent Claim
26 words
A marker according to claim 1, characterized by both of said spiral patterns comprising a substantially planar, conductive path on a surface of the dielectric sheet.
Claim 8
Dependent Claim
64 words
A marker according to claim 6, characterized by the cross sections of all portions of said spiral patterns and the spacing between adjacent portions being substantially greater than the thickness of said dielectric sheet such that the distributed capacitance resulting from the substantially registered portions of the two spiral patterns is increased and the capacitance between adjacent portions of each spiral pattern is decreased.
Claim 9
Dependent Claim
130 words
A method of forming a marker of claim 1, characterized by the following steps: a) forming two substantially identical, conductive multi-turn spiral patterns, each turn of which forms a substantially closed loop, b) positioning said spiral patterns on opposite surfaces of a dielectric sheet with each spiral pattern being oppositely wound with respect to the other when both are viewed from the same side of the sheet, opposing portions of each spiral pattern being positioned in substantial registry with an opposing portion of the opposite spiral pattern, and c) electrically contacting at least one predetermined portion of each spiral pattern with an opposing portion of the other spiral pattern to thereby decrease the resonant frequency of the circuit over that resulting if the respective spiral patterns are but capacitively coupled.
Claim 10
Dependent Claim
33 words
A method according to claim 8, characterized by providing a dielectric sheet having on both surfaces thereof a conductive layer and removing selected portions of each said layer to provide said spiral patterns.
Claim 11
Dependent Claim
70 words
A method according to claim 8, characterized by said steps of positioning and contacting comprising adhering two connected spiral patterns to the same side of a dielectric sheet and folding said sheet back upon itself proximate to the connection between the spiral patterns such that the conductive paths of the spiral patterns become positioned in substantial registry with each other, and with a double thickness of the dielectric sheet therebetween.
Claim 12
Dependent Claim
175 words
ll. An electronic article surveillance system (170) comprising a transmitter (172) for transmitting radio frequency energy at at least two predetermined frequencies, a marker (174) containing a circuit (186) resonant at at least said two predetermined frequencies, and a receiver (176) for receiving signals resulting from the circuit resonating at said two predetermined frequencies and for creating an output signal in response to the receipt of said resultant signals, characterized by said marker (174) circuit (186) comprising a dielectric sheet (11, 17) having on each surface thereof a conductive multi-turn spiral pattern (12 and 13, 16 and 18) each turn of which forms a substantially closed loop and is in substantial registration with an opposing turn of the spiral pattern on the opposite surface, each of the multi-turn spiral patterns being oppositely wound with respect to each other when both are viewed from the same side of the sheet to thereby form a series of closed loops having both inductive and distributed capacitive components which in combination resonate at at least said two predetermined frequencies.
Claim 13
Dependent Claim
175 words
ll. An electronic article surveillance system (170) comprising a transmitter (172) for transmitting radio frequency energy at at least two predetermined frequencies, a marker (174) containing a circuit (186) resonant at at least said two predetermined frequencies, and a receiver (176) for receiving signals resulting from the circuit resonating at said two predetermined frequencies and for creating an output signal in response to the receipt of said resultant signals, characterized by said marker (174) circuit (186) comprising a dielectric sheet (11, 17) having on each surface thereof a conductive multi-turn spiral pattern (12 and 13, 16 and 18) each turn of which forms a substantially closed loop and is in substantial registration with an opposing turn of the spiral pattern on the opposite surface, each of the multi-turn spiral patterns being oppositely wound with respect to each other when both are viewed from the same side of the sheet to thereby form a series of closed loops having both inductive and distributed capacitive components which in combination resonate at at least said two predetermined frequencies.
Claim 14
Dependent Claim
178 words
A marker (174) for use in an electronic article surveillance system (170) having a transmitter (172) for producing a radio frequency electromagnetic field periodically varying at at least two predetermined frequencies, and a receiver (176) for receiving signals resulting from the interaction of the marker with the field, and for creating an output signal in response to the receipt of said resultant signals, characterized by said marker (174) containing a circuit (186) comprising a dielectric sheet (11, 17) having on each surface thereof a conductive multi-turn spiral (12 and 13, 16 and 18) each turn of which forms a substantially closed loop and is in substantial registration with an opposing turn of the spiral on the opposite surface, each of the multi-turn spirals being oppositely wound with respect to each other when both are viewed from the same side of the sheet to thereby form a series of closed loops having both inductive and distributed capacitive components which in combination resonate at at least said two predetermined frequencies upon absorption of energy from said field at said frequencies.
Claim 15
Dependent Claim
178 words
A marker (174) for use in an electronic article surveillance system (170) having a transmitter (172) for producing a radio frequency electromagnetic field periodically varying at at least two predetermined frequencies, and a receiver (176) for receiving signals resulting from the interaction of the marker with the field, and for creating an output signal in response to the receipt of said resultant signals, characterized by said marker (174) containing a circuit (186) comprising a dielectric sheet (11, 17) having on each surface thereof a conductive multi-turn spiral (12 and 13, 16 and 18) each turn of which forms a substantially closed loop and is in substantial registration with an opposing turn of the spiral on the opposite surface, each of the multi-turn spirals being oppositely wound with respect to each other when both are viewed from the same side of the sheet to thereby form a series of closed loops having both inductive and distributed capacitive components which in combination resonate at at least said two predetermined frequencies upon absorption of energy from said field at said frequencies.
References Cited (Backward Citations)
No citation records indexed.
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