Resonant tag circuits useful in electronic security systems
First Claim
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1. A resonant tag circuit which comprises:
- an electrically insulating substrate,a first spiral conductive path on a first surface of said substrate,a second spiral conductive path on a second surface of said substrate,said first spiral conductive path and second spiral conductive path, forming inductors and being aligned so that they overlap each other over at least a portion of the length of said conductive paths thereby to form a distributed capacitor by virtue of said alignment,the degree of said overlap contributing to distributed capacitance being at least 70% of the overlap between conductive elements on opposing surfaces of said insulating substrate.
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Abstract
A resonant tag circuit is provided which is useful in conjunction with an electronic security system for preventing theft of articles from a protected area. The tag circuit comprises an electrically insulating substrate having a spiral conductive path on each surface of the substrate. The spiral conductive paths are positioned to overlap each other to effect distributed capacitance. The degree of overlap of the distributed capacitance portion of the conductive paths is such that it provides at least 70%, preferably 90% and most preferably 100% of the total overlapping portions of the circuit.
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14 Claims
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1. A resonant tag circuit which comprises:
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an electrically insulating substrate, a first spiral conductive path on a first surface of said substrate, a second spiral conductive path on a second surface of said substrate, said first spiral conductive path and second spiral conductive path, forming inductors and being aligned so that they overlap each other over at least a portion of the length of said conductive paths thereby to form a distributed capacitor by virtue of said alignment, the degree of said overlap contributing to distributed capacitance being at least 70% of the overlap between conductive elements on opposing surfaces of said insulating substrate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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Specification