Distributed capacitance LC resonant circuit

• US 4,598,276 A
• Filed: 11/06/1984
• Issued: 07/01/1986
• Est. Priority Date: 11/16/1983
• Status: Expired due to Term

• Current Assignee: Minnesota Mining and Manufacturing Co (3M Company)
• Original Assignee: Minnesota Mining and Manufacturing Co (3M Company)
• Inventors: Tait, William C.
• Primary Examiner(s): Swann, III, Glen R.
• Application Number:
  US06/667,607
• Time in Patent Office: 602 Days
• Field of Search: 340/572, 340/552, 340/553, 336/200, 343/895, 333/184-185, 333/138-140, 333/167-169, 333/174, 333/175, 333/177, 333/219
• US Class Current: 340/572.5
• CPC Class Codes: B32B 2519/02 RFID tags
• CPC Class Codes: G06K 19/0672 with resonating marks
• CPC Class Codes: G06K 19/07779 the inductive antenna being a coil
• CPC Class Codes: G06K 19/07783 the coil being planar
• CPC Class Codes: G06K 19/07784 the inductive antenna consisting of a plurality of coils stacked on top of one another
• CPC Class Codes: G08B 13/24 by interference with electromagnetic field distribution
• CPC Class Codes: G08B 13/2437 Tag layered structure, processes for making layered tags
• CPC Class Codes: G08B 13/244 Tag manufacturing, e.g. continuous manufacturing processes
• CPC Class Codes: G08B 13/2442 Tag materials and material properties thereof, e.g. magnetic material details

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-multi-turn 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.

Claims

1. An electronic article surveillance system comprising a transmitter for transmitting radio frequency energy at at least two predetermined frequencies,

a marker containing a circuit comprising a dielectric sheet having on each surface thereof a conductive multi-turn spiral 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, and

a receiver 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.

2. A marker for use in an electronic article surveillance system having a transmitter for producing a radio frequency electromagnetic field periodically varying at at least two predetermined frequencies, and a receiver 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, wherein said marker contains a circuit comprising a dielectric sheet having on each surface thereof a conductive multi-turn spiral 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.