Rfid-label with an element for regulating the resonance frequency

• US 20030169153A1
• Filed: 02/19/2003
• Published: 09/11/2003
• Est. Priority Date: 03/28/2000
• Status: Active Grant

• Current Assignee: Lucatron AG
• Original Assignee: Lucatron AG
• Inventors: Muller, Philipp
• Granted Patent: US 6,796,508 B2
• Time in Patent Office: Days
• US Class Current: 340/10.51
• CPC Class Codes: G06K 19/0672 with resonating marks
• CPC Class Codes: G06K 19/0726 the arrangement including a circuit for tuning the resonance frequency of an antenna on the record carrier
• CPC Class Codes: G06K 19/07749 the record carrier being capable of non-contact communication, e.g. constructional details of the antenna of a non-contact smart card
• CPC Class Codes: G08B 13/2414 using inductive tags
• CPC Class Codes: G08B 13/2417 having a radio frequency identification chip
• CPC Class Codes: G08B 13/2431 Tag circuit details

Abstract

The invention relates to an RFID label comprising a resonant circuit consisting of a coil and a capacitor. Said RFID label is provided with an additional element (13, 17, 20, 21) for regulating the resonance frequency of the resonant circuit, this element being applied to the surface of the RFID label after production of the same. The additional element can be especially, a sticker with a conductive layer, which is stuck in such a way that it at least partially overlaps individual conductive surfaces of the label in order to produce an additional capacitance or which is simply stuck into the coil in order to reduce the effective inductance of the coil. Alternatively, the element can be formed by a layer with high relative permittivity which is applied between two conductive surfaces.

Claims

1. RFID label with a substrate made of a plastic film and with conductive surfaces on the front and the back side of the substrate, the conductive surfaces forming, among other things, an electrical resonant circuit which comprises a coil (4) with at least one coil winding and a capacitor with a first capacitor plate on the front side of the substrate and a second capacitor plate on the back side of the substrate with another conductive surface (2) being arranged on the front side of the substrate conductively connected with the second plate of the capacitor on the back side of the substrate, characterized in that it is provided with an additional element (13, 17, 20, 21) subsequently applied to its surface which changes the resonant frequency of the resonant circuit.

2. RFID label according to claim 1, characterized in that it is provided with a sticker (13) with a metallic conductive layer, preferably made of aluminum.

3. RFID label according to claim 2, characterized in that the sticker (13) is applied to at least partly overlap at least two conductive surfaces arranged next to each other on the same side of the substrate, for the purpose of increasing the effective capacitance of the resonant circuit.

4. RFID label according to one of claims 2 or 3, characterized in that the sticker (13) is arranged to at least partly overlap the other conductive surface as well as one conductive surface which is essentially at the same electrical potential as the first plate of the capacitor, for the purpose of increasing the effective capacitance of the resonant circuit.

5. RFID label according to claim 3 or 4, characterized in that the sticker (13) is applied to the same side of the substrate as the conductive surfaces with which it acts jointly, preferably with an adhesive insulating layer (16) directly on these conductive surfaces.

6. RFID label according to one of claims 3 through 5, characterized in that the sticker (13) is applied to the opposite side of the substrate to the conductive surfaces with which it acts jointly.

7. RFID label according to one of claims 3 through 6, characterized in that the sticker (17) is conductively connected to a conductive surface on one side of the substrate and is also arranged in such a way that it at least partly overlaps another conductive surface of a different potential on the opposite side of the substrate.

8. RFID label according to claims 2 through 7, characterized in that the sticker (21) is applied at least partly in an area inside the coil (4) for the purpose of reducing the effective inductance of the resonant circuit.

9. RFID label according to claim 8, characterized in that the area inside the coil (4) has a center and that the sticker (21) is applied away from this center.

10. RFID label according to claims 1-9, characterized in that it is provided with a local layer (20) of a material having a high dielectric constant, preferably in the range between ε

_r 2 and 10, the local layer (20) bridging a gap between two conductive surfaces of a different electrical potential on the same side of the substrate.

11. RFID label according to claim 10, characterized in that the material can be applied in a liquid or paste state and subsequently solidifies and/or dries and/or hardens.

12. RFID label according to one of claims 10 or 11, characterized in that the local layer (20) bridges a gap between the other conductive surface as well as a conductive surface that is essentially at the same electrical potential as the first plate of the capacitor.

13. RFID label according to one of claims 1 through 12, characterized in that it is provided with an integrated semiconductor circuit in the form of a miniature chip, the electrical terminals of which being preferably connected, on one side, to the other conductive surface and, on the other side, to a conductive surface that is essentially at the same electrical potential as the first plate of the capacitor.