Variable capacitance coupling antenna

• US 6,522,308 B1
• Filed: 08/24/2001
• Issued: 02/18/2003
• Est. Priority Date: 01/03/2000
• Status: Expired due to Term

• Current Assignee: Ask S.A. (Paragon Group Limited)
• Original Assignee: Ask S.A. (Paragon Group Limited)
• Inventors: Mathieu, Christophe
• Primary Examiner(s): Wong, Don
• Assistant Examiner(s): VANNUCCI, JAMES
• Application Number:
  US09/914,236
• Time in Patent Office: 543 Days
• Field of Search: 343/895, 343/700.MS, 343/741, 343/742, 343/743, 343/744, 343/745, 343/749, 343/866, 340/572.5
• US Class Current: 343/895
• 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: G06K 19/07779 the inductive antenna being a coil
• CPC Class Codes: G06K 19/07783 the coil being planar
• CPC Class Codes: G06K 7/10336 the antenna being of the near field type, inductive coil
• CPC Class Codes: H01Q 1/2225 used in active tags, i.e. provided with its own power source or in passive tags, i.e. deriving power from RF signal
• CPC Class Codes: H01Q 7/005 with variable reactance for tuning the antenna
• CPC Class Codes: H05K 1/162 incorporating printed capacitors
• CPC Class Codes: H05K 1/165 incorporating printed inductors

Abstract

The invention thus concerns a coupling antenna connected to an electromagnetic wave transceiver device containing one or several integrated capacitors. This coupling antenna includes at least one screen printed turn (24) on a support (28) consisting of an insulating dielectric support and also includes a screen printed capacitor on the support, connected in parallel, thereby reducing the capacitance supplied by the capacitor(s) built into the device, so that the resulting capacitance forms a resonating circuit with the turn. The invention also concerns the fabrication process of such an antenna and the use of this antenna in a contactless or hybrid contact-contactless smart card.

Claims

1. A coupling antenna, connected to an electromagnetic wave transceiver device containing one or several built-in capacitors, said coupling antenna comprising at least one screen printed turn on a support consisting of an insulating dielectric substrate;

wherein said antenna also includes a capacitor having a first plate, an insulating layer and a second plate which are screen printed on said support, one end of said antenna being coupled to said first plate of said capacitor and the other end of said antenna being coupled to said second plate so that said capacitor is connected in parallel to said antenna, thus reducing the capacitance supplied by the built-in capacitor(s) in said device, so that the resulting capacitance forms a resonating circuit with said turn.

2. The coupling antenna according to claim 1, in which said capacitor consists of at least two plates of screen printed ink, superimposed and separated by a insulating strip of dielectric ink which is also screen printed.

3. The coupling antenna according to claim 1, in which the dielectric substrate forming the support is made of plastic material, paper or glass fabric impregnated with thermosetting or U.V. shrink resin.

4. The coupling antenna according to claim 1, in which the ink used to screen print the turns and capacitor plates is a polymer conductive ink charged with conductive elements.

5. The coupling antenna according to claim 2, in which said insulating strip is made up of at least two layers of dielectric ink giving it high insulating properties.

6. The coupling antenna according to claim 5, in which the dielectric ink forming the two layers of the insulating strip is a U.V. shrink type polymer ink.

7. A contactless smart card made up of a support featuring at least one coupling antenna according to claim 1, connected to a chip or a module.

8. The contactless smart card according to claim 7, in which said chip or said module have no internal capacitance.

9. The contactless smart card according to claim 7, in which the support is inserted between two card bodies, said card bodies being fixed to each side of said support, enabling said smart card to be stiffened.

10. The contactless smart card according to claim 9, in which the card body is fixed to the support of the antenna by hot or cold lamination.

11. A coupling antenna fabrication process comprising:

screen printing at least one antenna turn, the lower plate of a capacitor, antenna bonding pads of said antenna to one of a chip or a module, and a connection of the antenna to said lower plate of the capacitor, by depositing conductive ink onto a support,

performing a second screen printing of an insulating strip of said capacitor, by depositing dielectric ink upon the lower plate of the capacitor,

performing a third screen printing of the upper plate of said capacitor superimposed on said insulating strip, and the connection of the antenna to said upper plate of said capacitor.