Cutoff transmission and or reception antenna

• US 20060050008A1
• Filed: 10/11/2001
• Published: 03/09/2006
• Est. Priority Date: 10/11/2000
• Status: Abandoned Application

• Current Assignee: Ask S.A. (Paragon Group Limited)
• Original Assignee: Ask S.A. (Paragon Group Limited)
• Inventors: Morand, Sebastien, Berthault, Philippe
• Application Number:
  US10/149,251
• Publication Number:
  US 20060050008A1
• Time in Patent Office: Days
• US Class Current: 343/895
• 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 1/38 formed by a conductive layer on an insulating support patch antennas H01Q9/0407; microstrip dipole antennas H01Q9/065; microstrip slot antennas H01Q13/106; transmission line microstrip antennas H01Q13/206; manufacturing reflecting surfaces using insulating material for supporting the reflecting surface H01Q15/142
• CPC Class Codes: H01Q 7/00 Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop
• CPC Class Codes: H01Q 9/27 Spiral antennas

Abstract

An electromagnetic wave transmission and/or reception antenna (10) which includes a flat spiral wire, the spiral having at least two turns; the antenna including at least one cut (12) for the purpose of reducing the inter-turn capacitance. Such an antenna is used in a contactless communication system in which the reader transmits electromagnetic signals to a portable object (card or ticket) in order to identify the holder of the portable object when the latter transmits return identification signals to the reader.

Claims

1-7. -7. (canceled)

8. An electromagnetic transmission and/or reception antenna comprising a wire formed in a flat spiral having at least two turns, wherein said antenna includes at least one cut capable of reducing an inter-turn capacitance.

9. The antenna of claim 8, wherein said wire has a length at least equal to one fourth of the wavelength of an electromagnetic wave.

10. The antenna of claim 9, further comprising at least one additional cut, and wherein the cuts are distributed in such a way as to form equal portions of said wire on each side of the cut.

11. The antenna of claim 10, comprising three equally distributed cuts.

12. A contactless communication system, comprising a plurality of contactless cards each having an antenna, a card reader having the antenna of claim 8, such that the reader transmits electromagnetic signals to a contactless card in such a way as to be able to identify the holder of said contactless card when the latter transmits return identification signals to said reader.

13. The communication system of claim 12, wherein said contactless communication system is a system for gaining access to a controlled access zone.

14. The communication system of claim 13, wherein said electromagnetic signals have a frequency of 13.56 Hz.