Antenna circuit for non-contact IC card and method of manufacturing the same

• US 5,337,063 A
• Filed: 04/13/1992
• Issued: 08/09/1994
• Est. Priority Date: 04/22/1991
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Takahira, Kenichi
• Primary Examiner(s): Hajec, Donald
• Assistant Examiner(s): Ho, Tan
• Application Number:
  US07/867,538
• Time in Patent Office: 848 Days
• Field of Search: 343/741, 343/742, 343/743, 343/744, 343/895, 343/866, 343/867, 343/868, 343/745, 29/600
• US Class Current: 343/741
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• 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: G06K 19/0775 arrangements for connecting the integrated circuit to the antenna
• 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 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• 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 1/36 Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewithH01Q1/08, H01Q1/14 take precedence
• 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

Abstract

An antenna circuit for a non-contact IC card exchanges signals with an external device utilizing electromagnetic waves. The antenna circuit includes a coil and a capacitor connected to form a resonant circuit. The coil includes a main coil having a spiral conductive pattern disposed on a peripheral portion of a substrate and a plurality of adjusting patterns, each electrically connecting a portion of the conductive pattern corresponding to a desired number of turns of the main coil to an end of the main coil. The plurality of adjusting patterns are disconnected from the main coil, except for one adjusting pattern, to obtain a coil of desired inductance.

Claims

1. A method of manufacturing an antenna circuit of a non-contact IC card comprising:

forming a main coil having first and second ends and a multiple turn spiral conductive pattern on a first surface of a substrate having opposed first and second surfaces;

forming on the second surface of the substrate a plurality of adjusting patterns, each adjusting pattern electrically connecting a portion of the conductive pattern on the first surface corresponding to a respective number of turns of the main coil to the first end of the main coil;

cutting and thereby electrically disconnecting said plurality of adjusting patterns from the main coil except for one adjusting pattern to obtain a desired main coil inductance; and

connecting a capacitor to the second end of the main coil to form a resonant circuit.

2. A method of manufacturing an antenna circuit of a non-contact IC card comprising:

forming a conductive pattern on a peripheral portion of a surface of a substrate;

forming an at least partially spiral coil having an end from the conductive pattern and removing part of the conductive pattern along a spiral path while measuring the inductance of the conductive pattern;

stopping removal of part of the conductive pattern when a desired inductance is obtained; and

connecting the end of the coil to a capacitor to form a resonant circuit.

3. An inductor for forming an antenna circuit of a non-contact IC card comprising:

a substrate of a non-contact IC card, the substrate including opposed first and second surfaces;

an electrically conducting coil layer disposed on the first surface of the substrate having at least one turn with first and second ends disposed on the first surface of the substrate, the second end being located inside the at least one turn;

an electrically conducting adjusting pattern disposed on the first surface of the substrate outside the turn electrically connected to the electrically conducting coil layer; and

an electrically conducting pattern disposed on the second surface of the substrate and penetrating through the substrate at the adjusting pattern and at the second end, electrically connecting the second end to the adjusting pattern.

4. An inductor for forming an antenna circuit of a non-contact IC card comprising:

a substrate of a non-contact IC card, the substrate including opposed first and second surfaces;

an electrically conducting coil layer disposed on the first surface of the substrate in the form of a spiral coil including at least two turns with first and second ends disposed on the first surface of the substrate, the second end being located inside the at least two turns;

an electrically conducting adjusting pattern disposed on the first surface of the substrate outside the turns extending from and electrically connected to the electrically conducting coil layer; and

an electrically conducting pattern disposed on the second surface of the substrate and penetrating through the substrate at the adjusting pattern and at the second end, electrically connecting the second end to the adjusting pattern.

5. An inductor for forming an antenna circuit of a non-contact IC card comprising:

a substrate of a non-contact IC card, the substrate including opposed first and second surfaces;

an electrically conducting coil layer disposed on the first surface of the substrate in the form of a spiral coil including at least first, second, and third turns with first and second ends disposed on the first surface of the substrate and an intermediate connection point disposed on the first surface between the first and second ends, the second end being located inside the at least first, second, and third turns;

an electrically conducting adjusting pattern disposed on the first surface of the substrate outside the turns extending from and electrically connected to the electrically conducting coil layer; and

first and second electrically conducting patterns disposed on the second surface of the substrate, the first electrically conducting pattern penetrating through the substrate at the adjusting pattern and at the second end, electrically connecting the second end to the adjusting pattern, and the second electrically conducting pattern penetrating through the substrate at the intermediate connection point and at the second end, electrically connecting the intermediate connection point to the adjusting pattern.