Transponder unit and transport unit and card

• US 20040069856A1
• Filed: 04/03/2003
• Published: 04/15/2004
• Est. Priority Date: 10/04/2000
• Status: Active Grant

• Current Assignee: Assa Abloy AB
• Original Assignee: Sokymat
• Inventors: Konopitzky, Ego, Jurisch, Reinhard, Peitsch, Peter, Held, Philippe, Miehling, Martin
• Granted Patent: US 6,848,621 B2
• Time in Patent Office: Days
• US Class Current: 235/492
• 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 19/07756 the connection being non-galvanic, e.g. capacitive

Abstract

A transponder unit which can be integrated in a transport unit or a card or the like comprises, in addition to an encapsulated transponder (1) consisting of an integrated circuit (2), an aerial winding (3) having a resistance R_A and a capacitor (4) parallel thereto and having a capacitance C_A, a closed coupling circuit (5) consisting of secondary winding (7) coupled with the aerial winding (3) via a mutual inductance M_SA and a substantially larger primary winding (6) in series with said secondary winding and having fewer turns, for example only one turn. In order to achieve almost optimum energy transfer between a reading device (8) and the transponder (1) and to increase the permissible reading distance, the mutual inductance M_SA is adjusted so that it complies with the relationship M_{SA={square root}[(RA}/ω) (L_P+L_{S±2 MPS})], where ω²=1/(L_AC_A) is true for the receiving frequency ω of the transponder (1) and L_P and L_S are the inductances of the primary winding (6) and of the secondary winding (7) and M_PS is their mutual inductance.

Claims

1. Transponder unit which comprises a transponder (1) having an aerial winding (3) with an inductance LA and a resistance RA and having a capacitor (4) parallel to said aerial winding and having a capacitance CA, and a closed coupling circuit (5) having a secondary winding (7) with an inductance L_S, which is inductively coupled with the aerial winding (3) and a primary winding (6) of larger diameter with an inductance L_P, which is in series with the secondary winding (7) and is inductively coupled with it via a mutual inductance M_PS, characterized in that the mutual inductance M_SA which couples the secondary winding (7) to the aerial winding (3) follows the relationship M_SA{square root}=[(R_A/ω

) (L_P+L_S±

2M_PS)], where ω

corresponds to the receiving frequency of the transponder (1) and ω

²≈

1/(L_AC_A)

2. Transponder unit according to claim 1, characterized in that the mutual inductance M_PS of the primary winding (6) and of the secondary winding (7) and the inductances L_P, L_S thereof satisfy the relationship M_PS≦

(L_P+L_S)/100.

3. Transponder unit according to claim 1 or 2, characterized in that the primary winding (6) and the secondary winding (7) are arranged substantially in a plane and are wound in an opposite direction and that the area surrounded by the secondary winding (7) partly overlaps the area surrounded by the primary winding (6).

4. Transponder unit according to any of claims 1 to 3, characterized in that the secondary winding (7) has a larger number of turns than the primary winding (6).

5. Transponder unit according to any of claims 1 to 4, characterized in that the primary winding (6) has only one turn.

6. Transponder unit according to any of claims 1 to 5, characterized in that the diameter of the aerial winding (3) is not more than 150 mm.

7. Transponder unit according to any of claims 1 to 6, characterized in that the transponder (1) is encapsulated and the coupling circuit (5) is arranged outside the encapsulation.

8. Transport unit comprising an integrated transponder unit according to any of claims 1 to 7, characterized in that the primary winding (6) runs around the outside of the transport unit.

9. Transport unit according to claim 8, characterized in that it is a pallet, a container, a hanger or a bale.

10. Card comprising an integrated transponder unit according to any of claims 1 to 7, characterized in that the transponder (1), including the aerial coil (3), is encapsulated and the coupling circuit (5) is integrated in the card.