Transponder unit and transport unit and card

• US 6,848,621 B2
• Filed: 10/04/2001
• Issued: 02/01/2005
• Est. Priority Date: 10/04/2000
• Status: Expired due to Fees

• Current Assignee: Assa Abloy AB
• Original Assignee: Sokymat
• Inventors: Jurisch, Reinhard, Miehling, Martin, Konopitzky, Egon, Peitsch, Peter, Held, Philippe
• Primary Examiner(s): Lee, Michael G.
• Assistant Examiner(s): Nguyen, Kimberly D.
• Application Number:
  US10/381,602
• Publication Number:
  US 20040069856A1
• Time in Patent Office: 1,216 Days
• Field of Search: 235/492, 235/441, 235/444, 235/451, 235/493
• 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. The transponder unit includes, in addition to an encapsulated transponder of an integrated circuit, an aerial winding having a resistance R_A and a capacitor parallel thereto and having a capacitance C_A. A closed coupling circuit of secondary winding is coupled with the aerial winding by a mutual inductance M_SA and a substantially larger primary winding in series with the secondary winding and having fewer turns, for example only one turn. To achieve almost optimum energy transfer between a reading device and the transponder and to increase the permissible reading distance, the mutual inductance M_SA is adjusted to comply with the relationship M_SA=√{square root over ( )}[R_A/ω) (L_P+L_S+2M_PS)], where ω²=1/(L_AC_A) is true for the receiving frequency ω of the transponder and L_p and L_S are the inductances of the primary winding and of the secondary winding and M_PS is their mutual inductance.

Claims

1. Transponder unit comprising:

a transponder having an aerial winding with first inductance L_A and a resistance R_A and having a capacitor parallel to said aerial winding and having a capacitance C_A; and

a closed coupling circuit having a secondary winding with an inductance L_S, which is inductively coupled with the aerial winding and a primary winding of larger diameter with an inductance L_P, which is in series with the secondary winding and is inductively coupled with the secondary winding by a mutual inductance M_PS,

wherein a mutual inductance M_SA which couples the secondary winding to the aerial winding follows relationship M_SA=[(R_A/ω

) (L_P+L_S±

2M_PS)], where ω

corresponds to a receiving frequency of the transponder and ω

²≈

1/(L_AC_A).

2. Transponder unit according to claim 1, wherein the mutual inductance of the primary winding and of the secondary winding and the inductances thereof satisfy relationship M_PS≦

(L_P+L_S)/100.

3. Transponder unit according to claim 1, wherein the primary winding and the secondary winding are arranged substantially in a plane and are wound in opposite directions, and wherein an area surrounded by the secondary winding partly overlaps an area surrounded by the primary winding.

4. Transponder unit according to claim 1, wherein the secondary winding has a larger number of turns than the primary winding.

5. Transponder unit according to claim 1, wherein the primary winding has only one turn.

6. Transponder unit according to claim 1, wherein a diameter of the aerial winding is not more than 150 mm.

7. Transponder unit according to claim 1, wherein the transponder is encapsulated in an encapsulation and the closed coupling circuit is arranged outside the encapsulation.

8. Transport unit comprising an integrated transponder unit according to claim 1, wherein the primary winding runs around an outside of the transport unit.

9. Transport unit according to claim 8, wherein the transport unit is one of a pallet, a container, a hangar, or a bale.

10. Card comprising an integrated transponder unit according to claim 1, wherein the transponder, including the aerial coil, is encapsulated and the closed coupling circuit is integrated in the card.