Data Transmission Method and a Rfid Reader Provided With a Coil and a Control Circuit For Field Quenching Outside of a Communication Area

• US 20080136595A1
• Filed: 03/13/2006
• Published: 06/12/2008
• Est. Priority Date: 03/14/2005
• Status: Active Grant

• Current Assignee: Giesecke + Devrient Mobile Security GmBH (Giesecke & Devrient GmbH)
• Original Assignee: Giesecke & Devrient GmbH
• Inventors: Finkenzeller, Klaus
• Granted Patent: US 7,808,389 B2
• Time in Patent Office: Days
• US Class Current: 340/10.1
• 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: G06K 7/10316 using at least one antenna particularly designed for interrogating the wireless record carriers antennas in general H01Q1/22
• CPC Class Codes: G06K 7/10336 the antenna being of the near field type, inductive coil
• CPC Class Codes: H01Q 1/2216 used in interrogator/reader equipment
• CPC Class Codes: H01Q 21/29 Combinations of different interacting antenna units for giving a desired directional characteristic H01Q25/00 takes 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

The present invention relates to a method, a reading device and a system for transmitting data and/or energy between a reading device and a transponder unit. Via a first antenna coil of the reading device generating a first magnetic field data and/or energy are transmitted to the transponder unit. By means of a second antenna coil a second magnetic field with opposite sign is generated. Within a near field or communication range (12) of the reading device the second magnetic field is weaker than the first magnetic field. In a tap-proof range (13), i.e. outside the near field, the two magnetic fields have the same absolute value and cancel each other out due to the opposite signs.

Claims

1-24. -24. (canceled)

25. Method for transmitting data and/or energy between a reading device and a transponder unit comprising:

generating a magnetic field by means of a first antenna coil of a reading device, and generating a second magnetic field by means of a second antenna coil,

said second magnetic field being generated by the second antenna coil so that in a near field of the reading device its absolute value is smaller than that of the first magnetic field and outside the near field has approximately the same absolute value with opposite sign.

26. Method according to claim 25, including locating the center axis of the first antenna coil within the second antenna coil.

27. Method according to claim 25, including supplying the two antenna coils with currents, through which the magnetic fields resulting therefrom point in opposite directions.

28. Method according to claim 25, including supplying the two antenna coils with opposite-phase currents.

29. Method according to claim 25, including supplying the two antenna coils with currents whose amplitudes are proportional to each other.

30. Method according to claim 25, including connecting the currents in the two antenna coils to each other with respect to value and phase via a current mirror.

31. Method according to claim 25, including detecting a magnetic field strength outside the near field, and the magnetic field of at least one of the first and the second antenna coil is adapted in such a way that the detected magnetic field strength reaches a minimum value.

32. Method according to claim 25, wherein in the first antenna coil and the second antenna coil high-frequency magnetic fields having the same frequency are generated.

33. Method according to claim 25, wherein by means of the first magnetic field a useful signal containing data is at least one of sent to the transponder unit and received from the transponder unit.

34. Method according to claim 25, including adapting the field strengths of the two magnetic fields by changing the respective coil diameters, in order to define the near field of the reading device.

35. Reading device for transmitting data and/or energy between a reading device and at least one transponder unit, the reading device comprising one first antenna coil adapted to generate a first magnetic field, a second antenna coil adapted to generate a second magnetic field, and a control circuit for the first and the second magnetic field, wherein the control circuit is adapted to adjust the first and second magnetic fields in such a way that outside a near field of the reading device the second magnetic field has approximately the same absolute value and an opposite sign as the first magnetic field, and in the near field is weaker than the first magnetic field.

36. Reading device according to claim 35, wherein the reading device is adapted to supply the antenna coils with currents, through which the resulting magnetic fields point in opposite directions.

37. Reading device according to claim 35, wherein the control circuit is adapted to control the currents for the antenna coils in order to adjust the magnetic fields.

38. Reading device according to claim 35, wherein the control circuit comprises a current mirror.

39. Reading device according to claim 38, wherein the current mirror is adapted to derive the current for the second antenna coil from the current for the first antenna coil or vice versa.

40. Reading device according to claim 35, wherein the second antenna coil forms a serial resonant circuit with a serially connected capacitor, the resonance frequency of the serial resonant circuit corresponding to the transmission frequency of the reading device.

41. Reading device according to claim 35, including a resistor and/or an impedance, arranged between ground and the second antenna, and which resistor and impedance are controllable;

a field strength detector arranged to detect a filed strength outside the near field and to output a field strength signal;

said field strength signal serving as input value for controlling said resistor and impendence.

42. Reading device according to claim 35, including a device for evaluating a magnetic field strength outside the near field, wherein the control circuit is adapted to adjust the magnetic fields depending on the detected magnetic field strength in such a way that the magnetic field strength reaches a minimum value.

43. Reading device according to claim 42, wherein the device for evaluating the magnetic field strength outside the near field comprises a third antenna coil and a circuit for determining a magnetic field strength measured by the third antenna coil.

44. Reading device according to claim 35, wherein the second antenna coil has a diameter which is larger in comparison to that of the first antenna coil.

45. Reading device according to claim 35, wherein the first and the second antenna coil are arranged in one common plane.

46. Reading device according to claim 35, wherein the two antenna coils are arranged coaxially.

47. Reading device according to claim 35, wherein the reading device is adapted to at least one of sending to and receiving from the at least one transponder unit via the first antenna coil a useful signal containing data.

48. System for transmitting data and/or energy between a transponder unit and a reading device according to claim 35.