Methods and devices for the suppression of harmonics

• US 20060286938A1
• Filed: 08/29/2006
• Published: 12/21/2006
• Est. Priority Date: 01/29/1998
• Status: Active Grant

• Current Assignee: SATO Holdings Corporation
• Original Assignee: Graham Alexander Munro Murdoch
• Inventors: Murdoch, Graham Alexander Munro
• Granted Patent: US 7,711,332 B2
• Time in Patent Office: Days
• US Class Current: 455/73
• CPC Class Codes: G01S 13/74 Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems
• CPC Class Codes: G01S 13/75 using transponders powered from received waves, e.g. using passive transponders , or using passive reflectors
• 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 19/07749 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 19/07758 arrangements for adhering the record carrier to further objects or living beings, functioning as an identification tag
• CPC Class Codes: G06K 19/07777 the antenna being of the inductive type
• 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

Abstract

An antenna for suppressing harmonics of a signal transmitted from the antenna, the signal having a carrier with an imposed modulated data signal, the antenna including a modulator associated with a controlled variable impedance in series, the modulator being operable to modulate in accordance with the data signal, and being configured to produce a voltage across the antenna corresponding to a voltage provided by the controlled variable impedance.

Claims

1. A method of suppressing harmonics of a signal transmitted from an antenna, the signal having a carrier with an imposed modulated data signal, the method comprising the steps of:

providing a modulator associated with a controlled variable impedance, further providing the modulator in series with a load, the modulator being operable to modulate in accordance with the data signal, and being configured to produce a voltage across the antenna corresponding to a voltage provided by the controlled variable impedance.

2. A method as claimed in claim 1 wherein the antenna comprises a coil and a power storage system having a storage capacitor, with the controlled variable impedance being provided in series between the coil and the storage capacitor.

3. A method as claimed in claim 1 wherein the antenna comprises a coil and a power storage system having a rectifier and storage capacitor, with the controlled variable impedance being provided in series between the rectifier and the storage capacitor.

4. A method as claimed in claim 1 wherein the antenna comprises a coil and a power storage system having a storage capacitor, with the controlled variable impedance being provided in series between the coil and the power storage system.

5. A method as claimed in claim 1 wherein the antenna comprises a coil and a power storage system having a rectifier, with the controlled variable impedance being provided in series between the coil and the rectifier.

6. A method as claimed in claim 1 wherein the peak antenna voltage is clamped to the voltage across the controllable variable impedance plus the voltage of the power system with the storage capacitor acting as AC short circuit.

7. A method as claimed in claim 1 wherein closure of the switch causes the peak antenna voltage to clamp to the voltage of the power system with the storage capacitor acting as AC short circuit.

8. A method as claimed in claim 1 wherein the antenna comprises a coil and a power storage system having a storage capacitor, the modulation being faster than the response time of the storage capacitor for maintaining the DC operating point.

9. A method as claimed in claim 1 wherein in the antenna includes a coil and the controlled variable impedance is provided in series between the coil and a tuning capacitor of the antenna circuit.

10. A method as claimed in claim 9 wherein transponder circuitry is connected across the tuning capacitor.

11. A method as claimed in claim 10 wherein transponder circuitry is connected across the tuning capacitor and the controlled variable impedance, the controlled variable resistance being in series with the tuning capacitor.

12. A method as claimed in claim 11 wherein the transponder circuitry is connected across the tuning capacitor and the controlled variable impedance is provided in series between the coil and the transponder circuitry.

13. A method as claimed in claim 1 wherein the modulator includes a switch that is switched between to modulate the data signal onto the carrier for transmission.

14. A method as claimed in claim 13 wherein the switch is implemented by way of a FET or BJT switch.

15. A method as claimed in claim 1 wherein the controlled variable resistance is varied between two or more values.

16. A method as claimed in claim 1 wherein the switch varies the impedance of a series resistor.

17. A method as claimed in claim 1 wherein the controlled variable resistance is varied in a substantially stepwise manner to affect the current flowing through the antenna.

18. A method as claimed in claim 1 wherein the controlled variable resistance is varied in discrete steps to affect the current flowing through the antenna.

19. A method as claimed in claim 1 wherein the data signal is a baseband signal.

20. A method as claimed in claim 1 wherein the data signal is a high frequency sub-carrier with data modulated on to the sub-carrier for transmission.

21. A method as claimed in claim 20 wherein the data modulated on to the sub carrier for transmission is modulated using Phase Reverse Keying.

22. A method as claimed in claim 1 wherein the subcarrier is generated by dividing down the excitation frequency.

23. A method as claimed in claim 1 wherein the data modulated on to the sub carrier for transmission is modulated without a change in the DC operating point of the antenna.

24. A method as claimed in claim 1 wherein antenna includes a coil and the modulation involves a phase change of 180 degrees at the zero crossing of the coil current.

25. A method as claimed in claim 24 wherein a comparator is used to sense the zero crossing of the coil current.

26. A method as claimed in claim 1 wherein the modulator is operable to modulate in accordance with a data signal specific to a transceiver comprising the antenna.

27. A method as claimed in claim 1 wherein the controlled variable impedance is a variable resistance.

28. A method as claimed in claim 1 wherein the controlled variable impedance is a variable voltage.

29. A method as claimed in claim 1 wherein the configuration of the controlled variable impedance allows the modulator to provide a relatively high modulation switching rate.

30. A method as claimed in claim 1 wherein the switching rate is greater than a DC slew rate limit associated with the antenna.

31. A method as claimed in claim 1 operable in association with a RFID device.

32. An antenna for suppressing harmonics of a signal transmitted from the antenna, the signal having a carrier with an imposed modulated data signal, the antenna including a modulator associated with a controlled variable impedance in series, the modulator being operable to modulate in accordance with the data signal, and being configured to produce a voltage across the antenna corresponding to a voltage provided by the controlled variable impedance.

33. An antenna as claimed in claim 32 wherein the antenna comprises a coil and a power storage system having a storage capacitor, with the controlled variable impedance being provided in series between the coil and the storage capacitor.

34. An antenna as claimed in claim 32 wherein the antenna comprises a coil and a power storage system having a rectifier and storage capacitor, with the controlled variable impedance being provided in series between the rectifier and the storage capacitor.

35. An antenna as claimed in claim 32 wherein the antenna comprises a coil and a power storage system having a storage capacitor, with the controlled variable impedance being provided in series between the coil and the power storage system.

36. An antenna as claimed in claim 32 wherein the antenna comprises a coil and a power storage system having a rectifier, with the controlled variable impedance being provided in series between the coil and the rectifier.

37. An antenna as claimed in claim 32 wherein the peak antenna voltage is clamped to the voltage across the controllable variable impedance plus the voltage of the power system with the storage capacitor acting as AC short circuit.

38. An antenna as claimed in claim 32 wherein closure of the switch causes the peak antenna voltage to clamp to the voltage of the power system with the storage capacitor acting as AC short circuit.

39. An antenna as claimed in claim 32 wherein the antenna comprises a coil and a power storage system having a storage capacitor, the modulation being faster than the response time of the storage capacitor for maintaining the DC operating point.

40. An antenna as claimed in claim 32 wherein in the antenna includes a coil and the controlled variable impedance is provided in series between the coil and a tuning capacitor of the antenna circuit.

41. An antenna as claimed in claim 40 wherein transponder circuitry is connected across the tuning capacitor.

42. An antenna as claimed in claim 41 wherein transponder circuitry is connected across the tuning capacitor and the controlled variable impedance, the controlled variable resistance being in series with the tuning capacitor.

43. An antenna as claimed in claim 42 wherein the transponder circuitry is connected across the tuning capacitor and the controlled variable impedance is provided in series between the coil and the transponder circuitry.

44. An antenna as claimed in claim 32 wherein the modulator includes a switch that is switched between to modulate the data signal onto the carrier for transmission.

45. An antenna as claimed in claim 44 wherein the switch is implemented by way of a FET or BJT switch.

46. An antenna as claimed in claim 32 wherein the controlled variable resistance is varied between two or more values.

47. An antenna as claimed in claim 32 wherein the switch varies the impedance of a series resistor.

48. An antenna as claimed in claim 32 wherein the controlled variable resistance is varied in a substantially stepwise manner to affect the current flowing through the antenna.

49. An antenna as claimed in claim 32 wherein the controlled variable resistance is varied in discrete steps to affect the current flowing through the antenna.

50. An antenna as claimed in claim 32 wherein the data signal is a baseband signal.

51. An antenna as claimed in claim 32 wherein the data signal is a high frequency sub-carrier with data modulated on to the sub-carrier for transmission.

52. An antenna as claimed in claim 51 wherein the data modulated on to the sub carrier for transmission is modulated using Phase Reverse Keying.

53. An antenna as claimed in claim 32 wherein the subcarrier is generated by dividing down the excitation frequency.

54. An antenna as claimed in claim 32 wherein the data modulated on to the sub carrier for transmission is modulated without a change in the DC operating point of the antenna.

55. An antenna as claimed in claim 32 wherein antenna includes a coil and the modulation involves a phase change of 180 degrees at the zero crossing of the coil current.

56. An antenna as claimed in claim 55 wherein a comparator is used to sense the zero crossing of the coil current.

57. An antenna as claimed in claim 32 wherein the modulator is operable to modulate in accordance with a data signal specific to a transceiver comprising the antenna.

58. An antenna as claimed in claim 32 wherein the controlled variable impedance is a variable resistance.

59. An antenna as claimed in claim 32 wherein the controlled variable impedance is a variable voltage.

60. An antenna as claimed in claim 32 wherein the configuration of the controlled variable impedance allows the modulator to provide a relatively high modulation switching rate.

61. An antenna as claimed in claim 32 wherein the switching rate is greater than a DC slew rate limit associated with the antenna.

62. An antenna as claimed in claim 32 operable in association with a RFID device.

63. An antenna as claimed in claim 32 or 62 wherein the antenna comprises a transceiver.

64. An antenna as claimed in claim 32 or 62 wherein the antenna comprises a tuned antenna.

65. An antenna as claimed in claim 32 or 62 wherein the antenna comprises a transponder.