Methods and devices for the suppression of harmonics

• US 7,711,332 B2
• Filed: 08/29/2006
• Issued: 05/04/2010
• Est. Priority Date: 01/29/1998
• Status: Active Grant

• Current Assignee: SATO Holdings Corporation
• Original Assignee: Magellan Technology Pty. Ltd (SATO Holdings Corporation)
• Inventors: Murdoch, Graham Alexander Munro
• Primary Examiner(s): Yun; Eugene
• Application Number:
  US11/468,215
• Publication Number:
  US 20060286938A1
• Time in Patent Office: 1,344 Days
• Field of Search: 455/73, 455/343, 455/106, 455/41.2, 455/572, 455120-125, 455/107, 455/248.1, 455/108, 455/110, 455/126
• US Class Current: 455/107
• 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, the controlled variable impedance being selectable between at least two non-zero impedance values;

providing the modulator, wherein the modulator is connected in series between a load and the antenna, the modulator being operable to modulate in accordance with the signal; and

configuring the modulator to produce a voltage across the antenna corresponding to a voltage provided by the controlled variable impedance.

2. The method as claimed in claim 1, wherein the antenna comprises:

a coil;

a power storage system having a storage capacitor; and

wherein the controlled variable impedance is provided in series between the coil and the storage capacitor.

3. The method as claimed in claim 1, wherein the antenna comprises:

a coil;

a power storage system having a rectifier and a storage capacitor; and

wherein the controlled variable impedance is provided in series between the rectifier and the storage capacitor.

4. The method as claimed in claim 1, wherein the antenna comprises:

a coil;

a power storage system having a storage capacitor; and

wherein the controlled variable impedance is provided in series between the coil and the power storage system.

5. The method as claimed in claim 1, wherein the antenna comprises:

a coil

a power storage system having a rectifier; and

wherein the controlled variable impedance is provided in series between the coil and the rectifier.

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

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

8. The method as claimed in claim 1, wherein the antenna comprises:

a coil;

a power storage system having a storage capacitor; and

wherein the modulation is faster than a response time of a storage capacitor for maintaining a DC operating point.

9. The method as claimed in claim 1, wherein the antenna comprises:

a coil; and

wherein the controlled variable impedance is provided in series between the coil and a tuning capacitor of the antenna.

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

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

12. The 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. The method as claimed in claim 1, wherein the modulator includes a switch adapted to modulate the signal onto the carrier for transmission.

14. The method as claimed in claim 13, wherein the switch comprises a FET or BJT switch.

15. The method as claimed in claim 1, wherein the controlled variable impedance is varied between two or more values.

16. The method as claimed in claim 1, wherein a switch varies an impedance of a series resistor.

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

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

19. The method as claimed in claim 1, wherein the signal is a baseband signal.

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

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

22. The method as claimed in claim 1, wherein a subcarrier is generated by dividing down an excitation frequency.

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

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

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

26. The 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. The method as claimed in claim 1, wherein the controlled variable impedance is a variable resistance.

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

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

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

31. The method as claimed in claim 1, wherein the antenna is operable in association with a RFID device.

32. The method as claimed in claim 1 further comprising:

receiving a first signal and transmitting a second signal;

receiving from the antenna, via a signal processor, a third signal indicative of the first signal;

providing a fourth signal to the antenna for forming the second signal; and

providing the antenna with a dual Q factor by varying the impedance between the antenna and the signal processor, the dual Q factor being high for the first signal and low for the second signal.

33. The method according to claim 1 further comprising:

receiving a first signal and transmitting a second signal;

receiving from the antenna, via a signal processor, a third signal indicative of the first signal;

providing a fourth signal to the antenna for forming the second signal; and

varying a voltage across the antenna in a substantially stepwise manner to affect a variation in a current flowing through the antenna between a low and a high value for allowing transmission of the second signal without substantially effecting a receiving efficiency of the antenna.

34. The method according to claim 1 comprising:

receiving a first signal to a transceiver;

transmitting a fourth signal from the transceiver;

receiving the first signal, via the antenna, and, in response thereto, generating a second signal, the first signal having a first predetermined frequency;

providing the second signal to a receiving circuitry;

tuning the antenna with a tuning circuitry to have a resonant frequency at or about the first predetermined frequency; and

varying an impedance between the antenna and the tuning circuitry such that the second signal generates a third signal in the antenna at a second predetermined frequency and the antenna transmits a fourth signal derived from the third signal.

35. The method according to claim 1 comprising:

receiving a first signal via a coil having a first predetermined frequency;

transmitting a fourth signal;

connecting a capacitor in parallel with the coil for providing the antenna with a resonant frequency at or about the first predetermined frequency;

generating a second signal from the first signal;

disposing the modulator in series with the capacitor for both providing a varying impedance such that the second signal generates a third signal in the coil at a second predetermined frequency; and

transmitting, via the coil, a fourth signal derived from the third signal.

36. The method of claim 1, wherein the controlled variable impedance is selectable between at least three possible impedance values.

37. An antenna for suppressing harmonics of a signal transmitted from the antenna, the signal comprising a carrier with an imposed modulated data signal, the antenna comprising:

a modulator associated with a controlled variable impedance wherein the modulator is connected in series between a load and the antenna, wherein the controlled variable impedance is selectable between at least two non-zero impedance values;

wherein the modulator is operable to modulate in accordance with the data signal; and

wherein the modulator is configured to produce a voltage across the antenna corresponding to a voltage provided by the controlled variable impedance.

38. The antenna as claimed in claim 37, wherein the antenna further comprises:

a coil;

a power storage system having a storage capacitor; and

wherein the controlled variable impedance is provided in series between the coil and the storage capacitor.

39. The antenna as claimed in claim 37, wherein the antenna further comprises:

a coil;

a power storage system having a rectifier and a storage capacitor; and

wherein the controlled variable impedance is provided in series between the rectifier and the storage capacitor.

40. The antenna as claimed in claim 37, wherein the antenna further comprises:

a coil;

a power storage system having a storage capacitor; and

wherein the controlled variable impedance is provided in series between the coil and the power storage system.

41. The antenna as claimed in claim 37, wherein the antenna further comprises:

a coil;

a power storage system having a rectifier; and

wherein the controlled variable impedance is provided in series between the coil and the rectifier.

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

43. The antenna as claimed in claim 37, wherein closure of a switch causes a peak antenna voltage to clamp to a voltage of a power system with a storage capacitor acting as AC short circuit.

44. The antenna as claimed in claim 37, wherein the antenna further comprises:

a coil;

a power storage system having a storage capacitor; and

wherein the modulation is faster than a response time of a storage capacitor for maintaining a DC operating point.

45. The antenna as claimed in claim 37, wherein in the antenna further comprises:

a coil; and

wherein the controlled variable impedance is provided in series between the coil and a tuning capacitor of the antenna.

46. The antenna as claimed in claim 45, wherein a transponder circuitry is connected across the tuning capacitor.

47. The antenna as claimed in claim 46, wherein the transponder circuitry is connected across the tuning capacitor and the controlled variable impedance, the controlled variable impedance being in series with the tuning capacitor.

48. The antenna as claimed in claim 47, 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.

49. The antenna as claimed in claim 37, wherein the modulator includes a switch adapted to modulate the signal onto the carrier for transmission.

50. The antenna as claimed in claim 49, wherein the switch comprises a FET or BJT switch.

51. The antenna as claimed in claim 37, wherein the controlled variable impedance is varied between two or more values.

52. The antenna as claimed in claim 37, wherein a switch varies an impedance of a series resistor.

53. The antenna as claimed in claim 37, wherein the controlled variable impedance is varied in a substantially stepwise manner to affect current flowing through the antenna.

54. The antenna as claimed in claim 37, wherein the controlled variable impedance is varied in discrete steps to affect current flowing through the antenna.

55. The antenna as claimed in claim 37, wherein the signal is a baseband signal.

56. The antenna as claimed in claim 37, wherein the signal is a high-frequency sub-carrier with data modulated on to the sub-carrier for transmission.

57. The antenna as claimed in claim 56, wherein the data modulated on to the sub carrier for transmission is modulated using Phase Reverse Keying.

58. The antenna as claimed in claim 37, wherein a subcarrier is generated by dividing down an excitation frequency.

59. The antenna as claimed in claim 37, wherein the data modulated on to a sub carrier for transmission is modulated without a change in a DC operating point of the antenna.

60. The antenna as claimed in claim 37, wherein the antenna further comprises a coil and the modulation involves a phase change of 180 degrees at a zero crossing of a coil current.

61. The antenna as claimed in claim 60, wherein a comparator is used to sense the zero crossing of the coil current.

62. The antenna as claimed in claim 37, wherein the modulator is operable to modulate in accordance with a data signal specific to a transceiver comprising the antenna.

63. The antenna as claimed in claim 37, wherein the controlled variable impedance is a variable resistance.

64. The antenna as claimed in claim 37, wherein the controlled variable impedance is a variable voltage.

65. The antenna as claimed in claim 37, wherein the configuration of the controlled variable impedance allows the modulator to provide a relatively high modulation switching rate.

66. The antenna as claimed in claim 37, wherein a switching rate is greater than a DC slew rate limit associated with the antenna.

67. The antenna as claimed in claim 37, wherein the antenna is operable in association with a RFID device.

68. The antenna as claimed in claim 37, wherein the antenna comprises a transceiver.

69. The antenna as claimed in claim 37, wherein the antenna comprises a tuned antenna.

70. The antenna as claimed in claim 37, wherein the antenna comprises a transponder.

71. The antenna according to claim 37 comprising:

a tuned coil in which the first signal generates a first current and which supports a second current for generating said second signal; and

the modulator of the antenna through which said first and second currents flow for providing said coil with a dual Q factor, the dual Q factor being high for the first current and low for the second current.

72. The antenna according to claim 37, comprising:

a coil arranged to receive a first signal having a first predetermined frequency;

a capacitor connected in parallel with the coil operable to provide the antenna with a resonant frequency at or about the first predetermined frequency; and

wherein the modulator is disposed in series with the capacitor for providing a varying impedance such that a second signal generates a third signal in the coil at a second predetermined frequency whereby the coil transmits a fourth signal derived from the third signal.

73. The antenna of claim 37, wherein the controlled variable impedance is selectable between at least three possible impedance values.