Data transmission circuit having a station and a response circuit

• US 6,167,094 A
• Filed: 04/15/1999
• Issued: 12/26/2000
• Est. Priority Date: 10/15/1996
• Status: Expired due to Term

• Current Assignee: Infineon Technologies AG
• Original Assignee: Siemens AG
• Inventors: Reiner, Robert
• Primary Examiner(s): Vo, Don N.
• Assistant Examiner(s): PHU, PHUONG M
• Application Number:
  US09/292,182
• Time in Patent Office: 621 Days
• Field of Search: 375/258, 375/261, 455/41, 455/558, 235/492, 235/487, 235/382
• US Class Current: 375/258
• CPC Class Codes: H04B 5/00 Near-field transmission systems, e.g. inductive or capacitive transmission systems
• CPC Class Codes: H04B 5/22 Capacitive coupling
• CPC Class Codes: H04B 5/266 One coil at each side, e.g. with primary and secondary coils

Abstract

A data transmission circuit having a station and a response circuit. The station has an amplitude demodulator as well as a primary coil with a signal generator for producing an alternating magnetic field at a carrier frequency. The response circuit has a secondary coil as well as an amplitude modulator for influencing a load on the secondary coil, and the amplitude modulator is configured such that the alternating magnetic field can be modulated with a data signal. Particularly when the data transmission circuit is mass-produced, situations frequently occur in which the data signal modulated onto the alternating magnetic field by the response circuit can no longer be reconstructed at the station end. The object of the invention is thus to provide a data transmission circuit of this generic type, which always operates reliably. According to the invention, the response circuit has a phase modulator for influencing the electrical characteristics of the secondary coil. The amplitude modulator and/or the phase modulator being configured such that it or they can be driven, in particular, by at least one activation signal.

Claims

1. A data transmission circuit, comprising:

a station having an amplitude demodulator, a primary coil connected to said amplitude demodulator, and a signal generator connected to said primary coil for producing an alternating magnetic field at a carrier frequency; and

a response circuit having a secondary coil and an amplitude modulator for influencing a load on said secondary coil, said amplitude modulator configured such that the alternating magnetic field can be modulated with a data signal, said response circuit also having a phase modulator for influencing electrical characteristics of said secondary coil, and at least one of said amplitude modulator and said phase modulator to be driven by at least one modulation signal.

2. The data transmission circuit according to claim 1, wherein said response circuit is part of a smart card.

5. The data transmission circuit according to claim 1, wherein at least one of said amplitude modulator and said phase modulator can be driven such that a phase modulation is offset with respect to a phase of an amplitude modulation.

6. The data transmission circuit according to claim 5, wherein at least one of said amplitude modulator and said phase modulator can be driven such that the phase modulation leads the amplitude modulation by 90°

with respect to a signal period of the at least one modulation signal.

7. The data transmission circuit according to claim 5, wherein at least one of said amplitude modulator and said phase modulator can be driven such that the phase modulation lags the amplitude modulation by 90°

with respect to a signal period of the at least one modulation signal.

8. The data transmission circuit according to claim 1, wherein said amplitude modulator is a resistor that can be connected in parallel with said secondary coil.

9. The data transmission circuit according to claim 1, wherein said phase modulator is a capacitor that can be connected in parallel with said secondary coil.

10. The data transmission circuit according to claim 1, wherein said response circuit has at least one intermediate modulation apparatus for modulation of the data signal with an auxiliary carrier signal.

11. The data transmission circuit according to claim 1, wherein said response circuit has a clock derivation device for deriving an auxiliary carrier signal from the alternating magnetic field.

12. The data transmission circuit according to claim 11, wherein said response circuit has a phase-shifting device such that at least a first auxiliary carrier signal and at least a second auxiliary carrier signal can be produced from said clock derivation device, the first auxiliary carrier signal and the second auxiliary carrier signal are each phase-shifted by a specific amount with respect to one another.

13. The data transmission circuit according to claim 12, wherein said phase-shifting device has at least one frequency divider.

14. The data transmission circuit according to claim 11, wherein said amplitude demodulator has an input side and a bandpass filter disposed on said input side.

15. The data transmission circuit according to claim 14, wherein said bandpass filter has a mid-frequency substantially equal to a sum or to a difference of frequencies of a carrier signal and the auxiliary carrier signal.

16. The data transmission circuit according to claim 1, wherein at least one of said response circuit and said station are circuits for processing digital signals.

3. A data transmission circuit, comprising:

a station having a phase demodulator, a primary coil connected to said phase demodulator, and a signal generator connected to said primary coil for producing an alternating magnetic field; and

a response circuit having a secondary coil and an amplitude modulator for influencing electrical characteristics of said secondary coil, said amplitude modulator configured such that the alternating magnetic field can be modulated with a data signal, said response circuit also having a phase modulator for influencing the electrical characteristics of said secondary coil, and at least one of said amplitude modulator and said phase modulator can be driven by at least one modulation signal.

4. The data transmission circuit according to claim 3, wherein said response circuit is part of a smart card.

17. The data transmission circuit according to claim 3, wherein at least one of said amplitude modulator and said phase modulator can be driven such that a phase modulation is offset with respect to a phase of an amplitude modulation.

18. The data transmission circuit according to claim 17, wherein at least one of said amplitude modulator and said phase modulator can be driven such that the phase modulation leads the amplitude modulation by 90°

with respect to a signal period of the at least one modulation signal.

19. The data transmission circuit according to claim 17, wherein at least one of said amplitude modulator and said phase modulator can be driven such that the phase modulation lags the amplitude modulation by 90°

with respect to a signal period of the at least one modulation signal.

20. The data transmission circuit according to claim 3, wherein said amplitude modulator is a resistor that can be connected in parallel with said secondary coil.

21. The data transmission circuit according to claim 3, wherein said phase modulator is a capacitor that can be connected in parallel with said secondary coil.

22. The data transmission circuit according to claim 3, wherein said response circuit has at least one intermediate modulation apparatus for modulation of the data signal with an auxiliary carrier signal.

23. The data transmission circuit according to claim 3, wherein said response circuit has a clock derivation device for deriving an auxiliary carrier signal from the alternating magnetic field.

24. The data transmission circuit according to claim 23, wherein said response circuit has a phase-shifting device configured such that at least a first auxiliary carrier signal and at least a second auxiliary carrier signal can be produced from said clock derivation device, the first auxiliary carrier signal and the second auxiliary carrier signal are phase-shifted by a specific amount with respect to one another.

25. The data transmission circuit according to claim 24, wherein said phase-shifting device has at least one frequency divider.

26. The data transmission circuit according to claim 23, wherein said phase demodulator has an input side and a bandpass filter disposed on said input side.

27. The data transmission circuit according to claim 26, wherein said bandpass filter has a mid-frequency substantially equal to a sum or to a difference of frequencies of a carrier signal and the auxiliary carrier signal.

28. The data transmission circuit according to claim 3, wherein at least one of said response circuit and said station are circuits for processing digital signals.

29. A response circuit, comprising:

a secondary coil;

an amplitude modulator for influencing electrical characteristics of said secondary coil, said amplitude modulator configured such that an external alternating magnetic field can be modulated with a data signal; and

a phase modulator for influencing the electrical characteristics of said secondary coil, and at least one of said amplitude modulator and said phase modulator can each be driven by at least one modulation signal.

30. The response circuit according to claim 29, wherein the response circuit is used in one of a transponder and a smart card.

31. An improved method for modulating an external alternating magnetic field of a station, the improvement which comprises:

producing a modulation signal via a response circuit on a basis of a data signal for modulating the external alternating magnetic field with amplitude modulation and with phase modulation, and carrying out the modulating such that one sideband of a modulated alternating magnetic field is produced more strongly than the other sideband.

32. The method according to claim 31, which comprises carrying out the amplitude modulation with a phase shift with respect to the phase modulation.

33. The method according to claim 32, which comprises carrying out the amplitude modulation such that the phase shift is 90°

and is one of a leading and lagging phase shift.

34. The method according to claim 31, which comprises:

carrying out the amplitude modulation using an amplitude modulator driven by an amplitude modulation signal;

carrying out the phase modulation using a phase modulator driven by a phase modulation signal; and

producing at least one of the amplitude modulation signal and the phase modulation signal from modulation of the data signal with in each case one auxiliary carrier signal.

35. The method according to claim 34, which comprises deriving the one auxiliary carrier signal by frequency division from the external alternating magnetic field.

36. The method according to claim 34, which comprises using a plurality of auxiliary carrier signals having a phase shift of 90°

between them during the producing step.