Method for recognizing identification media

• US 7,598,872 B2
• Filed: 02/28/2005
• Issued: 10/06/2009
• Est. Priority Date: 03/03/2004
• Status: Active Grant

• Current Assignee: LEGIC Identsystems AG (Kirkbi A/S)
• Original Assignee: LEGIC Identsystems AG (Kirkbi A/S)
• Inventors: Koch, Andreas, Pl ss, Marcel, Hausmann, Peter
• Primary Examiner(s): Mehmood; Jennifer
• Application Number:
  US10/591,415
• Publication Number:
  US 20070188326A1
• Time in Patent Office: 1,681 Days
• Field of Search: 340/10.51, 340/10.52, 340/10.42, 340/572.4, 340/527.1, 340/10.33, 340/10.34, 235/440, 235/446, 235/451, 235/492, 235/375, 235/385
• US Class Current: 340/572.4
• 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 7/10039 interrogator driven, i.e. synchronous
• CPC Class Codes: G06K 7/10128 the step consisting of detection of the presence of one or more record carriers in the vicinity of the interrogation device

Abstract

The invention relates to a method for recognizing identification media in the communication area of a write/read device functioning according to the principle of inductive coupling in the MHz range, wherein an antenna is used for transmitting and receiving HF signals, in addition to a circuit for transmitting HF signals with a standard transmitter power output and a logic circuit for evaluating communication between a write/read device and an identification medium. A short inquiry signal consisting of several fundamental components of the HF field and having a standard transmission power output is periodically transmitted via a transmission path and the antenna and a response signal is detected on the antenna. The response signal is compared to a reference signal and a communication signal is transmitted in order to recognize an identification medium in the event that the response signal is different from the reference signal. This enables energy-saving, reliable recognition of identification media occurring in the field of communications for subsequent communication with the write/read device, particularly with respect to battery-operated write/read devices.

Claims

1. A method for detecting identification media within a communication range of an antenna for transmitting and receiving RF signals of a read/write unit which operates in accordance with the principle of inductive coupling of an RF field in the MHz frequency band and which has a transmitting path connected directly to the antenna,

a receiving path connected directly to the antenna,

a circuit for RF communication with at least one of a standard transmitting power or reduced transmitting power, and a logical circuit for evaluating a communication between the read/write unit and an identification medium, wherein

a short polling signal, which contains at least one of unmodulated or force excited oscillations of the RF field, is periodically emitted with the standard transmitting power via the transmitting path and the antenna,

that during the emission of the polling signal, a return signal with at least one of unmodulated or force excited oscillations of the RF field is detected at the antenna,

then the return signal is compared with a reference signal,

and then a communication signal is emitted for detecting an identification medium if the return signal differs from the reference signal.

2. The method according to claim 1, wherein the polling signal is shorter by at least two orders of magnitude than the communication signal.

3. The method according to claim 1, wherein the detection of the return signal is effected via the receiving path.

4. The method according to claim 1, wherein the detection of the return signal is effected via a separate detection path.

5. The method according to claim 1, wherein the comparison of return signal and reference signal is effected by the logical circuit.

6. The method according to claim 1, wherein the comparison of return signal and reference signal is effected in a separate logical circuit.

7. The method according to claim 1, wherein the comparison of return signal and reference signal is effected by means of a separate discrete circuit.

8. The method according to claim 1, wherein the return signal of the current measuring period is used as reference signal for the next measuring period.

9. The method according to claim 1, wherein the reference signal is changed over time in accordance with a stored reference signal profile.

10. The method according to claim 1, wherein the reference signal is self-adapting over time.

11. The method according to claim 1, wherein amplitudes of the return signal and reference signal are compared.

12. The method according to claim 1, wherein pulse widths of the return signal and reference signal are compared.

13. The method according to claim 1, wherein emission of the communication signal takes place if the return signal is below the reference signal by a defined threshold value.

14. The method according to claim 1, wherein the comparison of return signal and reference signal is effected by analog means via a comparator of a discrete circuit.

15. The method according to claim 1, wherein the comparison of return signal and reference signal, after an A/D conversion, is effected by digital means by the logical circuit or by a separate logical circuit.

16. The method according to claim 13, wherein the threshold value is defined by a comparator or its drive system.

17. The method according to claim 1, wherein there is a defined time delay between the beginning of the emission of a polling signal and the detection of the return signal.

18. The method according to claim 1, wherein the return signal contains at least 10 fundamental oscillations of the RF field.

19. The method according to claim 1, wherein the logical circuit is set from an idle mode into an operating mode before transmitting the polling signal.

20. The method according to claim 1, wherein the communication signal is emitted with a transmitting power reduced by at least a factor of 2.

21. The method according to claim 1, wherein the read/write unit adaptively determines in a self-learning manner whether the communication signal is emitted with standard transmitting power or with reduced transmitting power.

22. A read/write unit for detecting identification media within a communication range of an antenna for transmitting and receiving RF signals of the read/write unit which operates in accordance with the principle of inductive coupling of an RF field in the MHz frequency band and which has a transmitting path connected directly to the antenna,

a receiving path connected directly to the antenna,

a circuit for RF communication with at least one of a standard transmitting power or reduced transmitting power, and a logical circuit for evaluating a communication between the read/write unit and an identification medium, wherein

a short polling signal, which contains at least one of unmodulated or force excited oscillations of the RF field, can be periodically emitted with the standard transmitting power via the transmitting path and the antenna,

and during the emission of the polling signal, a return signal with at least one of unmodulated or force excited oscillations of the RF field can be detected at the antenna,

then the return signal can be compared with a reference signal,

and then a communication signal can be emitted for detecting an identification medium if the return signal differs from the reference signal.