Method for recognizing identification media

• US 20070188326A1
• Filed: 02/28/2005
• Published: 08/16/2007
• 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: Hausmann, Peter, Koch, Andreas, Pluss, Marcel
• Granted Patent: US 7,598,872 B2
• Time in Patent Office: Days
• US Class Current: 340/572.400
• 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 the 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 a standard transmitting power or less, and a logical circuit for evaluating a communication between the read/write unit and an identification medium, characterized in that

a short polling signal, which contains a number of fundamental 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 a number of fundamental 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. A method according to claim 1, wherein the polling signal is shorter by at least two orders of magnitude than the communication signal.

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

4. A method according to claim 1, that wherein the detection of the return signal is effected via a separate detection paths.

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

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

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

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

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

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

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

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

14. A 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. A 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 for or by a separate logical circuit.

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

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

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

21. A 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 the 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 a standard transmitting power or less, and a logical circuit for evaluating a communication between the read/write unit and an identification medium, characterized in that

a short polling signal, which contains a number of fundamental 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 a number of fundamental 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.