Detection of a contactless data storage device

• US 8,907,683 B2
• Filed: 09/28/2011
• Issued: 12/09/2014
• Est. Priority Date: 09/30/2010
• Status: Active Grant

• Current Assignee: LEGIC Identsystems AG (Kirkbi A/S)
• Original Assignee: LEGIC Identsystems AG (Kirkbi A/S)
• Inventors: Hausmann, Peter, Plss, Marcel, Schnaubelt, Matthias
• Primary Examiner(s): Vazquez, Arleen M
• Assistant Examiner(s): Andrews, Brent J
• Application Number:
  US13/246,995
• Publication Number:
  US 20120081131A1
• Time in Patent Office: 1,168 Days
• Field of Search: 324/309, 324/654, 340/572, 340/10.1, 340/10.4, 340/10.5, 343/702
• US Class Current: 324/654
• 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
• CPC Class Codes: H04B 5/26 using coils
• CPC Class Codes: H04B 5/77 for interrogation

Abstract

For detecting within a communication range of an antenna a contactless data storage device which is configured for inductive coupling with an electromagnetic field emitted by the antenna, a return signal is detected (S1) at the antenna during emission of an electromagnetic field pulse. During amplitude build-up of carrier oscillation at the beginning of the electromagnetic field pulse, an evaluation signal is generated (S2) based on the return signal, and the data storage device is detected (S3) based on the evaluation signal. By detecting the presence of the data storage device based on an evaluation signal generated during amplitude build-up, the detection of the data storage device can be initiated before carrier oscillation of the electromagnetic field pulse is stable. Consequently, the width of the electromagnetic field pulse can be shortened and, therefore, energy consumption for detecting the presence of the data storage device can be reduced.

Claims

1. A detection circuit for detecting, within a communication range of an antenna for emitting an electromagnetic field, a contactless data storage device which is configured for inductive coupling with the electromagnetic field, the detection circuit comprising:

a circuit for generating an electromagnetic field pulse comprising a carrier signal, wherein said carrier signal has an amplitude build-up which begins at the beginning of the electromagnetic field pulse and continues until the carrier signal reaches a maximum amplitude;

a connector for connecting electrically the detection circuit to the antenna and for receiving a return signal at the antenna during emission of the electromagnetic field pulse,

wherein the detection circuit is further configured to generate, entirely during said amplitude build-up of said carrier signal at the beginning of the electromagnetic field pulse, an evaluation signal based on the return signal, and

to detect the data storage device within the communication range based on the evaluation signal generated during the amplitude build-up and further based on a threshold value.

2. The detection circuit of claim 1, wherein the detection circuit is configured to determine, based on the evaluation signal, the slope of the amplitude build-up, and to detect the data storage device within the communication range based on the threshold value and the slope of the amplitude build-up.

3. The detection circuit of one of claim 1, wherein the detection circuit is configured to generate the evaluation signal as a comparative signal, during amplitude build-up of the carrier signal at the beginning of the electromagnetic field pulse, based on a comparison of the return signal and a comparative value, and to detect the presence of the data storage device based on the comparative signal generated during the amplitude build-up and the threshold value.

4. The detection circuit of claim 3, wherein the detection circuit is configured to generate the comparative signal to indicate exceeding oscillations of the return signal, an exceeding oscillation having an amplitude greater than the comparative value, and to detect the presence of the data storage device based on the number of exceeding oscillations within a defined time interval during the amplitude build-up and the threshold value.

5. The detection circuit of one of claim 1, wherein the detection circuit further comprises:

an Analog-Digital-converter and a Villard circuit for connecting the antenna to an input of the Analog-Digital-converter, the Villard circuit being configured to generate the evaluation signal, during the amplitude build-up of the carrier signal at the beginning of the electromagnetic field pulse, through current integration and transposition of the return signal from the antenna to a defined operating range of the Analog-Digital-converter, and the detection circuit is configured to detect the presence of the data storage device based on a digital value generated by the Analog-Digital-converter from the evaluation signal at a defined point in time during the amplitude build-up.

6. The detection circuit of claim 3, wherein the detection circuit is configured to generate the comparative signal to indicate the phasing of the return signal, to determine a phase shift between the comparative signal and carrier signal oscillations of the electromagnetic field pulses, and to detect the presence of the data storage device based on the phase shift and the threshold value.

7. The detection circuit of claim 6, wherein the detection circuit comprises an Exclusive-Or element for generating from the comparative signal and the carrier signal of the electromagnetic field pulses a phase signal indicative of the phase shift between the comparative signal and the carrier signal oscillation of the electromagnetic field pulses, and the detection circuit is configured to determine for an electromagnetic field pulse an average phase shift from the phase signal, and to detect the presence of the data storage device based on the average phase shift of electromagnetic field pulses and the threshold value.

8. The detection circuit of one of claim 1, wherein the detection circuit is configured to detect the data storage device based on an upper threshold value indicative of a reinforcing effect of an object in the communication range, and a lower threshold value indicative of an attenuating effect of an object in the communication range.

9. The detection circuit of one of claims 1, wherein the detection circuit is configured to define dynamically, threshold values depending on the evaluation signal generated during the amplitude build-up of a previously emitted electromagnetic field pulse.

15. The detection circuit of claim 2, wherein the detection circuit is configured to generate the evaluation signal as a comparative signal, during amplitude build-up of the carrier signal at the beginning of the electromagnetic field pulse, based on a comparison of the return signal and a comparative value, and to detect the presence of the data storage device based on the comparative signal generated during the amplitude build-up and the threshold value.

16. The detection circuit of claim 2, wherein the detection circuit comprises an Analog-Digital-converter and a Villard circuit for connecting the antenna to an input of the Analog-Digital-converter, the Villard circuit being configured to generate the evaluation signal, during the amplitude build-up of the carrier signal at the beginning of the electromagnetic field pulse, through current integration and transposition of the return signal from the antenna to a defined operating range of the Analog-Digital-converter, and the detection circuit is configured to detect the presence of the data storage device based on a digital value generated by the Analog-Digital-converter from the evaluation signal at a defined point in time during the amplitude build-up.

10. A method of detecting, within a communication range of an antenna for emitting an electromagnetic field, a contactless data storage device which is configured for inductive coupling with the electromagnetic field, the method comprising:

emitting, at the antenna, an electromagnetic field pulse, said electromagnetic field pulse comprising a carrier signal, wherein said carrier signal has an amplitude build-up which begins at the beginning of the electromagnetic field pulse and continues until the carrier signal reaches a maximum amplitude;

detecting, at the antenna, a return signal during emission of said electromagnetic field pulse,

generating, entirely during said amplitude build-up of said carrier signal at the beginning of the electromagnetic field pulse, an evaluation signal based on the return signal, and

detecting the data storage device within the communication range based on the evaluation signal generated during the amplitude build-up and further based on a threshold value.

11. The method of claim 10, further comprising:

determining, based on the evaluation signal, the slope of the amplitude build-up, and

detecting the data storage device within the communication range based on the threshold value and the slope of the amplitude build-up.

12. The method of one of claim 10, further comprising:

generating the evaluation signal as a comparative signal, during the amplitude build-up of the carrier signal at the beginning of the electromagnetic field pulse, based on a comparison of the return signal and a comparative value, the comparative signal indicating exceeding oscillations of the return signal having an amplitude greater than the comparative value, and

detecting the presence of the data storage device based on the number of exceeding oscillations within a defined time interval during the amplitude build-up.

13. The method of one of claim 10, further comprising:

connecting the antenna via a Villard circuit to an input of an Analog-Digital-converter,

generating the evaluation signal, during the amplitude build-up of the carrier signal at the beginning of the electromagnetic field pulse, transposing the return signal by the Villard circuit from the antenna to a defined operating range of the Analog-Digital-converter, and

detecting the presence of the data storage device based on a digital value generated by the Analog-Digital-converter from the evaluation signal provided at a defined point in time during the amplitude build-up.

14. The method of claim 10, further comprising:

generating the evaluation signal as a comparative signal, during the amplitude build-up of the carrier signal at the beginning of the electromagnetic field pulse, based on a comparison of the return signal and a comparative value, the comparative signal indicating the phasing of the return signal,

determining a phase shift between the comparative signal and carrier signal oscillations of the electromagnetic field pulses, and

detecting the presence of the data storage device based on the phase shift and the threshold value.

17. The method of claim 11, further comprising:

generating the evaluation signal as a comparative signal, during the amplitude build-up of the carrier signal at the beginning of the electromagnetic field pulse, based on a comparison of the return signal and a comparative value, the comparative signal indicating exceeding oscillations of the return signal having an amplitude greater than the comparative value, and

detecting the presence of the data storage device based on the number of exceeding oscillations within a defined time interval during the amplitude build-up.

18. The method of one of claim 11, further comprising:

connecting the antenna via a Villard circuit to an input of an Analog-Digital-converter,

generating the evaluation signal, during the amplitude build-up of the carrier signal at the beginning of the electromagnetic field pulse, transposing the return signal by the Villard circuit from the antenna to a defined operating range of the Analog-Digital-converter, and

detecting the presence of the data storage device based on a digital value generated by the Analog-Digital-converter from the evaluation signal provided at a defined point in time during the amplitude build-up.