SYSTEM AND METHOD FOR POSITIONING ACTIVE RFID TAG

• US 20100164723A1
• Filed: 12/31/2008
• Published: 07/01/2010
• Est. Priority Date: 12/31/2008
• Status: Active Grant

• Current Assignee: Mitac Technology Corporation (MiTAC Holdings Corp.)
• Original Assignee: Mitac Technology Corporation (MiTAC Holdings Corp.)
• Inventors: Hsu, Jen-Hao, Shiau, Jun-Ting, Yu, Chia-Chin
• Granted Patent: US 8,339,243 B2
• Time in Patent Office: Days
• US Class Current: 340/572.100
• 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 7/10079 the collision being resolved in the spatial domain, e.g. temporary shields for blindfolding the interrogator in specific directions

Abstract

A positioning system and method are provided to use multiple RFID readers to position a target object with an active RFID tag equipped thereon. The system and method defines a geometric center of the locations of the RFID readers as a first coordinate. When the RFID readers continuously receive RF signals of the active RFID tag, a corresponding signal intensity of each of the RF signals is calculated and compared to obtain an approaching vector corresponding to the location of the RFID reader with the greatest signal intensity of the RF signal. A positioned location of the target object is then approached from the first coordinate to a second coordinate according to the approaching vector. The first coordinate and the positioned location of the target object will be reset as the second coordinate. The reset first coordinate is output as the latest positioned location of the target object.

Claims

1. A system adapted to position a target object equipped with an active RFID (Radio Frequency Identification) tag by a plurality of RFID readers, the system comprising:

a receiving module receiving a RF (Radio Frequency) signal of the active RFID tag received from each of the RFID readers respectively, and a corresponding signal intensity of each of the RF signals being calculated;

a comparison module comparing the corresponding signal intensities of the RF signals to calculate an approaching vector corresponding to the location of the RFID reader with the greatest signal intensity of the RF signal;

a setting module defining a geometric center of the locations of the RFID readers as a first coordinate for a positioned location of the target object, and approaching the positioned location from the first coordinate to a second coordinate according to the approaching vector when the location of the RFID reader with the greatest signal intensity is determined, and then resetting the first coordinate as the location of the second coordinate after finish approaching; and

an output module outputting the location of the first coordinate reset by the setting module as the positioned location of the target object;

wherein the comparison module, the setting module and the output module continuously operates to output the latest positioned location of the target object when the receiving module continuously receives the RF signals.

2. The system as claimed in claim 1, wherein the RFID reader further calculates the signal intensity of each of the received RF signals.

3. The system as claimed in claim 1, wherein the comparison module further calculates the signal intensity of each of the received RF signals.

4. The system as claimed in claim 1 further comprising a positioning duration threshold, wherein the system is operative when the accumulated time for the positioning operations reaches the positioning duration threshold, the location of the first coordinate last output by the output module will be used as the positioned location of the target object.

5. The system as claimed in claim 1 further comprising a positioning times threshold, wherein the system is operative when the times of resetting the first coordinate reaches the positioning times threshold, the location of the first coordinate last output by the output module will be used as the positioned location of the target object.

6. The system as claimed in claim 1 further comprising a reset times threshold, wherein the system is operative when comparing through the comparison module, the times that the ranking of the signal intensities of the RF signals received by the RFID readers remain the same for the reset times threshold, the location of the first coordinate last output by the output module will be used as the positioned location of the target object.

7. The system as claimed in claim 1, wherein the setting module sets the location of the second coordinate as a midpoint between first coordinate and the RFID reader with the greatest signal intensity.

8. The system as claimed in claim 1, wherein the setting module sets the location of the second coordinate by approaching a unit length from the location of the current first coordinate towards the RFID reader with the greatest signal intensity.

9. A method adapted to use a plurality of RFID (Radio Frequency Identification) readers to position a target object with an active RFID tag equipped thereon, the method comprising the steps of:

defining a geometric center of the locations of the RFID readers as a first coordinate for a positioned location of the object;

repeating the following steps when the RFID readers continuously receive RF (Radio Frequency) signals of the active RFID tag;

receiving the RF signals of the active RFID tag through the RFID readers to calculate a corresponding signal intensity of each of the RF signals;

comparing corresponding signal intensity of each of the RF signals;

calculating an approaching vector corresponding to the location of the RFID reader with the greatest signal intensity of the RF signal;

approaching the positioned location of the target object from the first coordinate to a second coordinate according to the approaching vector;

resetting the first coordinate as the location of the second coordinate; and

outputting the reset first coordinate as the latest positioned location of the target object.

10. The method as claimed in claim 9, wherein the RFID reader further calculates the signal intensity of each of the received RF signals.

11. The method as claimed in claim 9 further comprising the step of calculating the signal intensity of each of the received RF signals.

12. The method as claimed in claim 9, wherein the repeated steps are terminated by a default positioning duration threshold.

13. The method as claimed in claim 9, wherein the repeated steps are terminated by a default positioning times threshold.

14. The method as claimed in claim 9 further comprising the steps of:

terminating the repeated steps if the ranking of the signal intensities of the RF signals received by the RFID readers remain the same for a reset times threshold; and

outputting the latest reset first coordinate as the positioned location of the target object.

15. The method as claimed in claim 9, wherein the location of the second coordinate is defined as a midpoint between the current first coordinate and the RFID reader with the greatest signal intensity of the RF signal.

16. The method as claimed in claim 9, wherein the location of the second coordinate by approaching a unit length from the location of the current first coordinate towards the RFID reader with the greatest signal intensity.

17. A system to use a plurality of RFID (Radio Frequency Identification) readers to position a target object with an active RFID tag equipped thereon, the positioning system comprising:

a receiving module receiving a RF (Radio Frequency) signal of the active RFID tag received from each of the RFID readers respectively;

a selection module randomly selecting two-by-two of the RFID readers to match a plurality of comparison pairs;

a comparison module comparing the RF signals of the RFID readers within the comparison pairs, and determining the RFID reader with the greater signal intensity within each of the comparison pairs;

a positioning module positioning an effective range of each of the RFID reader with the greater signal intensity within each of the comparison pairs to calculate an overlapped range of the effective ranges; and

an output module outputting the overlapped range as a positioned location of the target object.

18. The system as claimed in claim 17, wherein the RFID reader further calculates the signal intensity of each of the received RF signals.

19. The system as claimed in claim 17, wherein the comparison module further calculates the signal intensity of each of the received RF signals.

20. The system as claimed in claim 17, wherein the effective range indicates a half area that is divided by a middle line of the two RFID readers within the comparison pair and corresponding to the RFID reader with the greater signal intensity within the same comparison pair.