Locating a backscatter-based transponder

• US 8,643,472 B2
• Filed: 03/16/2011
• Issued: 02/04/2014
• Est. Priority Date: 12/13/2004
• Status: Active Grant

• Current Assignee: Atmel Corporation (Microchip Technology Incorporated)
• Original Assignee: Atmel Corporation (Microchip Technology Incorporated)
• Inventors: Fischer, Martin, Friedrich, Ulrich, Masuch, Jens, Pangels, Michael, Ziebertz, Dirk
• Primary Examiner(s): BROWN, VERNAL U
• Application Number:
  US13/049,649
• Publication Number:
  US 20110163851A1
• Time in Patent Office: 1,056 Days
• Field of Search: 340/10.1, 340/505, 340/12.5, 340/572.1, 340/5.61
• US Class Current: 340/10.1
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• 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: H04Q 5/22 the subordinate centre not permitting interconnection of subscribers connected thereto

Abstract

A method and apparatus for locating a transponder is provided. A carrier signal is transmitted by a base station and a transponder transmits a locating signal that is generated through phase modulation and backscattering of the carrier signal sent by the base station when the transponder is within a transmission range of the base station, whereby the transponder is located on the basis of the locating signal.

Claims

1. A method, comprising:

receiving by a transponder an unmodulated carrier signal from a base station;

transmitting a first locating signal in response to the transponder moving within range of a communication zone of the base station based on a field strength of the received carrier signal, the first locating signal generated through phase modulation and backscattering of the received unmodulated carrier signal sent by the base station;

discontinuing, in response to receiving a first selection command, transmission of the first locating signal;

receiving by the transponder a locating command;

transmitting by the transponder, in a persistent operating state, a second locating signal, the persistent operating state allowing the transponder to receive a switch-off command while simultaneously transmitting, without an interruption for receiving the switch-off command, the second locating signal; and

discontinuing transmission of the second locating signal, in response to one or more of;

receiving the switch-off command;

or

an expiration of a pre-determined period of time.

2. The method of claim 1, wherein transmitting the first locating signal in response to the transponder moving within range of the communication zone of the base station based on the field strength of the received carrier signal comprises determining if the field strength of the received carrier signal is sufficient for supplying power to the transponder.

3. The method of claim 1, wherein the first selection command is received in response to the base station receiving a locating signal from at least one additional transponder.

4. The method of claim 1, further comprising, in response to receiving the first selection command:

randomly determining a time slot associated with the transponder.

5. The method of claim 1, further comprising:

receiving a second selection command indicative of a start time slot associated with the transponder; and

transmitting an identification signal associated with the transponder.

6. The method of claim 5, wherein the locating command was sent in response to the identification signal.

7. The method of claim 1, wherein the switch-off command is associated with a start time for a second transponder.

8. An apparatus comprising:

means for receiving by a transponder an unmodulated carrier signal from a base station;

means for transmitting a first locating signal in response to the transponder moving within range of a communication zone of the base station based on a field strength of the received carrier signal, the first locating signal generated through phase modulation and backscattering of the received unmodulated carrier signal sent by the base station;

means for discontinuing, in response to receiving a first selection command, transmission of the first locating signal;

means for receiving by the transponder a locating command

means for transmitting by the transponder, in a persistent operating state, a second locating signal, the persistent operating state allowing the transponder to receive a switch-off command while simultaneously transmitting, without an interruption for receiving the switch-off command, the second locating signal; and

means for discontinuing transmission of the second locating signal, in response to one or more of;

receiving the switch-off command;

or

an expiration of a pre-determined period of time.

9. The apparatus of claim 8, wherein transmitting the first locating signal in response to the transponder moving within range of the communication zone of the base station based on the field strength of the received carrier signal comprises determining if the field strength of the received carrier signal is sufficient for supplying power to the transponder.

10. The apparatus of claim 8, wherein the first selection command is received in response to the base station receiving a locating signal from at least one additional transponder.

11. The apparatus of claim 8, further comprising, in response to receiving the first selection command:

means for randomly determining a time slot associated with the transponder.

12. The apparatus of claim 8, further comprising:

means for receiving a second selection command indicative of a start time slot associated with the transponder; and

means for transmitting an identification signal associated with the transponder.

13. The apparatus of claim 12, wherein the locating command was sent in response to the identification signal.

14. A circuit configured to perform operations comprising:

receiving by a transponder an unmodulated carrier signal from a base station; and

transmitting a first locating signal in response to the transponder moving within range of a communication zone of the base station based on a field strength of the received carrier signal, the first locating signal generated through phase modulation and backscattering of the received unmodulated carrier signal sent by the base station;

discontinuing, in response to receiving a first selection command, transmission of the first locating signal;

receiving by the transponder a locating command;

transmitting by the transponder, in a persistent operating state, a second locating signal, the persistent operating state allowing the transponder to receive a switch-off command while simultaneously transmitting, without an interruption for receiving the switch-off command, the second locating signal; and

discontinuing transmission of the second locating signal, in response to one or more of;

receiving the switch-off command;

or

an expiration of a pre-determined period of time.

15. The circuit of claim 14, wherein the circuit is further configured to determine if the field strength of the received carrier signal is sufficient for supplying power to the transponder.

16. The circuit of claim 14, wherein the first selection command is received in response to the base station receiving a locating signal from at least one additional transponder.

17. The circuit of claim 14, wherein the circuit is further configured to perform operations comprising:

randomly determining a time slot associated with the transponder.

18. The circuit of claim 14, wherein the circuit is further configured to perform operations comprising:

receiving a second selection command indicative of a start time slot associated with the transponder; and

transmitting an identification signal associated with the transponder.

19. The circuit of claim 18, wherein the locating command was sent in response to the identification signal.

20. The circuit of claim 14, wherein the switch-off command is associated with a start time for a second transponder.