Radio-frequency identification (RFID) tag employing unique reception window and method therefor

• US 20050156711A1
• Filed: 02/16/2005
• Published: 07/21/2005
• Est. Priority Date: 10/18/2002
• Status: Active Grant

• Current Assignee: Aeroscout Limited (Stanley Black & Decker, Inc.)
• Original Assignee: Aeroscout Limited (Stanley Black & Decker, Inc.)
• Inventors: Aljadeff, Daniel, Amsalem, Reuven
• Granted Patent: US 7,295,115 B2
• Time in Patent Office: Days
• US Class Current: 340/10.340
• CPC Class Codes: G01S 13/765 with exchange of information between interrogator and responder
• CPC Class Codes: G01S 13/878 Combination of several spaced transmitters or receivers of known location for determining the position of a transponder or a reflector G01S13/874 takes precedence
• CPC Class Codes: G01S 5/06 Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements G01S5/12 takes precedence
• CPC Class Codes: G06K 19/0705 the battery being connected to a power saving arrangement
• CPC Class Codes: G06K 19/0717 the sensor being capable of sensing environmental conditions such as temperature history or pressure
• 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 19/07345 by activating or deactivating at least a part of the circuit on the record carrier, e.g. ON/OFF switches

Abstract

A radio-frequency identification (RFID) tag employing a unique reception window and method for operating the tag system provides low-power operation for enhanced tag battery life, while providing addressable tags that can receive commands and data from the system, which can be a wireless local area network (WLAN) incorporating location finding for locating the tags. Interference with other tags and other transmitters is prevented by either using a sniffer circuit to determine that no network transmission is in progress, or by using a special non-interfering coding sequence. A receiver within the tag is operated for a predetermined period of time after a periodic transmission is made from the tag, and an address decoder determines if the tag is being addressed. The receiver can receive data and/or commands after being addressed and is shutdown if the window time elapses, the tag is not addressed, or at the completion of data/command transfer.

Claims

1. A wireless identification tag, comprising:

a battery for powering internal circuits of said tag;

a transmitter for transmitting signals encoding at least an identifier of said wireless identification tag;

a timer for activating said transmitter on a periodic basis to transmit said signals and deactivating said transmitter subsequent to transmitting said signals, whereby power consumption from said battery is conserved when said timer deactivates said transmitter;

a receiver for receiving system signals from an external system in communication with said tag, wherein said system signals include a tag address; and

a second timer for activating said receiver for a predetermined period of time subsequent to said transmitter transmitting said signals, whereby said system signals are received by said tag during a predictable window subsequent to transmissions of said tag, and whereby power consumption from said battery is further conserved.

2. The wireless identification tag of claim 1, wherein said receiver further comprises an address decoder for determining whether or not said tag address matches a particular address of said tag, and wherein said receiver is deactivated in response to determining that said tag address does not match said particular address of said tag.

3. The wireless identification tag of claim 2, wherein said predetermined period of time is extended in response to said address decoder determining that said tag address matches said particular address of said tag, whereby said receiver is operated in order to receive at least one of a command and data from said system.

4. The wireless identification tag of claim 1, further comprising a storage for storing parameters of said tag, said parameters including one or more values corresponding to:

said predetermined period of time, a period of said transmitted signals, a start time of said transmitted signals and an amplitude of said transmitted signals, and wherein said transmitter produces said transmitted signals in conformity with said stored parameters.

5. The wireless identification tag of claim 4, wherein said receiver receives commands from said external system and sets said parameters in conformity with said received commands.

6. The wireless identification tag of claim 4, wherein said receiver receives transmissions from said external system and sets said parameters in conformity with fields within an address of said transmissions.

7. The wireless identification tag of claim 4, wherein said transmitter further transmits at least a portion of said parameters, whereby said external system can determine one or more of said one or more values stored within said wireless identification tag.

8. The wireless identification tag of claim 1, further comprising a processor coupled to said receiver for responding to commands received from said system bearing a tag address matching a particular address of said tag.

9. The wireless identification tag of claim 8, wherein said processor implements at least one of said first timer, said second timer and said address decoder.

10. The wireless identification tag of claim 8, wherein said processor is coupled to a battery status monitor for determining a level of charge of said battery, wherein said processor receives a command from said receiver requesting transmission of battery status to said system, and wherein said transmitter transmits said battery status in conformity with reception of said command.

11. The wireless identification tag of claim 8, wherein, wherein said processor receives data from said receiver corresponding to a new identifier of said wireless identification tag, and wherein said processor replaces said identifier of said wireless identification tag with said new identifier.

12. The wireless identification tag of claim 1, further comprising a sniffer circuit for determining whether or not another device in communication with said system is transmitting, whereby said periodic transmission of said transmitter and said predetermined period of time is delayed in response to determining that said other device is transmitting.

13. The wireless identification tag of claim 1, wherein said system is a wireless local area network (WLAN), wherein said transmitter transmits signals on a WLAN channel and wherein said receiver receives WLAN system signals.

14. The wireless identification tag of claim 13, wherein said transmitter transmits a signal on said channel bearing an address not corresponding to any unit of said WLAN, whereby standard WLAN receivers within said WLAN ignore said signal.

15. The wireless identification tag of claim 13, wherein said transmitter transmits a spread spectrum direct sequence signal on said channel that has a direct sequence code differing from than a standard Barker direct sequence 11-bit code of said WLAN, whereby standard receivers within said WLAN reject said signal.

16. The wireless identification tag of claim 13, wherein said transmitter transmits a signal on said channel that has a preamble differing from than a standard preamble of said WLAN, whereby standard receivers within said WLAN reject said signal.

17. The wireless identification tag of claim 13, wherein said receiver receives a signal on said channel that has at least one of:

a modulation type, bit rate and format differing from a standard modulation type, bit rate and format of said WLAN, whereby standard receivers within said WLAN reject said signal while said receiver accepts said signal.

18. The wireless identification tag of claim 1, wherein said transmitter further includes an input for receiving data from an external device, and wherein said transmitter transmits a signal that bears information from said external device coupled to said input.

19. The wireless identification tag of claim 18, wherein said external device is a sensor.

20. A method of operating a wireless identification tag, comprising:

transmitting a signal from said identification tag at periodic intervals, said signal bearing an identifier of said wireless identification tag;

operating a receiver within said wireless identification time for only a predetermined period of time subsequent to an end of said periodic intervals, whereby signals from external devices may be received while reducing battery energy use by said receiver.

21. The method of claim 20, further comprising:

receiving signals from said external devices by said receiver, said signals bearing an identification tag address;

decoding said tag address to determine whether or not said tag address matches a particular address of said wireless identification tag; and

in response to determining that said tag address does not match said particular address, deactivating said receiver.

22. The method of claim 21, further comprising:

receiving signals from said external devices by said receiver, said signals bearing an identification tag address;

decoding said tag address to determine whether or not said tag address matches a particular address of said wireless identification tag; and

in response to determining that said tag address matches said particular address, keeping said receiver active after expiration of said predetermined period of time, whereby at least one of data and commands transmitted from said external devices to said wireless identification tag are received.

23. The method of claim 20, further comprising:

receiving signals from said external devices by said receiver;

decoding one or more parameters from said received signals, said transmission including one or more values corresponding to;

said predetermined period of time, a period of said signal, a start time of said signal and amplitude of said signal, and wherein said transmitting transmits said signal in conformity with said stored parameters.

24. The method of claim 20, wherein said transmitting transmits one or more stored parameter values corresponding to said predetermined period of time, a period of said signal, a start time of said signal and amplitude of said signal, whereby said external devices can determine said one or more stored parameter values.

25. A wireless identification tag comprising:

a battery for powering internal circuits of said tag;

a transmitter for transmitting tag signals encoding at least an identifier of said wireless identification tag;

a timer for activating said transmitter on a periodic basis to transmit said signals and deactivating said transmitter subsequent to transmitting said signals, whereby power consumption from said battery is conserved when said timer deactivates said transmitter;

means for receiving system signals bearing at least one of commands and data from an external system.

26. The wireless identification tag of claim 25, wherein said system is a wireless local area network (WLAN), and wherein said system signals and said tag signals are WLAN-compatible signals.