Battery assisted RFID system command set

• US 8,384,523 B1
• Filed: 09/05/2008
• Issued: 02/26/2013
• Est. Priority Date: 09/05/2008
• Status: Active Grant

• Current Assignee: Zest Labs, Inc.
• Original Assignee: Intelleflex Corporation
• Inventors: Dacus, Farron, van Niekerk, Johannes Albertus, Rodriquez, Alfonso
• Primary Examiner(s): Wong, Albert
• Assistant Examiner(s): MEHRAVARI, PETER CYRUS
• Application Number:
  US12/205,745
• Time in Patent Office: 1,635 Days
• Field of Search: 340/10.1, 340/10.33, 340/10.41, 340/5.1, 340/572.1, 340/10.3, 340/10.34, 713/320
• US Class Current: 340/10.1
• CPC Class Codes: G06K 7/10009 sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves
• CPC Class Codes: H04Q 2209/47 using RFID associated with sensors
• CPC Class Codes: H04Q 2209/75 by polling or interrogating the sub-stations
• CPC Class Codes: H04Q 2209/88 Providing power supply at the sub-station
• CPC Class Codes: H04Q 9/00 Arrangements in telecontrol or telemetry systems for selectively calling a substation from a main station, in which substation desired apparatus is selected for applying a control signal thereto or for obtaining measured values therefrom

Abstract

Specialized battery assisted command set design methods are disclosed that provide for interference rejection using highly sensitive but relatively broadband RFID tags. The command set design also supports RFID system RF power control for further interference control. The command set design also allows for convenient expansion to active transmitters and receivers in tags operating within the same system. Embodiments of the present invention provide RFID systems having battery-assisted, Semi-Passive RFID tags that operate with sensitive transistor based square law tag receivers utilizing a plurality of tag receiver dynamic range states. Embodiments of the present invention are also enhanced with receiver training and synchronizing methods suited to the high tag sensitivity and need for dynamic range state switching. These enhancements may employ pseudo-random sequence based receiver training, activation signaling, and frame synchronizing. Additional enhancement attained via power leveling methods that optimize the amount of transmitted power and interference from a reader in relation to the sensitivity of the RFID tags, their ranges from the reader, and the unique physics of the backscatter RFID radio link.

Claims

1. An RFID tag configured to receive an RFID Activation command structure that is transmitted from an RFID reader and processed in the RFID tag,

the RFID tag comprising:

an antenna;

circuitry coupled to the antenna, the circuitry being configured to process the command structure;

the command structure comprising;

a plurality of fields, the plurality of fields comprising;

a session/inventory flag identification field that specifies a session that the RFID reader will use after the RFID tag has been activated;

a field that indicates whether the RFID tag is to check a hibernate mode state of a session/inventory flag as a parameter upon which to base activation of the RFID tag;

a control field that specifies if tag session locking is to be in effect after activation of the RFID tag; and

a value that places the RFID tag in a tag session locked mode to prevent a response to a normal mode command with a differing session code than one indicated in the Activation command structure,

wherein the session/inventory flag state is controlled by an RFID reader programmable timer while in a hibernate mode,

wherein an activation of the RFID tag based on the timer controlled session/inventory flag state is related to system transmit power control operations such that the RFID tag accessed at a lower reader transmit power level temporarily does not respond to reader commands transmitted at a higher power level.

2. The RFID tag of claim 1 wherein the command structure further comprises a reader lock field that indicates if the RFID tag is operable to utilizes tag-to-reader locking with the first RFID reader after the at least one RFID tag has been activated.

3. The RFID tag of claim 1 wherein the command structure further comprises at least one duty cycle field, within the plurality of fields, that specifies a duty cycle of operation of a receiver within the activated RFID tag.

4. The RFID tag of claim 1 wherein a state machine operation is altered when the RFID tag is locked onto a first RFID reader, the altered state machine operation causing the activated RFID tag to ignore a command from a second RFID reader that does not feature an appropriate identification in the reader identification code field.

5. The RFID tag of claim 4 wherein a specialized reader command is provided that overrides the lock between the RFID tag and the first RFID reader and returns the RFID tag to a hibernate mode.

6. The RFID tag of claim 1 wherein the RFID tag is configured to check a hibernate mode tag-to-reader locking flag to identify whether the RFID tag locks to the first RFID reader while in the hibernate mode.

7. The RFID tag of claim 6 wherein the hibernate mode tag-to-reader locking flag is the same flag as a normal mode tag-to-reader locking flag.

8. The RFID tag of claim 1 wherein a tag state machine operation is altered from a passive tag operation mode into an interference rejecting mode when at least one RFID tag is in a session locked mode with a first RFID reader, the altered state machine operation causing the at least one RFID tag to ignore a command from a second RFID reader that does not feature an appropriate identification in a session field of said command.

9. The RFID tag of claim 8 wherein a specialized reader command is provided that overrides the locked tag session between the at least one RFID tag and the first RFID reader and returns the at least one RFID tag to a hibernate mode.

10. The RFID tag of claim 1 wherein the command structure further comprises at least one duty cycle field, within the plurality of fields, that describes a subsequent duty cycle of operation of the RFID tag when the RFID tag is activated.

11. An RFID reader configured to generate an RFID Activation command structure that is transmitted from the REED reader to an RFID tag,

the RFID tag comprising:

an antenna;

circuitry coupled to the antenna, the circuitry being configured to generate the command structure;

the command structure comprising;

a plurality of fields, the plurality of fields comprising;

a session/inventory flag identification field that specifies a session that the RFID reader will use after the set of RFID tags has been activated;

a field that indicates if at least one tag, within the set of RFID tags, is to check a hibernate mode state of a session/inventory flag as a parameter upon which to base activation of the at least one RFID tag;

a control field that specifies if tag session locking is to be in effect after activation of the at least one RFID tag; and

a value that places the at least one RFID tag in a tag session locked mode to prevent a response to a normal mode command with a differing session code than one indicated in the Activation command structure,

wherein the session/inventory flag state is controlled by an RFID reader programmable tinier while in a hibernate mode,

wherein an activation of the set of RFID tags based on the timer controlled session/inventory flag state is related to system transmit power control operations such that a subset of RFID tags that were accessed at lower reader transmit power levels temporarily do not respond to reader commands transmitted at higher power levels.

12. The RFID reader of claim 11 wherein a tag state machine operation is altered from a passive tag operation mode into an interference rejecting mode when at least one RFID tag is in a session locked mode with a first RFID reader, the altered state machine operation causing the at least one RFID tag to ignore a command from a second RFID reader that does not feature an appropriate identification in a session field of said command.

13. The RFID reader of claim 11 wherein a specialized reader command is provided that overrides the locked tag session between the at least one RFID tag and the first RFID reader and returns the at least one RFID tag to a hibernate mode.

14. The RFID reader of claim 11 wherein the command structure further comprises at least one duty cycle field, within the plurality of fields, that describes a subsequent duty cycle of operation of at least one receiver within the set of activated RFID tags.