Battery Assisted RFID Command Set and Interference Control

• US 20100060425A1
• Filed: 04/29/2009
• Published: 03/11/2010
• Est. Priority Date: 09/05/2008
• Status: Active Grant

• Current Assignee: Zest Labs, Inc.
• Original Assignee: Maxim Integrated Products, Inc. (Analog Devices, Inc.)
• Inventors: Van Niekerk, Johannes Albertus, Dacus, Farron, Rodriguez, Alfonso
• Granted Patent: US 8,436,714 B2
• Time in Patent Office: Days
• US Class Current: 340/10.100
• 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. 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. A method for generating an RFID activation command that is transmitted from an RFID reader and processed in an RFID tag, the method comprising:

generating a reader identification code that provides identification of the RFID reader to the RFID tag, the reader identification code provides authentication information that enables the RFID tag to exclusively lock onto the RFID reader after activation;

inserting the reader identification code in a first field within a command that communicate activation information between the RFID reader and the RFID tag; and

transmitting the command to the RFID tag.

2. The method of claim 1 further comprising the step of generating a reader lock code that indicates if the RFID tag is operable to utilize tag-to-reader locking with the RFID reader after the RFID tag has been activated.

3. The method of claim 1 further comprising the steps of generating and transmitting a duty cycle code within the activation command that sets a tag receiver duty cycle subsequent to activation of the RFID tag.

4. The method of claim 1 further comprising the steps of generating and transmitting a duty cycle code that is stored in a tag memory location to control a tag receive duty cycle within the RFID tag.

5. The method of claim 4 wherein the tag receive duty cycle relates to a post-activation normal mode tag receive duty cycle.

6. The method of claim 4 wherein the tag receive duty cycle relates to a hibernate mode tag receive duty cycle.

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

8. The method of claim 4 further comprising the step of generating a specialized reader command that overrides the lock between the RFID tag and the RFID reader and returns the RFID tag to a hibernate mode.

9. The method of claim 1 further comprising the step of checking a hibernate mode tag-to-reader locking flag and reader identification code to identify whether the RFID tag should lock to the RFID reader while in a hibernate mode.

10. The method of claim 9 wherein an activation command bit controls the hibernate mode tag-to-reader locking flag.

11. The method of claim 9 wherein a deactivation command bit controls the hibernate mode tag-to-reader locking flag.

12. The method of claim 9 wherein a register bit controls the hibernate mode tag-to-reader locking flag.

13. A method for generating an RFID activation command that is transmitted from an RFID reader and processed in an RFID tag, the command structure comprising:

generating a session/inventory flag identification code that identifies a session that the RFID reader may use after a set of RFID tags has been activated;

generating a session/inventory care/don'"'"'t care code that indicates if the RFID 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 RFID tag;

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

inserting the session/inventory flag identification code, the session/inventory care/don'"'"'t care code, and the control code within a plurality of fields in the RFID activation command; and

wherein the RFID reader specifies 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.

14. The method of claim 13 wherein a tag state machine operation is altered from a more-interference susceptible operation mode into a less-interference susceptible mode when the RFID tag is in a session locked mode with the RFID reader, the altered state machine operation causing the RFID tag to ignore a command from a second RFID reader that does not feature an appropriate identification in a session field of the activation command.

15. The method of claim 13 wherein a session/inventory flag state is controlled by an RFID reader programmable timer while in a hibernate mode.

16. The method of claim 13 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 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.

17. The method of claim 13 further comprising the steps of generating and transmitting a duty cycle code within the activation command that sets a tag receiver duty cycle subsequent to activation of the RFID tag.

18. The method of claim 13 further comprising the steps of generating and transmitting a duty cycle code that is stored in a tag memory location to control a tag receive duty cycle within the RFID tag.

19. The method of claim 18 whereby the tag receive duty cycle relates to a post-activation normal mode tag receive duty cycle.

20. The method of claim 18 whereby the tag receive duty cycle relates to a hibernate mode tag receive duty cycle.

21. A method of generating an RFID activation command that is transmitted from an RFID reader and processed in an RFID tag, the method comprising:

generating an air interface class identification code that identifies a subset of possible air interface classes associated with the RFID tag that are to respond to the reader activation command; and

inserting the air interface class identification code within the RFID activation command; and

transmitting the RFID activation command to the RFID tag.

22. The method of claim 21 further comprising the steps of:

generating an active transmitter setup code that provides information to the RFID tag related to operating parameters of an RFID active tag transmitter; and

inserting the active transmitter set-up code within the RFID activation command.

23. The method of claim 22 wherein the active transmitter setup code defines a set of tag transmit characteristics comprising at least one characteristic selected from a group consisting of a tag active transmit frequency or channel, an active transmit power, an active transmit modulation mode, and an active transmit data rate.

24. The method of claim 21 further comprising the step of inserting an active receiver set up code within the RFID activation command, the active receiver set up code provides information to the RFID tag related to operating parameters of an RFID active tag receiver.

25. A method for bringing a set of RFID tags into an interrogation/query round, the method comprising:

generating air interface class identification code that identifies a class of at least one RFID tag, within the set of RFID tags, that are to participate in the interrogation round;

inserting the air interface class identification code within an RFID interrogation command; and

transmitting the RFID interrogation command to the set of RFID tags.

26. A method for bringing a set of RFID tags into an interrogation/query round, the method comprising:

generating a sensor type identification code that identifies at least one sensor type required for each RFID tag, within the set of RFID tags, to participate in the interrogation round,

inserting the sensor type identification code within an RFID interrogation command; and

transmitting the RFID interrogation command to the set of RFID tags.

27. The method of claim 26 wherein the at least one identified sensor type is a Simple Sensor type.

28. The method of claim 27 wherein an additional field is provided to enable automatic Simple Sensor response by the set of RFID tags as part of a singulation process and wherein the set of RFID tags transmit Simple Sensor data and identifying data without using an additional command to read the Simple Sensor data.