Multidimensional sieving for high density low collision RFID tag fields

• US 20080180220A1
• Filed: 01/26/2007
• Published: 07/31/2008
• Est. Priority Date: 01/26/2007
• Status: Active Grant

• Current Assignee: RF Accelerated LLC
• Original Assignee: RF Accelerated LLC
• Inventors: Hollister, Allen, Armstrong, John T., Barta, Gary
• Granted Patent: US 10,817,679 B2
• Time in Patent Office: Days
• US Class Current: 340/10.2
• 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 7/10029 the collision being resolved in the time domain, e.g. using binary tree search or RFID responses allocated to a random time slot
• CPC Class Codes: G06K 7/10069 the collision being resolved in the frequency domain, e.g. by hopping from one frequency to the other frequency hopping or spread spectrum techniques H04B7/00
• CPC Class Codes: G06K 7/10217 parameter settings controlling the transmission power of the interrogator
• CPC Class Codes: G06K 7/10356 using a plurality of antennas, e.g. configurations including means to resolve interference between the plurality of antennas

Abstract

A system comprising an RFID Reader and an array of RFID Tags, where the tags have the ability to measure physical signal properties such as FM deviation and Received Signal Strength as examples and use these measurements to create a means to refrain from responding to the Reader, unless the measured values fall inside a range determined by a built in algorithm or decision tree or by the Reader and transmitted to the array of Tags in an outbound message. The system may also use non-physical parameters, including tokens sent by the Interrogator/Reader to the Tag field. Moreover, physical parameters may be divided into maskable and unmaskable parameters. Signal frequency is not maskable by the environment, for example, but signal amplitude and phase are maskable by the environment during propagation. Additionally, the number, the nature and the range of each Multidimensional Variable are set by the Interrogator at the start of a session. In this way, foreknowledge or good estimates of the tag population will lead to higher efficiency operation

Claims

1. An RFID system comprising:

a plurality of RFID tags, each of said plurality of RFID tags having a unique identification code defined by initializing selected Multidimensional Vector (MDV) parameters for receiving a signal and for generating a response signal based thereon, each of said RFID tags using a reply flag in association with said predetermined multidimensional vector for determining whether to respond to a received message addressed to all of said plurality of RFID tags.

2. The RFID system according to claim 1 wherein said Multidimensional Vector parameters consist of both environmentally maskable and unmaskable parameters.

3. The RFID system according to claim 2 wherein said unmaskable parameter is Frequency.

4. The RFID system according to claim 2 wherein said unmaskable parameter is Frequency Deviation.

5. The RFID system according to claim 2 wherein said unmaskable parameter is Spread Spectrum Code Parameters.

6. The RFID system according to claim 2 wherein said unmaskable parameter is Frequency Hop parameters.

7. The RFID system according to claim 2 wherein said unmaskable parameter is Timeslot choice.

8. The RFID system according to claim 2 wherein said maskable parameter is Direction.

9. The RFID system according to claim 2 wherein said maskable parameter is Phase.

10. The RFID system according to claim 2 wherein said maskable parameter is Polarization.

11. The RFID system according to claim 2 wherein said maskable parameter is Signal Strength.

12. A method for an interrogator/reader to identify an RFID tag from a plurality of RFID tags comprising:

(A) initializing user selected multidimensional vector parameters upon receiving a read command for each RFID tag wherein each selected multidimensional vector parameter for each RFID tag is defined by a range of minimum and maximum vector values and a resolution value;

(B) setting a reply flag to a logical true value for each RFID tag;

(C) generating for each said plurality of RFID tags an integer random number having an integer value within said range of minimum and maximum vector values for each selected multidimensional vector parameter;

(D) receiving interrogator/reader generated environmentally modified measured multidimensional vector parameter values at each of said plurality of RFID tags and generating a random number;

(E) determining whether said success flag value for each said plurality of RFID tags is true wherein if said success flag is true for a given said RFID tag, said RFID tag has previously been read and said reply flag for said RFID tag is set a logical false value;

(F) comparing during each interrogator/reader cycle, said interrogator/reader generated, environmentally modified measured values to each selected multidimensional vector parameter for each RFID tag defined by a range of minimum and maximum vector values and resolution values wherein when a match occurs said RFID tag will respond to said interrogator/reader;

(G) transmitting by each of said RFID tags when said generated random number matches within said range of minimum and maximum vector values and resolution values, a unique code for identification associated with each RFID tag and then, upon successful communication, setting said success flag to a logical true value;

(H) waiting by each of said RFID tag where said generated random number does not match within said range of minimum and maximum vector values and resolution values for a next interrogator/reader cycle; and

(I) examining said transmissions by each of said RFID tags by said interrogator/reader and ceasing the iterative transmission of said interrogator/reader cycle when no RFID tags respond by transmitting their unique code for identification, the said interrogator/reader transmits a command causing any remaining said RFID tags whose success flag is false to respond.

13. The method of claim 12 wherein the minimum and maximum vector values are calculated from a minimum value, a resolution value, and a number of steps.

14. The method of claim 12 wherein the minimum and maximum vector values are calculated from a maximum value, a resolution value, and a number of negative steps.

15. The method of claim 12 wherein the tags have been preprogrammed with environmentally maskable parameters.

16. The method of claim 12 wherein the reader/interrogator transmits its own unique identifier to the tag.

17. An RFID system, comprising:

(A) means for initializing user selected multidimensional vector parameters upon receiving a read command for each RFID tag wherein each selected multidimensional vector parameter for each RFID tag is defined by a range of minimum and maximum vector values and a resolution value;

(B) means for setting a reply flag to a logical true value for each RFID tag;

(C) means for generating for each said plurality of RFID tags an integer random number having an integer value within said range of minimum and maximum vector values for each selected multidimensional vector parameter;

(D) means for receiving interrogator/reader generated environmentally modified measured multidimensional vector parameter values at each of said plurality of RFID tags and generating a random number;

(E) means for determining whether said success flag value for each said plurality of RFID tags is true wherein if said success flag is true for a given said RFID tag, said RFID tag has previously been read and said reply flag for said RFID tag is set a logical false value;

(F) means for comparing during each interrogator/reader cycle, said interrogator/reader generated, environmentally modified measured values to each selected multidimensional vector parameter for each RFID tag defined by a range of minimum and maximum vector values and resolution values wherein when a match occurs said RFID tag will respond to said interrogator/reader;

(G) means for transmitting by each of said RFID tags when said generated random number matches within said range of minimum and maximum vector values and resolution values, a unique code for identification associated with each RFID tag and then, upon successful communication, setting said success flag to a logical true value;

(H) means for waiting by each of said RFID tag where said generated random number does not match within said range of minimum and maximum vector values and resolution values for a next interrogator/reader cycle; and

(I) means for examining said transmissions by each of said RFID tags by said interrogator/reader and ceasing the iterative transmission of said interrogator/reader cycle when no RFID tags respond by transmitting their unique code for identification, the said interrogator/reader transmits a command causing any remaining said RFID tags whose success flag is false to respond wherein the reader/interrogator transmits its own unique identifier to the tag.

18. The system of claim 17 further comprising means for calculating from a minimum value, a resolution value, and a number of steps for determining said minimum and maximum vector values.

19. The system of claim 17 further comprising means for calculating from a maximum value, a resolution value, and a number of negative steps for determining said minimum and maximum vector values.

20. The system of claim 17 further comprising means for preprogramming said tags with environmentally maskable parameters.