Wireless locating and tracking systems

• US 7,005,968 B1
• Filed: 06/07/2000
• Issued: 02/28/2006
• Est. Priority Date: 06/07/2000
• Status: Expired due to Term

• Current Assignee: Symbol Technologies, LLC (Zebra Technologies Corporation)
• Original Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Inventors: Bridgelall, Raj
• Primary Examiner(s): Holloway, III, Edwin C.
• Application Number:
  US09/588,833
• Time in Patent Office: 2,092 Days
• Field of Search: 340/10.42, 340/825.49, 340/572.1, 340/572.7, 340/572.5, 340/539.1, 340/539.12, 340/539.13, 342/44, 342/45, 342/42, 342/51, 342/450, 342/451, 235/385, 455/456, 455/456.1, 455/456.2, 455/101, 705/28, 705/29, 705/32, 367/2, 343/871
• US Class Current: 340/10.42
• CPC Class Codes: G01S 13/876 Combination of several spaced transponders or reflectors of known location for determining the position of a receiver G01S13/874 takes precedence
• CPC Class Codes: G06K 19/07767 the first and second communication means being two different antennas types, e.g. dipole and coil type, or two antennas of the same kind but operating at different frequencies
• CPC Class Codes: H01Q 1/2225 used in active tags, i.e. provided with its own power source or in passive tags, i.e. deriving power from RF signal
• CPC Class Codes: H01Q 21/29 Combinations of different interacting antenna units for giving a desired directional characteristic H01Q25/00 takes precedence
• CPC Class Codes: H01Q 3/247 by switching different parts of a primary active element

Abstract

A locating and tracking system is provided in which the assets desired to be located and tracked are associated with either radio frequency (RF) tags or radio frequency identification and radio frequency data communication (RFID/RFDC) devices. Depending on which device is attached to the asset, the other device is located at known locations. The RFID/RFDC devices interrogate and receive signals from the RF tags. The received information is sent to a host computer. With the location of either the RF tags or RFID/RFDC devices known, the assets may be located and tracked. An improved RF tag antenna design is also provided by using a switching mechanism connected to at least two antennas.

Claims

1. A method for tracking an asset with a radio frequency identification/radio frequency data communication (RFID/RFDC) device and a plurality of marker tags, comprising:

sending an interrogation signal from the RFID/RFDC device that has an interrogation range;

receiving a first response signal to the interrogation signal from a first marker tag located at a first known location within the interrogation range;

processing the first response signal with the RFID/RFDC device to determine a first identity of the first marker tag;

receiving a second response signal to the interrogation signal from a second marker tag located at a second known location within the interrogation range;

processing the second response signal with the RFID/RFDC device to determine a second identity of the second marker tag; and

processing the first identity of the first marker tag and the second identity of the second marker to track the asset.

2. The method defined in claim 1 wherein the asset is a person.

3. The method defined in claim 2 wherein the RFID/RFDC device is incorporation within a cell phone.

4. The method defined in claim 2 wherein the RFID/RFDC device is incorporated within a personal data assistant.

5. The method defined in claim 2 wherein the RFID/RFDC device is incorporated within pager.

6. The method defined in claim 1 wherein the first identity of the first marker tag and the second identity of the second marker tag are sent to a host computer system in response to a request from the host computer system and the host computer system conducts the processing of the first identity of the first marker tag and the second identity of the second marker to track the asset.

7. The method defined in claim 1 wherein a third response signal to the interrogation signal is received from a third marker tag of the plurality of markers located at a third known location within the interrogation range, the method further comprising processing the first response signal and the third response signal to determine which of the first marker tag and the third marker tag is closest to the RFID/RFDC device.

8. The method defined in claim 7 wherein the signal strength of the first response signal and third response signal received from the first marker tag and third marker tag are processed to determine which of the first marker tag and the third marker tag is closest to the RFID/RFDC device.

9. A system for tracking an asset with a plurality of marker tags located at known locations, comprising:

a radio frequency identification/radio frequency data communication (RFID/RFDC) device associated with the asset wherein the RFID/RFDC device;

sends an interrogation signal that has an interrogation range;

receives a first response signal to the interrogation signal from a first marker tag located at a first known location within the interrogation range;

processes the first response signal to identify a first identity of the first marker tag;

receives a second response signal to the interrogation signal from a second marker tag located at a second known location within the interrogation range;

processes the second response signal to identify a second identity of the second marker tag; and

a host computer system that receives the first identity of the first marker tag and the second identity of the second marker tag from the RFID/RFDC device and determines the location of the RFID/RFDC device from the first identity of the first marker tag and the second identity of the second marker tag.

10. The system defined in claim 9 wherein the asset is a person.

11. The system defined in claim 10 wherein the RFID/RFDC device is incorporated within a cell phone.

12. The system defined in claim 10 wherein the RFID/RFDC device is incorporated within a personal data assistant.

13. The system defined in claim 10 wherein the RFID/RFDC device is incorporated within a pager.

14. The system defined in claim 9 wherein the host computer system receives the first identity of the first marker tag and the second identity of the second marker tag from the RFID/RFDC device in response to a request from the host computer system.

15. The system defined in claim 9 wherein the RFID/RFDC device receives a third response signal from a third marker tag of the plurality of markers located at a third known location within the interrogation range in addition to receiving the first response signal from the first marker tag and wherein the RFID/RFDC device processes the received first response signal and third response signal to determine which of the first marker tag and third marker tag is closest to the RFID/RFDC device.

16. The system defined in claim 15 wherein the signal strength of the first response signal and the third response signal received from the first marker tag and the third marker tag are processed to determine which of the first marker tag and the second marker tag is closest to the RFID/RFDC device.