Method and apparatus for improving the interrogation range of an RF-Tag

• US 20010010495A1
• Filed: 03/08/2001
• Published: 08/02/2001
• Est. Priority Date: 10/19/1999
• Status: Abandoned Application

• Current Assignee: LGS Innovations LLC (CACI International Incorporated)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Pidwerbetsky, Alex, Helms, Howard David
• Application Number:
  US09/801,519
• Publication Number:
  US 20010010495A1
• Time in Patent Office: Days
• US Class Current: 340/572.7
• 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: G08B 13/2417 having a radio frequency identification chip
• CPC Class Codes: G08B 13/2462 Asset location systems combined with EAS inventory, tracking, logistic G06Q10/00; entrance control systems G07C9/00
• CPC Class Codes: G08B 13/2471 Antenna signal processing by receiver or emitter
• CPC Class Codes: G08B 13/2488 Timing issues, e.g. synchronising measures to avoid signal collision, with multiple emitters or a single emitter and receiver
• CPC Class Codes: H01Q 21/29 Combinations of different interacting antenna units for giving a desired directional characteristic H01Q25/00 takes precedence

Abstract

A method for increasing the interrogation range of an RF Tag in a radio communication system using RF Tags with two reflecting antenna elements. The second reflecting antenna element is predeterminately positioned, and preferably aligned, with respect to the first reflecting antenna element in the direction of expected incident RF radiation and is spaced from the first reflecting antenna element at a predetermined fixed distance. The first and second reflecting antenna elements are alternately pulsed on and off such that while the first reflecting antenna element is in a signal reflecting operating state, the second reflecting antenna element is in a substantially non-reflecting state and vice versa. The alternate pulsing and predetermined fixed spacing between the first and second elements generates a known phase difference between the reflected signals of the first and second reflecting antenna elements. The phase difference is preferably 180 degrees which may be achieved by spacing the second reflecting antenna element from the first reflecting antenna element at a distance equivalent to ¼ of the wavelength of the interrogating signals.

Claims

1. A method for increasing an interrogation range in an RF Tag monitoring system comprising an Interrogator and a first reflecting antenna element and a second reflecting antenna element for receiving RF signals from the Interrogator and reflecting back to the Interrogator modulated signals, wherein the second reflecting antenna element is fixedly positioned and spaced with respect to the first reflecting antenna element along a direction of expected receipt of the RF signals from the Interrogator, the method comprising the step of:

alternately pulsing the first and second reflecting antenna elements on and off such that while the first reflecting antenna element is in a reflecting mode the second reflecting antenna element is in a non-reflecting mode, and when the first reflecting antenna element is in the non-reflecting mode the second reflecting antenna element is in the reflecting mode.

2. The method set forth in

claim 1

, further comprising providing said first and second reflecting antenna element on one RF Tag.

3. The method set forth in

claim 1

, wherein said step of alternately pulsing generates a phase difference in a range of 60°

- 180°

between reflected modulated signals from the first and second reflecting antenna elements.

4. The method set forth in

claim 1

, wherein the RF signals have a wavelength (λ

) and the fixed position and spacing of the second reflecting element is with respect to said first reflecting element comprises a range of {fraction (1/12)} to ¼

of the wavelength of the RF signals.

5. The method set forth in

claim 1

, wherein said step of alternately pulsing generates a 180°

phase difference between reflected signals from the first and second reflecting antenna elements.

6. The method set forth in

claim 1

, wherein the RF signals have a wavelength (λ

) and the fixed positioning and spacing between the first and second reflecting antenna elements comprises ¼

wavelength (λ

/4) of the RF interrogating signals.

7. The method set forth in

claim 1

, wherein the fixed position of the second reflecting antenna element is axially aligned with the first reflecting antenna element.

9. The method set forth in

claim 7

, wherein said step of alternately pulsing generates a phase difference between the signals reflected from the first set of reflecting elements and the signals reflected from the second set of reflecting elements.

10. The method set forth in

claim 7

, wherein the RF signals have a wavelength (λ

) and said fixed spacing of said second set of reflecting elements with respect to said first set of reflecting elements comprises a range of {fraction (1/12)} to ¼

of the wavelength of the RF signals.

11. The method as set forth in

claim 7

, wherein the RF signals have a wavelength (λ

) wherein said fixed spacing comprises ¼

wavelength (λ

/4) of the interrogating RF signals.

12. The method set forth in

claim 9

, wherein said phase difference is in a range of 60°

to 180°

.

13. The method set forth in

claim 9

, wherein said phase difference is 180°

.

8. A method for increasing an interrogation range in an RF Tag monitoring system utilizing a Luneberg lens reflector as an RF Tag for receiving and reflecting RF signals, the Luneberg lens having a first and a second set of reflecting elements spaced from a modulating diode array, wherein the second set of reflecting elements is fixedly positioned and spaced with respect to the first set of reflecting elements along a direction of expected incident receipt of the RF signals by the Luneberg lens reflector, the method comprising the step of:

alternately pulsing the first and second sets of reflecting elements on and off such that while the first set of reflecting elements is in a reflecting mode, the second set of reflecting elements is in a non-reflecting mode, and when the first set of reflecting elements is in a non-reflecting mode, the second set of reflecting elements is in a reflecting mode.

14. An RF Tag communication system, comprising:

an Interrogator for transmitting RF signals;

a first antenna element and a second antenna element for receiving the RF signals from the Interrogator and for reflecting modulated signals back to the Interrogator, said at first and second antenna elements being fixedly spaced from one another along a direction of expected incident receipt of RF signals.

15. The RF Tag communication system in accordance with

claim 14

, further comprising an RF Tag having said first and second antenna elements disposed therein.

16. The RF Tag communication system in accordance with

claim 14

, wherein said first and second antenna elements are capable of being alternately pulsed on and off such that while one antenna element is in a reflecting mode, the other antenna element is in a non-reflecting mode and vice versa.

17. The RF Tag communication systems in accordance with

claim 14

, wherein said RF Tag further comprises a processor coupled to the first and second antenna elements for enabling the alternate pulsing of said first and second antenna elements.

18. The RF Tag communication system in accordance with

claim 14

, wherein the RF signals have a wavelength (λ

) and said fixed spacing of said at least two reflecting antenna elements with respect to each other comprises a range of {fraction (1/12)} to ¼

of the wavelength of the RF signals.

19. The RF Tag communication system in accordance with

claim 14

, wherein said fixed spacing comprises ¼

wavelength (λ

/4) of the RF signals.

20. The RF Tag communication system in accordance with

claim 14

, wherein said at least two reflecting antenna elements are positioned so as to be axially aligned with each other in the direction of expected incident receipt of the RF interrogating signals.

21. The RF Tag communication system in accordance with

claim 16

, wherein the alternate pulsing of said at least two reflecting antenna elements generates a predetermined phase difference in a range of 60°

- 180°

between signals reflected by the respective reflecting antenna elements.

22. The RF Tag communication system in accordance with

claim 17

, wherein said RF signals generated by the Interrogator comprise an initial transmission of information instructing said processor to effect said alternate on-off pulsing of the at least two reflecting antenna elements.

23. The RF Tag communication system in accordance with

claim 17

, wherein said processor is pre-programmed to alternately pulse said first and second antenna element, and wherein said RF signals generated by the Interrogator comprise an initial transmission to the RF Tag enabling the activation of the RF Tag.

24. The RF Tag communication system in accordance with

claim 21

, wherein said phase difference is 180°

.

25. An RP Tag communication system, comprising:

an Interrogator for transmitting RF signals;

a first, a second and a third reflecting antenna element for receiving the RF signals from the Interrogator and for reflecting modulated signals back to the Interrogator, and a processor, wherein said first, second and third antenna elements are arranged in a triangular configuration with respect to each other, said Interrogator transmitting an initial RF signal to instruct said processor to alternately pulse said first, second and third reflecting antenna elements on and off in predetermined pairs such that two antenna elements are pulsed on and off for a predetermined interval while the third remains off during the predetermined interval.

26. The RF Tag communication system in accordance with

claim 25

, further comprising an RF Tag in communication with said Interrogator, said first, second and third reflecting antenna elements being disposed on said RF Tag.

27. The RF Tag communication system in accordance with

claim 25

, wherein said predetermined pairs comprise said first and second antenna elements, said second and third antenna elements and said third and first antenna elements, and wherein said Interrogator monitors the strength of the reflected signals from said predetermined pairs and instructs said processor to utilize the pair that provides the strongest reflection signal.

28. An RF Tag communication system, comprising:

an Interrogator for transmitting RF signals;

a first, a second, a third and a fourth reflecting antenna element for receiving the RF signals from the Interrogator and for reflecting modulated signals back to the Interrogator, and a processor, wherein said antenna elements are arranged in a tetrahedral configuration, said Interrogator transmitting an initial RF signal to instruct said processor to alternately pulse said reflecting antenna elements on and off in predetermined pairs such that two antenna elements are pulsed on and off for a predetermined interval while the other two elements remain off during the predetermined interval.

29. The RF Tag communication system in accordance with

claim 28

, further comprising an at least one RF Tag, said first, second, third and fourth reflecting antenna elements being disposed in said at least one RF Tag.

30. The RF Tag communication system in accordance with

claim 28

, wherein said predetermined pairs comprise said first and second reflecting antenna elements, said second and third antenna elements, said third and fourth antenna elements, and said fourth and first antenna elements, and wherein said Interrogator monitors the strength of the reflected signals from said predetermined pairs and instructs said processor to utilize the pair that provides the strongest reflection signal.

31. A method for increasing an interrogation range in an RF Tag monitoring system comprising an Interrogator and a first reflecting antenna element and a second reflecting antenna element for receiving RF signals from the Interrogator and reflecting back to the Interrogator modulated signals, wherein the second reflecting antenna element is fixedly positioned and spaced with respect to the first reflecting antenna element along a direction of expected receipt of the RF signals from the Interrogator, the method comprising the step of:

alternately pulsing both the first and second reflecting antenna elements on and off together such that both reflecting antenna elements are simultaneously either in the reflecting mode or else in the non-reflecting mode.