Uncontrolled passive radio frequency identification tag and sytem with 3-D positioning

• US 20060158333A1
• Filed: 01/20/2006
• Published: 07/20/2006
• Est. Priority Date: 01/20/2005
• Status: Active Grant

• Current Assignee: Wright State University
• Original Assignee: Wright State University
• Inventors: Rigling, Brian, Garber, Fred
• Granted Patent: US 7,988,055 B2
• Time in Patent Office: Days
• US Class Current: 340/572.200
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• CPC Class Codes: G06K 7/10336 the antenna being of the near field type, inductive coil

Abstract

Passive radio frequency identification tags comprising a simple antenna and a circuit with a unique frequency-dependent response, in place of an RF-powered integrated circuit with control logic, is disclosed. The unique frequency-dependence of the circuit, which may simply be a feature of the antenna, conveys the tags identification. Multiple frequency-dependent circuit RFID tags can be simultaneously identified and located in 3-D space through use of antenna arrays and sampling at multiple frequencies in order to provide spatial resolution.

Claims

1. An uncontrolled passive radio frequency identification (PRFID) tag comprising a circuit pattern configured to have a unique response for each one of a plurality of predetermined frequencies of RF energy when illuminated by a spectrum of said RF energy.

2. The tag according to claim 1 wherein said response comprises a unique phase, a unique amplitude, and combinations thereof.

4. The tag according to claim 1 or 3 wherein said response is a spectral response over a range of operating/excitation frequencies, and exploits at least one of the operating/excitation frequencies at any given instance.

5. The tag according to claim 1 or 3 wherein in addition to said unique response, said tag has a response at a given frequency or frequencies identical to a response from a plurality of said tags in order to provide a known reference.

6. The tag according to claim 1 or 3 further comprising an additional integrated circuit to allow writing operations at short range to alter said response.

7. A radio frequency identification (RFID) tag system comprising:

the tag according to claim 1;

and

an RFID reader configured to illuminate said tag with said spectrum of RF energy, observe responses at multiple excitation frequencies , and decode said responses to a unique tag ID.

9. The system of claim 7 or 8, further comprises multiple reader antennas, and wherein said reader is configured to spatially resolve said responses from said tag in order to provide 3-D position information for said tag.

10. The system of claim 7 or 8, further comprises multiple reader antennas, and wherein said reader is configured to spatially resolve said responses from said tag in order to provide 3-D position information for said tag, and wherein said reader is configured to spatially separated and segment environmental clutter after providing said 3-D position information.

11. The system according to claim 7 or 8, wherein said reader has an operating range up to about 100 m.

12. The system according to claim 7 or 8 wherein said reader is configured to operated in at least one of monostatic, bistatic, and multistatic modes to interrogate said tag at every frequency of interest.

13. The system according to claim 7 or 8 wherein said response is a spectral response observed by qth antenna of the reader at pth frequency according to a measurement defined by:

$S_q<br><br>\left(f_p\right)=\underset{k=1}{\overset{M}{\sum <br><br>}}<br><br>A_{\mathrm{qk}}<br><br>H_k<br><br>\left(f_p\right)<br><br>\exp <br><br>\left(-j<br><br>\frac{2<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\Pi <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>f_p}{c}<br><br>R_{\mathrm{qk}}\right)$

where Aqk is an arbitrary gain/phase related to a physical channel between the tag and the reader, Rqk is a round-trip range (monostatic or bistatic) from the reader to the tag to the reader, which is a function of a known transmitter position tq, a known receiver position rq, and an unknown tag position xk, wherein in monostatic operation, the transmitter and receiver are collocated, and wherein said measurement is repeated for all antennas (for all q) and for all frequencies (for all p).

3. An uncontrolled passive radio frequency identification (pRFID) tag comprising:

a circuit pattern that is configured to provide a unique linear/nonlinear response when the tag is illuminated by a particular frequency of RF energy.

8. A radio frequency identification (RFID) tag system comprising:

the tag according to claim 3;

and

an RFID reader configured to illuminate said tag with multiple excitation frequencies, observe responses of a series of measurements at said multiple excitations frequencies, and decode said responses to a unique tag ID.