METHOD AND APPARATUS FOR LOCATING PASSIVE INTEGRATED TRANSPONDER TAGS

• US 20100207765A1
• Filed: 02/13/2009
• Published: 08/19/2010
• Est. Priority Date: 02/13/2009
• Status: Active Grant

• Current Assignee: Health Beacons, Inc. (Hologic Incorporated)
• Original Assignee: Health Beacons, Inc. (Hologic Incorporated)
• Inventors: Brander, Christopher, Reicher, Murray, Petcavich, Robert
• Granted Patent: US 8,973,584 B2
• Time in Patent Office: Days
• US Class Current: 340/572.100
• CPC Class Codes: A01K 11/006 Automatic identification systems for animals, e.g. electronic devices, transponders for animals identification systems for access to feeding pens A01K1/0209; ear tags with electronic identification means A01K11/004
• CPC Class Codes: A61B 2090/397 electromagnetic other than visible, e.g. microwave
• CPC Class Codes: A61B 5/06 Devices, other than using radiation, for detecting or locating foreign bodies for removing same A61B17/50 ; determining position of probes within or on the body of the patient
• CPC Class Codes: A61B 90/39 Markers, e.g. radio-opaque or breast lesions markers
• CPC Class Codes: G06K 2007/10524 Hand-held scanners
• 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 7/10297 arrangements for handling protocols designed for non-contact record carriers such as RFIDs NFCs, e.g. ISO/IEC 14443 and 18092 cryptographic protocols H04L9/00; network security protocols H04L63/00; real-time communication protocols in data switching networks H04L65/00; network protocols for data switching network services H04L67/00
• CPC Class Codes: G06K 7/10386 the interrogation device being of the portable or hand-handheld type, e.g. incorporated in ubiquitous hand-held devices such as PDA or mobile phone, or in the form of a portable dedicated RFID reader

Abstract

An apparatus for locating an embedded passive integrated transponder (PIT) tag is provided. An embodiment of the locating apparatus includes a resonator capable of electromagnetically coupling to the PIT tag, and a feedback circuit connected to the resonator and configured to monitor a load conductance of the resonator. A distance between the resonator and the PIT tag is indicated by a change in the monitored load conductance when the resonator and the PIT tag are electromagnetically coupled. Another embodiment includes a resonator capable of stimulating a response signal from a PIT tag, and a processing circuit capable of calculating the distance between the resonator and the PIT tag based on the amplitude of the response signal.

Claims

1. An apparatus for locating an embedded passive integrated transponder (PIT) tag comprising:

a resonator capable of electromagnetically coupling to the PIT tag; and

a feedback circuit connected to said resonator and configured for monitoring a load conductance of said resonator,

wherein a distance D between said resonator and the PIT tag is indicated by a change in said monitored load conductance when said resonator and the PIT tag are electromagnetically coupled.

2. The apparatus of claim 1, further comprising an oscillator configured to oscillate at a frequency substantially equal to an operating frequency of the PIT tag, and wherein said oscillator includes said resonator.

3. The apparatus of claim 2, wherein said feedback circuit is configured to adjust a bias current in said oscillator such that a substantially constant oscillation amplitude is maintained as said load conductance varies.

4. The apparatus of claim 3, wherein said feedback circuit comprises:

an amplitude peak detector connected to said oscillator;

an error amplifier configured to receive both a reference voltage as a first input and an output from said amplitude peak detector as a second input; and

a low-pass filter receiving an output from said error amplifier and transmitting an output to said oscillator to adjust said bias current.

5. The apparatus of claim 3, further comprising an analog-to-digital converter and a microprocessor, wherein said analog-to-digital converter measures the bias current and provides an output to said microprocessor.

6. The apparatus of claim 5, wherein said measured value of said bias current is converted to an audio and /or visual indication of said distance between said resonator and the PIT tag.

7. The apparatus of claim 6, further comprising:

a voltage-to-frequency converter generating a converter signal having a frequency within an audible range, said frequency varying in a pre-defined manner according to the distance between said resonator and the PIT tag;

an amplifier configured to amplify said converter signal; and

a speaker outputting said amplified converter signal as an audible tone.

8. The apparatus of claim 6, further comprising a display indicating said distance D in a graphical or numeric format.

9. An apparatus for locating an embedded PIT tag comprising:

a resonator capable of electromagnetically coupling to the PIT tag and outputting an interrogating signal;

a drive circuit configured to drive said resonator to stimulate a response signal from the PIT tag, wherein said response signal is superimposed over said interrogating signal in said resonator;

a demodulator configured to demodulate said combined interrogating signal and response signal output from said resonator;

a bandpass amplifier configured to receive an output of said demodulator and isolate and amplify said response signal; and

a peak detector configured to measure at least an amplitude of said amplified response signal,

wherein said amplitude is a function of a distance D between said resonator and the PIT tag.

10. The apparatus of claim 9, wherein said output of said demodulator is converted into an audio and/or visual indication of said distance between said resonator and the PIT tag.

11. The apparatus of claim 10, further comprising:

a voltage-to-frequency converter generating a converter signal having a frequency within an audible range, said frequency varying in a pre-defined manner according to an output of said peak detector;

an amplifier configured to amplify said converter signal; and

a speaker outputting said amplified converter signal as an audible tone.

12. The apparatus of claim 10, further comprising:

a frequency synthesizer outputting a synthesizer signal having a frequency within an audible range, said frequency varying according to an output of said peak detector;

a gain-controlled amplifier configured to amplify said synthesizer signal; and

a speaker outputting said amplified synthesizer signal as an audible tone.

13. The apparatus of claim 10, further comprising a display indicating said distance D between said resonator and the PIT tag in a graphical or numerical format.

14. The apparatus of claim 9, wherein an identification number associated with the PIT tag is also extracted from said output of said demodulator.

15. The apparatus of claim 9, wherein said resonator includes a search coil having a central longitudinal axis.

16. The apparatus of claim 15, wherein the search coil is rotatable about an axis orthogonal to said central longitudinal axis.

17. The apparatus of claim 9, further comprising:

a switch configured to adjust a frequency of said resonator; and

a frequency synthesizer to adjust a frequency of said drive circuit.

18. The apparatus of claim 9, wherein said resonator includes a search coil encased within a probe that can be inserted into an object containing the PIT tag.

19. A method for locating a PIT tag embedded in an object comprising the steps of:

providing an energized apparatus having a search coil and an indicator;

placing said search coil directly adjacent to an outer surface of the object such that said search coil electromagnetically couples with and identifies the PIT tag;

said apparatus displaying an indication value that indicates a distance D between said search coil and the PIT tag; and

repositioning said search coil on the outer surface of the object to obtain a new indication value until said indication value reaches a maximum,

wherein said indicator displays a maximum indication value when said distance D between said search coil and the PIT tag is at a minimum.

20. The method of claim 19, wherein said apparatus provides an audio signal having a frequency that varies according to said distance D between said search coil and the PIT tag.

21. The method of claim 19, further comprising the step of marking a surface of the object at about a center of the search coil to indicate a lateral position of the PIT tag.