CN116916852A

CN116916852A - Interrogation and detection system and method for radio frequency tags

Info

Publication number: CN116916852A
Application number: CN202280018426.2A
Authority: CN
Inventors: E·L·布兰南; A·G·马特米勒
Original assignee: Covidien LP
Current assignee: Covidien LP
Priority date: 2021-03-05
Filing date: 2022-01-26
Publication date: 2023-10-20

Abstract

The present disclosure presents an interrogation and detection system for detecting surgical instruments within a patient. The system comprises: an RFID tag configured to transmit a return signal when energized; a signal generator configured to generate an energizing signal for the RFID tag; and a coil antenna operatively coupled to the signal generator, the antenna configured to receive a return signal transmitted by the RFID tag. The coil antenna includes a primary coil, a secondary coil, and a core configured to couple electromagnetic energy from the secondary coil to the primary coil. The core comprises a non-magnetic insulating material. The secondary coil is configured to receive the return signal. The primary coil is configured to couple electromagnetic energy from the secondary coil. The RFID tag is attached to the surgical instrument.

Description

Interrogation and detection system and method for radio frequency tags

Technical Field

The present disclosure relates generally to interrogation and detection systems for Radio Frequency (RF) tags, and more particularly to interrogation, detection and inventory systems for Radio Frequency (RF) tags used within a surgical site.

Background

Prior to completion of the surgical procedure, it is often useful to determine whether an object associated with the surgical procedure is present within the patient. Such items may take various forms. For example, the object may take the form of an instrument, such as a scalpel, scissors, forceps, hemostat, and/or a clamp. Also, for example, the article may take the form of an associated accessory and/or disposable article, such as a surgical sponge, gauze, and/or pad. Failure to position the article prior to suturing may require additional surgical procedures to be performed and may have undesirable medical consequences in some cases.

Accordingly, there is a need for techniques that can provide presence detection and marking surgical item/implement identification functionality and inventory control of such marked items/implements in a medical environment. Specifically, the presence of, identifying, and maintaining inventory of, marked surgical items and materials used during the performance of a medical procedure is detected. The prior art may perform these functions either alone or in combination with each other, but the discrete solution approach and packaging used is not ideal for the application. More specifically, the components attached or affixed to the item being tracked are either too bulky, cumbersome or otherwise impeding in performing the procedure, or the detection and identification performance of the solution may rapidly degrade in the presence of a variable and uncontrolled dielectric or conductive material.

Accordingly, there is a need for improved presence detection, tagged item identification, and inventory functions in a medical environment.

Disclosure of Invention

The present disclosure relates to systems for detecting surgical objects and devices used in a body cavity during surgery, in particular, to antennas inserted directly into a surgical site.

In accordance with aspects of the present disclosure, an interrogation and detection system for detecting surgical instruments within a patient is presented. The system comprises: an RFID tag configured to transmit a return signal when energized; a signal generator configured to generate an energizing signal for the RFID tag; and a coil antenna operatively coupled to the signal generator, the antenna configured to receive a return signal transmitted by the RFID tag. The coil antenna includes a primary coil, a secondary coil, and a core configured to couple electromagnetic energy from the secondary coil to the primary coil. The core comprises a non-magnetic insulating material. The secondary coil is configured to receive the return signal. The primary coil is configured to couple electromagnetic energy from the secondary coil. The RFID tag is attached to the surgical instrument.

In one aspect of the disclosure, the "turns ratio" between the primary and secondary coils may be greater than or equal to 1:1. The "turns ratio" is the ratio between the first number of turns of the primary coil and the second number of turns of the secondary coil.

In another aspect of the present disclosure, the secondary coil may have a resonant frequency within 10% of the operating frequency of the return signal.

In yet another aspect of the disclosure, the secondary coil may have an inductance greater than or equal to 2.5 uH.

In yet another aspect of the present disclosure, the coil antenna may further include a first matching network electrically connected to the primary coil. The first matching network is configured to match an input impedance of the primary coil to an output impedance of the generator.

In yet another aspect of the present disclosure, the coil antenna may further include a second matching network electrically connected to the secondary coil. The second matching network is configured to match an input impedance of the secondary coil to an output impedance of the primary coil.

In an aspect of the disclosure, the primary coil may be a first planar coil.

In another aspect of the present disclosure, the secondary coil may be a second planar coil.

In yet another aspect of the present disclosure, the primary coil may include a first turn and a second turn.

In yet another aspect of the present disclosure, the first turn of the primary coil and the second turn of the primary coil may be arranged in an offset manner in a vertical orientation and a horizontal orientation.

In yet another aspect of the present disclosure, the secondary coil may include a first turn and a second turn.

In an aspect of the disclosure, the first turn of the primary coil and the second turn of the primary coil may be arranged in an offset manner in a vertical orientation and a horizontal orientation.

According to aspects of the present disclosure, a coil antenna configured to receive a return signal transmitted by an RFID tag is presented. The coil antenna includes a primary coil, a secondary coil, and a core configured to couple electromagnetic energy from the secondary coil to the primary coil. The core comprises a non-magnetic insulating material. The secondary coil is configured to receive the return signal. The primary coil is configured to couple electromagnetic energy from the secondary coil.

In another aspect of the disclosure, the primary coil and the secondary coil may each be planar coils.

In yet another aspect of the present disclosure, the primary coil may include a conductor.

In yet another aspect of the disclosure, the conductor of the primary coil includes a conductor that may have a configuration including a coaxial, planar, "C" shaped cross-sectional shape and/or a tubular cross-sectional shape.

In yet another aspect of the disclosure, the "turns ratio" between the primary and secondary coils may be greater than or equal to 1:1. The "turns ratio" is the ratio between the first number of turns of the primary coil and the second number of turns of the secondary coil.

In an aspect of the disclosure, the secondary coil may have a resonant frequency within 10% of the operating frequency of the return signal.

In accordance with aspects of the present disclosure, a method for inventory control of tagged items is presented. The method includes transmitting an energizing signal through a coil antenna operatively coupled to the signal generator, the coil antenna including a primary coil, a secondary coil, and a core configured to magnetically couple the secondary coil to the primary coil, the energizing signal configured to energize an RFID tag attached to the article and configured to transmit a return signal when energized; and receiving the return signal through the primary coil of the coil antenna.

In yet another aspect of the disclosure, the method may further include detecting and/or identifying the item based on the return signal. The article may comprise a surgical instrument.

According to aspects of the present disclosure, a coil configured to receive a return signal transmitted by an RFID tag includes a first turn conductor and a second turn conductor electrically connected to the first turn conductor.

In one aspect, the first turn conductors may be positioned in parallel relationship and offset with respect to the second turn conductors.

In an aspect of the disclosure, the first turn conductor may include a first inner edge and a first outer edge. The second turn of conductor may include a second inner edge and a second outer edge.

In another aspect of the present disclosure, the coils may be arranged in a circular, square, rectangular or oblong configuration.

In yet another aspect of the disclosure, the first turn conductors may overlap with the second turn conductors of the interleaved coil, wherein a majority of the second turn conductors do not overlap with the first turn conductors.

According to aspects of the present disclosure, a coil antenna configured to receive a return signal transmitted by an RFID tag includes a primary coil and a secondary coil. The secondary coil includes a first turn of conductor and a second turn of conductor electrically connected to the first turn of conductor. The secondary coil is configured to receive the return signal. The primary coil is configured to couple electromagnetic energy from the secondary coil.

In yet another aspect of the disclosure, the coil antenna may further include a core configured to couple electromagnetic energy to and from the secondary coil to the primary coil. The core comprises a non-magnetic insulating material.

In yet another aspect of the present disclosure, the first turn conductors may be positioned in parallel relationship and offset with respect to the second turn conductors.

In another aspect of the disclosure, the secondary coil may have an inductance greater than or equal to 2.5 uH.

In yet another aspect of the present disclosure, the coil antenna may further include a first matching network electrically connected to the primary coil. The first matching network may be configured to match an input impedance of the primary coil with an output impedance of the signal generator.

In accordance with aspects of the present disclosure, an interrogation and detection system for detecting surgical instruments within a patient is presented. The interrogation and detection system includes: an RFID tag configured to transmit a return signal when energized; a signal generator configured to generate an energizing signal for the RFID tag; and a coil antenna operatively coupled to the signal generator, the antenna configured to receive a return signal transmitted by the RFID tag. The RFID tag is attached to a surgical instrument within the patient. The coil antenna includes a primary coil and a secondary coil. The secondary coil includes a first turn of conductor and a second turn of conductor electrically connected to the first turn of conductor. The first turn conductors may be positioned in parallel relationship and offset with respect to the second turn conductors. The secondary coil is configured to receive the return signal. The primary coil is configured to couple electromagnetic energy from the secondary coil.

In yet another aspect of the disclosure, the secondary coil may be an air core coupled to the primary coil.

According to aspects of the present disclosure, the secondary coil may have an inductance greater than or equal to 2.5 uH.

In an aspect of the disclosure, the coil antenna may further include a first matching network electrically connected to the primary coil.

In another aspect of the disclosure, the coil antenna may further include a second matching network electrically connected to the secondary coil.

In yet another aspect of the present disclosure, the primary coil may be a first planar coil.

In yet another aspect of the present disclosure, the secondary coil may be a second planar coil.

In yet another aspect of the present disclosure, the primary coil may include two or more turns.

In an aspect of the disclosure, the secondary coil may include two or more turns.

In accordance with aspects of the present disclosure, an interrogation and detection system for detecting surgical instruments within a patient is presented. The interrogation and detection system includes: an RFID tag configured to transmit a return signal when energized; a signal generator configured to generate an energizing signal for the RFID tag; and a coil antenna operatively coupled to the signal generator, the antenna configured to receive a return signal transmitted by the RFID tag, the coil antenna comprising a coil array. The RFID tag is attached to a surgical instrument within the patient.

In another aspect of the present disclosure, the coil array may be configured to generate magnetic flux and direct a direction of the magnetic flux and/or an amplitude of the magnetic flux based on the energizing signal.

In yet another aspect of the present disclosure, a coil array includes a first coil and a second coil. The energizing signal may include a first current and a second current. The first and second coils may be configured to be independently energized by first and second currents, respectively.

In yet another aspect of the present disclosure, the second coil may be oriented at 0 degrees, 90 degrees, 180 degrees, and/or 270 degrees relative to the first coil.

In yet another aspect of the present disclosure, a first coil of the coil array may be energized with a first current in a clockwise direction and/or a counter-clockwise direction. A second coil of the coil array is energized with a second current in a clockwise direction and/or a counter-clockwise direction.

According to aspects of the present disclosure, each coil of the coil array may be arranged in a circular, square, rectangular, and/or oblong configuration.

In an aspect of the disclosure, each of the first coil and the second coil may be a planar coil.

In another aspect of the present disclosure, each of the first coil and the second coil may include one or more turns.

In yet another aspect of the present disclosure, each of the coils of the coil array may include a primary coil and a secondary coil. Each of the coils of the coil array may also have a "turns ratio" between the primary coil and the secondary coil that is greater than or equal to 1:1. The "turns ratio" is the ratio between the first number of turns of the primary coil and the second number of turns of the secondary coil.

According to aspects of the present disclosure, a coil array configured to receive a return signal transmitted by an RFID tag includes a first coil configured to generate a first magnetic field and a second coil configured to generate a second magnetic field. The coil array is configured to generate a magnetic flux and direct a direction of the magnetic flux and/or an amplitude of the magnetic flux based on an energizing signal from the signal generator.

In yet another aspect of the present disclosure, the energizing signal may include a first current and a second current. The first and second coils may be configured to be independently energized by first and second currents, respectively.

In an aspect of the disclosure, a first coil of the coil array may be energized with a first current in a clockwise direction and/or a counter-clockwise direction. A second coil of the coil array may be energized with a second current in a clockwise direction and/or a counter-clockwise direction.

In another aspect of the present disclosure, each coil of the coil array may be arranged in a circular, square, rectangular, and/or oblong configuration.

In yet another aspect of the present disclosure, each of the first coil and the second coil may be a planar coil.

In yet another aspect of the present disclosure, each of the first coil and the second coil may include one or more turns.

According to aspects of the present disclosure, each of the coils of the coil array may have an inductance of greater than or equal to 2.5 uH.

In one aspect of the present disclosure, a method for interrogating and detecting a surgical instrument within a patient is presented. The method comprises the following steps: transmitting an energizing signal through a coil antenna operatively coupled to the signal generator, the antenna configured to receive a return signal transmitted by the RFID tag, the coil antenna comprising a coil array; and receiving the return signal through the coil array. The coil array is configured to generate a magnetic flux and direct a direction of the magnetic flux and/or an amplitude of the magnetic flux based on the energizing signal.

In another aspect of the present disclosure, the energizing signal may include a first current and a second current. The method may further comprise: energizing a first coil of the coil array by a signal generator, the first coil being energized by a first current in a clockwise direction and/or a counter-clockwise direction; and energizing a second coil of the coil array by a second current in a clockwise direction and/or a counter-clockwise direction through the signal generator.

According to aspects of the present disclosure, a system for dynamically configuring a secondary air core coupling coil and exciting a magnetic field is presented. The system comprises: an RFID tag configured to transmit a return signal when energized, the RFID tag attached to a surgical instrument within a patient; a signal generator configured to generate an energizing signal for the RFID tag; and a coil antenna operatively coupled to the signal generator, the antenna configured to receive a return signal transmitted by the RFID tag, the coil antenna configured to excite the magnetic field in a plurality of directions based on the energizing signal.

In yet another aspect of the present disclosure, a coil antenna may include a coil array including a plurality of coils. Each coil of the coil array may include a primary coil and a secondary coil.

In yet another aspect of the disclosure, the coil antenna may further include a coil tuning network configured to tune the quality factor "Q" and/or the operating frequency of the primary coil.

In yet another aspect of the present disclosure, the tuning network may include: a real part match detection network configured to detect a real part of the energizing signal; an imaginary part match detection network configured to detect an imaginary part of the energizing signal; a dynamic matching network configured to tune a quality factor "Q" and/or a first resonant frequency of the primary coil; a processor; and a memory having stored thereon instructions that, when executed by the processor, cause the system to: detecting a real part of the energizing signal through a real part matching detection network; detecting a real part of the energizing signal through an imaginary part matching detection network; determining a second resonant frequency of the primary coil based on the detected real part and the detected imaginary part of the energizing signal; and tuning the primary coil to a second resonant frequency based on the determination by the dynamic matching network.

In an aspect of the disclosure, the tuning network may further include a power detection network configured to detect a power level from the power-on signal.

In another aspect of the disclosure, the instructions, when executed, may further cause the system to: the method includes detecting a power level of the energizing signal by a power detection network, determining a third resonant frequency of the primary coil, and tuning the primary coil to the third resonant frequency based on the determination by a dynamic matching network.

In yet another aspect of the present disclosure, the coil antenna may further include a termination network configured to enable or disable discrete secondary coils of the coil array.

In yet another aspect of the disclosure, the terminating network may include: an impedance sensor configured to sense an impedance of each of the secondary coils of the coil array; a step-down transformer configured to reduce an impedance of each of the secondary coils of the coil array; a dynamic capacitance set configured to provide a plurality of loads to each of the secondary coils of the coil array via a step-down transformer; a processor; and a memory having stored thereon instructions that, when executed by the processor, cause the system to: the method includes determining an impedance of the return signal by an impedance sensor, and setting a dynamic capacitance set to one of a plurality of loads based on the determination.

In yet another aspect of the disclosure, the secondary coil may be a configurable secondary coil comprising a plurality of configurable secondary coil portions. The configurable secondary coil may have a plurality of secondary coil configurations.

According to aspects of the present disclosure, the coil antenna may further include a steering network configured to enable at least one of the plurality of secondary coil configurations.

In one aspect of the disclosure, a system may include a surgical table. The coil antenna may be embedded in the surgical table.

In another aspect of the present disclosure, the coil array may include a first coil and a second coil. The energizing signal may include a first current and a second current. The first and second coils may be configured to be independently energized by first and second currents, respectively.

In yet another aspect of the present disclosure, a first coil of the coil array may be energized with a first current in a clockwise direction and/or a counter-clockwise direction. A second coil of the coil array may be energized with a second current in a clockwise direction and/or a counter-clockwise direction.

According to aspects of the present disclosure, a coil antenna includes a coil array configured to receive a return signal transmitted by an RFID tag. The coil array includes a first coil configured to generate a first magnetic field and a second coil configured to generate a second magnetic field. The coil array includes a plurality of coils configured to generate magnetic flux and direct a direction of the magnetic flux and/or an amplitude of the magnetic flux based on an energizing signal from the signal generator. Each coil of the coil array includes a primary coil and a secondary coil.

In yet another aspect of the present disclosure, the coil antenna may further include a coil tuning network configured to tune the quality factor "Q" and/or the operating frequency of each primary coil.

In an aspect of the disclosure, the tuning network may include a real part match detection network configured to detect a real part of the energizing signal; an imaginary part match detection network configured to detect an imaginary part of the energizing signal; a dynamic matching network configured to tune a quality factor "Q" and/or a first operating frequency of the primary coil; a processor; and a memory. The memory includes instructions stored thereon that, when executed by the processor, cause the coil antenna to: detecting a real part of the energizing signal through a real part matching detection network; detecting a real part of the energizing signal through an imaginary part matching detection network; determining a second operating frequency of the primary coil based on the detected real part and the detected imaginary part of the energizing signal; and tuning the primary coil to the second operating frequency based on the determination by the dynamic matching network.

In another aspect of the disclosure, the coil antenna may further include a termination network configured to enable or disable discrete secondary coils of the coil array.

In yet another aspect of the disclosure, the termination network may include a sensor configured to sense an impedance, a voltage, and/or a current of each of the secondary coils of the coil array.

In yet another aspect of the disclosure, the secondary coil may be a configurable secondary coil comprising a plurality of configurable secondary coil portions. The configurable secondary coil has a plurality of secondary coil configurations.

According to aspects of the present disclosure, a method for interrogating and detecting a surgical instrument within a patient includes: transmitting an energizing signal through a coil antenna operatively coupled to the signal generator, the antenna configured to receive a return signal transmitted by the RFID tag, the coil antenna comprising a coil array; a return signal is received through the coil array. The coil array is configured to generate a magnetic flux and direct a direction of the magnetic flux and/or an amplitude of the magnetic flux based on the energizing signal. The method further comprises the steps of: detecting a real part of the energizing signal through a real part matching detection network; detecting a real part of the energizing signal through an imaginary part matching detection network; determining a second operating frequency of the primary coil based on the detected real part and the detected imaginary part of the energizing signal; and tuning the primary coil to the second operating frequency based on the determination by the dynamic matching network.

According to aspects of the present disclosure, a system for dynamically tuning impedance matching between an antenna coil and a signal generator in real time includes: an RFID tag configured to transmit a return signal when energized, the RFID tag attached to a surgical instrument within a patient; a signal generator configured to generate an energizing signal for the RFID tag; a coil antenna operatively coupled to the signal generator, the antenna configured to receive a return signal transmitted by the RFID tag; and a real-time tuning network configured to dynamically tune an impedance match between the signal generator and the coil antenna.

In yet another aspect of the disclosure, the real-time tuning network may include: a tuning discriminator configured to determine a real part of the energizing signal and/or an imaginary part of the energizing signal; a phase compensation network configured to dynamically tune a phase of the matching impedance based on the determined imaginary part of the power-on signal; and an amplitude compensation network configured to dynamically tune the amplitude of the matching impedance based on the determined real part of the energizing signal. The imaginary part comprises a capacitive signal, an inductive signal and/or a composite signal. The real part includes the power-on signal current and/or the power-on signal voltage.

In one aspect of the disclosure, a real-time tuning discriminator may include: an impedance transformation network configured to transform the power-on signal from the signal generator to identify real and imaginary parts of the power-on signal; a rectifier configured to rectify the impedance-transformed signal; and a low pass filter configured to filter the rectified signal.

In another aspect of the disclosure, the real-time tuning network may further include a power detector configured to detect the power-on signal current and/or the power-on signal voltage.

In yet another aspect of the present disclosure, the phase compensation network may include: a dynamic capacitive element configured to select a frequency range that matches a phase of the impedance; and a transformer configured to reduce a voltage across the dynamic capacitive element.

In yet another aspect of the present disclosure, the amplitude compensation network may include: a dynamic capacitive element configured to select a frequency range that matches an amplitude of the impedance; and a transformer configured to reduce a voltage across the dynamic capacitive element.

In yet another aspect of the disclosure, the system may further include a processor and a memory including instructions stored thereon that, when executed, cause the system to: the method further includes determining an imaginary part of the energizing signal and dynamically tuning, by the phase compensation network, a phase of the matching impedance based on the determined imaginary part of the energizing signal.

In an aspect of the disclosure, the instructions, when executed, may further cause the system to: the method includes determining a real part of the energizing signal and dynamically tuning, by an amplitude compensation network, an amplitude of the matching impedance based on the determined real part of the energizing signal.

In another aspect of the present disclosure, a coil antenna may include a primary coil and a secondary coil.

In yet another aspect of the present disclosure, a tuning network may be disposed between the primary coil and the signal generator. The tuning network may be configured to tune the quality factor "Q" and/or the operating frequency of the primary coil.

In yet another aspect of the disclosure, the system may further include a second tuning network electrically coupled to the secondary coil and configured to tune a quality factor "Q" and/or an operating frequency of the secondary coil.

According to aspects of the present disclosure, a method for dynamically tuning an impedance match between an antenna coil and a signal generator in real time includes: determining a real part of the energizing signal of the signal generator and/or an imaginary part of the energizing signal of the signal generator; and dynamically tuning, by the phase compensation network, the phase of the matching impedance based on the determined imaginary part of the power-on signal.

In yet another aspect of the disclosure, the method may further comprise: determining a real part of the energizing signal; and dynamically tuning, by the amplitude compensation network, the amplitude of the matching impedance based on the determined real part of the energizing signal.

According to aspects of the present disclosure, a real-time tuning network configured to dynamically tune an impedance match between a signal generator and an antenna is presented. The real-time tuning network includes: a real-time tuning discriminator configured to determine a real part of the energizing signal and/or an imaginary part of the energizing signal from the signal generator; a phase compensation network configured to dynamically tune a phase of the matching impedance based on the determined imaginary part of the power-on signal; and an amplitude compensation network configured to dynamically tune the amplitude of the matching impedance based on the determined real part of the energizing signal. The imaginary part comprises a capacitive signal, an inductive signal and/or a composite signal. The real part includes the power-on signal current and/or the power-on signal voltage.

In yet another aspect of the present disclosure, a coil antenna may include a primary coil and a secondary coil.

In an aspect of the disclosure, a tuning network may be disposed between the primary coil and the signal generator. The tuning network is configured to tune the quality factor "Q" and/or the operating frequency of the primary coil.

According to aspects of the present disclosure, a system for matching impedance between an antenna and a signal generator includes: an RFID tag configured to transmit a return signal when energized; a signal generator configured to generate an energizing signal for the RFID tag; a coil antenna operatively coupled to the signal generator, the antenna configured to receive a return signal transmitted by the RFID tag; and a first transformer configured to match an impedance between the signal generator and the antenna. The RFID tag is attached to a surgical instrument within the patient.

In another aspect of the present disclosure, the first transformer may include a primary winding and a secondary winding. The system further includes a capacitor disposed in parallel with the primary winding of the first transformer, the capacitor configured to match an impedance between the signal generator and the antenna.

In yet another aspect of the disclosure, the system may further include a matching network disposed between the first transformer and the antenna. The matching network may be configured to match an impedance between the signal generator and the antenna.

In yet another aspect of the disclosure, the matching network may include a fixed matching network and/or a dynamic matching network. The dynamic matching network is configured to dynamically match an impedance between the signal generator and the antenna based on a parameter of the energizing signal.

In yet another aspect of the present disclosure, the parameters of the power-on signal may include power level, frequency, bandwidth, voltage, and/or current.

According to aspects of the disclosure, a second transformer may also be included that is configured to transform an impedance match between the matching network and the antenna. The second transformer may be disposed between the matching network and the antenna.

In an aspect of the disclosure, the second transformer may be a step-up transformer.

In another aspect of the disclosure, the system may further include a dynamic capacitive element configured to tune the impedance. The dynamic capacitive element may be disposed across the primary winding of the second transformer.

In yet another aspect of the present disclosure, the system may further comprise: a sensor configured to sense a signal indicative of a parameter of the energizing signal; a processor; and a memory. The memory includes instructions stored thereon that, when executed, cause the system to: sensing a signal indicative of a parameter of the energizing signal; determining a parameter of the energizing signal based on the sensed signal; and dynamically tuning the dynamic capacitive element based on the determined parameter of the power-on signal.

In yet another aspect of the present disclosure, the second transformer may include a primary winding and a secondary winding. The system further includes a bulk capacitance disposed across the secondary winding of the second transformer.

In yet another aspect of the present disclosure, the second transformer may include a step-down transformer.

According to aspects of the present disclosure, a system for matching impedance between an antenna and a signal generator includes: an RFID tag configured to transmit a return signal when energized; a signal generator configured to generate an energizing signal for the RFID tag; an antenna operatively coupled to the signal generator, the antenna configured to receive a return signal transmitted by the RFID tag; a transformer configured to match an impedance between the signal generator and the antenna; and a dynamic capacitive element configured to tune an impedance, the dynamic capacitive element disposed across the primary winding of the transformer. The RFID tag is attached to a surgical instrument within the patient.

In one aspect of the disclosure, the system may further comprise: a sensor configured to sense a signal indicative of a parameter of the energizing signal; a processor; and a memory. The memory includes instructions stored thereon that, when executed, cause the system to: sensing a signal indicative of a parameter of the energizing signal; determining a parameter of the energizing signal based on the sensed signal; and dynamically tuning the dynamic capacitive element based on the determined parameter of the power-on signal.

In another aspect of the present disclosure, the parameters of the energizing signal may include power level, frequency, bandwidth, voltage, and/or current.

In yet another aspect of the present disclosure, a transformer may include a primary winding and a secondary winding. The system may also include a bulk capacitance disposed across the secondary winding of the transformer.

In yet another aspect of the present disclosure, the transformer may be a step-down transformer.

In yet another aspect of the disclosure, the system may further include a matching network disposed between the transformer and the antenna, and the matching network is configured to match an impedance between the signal generator and the antenna.

In an aspect of the disclosure, the matching network may include a fixed matching network and/or a dynamic matching network. The dynamic matching network is configured to dynamically match an impedance between the signal generator and the antenna based on a parameter of the energizing signal.

According to aspects of the present disclosure, a method for tuning impedance matching between an antenna and a signal generator, the method comprising: sensing, by a sensor, a signal indicative of a parameter of the energizing signal; determining a parameter of the energizing signal based on the sensed signal; and dynamically tuning the dynamic capacitive element based on the determined parameter of the power-on signal. The dynamic capacitive element is disposed across a primary winding of a transformer disposed between the signal generator and the antenna.

Drawings

In the drawings, like reference numerals designate similar elements or acts. The dimensions and relative positioning of elements in the drawings are not necessarily drawn to scale. For example, the shapes of various elements and angles are not drawn to scale, and some of these elements are arbitrarily enlarged or reduced and positioned to improve drawing legibility. Furthermore, the particular shapes of the elements as drawn, are not intended to convey any information regarding the actual shape of the particular elements, and have been solely selected for ease of recognition in the drawings.

Various aspects of the presently disclosed antennas, RF tags, and articles containing them are described below with reference to the drawings.

FIG. 1 is a schematic diagram illustrating a surgical environment showing a medical provider using an interrogation and detection system to detect RFID-tagged items within a patient in accordance with one illustrated aspect;

FIG. 2 is a schematic diagram of an antenna for detecting a surgical instrument being used within a surgical site within a patient;

FIG. 3 is an image of an air core coupled secondary reader antenna coil;

FIG. 4 is a block diagram of the air core coupled secondary reader antenna coil of FIG. 3;

FIGS. 5A-5D are side cross-sectional views of a primary conductor and a secondary conductor of the air core coupled secondary reader antenna coil of FIG. 3;

FIG. 6A is a perspective view of the air core coupled secondary reader antenna coil of FIG. 3 with a non-interleaved secondary conductor configuration;

FIG. 6B is a side view of the air core coupled secondary reader antenna coil of FIG. 6A, wherein the secondary conductor has two turns;

FIG. 6C is a side view of the air core coupled secondary reader antenna coil of FIG. 6A, wherein the secondary conductor has four turns;

FIG. 7A is a perspective view of the air core coupled secondary reader antenna coil of FIG. 3 with a staggered secondary conductor configuration;

FIG. 7B is a top view of the air core coupled secondary reader antenna coil of FIG. 7A with a staggered secondary conductor configuration;

FIGS. 8A and 8B are illustrations of top views of planar coils;

FIG. 9 is an illustration of a top view of an interlaced planar coil;

10A and 10B are illustrations of conductors of the coils of FIGS. 8A and 9 in non-staggered and staggered arrangements;

FIG. 11 shows a graph depicting sensor output voltage versus height for interleaved coils and non-interleaved coils;

FIG. 12 shows a graph depicting sensor output voltage versus height for interleaved secondary coils and non-interleaved secondary coils;

FIG. 13 is a diagram depicting a top view of a coil array for use with the system of FIG. 1;

fig. 14A to 14F are diagrams showing the direction of a magnetic field with respect to a transmission line;

FIG. 15A is a perspective view of the coil array of FIG. 13, wherein each of the coils is energized in opposite directions;

FIG. 15B is a side view of the magnetic field of the coil array of FIG. 13, wherein each of the coils is energized in opposite directions;

FIG. 15C is a perspective view of the magnetic field of the coil array of FIG. 13, wherein each of the coils is energized in opposite directions;

FIG. 16A is a perspective view of the coil array of FIG. 13, wherein each of the coils is energized in the same direction;

FIG. 16B is a side view of the magnetic field of the coil array of FIG. 13, wherein each of the coils is energized in the same direction;

FIG. 16C is a perspective view of the magnetic field of the coil array of FIG. 13, wherein each of the coils is energized in the same direction;

17-19 are perspective views of a four-element coil array for use with the system of FIG. 1, wherein each of the coils is energized in a different direction;

FIG. 20 is a block diagram of a system for dynamically configuring secondary coils and exciting magnetic fields in multiple directions for use with the system of FIG. 1;

FIG. 21 is a block diagram of a four-element coil array for use with the system of FIG. 1;

fig. 22 is a block diagram of a tuning network for use with the coil array of fig. 20;

FIG. 23 is a block diagram of a termination network for use with the coil array of FIG. 20;

FIG. 24A depicts an H-field vector diagram when two pairs of coils are driven in phase;

FIG. 24B depicts an H-field vector diagram when two pairs of coils are driven in opposite phases;

FIG. 25A depicts vector field strength and direction for a "horizontal" current steering configuration in the X-Z plane;

FIG. 25B depicts vector field strength and direction for a "horizontal" current steering configuration in the X-Z plane;

FIG. 26 depicts an isometric view of H field strength in a configuration in which the secondary coil is terminated to eliminate contributions in a vertically oriented configuration;

FIG. 27 depicts a four-element coil array for use with the detection system 10 of FIG. 1;

28A-28C depict two-dimensional optimal Cartesian orientations for each discrete secondary coil configuration of the coil array of FIG. 27;

FIG. 29 is an isometric view of the coil array of FIG. 27;

FIGS. 30-32 are depictions of primary coil current directions, configurable secondary coil current directions, steering network configurations, and optimal RFID tag orientation directions for three possible configurations of the coil array of FIG. 29;

33-36, the system may include a configurable air core coupled secondary coil;

FIG. 37 depicts an exemplary two-element coil array for use with the detection system 10 of FIG. 1;

FIG. 38 depicts a high-level block diagram of a system for dynamically tuning an antenna coil to a generator of the interrogation and detection system of FIG. 1 in real-time;

FIG. 39 is a table depicting the dielectric constants and conductivities of various tissue types;

FIG. 40 is a schematic diagram of a tuning discriminator of the system of FIG. 38;

FIG. 41 is a schematic diagram of a phase compensation network and an amplitude compensation network of the system of FIG. 38;

FIG. 42 is an integrated Q factor sensor for use with the system of FIG. 38;

FIG. 43 is a graph showing the linear output of the "Q" factor sensor of FIG. 41;

FIG. 44 is a flow chart of a method for dynamically tuning the impedance match between an antenna coil and a generator in real time;

FIG. 45 is a diagram of a transformer for matching the output impedance of a signal generator to the antenna of the interrogation and detection system of FIG. 1;

FIG. 46 is a diagram of a loop antenna of the interrogation and detection system of FIG. 1;

FIG. 47 is a schematic diagram of a transformer model including parasitics;

FIG. 48 is a schematic diagram of a transformer model including the reflection of parasitic capacitance by the transformer;

FIG. 49 is a diagram of a transformer matching system for use with the interrogation and detection system of FIG. 1;

FIG. 50 is a diagram of a transformer matching system incorporating dynamic capacitive elements for parallel capacitance for use with the interrogation and detection system of FIG. 1; and is also provided with

Fig. 51 is a diagram of a system for matching the impedance of a generator to an antenna.

Detailed Description

In the following description, certain specific details are set forth in order to provide a thorough understanding of the disclosed aspects. One skilled in the relevant art will recognize, however, that aspects may be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In other instances, well-known structures associated with transmitters, receivers, or transceivers have not been shown or described in detail to avoid unnecessarily obscuring the description of the various aspects.

Reference throughout this specification to "one aspect" or "an aspect" means that a particular feature, structure, or characteristic described in connection with the aspect is included in at least one aspect. Thus, the appearances of the phrase "in one aspect" or "in an aspect" in various places throughout this specification are not necessarily all referring to the same aspect. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more aspects.

Fig. 1 depicts a surgical environment "E" in which a medical provider 12 operates an interrogation and detection system 10 for detecting Radio Frequency Identification (RFID) tags to determine whether an article, appliance or item 100a is present in a patient 18. The interrogation and detection system 10 may include a signal generator 200 and an antenna 300 coupled to the signal generator 200 by one or more communication paths (e.g., coaxial cable 250). In one aspect of the interrogation and detection system 10, the antenna 300 may take the form of a hand-held wand 300 a.

The article 100a may take various forms, such as instruments, accessories, and/or disposable articles useful in performing surgical procedures. For example, the article 100a may take the form of a scalpel, scissors, forceps, hemostat, and/or a clamp. Also, for example, the article 100a may take the form of a surgical sponge, gauze, and/or pad. The article 100a is marked, carried, attached, or otherwise coupled to the RFID tag 100. Aspects of the interrogation and detection system 10 disclosed herein are particularly well suited for operation with one or more RFID tags 100 that are not accurately tuned to a selected or selected resonant frequency. Thus, the RFID tag 100 does not require high manufacturing tolerances or expensive materials, and thus manufacturing costs may be low.

In use, the medical provider 12 may position the wand 300a in proximity to the patient 18 in order to detect one or more RFID tags 100 and thus the presence or absence of the article 100 a. In some aspects, the medical provider 12 may move the wand 300a along and/or across the body of the patient 18. For a detailed description of an exemplary interrogation and detection system, reference may be made to U.S. patent application publication 2004/0250819 entitled "apparatus and method for detecting items using a tag and broadband detection device (Apparatus and Method For Detecting Objects Using Tags And Wideband Detection Device)" filed on 3/29 of 2004, commonly owned by Blair et al, the entire contents of which are hereby incorporated by reference.

Referring now to fig. 2, an interrogation and detection system 10 for detecting a surgical instrument (e.g., article 100 a) within a patient includes a signal generator 200 to provide an energizing signal for one or more RFID tags 100 (fig. 1) attached to the article 100a (fig. 1). Each RFID tag 100 is configured to transmit a return signal when energized so that the antenna 300 can detect the return signal and confirm the presence of the item 100a within the patient 18. Antenna 300 is operatively coupled to signal generator 200 via communication cable 250. Wherein the communication cable 250 may have a variable length to provide a clinician operating the antenna 300 with a greater range of motion. In aspects, the antenna may comprise a wireless handheld unit, such as a battery powered unit.

In one aspect of interrogation and detection system 10, antenna 300 is an antenna 300 configured to be swung over surgical site 15, such as over the body of patient 18. For example, the antenna 300 may be maintained at a height of about four inches or about five inches above the body of the patient 18 in an attempt to detect the RFID tag so that a user may detect the presence of the object 100a within the patient 18.

The term "read range" as used in this disclosure includes the distance from the antenna 300 (e.g., reader coil) of the interrogation and detection system 10 to the geometric center of the RFID tag 100 (fig. 1). The term "orientation" as used in this disclosure includes the angle of incidence between the primary coil plane of the antenna 300 and the primary coil plane of the tag antenna or coil. Generally, the primary reader coil plane and the primary tag coil plane are parallel for optimal orientation. In the case where the most challenging orientation is that the primary reader coil plane and the primary tag coil plane are spatially orthogonal, a non-optimal orientation means that the primary reader coil plane and the primary tag coil plane are not parallel.

For handheld accessories, physical dimensions are important. The accessory needs to be constructed using shape factors that are advantageous for use in the intended application. For typical RFID applications, where communication between the interrogation and detection system 10 and the RFID tag 100 (fig. 1) is achieved via a coupled magnetic field, the read range and sensitivity to coil orientation are direct functions of coil area and orientation. In other words, a larger coil will perform better in terms of the range of communication possibilities and the relative orientation between the reader antenna 300 and the RFID tag coil. In the target application (detection and identification of the tagged surgical item), the acceptable physical dimensions of both the reader coil and the tag coil are smaller than those that would provide optimal read range performance and reduced sensitivity to orientation. In the case of RFID tag 100 (FIG. 1), the acceptable physical size of the tag component being tracked may be much smaller than ideal. To achieve an acceptable user experience in both performance and physical form factor, new approaches to maximize performance must be employed.

One of the limiting factors in the performance of interrogation and detection system 10 in the RFID arts relates to the optimal load conditions that the antenna coil may present to signal generator 200 (fig. 1). Mismatch or variation of the interface between the signal generator 200 (fig. 1) and the antenna 300 results in non-optimal transmission of RF power from the signal generator 200 to the antenna 300. These mismatches may cause RF energy to be reflected back into signal generator 200 rather than propagating into antenna 300 and then from antenna 300 into the wireless communication channel with RFID tag 100 (fig. 1). The conventional generator 200 of an RFID system is typically designed to be connected to a fixed static load having mainly only a real impedance component (z=re { }). However, tissue salinity will affect the quality factor "Q" and the impedance of the antenna 300 (e.g., reader coil). The quality factor "Q" of an antenna directly affects the bandwidth of the antenna and the gain of the antenna.

Typically, the generator 200 of the RFID system is intended to be connected to a 50 ohm characteristic impedance antenna. This convention allows a developer to consider the development of a reader solution from a coil or antenna solution. A typical antenna coil presents a mainly reactive (inductive, z=im { }) load impedance at the coil terminals. The matching network is used to connect the primary real generator (e.g., reader) output impedance to the primary reactive coil input impedance. This is typically done in two steps, where one aspect of the matching network is used to adapt to the real part of the target load and the other aspect of the matching network counteracts the reactive part of the coil load. The end result is an optimal transmission of RF energy to and from the generator and antenna 300 elements. In practice, the acceptable range of the complex portion of the load impedance in the antenna coil is limited due to the topology and component values required to construct an effective matching network. Empirically, for an actual matching network, the nominal value of the coil inductance may be between about 0.5uH and about 2.5 uH. Coils with reactive impedances outside this range can be difficult to match using conventional methods and are susceptible to component tolerances and drift.

The inductive impedance component of a coil is primarily a function of two main characteristics. Coil area and number of turns in the coil. For a given coil current, the magnitude of the magnetic field vector, and thus the ability to energize and communicate with the passive tag, is a direct function of both the coil area and the number of turns in the coil. In other words, as the coil area and/or the number of turns in the coil increases, the read range increases. Unfortunately, for coils intended for use in remote wireless magnetic-based communications, the inductance due to the coil area quickly eliminates the option of increasing the turns of the coil due to the increase in the inductive component of the impedance. The inductance is based on the square of the number of turns. Finally, the ability to maximize the performance of the antenna coil directly by physical characteristics is limited by the amount of inductive load the coil presents to the matching network. One approach that allows for increasing the coil inductance while maintaining an actual matching load impedance is of interest. The disclosed techniques may enable increased read range and/or sensitivity to antenna 300/RFID tag 100 orientation using non-traditional methods that enable increased coil area or increased number of coil turns.

In addition to the limitations associated with the allowable range of reactive impedance described above, the ability to tune the antenna to operate at resonance is also limited. Resonance in this context is the case where the inductor coils are loaded with equal and opposite capacitive loads (series or parallel). The resulting circuit is ideally able to sustain oscillations at the resonant frequency indefinitely. In accordance with the present disclosure, resonant circuit technology is used to improve coil antenna performance by providing a dimension of performance gain, commonly referred to as a quality factor (Q). The quality factor "Q" of an antenna is a way of describing the ratio of the reactive part of the impedance to the real part of the impedance (Im { }/Re { }). The reactive part of the impedance is theoretically lossless and the real part of the impedance is theoretically completely lossy. In other words, the energy imparted to the resonant coil antenna oscillates with an efficiency described by the ratio of the lossless impedance to the lossy impedance. The quality factor increases when the inductive and capacitive components are tuned to be equal to each other at the target operating frequency, and the energy ratio in the lossless component of the impedance increases when compared to the energy dissipated in the lossy portion of the impedance. Maximizing the quality factor "Q" is essentially the way free "gain" is achieved in the wireless communication channel. There are limitations in the allowable magnitude of the quality factor in conventional communication channels, but the limitations we specifically address with this solution relate to the ability to match the generator output channel to the antenna 300a resonant coil input.

For an ideal parallel resonant circuit, the magnitude of the impedance approaches infinity (open circuit) and the voltage across the coil element is maximized. For an ideal series resonant circuit, the impedance approaches zero "0" (short circuit) and the current through the coil element is maximized. Reader technology is not designed to drive open or short circuit loads, so we are forced to detune (tune away from resonance) the resonance properties in order to match the reader to the coil from a practical perspective. This results in a reduction of the free gain that can be achieved via the quality factor "Q". Furthermore, a change in the dielectric properties of the space around the antenna coil will shift the resonance frequency of the coil or degrade the coil performance due to an increase in the real part of the coil impedance.

Referring to fig. 3 and 4, an air core coupled secondary reader antenna coil 300 is shown in accordance with the present disclosure. The air core coupled secondary reader antenna coil 300 generally includes a transformer 310, a primary matching network 410, and a secondary matching network 420. As used herein, the term "air core" may include any non-magnetic insulating material, such as a polymer and/or air.

The transformer 310 generally includes a primary coil 302, a secondary coil 304, and a core 306 made of a non-magnetic insulating material (e.g., an air core and/or a polymer). Air has a dielectric constant of "1" and a loss tangent of about zero "0". It is contemplated that other materials (e.g., polyimide, polytetrafluoroethylene "PTFE," etc.) having a sufficiently low loss tangent at and/or near the operating frequency of the antenna 300 may be used for the core. The primary coil 302 and the secondary coil 304 may be mounted to an insulating material. The first matching network 410 is configured to match the input impedance of the primary coil 302 to the output impedance of the generator 200 (fig. 1). The second matching network 420 is configured to match the input impedance of the secondary coil 304 to the output impedance of the primary coil 302 in conjunction with the load presented by the patient or the ambient load.

Each of the primary coil 302 and the secondary coil 304 includes one or more turns. In aspects, the primary coil 302 and the secondary coil 304 may have the same or different number of turns from each other. For example, for a "turns ratio" of 1:1, the primary coil 302 may have one turn and the secondary coil 304 may have two turns. The "turns ratio" is the ratio of the primary winding and the secondary winding of the transformer relative to each other. The primary coil 302 and/or the secondary coil 304 may be, but are not limited to, any suitable shape, such as spiral, square, oval, and/or circular. In aspects, the primary coil 302 and/or the secondary coil 304 may have any suitable cross-section. For example, the cross-section of the primary coil 302 and/or the secondary coil 304 may be, but is not limited to, coaxial, planar, "C" shaped, and/or tubular. The primary coil 302 and the secondary coil 304 may be of any suitable width.

The air core 306 is configured to provide a path for a magnetic field to flow around to induce a voltage between the primary coil 302 and the secondary coil 304. By adding the air core 306 coupled secondary coil 304 to a conventional coil antenna, the challenges associated with the two points discussed above are reduced. It is possible to incorporate several turns (two or more turns) on the secondary coil 304 while maintaining a reasonably matched impedance as presented at the input terminal of the primary coil 302. This is due to the configuration of the relatively weakly coupled transformer 310 having a "turns ratio" of 1:n, where "N" is the number of turns on the secondary winding 304. The transformer 310 acts as an impedance transformer, essentially at 1/N ² The ratio of (2) gradually decreases the load (reactance). The end result is an inductance measured at the primary coil 302 terminals of less than N ² Allowing the secondary winding 304 inductance value to exceed about 2.5uH while maintaining a reasonably matched primary winding 302 reactance component from a practical point of view. Additionally, the secondary coil 304May be tuned to a resonance closer to the target operating frequency. When the load reflects through the air-core coupled transformer 310, it is reduced (parallel resonance) and the parasitic impedance inherent to the circuit shifts the resonance experienced by the primary coil 302, further allowing for an actual tuning situation.

The primary matching network 410 is configured to match the impedance between the primary coil 302 and the signal generator 200 to minimize mismatch that may result in RF energy being reflected back into the signal generator 200 rather than propagating into the primary coil 302. The secondary matching network 420 is configured to match the impedance between the secondary coil 304 and the primary coil 302 and between the secondary coil 304 and the tag coil (not shown) to minimize mismatch that may result in RF energy being reflected back into the signal generator 200 rather than propagating into the tag coil.

Referring to fig. 5A-5D, side cross-sectional views of the primary and secondary conductors of the air core coupled secondary reader antenna coil of fig. 3 are shown. Fig. 5A shows a transformer 310 having a "turns ratio" of n=2 in a non-interleaved configuration. The primary coil 302 includes a "C" shaped conductor 302a. The secondary coil 304 includes two planar conductors 304a. An air core 306 is disposed between the primary coil 302 and the secondary coil 304.

Fig. 5B shows a transformer 310 having a "turns ratio" of n=3 in a non-interleaved configuration. The primary coil 302 includes a "C" shaped conductor 302a. The secondary coil 304 includes three planar conductors 304a. An air core 306 is disposed between the primary coil 302 and the secondary coil 304.

Fig. 5C shows a transformer 310 having a "turns ratio" of n=4 in a non-interleaved configuration. The primary coil 302 includes a "C" shaped conductor 302a. The secondary coil 304 includes four planar conductors 304a. An air core 306 is disposed between the primary coil 302 and the secondary coil 304.

Fig. 5D shows a transformer 310 having a "turns ratio" of n=3 in an interleaved configuration. The staggered configuration reduces parasitic capacitance that can lead to low self-resonant frequencies. The primary coil 302 includes a "C" shaped conductor 302a. The secondary coil 304 includes three planar conductors 304a. An air core 306 is disposed between the primary coil 302 and the secondary coil 304. It is contemplated that any suitable number of turns may be used for transformer 310.

Referring to fig. 6A, a perspective view of the air core coupled secondary reader antenna coil 300 of fig. 3 with a non-interleaved secondary conductor configuration is shown. The primary coil 302 is shown with one turn and the secondary coil 304 is shown with two turns. Two terminals of the secondary coil 304 (e.g., "secondary coil+" 304b and "secondary coil-" 304C) may be configured for electrical communication with a second matching network 420 (fig. 2). Fig. 6B shows a side view of the air core coupled secondary reader antenna coil 300 of fig. 6A, where the secondary coil 304 has two turns and the primary coil 302 has one turn ("turns ratio" is n=2). Fig. 6C shows a side view of the air core coupled secondary reader antenna coil 300 of fig. 6A, where the secondary conductor has four turns ("turns ratio" is n=4).

Fig. 7A and 7B are views of the air core coupled secondary reader antenna coil 300 of fig. 3 with staggered secondary coil conductors 304B configured to reduce low self-resonant frequencies due to parasitic capacitance.

Referring to fig. 8A and 8B, a top view of a non-interleaved coil 800 according to the present disclosure is shown that may be used as the primary coil 302 and/or the secondary coil 304 of the reader antenna 300 (fig. 3). The first turn of conductors 802 of the non-interleaved coil 800 is located directly above the second turn of conductors 804 of the non-interleaved coil 800 with a core 806 (e.g., air or another dielectric material suitable as an insulator) disposed between the conductors of the first turn of conductors 802 and the second turn of conductors 804.

Large multi-turn magnetic field coil antennas have inherently low self-resonant frequencies due to parasitic capacitance. When designing a near field rfid reader antenna, it is desirable to use a coil design that is primarily inductive in order to ensure that current flowing through the coil is conducted through the entire coil. Doing so may maximize the field strength for a given coil current. As the parasitic capacitance increases, the current in the coil begins to return to the source through an undesired path, thereby reducing the effectiveness of the coil. Increasing the challenge is to design a competing goal of high coil factor "Q" (the ratio of reactive impedance to real impedance). A high-factor "Q" coil is one in which the ohmic real part of the resistance is minimized and the coil inductance is maximized. In various aspects, increasing the quality factor "Q" may be performed by increasing the conductor thickness (to compensate for the skin depth) and/or the conductor surface area (or width in the case of flat conductors). However, the parasitic capacitance between two conductors is a function of the conductor area and the distance between the conductors. Thus, increasing the width of the conductor results in a corresponding decrease in the self-resonant frequency. For an inductive coil, as the distance between coils increases, the spacing between adjacent coil windings increases to a point where the gain decreases as the coupling efficiency between individual coils decreases.

Referring to fig. 9, a top view of a non-interlaced coil 900 according to the present disclosure is shown that may be used as the primary coil 302 and/or the secondary coil 304 of the reader antenna 300 (fig. 3). As described in detail below, by interleaving the conductors of the interleaved coil 900, parasitic capacitance between the traces of the turns of the interleaved coil 900 may be reduced.

The first turn conductors 902 of the interleaved coil 900 are positioned in parallel relationship and offset to the second turn conductors 904 of the interleaved coil 900 and are in vertical and/or horizontal relationship to each other in the X, Y, Z coordinate system. There is a core 906 between the first turn of conductor 902 and the second turn of conductor 904. The core 906 may be air or other dielectric material suitable as an insulator. Although two turns are shown, any suitable number of turns (e.g., conductive layers) may be used by offsetting additional turns in vertical and/or horizontal relation to the previous turn of the conductor. For example, the interleaved coil 900 may include three turns, with a third turn being offset from the second turn conductor 904 in a manner similar to the second turn conductor 904 being offset from the first turn conductor 902.

The first turn of conductor 902 includes an inner edge 902a and an outer edge 902b. The second turn of conductor 904 includes an inner edge 904a and an outer edge 904b. The first turn conductors 902 may overlap with the second turn conductors 904 of the interleaved coil 900, wherein a majority (e.g., about > 50%) of the second turn conductors 904 do not overlap with the first turn conductors 902.

The first turn of conductors 902 and/or the second turn of conductors 904 may be, but are not limited to, any suitable shape, such as spiral, square, oval, and/or circular. In aspects, the first turn of conductors 902 and/or the second turn of conductors 904 may have any suitable cross-section. For example, the cross-section of the first turn of conductors 902 and/or the second turn of conductors 904 may be, but is not limited to, coaxial, planar, "C" shaped, and/or tubular. The first turn of conductors 902 and/or the second turn of conductors 904 may be any suitable width (e.g., copper approximately 1cm wide). It is contemplated that the first turn of conductor 902 and/or the second turn of conductor 904 may be monolithic, or that each turn of the coil may be a single piece that is electrically connected to the next turn.

The staggered coil 900 configuration combines an optimized conductor width and an optimized coil-to-coil configuration with a staggered individual coil element design. In various aspects, the interlaced coil 900 configuration may be packaged into a thin mattress-like coil array intended for use as a scanning accessory in the real-time detection of marked surgical items in an operating room environment. The staggered coil 900 configuration has advantages over other implementations (such as conventional planar coils) by preserving the coil area, which is a major characteristic of coil performance in terms of field strength. Furthermore, the staggered configuration has the added advantage of improving radiation transmission when compared to conventional coaxial coil designs due to the reduced number of x-y planar conductive layers that coexist in the multi-turn coil. The interleaved coil 900 configuration is effective in applications where a single coil is directly driven, and applications where an air core is utilized to couple a secondary coil. For example, in the interleaved coil 900 configuration, a reduction in parasitic capacitance and a subsequent increase in self-resonant frequency may be highly beneficial, where it may be advantageous to maximize coil inductance or improve coil efficiency.

Referring to fig. 10A and 10B, illustrations of conductors of the coils of fig. 8A and 9 in non-staggered and staggered arrangements are shown. The capacitance of two parallel coupled conductors (such as a non-interleaved configuration) is (E x a)/d, where "E" is the dielectric constant, where "d" is the distance between the conductors, and "a" is the width of the conductors. By interleaving the conductors, the capacitance is approximately (E x a x sin θ)/d, where θ is the angle between the bottom surface 902g of the first turn of conductor 902 and the edge of the second turn of conductor 904 nearest the first turn of conductor 902.

Referring to fig. 11, a graph depicting sensor output voltage versus height for a single drive interleaved coil and a single drive non-interleaved coil is shown. The graph also depicts exemplary relative field strength gains associated with interleaved and non-interleaved configurations, both with a single drive coil.

Referring to fig. 12, a graph depicting sensor output voltage versus height for interleaved secondary coils and non-interleaved secondary coils is shown. The graph also depicts an example of the relative field strength gain associated with an interleaved configuration and a non-interleaved configuration, both using a secondary coupling coil.

Referring to fig. 13, a top view of a coil array 1300 according to the present disclosure is shown that may be used as an antenna 300 (fig. 3) of the detection system 10 (fig. 1). Generally, the coil array includes two or more coils, for example, a first coil 1302 and a second coil 1304. The individual coils 1302, 1304 in the array are configured to be independently energizable so that the magnetic flux "B" of each of the coils can be independently directed. It is contemplated that each of the individual coils 1302, 1304 may include any number of turns. For example, each of the individual coils 1302, 1304 may each include two turns.

Referring to fig. 14A to 14F, diagrams showing the direction of a magnetic field with respect to the current of a transmission line are shown. The magnetic field strength "H" can be visualized by using the "right hand rule" (fig. 14A and 14B). The vector direction of the magnetic field strength "H" curls around the line current "I" to form a closed loop (fig. 14A). The magnetic flux density "B" is a measure of the total magnetic field across a given region and can be described by the equation b=uh. The magnetic flux density "B" generated by the line current "I" is directional in nature. In the case where the line current is an element of a closed loop antenna of arbitrary geometry, the magnetic flux density "B" at a given point in space is equal to the superimposed field from each individual line current "I" element (fig. 14C-14F). Thus, for a fixed position coil or coil array 1300 (fig. 13) with a static configuration for the current direction, the vector direction of the magnetic field strength "H" around the coil or array is fixed.

For a near field RFID communication system, a reader antenna coil (e.g., antenna 300 or coil array 1300 of fig. 1) is linked with a tag antenna coil of RFID tag 100 (fig. 1) via a magnetic flux density "B" derived from current flowing through antenna 300 (e.g., reader coil) (fig. 1). The tag coil captures this flux and uses the flux to energize the local tag electronics and transmit information back to the antenna 300 (fig. 1). The amount of magnetic flux density "B" captured by the tag determines the amount of energy available for the tag to perform its intended function. In an optimal orientation in which the tag coil is parallel and coaxial with the antenna 300 (fig. 1), the amount of captured magnetic flux density "B" is optimized. As the tag coil moves away from this optimal orientation, the amount of captured magnetic flux "B" decreases. Once the amount of magnetic flux density "B" captured by the tag is reduced to a point where insufficient energy is captured to achieve the activation energy required by the tag electronics, the reader-tag communication channel is lost.

For the case where the tag can be oriented in any direction on a fixed reader coil/reader coil array, each point in space above the coil/array will have a (orthogonal) magnetic field "H" vector that is optimal for a particular RFID tag 100 (fig. 1) orientation and at the same time is non-existent for another tag orientation at the same location. This means that the RFID tag 100 (fig. 1) may be discoverable and provide information if oriented in one direction, and the RFID tag 100 (fig. 1) may not be discoverable and provide information in a different orientation at the same location. For a handheld reader coil (e.g., antenna 300 of fig. 1), this problem can be overcome by changing the reader coil orientation to manually manipulate the angle of incidence from the reader coil. For a fixed array (e.g., coil array 1300 of fig. 1) located, for example, below the patient, the antenna orientation is fixed. This solution solves this problem by changing the direction of the magnetic field "H" vector via current steering in the coil array 1300. By scanning various current/coil element configurations, the magnetic field vector direction can be changed so that it can energize and communicate with the tag in other non-optimal orientations.

Referring to fig. 15A-15C and 16A-16C, a coil array 1300 and magnetic fields 1502, 1602 associated with the coil array under various excitations are shown. Based on the superposition principle, the magnetic field direction at a given location in space above the coil array 1300 will be the vector sum of the contributions from each of the current elements in the array. By controlling the direction of the current "I" (generated by the signal generator 200), the magnitude and direction of the magnetic flux "B" can be manipulated. The coils of the coil array 1300 may be driven independently, in series, or in parallel to achieve desired magnetic field characteristics. The coil array 1300 may be comprised of as few as two coils or as many as desired to provide the magnetic flux "B" direction and amplitude resolution required for the application.

Fig. 15A depicts a coil array 1300 in which the current flow "I" of the first coil 1302 is in a counterclockwise direction and the current flow "I" of the second coil 1304 is also in a clockwise direction. Fig. 15B depicts a side view of the magnetic flux 1502 intensity of the coil array 1300. Fig. 15C is a perspective view of the intensity of magnetic flux 1502 of coil array 1300. Here, the magnetic flux 1502 emanates from the first coil 1302 in a negative direction relative to the Y-axis, and the magnetic flux 1502 emanates from the second coil 1304 in a positive direction relative to the Y-axis.

Fig. 16A depicts a coil array 1300 in which the current flow "I" of the first coil 1302 is in a counterclockwise direction and the current flow "I" of the second coil 1304 is in a clockwise direction. Fig. 16B depicts the magnetic flux 1602 strength of the coil array 1300. Fig. 16C is a perspective view of the magnetic flux 1602 strength of the coil array 1300. Here, the magnetic flux 1602 emanates from the first coil 1302 in a negative direction relative to the "Y" axis, and the magnetic flux 1602 also emanates from the second coil 1304 in a negative direction relative to the Y axis.

Referring to fig. 17-19, there is shown a perspective view of a four-element coil array 1700 for use with the system of fig. 1, wherein each of the coils is energized in a different direction. The four-element coil array 1700 includes a first coil 1710 and a second coil 1720. The first pair of coils includes a first coil 1702 and a second coil 1704. The second pair of coils includes a third coil 1706 and a fourth coil 1708. Each of the coils 1702-1708 is configured to be independently steerable such that the current flow for any of the individual coils may be in a clockwise or counter-clockwise direction, thereby enabling manipulation of the magnitude and direction of the magnetic flux "B".

For example, in fig. 17, the current flow "I" in the first coil 1702 and the third coil 1706 is in a counterclockwise direction. The current flow "I" in the second coil 1704 and fourth coil 1708 is in a clockwise direction. With superposition, the direction of the magnetic flux "B" of the first pair of coils 1710 and the second pair of coils 1720 is in a positive direction with respect to the "X" axis.

For example, in fig. 18, the current flow "I" in the first coil 1702 and the second coil 1704 is in a clockwise direction. The current flow "I" in the third coil 1706 and fourth coil 1708 is in a counterclockwise direction. With superposition, the direction of the magnetic flux "B" of the first pair of coils 1710 and the second pair of coils 1720 is in a positive direction with respect to the "Z" axis.

For example, in fig. 19, the current flow "I" of all of the coils 1702 to 1708 is in a counterclockwise direction. The resulting direction of the magnetic flux "B" of the first pair of coils 1710 and the second pair of coils 1720 is in a positive direction with respect to the "Y" axis.

It is contemplated that the current "I" magnitude of each of the individual coils 1702-1708 may include positive or negative values, and that the current "I" direction of each of the individual coils may vary in a clockwise or counterclockwise manner to enable the magnetic flux "B" direction and/or magnitude to be directed to suit the application.

Referring to fig. 20, a block diagram of a system 2000 for dynamically configuring a secondary air core coupling coil and exciting an excitation field in multiple directions is shown that may be used as an antenna 300 (fig. 3) of the detection system 10 (fig. 1). The disclosed system provides both sufficient magnetic field strength to communicate with RFID tags within an acceptable read range and enables communication with RFID tags having arbitrary, non-optimal orientations relative to antenna 300 (fig. 3). The system 2000 generally includes: a multiplexer 2020; phase separator 2030 with phase control; a Low Voltage (LV) steering network 2040 (fig. 33) that enables current steering by a primary coil for a secondary coil configuration that is most suitable for exciting the RFID tag 100 (fig. 1) in a given orientation; a coil tuning network 2200 configured to tune the quality factor "Q" and/or operating frequency of the primary coils 1702a, 1704a, 1706a, 1708a of the coil array 1700 (fig. 21); and a coil termination network 2300 configured to enable and/or disable one or more secondary coils 1702b, 1704b, 1706b, 1708b of the coil array 1700. The term "operating frequency" may include the frequency band in which the component (e.g., antenna 300) is designed to operate.

For applications that provide both detection and identification of tagged surgical items, it may be desirable to implement a larger static antenna array 1300 (fig. 1) that is embedded in or integrated with a surgical table mattress. The static antenna array 1300 (fig. 1) has the distinct advantage of reducing the variability of the scanning cycles frequently associated with hand-held antennas. This variability is a result of differences in operator scanning techniques. The static antenna array 1300 is also attractive because it provides the option of increasing the size of the scanning accessory when compared to a handheld antenna. The increased size has the benefit of reducing the amount of time required for scanning and taking advantage of inherent performance advantages from a read range perspective associated with increased coil area.

For typical RFID applications, where communication between antenna 300 (fig. 3) and RFID tag 100 (fig. 1) is achieved via a coupling magnetic field, the read range and sensitivity to antenna 300 orientation are direct functions of coil area and orientation. Thus, a larger coil will generally perform better than a smaller coil in terms of the range of communication possibilities and the relative orientation between antenna 300 (fig. 3) and the RFID tag coil (not shown). For example, when performing the detection and identification of the tagged surgical item, the acceptable physical dimensions of both the antenna 300 (fig. 3) and the RFID tag coil are smaller than the physical dimensions that would provide optimal read range performance and reduced sensitivity to orientation. In the case of RFID tag 100 (FIG. 1), the acceptable physical size of the tracked tag component is much smaller than ideal.

As mentioned previously, the present disclosure combines the advantages of an air core coupled secondary configuration (fig. 3) with the benefits of field direction control via current steering and control in a multi-coil element array (fig. 18). Although an array of four elements is described below for simplicity, the array dimension (N x M) is not limited and can be extended to provide the coverage needed in the target form factor. Additionally, the array elements may take a fractal structure, where an array of smaller coil elements and air core coupled secondary coils may act as a single primary coil in a higher level array.

Referring to fig. 21, a block diagram of a four-element coil array 1700 for use with the detection system 10 of fig. 1 is shown. For this example, the coil array 1700 includes four (2 x 2) primary coils 1702a, 1704a, 1706a, 1708a and five discrete air core coupled secondary coils 1702b, 1704b, 1706b, 1708b. Each primary coil 1702a, 1704a, 1706a, 1708a may be operably connected to an associated coil tuning network 2200. Each secondary coil 1702b, 1704b, 1706b, 1708b may be operably connected to an associated configurable coil termination network 2300 and a High Voltage (HV) steering network 2040b.

Fig. 22 is a block diagram of a coil tuning network 2200 for use with the coil array 1700 of fig. 20. Coil tuning network 2200 generally includes a real match detection network 2210, an imaginary match detection network 2220, a power detection network 2230, a dynamic match network 2250, and a controller 2240. The RF signal may be represented by a complex number and generally includes a real part (e.g., in-phase) and an imaginary part (e.g., quadrature). The configurable termination networks 2200, 2300 may be controlled by a controller 2240. The real-part match detection network 2210 receives the input RF signal generated by the generator 200 (fig. 1) and is configured to detect a real part of the RF input signal (e.g., a signal indicative of the real part of the RF signal). The imaginary part match detection network 2220 is configured to detect an imaginary part of an RF input signal (e.g., a signal indicative of the imaginary part of the RF signal). In aspects, the real match detection network 2210 and/or the imaginary match detection network 2220 may be implemented using I/Q modulators. The power detection network 2230 is configured to detect RF power levels from the RF signals and provide the power levels to the controller 2240 for further processing. The power detection network 2230 may include, but is not limited to, for example, an RF detector diode. In aspects, the power detection network 2230 may be configured to detect voltage and/or current using a voltage and/or current sensor (e.g., a coil current detector) instead of or in addition to detecting RF power levels. In aspects, the power detection network 2230 may be located at an output of the dynamic matching network 2250, where it may be configured to determine a field strength generated by the coil. For example, the power detection network 2230 may be a coil current detector located at the output of the dynamic matching network 2250. In aspects, the power detection network 2230 may determine RF power by calculating a point-by-point product based on the acquired voltage and/or current. In aspects, the power detection network 2230 may determine RF power by post-processing the reader current signal and the reader voltage signal from fig. 40 through power factor correction using a combination of capacitive and inductive signals.

The controller 2240 is configured to receive signals from the real part match detection network 2210, the imaginary part match detection network 2220, the power detection network 2230, and control the dynamic match network 2250 based on the detected signals. The controller 2240 includes a processor and a memory, and is configured to execute instructions stored on the memory.

The dynamic matching network 2250 is configured to tune the quality factor "Q" and/or the resonant frequency of the primary coils 1702a, 1704a, 1706a, 1708a of the coil array 1700 (fig. 21). Dynamic matching network 2250 may include, but is not limited to, for example, a capacitor, an inductor, a varactor, a PIN diode, and/or a resistor. The dynamic matching network 2250 may include a range selection input 2254 configured to receive a range selection signal from the controller 2240 and to output an RF control signal based on the received range selection signal, the RF control signal changing the resonant frequency range of the one or more primary coils 1702a, 1704a, 1706a, 1708a by presenting a dynamic load to the one or more primary coils 1702a, 1704a, 1706a, 1708 a. The dynamic matching network 2250 may include a tuning control selection input 2252 configured to receive a tuning selection signal from the controller 2240 and to output an RF control signal based on the received tuning selection signal, the RF control signal changing the resonant frequency of the one or more primary coils 1702a, 1704a, 1706a, 1708a by presenting a dynamic load to the one or more primary coils 1702a, 1704a, 1706a, 1708 a. In aspects, the primary coils 1702a, 1704a, 1706a, 1708a may be driven independently or in a combination of series and/or parallel elements as desired to present an optimized load for a given configuration to the detection system 10 and the coil tuning network 2200.

Fig. 23 is a block diagram of a coil termination network 2300 for use with the coil array 1700 of fig. 20. The coil termination network 2300 generally includes: an impedance sensor 2310 configured to sense the impedance of one or more secondary coils 1702b, 1704b, 1706b, 1708b at a target operating frequency; a step-down transformer 2310 configured to step down the voltage of one or more secondary coils 1702b, 1704b, 1706b, 1708 b; a dynamic capacitance bank 2330 configured to provide switchable matching to one or more secondary coils 1702b, 1704b, 1706b, 1708b via a step-down transformer 2320; and a controller 2240. It is contemplated that the same and/or different controller may be used as the controller for coil tuning network 2200.

The coil termination network 2300 may be configured to enable or disable the discrete secondary coils 1702b, 1704b, 1706b, 1708b of the coil array 1700. The coil termination network 2300 may eliminate a resonant network (open circuit), it may short circuit the coil elements, or it may terminate the coil based on a load condition (by switching in a capacitor of a different value) that shifts the resonance characteristics to a region in the frequency domain, which makes it appear to be disconnected from a magnetic field perspective and/or from the load it presents to the detection system 10 (fig. 1) and the coil tuning network 2200.

Fig. 24A and 24B depict the relative magnetic field "H" strength and vector direction of the four-element array 1700. Fig. 24A depicts a vector diagram of the magnetic field "H" when two pairs of coils are driven in phase. Fig. 24B depicts a vector diagram of the magnetic field "H" when two pairs of coils are driven in opposite phases. FIG. 25A depicts vector field strength and direction for a "horizontal" current steering configuration in the X-Z plane. FIG. 25B depicts the vector field strength and direction for a "horizontal" current steering configuration in the X-Z plane. Fig. 26 depicts an isometric view of the strength of magnetic field "H" in a configuration in which the secondary coil is terminated to eliminate contributions in a vertically oriented configuration.

Referring to fig. 27, a diagram of a four-element coil array 2700 for use with the detection system 10 of fig. 1 is shown. For this example, the coil array includes four (2 x 2) primary coils 1702a, 1704a, 1706a, 1708a and five discrete air core coupled secondary coils 2702, 2704a, 2704b, 2706a, 2706b. Each primary coil 1702a, 1704a, 1706a, 1708a may be operably connected to an associated coil tuning network 2200. Each secondary coil 2702, 2704a, 2704b, 2706a, 2706b can be operably connected to an associated configurable coil termination network 2300. The configurable coil termination networks 2200, 2300 may be controlled by a controller 2030. The controller 2030 may perform a scan cycle that may include a series of different configurations that are intended to energize and communicate with the RFID tag 100 in any orientation. The two-dimensional optimal cartesian orientation of each discrete secondary coil configuration is shown in fig. 28A-28C.

Fig. 29 depicts an isometric view of coil array 2700 of fig. 27. Referring to fig. 30-32, primary coil currents i for three possible configurations of coil array 2700 of fig. 27 are shown _pri Direction, configurable secondary coil current i _sec Direction, guidance network 2040 configuration, and optimal RFID tag 100 orientation direction. For example, in FIG. 30, primary coil currents i of primary coils 1702a and 1704a (FIG. 28B) _pri And a secondary coil current i of secondary coil 2706a _sec The primary coil current i flowing in the counterclockwise direction while the primary coils 1706a and 1708a _pri And a secondary coil current i of secondary coil 2706b _sec Flows in a counterclockwise direction, thereby guiding the magnetic flux "B".

Referring to fig. 33-36, the system 3300 may include a configurable air core coupled secondary coil 3306. In various aspects, a single larger, more complex secondary coupling coil or array thereof may be used. The coil configuration may be determined via a specialized steering network 2040, 2040b that directs coupling currents through coil array elements (e.g., secondary coil portions 3306a, 3306b, 3306c, 3306 d) that produce a field vector direction that is capable of exciting the RFID tag 100 in any orientation. In aspects, the steering network 2040 may include switching networks 2042, 2044. The switching network 2042 may include, for example, a PIN switching diode or other electronically actuatable switch. In aspects, the pilot networks 2040, 2040b may include a switching network 2044 on the top and bottom surfaces of the printed circuit board 2046.

For example, the system 3300 may include four (2 x 2) primary coils 3304a, 3304b, 3304c, 3304d and a configurable air-core coupled secondary coil 3306. Each primary coil 3304a, 3304b, 3304c, 3304d has an associated coil tuning network 2200. The configurable air core coupled secondary winding 3306 generally includes a first portion 3306a, a second portion 3306b, a third portion 3306c, and a fourth portion 3306d. It is contemplated that any suitable number of sections 3306a, 3306b, 3306c, 3306d may be used. The configurable air core coupled secondary coil 3306 has a configurable coil termination network 2300.

The guide network 2040 is used to configure a configurable air core coupled secondary coil 3306 configuration that is best suited for energizing the RFID tag 100 in a given orientation. The configurable terminating network 2200 and the steered network 2040 are controlled by a controller 2240. The guide network 2040 may be located intermediate and/or between the various portions of the configurable air-core coupled secondary coil 3306 to enable the various portions 3306a, 3306b, 3306c, 3306d of the configurable air-core coupled secondary coil 3306 to be accessed and disconnected.

Fig. 37 depicts an example of a two element coil array 3700. The two-element coil array 3700 includes two primary coils 3706a and 3706b and three configurable secondary coils 3702, 3704a, 3704b. In aspects, the system 2000 can include a magnetic shield (not shown) positioned on a side of the coil array 3700 opposite the intended read direction or coincident with the primary coil element and/or the secondary coil element. The shield (not shown) may be made using ferrite sheets and/or similar high permeability materials.

Referring to fig. 38, there is shown a high-level block diagram of a system 3800 for dynamically tuning an antenna coil (e.g., primary coil 302 of fig. 3) to generator 200 of interrogation and detection system 10 of fig. 1 in real-time. The system 3800 for real-time dynamic tuning generally includes: a tuning discriminator 3802 configured to generate a signal for determining real and imaginary parts of an energizing signal; an analog-to-digital converter (a/D) 2242 configured to digitize the signal from the authentication network 3820; a phase compensation network 3840 configured to dynamically tune the matching impedance phase; an amplitude compensation network 3850 configured to dynamically tune the matching impedance; and a controller 2240. The system 3800 may be implemented as a primary side tuning network 410 (fig. 4), such as the tuning network 410 disposed between the generator 200 and the antenna 300 (fig. 3). Tuning network 2250 (fig. 40) may be used in a single coil antenna or multiple coil antennas.

Typically, auto-tuning occurs as discrete steps or states in the operation of the system. Auto-tuning occurs relatively infrequently and typically requires deactivation of the RFID communication channel. In surgical applications, this is not an acceptable situation, as antenna loading may vary constantly based on tissue properties, and it would be impractical, especially for handheld scanning accessories, to require multiple retuning steps during the scanning sequence.

For applications that provide both detection and identification of tagged surgical items, unique technical implementations and tuning methods are required to accommodate dynamic loading conditions presented in the outside surgical environment. Specifically, for RFID applications, the load presented to the antenna 300 or antenna array 1700 (fig. 17) is a function of the material properties of the various structures in close proximity to the antenna structure. These structures and their material properties vary due to a variety of factors including physical size, physical shape, physical orientation, distance from the antenna 300 or antenna array 1700 (fig. 17), uniformity, or lack of uniformity and/or boundary discontinuities.

To optimally transfer power into the field, the interface between the generator 200 and the antenna 300 needs to be tuned in real time or near real time in order to compensate for the continuously variable load conditions.

Referring to fig. 39, a table depicting the dielectric constants and conductivities of various tissue types is shown. Exemplary dielectric constants and conductivities for various tissue types can be found in https:// is.swiss/virtual-delivery/tissue-properties/database/dielectric-properties, which are incorporated by reference. The propagation and attenuation of RF energy generated by the generator 200 and antenna 300 depends on the material properties of the structures present in the field, and thus this variable needs to be accommodated. The disclosed techniques can compensate for changes in dielectric constant and shifts in resonance that are typically found under organic tissue loading conditions. For example, if the tissue type is muscle, the dielectric constant is about 138F/m and the electrical conductivity is 6.28mS/cm. However, if the tissue type is small intestine tissue, the permittivity is about 363F/m and the conductivity is 13.9mS/cm, which can present very different conditions for the antenna 300.

Referring to fig. 40, a diagram of a tuning evaluator 3802 of the system 3800 is shown, the tuning evaluator being configured to generate a signal for determining real and imaginary parts of an energizing signal. Tuning discriminator 3802 generally includes an impedance (Z) transformation network 3810, rectifiers 3822a, 3822b, low Pass Filters (LPF) 3824a, 3824b, and a power detector 2230. The tuning discriminator 3802 analyzes the power-on signal generated by the generator 200 and generates signals for calculating the impedance magnitude, such as power-on signal current and power-on signal voltage (e.g., real part). The tuning discriminator 3802 analyzes a phase difference between the voltage and the current of the energizing signal. For example, the diode 3822a in the inductive leg is forward biased and the diode 3822b in the capacitive leg is reverse biased with respect to the positive phase of the voltage (inductance). In another example, a negative relative phase (capacitance) forward biases diode 3822b in the capacitive branch and reverse biases diode 3822a in the inductive branch. The difference between the two bias voltages is determined and the result is positive with respect to Vref of the inductive signal and negative with respect to Vref of the capacitive signal. Either branch (capacitive or inductive) of the network may be used as a representation of the actual current flowing to the load, which may require additional post-processing. For example, the RMS version of the current, the RMS version of the voltage, and power factor correction may be used for post-processing of the power measurements. The power-on signal current signal and the power-on signal voltage signal are transmitted to the controller 2240 via the a/D converter 2242 in which the load impedance amplitude is calculated. The tuning discriminator 3802 also analyzes the energizing signal generated by the generator 200 and generates a composite signal, a capacitive signal, and an inductive signal (e.g., an imaginary part). And then all of them are transferred to the controller 2240 via the a/D converter 2242. Additionally, the composite signal is passed to a phase compensation network 3840 (fig. 38). In aspects, the composite reference signal may be pre-processed by the controller 2240 to compensate for non-linear effects. Tuning discriminator 3802 provides the advantage of significantly improving the performance of the analog-to-digital converter.

The Z-transform network 3810 is configured to analyze the power-on signal from the signal generator 200 to identify an imaginary part of the power-on signal. This frequency domain representation of the energizing signal is then transferred to rectifiers 3822a, 3822b for rectification. The rectifiers 3822a, 3822b may include one or more diodes that convert an alternating current signal (AC) of the energizing signal to a Direct Current (DC) signal (with some AC artifacts). The DC signal is then filtered by LPFs 3824a, 3824b to remove any residual AC artifacts (e.g., ripple and/or fundamental frequency of the power-on signal). The LPFs 3824a, 3824b may include passive (e.g., R/C networks) or active configurations (e.g., integrators). The output of the LPFs 3824a, 3824b include capacitive signals, inductive signals, and/or energizing signal currents. The capacitive signal and the inductive signal may be combined into a composite signal by a differential-to-single ended converter (e.g., a differential amplifier). The composite signal may be used by the controller 2240 for tuning the impedance magnitude provided to the antenna 300.

The power detector 2230 detects the power level of the power-on signal (e.g., typically about 1W to about 10W) by: sampling (e.g., via a coupler) the power-on signal; rectifying (e.g., by a diode) the sampled signal; and processes the signal by adding gain before transmitting the signal as a power-on signal voltage to the controller 2240.

The controller 2240 is configured to determine an optimal impedance match of the antenna 300 based on the capacitance signal, the inductance signal, the energizing signal current, the energizing signal voltage, and/or the composite signal. The controller 2240 automatically tunes the impedance phase and the impedance amplitude of the antenna 300 in real time based on the determined optimal impedance match. In aspects, the controller 2240 may include multiple independent control loops or may be comprised of several nested control loops for improved stability. The nesting order may be determined by a loop time constant and may be arranged in a variety of ways to optimize the overall system response.

Referring to fig. 41, a phase compensation network 3840 and an amplitude compensation network 3850 are shown. The phase compensation network 3840 is configured to tune the phase of the impedance match in real time. The phase compensation network 3840 generally includes one or more resistors, one or more diodes, and a voltage controlled dynamic capacitive element 3846 configured to be controlled by a range selection signal from the controller 2240. In aspects, the phase compensation network 3840 may include a transformer 3844 (e.g., a magnetic-based transformer and/or a directional coupler) to reduce the voltage across the dynamic capacitive element 3846. For example, the voltage may be reduced to a level typically found in commercial off-the-shelf options, as well as providing isolation from the signal generator 200, antenna 300, and/or compensation networks 3840, 3850. The use of transformer 3844 implements a ground plane reference control scheme. Only a single feedback channel is shown, but the concept extends to implementations using a separate channel for each voltage controlled capacitive element. Further, even though voltage controlled dynamic capacitance element 3846 may include a varactor and/or a voltage controlled capacitor.

The amplitude compensation network 3850 is configured to tune in real-time the amplitude of the impedance match provided to the antenna 300. Amplitude compensation network 3850 generally includes one or more resistors, one or more diodes, and a voltage controlled dynamic capacitive element 3856 configured to be controlled by a range selection signal from controller 2240. The amplitude adjustment signal is communicated from the controller 2240 to the amplitude compensation network 3850 and causes the amplitude compensation network 3850 to increase or decrease the amplitude of the impedance match. In aspects, the amplitude compensation network 3850 may include one or more transformers 3852 (e.g., magnetic-based transformers) to reduce the voltage across the dynamic capacitive element 3856. In various aspects, amplitude compensation network 3850 may be used for tuning networks 410 and 420 of fig. 4.

For the case of an air core coupled secondary coil 420 (e.g., fig. 4), the secondary coil 304 also benefits from real-time tuning. This has the effect of maintaining a majority of the primary reference reactive impedance and reduces the burden placed on the primary side tuning network 410 (fig. 4). Additionally, secondary coil auto-tuning maintains an optimal secondary coil 304 (fig. 4) resonant frequency, which increases the secondary coil 304 quality factor "Q" benefit.

The field strength at a particular distance or "read range" from the antenna 300 is a function of several physical parameters. These parameters may include the air gap present between the antenna 300 (fig. 1) and the surface of the conductive medium (patient), the thickness of the conductive medium (saline depth, tissue thickness), and the conductivity of the conductive medium (tissue). It can also be shown that the relative quality factor "Q" of the antenna 300 can be used to quantify these parameters so that, by just the quality factor "Q", we can establish the necessary system operating parameters to achieve a target field strength of a fixed height above the coil surface. This challenge stems from our ability to quantify the Q factor of the antenna coil in real time and then correlate that quality factor "Q" with the appropriate reader output to achieve the target field strength. The quality factor "Q" is a function of air gap, brine depth, and salinity.

Referring to fig. 42, an integrated Q-factor sensor for use with the system 3800 for real-time dynamic tuning is shown. Generally, for conductive media having a high salt content, the Q factor drops rapidly as the air gap between the RFID tag 100 and the antenna 300 decreases. This is because the conductive medium shunts current rather than current flowing through the desired coil before the conductive medium has a chance to conduct current through the current element of the antenna (e.g., one or more antenna coils, see fig. 3). The field strength in space is the integrated sum of each discrete current element and essentially we short-circuit the coil with a conductive medium. The quality factor "Q" is not easily measured directly. It can be seen that the coil current for a given power setting is an effective representation of the quality factor "Q". By embedding the air core coupled magnetic field pickup coil 4100 in the coil feeder network 4102, coil current (and/or voltage) can be measured without degrading coil performance.

An additional advantage of measuring the antenna coil quality factor "Q" for determining the required output power required to achieve a target field strength at a target distance from the antenna 300 relates to the information it provides in terms of the scanning technology of the handheld scanning accessory. The controller 2240 may be programmed with a target limit for the quality factor "Q" in which the physical proximity characteristics of the scanning accessory relative to the patient tissue may be established. These limitations can be used to provide real-time feedback to the operator in order to improve scanning efficiency and effectiveness. In particular, a quality factor "Q" may be interpreted as indicating whether the antenna 300 is too close to the patient (air gap), which may indicate whether the antenna 300 is too far from the patient, and the system 3800 may indicate whether the tissue load on the accessory is outside of an acceptable range. Furthermore, it is possible that the quality factor "Q" in combination with the coil inductance (phase) and the coil amplitude indicates the presence of interfering objects (e.g., metallic instruments) in the field.

In aspects, the system 3800 may utilize only a single voltage or current sensor, with the compensation routine adjusting the resonance of the secondary coil of the antenna 300 in order to maximize the sensed parameter. The simplified routine may incorporate a simple set point dithering technique in which a binary reduction is used to adjust the antenna 300 resonant frequency and/or Q factor based on the polarity of the sensed parameter (voltage and/or current) δ.

Referring to fig. 43, a graph showing the linear output of the "Q" factor sensor of fig. 41 is shown. The graph depicts normalized "Q" sensor output versus antenna coil current.

Referring to fig. 44, a flow chart of a method for dynamically tuning the impedance match between the antenna 300 and the generator 200 in real time is shown.

Referring now to fig. 44, a flowchart of a computer-implemented method 4400 for dynamically tuning the impedance matching between the antenna 300 and the generator 200 in real time is shown. Those skilled in the art will appreciate that one or more operations of the method 4400 may be performed, repeated, and/or omitted in a different order without departing from the scope of the disclosure. In various embodiments, the illustrated method 4400 may operate in the controller 2240 (fig. 38), in a remote device, or in another server or system. In various embodiments, some or all of the operations of the illustrated method 4800 can be operated using a surgical system (such as the interrogation and detection system 10 of fig. 1). Other variations are considered to be within the scope of the disclosure. The operations of fig. 44 will be described with respect to a controller, such as controller 2240 (fig. 38), but it should be understood that the illustrated operations are applicable to other systems and components thereof.

Initially, at step 4402, the signal generator 4402 transmits an energizing signal to the antenna 300 to which it is operatively coupled. The power-on signal is configured to power on the RFID tag 100 (FIG. 1).

Next, at step 4404, the controller 2240 determines the real and/or imaginary parts of the energizing signal through a tuning discriminator 3802 of the system 3800, which is configured to generate a signal for determining the real (e.g., current and/or voltage) and/or imaginary (e.g., phase) parts of the energizing signal. For example, the real part of the energizing signal may be about 10.2V.

Next, at step 4406, the controller 2240 dynamically tunes the phase of the matching impedance based on the determined imaginary part of the power on signal. The controller 2240 may tune the phase of the matching impedance based on the phase compensation network 3840.

Next, at step 4408, the controller 2240 dynamically tunes the magnitude of the matching impedance based on the determined real part of the power on signal. The controller 2240 may tune the magnitude of the matching impedance based on the magnitude compensation network 3840.

Referring to fig. 45, a transformer 310 for matching the output impedance of the generator 200 with the impedance of the antenna 300 is shown. Generally, the output of the generator will be 50 ohms and the impedance of the antenna 300 at or near the operating frequency will be about 50 ohms. If both generator 200 and antenna 300 are set to 50 ohm impedance, the maximum possible energy will be transferred. If the impedance of the antenna 300 and the generator 200 are not well matched, a smaller amount of power will be transferred. Due to geometry, structure or external disturbances, it may be desirable to use antennas with impedances not equal to 50 ohms. To correct for this, a matching network is typically placed between the antenna and the generator, which transforms the antenna impedance to 50 ohms. The disclosed techniques enable this matching, and thus more efficient construction and use of antenna geometries.

Referring to fig. 46, a loop antenna 300 is shown in accordance with the present disclosure that may be used as an antenna for the detection system 10 (fig. 45). The impedance of the antenna is based on the geometry of the antenna. The inductance of the loop antenna as shown in fig. 46 can be calculated using the following loop inductance equation:

wherein "L _{Loop circuit} "is the loop inductance," D "is the inner diameter of the loop," D "is the width of the loop conductor," u _r "is relative permeability" and "u _o "is the permeability of free space.

For example, where the antenna inductance is approximately 1.174uH, using the loop inductance equation, the diameter of the antenna will be calculated to be approximately 47.5cm for a 1cm wide copper conductor. This is a rather large antenna. However, it may be desirable to have an even larger antenna or an antenna with more turns. This may result in the antenna having an inductance of about ten or twenty times the value giving a 50 ohm matching load. In general, the use of matching networks with such large inductances may render component values unusable, or entirely impossible.

As the inductance of the antenna increases, the smaller the capacitance used in the matching network. Thus, loop antennas are made more and more difficult to manufacture, and the effectiveness of the antennas may decrease. For example, for a matching network for a 5.87uH antenna, the matching network is approximately a 6.9pF capacitor in parallel with the loop antenna. Thus, at this low level of capacitance, it is entirely possible that the manufacturing process may result in parasitic capacitances greater than this value, even without the addition of discrete components (e.g., discrete capacitors). This may be a result of cable parasitics or parasitic capacitances present in the turns of the multi-turn antenna.

The disclosed technique solves this problem by using a transformer. Adding a transformer element between the tuning network and the reader (e.g., generator output) would allow for the development of a higher impedance matching network that can then be transformed down to the desired 50 ohms for the reader. In various aspects, the transformer will change the impedance of the matching network by the square root of the "turns ratio".

For example, in the case of the matching network described above, the impedance of the matching network is transformed down to 50 ohms. In the case of 50 impedance on the primary side of the transformer and 500 ohm impedance on the secondary side, then it is desirable to have a "turns ratio" (N) ofOr a 3.16 transformer.

While generally represented as an ideal circuit that simply converts voltage, current, and impedance to other levels, practical transformers have additional parasitic components that can play a real role in the manner in which the circuit operates. At least these parasitics must be considered and in well-designed circuits, the parasitic components can be used as part of an impedance matching network.

There are many different topologies for impedance matching networks. They may have a series inductance, a parallel inductance, or a parallel capacitance, or other configuration. If carefully designed, transformers can be used in place of discrete impedance matching network components.

Referring to fig. 47, a schematic diagram of a transformer model 4700 including parasitics is shown. The transformer model 4700 generally includes a transformer 4702, a parallel capacitance (Cpar) 4704 of windings, leakage inductance (lk), and a mutual inductance (Lm) of windings. The transformer 4702 includes a primary winding 4702a and a secondary winding 4702b.

Referring to fig. 48, a schematic diagram is shown that includes a transformer model 4800 reflecting parasitic capacitance. The transformer model 4800 generally includes a transformer 4702, a parallel capacitance (Cpar) 4804 of windings, leakage inductance (lk), and a mutual inductance (Lm) of windings. The transformer 4702 includes a primary winding 4702a and a secondary winding 4702b.

The equation for reflecting the capacitance through the transformer is: c (C) _pri ＝n ² C _sec . This means that any capacitance placed on the secondary winding 4702b of the transformer 4702 will be multiplied by the square of the "turns ratio" on the primary winding (N ² ). In the case of the previous example, N ² =10, where "turns ratio" N is 3.16. Thus, a relative comparative capacitance of 10.3pF is required on the primary winding to implement our matching network component. For example, a capacitance of 10.3pF may be implemented by discrete components and/or by embedded printed circuit board capacitance. The benefit of this approach is that when leakage and magnetizing inductances are reflected through transformer 4702, they will be reduced.

Referring to fig. 49, a depiction of a transformer matching system 4900 for use with the interrogation and detection system of fig. 1 is shown. The transformer matching system 4900 incorporates a dynamic capacitive element 4704 as a shunt capacitance to tune the resonance of the antenna 300. System 4900 includes transformer 4702, dynamic capacitive element 4704, and controller 2240. The transformer 4704 is configured to provide voltage protection to the tuning capacitor 4704.

In aspects, the system 4900 enables dynamic tuning of the antenna resonance 410 (fig. 45). The system 4900 reflects the capacitance of the dynamic capacitive element 4704 (e.g., varactor) through the transformer 4702. This enables, for example, low voltage varactors to be used in high voltage systems. For example, the signal received by antenna 300 may reach up to about 1kV. If this is reflected down through a 1:10 transformer, the signal size will be only 100V. In this way, the dynamic capacitive element 4704 may be used to dynamically tune the antenna 300 while remaining within the voltage limits of the dynamic capacitive element 4704 (e.g., 300V for a varactor).

Referring to fig. 50, there is a depiction of a transformer matching system 5000 incorporating a dynamic capacitive element 4704 for parallel capacitance in accordance with the present disclosure. The system 5000 generally includes a transformer 4702, a high voltage bulk capacitance 5002 on a secondary winding 4702b of the transformer 4702, and a dynamic capacitive element 5004 on a primary winding 4702a of the transformer 4702.

The dynamic capacitive element 5004 is configured to provide a "trimming" capacitance to help trim the antenna resonance 300. Dynamic capacitive element 5004 is an element that acts as a capacitive reactance and is capable of being tuned by analog and/or digital signals. Dynamic capacitive element 5004 may include a varactor. For example, if the dynamic capacitive element 5004 is on the primary winding 4702a of the transformer 4702, the value of the dynamic capacitive element 5004 will decrease the square of the "turns ratio" (N as it reflects through the transformer 4702 ² ). For example, if dynamic capacitive element 5004 has a capacitance range of approximately 200pF and the square of the "turns ratio" (N ² ) =10, then on the secondary winding, this range will be only 20pF. If our tuning requirements require 100pF, then the dynamic capacitive element 5004 will not be able to tune the circuit. If a high voltage bulk capacitance of about 90pF is used instead on secondary winding 4702b, the tunable range of the circuit will be about 90pF to about 110pF.

In aspects, the controller 2240 may be configured to control the value of the dynamic capacitive element 5004. For example, the controller 2240 may control the tuning voltage of the dynamic capacitive element 5004 to tune the resonance of the antenna 300.

Referring to fig. 51, a system 5100 for matching an impedance of the generator 200 with the antenna 300 is shown. The system 5100 generally includes a first transformer 5104, an impedance matching network 5102, a dynamic capacitive element 5004, a second transformer 4702, an antenna 300, and a controller 2240.

The first transformer 5104 may be configured to transform a typical 50 ohm impedance of the generator 200 to an impedance other than 50 ohms. In aspects, the first transformer 5104 may include a step-up transformer or a step-down transformer. Careful design will allow the use of transformer parasitics as part of the matching network. For example, if parasitic capacitor 4704 would have a capacitance of about 20pF and the first variationThe presser 5104 has N ² =10, then on the secondary winding 5104b the capacitance will be about 200pF, which may be a suitable value for the matching network.

The matching network 5102 may include a fixed matching network (e.g., fixed capacitor and/or inductor values) and/or may include a dynamic matching network 2250 (fig. 22). The matching network 5102 is disposed between the first transformer 5104 and the second transformer 4702. The matching network 510 is configured to match the impedance of the output of the generator 200 to the impedance of the antenna 300. In aspects, the system 5100 can include a sensor 5108 configured to determine a parameter of the power-on signal. In aspects, the dynamic matching network 5102 may be configured to dynamically match impedance between the signal generator and the antenna based on parameters of the power-on signal (e.g., power level, frequency, bandwidth, voltage, and/or current). In aspects, the sensor 5105 may comprise, for example, a sensor that may be disposed in any suitable location in the circuit (e.g., before and/or after the matching network 5102, at the output of the signal generator 200 and/or on the feed line of the antenna 300).

The dynamic capacitance element 5004 is provided on the primary winding 4702a of the second transformer 4702. The dynamic capacitive element 5004 is configured to provide a tunable capacitance to an antenna resonance whose voltage exposure is limited by a transformer. The controller 2240 may be configured to generate a signal for tuning the capacitance value of the dynamic capacitance element 5004.

The second transformer 4702 is configured to transform the impedance of the dynamic capacitive element 5102 to produce the appropriate antenna resonance 300. In aspects, the system can further include a bulk capacitance 5002 configured to adjust the tuning range of the dynamic capacitive element 5004.

Antenna 300 may include a coil antenna, a loop antenna, an antenna array, and/or any other suitable antenna arrangement. For example, the system 5100 may be used to match a dipole antenna with the signal generator 200. In aspects, the second transformer may be a step-down transformer.

While aspects of the present disclosure have been illustrated in the accompanying drawings, it is not intended to be limited thereto, as the disclosure is intended to be as broad and should be read in the same manner as the scope of the disclosure is allowed in the art. Therefore, the above description should not be construed as limiting, but merely as exemplifications of particular aspects. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.

Claims

1. An interrogation and detection system for detecting surgical instruments within a patient, the interrogation and detection system comprising:

an RFID tag configured to transmit a return signal when energized, the RFID tag attached to a surgical instrument;

a signal generator configured to generate an energizing signal for the RFID tag; and

a coil antenna operatively coupled to the signal generator, the antenna configured to receive a return signal transmitted by the RFID tag, the coil antenna comprising:

a primary coil;

a secondary coil; and

a core configured to couple electromagnetic energy from the secondary coil to the primary coil, wherein the core comprises a non-magnetic insulating material,

wherein the secondary coil is configured to receive the return signal, and

wherein the primary coil is configured to couple electromagnetic energy to the secondary coil and to couple the electromagnetic energy from the secondary coil.

2. The system of claim 1, wherein a "turns ratio" between the primary coil and the secondary coil is greater than or equal to 1:1, wherein the "turns ratio" is a ratio between a first number of turns of the primary coil and a second number of turns of the secondary coil.

3. The system of claim 1, wherein the secondary coil has a resonant frequency within 10% of an operating frequency of the return signal.

4. The system of claim 1, wherein the secondary coil has an inductance greater than or equal to 2.5 uH.

5. The system of claim 1, wherein the coil antenna further comprises a first matching network electrically connected to the primary coil, wherein the first matching network is configured to match an input impedance of the primary coil to an output impedance of the signal generator.

6. The system of claim 1, wherein the coil antenna further comprises a second matching network electrically connected to the secondary coil, wherein the second matching network is configured to match an input impedance of the secondary coil to an output impedance of the primary coil.

7. The system of claim 1, wherein the primary coil is a first planar coil.

8. The system of claim 7, wherein the secondary coil is a second planar coil.

9. The system of claim 7, wherein the primary coil comprises a first turn and a second turn.

10. The system of claim 9, wherein the first turn of the primary coil and the second turn of the primary coil are arranged in an offset manner in a vertical orientation and a horizontal orientation.

11. The system of claim 8, wherein the secondary coil comprises a first turn and a second turn.

12. The system of claim 11, wherein the first turn of the primary coil and the second turn of the primary coil are arranged in an offset manner in a vertical orientation and a horizontal orientation.

13. A coil antenna configured to receive a return signal transmitted by an RFID tag, the coil antenna comprising:

a primary coil;

a secondary coil; and

wherein the secondary coil is configured to receive the return signal, and

wherein the primary coil is configured to couple electromagnetic energy from the secondary coil.

14. The coil antenna of claim 13, wherein the primary coil and the secondary coil are each planar coils.

15. The coil antenna of claim 13, wherein the primary coil comprises a conductor.

16. The coil antenna of claim 15, wherein the conductor of the primary coil comprises a conductor having a configuration including at least one of a coaxial, planar, "C" -shaped cross-sectional shape, and/or a tubular cross-sectional shape.

17. The coil antenna of claim 13, wherein a "turns ratio" between the primary coil and the secondary coil is greater than or equal to 1:1, wherein the "turns ratio" is a ratio between a first number of turns of the primary coil and a second number of turns of the secondary coil.

18. The coil antenna of claim 13, wherein the secondary coil has a resonant frequency within 10% of an operating frequency of the return signal.

19. A method for inventory control of tagged items, the method comprising:

transmitting an energizing signal through a coil antenna operatively coupled to a signal generator, the coil antenna comprising a primary coil, a secondary coil, and a core configured to magnetically couple the secondary coil to the primary coil, the energizing signal configured to energize an RFID tag attached to an article and configured to transmit a return signal when energized; and

the return signal is received through a primary coil of the coil antenna.

20. The method of claim 19, the method further comprising:

the article is detected or identified based on the return signal, wherein the article comprises a surgical instrument.

21. A coil configured to receive a return signal transmitted by an RFID tag, the coil comprising:

a first turn of conductor; and

a second turn conductor electrically connected to the first turn conductor.

22. The coil of claim 21 wherein said first turn of conductor is positioned in parallel relationship and offset with respect to said second turn of conductor,

wherein the first turn of conductor comprises a first inner edge and a first outer edge, and

wherein the second turn conductor comprises a second inner edge and a second outer edge.

23. The coil of claim 21, wherein the coil is arranged in at least one of a circular, square, rectangular, or oblong configuration.

24. The coil of claim 21, wherein the first turn conductors overlap the second turn conductors of an interleaved coil, wherein a majority of the second turn conductors do not overlap the first turn conductors.

25. A coil antenna configured to receive a return signal transmitted by an RFID tag, the coil antenna comprising:

a primary coil; and

a secondary coil, the secondary coil comprising:

a first turn of conductor; and

a second turn conductor electrically connected to the first turn conductor,

Wherein the secondary coil is configured to receive the return signal, and

26. The coil antenna of claim 25, further comprising a core configured to couple electromagnetic energy from the secondary coil to the primary coil and to couple the electromagnetic energy from the primary coil, wherein the core comprises a non-magnetic insulating material,

wherein the first turn conductors are positioned in parallel relationship and offset with respect to the second turn conductors.

27. The coil antenna of claim 25, wherein a "turns ratio" between the primary coil and the secondary coil is greater than or equal to 1:1, wherein the "turns ratio" is a ratio between a first number of turns of the primary coil and a second number of turns of the secondary coil.

28. The coil antenna of claim 25, wherein the secondary coil has a resonant frequency within 10% of an operating frequency of the return signal.

29. The coil antenna of claim 25, wherein the secondary coil has an inductance greater than or equal to 2.5 uH.

30. The coil antenna of claim 25, wherein the coil antenna further comprises a first matching network electrically connected to the primary coil, wherein the first matching network is configured to match an input impedance of the primary coil to an output impedance of the signal generator.

31. An interrogation and detection system for detecting surgical instruments within a patient, the interrogation and detection system comprising:

an RFID tag configured to transmit a return signal when energized, the RFID tag attached to a surgical instrument within the patient;

a primary coil; and

a secondary coil, the secondary coil comprising:

a first turn of conductor; and

a second turn conductor electrically connected to the first turn conductor,

wherein the first turn conductors are positioned in parallel relationship and offset with respect to the second turn conductors,

Wherein the secondary coil is configured to receive the return signal, and

32. The system of claim 31, wherein the secondary coil is an air core coupled to the primary coil.

33. The system of claim 31, wherein a "turns ratio" between the primary coil and the secondary coil is greater than or equal to 1:1, wherein the "turns ratio" is a ratio between a first number of turns of the primary coil and a second number of turns of the secondary coil.

34. The system of claim 31, wherein the secondary coil has an inductance greater than or equal to 2.5 uH.

35. The system of claim 31, wherein the coil antenna further comprises a first matching network electrically connected to the primary coil.

36. The system of claim 31, wherein the coil antenna further comprises a second matching network electrically connected to the secondary coil.

37. The system of claim 31, wherein the primary coil is a first planar coil.

38. The system of claim 31, wherein the secondary coil is a second planar coil.

39. The system of claim 37, wherein the primary coil comprises one or more turns.

40. The system of claim 38, wherein the secondary coil comprises one or more turns.

41. An interrogation and detection system for detecting surgical instruments within a patient, the interrogation and detection system comprising:

a coil antenna operatively coupled to the signal generator, the antenna configured to receive a return signal transmitted by the RFID tag, the coil antenna comprising a coil array.

42. The system of claim 41, wherein the coil array is configured to generate a magnetic flux and direct at least one of a direction of the magnetic flux or an amplitude of the magnetic flux based on the energizing signal.

43. The system of claim 41, wherein the coil array comprises a first coil and a second coil,

Wherein the energizing signal comprises a first current and a second current, an

Wherein the first and second coils are configured to be independently energized by the first and second currents, respectively.

44. The system of claim 43, wherein the second coil is oriented at least one of 0 degrees, 90 degrees, 180 degrees, or 270 degrees relative to the first coil.

45. The system of claim 44, wherein the first coil of the coil array is energized with the first current in at least one of a clockwise direction or a counter-clockwise direction, and wherein the second coil of the coil array is energized with the second current in at least one of a clockwise direction or a counter-clockwise direction.

46. The system of claim 43, wherein each coil of the array of coils is arranged in at least one of a circular, square, rectangular, or oblong configuration.

47. The system of claim 43, wherein each of the first coil and the second coil is a planar coil.

48. The system of claim 43, wherein each of the first coil and the second coil comprises one or more turns.

49. The system of claim 41, wherein each of the coils of the coil array comprises a primary coil and a secondary coil,

and wherein each of the coils of the coil array has a "turns ratio" between the primary coil and the secondary coil that is greater than or equal to 1:1, wherein the "turns ratio" is a ratio between a first number of turns of the primary coil and a second number of turns of the secondary coil.

50. A coil array configured to receive a return signal transmitted by an RFID tag, the coil array comprising:

a first coil configured to generate a first magnetic field; and

a second coil configured to generate a second magnetic field,

wherein the coil array is configured to generate a magnetic flux and direct at least one of a direction of the magnetic flux or an amplitude of the magnetic flux based on an energizing signal from a signal generator.

51. The coil array of claim 50, wherein the energizing signal comprises a first current and a second current, and

52. The coil array of claim 50, wherein the second coil is oriented at least one of 0 degrees, 90 degrees, 180 degrees, or 270 degrees relative to the first coil.

53. The coil array of claim 52, wherein the first coil of the coil array is energized with the first current in at least one of a clockwise direction or a counter-clockwise direction, and

wherein the second coil of the coil array is energized with the second current in at least one of a clockwise direction or a counter-clockwise direction.

54. The coil array of claim 51, wherein each coil of the coil array is arranged in at least one of a circular, square, rectangular, or oblong configuration.

55. The coil array of claim 51, wherein each of the first coil and the second coil is a planar coil.

56. The coil array of claim 51, wherein each of the first coil and the second coil comprises one or more turns.

57. The coil array of claim 50, wherein each of the coils of the coil array comprises a primary coil and a secondary coil,

58. The coil array of claim 50, wherein each of the coils of the coil array has an inductance greater than or equal to 2.5 uH.

59. A method for interrogating and detecting a surgical instrument within a patient, the method comprising:

transmitting an energizing signal through a coil antenna operatively coupled to the signal generator, the antenna configured to receive a return signal transmitted by the RFID tag, the coil antenna comprising an array of coils; and

a return signal is received by the coil array, wherein the coil array is configured to generate a magnetic flux and direct at least one of a direction of the magnetic flux or an amplitude of the magnetic flux based on the energizing signal.

60. The method of claim 59, wherein the power-on signal includes a first current and a second current, and

wherein the method further comprises:

Energizing a first coil of the coil array with the signal generator, the first coil being energized by the first current in at least one of a clockwise direction or a counter-clockwise direction, and

a second coil of the coil array is energized by the second current in at least one of a clockwise direction or a counter-clockwise direction by the signal generator.

61. A system for matching impedance between an antenna and a signal generator, the system comprising:

an RFID tag configured to transmit a return signal when energized, the RFID tag attached to a surgical instrument within a patient;

the signal generator is configured to generate an energizing signal for the RFID tag;

a coil antenna operatively coupled to the signal generator, the antenna configured to receive a return signal transmitted by the RFID tag; and

a first transformer configured to match the impedance between the signal generator and the antenna.

62. The system of claim 61, wherein the first transformer comprises a primary winding and a secondary winding,

Wherein the system further comprises a capacitor arranged in parallel with the primary winding of the first transformer, the capacitor being configured to match the impedance between the signal generator and the antenna.

63. The system of claim 61, further comprising a matching network disposed between the first transformer and the antenna, and configured to match the impedance between the signal generator and the antenna.

64. The system of claim 63, wherein the matching network comprises at least one of a fixed matching network or a dynamic matching network, wherein the dynamic matching network is configured to dynamically match the impedance between the signal generator and the antenna based on parameters of the energizing signal.

65. The system of claim 64, wherein the parameter of the power-on signal comprises at least one of a power level, a frequency, a bandwidth, a voltage, or a current.

66. The system of claim 63, further comprising a second transformer configured to transform an impedance match between the matching network and the antenna, the second transformer disposed between the matching network and the antenna.

67. The system of claim 66, wherein the second transformer is a step-up transformer.

68. The system of claim 67, further comprising a dynamic capacitive element configured to tune the impedance, the dynamic capacitive element disposed across the primary winding of the second transformer.

69. The system of claim 68, further comprising:

a sensor configured to sense a signal indicative of a parameter of the energizing signal;

a processor; and

a memory comprising instructions stored thereon that, when executed, cause the system to:

sensing the signal indicative of a parameter of the energizing signal;

determining a parameter of the energizing signal based on the sensed signal; and

the dynamic capacitive element is dynamically tuned based on the determined parameter of the energizing signal.

70. The system of claim 66, wherein the second transformer comprises a primary winding and a secondary winding, and

wherein the system further comprises a bulk capacitance disposed across the secondary winding of the second transformer.

71. The system of claim 66, wherein the second transformer is a step-down transformer.

72. A system for matching impedance between an antenna and a signal generator, the system comprising:

the antenna operatively coupled to the signal generator, the antenna configured to receive a return signal transmitted by the RFID tag;

a transformer configured to match the impedance between the signal generator and the antenna; and

a dynamic capacitive element configured to tune the impedance, the dynamic capacitive element disposed across the primary winding of the transformer.

73. The system of claim 72, the system further comprising:

a processor; and

Sensing the signal indicative of a parameter of the energizing signal;

74. The system of claim 73, wherein the parameter of the power-on signal comprises at least one of a power level, a frequency, a bandwidth, a voltage, or a current.

75. The system of claim 73, wherein the transformer comprises a primary winding and a secondary winding, and

wherein the system further comprises a bulk capacitance disposed across the secondary winding of the transformer.

76. The system of claim 72, wherein the transformer is a step-down transformer.

77. The system of claim 72, further comprising a matching network disposed between the transformer and the antenna, and configured to match the impedance between the signal generator and the antenna.

78. The system of claim 77, wherein the matching network comprises at least one of a fixed matching network or a dynamic matching network, wherein the dynamic matching network is configured to dynamically match the impedance between the signal generator and the antenna based on parameters of the energizing signal.

79. A method for tuning impedance matching between an antenna and a signal generator, the method comprising:

sensing, by a sensor, a signal indicative of a parameter of the energizing signal;

dynamically tuning a dynamic capacitive element based on the determined parameter of the energizing signal, wherein the dynamic capacitive element is disposed across a primary winding of a transformer disposed between the signal generator and the antenna.

80. The method of claim 79, wherein the parameter of the power-on signal comprises at least one of a power level, a frequency, a bandwidth, a voltage, or a current.

81. A system for dynamically tuning impedance matching between an antenna and a signal generator in real time, the system comprising:

a signal generator configured to generate an energizing signal for the RFID tag;

A real-time tuning network configured to dynamically tune the impedance match between the signal generator and the antenna.

82. The system of claim 81, wherein the real-time tuning network comprises:

a tuning discriminator configured to determine at least one of a real part of the energizing signal or an imaginary part of the energizing signal;

a phase compensation network configured to dynamically tune a phase of the matching impedance based on the determined imaginary part of the energizing signal; and

an amplitude compensation network configured to dynamically tune an amplitude of the matching impedance based on the determined real part of the energizing signal,

wherein the imaginary part comprises at least one of a capacitive signal, an inductive signal or a composite signal, and

wherein the real part comprises at least one of a power-on signal current or a power-on signal voltage.

83. The system of claim 82, wherein the real-time tuning discriminator comprises:

an impedance transformation network configured to transform the energizing signal from the signal generator to identify the real part and the imaginary part of the energizing signal;

A rectifier configured to rectify the impedance-transformed signal; and

a low pass filter configured to filter the rectified signal.

84. The system of claim 82, wherein the real-time tuning network further comprises a power detector configured to detect at least one of the power-on signal current or the power-on signal voltage.

85. The system of claim 82, wherein the phase compensation network comprises:

a dynamic capacitive element configured to select a frequency range of the phase of the matching impedance; and

a transformer configured to reduce a voltage across the dynamic capacitive element.

86. The system of claim 82, wherein the amplitude compensation network comprises:

a dynamic capacitive element configured to select a frequency range that matches the magnitude of the impedance; and

87. The system of claim 83, further comprising:

a processor; and

determining an imaginary part of the energizing signal; and

the phase of the matching impedance is dynamically tuned by the phase compensation network based on the determined imaginary part of the energizing signal.

88. The system of claim 87, wherein the instructions, when executed, further cause the system to:

determining a real part of the energizing signal; and

dynamically tuning the magnitude of the matching impedance based on the determined real part of the energizing signal by the magnitude compensation network.

89. The system of claim 82, wherein the coil antenna comprises:

a primary coil; and

and a secondary coil.

90. The system of claim 88, wherein the tuning network is disposed between the primary coil and the signal generator, and

wherein the tuning network is configured to tune a quality factor "Q" of the primary coil "

Or at least one of the operating frequencies.

91. The system of claim 89, further comprising a second tuning network electrically coupled to the secondary coil and configured to tune at least one of a quality factor "Q" or an operating frequency of the secondary coil.

92. A method for dynamically tuning impedance matching between an antenna coil and a signal generator in real time, the method comprising:

determining at least one of a real part of an energizing signal of the signal generator or an imaginary part of the energizing signal of the signal generator; and

the phase of the matching impedance is dynamically tuned by a phase compensation network based on the determined imaginary part of the energizing signal.

93. The method of claim 92, the method further comprising:

determining a real part of the energizing signal; and

the magnitude of the matching impedance is dynamically tuned by a magnitude compensation network based on the determined real part of the energizing signal.

94. A real-time tuning network configured to dynamically tune an impedance match between a signal generator and an antenna, the real-time tuning network comprising:

a real-time tuning discriminator configured to determine at least one of a real part of a power-on signal or an imaginary part of the power-on signal from the signal generator;

95. The real-time tuning network of claim 94, wherein the real-time tuning discriminator comprises:

a rectifier configured to rectify the impedance-transformed signal; and

a low pass filter configured to filter the rectified signal.

96. The real-time tuning network of claim 95, wherein the real-time tuning network further comprises a power detector configured to detect at least one of the power-on signal current or the power-on signal voltage.

97. The real-time tuning network of claim 95, wherein the phase compensation network comprises:

98. The real-time tuning network of claim 94, wherein the amplitude compensation network comprises:

99. The real-time tuning network of claim 95, wherein the coil antenna comprises:

a primary coil; and

and a secondary coil.

100. The real-time tuning network of claim 98, wherein said tuning network is disposed between said primary coil and said signal generator,

Or at least one of the operating frequencies.

101. A system for dynamically configuring a secondary air core coupling coil and exciting a magnetic field, the system comprising:

a coil antenna operatively coupled to the signal generator, the antenna configured to receive a return signal transmitted by the RFID tag, the coil antenna configured to excite an excitation field in a plurality of directions based on the energizing signal.

102. The system of claim 101, wherein the coil antenna comprises:

a coil array comprising a plurality of coils, wherein each coil of the coil array comprises:

a primary coil; and

and a secondary coil.

103. The system of claim 102, wherein the coil antenna further comprises a coil tuning network configured to tune a quality factor "Q" of the primary coil "

Or at least one of the operating frequencies.

104. The system of claim 103, wherein tuning the network comprises:

a real part match detection network configured to detect a real part of the energizing signal;

an imaginary part match detection network configured to detect an imaginary part of the energizing signal;

A dynamic matching network configured to tune at least one of a quality factor "Q" or a first resonant frequency of the primary coil;

a processor; and

a memory having stored thereon instructions that, when executed by the processor, cause the system to:

detecting a real part of the energizing signal through the real part matching detection network;

detecting a real part of the energizing signal through the imaginary part matching detection network;

determining a second resonant frequency of the primary coil based on the detected real part and the detected imaginary part of the energizing signal; and

tuning, by the dynamic matching network, the primary coil to the second resonant frequency based on the determination.

105. The system of claim 104, wherein the tuning network further comprises a power detection network configured to detect a power level from the power-on signal.

106. The system of claim 105, wherein the instructions, when executed, further cause the system to:

detecting the power level of the power-on signal through the power detection network;

determining a third resonant frequency of the primary coil; and

Tuning, by the dynamic matching network, the primary coil to the third resonant frequency based on the determination.

107. The system of claim 102, wherein the coil antenna further comprises a termination network configured to enable or disable discrete secondary coils of the coil array.

108. The system of claim 107, wherein the terminating network comprises:

an impedance sensor configured to sense an impedance of each of the secondary coils of the coil array;

a step-down transformer configured to reduce the impedance of each of the secondary coils of the coil array;

a dynamic capacitance set configured to provide a plurality of loads to each of the secondary coils of the coil array via the step-down transformer;

a processor; and

determining, by the impedance sensor, the impedance of the return signal; and

the dynamic capacitance set is set to one of the plurality of loads based on the determination.

109. The system of claim 102, wherein the secondary coil is a configurable air core coupled secondary coil comprising a plurality of configurable secondary coil sections, the configurable air core coupled secondary coil having a plurality of secondary coil configurations.

110. The system of claim 109, wherein the coil antenna further comprises a steering network configured to enable at least one secondary coil configuration of the plurality of secondary coil configurations.

111. The system of claim 101, further comprising a surgical table, wherein the coil antenna is embedded in the surgical table.

112. The system of claim 102, wherein the coil array comprises a first coil and a second coil,

113. The system of claim 112, wherein the first coil of the coil array is energized with the first current in at least one of a clockwise direction or a counter-clockwise direction, and wherein the second coil of the coil array is energized with the second current in at least one of a clockwise direction or a counter-clockwise direction.

114. A coil antenna, the coil antenna comprising:

a coil array configured to receive a return signal transmitted by an RFID tag, the coil array comprising:

a first coil configured to generate a first magnetic field; and

a second coil configured to generate a second magnetic field,

wherein the coil array comprises a plurality of coils configured to generate a magnetic flux and to direct at least one of a direction of the magnetic flux or an amplitude of the magnetic flux based on an energizing signal from a signal generator, wherein each coil of the coil array comprises:

a primary coil; and

and a secondary coil.

115. The coil antenna of claim 114, wherein the coil antenna further comprises a coil tuning network configured to tune at least one of a quality factor "Q" or an operating frequency of each primary coil.

116. The coil antenna of claim 114, wherein tuning the network comprises:

A dynamic matching network configured to tune at least one of a quality factor "Q" or a first operating frequency of the primary coil;

a processor; and

a memory having stored thereon instructions that, when executed by the processor, cause the coil antenna to:

determining a second operating frequency of the primary coil based on the detected real part and the detected imaginary part of the energizing signal; and

tuning the primary coil to the second operating frequency based on the determination by the dynamic matching network.

117. The coil antenna of claim 114, wherein the coil antenna further comprises a termination network configured to enable or disable discrete secondary coils of the coil array.

118. The coil antenna of claim 117, wherein the termination network comprises:

a sensor configured to sense at least one of an impedance, a voltage, or a current of each of the secondary coils of the coil array.

119. The coil antenna of claim 114, wherein the secondary coil is a configurable air core coupled secondary coil comprising a plurality of configurable secondary coil sections, the configurable air core coupled secondary coil having a plurality of secondary coil configurations.

120. A method for interrogating and detecting a surgical instrument within a patient, the method comprising:

transmitting an energizing signal through a coil antenna operatively coupled to the signal generator, the antenna configured to receive a return signal transmitted by the RFID tag, the coil antenna comprising an array of coils;

receiving a return signal through the coil array, wherein the coil array is configured to generate a magnetic flux and direct at least one of a direction of the magnetic flux or an amplitude of the magnetic flux based on the energizing signal;

detecting a real part of the energizing signal through a real part matching detection network;

detecting a real part of the energizing signal through an imaginary part matching detection network;

tuning the primary coil to the second operating frequency based on the determination by a dynamic matching network.