Patent Description:
The detection and/or monitoring of analyte levels, such as glucose, ketones, lactate, oxygen, hemoglobin Al C, or the like, can be vitally important to the health of an individual having diabetes. Diabetics generally monitor their glucose levels to ensure that they are being maintained within a clinically safe range, and may also use this information to determine if and/or when insulin is needed to reduce glucose levels in their bodies or when additional glucose is needed to raise the level of glucose in their bodies.

Growing clinical data demonstrates a strong correlation between the frequency of glucose monitoring and glycemic control. Despite such correlation, many individuals diagnosed with a diabetic condition do not monitor their glucose levels as frequently as they should due to a combination of factors including convenience, testing discretion, pain associated with glucose testing, and cost.

For these and other reasons, needs exist for improved analyte monitoring systems, devices, and methods. <CIT> relates to sensors and systems associated with sensors. <CIT> relates to chemical and biological sensors. <CIT> relates to implantable analyte sensing systems.

Example embodiments of systems, devices, and methods are described herein for determining analyte levels by detecting a frequency characteristic of an on body device. In many embodiments this frequency characteristic is a resonance or resonant frequency. The on body device can include an analyte sensor adapted to sense the analyte level in the body of a wearer and translate the analyte level to a resonance frequency. A separate device can wirelessly transmit an electromagnetic field at a range of frequencies and determine the resonance frequency based on the response received from the on body device. These embodiments can simplify the design of on body devices and/or reduce the cost associated therewith, by allowing removal of components such as an on-board power supply, a processor, and the like. Numerous example embodiments of hardware and software for use in determining the resonance frequency and corresponding analyte level are provided. Also provided are numerous example embodiments of calibrating or characterizing the devices to increase the accuracy of the frequency and/or analyte determinations.

The details of the subject matter set forth herein, both as to its structure and operation, may be apparent by study of the accompanying figures, in which like reference numerals refer to like parts. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the subject matter. Moreover, all illustrations are intended to convey concepts, where relative sizes, shapes and other detailed attributes may be illustrated schematically rather than literally or precisely.

Before the present subject matter is described in detail, it is to be understood that this disclosure is not limited to the particular embodiments described, as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to to be limiting.

Generally, embodiments of the present disclosure are used with systems, devices, and methods for detecting at least one analyte, such as glucose, in a bodily fluid (e.g., subcutaneously within the interstitial fluid ("ISF") or blood, within the dermal fluid of the dermal layer, or otherwise). Accordingly, many embodiments include in vivo analyte sensors structurally configured so that at least a portion of the sensor is, or can be, positioned in the body of a user to obtain information about at least one analyte of the body. However, the embodiments disclosed herein can be used with in vivo analyte monitoring systems that incorporate in vitro capability, as well as purely in vitro or ex vivo analyte monitoring systems, including those systems that are entirely non-invasive.

In vivo analyte monitoring systems can include a sensor that, while positioned in vivo, makes contact with the bodily fluid of the user and senses one or more analyte levels contained therein. The sensor can be part of an on body device that resides on or in the body of the user. In addition to the sensor, the on body device can include circuitry that interfaces with the sensor, e.g., to convert a sensor measurement to a detectable radio frequency (RF) characteristic.

The on body device, and variations thereof, can also be referred to as a "sensor device," an "on-body electronics device," or a "sensor communication device", to name a few. As used herein, these terms are not limited to devices with in vivo analyte sensors, and encompass devices that have ex vivo sensors of other types, whether biometric (e.g., photonic analyte sensors, heart rate sensors, temperature sensors, etc.) or non-biometric. The term "on body" encompasses devices that reside directly on the body (e.g., attached to the skin), are wholly within the body (e.g., a fully implanted device), or are in close proximity to the body, such as a wearable device (e.g., glasses, watch, wristband or bracelet, neckband or necklace, etc.).

In vivo monitoring systems can also include one or more reader devices that read information about a sensed level from the on body device. These reader devices can process and/or display the sensed analyte information, in any number of forms, to the user. These devices, and variations thereof, can be referred to as "handheld reader devices," "readers," "handheld electronics" (or handhelds), "portable data processing" devices or units, "information receivers," "receiver" devices or units (or simply receivers), "relay" devices or units, or "remote" devices or units, to name a few.

In vivo analyte monitoring systems can be differentiated from "in vitro" systems that contact a biological sample outside of the body, and "ex vivo" systems that gain information about the body or a substance within the body but that do so while remaining wholly outside the body without extracting a biological sample from inside the body. In vitro systems can include a meter device that has a port for receiving an analyte test strip carrying a bodily fluid of the user, which can be analyzed to determine the user's analyte level. As mentioned, the embodiments described herein can be used with in vivo systems, ex vivo systems, in vitro systems, and combinations thereof.

The embodiments described herein can be used to monitor and/or process information regarding any number of one or more different analytes. Analytes that may be monitored include, but are not limited to, acetyl choline, amylase, bilirubin, cholesterol, chorionic gonadotropin, glycosylated hemoglobin (HbAlc), creatine kinase (e.g., CK-MB), creatine, creatinine, DNA, fructosamine, glucose, glucose derivatives, glutamine, growth hormones, hormones, ketones, ketone bodies, lactate, peroxide, prostate-specific antigen, prothrombin, RNA, thyroid stimulating hormone, and troponin. The concentration of drugs, such as, for example, antibiotics (e.g., gentamicin, vancomycin, and the like), digitoxin, digoxin, drugs of abuse, theophylline, and warfarin, may also be monitored. In embodiments that monitor more than one analyte, the analytes may be monitored at the same or different times.

<FIG> is a block diagram depicting an example embodiment of an in vivo analyte monitoring system <NUM> having an on body device <NUM> ("OBD") and a reader device <NUM> that can communicate with each other wirelessly over path <NUM>. OBD <NUM> can include a housing <NUM> encompassing sensor electronics <NUM> communicatively coupled with analyte sensor <NUM>, which is configured for in vivo analyte monitoring.

Analyte sensor <NUM> can be located wholly outside of housing <NUM> or partially outside of housing <NUM> (as shown in <FIG>), and can include one or more electrodes <NUM> (e.g., one, two, three, or more) for contact with the user's bodily tissue or fluid. In the embodiment of <FIG>, sensor <NUM> includes two electrodes: a working electrode <NUM>-<NUM> and a counter (or reference) electrode <NUM>-<NUM>. The chemical and mechanical construction of electrochemical analyte sensors, and operation thereof, is known to those of ordinary skill in the art. Some non-limiting examples of analyte sensors <NUM> that can be used with the embodiments of system <NUM> are described in the following references: <CIT>"), <CIT>"), <CIT>"), <CIT>"), <CIT>"), and <CIT>").

Electrochemical sensors <NUM> often require the application of a voltage to permit the electrochemical analyte sensing reaction to occur. This voltage is sometimes referred to as a bias or poise voltage. This bias voltage can be supplied to sensor <NUM> by an artificial power supply (e.g., a battery) external to the sensor itself. The power supply is included within OBD <NUM> along with other circuitry for managing power usage. However, these extra components add complexity and cost to the design and manufacture of OBD <NUM>, and also can impact the shelf life and wear duration of OBD <NUM>.

Embodiments of OBD <NUM> can operate without and optionally omit an artificial power supply (e.g., a battery) external to the sensor and any additional circuitry responsible for management (e.g., connection and disconnection) of the power supply. For example, certain types of electrochemical sensors <NUM> are capable of measuring analyte levels without a power supply external to the sensor (e.g., a discrete battery such as a button cell or coin cell battery, or others) that provides the bias voltage. Such sensors <NUM> are sometimes referred to as continually self-biased sensors or self-powered sensors, and examples of these sensors are described in <CIT>") and/or <CIT>. Continually self-biased sensors can, e.g., measure analyte levels with power spontaneously generated by the sensor itself upon insertion into the user's body using electrochemical reactants on the sensor's electrodes. Embodiments of OBD <NUM> that incorporate, for example, such a continually self-biased sensor can include no power supply external to the sensor, and this can in turn reduce the complexity and cost of OBD <NUM>, as well as improve the shelf life and wear duration of OBD <NUM>.

In some embodiments OBD <NUM> can include a power supply external to the sensor as well as transistor-based logic requiring an active bias for operation (e.g., an analog to digital converter, digital to analog converter, microcontroller, processor, digital signal processor, ASIC, and the like) such as that typically fabricated on a semiconductor chip and mounted on a printed circuit board. In these and other embodiments OBD <NUM> can include active communication circuitry (e.g., circuitry for generating transmissions spontaneously according to a wireless protocol such as Bluetooth, Bluetooth Low Energy, Wi-Fi, proprietary protocols (e.g., in a UHF band), and the like).

In other embodiments, it is desirable to minimize the cost and complexity of OBD <NUM>. In these other embodiments, a power supply can be omitted from OBD <NUM>, as well as some or all active circuitry. OBD <NUM> can include only passive transistor circuitry that does not require the presence of a continual bias for operation. Examples of transistor-based active circuitry that can be omitted include any and all of, e.g., an analog to digital converter, digital to analog converter, microcontroller, processor, digital signal processor, ASIC, volatile memory, circuitry for generating transmissions spontaneously (e.g., without prompting or power harvesting) according to a wireless protocol such as Bluetooth, Bluetooth Low Energy, Wi-Fi, proprietary protocols (e.g., in a UHF band), and the like. The omission of the power source and active circuitry can be the result of, in some examples, reliance upon power generated by a continually self-biased sensor to change a resonance frequency of variable frequency circuit <NUM>, the frequency of which can be detected passively by an actively transmitting interrogation device (such as reader device <NUM>). Other approaches not relying on a continually self-biased sensor can also be used. Also, in some embodiments OBD <NUM> can omit a power supply and instead utilize a charge storing device (e.g., a capacitor bank) that can store charge harvested from other sources, like from a wireless RF signal or inductive coupling (e.g., NFC) or from the sensor operation itself (e.g., as with a self-biased sensor).

An insertion device (not shown) can be used to position all or a portion of analyte sensor <NUM> through an external surface of the user's skin and into contact with the user's bodily fluid. In doing so, the insertion device can also position OBD <NUM> with adhesive patch <NUM> onto the skin. In other embodiments, the insertion device can position sensor <NUM> first, and then accompanying sensor electronics (e.g., a transmitter) can be coupled with sensor <NUM> afterwards, either manually or with the aid of a mechanical device. Examples of insertion devices are described in <CIT>, <CIT>, <CIT>, <CIT>, and <CIT>.

<FIG> is an illustrative view depicting an example embodiment of system <NUM> with OBD <NUM> mounted on the skin or body <NUM> of a human user with a portion of analyte sensor <NUM> inserted into the body (shown dashed). Housing <NUM> of OBD <NUM> can be coupled with a flexible patch <NUM>, which can have adhesive on an underside surface to adhesively couple OBD <NUM> to the user's body <NUM>. A topside surface of patch <NUM> can also include adhesive for coupling with housing <NUM>. Other forms of body attachment to the body may be used, in addition to or instead of adhesive. Analyte sensor <NUM> can extend from within housing <NUM>, through patch <NUM> and project away from housing <NUM>. A handheld or portable reader device <NUM> is shown in close proximity with OBD <NUM> for wireless communication over path <NUM>.

After insertion, analyte sensor <NUM> can generate and output a signal or stimulus that is based upon (e.g., in relation to, in proportion to, directly or indirectly corresponding to, or others) the level of the analyte in body <NUM> that is measured with the one or more electrodes <NUM>. This sensor output can be, e.g., an electrical voltage or current. Sensor electronics <NUM> can include a variable frequency circuit <NUM>. The sensor output is provided to circuit <NUM>, and a frequency characteristic of circuit <NUM> can be varied, modified, or changed automatically based upon (e.g., in relation to, in proportion to, directly or indirectly corresponding to, or others) a characteristic of the sensor output (e.g., a current magnitude and/or polarity, a voltage magnitude and/or polarity, or others).

In many embodiments, reader device <NUM> can generate an electromagnetic field at one or more frequencies and detect the frequency characteristic (e.g., a resonance frequency) of variable frequency circuit <NUM> of OBD <NUM> by inductively coupling with circuit <NUM>. To establish the inductive coupling, reader device <NUM> is, in many embodiments, placed in close proximity with OBD <NUM> (e.g., within a few feet or a few inches as depicted in <FIG>). While the range is dependent upon output power, receiver sensitivity and the antennas, in some embodiments, reader device <NUM> is positioned within <NUM> centimeters (cm) of OBD <NUM> to establish the inductive coupling. In other embodiments, the range of reader device <NUM> is shorter, for example, <NUM> or less. Reader device <NUM> can use the detected frequency characteristic to determine the measured analyte level and output (e.g., display) the analyte level to the user.

As mentioned above, OBD <NUM> can also be placed wholly within the body (e.g., a fully implanted device). In such embodiments, reader <NUM> can read the analyte level through the skin and/or other body tissue and fluid. Reader <NUM> can be manually held in close proximity to OBD <NUM> and/or can be held in place or worn over OBD <NUM> by a band or strap (e.g., armband, bracelet, neckband, waistband or belt, etc.) or other attachable device, such as an adhesive-based device.

Referring back to <FIG>, reader device <NUM> can communicate the measured analyte level to other devices within system <NUM>. For example, reader device <NUM> can be capable of wired, wireless, or combined communication with a computer system <NUM> (local or remote) over communication path (or link) <NUM>. In embodiments where path <NUM> is wireless, a Wi-Fi protocol, Bluetooth or Bluetooth Low Energy protocol, a near field communication (NFC) protocol, RFID protocol, proprietary protocol, or others can be used. Reader device can also communicate with or through a network <NUM> (e.g., such as a mobile telephony network, the internet or the cloud) over communication path (or link) <NUM>. Communication through network <NUM> can include communications sent to and from computer system <NUM> via communication link (or path) <NUM>, communications sent to and from trusted computer system <NUM> over communication path (or link) <NUM>, and/or communications to other devices. Communication paths <NUM>, <NUM>, <NUM>, and <NUM> can be wireless, wired, or both, can be uni-directional or bi-directional, and can be direct or indirect through intermediaries. In some embodiments, communication paths <NUM> and <NUM> can be the same path. Example embodiments of reader device <NUM> are described in further detail herein. Further example embodiments are described in <CIT> (the '<NUM> Publication). While only one reader <NUM> is shown, there can be one or more readers <NUM> that can interrogate device <NUM> and each reader <NUM> can communicate and share data with one another.

Computer system <NUM> may be another reader device <NUM>, a personal computer, a server terminal, a laptop computer, a tablet, or other suitable data processing device. Computer system <NUM> can be (or include) software for analyte data management and analysis and communication with the components in analyte monitoring system <NUM>. Computer system <NUM> can be used by the user or a medical professional to display and/or analyze the biometric data measured by OBD <NUM>. In some embodiments, OBD <NUM> can communicate the biometric data directly to computer system <NUM> without an intermediary such as reader device <NUM>, or indirectly using an internet connection (also optionally without first sending to reader device <NUM>). Operation and use of computer system <NUM> are further described in the '<NUM> Publication. Analyte monitoring system <NUM> can also be configured to operate with a data processing module (not shown), also as described in the '<NUM> Publication.

Trusted computer system <NUM> can be within the possession of the manufacturer or distributor of OBD <NUM>, either physically or virtually through a secured connection, and can be used to perform authentication of OBD <NUM>, to provide one or more calibration values for OBD <NUM>, used for secure storage of the user's biometric data, used for provision of software updates or revisions, used as a server that serves a data analytics program (e.g., accessible via a web browser) for performing analysis on the user's measured data, or other functions.

Examples embodiments of OBD <NUM> are capable of varying a frequency characteristic based upon a sensor measurement that corresponds to the user's analyte (e.g., glucose) level. The sensor measurement can be in the form of an electrical signal, such as a current or voltage. The electrical signal can vary with the analyte level in linear or non-linear fashion. For example, the sensor current can increase proportionally with the concentration of analyte in the bodily fluid being measured. Variable frequency circuit <NUM> can have a frequency characteristic that varies linearly or non-linearly with the electrical signal. This relationship can be direct (e.g., such that the value of the frequency characteristic increases as the electrical signal output from the sensor increases) or indirect (e.g., such that the value of the frequency characteristic increases as the electrical signal output from the sensor decreases).

<FIG> is a schematic diagram of an example embodiment of components of OBD <NUM>. Here, OBD <NUM> includes analyte sensor <NUM> electrically coupled with variable frequency circuit <NUM>. In this embodiment, analyte sensor <NUM> is a continually self-biased sensor that includes a working electrode <NUM>-<NUM> and a counter electrode <NUM>-<NUM> (the locations of which can be reversed). Power for OBD <NUM> is generated by the continually self-biased sensor <NUM> and no power supply external to sensor <NUM> is required (and can either be omitted or included depending upon the needs of the application).

Variable frequency circuit <NUM> can be configured in numerous ways. Here, circuit <NUM> is configured as an RLC circuit with a variable impedance. Circuit <NUM> includes a first resistor <NUM> coupled between electrodes <NUM>-<NUM> and <NUM>-<NUM>. A second resistor <NUM> is coupled between node <NUM> (between resistor <NUM> and electrode <NUM>-<NUM>) and node <NUM>. A capacitor <NUM> is coupled between node <NUM> and node <NUM>. An inductor <NUM> is coupled between node <NUM> and node <NUM> (indicated here as ground). The resistive value of resistors <NUM> and <NUM> can be derived from the presence of a discrete resistive component and/or the inherent resistance of conductive wires, traces, or components (or portions thereof) forming circuit <NUM>. Similarly, the capacitance value of capacitor <NUM> can be derived from the presence of a discrete component exhibiting capacitance (e.g., a capacitor) and/or the inherent capacitance of conductive wires, traces, or components (or portions thereof) forming circuit <NUM>. Inductor <NUM> can include an antenna configured to inductively couple with an interrogating transmission device (e.g., reader <NUM>). The antenna can be configured as, for example, a loop antenna (with one or more circular loops, polygonal loops, or combinations thereof). Other antenna configurations can also be used. The inductive value of inductor <NUM> is derived from the inductance of the antenna, and can also be derived from the presence of a discrete inductive component and/or the inherent inductance of conductive wires, traces, or components (or portions thereof) forming circuit <NUM>.

A variable impedance component <NUM> is coupled between node <NUM> and node <NUM>. Variable impedance component <NUM> has an impedance that changes with the electrical stimulus applied to it. In many embodiments, variable impedance component <NUM> is a variable capacitor having a capacitance that changes in response to a voltage applied across it. The variable capacitor can be, for example, a varactor diode as shown here with its cathode coupled to node <NUM> and its anode connected to node <NUM>. Varactor diodes can exhibit voltage dependent capacitance when operated in a reverse biased state. Other types of variable impedance components can also be used, such as other devices that exhibit variable capacitance and devices that exhibit variable inductance. Several examples include but are not limited to metal-oxide semiconductor field-effect transistors (MOSFETs) and bipolar transistors.

During operation, sensor <NUM> generates a current (Is) that flows through resistor <NUM>. The magnitude of the current is based upon the level of the analyte being measured in the wearer's body. A voltage is exhibited across resistor <NUM> based upon the magnitude of the current (V=IR). A corresponding voltage is applied across varactor diode <NUM>. The magnitude of the voltage applied across varactor diode <NUM> is proportional to that applied across resistor <NUM> but may differ depending on the resistance of resistor <NUM>. The capacitance exhibited by varactor diode <NUM> is dependent upon the voltage applied across diode <NUM>, which in turn is dependent upon the magnitude of the current generated by the sensor.

Circuit <NUM> exhibits a frequency characteristic, such as a resonance frequency, that is dependent upon the impedance of circuit <NUM>, as determined by the fixed capacitance of capacitor <NUM>, the fixed inductance of inductor <NUM>, and the variable capacitance of varactor diode <NUM>. As the capacitance of varactor diode <NUM> changes, so does the resonance frequency of circuit <NUM>. The resonance frequency of circuit <NUM> is given by the equation (<NUM>) below: <MAT> where f is the resonance frequency in hertz, L is the inductance of component <NUM> in henrys, and C is the total capacitance in farads. In <FIG>, the total capacitance is determined by the fixed capacitor <NUM> and the varying capacitance of diode <NUM>. A change in Is causes a change in the variable capacitance of diode <NUM>, which in turn changes the resonance frequency of the circuit.

<FIG> is a plot depicting examples of three different LC resonance frequency responses exhibited by circuit <NUM> with three different voltages applied across varactor diode <NUM>. Here, circuit <NUM> can exhibit a first resonance frequency response <NUM> having a center frequency f1 when a first voltage is applied across varactor diode <NUM>, a second resonance frequency response <NUM> having a center frequency f2 when a second voltage is applied across diode <NUM>, and a third resonance frequency response <NUM> having a center frequency f3 when a third voltage is applied across diode <NUM>. Each residence frequency response is dependent upon the current generated by sensor <NUM>, which in turn is dependent upon the level of analyte in the user's body. Thus, OBD <NUM> can exhibit a frequency response that is dependent upon the user's sensed analyte level. As mentioned, circuit <NUM> can be configured such that the resonance frequency response either increases or decreases with an increase to the user's analyte level.

The number and arrangement of components of OBD <NUM> can vary, depending on the desired frequency response. For example, in the embodiments described herein an additional capacitor can be added in parallel with varactor diode <NUM> (e.g., between node <NUM> and <NUM>). <FIG> is a schematic diagram of another example embodiment of OBD <NUM> where a second variable capacitor <NUM>-<NUM> (e.g., varactor diode) is used in place of capacitor <NUM> of <FIG>. In this embodiment the DC voltage at node <NUM> is also applied to varactor diode <NUM>-<NUM>, which increases the potential capacitance change of the circuit.

<FIG> is a schematic diagram of another example embodiment of OBD <NUM>. Like the embodiment of <FIG>, in this embodiment analyte sensor <NUM> can be a continually self-biased sensor that generates power for OBD <NUM> without a power supply external to sensor <NUM>. Here, capacitor <NUM> is in parallel with resistor <NUM> between nodes <NUM> and <NUM>. Resistor <NUM> is coupled between nodes <NUM> and <NUM>. A second capacitor <NUM> is coupled between nodes <NUM> and <NUM>. As with capacitor <NUM>, the capacitance value of capacitor <NUM> can be derived from the presence of a discrete component exhibiting capacitance (e.g., a capacitor) and/or the inherent capacitance of conductive wires, traces, or components forming circuit <NUM>.

Instead of a single varactor diode <NUM>, the embodiment of <FIG> includes multiple varactor diodes <NUM>-<NUM> through <NUM>-<NUM>. Varactor diodes <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM> are in parallel with each other with their cathodes connected to node <NUM> and their anodes connected to node <NUM> and form a first bank. Varactor diodes <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM> are also in parallel with each other and have their cathodes connected to node <NUM> and their anodes connected to node <NUM> and form a second bank. Inductor <NUM> in the form of a loop antenna is coupled between nodes <NUM> and <NUM>. The frequency range of this embodiment for a given voltage range is relatively higher than the embodiment of <FIG>. The resistance of the antenna <NUM> is preferably nearly zero or negligible, such that both banks of diodes <NUM> see the same or substantially the same voltage change, and can be conceptualized as one bank of parallel diodes <NUM>. A true parallel arrangement can also be used (e.g., with all six cathodes coupled with node <NUM> and all six anodes coupled with node <NUM>) provided a capacitor or other DC block is in series with inductor <NUM>. The component tolerance of diodes <NUM>-<NUM> through <NUM>-<NUM> is averaged, and the capacitance of the diodes within each bank are summed together. Thus, the range of capacitance change in circuit <NUM> can be increased as compared to an embodiment having one diode <NUM> and one fixed capacitor <NUM>.

Detection of the resonance frequency can be accomplished by use of an interrogation device, such as reader device <NUM>. <FIG> is a schematic view depicting an example embodiment of a variable frequency circuit <NUM> that can be present within reader device <NUM>. Circuit <NUM> can include a variable DC source <NUM> coupled with a variable impedance (e.g., RLC) circuit <NUM> that includes a resistor <NUM> coupled between the source and a node <NUM>, a variable impedance component <NUM> coupled between node <NUM> and node <NUM> (e.g., ground), a capacitor <NUM> coupled between node <NUM> and <NUM> and an inductor <NUM> coupled between node <NUM> and node <NUM>. In this embodiment, the variable impedance component <NUM> is a varactor diode with its cathode coupled to node <NUM> and its anode coupled to node <NUM>. Any arrangement of one or more varactor diodes <NUM> can be used in serial, parallel, or combination thereof.

The resistive value of resistor <NUM> can be derived from the presence of a discrete resistive component and/or the inherent resistance of conductive wires, traces, or components (or portions thereof) forming circuit <NUM>. Similarly, the capacitance value of capacitor <NUM> can be derived from the presence of a discrete component exhibiting capacitance (e.g., a capacitor) and/or the inherent capacitance of conductive wires, traces, or components (or portions thereof) forming circuit <NUM>. Inductor <NUM> can include an antenna configured to inductively couple with circuit <NUM>. The antenna can be configured as, for example, a loop antenna (with one or more circular loops, polygonal loops, or combinations thereof). Other antenna configurations can also be used. The inductive value of inductor <NUM> is derived from the inductance of the antenna, and can also be derived from the presence of a discrete inductive component and/or the inherent inductance of conductive wires, traces, or components (or portions thereof) forming circuit <NUM>.

Application of a DC voltage from source <NUM> to circuit <NUM> will apply a voltage across varactor diode <NUM> and cause it to assume a capacitive value. That capacitive value will determine the impedance and a corresponding resonance frequency of circuit <NUM>. When variable frequency circuit <NUM> is in proximity with variable frequency circuit <NUM>, application of an RF frequency or set of RF frequencies to circuit <NUM> (such as with an RF generator) can cause circuits <NUM> and <NUM> to inductively couple where inductance of circuit <NUM> is reflected into circuit <NUM>. The inductive coupling can allow the resonance frequency of circuit <NUM> to be detected as will be described in more detail below.

The control voltage (VC), e.g., the voltage output from DC source <NUM>, can be adjusted to cause the impedance and resonance frequency of circuit <NUM> to change. <FIG> is a plot of an example where VC increases continuously over time (t) at a constant rate, which has the effect of changing the resonance frequency of circuit <NUM> at a similar rate. <FIG> is a plot of another example where VC is increased over time (t), but here the increase occurs in a stepped fashion. This causes the resonance frequency of circuit <NUM> to jump from one value and settle on another. <FIG> is plot of an example frequency response of circuit <NUM> to the stepped voltages depicted in <FIG>. In this embodiment, voltage <NUM> results in frequency response <NUM>, voltage <NUM> results in frequency response <NUM>, voltage <NUM> results in frequency response <NUM>, voltage <NUM> results in frequency response <NUM>, and voltage <NUM> results in frequency response <NUM>.

<FIG> is a block diagram depicting an example embodiment of reader device <NUM> configured to act as an interrogator of circuit <NUM>. Reader device <NUM> can be a dedicated reader device (configured for communication other than using mobile telephony) or can be or can include a mobile telephone including, but not limited to, a Wi-Fi or internet enabled smart phone, tablet, or personal digital assistant (PDA). Examples of smart phones can include those mobile phones based on a Windows® operating system, Android™ operating system, iPhone® operating system, Palm® WebOS™, Blackberry® operating system, or Symbian® operating system, with data network connectivity functionality for data communication over an internet connection and/or a local area network (LAN). Reader device <NUM> can be configured as a modular attachment to a mobile telephone that can, e.g., plug into a wired port of the mobile telephone or can be in communication with the telephone via a wireless connection (e.g., Bluetooth, Wi-Fi, etc.) either directly or indirectly through a relay device. Such a configuration can allow a commercially available mobile telephone to be converted into a device capable of interrogating circuit <NUM>. Reader device <NUM> can also be configured as a mobile smart wearable electronics assembly, such as an optical assembly that is worn over or adjacent to the user's eye (e.g., a smart glass or smart glasses, such as Google glasses) or devices that are worn around or in the proximity of the user's wrist (e.g., a watch, etc.), neck (e.g., a necklace, etc.), head (e.g., a headband, hat, etc.), chest, or the like.

Here, reader <NUM> includes processing circuitry <NUM> with memory <NUM>, optional RF communication circuitry <NUM> and antenna <NUM>, display <NUM>, user interface <NUM>, power management circuitry <NUM>, power supply <NUM>, frequency generator <NUM>, buffer <NUM>, variable impedance circuit <NUM>, matching circuitry <NUM> and <NUM>, receiver <NUM>, and antenna <NUM>. <FIG> is an abbreviated representation of the hardware and functionality that can reside within reader <NUM> and those of ordinary skill in the art will readily recognize that other hardware and functionality (e.g., codecs, drivers, glue logic, clocks) can also be included. Some connections between the components of reader device <NUM> are shown to facilitate understanding of the operation of the circuitry, however reader device <NUM> will typically have a volume of interconnections too numerous for depiction here and thus a number of interconnections are omitted for clarity.

Processing circuitry <NUM> can include one or more processors, microprocessors, controllers, and/or microcontrollers, each of which can be a discrete chip or distributed amongst (and a portion of) a number of different chips. Processing circuitry <NUM> can include digital signal processor <NUM>, which can be implemented in hardware and/or software of processing circuitry <NUM>. In some embodiments, DSP <NUM> is a discrete semiconductor chip. Processing circuitry <NUM> can be communicatively coupled with the other components of <FIG>. Processing circuitry <NUM> can execute software instructions stored on memory <NUM> that cause processing circuitry <NUM> to take a host of different actions and control the other components in reader <NUM>.

Processing circuitry <NUM> can be coupled with variable impedance circuit <NUM> at node <NUM>. In this embodiment, variable impedance circuit <NUM> includes a bank of eight varactor diodes <NUM>-<NUM> through <NUM>-<NUM>, each having their cathodes coupled with node <NUM>. The anodes of diodes <NUM>-<NUM> through <NUM>-<NUM> are coupled with node <NUM> and the anodes of diodes <NUM>-<NUM> through <NUM>-<NUM> are coupled with node <NUM>. Other arrangements of varactor diodes <NUM> can also be used. Processing circuitry <NUM> can control the adjustable control voltage (VC), and can include circuitry for outputting VC to node <NUM> (with power supply <NUM> acting as the DC source <NUM> of <FIG>) to control the capacitance of diodes <NUM>. Inductor <NUM> is in the form of a loop antenna <NUM> that provides the inductance (or substantially all inductance) of circuit <NUM>. As with the embodiment of <FIG>, one or more other resistive, capacitive, and/or inductive components can be included, but are not shown here for clarity.

Frequency generator <NUM> includes circuitry that generates the sweeping RF frequency applied to antenna <NUM>. RC or LC oscillator circuits combined with crystal controlled phase locked loop (PLL) circuits can be used to generate the sweeping RF frequency. This sweeping RF frequency can be used for detection of circuit <NUM>'s resonance frequency. The output from frequency generator <NUM> can be passed through a buffer or gain circuit <NUM> that can adjust the gain of the output signal, which is then passed through a matching circuit <NUM> for matching impedance. The RF frequency signal is then propagated or transmitted from antenna <NUM>, which in this embodiment is configured as a loop antenna. Loop antenna <NUM> can have one or more circular loops, polygonal loops, or combinations thereof. Other antenna configurations can also be used.

A second matching circuit <NUM> is located between node <NUM> and a receiver <NUM>. Receiver <NUM> can capture the signal received at antenna <NUM> and output the signal to processing circuitry <NUM>, which can then use DSP <NUM> to analyze whether the resonance frequency of circuit <NUM> has been detected. Example embodiments of detecting the resonance frequency are described in more detail below.

Processing circuitry <NUM> can also perform other software and/or hardware routines. For example, processing circuitry <NUM> can interface with communication circuitry <NUM> and perform analog-to-digital conversions, encoding and decoding, other digital signal processing and other functions that facilitate the conversion of voice, video, and data signals into a format (e.g., in-phase and quadrature) suitable for provision to communication circuitry <NUM>, and can cause communication circuitry <NUM> to transmit the RF signals wirelessly over links <NUM> and/or <NUM>.

Communication circuitry <NUM> can be implemented as one or more chips and/or components (e.g., transmitter, receiver, transceiver, and/or other communication circuitry) that perform wireless communications over links <NUM> and/or <NUM> under the appropriate protocol (e.g., Wi-Fi, Bluetooth, Bluetooth Low Energy, Near Field Communication (NFC), Radio Frequency Identification (RFID), proprietary protocols, and others. One or more other antennas <NUM> can be included with communication circuitry <NUM> as needed to operate with the various protocols and circuits. In some embodiments, communication circuitry <NUM> can share antenna <NUM> for transmission over links <NUM>, <NUM>, and/or <NUM>. Processing circuitry <NUM> can also interface with communication circuitry <NUM> to perform the reverse functions necessary to receive a wireless transmission and convert it into digital data, voice, and video. RF communication circuitry <NUM> can include a transmitter and a receiver (e.g., integrated as a transceiver) and associated encoder logic. Reader <NUM> can also include communication circuitry and interfaces for wired communication (e.g., a USB port, etc.) as well as circuitry for determining the geographic position of reader device <NUM> (e.g., global positioning system (GPS) hardware).

Processing circuitry <NUM> can also be adapted to execute the operating system and any software applications that reside on reader device <NUM>, process video and graphics, and perform those other functions not related to the processing of communications transmitted and received. Any number of applications (also known as "user interface applications") can be executed by processing circuitry <NUM> on a dedicated or mobile phone reader device <NUM> at any one time, and may include one or more applications that are related to a diabetes monitoring regime, in addition to the other commonly used applications, e.g., smart phone apps that are unrelated to such a regime like email, calendar, weather, sports, games, etc..

Memory <NUM> can be shared by one or more of the various functional units present within reader device <NUM>, or can be distributed amongst two or more of them (e.g., as separate memories present within different chips). Memory <NUM> can also be a separate chip of its own. Memory <NUM> is non-transitory, and can be volatile (e.g., RAM, etc.) and/or non-volatile memory (e.g., ROM, flash memory, F-RAM, etc.).

Power supply <NUM> can include one or more batteries, which can be rechargeable or single-use disposable batteries. Power management circuitry <NUM> can regulate battery charging and power supply monitoring, boost power, perform DC conversions, and the like.

Display <NUM> can be a non-interactive display or touchscreen display, and can output information to the user and/or accept an input from the user. One or more optional user interface (UI) components <NUM> can be present, such as one or more of a button, actuator, touch sensitive switch, capacitive switch, pressure sensitive switch, jog wheel or the like, to input data, commands, or otherwise control the operation of reader device <NUM>. In certain embodiments, display <NUM> and UI component <NUM> may be integrated into a single component, for example, where the display can detect the presence and location of a physical contact touch upon the display, such as a touch screen user interface. In certain embodiments, UI component <NUM> may include a microphone and reader device <NUM> may include software configured to analyze audio input received from the microphone, such that functions and operation of the reader device <NUM> may be controlled by voice commands. In certain embodiments, an output component of reader device <NUM> includes a speaker (not shown) for outputting information as audible signals.

Reader device <NUM> may also include an integrated or attachable in vitro glucose meter, including an in vitro test strip port (not shown) to receive an in vitro glucose test strip for performing in vitro blood glucose measurements.

Reader device <NUM> can display the measured biometric data wirelessly received from OBD <NUM> and can also be configured to output alarms, alert notifications, glucose values, etc., which may be visual, audible, tactile, or any combination thereof. Further details and other display embodiments can be found in, e.g.,<CIT>, which is incorporated herein by reference in its entirety for all purposes.

Reader device <NUM> can be integrated with a drug (e.g., insulin, etc.) delivery device such that they, e.g., share a common housing, or can be combined with a drug delivery device, e.g., such that one of the two devices is plugged into the other or wirelessly linked to the other. Examples of such drug delivery devices can include medication pumps having a cannula that remains in the body to allow infusion over a multi-hour or multi-day period (e.g., wearable pumps for the delivery of basal and bolus insulin). Reader device <NUM>, when combined with a medication pump, can include a reservoir to store the drug, a pump connectable to transfer tubing, and an infusion cannula. The pump can force the drug from the reservoir, through the tubing and into the diabetic's body by way of the cannula inserted therein. Other examples of drug delivery devices that can be included with (or integrated with) reader device <NUM> include portable injection devices that pierce the skin only for each delivery and are subsequently removed (e.g., insulin pens). A reader device <NUM>, when combined with a portable injection device, can include an injection needle, a cartridge for carrying the drug, an interface for controlling the amount of drug to be delivered, and an actuator to cause injection to occur. The device can be used repeatedly until the drug is exhausted, at which point the combined device can be discarded, or the cartridge can be replaced with a new one, at which point the combined device can be reused repeatedly. The needle can be replaced after each injection.

The combined device can function as part of a closed-loop system (e.g., an artificial pancreas system requiring no user intervention to operate) or semi-closed loop system (e.g., an insulin loop system requiring seldom user intervention to operate, such as to confirm changes in dose). For example, the diabetic's analyte level can be monitored in a repeated automatic fashion by interrogation of OBD <NUM>, and the appropriate drug dosage to control the diabetic's analyte level can be automatically determined and subsequently delivered to the diabetic's body. Software instructions for controlling the pump and the amount of insulin delivered can be stored in the memory of reader device <NUM> and executed by processing circuitry <NUM>. These instructions can also cause calculation of drug delivery amounts and durations (e.g., a bolus infusion and/or a basal infusion profile) based on the analyte level measurements obtained from OBD <NUM>.

One example embodiment of a searching process is described with respect to <FIG>. <FIG> is a schematic view depicting an example embodiment where interrogating circuit <NUM> is in close proximity for inductive coupling to variable frequency circuit <NUM> of OBD <NUM>. <FIG> is a plot of frequency versus time depicting an example of frequencies produced by frequency generator <NUM> for transmittal or propagation from antenna <NUM> of circuit <NUM>. Here, the sweep frequency (fS) (which can be a discrete frequency or a range of frequencies) increases continuously from a first frequency or range of frequencies (f1) to a second frequency or range of frequencies (f2). In other embodiments, fS can be varied in a stepped fashion, either moving from one adjacent step to the next or by hopping frequencies such that certain frequencies are skipped.

<FIG> is a plot of voltage (V) versus frequency (f) with various examples of frequency responses <NUM>-<NUM> captured by receiver <NUM> of reader <NUM>. Reader <NUM> can be programmed to detect the resonance frequency of circuit <NUM> by varying both the sweep frequency (fS) and the control voltage (VC). Variation of the control voltage changes the impedance of circuit <NUM> and varies range of frequencies that receiver <NUM> captures. For example, a first control voltage can result is receipt of frequencies in the range fA-fB, where a second control voltage can result in receipt of frequencies fC-fD. These frequency ranges can be overlapping or non-overlapping and can be referred to as receiving windows. <FIG> depicts examples of five responses captured with receiver <NUM> tuned, at different times, to five different receiving windows: response <NUM> in receiving window <NUM>, response <NUM> in receiving window <NUM>, response <NUM> in receiving window <NUM>, response <NUM> in receiving window <NUM>, response <NUM> in receiving window <NUM>. Each receiving window <NUM>-<NUM> can be overlapping and can vary in size or width (i.e., the range of frequencies within the window). Receiving window width can be determined by the measurement resolution of the system. Processor <NUM> can be programmed to cause generation of a particular range of sweep frequencies for each window. The size of each window can be the same or different depending on the position of the receiving window within the overall frequency band in which the system is operating.

With receiver <NUM> tuned to a particular receiving window, a range of transmission frequencies can be varied or swept (e.g., such as the example sweep from f1-f2 shown in <FIG>). As the transmission frequencies are swept, one or more frequency responses (e.g., responses <NUM>-<NUM>) will be generated sequentially and captured by receiver <NUM> for each receiving window. Receiver <NUM> can output the captured response or data indicative of the response for analysis by DSP <NUM>. The size and shape of the frequency responses will vary depending on the degree of inductive coupling that is present between circuits <NUM> and <NUM>.

A low degree of inductive coupling can result in a single peak such as depicted in responses <NUM> and <NUM>, which are relatively far from the resonance frequency fR of circuit <NUM>. As the receiving window more closely approximates fR, a higher degree of inductive coupling occurs and the response begins to shift from the single peak form to a double peak form like that depicted in responses <NUM>, <NUM>, and <NUM>. This type of behavior is similar to that of a double tuned amplifier, where the response is critically coupled when two peaks begin to form, and the peaks become more pronounced and further apart as the coupling coefficient (k) grows (e.g., an overcoupled state).

Response <NUM> is a double-peak response with peaks at different heights or magnitudes. Here the lower frequency peak has a greater magnitude than the higher frequency peak. Conversely, response <NUM> is a double-peak response with a reverse shape where the lower frequency peak has a lesser magnitude than the higher frequency peak. Response <NUM> is a double-peak response where the peaks are of the same or substantially the same height (magnitude), which can be indicative of centering around fR. Reader <NUM> can, in some embodiments, monitor for and detect the occurrence of the equal height response <NUM>, and use this response to determine fR. <FIG> is a plot of voltage versus time depicting examples of the output of receiver <NUM> overlaid in the time domain. Output signature <NUM> corresponds to response <NUM> of <FIG>. Once fR is determined, processing circuitry <NUM> can execute programming to determine the corresponding analyte level of the user, which can then be output to the user on display <NUM> and/or transmitted to another device via communication circuity <NUM>.

<FIG> is a plot of voltage versus frequency with an example of a double peak response <NUM> suitable for use in determining the resonance (or resonant) frequency (fR) of circuit <NUM>. When peaks <NUM> and <NUM> are the same or substantially the same height they will also be symmetric, or substantially symmetric, and a trough <NUM> (or inverted peak) will be present between them. If a readily identifiable V value for the minimum of trough <NUM> exists, then that value can be used as the resonance frequency (fR). In some cases, trough <NUM> may have multiple frequencies at the minimum value (e.g., trough <NUM> has a flat bottom). To account for this, DSP <NUM> can divide the distance between the maximum Z value of the two symmetric peaks <NUM> and <NUM> and the minimum V value of trough <NUM> between the peaks. Response <NUM> will have this V value at four frequencies. The maximum and minimum of the four frequencies can be ignored and the two remaining frequencies (the two middlemost frequencies) fX and fY can be identified. The average of fX and fY is the value half way between them and corresponds (or closely approximates) the resonance frequency fR according to (<NUM>) below: <MAT> This approach can determine fR with certainty as the slope of response <NUM> in the regions of fX and fY is significant and thus allows fX and fY to be readily ascertained.

Determination of the corresponding analyte level from the detected resonance frequency can be accomplished in various ways. The following examples make reference to numerical values for ease of description of the underlying concepts. These numerical values are examples only and in no way limit the subject matter to only such values. Actual implementations can and will vary.

<FIG> is an example of a correlation <NUM> between glucose level and resonance frequency for the embodiment of <FIG>, where the example sensor has a resonance frequency of <NUM> Megahertz (Mhz) at a glucose level of zero mmol/L and a value of <NUM> at a glucose level of <NUM> mmol/L.

In some embodiments, correlation <NUM> can be stored in memory <NUM> of reader device <NUM> in the form of a look-up table, array, or other data structure that maps many different resonance frequencies to their corresponding glucose concentrations. Processing circuitry <NUM> can cross-reference the detected resonance frequency and determine the corresponding glucose concentration. In other embodiments, correlation <NUM> can be coded in the software instructions executed by processing circuity <NUM> in the form of an algorithm. For example, if correlation <NUM> is linear or substantially linear, the algorithm can be in the form of (fR-b)/s =g, where fR is the measured resonance frequency, b is a predetermined value corresponding to the frequency offset measured at the y-axis intercept, s is a predetermined value of the slope of the linear correlation, and g is the corresponding glucose level. Processing circuitry <NUM> can determine the glucose concentration by inputting the measured resonance frequency into this formula. Non-linear correlations can utilize more complex polynomial relationships, or can be approximated with different linear relationships for various regions.

Correlation <NUM>, whether in the form of a data structure or algorithm, can be obtained theoretically, experimentally, or a combination thereof. In some embodiments it is desirable to characterize each OBD <NUM>, e.g., during assembly and/or final testing by the manufacturer. Each OBD <NUM> can be subjected to a in vitro test by exposing sensor <NUM> to one or more test solutions having various concentrations of analyte (e.g., glucose), while at the same time measuring the resulting resonance frequency. For example, sensor <NUM> can be tested in solution with zero glucose, and then subjected to one or more additional exposures to solutions having other differing non-zero glucose concentrations. In some embodiments the sensor <NUM> may only be exposed to test solution once (either zero or non-zero glucose concentration). This process can be used to generate the look-up data structure directly (e.g., if many different glucose concentration tests are performed), or can be used to obtain a subset of correlation points, and a data regression can be performed to fit a linear or non-linear line or curve from which the lookup data structure and/or algorithm (e.g., values for slope and intercept) can be obtained.

In some embodiments, a current can be applied to variable frequency circuit <NUM> to simulate that which would be applied by sensor <NUM> (Is) at various glucose concentrations, and the resulting resonance frequency can be detected and correlation <NUM> generated. In other embodiments, measurements of the resistance, capacitance, and/or inductance of the components of OBD <NUM> can be obtained and used algorithmically determine the frequency correlation. For example, the impedance (e.g., capacitance) to voltage correlation of the one or more components <NUM> can be measured or characterized and used to determine the frequency correlation. Such approaches permit characterization of circuit <NUM> without actually exposing sensor <NUM> to glucose solution during the testing process. In such cases the resonance frequency when sensor <NUM> is dry (as described below) can be used for correlation of the sensor <NUM> at a zero analyte level. In other embodiments, sensor <NUM> to can be tested when dry and then one or more times in test solution (e.g., with zero or non-zero analyte levels). This process can be used to generate the look-up data structure directly (e.g., if many different current tests are performed), or can be used to obtain a subset of correlation points, and a data regression can be performed to fit a linear or non-linear line or curve from which the look-up data structure and/or algorithm (e.g., values for slope and intercept) can be obtained.

In embodiments where sensor <NUM> is not exposed to test solution, a second correlation can be utilized to convert sensor current (IS) to the glucose concentration (or to apply calibration to adjust the determined glucose concentration to a calibrated value). The process of correlating sensor measurements to analyte values is well known to those of ordinary skill in the art, and can be accomplished by use of look-up data structures and/or algorithms with or without sensor calibration values.

In still other embodiments, a universal correlation can be used that applies to all OBDs <NUM> and readers <NUM>. For example, in systems <NUM> where inter-device impedance variations are minimal, a universal correlation can be derived and used by all devices in determining analyte level from a measured resonance frequency.

In some embodiments, a universal correlation can be used and modified by calibration values specific to a particular OBD <NUM>. <FIG> is a plot of simulated sensor current versus resonance frequency. A universal linear correlation is given by trace <NUM>, and a linear correlation measured for a particular OBD <NUM> is given by trace <NUM>. The offset for universal correlation <NUM> (OU) differs from that of the actual measured correlation <NUM> (OA), and the slope differs for both correlations <NUM> and <NUM> as well. These differences can be quantified and stored as frequency calibration values (offset difference and/or slope difference) particular to that OBD <NUM>. Reader device <NUM> can utilize these frequency calibration values to adjust the determined resonance frequency measurement, or inferred sensor measurement (e.g., Is) accordingly.

Correlation <NUM> and/or frequency calibration values specific to a particular OBD <NUM> (OBD-specific data) can be made available to reader device <NUM> (or other device) in a number of different ways. The OBD-specific data can be transferred to reader device <NUM> in the form of the actual value(s) or in the form of a code that corresponds to the actual value(s). The code can be translated to the corresponding value by use of a lookup data structure or algorithm (e.g., stored in memory <NUM> of reader <NUM>). If OBD <NUM> includes non-transitory non-volatile memory, then the OBD-specific data can be stored in that memory and communicated to reader device over link <NUM> as part of any communication between OBD <NUM> and reader device <NUM>. For example, upon activation of OBD <NUM> by reader device <NUM>, or in the process of detecting the resonance frequency, or immediately after the resonance frequency is detected, OBD <NUM> can provide the OBD-specific data (either automatically or in response to a specific request for such).

In other embodiments, the OBD-specific data can instead be printed on the packaging (or packaging inserts) of OBD <NUM> or directly on the housing of OBD <NUM>. In these embodiments, the user can read the OBD-specific data and manually input it into reader <NUM>, or alternatively use reader <NUM> to automatically obtain the OBD-specific data from the packaging or housing for OBD <NUM> (e.g., by optically scanning a barcode). In other embodiments, the calibration code can be readable from a calibration code module that can be plugged into reader <NUM>. In still other embodiments, an NFC scannable device (e.g., a tag) can be placed on the packaging, or on or within OBD <NUM>, and that NFC scannable device can be scanned by reader <NUM> to obtain the calibration code. The NFC scannable device can also include a unique sensor ID to identify the sensor and start a wear duration clock (e.g., if the sensor has a limited lifespan) so that reader <NUM> will know when the sensor expires.

In other embodiments, the OBD-specific data can be uploaded to, e.g., trusted computer system <NUM>, and then subsequently retrieved or downloaded by reader device <NUM> over network <NUM>. In these embodiments, reader device <NUM> can obtain an identifier for OBD <NUM> (either by scanning OBD <NUM> or by manually or automatically obtaining the identifier, etc.) and transmit it to trusted computer system <NUM> which can then locate the OBD-specific data and communicate it back to reader device <NUM> over a network <NUM>.

All of the foregoing embodiments pertaining to characterization of circuitry can likewise be applied to reader <NUM>, such as circuit <NUM> of reader <NUM>. For example, if component variation causes a particular reader <NUM> to measure a resonance frequency to be slightly higher than the actual value, such can be quantified through characterization (e.g., testing) of reader <NUM>. Such information (e.g., in the form of a +/- frequency offset and/or slope) can be stored in memory <NUM> of reader <NUM> and used to calibrate reader <NUM> to more accurately determine the measured resonance frequency and/or analyte level.

Referring back to the embodiment of <FIG>, a process of determining the resonance frequencies with non-limiting example values is provided. In this example resistor <NUM> is <NUM> Megaohms (MΩ) and inductor <NUM> is <NUM> nanoHenries (nH). The value for resistor <NUM> is between <NUM> and <NUM> MΩ (e.g., <NUM> MΩ in this example) and is used to block the AC signal from circuit <NUM> to resistor <NUM>. The DC voltage at nodes <NUM> and <NUM> can be assumed to be the same with negligible current through resistor <NUM>. The total capacitance of the varactor diodes <NUM>-<NUM> and <NUM>-<NUM> with no current (Is) is <NUM> picoFarads (pF) (when sensor <NUM> is dry) and <NUM> pF (when sensor <NUM> is wet). Generally, a small amount of AC leakage exists when sensor <NUM> is wet, and no AC leakage exists when sensor <NUM> is dry, which accounts for the difference in capacitance values between the two states, although in both cases there is no DC current output from sensor <NUM>. At a glucose concentration of <NUM> mmol/L, the total capacitance is <NUM> pF. A current of 30nA will flow through the <NUM> MΩ resistor and place a voltage of <NUM> mV across diode <NUM>. In this embodiment, sensor <NUM> has an output range of <NUM>-<NUM> nanoAmps (nA) for a glucose range of <NUM>-<NUM> mmol/L with a <NUM>:<NUM> correlation. Using equation (<NUM>) described with respect to <FIG>, circuit <NUM> will have a resonance frequency of <NUM> (wet) with no current and <NUM> with <NUM> nA of current. All of the values stated here are merely examples and those of ordinary skill in the art will understand that such values will vary depending on the implementation. Resonance frequencies for other sensor currents can also be determined based on <FIG>.

Determining a glucose result on reader <NUM> from matching the resonance frequency can be the reverse process. For example, reader circuit <NUM> can be calibrated like sensor circuit <NUM> (e.g., with a slope and/or intercept) to define the correlation so that the change in capacitance from the matched frequency to the no load frequency can be used to determine the equivalent applied voltage to varactor diode <NUM>. The voltage divided by the resistance of resistor <NUM> gives the equivalent current (Is) from sensor <NUM>. The glucose value can then be algorithmically calculated to compensate for the sensor response.

Various techniques can be employed to determine the resonance frequency. The process of holding reader device <NUM> in proximity with OBD <NUM> and searching for the resonance frequency can be referred to as a scan. <FIG> is a flow diagram depicting an example embodiment of a method of scanning <NUM>. At <NUM>, a first receiving window is set, e.g., by processing circuitry <NUM> causing application of a constant voltage (VC) to variable impedance circuit <NUM> of reader device <NUM>. At <NUM>, a range of frequencies fS can be propagated or swept by reader device <NUM> using frequency generator <NUM>, and the response can be captured (e.g., with receiver <NUM>). At <NUM>, it is determined by processing circuitry <NUM> whether the resonance frequency (fR) was detected in the captured response. If so, then at <NUM> processing circuitry <NUM> of reader device <NUM> can use the detected fR to determine the corresponding analyte level (e.g., by use of a proprietary algorithm that applies the correlation value, or otherwise), which can then be output to the user (e.g., on display <NUM>). If fR is not detected, then at <NUM> the constant voltage (VC) can be adjusted to set a new receiving window and, at <NUM>, a range of frequencies fS can be swept by reader device <NUM>. This range of frequencies can be the same or different from those frequencies swept at <NUM>, as will be described below. The method can then revert to the determination at <NUM>, and the process can repeat until the resonance frequency fR is detected. Although not shown, if all receiving windows are cycled through without detecting the resonance frequency fR, or the method otherwise fails, then processing circuitry <NUM> can generate an indication of error or failure that can then be output to the user (e.g., on display <NUM>).

<FIG> is a flow diagram depicting another example embodiment of a method <NUM> of scanning. In this embodiment, if the resonance frequency fR is detected at <NUM>, then the value of the resonance frequency can be more precisely determined by an optional refined detection <NUM>. For example, once fR is detected at <NUM> using a particular receiving window and VC (e.g., <NUM> volts), the VC corresponding to that receiving window can be adjusted by increments less than those used to index between receiving windows. For example, if the first round of indexing occurred at VC increments of <NUM> volts, then upon detecting fR, VC can be adjusted by smaller increments (e.g., <NUM> volts), each time sweeping at least the corresponding fS frequencies to more accurately determine or refine the value of fR. If the detected resonance frequency fR is determined to be on the lower frequency side of the receiving window, then VC can be lowered in smaller incremental steps until fR is fully matched. Once fR is identified, reader device <NUM> can determine the corresponding analyte level at <NUM> and then output to the user if desired.

Three sets of example embodiments of setting the receiving window and sweeping frequencies will now be described, each of which can be implemented with method <NUM> of <FIG>. These embodiments will be described with reference to the example frequency vs time plots of <FIG>, where the frequencies being swept and the receiving window are indicated by reference numerals <NUM> and <NUM>, respectively. These embodiments are merely examples and are not exhaustive of every manner of performing a scan. While these embodiments are described with receiving windows that are adjacent but non-overlapping, those of ordinary skill in the art will understand that each adjacent receiving window can also partially overlap. Also, these embodiments are described with sweeps that increase in frequency over time (e.g., from fmin to fmax), but these embodiments can be similarly implemented with sweeps that decrease in frequency over time (e.g., from fmax to fmin).

In a first set of embodiments, described with reference to <FIG>, each receiving window <NUM> has a bandwidth that is less than the overall range of frequencies in which the resonance frequency can be detected (e.g., fmin through fmax). Reader device <NUM> (e.g., processing circuitry <NUM>) can be programmed to initially sweep the full frequency (fS) range (fmin - fmax) of OBD <NUM> while a constant VC (e.g., <NUM> volts) is applied to circuit <NUM> to set a specific receiving window <NUM> (e.g., fmin-fA). This can entail sweeping fS frequencies outside of receiving window <NUM>. If the resonance frequency (fR) is not detected, processing circuitry <NUM> can adjust VC (e.g., <NUM> volts) to move or index to a new value and thus a new receiving window <NUM> (e.g., fA-fB) and, then reader <NUM> can sweep the full range of fS again. This process can continue iteratively until fR is detected and identified (e.g., a double peak response <NUM>). Although not required, preferably the process is fast enough to occur within a single scan of OBD <NUM> (e.g., less than <NUM> or <NUM> seconds).

In a second set of embodiments, after a first sweep like that of <FIG>, reader <NUM> can index to a new (second) receiving window <NUM> (e.g., fB-fC) and sweep a range of fS less than the full range of fS. For example, the second sweep can begin at the lowest frequency in the current receiving window (e.g., fA) and proceed to fmax as depicted in <FIG>. The third sweep can then begin at a still higher frequency (e.g., fB) and proceed to fmax as depicted in <FIG>. Alternatively, in opposite fashion, each sweep can begin at fmin and proceed to the highest frequency within the active receiving window. In another variation, the sweep frequencies can be commensurate with each receiving window such that each sweep includes only those frequencies within the current receiving window, as depicted in the sequence of <FIG>. For example, if the first receiving window was fmin to fA (<FIG>), then upon indexing to a second window at fA-fB, the fS sweep can begin at fA and proceed to fB (<FIG>), and then upon indexing to a third window at fB-fC, the fS sweep can begin at fB and proceed to fC (<FIG>). Thus, upon indexing, the fS sweep would not repeat frequencies already examined with the prior receiving window. Further, the fS sweep can be stopped once it is determined that the frequencies within the particular receiving window have already been transmitted (e.g., fB is reached). This process can be iteratively repeated until fR is identified. Thus, in some embodiments, a single sweep of fmin to fmax can be performed with the receiving window being indexed each time fS reaches the beginning of the next receiving window.

In a third set of embodiments, each of the first and second set of embodiments can be practiced but reader device <NUM> can be programmed to use, as the first receiving window, the same receiving window in which fR was detected the last time a scan was performed. Thus, if the measured analyte has not changed significantly the scan time can be reduced. For example, if fR was detected in the fC-fD window during the last scan, then the next scan can begin with VC set to the fC-fD window. In some embodiments, instead of using the receiving window in which fR was last detected, reader device <NUM> can track the average or median analyte level of the user and start with the receiving window that corresponds to the most recently determined average or median value. Thus, if fR was last detected in the fC-fD window, but the average value indicates the fD-fE window, then the next scan can initiate with the receiving window set to the fD-fE window. In both embodiments if fR is detected then the scan can stop. If not, then the receiving window can be indexed to the receiving windows immediately adjacent to the recently swept window in any desired order. For example, if fR is not detected upon initially sweeping the fD-fE window, then the fC-fD window can be swept next, followed by the fE-fF window, followed by the fB-fC window, and so forth until fR is detected. In some embodiments, processing circuitry <NUM> can be programmed to center the first receiving window around the last detected fR to optimize the search, and then proceed by indexing receiving windows from there.

While these embodiments utilize a receiving window that is smaller than the overall band of frequencies in which the resonance frequency can exist, other embodiments can utilize a receiving window that is as broad as the overall band of frequencies such that moving the receiving window is not required.

Various aspects of the present subject matter are set forth below, in review of, and/or in supplementation to, the embodiments described thus far, with the emphasis here being on the interrelation and interchangeability of the following embodiments. In other words, an emphasis is on the fact that each feature of the embodiments can be combined with each and every other feature unless explicitly stated otherwise or logically implausible.

In many example embodiments, a method of detecting an analyte sensor measurement is provided, the method including: outputting, by an analyte sensor of a first device, an electrical current or voltage that corresponds to an analyte level of a user, where the analyte sensor is electrically coupled with a circuit having a frequency characteristic adapted to vary according to the electrical current or voltage; wirelessly detecting the frequency characteristic of the circuit with a second device; and determining the analyte level of the user based on the detected frequency characteristic.

In these embodiments, the frequency characteristic can be a resonance frequency. The circuit can have an impedance that varies according to the electrical current or voltage. The circuit can include a component having a capacitance that varies according to the electrical current or voltage. The electrical current or voltage can be applied to the component, and the method can further include: outputting, by the analyte sensor, a varying electrical current or voltage that corresponds to a varying analyte level of a user, where the impedance of the circuit varies with the varying electrical current or voltage. The resonance frequency of the circuit can vary with the varying impedance of the circuit.

In these embodiments, the circuit can include an antenna. The analyte level of the user can be determined with the detected frequency characteristic and a frequency calibration value. The circuit can include at least one varactor diode. The second device can wirelessly detect the frequency characteristic of the circuit by inductively coupling with the circuit.

In these embodiments, the frequency characteristic can be a resonance frequency, and the circuit can be a first variable impedance circuit, and where detecting the resonance frequency of the circuit can include: applying a voltage to a second variable impedance circuit of the second device; propagating, by the second device, a plurality of sweep frequencies to the first variable impedance circuit; capturing, by the second device, a response to the plurality of sweep frequencies; and determining, by the second device, the resonance frequency of the first variable impedance circuit. In these embodiments, determining, by the second device, the resonance frequency of the circuit, can include: detecting a dual peak frequency response; and determining a center frequency of the dual peak frequency response.

In these embodiments, determining the analyte level of the user based on the detected frequency characteristic can include applying a calibration value. The second device can be a reader device, and the method can further include using the reader device to read the calibration value from an NFC tag or optical bar code. The second device can be a reader device, and the method can further include downloading, by the reader device, the calibration value over a network. The first device can be an on body device, and the calibration value can be stored in memory of the on body device. The method can further include transmitting the calibration value from the on body device to the reader device.

In these embodiments, the frequency characteristic can be a resonance frequency, and the circuit can be a first variable impedance circuit, where detecting the resonance frequency of the circuit can include: setting a first receiving window of the second device; and propagating, by the second device, a first plurality of sweep frequencies to the first device. The bandwidth of the first receiving window can be smaller than and included within a bandwidth of the first plurality of sweep frequencies. The method can further include determining whether a resonance frequency of the circuit is detected within the receiving window. The method can further include, if the resonance frequency of the circuit is not detected within the first receiving window, setting a second receiving window of the second device and propagating, by the second device, a second plurality of sweep frequencies to the first device. The first and second receiving windows can be different. The first and second receiving windows can be such that they do not overlap. The first and second pluralities of sweep frequencies can be the same or different. The first plurality of sweep frequencies can be commensurate with the first receiving window. The second plurality of sweep frequencies can be commensurate with the second receiving window.

In these embodiments, the method can further include outputting the analyte level of the user on a display. The method can further include outputting the analyte level of the user on a display of the second device.

In these embodiments, the analyte sensor can be a self-biased analyte sensor. The analyte sensor can output the electrical current or voltage that corresponds to the analyte level of the user without power from an artificial power source. The analyte level can be a glucose level.

In many embodiments, a system for detecting an analyte sensor measurement is provided, the system including: a first device including: an analyte sensor adapted to output an electrical current or voltage that corresponds to an analyte level of a user; and a circuit coupled with the analyte sensor, where the circuit has a frequency characteristic adapted to vary according to the electrical current or voltage output by the analyte sensor; and a second device adapted to wirelessly detect the frequency characteristic of the circuit and determine the analyte level of the user based on the detected frequency characteristic.

In these embodiments, the frequency characteristic can be a resonance frequency. The circuit can have an impedance that varies according to the electrical current or voltage. The circuit can include a component having a capacitance that varies according to the electrical current or voltage. The circuit can include an antenna. The circuit can include at least one varactor diode. The second device can be adapted to wirelessly detect the frequency characteristic of the circuit by inductive coupling with the circuit. The first device can be an on body device and the second device can be a reader device.

In these embodiments, the second device can include processing circuitry and a non-transitory memory on which instructions are stored that, when executed by the processing circuitry, cause the processing circuitry to determine the analyte level of the user with the detected frequency characteristic. The instructions, when executed by the processing circuitry, can cause the processing circuitry to determine the analyte level of the user with the detected frequency characteristic and a frequency calibration value. The first device can include non-transitory memory on which is stored the frequency calibration value. The frequency characteristic can be a resonance frequency, the circuit can be a first variable impedance circuit, and the second device can include a second variable impedance circuit. The instructions, when executed by the processing circuitry, can cause the processing circuitry to output a control voltage to the second variable impedance circuit. The second device can be configured such that the second variable impedance circuit sets a receiving window for the second device.

In these embodiments, the second device can further include a frequency generator adapted to output a plurality of sweep frequencies to the first device. The second device can include processing circuitry and a non-transitory memory on which instructions are stored that, when executed by the processing circuitry, can cause the processing circuitry to determine the plurality of sweep frequencies output by the frequency generator.

In these embodiments, the second device further can include a receiver adapted to induce or capture a response from the first device. The second device can include processing circuitry and a non-transitory memory on which instructions are stored that, when executed by the processing circuitry, can cause the processing circuitry to determine the frequency characteristic of the circuit from the captured response.

In these embodiments, the second device can include processing circuitry and a non-transitory memory on which instructions are stored that, when executed by the processing circuitry, cause the processing circuitry to determine the frequency characteristic of the circuit by detection of a dual peak frequency response. The instructions, when executed by the processing circuitry, can cause the processing circuitry to determine a center frequency of the dual peak frequency response. The instructions, when executed by the processing circuitry, can cause the processing circuitry to determine the analyte level of the user from at least the center frequency of the dual peak frequency response.

In these embodiments, the second device can include a user interface into which a frequency calibration value for the circuit can be input. The second device can be adapted to wirelessly receive a frequency calibration value for the circuit from the first device. The second device can be adapted to download a frequency calibration value for the circuit over a network.

In these embodiments, the second device can include processing circuitry and a non-transitory memory on which instructions are stored that, when executed by the processing circuitry, cause the processing circuitry to set a first receiving window of the second device and cause propagation of a first plurality of sweep frequencies to the first device. The bandwidth of the first receiving window can be smaller than and included within a bandwidth of the first plurality of sweep frequencies. The instructions, when executed by the processing circuitry, can cause the processing circuitry to determine whether a resonance frequency of the circuit is detected within the receiving window. The instructions, when executed by the processing circuitry, can cause the processing circuitry to, if the resonance frequency of the circuit is not detected within the first receiving window, set a second receiving window of the second device and cause propagation of a second plurality of sweep frequencies to the first device. The first and second receiving windows can be different. The first and second receiving windows can be such that they do not overlap. The first and second pluralities of sweep frequencies can be the same. The first and second pluralities of sweep frequencies can be different. The first plurality of sweep frequencies can be commensurate with the first receiving window. The second plurality of sweep frequencies can be commensurate with the second receiving window.

In these embodiments, the second device can further include a display adapted to output the analyte level of the user. The analyte sensor can be a self-biased analyte sensor. The analyte sensor can be adapted to output the electrical current or voltage that corresponds to the analyte level of the user without power from an artificial power source. The analyte level can be a glucose level.

In many embodiments, a device for detecting an analyte sensor measurement is provided, the device including: an analyte sensor adapted to output an electrical current or voltage that corresponds to an analyte level of a user; and a circuit coupled with the analyte sensor, where the circuit has a frequency characteristic adapted to vary according to the electrical current or voltage output by the analyte sensor.

In these embodiments, the device can be configured as an on body device. The circuit can have an impedance that varies according to the electrical current or voltage. The circuit can include a component having a capacitance that varies according to the electrical current or voltage. The circuit can include an antenna. The device can include a non-transitory memory on which is stored a frequency calibration value. The analyte sensor can be a self-biased analyte sensor. The analyte sensor can be adapted to output the electrical current or voltage that corresponds to the analyte level of the user without power from an artificial power source. The circuit can include at least one varactor diode. The circuit can include an inductor and a capacitor.

In many embodiments, a reader device for detecting an analyte sensor measurement is provided, the reader device including: processing circuitry; and non-transitory memory on which is stored a plurality of instructions that, when executed, cause the processing circuitry to cause propagation of a plurality of sweep frequencies to a sensor device, detect a frequency characteristic of the sensor device, and determine an analyte level of a user of the sensor device based on the detected frequency characteristic.

In these embodiments, the frequency characteristic can be a resonance frequency. The instructions, when executed by the processing circuitry, can cause the processing circuitry to determine the analyte level of the user with the detected frequency characteristic and a frequency calibration value.

In these embodiments, the reader device can further include a variable impedance circuit. The instructions, when executed by the processing circuitry, can cause the processing circuitry to output a control voltage to the variable impedance circuit. The reader device can be configured such that a voltage applied to the variable impedance circuit sets a receiving window for the reader device.

In these embodiments, the reader device can include a frequency generator adapted to output a plurality of sweep frequencies. The instructions, when executed by the processing circuitry, can cause the processing circuitry to control the plurality of sweep frequencies output by the frequency generator.

In these embodiments, the reader device can further include a receiver adapted to induce and/or capture a response from the sensor device. The instructions, when executed by the processing circuitry, can cause the processing circuitry to determine the frequency characteristic of the sensor device from the captured response.

In these embodiments, the instructions, when executed by the processing circuitry, can cause the processing circuitry to determine the frequency characteristic of the circuit by detection of a dual peak frequency response. The instructions, when executed by the processing circuitry, can cause the processing circuitry to determine a center frequency of the dual peak frequency response. The instructions, when executed by the processing circuitry, can cause the processing circuitry to determine the analyte level of the user from at least the center frequency of the dual peak frequency response.

In these embodiments, the reader device can further include a user interface into which a frequency calibration value for the sensor device can be input, where the instructions, when executed by the processing circuitry, cause the processing circuitry to use the frequency calibration value to determine the analyte level of the user. The reader device can be adapted to wirelessly receive a frequency calibration value for the sensor device. The reader device can be adapted to download a frequency calibration value for the sensor device over a network.

In these embodiments, the instructions, when executed by the processing circuitry, can cause the processing circuitry to set a first receiving window of the device and cause propagation of a first plurality of sweep frequencies to the sensor device. The bandwidth of the first receiving window can be smaller than and included within a bandwidth of the first plurality of sweep frequencies. The instructions, when executed by the processing circuitry, can cause the processing circuitry to determine whether a resonance frequency of the sensor device is detected within the receiving window. The instructions, when executed by the processing circuitry, can cause the processing circuitry to, if the resonance frequency of the sensor device is not detected within the first receiving window, set a second receiving window and cause propagation of a second plurality of sweep frequencies to the sensor device. The first and second receiving windows can be different. The first and second receiving windows can be such that they do not overlap. The first and second pluralities of sweep frequencies can be the same or different. The first plurality of sweep frequencies can be commensurate with the first receiving window. The second plurality of sweep frequencies can be commensurate with the second receiving window.

In these embodiments, the analyte level can be a glucose level. The reader device can be adapted to wirelessly detect the frequency characteristic of the circuit by inductive coupling with the circuit.

Computer program instructions for carrying out operations in accordance with the described subject matter may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, JavaScript, Smalltalk, C++, C#, Transact-SQL, XML, PHP or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The program instructions may execute entirely on the user's computing device (e.g., reader) or partly on the user's computing device. The program instructions may reside partly on the user's computing device and partly on a remote computing device or entirely on the remote computing device or server, e.g., for instances where the identified frequency is uploaded to the remote location for processing. In the latter scenario, the remote computing device may be connected to the user's computing device through any type of network, or the connection may be made to an external computer.

It should be noted that all features, elements, components, functions, and steps described with respect to any embodiment provided herein are intended to be freely combinable and substitutable with those from any other embodiment. If a certain feature, element, component, function, or step is described with respect to only one embodiment, then it should be understood that that feature, element, component, function, or step can be used with every other embodiment described herein unless explicitly stated otherwise. This paragraph therefore serves as antecedent basis and written support for the introduction of claims, at any time, that combine features, elements, components, functions, and steps from different embodiments, or that substitute features, elements, components, functions, and steps from one embodiment with those of another, even if the following description does not explicitly state, in a particular instance, that such combinations or substitutions are possible. It is explicitly acknowledged that express recitation of every possible combination and substitution is overly burdensome, especially given that the permissibility of each and every such combination and substitution will be readily recognized by those of ordinary skill in the art.

Claim 1:
A system (<NUM>) for detecting an analyte sensor measurement, the system comprising:
a first device (<NUM>) comprising:
an analyte sensor (<NUM>) configured to output an electrical current or a voltage that corresponds to an analyte level of a user; and
a circuit (<NUM>) coupled with the analyte sensor (<NUM>), wherein the circuit has a frequency characteristic configured to vary according to the electrical current or the voltage output by the analyte sensor (<NUM>); and
a second device (<NUM>) configured to wirelessly detect the frequency characteristic of the circuit (<NUM>) and determine the analyte level of the user based on the detected frequency characteristic.