Patent ID: 12193780

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIGS.1and2are schematic views of sensor systems embodying aspects of the present invention. In one non-limiting embodiment, the system includes a sensor100and an external sensor transceiver101. In the embodiments shown inFIGS.1and2, the sensor100may be in a living animal (e.g., implanted in a living human). The sensor100may be, for example, in a living animal's arm, wrist, leg, abdomen, or other region of the living animal suitable for sensor implantation or insertion. For example, in one non-limiting embodiment, the sensor100may be implanted subcutaneously. In some embodiments, the sensor100may be an optical sensor (e.g., a fluorometer). The sensor100may be configured to determine a concentration of an analyte (e.g., glucose or oxygen) in a medium (e.g., interstitial fluid or blood) of the living animal. In some embodiments, the sensor100may be a chemical or biochemical sensor.

A sensor transceiver101may be an electronic device that communicates with the sensor100to power the sensor100and/or obtain analyte (e.g., glucose) readings from the sensor100. In non-limiting embodiments, the transceiver101may be a handheld transceiver, a wristwatch, an armband, or other device placed in close proximity to the sensor100. In one embodiment, positioning (i.e., hovering or swiping/waiving/passing) the transceiver101within range over the sensor implant site (i.e., within proximity of the sensor100) will cause the transceiver101to automatically convey a measurement command to the sensor100and receive a reading from the sensor100.

In some embodiments, the sensor transceiver101may include an inductive element103, such as, for example, a coil. The sensor transceiver101may generate an electromagnetic wave or electrodynamic field (e.g., by using a coil) to induce a current in an inductive element114of the sensor100, which powers the sensor100(e.g., through an inductive link of, for example, 13.56 MHz). The sensor transceiver101may also convey data (e.g., commands) to the sensor100. For example, in a non-limiting embodiment, the sensor transceiver101may convey data by modulating the electromagnetic wave used to power the sensor100(e.g., by modulating the current flowing through a coil103of the sensor transceiver101). The modulation in the electromagnetic wave generated by the transceiver101may be detected/extracted by the sensor100. Moreover, the sensor transceiver101may receive data (e.g., measurement information) from the sensor100. For example, in a non-limiting embodiment, the sensor transceiver101may receive data by detecting modulations in the electromagnetic wave generated by the sensor100, e.g., by detecting modulations in the current flowing through the coil103of the sensor transceiver101.

The inductive element103of the sensor transceiver101and the inductive element114of the sensor100may be in any configuration that permits adequate field strength to be achieved when the two inductive elements are brought within adequate physical proximity. For example, in one non-limiting embodiment, as illustrated inFIG.2, the inductive element103, which may be in a wrist band or arm band, may wrap around the sensor100. However, this is not required, and, in alternative embodiments, as illustrated inFIG.1, the inductive element103does not wrap around the sensor100.

The external sensor transceiver101may read measured analyte (e.g., glucose) data from a subcutaneous sensor100. After reading the values are read from the sensor100, the external sensor transceiver may process, store, and/or display the data. In some embodiments, the external sensor transceiver101may also transmit data (e.g., via USB port) to a personal computer (PC) for further processing and/or display. Clinical technicians and/or doctors may use the external transceiver101to monitor their patients' glucose readings by uploading history logs from a transceiver101to a PC application for review and analysis. In some embodiments, doctors may have the option to set up alert profiles for their patients. Patients may read the analyte value displayed on the external sensor transceiver101and may view alerts and warnings are set up by the doctor or themselves.

In some embodiments, a unique transceiver identification (ID) may be associated with the external sensor transceiver101, and the external sensor transceiver101may be configured to convey the transceiver ID (e.g., using the inductive element103) to the sensor100. In some embodiments, the sensor100may use the unique transceiver ID to distinguish the external sensor transceiver101from other external sensor transceivers that may also be used to convey power and data to the sensor100and receive data from the sensor100. In some non-limiting embodiments, the sensor100may use the unique transceiver ID to determine whether the external sensor transceiver101is a new sensor transceiver (e.g., an external sensor transceiver101that has not previously been used with the sensor100or is different than the external sensor transceiver101last used with the sensor100).

In one non-limiting embodiment, sensor100includes a sensor housing102(i.e., body, shell, capsule, or encasement), which may be rigid and biocompatible. In exemplary embodiments, sensor housing102may be formed from a suitable, optically transmissive polymer material, such as, for example, acrylic polymers (e.g., polymethylmethacrylate (PMMA)). In some embodiments, the sensor housing102may any shape suitable for implantation or insertion into a living animal. For instance, in some non-limiting embodiments, the sensor housing102may be cylindrical, pill-shaped, disc-shaped, spherical, or rectangular prism-shaped.

In some embodiments, the sensor100includes indicator molecules104. Indicator molecules104may be fluorescent indicator molecules (e.g., Trimethyltrifluromethylsilane (TFM) fluorescent indicator molecules) or absorption indicator molecules. In some embodiments, the indicator molecules104may reversibly bind an analyte (e.g., glucose). When an indicator molecule104has bound the analyte, the indicator molecule may become fluorescent, in which case the indicator molecule104is capable of absorbing (or being excited by) excitation light329and emitting light331. In one non-limiting embodiment, the excitation light329may have a wavelength of approximately 378 nm, and the emission light331may have a wavelength in the range of 400 to 500 nm. When no glucose is bound, the indicator molecule104may be only weakly fluorescent.

In some non-limiting embodiments, sensor100may include a polymer graft/matrix layer106coated, diffused, adhered, or embedded on at least a portion of the exterior surface of the sensor housing102, with the indicator molecules104distributed throughout the polymer graft106. In some embodiments, the polymer graft106may be a fluorescent analyte indicating polymer. In one non-limiting embodiment, the polymer may be biocompatible and stable, grafted onto the surface of sensor housing102, designed to allow for the direct measurement of interstitial fluid (ISF) glucose after subcutaneous implantation of the sensor100.

In some embodiments, the sensor100may include a light source108, which may be, for example, a light emitting diode (LED) or other light source, that emits radiation, including radiation over a range of wavelengths that interact with the indicator molecules104. In other words, the light source108may emit the excitation light329that is absorbed by the indicator molecules104in the polymer graft106. As noted above, in one non-limiting embodiment, the light source108may emit excitation light329that is ultraviolet (UV) light (e.g., light with a wavelength of approximately 378 nm). In one embodiment, the graft106may be positioned to receive excitation light329emitted by the light source108.

In some embodiments, the sensor100may also include one or more photodetectors (e.g., photodiodes, phototransistors, photoresistors or other photosensitive elements). For example, in the embodiment illustrated inFIGS.1and2, sensor100may have a first photodetector224and a second photodetector226. In one non-limiting embodiment, as illustrated inFIGS.1and2, the first photodetector224may be a signal photodetector (i.e., read photodetector), and the second photodetector226may be a reference photodetector226. However, the sensor100is not required to have more than one photodetector, and, in some alternative embodiments, the sensor100may only include the first photodetector224.

Some part of the excitation light329emitted by the light source108may be reflected from the polymer graft106back into the sensor100as reflection light333, and some part of the absorbed excitation light may be emitted as emitted (fluoresced) light331. In one non-limiting embodiment, the emitted light331may have a higher wavelength than the wavelength of the excitation light329. The reflected light333and emitted (fluoresced) light331may be absorbed by the one or more photodetectors (e.g., first and second photodetectors224and226) within the body of the sensor100.

In some embodiments, the sensor100may include one or more filters112. As illustrated inFIG.2, each of the one or more photodetectors may be covered by a filter112. Each of the one or more filters112may allow only a certain subset of wavelengths of light to pass through. In some embodiments, the one or more filters112may be thin glass filters. In some embodiments, the one or more filters112may be thin film (dichroic) filters deposited on the glass and may pass only a narrow band of wavelengths and otherwise reflect most of the light.

In some non-limiting embodiments, the first photodetector224may be covered by a filter112that is a signal filter. The signal filter may be configured to pass a narrow band of wavelengths including the wavelength of the emission light331emitted (e.g., fluoresced) by the indicator molecules104in the graft106. For instance, in one non-limiting embodiment, the peak emission of the indicator molecules104may occur around 435 nm, and the signal filter may pass light in the range of 400-500 nm and prevent other light from reaching the first photodetector224(e.g., by reflecting most of the light outside the 400-500 nm range). However, this is not required, and, in other embodiments, the emission light331may have a different peak emission wavelength, and/or the signal filter may pass light in a different (e.g., narrower, expanded, or shifted) wavelength range.

In some non-limiting embodiments, the second photodetector226may be covered by a filter112that is a reference filter. The reference filter may be configured to pass a narrow band of wavelengths including the wavelength of a reference light333. In one non-limiting embodiment, the reference light333passed by the reference filter may have the same wavelength as the excitation light329(e.g., 378 nm), and the reference filter may pass light in a narrow band (e.g., 350-400 nm) including the wavelength of the excitation light329and prevent other light from reaching the second photodetector226. However, this is not required, and, in other embodiments, the reference light333passed by the reference filter may have a different wavelength than the excitation light329(e.g., the wavelength of light emitted by reference indicator molecules that are unaffected or generally unaffected by the presence and/or concentration of the analyte), and/or the reference filter may pass light in a different (e.g., narrower, expanded, or shifted) wavelength range.

The first photodetector224may be configured to (a) receive the emission light331that is emitted from the indicator molecules104in the graft106and (b) generate a signal indicative of the amount of light received thereby. In some embodiments, higher analyte (e.g., glucose or oxygen) levels/concentrations correspond to a greater amount of emission light331(e.g., fluorescence) of the indicator molecules104in the graft106, and, therefore, a greater number of photons striking the first photodetector224.

The second photodetector226may be configured to receive the reference light333and generate a signal indicative of the amount of light received thereby. In some embodiments, the reference light333may have the same wavelength as the excitation light329emitted by the light source108and, as illustrated inFIG.1, may include a portion of the excitation light329that is reflected from the graft106. In some alternative embodiments, the reference light333may have a different wavelength than the excitation light329(e.g., the wavelength of light emitted by reference indicator molecules that are unaffected or generally unaffected by the presence and/or concentration of the analyte).

In some embodiments, the substrate116may be a circuit board (e.g., a printed circuit board (PCB)) on which circuit components (e.g., analog and/or digital circuit components) may be mounted or otherwise attached. However, in some alternative embodiments, the substrate116may be a semiconductor substrate having circuitry fabricated therein. The circuitry may include analog and/or digital circuitry. In some embodiments, the circuitry may include one or more processors (e.g., microprocessors). Also, in some semiconductor substrate embodiments, in addition to the circuitry fabricated in the semiconductor substrate, circuitry may be mounted or otherwise attached to the semiconductor substrate116. In other words, in some semiconductor substrate embodiments, a portion or all of the circuitry, which may include discrete circuit elements, an integrated circuit (e.g., an application specific integrated circuit (ASIC)) and/or other electronic components, may be fabricated in the semiconductor substrate116with the remainder of the circuitry is secured to the semiconductor substrate116, which may provide communication paths between the various secured components. In some embodiments, circuitry of the sensor100may incorporate some or all of the structure described in U.S. patent application Ser. No. 13/650,016, which is incorporated herein by reference in its entirety, with particular reference toFIG.11D.

FIG.3is block diagram illustrating the functional blocks of the circuitry of sensor100according to a non-limiting embodiment in which the circuitry is fabricated in the semiconductor substrate116. As shown in the embodiment ofFIG.3, in some embodiments, an input/output (I/O) frontend block536may be connected to the external inductive element114, which may be in the form of a coil220, through coil contacts428aand428b.The I/O frontend block536may include a rectifier640, a data extractor642, a clock extractor644, clamp/modulator646and/or frequency divider648. Data extractor642, clock extractor644and clamp/modulator646may each be connected to external coil220through coil contacts428aand428b.The rectifier640may convert an alternating current produced by coil220to a direct current that may be used to power the sensor100. For instance, the direct current may be used to produce one or more voltages, such as, for example, voltage VDD_A, which may be used to power the one or more photodetectors (e.g., photodetectors224and226). In one non-limiting embodiment, the rectifier640may be a Schottky diode; however, other types of rectifiers may be used in other embodiments. The data extractor642may extract data from the alternating current produced by coil220. The clock extractor644may extract a signal having a frequency (e.g., 13.56 MHz) from the alternating current produced by coil220. The frequency divider648may divide the frequency of the signal output by the clock extractor644. For example, in a non-limiting embodiment, the frequency divider648may be a 4:1 frequency divider that receives a signal having a frequency (e.g., 13.56 MHz) as an input and outputs a signal having a frequency (e.g., 3.39 MHz) equal to one fourth the frequency of the input signal. The outputs of rectifier640may be connected to one or more external capacitors118(e.g., one or more regulation capacitors) through contacts428hand428i.

In some embodiments, an I/O controller538may include a decoder/serializer650, command decoder/data encoder652, data and control bus654, data serializer656and/or encoder658. The decoder/serializer650may decode and serialize the data extracted by the data extractor642from the alternating current produced by coil220. The command decoder/data encoder652may receive the data decoded and serialized by the decoder/serializer650and may decode commands therefrom. The data and control bus654may receive commands decoded by the command decoder/data encoder652and transfer the decoded commands to the measurement controller532. The data and control bus654may also receive data, such as measurement information, from the measurement controller532and may transfer the received data to the command decoder/data encoder652. The command decoder/data encoder652may encode the data received from the data and control bus654. The data serializer656may receive encoded data from the command decoder/data encoder652and may serialize the received encoded data. The encoder658may receive serialized data from the data serializer656and may encode the serialized data. In a non-limiting embodiment, the encoder658may be a Manchester encoder that applies Manchester encoding (i.e., phase encoding) to the serialized data. However, in other embodiments, other types of encoders may alternatively be used for the encoder658, such as, for example, an encoder that applies 8B/10B encoding to the serialized data.

The clamp/modulator646of the I/O frontend block536may receive the data encoded by the encoder658and may modulate the current flowing through the inductive element114(e.g., coil220) as a function of the encoded data. In this way, the encoded data may be conveyed wirelessly by the inductive element114as a modulated electromagnetic wave. The conveyed data may be detected by an external reading device by, for example, measuring the current induced by the modulated electromagnetic wave in a coil of the external reading device. Furthermore, by modulating the current flowing through the coil220as a function of the encoded data, the encoded data may be conveyed wirelessly by the coil220as a modulated electromagnetic wave even while the coil220is being used to produce operating power for the sensor100. See, for example, U.S. Pat. Nos. 6,330,464 and 8,073,548, which are incorporated herein by reference in their entireties and which describe a coil used to provide operative power to an optical sensor and to wirelessly convey data from the optical sensor. In some embodiments, the encoded data is conveyed by the sensor100using the clamp/modulator646at times when data (e.g., commands) are not being received by the sensor100and extracted by the data extractor642. For example, in one non-limiting embodiment, all commands may be initiated by an external sensor transceiver (e.g., transceiver101ofFIGS.1and2) and then responded to by the sensor100(e.g., after or as part of executing the command). In some embodiments, the communications received by the inductive element114and/or the communications conveyed by the inductive element114may be radio frequency (RF) communications. Although, in the illustrated embodiments, the sensor100includes a single coil220, alternative embodiments of the sensor100may include two or more coils (e.g., one coil for data transmission and one coil for power and data reception).

In an embodiment, the I/O controller538may also include a nonvolatile storage medium660. In a non-limiting embodiment, the nonvolatile storage medium660may be an electrically erasable programmable read only memory (EEPROM). However, in other embodiments, other types of nonvolatile storage media, such as flash memory, may be used. The nonvolatile storage medium660may receive write data (i.e., data to be written to the nonvolatile storage medium660) from the data and control bus654and may supply read data (i.e., data read from the nonvolatile storage medium660) to the data and control bus654. In some embodiments, the nonvolatile storage medium660may have an integrated charge pump and/or may be connected to an external charge pump. In some embodiments, the nonvolatile storage medium660may store identification information (i.e., traceability or tracking information), measurement information and/or setup parameters (i.e., calibration information). In one embodiment, the identification information may uniquely identify the sensor100. The unique identification information may, for example, enable full traceability of the sensor100through its production and subsequent use. In one embodiment, the nonvolatile storage medium660may store calibration information for each of the various sensor measurements. In some embodiments, the nonvolatile storage medium660may store one or more transceiver IDs conveyed to the sensor100. In some non-limiting embodiments, the nonvolatile storage medium660may store the date of sensor implant, which may enable a physician to know when the sensor100should be replaced.

In some embodiments, the analog interface534may include a light source driver662, analog to digital converter (ADC)664, a signal multiplexer (MUX)666and/or comparator668. In a non-limiting embodiment, the comparator668may be a transimpedance amplifier, in other embodiments, different comparators may be used. The analog interface534may also include light source108, one or more photodetectors (e.g., first and second photodetectors224and226), and/or a temperature sensor670(e.g., temperature transducer).

In some embodiments, the one or more photodetectors (e.g., photodetectors224and226) may be mounted on the semiconductor substrate116, but, in some preferred embodiments, the one or more photodetectors may be fabricated in the semiconductor substrate116. In some embodiments, the light source108may be mounted on the semiconductor substrate116. For example, in a non-limiting embodiment, the light source108may be flip-chip mounted on the semiconductor substrate116. However, in some embodiments, the light source108may be fabricated in the semiconductor substrate116.

In a non-limiting, exemplary embodiment, the temperature transducer670may be a band-gap based temperature transducer. However, in alternative embodiments, different types of temperature transducers may be used, such as, for example, thermistors or resistance temperature detectors. Furthermore, like the light source108and one or more photodetectors, in one or more alternative embodiments, the temperature transducer670may be mounted on semiconductor substrate116instead of being fabricated in semiconductor substrate116.

The light source driver662may receive a signal from the measurement controller532indicating the light source current at which the light source108is to be driven, and the light source driver662may drive the light source108accordingly. The light source108may emit radiation from an emission point in accordance with a drive signal from the light source driver662. The radiation may excite indicator molecules104distributed throughout the graft106. The one or more photodetectors (e.g., first and second photodetectors224and226) may each output an analog light measurement signal indicative of the amount of light received by the photodetector. For instance, in the embodiment illustrated inFIG.3, the first photodetector224may output a first analog light measurement signal indicative of the amount of light received by the first photodetector224, and the second photodetector226may output a first analog light measurement signal indicative of the amount of light received by the second photodetector226. The comparator668may receive the first and second analog light measurement signals from the first and second photodetectors224and226, respectively, and output an analog light difference measurement signal indicative of the difference between the first and second analog light measurement signals. The temperature transducer670may output an analog temperature measurement signal indicative of the temperature of the sensor100. The signal MUX666may select one of the analog temperature measurement signal, the first analog light measurement signal, the second analog light measurement signal and the analog light difference measurement signal and may output the selected signal to the ADC664. The ADC664may convert the selected analog signal received from the signal MUX666to a digital signal and supply the digital signal to the measurement controller532. In this way, the ADC664may convert the analog temperature measurement signal, the first analog light measurement signal, the second analog light measurement signal, and the analog light difference measurement signal to a digital temperature measurement signal, a first digital light measurement signal, a second digital light measurement signal, and a digital light difference measurement signal, respectively, and may supply the digital signals, one at a time, to the measurement controller532.

In some embodiments, the measurement controller532may receive one or more digital measurements and generate measurement information, which may be indicative of the presence and/or concentration of an analyte (e.g., glucose) in a medium in which the sensor100is implanted. In some embodiments, the generation of the measurement information may include conversion of a digitized raw signal (e.g., the first digital light measurement signal) into a glucose concentration. For accurate conversion, the measurement controller532may take into consideration the optics, electronics, and chemistry of the sensor100. Further, in some embodiments, the measurement controller532may be used to obtain a purified signal of glucose concentration by eliminating noise (e.g., offset and distortions) that is present in the raw signals (e.g., the first digital light measurement signals).

In some embodiments, the circuitry of sensor100fabricated in the semiconductor substrate116may additionally include a clock generator671. The clock generator671may receive, as an input, the output of the frequency divider648and generate a clock signal CLK. The clock signal CLK may be used by one or more components of one or more of the I/O frontend block536, I/O controller538, measurement controller532, and analog interface534.

In a non-limiting embodiment, data (e.g., decoded commands from the command decoder/data encoder652and/or read data from the nonvolatile storage medium660) may be transferred from the data and control bus654of the I/O controller538to the measurement controller532via transfer registers and/or data (e.g., write data and/or measurement information) may be transferred from the measurement controller532to the data and control bus654of the I/O controller538via the transfer registers.

In some embodiments, the circuitry of sensor100may include a field strength measurement circuit. In embodiments, the field strength measurement circuit may be part of the I/O front end block536, I/O controller538, or the measurement controller532or may be a separate functional component. The field strength measurement circuit may measure the received (i.e., coupled) power (e.g., in mWatts). The field strength measurement circuit of the sensor100may produce a coupling value proportional to the strength of coupling between the inductive element114(e.g., coil220) of the sensor100and the inductive element of the external transceiver101. For example, in non-limiting embodiments, the coupling value may be a current or frequency proportional to the strength of coupling. In some embodiments, the field strength measurement circuit may additionally determine whether the strength of coupling/received power is sufficient to perform an analyte concentration measurement and convey the results thereof to the external sensor transceiver101. For example, in some non-limiting embodiments, the field strength measurement circuit may detect whether the received power is sufficient to produce a certain voltage and/or current. In one non-limiting embodiment, the field strength measurement circuit may detect whether the received power produces a voltage of at least approximately 3V and a current of at least approximately 0.5 mA. However, other embodiments may detect that the received power produces at least a different voltage and/or at least a different current. In one non-limiting embodiment, the field strength measurement circuit may compare the coupling value field strength sufficiency threshold.

In the illustrated embodiment, the clamp/modulator646of the I/O circuit536acts as the field strength measurement circuit by providing a value (e.g., Icouple) proportional to the field strength. The field strength value Icouplemay be provided as an input to the signal MUX666. When selected, the MUX666may output the field strength value Icoupleto the ADC664. The ADC664may convert the field strength value Icouplereceived from the signal MUX666to a digital field strength value signal and supply the digital field strength signal to the measurement controller532. In this way, the field strength measurement may be made available to the measurement controller532and may be used in initiating an analyte measurement command trigger based on dynamic field alignment. However, in an alternative embodiment, the field strength measurement circuit may instead be an analog oscillator in the sensor100that sends a frequency corresponding to the voltage level on a rectifier640back to the transceiver101.

In some embodiments, the sensor100may be used to obtain accurate analyte measurements (e.g., ISF glucose readings) in patients, and the circuitry of the sensor100(which may, for example, include measurement controller532) may convert the raw signal generated by the photodetector224into an analyte (e.g., glucose) concentration. For accurate conversion, the circuitry of the sensor100may take into consideration the optics, electronics, and chemistry of the sensor100. Further, in some embodiments, the circuitry may be used to obtain a purified signal of glucose concentration by eliminating noise (e.g., offset and distortions) that are present in raw signals from the sensor100.

In some embodiments, the sensor100may store measurement information from one or more previous measurements (e.g., in nonvolatile storage medium660). In some embodiments, the sensor100may store one or more transceiver IDs conveyed from one or more external sensor transceivers101(e.g., in nonvolatile storage medium660). In some embodiments, the sensor100may use a received transceiver ID to determine whether the external sensor transceiver101that conveyed the transceiver ID is a new external sensor transceiver (e.g., an external sensor transceiver101that has not previously been used with the sensor100or is different than the external sensor transceiver101last used with the sensor100). In some non-limiting embodiments, if the sensor100determines that the external sensor transceiver101is a new external sensor transceiver, the sensor100may store the transceiver ID conveyed from the new external sensor transceiver and/or convey stored measurement information from one or more previous measurements. By doing so, the sensor100may eliminate or reduce gaps in measurement information for the new external sensor transceiver.

FIG.4illustrates an exemplary sensor control process400that may be performed by the sensor100, which may be, for example, implanted within a living animal (e.g., a living human), in accordance with an embodiment of the present invention. The inductive element114of sensor100and the inductive element103of the external sensor transceiver101may be coupled within an electrodynamic field.

The sensor control process400may begin with a step402of generating operational power using the electrodynamic field. In one embodiment, the electrodynamic field may induce a current in inductive element114of sensor100, and the input/output (I/O) front end block536may convert the induced current into power for operating the sensor100. In a non-limiting embodiment, rectifier640may be used to convert the induced current into operating power for the sensor100.

The sensor control process400may include a step404in which the sensor100determines whether a command has been received (e.g., decoded from modulation of the electrodynamic field). In one non-limiting embodiment, the I/O front end block536and I/O controller538may convert the induced current into power for operating the sensor100and extract and decode any received commands from the induced current. In a non-limiting embodiment, rectifier640may be used to convert the induced current into operating power for the sensor100, data extractor642may extract data from the current induced in inductive element114, decoder/serializer650may decode and serialize the extracted data, and command decoder/data encoder652may decode one or more commands from the decoded and serialized extracted data. Any decoded commands may then be sent to measurement controller532via the data and control bus654.

Examples of commands that may be received and executed by the sensor100may include measurement commands, get result commands, and/or get traceability information commands. The commands may include a transceiver ID identifying the external transceiver101that conveyed the command. Examples of measurement commands may include measurement sequence commands (i.e., commands to perform a sequence of measurements and, after finishing the sequence, transmit the resulting measurement information), measure and save commands (i.e., commands to perform a sequence of measurements and, after finishing the sequence, save the resulting measurement information without transmitting the resulting measurement information), and/or single measurement commands (i.e., commands to perform a single measurement). The single measurement commands may be commands to save and/or transmit the measurement information resulting from the single measurement. The measurement commands may or may not include setup parameters (i.e., calibration information). Measurement commands that do not have setup parameters may, for example, be executed using stored setup parameters (e.g., in nonvolatile storage medium660). Other measurement commands, such as measurement commands to both save and transmit the resulting measurement information, are possible. The commands that may be received and executed by the sensor100may also include commands to update the stored the setup parameters. The examples of commands described above are not exhaustive of all commands that may be received and executed by the sensor100, which may be capable of receiving and executing one or more of the commands listed above and/or one or more other commands.

If a command has not been received, the sensor control process400may return to step402. However, this is not required, and, in an alternative embodiment, if a command has not been received, the sensor control process400may proceed to step410to determine whether a transceiver ID has been received.

If one or more commands have been received, in step406, the sensor100may determine whether the one or more received commands include a measurement command. If the one or more received commands include a measurement command, in step408, the sensor100may execute the measurement command (e.g., under control of the measurement controller532). In one non-limiting embodiment, in step408, the sensor100may execute a measurement command execution process500, which is described in further detail below with reference toFIG.5.

If the sensor100determines in step406that the one or more received commands do not include a measurement command (or following completion of measurement command execution in step408), the sensor100may, in a step410, determine whether a transceiver ID has been received (e.g., decoded from modulation of the electrodynamic field). The transceiver ID may be conveyed to the sensor100as part of a command (e.g., in a transceiver ID field of a command), before or after a command is conveyed is conveyed, or as a separate/independent conveyance.

If the sensor100determines in step410that a transceiver ID has not been received, the sensor control process400may return to step402. If the sensor100determines in step410that a transceiver ID has been received, the sensor100may, in a step412, determine whether the received transceiver ID is a new transceiver ID. For example, in non-limiting embodiments, the sensor100may determine whether the received transceiver ID is a new transceiver ID by determining whether the received transceiver ID matches a transceiver ID previously stored to the nonvolatile storage medium660of the sensor100. If no transceiver IDs have been previously stored or none of the previously stored transceiver IDs matches the received transceiver ID, the sensor100may determine that the received transceiver ID is a new transceiver ID.

For instance, in one non-limiting embodiments, the measurement controller532may access any transceiver IDs stored in the nonvolatile storage medium660(e.g., via the data and control bus654) and compare the accessed transceiver ID(s) to the received transceiver ID to determine whether the received transceiver ID has already been stored in the nonvolatile storage medium660. In one non-limiting alternative embodiment, the sensor100may determine that the received transceiver ID is a new transceiver ID if the received transceiver ID is different than the transceiver ID most recently stored to the nonvolatile storage medium660. In another non-limiting alternative embodiment, the nonvolatile storage medium660may store no more than one transceiver ID at a time, and the sensor100may determine that the received transceiver ID is a new transceiver ID if the received transceiver ID is different than the one and only transceiver ID stored in the nonvolatile storage medium660.

If the sensor100determines in step412that the received transceiver ID is not new, the sensor control process400may return to step402. If the sensor100determines in step412that the received transceiver ID is new, the sensor100may, in a step414, save the received transceiver ID (e.g., by storing the received transceiver ID in the nonvolatile storage medium660). For example, in non-limiting embodiments, after comparing the accessed transceiver ID(s) to the received transceiver ID and determining that the received transceiver ID has not already been stored in the nonvolatile storage medium660(step412), the measurement controller532may store the received transceiver ID in the nonvolatile storage medium660(e.g., via the data and control bus654). For instance, in one non-limiting embodiment, the measurement controller532may output the received transceiver ID to the data and control bus654, which may transfer the received transceiver ID to the nonvolatile storage medium660. The nonvolatile storage medium660may store the received transceiver ID. In some embodiments, the measurement controller532may output, along with the received transceiver ID, an address at which the received transceiver ID is to be saved in the nonvolatile storage medium660.

In the non-limiting alternative embodiment where the nonvolatile storage medium660stores no more than one transceiver ID at a time, saving/storing the received transceiver ID in step414may overwrite/replace a previously stored transceiver ID.

If the sensor100determines in step412that the received transceiver ID is new, the sensor100may, in a step416, convey stored measurement information to the external sensor transceiver101. For example, in one non-limiting embodiment, after comparing the accessed transceiver ID(s) to the received transceiver ID and determining that the received transceiver ID has not already been stored in the nonvolatile storage medium660(step412), the measurement controller532may request stored measurement information. In response to a request from the measurement controller532, the nonvolatile storage medium660may output stored measurement information to the data and control bus654, and the data and control bus654may transfer the retrieved measurement information to the measurement controller532. The measurement controller532may output the retrieved measurement information to the data and control bus654. The data and control bus654may transfer the measurement information to the command decoder/data encoder652, which may encode the retrieved measurement information. The data serializer656may serialize the encoded retrieved measurement information. The encoder658may encode the serialized retrieved measurement information. The clamp/modulator646may modulate the current flowing through the inductive element114(e.g., coil220) as a function of the encoded retrieved measurement information. In this way, the encoded retrieved measurement information may be conveyed wirelessly by the inductive element114as a modulated electromagnetic wave. In some embodiments, the encoded retrieved measurement information wirelessly conveyed by the sensor100may be received by the sensor transceiver1500. In some alternative embodiment, the data and control bus654may transfer the retrieved measurement information to the command decoder/data encoder652without first transferring the retrieved measurement information to the measurement controller532.

In some embodiments, the nonvolatile storage medium660may contain measurement information from multiple measurements. In some embodiments, in step416, the sensor100may convey the measurement information from the multiple measurements (e.g., new measurement information first or oldest measurement information first). In one embodiment, the sensor100may access and convey the measurement information from the multiple measurements one at a time.

In some embodiments, after storing a new transceiver ID (step414) and conveying stored measurement information (step416), the sensor control process400may return to step402.

Although not illustrated inFIG.4, the sensor control process400may include additional steps to determine whether the one or more received commands include commands other than a measurement command (e.g., a get result command and/or get traceability information command) and, if so, execute the command(s). Also, although the steps of the sensor control process400are illustrated in a particular order inFIG.4, in alterative embodiments, some steps of the sensor control process400may be carried out in a different order. For example, the sensor100may convey stored measurement information in step416before storing a new transceiver ID in step414. For another example, the sensor100may determine whether a transceiver ID has been received (step410) before determining whether a measurement command has been received (step406).

FIG.5illustrates a measurement command execution process500that may be performed in step408of the sensor control process400by the sensor100to execute a measurement command received by the sensor100in accordance with an embodiment of the present invention. In a non-limiting embodiment, the measurement command execution process500may begin with a step502in which a measurement and conversion process may be performed. The measurement and conversion process may, for example, be performed by the analog interface534under control of the measurement controller532. In one embodiment, the measurement and conversion sequence may include generating one or more analog measurements (e.g., using one or more of temperature transducer670, light source108, first photodetector224, second photodetector226, and/or comparator668) and converting the one or more analog measurements to one or more digital measurements (e.g., using ADC664). One example of the measurement and conversion process that may be performed in step502is described in further detail below with reference toFIG.6.

At step504, the sensor100may generate measurement information in accordance with the one or more digital measurements produced during the measurement and conversion sequence performed in step502. Depending on the one or more digital measurements produced in step502, the measurement information may be indicative of the presence and/or concentration of an analyte in a medium in which the sensor100is implanted. In one embodiment, in step504, the measurement controller532may receive the one or more digital measurements and generate the measurement information.

In some embodiments, the measurement command execution process500may include a step506in which the sensor100saves the measurement information generated in step504. In one non-limiting embodiment, in step506, the measurement controller532may output the measurement information to the data and control bus654, which may transfer the measurement information to the nonvolatile storage medium660. The nonvolatile storage medium660may save the received measurement information. In some embodiments, the measurement controller532may output, along with the measurement information, an address at which the measurement information is to be saved in the nonvolatile storage medium660. In some embodiments, the nonvolatile storage medium660may be configured as a first-in-first-out (FIFO) or last-in-first-out (LIFO) memory with respect to the stored measurement information.

In some embodiments, the measurement command execution process500may include a step508in which the sensor100conveys the measurement information. In one non-limiting embodiment, in step508, the measurement controller532may output the measurement information to the data and control bus654. The data and control bus654may transfer the measurement information to the command decoder/data encoder652, which may encode the measurement information. The data serializer656may serialize the encoded measurement information. The encoder658may encode the serialized measurement information. The clamp/modulator646may modulate the current flowing through the inductive element114(e.g., coil220) as a function of the encoded measurement information. In this way, the encoded measurement information may be conveyed wirelessly by the inductive element114as a modulated electromagnetic wave. In some embodiments, the encoded measurement information wirelessly conveyed by the sensor100may be received by the sensor transceiver101, which may display the received measurement information (e.g., as a value representing the concentration of the analyte) so that a user (e.g., the patient, a doctor and/or others) can read the measurement information.

In some embodiments, the measurement command execution process600that may be performed in step406of the sensor control process400by the sensor100to execute a measurement command received by the sensor100may be completed, and, at this time, the sensor control process400may return to step410.

FIG.6illustrates a measurement and conversion process600, which is an example of the measurement and conversion process that may be performed in step502of the measurement command execution process500, in accordance with an embodiment of the present invention.

At step602, the sensor100may load setup parameters (i.e., calibration information) for performing one or more measurements in accordance with the received measurement command. For example, in one embodiment, the measurement controller532may load one or more setup parameters by setting up one or more components (e.g., light source108, first photodetector224, second photodetector226, comparator668and/or temperature transducer534) of the analog interface534with the setup parameters. In some embodiments, the nonvolatile storage medium660may store saved setup parameters. Further, as noted above, in some embodiments, the measurement commands may or may not include setup parameters. In a non-limiting embodiment, if the measurement command includes one or more setup parameters, the measurement controller532may setup one or more components of the analog interface534with the setup parameters with the one or more setup parameters included in the measurement command. However, if the measurement command does not include one or more setup parameters, the measurement controller532may obtain saved setup parameters stored in the nonvolatile storage medium660and setup one or more components of the analog interface534with the saved setup parameters obtained from the nonvolatile storage medium660.

At step604, the sensor100may perform a light source bias measurement and conversion. For example, in some embodiments, while the light source108is on (i.e., while the light source108, under the control of the measurement controller532, is emitting excitation light329and irradiating indicator molecules104), the analog interface534may generate an analog light source bias measurement signal. In one embodiment, the ADC664may convert the analog light source bias measurement signal to a digital light source bias measurement signal. The measurement controller532may receive the digital light source bias measurement signal and generate (e.g., in step504of the measurement command execution process500) the measurement information in accordance with the received digital light source bias measurement signal. In a non-limiting embodiment, the analog interface534may generate the analog light source bias measurement signal by sampling the voltage and the current in the output of the current source that feeds the light source108.

At step606, the sensor100may perform a light source-on temperature measurement and conversion. For example, in some embodiments, while the light source108is on (i.e., while the light source108, under the control of the measurement controller532, is emitting excitation light and irradiating indicator molecules104), the analog interface534may generate a first analog temperature measurement signal indicative of a temperature of the sensor100. In one embodiment, the temperature transducer670may generate the first analog temperature measurement signal while the light source108is on. The ADC664may convert the first analog temperature measurement signal to a first digital temperature measurement signal. The measurement controller532may receive the first digital temperature measurement signal and generate (e.g., in step504of the measurement command execution process500) the measurement information in accordance with the received first digital temperature measurement signal.

At step608, the sensor100may perform a first photodetector measurement and conversion. For example, in some embodiments, while the light source108is on (i.e., while the light source108, under the control of the measurement controller532, is emitting excitation light and irradiating indicator molecules104), the first photodetector224may generate a first analog light measurement signal indicative of the amount of light received by the first photodetector224and output the first analog light measurement signal to the signal MUX666. The signal MUX666may select the first analog light measurement signal and, the ADC664may convert the first analog light measurement signal to a first digital light measurement signal. The measurement controller532may receive the first digital light measurement signal and generate (e.g., in step504of the measurement command execution process500) the measurement information in accordance with the received first digital light measurement signal.

In a non-limiting embodiment, first photodetector224may be a part of a signal channel, the light331received by the first photodetector224may be emitted by indicator molecules104distributed in the polymer graft106, and the first analog light measurement signal may be an indicator measurement.

At step610, the sensor100may perform a second photodetector measurement and conversion. For example, in some embodiments, while the light source108is on (i.e., while the light source108, under the control of the measurement controller532is emitting excitation light and irradiating indicator molecules104), the second photodetector226may generate a second analog light measurement signal indicative of the amount of light received by the second photodetector226and output the second analog light measurement signal to the signal MUX666. The signal MUX666may select the second analog light measurement signal and, the ADC664may convert the second analog light measurement signal to a second digital light measurement signal. The measurement controller532may receive the second digital light measurement signal and generate (e.g., in step504of the measurement command execution process500) the measurement information in accordance with the received second digital light measurement signal.

In a non-limiting embodiment, second photodetector226may be a part of a reference channel, the light333received by the second photodetector226may be reflected by the polymer graft106, and the second analog light measurement signal may be a reference measurement. However, this is not required, and, for example, in one alternative embodiment, the light333received by the second photodetector226may be emitted by reference indicator molecules (e.g., in polymer graft106) that are unaffected or generally unaffected by the presence and/or concentration of the analyte.

At step612, the sensor100may perform a difference measurement and conversion. For example, in some embodiments, while the light source108is on (i.e., while the light source108, under the control of the measurement controller532, is emitting excitation light and irradiating indicator molecules104), (i) the first photodetector224may generate a first analog light measurement signal indicative of the amount of light received by the first photodetector224, and (ii) the second photodetector226may generate a second analog light measurement signal indicative of the amount of light received by the second photodetector226. The comparator668may receive the first and second analog light measurement signals and generate an analog light difference measurement signal indicative of a difference between the first and second analog light measurement signals. The comparator668may output the analog light difference measurement signal to the signal MUX666. The signal MUX666may select the analog light difference measurement signal and, the ADC664may convert the analog light difference measurement signal to a digital light difference measurement signal. The measurement controller532may receive the digital light difference measurement signal and generate (e.g., in step504of the measurement command execution process500) the measurement information in accordance with the received digital light difference measurement signal.

In a non-limiting embodiment, first photodetector224may be a part of a signal channel, second photodetector226may be a part of a reference channel, and the analog light difference measurement signal may be indicative of the difference in (a) light emitted by indicator molecules104distributed in polymer graft106and affected by the concentration of an analyte in the medium in which sensor100is implanted, and (b) excitation light reflected by the polymer graft106and unaffected or generally unaffected by the concentration of the analyte in the medium in which sensor100is implanted. However, this is not required, and, for example, in one alternative embodiment, the analog light difference measurement signal may be indicative of the difference in (a) light emitted by indicator molecules104distributed in polymer graft106and affected by the concentration of an analyte in the medium in which sensor100is implanted, and (b) light emitted by reference indicator molecules (e.g., in polymer graft106) that are unaffected or generally unaffected by the presence and/or concentration of the analyte.

At step614, the sensor100may perform a second photodetector ambient measurement and conversion. For example, in some embodiments, while the light source108is off (i.e., while the light source108, under the control of the measurement controller532is not emitting light), the second photodetector226may generate a second analog ambient light measurement signal indicative of the amount of light received by the second photodetector226and output the second analog ambient light measurement signal to the signal MUX666. The signal MUX666may select the second analog ambient light measurement signal and, the ADC664may convert the second analog ambient light measurement signal to a second digital ambient light measurement signal. The measurement controller532may receive the second digital ambient light measurement signal and generate (e.g., in step504of the measurement command execution process500) the measurement information in accordance with the received second digital ambient light measurement signal.

At step616, the sensor100may perform a first photodetector ambient measurement and conversion. For example, in some embodiments, while the light source108is off (i.e., while the light source108, under the control of the measurement controller532, is not emitting light), the first photodetector224may generate a first analog ambient light measurement signal indicative of the amount of light received by the first photodetector224and output the first analog ambient light measurement signal to the signal MUX666. The signal MUX666may select the first analog ambient light measurement signal and, the ADC664may convert the first analog ambient light measurement signal to a first digital ambient light measurement signal. The measurement controller532may receive the first digital ambient light measurement signal and generate (e.g., in step504of the measurement command execution process500) the measurement information in accordance with the received first digital ambient light measurement signal.

At step618, the sensor100may perform a light source-off temperature measurement and conversion. For example, in some embodiments, while the light source108is off (i.e., while the light source108, under the control of the measurement controller532, is not emitting light), the analog interface534may generate a second analog temperature measurement signal indicative of a temperature of the sensor100. In one embodiment, the temperature transducer670may generate the second analog temperature measurement signal while the light source108is off. The ADC664may convert the second analog temperature measurement signal to a second digital temperature measurement signal. The measurement controller532may receive the second digital temperature measurement signal and generate (e.g., in step504of the measurement command execution process500) the measurement information in accordance with the received second digital temperature measurement signal.

Accordingly, in an embodiment in which sequence steps604-618of measurement and conversion process600are performed, the measurement controller532may generate measurement information in accordance with (i) the first digital temperature measurement signal, (ii) the first digital light measurement signal, (iii) the second digital light measurement signal, (iv) the digital light difference measurement signal, (v) the second digital temperature measurement signal, (vi) the first digital ambient light measurement signal, and (vii) the second digital ambient light measurement signal. In a non-limiting embodiment, the calculation of the concentration of the analyte (e.g., performed by the measurement controller532of sensor100and/or sensor transceiver101) may include subtracting the digital ambient light signals from the corresponding digital light measurement signals. The calculation of the concentration of the analyte may also include error detection. In some embodiments, the measurement controller532may incorporate methods for attenuating the effects of ambient light, such as, for example, those described in U.S. Pat. No. 7,227,156, which is incorporated herein by reference in its entirety.

In some embodiments, the measurement controller532may generate measurement information that merely comprises the digital measurement signals received from the analog interface534. In some embodiments, the sensor100may convey the digital measurement signals to an external transceiver101, and the external transceiver101may use the digital measurement signals to determine (i.e., calculate and/or estimate) the concentration of an analyte in the medium in which the sensor100is implanted. In some non-limiting embodiments, the analyte may be glucose, and the transceiver101may calculate glucose concentration in the manner described in U.S. Patent Application Publication No. 2014/0018644, which is incorporated by reference herein in its entirety. However, in some alternative embodiments, the measurement controller532may process the digital signals received from the analog interface534and determine (i.e., calculate and/or estimate) the concentration of an analyte in the medium in which the sensor100is implanted, and the measurement information may, additionally or alternatively, include the determined concentration. In some embodiments, the analyte may be glucose, and the measurement controller532may calculate glucose concentration in the manner described in U.S. Patent Application Publication No. 2013/0331667, which is incorporated by reference herein in its entirety.

In some embodiments, light source108may be turned on before execution of step604and not turned off until after execution of step612. However, this is not required. For example, in other embodiments, the light source108may be turned on during measurement portions of steps604-612and turned off during the conversion portions of steps604-612.

Furthermore, althoughFIG.6illustrates one possible sequence of the measurement and conversion process600, it is not necessary that steps604-618of the measurement and conversion process600be performed in any particular sequence. For example, in one alternative embodiment, light measurement and conversion steps604-612may be performed in a different order (e.g.,606,610,612,608,604), and/or ambient light measurement and conversion steps614-618may be performed in a different order (e.g.,616,618,614). In some embodiments, the light source on temperature measurement may be used to provide an error flag in each individual measurement (e.g., by using a comparator to comparing the light source on temperature measurement to threshold value). In another alternative embodiment, ambient light measurement and conversion steps614-618may be performed before light measurement and conversion steps604-612. In still another alternative embodiment, steps604-618of the measurement and conversion process600may be performed in a sequence in which all of the steps of one of light measurement and conversion steps604-612and ambient light measurement and conversion steps614-618are completed before one or more steps of the other are executed (e.g., in one embodiment, steps604-618may be performed in the sequence604,606,608,616,614,610,612,618). Also, in yet another alternative embodiment, the sensor100may perform only a portion (i.e., less than all) of measurement and conversion sequence steps604-618and/or additional measurement and conversion sequence steps.

FIGS.7A and7Billustrates the timing of an exemplary embodiment of the measurement and conversion process600described with reference toFIG.6.

In addition, when a new transceiver101is used with an implanted sensor100, the new transceiver101may not have sensor calibration parameters and/or information regarding user preferences/settings. In some embodiments, calibration parameters and information regarding user preferences/settings may be stored in the sensor100(e.g., in the non-volatile storage medium660), and the sensor100may convey the stored calibration parameters and/or information regarding user preferences/settings to the new transceiver101(e.g., after determining the transceiver ID from the new transceiver101is a new or different transceiver ID (see step412ofFIG.4). In some embodiments, the calibration parameters and information regarding user preferences/settings may additionally or alternatively be stored in an external memory stick (e.g., USB or Secure Digital (SD) card) or smartphone that is utilized with an external transceiver101before switching to the new external transceiver101. In some embodiments, the calibration parameters and information regarding user preferences/settings may additionally or alternatively be stored on a web portal. The new external transceiver101may receive/download the calibration parameters and/or information regarding user preferences/settings from the sensor, external memory stick, smartphone, or web portal using wired or wireless connection. Accordingly, multiple transceivers101may be used with an implanted sensor100throughout the lifetime of the sensor100without having to reinitiate a calibration process and/or adjust the transceiver to the user preferred setting each time the a new transceiver101is used with the sensor100.

Embodiments of the present invention have been fully described above with reference to the drawing figures. Although the invention has been described based upon these preferred embodiments, it would be apparent to those of skill in the art that certain modifications, variations, and alternative constructions could be made to the described embodiments within the spirit and scope of the invention. For example, the circuitry of the sensor100may be implemented in hardware, software, or a combination of hardware and software. The software may be implemented as computer executable instructions that, when executed by a processor, cause the processor to perform one or more functions. Also, although the present invention has been described with reference to specific embodiments having a sensor and transceivers, the present invention is not limited to systems having a sensor and transceivers and is additionally applicable to any communication system having one node that communicates with one or more other nodes each having a unique identification code.

For another example, although in some embodiments, as illustrated inFIGS.1and2, the sensor100may be an optical sensor, this is not required, and, in one or more alternative embodiments, sensor100may be a different type of analyte sensor, such as, for example, a diffusion sensor or a pressure sensor. Also, although in some embodiments, as illustrated inFIGS.1and2, the analyte sensor100may be a fully implantable sensor, this is not required, and, in some alternative embodiments, the sensor100may be a transcutaneous sensor having a wired connection to the transceiver101. For example, in some alternative embodiments, the sensor100may be located in or on a transcutaneous needle (e.g., at the tip thereof). In these embodiments, instead of wirelessly communicating using inductive elements103and114, the sensor100and transceiver101may communicate using one or more wires connected between the transceiver101and the transceiver transcutaneous needle that includes the sensor100. For another example, in some alternative embodiments, the sensor100may be located in a catheter (e.g., for intravenous blood glucose monitoring) and may communicate (wirelessly or using wires) with the transceiver101.