A system and method for treating congestive heart failure in a patient, including: implanting at least one pressure sensor in a desired location within the patient; providing an ex- vivo interrogation system and monitoring system that can be configured to optionally affect at least one of: selectively energizing the at one pressure sensor, receiving a return or output signal from the at one pressure sensor, processing the return signal, and displaying processed data derived from the at least one pressure sensor to a physician. The system and method also includes deriving diagnostic and treatment information from the processed data and sending diagnostic and treatment information to the patient.
A61B 5/02 - Measuring pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography; Heart catheters for measuring blood pressure
A method for monitoring data in a clinical environment comprises receiving information indicative of a number of ambulatory sensing systems in a measurement environment comprising a plurality of ambulatory sensing systems. The method also comprises establishing a communication scheme associated with the measurement environment based on the number of ambulatory sensing systems in the measurement environment. The method further comprises providing, to each ambulatory sensing system, information indicative of the established communication scheme. The method also comprises configuring, in a central data module associated with the measurement environment, parameters for communicating with each respective ambulatory sensing system in accordance with the established control scheme.
G01B 7/04 - Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width, or thickness specially adapted for measuring length or width of objects while moving
3.
METHODS FOR THE TREATMENT OF CARDIOVASCULAR CONDITIONS
Provided herein are methods and systems for the treatment of cardiovascular conditions, including pulmonary hypertension (PH), in subjects that are being treated with a phosphodiesterase-S (PDE-5) inhibitor. For example, provided are methods of evaluating the progression or improvement of a cardiovascular condition in a subject being administered a treatment regimen that includes a PDE-5 inhibitor, or predicting an outcome in a subject being administered a treatment regimen that includes PDE-5 inhibitor. Methods can include obtaining one or more pulmonary arterial (PA) hemodynamic readings comprising a PA hemodynamic waveform from the subject using an implantable pressure sensor, processing the PA hemodynamic waveform to obtain a cardiovascular parameter, and comparing the cardiovascular parameter obtained from the subject to a standard to determine or predict the progression of the cardiovascular condition, the improvement of the cardiovascular condition, the outcome of the cardiovascular condition, or a combination thereof.
Provided herein are devices, systems, and methods for assessing, treating, and for developing new treatments for pulmonary arterial hypertension (PAH) using pulmonary artery pressure (PAP) values and/or cardiac output (CO) estimates. The system for evaluating progress of pulmonary arterial hypertension (PAH) includes a device configured to obtain a pulmonary artery pressure waveform, a processor, and a memory coupled to the processor. The memory causes the processor to receive the pulmonary artery pressure waveform, determine one or more pulmonary artery pressure (PAP) values, and estimate cardiac output (CO).
The present disclosure is directed to a system having a database operable to receive at least one physiological parameter data from at least one of an electronic medical record (EMR) portal configured for receiving EMR data from an electronic medical record; a healthcare provider (HCP) portal configured for receiving HCP data; a patient portal configured for receiving patient data; and a medical device portal configured for receiving medical device data; for calculating secondary parameters from scoring algorithms, trend algorithms, parameter algorithms and treatment algorithms; then displaying the data and secondary parameters in a graphical format in order to for detect, diagnose and treat chronic disease in patients.
Provided herein are methods for assessing, treating, and for developing new treatments for COPD. Methods can involve obtaining one or more PA hemodynamic readings from a subject with COPD, processing the PA hemodynamic readings to obtain one or more PA hemodynamic parameters, and using the one or more PA hemodynamic parameters to assess, treat, and/or develop new treatments for COPD. The methods can optionally be used to evaluate the progress of (COPD) in a subject, or to predict an outcome in a subject having COPD.
Systems and methods using a database of physiological information for the design, development, testing and use of therapeutics. In one aspect, the physiological information can include at least one of: hemodynamic monitoring information, pulmonary arterial pressure, cardiac output, heart rate, respiratory rate, peripheral vascular resistance, total peripheral resistance or dicrotic notch information. Optionally, the cardiovascular physiology information can include ambulatory physiological information.
A wireless sensor having a primary passive electrical resonant circuit that has an intrinsic electrical property that is variable in response to a characteristic of a patient and a secondary passive electrical resonant circuit. In one aspect, the primary passive resonant circuit can be positioned into a tuned position in response to the actuation of the secondary passive electrical resonant circuit. In a further aspect, in the tuned position, the primary passive electrical resonant circuit, in response to an energizing signal produced by an ex- vivo source of RF energy, is configured to generate a sensor signal characterized by a resonant frequency that is indicative of the characteristic.
A ventricular shunt systems and methods of preventing hydrocephalus are described herein. In one aspect, the ventricular shunt system has at least one pressure sensor that is configured to be selectively electromagnetically coupled to an ex-vivo source of RF energy and is variable in response to the pressure in a patient's ventricle.
A61M 25/088 - Introducing, guiding, advancing, emplacing or holding catheters using an additional catheter, e.g. to reach relatively inaccessible places
A61B 5/027 - Measuring blood flow using electromagnetic means, e.g. electromagnetic flow meter using catheters
Disclosed are hypertension systems and related methods that include a blood pressure sensor located or implanted under the skin of a patient, and electronics, which may have the size and shape of a wrist watch, for example, that monitors the blood pressure of the patient by communicating with the implanted sensor.
A61B 5/02 - Measuring pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography; Heart catheters for measuring blood pressure
A61B 5/0215 - Measuring pressure in heart or blood vessels by means inserted into the body
A61B 5/053 - Measuring electrical impedance or conductance of a portion of the body
11.
PHYSICAL PROPERTY SENSOR WITH ACTIVE ELECTRONIC CIRCUIT AND WIRELESS POWER AND DATA TRANSMISSION
Wireless sensors configured to record and transmit data as well as sense and, optionally, actuate to monitor physical properties of an environment and, optionally, effect changes within that environment, m one aspect, the wireless sensor can have a power harvesting unit; a voltage regulation unit, a transducing oscillator unit, and a transmitting coil. The voltage regulation unit is electrically coupled to the power harvesting unit and is configured to actuate at a minimum voltage level. The transducing oscillator unit is electrically coupled to the voltage regulation unit and is configured to convert a sensed physical property into an electrical signal. Also, the transmitting coil is configured to receive the electrical signal and to transmit the electrical signal to an external antenna.
This application relates to an apparatus and system for sensing strain on a portion of an implant positioned in a living being. In one aspect, the apparatus has at least one sensor assembly that can be mountable thereon a portion of the implant and that has a passive electrical resonant circuit that can be configured to be selectively electromagnetically coupled to an ex-vivo source of RF energy. Each sensor assembly, in response to the electromagnetic coupling, can be configured to generate an output signal characterized by a frequency that is dependent upon urged movement of a portion of the passive electrical resonant circuit and is indicative of strain applied thereon a portion of the respective sensor assembly.
A61B 5/00 - Measuring for diagnostic purposes ; Identification of persons
G01L 1/20 - Measuring force or stress, in general by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
13.
SYSTEM AND APPARATUS FOR IN-VIVO ASSESSMENT OF RELATIVE POSITION OF AN IMPLANT
A system and apparatus for providing an in- vivo assessment of relative movement of an implant that is positioned in a living being is provided that comprises a first assembly and a second assembly that are positioned within the living being. The first assembly comprises a passive electrical resonant circuit that is configured to be selectively electromagnetically coupled to an ex-vivo source of RF energy and, in response to the electromagnetic coupling, generates an output signal characterized by a frequency that is dependent upon a distance between the first assembly and the second assembly at the time of the electromagnetic coupling.
A61F 2/44 - Joints for the spine, e.g. vertebrae, spinal discs
A61B 18/18 - Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by applying electromagnetic radiation, e.g. microwaves
A communication system for communicating with an implanted wireless sensor is provided. A transmit antenna element can propagate an energizing signal onto a communication medium and a receive antenna element can recover a responsive implanted sensor response signal. The antenna box (204) includes a power amplifier for amplifying the energizing signal and timing regeneration circuitry for detecting an end to signals and outputting control signals for selecting mode operation. The antenna box can receive the energizing signal from the antenna cable (208) in a transmit mode and provide the implanted sensor response signal to the antenna cable in a receive mode. The antenna box can communicate with an electronic box (210) and/or conversion box (206) that provide and receive signals and provide power via the antenna cable.
Aspects and embodiments of the present invention provide a loosely-coupled oscillator including a sensor circuit and an electronic device that are not physically connected. In some embodiments, the electronic device includes an amplifier stage and a feedback network and the sensor circuit includes one or more LC circuits. When electromagnetically connected, the sensor circuit and electronic device form an oscillator that is adapted to output an oscillation signal. The resonant frequency of the sensor circuit can be obtained based on the oscillation signal. The sensor circuit may be implanted into an object and the resonant frequency of the sensor circuit can be used to determine characteristics of the object.
G01D 5/12 - Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
A pressure cavity is durable, stable, and biocompatible and configured in such a way that it constitutes pico to nanoliter-scale volume. The pressure cavity is hermetically sealed from the exterior environment while maintaining the ability to communicate with other devices. Micromachined, hermetically-sealed sensors are configured to receive power and return information through direct electrical contact with external electronics. The pressure cavity and sensor components disposed therein are hermetically sealed from the ambient in order to reduce drift and instability within the sensor. The sensor is designed for harsh and biological environments, e.g. intracorporeal implantation and in vivo use. Additionally, novel manufacturing methods are employed to construct the sensors.
G01L 9/12 - Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in capacitance
17.
METHOD AND APPARATUS FOR MEASURING PRESSURE INSIDE A FLUID SYSTEM
A disclosed method determines fluid pressure inside a vessel without compromising the integrity of the vessel. A sensor is positioned in operative communication with the external wall of the vessel such that expansion of the external wall of the vessel exerts a force against the sensor that is directed substantially radially outward with respect to the vessel. A substantially radially inward force is caused to be directed against the sensor in response to the substantially radially outward force exerted by the external vessel wall. The sensor can thus be used to detect the magnitude of the substantially radially outward force. A disclosed apparatus determines fluid pressure inside a vessel without compromising the integrity of the vessel. The apparatus includes a sensor and a band operatively associated with the sensor and configured to at least partially encircle the vessel so as to retain the sensor in operative communication against the external wall of the vessel.
Aspects and embodiments of the present invention provide a system for obtaining, processing and managing data from an implanted sensor. In some embodiments, a patient or other persons can use a flexible antenna to obtain data from the implanted sensor. The flexible antenna includes at least one transmit loop and at least one receive loop. The transmit loop is adapted to propagate energizing signals to the implanted sensor. The receive loop is adapted to detect a response signal from the implanted sensor. The transmit loop includes a capacitor formed by a discontinuous area. The capacitor is adapted to allow the loop to be tuned. The flexible antenna can communicate with a patient device that collects the data from the implanted sensor, creates a data file and transmits the data file to a remote server over a network. A physician or other authorized person may access the remote server using an access device.
Embodiments of the present invention are directed to a cable assembly that is adapted to be connected to an antenna and a base unit. The cable assembly may be relatively flat with shielding and structures to reduce ground currents or other interference. Embodiments of the cable assembly include at least two coaxial cables for transmit and receive signals that are separated to reduce crosstalk or other interference. The cable may also include one or more inner cables, such as differential or switching pairs, between the two coaxial cables to provide cables for control, power, switching, or other functions. The inner cables may be positioned in parallel to each other and to each of the coaxial cables. In some embodiments, the inner cables include a first inner cable located at a first end of the inner cables and a second inner cable located at a second end of the inner cables. One coaxial cable may be positioned adjacent and parallel to the first inner cable, which the other coaxial cable may be positioned adjacent and parallel to the second inner cable.
A method and apparatus for determining cardiac parameters within the body of a patient includes a wireless sensor positioned in the patient's pulmonary artery. An external RF telemetry device communicates wirelessly with the sensor and interrogates the sensor to determine changes in pressure in the pulmonary artery over time. The peak pressure difference is determined. Then, assuming zero blood flow velocity at the time of valve opening and at the time of valve closing, a velocity-time function is determined. The velocity-time function is used to determine a velocity-time integral. The velocity-time integral is then used to determine cardiac stroke volume. The cardiac stroke volume is multiplied times the heartbeat rate to determine cardiac output. The cardiac output can be monitored over time to determine continuous cardiac output.
Aspects of the present invention determine the resonant frequency of a sensor by obtain sensor signals in response to three energizing signals, measure the phase of each sensor signal, and using a group phase delay to determine the resonant frequency. The phase difference between the first and second signal is determined as a first group phase delay. The phase difference between the second and third signal is determined as a second group phase delay. The first group phase delay and second group phase delay are compared. Based on the comparison, the system may lock on the resonant frequency of the sensor or adjust a subsequent set of three energizing signals.
An implant assembly for releasing into a vessel at an implant location includes an intracorporeal device and an anchor. The anchor comprises a pair of resiliently deformable loops operatively associated with the intracorporeal device, both of the loops extending toward the same side of a plane defined by the intracorporeal device. The deformable loops have a relaxed state and a deformed state. When the deformable loops are in a relaxed state, the implant assembly has a major dimension in a direction out of the plane that is greater than the diameter of a vessel at the implant location. The loops are deformable to permit insertion of the implant assembly into the vessel. The tendency of the loops to return to their relaxed state exerts a force on a wall of the vessel that imposes the intracorporeal device against an opposite wall of the vessel.
A61B 5/02 - Measuring pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography; Heart catheters for measuring blood pressure
23.
CAPACITOR ELECTRODE FORMED ON SURFACE OF INTEGRATED CIRCUIT CHIP
A sensor has a sensor housing defining a cavity (14) therein. A first wall (16) partially defining the cavity (14) is deflectable under a physiologically relevant range of pressures. An integrated circuit chip (26) bearing electronics is fixedly mounted within the cavity (14). A capacitor comprises first and second capacitor plates (20, 22) in generally parallel, spaced-apart relation. The first capacitor plate (22) is physically coupled to the deflectable wall (IS) so as to move as the wall deflects, and the second capacitor plate (20) is carried by the chip (26). The second capacitor plate is in electrical communication with the input pad of the chip.
G01L 9/12 - Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in capacitance
24.
INTEGRATED CMOS-MEMS TECHNOLOGY FOR WIRED IMPLANTABLE SENSORS
Disclosed are wired implantable integrated CMOS-MEMS sensors and fabrication methods. A first ceramic substrate comprising a biocompatible material such as fused silica is provided. A polysilicon layer is formed on the first substrate. An integrated circuit is fabricated adjacent to the surface of the first substrate. A passivation layer is formed on the integrated circuit. A conductive area is formed on the passivation layer that provides electrical communication with the integrated circuit. A feedthrough is formed through the first substrate that contacts the conductive area and provides for external electrical communication to the integrated circuit. A second ceramic substrate or cap comprising a biocompatible material is fused to the first substrate so as to form a cavity that encases the integrated circuit and form a sensor. The cavity is preferably a pressure cavity which cooperates to form a pressure sensor.
A hermetically sealed pressure cavity (52) from the exterior environment operable to communicate with external devices via electrical feedthroughs (64,65,80,82). Sensor components (56,57) are configured to receive power and return information through direct electrical contact with external electronics. The pressure cavity (52) and sensor components (56,57) disposed therein are hermetically sealed from ambient pressure. The sensor is designed for harsh and biological environments, e g, intracorporeal implantation and in vivo use.
G01L 7/08 - Measuring the steady or quasi-steady pressure of a fluid or a fluent solid material by mechanical or fluid pressure-sensitive elements in the form of elastically-deformable gauges of the flexible-diaphragm type
G01L 9/00 - Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
A61B 5/03 - Measuring fluid pressure within the body other than blood pressure, e.g. cerebral pressure
26.
PREVENTING FALSE LOCKS IN A SYSTEM THAT COMMUNICATES WITH AN IMPLANTED WIRELESS SENSOR
The present invention determines the resonant frequency of a wireless sensor by adjusting the phase and frequency of an energizing signal until the frequency of the energizing signal matches the resonant frequency of the sensor. The system energizes the sensor with a low duty cycle, gated burst of RF energy having a predetermined frequency. The system receives the ring down response of the sensor and determines the resonant frequency of the sensor, which is used to calculate a physical parameter. The system uses a pair of phase locked loops to adjust the phase and the frequency of the energizing signal. The system identifies false locks by detecting an unwanted beat frequency in the coupled signal, as well as determining whether the coupled signal exhibits pulsatile characteristics that correspond to blood pressure.
A61B 5/00 - Measuring for diagnostic purposes ; Identification of persons
G08C 17/04 - Arrangements for transmitting signals characterised by the use of a wireless electrical link using magnetically coupled devices
G01L 9/12 - Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in capacitance
G01D 5/241 - Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying capacitance by relative movement of capacitor electrodes
27.
COUPLING LOOP, CABLE ASSEMBLY AND METHOD FOR POSITIONING COUPLING LOOP
A coupling loop or antenna is provided that can be used with a system that determines the resonant frequency of a sensor by adjusting the phase and frequency of an energizing signal until the frequency of the energizing signal matches the resonant frequency of the sensor. The coupling loop includes multiple loops. Preferably two tuned loops are used for transmitting the energizing signal to the sensor and an un-tuned loop is used for receiving the sensor signal from the sensor. A cable attached to the coupling loop provides maximum isolation between the energizing signal and the sensor signal by maximizing the distance between the coaxial cables that carry the signals and maintaining the relative positions of the coaxial cables throughout the cable assembly. Orientation features on the housing for the coupling loop and the sensor are provided to assist in positioning the coupling loop relative to the sensor to maximize the coupling between the sensor signal and the coupling loop.
An apparatus for implanting an implant device having a corkscrew-type anchor associated therewith into a patient includes an elongated, flexible shaft. A retention mechanism is located at the distal end of the shaft for retaining the device at the distal end of the shaft. The apparatus includes means selectively operable for disengaging the retention mechanism from the implant device when the anchor has been anchored into tissue at a target site. In another aspect, an apparatus for releasing an implant into a vessel within a patient includes an elongated shaft for inserting into the vessel of the patient. A tether wire extends through the proximal portion of a secondary lumen, exits a first port, engages a portion of the implant, enters a second port, and extends through at least a portion of a distal portion of the secondary lumen. The implant is thereby tethered to the side of the elongated shaft, and pulling the tether wire disengages the tether wire from the distal portion of the secondary lumen and the implant so as to release the implant from the shaft.
A sensor suitable for in vivo implantation has a capacitive circuit and a three-dimensional inductor coil connected to the capacitive circuit to form an LC circuit. The LC circuit is hermetically encapsulated within an electrically insulating housing. An electrical characteristic of the LC circuit is responsive to a change in an environmental parameter.
A method of manufacturing a sensor for in vivo applications includes the steps of providing two wafers of an electrically insulating material. A recess is formed in the first wafer, and a capacitor plate is formed in the recess of the first wafer. A second capacitor plate is formed in a corresponding region of the second wafer, and the two wafers are affixed to one another such that the first and second capacitor plates are arranged in parallel, spaced-apart relation.
G01L 9/00 - Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
An electromagnetically coupled hermetic chamber includes a body defining a hermetic chamber. A first conductive structure is disposed within the hermetic chamber, and a second conductive structure is attached to the body outside of the hermetic chamber. The first conductive structure is electromagnetically coupled to the second conductive structure without direct electrical paths connecting the first and second conductive structures. Thus the first conductive structure can be coupled to external electronics without the need for electrical feedthroughs or vias that could compromise the integrity of the hermetic chamber.
The present invention determines the resonant frequency of a sensor by adjusting the phase and frequency of an energizing signal until the frequency of the energizing signal matches the resonant frequency of the sensor. The system energizes the sensor with a low duty cycle, gated burst of RF energy having a predetermined frequency or set of frequencies and a predetermined amplitude. The energizing signal is coupled to the sensor via magnetic coupling and induces a current in the sensor which oscillates at the resonant frequency of the sensor. The system receives the ring down response of the sensor via magnetic coupling and determines the resonant frequency of the sensor, which is used to calculate the measured physical parameter. The system uses a pair of phase locked loops to adjust the phase and the frequency of the energizing signal.
An implant assembly is implanted in vivo within a vascular system in which a vessel divides at a furcation into two sub-vessels, with smaller diameters. An implant assembly is released into a vessel e.g. a pulmonary arterial vessel. The assembly has a diameter smaller than or substantially equal to the inner diameter of the vessel and larger than the inner diameters of the sub-vessels. The implant assembly moves downstream along with the blood flow. Reaching the furcation where the vessel divides, the implant assembly is too large and not sufficiently compliant to fit through either of the smaller branch vessels, thus lodges at the furcation, prevented from moving downstream by it's size and stiffness and upstream by the blood flow. Alternatively, the implant assembly, upon release, travels down a narrowing vessel until an interference fit is created between the anchor structure and the vessel wall, thereby preventing further distal movement.
A pressure cavity is durable, stable, and biocompatible and configured in such a way that it constitutes pico to nanoliter-scale volume. The pressure cavity is hermetically sealed from the exterior environment while maintaining the ability to communicate with other devices. Micromachined, hermetically-sealed sensors are configured to receive power and return information through direct electrical contact with external electronics. The pressure cavity and sensor components disposed therein are hermetically sealed from the ambient in order to reduce drift and instability within the sensor. The sensor is designed for harsh and biological environments, e.g. intracorporeal implantation and in vivo use. Additionally, novel manufacturing methods are employed to construct the sensors.
A method of manufacturing a hermetically-sealed chamber with an electrical feedthrough includes the step of hermetically fixing an electrode to a substrate in a predetermined location on the substrate. A passage is formed through the substrate through the predetermined location such that at least a portion of the electrode is exposed to the passage. The passage is then at least partially filled with an electrically conductive material. A housing is then formed including the substrate such that the housing defines a chamber, with the electrode being disposed within the housing and the chamber being hermetically sealed. The electrode within the chamber can be placed in electrical communication with an exterior electrical component by way of the electrically conductive material in the passage.
The present invention determines the resonant frequency of a sensor (120) by adjusting the phase and frequency of an energizing signal until the frequency of the energizing signal matches the resonant frequency of the sensor (120). The system energizes the sensor (120) with a low duty cycle, gated burst of RF energy having a predetermined frequency or set of frequencies and a predetermined amplitude. The energizing signal is coupled to the sensor (120) via magnetic coupling and induces a current in the sensor (120), which oscillates at the resonant frequency of the sensor (120). The system receives the ring down response of the sensor (120) via magnetic coupling and determines the resonant frequency of the sensor (120), which is used to calculate the measured physical parameter. The system uses a pair of phase locked loops to adjust the phase and the frequency of the energizing signal.
G01R 23/00 - Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
G01R 23/08 - Arrangements for measuring frequency, e.g. pulse repetition rate; Arrangements for measuring period of current or voltage by converting frequency into an amplitude of current or voltage using response of circuits tuned off resonance
G01R 23/12 - Arrangements for measuring frequency, e.g. pulse repetition rate; Arrangements for measuring period of current or voltage by converting frequency into phase shift
G01R 23/175 - Spectrum analysis; Fourier analysis by delay means, e.g. tapped delay lines
G01R 25/00 - Arrangements for measuring phase angle between a voltage and a current or between voltages or currents
G01D 1/14 - Measuring arrangements giving results other than momentary value of variable, of general application giving a distribution function of a value, i.e. number of times the value comes within specified ranges of amplitude
H03L 7/00 - Automatic control of frequency or phase; Synchronisation
H01Q 7/00 - Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop
H04B 15/00 - Suppression or limitation of noise or interference