RU2787461C9 - Device and method for inductive reading for non-invasive measurement of mechanical activity of patient’s heart and lungs - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: group of inventions relates to medicine, namely to non-invasive study of such physiological characteristics as patient’s heart and lungs dynamics. A method for inductive reading for non-invasive measurement of mechanical activity of heart and lungs is implemented using an inductive reading device. The device contains a resonator circuit formed by the first loop part connected to a capacitor, the second loop part, current-conductive lines, and an active buffer component. The first and the second loop parts are formed by current-conductive lines and spaced from each other in a radial direction along sections of current-conductive lines. The active buffer component electrically connects an output of the resonator circuit to the second loop part and provides amplification of current voltage. An output signal of the active buffer component excites alternating current in the second loop part. The first and the second loop parts are located so that an average radial distance between current-conductive lines is not less than a distance between the second loop part and an area in contact with patient’s tissue.

EFFECT: reduction in sensitivity to motion artefacts and, respectively, sensitivity of a device to movement without an additional complicated circuit and a low catching force.

14 cl, 5 dwg

Description

FIELD OF TECHNOLOGY

The invention relates to an inductive sensing device for coupling electromagnetic signals transmitted to and from a medium.

BACKGROUND OF THE INVENTION

Inductive reading can be used as a means to non-invasively examine the properties of the body.

For example, US 2016223483 discloses spectrographic analysis of materials using inductive multi-frequency sensors, EP1901651 discloses a method and apparatus for inductive measurement of body resistance. In one preferred application, inductive reading can be used as a means for non-invasively investigating physiological characteristics, in particular heart and lung dynamics.

Inductive sensing is based on magnetic induction and has several advantages over conductive and capacitive sensing.

The advantage over conductive readings such as bioimpedance measurements is that there is no need for adhesive electrodes; reading can be done without contact and/or through non-conductive material such as textiles and plastics. In addition, inductive-sensing signals are significantly less susceptible to motion artifact distortion.

The advantage over capacitive sensing is that inductive sensing is based on magnetic fields rather than electric fields, and as a result is more sensitive to changes at greater depths of penetration into the body, as opposed to changes that occur only at skin level. . This is because magnetic fields penetrate deeper into the body than electric fields, and therefore magnetic fields can be used to measure changes in properties inside the body at greater depths, while electric fields are mainly useful only for measuring effects on the skin surface, such as changes in skin properties (eg permeability) or skin movement (skin proximity).

Coil-based inductive sensors function by establishing an inductive coupling with electromagnetic signals (i.e. electromagnetic waves or oscillations), with the propagation of signals through the coil resulting in a change in the current passing through the coil, which can be measured and used to determine the properties of the propagating signal (including, for example, frequency spectrum, amplitude, and phase image).

An electromagnetic excitation signal may be transmitted to the body to be examined. The electromagnetic excitation signal causes magnetic induction in the body, i.e. generation of eddy currents in body tissue due to the application of an external magnetic field. These eddy currents in turn generate electromagnetic signals propagating from the body, which interact with the applied fields in such a way that they can be read by the coil.

Movements of tissue in the body can manifest themselves as changes in the volumes of local areas of the tissue and as changes in the conductive or dielectric properties of the tissue. These changes then cause amplitude and/or phase modulations of the electromagnetic signal emitted from the body in response to electromagnetic stimulation. By monitoring these changes, the movement and size changes of elements within the body can be detected and tracked, as well as changes in conduction and dielectric properties can be tracked. For example, heart contractions manifest themselves mainly as the movement of blood, and breathing manifests itself mainly as changes in the conduction of the lung.

The received signals can be read quantitatively by measuring the oscillation frequency or resonance of the transmitting coil.

There are two main known approaches to reading secondary magnetic signals received from a stimulated sample. The first is based on using a resonator circuit and a coupled coil and reading the received signals based on the change in the resonant frequency of the circuit. The second is to read the received signals as small voltages induced in a specialized receiving coil.

All known resonator-based inductive sensors use a single loop for both primary magnetic field generation and secondary magnetic field induction. In contrast, prior art devices that operate by reading signals as induced voltages use separate transmit coil(s) and receive coil(s); prior art devices using dedicated transmit and receive coils do not operate by reading changes in resonant frequency.

It has been found that inductive sensors that use a single loop to both generate and detect magnetic fields have the problem that the detected signals are very sensitive to motion artifacts (data distortions that occur when the sensor is moved relative to the body being examined). ). It should be understood that this occurs for the following reasons. The strength of the generated secondary eddy currents decreases with distance from the loop generating the signal. For this reason, the eddy currents induced on the surface of the body being examined are stronger than the eddy currents induced in the target deeper tissue. Surface generated currents are generally not useful for most sensing applications, only deeper currents are useful. In addition, surface eddy currents are naturally very close to the resonant loop wire and therefore have a strong effect on the detected signal. As a result, small changes in the distance between the loop and the tissue of interest can lead to signal artifacts that are significantly larger than desired deeper tissue signals, such as cardiac or respiratory signals.

Inductive sensors based on separate transmitter and receiver coils have another problem in that the detectable voltages in the receiver loop are extremely small and furthermore rely heavily on direct magnetic coupling to the transmitter coil. Complex compensating circuits, such as locking amplifiers and heavily shielded multiplexers, must be used to extract very poorly readable signals. This increases the complexity, cost, and form factor of such devices, and their added complexity increases the likelihood of failure.

What is needed is an improved inductive-based sensor that is able to overcome the problem of motion artifacts that occur in single coil devices without the added complexity and low sensing force of prior art dual coil designs.

WO2018/127488 A1 discloses a magnetic inductive sensing device comprising a loop antenna (10) for inductively coupling electromagnetic (EM) signals emitted from a medium in response to stimulation of an electromagnetic excitation medium.

WO2008015598 A2 discloses a sensor for detecting the passage of a pulse wave from the arterial system of a subject. The sensor is configured to be placed in a reading position on the outer part of the object's body.

KR20160034882 discloses a biomagnetic signal reader: a biomagnetic sensor for measuring a biomagnetic signal; and an instrumentation amplifier for removing the noise signal and amplifying the biomagnetic signal sensed by the biomagnetic sensor. The biomagnetic signal and amplifier are combined as a system on a chip (SOC).

SHAO QI et al.: "Efficiency Analysis and Optimization of a Wireless Power Transfer System for Freely Moving Biomedical Implants" discloses an efficiency model based on a coil impedance model and a receiving circuit circuit model. In accordance with the design constraints, the optimal design parameters for the worst case were determined. The results show that the combination of a dual-layer take-up coil and a half-bridge rectifier has more advantages in terms of size, efficiency, and safety, which is preferred in the take-up unit.

DISCLOSURE OF THE INVENTION

The present invention is defined in the claims.

In accordance with an example corresponding to one aspect of the invention, an inductive sensing device for inductively coupling electromagnetic signals transmitted to and from a medium is provided, comprising:

a first loop portion connected to the capacitor to form a resonator circuit;

the second loop part;

respective conductive lines forming the first and second loop portions spaced apart from each other in the radial direction at least along sections of the conductive lines; And

the output of the resonator circuit is electrically connected to the second loop part by means of an active buffer component, wherein the active buffer component is configured to realize voltage over current amplification, and the output signal of the active buffer component is configured to drive an alternating current in the second loop part.

The invention is thus based on the use of a loosely coupled two-loop design comprising a first loop which is part of the resonator circuit and can mainly be used for signal sensing, and a second loop which is not directly part of the resonator circuit that is actively driven, and can be used as the main source of generated signals, with both loops loosely coupled via an active buffer component.

Communication provides synchronous operation of two loops: with currents of the same frequency and in phase with each other. This provides a cooperative guarantee that one loop does not introduce noise into the signals of the other loop. However, at the same time, buffering provides partial electrical isolation of the two loops. In particular, the isolation is one-sided: the first loop is isolated from current fluctuations in the second loop. Thus, the magnetic fields found in the second (excited) loop do not affect the resonator frequency; and only the magnetic fields found in the first (resonator) loop affect the frequency of the resonator.

As a result, the output of the resonator circuit can be used as a readout output for a device (eg, for taking physiological measurements) that is not affected by fluctuations in the second loop. This eliminates the aforementioned problems of two-loop configurations in which the driver loop interferes with the signal readout in the resonant loop.

In addition, the amplification provided by the buffer component ensures that the currents in the second loop portion are stronger than the currents in the first loop portion. This means that the second loop part is the dominant source of transmitted magnetic signals (magnetic fields directed into the tissue), as well as the main source of excitation of secondary eddy currents induced on the tissue surface.

As noted above, surface eddy currents mainly cause motion artifacts due to their inevitable proximity to the conductive line (wire) of the loop that stimulates them. However, since the first and second loop portions are at least partially radially spaced apart in the present design, the dominant surface fields in the radial direction are always closest to the second loop and therefore only significantly affect the second loop. However, due to the buffering of this (second) loop from the main resonant loop (first loop), any fluctuations in the second loop do not affect the frequency in the resonator circuit. Therefore, the output signal of the resonator circuit is much less affected by secondary surface eddy currents than in known devices.

Fluctuations in the second loop are also quickly overcome by active excitation, which provides a strong effect that suppresses any surface artifacts.

At least partial spacing in the radial direction (i.e., spacing at least along portions of the loops) also minimizes direct coupling between the two loops (direct coupling occurs only when the conductive line of one loop completely overlaps or overlaps the line of the second loop) . This eliminates the problem of the read signal when it is suppressed by the feedforward from the second loop (or vice versa). This improves the sensitivity and quality of the signal.

In general, the advantages of the device of the present invention can be summarized as follows:

the amplification provided by the buffer element means that the second loop is the dominant source of surface eddy currents;

the distance between the two loops means that these dominant surface eddy currents only significantly affect the second loop;

buffering between the two loops means that the effect of surface eddy currents on the second loop is essentially isolated from the effect on the frequency of the resonator (whose output provides the measurement signal);

however, the loose coupling via the buffer element ensures that the two loops operate in synchrony, which eliminates the problem associated with known two-loop solutions where only a very weak measurement signal (on top of a strong background signal) can be detected due to target returns picked up by only one from loops. Instead, synchronism means that the signals reflected from the target are received by the entire system of both loops. In particular, the signal can be measured as the change in frequency and/or amplitude of the entire combined system of two synchronous loops. This eliminates the need for complex compensating electronics such as locking amplifiers or shielded multiplexers.

Thus, the new buffer link design provided by the present invention greatly reduces the effects of surface artifacts and hence the sensitivity of the device to movement, while at the same time avoiding various difficulties associated with prior art two-loop designs.

The frequency in the controlled loop is determined by the output signal of the amplifier (active buffer component), while in at least some examples the resonating loop can effectively work as an oscillator operating independently, while its frequency is determined by the induction of magnetic fields in the resonating loop.

The reader finds a preferred use for reading electromagnetic signals emitted from the medium in response to the transmission of electromagnetic excitation signals to the medium. The drive signals are generated by a combination of the first and second loop portions, with the second loop portion providing the primary source. The resonance of the first loop is preferably excited by magnetic coupling with the second loop, the second loop being actively driven (by the active buffer component).

By holding the antenna close to the medium, such as a body, the signals are inductively introduced into the medium, and the induced electromagnetic response signals (usually simultaneously) return back to the resonator (first) loop. This mutual connection causes changes in the electrical characteristics of the current in the first loop, which can be detected to establish the properties of the stimulated medium.

Therefore, the first loop can effectively act as a reading loop. The second loop can effectively act as an excitatory (or transmitting) loop.

For the avoidance of doubt, "radially spaced" means spaced apart or spatially separated or spatially offset in a direction parallel to the plane defined by the corresponding loop. Therefore, at least portions of the conductive lines forming each of the first and second loop portions can be spaced apart or separated in a direction parallel to the plane defined by either the first or second loop. The loops in this case do not completely overlap radially or overlap each other. In this case, there is a non-zero average radial distance between the conductive lines of the two loops. The conductive lines of the two loops are radially displaced relative to each other or at least partially displaced in the radial direction.

In some examples, for example, the first loop portion may have a smaller radius than the second and may be inserted into the second (or vice versa) in the radial direction.

In other examples, the loops can be completely separated from each other in the radial direction without any overlap of wires.

In additional examples, the loops may partially overlap, with the conductive lines of the two loops intersecting at one or more points, but there is no exact or complete overlap of the conductive wires of the loops in the radial direction, i. loops are radially offset from each other. For example, respective interior regions defined by each of the first and second loop portions may partially overlap such that the conductive lines of the first and second loop portions intersect at two or more points.

Such a design has the additional advantage that discontinuous direct coupling between loops can be minimized in cases where the conductive line of one loop passes near the center point or portion of the interior region covered by the other loop. This means that the gain of the buffer amplifier can be increased without the risk of, for example, uncontrolled or uncontrolled amplifier amplitude due to feed-forward loops. This increased gain is advantageous for maximizing the current in the second (transmitting) loop portion over the first (reading) loop portion (so that the second loop dominates in terms of transmitted signals).

Each loop part can be a (completely) closed loop part, i. e. each loop part forms or defines a corresponding closed loop part. These corresponding closed loops are separate. Each loop is formed by at least one conductive line that forms a loop.

Buffer components are a well-known class of electrical components, and the skilled person knows the means to implement such a component. Buffer components are otherwise known in the art as buffer amplifiers or simply buffers. For example, in this case, a buffer is used that is configured to implement voltage over current amplification. In general, a buffer component is an electrical component that provides for the conversion of electrical impedance from one circuit (or part of a circuit) to another in order to prevent the signal source from being subjected to any currents (or voltages for the current buffer) that the load may produce. The signal is "buffered" from the load currents. There are two main types of buffer: voltage buffer and current buffer.

The first loop part is preferably arranged to magnetically interact with the second loop part (i.e., configured to be magnetically coupled to the second loop part) such that, in use, excitation of current in the second loop part by the active buffer component magnetically induces a synchronous current in the first loop part.

"Synchronous" means synchronous with the current of the second loop part, for example, current oscillations of common frequency are generated in the first and second loop. The currents of the two loops can be in-phase with each other or have a fixed phase lag or phase offset (i.e. the frequencies are fixed).

The advantage of this design is that the oscillation of the first loop (resonator circuit) does not require a special attenuation compensation circuit (eg, an active oscillator) to maintain or initiate the oscillation of the resonator. Instead, the resonator oscillates due to the presence of a magnetic connection with the second loop, which is excited by the active buffer component. As a result, the power consumption and the cost of the device are reduced, for example, by reducing the number of components.

In addition, this provides the additional benefit that synchronization between the first and second loops is established as soon as the device starts to operate (as opposed to the short delay that would otherwise occur as the synchronization is stabilized by a weak buffer link).

In addition, the absence of an active drive component for the resonator loop minimizes the sensitivity of the device to electric fields while maintaining sensitivity to a magnetic field. This is because an active drive component, such as a drive oscillator or other damping compensation element, typically introduces parasitic capacitances into the resonator. Such parasitic capacitances are sensitive to electric fields due to capacitive coupling with any nearby objects, for example, in this case, the surface of the skin. Consequently, the absence of an exciting component for the resonator loop (the first loop part) significantly reduces the discontinuous capacitive coupling with the surface of the body under study.

Each loop part can be formed by a loop with one turn.

Keeping the windings small preferably minimizes capacitive effects between the wires forming each of the loops. However, one winding is not essential, and in other examples, one or both of the loop portions may comprise multiple windings.

Each loop portion may be formed by a closed loop, such as a closed loop with one turn. The loop may be a loop of a conducting line, such as a wire.

The active buffer element may be configured to drive the second loop at a frequency that matches the resonant frequency of the resonator circuit. The active buffer component does not actively set the frequency at which the second loop is oscillated, but is instead configured to amplify the received output of the first (resonator) loop portion, this amplified signal being provided as the drive signal for the first (transmit) loop portion.

It should be noted that after the first actuation of the reader in the resonator loop (the first loop part) there is no current fluctuation. However, small noise fluctuations will always be present in the first loop part. The electrical configuration ensures that, when the amplifier is driven, amplification of these oscillations will quickly result in the initiation of oscillations in the two loop portions. In particular, the amplitude will rapidly increase until the loop gain reaches 1. In addition, the loose-coupling design between the coils results in the system stabilizing in a state of synchronous currents in both loops and with zero or fixed phase delay. The regime (frequency, amplitude) in which the system begins to generate oscillations will be the one in which the Barkhausen stability criterion is satisfied.

According to one or more embodiments, the inductive sensing device may further comprise an adjustable or adjustable phase delay element coupled between the active buffer component and the second loop portion. The adjustable phase delay element applies an adjustable (eg, user-adjustable or auto-adjustable) phase delay to the output signal of the active buffer component before the output signal is applied to the second loop portion.

This may, for example, allow any phase delays, such as those induced by an active buffer component or connection to the second loop part, to be compensated. In particular, the phase delay element may be configured to apply a phase delay such that the output signal applied to the second loop portion is in phase with the oscillation (i.e. current) of the first loop portion (or with a fixed phase shift of 2π or a multiple thereof) . This is advantageous because in order for the oscillations in both loops to start and continue stably and in synchrony with each other, the Barkhausen criterion must be met. This preferably requires that the oscillations (ie currents) of the first and second loop portions be in phase (or separated by a fixed phase delay multiple of 2π). The phase delay element may be dynamically adjusted (eg, by a controller or processor) to maintain this zero or constant phase shift.

The output of the resonator circuit may also be connected to a signal output connector for connection to a signal processing means.

The output connector can be a terminal block or connection point for making a connection to a signal processing facility. The signal processing means may be external to the provided reader or may be part of the device.

Only the resonator loop output is used for signal processing, to analyze the signals received from the stimulated body.

The inductive sensing device, in some embodiments, may comprise a damping compensation circuit electrically coupled to the resonator circuit, configured to actively compensate for current decay in the resonator circuit.

As noted above, the resonator circuit is preferably driven by magnetic coupling to the second loop, the second loop being actively driven by the active buffer component. However, in cases where the coupling is not strong enough to ensure this, a separate attenuation compensation component in the resonator circuit can be provided to ensure that the resonator circuit continues or begins to oscillate.

The damping compensation circuit is preferably configured to supply an active drive current to the first loop portion. In the examples, active drive current may be provided at a frequency corresponding to the (natural) resonant frequency of the resonator circuit.

The damping compensation circuit may, for example, comprise an active oscillator.

As noted above, the distance between the first loop portion and the second loop portion ensures that the prevailing surface eddy currents generated by the second loop leave the first loop relatively unaffected. The distance between the conductive lines of the two loops relative to the distance between the loops and the body surface being examined is a significant factor in this effect.

Accordingly, in preferred embodiments, the inductive device may comprise a support structure having a tissue contact area for application to an arbitrary tissue surface, wherein the first and second loop portions are mounted on the support structure and oriented to output and receive magnetic signals in the direction of said contact area. , and arranged so that the average distance between the respective conductive lines, each of which forms the first and second loop parts, is equal to the distance between the second loop part and the contact area or greater than the distance between the second loop part and the contact area.

The average distance may refer to the arithmetic average distance.

The average distance, for example, can be determined by summing and averaging the radial distance between the conductive lines of the two loops over the entire periphery of the two loops. This may include combining the radial distance around the conductive lines and dividing by, for example, the circumference of one of the loops.

For example, the first and second loops may be oriented toward the contact area.

Thus, this embodiment provides for the separation in the radial direction of the two loops (in particular, between the conductive lines of the two loops) as compared to the separation of at least the second loop from the tissue surface being examined in use.

By placing the wire of the first (resonating) loop at a sufficiently large distance from the wire of the second (actively controlled) loop (at least at a distance equal to the distance to the tissue surface or more), capturing unwanted surface fields from the surface (created by the dominant first loop) of the resonating loop decreases. Therefore, the motion sensitivity of the sensor, which is basically the sensitivity to changes in unwanted secondary magnetic fields emanating from the tissue surface, is further reduced.

When determining the average distance between loop lines, the fact that the lines may not be perfectly concentric or aligned is taken into account. Therefore, the distance between the lines may vary at different points along the periphery of the corresponding loop. The average interval is an important measurement.

As noted above, the device may also include signal processing means, an output of the resonator circuit connected to the signal processing means, and the signal processing means configured to determine a measurement of one or more physiological parameters based on the output signal.

In particular, the signal processing means is preferably configured to analyze the (resonant) frequency of the resonator circuit and determine the measurement of a physiological parameter based on said frequency.

Alternatively, the signal processing means may be configured to analyze the oscillation amplitude of the resonator circuit (the first loop portion) and determine a physiological parameter measurement based on said amplitude.

According to one or more embodiments, the resonator circuit capacitor may have an adjustable capacitance. This increases the flexibility of the device because the resonant frequency of the resonator circuit can be tuned, adjusted, or configured to suit various specific applications.

According to one or more preferred embodiments, the device may include an additional capacitor connected to the second loop portion.

This provides the additional benefit of reduced heat generation in the active buffer component. In particular, when the direction of the current is reversed in the second loop part, the magnetic field energy of the second loop part is temporarily stored in the capacitor during each oscillation cycle. This reduces heat dissipation in the voltage amplifier.

The additional capacitor can preferably be made with a capacitance of such a value as to set the oscillation frequency of the second loop part, which corresponds to the natural frequency of the first loop part.

By selecting the capacitance for the second loop (for example, by microprocessor control) so that the second loop operates at or near the natural frequency of the first loop portion, heat dissipation in the voltage amplifier is minimized. This is particularly advantageous in applications where low power consumption is important (e.g. wearable inductive sensors with limited battery capacity).

In the absence of a capacitor, the amplifier would have to actuate each cycle to convert the received frequency from the first loop to the resonant frequency of the second loop (i.e. overcome the mismatch between them). This would lead to heat generation and energy consumption.

The natural frequency means the frequency of natural electrical resonance. The second loop, in the absence of a capacitor, usually has a very high natural frequency. By adding a tuning capacitor, the radial frequency can be reduced, in particular by the amount ω0 = (LC) ^-1/2 where L is the loop inductance and C is the total capacitance of the loop and the added tuning capacitor. It can be reduced in such a way that the natural frequency of the second loop approaches the natural frequency of the first loop. This reduces the required work of the amplifier and consequently reduces power consumption.

The additional capacitor for the second loop part may have an adjustable capacitance.

This increases the flexibility of the device, since the second loop can be configured, for example, to match the different possible resonant frequencies of the resonator circuit.

The capacitance of the capacitor may be dynamically adjusted (eg, by a processor or controller) to maintain the operating frequency of the second loop portion substantially in accordance with the frequency of the first loop portion.

The device can be made so that the first and second loop parts occupy a common plane. This is preferred as this layout minimizes the form factor.

For example, the device may include a support portion or a support structure on which the first and second hinge portions are mounted. Then the support part may have the first and second loop parts located in the same plane.

In addition, the first and second loop parts can be inserted into each other (ie, one loop is located inside the other). This naturally requires one loop to have a smaller radius than the other. Preferably the second loop part is inserted inside the first. Therefore, the first and second loops form a nested loop construction. For example, each of the two loops may define (enclose) an interior region, with the interior of one loop being entirely contained within the interior of the other loop. For example, one loop may have a smaller radius and have an interior that completely overlaps the interior of another loop (larger radius).

A nested design like this preferably saves space. In this case, the radial distance between the respective conductive lines of the two loops can be ensured by the mismatch of the radii of the two loops.

According to one or more examples, respective interior regions defined by each of the first and second loop portions may be partially overlapped such that the conductive lines of the first and second loop portions intersect at two or more points. In this case, the loops may partially overlap and partially not overlap.

Examples in accordance with a further aspect of the invention provide an inductive sensing method comprising transmitting electromagnetic signals to a medium, the method using a loop structure comprising:

a first loop portion connected to the capacitor to form a resonator circuit, and

second loop part

respective conductive lines forming the first and second loop portions spaced from each other in the radial direction, and

an output of the resonator circuit electrically connected to the second loop part by means of an active buffer component configured to implement voltage over current amplification, wherein

the method includes driving an alternating current in the second loop part by means of an output signal of the active buffer component.

The additional embodiments described above with respect to the apparatus aspect of the present invention may be applied with equal advantage to the method aspect of the invention described above.

In accordance with one set of preferred embodiments, the method includes holding said loop structure relative to the surface of the medium under test in such a way that the distance from the second loop part to the surface of the medium is equal to or less than the minimum distance between the conductive lines of the first and second loop parts.

This thus provides the preferred relatively spaced arrangement described above, in which the minimum distance between the loop portions and the surface to be examined is less than or equal to the distance between the conductive lines of the loops themselves. Moreover, the distance between the conductive lines may be formed by the support structure on which the hinges are installed, or may be formed by the configuration in which the user holds the device.

These and other aspects of the invention will be apparent and explained with reference to the embodiments described below.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention and a clearer idea of how it can be put into practice, reference will now be made, by way of example only, to the accompanying drawings, in which:

FIG. 1 shows an exemplary inductive sensing device in accordance with one or more embodiments;

FIG. 2 shows in more detail a construction diagram of the exemplary reader of FIG. 1;

FIG. 3 schematically depicts an exemplary support structure housing an exemplary reader in accordance with one or more embodiments;

FIG. 4 shows various designs for an exemplary reader in accordance with various possible exemplary embodiments; And

FIG. 5 shows yet another exemplary reader design in which the first and second loop portions partially overlap.

IMPLEMENTATION OF THE INVENTION

The invention will be described with reference to the drawings.

It should be understood that while the detailed description and specific examples show exemplary embodiments of devices, systems, and methods, they are provided for purposes of illustration only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the devices, systems, and methods of the present invention will become more apparent from the description below, the appended claims, and the accompanying drawings. It should be understood that the drawings are schematic and not to scale. It is also to be understood that the same reference numerals are used throughout the drawings to refer to the same or like parts.

The invention provides an inductive sensing device comprising first and second loops, wherein the first loop is connected to a capacitor to form a resonator circuit, and the resonator circuit and the second loop are coupled via an active buffer component. The active buffer component provides voltage over current amplification, and the output of the buffer component controls the current in the second loop. The conductive lines forming each of the first and second loop portions are spaced apart in the radial direction.

In preferred examples, the second loop portion has a smaller radius than the first and is inserted inside the first.

Recent innovations in inductive sensing have made it possible to easily and non-contactly measure the mechanical activity of internal anatomical structures such as the heart and lungs. Such sensors can be preferably implemented in wearable patient monitors, non-contact patient monitoring, and also for quick selective measurements.

The working principle of inductive reading is based on Faraday's law. An oscillatory primary magnetic field is generated by the generating loop, and it induces, according to Faraday's law of induction, eddy currents in the tissue under study. The eddy currents create a secondary magnetic field, which is detected by the trapping loop. For example, respiration, contraction of the heart and expansion of the aorta or other arteries change the geometry of the conductive structures under study, this also changes the eddy currents and, consequently, the secondary magnetic field. Therefore, this can be detected in the signal that is received by the trapping loop.

Recent developments, for example, have significantly improved signal strength by shifting the operating frequency to the new 50 - 500 MHz range and by improving the protection of electronics from electrical noise. The inventors have found that inductive sensors that operate with a single loop as part of the resonator provide the highest signal to noise ratio.

As noted above, a disadvantage of known single-loop sensors is their very high sensitivity to motion artifacts caused by dominant surface eddy currents. The inductive sensing device of the present invention substantially eliminates this problem.

In general, the advantages of the device of the present invention can be summarized as follows:

the amplification provided by the buffer element means that the second loop is the dominant source of surface eddy currents;

the distance between the two loops means that these dominant surface eddy currents only significantly affect the second loop;

buffering between the two loops means that the effect of surface eddy currents in the second loop is isolated from the effect on the frequency of the resonator (whose output provides the measurement signal);

however, loose coupling by the buffer element ensures that the two loops operate in sync, which prevents interaction between the two loops; in particular, suppression of the resonator frequency by phase-shifted magnetic signals coming from the dominant second loop is eliminated.

FIG. 1 shows an exemplary inductive sensing device 12 in accordance with one or more embodiments of the present invention, wherein the device is for inductively coupling electromagnetic signals transmitted to and from a medium.

The inductive sensing device 12 includes a first loop portion 16 and a second loop portion 24. The first loop portion is connected to a capacitor 18 to form a resonator circuit 20. The resonant frequency of the resonator circuit is determined (at least in part) by the capacitance of the resonator circuit.

Each of the first and second loop parts is formed by a closed loop with one turn of a conductive line, for example, a wire.

Corresponding conductive lines of the first 16 and second 24 loop parts are spaced from each other in the radial direction. In the example of FIG. 1, the radial distance is ensured by the fact that the second loop part has a smaller radius than the first loop part and is inserted inside the first, i.e. located inside the first. For example, the corresponding inner region of the second loop portion 24 is entirely contained within the inner region of the first loop portion 16 of greater radius. However, this particular location is not essential (as will be described below). In this example, these two elements occupy a common plane, but this is also not essential, and in the alternative, they can be, for example, axially offset from each other.

The output of the resonator circuit 20 is electrically coupled to the second loop portion 24 via an active buffer component 28. The buffer component provides a buffering function that implements one-way electrical isolation of the resonator circuit from the second circuit portion so that the resonator circuit 20 is isolated from electrical fluctuations in the second loop portion 24.

The active buffer component 28 is also configured to implement voltage over current amplification, and the output signal of the active buffer component is configured to excite an alternating current in the second loop portion 24.

As noted earlier, buffer components are a well-known class of electrical components, and the skilled person will know the means to implement such a component. Buffer components are otherwise known in the art as buffer amplifiers or simply buffers. For example, in this case, a buffer is used that is configured to implement voltage over current amplification. In general, a buffer component is an electrical component that converts electrical impedance from one circuit (or part of a circuit) to another in order to prevent the signal source from being subjected to any currents (or voltages for the current buffer) that the load may produce. The signal is "buffered" from the load currents. There are two main types of buffer: voltage buffer and current buffer.

In this case, the first loop portion 24 is buffered against current fluctuations in the second loop portion. Therefore, in this case, the second loop part can be understood as "load".

The active buffer component 28 may include a voltage buffer connected to a voltage-to-current amplifier to thereby implement buffering and amplification functions. A voltage-over-current amplifier is preferred as it assists in generating the current required to generate the oscillations in the second loop portion (the transmission loop).

In some examples, the active buffer component 28 may include an operational amplifier coupled to a voltage-to-current amplifier.

In the example shown, the first loop portion and the resonator female circuit are further provided with an electromagnetic shielding element 34 configured to shield the first loop portion and the capacitor 18 from electric fields. The shielding element can be, for example, a shielding plate or a housing. It may be made of metal. It may delimit one or more slots or holes in the element body to prevent eddy currents in the shield element and hence interfering magnetic fields. However, the shielding element is not required and is not related to the operation of the reader.

The shield element 34 is in some cases grounded, as shown in FIG. 1 while the resonator circuit 20 is not grounded. The shield 34 and the first loop portion 16 are separated by an insulating separating medium, such as a dielectric layer.

The output of the active buffer component 28 is further connected to the signal output connector 30 for connection to the signal processing means. In some cases, the inductive device 12 may include signal processing means for analyzing the frequency of the resonator circuit and, based on this, measuring one or more physiological parameters.

In use, the output signals of the resonator 20 at said signal output connector 30 can be analyzed by a signal processing means (comprising, for example, control and readout electronics). Information about the body being examined, such as heart and/or respiration information, will be present in the frequency of the resonator, which can be measured by the signal processing means. In particular, information concerning the investigated medium can be detected in the form of changes in the frequency of the resonator circuit.

A heart pulse, for example, may be seen as small but clearly detectable changes in the frequency of the resonator circuit 20, and respiration may be detected as larger, slower changes in the frequency of the resonator circuit 20.

In the example of FIG. 1, the device is configured such that the first and second loop portions 24 occupy a common plane and also such that the second loop portion 24 is smaller than and inserted into the first loop portion. This provides a compact placement in space.

FIG. 2 is a schematic diagram of the exemplary inductive sensing device shown in FIG. 1.

An active buffer element 28 is shown. The voltage over current amplification is provided in conjunction with buffering between the resonator circuit 20 and the second loop portion 24.

As discussed in the previous section, in the preferred embodiment, the first 16 and second 24 loop portions are magnetically interoperable (i.e., the first loop is positioned to be magnetically coupled to the second loop), such that when used, excitation of current in the second loop part by the active buffer component 28 magnetically induces a synchronous current in the first loop part. Such magnetic interaction can be achieved through a wide range of different relative spatial arrangements of the loops. In the examples in FIG. 1 and 2 loops are located in the plane and nested one into the other. However, as discussed in more detail below, magnetic coupling can also be achieved in examples where the loops are adjacent, i.e. side by side to each other.

This design provides the additional advantage that it does not require a damping compensator (eg, an active oscillator) associated with the resonator circuit 20 to initiate and/or maintain the oscillation of the resonator. Instead, the resonator oscillates due to magnetic coupling to the second loop, which is driven by an active buffer element 28.

The advantages of optionally not having a dedicated damping compensator include, firstly, that the resonator circuit does not require a dedicated excitation oscillator, which saves energy and costs by reducing the number of parts. In addition, the timing between the first 16 and second 24 loops is established as soon as the resonator oscillates, rather than after a slight delay, since the timing is stabilized by loop buffering. Moreover, sensitivity to electric field is minimized while sensitivity to magnetic fields is maintained.

This is because an active drive component, such as a drive oscillator or other damping compensation element, typically introduces parasitic capacitances into the resonator. Such parasitic capacitances are sensitive to electric fields due to capacitive coupling with any nearby objects, for example, in this case with the surface of the body under study. Consequently, the absence of an exciting component for the resonator circuit (the first loop part) significantly reduces the discontinuous capacitive coupling with the surface of the body under study.

Electric fields are not useful for inductive reading and introduce noise into the read signal.

The use of magnetic feedback to initiate oscillation generation has been used in previous unrelated fields, such as with so-called Armstrong oscillators. However, this principle has never been applied in the context of an inductive sensing device as in the embodiments of the present invention. In particular, for known Armstrong generators, sensitivity to inductive and capacitive coupling with external bodies is considered detrimental, and the circuit is designed to minimize such coupling. In contrast, for the embodiments of the present invention, the objective of the device is to magnetically couple to external bodies.

Therefore, in embodiments of the present invention, relatively large, optionally electrically shielded, single winding loops can be used with advantage in some examples. In contrast, known Armstrong generators usually contain small coils with many windings.

For example, for inductive sensors according to embodiments of the present invention (e.g., for vital sign monitoring purposes), typical loop diameters can be from 1 cm to 5 cm. Typically, the loops can have a diameter of more than 1 cm. The loops preferably have only one winding. Loops larger than 1 cm in diameter and with one winding would not be preferred for use in Armstrong generators, as this would make the electronic parts too bulky and would also lead to increased coupling to external bodies, which is undesirable for Armstrong generators.

The described magnetic interaction is not essential to the invention. The benefits of inventive design are not inextricably linked to such a feature. Alternatively, a dedicated damping compensation circuit may instead be provided, for example, for the purpose of initiating or sustaining oscillations in the resonator circuit 20. An oscillator may be provided, for example, to initiate and/or maintain oscillations of the resonator circuit.

FIG. 2 schematically depicts such an optional attenuation compensation circuit 32 electrically coupled to the resonator circuit 20, configured to actively compensate for current attenuation in the resonator circuit. The damping compensation circuit may, in the examples, comprise an oscillator circuit.

If, for example, the direct magnetic coupling between the second (driven) loop 24 and the first (resonator) loop 16 is too weak or too unstable for the resonator circuit 20 to oscillate through this coupling alone, then the circuit can be made more reliable by providing a dedicated attenuation compensation circuit 32 electrically coupled to the resonator circuit. The device in this case no longer depends on a direct magnetic connection between the second loop 24 and the first loop 16.

In accordance with one set of preferred embodiments, the exemplary inductive sensing device circuitry may further include an adjustable or configurable phase delay element coupled between the active buffer component 28 and the second loop portion 24. The adjustable phase delay element applies an adjustable (e.g., user configurable) phase delay. to output a signal of the active buffer component 28 before supplying the output to the second loop portion.

This may, for example, allow any phase delays, such as those induced by the active buffer component 28 or connection to the second loop, to be compensated for. In particular, the phase delay element can be configured to apply a phase delay such that the output signal applied to the second loop part is in-phase with the fluctuations (i.e. current) of the first loop part (or with a fixed phase shift of 2π or a multiple of it) . This is advantageous because in order for the oscillations in both loops to start and continue stably and in synchrony with each other, the Barkhausen criterion must be met. This preferably requires that the oscillations (ie currents) of the first and second loop portions be in phase (or separated by a fixed phase delay multiple of 2π).

In use, the first 16 and second 24 loop portions of device 12 are held near the body or medium of interest, and the second loop portion is energized by an active buffer component which, in preferred examples, then magnetically couples the resonator circuit 20 to oscillate. Both the second loop part and the first loop part of the resonator circuit generate excitation signals that are directed to the tissue under study. As noted above, the second loop portion 24 provides a dominant source of transmit or stimulus signals due to the higher current amplitude in this loop due to the amplification provided by the active buffer component 28.

Signals from both loops enter the tissue under study. The second loop part dominates the eddy currents induced in the tissue under study. The induced eddy currents create secondary magnetic fields. These secondary fields are detected both by the second loop part 24 and by the resonator circuit 20. However, the pickup strength is much higher in the resonator circuit 20 due to the resonance effect (which effectively amplifies the induced inductance signals in the first loop 16 of this circuit). Although the pickup strength is higher in the first loop, the sensitivity to motion artifacts (i.e. movements of the loop relative to the surface) is much higher in the second loop due to the second loop's great radial proximity to the dominant surface eddy current signals.

In addition, only the signals sensed in the first loop portion (resonator circuit) are used to measure the signals, which are applied to the structure output connector 30 . In particular, the signals read in the resonator circuit cause changes in the oscillation frequency of the resonator, which can be read by the signal processing electronics. The signals read in the first loop portion are prevented from affecting the frequency of the first loop portion of the buffer component 28. In addition, any changes induced in the current of the second loop 24 are actively suppressed by the gain applied by the amplifying buffer component, which maintains a stable current frequency in the second loop. Therefore, the signals read in the second loop are not actually taken into account or discarded and are not used for measurement.

According to preferred examples, inductive sensing device 22 can be used to determine physiological parameters and properties, such as the movement of air, fluid and/or tissues in a patient's body. The system can be successfully used, in particular, for example, to determine respiratory movements.

In these examples, the device is capable of detecting air, fluid, and/or tissue movements (eg, caused by breathing or heartbeat) by measuring the modulation of the reflected signal inductance caused by these movements.

In accordance with one or more embodiments, the device may include a support structure for mounting components in a particularly preferred location.

FIG. 3 shows an example of an inductive sensing device 12 comprising a support structure in the form of a housing 48 within which the first and second loop portions are mounted (and the associated circuit design of FIGS. 1 and 2). The body 48 has first 16 and second 24 loop portions installed in a certain spatial configuration relative to the area 52 of the body in contact with the tissue. The tissue contact area is formed by the sole or base of the housing and includes an outer contact surface for application to an arbitrary tissue surface 54 (or other, for example, inorganic, body surface). Loops are shown only schematically, and circuit design is not shown.

The first 16 and second 24 loop parts are installed inside the housing 48 and are oriented towards the area 52 in contact with the fabric, for the output and reception of magnetic signals in the direction of the specified area of contact. The radial distance 42 between the conductive lines forming the first 16 and second 24 loops is equal to or greater than the distance 44 between the second and first loops and the area in contact with the tissue.

As noted above, in accordance with any embodiment of the present invention, inductive sensing device 12 may also include signal processing means configured to receive as input the output of resonator circuit 20. The signal processing means may be configured to derive one or more physiological parameters based on read characteristics of the signal obtained at the output of the resonator circuit. This may, for example, include one or more vital signs such as, for example, heart rate, pulse rate, tidal volume, respiratory rate, systolic volume, systolic volume variation, cardiac output, or aortic height/pressure/diameter modulation. or arterial pulse.

The device may be an inductive physiological readout device for reading one or more physiological parameters of the subject's body. Physiological parameters may include, for example, one or more of the vital signs listed above.

The signal processing means is preferably configured to determine a measurement of one or more physiological parameters based on detected changes in the oscillation frequency of the resonator circuit.

The particular means used to implement the signal processing is not essential to the invention. By way of example, the signal processing means may comprise, for example, an automatic phase-locked loop (PLL) base signal analyzer. Alternatively, or in addition, any other signal processing means may be used, as will be apparent to those skilled in the art.

In accordance with one or more examples, the reader 12 may also include an additional capacitor connected to the second loop portion 24. This provides an advantage in terms of reducing the heat generation of the active buffer component 28. In particular, when the current is reversed in the second loop 24 , the energy of the magnetic field of the second loop is temporarily stored in the capacitor during each oscillation cycle. This reduces heat dissipation in the voltage amplifier.

For example, the capacitance of the capacitor for the second loop 24 may be selected or configured, for example, by a microprocessor, such that the second loop operates at or near the frequency of the first loop portion 16. In this case, heat generation on the active buffer component 28 is minimized. This is particularly advantageous, for example, in applications where low power consumption is important (eg in the case of wearable sensors with limited battery capacity).

In some examples, the capacitor for the second loop portion may be an adjustable or adjustable capacitor having an adjustable or controllable capacitance. The capacitance of the capacitor can be dynamically adjusted (eg by a microprocessor) so that the operating frequency of the second loop portion is substantially the same as the operating frequency of the first loop portion.

In the absence of a capacitor, an active buffer component might be required on each cycle to act, for example, to compensate for a mismatch between two loop frequencies. This would lead to heat generation and energy consumption.

A variable capacitor, such as a dynamically variable capacitor on the second loop portion, allows the natural frequency of the second loop to approach the natural frequency of the first loop. This reduces the required operation of the active buffer amplifier and thus reduces power consumption.

The relative position of the first 16 and second 24 loop parts is not critical to the invention. However, the wires of the first and second loops must be spaced apart in the radial direction (i.e. not touching). As discussed, the minimum distance between wires should preferably be greater than the distance to the body surface being examined. This can be provided with an appropriate housing or support structure as described above.

In various examples, the second loop 24 may be, for example, outside the first loop 16 or inside the first loop. A number of possible designs are, for example, illustrated in FIG. 4(a)-(h). Another option (not shown) is to place the first loop part 16 of the loop inside the second loop part 24.

FIG. 4(a)-(d) show various designs, each having an attenuation compensation circuit 32 connected to a resonator circuit formed by the first loop portion 16. In FIG. 4(a)-(d) show various embodiments in which the second loop portion 24 is either outside or inside the first loop portion 16, and the second loop portion 24 either contains or does not contain a dedicated additional capacitor. In case an additional capacitor is provided, it is shown electrically connected to the control electronics 62 for configuring the capacitor. In this case, the capacitor has a capacitance controlled, for example, by a microprocessor included in the control electronics. The control electronics 62 also includes signal processing means for analyzing the output of the resonator circuit formed by the first loop portion 16, the output of the active buffer element being connected to the control electronics for this purpose.

It should be noted that the attenuation compensation circuit 32 is designated "-R" because this component can be understood in general terms as providing an effective negative resistance to compensate for losses in the resonator. As noted above, in the examples this can be facilitated, for example, by an active excitation oscillator.

FIG. 4(e)-(h) illustrate the same loop arrangements and the presence or absence of an additional capacitor as in FIG. 4(a)-(d), but only without the attenuation compensation circuit associated with the resonator circuit formed by the first loop portion 16.

According to a further preferred set of examples, the first 16 and second 24 loop portions may have respective interior regions that partially overlap such that their respective conductive lines intersect at two or more points. Thus, the two loops are radially offset from each other. An example of such an arrangement is shown schematically in FIG. 5.

It can be seen that although in this example the two loops partially overlap, there is no exact or complete overlap of the conductive wires of the loops in the radial direction, i. the loops are spaced apart from each other in the radial direction. The loops partially overlap and partially do not overlap. Therefore, the respective conductive lines of the first 16 and the second 24 loop portions are not radially spaced from each other along the entire periphery of each loop portion, but only through certain sections, while the respective conductive lines intersect at two points.

In the illustrated construction, the conductive line of each of the loops 16, 24 extends near a central point or portion of the interior area covered by the other loop. This has the additional advantage that a discontinuous direct connection between loops can be minimized. This means that the gain of the buffer amplifier can be increased without the risk of, for example, uncontrolled or uncontrolled amplifier amplitude due to feed-forward. This increased gain is advantageous for maximizing the current in the second (transmitting) loop portion over the first (reading) loop portion (so that the second loop dominates in terms of transmitted signals).

In this example, the radial distance between the respective conductive lines forming the first and second loop portions is non-uniform, i.e. the radial distance changes at different points around the loops.

According to one or more examples, a controller may be provided to control or coordinate the functionality of the inductive sensing device. For example, it may be configured to execute a control program to operate the reader, in some cases responsive to input control commands received from a user or operator. A user interface means, such as a control interface such as a control panel, a touch screen, or a software tool, may be provided for this purpose.

The controller may be implemented in a variety of ways in software and/or hardware to perform various desired functions. A processor is one example of a controller that uses one or more microprocessors that can be programmed using software (eg, microcode) to perform the required functions. However, the controller may be implemented with or without a processor, and may also be implemented as a combination of specialized hardware to perform some functions and a processor (eg, one or more programmed microprocessors and associated circuitry) to perform other functions.

Examples of controller components that may be used in various embodiments of the present disclosure include, but are not limited to, conventional microprocessors, application specific integrated circuits (ASICs), and field programmable gate arrays (FPGAs).

In various implementations, a processor or controller may be associated with one or more storage media such as volatile and non-volatile computer memory such as RAM, PROM, EPROM, and EEPROM. The storage media may be encoded with one or more programs that, when executed on one or more processors and/or controllers, perform the desired functions. Various storage media may be affixed to the processor or controller, or may be portable such that one or more programs stored thereon may be downloaded to the processor or controller.

Examples in accordance with a further aspect of the invention provide an inductive sensing method comprising transmitting electromagnetic signals to a medium, the method using a loop structure comprising:

a first loop portion 16 connected to a capacitor to form a resonator circuit 20, and

the second loop part 24,

respective conductive lines forming the first and second loop portions spaced from each other in the radial direction, and

an output of the resonator circuit electrically connected to the second loop part by means of an active buffer component 28 configured to implement voltage over current amplification, wherein

the method includes driving an alternating current in the second loop part by means of an output signal of the active buffer component.

In accordance with preferred embodiments, the method may include holding said loop structure relative to the surface of the medium under test in such a way that the distance from the second loop portion 24 to the surface of the medium is equal to or less than the minimum distance between the conductive lines of the first and second loops.

Variations of the disclosed embodiments may be understood and implemented by those skilled in the art in the practice of the claimed invention based on a study of the drawings, description and appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the grammatical form of the singular does not exclude the presence of a plurality. One processor or other device can perform the functions of several elements specified in the claims. The fact that certain measures are set forth in mutually distinct dependent claims does not mean that a combination of these measures cannot be used to advantage. The computer program may be stored/distributed on a suitable medium, such as an optical storage medium or solid state media provided with or as part of other equipment, but may also be distributed in other forms, such as over the Internet or other wired or wireless telecommunications systems. No reference positions in the claims are to be construed as limiting the scope.

Claims (26)

1. An inductive reading device (12) for non-invasive measurement of the mechanical activity of the patient's heart and lungs, comprising: a resonator circuit (20) formed by the first loop portion (16) connected to the capacitor (18); and the second loop part (24); respective conductive lines forming the first and second loop portions spaced apart from each other in the radial direction at least along sections of the conductive lines; characterized in that the device also contains an active buffer component (28) through which the output of the resonator circuit is electrically connected to the second loop part, wherein the active buffer component is configured to implement voltage amplification over current, and the output signal of the active buffer component is configured to excite an alternating current in the second loop part, moreover, the first and second (24) loop parts are located so that the average radial distance between the conductive lines forming the first and second loop parts is not less than the distance between the second loop part and the area in contact with the fabric. 2. The device (12) according to claim 1, in which each loop part (16, 24) is formed by a loop with one turn. 3. Apparatus (12) according to claim 1 or 2, wherein the output of the resonator circuit (20) is further connected to a signal output connector for connection to the signal processing means. 4. Device (12) according to any one of paragraphs. 1-3, which further comprises an attenuation compensation circuit electrically coupled to the resonator circuit (20) and configured to actively compensate for current attenuation in the resonator circuit. 5. Device (12) according to claim 4, wherein the attenuation compensation circuit comprises an oscillator configured to provide an active drive current in the first loop portion (16). 6. Device (12) according to any one of paragraphs. 1-5 comprising a support structure having a tissue contact area for application to a patient's tissue surface, wherein the first and second (24) loop parts are mounted on the support structure and oriented to output and receive magnetic signals in the direction of the specified contact area. 7. Device (12) according to any one of paragraphs. 1-6 further comprising signal processing means, wherein the output of the resonator circuit (20) is connected to signal processing means configured to performing a measurement of one or more physiological parameters of mechanical activity of the patient's heart and lungs based on the output signal. 8. Device (12) according to any one of paragraphs. 1-7, containing an additional capacitor connected to the second loop part (24). 9. The device (12) according to claim 8, in which the additional capacitor is made with a capacitance having such a value to set the oscillation frequency of the second loop part corresponding to the natural frequency of the first loop part (16). 10. Device (12) according to claim 8 or 9, in which the additional capacitor has an adjustable capacitance. 11. The device (12) according to any one of paragraphs. 1-10, made so that the first and second (24) loop parts occupy a common plane. 12. The device (12) according to any one of paragraphs. 1-11, in which one of the first and second (24) loop parts are inserted one into the other. 13. The device according to any one of paragraphs. 1-12, wherein respective interior regions formed by each of the first and second loop portions partially overlap so that the conductive lines of the first and second loop portions intersect at two or more points. 14. The method of inductive reading for non-invasive measurement of the mechanical activity of the heart and lungs of the patient, including the transmission of electromagnetic signals into the environment, and the method uses a loop structure containing: a first loop part (16) connected to a capacitor to form a resonator circuit (20), a second loop part (24), corresponding conductive lines forming the first and second loop parts, spaced apart from each other in the radial direction along at least sections of the conductive lines, output of the resonator circuit, electrically connected to the second loop part by means of an active buffer component (28), configured to implement voltage amplification over current, moreover the method includes excitation of alternating current in the second loop part by means of the output signal of the active buffer component, moreover, the distance from the second loop part (24) to the surface of the patient's tissue to be examined is not more than the distance between the conductive lines of the first and second loop parts.

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