System for vital-parameter detection

Abstract

A system (1) for vital-parameter detection (1) comprises: - a sensor arrangement (10) with at least one signal line (12), which is disposed within a detection area (D) and is adapted to propagate an electromagnetic signal, and at least one coupling element (15), which is disposed so that an electromagnetic coupling between the coupling element (15) and the signal line (12) is influenceable by a body part (50, 51) of a living being in a coupling region (C) associated with the coupling element (15); and - a control device (30) that is operatively coupled to the at least one signal line (12), wherein the control device (30) is adapted to perform at least one detection process (100) which includes: - applying (110) a time-dependent first detection signal (S) to each signal line (12) and receiving a first reflection signal (R) from the signal line (12); - based on the first reflection signal (R), determining (120) a proximity position (P) of a body part (50, 51) using time-domain reflectometry, wherein the proximity of the body part (50, 51) leads to a reflection that contributes to the first reflection signal (R); and - if the proximity position (P) corresponds to a coupling region (C), performing (190) a signal analysis based on at least one signal (R, T) that is influenceable by the electromagnetic coupling between the coupling element (15) and the signal line (12) and thus is influenceable by the body part (50, 51) in the coupling region (C), to obtain (220) an analysis result, and to determine (270) at least one vital parameter of the living being based on at least one analysis result.

Description

System for Vital-Parameter DetectionTechnical field

[0001] The invention relates to a system for vital-parameter detection, and to amethod for vital-parameter detection. Background of the Invention

[0002] In modern vehicles there can be various sensors for detecting the presenceand / or position of an occupant or a body part of an occupant. For instance, there are sensors for occupancy detection of vehicle seats or hands-off-detection sensors for the steering wheel. These and other sensors, which can be referred to as “body- detection sensors”, can be required due to a variety of reasons, oftentimes for safety reasons. For example, depending on the occupancy of a seat, seat belt reminders can be triggered, or the air bag function can be adapted. Similarly, if sensor signals indicate that the driver has removed his hands from the steering wheel, a warning signal can be output, or some safety measure can be initiated.

[0003] While simple body-detection sensors, e.g. foil-based sensors, may beadapted for detecting pressure exerted by a human body, there are also sensors which use electromagnetic fields for body detection, e.g. capacitive sensors. Such sensors, which use the influence of the human body on the electromagnetic field for detection, can be more sensitive and may also be able to distinguish human body parts from inanimate objects. However, under safety aspects, the physical condition of an occupant, especially the driver, would also be of interest. This may refer to vital parameters such as heartbeat rate, respiratory rate, blood oxygen level, hydration level, or others. Being able to detect such vital parameters could help to discover health problems and thus-related safety issues at an early stage. Object of the invention

[0004] It is thus an object of the present invention to provide efficient means forvital-parameter detection of an occupant in a vehicle.

[0005] This problem is solved by a system according to claim 1.General Description of the Invention

[0006] The invention relates to a system for vital-parameter detection. The systemcould be used for different applications, e.g., in a portable device, or it could be installed in a building. In particular, it can be installed in a vehicle. The vehicle may be a road vehicle like a car, but could also be a train, a water vehicle, or an aircraft. The term “vital-parameter detection” refers to measuring or at least estimating a vital parameter, wherein it should be understood that the measurement or the estimate may be more or less accurate. More specifically, the invention relates to a system for non-invasive vital-parameter detection, wherein “non-invasive” means that the vital parameter can be detected without inserting any instrument into a living being’s body. The term “vital parameter” is to be understood in a wide sense in this context. It refers to heart rate, respiratory rate, as well as to characteristic blood parameters, i.e., parameters that refer to blood composition, but also other parameters, e.g. a hydration level.

[0007] The system comprises a sensor arrangement with at least one signal line,which is disposed within a detection area and is adapted to propagate an electromagnetic signal, and at least one coupling element, which is disposed so thatan electromagnetic coupling between the coupling element and the signal line isinfluenceable by a body part of a living being in a coupling region associated withthe coupling element. Here and in the following, the term “living being” refers in particular to a person, i.e., a human being, but also may refer to an animal, e.g., a pet or a farm animal. The sensor arrangement can be a single, coherent component or assembly. Preferably, it comprises a carrier, like a dielectric carrier, on which theat least one signal line and the at least one coupling element are disposed. However,the sensor arrangement could also comprise a plurality of components that are notdirectly connected. The sensor arrangement may comprise a single signal line or aplurality of signal lines. Each signal line is disposed within an area which is referred to as the “detection area”. The detection area may correspond to a surface of an object, although in operational state, at least any conductive component of the sensor array is preferably covered by a non-conductive material to avoid direct contact by a living being, as well as for aesthetical reasons.

[0008] The at least one signal line does not have to cover the detection areacompletely, although it is preferred that no point within the detection area is furtheraway from the signal line than a certain maximum distance, which may be e.g. a few cm or mm. As suggested by the name “line”, the signal line may have a generally linear or “one-dimensional” shape, although there are embodiments in which its shape is rather planar or “two-dimensional”. In order to provide a better coverage of the detection area, the signal line may have a curvy shape, especially a meandering shape. The signal line is at least partially made of conductive material, preferably metal. However, its structure may comprise other materials. This also includes the possibility that the signal line is not coherent but comprises a plurality of elementsthat are in close proximity to each other, but not connected. In any case, the signalline is adapted to propagate an electromagnetic signal. Such an electromagnetic signal may comprise electric field components as well as magnetic field components. It may coincide with an electric current along the signal line. The signal line is adapted so that the electromagnetic signal can propagate, spread or move along the signal line. It will be understood that this may depend on the frequency of the signal. The electromagnetic signal may in particular comprise a radio-frequency spectrum, having at least one frequency from 20 kHz to 300 MHz. Such a signal is hereinafter referred to as a radio-frequency signal or RF signal. In someembodiments, the term “radio-frequency signal” may refer to signal that comprisesat least one frequency of up to 1 GHz, 5 GHz, 8 GHz, or 10 GHz. Corresponding tothe radio-frequency signal, the signal line may be referred to as a radio-frequencysignal line or RF signal line. Some signals may propagate better than others, whilesome signals may not be able to propagate at all, e.g., due to a cut-off frequency of the signal line. In some embodiments, the signal line has a constant characteristic impedance, i.e., the characteristic impedance does not change along the signal line. However, this is not imperative.

[0009] The sensor arrangement also comprises at least one coupling element. Thecoupling element preferably comprises a conductive material, specifically a metal. Itmay be linear, i.e., one-dimensional, or planar, i.e., two-dimensional. In case of aplanar layout, various geometries are possible, e.g., circular, rectangular or anyother shape. It can be coherent or it may comprise a plurality of elements that are in close proximity to each other, but not connected. Preferably, the coupling element is disposed in proximity to the signal line, wherein the distance from the signal linecan depend on the specific embodiment. As a rule, the coupling element is electrically isolated from the signal line.

[0010] A coupling region is associated to each coupling element, and vice versa. Ifthere is a plurality of coupling elements, a dedicated coupling region may be associated with each coupling element. However, it is also possible that a single coupling region is associated with more than one coupling element. The coupling element may be disposed in the coupling region that is associated with it. Preferably, each coupling region is coherent. The coupling region is normally a three- dimensional region, although it may be possible to define a two-dimensional coupling region, depending on the embodiment. The coupling region can at least partially be disposed above or below the detection area. Depending on the embodiment, a maximum dimension of the coupling region may correspond to, e.g., between 1% and 50% of a maximum dimension of the detection area, but smaller or larger percentages are also possible.

[0011] The coupling element and the signal line may interact with each otherthrough electric and / or magnetic fields. This interaction is referred to as an“electromagnetic coupling”, one could also say a capacitive and / or inductive coupling. Preferably, the coupling is mainly capacitive. An electromagnetic field between the signal line and the coupling element may extend into a space outside of the sensor arrangement, specifically above the detection area. The effective extent of the electromagnetic field may define the coupling region. If a body part of a living being, e.g., a finger, a hand, an arm, a foot etc. moves into this space, there will be an interaction between the electromagnetic field and the body part. Therefore, the electromagnetic coupling between the coupling element and thesignal line can be influenced by a body part of a living being in the coupling region.One can also say that an electromagnetic field between the coupling element andthe signal line is influenceable by a body part of a living being in the coupling region.In other words, the coupling without the body part is different from the coupling when the body part is present. Moreover, the coupling can depend on the size, the position, the composition and other properties of the body part. The couplingelement should couple well to the signal line and the coupling should preferablychange significantly in the presence of a body part. The coupling element may e.g.have a single resonant frequency. Alternatively, it can be designed with severalresonant frequencies that are adapted so that they are within the range where thepermittivity of the body part (or a certain component like blood) changes the most independence of a given vital parameter. Non-resonant designs are also possible,e.g., meandering line shapes.

[0012] The system also comprises a control device that is operatively coupled tothe at least one signal line. The control device can be disposed on the same carrier as the sensor arrangement, but may also be disposed on a separate carrier, in a separate housing, or the like. It may perform various functions, some of which will be explained below. Although the control device comprises at least one hardware component, some of its aspects may be software-implemented. It is operatively coupled to the at least one signal line. This may refer to an electrically conductive coupling, i.e., an electric connection. However, it may also refer to a non-conductive coupling, e.g., a capacitive and / or inductive coupling. As a rule, the operative coupling allows for a bi-directional signal transfer between the control device and the respective signal line. The control device can be connected to the sensor arrangement via a connection interface. The connection interface may enable a detachable connection, e.g., a socket-and-plug connection.

[0013] The control device is adapted to perform at least one detection process. Insome embodiments, a plurality of detection processes can be performed. Thedetection process (or each detection process) includes at least the following threesteps. These steps are preferably performed in the sequence in which they arementioned but could also be performed in a different order and / or simultaneously.

[0014] In one step of the process, the control device applies a time-dependent firstdetection signal to each signal line and receives a first reflection signal from thesignal line. The first detection signal is an electromagnetic signal which is applied to the signal line. In case of several signal lines, it is possible that different first detection signals are applied to different signal lines, but it could also be the samefirst detection signal for each signal line. The signal is time-dependent, i.e., itchanges over time. Preferred types of first detection signals will be discussed below. The first detection signal propagates along the signal line and gives rise to the first reflection signal, which propagates in the opposite direction back to the control device. It will be understood that the two signals overlap within the signal line. Depending on the characteristics of the first detection signal and the reflectioncharacteristics of the signal line, the signals may even overlap within the control device. However, it is preferred that the first detection signal can be transmitted into the signal line before the first reflection signal arrives at the control device. It will be understood that any impedance discontinuities lead to significant reflections. Such discontinuities can in particular be due to a body part (or other object) in theproximity of the signal line. The first reflection signal, or a relevant part thereof, canbe stored in a memory of the control device for further reference.

[0015] In another step, the control device determines, based on the first reflectionsignal, a proximity position of a body part using time-domain reflectometry usingtime-domain reflectometry, wherein the proximity of the body part leads to a reflection that contributes to the first reflection signal. It will be understood that this is only possible when the body part is sufficiently close to the signal line, wherein the necessary proximity for a successful detection depends on the embodiment. The proximity of the body part influences the impedance of the signal line and gives rise to an impedance discontinuity. This leads to a reflection that contributes to thereflection signal. Qualitatively, the time-of-arrival of the reflection at the controldevice can be used to deduce a position with respect to the signal line. Also, if the arrangement of the signal line in the detection area is known, a position with respect to the detection area can be deduced. “Determining” the proximity position is to be understood in the sense that the proximity position is deduced, found, detected, estimated and / or calculated. The proximity position is determined based on amethod generally referred to as time-domain reflectometry (TDR). Preferably, the“proximity position” is a position with respect to the detection area and / or withrespect to the signal line. Specifically, the proximity position is a position within the signal line from which the reflection originates, and the control device is adapted todetermine the proximity position based on the timing of the reflection relative to thedetection signal. Thus, the proximity position corresponds to a portion of the signal line, and to a portion of the detection area. As a rule, the proximity position can only be determined with a certain accuracy that will depend on the embodiment. Also, the proximity position may correspond to an area or region, not to a single point, due to the extent of the body part. In some embodiments, a single value for the proximity position can be determined, e.g., corresponding to the centre of the region in which the body part is disposed. In other embodiments, a range or interval canbe determined, representing the extent of the body part. It will be understood that the proximity position corresponds to a position in which the body part may be in contact with the surface of an object or device in which the sensor arrangement is installed. This could be a surface region that is touched by the hand of a person or the like. It should be noted that the control device is preferably adapted to determine a plurality of proximity positions when a plurality of body parts are sufficiently closeto the signal line.

[0016] In another step of the detection process, the control device performs, if theproximity position corresponds to a coupling region, a signal analysis based on at least one signal that is influenceable by the electromagnetic coupling between thecoupling element and the signal line and thus is influenceable by the body part inthe coupling region, to obtain an analysis result. The signal could be the first reflection signal, but it could also be a different signal, as will be explained below. The signal can be received through the signal line, but it could also be received through a different line, as will also be explained below. In any case, the signal is influenceable by the body part in the coupling region. This, in turn, is due to the abovementioned influence on the electromagnetic coupling between the signal line and the coupling element. Therefore, one can also say that the signal is influenceable by the electromagnetic coupling. Since the coupling element isseparate from the signal line, electromagnetic fields between them may have afurther extent than electromagnetic fields that are only associated with the signal line itself. For instance, such electromagnetic fields can penetrate deeper into the body part, therefore being influenced by the inside of the body part. By first determining the proximity position, it can be checked if a body part is actually in a position in which it has a (relevant) influence on the electromagnetic coupling. This can be a precondition for the signal analysis. It is not ruled out that the signal analysis could be performed even if the proximity position does not correspond to a coupling region. However, in such a case, the information that could be gained from such a signal analysis would be limited. The proximity position “corresponding to” a coupling region preferably means that the proximity position is within the coupling region and / or overlaps with the coupling region. It may also refer to the proximity position being not further away from the coupling region than a certain predefined threshold. The signal analysis is based on at least one signal that is influenceableby the body part, but it may be based on a plurality of such signals. Also, “based on” is to be understood in a non-exclusive sense, i.e., the signal analysis can also be based on further parameters, quantities, or signals. The result of the signal analysis is herein referred to as the analysis result. This may correspond to a single value or a plurality of values. The analysis result can be stored in a memory of the controldevice. The analysis result depends on the electromagnetic coupling between thecoupling element and the signal line, i.e., it is influenceable by the electromagneticcoupling.

[0017] In addition to the above-described detection process(es), the control deviceis adapted to determine at least one vital parameter of the living being based on atleast one analysis result. If only one detection process has been performed, the vitalparameter may be determined based on the single analysis result. In case of a plurality of detection processes, an analysis result is available for each detection process. Therefore, a plurality of analysis results can be used to determine the vital parameter. In any case, since the electromagnetic coupling between the signal line and the coupling element can be influenced by the interior of the body part, each analysis result can give important insight into properties of the body part. Thus, it is possible to determine at least one vital parameter based on the analysis result(s). Preferably, the control device is adapted to determine the vital parameter(s) based on a machine learning technique and / or based on artificial intelligence.

[0018] The inventive system applies a two-phase approach for the detectionprocess. In a first phase, it is determined whether a body part is in proximity to the signal line and where it is positioned. This information alone can be used for purposes like hands-off-detection or occupancy detection in a vehicle. Furthermore, this serves as a preparation for the second phase, in which the signal analysis is performed. For this phase, it is important to ascertain that the body part is in a suitable proximity position. Since this can be established by the first phase, the analysis result has a high reliability and allows to determine a vital parameter in a reliable manner.

[0019] The abovementioned carrier can preferably be a flexible dielectric carrier,which may also be referred to as a dielectric carrier foil. The signal line, the coupling element and / or other elements can be applied to the carrier by flex circuittechnologies. This refers to, e.g., screen printing, inkjet printing, flex PCB or etched aluminum laminates on polymer foil.

[0020] It is preferred that for each detection process, if the proximity positioncorresponds to a coupling region, the control device is adapted to apply a time-dependent second detection signal to the signal line, to receive a second reflectionsignal from the signal line and to perform the signal analysis at least based on thesecond reflection signal. In other words, the first detection signal is only used fordetermining the proximity position(s). Then, a dedicated second detection signal is used for causing a second reflection signal on which the signal analysis is at least partially based. As mentioned above, the signal analysis can further be based on additional quantities or parameters. In some embodiments, the control device comprises a first signal generator for generating the first detection signal and a second signal generator for generating the second detection signal. In other embodiments, a single signal generator may be used for both detection signals. The first and second detection signal may be identical, i.e., they may have an identical waveform, or they may be different. In an embodiment with a plurality of signal lines,it is possible that the first detection signal is applied simultaneously to all signal lines,whereas the second detection signal is applied sequentially to the different signal lines. This may help to avoid any cross-coupling between the signal lines.

[0021] The first detection signal and / or the second detection signal is preferably apulse signal. The pulse length and the pulse interval can be selected so that any reflection from one pulse reaches the control device after the pulse has left the control device but before the next pulse is generated. However, at least onedetection signal can have another waveform, e.g., it can be a modulated signal, afrequency-swept signal, a pseudo random phase-shift keyed signal, a pseudorandom signal or a step function. Also, the first detection signal and / or the seconddetection signal is preferably a radio-frequency signal as defined above.

[0022] In a preferred embodiment, at least one coupling element is operativelycoupled to the control device through a receiver line, and the control device isadapted to receive a transmission signal through the receiver line in response to the second detection signal and to perform the signal analysis at least based on the transmission signal. The coupling between the control device and the coupling element through the receiver line can be an electrically conductive connection. As adetection signal propagates through the signal line, the electromagnetic coupling gives rise to a transmission signal in the coupling element, which then propagates through the receiver line to the control device. The control device can use the transmission signal, optionally together with a reflection signal, as a basis for the signal analysis. While the coupling element and the receiver line are referred to as different elements, they may be made of the same material and may be connected in a way that does not allow for a clear, unambiguous distinction. In some embodiments, the coupling element could simply be an end portion of the receiver line. The receiver line is at least partially made of conductive material, specifically metal, but its structure may comprise other materials. Like the signal line, it may not be coherent but comprise a plurality of elements that are in close proximity to each other, but not connected. In any case, the receiver line is adapted to propagate the transmission signal. The receiver line can be disposed on the same carrier as the signal line and the coupling element and can be produced with the same techniques.Like the signal line, the receiver line is preferably a radio-frequency receiver line andis adapted for propagation of a radio-frequency signal.

[0023] It should be noted, though, that there are embodiments without any receiverlines. Also, in some embodiments, there may be a plurality of signal lines which are coupled through at least one coupling element. For the signal analysis, a detection signal may be applied to a first signal line while a second signal line is operated like a receiver line, i.e., a transmission signal in this second signal line can be detected and used for signal analysis. After that, a detection signal can be applied to the second signal line and a transmission signal in the first signal line can be detected.

[0024] In order to minimize any coupling between the receiver line and the signalline, the sensor arrangement may comprise a shielding structure that overlaps with at least one receiver line. Such a shielding structure may comprise a dielectric layer that covers the at least one receiver line. The dielectric layer preferably has a higher permittivity than the carrier. Alternatively or additionally, the shielding structure can comprise a metallic ground plane that is disposed underneath the carrier. Since the presence of the shielding structure also influences the characteristic impedance, itmay be necessary to insert a matching element into the receiver line near the edgeof the shielding structure. In some embodiments, a receiver line may cross a signalline. In such a case, a dielectric spacer can be disposed between the lines in order to electrically insulate them and to minimize unwanted electromagnetic coupling.

[0025] The at least one signal line and the at least one receiver line can be realizedin various ways. While each of these lines may have a uniform configuration alongits length, it may also comprise a plurality of different portions. Preferably, at leastone line comprises a differential transmission line, a microstrip line, a coplanar waveguide, a strip line, a substrate-integrated waveguide, a dielectric rod, a slot line,and / or a metamaterial. The metamaterial comprises a periodic, quasi-periodic oraperiodic structure of unit cells. Each unit cell may comprise a conductive (e.g., metallic) resonator. By a suitable design of the unit cells, the radiation characteristic of the metamaterial can be adapted in certain ways. This could be used to direct an electromagnetic field towards a coupling element, or the like. In some embodiments at least one coupling element may also comprise a metamaterial.

[0026] It is conceivable to determine various types of vital parameters with theinventive system. Depending on the application of the system, various kinds of parameters can be of interest and may be detectable. Without being limited to these, the at least one vital parameter may preferably be selected from a heartbeat rate, arespiratory rate, a blood oxygen level, a blood glucose level, a blood alcohol level,and a hydration level. Vital parameters that are related to substances in the bloodcan be detected using microwave signals since they have an impact on thefrequency dependent dielectric function (or permittivity) of the blood. An accurate analysis of the spectral response of blood and surrounding human tissue can therefore be used to evaluate the amount of such substances in the blood. To realize a proper determination of the respective amount, it is not necessary to understand the underlying physical interactions in detail. Especially when machine learning techniques are employed, adequate evaluation criteria can be found through a calibration process. In such a process, body parts with known substance amounts can be detected by the system and the respective signals (e.g., transmission and / or reflection signal) can be used to find a relationship between the signal and the substance amount. In order to determine heartbeat or respiratory rates, different techniques can be employed, as will be explained below.

[0027] One embodiment provides that the control device is adapted to perform aplurality of detection processes and to determine at least one vital parameter basedon an averaging process over the plurality of detection processes. It will be understood that an averaging process helps to reduce statistical errors. Also, the individual detection process can be performed very fast, wherefore a plurality of detection processes can be completed before any significant movement of the body part can occur. Thus, all detection processes used for the averaging process can be considered as taking place under identical conditions. It will be understood that the signals and / or the analysis results for different detection processes can be stored in a memory of the control device at least until the averaging process has been completed.

[0028] Alternatively or additionally, the control device can be adapted to perform aplurality of detection processes and to determine at least one vital parameter based on periodic variations among the plurality of detection processes. This pertains in particular to heartbeat rate or respiratory rate. Heartbeat and breathing give rise to oscillating movements of the body part. While these movements may be accompanied by non-oscillating movements, they can still be detected within a frequency spectrum of the body movement. Although these rates are variable, they can be considered as constant for a limited time period. For analysis purposes, it may be useful to consider the base frequency as well as upper harmonics thereof. Any movement of the body part will influence the electromagnetic coupling between the signal line and the coupling element. Therefore, it will also be recognizable by comparing the analysis results for different points in time. The signals and / or the analysis results for different detection processes can be stored in a memory of the control device. Then, they can be examined for periodic variations to determine the vital parameter.

[0029] It has been found that the specific influence of a vital parameter on theelectromagnetic coupling, and on the signal, can be temperature-dependent. Therefore, it is preferred that the control device is adapted to determine the at least one vital parameter based on a reference temperature for the coupling region.Specifically, the control device can be adapted to perform the signal analysis basedon the abovementioned at least one signal and the reference temperature. The reference temperature can be measured by a sensor that can be located in or near the coupling region but could also be located in a different location which can beassumed to have at least a similar temperature. In one embodiment, the system cancomprise a temperature sensor for measuring the reference temperature. This temperature sensor can be connected to the control device. In some cases, it may even be integrated into the control device, e.g., within a housing of the controldevice. The reference temperature may also be used to distinguish a body part froman inanimate object.

[0030] One embodiment provides that the control device is adapted to determinethe at least one vital parameter based on a comparison between one signal and a reference signal. The reference signal, which may be stored in a memory of the control device, preferably represents a state in which no body part is near a signal line, especially not in or near a coupling region. By comparing the measured signal, e.g. the first reflection signal, the second reflection signal or the transmission signal, with its corresponding reference signal, any features that are not due to the presence of the body part can be easily identified and disregarded. It will be understood that there should be a different reference signal for each type of signal, i.e., the reference signal for the transmission signal should be different from the reference signal for the first or second reflection signal. If the first and second detection signals are different from each other, their respective reference signals also should be different.

[0031] It is conceivable to use one reference signal for every detection process.However, depending on various factors, the respective signal may change even without the presence of a body part, wherefore it may be useful to update the reference signal from time to time. According to a preferred embodiment, the control device is adapted to record at least one of the reflection signals and the transmission signal and, if no body part is detected, at least one reference signals is updated based on a recorded signal.

[0032] In some embodiments, the control device may use a signal in its time-domain representation for the signal analysis. In other cases, the control device isadapted to determine a frequency spectrum of at least one signal. The frequency spectrum can show more clearly the influence of, e.g., substances in the blood. Inparticular, a Fast Fourier Transform (FFT) can be used to determine the frequencyspectrum. Also, an object, in particular a body part, can be identified based on thefrequency spectrum.

[0033] In an embodiment, the control device is adapted to determine time-domainfeatures of a portion of the first reflection signal that corresponds to an interaction with a body part, which time-domain features preferably include a start time, an endtime, and / or an amplitude. The control device analyses the first reflection signal intime-domain representation, e.g., using a comparison with its reference signal. Then, one or several portions of the signal can be identified which correspond to an interaction with a body part. One could also say that these represent reflections caused by the presence of the body part. These portions can be characterized e.g.,by a start time, by an end time, and / or by an amplitude. Any or all of these features,which are herein referred to as time-domain features, can be recorded and characterize the interaction with the body part. Implicitly, the start time and end time also characterize the proximity position.

[0034] Preferably, the control device is adapted to perform a time-domain gatingon at least one signal based on the determined time-domain features. This pertains particularly to the second reflection signal, the transmission signal, and their respective reference signals. Time-domain gating means that any portion of the signal that is outside the interval given by the start time and the end time is removed or disregarded. This greatly simplifies the signal analysis.

[0035] The inventive system can be used for a variety of applications. In particular,it can be used in a vehicle, e.g. for occupancy detection or hands-off-detection. In such an embodiment, the sensor arrangement is disposed in a vehicle interior component and the detection area corresponds to a surface of the vehicle interior component. The vehicle interior component can be, e.g., a steering wheel, a trim panel, a door handle, a vehicle seat etc. However, other applications are also within the scope of the invention. Such applications include overnight unintrusive elderly care monitoring, monitoring and prevention of nocturnal hypoglycemic episodes (and reduction of the correlated hypoglycemia unawareness conditions), contactless monitoring of vital signs of NICU / pediatrics unit’s patients, sudden infant death syndrome (SIDS) prevention. For any of these applications, the sensorarrangement could be disposed, e.g., in a bed, a mattress, a pillow, or a blanket.The system may also be used for monitoring of vital signs of pets or of farm animals.In such a case, the sensor arrangement may be disposed e.g., in a stable floor, a cage, an animal’s basket, a mat, or a blanket.

[0036] The invention further relates to a method for vital-parameter detection,using:- a sensor arrangement with at least one signal line, which is disposed within adetection area and is adapted to propagate an electromagnetic signal, and at least one coupling element, which is disposed so that an electromagnetic coupling between the coupling element and the signal line is influenceable bya body part of a living being in a coupling region associated with the couplingelement; and- a control device that is operatively coupled to the at least one signal line,According to the method, the control device performs at least one detection processwhich includes:- applying a time-dependent first detection signal to each signal line andreceiving a first reflection signal from the signal line;- based on the first reflection signal, determining a proximity position of a bodypart; and- if the proximity position corresponds to a coupling region, performing a signalanalysis based on at least one signal that is influenceable by the body part in the coupling region, to obtain an analysis result,and determines at least one vital parameter of the living being based on at least oneanalysis result.

[0037] All these terms have been explained above with reference to the inventivesystem and therefore will not be explained again. Preferred embodiments of the inventive method correspond to those of the inventive system. Brief Description of the Drawings

[0038] Further details and advantages of the present invention will be apparentfrom the following detailed description of not limiting embodiments with reference tothe attached drawings, wherein:Fig. 1 is a schematic top view of an inventive system with a first embodiment of asensor arrangement;Fig. 2 is a schematic side view of a steering wheel with the system from fig.1;Fig. 3 is a perspective view of a vehicle seat with two systems from fig. 1;Fig. 4 is a side view of a vehicle door with the system from fig. 1;Fig. 5 is a schematic view of a control device of the system from fig. 1;Fig.6 is a flow chart of an inventive method;Fig. 7 shows the steering wheel from fig.2 with a hand of a person, and a firstgraph of a reflection signal;Fig. 8 shows the steering wheel from fig.2 with two hands in a first position, and asecond graph of a reflection signal;Fig. 9 shows the steering wheel from fig.2 with two hands in a second position,and a third graph of a reflection signal;Fig. 10 is a schematic top view of a second embodiment of a sensor arrangement;Fig. 11 is a schematic top view of a third embodiment of a sensor arrangement;Fig. 12 is a schematic top view of a fourth embodiment of a sensor arrangement;Fig. 13 is a schematic top view of a fifth embodiment of a sensor arrangement;Fig. 14 is a schematic top view of a part of a sixth embodiment of a sensorarrangement; and Fig.15 is a schematic view of another embodiment of a control device of an inventive system. Description of Preferred Embodiments

[0039] Fig.1 is a schematic view of a system 1 for vital-parameter detection. Thesystem 1 comprises a sensor arrangement 10 with a signal line 12, which is disposed within a detection area D on a flexible dielectric carrier 11. The signal line12 in this embodiment has a meandering shape and may be comparatively long,e.g., 1 – 10 m. Therefore, it can cover a large detection area D in that no point ofthis detection area D is further away from the signal line 12 than, e.g., a fewmillimeters. The signal line 12 may be designed as a differential transmission line inorder to reduce the noise level. The system 1 also comprises a connection interface 25 by which the sensor arrangement 10 is connected to a control device 30, which could also be referred to as a control module. Depending on the design of theconnection interface 25, a transformer and / or transition element 13 from single ended line to a differential type transmission line may be required. Also, two coupling elements 15 are disposed on the carrier 11, each being electrically isolated from thesignal line 12 but in proximity thereto. In this embodiment, the coupling elements 15may also be referred to as receiver antennas. Each coupling element 15 is connected to a receiver line 16. The signal line 12, the coupling elements 15 andthe receiver lines 16 can be printed onto the carrier 11. A coupling region C isassociated with each coupling element 15. When an electromagnetic detection signal S is applied to and propagates through the signal line 12, this gives rise to atransmission signal T in each coupling element 15 and receiver line 16, due to anelectromagnetic coupling between the coupling element 15 and the signal line 12. The electromagnetic coupling between the coupling element 15 and the signal line12 may be mainly of capacitive nature. As will be explained further below, thecoupling is influenceable by a body part 50 of a living being in the coupling regionC.

[0040] In order to minimize the cross coupling in between the receiver lines 16and / or between the receiver lines 16 and the signal line 12, a shielding structure 20 is added to a portion of the sensor arrangement 10. The shielding structure may bea thin layer of dielectric with comparably large permittivity, e.g., ^^=12, on top of thereceiver lines 16. In particular, the permittivity of the shielding structure 20 may be significantly higher than that of the one used for the carrier 11 (which may be, e.g., ^^=3). Alternatively, the shielding structure 20 may be a metallic ground planeunderneath the carrier 11. Also, the dielectric cover layer may be combined with ametallic ground plane underneath the carrier. Furthermore, another ground plane may be disposed above the dielectric cover. A matching element 17 may be required on every receiver line 16 to improve the transition between the parts overlapping the shielding structure area 20 and the parts outside the shielding structure 20.

[0041] The sensor arrangement 10 may be fabricated using flex circuittechnologies like screen printing, inkjet printing, flex PCB or etched aluminum laminates on polymer foil. The additional dielectric layer of the shielding structure 20 covering the receiver lines 16 can be printed, or it can be a polymer film that is attached with an adhesive layer.

[0042] The sensor arrangement 10 can be integrated into various components, likecomponents 60-65 of a vehicle like a car. Fig.2 shows a steering wheel 60 with the sensor arrangement 10 integrated into the surface 60.1 of the rim, while the control device 30 and the interface 25 are integrated into the center of the steering wheel 60. The steering wheel 60 comprises a rigid metallic frame, several layers of foam spacer and a leather trim. The foil-based sensor arrangement 10 is wrapped around the steering wheel and is folded so that it covers most of the areas around the rim of the steering wheel 60, just underneath the leather trim. Thus, the signal line 12 and the coupling elements 15 are as close as possible to a body part 50 to be detected. The surface 60.1 corresponds to the detection area D. In this embodiment, the vertical length of the sensor arrangement 10 in fig. 1 corresponds to the circumference of the steering wheel 60. Due to the typical size of the sensor (lengthcirca 1.5 m), standard printed circuit board techniques may not be suitable.Additionally, the integration of the sensor into the steering wheel 60 or similarcomponents with curved and / or angled surfaces requires the sensor arrangement 10 to be flexible.

[0043] Fig.3 shows a vehicle seat 61 with two sensor arrangements 10. One sensorarrangement 10 is disposed under a surface 61.1 of a backrest, while anothersensor arrangement 10 is disposed und a surface 61.2 of a seat base. Again, the sensor arrangement can be integrated close to the outer surface 61.1, 61.2, e.g., underneath a leather or textile trim. Thus, the interaction with a body part is maximized, but the sensor arrangement 10 is not visible to the user of the car.

[0044] In Fig. 4, a door 62 of a car is shown with some of the typical elements ofthe interior. This includes an interior haptic panel 63, an arm rest 64, and a handle 65. The sensor arrangement 10 is shown integrated into the arm rest 64 and the handle 65, but could alternatively or additionally also be integrated into the haptic panel 63. Since the sensor arrangement 10 is flexible and can be adapted to various curved surface shapes, it can be integrated into any of these components 63-65,ideally so that is partially disposed around an arm and / or a hand of the user, therebymaximizing the electromagnetic interaction with the respective body part 50.

[0045] A first embodiment of the control device 30 will now be described withreference to fig.5. The control device 30 comprises a signal generator 33 whichcreates pulses to be sent onto the signal line 12 as a detection signal S, S’. Thissignal generator 33 can be a simple voltage supply which creates a fast voltageramp when being switched. The voltage switching ramp may preferably be shorter than 200 ps, ideally shorter than 50 ps. This means that the signal spectrum on thesignal line 12 contains significant amplitude in the range of DC – 5 GHz or DC – 20GHz, respectively. The duration and the shape of the ramp can be realized using analog circuitry. The voltage is provided to the signal line 12 on the sensor via an unbalanced connection line 36. Additionally, this voltage is provided via a power splitter 35 and a reference line 37 to a control interface 34 as reference. A reflectionsignal R, R’, which returns from the signal line 12, is received through the sameconnection line 36 and is also sent to the control interface 34 via the power splitter35 and a return line 38. Therefore, the power splitter 35 needs to support signals in both directions (i.e., it needs to be a bi-directional coupler).

[0046] The receiver lines 16 are both connected to the control interface 34 via afirst receiver-connection line 39 and a second receiver-connection line 40, respectively. Thus, the control interface 34 can receive transmission signals T from each receiver line 16. The control interface 34 comprises an analog-to-digital converter (ADC), which digitizes all input signals. Both the control interface 34 andthe signal generator 33 are controlled by a processing unit 32. This processing unittriggers the detection signal S sent from the signal generator 33, as well as theacquisition of the control interface 34. A software-and-digital-memory unit 31 is used for higher level control and evaluation of the signal processing and algorithm. Alternatively to the embodiment described above, the system 1 may operate athigher frequencies, e.g., DC-20 GHz, for more accurate results. Another alternativeembodiment may operate at even higher frequencies, possibly using carrier frequencies and demodulation with carrier frequencies in the millimeter-wave band.

[0047] Fig. 6 is a flow chart illustrating an inventive method for vital-parameterdetection, which can be realized with the system 1 of fig.1. After the start, the control device 30 performs a detection process 100 which includes, as a first step 110, applying a first detection signal S to each signal line 12 and receiving a first reflection signal R from the signal line 12. Then, in a second step 120, the control device 30determines a proximity position P of a body part 50 with respect to the detectionarea D based on the first reflection signal R. In other words, the proximity positionP of the body part 50 is detected using time-domain-reflectometry techniques. Thismay be the proximity position(s) P of one or two hands 51 on the steering wheel 60,as illustrated by figs. 7-9. When travelling along the signal line 12, reflections of different amplitude will occur at any impedance discontinuity. This includesdiscontinuities which are formed due to body parts 50 in the proximity of the signalline 12. On the one hand, the proximity positions P can be used to determinewhether the hands 51 of the driver are in a reasonable position for driving (hands-off-detection). On the other hand, the proximity positions P are needed to determine whether a vital parameter can be determined successfully.

[0048] In another step 130, which could alternatively be performed before or inbetween steps 110 and 120, the control device 30 determines a temperature using a temperature sensor not shown in the figures. The temperature should at least approximately be equal to the temperature in the detection area D. Then, at 140, the control device 30 determines whether the first reflection signal R is perturbed,e.g. by the presence of a body part 50. The signal is considered as unperturbed if itis close to a predefined reference signal Rrefstored in the control device 30, togetherwith another reference signal Tref for the transmission signal T. If the first reflectionsignal R is unperturbed, the control device 30 initiates updates of the referencesignals in step 150. In this step, another detection signal S is generated and theresulting reflection signal R and the transmission signal T are recorded as reference signals Rref, Tref. The previously measured temperature is also recorded. Then, the method returns to step 110.

[0049] If the signal is perturbed, though, the method continues at step 160, wheretime-domain features ti, ri are extracted from the first reflection signal R. In case of two reflections, these time-domain features include, as shown in fig.8, a first amplitude r1, a second amplitude r2, a first start time t1, a first end time t2, a second start time t3 and a second end time t4. These features are recorded for further reference. It should be noted that this step 160 could also be included in step 120. In another step 170, it is determined if the proximity position P corresponds to acoupling region C and the body part 50 is therefore in a position suited for vital-parameter detection. If not, the method returns to step 110. If so, the methodcontinues with step 180 in which a second detection signal S’ is sent through thesignal line 12, and a second reflection signal R' and transmission signals T from each receiver line 16 are detected. Then, the control device 30 performs a signalanalysis 190. In a first step 200 of this signal analysis 190, the control device 30 performs a time-domain gating process to the second reflection signal R’, the transmission signal T, and the reference signals Rref, Tref. The time gating is based on the previously recorded time-domain features.

[0050] In an optional step 210, a frequency spectrum of the signals R, T isdetermined using a Fast Fourier Transform. Then, in another step 220, the control device 30 performs an AI-based analysis of the signals R, T, which results in ananalysis result. The AI may be a trained neural network. In other embodiments,classical machine learning techniques can be sufficient. The previously measured temperature is an important input parameter to the AI, as the spectral signatures of vital parameters may depend on it. Moreover, the reference temperature may beused to distinguish a body part 50, 51 from an inanimate object. The extracted timedomain features ti, ri are important for the AI because they can contain more precise information on the positioning of the target. If for instance some textile (clothing) isin between the body part 50 to be analyzed and the sensor arrangement 10, thedepth where the electromagnetic signal interacts with tissue that gives the required response is larger. The time domain features ti, ri can give hints on these conditions to the AI.

[0051] The analysis result may immediately yield certain values for vital parameterslike blood oxygen content, blood glucose content or blood alcohol content. It may further comprise data that can be used to determine vital parameters like heart rate or breathing rate if these data are determined repeatedly.

[0052] In step 230, it is determined whether the number of analysis results isalready sufficient. If not, the analysis result, together with the current time, is recorded at step 240 and the method returns to step 110. This repetition can be done at a high rate, if necessary. Assuming, e.g., that the signal line 12 is shorter than 10 m, the signal can propagate forth and back along the full length of the signalline within 100 ns and no further reflection are expected. This means that a repetitionrate of up to 10 MHz is possible without having features from several pulses disturbing each other. Given that the movements of hands 51 or other body parts50 are rather slow, an update rate of, e.g., about 1 kHz is sufficient.

[0053] If there are enough analysis results, an averaging process is performed atstep 250 to improve the reliability, e.g., of blood content values. In another step 260,the analysis results for various points in time are analyzed for periodic variations to determine a heart rate and / or a breathing rate. This may include an analysis of the base frequency as well as upper harmonics. Based on steps 250 and 260, the vital parameters are determined in step 270. The vital parameters can be used to issue a warning to a user, e.g., to a driver, or even to initiate autonomous safety measures. These could include, e.g., preventing a driver with an increased blood alcohol level from starting the car or the like.

[0054] Fig.7 shows a situation in which only one hand 51 is in the proximity of thesensor arrangement 10 and some fingers are in contact with the steering wheel 60. In this example, the signal line 12 is short ended, wherefore a distinct reflection is visible at the end of the recorded time even without the presence of any body part 50. This feature will be visible in all scenarios and can serve as a reference marker. In this situation, the first reflection signal R also contains features from the contact with the hand 51. Although these features are not intense enough to be used for vital signs detection, the reflection signal is not clean enough to be used for newreference signals Rref, Tref. Also, the proximity position P of the hand 51 does notcorrespond to a coupling region C.

[0055] Fig.8 shows a situation in which both hands 51 are tight on the steeringwheel 60 showing a full hand grasp. In this case, the hands 51 are covering bothcoupling regions C, wherefore the proximity positions P are suitable for vital-parameter detection. The first reflection signal R is significantly perturbed by the fullhand grasp showing distinct features. These can be used for extracting time-domain features ri, ti as described above.

[0056] In Fig.9 a third situation is shown in which only one hand 51 is in a full graspposition and the other hand 51 is not. For some applications, this can give enoughfeedback for vital-parameter detection, even though only one proximity position P corresponds to a coupling region C.

[0057] Fig.10 shows a second embodiment of a sensor arrangement 10 for aninventive system 1. This embodiment is largely similar to the one shown in fig.1 but comprises two signal lines 12 and four coupling elements 15 with corresponding receiver lines 16. Due to the layout, the receiver lines 16 cross one of the signallines 12. In order to avoid electrical contact, a dielectric spacer 21 is interposedbetween them. In such an embodiment, the signal lines 12 could be operatedsimultaneously during the TDR measurement (i.e., with the first detection signal S), but could be operated sequentially for the vital-parameter detection (i.e., with the second detection signal S’).

[0058] Regarding the coupling elements 15, different geometries are possible. Forinstance, these could be patch antennas with a circular, rectangular or other shape. These coupling elements 15 (“antennas”) are not required to radiate efficiently. Most important is that they couple to the signal lines 12 and that the transmitted amplitudechanges significantly in the presence of the body part 50 to be analyzed. In the caseof resonant antenna designs with a single resonant frequency, the antenna shouldbe a broadband antenna. Alternatively, it can be designed with several resonant frequencies, or it can be a non-resonant antenna, e.g., with a meander line shape.

[0059] In this embodiment all four coupling elements 15 constitute a single, largecoupling region C. However, the transmission signal T from the different receiver lines will be different and the evaluation of all reflection signals R and transmission signals T can improve the accuracy of the evaluation of vital parameters. The abovementioned temperature sensor may be located on the dielectric carrier 11 close to the coupling region C. Alternatively, the temperature sensor may be disposed inside of the control device 30. The latter configuration is less accurate, but it can be enough for the detection of certain vital parameters.

[0060] In the embodiment shown in fig.10, the transition element 13 is either notneeded due to design of the connections to the signal generator 33, or it is placedon the circuit board of the control device 30.

[0061] Fig.11 shows a third embodiment of a sensor arrangement 10, which alsocomprises two signal lines 12 but no separate receiver lines. The two signal lines 12 can both be used for the TDR evaluation and may give a better precision when estimating the proximity position P of body parts 50. For the estimation of vital parameters, the transmission from one signal line 12 to the other is measured. Instead of separate receiver lines 15, passive coupling elements 15 are used which create strong near field coupling between the signal lines 12, especially in the presence of body parts 50. The coupling regions C can be adjusted by the design of the coupling elements 15.

[0062] Fig.12 shows a fourth embodiment, in which the receiver lines 16 aredesigned as differential transmission lines. This is especially helpful when the receiver lines 16 are long since it reduces noise. Additionally, it can be interesting if multilayer prints for a shielding structure 20 should be avoided.

[0063] Fig.13 shows a fifth embodiment of a sensor arrangement 10, which is theleast complex one. It comprises only one signal line 12 and no separate receiver line. To support the interaction with the body part 50, two passive coupling elements 15 are included, each of which constitutes a coupling region C. When using thisconfiguration, in order to get enough feedback from the body part 50 to be analyzed,it is advantageous for the sensor arrangement 10 to have a large surface area in close proximity to the body part 50. E.g., the sensor arrangement 10 could partially wrap around the body part 50.

[0064] Using suitable time-domain filtering techniques, the reflection signal R, R’from a single signal line 12 can be evaluated so that significant features originating from mutual coupling of the (at least) two passive coupling elements 15 can be extracted. Since the mutual coupling of these coupling elements 15 is linked to electromagnetic fields that reach further out than most other impedance discontinuities, it can bring information from deeper tissue layers, just like transmission mode measurements that are possible with the first to fourth embodiment. This may be referred to as a pseudo-transmission-mode measurement.

[0065] Depending on the exact application or position where the sensorarrangement 10 is integrated, or on the materials which surround the sensor arrangement 10, different types of signal lines 12 can be beneficial. This includes common transmission line geometries known in RF engineering, such as microstrip line, coplanar waveguide, strip line, substrate integrated waveguide, dielectric rods and / or slot line.

[0066] Especially in the case of higher frequencies designs, non-radiating or weakradiating lines of periodic elements which support surface wave propagation are possible. Such arrangements of periodic elements are often referred to as photonic crystals, metamaterials, meta-surfaces, high impedance surfaces or the buildingblocks of leaky-wave antennas. Both the signal lines 12 and the receiver lines 16could be designed from any one of these examples or combinations thereof. Apossible design is shown in fig. 14. In this case, the signal line 12 comprises a microstrip-line portion 12.1, a tapered transition portion 12.2, and a periodic array portion 12.3, which is designed for carrying surface waves.

[0067] Even though several embodiments show the signal line 12 in a meanderingshape, this is not necessary for the operation of the sensor arrangement 10. It can, however, help to increase the spatial resolution of the TDR evaluation. In some embodiments, the dielectric carrier 11 can be made from rigid circuit board material instead of a flexible material.

[0068] Fig.15 shows an alternative embodiment of a control device 30, whichcomprises two signal generators 33, 43. A first signal generator 33 is used for the time domain reflectometry measurements, i.e., for generating the first detection signal S. A second signal generator 43 is used for all subsequent processing steps, specifically for generating the second detection signal S’. By adapting thecorresponding analog circuit, the generated detection signal S, S’ of each generatoris configured to perform the specific measurement in an optimal way. A switch 41controlled by the processing unit 32 connects the required signal generator 33, 43with the sensor for each processing step. Two filter stages 42, 46 are included to make sure that both the detection signals S, S’ and the reflection signals R, R’ are optimally adapted for the measurement and acquisition. If higher frequencies ofoperation are required, it might be beneficial to include a frequency multiplier 45 forfrequency down conversion in the receiver chain. Additionally, an amplifier 44 might be necessary. This configuration is for instance meaningful if the sensorarrangement 10 is supposed to operate within the ultra-wide band or within higherfrequency bands in the millimeter-wave range.List of Reference Symbols 1system10 sensor arrangement11 carrier12 signal line12.1 microstrip-line portion12.2 transition portion12.3 array portion13 transition element15 coupling element16 receiver line17 matching element20 shielding structure21 spacer25 interface30 control device31 software-and-digital-memory unit32 processing unit33, 43 signal generator34 control interface35 splitter36 connection line37 reference line38 return line39, 40 receiver-connection line41 switch42, 46 filter stage44 amplifier45 frequency multiplier50 body part51 hand60 steering wheel60.1, 61.1, 61.2 surface61 seat62 door63 haptic panel64 arm rest65 handleC coupling regionD detection areaP proximity positionR, R’ reflection signalS, S’ detection signalT transmission signalri amplitudes ti start / end times

Claims

Claims1. A system (1) for vital-parameter detection, comprising:- a sensor arrangement (10) with at least one signal line (12), which is disposedwithin a detection area (D) and is adapted to propagate an electromagnetic signal, and at least one coupling element (15), which is disposed so that anelectromagnetic coupling between the coupling element (15) and the signalline (12) is influenceable by a body part (50, 51) of a living being in a couplingregion (C) associated with the coupling element (15); and -a control device (30) that is operatively coupled to the at least one signal line(12), wherein the control device (30) is adapted to perform at least one detection process (100) which includes: -applying (110) a time-dependent first detection signal (S) to each signal line(12) and receiving a first reflection signal (R) from the signal line (12); -based on the first reflection signal (R), determining (120) a proximity position(P) of a body part (50, 51) using time-domain reflectometry, wherein theproximity of the body part (50, 51) leads to a reflection that contributes to thefirst reflection signal (R); and- if the proximity position (P) corresponds to a coupling region (C), performing(190) a signal analysis based on at least one signal (R, T) that is influenceable by the electromagnetic coupling between the coupling element (15) and the signal line (12) and thus is influenceable by the body part (50,51) in the coupling region (C), to obtain (220) an analysis result, and to determine (270) at least one vital parameter of the living being based on at least one analysis result.

2. A system according to claim 1, wherein for each detection process, if theproximity position (P) corresponds to a coupling region (C), the control device (30) is adapted to apply a time-dependent second detection signal (S’) to the signal line (12), to receive a second reflection signal (R’) from the signal line(12) and to perform (190) the signal analysis at least based on the second reflection signal (R’).

3. A system according to any of the preceding claims, wherein at least onecoupling element (15) is operatively coupled to the control device (30) through a receiver line (16), and the control device (30) is adapted to receive a transmission signal (T) through the receiver line (16) in response to the second detection signal (S’) and to perform (190) the signal analysis at least based on the transmission signal (T).

4. A system according to any of the preceding claims, wherein at least one line(12, 16) comprises a differential transmission line, a microstrip line, a coplanar waveguide, a strip line, a substrate-integrated waveguide, a dielectric rod, a slot line, and / or a metamaterial.

5. A system according to any of the preceding claims, wherein the at least one vitalparameter is selected from a heartbeat rate, a respiratory rate, a blood oxygen level, a blood glucose level, a blood alcohol level, and a hydration level.

6. A system according to any of the preceding claims, wherein the control device(30) is adapted to perform a plurality of detection processes (100) and to determine at least one vital parameter based on an averaging process (250) over the plurality of detection processes (100).

7. A system according to any of the preceding claims, wherein the control device(30) is adapted to perform a plurality of detection processes (100) and to determine at least one vital parameter based on periodic variations among the plurality of detection processes (100).

8. A system according to any of the preceding claims, wherein the control device(30) is adapted to determine the at least one vital parameter based on areference temperature for the coupling region (C).

9. A system according to any of the preceding claims, wherein the control device(30) is adapted to determine the at least one vital parameter based on a comparison between one signal (R, R’, T) and a reference signal (Rref, Tref).

10. A system according to any of the preceding claims, wherein the control device(30) is adapted to record at least one of the reflection signals and the transmission signal and, if no body part is detected, update (150) at least one reference signal (Rref, Tref) based on a recorded signal.

11. A system according to any of the preceding claims, wherein the control device(30) is adapted to determine (210) a frequency spectrum of at least one signal (R, R’, T).

12. A system according to any of the preceding claims, wherein the control device(30) is adapted to determine time-domain features (ri, ti) of a portion of the firstreflection signal (R) that corresponds to an interaction with a body part (50, 51), which time-domain features (ri, ti) preferably include a start time(t1, t3), an endtime (t2, t4) and / or an amplitude (r1, r2).

13. A system according to claim 12, wherein the control device (30) is adapted toperform a time-domain gating on at least one signal (R, Rref, T, Tref) based on the determined time-domain features (ri, ti).

14. A system according to any of the preceding claims, wherein the sensorarrangement (10) is disposed in a vehicle interior component (60-65) and the detection area (D) corresponds to a surface (60.1, 61.1, 61.2) of the vehicle interior component (60-65).

15. A method for vital-parameter detection, using:- a sensor arrangement (10) with at least one signal line (12), which is disposedwithin a detection area (D) and is adapted to propagate an electromagneticsignal, and at least one coupling element (15), which is disposed so that anelectromagnetic coupling between the coupling element (15) and the signalline (12) is influenceable by a body part (50, 51) of a living being in a couplingregion (C) associated with the coupling element (15); and- a control device (30) that is operatively coupled to the at least one signal line(12), wherein the control device (30) performs at least one detection process (100) which includes -applying (110) a time-dependent first detection signal (S) to each signal line(12) and receiving a first reflection signal (R) from the signal line (12); -based on the first reflection signal (R), determining (120) a proximity position(P) of a body part (50, 51) using time-domain reflectometry, wherein theproximity of the body part (50, 51) leads to a reflection that contributes to the first reflection signal (R); and- if the proximity position (P) corresponds to a coupling region (C), performing(190) a signal analysis based on at least one signal (R’, T) that is influenceable by the electromagnetic coupling between the coupling element (15) and the signal line (12) and thus is influenceable by the body part (50,51) in the coupling region (C), to obtain (220) an analysis result, and determines (270) at least one vital parameter of the living being based on at least one analysis result.

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