Measurement device

Abstract

This measurement device comprises: a first substrate that is formed of a dielectric and that has a first main surface on which a signal line is provided and a second main surface which is on the opposite side from the first main surface and on which provided is a ground conductor having a surface area greater than the surface area of the signal line in plan view; and a second substrate that has greater bending rigidity than the first substrate and that has a third main surface connected to the second main surface via the ground conductor. Said measurement device measures information concerning the permittivity of a living body.

Description

Measuring equipment

[0001] The present embodiment relates to a measurement device.

[0002] The dielectric constant of a living body is known to be related to biological information such as blood sugar levels.

[0003] Patent No. 6771372 Patent No. 6305444

[0004] An object of the present invention is to provide a measuring device that can measure information related to the dielectric constant of a living body with high accuracy.

[0005] According to the present invention, the measurement device includes a first substrate made of a dielectric, the first substrate having a signal line on a first main surface and a ground conductor on a second main surface opposite the first main surface, the ground conductor having a surface area in a plan view larger than the surface area of ​​the signal line, and a second substrate having a bending rigidity greater than that of the first substrate and having a third main surface connected to the second main surface via the ground conductor, and measures information related to the dielectric constant of a living body.

[0006] The present invention has an effect of providing a measuring device that can measure information relating to the dielectric constant of a living body with high accuracy.

[0007] FIG. 1 is a diagram showing the complex dielectric constants of a plurality of aqueous solutions with different glucose concentrations. FIG. 2 is a top view of a blood glucose level measuring device according to an embodiment. FIG. 3 is a cross-sectional view of a blood glucose level measuring device according to an embodiment taken along the III-III plane shown in FIG. 2. FIG. 4 is a cross-sectional view of a blood glucose level measuring device according to an embodiment taken along the IV-IV plane shown in FIG. 2. FIG. 5 is a schematic diagram showing an electromagnetic field distribution. FIG. 6 is a diagram for explaining a change in the phase of an AC signal passing through a signal line of a sensor according to an embodiment. FIG. 7 is a diagram for explaining the transition of the phase lead over time. FIG. 8 is a diagram showing an example of the relationship between the thickness of a sensor substrate and measurement sensitivity according to an embodiment. FIG. 9 is a diagram showing an example of a change in the phase lead due to pressure received by a sensor according to an embodiment. FIG. 10 is a diagram showing the configuration of an integrated circuit according to an embodiment. FIG. 11 is a flowchart showing an example of the operation of a blood glucose level measuring device according to an embodiment. FIG. 12 is a cross-sectional view of a blood glucose level measuring device according to Modification 1 taken along the XZ plane. FIG. 13 is a top view of a blood glucose level measuring device according to Modification 2.

[0008] (Embodiment) It is known that the concentration of glucose contained in the interstitial fluid of the dermis layer correlates with the concentration of glucose in the blood, that is, the blood sugar level.

[0009] Furthermore, the dielectric constant of the liquid varies depending on the concentration of glucose contained in the liquid.

[0010] 1 is a diagram showing the complex dielectric constants of a number of aqueous solutions with different glucose concentrations, in which the vertical axis represents the imaginary part of the complex dielectric constant and the horizontal axis represents frequency.

[0011] As shown in Figure 1, the imaginary part of the complex permittivity (hereinafter, the imaginary part of the complex permittivity will be simply referred to as the imaginary part) has different frequency characteristics depending on the glucose concentration. As shown by the arrow on the right side of the graph, the glucose concentration increases downward and decreases upward. As shown in the figure, at frequencies higher than the inflection point 300 near 10 GHz, the imaginary part decreases as the glucose concentration in the aqueous solution increases. Furthermore, in the frequency range 310, the interval between the three curves is wide, indicating that the imaginary part changes significantly with changes in glucose concentration.

[0012] The real part of the complex dielectric constant (hereinafter simply referred to as the real part) changes in the opposite direction to the imaginary part. That is, at frequencies higher than the inflection point 300, the real part increases as the glucose concentration in the aqueous solution increases. In the above-mentioned frequency range 310, the real part exhibits a greater dependency on the glucose concentration, just like the imaginary part. Hereinafter, dielectric constant will refer to the real part of the complex dielectric constant.

[0013] The dielectric constant of human skin, specifically the dermis layer, has a dependency on the glucose concentration in the interstitial fluid of the dermis layer similar to the glucose concentration dependency shown in Figure 1. As described above, there is a correlation between the glucose concentration in the interstitial fluid of the dermis layer and the blood glucose level. Therefore, if the value of the dielectric constant of the skin can be obtained, the blood glucose level can be estimated. In the embodiment, the measurement device estimates the blood glucose level as information related to the dielectric constant of the skin.

[0014] In the embodiment, a sensor having a transmission line structure is used. An AC signal flows through a signal line. When a subject touches the signal line, the wavelength of the AC signal flowing through the signal line changes depending on the dielectric constant of the skin touching the signal line. This change in wavelength is related to the dielectric constant of the skin. The measurement device measures the blood glucose level by measuring the change in wavelength of the AC signal flowing through the signal line.

[0015] The measurement device may be implemented in any device or electronic device. For example, the measurement device may be implemented in a wearable device such as a smart watch. The measurement device may also be configured as a stationary measurement device.

[0016] Furthermore, the information about the dielectric constant of a living body obtained by the measuring device is not limited to blood glucose levels. For example, the dielectric constant of a living body may also be affected by the amount of cancer cells. Therefore, the amount of cancer cells may be measured as information about the dielectric constant of a living body.

[0017] Hereinafter, a blood glucose level measuring device 1 will be described as an example of a measuring device with reference to the drawings. However, the present invention is not limited to this embodiment.

[0018] Fig. 2 is a top view of the blood glucose level measuring device 1. Fig. 3 is a cross-sectional view of the blood glucose level measuring device 1 taken along the III-III plane shown in Fig. 2. Fig. 4 is a cross-sectional view of the blood glucose level measuring device 1 taken along the IV-IV plane shown in Fig. 2.

[0019] The blood glucose measuring device 1 includes a rectangular, flat sensor 10. The thickness direction of the sensor 10 is defined as the Z direction, the direction in which one side of the rectangular shape of the sensor 10 extends is defined as the X direction, and the direction in which the other side of the rectangular shape of the sensor 10 extends, perpendicular to the X direction, is defined as the Y direction, and the positional relationship and orientation of the components of the sensor 10 will be described below. Note that the shape of the sensor 10 does not necessarily have to be rectangular.

[0020] The sensor 10 includes a dielectric sensor substrate 14. The dielectric material that makes up the sensor substrate 14 is one of fluororesin, polyphenylene ether resin, ceramics, liquid crystal polymer resin, and polyimide resin, or a combination of two or more of these materials. By using these materials, the sensor characteristics are improved, enabling highly accurate measurement of information related to the dielectric constant of a living body.

[0021] The sensor substrate 14 has a relative dielectric constant of 4 or more and 20 or less. Alternatively, the relative dielectric constant is 5 or more and 15 or less. Alternatively, the relative dielectric constant is 6 or more and 12 or less. If the relative dielectric constant of the sensor substrate is high, it approaches the relative dielectric constant of the skin, thereby reducing loss due to high-frequency signals. This improves the sensor characteristics and enables highly accurate measurement of information related to the dielectric constant of the living body. The relative dielectric constant can be improved, for example, by increasing the amount of ceramic contained in the sensor substrate 14. Specifically, this can be achieved, for example, in a composite material of fluororesin and ceramic.

[0022] A signal line 12 made of a conductor is provided on a portion of one surface 14a of the sensor substrate 14. When the sensor substrate 14 is viewed in a plan view, the signal line 12 has the shape of a line segment extending in the Y direction. A flat ground conductor 15 is provided on a surface 14b of the sensor substrate 14 opposite the surface 14a. The ground conductor 15 is formed over the entire surface of the surface 14b except for the areas where the pair of through holes 17 are formed and their vicinity. This makes the surface area of ​​the ground conductor 15 larger than the surface area of ​​the signal line 12 when viewed in a plan view.

[0023] The sensor substrate 14 is an example of a first substrate, the surface 14a is an example of a first main surface, and the surface 14b is an example of a second main surface.

[0024] Both ends of the signal line 12 are connected to a pair of conductors 16 that penetrate the sensor substrate 14 in the Z direction. A pair of through holes that penetrate the sensor substrate 14 in the Z direction is provided at positions corresponding to both ends of the signal line 12, and the conductors 16 are provided by providing metal on the wall surfaces of the through holes or by filling the through holes with metal. Each of the pair of conductors 16 passes through a different one of the pair of through holes 17 and is connected to the integrated circuit 21. Note that the conductors 16 from each through hole 17 to the integrated circuit 21 are not shown in the drawing.

[0025] The signal line 12, the sensor substrate 14, and the ground conductor 15, depending on their shapes and materials, form a structure including a microstrip line, which is a type of transmission line (hereinafter referred to as a microstrip line structure).

[0026] The entire surface 14a, including the signal line 12, is covered with an insulating film 11. The insulating film 11 is made of an insulating material such as solder resist. When measuring a blood glucose level, the subject presses the skin of, for example, a finger against the signal line 12 from above the insulating film 11. In other words, the surface of the insulating film 11 serves as a skin contact surface 31, which is the surface that comes into contact with the subject's skin.

[0027] The insulating film 11 does not necessarily have to be provided. If the insulating film 11 is not provided, the subject will directly touch the signal line 12 when measuring the blood glucose level. By providing the insulating film 11, it is possible to prevent the signal line 12 from becoming dirty or rusting due to the subject directly touching the signal line 12.

[0028] When measuring the blood glucose level, the integrated circuit 21 sends an AC electrical signal to the signal line 12 via the pair of conductors 16. The integrated circuit 21 then obtains the blood glucose level based on a comparison between the electrical signal that has passed through the signal line 12 (a sensor-passing signal, which will be described later) and the electrical signal that has not passed through the signal line 12 (a local signal, which will be described later).

[0029] Here, the principle of obtaining blood glucose levels will be explained.

[0030] 5 is a schematic diagram showing the electromagnetic field distribution. Arrows E indicate electric field vectors, and dotted lines H indicate magnetic field distribution. Note that in this and subsequent figures, the insulating film 11 may be omitted from illustration.

[0031] When an AC signal flows through the signal line 12, an electric field vector E is formed around the signal line 12. Most of the electric field vector E1 is concentrated between the signal line 12 and the ground conductor 15, but some electric field vector E2 exits from the surface 14a to the outside of the sensor substrate 14. When the skin 201 is in contact with the signal line 12, the electric field vector E2 passes through the skin 201, causing a change in the wavelength of the AC signal flowing through the signal line 12. The change in the wavelength of the AC signal flowing through the signal line 12 will be described below.

[0032] The following equation (1) is a general transmission line equation for voltage. A and B are constants, and x is the position on the transmission line. α is the initial phase. β is the phase constant, which represents the amount of phase lead per unit length.

[0033] The first term on the right side of equation (1) represents a traveling wave, and the second term represents a reflected wave. In this embodiment, it is assumed that the impedance of signal line 12 and the impedance of a phase detector (phase detector 212, described below) electrically connected to signal line 12 are matched. In this transmission line, no unwanted waves are generated at the connection point between signal line 12 and phase detector 212, so the second term is zero. Therefore, the transmission line equation for signal line 12 in this embodiment can be expressed by the following equation (2).

[0034] The phase constant β can be transformed into the following equation (3): L is the inductor of the circuit model equivalent to the transmission line, C is the capacitance of the circuit model equivalent to the transmission line, ε γ＿ｅｆｆ is the effective relative permittivity, ε ０ is the dielectric constant of a vacuum, μ ０ is the magnetic permeability of a vacuum, and c is the speed of light.

[0035] From equation (3), the effective relative permittivity ε γ＿ｅｆｆ It can be seen that the larger the effective relative dielectric constant ε γ＿ｅｆｆ The larger the value, the larger the phase lead per unit length.

[0036] As described above, when skin 201 is pressed against signal line 12, electric field vector E2 passes through skin 201. Therefore, the amount of phase lead of the AC signal passing through signal line 12 changes depending on the dielectric constant of skin 201.

[0037] When a subject eats, their blood glucose level rises, and the glucose concentration in the interstitial fluid in the dermis layer rises. In a specific frequency range (e.g., a frequency range higher than the inflection point 300 in FIG. 1 ), the higher the glucose concentration, the higher the dielectric constant. Therefore, as the subject's blood glucose level rises, the phase of the AC signal passing through the signal line 12 advances.

[0038] FIG. 6 is a diagram for explaining a change in the phase of an AC signal passing through the signal line 12. In FIG.

[0039] For ease of understanding, it is assumed here that when the subject is fasting, the wavelength of the AC signal at the dielectric constant of skin 201 in this fasting state is equal to the length (here, the length in the Y direction) from the input end (left end) to the output end (right end) of signal line 12. In other words, when the subject touches signal line 12 while fasting, an AC signal is transmitted with a wavelength equal to the length of signal line 12, as shown in FIG. 6A . Therefore, when the phase of the AC signal at the input end of signal line 12 is 0 radians, the phase of the AC signal at the output end of signal line 12 is also 0 radians.

[0040] When the subject touches signal line 12 after eating and their blood glucose level rises, the wavelength of the AC signal passing through signal line 12 shortens, as shown in Fig. 6(B). When the phase of the AC signal input to one end of signal line 12 is 0 radians, the phase of the AC signal output from the other end of signal line 12 advances in accordance with the amount the wavelength has shortened, compared to the phase shown in Fig. 6(A). The amount of phase advance of the AC signal passing through signal line 12 relative to the fasting state is denoted as phase advance Rd.

[0041] 7 is a diagram illustrating the time transition of the phase lead Rd. In this diagram, the horizontal axis represents the time elapsed since a meal, the left vertical axis represents the blood glucose level, and the right vertical axis represents the phase.

[0042] As shown in Figure 7, when the subject eats a meal, the subject's blood glucose level begins to rise compared to when the subject is fasting. Then, the phase lead Rd increases in response to the rise in blood glucose level. Then, when the blood glucose level changes from rising to falling, the phase lead Rd changes from increasing to decreasing. Thus, the phase lead Rd changes in conjunction with changes in blood glucose level, with the fasting blood glucose level as the reference.

[0043] The blood glucose level measuring device 1 calculates the phase lead amount Rd and calculates the blood glucose level based on the phase lead amount Rd.

[0044] In the sensor 10 having the above-described structure, the thickness of the sensor substrate 14 affects the measurement sensitivity.

[0045] 8 is a diagram showing an example of the relationship between the thickness of the sensor substrate 14 and the measurement sensitivity. As shown in this diagram, the thinner the sensor substrate 14, the larger the phase lead Rd. This means that the thinner the sensor substrate 14, the higher the measurement sensitivity.

[0046] When measuring a blood glucose level, pressure is applied to the sensor 10 by pressing the subject's skin 201 against the skin contact surface 31. The pressure applied to the sensor 10 changes the shape and internal stress of each component of the microstrip line structure, such as the signal line 12, the sensor substrate 14, and the ground conductor 15, and thereby changes the transmission characteristics of the electromagnetic field distribution of the microstrip line structure. As a result, the phase of the AC signal passing through the signal line 12 changes.

[0047] 9 is a diagram showing an example of a change in the phase lead Rd due to pressure applied to the sensor 10. As shown in this diagram, the phase lead Rd changes depending on the pressure applied to the skin contact surface 31.

[0048] Since the phase lead Rd changes in response to the pressure applied to the skin contact surface 31, the measured blood glucose level changes in response to the pressure. The greater the change in the measured blood glucose level, the greater the change in each component of the microstrip line structure. In other words, the thinner the sensor substrate 14, the higher the measurement sensitivity, but on the other hand, the greater the change in the measured blood glucose level due to the pressure applied to the skin contact surface 31.

[0049] Therefore, in this embodiment, to enable accurate measurement of blood glucose levels, sensor 10 includes support substrate 13 that suppresses deformation of sensor substrate 14. More specifically, as shown in Figures 3 and 4, support substrate 13 has surface 13a. Surface 13a is connected to surface 14b of sensor substrate 14 via ground conductor 15. Surfaces 13a and 14b face each other, and ground conductor 15 is located between surfaces 13a and 14b.

[0050] With the above configuration, even if pressure is applied to the skin contact surface 31, changes in the shape of each component of the microstrip line structure are suppressed, thereby suppressing changes in the measured blood glucose level due to the pressure. Specifically, when the sensor substrate 14 is bent, the support substrate 13 is configured to suppress the bending. Because changes in the shape of each component of the microstrip line structure can be suppressed, the sensor substrate 14 can be made thinner, thereby improving measurement sensitivity. By making the sensor substrate 14 thinner, blood glucose levels can be measured with high accuracy.

[0051] In order to suppress changes in the shape of each component of the microstrip line structure, the support substrate 13 is configured to have, for example, a bending rigidity greater than that of the sensor substrate 14. In the example shown in Figures 3 and 4, the thickness T1 of the support substrate 13 is made greater than the thickness T2 of the sensor substrate 14, so that the bending rigidity of the support substrate 13 is made greater than that of the sensor substrate 14.

[0052] The material of the support substrate 13 may be different from the material of the sensor substrate 14. The support substrate 13 may be made of a material with high bending rigidity, such as epoxy glass, low temperature co-fired ceramics (LTCC), or aluminum oxide.

[0053] The support substrate 13 is an example of a second substrate, the surface 13a is an example of a third main surface, and the surface 13b is an example of a fourth main surface.

[0054] An integrated circuit 21 and passive components 22 are provided on a surface 13b opposite to the surface 13a of the support substrate 13. The passive components 22 are a group of components that generate power to drive the integrated circuit 21, and may include resistors, capacitors, coils, etc. The integrated circuit 21 performs various processes, including measuring blood glucose levels, based on the power supplied from the passive components 22.

[0055] 10 is a diagram showing the configuration of the integrated circuit 21. The integrated circuit 21 includes an oscillator circuit 211, a phase detector 212, and an arithmetic circuit 213.

[0056] The oscillator circuit 211 oscillates an AC signal of a single frequency. The frequency of the AC signal oscillated by the oscillator circuit 211 is a frequency selected from a range in which the dielectric constant of the skin can change depending on the blood sugar level. The oscillator circuit 211 oscillates an AC signal of a frequency selected from, for example, range 310 in FIG. 1 . Note that the frequency of the AC signal oscillated by the oscillator circuit 211 may be selected from a range other than range 310.

[0057] The transmission path of the AC signal connected to the oscillator circuit 211 is branched into two, one of which is connected to the input end of the signal line 12, and the other of which is connected to the phase detector 212. The output end of the signal line 12 is connected to the phase detector 212. Thus, the phase detector 212 receives an AC signal that has passed through the signal line 12 and an AC signal that has not passed through the signal line 12. The AC signal that passes through the signal line 12 and is input to the phase detector 212 is referred to as a sensor passing signal. The AC signal that does not pass through the signal line 12 and is input to the phase detector 212 is referred to as a local signal.

[0058] The AC signal oscillated by the oscillator circuit 211 is an example of a first signal. The AC signal that has passed through the signal line 12, i.e., a sensor passing signal, is an example of a second signal. The AC signal that has not passed through the signal line 12, i.e., a local signal, is an example of a third signal.

[0059] The phase detector 212 detects a phase difference Rx between the sensor passing signal and the local signal, and inputs the detected value of the phase difference to the arithmetic circuit 213. The phase detector 212 may also be referred to as a phase comparator.

[0060] The arithmetic circuit 213 is a processor that executes predetermined arithmetic processing. The arithmetic circuit 213 is, for example, a microcomputer unit including a central processing unit (CPU) and a memory that stores a program, and the CPU executes arithmetic processing based on the program. The arithmetic circuit 213 may be configured by a hardware circuit such as a field-programmable gate array (FPGA) or an application-specific integrated circuit (ASIC).

[0061] The arithmetic circuit 213 performs calculations based on the phase difference Rx input from the phase detector 212 to obtain the measured value of the blood glucose level of the subject.

[0062] The arithmetic circuit 213 may output the blood glucose measurement value in any manner. If the blood glucose measuring device 1 is connected to an output device such as a display device or speaker, the arithmetic circuit 213 may output the blood glucose measurement value to the output device such as a display device or speaker. If the blood glucose measuring device 1 has a memory, the arithmetic circuit 213 may output the blood glucose measurement value to the memory. If the blood glucose measuring device 1 is connected to a communication device, the arithmetic circuit 213 may output the blood glucose measurement value to an external device via the communication device.

[0063] 11 is a flowchart showing an example of the operation of the blood glucose level measuring device 1. The series of operations shown in this figure is performed while the subject is in contact with the skin contact surface 31 in order to measure the blood glucose level.

[0064] The phase detector 212 acquires the phase difference Rx between the sensor passing signal and the local signal (S101). The phase difference Rx is input to the arithmetic circuit 213.

[0065] The arithmetic circuit 213 obtains the phase lead Rd by subtracting the fasting phase difference Ri, which is the phase difference Rx between the sensor passing signal and the local signal when the subject is in a fasting state, from the phase difference Rx obtained in S101 (S102).

[0066] The fasting phase difference Ri is assumed to be measured in advance and stored in the arithmetic circuit 213 or in a memory accessible to the arithmetic circuit 213. For example, if the blood glucose measuring device 1 is implemented in a wearable device, the subject is asked to wear the blood glucose measuring device 1 all day, and the arithmetic circuit 213 stores the transition of the phase difference Rx during the wearing period. The arithmetic circuit 213 then stores the minimum value of the phase difference Rx as the fasting phase difference Ri. Note that the method of acquiring the fasting phase difference Ri is not limited to this.

[0067] Similarly to the fasting phase difference Ri, the fasting blood glucose level Bi, which is the blood glucose level when the subject is in a fasting state, is measured in advance and stored in the arithmetic circuit 213 or in a memory accessible to the arithmetic circuit 213 in association with the fasting phase difference Ri. The method for measuring the fasting blood glucose level Bi is not limited to a specific method. The fasting blood glucose level Bi can be measured, for example, by drawing blood.

[0068] Following S102, the arithmetic circuit 213 acquires the blood glucose fluctuation Bv from the fasting blood glucose Bi based on the phase lead Rd (S103).

[0069] For example, a calibration curve (referred to as a first calibration curve) representing the relationship between the phase lead Rd and the fluctuation Bv is obtained in advance by simulation or an experiment using one or more subjects. The first calibration curve may be a function or may be information in a table format. The first calibration curve is stored in advance in the arithmetic circuit 213 or in a memory accessible to the arithmetic circuit 213. In S103, the arithmetic circuit 213 obtains the fluctuation Bv at the time of execution of S103 based on the phase lead Rd obtained in S102 and the first calibration curve.

[0070] Following S103, the arithmetic circuit 213 adds the fluctuation Bv obtained in S103 to the fasting blood glucose level Bi to obtain a measured blood glucose level (S104). Then, the operation of the blood glucose level measuring device 1 ends.

[0071] (Modification 1) The structure of the transmission line including the signal line 12 is not limited to the microstrip line structure. As an example of a transmission line structure different from the microstrip line structure, a blood glucose level measuring device 1a according to Modification 1 will be described.

[0072] 12 is a cross-sectional view of the blood glucose measuring device 1a taken along the ZX plane. As shown in the figure, in the blood glucose measuring device 1a, ground conductors 15a are provided on the surface 14a of the sensor substrate 14 so as to sandwich the signal line 12 from both sides. In other words, the sensor substrate 14, ground conductor 15, signal line 12, and ground conductor 15a form a structure including a coplanar line with a ground, which is a type of transmission line different from a microstrip line.

[0073] In this way, various structures other than the microstrip line structure can be applied to the structure of the transmission line including the signal line 12.

[0074] 13 is a top view of a blood glucose level measuring device 1b according to Modification 2. As shown in this figure, the blood glucose level measuring device 1b includes a signal line 12b instead of the signal line 12. The signal line 12b has an Archimedes spiral shape.

[0075] In this way, the shapes of the signal lines 12 and 12b can be modified in various ways.

[0076] (Variation 3) The arithmetic circuit 213 obtains the blood glucose level based on the phase difference between the sensor passing signal and the local signal. The arithmetic circuit 213 may obtain the blood glucose level based on the frequency difference between the sensor passing signal and the local signal, instead of the phase difference between the sensor passing signal and the local signal.

[0077] For example, the oscillator circuit 211 oscillates a chirp signal. The integrated circuit 21 includes a mixer circuit instead of the phase detector 212. The mixer circuit generates a beat frequency signal indicating the frequency difference between the sensor passing signal and the local signal, and inputs the beat frequency signal to the arithmetic circuit 213. The arithmetic circuit 213 obtains a blood glucose measurement value based on the beat frequency signal.

[0078] In this way, the arithmetic circuit 213 may acquire the blood glucose level based on the phase difference between the sensor passing signal and the local signal, or may acquire the blood glucose level based on the frequency difference between the sensor passing signal and the local signal. In other words, the arithmetic circuit 213 is configured to acquire the blood glucose level based on a comparison between the sensor passing signal and the local signal.

[0079] As described above, the sensor substrate 14 is made of a dielectric material, the signal line 12 is provided on the surface 14a of the sensor substrate 14, and the ground conductor 15 is provided on the surface 14b opposite to the surface 14a. The surface area of ​​the ground conductor 15 in a plan view is larger than the surface area of ​​the signal line 12. The support substrate 13 has a bending rigidity greater than that of the sensor substrate 14, and has a surface 13a that is connected to the surface 14b via the ground conductor 15.

[0080] Therefore, it is possible to increase the sensitivity of blood glucose level measurement by thinning the sensor substrate 14 while suppressing fluctuations in the blood glucose level measurement caused by pressure on the skin contact surface 31. In other words, it is possible to measure blood glucose level, which is an example of information related to the dielectric constant of a living body, with high accuracy.

[0081] The sensor substrate 14 may be made of any one of fluororesin, polyphenylene ether resin, ceramics, liquid crystal polymer resin, and polyimide resin, or a combination of two or more of these materials.

[0082] As a result, the sensor substrate 14, the signal line 12, and the ground conductor 15 can form a transmission line structure.

[0083] The sensor substrate 14 has a relative dielectric constant of 4 or more and 20 or less.

[0084] Therefore, the relative dielectric constant of the sensor substrate 14 can be made close to that of the skin, thereby reducing loss due to high frequency signals. As a result, the sensor characteristics are improved and information related to the dielectric constant of the living body can be measured with high accuracy.

[0085] The support substrate 13 may also be made of epoxy glass, LTCC, or aluminum oxide.

[0086] This allows the support substrate 13 to suppress deformation of the sensor substrate 14 .

[0087] Furthermore, the support substrate 13 can be configured to be thicker than the sensor substrate 14 .

[0088] This allows the support substrate 13 to suppress deformation of the sensor substrate 14 .

[0089] In addition, the blood glucose level measuring devices 1, 1a, and 1b are equipped with an oscillation circuit 211 that oscillates an AC signal, and an arithmetic circuit 213 that acquires the blood glucose level based on a comparison between a sensor passing signal, which is an AC signal that has passed through the signal line 12, and a local signal, which is an AC signal that has not passed through the signal line 12.

[0090] This allows blood glucose levels to be measured.

[0091] An integrated circuit 21 including an oscillator circuit 211 and an arithmetic circuit 213 may be provided on a surface 13b opposite to the surface 13a of the support substrate 13.

[0092] The support substrate 13 does not necessarily have to be more rigid than the sensor substrate 14. The sensor substrate 14 is made of any one of fluororesin, polyphenylene ether resin, ceramics, liquid crystal polymer resin, and polyimide resin, or a composite material of two or more of these materials, and the support substrate 13 may be made of a material different from that of the sensor substrate 14.

[0093] When the support substrate 13 is made of a material different from that of the sensor substrate 14, the support substrate 13 may be made of, for example, epoxy glass, LTCC, or aluminum oxide.

[0094] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims.

[0095] 1, 1a, 1b Blood glucose measuring device, 10 Sensor, 11 Insulating film, 12, 12b Signal line, 13 Support substrate, 13a, 13b, 14a, 14b Surface, 14 Sensor substrate, 15, 15a Ground conductor, 16 Conductor, 17 Through hole, 21 Integrated circuit, 22 Passive component, 31 Skin contact surface, 201 Skin, 211 Oscillator circuit, 212 Phase detector, 213 Arithmetic circuit, 300 Inflection point, 310 Range.

Claims

1. A measuring device for measuring information related to the dielectric constant of a living body, comprising: a first substrate made of a dielectric material, the first substrate having a signal line on a first main surface and a ground conductor on a second main surface opposite the first main surface, the ground conductor having a surface area larger than that of the signal line in a plan view; and a second substrate having a bending rigidity greater than that of the first substrate and a third main surface connected to the second main surface via the ground conductor.

2. The measuring device according to claim 1, wherein the first substrate is made of one of fluororesin, polyphenylene ether resin, ceramics, liquid crystal polymer resin, and polyimide resin, or a combination of two or more of these materials.

3. The measuring device according to claim 1, wherein the first substrate has a relative dielectric constant of 4 or more and 20 or less.

4. The measuring device according to claim 1, wherein the second substrate is made of epoxy glass, low temperature co-fired ceramics (LTCC), or aluminum oxide.

5. The measuring device of claim 1, wherein the second substrate is thicker than the first substrate.

6. A measuring device for measuring information related to the dielectric constant of a living organism, comprising: a first substrate having a signal line on a first main surface, a ground conductor on a second main surface opposite the first main surface, the ground conductor having a surface area larger than that of the signal line in a plan view, and made of a first material which is any one of fluororesin, polyphenylene ether resin, ceramics, liquid crystal polymer resin, and polyimide resin, or a composite of two or more of these materials; and a second substrate made of a second material different from the first material, having a third main surface connected to the second main surface via the ground conductor.

7. The measuring device according to claim 6, wherein the second material is made of epoxy glass, LTCC, or aluminum oxide.

8. The measuring device according to any one of claims 1 to 7, further comprising: an oscillator circuit that oscillates a first AC signal; and an arithmetic circuit that acquires information relating to the dielectric constant of a living body based on a comparison between a second signal, which is the first signal that has passed through the signal line, and a third signal, which is the first signal that has not passed through the signal line.

9. The measuring device according to claim 8, wherein the oscillator circuit and the arithmetic circuit are provided on a fourth main surface of the second substrate opposite to the third main surface.

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