Measuring device and measuring system

Abstract

To provide a measuring device capable of improving measurement accuracy.SOLUTION: A measuring device 10 includes: a ring-shaped transmission line 110; a first ground layer 121; a second ground layer 122; a first dielectric layer 130; a second dielectric layer 140; a pair of power supply terminals 161 and 162 for supplying the power to the transmission line 110; and a plurality of ground terminals that electrically connect the first ground layer 121 and the second ground layer 122. The first dielectric layer 130 has a cavity 131 for placing a measurement object. In the planar view, the power supply terminals 161 and 162 are located at the intersection points of the straight line L1x and the transmission line 110, respectively. The plurality of ground terminals includes ground terminals 171a, 172a, 173a, and 174a. The spacing between each of the ground terminal 171a and the ground terminal 172a and the power supply terminal 161, and the spacing between ground terminal 173a and 174a and each of the power supply terminals 162, are both one-quarter or less of the wavelength corresponding to the highest frequency in the measurement frequency band.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a measurement device and a measurement system. [Background technology]

[0002] Patent Document 1 discloses a measurement device including a ring-shaped transmission line, two ground layers arranged on either side of the transmission line, and a dielectric layer that is positioned to overlap the transmission line in a plan view and has a gap for placing an object to be measured. The ring-shaped transmission line and the two ground layers form a coplanar waveguide (CPW). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-147615 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the conventional measurement device described above generates unnecessary resonances in the measurement. Multiple resonance peaks, including the unnecessary resonances, overlap, making it difficult to measure the resonance frequency and unloaded Q, resulting in low measurement accuracy.

[0005] Therefore, the present disclosure provides a measurement device and a measurement system that can improve measurement accuracy. [Means for solving the problem]

[0006] A measurement device according to one aspect of the present disclosure includes a ring-shaped transmission line, a first ground layer provided inside the ring formed by the transmission line and spaced apart from the transmission line, a second ground layer provided outside the ring formed by the transmission line and spaced apart from the transmission line, a first dielectric layer provided below the first ground layer and the second ground layer, a second dielectric layer provided above each of the transmission line, the first ground layer, and the second ground layer, a first power supply terminal and a second dielectric layer disposed on the second dielectric layer for supplying power to the transmission line. a second feeding terminal and four or more ground terminals electrically connecting the first ground layer and the second ground layer, the first dielectric layer being a space provided at a position overlapping the transmission line in a plan view, the space having a space for placing an object to be measured, the first feeding terminal and the second feeding terminal being respectively arranged at two intersections between the transmission line and a first straight line passing through the center of a ring formed by the transmission line in a plan view, and the four or more ground terminals being arranged along the transmission line in a plan view, the first feeding terminal and the second feeding terminal being one or more first ground terminals arranged side by side with the first feed terminal on an opposite side of the first ground terminal along the transmission line in a planar view; one or more third ground terminals arranged side by side with the second feed terminal along the transmission line in a planar view; and one or more fourth ground terminals arranged side by side with the second feed terminal on an opposite side of the third ground terminal along the transmission line in a planar view, wherein an arrangement distance between a first ground terminal of the one or more first ground terminals closest to the first feed terminal and the first feed terminal, an arrangement distance between a second ground terminal of the one or more second ground terminals closest to the first feed terminal and the first feed terminal, an arrangement distance between a third ground terminal of the one or more third ground terminals closest to the second feed terminal and the second feed terminal, and an arrangement distance between a fourth ground terminal of the one or more fourth ground terminals closest to the second feed terminal and the second feed terminal are all equal to or less than one-fourth of a wavelength corresponding to an upper frequency of a measurement frequency band.

[0007] A measurement system according to one aspect of the present disclosure includes the measurement device according to the above aspect and an arithmetic circuit that calculates the relative dielectric constant of the object to be measured based on the transmission characteristics of the transmission line. [Effects of the Invention]

[0008] According to the present disclosure, measurement accuracy can be improved. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing the configuration of a measurement system according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view of the resonator according to the embodiment. [Figure 3] FIG. 3 is a cross-sectional view of the resonator according to the embodiment when a measurement target is placed on the resonator. [Figure 4] FIG. 4 is a plan view of the resonator according to the embodiment. [Figure 5] FIG. 5 is a plan view of the resonator according to the embodiment, seen through the second dielectric layer, the power supply terminal, and the ground terminal. [Figure 6] FIG. 6 is a cross-sectional view of the resonator according to the embodiment taken along line VI-VI in FIG. [Figure 7] FIG. 7 is an enlarged plan view of a region in the vicinity of a feed terminal of the resonator according to the embodiment. [Figure 8] FIG. 8 is a plan view showing the positional relationship between the ground terminal, the transmission line, and the ground layer included in the resonator according to the embodiment. [Figure 9] FIG. 9 is a cross-sectional view of the resonator according to the embodiment taken along line IX-IX in FIG. [Figure 10] FIG. 10 is a diagram showing an example of transmission characteristics of a transmission line measured by a measurement system according to a comparative example. [Figure 11] FIG. 11 is a diagram illustrating an example of transmission characteristics of a transmission line measured by the measurement system according to the embodiment. [Figure 12A]FIG. 12A is a cross-sectional view illustrating one step of a method for manufacturing a resonator according to an embodiment. [Figure 12B] FIG. 12B is a cross-sectional view illustrating one step of the method for manufacturing the resonator according to the embodiment. [Figure 12C] FIG. 12C is a cross-sectional view illustrating one step of the method for manufacturing the resonator according to the embodiment. [Figure 12D] FIG. 12D is a cross-sectional view illustrating one step of the method for manufacturing the resonator according to the embodiment. [Figure 12E] FIG. 12E is a cross-sectional view illustrating one step of the method for manufacturing the resonator according to the embodiment. [Figure 13] FIG. 13 is a flowchart showing the operation of the measurement system according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] (Summary of the Disclosure) A measurement device according to a first aspect of the present disclosure includes a ring-shaped transmission line, a first ground layer provided inside the ring formed by the transmission line and spaced apart from the transmission line, a second ground layer provided outside the ring formed by the transmission line and spaced apart from the transmission line, a first dielectric layer provided below the first ground layer and the second ground layer, a second dielectric layer provided above the transmission line, the first ground layer, and the second ground layer, and a first power supply terminal and a second dielectric layer disposed on the second dielectric layer for supplying power to the transmission line. and a second power supply terminal, and four or more ground terminals electrically connecting the first ground layer and the second ground layer, the first dielectric layer having a space provided at a position overlapping the transmission line in a plan view, for placing an object to be measured, the first power supply terminal and the second power supply terminal being respectively disposed at two intersections between the transmission line and a first straight line passing through the center of a ring formed by the transmission line in a plan view, and the four or more ground terminals being disposed along the transmission line in a plan view. one or more first ground terminals arranged side by side with the first feed terminal on an opposite side of the first ground terminal along the transmission line in a planar view; one or more third ground terminals arranged side by side with the second feed terminal along the transmission line in a planar view; and one or more fourth ground terminals arranged side by side with the second feed terminal on an opposite side of the third ground terminal along the transmission line in a planar view, wherein an arrangement distance between a first ground terminal of the one or more first ground terminals closest to the first feed terminal and the first feed terminal, an arrangement distance between a second ground terminal of the one or more second ground terminals closest to the first feed terminal and the first feed terminal, an arrangement distance between a third ground terminal of the one or more third ground terminals closest to the second feed terminal and the second feed terminal, and an arrangement distance between a fourth ground terminal of the one or more fourth ground terminals closest to the second feed terminal and the second feed terminal are all equal to or less than one-fourth of a wavelength corresponding to an upper frequency of a measurement frequency band.

[0011] In a coplanar resonator, not only differential mode resonance but also common mode resonance occurs at discontinuities in the transmission line (specifically, near the feed terminal). Common mode resonance is an unwanted resonance that is not suitable for measurement because the localization of the electric field near the transmission line is weak. The larger the potential difference between the first and second ground layers, the stronger the common mode resonance.

[0012] In contrast, in the measurement device according to this embodiment, the first and second ground terminals are arranged on either side of the first power supply terminal at an interval equal to or less than ¼ of the wavelength corresponding to the upper limit frequency of the measurement frequency band. The same is true for the second power supply terminal, the third ground terminal, and the fourth ground terminal. This short-circuits the first and second ground layers near the first and second power supply terminals, respectively, thereby sufficiently reducing the potential difference between the first and second ground layers. This suppresses common-mode resonance, thereby improving measurement accuracy.

[0013] A measurement device according to a second aspect of the present disclosure is the measurement device according to the first aspect, wherein the four or more ground terminals include n (n is a natural number greater than or equal to 2) each of the first ground terminal, the second ground terminal, the third ground terminal, and the fourth ground terminal, wherein the n first ground terminals are arranged side by side along the transmission line such that the spacing between adjacent first ground terminals is equal to or less than ½ of the wavelength, the n second ground terminals are arranged side by side along the transmission line such that the spacing between adjacent second ground terminals is equal to or less than ½ of the wavelength, the n third ground terminals are arranged side by side along the transmission line such that the spacing between adjacent third ground terminals is equal to or less than ½ of the wavelength, and the n fourth ground terminals are arranged side by side along the transmission line such that the spacing between adjacent fourth ground terminals is equal to or less than ½ of the wavelength.

[0014] In the high frequency range of the measurement frequency band, the ground terminals can function as distributed constant elements, which can cause weak common-mode resonances in the ground terminals. In contrast, the measurement device according to this embodiment provides multiple first, second, third, and fourth ground terminals, thereby suppressing common-mode resonances that occur secondarily in the ground terminals. Furthermore, by setting the spacing between adjacent ground terminals to less than half the wavelength corresponding to the upper limit frequency of the measurement frequency band, resonances between the ground terminals can also be suppressed. This suppresses resonances that are unnecessary for measurement, improving measurement accuracy.

[0015] A measurement device according to a third aspect of the present disclosure is the measurement device according to the first or second aspect, wherein the four or more ground terminals further include four fifth ground terminals, each of which is arranged, in a plan view, at four intersections between two second straight lines passing through the center of the ring and the transmission line, and each of the two second straight lines forms an angle of 45 degrees with respect to the first straight line.

[0016] In a coplanar resonator having a ring-shaped transmission line, if the potential of the first ground layer inside the ring formed by the transmission line is not sufficiently stabilized and becomes floating, the first ground layer can function as a patch resonator. In contrast, the measurement device according to this embodiment is provided with four fifth ground terminals, which stabilizes the potential of the first ground layer. This makes it possible to suppress resonances unnecessary for measurement and improve measurement accuracy.

[0017] A measurement device according to a fourth aspect of the present disclosure is the measurement device according to any one of the first to third aspects, wherein the four or more ground terminals are arranged in mirror symmetry with the first straight line as the axis of symmetry.

[0018] This makes it possible to suppress local variations in the electric field distribution, thereby suppressing resonances that are unnecessary for measurement and improving measurement accuracy.

[0019] A measurement device according to a fifth aspect of the present disclosure is the measurement device according to any one of the first to fourth aspects, wherein a portion of the second dielectric layer fills the gap between the transmission line and each of the first ground layer and the second ground layer.

[0020] This stabilizes the dielectric constant of the gap between the transmission line and each of the first and second ground layers, thereby suppressing local variations in the dielectric constant and improving measurement accuracy.

[0021] A measurement device according to a sixth aspect of the present disclosure is the measurement device according to any one of the first to fifth aspects, further comprising a third dielectric layer provided below the first dielectric layer, and the third dielectric layer has an opening communicating with the space.

[0022] This allows the object to be easily placed in the space provided in the first dielectric layer through the opening provided in the third dielectric layer. For example, when the object to be measured is a liquid or powder, the filling rate of the object to be measured in the space can be increased, thereby improving measurement accuracy.

[0023] A measurement device according to a seventh aspect of the present disclosure is a measurement device according to any one of the first to sixth aspects, wherein each of the four or more ground terminals has a conductive layer provided on the second dielectric layer, a first via that penetrates the second dielectric layer and connects the conductive layer to the first ground layer, and a second via that penetrates the second dielectric layer and connects the conductive layer to the second ground layer, and in a planar view, a third straight line connecting the centers of the first via and the second via passes through the center of the ring.

[0024] This allows the ground terminal to have a symmetrical structure with respect to the third line that passes through the center of the ring formed by the transmission line, which reduces bias in the electromagnetic field distribution caused by the ground terminal near the transmission line and suppresses unwanted resonance.

[0025] A measurement device according to an eighth aspect of the present disclosure is the measurement device according to the seventh aspect, wherein, in a planar view, for each of the four or more ground terminals, the shortest distance between the contour of the conductive layer and the contour of the first via is equal to the shortest distance between the contour of the first via and the contour of the first ground layer, and the shortest distance between the contour of the conductive layer and the contour of the second via is equal to the shortest distance between the contour of the second via and the contour of the second ground layer.

[0026] This allows the ground terminal to be smaller, and therefore the measurement frequency band of the resonator 100 can be broadened.

[0027] A measurement device according to a ninth aspect of the present disclosure is the measurement device according to the seventh or eighth aspect, wherein, in a planar view, for each of the four or more ground terminals, the shortest distance between the contour of the first via and the contour of the first ground layer is shorter than the width of the gap between the first ground layer and the transmission line, and the shortest distance between the contour of the second via and the contour of the second ground layer is shorter than the width of the gap between the second ground layer and the transmission line.

[0028] This allows the ground terminal to be made smaller, thereby broadening the measurement frequency band of the resonator 100. Furthermore, since the first and second vias are disposed in positions close to the contours of the first and second ground layers, respectively, the common mode suppression effect can be improved.

[0029] A measurement device according to a tenth aspect of the present disclosure is the measurement device according to any one of the seventh to ninth aspects, wherein, in a planar view, the distance between the center line of the transmission line and the center of the first via and the distance between the center line and the center of the second via are equal to each other.

[0030] This allows the ground terminal to be symmetrical with respect to the center line of the transmission line, which reduces bias in the electromagnetic field distribution caused by the ground terminal near the transmission line and suppresses unwanted resonance.

[0031] A measurement system according to an eleventh aspect of the present disclosure includes the measurement device according to any one of the first to tenth aspects, and an arithmetic circuit that calculates the relative dielectric constant of the object to be measured based on the transmission characteristics of the transmission line.

[0032] This makes it possible to suppress unnecessary resonances and improve measurement accuracy, similar to the above-described measuring device.

[0033] Hereinafter, the embodiments will be specifically described with reference to the drawings.

[0034] The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, component placement and connection configurations, steps, and step order shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Furthermore, among the components in the following embodiments, components not described in the independent claims are described as optional components.

[0035] Furthermore, each figure is a schematic diagram and is not necessarily an exact illustration. Therefore, for example, the scales of the figures do not necessarily match. Furthermore, in each figure, substantially the same components are given the same reference numerals, and redundant explanations are omitted or simplified.

[0036] Furthermore, in this specification, terms indicating the relationship between elements, such as parallel or perpendicular, terms indicating the shape of elements, such as circular or annular, and numerical ranges are not expressions that only express a strict meaning, but are expressions that also include a substantially equivalent range, for example, a difference of about a few percent.

[0037] In this specification, the x-axis, y-axis, and z-axis refer to the three axes of a three-dimensional Cartesian coordinate system. In this specification, the z-axis is defined as an axis parallel to the thickness direction of the first dielectric layer of the resonator. Unless otherwise specified, the term "planar view" refers to a view from the positive side of the z-axis.

[0038] Furthermore, in this specification, the terms "upper" and "lower" do not refer to the upward direction (vertically upward) and downward direction (vertically downward) in absolute spatial recognition, but are used as terms defined by a relative positional relationship based on the stacking order in a stacked configuration. Specifically, "upper" refers to the direction in which the second dielectric layer is provided relative to the first dielectric layer, and is represented in this specification as the positive direction of the z-axis. "Lower" is the opposite direction of "upper" and is represented in this specification as the negative direction of the z-axis. Furthermore, the terms "upper" and "lower" are used not only when two components are arranged with a gap between them and another component is present between them, but also when two components are arranged closely together and the two components are in contact with each other.

[0039] Furthermore, in this specification, ordinal numbers such as "first" and "second" do not refer to the number or order of components unless otherwise specified, but are used for the purpose of avoiding confusion and distinguishing between components of the same type.

[0040] (Embodiment) [1. Configuration] First, the configuration of a measurement system according to an embodiment will be described with reference to Fig. 1. Fig. 1 is a diagram showing the configuration of a measurement system 1 according to this embodiment.

[0041] The measurement system 1 shown in Fig. 1 is a system for calculating the dielectric properties of a measurement object 190 (see Fig. 3). The measurement object 190 is, for example, a powder. The dielectric properties are one of the dielectric constant and the dielectric loss tangent. Alternatively, the dielectric properties are both the dielectric constant and the dielectric loss tangent.

[0042] As shown in FIG. 1, the measurement system 1 includes a measurement device 10 and an arithmetic circuit 20.

[0043] The measurement device 10 includes a resonator 100 and a network analyzer 101 .

[0044] The resonator 100 also functions as a container (jig) for accommodating the measurement object 190. The specific configuration of the resonator 100 will be described later.

[0045] The network analyzer 101 is an example of a measuring instrument that measures the transmission characteristics of a transmission line 110 (see FIG. 2 ) of the resonator 100 by supplying a high-frequency signal of a predetermined frequency to the transmission line 110. The network analyzer 101 includes, for example, a high-frequency signal generator that generates and outputs a high-frequency signal, and a detector that detects the transmission characteristics of the transmission line 110.

[0046] The arithmetic circuit 20 calculates at least one of the dielectric constant and the dielectric loss tangent of the object to be measured 190 based on the transmission characteristics of the transmission line 110 .

[0047] The arithmetic circuit 20 is realized, for example, by an LSI (Large Scale Integration) which is an integrated circuit (IC). Note that the integrated circuit is not limited to an LSI, and may be a dedicated circuit or a general-purpose processor. For example, the arithmetic circuit 20 may be one or more microcontrollers. The microcontroller includes, for example, a non-volatile memory in which a program is stored, a volatile memory which is a temporary storage area for executing the program, input / output ports, a processor which executes the program, etc. Furthermore, the arithmetic circuit 20 may be a programmable FPGA (Field Programmable Gate Array) or a reconfigurable processor in which the connections and settings of circuit cells in the LSI can be reconfigured. The functions executed by the arithmetic circuit 20 may be realized by software or by hardware.

[0048] [2. Resonator structure] Next, the structure of the resonator 100 will be described with reference to FIGS.

[0049] 2, 3, and 6 are cross-sectional views of the resonator 100 according to the present embodiment. FIGS. 4 and 5 are plan views of the resonator 100 according to the present embodiment. Specifically, FIG. 2 shows a cross section of the resonator 100 taken along line II-II in FIGS. 4 to 6. FIG. 3 shows a cross section of the resonator 100 when a measurement target 190 is placed in the resonator 100 shown in FIG. 2. FIG. 6 shows a cross section of the resonator 100 taken along line VI-VI in FIG. 2. FIG. 4 is a plan view of the resonator 100 shown in FIG. 2 as seen from the positive side of the z-axis. FIG. 5 is a plan view of the resonator 100 shown in FIG. 2 as seen from the positive side of the z-axis, with the second dielectric layer 140, the power supply terminals 161 and 162, and the ground terminals 171a to 171e, 172a to 172e, 173a to 173e, and 174a to 174e seen through.

[0050] 2, the resonator 100 includes a transmission line 110, a first ground layer 121, a second ground layer 122, a first dielectric layer 130, a second dielectric layer 140, a third dielectric layer 150, and power supply terminals 161 and 162. The resonator 100 also includes four or more ground terminals. In this embodiment, the four or more ground terminals include a plurality of ground terminals 171a to 171e, 172a to 172e, 173a to 173e, and 174a to 174e, as shown in FIG.

[0051] The transmission line 110 is a ring-shaped transmission line. Specifically, as shown in Fig. 5, the transmission line 110 is in the shape of a circular ring. The center of the ring of the transmission line 110 is point C shown in Fig. 5. The width (line width) of the transmission line 110 is constant along the circumferential direction.

[0052] If the length (circumference) of the transmission line 110 is L1, the resonance frequency f is expressed by the following equation (1). Note that the length L1 of the transmission line 110 is the resonator length and can be regarded as an integer multiple of the resonance wavelength λ, so it can be expressed as L1=mλ, where m is an integer.

[0053]

number

[0054] In equation (1), ν is the speed of the signal propagating through the transmission line 110. c is the speed of light. ε ref is the effective dielectric constant of the transmission line 110. When the effective dielectric constant is 3.1, it can be seen from equation (1) that the length L1 of the transmission line 110 needs to be 2.16 mm or more to measure at a frequency of 79 GHz. By increasing the length L1 of the transmission line 110, resonance can be generated from low to high frequency bands, making it possible to measure dielectric properties.

[0055] The first ground layer 121 is provided inside the ring formed by the transmission line 110 and spaced apart from the transmission line 110. The shape of the first ground layer 121 in plan view is a circle centered at point C. A circular ring-shaped gap 123 having a constant line width W1 is provided between the first ground layer 121 and the transmission line 110 along the circumferential direction.

[0056] The second ground layer 122 is provided outside the ring formed by the transmission line 110 and spaced apart from the transmission line 110. The second ground layer 122 has a planar shape that is annular with a predetermined width and centered at point C. A circular ring-shaped gap 124 having a constant line width W2 is provided between the second ground layer 122 and the transmission line 110 along the circumferential direction. The line width W2 is equal to the line width W1. The line widths W1 and W2 are also called slot widths. The gaps 123 and 124 form a concentric double ring centered at point C.

[0057] The transmission line 110, the first ground layer 121, and the second ground layer 122 are formed using a conductive material. The conductive material is, for example, a metal material such as copper. The transmission line 110, the first ground layer 121, and the second ground layer 122 can be formed using the same material. For example, a copper foil can be attached to the main surface of the first dielectric layer 130 before the cavity 131 is formed, and then the double ring-shaped portion can be removed to form the transmission line 110, the first ground layer 121, and the second ground layer 122. The removal can be performed by, for example, etching, but is not limited to, a metal thin film can be formed on the main surface of the first dielectric layer 130 by vapor deposition, sputtering, plating, or the like, instead of attaching the copper foil. The thickness of the transmission line 110 is equal to or greater than the skin depth d0 of the resonant frequency. The skin depth d0 is expressed by the following equation (2):

[0058]

number

[0059] In equation (2), π is the constant of the circumference of a circle. f is the resonant frequency. μ is the magnetic permeability of the transmission line 110. σ is the conductivity of the transmission line 110. For example, if the transmission line 110 is made of copper, σ is 5.9×10 7 S / m. By forming the thickness of the transmission line 110 to be sufficiently thicker than the skin depth d0, it is possible to suppress an increase in measurement error due to variations in the thickness of the transmission line 110. For example, when the frequency is 79 GHz, the thickness of the transmission line 110 is 1 μm or more.

[0060] In this embodiment, the transmission line 110, the first ground layer 121, and the second ground layer 122 are provided so that their upper surfaces are flush with each other. That is, the transmission line 110, the first ground layer 121, and the second ground layer 122 are provided so as to be in contact with the lower surface of the second dielectric layer 140.

[0061] The thickness of the transmission line 110 is the same as the thickness of the outer peripheral end of the first ground layer 121 and the thickness of the inner peripheral end of the second ground layer 122. The outer peripheral end of the first ground layer 121 is a portion of the first ground layer 121 exposed to the cavity 131 of the first dielectric layer 130. The inner peripheral end of the second ground layer 122 is a portion of the second ground layer 122 exposed to the cavity 131. As shown in FIG. 2 , the thickness of the outer peripheral end of the first ground layer 121 is thinner than the thickness of a portion sandwiched between the first dielectric layer 130 and the second dielectric layer 140. The thickness of the inner peripheral end of the second ground layer 122 is thinner than the thickness of a portion sandwiched between the first dielectric layer 130 and the second dielectric layer 140. This is because parts of the transmission line 110, the first ground layer 121, and the second ground layer 122 are removed when the cavity 131 is formed. The first ground layer 121 and the second ground layer 122 may each be formed to have a constant thickness. The transmission line 110, the first ground layer 121, and the second ground layer 122 may all have the same constant thickness.

[0062] The first dielectric layer 130 is provided below the first ground layer 121 and the second ground layer 122 (on the negative side of the z-axis). The first dielectric layer 130 has a space (specifically, a cavity 131) for placing the object to be measured 190. The cavity 131 is provided at a position overlapping the transmission line 110 in a plan view. Specifically, as shown in FIG. 6 , the cavity 131 has a circular ring shape. The width (line width) of the cavity 131 is wider than the line width of the transmission line 110. The transmission line 110 is disposed adjacent to the cavity 131. The transmission line 110 and the first dielectric layer 130 are not in contact with each other. The depth of the cavity 131, i.e., the thickness of the first dielectric layer 130, is greater than the thickness of the transmission line 110.

[0063] The first dielectric layer 130 is formed using a dielectric material. Specifically, the first dielectric layer 130 includes at least one material selected from the group consisting of resin, glass, and LTCC (Low Temperature Co-fired Ceramics). The relative permittivity and dielectric loss tangent of the first dielectric layer 130 are known values.

[0064] The outer shape of the first dielectric layer 130 in a plan view is, for example, circular. For example, the outer circumferential contour of the first dielectric layer 130 and the outer circumferential contour of the second ground layer 122 coincide in a plan view. The first dielectric layer 130 is fixed to the first ground layer 121 and the second ground layer 122. This makes it possible to suppress deviation in the positional relationship between the cavity 131 and the transmission line 110.

[0065] 2 , a gap 123 between the first ground layer 121 and the transmission line 110 and a gap 124 between the second ground layer 122 and the transmission line 110 are filled with a portion of the second dielectric layer 140. By filling the gaps 123 and 124 with a portion of the second dielectric layer 140, the distance between the transmission line 110 and the first ground layer 121 or the second ground layer 122 can be kept constant. The second dielectric layer 140 can prevent the distance between the transmission line 110 and the first ground layer 121 or the second ground layer 122 from changing due to an impact or the like when the object to be measured 190 is placed in the cavity 131. Furthermore, by filling the gaps 123 and 124 with a portion of the second dielectric layer 140, it is possible to prevent the object to be measured 190 from entering the gaps 123 and 124.

[0066] The second dielectric layer 140 is provided above the transmission line 110, the first ground layer 121, and the second ground layer 122. The second dielectric layer 140 is a support member for the transmission line 110, the first ground layer 121, and the second ground layer 122.

[0067] The second dielectric layer 140 is formed using a dielectric material. Specifically, the second dielectric layer 140 includes at least one material selected from the group consisting of resin, glass, and LTCC. The second dielectric layer 140 may be formed using the same material as the first dielectric layer 130. The relative dielectric constant and dielectric loss tangent of the second dielectric layer 140 are known.

[0068] The third dielectric layer 150 is provided below the first dielectric layer 130. The third dielectric layer 150 includes at least one material selected from the group consisting of resin, glass, and LTCC. The third dielectric layer 150 may be formed using the same material as the first dielectric layer 130 or the second dielectric layer 140. The relative dielectric constant and dielectric loss tangent of the third dielectric layer 150 are known.

[0069] The third dielectric layer 150 has an opening 151 that communicates with the cavity 131 provided in the first dielectric layer 130. The opening 151 penetrates the third dielectric layer 150, exposing the cavity 131 to the outside of the resonator 100. The shape and size of the opening 151 in a plan view are the same as the shape and size of the cavity 131. As shown in FIG. 3 , a measurement object 190 can be easily placed in the cavity 131 via the opening 151.

[0070] In this embodiment, the resonator 100 can be formed by a processing method similar to that used for a printed circuit board. Specifically, the first dielectric layer 130 is a core material, and the second dielectric layer 140 and the third dielectric layer 150 are prepregs. For example, the first dielectric layer 130 and the second dielectric layer 140 have a thickness of 100 μm, and the third dielectric layer 150 has a thickness of 200 μm. Note that the thickness and material of each layer are merely examples and are not particularly limited. A specific method for manufacturing the resonator 100 will be described later.

[0071] The power supply terminals 161 and 162 are a first power supply terminal and a second power supply terminal arranged on the second dielectric layer 140 for supplying power to the transmission line 110. The power supply terminals 161 and 162 also function as detection terminals for detecting the transmission characteristics of the transmission line 110.

[0072] The feed terminals 161 and 162 are each disposed at a position overlapping the transmission line 110 in a planar view. For example, as shown in FIG. 4, the feed terminals 161 and 162 are disposed at two intersections of a line L1x and the transmission line 110 in a planar view. The line L1x is an example of a first line, and is a line that passes through a point C, which is the center of a ring formed by the transmission line 110, in the xy plane. In this embodiment, the feed terminals 161 and 162 are in a point-symmetric relationship with respect to the point C as the center of symmetry. The feed terminals 161 and 162 are also in a line-symmetric relationship with respect to the lines L1x and L1y, which are the axes of symmetry. The line L1y is a line that passes through the point C and is perpendicular to the line L1x in the xy plane.

[0073] The feed terminals 161 and 162 are electrically connected to the transmission line 110. For example, the feed terminals 161 and 162 are electromagnetically coupled to the transmission line 110. The feed terminals 161 and 162 are each connected to the network analyzer 101. The feed terminals 161 and 162 supply a high-frequency signal supplied from the network analyzer 101 to the transmission line 110 by coupling. This allows the transmission line 110 (resonator 100) to be excited.

[0074] The strength of the electromagnetic coupling between each of the feed terminals 161 and 162 and the transmission line 110 varies depending on the overlapping area between each of the feed terminals 161 and 162 and the transmission line 110 in a plan view. Specifically, the larger the overlapping area, the stronger the electromagnetic coupling and the higher the peak intensity of the resonance. The smaller the overlapping area, the weaker the electromagnetic coupling and the lower the peak intensity of the resonance. If the peak intensity is too low, the device will be more susceptible to noise, and if the peak intensity is too high, it will be difficult to detect the appropriate resonance.

[0075] In this embodiment, the peak intensity S of each of the multiple resonances is 21 (See Figure 11) is adjusted to approach -20 dB. For example, the resonance peak intensity S 21Alternatively, the overlap area is adjusted so that the resonance peak intensity S 21 The overlap area may be adjusted to accommodate more.

[0076] 2 and 4, the power supply terminals 161 and 162 do not overlap the entire transmission line 110 on the x-axis (the straight line L1x in FIG. 4), but overlap part of the transmission line 110, the second ground layer 122, and the gap 124. For example, the power supply terminals 161 and 162 overlap only half the line width of the transmission line 110. Note that the power supply terminals 161 and 162 may also overlap part of the transmission line 110, the first ground layer 121, and the gap 123.

[0077] 4 are an example of the four or more ground terminals included in the measurement device 10, and electrically connect the first ground layer 121 and the second ground layer 122. In this embodiment, the four or more ground terminals include the same number (n) of first ground terminals, second ground terminals, third ground terminals, and fourth ground terminals, where n is a natural number greater than or equal to 2. In this embodiment, n=4, but is not limited to this. The four or more ground terminals also include four fifth ground terminals.

[0078] The ground terminals 171a to 171d are each an example of a first ground terminal, and are arranged alongside the power supply terminal 161 along the transmission line 110 in a plan view. The ground terminal 171a is the ground terminal closest to the power supply terminal 161 among the n first ground terminals. The ground terminals 171a, 171b, 171c, and 171d are arranged in this order from the power supply terminal 161 in a counterclockwise (left-handed) direction along the transmission line 110.

[0079] Each of the ground terminals 172a to 172d is an example of a second ground terminal, and is arranged along the transmission line 110 on the opposite side of the ground terminal 171a in plan view, alongside the power supply terminal 161. The ground terminal 172a is the ground terminal closest to the power supply terminal 161 among the n second ground terminals. The ground terminals 172a, 172b, 172c, and 172d are arranged in this order clockwise (right-handed) from the power supply terminal 161 along the transmission line 110.

[0080] The ground terminals 173a to 173d are each an example of a third ground terminal, and are arranged alongside the power supply terminal 162 along the transmission line 110 in a plan view. The ground terminal 173a is the ground terminal closest to the power supply terminal 162 among the n third ground terminals. The ground terminals 173a, 173b, 173c, and 173d are arranged in this order clockwise (right-handed) from the power supply terminal 162 along the transmission line 110.

[0081] Each of the ground terminals 174a to 174d is an example of a fourth ground terminal, and is arranged alongside the power supply terminal 162 on the opposite side of the ground terminal 173a along the transmission line 110 in a plan view. The ground terminal 174a is the ground terminal that is closest to the power supply terminal 162 among the n fourth ground terminals. The ground terminals 174a, 174b, 174c, and 174d are arranged in this order in a counterclockwise (left-handed) direction from the power supply terminal 162 along the transmission line 110.

[0082] The ground terminals 171e, 172e, 173e, and 174e are each an example of a fifth ground terminal, and are arranged, in plan view, at four intersections between each of the two straight lines L2a and L2b and the transmission line 110. The straight lines L2a and L2b form an angle of 45 degrees with the straight line L1x.

[0083] In this embodiment, the 20 ground terminals provided in the measurement device 10 are arranged in mirror symmetry with respect to the line L1x as the axis of symmetry. Specifically, the 20 ground terminals are arranged in mirror symmetry with respect to the line L1y as the axis of symmetry. Specific examples of the arrangement and configuration of the 20 ground terminals are described below.

[0084] The power supply terminals 161 and 162 and the ground terminals 171a to 171e, 172a to 172e, 173a to 173e, and 174a to 174e are all formed using a conductive material. The conductive material is, for example, a metal material such as copper. The power supply terminals 161 and 162 and the ground terminals 171a to 171e, 172a to 172e, 173a to 173e, and 174a to 174e can be formed using the same material. For example, the power supply terminals 161 and 162 and the ground terminals 171a to 171e, 172a to 172e, 173a to 173e, and 174a to 174e can be formed by laminating copper foil on the upper surface of the second dielectric layer 140 and then partially removing it.

[0085] [3. Characteristic structure of the resonator] Next, the characteristic configuration of the resonator 100 will be described mainly using FIGS. 7 to 9, with reference to FIGS. 2 to 6 as appropriate.

[0086] Fig. 7 is an enlarged plan view of a region near the feed terminal 161 of the resonator 100 according to this embodiment. Fig. 8 is a plan view showing the positional relationship between the ground terminal 171a of the resonator 100 according to this embodiment and the transmission line 110, the first ground layer 121, and the second ground layer 122. Fig. 9 is a cross-sectional view of the resonator 100 according to this embodiment taken along line IX-IX in Fig. 8. Note that the center line CL of the transmission line 110 is actually curved along the circumference, but is represented by a straight line in Fig. 8. The same applies to the outlines of the transmission line 110, the first ground layer 121, and the second ground layer 122.

[0087] The resonator 100 according to this embodiment is characterized by the arrangement of the multiple ground terminals. By arranging the multiple ground terminals at appropriate positions, it is possible to suppress unwanted resonances occurring in the resonator 100 within the measurement frequency band. The unwanted resonances affect the resonance frequency and unloaded Q of the resonances originally used for measurement, thereby reducing the measurement accuracy and precision of the dielectric constant and dielectric loss of the measurement target 190. The unloaded Q is defined as the average value of electromagnetic field energy accumulated in the resonator per unit time divided by the average value of electromagnetic field energy consumed in the resonator per unit time in an ideal state in which electromagnetic field energy does not flow into or out of the resonator. In the resonator 100 according to this embodiment, the arrangement of the multiple ground terminals is optimized to suppress the generation of unwanted resonances occurring in the measurement frequency band. The optimization method will be described in detail below.

[0088] In the resonator 100 according to this embodiment, the arrangement, size, and shape of the components are in a mirror-symmetric relationship with respect to the straight lines L1x and L1y as axes of symmetry. Therefore, to avoid redundant explanation, the following description will focus on the structure included in the first quadrant in an orthogonal two-dimensional coordinate system with point C as the center and the straight lines L1x and L1y as the two axes.

[0089] First, in resonator 100, a group of components including transmission line 110, first ground layer 121, and second ground layer 122 operate as a coplanar line having the same slot width. Therefore, resonator 100 operates as a ring resonator including a coplanar line. To suppress unwanted resonances described below, it is desirable for the coplanar lines to have the same slot width, but this is not an essential condition.

[0090] The characteristic impedance for the differential mode, which is the main propagation mode of the coplanar line, can be set to, for example, 50 Ω, but it is equally possible to use coplanar lines with other characteristic impedances. Therefore, it goes without saying that the line width and slot width of the transmission line 110 can be freely set. Note that increasing the slot width reduces the sensitivity of the resonator 100 to local variations in the permittivity and dielectric loss of the object under test 190 inserted into the cavity 131. While this has the advantage of making it easier to achieve measurement stability, it can also cause unwanted resonance or a decrease in the unloaded Q due to radiation loss. Therefore, it is desirable to select the slot width according to the measurement situation.

[0091] In a coplanar line, in a planar view such as that shown in FIG. 4, clockwise (right-handed) traveling waves and counterclockwise (left-handed) traveling waves can equally exist along the transmission line 110. When the frequency is fixed, both traveling waves have the same propagation wavelength. For traveling waves in each direction, the resonator 100 resonates at the resonant frequency f shown in Equation (1). Therefore, in the resonator 100, resonances due to two traveling waves are degenerated at each resonant frequency. When measuring the dielectric constant and / or dielectric loss of the measurement target 190 using the resonator 100, it is essential to obtain the peak frequency, peak half-maximum frequency width, and passing power value for one resonant mode. To achieve this, it is important for measurement accuracy that the two degenerate resonances of the resonator 100 are not separated. This is because, if the degeneracy is released and the two resonances show different resonance frequencies, the peak half-maximum frequency width is no longer determined solely by the resonance characteristics of the resonator 100, and the extraction accuracy of the dielectric constant and / or dielectric loss of the measurement object 190 decreases. For this reason, in this embodiment, the power supply terminals 161 and 162 and four or more ground terminals are arranged at positions that are mirror-symmetrical with respect to the two orthogonal straight lines L1x and L1y, respectively. This suppresses the degeneracy separation of the resonances.

[0092] The equality of the waveguiding characteristics in the propagation direction of the electromagnetic wave is a feature that all high-frequency lines possess. In addition to this feature, a coplanar line also has the ability to transmit traveling waves with two different electromagnetic field distributions. These two different electromagnetic field distributions are called differential mode and common mode. A plane containing the center line CL (see FIG. 7) of the transmission line 110 and parallel to the substrate normal (z-axis direction) is taken as the plane of mirror symmetry. In the differential mode, the electric field is incident perpendicular to the plane of mirror symmetry, while in the common mode, the magnetic field is incident perpendicular to the plane of mirror symmetry. Furthermore, in the differential mode, the electric field is localized near the transmission line 110, while in the common mode, the electric field is weakly localized. Due to the difference in the electromagnetic field distributions between the two modes, it is desirable to use differential mode resonance to stably measure the permittivity and / or dielectric loss of the object to be measured 190 placed in the cavity 131.

[0093] Generally, the differential mode and the common mode have different propagation wavelengths. Therefore, according to Equation (1), a large number of resonances originating from each mode are generated in the resonator 100, as shown in Fig. 10. When a large number of resonance modes are generated, multiple peaks overlap as shown in Fig. 10, and the frequency intervals between the peaks are also unequal, which makes it difficult to distinguish between the resonances.

[0094] 10 is a diagram showing an example of transmission characteristics of a transmission line measured by a measurement system according to a comparative example. The measurement system according to the comparative example differs from the measurement system 1 according to the present embodiment in the configuration of the resonator. Specifically, compared to the resonator 100 according to the present embodiment, the resonator according to the comparative example has a configuration in which, instead of the ground terminals 171a-171e, 172a-172e, 173a-173e, and 174a-174e, two ground terminals are arranged at the intersection of the straight line L1y and the transmission line 110.

[0095] Furthermore, resonance due to common mode radiates electromagnetic field energy to the outside, making it impossible to achieve a high unloaded Q. Considering the problems of low unloaded Q and the effect on other resonances, suppressing resonance due to common mode is important for improving measurement accuracy. For this reason, in resonator 100 according to this embodiment, ground terminals 171a and 172a are arranged close to feed terminal 161, with feed terminal 161 sandwiched therebetween. Furthermore, ground terminals 173a and 174a are arranged close to feed terminal 162, with feed terminal 162 sandwiched therebetween.

[0096] A common mode is particularly likely to be generated near the intersection between the power supply terminal 161 and the transmission line 110. Therefore, the ground terminals 171a and 172a compensate for the same potential and phase between the first ground layer 121 and the second ground layer 122, thereby suppressing the generation of the common mode. The same is true near the intersection between the power supply terminal 162 and the transmission line 110, where the ground terminals 173a and 174a can suppress the generation of the common mode.

[0097] The principle of suppression by the ground terminals is as follows. At the intersections of a plane including a radius (e.g., a straight line L1x) centered at the center point C of the resonator 100 and the substrate normal (z-axis), and the annular edge (outer circumferential contour) of the first ground layer 121 and the annular edge (inner circumferential contour) of the second ground layer 122, the planes are at the same potential in the differential mode but are at different potentials in the common mode. Therefore, by short-circuiting the vicinity of the intersections using the ground terminals, the common mode can be effectively suppressed. Therefore, by arranging the ground terminals 171a and 171b near the power supply terminal 161, where the common mode is likely to occur, the occurrence of resonance due to the common mode can be suppressed.

[0098] In order to suppress common-mode resonance across the entire measurement frequency band of the resonator 100 according to this embodiment, the arrangement distance P1 between the feed terminal 161 and the ground terminal 171a is set to ¼ or less of the wavelength λ corresponding to the upper limit frequency of the measurement frequency band. The wavelength λ corresponding to the upper limit frequency of the measurement frequency band is a value converted into a common-mode propagation wavelength. The common-mode propagation wavelength can be approximately calculated by dividing the wavelength in a vacuum (=speed of light / frequency) at a frequency by the ½ power of the average relative dielectric constant of the measurement object 190 and the second dielectric layer 140 placed in the cavity 131. The upper limit frequency of the measurement frequency band is, for example, 110 GHz. As shown in FIG. 7 , the arrangement distance P1 is defined as the length along the center line CL (arc) between two intersections of the center line CL of the transmission line 110 with the center line (straight line L1x) of the feed terminal 161 and the center line (straight line L3a) of the ground terminal 171a. The upper limit frequency of the measurement frequency band can be regarded as the upper limit frequency of the network analyzer 101.

[0099] When the upper limit frequency of the measurement frequency band is fixed based on the above-described method for suppressing resonance caused by common modes, it becomes necessary to shorten the arrangement distance P1 between power supply terminal 161 and ground terminal 171a in order to measure a measurement object 190 with a higher dielectric constant. If the minimum pattern distance between power supply terminal 161 and ground terminal 171a, which are arranged at arrangement distance P1 determined by the common mode propagation wavelength, is smaller than the minimum value of the minimum pattern distance determined by the circuit pattern drawing process, conversely, the upper limit frequency of the measurement frequency band or the upper limit of the measurable dielectric constant of measurement object 190 is determined from the minimum value of the minimum pattern distance determined by the drawing process.

[0100] As a specific example of the arrangement of ground terminal 171a, if a paraelectric material with a dielectric constant of 3.4 and a thickness of 100 μm is used as second dielectric layer 140 and the minimum gap between copper foil patterns that can be processed by etching is 70 μm, by arranging power supply terminal 161 and ground terminal 171a so that the minimum distance between them is 70 μm, it is possible to set the upper limit of the measurement frequency to 110 GHz or higher even when measurement object 190 with a relative dielectric constant of 6 is placed in cavity 131.

[0101] 7, the arrangement distance between ground terminal 172a and feed terminal 161, the arrangement distance between ground terminal 173a and feed terminal 162, and the arrangement distance between ground terminal 174a and feed terminal 162 are all equal to or less than ¼ of wavelength λ corresponding to the upper limit frequency of the measurement frequency band. Furthermore, the arrangement distance P1 between ground terminal 171a and feed terminal 161, the arrangement distance between ground terminal 172a and feed terminal 161, the arrangement distance between ground terminal 173a and feed terminal 162, and the arrangement distance between ground terminal 174a and feed terminal 162 are all equal to one another.

[0102] In this embodiment, as shown in FIGS. 2 and 7 , in addition to ground terminal 171a, three adjacent ground terminals, 171b, 171c, and 171d, are arranged side by side. This is to enhance the suppression effect of common-mode-induced resonance near the upper limit frequency of the measurement frequency band, even when a high-dielectric-constant measurement object 190 is placed in cavity 131. In the low frequency range of the measurement frequency band, the propagation wavelengths of the differential mode and common mode are long, so ground terminal 171a functions as a short-circuiting line. However, in the high frequency range of the measurement frequency band, the size of ground terminal 171a becomes the same as the propagation wavelengths of both modes, and it begins to function as a distributed constant element. Therefore, in the high frequency range of the measurement frequency band, a weak common mode is generated even in ground terminal 171a. These secondary common-mode-induced resonances can be suppressed by multiple ground terminals (specifically, ground terminals 171b, 171c, and 171d).

[0103] The placement of each ground terminal is determined in accordance with the policy described for ground terminal 171a. Specifically, the placement interval between adjacent ground terminals is set to ½ or less of the wavelength (converted to a common-mode propagation wavelength) λ corresponding to the upper limit frequency of the measurement frequency band when measurement object 190 having the measurement upper limit relative dielectric constant is placed in cavity 131. Specifically, as shown in Fig. 7, the placement interval P2ab between ground terminal 171a and ground terminal 171b, the placement interval P2bc between ground terminal 171b and ground terminal 171c, and the placement interval P2cd between ground terminal 171c and ground terminal 171d are all ½ or less of the wavelength λ.

[0104] The arrangement interval P2ab is defined as the length along the center line CL (arc) between two intersections of the center line CL of the transmission line 110 with the center line (straight line L3a) of the ground terminal 171a and the center line (straight line L3b) of the ground terminal 171b. The same applies to the arrangement intervals P2bc and P2cd. In this embodiment, the arrangement intervals P2ab, P2bc, and P2cd are equal to each other, but are not limited to this.

[0105] In the explanation of ground terminal 171a, it was stated that the arrangement interval P1 between power supply terminal 161 and ground terminal 171a is λ / 4 or less in terms of common mode propagation wavelength, but in the case of ground terminal 171a, resonance is generated between ground terminal 171a and ground terminal 172a (not shown in FIG. 7), which is in a mirror-symmetric relationship with respect to ground terminal 171a with respect to line L1x as the axis of symmetry. This is consistent with the description that the arrangement interval between adjacent ground terminals is λ / 2 or less.

[0106] 7, the same applies to ground terminals 172a to 172d, ground terminals 173a to 173d, and ground terminals 174a to 174d. Specifically, ground terminals 172a to 172d are arranged side by side along transmission line 110 so that the spacing between adjacent ground terminals is λ / 2 or less. Ground terminals 173a to 173d are arranged side by side along transmission line 110 so that the spacing between adjacent ground terminals is λ / 2 or less. Ground terminals 174a to 174d are arranged side by side along transmission line 110 so that the spacing between adjacent ground terminals is λ / 2 or less.

[0107] Increasing the number of ground terminals can suppress common-mode resonances up to higher frequency bands. However, in this embodiment, the number of ground terminals aligned in one direction from the feed terminal 161 is not limited to four. Furthermore, the ground terminals do not necessarily need to be spaced evenly. However, from the perspective of common-mode suppression, it is desirable to arrange the ground terminals so that their center lines coincide with the radius vectors centered on point C, which is the center of the resonator 100. Furthermore, increasing the number of ground terminals reduces the unloaded Q of the resonator 100, particularly reducing the accuracy of dielectric loss measurement. For this reason, it is desirable to set the minimum number of ground terminals that suppresses common-mode resonances in the measurement frequency band. In the first quadrant of the resonator 100 shown in FIG. 7, this minimum number is one, i.e., ground terminal 171a. However, more than the minimum number of ground terminals may be installed to suppress other unwanted resonances, as described below.

[0108] In addition to the common mode described above, the resonator 100 also generates an unwanted mode, a resonance generated only by the first ground layer 121. Specifically, because the first ground layer 121 can be considered an isolated circular patch resonator, this resonance exhibits an electromagnetic field distribution similar to that of a microstrip antenna using a circular patch. Because the two power supply terminals 161 and 162 are located on the line L1x, the fundamental resonance of the first ground layer 121 is a resonance with the line L1y as a "node." Note that the "node" refers to the position where the electric field intensity is minimum on the annular edge (outer peripheral contour) of the first ground layer 121. Therefore, by placing a ground terminal on the coplanar line at a position other than the line L1y, the fundamental resonance of the circular patch resonance can be suppressed. Note that the closer the ground terminal is to the line L1x, the greater the suppression effect of the fundamental resonance.

[0109] When the upper limit frequency of the measurement frequency band is higher than the fundamental resonant frequency of the circular patch resonance, a higher-order circular patch resonance is generated on the first ground layer 121. However, due to the two-mirror symmetry of the resonator 100, only even modes of the circular patch resonance are generated. Here, the mode order is defined as the number of nodes of the electromagnetic field resonance appearing in the structure shown in FIG. 4 minus one. Therefore, the next circular patch resonance generated is a resonance with nodes on lines L2a and L2b that form a 45° angle with line L1x. Like the fundamental resonance of the circular patch resonance, this resonance can also be suppressed by providing a ground terminal near the feed terminal 161 or 162 at a location other than the node on the coplanar line.

[0110] By repeating the above operations, it is possible to suppress the generation of circular patch resonance that appears in the measurement frequency band.

[0111] For example, as shown in FIG. 4, ground terminals 171e, 172e, 173e, and 174e are arranged at four intersections between the transmission line 110 and lines L2a and L2b, which form a 45° angle with line L1x. In this example, the ground terminals 171e, 172e, 173e, and 174e suppress the fundamental resonance of the circular patch resonance. Furthermore, if the dielectric constant of the second dielectric layer 140 is set to 3.4 and the radius of the transmission line 110 is set to 4 mm, the four ground terminals 171a to 171d can suppress the second and fourth-order resonances of the circular patch resonance that appear up to the 110 GHz band. The same applies to the ground terminals 172a to 172d, 173a to 173d, and 174a to 174d. These four ground terminals are arranged so that the minimum spacing between adjacent ground terminal patterns is 70 μm.

[0112] Next, the structure of each of the ground terminals 171a to 171e, 172a to 172e, 173a to 173e, and 174a to 174e included in the resonator 100 according to the present embodiment will be described with reference to Figures 8 and 9. Note that since the ground terminals have the same structure, the ground terminal 171a will be described below as a representative.

[0113] 8 and 9, the ground terminal 171a of the present embodiment has a short-circuit line 180 and two vias 181 and 182. The short-circuit line 180 and the vias 181 and 182 electrically connect and short-circuit the first ground layer 121 and the second ground layer 122.

[0114] The short-circuit line 180 is an example of a conductive layer provided on the second dielectric layer 140. Specifically, the short-circuit line 180 is formed on the same layer as the power supply terminals 161 and 162. The short-circuit line 180 is provided so as to cross the transmission line 110. As shown in FIG. 8, the short-circuit line 180 has an elongated oval shape along a straight line L3 in a plan view. In this embodiment, the straight line L3, which is the center line of the short-circuit line 180, passes through point C, which is the center of the resonator 100. The straight line L3 corresponds to the straight lines L3a, L3b, L3c, and L3d shown in FIG.

[0115] Two vias 181 and 182 each penetrate the second dielectric layer 140. The via 181 is an example of a first via, and connects the short-circuit line 180 to the first ground layer 121. The via 182 is an example of a second via, and connects the short-circuit line 180 to the second ground layer 122. The centers of the vias 181 and 182 are each located on the line L3.

[0116] The vias 181 and 182 are formed by, for example, forming through-holes that penetrate the second dielectric layer 140 using a mechanical drill or a laser, and then copper-plating the inner walls. The measurement frequency can be increased by reducing the diameter of the vias 181 and 182. The small-diameter vias 181 and 182 can be easily formed by laser processing.

[0117] By reducing the size of the ground terminal 171a, it is possible to widen the measurement frequency band of the resonator 100. Specifically, in addition to small-diameter vias 181 and 182, a short-circuit wire 180 with a small line width is used. In the example shown in Fig. 8, the short-circuit wire 180 has a line width of 2R, where R is the minimum land radius defined by the via formation method.

[0118] In order to enhance the common mode suppression effect described above, the two vias 181 and 182 are placed as close as possible to the edges of the copper foil patterns of the first ground layer 121 and the second ground layer 122. In the example shown in Fig. 8, the two vias 181 and 182 are placed with a minimum offset amount d of the wall surfaces of the vias 181 and 182 from the outer periphery of the short-circuit line 180.

[0119] 8, the shortest distance between the outline of short-circuit line 180 and the outline of via 181 is equal to the shortest distance between the outline of via 181 and the outline of first ground layer 121. Moreover, the shortest distance between the outline of short-circuit line 180 and the outline of via 182 is equal to the shortest distance between the outline of via 182 and the outline of second ground layer 122. These shortest distances are the minimum offset amount d.

[0120] Furthermore, the shortest distance d between the outline of the via 181 and the outline of the first ground layer 121 is shorter than the width W1 of the gap between the first ground layer 121 and the transmission line 110. The shortest distance d between the outline of the via 182 and the outline of the second ground layer 122 is shorter than the width W2 of the gap between the second ground layer 122 and the transmission line 110. Furthermore, in a plan view, the distance D1 between the center line CL of the transmission line 110 and the center of the via 181 and the distance D2 between the center line CL of the transmission line 110 and the center of the via 182 are equal to each other.

[0121] By using the resonator 100 configured as described above, multiple resonance peaks can be obtained in the measurement frequency band, as shown in Fig. 11. Fig. 11 is a diagram showing an example of the transmission characteristics of the transmission line 110 measured by the measurement system 1 according to this embodiment. In Fig. 11, the horizontal axis represents the frequency of the high-frequency signal supplied to the transmission line 110, and the vertical axis represents the power passing characteristic (|S 21 |).

[0122] While overlapping of peaks occurs in the comparative example shown in FIG. 10, no overlapping of peaks occurs in the resonator 100 according to this embodiment. Each peak appears at approximately constant frequency intervals and is a steep peak. When the measurement object 190 is placed in the cavity 131, the resonant frequency and unloaded Q (half-width and peak intensity) of the peak change. By measuring this change, the dielectric characteristics of the measurement object 190 can be calculated with high accuracy.

[0123] [4. Manufacturing method] Next, a method for manufacturing the resonator 100 of the measurement device 10 according to this embodiment will be described with reference to Figures 12A to 12E. Each of Figures 12A to 12E is a cross-sectional view for explaining one step of the method for manufacturing the resonator 100 according to this embodiment.

[0124] The resonator 100 is fabricated, for example, by the following multilayer circuit board method.

[0125] (Step S1: Copper foil processing) First, as shown in Fig. 12A, a core material 200 with copper foil on both sides is prepared. The core material 200 includes a core 230 and copper foils 210 and 220 provided on both sides of the core 230. The core 230 is processed to form the first dielectric layer 130. Furthermore, the copper foil 210 is processed to form the transmission line 110, the first ground layer 121, and the second ground layer 122.

[0126] As the core material 200, for example, a thick core material can be used to prevent warping of the entire substrate of the resonator 100 and to ensure the volume of the cavity 131 in which the object to be measured 190 is placed. In this embodiment, since the penetration of the electromagnetic field into the inside of the first dielectric layer 130 is small, a core material having either a high dielectric constant or a high dielectric loss, or both, can be used. The core material 200 having such characteristics is relatively inexpensive and easy to process, and therefore is suitably used as the first dielectric layer 130.

[0127] As shown in FIG. 12B, the transmission line 110, the first ground layer 121, and the second ground layer 122 are formed by partially removing the copper foil 210 on the upper surface of the core 230. The copper foil 220 on the lower surface of the core 230 is also completely removed. This copper foil processing is performed using a subtractive technique consisting of photolithography and etching, but additive techniques that make extensive use of plating can also be used. Note that when comparing the upper and lower surfaces of the core 230, there is a large difference in the copper remaining ratio (= the ratio of the copper foil remaining area to the board area) on the surfaces. Therefore, to prevent the core 230 from warping after the copper foil processing (step S1) is performed, it is desirable to use a sufficiently thick dielectric material for the core 230.

[0128] (Step S2) Next, prepreg material 240 is bonded to the upper surface of core 230 after step S1, and prepreg material 250 is bonded to the lower surface. Prepreg materials 240 and 250 are processed to form second dielectric layer 140 and third dielectric layer 150. Prepreg materials 240 and 250 may be, for example, prepreg materials that can be bonded by thermocompression bonding. In this processing, prepreg material 240 is filled in gaps 123 and 124 between transmission line 110 and first ground layer 121 and second ground layer 122, respectively, during bonding.

[0129] The resonant frequency f and unloaded Q of the resonator 100 when the object to be measured 190 is not placed in the cavity 131 are mainly determined by the dielectric constant and dielectric loss tangent of the second dielectric layer 140. To achieve high measurement sensitivity for the object to be measured 190, a prepreg material 240 with as low a relative dielectric constant and as small a dielectric loss tangent as possible is used for the second dielectric layer 140. Since such prepreg material 240 is generally expensive, using it for the second dielectric layer 140, which does not require a large thickness, can achieve high measurement sensitivity while keeping costs down. Note that measurement sensitivity corresponds to the amount of change in the resonant frequency f and unloaded Q when the object to be measured 190 is placed in the cavity 131.

[0130] The prepreg material 250 can be made of the same material as the prepreg material 240 and can be bonded to the core 230 in the same process. This makes it possible to suppress warping of the core 230 as a whole.

[0131] (Step S3) Next, as shown in Fig. 12D, copper foil 260 is laminated on the upper surface of prepreg material 240 (second dielectric layer 140) after step S2. At this time, although not shown in Fig. 12D, before laminating copper foil 260, vias are formed in prepreg material 240 to connect ground terminals to first ground layer 121 and second ground layer 122. The vias are formed by, for example, laser processing or the like.

[0132] The power supply terminals 161 and 162 and the ground terminals 171a to 171e, 172a to 172e, 173a to 173e, and 174a to 174e are formed by removing portions of the laminated copper foil 260. The subtractive and additive techniques described in step S1 can be used as the forming method. Note that, in the step of forming the copper foil 260 shown in FIG. 12D, copper foil may also be formed on the underside of the prepreg material 250 to suppress warpage. Even in this case, since there is no need to form a circuit on the underside of the prepreg material 250, the copper foil formed by either the additive or subtractive method may be completely removed.

[0133] (Step S4) Finally, the cavity 131 is formed, thereby producing the resonator 100 shown in FIG. 2. The cavity 131 can be formed by router processing. Specifically, the cavity processing starts from the prepreg material 250 side shown in FIG. 12D, and the opening 151 and the cavity 131 are formed in that order. During this process, the electrical resistance between the second ground layer 122 and the router cutting tool is monitored. When a sudden drop in electrical resistance is observed, it can be determined that the tip of the router cutting tool has come into contact with the second ground layer 122. Therefore, the movement of the router cutting tool in the cavity depth direction (z-axis direction) is stopped, and processing is performed only in the horizontal direction, thereby completing the production of the resonator 100. According to this process, an opening 151 having the same shape as the cavity 131 is formed in the third dielectric layer 150.

[0134] The above manufacturing method is merely an example, and there is no particular limitation on the manufacturing method as long as the resonator 100 can be manufactured.

[0135] [5. Operation] Next, the operation (measurement method) of the measurement system 1 according to this embodiment will be described with reference to Fig. 13. Fig. 13 is a flowchart showing the operation of the measurement system 1 according to this embodiment.

[0136] 13, first, a measurement object 190 is placed in a cavity 131 (S10). The measurement object 190 is, for example, a powder, and its particle size is sufficiently smaller than that of the transmission line 110. As an example, the particle size of the powder is 1 / 100 or less of the line width of the transmission line 110.

[0137] Next, network analyzer 101 measures the transmission characteristics of transmission line 110 (S12). Specifically, network analyzer 101 supplies a high-frequency signal to transmission line 110 via power supply terminals 161 and 162, and measures the transmission characteristics of transmission line 110. For example, by scanning the frequency of the high-frequency signal within a predetermined frequency band, the transmission characteristics as shown in FIG. 11 can be obtained.

[0138] 11, the power transfer characteristics have multiple peaks due to resonance at predetermined frequency intervals. The obtained power transfer characteristics are output from the network analyzer 101 to the arithmetic circuit 20.

[0139] Next, as shown in Fig. 13, the arithmetic circuit 20 calculates the resonant frequency and the Q value (unloaded Q) (S14). The resonant frequency and the Q value are calculated for each peak. The resonant frequency is the frequency corresponding to the maximum value of the peak. The Q value is expressed by the following equation (3).

[0140]

number

[0141] In equation (3), f is the resonant frequency, Δf is the half-power width, and IL is the insertion loss.

[0142] Next, the arithmetic circuit 20 calculates the dielectric characteristics of the apparent object of measurement 190 (S16). Specifically, the arithmetic circuit 20 calculates the resonant frequency and Q value by electromagnetic field analysis (electromagnetic field simulator) and optimizes them to match the measured values ​​of the transmission characteristics. For example, for each peak in FIG. 11, the simulation results are fitted to the measured values ​​to optimize the simulation parameters. This calculates at least one of the relative permittivity and dielectric loss tangent of the object of measurement 190. Note that the electromagnetic field analysis requires the structure and material properties of the resonator 100, which are known values. Specifically, the size (line width, diameter) and shape of the transmission line 110, the size (width, height, diameter) and shape of the cavity 131, and the size, shape, and material properties (relative permittivity) of each of the first dielectric layer 130, the second dielectric layer 140, and the third dielectric layer 150 are used in the electromagnetic field analysis.

[0143] Next, the arithmetic circuit 20 calculates the dielectric characteristics of the object 190 from the apparent dielectric characteristics of the object 190 and the filling rate of the object 190 relative to the cavity 131 (S18). There is a positive correlation between the filling rate and the apparent relative dielectric constant. Specifically, as the filling rate increases, the apparent relative dielectric constant increases.

[0144] The filling rate is calculated based on the specific gravity of the measurement object 190, the weight of the measurement object 190, and the volume of the cavity 131. Specifically, the arithmetic circuit 20 calculates the filling rate based on the following equation (4).

[0145] (4) Filling rate = (weight of measurement object 190) ÷ (specific gravity of measurement object 190) ÷ (volume of cavity 131)

[0146] The weight of the measurement object 190 is obtained by actual measurement. For example, the weight of the measurement object 190 is obtained by calculating the difference between the actual measured value of the weight of the resonator 100 before the measurement object 190 is placed in the cavity 131 and the actual measured value of the weight of the resonator 100 after the measurement object 190 is placed in the cavity 131. The specific gravity of the measurement object 190 and the volume of the cavity 131 are each known values ​​that have been measured in advance, for example.

[0147] The arithmetic circuit 20 calculates the dielectric properties of the object to be measured 190 from the apparent dielectric properties and filling rate of the object to be measured 190 based on, for example, the volume fraction, the logarithmic alligation (Richtneker's equation), the Maxwell-Garnett equation, the Rayleigh equation, etc.

[0148] The calculation circuit 20 also calculates the dielectric loss tangent tanδ of the object 190 to be measured. p can be calculated. p is the apparent dielectric tangent tanδ s , the above-mentioned relative permittivity ε p For example, when following the volume fraction, the following formula (12) can be used.

[0149] (5) tanδ s =Φ p tanδ p +Φ a tanδ a

[0150] In equation (5), tanδ a is the dielectric loss tangent of air. Therefore, the dielectric loss tangent of the measurement object 190 can be calculated. Here, only an example according to the volume fraction is shown, but other equations can also be used to calculate the dielectric loss tangent in the same way.

[0151] As described above, the measurement system 1 according to this embodiment can accurately measure the dielectric characteristics of the measurement object 190 over a wide frequency band using the resonator 100. There is no need to prepare resonators with different line lengths for the transmission line 110, and the measurement frequency band can be widened using only one resonator 100, i.e., the same jig (container).

[0152] In the measurement system 1, measurements may be performed multiple times with different filling rates of the measurement object 190. This can further improve the accuracy of calculating the dielectric properties.

[0153] (Other embodiments) While the measurement device and measurement system according to one or more aspects have been described above based on the embodiments, the present disclosure is not limited to these embodiments. As long as they do not deviate from the gist of the present disclosure, various modifications conceivable by those skilled in the art to the present embodiments and configurations constructed by combining components of different embodiments are also included within the scope of the present disclosure.

[0154] For example, in the above embodiment, the measurement object 190 is a powder, but is not limited to this. The measurement object 190 may be, for example, a liquid, a gel-like substance, or a gas.

[0155] Furthermore, the measurement device 10 may include only four ground terminals 171a, 172a, 173a, and 174a, and may not include the remaining ground terminals 171b to 171e, 172b to 172e, 173b to 172e, and 174b to 174e. Furthermore, if the measurement device 10 includes additional ground terminals in addition to the four ground terminals 171a, 172a, 173a, and 174a, the measurement device 10 may include multiple ground terminals in mirror symmetry with respect to the line L1x as the axis of symmetry, thereby suppressing in-plane variations in the electric field. For example, if the measurement device 10 includes the ground terminal 171b, the measurement device 10 may include the ground terminals 172b, 173b, and 174b. That is, the measurement device 10 may include multiple sets of ground terminals, each set consisting of four ground terminals positioned in a mirror-symmetric relationship. The four ground terminals may also be mirror-symmetric with respect to the line L1y as the axis of symmetry.

[0156] Although the example has been described in which the arrangement, size, and shape of the components of the resonator 100 are in a mirror-symmetric relationship with respect to each of the straight lines L1x and L1y as axes of symmetry, the present invention is not limited to this. At least one of the components of the resonator 100 does not have to be in a mirror-symmetric relationship.

[0157] Furthermore, the gaps 123 and 124 between the transmission line 110 and the first ground layer 121 and the second ground layer 122 may not be filled with a portion of the second dielectric layer 140. For example, the gaps 123 and 124 may be filled with a portion of the first dielectric layer 130. Alternatively, the gaps 123 and 124 may be filled with a dielectric material different from both the second dielectric layer 140 and the first dielectric layer 130.

[0158] Furthermore, gaps 123 and 124 may be left unfilled and may be spaces communicating with cavity 131. In this case, since measurement object 190 may also enter gaps 123 and 124, the volumes of gaps 123 and 124 may need to be taken into consideration when calculating the dielectric constant.

[0159] Furthermore, the opening 151 does not have to be provided in the third dielectric layer 150. For example, the third dielectric layer 150 may be a cover member that covers the cavity 131. Specifically, the third dielectric layer 150 may be detachable from the second dielectric layer 140. For example, after the measurement object 190 is placed in the cavity 131 with the third dielectric layer 150 removed, the third dielectric layer 150 is fixed to the first dielectric layer 130 so as to cover the cavity 131. The fixing is performed, for example, by a clamp member or a screw (not shown).

[0160] Furthermore, in the above-described embodiments, the processes performed by the network analyzer 101 or the arithmetic circuit 20 may be performed by another processing unit. The order of multiple processes may be changed, or multiple processes may be performed in parallel. The allocation of the components of the measurement system 1 to multiple devices is an example. For example, components included in one device may be included in another device. Furthermore, the measurement system 1 may be realized as a single device.

[0161] For example, the processing described in the above embodiments may be realized by centralized processing using a single device (system), or may be realized by distributed processing using multiple devices. Furthermore, the processor that executes the program may be a single processor or multiple processors. That is, centralized processing or distributed processing may be performed.

[0162] In the above embodiments, all or some of the components such as the control unit may be configured with dedicated hardware, or may be realized by executing a software program suitable for each component. Each component may be realized by a program execution unit such as a CPU (Central Processing Unit) or a processor reading and executing a software program recorded on a recording medium such as an HDD (Hard Disk Drive) or semiconductor memory.

[0163] Furthermore, the general or specific aspects of the present disclosure may be realized as a system, an apparatus, a method, an integrated circuit, or a computer program. Alternatively, they may be realized as a computer-readable non-transitory recording medium such as an optical disk, a HDD, or a semiconductor memory on which the computer program is stored. Alternatively, they may be realized as any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium.

[0164] Furthermore, various modifications, substitutions, additions, omissions, etc. can be made to the above-described embodiments within the scope of the claims or their equivalents. [Industrial Applicability]

[0165] The present disclosure can be used, for example, in a measuring device. [Explanation of symbols]

[0166] 1. Measurement System 10. Measuring equipment 20 Arithmetic circuit 100 resonators 101 Network Analyzer 110 Transmission Line 121 First Ground Layer 122 Second Ground Layer 123, 124 gap 130 First dielectric layer 131 Cavity 140 Second dielectric layer 150 Third dielectric layer 151 Aperture 161, 162 Power supply terminal 171a, 171b, 171c, 171d, 171e, 172a, 172b, 172c, 172d, 172e, 173a, 173b, 173c, 173d, 173e, 174a, 174b, 174c, 174d, 174e Ground terminal 180 Short-circuit wire 181, 182 via 190 Measurement Object 200 core material 210, 220, 260 copper foil 230 cores 240, 250 prepreg material

Claims

1. a ring-shaped transmission line; a first ground layer provided inside the ring formed by the transmission line and spaced apart from the transmission line; a second ground layer provided outside the ring formed by the transmission line and spaced apart from the transmission line; a first dielectric layer provided below the first ground layer and the second ground layer; a second dielectric layer provided above the transmission line, the first ground layer, and the second ground layer; a first feed terminal and a second feed terminal disposed on the second dielectric layer for feeding the transmission line; four or more ground terminals electrically connecting the first ground layer and the second ground layer, the first dielectric layer has a space provided at a position overlapping the transmission line in a plan view, the space being for placing a measurement object; the first feed terminal and the second feed terminal are respectively disposed at two intersections between the transmission line and a first line passing through a center of a ring formed by the transmission line in a plan view; The four or more ground terminals are: one or more first ground terminals arranged alongside the first power supply terminal along the transmission line in a plan view; one or more second ground terminals arranged alongside the first power supply terminal on the opposite side of the first ground terminal along the transmission line in a plan view; one or more third ground terminals arranged alongside the second power supply terminal along the transmission line in a plan view; one or more fourth ground terminals arranged alongside the second power supply terminal on the opposite side of the third ground terminal along the transmission line in a plan view; an arrangement interval between a first ground terminal among the one or more first ground terminals that is closest to the first feed terminal and the first feed terminal, an arrangement interval between a second ground terminal among the one or more second ground terminals that is closest to the first feed terminal and the first feed terminal, an arrangement interval between a third ground terminal among the one or more third ground terminals that is closest to the second feed terminal and the second feed terminal, and an arrangement interval between a fourth ground terminal among the one or more fourth ground terminals that is closest to the second feed terminal and the second feed terminal are all equal to or less than ¼ of a wavelength corresponding to an upper limit frequency of a measurement frequency band; Measuring equipment.

2. the four or more ground terminals include n (n is a natural number equal to or greater than 2) first ground terminals, n (n is a natural number equal to or greater than 2) second ground terminals, n (n is a natural number equal to or greater than 2) third ground terminals, and n (n is a natural number equal to or greater than 2) fourth ground terminals, the n first ground terminals are arranged side by side along the transmission line such that the spacing between adjacent first ground terminals is equal to or less than half the wavelength, the n second ground terminals are arranged side by side along the transmission line such that the spacing between adjacent second ground terminals is equal to or less than half the wavelength, the n third ground terminals are arranged side by side along the transmission line such that the spacing between adjacent third ground terminals is equal to or less than half the wavelength, the n fourth ground terminals are arranged side by side along the transmission line such that the spacing between adjacent fourth ground terminals is equal to or less than half the wavelength; The measuring device according to claim 1 .

3. the four or more ground terminals further include four fifth ground terminals; the four fifth ground terminals are respectively arranged at four intersections of two second straight lines passing through the center of the ring and the transmission line in a plan view; Each of the two second straight lines forms an angle of 45 degrees with respect to the first straight line. The measuring device according to claim 1 .

4. the four or more ground terminals are arranged in mirror symmetry with respect to the first straight line as an axis of symmetry; The measuring device according to any one of claims 1 to 3.

5. a portion of the second dielectric layer fills gaps between the transmission line and each of the first ground layer and the second ground layer; The measuring device according to any one of claims 1 to 3.

6. Further, a third dielectric layer is provided below the first dielectric layer, The third dielectric layer has an opening communicating with the space. The measuring device according to any one of claims 1 to 3.

7. Each of the four or more ground terminals is a conductive layer disposed on the second dielectric layer; a first via that penetrates the second dielectric layer and connects the conductive layer and the first ground layer; a second via that penetrates the second dielectric layer and connects the conductive layer and the second ground layer; a third line connecting the centers of the first vias and the second vias passes through the center of the ring in a plan view; The measuring device according to any one of claims 1 to 3.

8. In each of the four or more ground terminals, in a plan view, the shortest distance between the contour of the conductive layer and the contour of the first via is equal to the shortest distance between the contour of the first via and the contour of the first ground layer; the shortest distance between the contour of the conductive layer and the contour of the second via is equal to the shortest distance between the contour of the second via and the contour of the second ground layer; 8. The measuring device according to claim 7.

9. In each of the four or more ground terminals, in a plan view, a shortest distance between an outline of the first via and an outline of the first ground layer is shorter than a width of a gap between the first ground layer and the transmission line; the shortest distance between the contour of the second via and the contour of the second ground layer is shorter than the width of the gap between the second ground layer and the transmission line; 8. The measuring device according to claim 7.

10. In a plan view, a distance between a center line of the transmission line and a center of the first via and a distance between the center line and a center of the second via are equal to each other.

8. The measuring device according to claim 7.

11. The measuring device according to any one of claims 1 to 3, a calculation circuit that calculates the relative dielectric constant of the object to be measured based on the transmission characteristics of the transmission line, Measurement system.

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