Dielectric spectroscopy measurement device

Abstract

This dielectric spectroscopy measurement device comprises: antenna units (110, 113) formed on a substrate and each having an open end on the front surface side of the substrate in contact with a sample to be measured; and a dielectric constant measurement unit (2) for applying an electric field to the sample via the antenna units (110, 113) and calculating the dielectric constant of the sample from a reflected wave from the sample received by the antenna units (110, 113). Each of the antenna units (110, 113) includes a dielectric film disposed on the open end.

Description

Dielectric Spectroscopy

[0001] The present invention relates to a dielectric spectroscopic measuring device used for measuring component concentrations and the like.

[0002] As the aging population advances, addressing adult diseases is becoming a major issue. Tests such as blood glucose levels require blood sampling, which places a significant burden on patients. For this reason, non-invasive constituent concentration measurement devices that do not require blood sampling are attracting attention. One such non-invasive constituent concentration measurement device is one that uses dielectric spectroscopy. Dielectric spectroscopy irradiates electromagnetic waves into the skin, utilizes the interaction between the blood constituents being measured (e.g., glucose molecules) and water to absorb the electromagnetic waves, and observes the amplitude and phase of the electromagnetic waves.

[0003] A conventional device is one that uses a coaxial probe to irradiate an electromagnetic wave in the microwave to millimeter wave band onto a measurement target (see Patent Document 1). The configuration of the dielectric spectroscopy measurement device using the coaxial probe disclosed in Patent Document 1 is shown in Fig. 13. The dielectric spectroscopy measurement device is composed of a coaxial probe 1000 whose end on the sample side of the measurement target is an open end, a sensor unit 1001, and a vector network analyzer (hereinafter referred to as VNA) 1002.

[0004] In reflection measurement instruments that calculate the reflection coefficient by measuring incident and reflected voltages, it is known that drift errors in the reflection coefficient occur due to fluctuations in environmental temperature and vibrations and stresses applied to the measurement cable. Generally, as shown in Figure 13, a sensor unit 1001 is connected to a coaxial probe 1000, and the sensor unit 1001's sequential calibration function is used to calibrate the fluctuations that occur in the VNA 1002 and the measurement cable for each measurement. This sequential calibration function can reduce cable instability and system drift errors.

[0005] 14 , the sensor unit 1001 includes a coaxial probe 1000, a dielectric substrate 1003, a switch 1004, a load unit 1005, an RF terminal 1006, and a control terminal 1007. The coaxial probe 1000, the switch 1004, the load unit 1005, the RF terminal 1006, and the control terminal 1007 are mounted on the dielectric substrate 1003. The coaxial probe 1000 includes a plurality of coaxial probe units. The probe units include at least one antenna unit 1008, an open unit 1009, and a short unit 1010.

[0006] In microwave and millimeter-wave radio frequency (RF) technology, a known configuration is to integrate an integrated circuit (IC), an antenna, and a sensor on the same dielectric substrate to reduce insertion loss between the IC and the antenna or sensor, and multilayer wiring boards are used to optimize the layout of signal lines and power lines and reduce the board area. Vias and through-holes that penetrate the board are used as structures for transmitting RF signals between layers of a multilayer wiring board.

[0007] Patent Document 1 discloses a pseudo-coaxial line structure in which a plurality of ground vias are provided around a high-frequency signal via formed vertically penetrating from the top layer to the bottom layer of a multilayer wiring board in which conductor layers and insulator layers are alternately stacked. In the example disclosed in Patent Document 1, this pseudo-coaxial line structure is adopted to form an antenna portion 1008, an open portion 1009, and a short portion 1010.

[0008] The antenna section 1008 has a pseudo-coaxial line structure in which the end that comes into contact with the sample to be measured is an open end. The open section 1009 also has a pseudo-coaxial line structure in which the end that comes into contact with air is an open end. The short section 1010 also has a pseudo-coaxial line structure in which the center conductor and ground are electrically connected at the tip. The load section 1005 formed on the dielectric substrate 1003 is composed of a resistor formed between the signal line and ground, and terminates the signal line.

[0009] Furthermore, a switch 1004, an RF terminal 1006, and a control terminal 1007 are mounted on the dielectric substrate 1003. The antenna section 1008, the open section 1009, the short section 1010, and the load section 1005 are each connected to a selection terminal of the switch 1004. This allows the switch 1004 to select one of the antenna section 1008, the open section 1009, the short section 1010, and the load section 1005. The control terminal of the switch 1004 is connected to the control terminal 1007.

[0010] VNA 1002 outputs a control signal to switch 1004 via control terminal 1007. As a result, VNA 1002 switches switch 1004 so that one of short section 1010, open section 1009, and load section 1005 is connected to the RF terminal of VNA 1002 via RF terminal 1006. VNA 1002 sequentially connects short section 1010, open section 1009, and load section 1005 to the RF terminal of VNA 1002 and performs reflection measurements on each. VNA 1002 then calculates calibration coefficients (S parameters of the error circuit present in VNA 1002) from the results of the reflection measurements. Calculating the calibration coefficients in this manner makes it possible to calculate a reflection coefficient from which the measurement error of VNA 1002 has been removed.

[0011] With the open end of antenna section 1008 in contact with the sample, VNA 1002 switches switch 1004 so that antenna section 1008 is connected to the RF terminal of VNA 1002 via RF terminal 1006. VNA 1002 applies an electric field from antenna section 1008 to the sample, and calculates the reflection coefficient of the sample based on the voltage amplitude and phase of the wave reflected by the sample and the voltage of the incident wave measured by VNA 1002.

[0012] In the dielectric spectroscopy described above, the electric field concentrates at the opening of the substrate where the antenna portion 1008 is formed, resulting in a high electric field density, and therefore, if the contact state with the sample changes and a gap occurs between the sample and the antenna portion 1008, the reflected wave fluctuates significantly. As a result, stable measurement becomes difficult when the contact state with the sample changes, and the fluctuation in the reflected wave causes an error in the reflection coefficient, making it impossible to accurately measure the dielectric constant of the sample.

[0013] Patent No. 6771372

[0014] The present invention has been made to solve the above-mentioned problems, and has an object to provide a dielectric spectroscopy measuring device that can reduce measurement errors in dielectric constant due to changes in the contact state with the sample.

[0015] The dielectric spectroscopy measuring device of the present invention comprises an antenna unit formed on a substrate, the end of which on the surface side of the substrate that comes into contact with a sample to be measured being an open end, and a dielectric constant measuring unit configured to apply an electric field to the sample via the antenna unit and calculate the dielectric constant of the sample from the result of receiving a reflected wave from the sample by the antenna unit, wherein the antenna unit is characterized in that it comprises a dielectric film disposed at the open end.

[0016] According to the present invention, by disposing a dielectric film on the open end of the antenna, it is possible to reduce the possibility of a gap occurring between the antenna and the sample to be measured. In this invention, it is possible to suppress fluctuations in the reflected wave due to changes in the contact state with the sample, and it is possible to reduce measurement errors in the reflection coefficient. As a result, it is possible to accurately measure the dielectric constant of the sample to be measured.

[0017] FIG. 1 is a block diagram showing the configuration of a dielectric spectroscopy measurement apparatus according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view of a sensor unit according to the first embodiment of the present invention. FIG. 3 is a cross-sectional view of a sensor unit according to the first embodiment of the present invention. FIG. 4 is a plan view of an antenna unit according to the first embodiment of the present invention. FIG. 5 is a bottom view of an antenna unit according to the first embodiment of the present invention. FIG. 6A is a plan view of a portion of a dielectric substrate on which a switch, an RF terminal, a control terminal, and a multilayer wiring board are mounted in the first embodiment of the present invention. FIG. 6B is a bottom view of a portion of a dielectric substrate on which a switch, an RF terminal, a control terminal, and a multilayer wiring board are mounted in the first embodiment of the present invention. FIG. 7 is a cross-sectional view of a portion of a dielectric substrate on which a switch, an RF terminal, and a multilayer wiring board are mounted in the first embodiment of the present invention. FIG. 8 is a cross-sectional view of an antenna unit according to a second embodiment of the present invention. FIG. 9 is a cross-sectional view showing another configuration of a coaxial probe according to the first and second embodiments of the present invention. FIG. 10 is a cross-sectional view showing another configuration of a coaxial probe according to the first and second embodiments of the present invention. FIG. 11 is a cross-sectional view showing another configuration of an antenna unit according to the first and second embodiments of the present invention. Fig. 12 is a block diagram showing an example of the configuration of a computer that realizes the dielectric constant measuring unit according to the first and second embodiments of the present invention. Fig. 13 is a block diagram showing the configuration of a conventional dielectric spectroscopy measuring device. Fig. 14 is a block diagram showing the configuration of a conventional sensor unit.

[0018] [First embodiment] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 shows the configuration of a dielectric spectroscopy measurement device according to a first embodiment of the present invention. The dielectric spectroscopy measurement device comprises a sensor unit 1 and a dielectric constant measurement unit 2. The dielectric constant measurement unit 2 may be, for example, a vector network analyzer (VNA). The sensor unit 1 comprises a dielectric substrate 10, a coaxial probe 11, a switch 12, an RF terminal 14, and a control terminal 15.

[0019] 2 and 3 are cross-sectional views of the sensor unit 1. The coaxial probe 11, the switch 12, the RF terminal 14, and the control terminal 15 are mounted on a dielectric substrate 10. However, the switch 12, the RF terminal 14, and the control terminal 15 are not shown in FIGS.

[0020] The coaxial probe 11 includes multiple coaxial probe sections. As shown in Fig. 1, the probe sections include antenna sections 110 and 113, an open section 111, a short section 112, and a load section 114. The short section 112 and the load section 114 are omitted from Fig. 2 and are shown in Fig. 3.

[0021] Patent Document 1 discloses a pseudo-coaxial line structure in which a plurality of ground vias are provided around a high-frequency signal via formed vertically penetrating from the top layer to the bottom layer of a multilayer wiring board in which conductor layers and insulator layers are alternately stacked. In this embodiment, this pseudo-coaxial line structure is adopted to form antenna portions 110 and 113, an open portion 111, and a short portion 112.

[0022] The antenna unit 110 has a pseudo-coaxial line structure in which the end that comes into contact with the sample to be measured (upper side in FIG. 2) is an open end. In the antenna unit 110, a land 1100 made of a conductor is formed on the upper surface of the topmost insulator layer 22 of the multilayer wiring substrate 21, and a land 1101 made of a conductor is formed on the lower surface of the bottommost insulator layer 25. The lands 1100 and 1101 are connected by a high-frequency signal via 1102, which is a conductor that vertically penetrates the insulator layers 22 to 25 along the stacking direction of the conductor layers 26 to 30.

[0023] A conductor layer 26 serving as a ground conductor is formed in the same layer as the land 1100 but in an area outside the land 1100. A dielectric film 1107 is formed on the land 1100 and the conductor layer 26. The land 1100 and the conductor layer 26 are separated by a conductor removal area 1103 that is circular in plan view and is an area without a conductor and filled with a dielectric. A conductor layer 30 serving as a ground conductor is formed in the same layer as the land 1101 but in an area outside the land 1101. The land 1101 and the conductor layer 30 are separated by a conductor removal area 1104 that is circular in plan view and is without a conductor. In the present invention, a plan view is defined as a view of the sensor unit 1 from above (the sample side).

[0024] A plurality of conductor layers 27 to 29 serving as ground conductors are formed inside the multilayer wiring board 21. The layers on which the conductor layers 27 to 29 are formed have conductor removal areas 1105 that are circular in plan view and are areas without conductors and filled with dielectric. A high-frequency signal via 1102 passes through the centers of the conductor removal areas 1103 to 1105. In the antenna section 110, the conductor layers 26 to 30 are connected by a through via (through hole) 1106.

[0025] The insulator layers 22 to 25, the lands 1100 and 1101, the high-frequency signal via 1102 that vertically penetrates the insulator layers 22 to 25, the conductor layers 26 to 30 around the high-frequency signal via 1102, and the through via 1106 that connects the conductor layers 26 to 30 form a pseudo-coaxial line. The high-frequency signal via 1102 and the conductor removal areas 1103 to 1105 are circular in plan view, and the impedance of the pseudo-coaxial line can be designed according to the sample to be measured based on the diameter of the high-frequency signal via 1102, the diameters of the conductor removal areas 1103 to 1105 that surround it, the dielectric constants of the dielectrics of the insulator layers 22 to 25, and the dielectric constant of the dielectric film 1107.

[0026] The antenna section 113 has a pseudo-coaxial line structure in which the end that comes into contact with the sample to be measured (the upper side in FIG. 2) is an open end. In the antenna section 113, a land 1130 made of a conductor is formed on the upper surface of the insulator layer 22, and a land 1131 made of a conductor is formed on the lower surface of the insulator layer 25. The lands 1130 and 1131 are connected by a high-frequency signal via 1132, which is a conductor that vertically penetrates the insulator layers 22 to 25 along the stacking direction of the conductor layers 26 to 30.

[0027] A dielectric film 1137 is formed on the land 1130 and the outer conductor layer 26. The dielectric film 1137 has a different thickness from the dielectric film 1107. The land 1130 and the conductor layer 26 are separated by a conductor removal region 1133 that is circular in plan view and is a region that is free of conductor and filled with dielectric. The land 1131 and the outer conductor layer 30 are separated by a conductor removal region 1134 that is circular in plan view and is free of conductor.

[0028] In the antenna section 113, the layer on which the conductor layers 27 to 29 are formed has a conductor removal area 1135 that is circular in plan view and is an area filled with a dielectric and has no conductor. A high-frequency signal via 1132 passes through the center of the conductor removal areas 1133 to 1135. In the antenna section 113, the conductor layers 26 to 30 are connected by a through via (through hole) 1136.

[0029] The insulator layers 22 to 25, the lands 1130, 1131, the high-frequency signal via 1132 that vertically penetrates the insulator layers 22 to 25, the conductor layers 26 to 30 around the high-frequency signal via 1132, and the through via 1136 that connects the conductor layers 26 to 30 form a pseudo-coaxial line.

[0030] The open portion 111 has a pseudo-coaxial line structure in which the end on the side in contact with air (upper side in FIG. 2 ) is an open end. In the open portion 111, an opening 1117 (recess) which is a removed area having a circular shape in plan view is formed in the uppermost conductor layer 26 and insulator layer 22 of the multilayer wiring board 21 so that the lower insulator layer 23, conductor layer 27, and high-frequency signal via 1112 are exposed to the air. A land 1111 made of a conductor is formed on the underside of the lowermost insulator layer 25. A high-frequency signal via 1112 which is a conductor that vertically penetrates the insulator layers 23 to 25 along the stacking direction of the conductor layers 26 to 30 is formed so as to be connected to the land 1111.

[0031] The land 1111 and the conductor layer 30 are separated by a conductor removal area 1113 that is circular in plan view and has no conductor. The high-frequency signal via 1112 and the conductor layer 27 are separated by a conductor removal area 1114 that is circular in plan view and has no conductor. In the open portion 111, the layer on which the conductor layers 28 and 29 are formed has a conductor removal area 1115 that is circular in plan view and has no conductor and is filled with a dielectric. The high-frequency signal via 1112 passes through the centers of the conductor removal areas 1113 to 1115. In the open portion 111, the conductor layers 27 to 30 are connected by a through via 1116.

[0032] The insulator layers 23 to 25, the land 1111, the high-frequency signal via 1112 that vertically penetrates the insulator layers 23 to 25, the conductor layers 27 to 30 around the high-frequency signal via 1112, and the through via 1116 that connects the conductor layers 27 to 30 form a pseudo-coaxial line.

[0033] 3, the short-circuit portion 112 has a pseudo-coaxial line structure in which the center conductor (high-frequency signal via) and ground are electrically connected at the tip. In the short-circuit portion 112, a land 1120 made of a conductor is formed on the underside of the lowest insulator layer 25 of the multilayer wiring substrate 21. The conductor layer 27 and the land 1120 are connected by a high-frequency signal via 1121, which is a conductor that vertically penetrates the insulator layers 23 to 25 along the stacking direction of the conductor layers 26 to 30.

[0034] The land 1120 and the conductor layer 30 are separated by a conductor removal area 1122 that is circular in plan view and has no conductor. In the short section 112, the layer on which the conductor layers 28 and 29 are formed has a conductor removal area 1123 that is circular in plan view and is an area filled with a dielectric and has no conductor. The high-frequency signal via 1121 passes through the centers of the conductor removal areas 1122 and 1123. In the short section 112, the conductor layers 27 to 30 are electrically connected by a through via 1124.

[0035] The insulator layers 23 to 25, the land 1120, the high-frequency signal via 1121 that vertically penetrates the insulator layers 23 to 25, the conductor layers 28 to 30 around the high-frequency signal via 1121, and the through via 1124 that connects the conductor layers 27 to 30 form a pseudo-coaxial line. In the short portion 112, the phase of the incident signal is inverted and the signal is almost totally reflected.

[0036] Pads 40 to 43 made of conductors and a conductor layer 45 serving as a ground conductor are formed on the upper surface of the dielectric substrate 10. The pads 40 to 43 are separated from the conductor layer 45 by conductor removal areas 46 to 49 that are circular in plan view and have no conductor. Pads 51 to 55 made of conductors and a conductor layer 56 serving as a ground conductor are formed on the lower surface of the dielectric substrate 10. The pads 51 to 55 are separated from the conductor layer 56 by conductor removal areas 57 to 61 that are circular in plan view and have no conductor. As shown in FIG. 3 , the pad 55 and the conductor layer 56 are connected by a resistor 1150 that constitutes the load section 114.

[0037] The pads 40 and 51 are connected by a high-frequency signal via 62, which is a conductor that penetrates vertically through the dielectric substrate 10. The conductor layers 45 and 56 are connected by a penetrating via (through-hole) 67, which is a conductor that penetrates vertically through the dielectric substrate 10. The dielectric substrate 10, the pads 40 and 51, the high-frequency signal via 62, the conductor layers 45 and 56 around the high-frequency signal via 62, and the penetrating via 67 connecting the conductor layers 45 and 56 form a pseudo-coaxial line. Figure 4 is a plan view of the antenna unit 110, and Figure 5 is a bottom view of the antenna unit 110. In Figure 5, reference numeral 120 denotes a microstrip line connected to the pad 51 of the antenna unit 110.

[0038] The pads 41 and 52 are connected by a high-frequency signal via 63, which is a conductor that penetrates vertically through the dielectric substrate 10. The dielectric substrate 10, the pads 41 and 52, the high-frequency signal via 63, the conductor layers 45 and 56 around the high-frequency signal via 63, and the through via 67 that connects the conductor layers 45 and 56 together form a pseudo-coaxial line.

[0039] The pads 42 and 53 are connected by a high-frequency signal via 64, which is a conductor that penetrates vertically through the dielectric substrate 10. The dielectric substrate 10, the pads 42 and 53, the high-frequency signal via 64, the conductor layers 45 and 56 around the high-frequency signal via 64, and the through via 67 that connects the conductor layers 45 and 56 together form a pseudo-coaxial line.

[0040] The pads 43 and 54 are connected by a high-frequency signal via 65, which is a conductor that penetrates vertically through the dielectric substrate 10. The dielectric substrate 10, the pads 43 and 54, the high-frequency signal via 65, the conductor layers 45 and 56 around the high-frequency signal via 65, and the through via 67 that connects the conductor layers 45 and 56 together form a pseudo-coaxial line.

[0041] The land 1101 and pad 40, the land 1111 and pad 41, the land 1120 and pad 42, the land 1131 and pad 43, and the conductor layer 30 and conductor layer 45 are connected by solder 68. In this way, the multilayer wiring board 21 having the antenna portions 110 and 113, the open portion 111, and the short portion 112 formed therein is mounted on the dielectric substrate 10.

[0042] Furthermore, a switch 12, an RF terminal 14, and a control terminal 15 are mounted on the dielectric substrate 10. Fig. 6A is a plan view of the portion of the dielectric substrate 10 on which the switch 12, the RF terminal 14, the control terminal 15, and the multilayer wiring board 21 are mounted, and Fig. 6B is a bottom view of the same portion as Fig. 6A . Fig. 7 is a cross-sectional view of the portion of the dielectric substrate 10 on which the switch 12, the RF terminal 14, and the multilayer wiring board 21 are mounted. Note that in Figs. 6A and 6B, the antenna sections 110 and 113, the open section 111, the short section 112, and the load section 114 are depicted in a different positional relationship from Figs. 2 and 3 to make the arrangement of each section easier to understand. Also, in Fig. 6B, the conductor layer 56 is omitted.

[0043] The switch 12, RF terminal 14, control terminal 15, and resistor 1150 are mounted on the lower surface of the dielectric substrate 10. The pad 51 of the antenna unit 110 and the first selection terminal of the switch 12 are connected by a microstrip line 120 made of a conductor. The pad 52 of the open unit 111 and the second selection terminal of the switch 12 are connected by a microstrip line 121 made of a conductor. The pad 53 of the short unit 112 and the third selection terminal of the switch 12 are connected by a microstrip line 122 made of a conductor. The pad 54 of the antenna unit 113 and the fourth selection terminal of the switch 12 are connected by a microstrip line 123 made of a conductor. The pad 55 of the load unit 114 and the fifth selection terminal of the switch 12 are connected by a microstrip line 124 made of a conductor. The RF terminal 14 and the input terminal of the switch 12 are connected by a microstrip line 125. The control terminal 15 and the control terminal of the switch 12 are connected by a microstrip line 126.

[0044] Next, measurement of the complex permittivity of a sample will be described. The permittivity measuring unit 2 outputs a control signal to the switch 12 via the control terminal 15. As a result, the permittivity measuring unit 2 switches the switch 12 so that one of the short unit 112, the open unit 111, the antenna units 110 and 113, and the load unit 114 is connected to a port of the permittivity measuring unit 2 via the RF terminal 14. The permittivity measuring unit 2 connects the open unit 111 to the port of the permittivity measuring unit 2 to output an RF signal, and calculates the reflection coefficient of the open unit 111 (air) based on the voltage amplitude and phase of the reflected wave reflected by the open unit 111 and the voltage of the incident wave measured by the permittivity measuring unit 2.

[0045] Similarly, the dielectric constant measuring unit 2 connects the short portion 112 to a port of the dielectric constant measuring unit 2 and outputs an RF signal, and calculates the reflection coefficient of the short portion 112 (the metal constituting the conductor layer 27) based on the voltage amplitude and phase of the reflected wave reflected by the short portion 112 and the voltage of the incident wave measured by the dielectric constant measuring unit 2. Furthermore, with the dielectric film 1107 of the antenna portion 110 in contact with a known liquid sample (e.g., pure water), the dielectric constant measuring unit 2 connects the antenna portion 110 to a port of the dielectric constant measuring unit 2 and outputs an RF signal, and calculates the reflection coefficient of the liquid sample based on the voltage amplitude and phase of the reflected wave reflected by the liquid sample and the voltage of the incident wave measured by the dielectric constant measuring unit 2.

[0046] Next, the dielectric constant measuring unit 2 outputs a control signal to the switch 12 via the control terminal 15 while the dielectric film 1107 of the antenna unit 110 is in contact with the sample to be measured. As a result, the dielectric constant measuring unit 2 switches the switch 12 so that the antenna unit 110 is connected to the port of the dielectric constant measuring unit 2 via the RF terminal 14. The dielectric constant measuring unit 2 outputs an RF signal to apply an electric field to the sample from the antenna unit 110, and calculates the reflection coefficient of the sample to be measured based on the voltage amplitude and phase of the reflected wave reflected by the sample and the voltage of the incident wave measured by the dielectric constant measuring unit 2. The complex dielectric constant can be calculated from the measured reflection coefficient as follows.

[0047]

[0048] where ε ＊ is the dielectric constant of the sample to be measured, ε Ａ ＊ is the known dielectric constant of air, ε Ｂ ＊ is the known dielectric constant of the metal constituting the conductor layer 27, ε Ｃ ＊ is the known dielectric constant of the liquid sample. ＊ is the complex reflection coefficient, and the reflection coefficient obtained by measurement is Γ ｉ , the phase is φ ｉ Then, it is expressed by the following equation (2).

[0049]

[0050] ρＡ ＊ is the measurement result for the open portion 111, and ρ Ｂ ＊ is the measurement result for the short circuit part 112, and ρ Ｃ ＊ is the measurement result when the dielectric film 1107 of the antenna part 110 is in contact with the liquid sample, and ρ ＊ and correspond to the measurement results of the sample to be measured. In this way, the dielectric constant measuring unit 2 can calculate the complex dielectric constant of the sample from the measurement results of the reflection coefficients of the air, metal, and liquid sample measured in advance, the measurement result of the reflection coefficient of the sample to be measured, and the known complex dielectric constants of the air, metal, and liquid sample.

[0051] The load section 114 is used for calibrating the VNA. The one-port calibration method for a VNA using an open standard, a short standard, and a load standard as calibration standards is known as SOL calibration. In SOL calibration, three standards, an open standard, a short standard, and a load standard, are connected to the VNA ports to measure calibration data. This calibration data makes it possible to eliminate frequency response reflection tracking, directivity, and source match of the measurement system in reflection measurements using the port to be calibrated.

[0052] In this embodiment, the dielectric constant measurement unit 2 outputs a control signal to the switch 12 via the control terminal 15. As a result, the dielectric constant measurement unit 2 switches the switch 12 so that one of the short unit 112, the open unit 111, and the load unit 114 is connected to a port of the dielectric constant measurement unit 2 via the RF terminal 14. The dielectric constant measurement unit 2 sequentially connects the short unit 112, the open unit 111, and the load unit 114 to the port of the dielectric constant measurement unit 2, and performs reflection measurements on each. The dielectric constant measurement unit 2 then calculates a calibration coefficient (the S parameter of the error circuit present in the dielectric constant measurement unit 2) from the result of the reflection measurement. Calculating the calibration coefficient in this way makes it possible to calculate a reflection coefficient from which the measurement error of the dielectric constant measurement unit 2 has been removed. The method of calculating the calibration coefficient using SOL calibration is a well-known technique.

[0053] As described above, in this embodiment, the antenna units 110 and 113, the short unit 112, the open unit 111, and the load unit 114 are integrated on the same substrate, thereby reducing drift errors caused by coaxial probes. Since they are all on the same substrate, the temperature difference between the antenna units 110 and 113, the short unit 112, the open unit 111, and the load unit 114 is reduced, thereby improving calibration accuracy.

[0054] Furthermore, in this embodiment, by forming dielectric films 1107 and 1137 on the open ends of the antenna units 110 and 113, the possibility of a gap occurring between the antenna units 110 and 113 and the sample to be measured can be reduced. In this embodiment, fluctuations in the reflected wave due to changes in the contact state with the sample can be suppressed, and measurement errors in the reflection coefficient can be reduced. As a result, in this embodiment, the dielectric constant of the sample to be measured can be accurately measured.

[0055] Furthermore, in this embodiment, multiple antenna units 110, 113 are formed on the coaxial probe 11, and dielectric films 1107, 1137 of different thicknesses are formed on the antenna units 110, 113, respectively. In this embodiment, sensitivity to the sample to be measured can be adjusted by selectively using either the antenna unit 110 or 113. In this embodiment, two antenna units are used, but three or more antenna units may be formed.

[0056] The microstrip lines 120 to 126 on the dielectric substrate 10 are made of a metal material, for example, with a conductor width of 100 to 300 μm and a spacing of 50 μm, such as Au, Cu, or Al.

[0057] The multilayer wiring substrate 21 is, for example, several centimeters by several centimeters square, and has a thickness of 10 to 500 μm. Materials for the insulator layers 22 to 25 (dielectrics) include FR4 (Flame Retardant Type 4), Megtron 6 (registered trademark), Teflon (registered trademark), LCP (Liquid Crystal Polymer), polyimide, and LTCC (Low Temperature Co-fired Ceramics). Materials for the dielectric films 1107 and 1137 include, for example, resin and alumina.

[0058] Second Embodiment In the first embodiment, the dielectric films 1107 and 1137 are formed so as to fill the spaces between the lands 1100 and 1130 of the antenna portions 110 and 113 and the conductor layer 26 with a dielectric, but it is also possible to attach a dielectric film to the open ends of the antenna portions 110 and 113. A cross-sectional view of the antenna portions 110 and 113 in this case is shown in FIG.

[0059] In this embodiment, a dielectric film 1107a is bonded to the upper surfaces of the land 1100 and the outer conductor layer 26 in the antenna unit 110, and a dielectric film 1137a is bonded to the upper surfaces of the land 1130 and the outer conductor layer 26 in the antenna unit 113. The land 1100 and the conductor layer 26 are separated by a conductor removal area 1103a that is circular in plan view and is an area where no conductor is present. The land 1130 and the conductor layer 26 are separated by a conductor removal area 1133a that is circular in plan view and is an area where no conductor is present. As with the first embodiment, the dielectric film 1137a has a different thickness from the dielectric film 1107a. The configuration of the dielectric spectroscopy measurement device other than the antenna units 110 and 113 is the same as that of the first embodiment.

[0060] In the first embodiment, there are areas with conductors (lands 1100, 1130 and conductor layer 26) and areas without conductors 1103, 1133 at the open ends of antenna units 110, 113, resulting in a step. Therefore, if dielectric films 1107, 1137 are formed to cover the open ends of antenna units 110, 113, the step may impair the flatness of the surfaces of dielectric films 1107, 1137.

[0061] On the other hand, in the present embodiment, dielectric films 1107a are bonded to the respective upper surfaces of the land 1100 (center conductor) and the outer conductor layer 26 (ground conductor) in the antenna unit 110, and dielectric films 1137a are bonded to the respective upper surfaces of the land 1130 (center conductor) and the outer conductor layer 26 in the antenna unit 113. As a result, in the present embodiment, the flatness of the surfaces of the dielectric films 1107a and 1137a can be improved compared to the first embodiment, and the possibility of gaps occurring between the antenna units 110 and 113 and the sample to be measured can be further reduced.

[0062] When the dielectric films 1107, 1107a, 1137, and 1137a are disposed at the open ends of the antenna units 110 and 113 as in the first and second embodiments, reflected waves are generated from the dielectric films 1107, 1107a, 1137, and 1137a. Therefore, in the dielectric constant measuring unit 2, the antenna units 110 and 113 are connected to the dielectric constant measuring unit 2 via the switch 12 and the RF terminal 14 in a state in which no sample to be measured is present, and an RF signal is output to measure in advance the reflected waves reflected by the dielectric films 1107, 1107a, 1137, and 1137a.

[0063] By this preliminary measurement, when the dielectric constant measuring unit 2 performs a reflection measurement while the dielectric films 1107, 1107a, 1137, and 1137a are in contact with the sample to be measured, it is possible to distinguish between the reflected waves from the sample to be measured and the reflected waves from the dielectric films 1107, 1107a, 1137, and 1137a, and to extract only the reflected waves from the sample to be measured.

[0064] Similarly, when a reflection measurement is performed while the dielectric films 1107, 1107a, 1137, and 1137a are in contact with a known liquid sample (e.g., pure water), the dielectric constant measuring unit 2 can distinguish between the reflected waves from the liquid sample and the reflected waves from the dielectric films 1107, 1107a, 1137, and 1137a, and can extract only the reflected waves from the liquid sample.

[0065] In the first and second embodiments, the microstrip lines 120 to 126 connecting the coaxial probe 11 and the switch 12 are formed on the bottom surface of the dielectric substrate 10. However, they may also be formed on the top surface of the dielectric substrate 10. Cross-sectional views of this case are shown in FIGS. 9 and 10. In addition to the above configuration, a pad 44 made of a conductor is formed on the top surface of the dielectric substrate 10. The pad 44 and the conductor layer 45 are separated from each other by a conductor removal area 50 that is circular in plan view and lacks any conductor. The pads 44 and 55 are connected by a high-frequency signal via 66, which is a conductor that penetrates vertically through the dielectric substrate 10. The dielectric substrate 10, the pads 44 and 55, the high-frequency signal via 66, the conductor layers 45 and 56 around the high-frequency signal via 66, and the through via 67 connecting the conductor layers 45 and 56 form a pseudo-coaxial line.

[0066] The pad 40 of the antenna section 110 and the first selection terminal of the switch 12, the pad 41 of the open section 111 and the second selection terminal of the switch 12, the pad 42 of the short section 112 and the third selection terminal of the switch 12, the pad 43 of the antenna section 113 and the fourth selection terminal of the switch 12, and the pad 44 of the load section 114 and the fifth selection terminal of the switch 12 are connected by microstrip lines formed on the upper surface of the dielectric substrate 10. The pads 51 to 54 and the high-frequency signal vias 62 to 65 are no longer necessary.

[0067] 9 and 10 show the case where the microstrip line connecting the coaxial probe 11 and the switch 12 is formed on the upper surface of the dielectric substrate 10 in the first embodiment, but in the second embodiment, the microstrip line connecting the coaxial probe 11 and the switch 12 may be formed on the upper surface of the dielectric substrate 10.

[0068] Furthermore, in the first and second embodiments, the antenna portion 110 and the antenna portion 113 are formed on the same multilayer wiring board 21, but they may be formed on different multilayer wiring boards. A cross-sectional view of this case is shown in Fig. 11. In the example of Fig. 11, the antenna portion 110 is formed on the multilayer wiring board 21, and the antenna portion 113 is formed on the multilayer wiring board 21a. The multilayer wiring board 21a corresponds to the multilayer wiring board 21 in which the conductor layers 26-30 are replaced with conductor layers 26a-30a and the insulator layers 22-25 are replaced with insulator layers 22a-25a.

[0069] The dielectric constant measuring unit 2 described in the first and second embodiments can be realized by a computer equipped with a CPU (Central Processing Unit), a storage device, and an interface, and a program that controls these hardware resources. An example of the configuration of this computer is shown in FIG.

[0070] The computer includes a CPU 300, a storage device 301, a communication device 303, a transmitter 302, a receiver 304, a directional coupler 305, a power supply 306, a transformer 307, and a regulator 308. The transmitter 302 and the receiver 304 are connected to the sensor unit 1 via the directional coupler 305. Electromagnetic waves in the microwave band generated by the transmitter 302 are irradiated onto the measurement sample. A signal reflected from the measurement sample is input from the sensor unit 1 via the directional coupler 305 to the receiver 304, converted into a digital signal, and then read by the CPU 300. The CPU 300 outputs a control signal to the sensor unit 1 and controls the switch 12 to sequentially read the reflected signals from the antenna units 110 and 113, the short unit 112, the open unit 111, and the load unit 114.

[0071] In such a computer, a program for implementing the dielectric spectroscopy measurement method of the present invention is stored in a storage device 301. A CPU 300 executes the control and arithmetic processing described in the first and second embodiments in accordance with the program stored in the storage device 301. The reflection coefficient and dielectric constant obtained by the processing are transmitted to an external computer by a communication device 303 connected to the CPU 300. For example, a frequency synthesizer using a phase-locked loop is used as the transmitter 302. For example, a double-balanced mixer is used as the receiver 304. A circulator may be used instead of the directional coupler 305.

[0072] While the example in Figure 14 shows an example of a direct conversion transmission / reception configuration, a low IF (Intermediate Frequency) transmission / reception configuration may also be adopted by adding a transmitter with a slightly different transmission frequency. The power supply 306 supplies power to each device. For example, a DC-DC converter is used as the transformer 307. The regulator 308 converts the input voltage from the transformer 307 to the desired voltage. A linear regulator that can operate even with a low input / output potential difference is used as the regulator 308. A lithium-ion battery or the like is used as the power supply 306.

[0073] Some or all of the above embodiments can be described as, but are not limited to, the following supplementary notes.

[0074] (Supplementary Note 1) The dielectric spectroscopy measuring device of the present invention comprises an antenna unit formed on a substrate, the end of which on the surface side of the substrate that comes into contact with a sample to be measured being an open end, and a dielectric constant measuring unit configured to apply an electric field to the sample via the antenna unit and calculate the dielectric constant of the sample from the result of receiving a reflected wave from the sample by the antenna unit, wherein the antenna unit comprises a dielectric film disposed at the open end.

[0075] (Supplementary Note 2) In the dielectric spectroscopy measurement device according to Supplementary Note 1, the dielectric film is formed so as to cover the open end of the antenna portion.

[0076] (Supplementary Note 3) In the dielectric spectroscopy measurement device described in Supplementary Note 1, the antenna unit has a coaxial line structure in which a ground conductor is disposed around a center conductor which is a signal line, and the dielectric film is bonded to the upper surfaces of the center conductor and the ground conductor at the open end of the antenna unit.

[0077] (Appendix 4) In the dielectric spectroscopy measuring device described in any one of Appendices 1 to 3, the antenna portions are formed at multiple locations on the substrate, and the dielectric films disposed at the open ends of the antenna portions have different thicknesses.

[0078] (Appendix 5) In the dielectric spectroscopy measurement device described in any one of Appendices 1 to 3, the antenna units are formed on a plurality of substrates, respectively, and the dielectric films disposed at the open ends of the antenna units have different thicknesses.

[0079] 1...sensor section, 2...dielectric constant measuring section, 10...dielectric substrate, 11...coaxial probe, 12...switch, 14...RF terminal, 15...control terminal, 21, 21a...multilayer wiring substrate, 110, 113...antenna section, 111...open section, 112...short section, 114...load section, 1107, 1107a, 1137, 1137a...dielectric film.

Claims

1. A dielectric spectroscopy measurement device comprising: an antenna unit formed on a substrate, the end of the substrate on the surface side that comes into contact with the sample to be measured being an open end; and a dielectric constant measurement unit configured to apply an electric field to the sample via the antenna unit and calculate the dielectric constant of the sample from the result of receiving a reflected wave from the sample by the antenna unit, wherein the antenna unit has a dielectric film disposed at the open end.

2. A dielectric spectroscopy measuring device according to claim 1, wherein the dielectric film is formed so as to cover the open end of the antenna portion.

3. A dielectric spectroscopy measuring device according to claim 1, wherein the antenna section has a coaxial line structure in which a ground conductor is arranged around a center conductor which is a signal line, and the dielectric film is bonded to the upper surfaces of the center conductor and the ground conductor at the open end of the antenna section.

4. A dielectric spectroscopy measuring device according to any one of claims 1 to 3, characterized in that the antenna parts are formed at a plurality of locations on the substrate, and the dielectric films arranged at the open ends of the antenna parts have different thicknesses.

5. A dielectric spectroscopy measuring device according to any one of claims 1 to 3, characterized in that the antenna parts are formed on a plurality of substrates, and the dielectric films arranged on the open ends of the antenna parts have different thicknesses.

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