JP2012008749A - Manufacturing method of passive sensor, measurement method by wireless sensor system, passive sensor and wireless sensor system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a passive sensor capable of obtaining high measurement accuracy even with individual differences due to manufacturing variations of a sensor device, and a manufacturing method of the passive sensor.SOLUTION: A passive sensor 10 comprises an antenna 11 and a SAW resonator 12. A resonance frequency fsc of the passive sensor 10 is a frequency-shifted value of a resonance frequency fsaw of the SAW resonator 12 by an amount according to a difference in impedance between the antenna 11 and the SAW resonator 12. Using this, the SAW resonator 12 is classified into an identification group Gr on the basis of the resonance frequency fsaw. For each identification group Gr, antenna modules 110A-110E each having different impedance are formed, and are combined with the SAW resonator 12 on the basis of the identification group Gr to form the passive sensor 10. Consequently, even when the SAW resonator 12 has individual differences, the resonance frequency of the passive sensor 10 is within a predetermined frequency error range Δfsc.

Description

  The present invention relates to a passive sensor including a resonator whose resonance frequency changes according to a physical quantity, a method for manufacturing the passive sensor, a wireless sensor system using the passive sensor, and a measurement method using the wireless sensor system. .

  Conventionally, as a passive sensor for measuring a predetermined physical quantity (temperature, pressure, etc.), as shown in Patent Document 1, there is a passive sensor using a sensor element such as a SAW resonator and an antenna connected to the sensor element. Such a passive sensor utilizes the fact that the resonance frequency of the SAW resonator changes depending on temperature and pressure, and transmits the measurement result from the antenna to the parent device.

Japanese translation of PCT publication No. 2003-508739

  However, since the resonance frequency of a sensor element such as a SAW resonator depends on the shape of the sensor element, in a passive sensor using such a sensor element, the measurement accuracy greatly depends on the formation accuracy of the sensor element.

  However, when the required measurement accuracy is high, it is not easy to manufacture the sensor element within the range of manufacturing variation that satisfies the measurement accuracy.

  Accordingly, an object of the present invention is to provide a passive sensor and a method for manufacturing the passive sensor that can obtain high measurement accuracy even if there is an individual difference due to manufacturing variation of sensor elements.

  The present invention provides a sensor element that outputs a resonance signal having a frequency corresponding to a physical quantity sensed by an excitation signal from the outside, and an antenna that is connected to the sensor element and transmits and receives a communication signal based on the excitation signal and the resonance signal. The present invention relates to a method for manufacturing a passive sensor. This manufacturing method has a sensor element selection process, an antenna module formation process, and a passive sensor formation process. In the sensor element sorting step, the sensor elements are sorted into a plurality of groups based on the resonance frequency by the excitation signal. In the antenna module forming step, an antenna module including an antenna having a different shape for each group is formed. In the passive sensor formation step, a passive sensor is formed by combining an antenna module and a sensor element according to a group of sensor elements. In such a manufacturing process, the antenna module forming process forms the antenna in a shape that shifts the resonance frequency of the sensor element to the desired resonance frequency of the passive sensor.

  In this manufacturing method, the shape of the antenna is appropriately set for each group corresponding to the resonance frequency of the sensor element. Thereby, even if there is an individual difference in the resonance frequency due to manufacturing variations of sensor elements, the resonance frequency of a communication signal transmitted (output) as a passive sensor is constant. In other words, it is possible to configure a passive sensor that can output a communication signal that can achieve a desired measurement accuracy without being affected by individual differences in sensor elements.

  In the passive sensor manufacturing method of the present invention, the sensor element is formed of a SAW resonator. In the antenna module forming step, the antenna is formed in a shape in which the resonance frequency is shifted by the impedance of the antenna.

  In this manufacturing method, a specific method for setting the shape of an antenna when a SAW resonator is specifically used as a sensor element and the SAW resonator is used is shown.

  In the method for manufacturing a passive sensor according to the present invention, the sensor element is formed of a crystal resonator. In the antenna module forming step, the antenna is formed in a shape in which the resonance frequency is shifted by the inductance included in the impedance of the antenna.

  This manufacturing method shows a specific method for setting the antenna shape when a crystal resonator is specifically used as the sensor element and the crystal resonator is used.

  Further, in the antenna module forming step in the passive sensor manufacturing method of the present invention, the antenna is formed by a dipole antenna including a radiation electrode portion and a wiring electrode portion. And in an antenna module formation process, an impedance is adjusted with the opening angle of a radiation electrode part.

  This manufacturing method shows a specific use of a dipole antenna as an antenna and an impedance adjustment method when the dipole antenna is used.

  In the antenna module forming step in the passive sensor manufacturing method of the present invention, the antenna is formed by an electromagnetically coupled antenna including a wound electrode portion and a wiring electrode portion. In the antenna module forming step, the impedance is adjusted according to the number of turns or / and the opening area of the wound electrode portion.

  In this manufacturing method, an electromagnetic coupling antenna is specifically used as an antenna, and an impedance adjustment method in the case of using the electromagnetic coupling antenna is shown.

  Moreover, the passive sensor formation process in the manufacturing method of the passive sensor of this invention adjusts an impedance with the connection position of the said sensor element with respect to the wiring electrode part of an antenna.

  This manufacturing method shows another method for adjusting impedance for an antenna different from the above-described shape. In this manufacturing method, the impedance is adjusted by the position of the sensor element with respect to the wiring electrode part of the antenna, that is, the electrode length of the wiring electrode part that connects the radiation electrode part or the wound electrode part and the sensor element.

  In addition, the present invention provides a wireless sensor system that measures a physical quantity sensed by a sensor element with a master unit connected to the passive sensor by wireless communication based on a resonance frequency of a communication signal transmitted from a passive sensor including the sensor element. Relates to the measurement method. The measurement method using the wireless sensor system includes a passive sensor manufacturing process for manufacturing a passive sensor by the above-described passive sensor manufacturing method, and includes a physical quantity detection process and a physical quantity calculation process. The physical quantity detection step detects a physical quantity using the passive sensor manufactured as described above, and generates a communication signal. In the physical quantity calculation step, the resonance frequency of the communication signal is analyzed using the master unit, and the physical quantity is calculated based on the analyzed resonance frequency.

  In this measurement method, individual differences of sensor elements are not affected by the resonance frequency of the communication signal, and therefore, a physical quantity can be measured with high accuracy in the parent device that performs measurement using the resonance frequency of the communication signal.

  According to the present invention, it is possible to realize a passive sensor that suppresses measurement errors due to individual differences of sensor elements and obtains high measurement accuracy.

1 is an external perspective view showing a configuration of a passive sensor 10 according to a first embodiment. It is a figure which shows the formation concept of the passive sensor of 1st Embodiment, and the formation concept of a passive sensor. It is the flowchart which shows the pre-stage process which manufactures the passive sensor 10 which concerns on 1st Embodiment, and the flowchart which shows the manufacturing process of the passive sensor 10. FIG. It is a top view which shows each structure of antenna module 110A-110E which concerns on 1st Embodiment. 1 is a block diagram illustrating a configuration of a wireless sensor system 1 according to a first embodiment. It is an external appearance perspective view of the passive sensor 30 which concerns on 2nd Embodiment. It is a top view which shows the structure of antenna module 310A-310E which concerns on 2nd Embodiment, respectively. This is an equivalent circuit of the measurement system as seen from the base unit 20A side when the crystal resonator 12A resonates. It is a top view which shows the structural example of the some passive sensor which concerns on 3rd Embodiment.

  A passive sensor, a passive sensor manufacturing method, a wireless sensor system, and a measurement method according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an external perspective view of a passive sensor 10 according to the present embodiment.

  The wireless sensor system 1 includes a passive sensor 10 and a parent device 20. Passive sensor 10 and base unit 20 perform communication by electromagnetic field coupling or radio wave transmission / reception. The communication mode is not limited to electromagnetic field coupling, but may be based on electromagnetic induction or radio wave radiation.

  The passive sensor 10 is functionally provided with an antenna 11 composed of a dipole antenna and a SAW resonator 12.

  The passive sensor 10 includes a base substrate 100 made of PET having a flat plate shape and insulating properties. On the surface of the base substrate 100, a radiation electrode 111 and a wiring electrode 112 are formed. The wiring electrodes 112 are electrode patterns that are arranged in parallel with each other and extend in a predetermined length along a predetermined direction. The radiation electrode 111 has a shape extending from one end of the wiring electrode 112 in a direction that forms a predetermined angle with respect to the wiring electrode 112. At this time, the pair of radiation electrodes 111 is formed in a shape extending in a symmetric direction with respect to the wiring electrode 112. Furthermore, each of the pair of radiation electrodes 111 is formed to have a length of about ¼ wavelength (λ / 4) of the wavelength λ of the communication signal, and to have a length of about λ / 2 as a whole. With this shape, the antenna 11 that becomes the radiation electrode 111 and the wiring electrode 112 functions as a dipole antenna.

  The SAW resonator 12 has an IDT electrode formed on a piezoelectric substrate, and has an external connection terminal connected to the IDT electrode. The SAW resonator 12 is mounted at a predetermined position of the wiring electrode 112 on the surface of the base substrate 100. For example, as shown in FIG. 1, the SAW resonator 12 is mounted near the end of the wiring electrode 112 opposite to the radiation electrode 111. The SAW resonator 12 and the wiring electrode 112 are also electrically connected.

  With such a configuration, the passive sensor 10 having a simple structure in which the antenna 11 is connected to the SAW resonator 12 and does not require a battery is realized. Then, when such a passive sensor 10 receives a pulsed excitation signal from the outside (master 20 described later) by the antenna 11, the excitation signal is applied to the SAW resonator 12. The SAW resonator 12 resonates at a resonance frequency corresponding to a sensed physical quantity (for example, magnetic strength) by the excitation signal, and outputs a resonance signal having the resonance frequency fsaw over a predetermined time length. The resonance frequency of the resonance signal is shifted by the SAW resonator 12 according to the impedance matching state between the SAW resonator 12 and the antenna 11. The antenna 11 radiates (transmits) a signal having the frequency shifted resonance frequency fsc. The signal of the resonance frequency shifted in frequency becomes a “communication signal”.

  Although details will be described later, the base unit 20 receives the communication signal from the passive sensor 10, detects the resonance frequency by performing frequency analysis of the communication signal, and based on the detected resonance frequency fsc, the physical quantity (For example, magnetic strength) is calculated.

  Here, the SAW resonator 12 has manufacturing variations in characteristics, that is, the resonance frequency fsaw, depending on process conditions such as the pattern width, length, and thickness of the IDT electrode. Therefore, when the shape of the antenna 11 is one type and the relationship between the resonance frequency and the physical quantity is uniquely stored and referenced on the base unit 20 side, the measurement result of the physical quantity is caused by the manufacturing variation of the SAW resonator 12. Variation will also occur. Therefore, in the present application, a decrease in measurement accuracy due to manufacturing variations of the SAW resonator 12 is suppressed by the following method.

<Concept of forming passive sensor 10>
FIG. 2A shows the concept of forming the passive sensor of this embodiment, and FIG. 2B shows the concept of forming the conventional passive sensor. FIG. 3A is a flowchart illustrating a pre-stage process for manufacturing the passive sensor 10, and FIG. 3B is a flowchart illustrating a manufacturing process of the passive sensor 10.

<Pre-stage process for manufacturing passive sensor 10>
First, a SAW resonator corresponding to the magnetic intensity range to be sensed is formed. At this time, the SAW resonator 12 is designed and formed so that a resonance frequency capable of wireless communication, specifically, 950 MHz, is set as a design frequency, that is, a reference frequency Fo. At the same time, the reference resonance frequency Fsc of the passive sensor 10 composed of the SAW resonator 12 and the antenna 11 is set (FIG. 3A: S901).

  Next, the frequency error width Δfsc as the passive sensor 10 as shown in FIG. 2A is calculated from the required measurement error ΔER of the magnetic strength and the theoretical magnetic strength-frequency characteristics of the SAW resonator 12. (FIG. 3: S902). Thereby, the frequency error width Δfsc conforming to the specification of the measurement error ΔER as the passive sensor 10 can be set.

  Based on the frequency error width Δfsc of the passive sensor 10, a frequency error width Δfq for grouping the SAW resonators 12 as shown in FIG. 2A is set (FIG. 3A: S903).

  Next, as shown in FIG. 2A, the reference group Fo of the SAW resonator 12 is used as a reference (for example, the center frequency of all frequency bands classified into groups), and the identification group for each frequency band of the frequency error width Δfq. Gr is set (FIG. 3A: S904).

  Specifically, as shown in FIG. 2A, the band of the frequency error width Δfq including the reference frequency Fo is set as the identification group GrC, and the band of the frequency error width Δfq close to the high frequency side of the identification group GrC is set. It is assumed that the identification group B and the band of the frequency error width Δfq that is closer to the high frequency side are the identification group A. Further, a frequency error width Δfq band close to the low frequency side of the identification group GrC is set as an identification group D, and a frequency error width Δfq frequency close to the low frequency side is set as an identification group E.

  Then, based on the reference frequency Fo and the frequency error Δfq, an upper limit frequency and a lower limit frequency, that is, a threshold frequency Thf is set for each of the identification groups GrA, GrB, GrC, GrD, and GrE (FIG. 3 (A): S905). Thereby, the preparation for classifying the SAW resonator 12 for each identification group Gr is completed.

  In a process separate from such group classification, antenna modules 110A-110E having different antenna shapes are formed for each identification group Gr (FIG. 3A: S911). The antenna modules 110 </ b> A- 110 </ b> E shown here are modules in which only the antenna 11 is formed on the surface of the base substrate 100 and the SAW resonator 12 is not mounted.

  FIG. 4 is a plan view showing the configuration of each of the antenna modules 110A to 110E according to this embodiment. In antenna modules 110A-110E shown in FIGS. 4A to 4E, the wiring electrodes 112 constituting the antenna 11 have the same shape, but the shape of the radiation electrode 111 is different.

  The radiation electrode 111A of the antenna module 110A, the radiation electrode 111B of the antenna module 110B, the radiation electrode 111C of the antenna module 110C, the radiation electrode 111D of the antenna module 110D, and the radiation electrode 111E of the antenna module 110E are the radiation electrodes. Have the same electrode length and different opening angles. Specifically, the opening angle of the radiation electrode 111A is θ1 (for example, 180 ° as shown in FIG. 4A), and the opening angle of the radiation electrode 111B is θ2 (<θ1). The opening angle of the radiation electrode 111C is θ3 (<θ2), and the opening angle of the radiation electrode 111D is θ4 (<θ3). The opening angle of the radiation electrode 111E is θ5 (<θ4). That is, the opening angles θ1, θ2, θ3, θ4, and θ5 of the antenna modules 110A, 110B, 110C, 110D, and 110E have the following relationship.

θ1>θ2>θ3>θ4> θ5
As a result, the impedances ZanA, ZanB, ZanC, ZanD, and ZanE of the antenna modules 110A, 110B, 110C, 110D, and 110E have the following relationship.

ZanA>ZanB>ZanC>ZanD> ZanE
Here, the impedances ZanA, ZanB, ZanC, ZanD, and ZanE, that is, the opening angles θ1, θ2, θ3, θ4, and θ5, indicate that the frequency fsaw of the SAW resonator of each identification group GrA, GrB, GrC, Grd, GrE is SAW resonance. Due to mismatching between the child 12 and the antenna 11, when the frequency is shifted to the frequency fsc as the passive sensor 10, the frequency is set within the frequency error width Δfsc centered on the reference frequency Fsc. .

  As a specific example, in the case of the identification group GrC, the antenna module 110C having the aperture angle θ3 and the impedance ZanC is combined with the SAW resonator 12 belonging to the identification group GrC. Thereby, the resonance frequency fsc as the passive sensor 10 is different from the resonance frequency fsaw of the SAW resonator 12 between the frequency band of the identification group GrC and the frequency band of the frequency error width Δfsc centered on the reference frequency Fsc. It becomes the frequency shifted by the impedance ZanC according to. As a result, the frequency fsc as the passive sensor 10 surely falls within the frequency within the frequency error width Δfsc around the reference frequency Fsc.

  Such a group classification standard of the SAW resonator 12 and the antenna modules 110A to 110E for each identification group Gr are prepared, and the passive sensor 10 is manufactured as follows.

  First, an excitation signal is individually applied to the SAW resonator 12, and each resonance frequency fsaw is measured (FIG. 3B: S101). At this time, the resonance frequency fsaw of the SAW resonator 12 is different for each individual due to manufacturing variations.

  Next, the resonance frequency fsaw measured for each SAW resonator 12 is compared with the threshold frequency Thf for group classification, and each SAW resonator 12 is classified into one of the identification groups GrA, GrB, GrC, Grd, and GrE. And associate them (FIG. 3B: S102).

  Next, antenna modules 110A-110E are selected for each identification group GrA-GrE to which the SAW resonator 12 belongs. Then, the SAW resonator 12 is mounted on the selected antenna module 110A-110E to complete the passive sensor 10 (FIG. 3B: S103). For example, if the SAW resonator 12 belongs to the identification group GrA, the antenna module 110A is selected, and the passive sensor 10 is formed by mounting the SAW resonator 12 on the antenna module 110A. For example, if the SAW resonator 12 belongs to the identification group GrD, the antenna module 110D is selected, and the passive sensor 10 is formed by mounting the SAW resonator 12 on the antenna module 110D.

  In this way, by selecting the antenna module 110 having different impedance for each identification group Gr to which the SAW resonator 12 belongs and mounting the SAW resonator 12, the resonance frequency fsaw as the SAW resonator 12 has a large variation. In addition, the variation of the resonance frequency fsc as the passive sensor 10 can be reduced. Then, by setting the frequency error width Δfsc as the passive sensor 10 in accordance with the measurement error range ΔER of the required specification, the resonance frequency fsaw of the SAW resonator 12 is more than the frequency error corresponding to the measurement error range ΔER. Even if there is a large variation, the resonance frequency fsc as the passive sensor 10 surely falls within the frequency error corresponding to the measurement error range ΔER. As a result, it is possible to measure a physical quantity (such as magnetic strength) according to the required measurement error accuracy.

  If the group classification is not performed as in the conventional case, as shown in FIG. 2B, the measurement error range Δfscp reflects the frequency error range Δfqp of the SAW resonator 12 as it is, and the measurement error range Δfscp is higher than the error range. When accuracy is required, it cannot respond. However, if the configuration and method of the present embodiment are used, even if measurement accuracy higher than the frequency error range of the SAW resonator 12 is required, it can be dealt with with certainty.

  The passive sensor 10 formed by such a manufacturing method can be applied to a wireless sensor system 1 as shown in FIG. FIG. 5 is a block diagram showing a configuration of the wireless sensor system 1 of the present embodiment.

  The wireless sensor system 1 includes a passive sensor 10 and a parent device 20. The passive sensor 10 includes an antenna 11 and a SAW resonator 12 and is manufactured as described above.

  The base unit 20 includes a control unit 21, a transmission signal generation unit 22, a transmission / reception unit 23, a base unit side antenna 24, a measurement unit 25, a display unit 26, and an operation unit 27.

  The control unit 21 performs overall control of the parent device 20. Further, the control unit 21 executes various control processes in accordance with operation inputs from the operation unit 27. For example, when receiving an operation input for magnetic intensity measurement from the operation unit 27, the transmission signal generation unit 22 is controlled to generate the pulsed excitation signal SpL.

  The transmission signal generation unit 22 receives the generation control of the pulsed excitation signal SpL, generates a pulsed excitation signal SpL composed of a carrier wave with a predetermined frequency, and supplies the pulsed excitation signal SpL to the transmission / reception unit 23. The carrier frequency of the pulsed excitation signal SpL is close to the resonance frequency of the quartz crystal resonator 110, specifically, a predetermined frequency within the communication frequency band between the parent device side antenna 24 and the antenna 11 of the passive sensor 10. Is set.

  At the time of transmission, the transmission / reception unit 23 outputs the pulsed excitation signal SpL to the parent device side antenna 24. The base unit side antenna 24 is composed of a dipole antenna similar to the antenna 11 of the passive sensor 10, and radiates a pulsed excitation signal SpL with a predetermined directivity.

  The antenna 11 of the passive sensor 10 receives the pulsed excitation signal SpL and applies it to the SAW resonator 12. The SAW resonator 12 is excited by the pulsed excitation signal SpL and resonates. At this time, the SAW resonator 12 resonates at a resonance frequency fsaw corresponding to the sensed magnetic intensity PP, and outputs a resonance signal. While the resonance signal is transmitted to the antenna 11, the resonance frequency shifts due to mismatching between the antenna 11 and the SAW resonator 12. As a result, the communication signal Sfp having a shifted resonance frequency is radiated from the antenna 11.

  Returning to the main unit 20, at the time of reception, the main unit side antenna 24 receives the communication signal Sfp radiated from the antenna 11 of the passive sensor 10 (signal of the resonance frequency fsc of the passive sensor 10) and outputs it to the transmission / reception unit 23. . The transmission / reception unit 23 outputs the communication signal Sfp to the measurement unit 25.

  The measurement unit 25 includes a frequency conversion unit 251, a physical detection unit 252, and a storage unit 253. The frequency conversion unit 251 acquires a frequency spectrum from the communication signal Sfp on the time axis by FFT processing or the like. The storage unit 253 stores in advance the relationship between the frequency of the input signal, that is, the communication signal Sfp, and the magnetic strength. The physical quantity detector 252 detects the frequency spectrum peak of the input resonance signal Sfp, and reads the magnetic intensity associated with the peak frequency from the storage unit 253, thereby calculating the magnetic intensity. The calculated magnetic intensity is output to the display unit 26 and the like. The display unit 26 displays the magnetic intensity detection result.

  And as mentioned above, by using the passive sensor 10 with small frequency variation, naturally the measurement accuracy as a wireless sensor system can also be improved.

  Next, a passive sensor according to a second embodiment and a method for manufacturing the passive sensor will be described with reference to the drawings. In the first embodiment described above, an example in which the passive sensor 10 and the parent device 20 are wirelessly communicated by radio waves using a dipole antenna has been shown. However, in the present embodiment, the passive sensor 30 and the parent device 20A are coupled by electromagnetic field coupling. A case of wireless communication with (not shown) is shown.

  In the first embodiment, the example in which the magnetic intensity is measured using the SAW resonator 12 as the sensor element is shown. However, in the present embodiment, for example, a crystal whose resonance frequency is 13.56 MHz is used as the sensor element. The case where temperature is measured using the vibrator 12A is shown.

  FIG. 6 is an external perspective view of the passive sensor 30 according to the present embodiment. The passive sensor 30 includes a base substrate 300 made of PET having a flat plate shape and insulating properties. A wound electrode 311 having a predetermined number of turns in a plan view is formed on the surface of the base substrate 300. Wiring electrodes 312 are connected to both ends of the wound electrode 311. A crystal resonator 12A is mounted at a predetermined position on the wiring electrode 312 opposite to the wound electrode 311. Thereby, the passive sensor 30 is formed.

  When the passive sensor 30 using such electromagnetic field coupling is used, as shown in the first embodiment, the crystal resonators 12A are classified into groups based on the resonance frequency, and antennas corresponding to the identification groups Gr are used. The modules 310A, 310B, 310C, 310D, and 310E are selected to form the passive sensor 30. FIG. 7 is a plan view showing the configuration of the antenna modules 310A to 310E according to this embodiment. The antenna modules 310A-310E are different in electrode length, number of turns, and central opening area of the wound electrodes 311A, 311B, 311C, 311D, 311E, respectively, and have substantially the same outer shape.

  In the case of the electromagnetic coupling type, each antenna module 310A-310E is set based on the concept shown below. FIG. 8 is an equivalent circuit of the measurement system as seen from the parent device 20A side when the crystal resonator 12A resonates. As shown in FIG. 8, when the measurement system is viewed from the master unit 20A in a state in which the crystal unit 12A is a resonator and the master unit 20A and the passive sensor 30 are electromagnetically coupled, the master unit side has a circuit capacitor ( Capacitance Cp), circuit resistance (resistance value Rp), and antenna coil (inductance Lp) are connected in series between both terminals of the measurement circuit. The passive sensor 30 has a circuit configuration in which a series connection closed loop including an antenna coil (inductance Lsc), a wiring resistance (resistance value Rsc), and a crystal resonator 12A is formed. In such a case, the impedance Zq of the crystal unit 12A is set to Zq = Rq + jXq. Thereby, impedance Z which looked at the passive sensor 12A side from the measurement circuit can be expressed by the following equation.

  Here, k represents a coupling coefficient between the antenna 31 of the passive sensor 30 and the parent device side antenna 24 of the parent device 20A. Ω is the angular frequency of the communication signal.

  As shown in (Expression 1), the reactance component of the impedance Z when the passive sensor 12A is viewed from the measurement circuit depends on the reactance component Xq of the crystal resonator 12A and the inductance Lsc of the antenna coil, and the resonance frequency of the passive sensor 30 Is dependent on the inductance Lsc of the antenna coil.

  Therefore, as shown in FIG. 7, antennas having different inductances can be realized by changing the number of turns, the electrode length, and the opening area of the wound electrodes 311A to 311E of the antenna modules 310A to 310E. Then, the inductance of each antenna module 310A-310E is set for each identification group Gr, as shown in the first embodiment. That is, the resonance frequency of the passive sensor 30 obtained by the frequency shift due to mismatching between the crystal resonator 12A and the antenna 31 is a predetermined frequency according to the measurement accuracy regardless of the crystal resonator 12A of any identification group Gr. The inductance Lsc is set by adjusting the number of turns of the wound electrode, the electrode length, the opening area, and the like so as to fall within the error width Δfsc. At this time, the inductance Lsc may be set by adjusting at least one element of the number of turns, the electrode length, and the opening area.

  As described above, when the crystal unit 12A is identified by the identification group GrA-GrE, and the antenna module 310A-310E is selected according to the identification group GrA-GrE to manufacture the passive sensor 30, the same as in the first embodiment. In addition, a passive sensor and a wireless sensor system corresponding to the required measurement accuracy can be realized without being affected by individual differences in the crystal resonator 12A. Furthermore, as shown in the present embodiment, the resonance frequency can be adjusted only by the inductance. Thereby, the design load of the antenna module can be reduced.

  Next, a passive sensor and a method for manufacturing the passive sensor shown in the third embodiment will be described with reference to the drawings. FIG. 9 is a plan view showing a structural example of a plurality of passive sensors according to the present embodiment.

  As shown in FIG. 9, in the passive sensors 40A, 40B, and 40C of this embodiment, the shapes of the radiation electrode 411 and the wiring electrode 412 are the same. That is, the shape of the antenna module is the same, and a dipole antenna is used as in the first embodiment. However, in the passive sensors 40A, 40B, and 40C, the mounting position of the SAW resonator 12 with respect to the wiring electrode 412 is different. Specifically, in the passive sensor 40A, the SAW resonator 12 is mounted along the wiring electrode 412 at a position of a length DLa from the radiation electrode 411. In the passive sensor 40B, the SAW resonator 12 is mounted at a position of a length DLb (<DLa) from the radiation electrode 411. In the passive sensor 40C, the SAW resonator 12 is mounted at a position of a length DLc (<DLb) from the radiation electrode 411. In this way, even when the shape of the radiation electrode 411 is made the same and the mounting position of the SAW resonator 12 with respect to the wiring electrode 412 is changed, the impedance can be made different and the shift amount of the resonance frequency can be adjusted. Can do. Furthermore, with this manufacturing method, only one type of antenna module needs to be formed, and the manufacturing load of the antenna module can be reduced.

  In the above-described embodiment, the example in which the SAW resonator and the crystal resonator are used as the sensor element has been described. However, if the element has a resonance frequency that changes according to a predetermined physical quantity to be sensed, the piezoelectric resonator, An element such as a tuning fork resonator can be used. Moreover, although the example which measures a magnetic intensity or temperature as a physical quantity was shown, even if it is another physical quantity which can be detected with another resonant sensor element, it can be made into a measuring object.

  In the first and third embodiments, an example of wireless communication using a radio wave by a dipole antenna is shown. In the second embodiment, an example of wireless communication by electromagnetic field coupling is shown. A method such as a field coupling method and the shape of the antenna may be appropriately set according to the frequency used for communication and the shape specification of the passive sensor. At this time, it is better if the impedance and inductance can be easily adjusted.

10, 30, 40A, 40B, 40C-passive sensor, 11-antenna unit, 12-SAW resonator, 12A-crystal resonator, 20, 20A-base unit, 21-control unit, 22-transmission signal generation unit, 23 -Transmitter / receiver, 24-Main unit side antenna, 25-Measuring unit, 26-Display unit, 27-Operation unit, 100, 300-Base substrate, 110, 110A, 110B, 110C, 110D, 110E-Antenna module, 111A, 111B, 111C, 111D, 111E, 411-radiation electrode, 112, 312, 412-wiring electrode, 311- wound electrode,

Claims (15)

A sensor element that outputs a resonance signal having a frequency corresponding to a physical quantity to be detected by an external excitation signal;
An antenna connected to the sensor element and transmitting and receiving a communication signal based on the excitation signal and the resonance signal, and a passive sensor manufacturing method comprising:
A sensor element sorting step of sorting sensor elements into a plurality of groups at a resonance frequency by the excitation signal;
An antenna module forming step of forming an antenna module having antennas of different shapes for each group;
In accordance with the group of sensor elements, a passive sensor forming step of forming a passive sensor by combining the antenna module and the sensor element,
The antenna module forming step is a method of manufacturing a passive sensor, which is a step of forming the antenna in a shape that shifts the resonance frequency of the sensor element to a desired resonance frequency of the passive sensor. It is a manufacturing method of the passive sensor according to claim 1,
The sensor element is formed of a SAW resonator,
The antenna module forming step is a method of manufacturing a passive sensor, which is a step of forming the antenna in a shape in which a resonance frequency is shifted by the impedance of the antenna. It is a manufacturing method of the passive sensor according to claim 1,
The sensor element is formed of a crystal resonator,
The antenna module forming step is a method of manufacturing a passive sensor, which is a step of forming the antenna in a shape in which a resonance frequency is shifted by an inductance included in the impedance of the antenna. It is a manufacturing method of the passive sensor as described in any one of Claims 1 thru | or 3, Comprising:
The antenna module forming step includes
The antenna is formed by a dipole antenna composed of a radiation electrode portion and a wiring electrode portion,
A method for manufacturing a passive sensor, which is a step of adjusting the impedance according to an opening angle of the radiation electrode portion. It is a manufacturing method of the passive sensor as described in any one of Claims 1 thru | or 3, Comprising:
The antenna module forming step includes
The antenna is formed by an electromagnetically coupled antenna composed of a wound electrode portion and a wiring electrode portion,
A method of manufacturing a passive sensor, which is a step of adjusting the impedance according to the number of turns or / and the opening area of the wound electrode portion. It is a manufacturing method of the passive sensor as described in any one of Claim 4 or Claim 5, Comprising:
The passive sensor forming step is a method of manufacturing a passive sensor, which is a step of adjusting the impedance according to a connection position of the sensor element with respect to the wiring electrode portion of the antenna. A measurement method of a wireless sensor system that measures a physical quantity sensed by the sensor element by a master unit connected to the passive sensor by wireless communication based on a resonance frequency of a communication signal transmitted from a passive sensor including the sensor element. There,
A passive sensor manufacturing process for manufacturing a passive sensor by the passive sensor manufacturing method according to any one of claims 1 to 6.
A physical quantity detection step of detecting the physical quantity using a manufactured passive sensor and generating the communication signal;
A measurement method for a wireless sensor system, comprising: using the parent device to analyze a resonance frequency of the communication signal and calculating the physical quantity based on the analyzed resonance frequency. A sensor element that outputs a resonance signal having a frequency corresponding to a physical quantity to be detected by an external excitation signal;
An antenna that is connected to the sensor element and transmits and receives a communication signal based on the excitation signal and the resonance signal;
The said antenna is a passive sensor which consists of a shape which has the impedance from which the frequency of the communication signal transmitted from the said antenna becomes a desired resonant frequency as a passive sensor based on the resonant frequency of the said sensor element. The passive sensor according to claim 8,
The antenna is a dipole antenna comprising a radiation electrode portion and a wiring electrode portion connecting the radiation electrode portion to the sensor element,
The radiation electrode portion is a passive sensor having an opening angle corresponding to the impedance. The passive sensor according to claim 8,
The antenna is an electromagnetically coupled antenna comprising a wound electrode part and a wiring electrode part that connects the wound electrode part to the sensor element,
The wound electrode unit is a passive sensor having a number of turns and / or an opening area corresponding to the impedance. It is a passive sensor as described in any one of Claims 8 thru | or 10, Comprising:
The said wiring electrode part is a passive sensor which consists of length according to the said impedance. It is a passive sensor as described in any one of Claims 8 thru | or 11, Comprising:
The sensor element is a passive sensor that is a SAW resonator. It is a passive sensor as described in any one of Claims 8 thru | or 11, Comprising:
The sensor element is a passive sensor that is a crystal resonator. A passive sensor according to any one of claims 8 to 13,
The antenna is a passive sensor whose shape is determined by an inductance included in the impedance. A passive sensor according to any one of claims 8 to 14, and
A wireless sensor system comprising: a master device that transmits the excitation signal to the passive sensor, receives the communication signal, and calculates the physical quantity based on a resonance frequency of the communication signal.