Sensor tag, method for reading the sensor tag and sensor system with sensor tag

Abstract

Sensor tag comprising: a plurality of conductors arranged close together and forming a resonant element; and a sensing unit arranged between the plurality of conductors and having a physical property which changes as a result of a change in a physical quantity of an object to be sensed by the sensing unit.

Description

TECHNICAL FIELDThe present disclosure relates to a sensor tag, a method of reading the sensor tag, and a sensor system using the sensor tag.PRIOR ARTA general tag represented by the tag described in Patent Literature 1, which is common to the sensor tag according to the present disclosure, has a detection unit. The detection unit displays a physical quantity of an object sensed by the detection unit by a change in a characteristic of the detection unit based on an electromagnetic wave reflection characteristic of the detection unit, for example, by a change in dielectric constant or conductivity, as described in Patent Literature 1.Patent Literature 2 discloses an apparatus in which there are a plurality of sensors for determining one of a plurality of physical properties such as pressure, temperature, chemicals and other physical conditions. Generally, the sensors include a resonant circuit having an inductor electromagnetically coupled to a transmit antenna. When an excitation signal is applied to the antenna, a current is induced in the sensor circuit. This current oscillates at the resonant frequency of the sensor circuit. The resonant frequency and bandwidth of the sensor circuit is determined with an impedance analyzer, a transmitting and receiving antenna system or a chirp interrogation system. The resonant frequency can also be determined with a simple analog circuit with a transmitter. The sensors are designed so that either the resonant frequency or the bandwidth of the sensor circuit, or both, depends on the physical properties such as pressure, temperature, presence of a chemical substance, or other conditions of a particular environment. The physical properties are calculated on the basis of the determined resonant frequency and bandwidth.Patent Literature 3 discloses a sensor tag including an antenna and connection conductors formed on a surface of a flexible substrate. A sensor element is mounted on land conductors of the connection conductors. The sensor element is composed of a crystal vibrator and an RFIC. The crystal vibrator receives an excitation signal from the outside and generates a resonance signal having a resonance frequency corresponding to the measured temperature. The RFIC stores equivalent circuit constant information comprising at least one equivalent inductance or equivalent capacitance of the crystal vibrator.Patent Literature 4 discloses improved surface acoustic wave (SAW) sensors and wireless SAW sensor tag interface devices, including low loss devices, devices that allow improved utilization of time diversity for device identification, and devices suitable for use in band limited environments (such as the ISM band) and for use in ultra wideband applications. Antennas for use with both SAW sensors and / or tags and with wireless transmit / receive systems are also disclosed, including antennas suitable for operation in conductive media and in high metal environments, where the antennas are used to activate and read the SAW sensors and / or tags. SAW sensors and sensor tags and related methods for measuring scaled voltages and currents in electrical conductors via measurements of the electric and magnetic fields thereof are disclosed.REFERENCE LISTPATENT LITERATUREPatent Literature 1: JP 2021-89725 APatent Literature 2: U.S. Pat. No. 6,278,379 B1Patent Literature 3: U.S. Pat. No. 10,234,334 B2Patent Literature 4: US 2017 / 0010308 A1SUMMARY OF THE INVENTIONTECHNICAL PROBLEMHowever, in the above-described tag, there is a problem that the above-described detection unit cannot detect the physical quantity of the object when the dielectric constant or the conductivity of the detection unit does not change although the physical quantity of the object changes.The object of the present disclosure is to provide a sensor tag capable of detecting a physical quantity of an object even if the conductivity or the dielectric constant of a detection unit does not change although the physical quantity of the object changes.SOLUTION OF THE OBJECTIn order to solve the above-described problem, a sensor tag according to the present disclosure includes a plurality of conductors that are arranged close to each other and form a resonance element; and a detection unit that is arranged between the plurality of conductors and has a physical property that changes due to a change in a physical size of an object to be detected by the detection unit.ADVANTAGEOUS EFFECTS OF THE INVENTIONWith the sensor tag according to the present disclosure, a physical quantity of an object can be detected even when the conductivity or the dielectric constant of a detection unit does not change although the physical quantity of the object changes.BRIEF DESCRIPTION OF THE DRAWINGSFIG. 1 shows a configuration of a sensor tag ST of a first embodiment. FIG. 2A illustrates an operation (part 1( 1)) of the sensor tag ST of the first embodiment. FIG. 2B illustrates an operation (part 1( 2)) of the sensor tag ST of the first embodiment. FIG. 2C shows an operation (part 1 ( 3)) of the sensor tag ST of the first embodiment. FIG. 3A illustrates an operation (part 2( 1)) of the sensor tag ST of the first embodiment. FIG. 3B illustrates an operation (part 2( 2)) of the sensor tag ST of the first embodiment. FIG. 4 illustrates an operation (part 3) of the sensor tag ST of the first embodiment. FIG. 5 shows a configuration (part 1) of a sensor tag ST of a second embodiment. FIG. 6 shows a configuration (part 2) of the sensor tag ST of the second embodiment. FIG. 7 shows a configuration (part 3) of the sensor tag ST of the second embodiment. FIGS. 8A to 8C are each a schematic diagram showing a displacement and a displacement amount of the sensor tag ST of the second embodiment. FIG. 9 shows the frequency characteristic (part 1) of a reflection value of the second embodiment. FIG. 10 shows the frequency characteristic (part 2) of the reflection value of the second embodiment. FIG. 11 shows the frequency characteristic (part 3) of the reflection value of the second embodiment. FIG. 12 shows a configuration of a sensor tag ST of a third embodiment. FIG. 13 shows an electric circuit DK of a detection unit 32 of the third embodiment. FIG. 14 shows a configuration (part 1) of a fourth embodiment. FIG. 15 shows a configuration (part 2) of the fourth embodiment. FIG. 16 shows the frequency characteristic of a reflection value of the fourth embodiment. FIG. 17 shows a configuration of a sensor tag ST of a fifth embodiment. FIG. 18A shows a configuration (part 1) of a sensor tag ST of a sixth embodiment. FIG. 18B shows a configuration (part 2) of the sensor tag ST of the sixth embodiment. FIG. 18C shows a configuration (part 3) of the sensor tag ST of the sixth embodiment. FIG. 19 shows the frequency characteristic (without shift) of a reflection value of the sixth embodiment. FIG. 20 shows the frequency characteristic (displacement in the X direction) of the reflection value of the sixth embodiment. FIG. 21 shows the frequency characteristic (Y-direction shift) of the reflectance of the sixth embodiment. FIG. 22 shows the frequency characteristic (Z-direction shift) of the reflection value of the sixth embodiment. FIG. 23 shows an arrangement (part 1) of a sensor tag ST of a seventh embodiment. FIG. 24 shows an arrangement (part 2) of the sensor tag ST of the seventh embodiment. FIG. 25 shows the shape and dimensions of the sensor tag ST of the seventh embodiment. FIG. 26 shows an operation of the sensor tag ST of the seventh embodiment. FIG. 27 shows the calculation results (vibration in the X direction) of an n-th order coefficient Cn of the seventh embodiment. FIG. 28 shows the calculation results (vibration in the Y direction) of the coefficient Cn of the seventh embodiment of the n-th order. FIG. 29 shows the calculation results (vibration in the Z direction) of the coefficient Cn of the seventh embodiment. FIG. 30 shows a configuration of a sensor system SS of an eighth embodiment. FIG. 31 shows a configuration of a sensor system SS of a ninth embodiment.DESCRIPTION OF THE EMBODIMENTSEmbodiments of a sensor tag, a method of reading a sensor tag, and a sensor system using a sensor tag according to the present disclosure will be described.Hereinafter, for convenience of description and understanding, the names of a plurality of components will be collectively referred to with a reference sign. For example, a reference sign "11" may refer to the two terms "conductor 11 a" and "conductor 11 b".First Embodiment.< Embodiment>A sensor tag of a first embodiment will be described.<Konfiguration of First Embodiment>FIG. 1 shows a configuration of a sensor tag ST of the first embodiment.As illustrated in FIG. 1, the sensor tag ST of the first embodiment includes a plurality of conductors 11, i.e., a conductor 11 aand a conductor 11 b, and a detection unit 12.The "plurality of conductors 11" corresponds to a "plurality of conductors", the detection unit 12 corresponds to a "detection unit", and a resonance element 13 corresponds to a "resonance element".The conductor 11 aand the conductor 11 bare members constituting the resonance element 13. The conductor 11a and the conductor 11b are close to each other, namely so close that they can be coupled electromagnetically.The detection unit 12 is disposed between the conductor 11 aand the conductor 11 b. In the detection unit 12, a physical property changes with a change in a physical quantity BR (not illustrated) of an object TB (corresponding to, for example, a monitoring target KTB illustrated in FIG. 30 and an identification target STB illustrated in FIG. 31 ) to be detected by the detection unit 12, and for example, a shape of the detection unit 12 changes.< Of First Embodiment>FIGS. 2A and 2B illustrate an operation (part 1) of the sensor tag ST of the first embodiment.FIGS. 3A and 3B show an operation (part 2) of the sensor tag ST of the first embodiment.FIG. 4 illustrates an operation (part 3) of the sensor tag ST of the first embodiment.When the physical quantity BR of the object TB to be detected by the detection unit 12 changes, the shape of the detection unit 12 changes in the sensor tag ST. A combination of the type of the physical quantity BR of the object TB and the type of the detection unit 12 is, for example, as follows. (1) The physical quantity BR of the object TB is a displacement, a mechanical vibration, a pressure, or the like, and the detection unit 12 is a spring, a rubber, or the like. (2) The physical quantity BR of the object TB is the temperature or the like, and the detection unit 12 is a thermoplastic resin or the like.As described above, when the shape of the detection unit 12 changes, the relative positional relationship between the conductor 11 aand the conductor 11 b, that is, the distance between the conductor 11 aand the conductor 11 bchanges.As described above, when the relative positional relationship between the conductor 11 aand the conductor 11 bchanges, the frequency characteristic of a reflection coefficient or a transmission coefficient of the resonance element 13 changes.Here, the "reflection coefficient" and the "transmission coefficient" represent the amount of reflection or transmission of an electromagnetic wave and the amount of phase change at this time.When the change in the frequency characteristic of the reflection coefficient or the transmission coefficient of the resonance element 13 caused by the change in the physical quantity BR of the object TB is to be observed, a reading device YS (e.g., shown in FIG. 23 ) irradiates the sensor tag ST with an electromagnetic wave (corresponding to, e.g., a transmission wave SH, the transmission wave SH shown in FIG. 23 ) and receives a reflected wave or a transmitted wave (corresponding to, e.g., a reflected wave HH shown in FIG. 23 ) with a frequency characteristic that changes due to the change in the physical quantity BR of the object TB from the sensor tag ST, thereby observing the frequency characteristic of the reflected wave or the transmitted wave.Based on the observed frequency characteristics of the reflected wave HH and the like, it is possible to estimate the state of the detection unit 12, i.e., the expansion / contraction state (illustrated in FIGS. 2A and 2B ) which is a strain, by referring to the correspondence relationship (illustrated in FIG. 2C ) between the frequency characteristics of the reflected wave HH and the like and the state of the detection unit 12 calculated in advance or detected in advance by an experiment.Moreover, the physical size of the object TB can be estimated from the correspondence relationship (illustrated in FIGS. 3A and 3B ) between the state of the detection unit 12 and the physical size BR of the object TB. For example, when the length of the detection unit 12, i.e., the distance between the conductor 11 aand the conductor 11 bis Z 1 (mm), it can be estimated that the physical quantity BR of the object TB is Z 1 (mm), and when the distance between the conductor 11 aand the conductor 11 bis Z 2 (mm), it can be estimated that the physical quantity of the object TB is Z 2 (mm).Instead of the above two correspondence relationships (illustrated in FIGS. 2A to 2C and FIGS. 3A and 3B ), a correspondence relationship (illustrated in FIG. 4 ) between the frequency characteristics of the reflected wave HH and the like and the physical quantity BR of the object TB may be used. For example, a physical quantity BR 1 of the object TB and a physical quantity BR 2 of the object TB can be distinguished.< Of First Embodiment>As described above, in the sensor tag ST of the first embodiment, when the physical quantity BR of the object TB changes, the shape, which is an example of the physical properties of the detection unit 12, changes, thereby changing the relative position between the conductor 11 aand the conductor 11 b. In addition, the frequency characteristics of the reflected wave HH and the like change due to the reflection or the like of the sensor tag ST because the reflection coefficient or the transmission coefficient of the resonance element 13 changes due to a change in the relative position between the conductor 11 aand the conductor 11 b. Consequently, the physical quantity BR of the object TB can be estimated by observing the above-described frequency characteristics.With the sensor tag ST of the first embodiment operating as described above, it is possible to detect the physical quantity BR of the object TB without requiring electrical characteristics (conductivity or dielectric constant) required for conventional detection units.Second Embodiment.< Embodiment>A sensor tag of a second embodiment will be described.The sensor tag ST of the second embodiment detects the displacement or vibration of the object TB as the physical quantity BR of the object TB.<Konfiguration of Second Embodiment>FIG. 5 shows a configuration (part 1) of the sensor tag ST of the second embodiment.FIG. 6 shows a configuration (part 2) of the sensor tag ST of the second embodiment.FIG. 7 shows a configuration (part 3) of the sensor tag ST of the second embodiment.As illustrated in FIG. 5, the sensor tag ST of the second embodiment has a configuration substantially corresponding to the configuration of the sensor tag ST of the first embodiment (illustrated in FIG. 1 ).On the other hand, the sensor tag ST of the second embodiment is different from the sensor tag ST of the first embodiment in that the detection unit 22 is a spring (made of any material) as illustrated in FIG. 5.The sensor tag ST of the second embodiment includes a substrate 24 aand a substrate 24 bas illustrated in FIG. 5. The substrate 24a carries a conductor 21a and the substrate 24b carries a conductor 21b. The dimensions of the conductor 21a and the conductor 21b are shown, for example, in Fig. 6.As illustrated in FIG. 5, the conductor 21 aand the substrate 24 aform an upper layer 25 of the sensor tag ST, and similarly, the conductor 21 band the substrate 24 bform a lower layer 26 of the sensor tag ST.As illustrated in FIG. 7, the upper layer 25 is fixed to the lower surface of the object to be detected TB 1, while the lower layer 26 is fixed to the upper surface of the object to be detected TB 2. Specifically, the upper layer 25 and the lower layer 26 are provided between two separate components forming a structure (bridge or the like), or are provided between two separate components forming an electronic device.< Of Second Embodiment>Hereinafter, it is assumed that the position of the object TB 1 (illustrated in FIG. 7 ) is fixed while the position of the object TB 2 (illustrated in FIG. 7 ) is displaced.FIGS. 8A to 8C are each a schematic diagram showing a displacement and a displacement amount of the sensor tag ST of the second embodiment.Here, a "reference state" is defined as a state in which the upper layer 25 and the lower layer 26 completely overlap each other as viewed in the Z-axis direction, and a state in which the position of the lower layer 26 in the Z-direction is a specific position (FIG. 8C shows the "lower layer 26 (before displacement)"). The shift amounts dx, dy and dz (in mm units) are defined as shift amounts from the "reference state" as shown in Figs. 8A to 8C.When the position of the object TB 2 is displaced, the shape of the detection unit 22 changes, the relative position between the conductor 21 aand the conductor 21 bchanges, and the frequency characteristic of the reflection coefficient or the transmission coefficient of a resonance element 23 changes as in the first embodiment.FIG. 9 shows the frequency characteristic (part 1) of the reflection amount of the second embodiment.FIG. 10 shows the frequency characteristic (part 2) of the reflection value of the second embodiment.FIG. 11 shows the frequency characteristic (part 3) of the reflection value of the second embodiment.The frequency characteristics of the reflection amount shown in FIGS. 9, 10 to 11 show the magnitude of the reflection coefficient of the sensor tag ST with respect to an electromagnetic wave, more specifically, an X-polarized wave (polarized wave vibrating in the X direction) when the object TB 2 is displaced in one of the three directions X, Y, and Z.The frequency characteristics of the reflection value illustrated in FIGS. 9, 10 to 11 are calculated by, for example, two-dimensionally arranging a large number of sensor tags ST (illustrated in FIG. 1 ) at intervals of 25 mm on an XY plane to increase the reflection value to be obtained.As shown in FIGS. 9, 10 to 11, the frequency characteristic of the reflection value changes when the object TB 2 is displaced in any of the directions X, Y, and Z. On the other hand, the frequency characteristic of the reflection value differs depending on which X, Y and Z directions the object TB2 is displaced and whether the displacement amount is large or small.As in the first embodiment, the reader YS irradiates the sensor tag ST with the transmission wave SH and receives the reflected wave HH or the like from the sensor tag ST, thereby observing the frequency characteristic of the reflected wave HH or the like of the resonance element 23.In a substantially similar manner to the first embodiment, it is possible to estimate the state of the detection unit 22 based on the observed frequency characteristics of the reflected wave HH and the like by referring to the correspondence relationship between the frequency characteristics of the reflected wave HH and the like calculated in advance or experimented in advance and the state of the detection unit 22, and further estimate the displacement direction and the displacement amount of the object TB 2.< Of Second Embodiment>As described above, in the sensor tag ST of the second embodiment, the displacement direction and the displacement amount of the object TB 2 can be detected even when the conductivity or the dielectric constant of the detection unit 22 does not change in response to the change of the object TB 2.Third Embodiment.< Embodiment>A sensor tag of a third embodiment will be described.In the sensor tag ST of the third embodiment, in a detection unit 32, a circuit constant of an electric circuit DK (illustrated in FIG. 13 ) changes.<Konfiguration of Third Embodiment>FIG. 12 shows a configuration of the sensor tag ST of the third embodiment.FIG. 13 shows the electric circuit DK of the detection unit 32 of the third embodiment.As illustrated in FIG. 12, the sensor tag ST of the third embodiment has a configuration substantially corresponding to the configuration of the sensor tag ST of the first embodiment (illustrated in FIG. 1 ).In the sensor tag ST of the third embodiment, unlike the sensor tag ST of the first embodiment, in the detection unit 32, a circuit constant of the electric circuit DK (illustrated in FIG. 13 ) of the detection unit 32 changes with a change in the physical quantity BR of the object TB.< Of Third Embodiment>When the physical quantity BR of the object TB changes, the circuit constant of the electric circuit DK of the detection unit 32 changes, for example, as illustrated in FIG. 13, the size of a resistor TE, an inductance IN, or a capacitor CA constituting the electric circuit DK that corresponds to a varactor diode that is an active element changes.For example, when the physical quantity BR of the object TB changes, in other words, when the value of the reverse bias voltage applied to the varactor diode changes, the value of the capacitor CA of the electric circuit DK changes due to the characteristic of the varactor diode.The combination of the physical quantity BR of the object TB and the detection unit 32 is, for example, as follows. (1) The physical quantity BR of the object TB is a voltage, an electric field, or the like, and the detection unit 32 is a diode or the like. (2) The physical quantity BR of the object TB is a magnetic field or the like, and the detection unit 32 is a magnetic sensor or the like. (3) The physical size of the object TB is light or the like, and the detection unit 32 is a CdS sensor or the like. (4) The object TB is the temperature or the like, and the detection unit 32 is a thermistor or the like. (5) The object TB is moisture or the like, and the detection unit 32 is a moisture sensor or the like. (6) The object TB is a gas or the like, and the detection unit 32 is a gas sensor or the like.When the circuit constant of the electric circuit DK of the detection unit 32 changes, the electric connection state (the situation where a conductor 31 aand a conductor 31 bare electrically connected) changes, and the frequency characteristic of the reflection coefficient or the transmission coefficient of a resonance element 33 changes.As in the first embodiment, the reading device YS irradiates the sensor tag ST with the transmission wave SH and receives the reflected wave HH or the like from the sensor tag ST, thereby observing the frequency characteristic of the reflected wave HH and the like of the resonance element 33.In a substantially similar manner to the first embodiment, it is possible to estimate the state of the detection unit 32 based on the observed frequency characteristics of the reflected wave HH and the like by referring to the correspondence relationship between the frequency characteristics of the reflected wave HH and the like calculated in advance or experimented in advance and the state of the detection unit 32, and further estimate the physical quantity BR of the object TB.< Of Third Embodiment>As described above, in the sensor tag ST of the third embodiment, the physical quantity BR of the object TB can be estimated even when the conductivity or the dielectric constant of the detection unit 32 does not change in response to the change of the object TB.Fourth Embodiment.< Embodiment>A sensor tag of a fourth embodiment will be described.The sensor tag ST of the fourth embodiment detects an electric field representing the physical quantity BR of the object TB.<Konfiguration of Fourth Embodiment>FIG. 14 shows a configuration (part 1) of the fourth embodiment.FIG. 15 shows a configuration (part 2) of the fourth embodiment.As illustrated in FIG. 14, the sensor tag ST of the fourth embodiment has a configuration substantially corresponding to the configuration of the sensor tag ST of the first embodiment (illustrated in FIG. 1 ).In the sensor tag ST of the fourth embodiment, unlike the sensor tag ST of the first embodiment, the detection unit 42 is a varactor diode. The sensor tag ST of the fourth embodiment also includes a substrate 44. the substrate 44 supports a conductor 41 aand a conductor 41 b. The dimensions of the conductor 41a and the conductor 41b are shown in Fig. 15, for example.< Of Fourth Embodiment>FIG. 16 shows the frequency characteristic of the reflection value of the fourth embodiment.Hereinafter, it is assumed that the sensor tag ST is disposed in the vicinity of an electromagnetic noise source on the electronic circuit, for example, an IC chip.The above-described electromagnetic noise source emits an electromagnetic wave, an electric field is generated between the conductor 41 aand the conductor 41 bbased on the electromagnetic wave, and as a result, a voltage is generated between the conductor 41 aand the conductor 41 b. When the direction of the generated voltage is along the reverse bias direction of the varactor diode of the detection unit 42, the circuit constant of the detection unit 42, particularly the capacitance of the capacitor, changes depending on the magnitude of the voltage.When the capacitance of the capacitor changes, the electrical connection state of the conductor 41 aand the conductor 41 bchanges, and as a result, the frequency characteristics of the reflected wave HH and the like of the sensor tag ST change.FIG. 16 is calculated according to a similar method as in FIGS. 9, 10 to 11 of the second embodiment. As shown in FIG. 16, the frequency characteristic of the reflection amount changes when the reverse bias value is changed to 0 V, 0.1 V, and 0.2 V.As in the first embodiment, the reading device YS irradiates the sensor tag ST with the transmission wave SH and receives the reflected wave HH or the like reflected from the sensor tag ST, thereby observing the frequency characteristic of the reflected wave HH or the like of a resonance element 43.In a substantially similar manner to the first embodiment, it is possible to estimate the state of the detection unit 22 based on the observed frequency characteristics of the reflected wave HH and the like by referring to the correspondence relationship between the frequency characteristics of the reflected wave HH and the like calculated in advance or experimented in advance and the state of the detection unit 22, and further estimate the reverse bias voltage applied to the detection unit 42, i.e., estimate the magnitude of the electric field of the object TB.< Of Fourth Embodiment>As described above, in the sensor tag ST of the fourth embodiment, the electric field of the object TB can be detected even when the conductivity or the dielectric constant of the detection unit 42 does not change in response to the change in the electric field of the object TB.<>Instead of the above-described electromagnetic noise propagating through the space, i.e., the so-called radiation noise, the electromagnetic noise propagating through the wiring of the electronic circuit, i.e., the so-called conduction noise, may be detected. In a case where line noise is to be detected, two locations where a voltage due to electromagnetic noise occurs on the line are electrically connected in one-to-one correspondence to the conductor 41 aand the conductor 41 b, i.e., the wiring is performed such that a voltage due to electromagnetic noise occurs between the conductor 41 aand the conductor 41 b. Thus, the conduction noise can be detected as described above.Fifth Embodiment.< Embodiment>In a fifth embodiment, a sensor tag will be described.In contrast to the first to fourth embodiments in which the physical quantity BR of the object TB is directly detected, the sensor tag ST of the fifth embodiment indirectly detects the physical quantity BR of the object TB by combining a plurality of detection units.<Konfiguration of Fifth Embodiment>FIG. 17 shows a configuration of a sensor tag ST of the fifth embodiment.As illustrated in FIG. 17, the sensor tag ST of the fifth embodiment has a configuration substantially corresponding to the configuration of the sensor tag ST of the first embodiment (illustrated in FIG. 1 ).The sensor tag ST of the fifth embodiment includes, in addition to a main detection unit 52, a sub detection unit 52 aand a sub detection unit 52 b(this corresponds to the detection unit 42 of the fourth embodiment illustrated in FIG. 14 ). The sub-detection unit 52 aand the sub-detection unit 52 bare, for example, vibration sensors including piezoelectric elements. The sub detection unit 52 aand the sub detection unit 52 bare arranged in parallel with the main detection unit 52 between a conductor 51 aand a conductor 51 b.< Of Fifth Embodiment>In the sensor tag ST of the fifth embodiment, when the physical quantity BR of the object TB changes, the physical characteristics of the sub-detection unit 52 aand the sub-detection unit 52 bchange. When the physical properties of the sub-detection unit 52 aand the sub-detection unit 52 bchange, the physical properties of the main detection unit 52 also change.The main detection unit 52, unlike the detection units 12 to 42 of the first to fourth embodiments that directly detect the physical quantity BR of the object TB, indirectly detects the physical quantity BR via the sub detection unit 52 aand the sub detection unit 52 b.When the object TB vibrates, the sub detection unit 52 aand the sub detection unit 52 bgenerate a voltage. Thereby, a voltage is generated between the conductor 51 aand the conductor 51 b.When the direction of the voltage between the conductor 51 aand the conductor 51 bis along the reverse bias direction of the varactor diode of the main detection unit 52, the circuit constant of the main detection unit 52, particularly, the size of the capacitor, changes depending on the size of the voltage.Thereafter, as with the sensor tag ST of the fourth embodiment, the magnitude of the reverse bias voltage applied to the main detection unit 52 can be estimated by observing the frequency characteristic of the reflection amount, and moreover, the vibration of the object TB can be estimated from the magnitude of the reverse bias voltage.< Of Fifth Embodiment>As described above, in the sensor tag ST of the fifth embodiment, the vibration of the object TB can be detected even when the conductivity or the dielectric constant of the main detection unit 52, the sub detection unit 52 a, and the sub detection unit 52 bdoes not change in response to the change in the physical quantity BR of the object TB.Sixth Embodiment.< Embodiment>In a sixth embodiment, a sensor tag will be described.For the sensor tag ST of the sixth embodiment, a chipless RFID technology is used, and specifically, identification information is added to the sensor tag ST of the first to fifth embodiments.<Konfiguration of Sixth Embodiment>FIGS. 18A to 18C each show a configuration of the sensor tag ST of the sixth embodiment.The sensor tag ST of the sixth embodiment has a configuration substantially similar to the configuration of the sensor tag ST of the second embodiment (illustrated in FIG. 5 ).As shown in FIGS. 18A to 18C, the upper layer 25 of the sensor tag ST of the sixth embodiment has a conductive pattern having a single or double loop structure corresponding to the identification information "01", "10", and "11", unlike the sensor tag ST of the second embodiment. As shown in Figs. 18A to 18C, the presence or absence of the inner line pattern corresponds to whether the lower bit of the identification information is 1 or 0, and similarly, the presence or absence of the outer line pattern corresponds to whether the upper bit of the identification information is 1 or 0.< Of Sixth Embodiment>FIG. 19 shows the frequency characteristic (without shift) of the reflection value of the sixth embodiment.FIG. 20 shows the frequency characteristic (displacement in the X direction) of the reflection amount of the sixth embodiment.FIG. 21 shows the frequency characteristic (Y-direction shift) of the reflection amount of the sixth embodiment.FIG. 22 shows the frequency characteristic (Z-direction shift) of the reflection amount of the sixth embodiment.The sensor tag ST of the sixth embodiment performs an operation substantially corresponding to the operation (illustrated in FIGS. 8, 9, 10 to 11 ) of the sensor tag ST of the second embodiment.FIGS. 19, 20, 21 to 22 are calculated according to a similar method as in FIGS. 9, 10 to 11 of the second embodiment. The shift amounts dx, dy and dz shown in Figs. 8A to 8C of the second embodiment are 2 mm, 2 mm and -2 mm, respectively.Since the structure of the conductor 21 a(illustrated in FIG. 5 ) of the upper layer 25, i.e., the presence or absence of the inner conduction pattern and the presence or absence of the outer conduction pattern (illustrated in FIGS. 18A to 18C ) are different for each of the identification information "01", "10", and "11", the frequency characteristics of the reflection coefficient or the transmission coefficient of the resonance element 23 (illustrated in FIG. 5 ) are different for each of the identification information "01", "10", and "11", even when the displacement amount of the object TB is the same.By using the sensor tag ST (shown in FIG. 18A ) having the identification information "01", the sensor tag ST (shown in FIG. 18B ) having the identification information "10", and the sensor tag ST (shown in FIG. 18C ) having the identification information "11", different frequency characteristics depending on the amount of displacement of the object TB are obtained. This makes it possible to detect the displacement amount of the object TB and to read whether the identification information of the sensor tag ST is "01", "10", or "11" based on the reception situations of the three sensor tags ST.< Of Sixth Embodiment>As described above, in the sensor tag ST of the sixth embodiment, even when the conductivity or the dielectric constant of the detection unit 22 does not change according to the displacement amount of the object TB, the displacement amount of the object TB can be detected, and the identification information "01", "10", and "11" can be read.Seventh Embodiment.< Embodiment>In a seventh embodiment, a sensor tag will be described.The sensor tag ST of the seventh embodiment specifically serves to detect a change in the physical quantity BR with temporal periodicity of the object TB and read the period and amplitude of the change using the sensor tag ST of the first to sixth embodiments.<Konfiguration of Seventh Embodiment>FIG. 23 shows an arrangement (part 1) of the sensor tag ST of the seventh embodiment.FIG. 24 shows an arrangement (part 2) of the sensor tag ST of the seventh embodiment.FIG. 25 shows the shape and dimensions of the sensor tag ST of the seventh embodiment.FIG. 26 shows an operation of the sensor tag ST of the seventh embodiment.As illustrated in FIG. 24, the sensor tag ST of the seventh embodiment has a configuration substantially corresponding to the configuration of the sensor tag ST of the second embodiment (illustrated in FIG. 5 ).On the other hand, in the sensor tag ST of the seventh embodiment, unlike the sensor tag ST of the second embodiment, as illustrated in FIG. 24, a printed circuit board DB is disposed on a back surface of the lower layer 26 of the sensor tag ST with spacers SP interposed therebetween.The upper layer 25 and the lower layer 26 of the sensor tag ST have the shapes and dimensions shown in FIG. 25.As illustrated in FIG. 23, the reader YS transmits the transmission wave SH to the sensor tag ST, receives the reflected wave HH from the sensor tag ST, and calculates a spectrum of the received reflected wave HH.< Of Seventh Embodiment>In the seventh embodiment, as in the second embodiment, it is assumed that the vibration of the object TB is detected.< Operating Principle>The sensor tag ST of the seventh embodiment operates as follows.When the physical quantity BR of the object TB changes, the shape of the detection unit 22 (illustrated in FIG. 5 ), the relative position between the conductor 21 aand the conductor 21 b(illustrated in FIG. 5 ) changes, and the frequency characteristic of the reflection coefficient or the transmission coefficient of the resonance element 23 changes.The reader YS monitors a spectrum of the reflected wave HH or the like reflected by the sensor tag ST from the transmission wave SH transmitted from the reader YS. The reader YS detects the frequency of the periodic change from the frequency intervals of the spectrum and, on the other hand, the amplitude of the periodic change from the pattern of the spectrum.< Of Operation>Specifically, the sensor tag ST of the seventh embodiment operates as follows.The reflection value of the sensor tag ST is 0 dB because the circuit board DB is present (as illustrated in FIG. 24 ).A reflection phase in the sensor tag ST is illustrated in FIG. 26. FIG. 26 is calculated according to a similar method as in FIGS. 9, 10 to 11 of the second embodiment.When the detection unit 22 detects the change in the physical quantity BR with temporal periodicity, the reflection amount and the reflection phase of the resonance element 23, in other words, the reflection coefficient, have temporal periodicity.Therefore, a reflection coefficient R is expressed by the following Fourier series.Cn is an nth-order coefficient, fv is a change frequency of the physical quantity BR of the object TB, and t is time. The coefficient Cn is calculated as follows.Tv is a period of change in the physical quantity BR of the object TB and is a reciprocal of fv. From the above equation, an electric field Er of the reflected wave HH can be expressed as follows.Ei is an electric field of the transmission wave SH radiated from the reader YS, and A and fi are amplitude and frequency of Ei, respectively. As described above, the reflected wave HH has a harmonic component fi+nfvin addition to fiwhen the reader YS transmits the transmission wave SHat a single frequency fi.The reader YS transmits the transmission wave SH at a single frequency. When the physical quantity BR of the object TB periodically varies in time, the harmonic component calculated by the above equation appears in the spectrum of the reflected wave HH.FIG. 27 shows the calculation results (vibration in the X direction) of an n-th order coefficient Cn of the seventh embodiment.FIG. 28 shows the calculation results (vibration in the Y direction) of an n-th order coefficient Cn of the seventh embodiment.FIG. 29 shows the calculation results (vibration in the Z direction) of an n-th order coefficient Cn of the seventh embodiment.Ax, Ay, and Az are amplitudes (in mm) of the vibration of the object TB.In FIGS. 27, 28 to 29, it is assumed that X-polarized waves are incident.Cnrepresents the amplitude of an n-th harmonic frequency component, so that the spectrum of the reflected wave HHalso has a similar pattern as illustrated in FIGS. 27, 28 to 29.The spectrum described above is a discrete spectrum having a component at the frequency of (fi+nfv). The frequency intervals of the spectrum are determined by fv, i.e. the frequency of the periodic change.The pattern of the spectrum is determined by the amplitude of the periodic variation. Therefore, the frequency and the amplitude of the periodic change can be estimated from the correspondence relationship between the spectrum of the reflected wave HH calculated in advance or experimentally determined and the spectrum of the observed reflected wave HH.< Of Seventh Embodiment>As described above, in the seventh embodiment, for example, the change frequency and the change amplitude of the physical quantity BR of the object TB can be read without obtaining the spectrum of the reflected wave by sampling the frequency of the electromagnetic wave transmitted from the reading device YS, that is, by setting the frequency of the transmission wave SH transmitted from the reading device YS to a single frequency, observing the harmonic component that appears when the physical quantity BR of the object TB varies with time, and analyzing the pattern of the observed harmonic component.Eighth Embodiment.<Acht Embodiment>In an eighth embodiment, a sensor tag system will be described.A sensor system SS of the eighth embodiment uses the sensor tag ST of the first to seventh embodiments to detect failure and abnormality of electric devices, a structure, and the like that are the monitoring target KTB, and the states of the electric devices, the structure, and the like are monitored.<Konfiguration of Eighth Embodiment>FIG. 30 shows a configuration of the sensor system SS of the eighth embodiment.As illustrated in FIG. 30, the sensor system SS of the eighth embodiment includes the sensor tags ST 1 to ST 3 (corresponding to the sensor tags ST of the first to seventh embodiments). As illustrated in FIG. 30, the sensor tags ST 1 to ST 3 are disposed on surfaces of electrical devices, structures, and the like that constitute the monitoring target KTB.< Of Eighth Embodiment>The reader YS detects a change (e.g., vibration of a bridge, vibration of a structure, and electromagnetic noise in a structure and in the vicinity of an electronic device) of the physical quantity BR of the monitoring target KTB via the sensor tags ST 1 to ST 3 using the detection method described in the first to seventh embodiments.The reading device YS compares the detected physical quantity BR of the monitoring target KTB with, for example, a predetermined threshold value to determine whether or not an abnormality has occurred in the monitoring target KTB.< Of Eighth Embodiment>As described above, in the sensor system SS of the eighth embodiment, it is possible to monitor the state of the monitoring target KTB such as an electric device and a structure using the sensor tag ST of the first to seventh embodiments, that is, using the sensor tag ST that achieves the effects of the first to seventh embodiments.Ninth Embodiment.< Embodiment>A sensor system of the ninth embodiment will be described.The sensor system SS of the ninth embodiment uses the sensor tag ST of the first to seventh embodiments to identify an individual such as an electronic device and a robot. For the identification, for example, the identification information (illustrated in FIGS. 18A to 18C ) described in the sixth embodiment is used.In addition to the above-mentioned identification, the sensor system SS of the ninth exemplary embodiment identifies a person on the basis of what are known as artifact metrics, more precisely on the basis of features of the person in which the sensor tag ST is located.<Konfiguration of Ninth Embodiment>FIG. 31 shows a configuration of the sensor system SS of the ninth embodiment.As illustrated in FIG. 31, the sensor system SS of the ninth embodiment includes a sensor tag ST (corresponding to the sensor tag ST of the first to seventh embodiments).< Of Ninth Embodiment>The reading device YS detects a change in the physical quantity BR (e.g., vibrations and electromagnetic noises of an unmanned aerial vehicle and electromagnetic noises of an electronic device) of the identification target STB (e.g., an unmanned aerial vehicle) via the sensor tag ST using the detection method described in the first to seventh embodiments.The reader YS compares the detected physical quantity BR of the identification target STB with, for example, a threshold value determined by artifact metrics, for example, pre-detected information indicating a relationship between the type of the person, the identification information, and the physical quantity BR, and thus determines whether or not the identification target STB is proper or incorrect, i.e., whether or not the identification target STB is genuine.< Of Ninth Embodiment>As described above, in the sensor system SS of the ninth embodiment, it is possible to identify an individual such as an electronic device and a robot using the sensor tag ST of the first to seventh embodiments, that is, using the sensor tag ST that achieves the effects of the first to seventh embodiments.The above-described embodiments may be combined without departing from the gist of the present disclosure, and components in each embodiment may be eliminated or changed as appropriate, or other components may be added.INDUSTRIAL APPLICABILITYA sensor tag according to the present disclosure may be used to detect a physical quantity of an object even if the conductivity or the dielectric constant of a detection unit does not change although the physical quantity of the object changes.LIST OF REFERENCE CHARACTERS11 a: conductor, 11 b: conductor, 12: detection unit, 13: resonant element, 21 a: conductor, 21 b: conductor, 22: detection unit, 23: resonant element, 24 a: substrate, 24 b: substrate, 25: upper layer, 26: lower layer, 31 a: conductor, 31 b: conductor, 32: detection unit, 33: resonant element, 41 a: conductor, 41 b: conductor, 42: detection unit, 43: resonant element, 44: substrate, 51 a: conductor, 51 b: conductor, 52: main detection unit, 52 a: sub-detection unit, 52 b: sub-detection unit, BR: physical quantity, BR 1: physical quantity, BR 2: physical quantity, CA: capacitor, Cn: coefficient, DK: electric circuit, dx: displacement amount, dy: displacement amount, dz: displacement amount, Er: electric field, fi: single frequency, HH: reflected wave, IN: inductor, KTB: monitoring target, R: reflection coefficient, SH: transmission wave, SP: spacer, SS: sensor system, ST: sensor tag, ST 1: sensor tag, ST 3: sensor tag, STB: identification target, TB: object, TB 1: object, TB 2: object, TE: resistor, YS: reader

Claims

A sensor tag, comprising: a plurality of conductors arranged close to each other and forming a resonance element; and a detection unit arranged between the plurality of conductors and having a physical property that changes due to a change in a physical size of an object to be detected by the detection unit.The sensor tag according to claim 1, wherein the relative positions of the plurality of conductors change depending on a change in the shape of the sensor unit.The sensor tag according to claim 2, wherein the sensor unit is a spring.The sensor tag according to claim 1, wherein the sensing unit comprises an electric circuit whose circuit constant changes depending on a change in a physical quantity of the object.The sensor tag of claim 4, wherein the electrical circuit is an active element.A sensor tag comprising: a plurality of conductors arranged close to each other and forming a resonance element; and a main detection unit and a sub detection unit arranged between the plurality of conductors, wherein a physical property of the main detection unit changes due to a change in a physical property of the sub detection unit due to a change in a physical size of an object to be detected by the main detection unit and the sub detection unit.The sensor tag according to claim 6, wherein the sub-sensing unit is capable of sensing vibrations that are a physical quantity of the object, and the main sensing unit includes an active element whose physical characteristics change by application of a voltage generated due to the sensing of the vibrations by the sub-sensing unit.The sensor tag according to the sensor tag 1, further comprising: at least one line pattern for indicating identification information.The sensor tag of claim 8, wherein the at least one conductive pattern is in the form of a loop.The sensor tag according to claim 1, wherein a plurality of two-dimensionally arranged elements, each of the plurality of elements including the plurality of conductors and the sensing unit.A method for reading a sensor tag, the method comprising: estimating a period and amplitude of a change in a physical quantity of the object due to a change in a reflection characteristic or a transmission characteristic of the sensor tag according to any one of claims 1 to 6, in response to receiving a transmission wave having a single frequency.The method for reading a sensor tag according to claim 11, wherein a period and amplitude of vibration of the object are estimated.The method for reading a sensor tag according to claim 11, wherein a period and amplitude of the oscillations of electromagnetic noise are estimated.A sensor system comprising: the sensor tag according to any one of claims 1 to 10.The sensor system of claim 14, wherein a state of the object is monitored.The sensor system of claim 14, wherein an individual identification of the object is performed.

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