JP4947713B2 - Vibration detector - Google Patents

Description

  The present invention relates to a vibration detection device that detects mechanical external vibrations, and more particularly to a vibration detection device that can detect mechanical vibrations far away by radio.

  Development of a vibration detection device that detects external vibration with a sensor unit separated from the main body and transmits anomaly to the main body by wireless communication for the purpose of use as a security device such as a vehicle anti-theft device or an intrusion detection device Is underway. A system that separates the interrogator, which is the main body, and the sensor unit and wirelessly transmits information between them is a particularly advantageous method when the attachment target of the sensor unit can move, such as a vehicle anti-theft device.

  Patent Document 1 discloses an example of an abnormality monitoring system in which various abnormalities such as mechanical external vibration applied to such an attachment target are detected by a detection device, and are transmitted wirelessly to an interrogator as abnormal state information. Is disclosed. The configuration of this abnormality monitoring system will be described with reference to FIG. FIG. 5 is an example of a configuration diagram of a main part of a vibration detection device in the abnormality monitoring system described in Patent Document 1. The vibration detection device 51 includes a vibration sensor 57 and a power supply unit 56, and further includes a vibration sensor unit 52 including various processing circuits having a CPU (central processing unit), and an interrogator 53 as a main body. Among these, various settings of the interrogator 53 can be changed by transmitting setting instruction information 55 from the control device 54 to the interrogator 53.

  The configuration of the vibration sensor unit 52 which is a sensor device that detects external vibration is as follows. When external vibration is detected by the vibration sensor 57, the vibration information is sent to the detection information acquisition unit 62 in the control unit 60. Further, it is sent to the abnormality determination unit 63, and the abnormality determination unit 63 reads the threshold information 66 stored in the storage unit 61 and compares it with the vibration information. If it is determined that the vibration is abnormal, the vibration information is transmitted to the information transmission instruction unit 64 and transmitted to the wireless transmission unit 59, and is transmitted to the interrogator 53 as abnormal state information 67 therefrom. The power supply unit 56 is a battery and supplies power to various parts of the vibration sensor unit 52.

  On the other hand, separately from the case where the external vibration is detected, the time measuring unit 58 counts the elapsed time according to the instruction of the power supply determining unit 65, and instructs the information transmission instruction unit 64 every time 2 minutes pass. The signal is transmitted to the interrogator 53. Unlike the abnormal state information 67, this wireless signal is used to notify the interrogator 53 that the vibration sensor unit 52 is operating normally even when the vibration sensor 57 does not detect external vibration. It is. By fixing the transmission interval of this radio signal every 2 minutes, the wireless transmission to the interrogator 53, which has been performed at any time even before normal operation, is canceled, and the battery life in the power supply unit 56 is improved. Yes. Non-Patent Document 1 is a general reference document that discusses the intensity of scattered waves when electromagnetic waves radiated from an antenna are scattered and returned to the antenna again.

JP 2006-79284 A Yasuto Mushiaki “Antenna / Radio Wave Propagation” Corona, Inc. Published December 25, 2002 39th Edition p. 41

  As disclosed in Patent Document 1, in a conventional vibration detection device, for example, a piezoelectric element is used as a detection element of a vibration sensor unit, and a potential difference due to an electromotive force induced in the piezoelectric element by external vibration is detected as an electric signal. Was. The control unit in the vibration sensor unit performs signal processing such as amplification and filtering of the electrical signal, and a series of arithmetic processing for determining the presence or absence of external vibration, and then information on the external vibration from the wireless transmission unit. To the interrogator as electromagnetic waves. As described above, in the system of the conventional vibration detection device, the presence of the vibration sensor, the control unit, the wireless transmission unit, and the power supply unit for driving each unit is indispensable. Therefore, since the vibration sensor unit requires a complicated system processing configuration and at least a power source, it is difficult to reduce the size and weight of a general tag shape. In addition, since it has a built-in power source such as a battery, there are restrictions on its operating time and usage environment.

  If the vibration sensor unit is equipped with a power supply circuit such as a rectenna circuit that extracts electromotive force from electromagnetic waves transmitted from the interrogator, it is possible to omit the battery and avoid restrictions on operating time and usage environment. is there. However, in this case, since a rectenna circuit having a relatively complicated configuration is further added to the vibration sensor unit, it is difficult to reduce the size. In addition, since the amount of power supplied by the rectenna circuit is generally small, it is difficult to mount various processing circuits having a CPU as in the case of Patent Document 1 in the vibration sensor unit. It is necessary to develop a transmission circuit separately.

  Accordingly, an object of the present invention is a vibration detection device including a vibration sensor unit and an interrogator, wherein information communication between the vibration sensor unit and the interrogator is performed wirelessly, and the vibration sensor unit Is to provide a vibration detection device that does not have a complicated power supply circuit such as a rectenna circuit as well as a battery. In addition, a vibration detection device that can downsize the vibration sensor unit by providing a simple circuit for transmitting information including external vibration detected by the vibration sensor unit to the interrogator is provided. It is to be.

  According to the present invention, an antenna having a pair of electrode terminals, a piezoelectric element electrically connected between the pair of electrode terminals and capable of detecting external vibration, and electrically connected in parallel with the piezoelectric element. A vibration sensor unit having a diode, a function of radiating electromagnetic waves to the vibration sensor unit, and a function of receiving the scattered waves formed by scattering the electromagnetic waves received by the vibration sensor unit and monitoring the scattered waves A vibration detection device comprising: an interrogator comprising: the scattering caused by a change in impedance of the diode in a frequency band of the electromagnetic wave due to a potential difference induced in the piezoelectric element by the external vibration. By detecting a change in at least one of wave intensity and frequency, a vibration detection device for detecting the external vibration can be obtained.

  Here, as a solution in the present invention, a diode is connected between the first terminal and the second terminal, which are a pair of electrode terminals provided in the antenna of the vibration sensor unit. It is configured to have a piezoelectric element electrically connected in parallel and capable of detecting external vibration. When an electromagnetic wave of a specific frequency is radiated from the interrogator to the vibration sensor unit, the frequency difference of the radiated electromagnetic wave is constant due to the potential difference due to the electromotive force excited by the piezoelectric element due to external vibration and the action of the diode. The second electromagnetic wave whose frequency is shifted by the value of is excited as a scattered wave in the antenna.

  This second electromagnetic wave includes electromagnetic waves of two types of frequency components shifted from the first electromagnetic wave radiated from the interrogator by a fixed frequency in the high frequency direction and the low frequency direction. The shift amount corresponds to the frequency of the external vibration detected by the vibration sensor unit. Further, the relative intensity of the second electromagnetic wave with respect to the received first electromagnetic wave varies depending on the intensity of the detected external vibration. At this time, when the external vibration is not applied to the vibration sensor unit, the electromagnetic wave of the component whose frequency is shifted is not included in the second electromagnetic wave. However, the electromagnetic wave having the same frequency component as that of the first electromagnetic wave is always included in the second electromagnetic wave as long as the vibration sensor unit can operate. Therefore, the vibration detection device according to the present invention can always check whether the vibration detection device is operating normally by detecting the electromagnetic wave having the same frequency component as the first electromagnetic wave, which is included in the second electromagnetic wave. Has characteristics.

  That is, the present invention provides an antenna having a pair of electrode terminals, a piezoelectric element electrically connected between the pair of electrode terminals and capable of detecting external vibration, and electrically connected in parallel with the piezoelectric element. A vibration sensor unit having a diode, a function of radiating electromagnetic waves to the vibration sensor unit, and a function of receiving the scattered waves formed by scattering the electromagnetic waves received by the vibration sensor unit and monitoring the scattered waves A vibration detection device comprising: an interrogator comprising: the scattering caused by a change in impedance of the diode in a frequency band of the electromagnetic wave due to a potential difference induced in the piezoelectric element by the external vibration. The vibration detection device detects the external vibration by detecting a change in at least one of wave intensity and frequency.

  The interrogator includes an antenna, and at least one of the antenna included in the interrogator and the antenna included in the vibration sensor unit is a dipole antenna.

  According to the present invention, in the vibration detection device that separates the interrogator and the vibration sensor unit and transmits the detection result of the external vibration in the vibration sensor unit to the interrogator by electromagnetic waves, a battery or a rectenna circuit is provided on the vibration sensor unit side. Therefore, it is possible to configure a vibration detection device that has few restrictions on the period of use and the environment of use of the vibration sensor unit. In addition, the detection of external vibration in the vibration sensor unit and the transmission circuit of the detection result also have a simple configuration with a small number of parts. For this reason, it is easy to reduce the size and weight of the vibration sensor part, and the vibration sensor part can be made into a small shape such as a tag shape, so that there is a restriction on the attachment location to the vibration test object that is the object of vibration measurement. Can be small. Furthermore, since the vibration sensor unit is small and light, there is little possibility of restraining the vibration of the vibration test specimen, so that highly accurate vibration measurement is possible. Even when no external vibration is applied, it is possible to confirm whether the vibration detection device is operating normally by receiving the electromagnetic wave from the vibration sensor unit.

  Hereinafter, the operation of the vibration detection apparatus according to the embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing the principle of detection of external vibration in the vibration detection device according to the present invention. A diode and a piezoelectric element are electrically connected between a first terminal and a second terminal of an antenna provided in the vibration sensor unit. The case where it is connected in parallel is shown. In FIG. 1, the vibration detection device includes an interrogator 17 and a vibration sensor unit 11, and the interrogator 17 includes an antenna unit 18. When the first electromagnetic wave 15 is radiated from the antenna unit 18, a part of the transmission power is scattered by the antenna 12 provided in the vibration sensor unit 11, and a part of the scattered electromagnetic wave is Two electromagnetic waves are received again by the antenna 18 of the interrogator 17. Here, the vibration sensor unit 11 has a configuration in which a diode 13 and a piezoelectric element 14 are electrically connected in parallel between a first terminal and a second terminal of the antenna 12, and other circuit elements are Basically unnecessary. For this reason, it is possible to configure a circuit suitable for miniaturization of the apparatus with a small number of necessary circuit elements.

  When an external vibration is applied to the piezoelectric element 14 constituting the circuit, a potential difference is induced between both electrodes of the piezoelectric element 14 due to the vibration, and thereby the impedance of the diode 13 changes. That is, when the potential difference due to the electromotive force of the piezoelectric element 14 is given in a direction in which a forward bias is applied to the diode 13, the impedance of the diode 13 shows a small value. On the other hand, when a potential difference that is a reverse bias is applied from the piezoelectric element 14 to the diode 13, the impedance of the diode 13 shows a large value. Therefore, the impedance of the diode 13 connected between the first terminal and the second terminal, which is the feeding point of the antenna 12, varies according to the period of the external vibration applied, and the magnitude of this impedance change is It is related to strength. Therefore, the power intensity and frequency component of the second electromagnetic wave 16 that is scattered by the antenna 12 of the vibration sensor unit 11 and received by the antenna unit 18 of the interrogator 17 changes according to the relationship between the impedance and the scattered wave described later. . Therefore, by analyzing the received second electromagnetic wave 16, it is possible to know information about external vibration given to the vibration sensor unit 11.

  In the vibration detection device of the present invention, the relationship between the first electromagnetic wave emitted by the interrogator and the received second electromagnetic wave is as follows. First, consider the received power due to the scattered wave received by the antenna unit of the interrogator when the load resistance Rl is connected to the antenna of the vibration sensor unit. First, the effective scattering cross-section As of the antenna of the vibration sensor unit having a pair of electrode terminals to which the load resistance Rl is connected is expressed by Equation 1 from the description on page 41 of Non-Patent Document 1.

Here, R is the radiation resistance of the antenna of the vibration sensor unit, λ is the wavelength of the first electromagnetic wave, and Gr is the gain of the antenna of the vibration sensor unit. The number 1, when the load resistance R _l varies relative to the radiation resistance R of the antenna of the vibration sensor unit is seen to vary the effective scattering cross section A _s accordingly.

Next, the transmission power W _t emitted as a first electromagnetic wave from the interrogator is, consider the effect that is scattered at the antenna of the vibration sensor unit having an effective scattering cross section A _s. At this time, a part of the second electromagnetic wave that is a scattered wave in the antenna is received again by the antenna unit of the interrogator. Maximum active power W _e of the second electromagnetic wave interrogator receives is expressed as the number 2.

Here, G _a gain of the antenna of the interrogator, d is the propagation distance between the antenna of the vibration sensor portion and the antenna portion of the interrogator. A _e is the maximum effective power area that can be taken out by the antenna unit of the interrogator, and is expressed by Equation 3 from the description on page 41 of Non-Patent Document 1.

  Here, when Expression 3 is substituted into Expression 2, Expression 4 is obtained.

Thus, W _e is the number 1, than the number 4, is expressed as the number 5.

Here, again W _e is the maximum active power of the second electromagnetic wave is scattered wave, R represents the radiation resistance of the antenna of the vibration sensor unit, the load resistance R _l is connected to the antenna of the vibration sensor unit, lambda first wave , G _a is the gain of the antenna of the interrogator, G _r is the gain of the antenna of the vibration sensor, d is the propagation distance between the two antennas, and W _t is the transmission power from the interrogator. Therefore, the relationship between the maximum effective power of the scattered wave by the antenna of the sensor unit and the load resistance is derived from Equation 5.

Here, consider a case where the load resistance R _l of the vibration sensor unit periodically changes. When a potential difference is induced in the piezoelectric element of FIG. 1 by external vibration, an AC bias is applied to the diode, so that the impedance varies with the frequency of the external vibration and repeats a large value and a small value. It will be. Therefore, the load resistance R _l connected to the antenna of the vibration sensor unit is expressed by Equation 6.

Here, ΔR _l is the maximum change amount of the load resistance R _l , f _v is a fluctuation frequency due to external vibration, t is time, and R _lb is a bias resistance.

Further, the transmission power W _t radiated from the interrogator to the sensor unit is expressed by Equation 7.

Here, W _t0 and f ₀ are the maximum power radiated from the interrogator and its frequency, respectively. In general, f ₀ is much larger than f _v .

Therefore, the maximum active power W _e of the second electromagnetic wave interrogator receives substitutes the number 6 and number 7 to number 5 above, expressed as the number 8.

Here, if the number 9 is established, the maximum active power W _e of the second wave of the is expressed as the number 10.

The first term in the parentheses {} of the formula 10 indicates the f ₀ component having the same frequency as that of the first electromagnetic wave radiated from the interrogator among the second electromagnetic waves. Item 3 shows components of f ₀ −f _v and f ₀ + f _v , which are components modulated by the variation frequency fv, of the load resistance R ₁ connected to the antenna of the vibration sensor unit. Therefore, by analyzing the components of the second and third terms, it is possible to determine the variation component of the load resistance R _l of the vibration sensor unit. Wherein the street, the point variation of the load resistance R _l of the vibration sensor unit because than synchronized to an external vibration sensor unit is measuring, in this apparatus, the sensor unit is separate from the interrogator It is possible to detect external vibrations at and to propagate the information to the interrogator by wireless communication. That is, it can function as a vibration detection device that can detect vibrations in the distance by radio.

FIG. 2 is a graph schematically showing the relationship between the value of the load resistance R _l connected to the antenna of the vibration sensor unit and the sideband intensity of the second electromagnetic wave by the vibration detection device of the present invention, The horizontal axis is the resistance value, and the vertical axis is the electromagnetic wave intensity. According to FIG. 2, the sideband intensity of the second electromagnetic wave decreases as the value of the load resistance R _l increases. This is what has been represented in Equation 5 above, the transmission power W _t from the interrogator to meet the relationship between the R _l and W _e in the case of the constant. In addition, in FIG. 2, when the radiation resistance R of the antenna of the vibration sensor unit is increased, the radiation resistance R is from 21 when the value of the radiation resistance R is small, 22 when the value of R is medium, and 23 when the value of R is large. In turn, it is shown that the sideband intensity of the second electromagnetic wave gradually increases. This change occurs regardless of the value of the load resistance R _l at the vibration sensor unit.

FIG. 3 is a graph schematically showing the spectrum of the second electromagnetic wave when external vibration is applied to the vibration sensor unit in the vibration detection device of the present invention, where the horizontal axis represents frequency and the vertical axis represents electromagnetic wave intensity. is there. The second electromagnetic wave received by the antenna unit of the interrogator has a spectrum composed of a carrier wave 31 having the same frequency component as the first electromagnetic wave and two sidebands 32 and 33 having vibration information existing on both sides thereof. Show. In the case of the first solution of the present invention, the strength of the two sidebands 32 and 33 depends on the strength of the external vibration measured by the sensor unit, and the frequency of the two sidebands is The spectrum shifted left and right by the frequency f _{v of the} external vibration measured around the frequency f _{0 of the} carrier wave 31 is shown. It should be noted that the intensity of the two sidebands becomes substantially the same value due to the above-described equation (10).

  FIG. 4 is a graph schematically showing the relationship between the intensity and propagation distance of the carrier wave 41 and the sideband 42 of the second electromagnetic wave received by the antenna unit of the interrogator in the vibration detection device of the present invention. Yes, the horizontal axis represents the propagation distance, and the vertical axis represents the electromagnetic wave intensity. Although the intensity of the sidebands 42 suddenly decreases as the propagation distance increases, the intensity gradually decreases thereafter, and even if there is some propagation distance, the interrogator antenna section changes the sidebands 42. It can be seen that it is possible to receive at the strength of.

  The piezoelectric element mounted on the vibration sensor unit of the present invention, which detects an external vibration and generates a potential difference, has a cantilever structure, both of which have an optimal vibration mode according to the assumed form of external vibration. A piezoelectric element having a cantilever structure or a diaphragm structure is preferable. For example, when a piezoelectric element having a cantilever structure is manufactured, a film formation technique such as an RF-sputtering method or an aerosol deposition method is used on a silicon piece having a cantilever structure as a structure, and the thickness is about 10 μm. A PZT film may be laminated to form a piezoelectric vibrator. In addition, it is preferable to form a Pt / Ti film as an electrode in the thickness direction of the PZT film that is a piezoelectric body by the same method. This electrode is electrically connected to a first terminal and a second terminal of an antenna provided in the vibration sensor unit. As is well known, the resonance frequency and strain amount of a vibrator having a cantilever structure are defined by its dimensions, Young's modulus, and density.

  In order to improve the sensitivity of the vibration detection device and extend the propagation distance between the interrogator and the vibration sensor unit, it is necessary to use a semiconductor element that exhibits a large impedance change even for a small potential difference in the vibration sensor unit. Preferably, a PIN diode can be used. A general diode has a forward rising voltage of about 0.6 V, but a Schottky diode has a lower rising voltage than that and can be driven at a high frequency corresponding to the frequency band used as the first electromagnetic wave. Therefore, it can also be used suitably.

  A vibration detector based on the solution of the present invention was manufactured as follows, and the wireless transmission distance was measured. First, half-wave dipole antennas were used as antennas of the interrogator and vibration sensor, respectively. The radiated power of the first electromagnetic wave from the interrogator was 10 dBm (frequency: 2.45 GHz) defined as the upper limit of the output of the specific low-power radio station in the Radio Law. In addition, the reception sensitivity of the interrogator was selected to be −80 dBm in consideration of environmental noise as a general guide. The half-wave dipole antenna described above has a 36 μm-thick copper foil laminated on an FR-4 substrate (FR-4 grade weather-resistant glass cloth base epoxy resin laminate) with a total length of about 30 mm (a gap of 2 mm in the center). Between which a diode and a piezoelectric element as a vibration detecting element were mounted), and a rectangular pattern having a width of about 10 mm was used.

As the diode in the vibration sensor unit, a PIN diode: product number BAP50-03 (manufactured by Philips, The Netherlands) was used. In addition, a piezoelectric element is formed by laminating a PZT film having a thickness of 10 μm on the silicon piece having the cantilever structure by RF-sputtering, and this is packaged to be parallel to the PIN diode as a vibration detection element. Connected to. When this vibration detection element is used as a security device, the object of vibration detection is mainly glass vibration. The vibration detection element in the embodiment is designed so that the sensitivity of vibration detection increases from a few kHz, which is a vibration generated when the glass sheet is struck strongly, to a frequency of about 200 kHz, which is strongly detected when the glass is broken. Therefore, when an acceleration of 1 G (9.8 m / s ² ) due to vibration of such a frequency is detected, it has an output voltage of 0.1 V _pp (Peak to Peak). Note that the magnitude of acceleration detected by the vibration detection element and the output voltage at that time are in a substantially proportional relationship. Twenty vibration detection elements were produced and used for the following measurements.

  An ultrasonic transducer that generates vibrations from 1 kHz to 200 kHz was installed on a metal plate, and the vibration detection element of the vibration sensor unit of the present invention was attached to the metal plate. The output intensity of the ultrasonic transducer installed on the metal plate is adjusted so that 2G acceleration is applied to the vibration detecting element. This acceleration is comparable to the strength of vibration generated when a general glass plate used as a window glass is broken. An ultrasonic vibration of these frequencies is generated in the ultrasonic transducer, the vibration detection element detects the vibration, and the interrogator receives the second electromagnetic wave transmitted by the vibration sensor. Here, the distance between the interrogator and the vibration sensor unit was sequentially changed, the maximum distance at which the second electromagnetic wave could be measured as a significant signal by the interrogator was defined as the maximum radio propagation distance, and the distance was measured. . The maximum wireless propagation distance varies depending on the frequency of vibration generated by the ultrasonic transducer, and varies depending on the vibration detecting element. However, the maximum wireless propagation distance in the combination of the vibration sensor unit and the interrogator is in the range of 0.8 to 2 m regardless of the frequency between 1 kHz and 200 kHz and any of the 20 vibration detection elements. Met. This propagation distance is a distance that can be sufficiently used as a vibration detection device when a vehicle antitheft device is assumed.

  Next, assuming a use as a vehicle antitheft device, the vibration detection element according to the present invention was attached to a door glass of a passenger car, and a window glass destructive test was performed. From the 20 vibration detection elements, an element having the shortest maximum radio propagation distance of 0.8 m is selected, and this is attached to the door glass, and is positioned at a distance of 0.8 m from the vibration sensor unit. An interrogator antenna was placed. In this state, the door glass was smashed with a hammer, and the vibration generated at that time was detected by the vibration detection element, and it was measured whether it could be transmitted as a significant signal to the interrogator. As a result, the interrogator succeeded in receiving the second electromagnetic wave from the vibration sensor unit as a significant signal. From this, it can be said that the vibration detection device according to the present invention can sufficiently withstand use for crime prevention.

  As described above, according to the present invention, it is possible to realize a vibration detection device configured to separate an interrogator and a vibration sensor unit and transmit an external vibration detection result in the vibration sensor unit to the interrogator using electromagnetic waves. Can do. As a result, the vibration sensor unit does not have a complicated power supply circuit such as a battery or a rectenna circuit, and the external vibration detection element and the detection result transmission circuit in the vibration sensor unit have a simple configuration with a small number of parts. Can be realized. As a result, it is possible to realize highly accurate vibration measurement by reducing the size and weight of the vibration sensor unit and reducing the restraint of vibration of the vibration test object that is the object of vibration measurement. It should be noted that the above description is for explaining the effects in the case of the embodiment of the present invention, and is not intended to limit the invention described in the claims or to reduce the scope of the claims. Absent. Moreover, each part structure of this invention is not restricted to said embodiment, A various deformation | transformation is possible within the technical scope as described in a claim.

The figure which showed the principle of the detection of the external vibration in the vibration detection apparatus in the solution means of this invention. Graph showing the relationship between the load resistance R _l and sideband intensity of the second electromagnetic wave at the antenna of the vibration sensor unit in the vibration detecting device of the present invention. The graph which showed typically the spectrum of the 2nd electromagnetic wave in the vibration detection device of the present invention. The graph which showed typically the relationship between the intensity | strength of the carrier wave and sideband of 2nd electromagnetic waves, and propagation distance in the vibration detection apparatus of this invention. The example of the block diagram of the principal part of the detection apparatus in the prior art of a vibration detection apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Vibration sensor part 12 Antenna 13 Diode 14 Piezoelectric element 15 1st electromagnetic wave 16 2nd electromagnetic wave 17 Interrogator 18 Antenna part 21 When radiation resistance R is small 22 When radiation resistance R is medium 23 When radiation resistance R is large 31 , 41 Carrier waves 32, 33, 42 Sideband 51 Vibration detection device 52 Vibration sensor unit 53 Interrogator 54 Control device 55 Setting instruction information 56 Power supply unit 57 Vibration sensor 58 Timekeeping unit 59 Wireless transmission unit 60 Control unit 61 Storage unit 62 Detection Information acquisition unit 63 Abnormality determination unit 64 Information transmission instruction unit 65 Power supply determination unit 66 Threshold information 67 Abnormal state information

Claims (2)

A vibration having an antenna having a pair of electrode terminals, a piezoelectric element electrically connected between the pair of electrode terminals and capable of detecting external vibration, and a diode electrically connected in parallel with the piezoelectric element. A sensor unit;
A vibration provided with an interrogator having a function of radiating electromagnetic waves to the vibration sensor unit and a function of receiving scattered waves formed by scattering the electromagnetic waves received by the vibration sensor unit and monitoring the scattered waves. A detection device,
By detecting a change in at least one of the intensity and frequency of the scattered wave caused by a change in impedance of the diode in the frequency band of the electromagnetic wave due to a potential difference induced in the piezoelectric element by the external vibration. A vibration detection apparatus for detecting the external vibration.   The vibration detection apparatus according to claim 1, wherein the interrogator includes an antenna, and at least one of the antenna included in the interrogator and the antenna included in the vibration sensor unit is a dipole antenna.

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