JP4539920B2 - Vibration wave detection method and apparatus - Google Patents

Description

  The present invention relates to a vibration wave detection method and apparatus for electrically detecting the intensity of a vibration wave for each frequency band using a plurality of resonators having different resonance frequencies.

  A plurality of resonators having different resonance frequencies are arranged and selectively resonated with a specific resonance frequency for each resonator with respect to a vibration wave such as a sound wave, and the resonance level of each resonator is electrically There is a resonator array type vibration sensor that converts and outputs a dynamic signal and detects the intensity of each vibration wave in each frequency band (for example, Non-Patent Document 1 or Non-Patent Document 2).

  In a conventional vibration sensor, a piezoresistor is formed near the support portion of the resonator, and a change in the resistance value of the piezoresistor caused by the vibration (resonance) of the resonator is detected by a Wheatstone bridge, etc. A typical output signal. In particular, the sensor of Non-Patent Document 2 obtains an output signal while switching the Wheatstone bridge output in each resonator by a multiplexer.

  A method of controlling the gain of a specific frequency band of an input vibration wave with a simple circuit configuration of a resonator array type has been proposed (Patent Document 1 or Patent Document 2). For example, in the technique of Patent Document 1, in a resonator array type vibration sensor, each piezoresistor provided in each resonance beam is connected in parallel. The gain in a specific frequency band is controlled by changing the power supply voltage applied to the parallel circuit or changing the resistance value by changing the shape of the piezoresistor.

Further, the technique of Patent Document 2 utilizes the fact that the magnitude of distortion varies depending on the position of the resonant beam, so that the piezoresistor is applied to each resonant beam so that the level of the output signal in each frequency band becomes a desired level. Is adjusted to control the gain of a specific frequency band.
W. Benecke et al., "A Frequency-Selective, Piezoresistive Silicon Vibration Sensor," Digest of Technical Papers of TRANSDUCERS '85, pp. 105-108 (1985) E. Peeters et al., "Vibration Signature Analysis Sensors for Predictive Diagnostics," Proceedings of SPIE '97, vol. 3224, pp. 220-230 (1997) JP 2000-46639 A JP 2000-46640 A

  When dealing with vibration phenomena and acoustic signals, expressing a signal as a complex number enables various analyzes and conversions such as instantaneous amplitude / phase detection and signal modulation / demodulation. A conventional acoustic / vibration sensor such as a microphone is a device that converts a physical quantity such as sound pressure at each time into an electric signal, and an output is a single real signal. In general, in order to convert a real signal into a corresponding complex signal, an operation called the following Hilbert transform is required. This operation is non-causal and cannot be performed in real time on wideband signals. For this reason, the complex number representation of signals can be actually applied only to narrowband signals that are handled in the communication field.

という関係がある。ここにｐ．ｖ．はＣａｕｃｈｙの主値

を意味する。 In general, there is the following Hilbert transform relationship between the real part and the imaginary part of the analytic function (edited by the Mathematical Society of Japan, Iwanami Mathematics Dictionary 3rd Edition (1985), p. 520).
A regular function in the upper half plane (y ≧ 0) of the complex variable z = x + ji,
φ (z) = U (x, y) + jV (x, y)
Boundary value on the real axis of
f (x) = U (x, 0), g (x) = − V (x, 0)
, When f and g are real integral functions (f, gεL1 (−∞, ∞)),

There is a relationship. P. v. Is the main value of Cauchy

Means.

  g is called a Hilbert transform of f, and f and g are called a Hilbert transform pair. The Hilbert transform is a function that connects the real part and the imaginary part of the analytic function.

It is convenient to analyze physical phenomena, particularly vibration phenomena, on a complex plane. In general, in a vibration phenomenon, one of the real part and the imaginary part is in a differential relationship according to Euler's formula e ^jθ = cos θ + jsin θ. For example, there is a relationship of velocity or acceleration to displacement or velocity. In order to grasp a phenomenon from an instantaneous value, only one piece of information (for example, displacement) related to the relationship is insufficient, and both (for example, displacement and speed) need to be known.

  Since the relationship between the real part and the imaginary part forms a Hilbert transform pair, the other can be derived by the above equation of g or f. However, as shown in equation (1), as the integral of the interval (−∞, ∞) The observation of a certain period (at least one period in the periodic function) is necessary. A conventional vibration wave detection device can detect only one piece of information. If information on both real and imaginary parts can be detected with instantaneous values, the phenomenon can be grasped instantaneously.

  For example, as disclosed in Patent Document 1, a frequency characteristic that can be dynamically changed is realized by applying a bias voltage of a piezoresistance detector according to the resonance frequency of the resonance beam. However, in the conventional method, the vibration wave detection load is limited to positive and negative real numbers, and a complex load necessary for realizing an arbitrary impulse response cannot be given.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a vibration wave detection method and apparatus capable of applying an arbitrary complex load.

The vibration wave detection method according to the first aspect of the present invention includes:
Vibration in which vibration waves are propagated to a plurality of resonators that resonate at different specific frequencies, and an electrical output associated with resonance of each of the resonators by the frequency is detected by a detector provided in each of the resonators. A wave detection method,
Applying an alternating bias voltage having a different phase for each resonator at a frequency common to the detectors of the plurality of resonators,
Combining the outputs of the plurality of resonator detectors;
It is characterized by that.

  Further, the AC bias voltage has a different amplitude in at least one of the plurality of resonators to which the AC bias voltage is applied.

  In particular, the plurality of resonators are divided into a plurality of groups, and the AC bias voltage having a common amplitude and phase is applied to the resonators included in each group.

  Preferably, an upper side band of the combined output of the detectors of the plurality of resonators is extracted by a filter, and a signal of a Hilbert transform pair is output by quadrature correlation detection.

  The combined output of the plurality of resonator detectors may be transmitted wirelessly to the filter.

The vibration wave detection device according to the second aspect of the present invention is:
A plurality of resonators each resonating at a different specific frequency;
A detector provided in each of the plurality of resonators for detecting an electrical output accompanying resonance at the frequency of each of the resonators by vibration waves propagated to the plurality of resonators;
Bias applying means for applying an AC bias voltage having a different phase for each of the resonators at a frequency common to a detector provided in each of the plurality of resonators;
Output combining means for combining the outputs of the detectors provided in each of the plurality of resonators;
It is characterized by providing.

  Further, the AC bias voltage applied by the bias applying unit has different amplitudes in at least one of the plurality of resonators.

  In particular, the bias applying means divides the plurality of resonators into groups, and applies an AC bias voltage having a common amplitude and phase to the resonators of each group for each group.

Preferably, filtering means for filtering and extracting the upper side band from the combined output of the detectors provided in each of the plurality of resonators combined by the output combining means,
Quadrature detection means for detecting a quadrature correlation of the upper side band extracted by the filtering means and outputting a signal of a Hilbert transform pair;
It is characterized by providing.

  Note that wireless transmission means for wirelessly transmitting a combined output of detector outputs provided in each of the plurality of resonators combined by the output combining means to the filtering means may be provided.

  Preferably, the detector is a piezoresistor.

  The detector may be a capacitive element.

  According to the vibration wave detection method and vibration wave detection apparatus of the present invention, it is possible to realize an arbitrary complex load. Then, it can be read and transmitted as an RF modulation signal having two degrees of freedom of a real part and an imaginary part by adding an arbitrary complex frequency characteristic.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated. An acoustic sensor that uses sound waves as vibration waves to be detected will be described below as an example.

  FIG. 1 is a diagram showing an example of a sensor main body in the vibration wave detection apparatus of the present invention. The sensor body 1 formed on the semiconductor silicon substrate 20 includes a diaphragm 2 that receives an input sound wave, a transverse beam 3 that is continuous with the diaphragm 2, an end plate 4 that is continuous with the tip of the transverse beam 3, and both sides of the transverse beam 3. Are composed of a plurality (n) of resonant beams 51a, 51b to 5na, 5nb (hereinafter collectively referred to as resonant beams 5), all of which are made of semiconductor silicon. Yes. The resonance beams 5 on both sides of the transverse beam 3 have the same resonance frequency, and n pairs of resonance beams 5 are formed in pairs.

  In this embodiment, in order to simplify mathematical handling and facilitate understanding, a pair of resonant beams having the same resonant frequency is arranged on both sides of the transverse beam 3. Similar results can be obtained even if the resonant beam 5 is arranged only on one side of the transverse beam. However, in that case, the sensitivity of the sensor is halved.

  The width of the transverse beam 3 is the thickest at the end of the diaphragm 2, gradually becomes narrower from there toward the end plate 4, and becomes the narrowest at the end of the end plate 4. Each resonant beam 5 is a resonator whose length is adjusted to resonate at a specific frequency.

但し、Ｃ：実験的に決定される定数
ａ：各共振ビーム５の厚さ
Ｘ：各共振ビーム５の長さ
Ｙ：材料物質（半導体シリコン）のヤング率
ｓ：材料物質（半導体シリコン）の密度 The plurality of resonance beams 5 selectively vibrate at a resonance frequency f expressed by the following equation (3).

Where C: constant determined experimentally a: thickness of each resonance beam 5 X: length of each resonance beam 5 Y: Young's modulus of material substance (semiconductor silicon) s: density of material substance (semiconductor silicon)

  As can be seen from the above equation (3), the resonance frequency f can be set to a desired value by changing the thickness a or the length X of the resonance beam 5. Each resonance beam 5 has a unique resonance frequency. In this example, the thickness a of all the resonant beams 5 is constant, and the length X of the resonance beam 5 is gradually increased from the right side (diaphragm 2 side) to the left side (end plate 4 side), and the right side (diaphragm). The resonance frequency at which each resonance beam 5 inherently vibrates from the second side to the left side (end plate 4 side) is set from a high frequency to a low frequency.

  The sensor body 1 configured as described above is manufactured on the semiconductor silicon substrate 20 by using a micromachining technique. The vibration energy input from the diaphragm 2 is distributed to the respective resonance beams 5 through the transverse beams 3, absorbed by the mechanical-electric converters of the respective resonance systems, converted into signal energy, and extracted.

(Embodiment 1)
FIG. 2 is a circuit diagram showing an example of the vibration wave detection apparatus of the present invention using such a sensor body 1. Piezoresistors 61a, 61b to 6na, 6nb (hereinafter collectively referred to as piezoresistors 6) made of polysilicon are formed in the distortion generating portions (crossing beam 3 side) of each resonance beam 5 of the sensor body 1. The plurality of piezoresistors 6 are connected in parallel, and one end of the piezoresistor 6 has AC power supplies 71a, 71b to 7na, 7nb (hereinafter collectively referred to as AC power supply 7) having different amplitudes and phases at a common frequency. The other end is connected to the negative input terminal of the operational amplifier 10. The + input terminal of the operational amplifier 10 is grounded. The opposing resonant beams 5 are applied with AC bias voltages having opposite phases. In Figure 2, indicates that the inverse of the phase at the negative sign of the voltage V _i.

The voltages V _{1 to} V _n may be the same. At least one of the phases φ _{1 to} φ _n has a different phase from the others.

Next, the operation of the vibration wave detection device shown in FIG. 2 will be described. In general, the relative change rate of the resistance value R of the resistor is expressed by the following equation (4), where ν is the Poisson's ratio of the resistor, l is the length, and ρ is the specific resistance.

In the piezoresistor 6 formed on the semiconductor silicon substrate 20, the change in specific resistance due to strain is main. When the piezoresistance coefficient is π and the Young's modulus is E, the relative change rate of the resistance value R of the piezoresistor is as follows. It may be expressed by the following formula (5).

  An output form in which the vibration output of each resonance beam 5 is added to one signal line as a waveform and output as in the vibration wave detection device of FIG. 2 is referred to as a combined output of vibration waveforms. The role of the sensor body 1 in this case is to efficiently convert mechanical vibrations into electrical signals and to adjust frequency characteristics on the electrical signals based on mechanical frequency decomposition.

  FIG. 9 is a circuit diagram showing an example of the output format of the sum of the vibration waveforms of the resonant beam 5 by the piezoresistor 6 using the sensor body 1. In the circuit of FIG. 9, a positive DC bias is applied to the upper resonance beams 51a to 5na, a negative DC bias is applied to the lower resonance beams 51b to 5nb, and the vibration output of each resonance beam 5 is one waveform. Are added to the signal lines and output. Here, for ease of understanding, it is assumed that the upper and lower resonant beams 5 to be paired vibrate in opposite phases, and the upper and lower piezoresistors 6 expand and contract in opposite phases.

In FIG. 9, the resistance value of the piezoresistor on the i-th resonance beam 5 _i is R _i + δR _i (t) on the upper side, R _i −δR _i (t) on the lower side, and the voltage of the other common terminal of the upper and lower resistors. Is V ₀ , −V ₀ , the current flowing into the virtual ground point of the operational amplifier is expressed by the following equation (6).

合成出力の荷重Ｗ_ｉは、抵抗Ｒ_ｉを調整することによって可変である。しかし、実際にはチップ製造時のトリミングなど固定的になる。 And it is taken out by the feedback resistance _Rf as an oscillating voltage expressed by the following formula (7).

The combined output load W _i is variable by adjusting the resistance R _i . However, in practice, trimming during chip manufacturing is fixed.

It can be considered that the bias voltage is changed for each resonance beam 5 by utilizing the fact that the output is proportional to the bias voltage V ₀ by the above method. FIG. 10 is a circuit diagram showing an example of a piezoresistive combined output using a plurality of bias voltage lines. Using the circuit of FIG. 10, dynamic gain adjustment for each frequency is possible. When the bias voltage of the i-th beam is ± V _i , the output voltage V _out is expressed by the following equation (8).

  However, since the number of wirings that can be passed through the transverse beam 3 is increased, bias control in which the resonant beams 5 are grouped becomes necessary when the number of the resonant beams 5 increases.

  The vibration wave detection method shown in FIG. 10 has variable frequency characteristics, but the gain that can be set for each frequency is limited to a real number. The gain at the time of frequency filtering becomes real or pure imaginary only when the impulse response is symmetric or antisymmetric. If the gain set for each frequency is limited to a real number, an arbitrary impulse response cannot be realized.

In the vibration wave detection apparatus of the present invention shown in FIG. 2, a variable load filter that realizes a more general frequency response can be realized. As shown in FIG. 2, the resonance frequency of the i-th resonance beams 5ia and 5ib is ω _i , the resistance value of the piezoresistor is R _i , and the resistance change is δR _i (t). A sinusoidal AC voltage having a frequency Ω, an amplitude V _i , and a phase φ _i is applied to an individual terminal of each piezoresistor 6ia. The negative phase voltage of the same sine wave AC voltage is supplied to the negative phase side piezoresistor 6ib. A common terminal of the positive-phase and negative-phase piezoresistors 6 is added to the input terminal of the transfer impedance type operational amplifier 10. The transfer impedance type operational amplifier 10 is a current-voltage conversion amplifier having an input impedance of 0 and an output impedance of 0.

ただし、Ｈ_ｉ≡２Ｖ_ｉ／Ｒ_ｉは変調の利得係数、Ｆ_ｉ（ｔ，ω_ｉ）≡δＲ_ｉ（ｔ）／Ｒ_ｉは共振ビーム５ｉの振動時間波形である。Ｆ_ｉ（ｔ，ω_ｉ）はFishbone構造のセンサ本体１の特性によってω_ｉ近傍の比較的狭帯域なスペクトル分布を有する。 At this time, the current flowing into the amplifier from the i-th resonance beams 5ia and 5ib is expressed by the following equation (9).

Here, H _i ≡2V _i / R _i is a modulation gain coefficient, and F _i (t, ω _i ) ≡δR _i (t) / R _i is a vibration time waveform of the resonant beam 5i. F _i (t, ω _i ) has a relatively narrow spectral distribution in the vicinity of ω _{i due to} the characteristics of the sensor body 1 having a Fishbone structure.

The total waveform of the output currents of all the resonant beams 5 is expressed by the following formula (10), where N is the total number of pairs of the resonant beams 5.

とおける場合、すなわちＦ（ω）及びＨ（ω）は正の周波数ω≧０のみで非零な複素関数である場合を考えると、出力電流は次の式（１３）で書かれる。ここで、虚数単位を文字ｊで表す。またＲｅは実部を、関数記号の右肩につけた^＊は複素共役を表す（以下同じ）。

Furthermore, it can be assumed that the output of each resonant beam is sufficiently narrow,

In other words, when F (ω) and H (ω) are non-zero complex functions with only a positive frequency ω ≧ 0, the output current is written by the following equation (13). Here, the imaginary unit is represented by the letter j. Re indicates the real part, and ^* with the function symbol on the right shoulder indicates the complex conjugate (the same applies hereinafter).

Equation (12), F (omega) of the inverse Fourier transform ^(represented by ^{F -1)} at which the analysis of input signal f (t),
f (t) = F ⁻¹ {F (ω)}
This means that the filter result by the complex frequency characteristic H (ω) is modulated at the carrier frequency Ω and obtained in the upper sideband (hereinafter referred to as the upper sideband). Further, f ^* (− t), that is, the inverse Fourier transform of F ^* (ω) f ^* (− t) = F ⁻¹ {F ^* (ω)}
The filter result by H (ω) is obtained in the lower sideband (hereinafter referred to as the lower sideband).

  This process is shown in FIG. FIG. 3 is a spectral distribution that schematically represents the action of amplitude phase modulation after frequency decomposition. The frequency-resolved input signal is individually multiplied by a certain complex amplitude Hi, and given a frequency shift of the carrier frequency Ω. These synthesis results in multiplication by the frequency characteristic of H (ω) and modulation by a carrier wave having a constant frequency Ω. For example, the input spectrum distribution A that is frequency-resolved into a certain resonant beam 5 becomes a spectrum distribution B that is frequency-shifted by the carrier frequency Ω. A composite of the spectrum that is decomposed and frequency shifted by the carrier frequency Ω is obtained as the spectral distribution of the upper sideband.

This result is different from simply filtering the acoustic signal f (t) with the frequency characteristic H (ω) and then modulating it with the carrier frequency Ω. In the case of filtering with the frequency characteristic H (ω) and modulating with the carrier frequency Ω, the negative frequency of the acoustic signal undergoes a gain change of H ^* (ω). In contrast, the method of the present invention multiplies the same gain of H (ω) as the positive frequency.

のように周波数応答Ｈ^＊（ω）あるいはインパルス応答ｈ^＊（−ｔ）によるフィルタ出力である。ここで、関数の間の記号＊は畳み込みを表す。式（１４）は、複素共役の逆フーリエ変換

から導かれる。 FIG. 4 shows the spectral distribution of the combined signal in consideration of the lower sideband and the frequency shift of −Ω. Consider the meaning of each sideband component. The component on the right side (upper side band) of the carrier frequency Ω is an output of a desired filter characteristic converted into an analytic signal. The left component (lower sideband) of the carrier frequency Ω is expressed by the following equation (14)

As shown, the filter output is based on the frequency response H ^* (ω) or the impulse response h ^* (− t). Here, the symbol * between functions represents convolution. Equation (14) is a complex conjugate inverse Fourier transform.

Derived from.

In the negative frequency region, it can be seen that the component on the left side of −Ω is the complex conjugate of the output of the desired filter characteristic, and the component on the right side of −Ω is the complex conjugate of the filter output of the above H ^* (ω). . Incidentally, it equal the bias voltage V ₀ ~V _n, the frequency characteristics of the vibration wave detecting device becomes flat. The filter characteristics can be changed by changing the bias voltages V _{0 to} V _n .

  As described above, the upper sideband and the lower sideband have different meanings as signals. The synthesized output of the resonant beam 5 needs to be demodulated after separating the upper sideband and the lower sideband. The combined output signal may be directly demodulated, but may be transmitted wirelessly as it is modulated at the carrier frequency Ω.

  FIG. 5 is a block diagram illustrating a configuration example of a vibration wave detection device using radio. 5A shows a circuit on the sensor side, and FIG. 5B shows a circuit on the receiving side. As shown in FIG. 5A, on the sensor side, the signal modulated by the sensor body 1 is impedance-matched by a transformer 11, amplified by an amplifier 12, and transmitted wirelessly from an antenna 13S.

  On the receiving side shown in FIG. 5B, the upper sideband and the lower sideband of the signal received by the antenna 13R and amplified by the amplifier 14 are separated by the bandpass filter (BPF) 15. At the same time, the carrier frequency Ω is reproduced using a PLL (Phase Locked Loop) 16 or the like. A phase shifter (Phase Shifter) 17 generates carrier frequencies having phases of 0 ° and 90 ° from the carrier frequency, and performs quadrature detection of the upper sideband (USB: Upper Side Band) separated by the BPF 15. The USB is multiplied by a carrier frequency having a phase of 0 ° and 90 ° by a multiplier 18, and a detection output is obtained through a low-pass filter (LPF) 19. The two signals after detection of the orthogonal correlation form a Hilbert transform pair of the output of the set complex weight filter. That is, the real part signal is obtained from the phase of 0 °, and the imaginary part signal is obtained from the phase of 90 °.

  The applied AC bias voltage may not be a sine wave. This is because harmonics can be suppressed when the upper sideband is extracted by appropriately adjusting the BPF 15. The AC bias voltage can be, for example, a rectangular wave.

  As described above, according to the vibration wave detection apparatus of the present invention, an arbitrary complex load can be realized. Then, it can be read and transmitted as an RF modulation signal having two degrees of freedom of a real part and an imaginary part by adding an arbitrary complex frequency characteristic.

  The vibration wave detection method of the present invention can be used in any scene where a conventional microphone or vibration sensor is used. Furthermore, it can be used in the following cases that have not been possible in the past.

  Vibration / acoustic detection with high time resolution based on feature extraction of complex waveforms. For example, an abnormal sound can be detected instantaneously in a machine that is continuously operating. Moreover, a wideband AM / FM demodulator can be realized as a possibility. And since it can detect a polyphase output signal consistently, it can be applied to highly accurate waveform measurement.

(Modification of Embodiment 1)
FIG. 6 shows an example of a vibration wave detector that divides the resonant beam 5 into groups and applies an AC bias voltage. When the number of the resonant beams 5 is increased, it is difficult to apply AC bias voltages having different phases to all the resonant beams 5 due to the limitation of the number of wirings that can be passed through the transverse beam 3. For example, as shown in FIG. 6, the resonance beams 5 are divided into groups, and an AC bias voltage having a common amplitude and phase is applied to the resonance beams 5 included in each group.

In the example of FIG. 6, an AC bias voltage having an amplitude V ₁ and a phase φ ₁ is applied to the resonant beams 51a and 52a. An AC bias voltage having an amplitude −V ₁ and a phase φ ₁ is applied to the resonance beams 51b and 52b. Similarly, two adjacent resonant beams 5 are grouped, and an AC bias voltage having a common amplitude and phase is applied to each group. In this way, the degree of freedom of the amplitude and phase of the complex number load is reduced, but the complex number load remains unchanged, and a large number of resonance beams 5 can be provided within the limit of the number of wires of the transverse beam 3.

  In the example of FIG. 6, two adjacent resonance beams 5 are grouped, but the number of one group of resonance beams 5 may be three or more. Further, the number of the set of resonance beams 5 may be different for each set. Furthermore, instead of the adjacent resonance beams 5, for example, a combination of resonance beams 5 selected every m beams may be set, and an AC bias voltage having a common amplitude and phase may be applied to each set. It is designed according to the acquired complex frequency characteristic what kind of group is divided and what kind of amplitude and phase AC bias voltage is applied to each group.

(Embodiment 2)
FIG. 7 is a circuit diagram showing an example of the vibration wave detection device of the present invention when the detector is a capacitor.

  Electrodes 91a, 91b to 9na, and 9nb (hereinafter collectively referred to as electrodes 9) are provided on the semiconductor silicon substrate 20 at positions facing the front end portions 81a, 81b to 8na, and 8nb (hereinafter collectively referred to as the front end portions 8) of the respective resonance beams 5. And a capacitor is constituted by the tip 8 of each resonance beam 5 and each electrode 9 opposed thereto. The tip 8 of the resonant beam 5 is a movable electrode whose position moves up and down with vibration, while the electrode 9 formed on the semiconductor silicon substrate 20 is a fixed electrode whose position does not move. When the resonant beam 5 vibrates at a specific frequency, the distance between the counter electrodes varies, so that the capacitance of the capacitor changes.

  The plurality of electrodes 9 are connected in parallel and connected to the negative input terminal of the operational amplifier 10. The + input terminal of the operational amplifier 10 is grounded. The tip 8 of the resonance beam 5 is connected to AC power supplies 71a, 71b to 7na, 7nb having different amplitudes and phases at a common frequency. Similar to the circuit of FIG. 2, alternating bias voltages having opposite phases are applied to the opposed resonant beams 5.

When the specific resonance beam 5 resonates, the distortion causes the distance between the tip 8 of the resonance beam 5 and the electrode 9 to change, and the capacitance of the capacitor between them changes. It is obtained as an output (voltage V ₊ ).

When the detector is a capacitor, it can be considered as the impedance Z _i of the capacitor C _i instead of the resistor R _{i in} the equations (4) to (13).
Z _i = 1 / (jΩCi)
In this case, the impedance Z _i includes the frequency (angular frequency), but since the carrier frequency Ω is constant and common, it is handled in the same manner as the resistance in consideration of the change by 1 / j = −j. be able to. Since the amplitude H _i includes the imaginary number j, the phase of the output changes by 90 ° compared to the case of the piezoresistor 6, and the real part and the imaginary part of the demodulated output are switched. As in the case where the detector is a resistor, it can be read and transmitted as an RF modulation signal having two degrees of freedom of a real part and an imaginary part by adding an arbitrary complex frequency characteristic.

(Modification of Embodiment 2)
FIG. 8 shows an example of a vibration wave detector that applies an AC bias voltage by dividing the resonant beam 5 into groups when the detector is a capacitor. When the number of the resonant beams 5 is increased, it is difficult to apply AC bias voltages having different phases to all the resonant beams 5 due to the limitation of the number of wirings that can be passed through the transverse beam 3.

  Similar to the modification (FIG. 6) with respect to the first embodiment, two adjacent resonance beams 5 are grouped, and an AC bias voltage having a common amplitude and phase is applied to each group. In this way, the degree of freedom of the amplitude and phase of the complex number load is reduced, but the complex number load remains unchanged, and a large number of resonance beams 5 can be provided within the limit of the number of wires of the transverse beam 3.

  Also in the example of FIG. 8, two adjacent resonance beams 5 are grouped, but the number of one group of resonance beams 5 may be three or more. Further, the number of the set of resonance beams 5 may be different for each set. Furthermore, instead of the adjacent resonance beams 5, for example, a combination of resonance beams 5 selected every m beams may be set, and an AC bias voltage having a common amplitude and phase may be applied to each set. It is designed according to the acquired complex frequency characteristic what kind of group is divided and what kind of amplitude and phase AC bias voltage is applied to each group.

  As described above, according to the vibration wave detection apparatus of the present invention, it is possible to realize an arbitrary complex load even when the detector is a capacitor. Then, it can be read and transmitted as an RF modulation signal having two degrees of freedom of a real part and an imaginary part by adding an arbitrary complex frequency characteristic.

  In addition, the above-described hardware configuration is an example, and can be arbitrarily changed and modified.

It is a figure which shows an example of the sensor main body in the vibration wave detection apparatus of this invention. It is a circuit diagram which shows an example of the vibration wave detection apparatus of this invention. It is the spectrum distribution which represents typically the effect | action of the amplitude phase modulation after frequency decomposition. It is a spectrum distribution figure of a synthetic signal in consideration of a lower side band and a frequency shift of −Ω. It is a block diagram which shows the structural example of the vibration wave detection apparatus using a radio | wireless. It is a figure which shows the example of the vibration wave detection apparatus which divides | segments a resonant beam into a group and applies an alternating current bias voltage. It is a circuit diagram which shows an example of the vibration wave detection apparatus of this invention in case a detector is a capacitor. It is a figure which shows the example of the vibration wave detection apparatus which divides | segments a resonant beam into a group and applies an alternating current bias voltage when a detector is a capacitor. It is a circuit diagram showing an example of the output format of the sum of the vibration waveform of the resonant beam by a piezoresistor. It is a circuit diagram showing an example of a combined output of a piezoresistive method using a plurality of bias voltage lines.

Explanation of symbols

1 Sensor body
2 Diaphragm
3 Cross beam
4 End plate 51a, 51b, 52a, 52b,
5ia, 5ib, 5na, 5nb Resonant beam 61a, 61b, 62a, 62b,
6ia, 6ib, 6na, 6nb Piezoresistors 71a, 71b, 72a, 72b,
7na, 7nb AC power supply 81a, 81b, 82a, 82b,
8ia, 8ib, 8na, 8nb Tip 91a, 91b, 92a, 92b,
9ia, 9ib, 9na, 9nb electrode
10 operational amplifier
11 Transformer
12, 14 amplifier
13S, 13R antenna
15 Bandpass Filter (BPF)
16 PLL
17 Phase Shifter
18 multiplier
19 Low-pass filter (LPF)
20 Semiconductor silicon substrate

Claims (12)

Vibration in which vibration waves are propagated to a plurality of resonators that resonate at different specific frequencies, and an electrical output associated with resonance of each of the resonators by the frequency is detected by a detector provided in each of the resonators. A wave detection method,
Applying an alternating bias voltage having a different phase for each resonator at a frequency common to the detectors of the plurality of resonators,
Combining the outputs of the plurality of resonator detectors;
A vibration wave detection method characterized by the above.   2. The vibration wave detection method according to claim 1, wherein the AC bias voltage has different amplitudes in at least one of the plurality of resonators to which the AC bias voltage is applied.   3. The plurality of resonators are divided into a plurality of groups, and the AC bias voltage having a common amplitude and phase is applied to the resonators included in each group. The vibration wave detection method described in 1.   4. The upper band of the combined output of the detectors of the plurality of resonators is extracted by a filter, and a signal of a Hilbert transform pair is output by quadrature correlation detection. The vibration wave detection method according to the item.   5. The vibration wave detection method according to claim 4, wherein the combined output of the plurality of resonator detectors is wirelessly transmitted to the filter. A plurality of resonators each resonating at a different specific frequency;
A detector provided in each of the plurality of resonators for detecting an electrical output accompanying resonance at the frequency of each of the resonators by vibration waves propagated to the plurality of resonators;
Bias applying means for applying an AC bias voltage having a different phase for each of the resonators at a frequency common to a detector provided in each of the plurality of resonators;
Output combining means for combining the outputs of the detectors provided in each of the plurality of resonators;
A vibration wave detection device comprising:   The vibration wave detecting apparatus according to claim 6, wherein the AC bias voltage applied by the bias applying unit has different amplitudes in at least one of the plurality of resonators.   The bias applying means divides the plurality of resonators into groups, and applies an AC bias voltage having a common amplitude and phase to the resonators of each group for each group. The vibration wave detection apparatus as described. Filtering means for filtering and extracting the upper sideband from the combined output of the detectors provided in each of the plurality of resonators combined by the output combining means;
Quadrature detection means for detecting a quadrature correlation of the upper side band extracted by the filtering means and outputting a signal of a Hilbert transform pair;
The vibration wave detection device according to claim 6, comprising: A wireless transmission means for wirelessly transmitting a combined output of detector outputs provided in each of the plurality of resonators combined by the output combining means to the filtering means;
The vibration wave detection apparatus according to claim 9.   The vibration detector according to any one of claims 6 to 10, wherein the detector is a piezoresistor.   The vibration detector according to claim 6, wherein the detector is a capacitive element.

Images