JP4930769B2 - Oscillator - Google Patents

Description

  The present invention relates to an oscillator using MEMS technology.

  While the demand for miniaturization and high precision of electronic devices such as wireless portable devices such as mobile phones and personal computers is increasing, such electronic devices require a small and stable high-frequency signal source. It is essential. A typical electronic component for satisfying this requirement is a crystal resonator. A quartz resonator is known to have a very high resonance sharpness (ie, Q value), which is an index of the quality of an oscillation element, and exceeds 10,000 because of good crystal stability. This is the reason why crystal resonators are widely used as stable high-frequency signal sources for wireless portable devices and personal computers. However, it has become clear that this quartz crystal resonator cannot sufficiently satisfy the recent demand for further downsizing.

Therefore, in recent years, a MEMS oscillator using a small MEMS vibrator formed by MEMS (Micro-Electro-Mechanical-System) technology using silicon instead of a quartz vibrator has been reported (Non-patent Document 1). . MEMS oscillators can be downsized compared to crystal oscillators and are easy to cope with high frequencies, so that they are expected to spread especially to small devices such as mobile phones. In addition, since the MEMS resonator can be manufactured using silicon, it can be integrated with the peripheral circuit in one chip.
T. Mattila et al., “14MHz Micromechanical Oscillator”, The 11th International Conference on Solid-State Sensors and Actuators, Munich, Germany, 2001

  However, according to the MEMS oscillator according to the above-described prior art, only one fundamental frequency can be obtained. Therefore, when a frequency other than the fundamental frequency is required, it is necessary to divide or multiply the fundamental frequency depending on the application. There is a problem that an external circuit such as a frequency divider or a frequency multiplier is required.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an oscillator using a small MEMS vibrator capable of selecting and outputting one fundamental frequency from a plurality of fundamental frequencies.

An oscillator according to the present invention includes an output vibrator provided so as to be able to vibrate mechanically,
A DC voltage application unit that applies a DC voltage to the output vibrator; and a plurality of excitation electrodes that are arranged along a longitudinal direction of the output vibrator, the antinode of vibration of the output vibrator A plurality of excitation electrodes that are arranged in the vicinity of each other and interact with each other via an electric field with the output vibrator, and are electrically connected to the plurality of excitation electrodes, and the resonance of the output vibrator An oscillation circuit that oscillates at a frequency and outputs an oscillation signal, and an electrical connection path from the oscillation circuit to each of the excitation electrodes, thereby changing a natural vibration mode of the output vibrator A frequency selection circuit .
According to the above configuration, the DC voltage application unit applies a DC voltage to the output vibrator, and the excitation electrode interacts with the output vibrator via an electric field to output the output vibrator. The natural vibration mode is changed by exciting the vibrator, and the oscillation circuit can oscillate at a resonance frequency corresponding to the natural vibration mode of the output vibrator and output an oscillation signal.

In addition, for example, the oscillator further includes a basic frequency selection circuit that is connected between the excitation electrode and the oscillation circuit and that selects an electrical connection path from the oscillation circuit to the excitation electrode. Features.
According to the above configuration, the fundamental frequency selection circuit can change the method of applying a voltage to the excitation electrode by selecting the electrical connection path from the oscillation circuit to the excitation electrode. A desired vibration mode is selected by acting on a desired position of the vibrator for vibration via an electric field, and the oscillation circuit can oscillate at a desired resonance frequency of the vibrator for output and output an oscillation signal.

Further, in the oscillator according to the present invention, the output vibrator is disposed to face a support layer that is a semiconductor substrate, at least a part of which is fixed to an insulating layer on the support layer, and the plurality of excitation vibrators An electrode is arranged to face the support layer, and the whole is fixed to the insulating layer on the support layer.
According to the above configuration, since the output vibrator and the excitation electrode can be formed on the same semiconductor substrate, the size can be reduced.

The oscillator according to the present invention is characterized in that the plurality of excitation electrodes are arranged on one side of the output vibrator along a long side direction of the output vibrator.
According to the above configuration, the oscillator can oscillate at the resonance frequency of the desired vibration mode of the output vibrator according to the arrangement position of the excitation electrode and output an oscillation signal.

The oscillator according to the present invention is characterized in that the plurality of excitation electrodes are arranged on both sides of the output vibrator along the long side direction of the output vibrator.
According to the above configuration, the oscillator can oscillate at the resonance frequency of the desired vibration mode of the output vibrator according to the arrangement position of the excitation electrode and output an oscillation signal.

The oscillator according to the present invention is characterized in that a DC positive voltage is applied to the output vibrator and the support layer is grounded.
According to the above configuration, the oscillation circuit can oscillate at the resonance frequency of the output vibrator.

The oscillator according to the present invention is characterized in that the output vibrator is grounded and a negative DC voltage is applied to the support layer.
According to the above configuration, the oscillation circuit can oscillate at a frequency that is half the resonance frequency of the output vibrator.

  According to the present invention, by arranging the excitation electrode at a position corresponding to the antinode of the vibration of the output vibrator, the position of the electrostatic force generated in the output vibrator is controlled, and the natural vibration of the output vibrator is controlled. Since the mode is changed, an oscillator using a small MEMS vibrator capable of selecting and outputting one fundamental frequency from a plurality of fundamental frequencies can be provided.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram of an oscillator according to an embodiment of the present invention. As shown in the figure, the oscillator includes a vibrator 100, a DC bias voltage application circuit 101, a fundamental frequency selection circuit 102, and an output oscillation circuit 103.

  The vibrator 100 is connected to the DC bias voltage application circuit 101 and also to the fundamental frequency selection circuit 102. The fundamental frequency selection circuit 102 is connected to the output oscillation circuit 103.

Next, the operation of the oscillator according to this embodiment will be described in detail.
First, the DC bias voltage application circuit 101 applies a DC bias voltage to the vibrator 100 so that it can be driven by electrostatic force. Next, the fundamental frequency selection circuit 102 selects the resonance frequency of the vibrator 100, and the output oscillation circuit 103 oscillates at the resonance frequency of the vibrator 100 and outputs an output oscillation signal.
As described above, this oscillator outputs an oscillation signal having a frequency selected by the basic frequency selection circuit 102.

Next, an example of each component of the oscillator according to the present embodiment described above will be described in detail.
First, a first example of the configuration of the vibrator 100 will be described with reference to FIG.
As shown in the figure, the vibrator 100 includes an output vibrator (cantilever) 201, output vibrator electrode pads 202 and 203, excitation electrode pads 204 to 206, excitation electrodes 207 to 209, a support layer 210, Insulating layers 211 to 215 and fixing portions 216 and 217 are included.

In the output vibrator (cantilever) 201, fixing portions 216 and 217 are fixed to the upper surface of the support layer 210 via insulating layers 211 and 212.
The output vibrator (cantilever) 201 is provided at the same height as the fixing portions 216 and 217, and there is no insulating layer between the output vibrator (cantilever) 201 and the support layer 210 to form a gap. Yes. Thereby, the output vibrator (cantilever) 201 can vibrate mechanically. The output vibrator electrode pads 202 and 203 are provided on the fixing portions 216 and 217, respectively, and are electrically connected to the output vibrator (cantilever) 201.

  In addition, the excitation electrodes 207 to 209 are fixed to the upper surface of the support layer 210 via insulating layers 213 to 215. The excitation electrode pads 204 to 206 are provided on the excitation electrodes 207 to 209, respectively, and are electrically connected to the excitation electrodes 207 to 209, respectively.

  The vibrator 100 is formed by MEMS technology using an SOI (Silicon-On-Insulator) substrate. The SOI substrate has an active layer, an insulating layer, and a support layer 210. Of these layers, the active layer (silicon) is used to form the output vibrator (cantilever) 201 and the excitation electrodes 207 to 209. The output vibrator (cantilever) 201 and the excitation electrodes 207 to 209 are formed by etching so as to face the support layer 210 and be adjacent to each other. The excitation electrodes 207 to 209 are arranged so as to be positioned on the antinodes of the vibration of the vibrator output vibrator (cantilever) 201. In order to make this vibrator output vibrator (cantilever) 201 function as a movable electrode, the resistance of the active layer is lowered in advance by impurity doping or the like.

Further, by removing the insulating layer on the lower surface other than the fixed portions 216 and 217 of the output vibrator (cantilever) 201 by etching after the processing of the active layer, the output vibrator (cantilever) 201 and the support layer 210 are removed. A gap (air gap) is formed between the two. The insulating layers 211 and 212 on the lower surfaces of the fixing portions 216 and 217 remaining without being etched electrically insulate the support layer 210 and the output vibrator (cantilever) 201 from each other, and via the fixing portions 216 and 217. Fix it. With such a configuration, the output vibrator (cantilever) 201 can vibrate using the fixing portions 216 and 217 as fulcrums.
The support layer 210 is a semiconductor (silicon) substrate, which mechanically fixes the output vibrator (cantilever) 201 and also functions as a fixed electrode.

  Further, the output vibrator electrode pads 202 and 203 are formed on the upper surfaces of the fixing portions 216 and 217 of the output vibrator (cantilever) 201 by vapor deposition of aluminum (Al), and the excitation electrode pads 204 to 206 are excited. The electrodes 207 to 209 are formed on the upper surfaces of the electrodes. And each pad is electrically connected to an external circuit using wire bonding etc. which are not illustrated.

Next, the operation principle of the vibrator 100 will be described.
FIG. 3A is an operation principle diagram showing a vibrator. As shown in this figure, the MEMS vibrator includes a capacitive element between electrodes having a gap. In the figure, 301 is a spring, 302 is a weight, 303 is a substrate, 304 is an excitation electrode, 305 is an electrode, 306 is an AC power source, and 307 is a DC power source. The MEMS vibrator is driven by electrostatic force by applying a voltage. At that time, by applying a DC bias voltage in addition to the AC signal, the same electrical characteristics (for example, Q value) as the quartz vibrator are obtained. It can be used as a vibrator of an oscillator with the same configuration as a crystal oscillator.

As shown in FIG. 3B, the voltage V applied to the electrodes of the MEMS vibrator is obtained by using the DC bias voltage v ₀ and the amplitude δ of the AC signal,
V = v ₀ + δe ^jωt
It can be expressed as.

Next, with reference to FIG. 4, a voltage application state to each electrode of the vibrator 100 and an electrostatic force acting on the vibrator will be described.
In the figure, reference numerals 400 to 402 denote DC bias voltage sources. The other components are the same as those of the vibrator 100 described with reference to FIG.

  The DC bias voltage source 400 (voltage value Vbias) has a positive electrode connected to the output transducer electrode pad 202 and a negative electrode grounded. The DC bias voltage source 401 (voltage value + Va) has a positive electrode connected to the excitation electrode pad 204 and a negative electrode grounded. The DC bias voltage source 402 (voltage value −Va) has a negative electrode connected to the excitation electrode pad 206 and a positive electrode grounded. The support layer 210 and the excitation electrode pad 205 are grounded. Note that the voltage value Vbias> Va.

Next, the electrostatic force acting on the vibrator in the voltage application state shown in FIG.
Since the output vibrator (cantilever) 201 is applied with the voltage Vbias, an electrostatic force acts between the excitation electrodes 207 to 209 to which a predetermined voltage is applied. That is, the magnitude of the electrostatic force F acting on the output vibrator (cantilever) 201 is proportional to the potential difference between the vibrator and the electrode.

Here, the electrostatic force acting between the output vibrator (cantilever) 201 and the excitation electrode 207 is Fa, the electrostatic force acting between the excitation electrode 208 is Fb, and the static electricity acting between the excitation electrode 209 The force is Fc. In this case, the potential of the output vibrator (cantilever) 201 is + Vbias and Vbias> Va.
| Fa | <| Fb | <| Fc |
Satisfy the relationship.

Next, a change in the natural vibration mode when the electrostatic force as described above is applied to the output vibrator (cantilever) 201 will be described with reference to FIG.
FIG. 5A is an explanatory diagram of the natural vibration mode of the output vibrator in which one point is fixed.
In the figure, reference numeral 500 denotes an output vibrator, and reference numeral 501 denotes a fulcrum. The length of the output vibrator 500 is L, the height is b, and the width is t. Further, it is assumed that the output vibrator 500 vibrates in the vibration direction shown in FIG.

5B, 5C, and 5D are schematic views when the vibration of the output vibrator 500 is observed from the observation direction shown in FIG.
FIG. 5B shows the vibration in the first mode. As shown in the figure, the output vibrator 500 vibrates with the fulcrum 501 fixed, and the opposite side of the fulcrum 501 is the antinode of vibration.
FIG. 5C shows the vibration of the secondary mode. As shown in the figure, the output vibrator 500 vibrates with the fulcrum 501 fixed, and the position of the output vibrator 500 having a length of 0.774L becomes a vibration node.
FIG. 5D shows the vibration in the third mode. As shown in the figure, the output vibrator 500 vibrates with the fulcrum 501 fixed, and the position of the output vibrator 500 having a length of 0.5 L and a position of 0.868 L are nodes of vibration.

FIG. 5E is a principle diagram of the natural vibration mode of the vibrator having both ends fixed.
In the figure, 510 is an output vibrator and 511 is a fulcrum. The length of the output vibrator 510 is L, the height is b, and the width is t. The output vibrator 510 is assumed to vibrate in the vibration direction shown in FIG.

FIGS. 5F, 5G, and 5H are schematic views when the vibration of the output vibrator 510 is observed from the observation direction shown in FIG.
FIG. 5 (f) represents the vibration in the first mode. As shown in the figure, the output vibrator 510 vibrates with the fulcrums 511 at both ends fixed, and the intermediate point in the length direction of the output vibrator 510 becomes the antinode of the maximum amplitude.
FIG. 5G shows the vibration in the secondary mode. As shown in the figure, the output vibrator 510 vibrates with the fulcrums 511 at both ends fixed, and the position of the output vibrator 510 with a length of 0.5 L becomes a vibration node.
FIG. 5 (h) represents the vibration of the third mode. As shown in the figure, the output vibrator 510 vibrates with the fulcrums 511 at both ends fixed, and the position of 0.359 L in length from the fulcrums 511 at both ends of the output vibrator 510 becomes a vibration node. .

  The resonance frequency in each of these natural vibration modes is expressed as follows: the Young's modulus of the vibrator is E, and the density of the vibrator is ρ.

It can be expressed as.

Next, the connection of the vibrator 100 will be described with reference to FIG.
FIG. 6A is a connection diagram of the vibrator. In the figure, 600 is a DC bias voltage source, 601 is an AC voltage source, 602 to 604 are switches, 605 is a terminal (1), and 606 is a terminal (2). The other components are the same as those of the vibrator 100 described with reference to FIG.

DC bias voltage application circuit 101: DC bias voltage source 600 (voltage value Vb) has a positive electrode connected to output transducer electrode pad 203 and a negative electrode grounded. Both ends of the AC voltage source 601 are connected to the terminal (1) 605 and the terminal (2) 606.
Basic frequency selection circuit 102: The switches 602 to 604 can switch the connection between three states. The switch 602 has one end connected to the excitation electrode pad 204 and two terminals out of the other three terminals. Each is connected to terminal (1) 605 and terminal (2) 606, and one terminal is open. In addition, one end of the switch 603 is connected to the excitation electrode pad 205, two of the other three terminals are connected to the terminal (1) 605 and the terminal (2) 606, respectively, and one terminal is opened. Yes. The switch 604 has one end connected to the excitation electrode pad 206, two of the other three terminals connected to the terminal (1) 605 and the terminal (2) 606, respectively, and one terminal opened. Yes. The support layer 210 is grounded.

  FIG. 6B is a waveform diagram of the AC voltage source. In the figure, reference numeral 610 denotes a waveform of the AC voltage source 601. In the figure, the horizontal axis indicates time, and the vertical axis indicates voltage value. The maximum value of the waveform 610 is the voltage Vac, and Vb> Vac. The frequency of the AC voltage is made equal to the resonance frequency of the output vibrator (cantilever) 201.

  In the figure, a simplified circuit configuration is shown in which an AC voltage is applied to the excitation electrode pads 204 to 206 in order to explain the principle of the change in the natural vibration mode. The oscillation circuit 103 is connected. Thus, an oscillation signal can be obtained by interacting between the output vibrator (cantilever) 201 and the excitation electrodes 207 to 209 via an electric field.

Next, the operation of the vibrator 100 will be described with reference to FIG.
FIG. 7 is a schematic diagram illustrating the natural vibration mode of the vibrator. This figure is a schematic view of the vibrator 100 as viewed from above.
Fig.7 (a) is a schematic diagram of a non-vibration state. In the figure, 700 indicates the position of the output vibrator (cantilever) 201. In the no-vibration state, the position 700 of the output vibrator (cantilever) 201 is a straight line.

  FIG. 7B is a schematic diagram of the vibration state of the primary mode. Reference numeral 701 denotes a position where the output vibrator (cantilever) 201 vibrates closest to the excitation electrode 208, and reference numeral 702 denotes a position where the output vibrator (cantilever) 201 vibrates most away from the excitation electrode 208. Reference numeral 703 denotes a vibration center position of the output vibrator (cantilever) 201.

  The vibration center position 703 of the output vibrator (cantilever) 201 is affected by the DC bias voltage source 600 (voltage Vb) applied to the output vibrator (cantilever) 201, and an attractive force acts on the excitation electrode 208 side. Bend.

When the primary mode vibration shown in the figure is generated, it is necessary to set the excitation electrode connection state shown in FIG. 7C.
FIG. 7C is a diagram illustrating a connection state of the excitation electrodes during the vibration in the primary mode.
As shown in the figure, all of the excitation electrodes 207 to 209 in FIG. 6 are connected to the terminal (1) 605 during the vibration in the primary mode. That is, all of the switches 602 to 604 are connected to the terminal (1) 605 side. Thus, an AC voltage having the same phase is applied to the excitation electrodes 207 to 209 by the AC voltage source 601, and the electrostatic force exerted on the output vibrator (cantilever) 201 by the excitation electrodes 207 to 209 is always the same. Since the magnitude of the electrostatic force changes uniformly according to the phase of the AC voltage, the vibration of the primary mode is generated.

Next, the vibration mode in the secondary mode will be described.
FIG. 7D is a schematic diagram of the vibration mode in the secondary mode. 704 is a position where the output vibrator (cantilever) 201 vibrates and the antinode is closest to the excitation electrode 207, and 705 is a position where the output vibrator (cantilever) 201 vibrates and the antinode is most close to the excitation electrode 209. It is a close position.
When the secondary mode vibration shown in the figure is generated, it is necessary to connect the excitation electrodes shown in FIG. 7 (e).

FIG. 7E is a diagram illustrating a connection state of the excitation electrodes during the secondary mode vibration.
As shown in the figure, during secondary mode vibration, the excitation electrode 207 in FIG. 6 is connected to the terminal (1) 605, the excitation electrode 209 is connected to the terminal (2) 606, and the excitation electrode 208 is Opened. That is, the switch 602 is connected to the terminal (1) 605 side, the switch 604 is connected to the terminal (2) 606 side, and the switch 603 is opened. This is the connection state of the switch shown in FIG.

As a result, alternating voltages having opposite phases are applied to the excitation electrodes 207 and 209, and no voltage is applied to the excitation electrode 208, so that the excitation electrode 207 exerts the output vibrator (cantilever) 201. Since the electrostatic force and the electrostatic force exerted on the output vibrator (cantilever) 201 by the excitation electrode 209 are always different in strength at a certain moment, the vibration of the secondary mode having two antinodes and one node. Occurs.
In this case, since the resonance frequency of the output vibrator (cantilever) 201 is about 2.8 times the resonance frequency in the primary mode, the frequency of the AC voltage source 601 needs to be set to about 2.8 times. There is.

  In other words, the resonance frequency of the desired natural vibration mode can be obtained by the AC voltage applied to the excitation electrodes 207 to 209 disposed on the vibration antinode of the output vibrator (cantilever) 201. In the above description, the example up to the secondary mode has been described. However, the resonance frequency of the natural vibration mode of the tertiary mode or higher can be obtained by changing the number of the excitation electrodes, the arrangement position, and the voltage application state. .

Next, another method for applying a voltage to the vibrator 100 will be described.
First, with reference to FIG. 8, the state of voltage application to the electrodes of the vibrator 100 and the electrostatic force acting on the vibrator will be described.
In the figure, reference numerals 400 to 402 denote DC bias voltage sources. The other components are the same as those of the vibrator 100 described with reference to FIG.

  The DC bias voltage source 400 (voltage value Vbias) has a positive electrode connected to the output vibrator electrode pad 202 and a negative electrode connected to the support layer 210. The DC bias voltage source 401 (voltage value + Va) has a positive electrode connected to the excitation electrode pad 204 and a negative electrode grounded. The DC bias voltage source 402 (voltage value −Va) has a negative electrode connected to the excitation electrode pad 206 and a positive electrode grounded. The output vibrator electrode pad 202 and the excitation electrode pad 205 are grounded. It is assumed that voltage value Vbias> voltage value Va.

Next, the electrostatic force acting on the vibrator in the voltage application state shown in FIG.
An electrostatic force acts between the output vibrator (cantilever) 201 and the excitation electrodes 207 to 209 to which a predetermined voltage is applied. That is, the magnitude of the electrostatic force F acting on the output vibrator (cantilever) 201 is proportional to the potential difference between the vibrator and the electrode.

Here, the electrostatic force acting between the output vibrator (cantilever) 201 and the excitation electrode 207 is Fa, the electrostatic force acting between the excitation electrode 208 is Fb, and the static electricity acting between the excitation electrode 209 The force is Fc. In this case, since the potential of the output vibrator (cantilever) 201 is GND, each electrostatic force described above is
Fa = Fc, Fb = 0
Satisfy the relationship. That is, the electrostatic force in the same direction acts on the output vibrator (cantilever) 201 even if the voltages applied to the excitation electrode 207 and the excitation electrode 209 have opposite polarities.

Next, the connection of the vibrator 100 will be described with reference to FIG.
FIG. 9A is a connection diagram of the vibrator. In the figure, 600 is a DC bias voltage source, 901 is an AC voltage source, 602 to 604 are switches, 605 is a terminal (1), and 606 is a terminal (2). The other components are the same as those of the vibrator 100 described with reference to FIG.

  The DC bias voltage source 600 (voltage value Vb) has a positive electrode connected to the output vibrator electrode pad 203 and a negative electrode connected to the support layer 210. Both ends of the AC voltage source 901 are connected to the terminal (1) 605 and the terminal (2) 606. The switches 602 to 604 can switch the connection between three states. One end of the switch 602 is connected to the excitation electrode pad 204, and two terminals among the other three terminals are the terminal (1) 605, respectively. And terminal (2) 606, and one terminal is open. In addition, one end of the switch 603 is connected to the excitation electrode pad 205, two of the other three terminals are connected to the terminal (1) 605 and the terminal (2) 606, respectively, and one terminal is opened. Yes. The switch 604 has one end connected to the excitation electrode pad 206, two of the other three terminals connected to the terminal (1) 605 and the terminal (2) 606, respectively, and one terminal opened. Yes. The output transducer electrode pad 203 is grounded.

  FIG. 9B is a waveform diagram of the AC voltage source. In the figure, reference numeral 910 denotes a waveform of the AC voltage source 901. In the figure, the horizontal axis indicates time, and the vertical axis indicates voltage value. The maximum value of the waveform 910 is the voltage Vac, and Vb> Vac. Further, as described above, since the electrostatic force acts in the same direction even if the polarity of the voltage applied to the excitation electrode is in the reverse direction, the frequency of the AC voltage source 901 is the resonance frequency of the output vibrator (cantilever) 201. Half of that.

  In the figure, a simplified circuit configuration in which an AC voltage is applied to the excitation electrode pads 204 to 206 is used to explain the principle of the change of the natural vibration mode. The oscillation circuit 103 is connected. Thus, an oscillation signal can be obtained by interacting between the output vibrator (cantilever) 201 and the excitation electrodes 207 to 209 via an electric field.

Next, the operation of the vibrator 100 will be described with reference to FIG.
FIG. 10 is a schematic diagram illustrating the natural vibration mode of the vibrator. This figure is a schematic view of the vibrator 100 as viewed from above.
FIG. 10A is a schematic diagram in a no-vibration state. In the figure, 700 indicates the position of the output vibrator (cantilever) 201. In the no-vibration state, the position 700 of the output vibrator (cantilever) 201 is a straight line.

FIG. 10B is a schematic diagram of the vibration state in the primary mode. Reference numeral 1001 denotes a position where the output vibrator (cantilever) 201 vibrates closest to the excitation electrode 208. Reference numeral 1002 denotes a position where the output vibrator (cantilever) 201 vibrates most away from the excitation electrode 208. Reference numeral 1003 denotes a vibration center position of the output vibrator (cantilever) 201.
The vibration center position 1003 of the output vibrator (cantilever) 201 is not curved because the vibrator potential is GND.
In the case of the vibration in the primary mode shown in the figure, it is necessary to make the connection state of the excitation electrode shown in FIG.

FIG. 10C is a diagram illustrating a connection state of the excitation electrodes during the first mode vibration.
As shown in the figure, all of the excitation electrodes 207 to 209 in FIG. 9 are connected to the terminal (1) 605 during the vibration in the primary mode. That is, all of the switches 602 to 604 are connected to the terminal (1) 605 side. As a result, an AC voltage having the same phase is applied to the excitation electrodes 207 to 209, and the electrostatic force exerted on the output vibrator (cantilever) 201 by the excitation electrodes 207 to 209 is always in the same direction. First-order mode vibration occurs.

Next, the vibration mode in the secondary mode will be described.
FIG. 10D is a schematic diagram of the vibration mode in the secondary mode. Reference numeral 1004 denotes a position where the output vibrator (cantilever) 201 vibrates and the antinode is closest to the excitation electrode 207, and reference numeral 1005 denotes an output vibrator (cantilever) 201 vibrates and the antinode is the most to the excitation electrode 209. It is a close position.
In the case of the secondary mode vibration shown in the figure, it is necessary to set the excitation electrode connection state shown in FIG.

FIG. 10E is a diagram illustrating a connection state of the excitation electrodes during secondary mode vibration.
As shown in the figure, at the time of secondary mode vibration, the excitation electrode 207 in FIG. 9 is connected to the terminal (1) 605, the excitation electrode 209 is connected to the terminal (2) 606, and the excitation electrode 208 is Opened. That is, the switch 602 is connected to the terminal (1) 605 side, the switch 604 is connected to the terminal (2) 606 side, and the switch 603 is opened. This is the connection state of the switch shown in FIG.

  As a result, alternating voltages having opposite phases are applied to the excitation electrodes 207 and 209, and no voltage is applied to the excitation electrode 208, so that the excitation electrode 207 exerts the output vibrator (cantilever) 201. Since the electrostatic force and the electrostatic force exerted on the output vibrator (cantilever) 201 by the excitation electrode 209 are always the same magnitude, the vibration of the second mode is performed with the portion of the excitation electrode 208 not subjected to the electrostatic force as a node. Will occur.

In this case, since the resonance frequency of the output vibrator (cantilever) 201 is about 2.8 times the resonance frequency in the primary mode, the frequency of the AC voltage source 901 needs to be set to about 2.8 times. There is.
By applying the DC bias voltage as described above, in the primary mode, it is possible to obtain an oscillation frequency that is half of the resonance frequency of the output vibrator (cantilever) 201. In this case, it is possible to obtain an oscillation frequency about 2.8 times that.

Next, an example of an oscillation circuit will be described with reference to FIG.
The oscillation circuit shown in the figure is a circuit example of the output oscillation circuit 103 described with reference to FIG. This oscillation circuit is a circuit to which a Colpitts oscillation circuit generally used in a crystal oscillator is applied.

  As shown in the figure, the oscillation circuit includes a vibrator 1100, a switch 1101, DC component cutting capacitors 1102 and 1103, load capacitors 1104 and 1105, load resistors 1108, inverters (amplifiers) 1110 and 1111, and an oscillation signal output terminal 1120. Consists of Here, the vibrator 1100 represents the vibrator 100 illustrated in FIG. 2, and the switch 1101 represents the switches 604 to 606 illustrated in FIG. 6. Here, the vibrator 1100 is an example of two terminals and the switch 1101 is an example of two input / output terminals, but the number of terminals is not limited to this example.

  Two input ends of the switch 1101 are connected to both ends of the vibrator 1100. One end of each of the DC component cut capacitors 1102 and 1103 is connected to the two output terminals of the switch 1101.

The other end of the DC component cutting capacitor 1102 is connected to one end of a load capacitor 1104, and is connected to an input end of an inverter (amplifier) 1110 and one end of a load resistor 1108. The other end of the DC component cutting capacitor 1103 is connected to one end of a load capacitor 1105, and the output end of the inverter (amplifier) 1110, the input end of the inverter (amplifier) 1111, and the other end of the load resistor 1108. Connected.
The other ends of the load capacitors 1104 and 1105 are grounded. The output of the inverter (amplifier) 1111 is connected to the oscillation signal output terminal 1120.

Next, the operation of the oscillation circuit will be described.
The oscillation circuit oscillates at the resonance frequency of the vibrator 1100 and outputs an oscillation signal from the oscillation signal output terminal 1120. Here, as described with reference to FIG. 7, the natural vibration mode of the vibrator 1100 can be changed by switching the switch 1101, and the oscillation frequency of the oscillator can be changed by changing the resonance frequency. This functions as a fundamental frequency selection circuit in the present invention.

  By using the configuration described above, the oscillator according to the present embodiment selects one fundamental frequency from a plurality of fundamental frequencies using not only the primary mode but also the natural vibration mode of the secondary mode or higher. An oscillation signal can be output.

Next, a second configuration example of the vibrator will be described.
FIG. 12 is a perspective view illustrating a second configuration example of the vibrator.
As shown in the figure, the vibrator 1200 includes an output vibrator (cantilever) 1201, output vibrator electrode pads 1202 and 1203, excitation electrode pads 1204 to 1209, excitation electrodes 1210 to 1215, a support layer 1216, Insulating layers 1217 to 1224 and fixing portions 1225 and 1226 are included.

In the output vibrator (cantilever) 1201, fixing portions 1225 and 1226 are fixed to the upper surface of the support layer 1216 via insulating layers 1217 and 1218.
The output vibrator (cantilever) 1201 is provided at the same height as the fixed portions 1225 and 1226, and there is no insulating layer between the output vibrator (cantilever) 1201 and the support layer 1216, thus forming a gap. Yes. Thereby, the output vibrator (cantilever) 1201 can mechanically vibrate. The output vibrator electrode pads 1202 and 1203 are provided on the fixing portions 1225 and 1226, respectively, and are electrically connected to the output vibrator (cantilever) 1201.

  Further, the excitation electrodes 1210 to 1215 are fixed to the upper surface of the support layer 1216 via insulating layers 1217 to 1224. The excitation electrode pads 1204 to 1209 are provided on the excitation electrodes 1210 to 1215, respectively, and are electrically connected to the excitation electrodes 1210 to 1215, respectively.

  The vibrator 1200 is formed by MEMS technology using an SOI (Silicon-On-Insulator) substrate. The SOI substrate includes an active layer, an insulating layer, and a support layer 1216. Of these layers, the active layer (silicon) is used to form an output vibrator (cantilever) 1201 and excitation electrodes 1210 to 1215. The output vibrator (cantilever) 1201 and the excitation electrodes 1210 to 1215 are formed by etching so as to face the support layer 1216 and be adjacent to each other. The excitation electrode 1210 and the excitation electrode 1213, the excitation electrode 1211 and the excitation electrode 1214, and the excitation electrode 1212 and the excitation electrode 1215 face each other, and the vibration output of the vibrator output vibrator (cantilever) 1201. It arrange | positions so that it may be located in. In order to make this vibrator output vibrator (cantilever) 1201 function as a movable electrode, the resistance of the active layer is lowered in advance by impurity doping or the like.

Further, by removing the insulating layer on the lower surface other than the fixed portions 1225 and 1226 of the output vibrator (cantilever) 1201 by etching after the processing of the active layer, the output vibrator (cantilever) 1201 and the support layer 1216 A gap (air gap) is formed between the two. Insulating layers 1217 and 1218 on the lower surface of the fixing portions 1225 and 1226 that remain without being etched electrically insulate the support layer 1216 and the output vibrator (cantilever) 1201 from each other and through the fixing portions 1225 and 1226. Fix it. With such a configuration, the output vibrator (cantilever) 1201 can vibrate with the fixed portions 1225 and 1226 as fulcrums.
The support layer 1216 is a semiconductor (silicon) substrate, which mechanically fixes the output vibrator (cantilever) 1201 and also functions as a fixed electrode.

  Furthermore, output vibrator electrode pads 1202 and 1203 are formed on the upper surfaces of the fixing portions 1225 and 1226 of the output vibrator (cantilever) 1201 by vapor deposition of aluminum (Al), respectively. In addition, excitation electrode pads 1204 to 1209 are formed on the upper surfaces of the excitation electrodes 1210 to 1215, and the respective pads are electrically connected to an external circuit using wire bonding (not shown).

Next, with reference to FIG. 13, the voltage application state to each electrode of the vibrator 1200 and the electrostatic force acting on the vibrator will be described.
In the figure, reference numerals 1300 to 1302 denote DC bias voltage sources. The other components are the same as those of the vibrator 1200 described with reference to FIG.

  The DC bias voltage source 1300 (voltage value Vbias) has a positive electrode connected to the output vibrator electrode pad 1202 and a negative electrode grounded. The DC bias voltage source 1301 (voltage value Va) has a positive electrode connected to the excitation electrode pad 1204 and a negative electrode grounded. The DC bias voltage source 1302 (voltage value Va) has a negative electrode connected to the excitation electrode pad 1206 and a positive electrode grounded. The support layer 1216 and the excitation electrode pads 1205, 1207, 1208, and 1209 are grounded. It is assumed that voltage value Vbias> voltage value Va.

Next, the electrostatic force acting on the vibrator in the voltage application state shown in FIG.
Since the output vibrator (cantilever) 1201 is applied with the voltage value Vbias, an electrostatic force acts between the excitation electrodes 1210 to 1215 to which a predetermined voltage is applied. That is, the magnitude of the electrostatic force F acting on the output vibrator (cantilever) 1201 is proportional to the potential difference between the vibrator and the electrode.

Here, the electrostatic force acting between the output vibrator (cantilever) 1201 and the excitation electrodes 1210 and 1213 is Fa, the electrostatic force acting between the excitation electrodes 1211 and 1214 is Fb, and the excitation electrodes 1212 and 1215. Let Fc be the electrostatic force acting between the two. In this case, the potential of the output vibrator (cantilever) 1201 is + Vbias and Vbias−Va <Vbias + Va.
| Fa | <| Fc |, Fb = 0
Satisfy the relationship.

Next, the connection of the vibrator 1200 will be described with reference to FIG.
FIG. 14A is a connection diagram of the vibrator. In the figure, 1400 is a DC bias voltage source, 1401 is an AC voltage source, 1402 to 1407 are switches, 1408 is a terminal (1), and 1409 is a terminal (2). The other components are the same as those of the vibrator 1200 described with reference to FIG.

  The DC bias voltage source 1400 (voltage value Vb) has a positive electrode connected to the output vibrator electrode pad 1203 and a negative electrode grounded. The AC voltage source 1401 has both ends connected to the terminal (1) 1408 and the terminal (2) 1409. The switches 1402 to 1407 can switch the connection between three states. One end of the switch 1402 is connected to the excitation electrode pad 1204, and two of the other three terminals are the terminal (1) 1408. And the terminal (2) 1409, and one terminal is open. The switch 1403 has one end connected to the excitation electrode pad 1205, two of the other three terminals connected to the terminal (1) 1408 and the terminal (2) 1409, and one terminal opened. Yes. In addition, one end of the switch 1404 is connected to the excitation electrode pad 1206, two of the other three terminals are connected to the terminal (1) 1408 and the terminal (2) 1409, respectively, and one terminal is opened. Yes.

  The switch 1405 has one end connected to the excitation electrode pad 1207, two of the other three terminals connected to the terminal (1) 1408 and the terminal (2) 1409, and one terminal opened. Yes. The switch 1406 has one end connected to the excitation electrode pad 1208, two of the other three terminals connected to the terminal (1) 1408 and the terminal (2) 1409, respectively, and one terminal opened. Yes. In addition, one end of the switch 1407 is connected to the excitation electrode pad 1209, two of the other three terminals are connected to the terminal (1) 1408 and the terminal (2) 1409, respectively, and one terminal is opened. Yes. The support layer 1216 is grounded.

  FIG. 14B is a waveform diagram of the AC voltage source. In the figure, reference numeral 1410 denotes a waveform of the AC voltage source 1401. In the figure, the horizontal axis indicates time, and the vertical axis indicates voltage value. The maximum value of the waveform 1410 is the voltage Vac, and Vb> Vac. The frequency of the AC voltage is made equal to the resonance frequency of the output vibrator (cantilever) 1201.

  In this figure, a simplified circuit configuration in which an AC voltage is applied to the excitation electrode pads 1204 to 1209 is used in order to explain the principle of the change of the natural vibration mode. The oscillation circuit 103 is connected. Thus, an oscillation signal can be obtained by interacting between the output vibrator (cantilever) 1201 and the excitation electrodes 1210 to 1215 via an electric field.

Next, the operation of the vibrator 1200 will be described with reference to FIG.
FIG. 15 is a schematic diagram illustrating the natural vibration mode of the vibrator. This figure is a schematic view of the vibrator 1200 as viewed from above.
FIG. 15A is a schematic diagram in a no-vibration state. In the figure, reference numeral 1500 denotes the position of the output vibrator (cantilever) 1201. In the no-vibration state, the position 1500 of the output vibrator (cantilever) 1201 is a straight line.

  FIG. 15B is a schematic diagram of the vibration state of the primary mode. Reference numeral 1501 denotes a position where the output vibrator (cantilever) 1201 vibrates closest to the excitation electrode 1214, and 1502 denotes a position where the output vibrator (cantilever) 1201 vibrates closest to the excitation electrode 1211. Reference numeral 1503 denotes a vibration center position of the output vibrator (cantilever) 1201.

When the primary mode vibration shown in the figure is generated, it is necessary to set the connection state of the excitation electrodes shown in FIG.
FIG. 15C is a diagram showing a connection state of the excitation electrodes during the primary mode vibration.
As shown in the figure, during the primary mode vibration, the excitation electrodes 1213 to 1215 in FIG. 14 are connected to the terminal (1) 1408, and the excitation electrodes 1210 to 1212 are connected to the terminal (2) 1409. That is, the switches 1405 to 1407 are connected to the terminal (1) 1408 side, and the switches 1402 to 1404 are connected to the terminal (2) 1409 side. This is the connection state of the switch shown in FIG.

  Accordingly, an alternating voltage having the same phase is applied to the excitation electrodes 1210 to 1212, and an alternating voltage having a phase opposite to that of the excitation electrodes 1210 to 1212 is applied to the excitation electrodes 1213 to 1215. Accordingly, the electrostatic force exerted on the output vibrator (cantilever) 1201 by the excitation electrodes 1210 to 1212 is always opposite to the electrostatic force exerted on the output vibrator (cantilever) 1201 by the excitation electrodes 1213 to 1215. Therefore, the first mode vibration is generated.

Next, the vibration mode in the secondary mode will be described.
FIG. 15D is a schematic diagram of the vibration mode in the secondary mode. 1504 is the position where the output vibrator (cantilever) 1201 vibrates and the antinode is closest to the excitation electrodes 1212 and 1213, and 1505 is the position where the output vibrator (cantilever) 1201 vibrates and the antinode is the most excitation electrode. It is a position approaching 1210 and 1215.
When the secondary mode vibration shown in the figure is generated, it is necessary to set the excitation electrode connection state shown in FIG.

FIG. 15E is a diagram showing a connection state of the excitation electrodes during secondary mode vibration.
As shown in the figure, at the time of vibration in the secondary mode, the excitation electrodes 1212 and 1213 in FIG. 14 are connected to the terminal (1) 1408, and the excitation electrodes 1210 and 1215 are connected to the terminal (2) 1409. The electrodes 1211 and 1214 are opened. That is, the switches 1404 and 1405 are connected to the terminal (1) 1408 side, the switches 1402 and 1407 are connected to the terminal (2) 1409 side, and the switches 1403 and 1406 are opened.

Thereby, an alternating voltage having the same phase is applied to the excitation electrodes 1212 and 1213, and an alternating voltage having an opposite phase to that of the excitation electrodes 1212 and 1213 is applied to the excitation electrodes 1210 and 1215. No voltage is applied to 1211, 1214.
Therefore, the electrostatic force exerted on the output vibrator (cantilever) 1201 by the excitation electrodes 1210 and 1213 and the electrostatic force exerted on the output vibrator (cantilever) 1201 by the excitation electrodes 1212 and 1215 are always in opposite directions. Therefore, the vibration of the secondary mode having two antinodes and one node occurs.

In this case, since the resonance frequency of the output vibrator (cantilever) 1201 is about 2.8 times the resonance frequency in the primary mode, the frequency of the AC voltage source 1401 must also be set to about 2.8 times. There is.
That is, when the above-described vibrator 1200 is used, an oscillation frequency having a fundamental frequency of about 2.8 times that of the secondary mode can be obtained in addition to the fundamental frequency that is the primary mode.

Next, a third configuration example of the vibrator will be described.
FIG. 16 is a perspective view showing a third configuration example of the vibrator.
As shown in the figure, the vibrator 1600 includes an output vibrator (cantilever) 1601, an output vibrator electrode pad 1602, excitation electrode pads 1603 to 1605, excitation electrodes 1606 to 1608, a support layer 1609, and an insulating layer. 1616 to 1613 and a fixed portion 1614.

The output vibrator (cantilever) 1601 has a fixing portion 1614 fixed to the upper surface of the support layer 1609 with an insulating layer 1610 interposed therebetween.
The output vibrator (cantilever) 1601 is provided at the same height as the fixed portion 1614, and there is no insulating layer between the output vibrator (cantilever) 1601 and the support layer 1609, and there is a gap. Thereby, the output vibrator (cantilever) 1601 can vibrate mechanically. The output vibrator electrode pad 1602 is provided on the fixed portion 1614 and is electrically connected to the output vibrator (cantilever) 1601.

  The excitation electrodes 1606 to 1608 are fixed to the upper surface of the support layer 1609 through insulating layers 1611 to 1613. The excitation electrode pads 1603 to 1605 are provided on the excitation electrodes 1606 to 1608, respectively, and are electrically connected to the excitation electrodes 1606 to 1608, respectively.

  The vibrator 1600 is formed by MEMS technology using an SOI (Silicon-On-Insulator) substrate. The SOI substrate includes an active layer, an insulating layer, and a support layer 1609. Among these layers, the active layer (silicon) is used to form an output vibrator (cantilever) 1601 and excitation electrodes 1606 to 1608. The output vibrator (cantilever) 1601 and the excitation electrodes 1606 to 1608 are formed to be opposite to the support layer 1609 and adjacent to each other by etching. The excitation electrodes 1606 to 1608 are arranged so as to be positioned on the antinodes of vibration of the vibrator output vibrator (cantilever) 1601. In order to make this vibrator output vibrator (cantilever) 1601 function as a movable electrode, the resistance of the active layer is lowered in advance by impurity doping or the like.

Further, by removing the insulating layer on the lower surface other than the fixed portion 1614 of the output vibrator (cantilever) 1601 by etching after the processing of the active layer, the gap between the output vibrator (cantilever) 1601 and the support layer 1609 is removed. A gap is formed. The insulating layer 1610 on the lower surface of the fixing portion 1614 that remains without being etched electrically insulates the support layer 1609 and the output vibrator (cantilever) 1601 and fixes them via the fixing portion 1614. With such a configuration, the output vibrator (cantilever) 1601 can vibrate with the fixed portion 1614 as a fulcrum.
The support layer 1609 is a semiconductor (silicon) substrate, which mechanically fixes the output vibrator (cantilever) 1601 and also functions as a fixed electrode.

  Further, an output vibrator electrode pad 1602 is formed on the upper surface of the fixed portion 1614 of the output vibrator (cantilever) 1601 by vapor deposition of aluminum (Al). In addition, excitation electrode pads 1603 to 1605 are formed on the upper surfaces of the excitation electrodes 1606 to 1608, respectively, and the respective pads are electrically connected to an external circuit using wire bonding (not shown).

Next, with reference to FIG. 17, the state of voltage application to the electrodes of the vibrator 1600 and the electrostatic force acting on the vibrator will be described.
In the figure, reference numerals 1700 to 1702 denote DC bias voltage sources. The other components are the same as those of the vibrator 1600 described with reference to FIG.

  The DC bias voltage source 1700 (voltage value Vbias) has a positive electrode connected to the output vibrator electrode pad 1602 and a negative electrode connected to the support layer 1609. The DC bias voltage source 1701 (voltage value + Va) has a positive electrode connected to the excitation electrode pad 1603 and a negative electrode grounded. The DC bias voltage source 1702 (voltage value −Va) has a negative electrode connected to the excitation electrode pad 1605 and a positive electrode grounded. The output vibrator electrode pad 1602 and the excitation electrode pad 1604 are grounded. It is assumed that voltage value Vbias> voltage value Va.

Next, the electrostatic force acting on the vibrator in the voltage application state shown in FIG.
An electrostatic force acts between the output vibrator (cantilever) 1601 and the excitation electrodes 1603 to 1605 to which a predetermined voltage is applied. That is, the magnitude of the electrostatic force F acting on the output vibrator (cantilever) 1601 is proportional to the potential difference between the vibrator and the electrode.

Here, the electrostatic force acting between the output vibrator (cantilever) 1601 and the excitation electrode 1606 is Fa, the electrostatic force acting between the excitation electrode 1607 is Fb, and the static electricity acting between the excitation electrode 1608 The force is Fc. In this case, since the potential of the output vibrator (cantilever) 1601 is GND, each electrostatic force described above is
| Fa | <| Fb | <| Fc |
Satisfy the relationship.

Next, connection of the vibrator 1600 will be described with reference to FIG.
FIG. 18A is a connection diagram of the vibrator. In the figure, 1800 is a DC bias voltage source, 1801 is an AC voltage source, 1802 to 1804 are switches, 1805 is a terminal (1), and 1806 is a terminal (2). The other components are the same as those of the vibrator 1600 described with reference to FIG.

  The DC bias voltage source 1800 (voltage value Vb) has a positive electrode connected to the output vibrator electrode pad 1602 and a negative electrode connected to the support layer 1609. Both ends of the AC voltage source 1801 are connected to the terminal (1) 1805 and the terminal (2) 1806. The switches 1802 to 1804 can switch the connection between three states. One end of the switch 1802 is connected to the excitation electrode pad 1603, and two of the three terminals at the other end are the terminal (1) 1805, respectively. And the terminal (2) 1806, and one terminal is open. Further, one end of the switch 1803 is connected to the excitation electrode pad 1604, two of the other three terminals are connected to the terminal (1) 1805 and the terminal (2) 1806, respectively, and one terminal is opened. Yes. Further, one end of the switch 1804 is connected to the excitation electrode pad 1605, two of the other three terminals are connected to the terminal (1) 1805 and the terminal (2) 1806, respectively, and one terminal is opened. Yes. The output transducer electrode pad 1602 is grounded.

  FIG. 18B is a waveform diagram of the AC voltage source. In the figure, reference numeral 1810 denotes the waveform of the AC voltage source 1801. In the figure, the horizontal axis indicates time, and the vertical axis indicates voltage value. The maximum value of the waveform 1810 is the voltage Vac, and Vb> Vac. Further, as described above, even if the polarity of the voltage applied to the excitation electrode is in the reverse direction, the electrostatic force acts in the same direction. Therefore, the frequency of the AC voltage source 1801 is the resonance frequency of the output vibrator (cantilever) 1601. Half of that.

  In the figure, a simplified circuit configuration in which an AC voltage is applied to the excitation electrode pads 1603 to 1605 is used to explain the principle of the change of the natural vibration mode. The oscillation circuit 103 is connected. Thus, an oscillation signal can be obtained by interacting between the output vibrator (cantilever) 1601 and the excitation electrodes 1606 to 1608 via an electric field.

Next, the operation of the vibrator 1600 will be described with reference to FIG.
FIG. 19 is a schematic diagram illustrating the natural vibration mode of the vibrator. This figure is a schematic view of the vibrator 1600 as viewed from above.
FIG. 19A is a schematic diagram in a no-vibration state. In the figure, 1900 represents the position of an output transducer (cantilever) 1601. In the no-vibration state, the position 1900 of the output vibrator (cantilever) 1601 is a straight line.

FIG. 19B is a schematic diagram of the vibration state of the primary mode. Reference numeral 1901 denotes a position where the output vibrator (cantilever) 1601 vibrates closest to the excitation electrode 1608, and 1902 denotes a position where the output vibrator (cantilever) 1601 vibrates most away from the excitation electrode 1608. Reference numeral 1903 denotes the vibration center position of the output vibrator (cantilever) 1601.
The vibration center position 1903 of the output vibrator (cantilever) 1601 is affected by the DC bias voltage source 1800 (voltage Vb) applied to the output vibrator (cantilever) 1601, and an attractive force acts on the excitation electrode 1608 side. Bend.
In the case of the vibration in the primary mode shown in the figure, it is necessary to set the excitation electrode connection state shown in FIG.

FIG. 19C is a diagram illustrating a connection state of the excitation electrodes during the vibration in the primary mode.
As shown in the figure, all of the excitation electrodes 1606 to 1608 in FIG. 18 are connected to the terminal (1) 1805 at the time of vibration in the primary mode. That is, all of the switches 1802 to 1804 are connected to the terminal (1) 1805 side. As a result, AC voltages having the same phase are applied to the excitation electrodes 1606 to 1608, and the electrostatic force exerted on the output vibrator (cantilever) 1601 by the excitation electrodes 1606 to 1608 is always in the same direction. First-order mode vibration occurs.

Next, the vibration mode in the secondary mode will be described.
FIG. 19D is a schematic diagram of the vibration mode in the secondary mode. Reference numeral 1904 denotes a position where the output vibrator (cantilever) 1601 vibrates and the free end is closest to the excitation electrode 1608. Reference numeral 1905 denotes the output vibrator (cantilever) 1601 vibrates and the free end is the excitation electrode most. It is a position away from 1608.
In the case of the vibration in the secondary mode shown in the figure, it is necessary to make the connection state of the excitation electrode shown in FIG.

FIG. 19 (e) is a diagram showing a connection state of the excitation electrodes during secondary mode vibration.
As shown in the figure, at the time of vibration in the secondary mode, the excitation electrodes 1606 and 1607 in FIG. 18 are connected to the terminal (1) 1805 and the excitation electrode 1608 is opened. That is, the switches 1802 and 1803 are connected to the terminal (1) 1805 side, and the switch 1804 is opened. This is the connection state of the switch shown in FIG.

  As a result, an alternating voltage having the same phase is applied to the excitation electrodes 1606 and 1607, and no voltage is applied to the excitation electrode 1608. Accordingly, the electrostatic force exerted on the output vibrator (cantilever) 1601 by the excitation electrodes 1606 and 1607 becomes a force whose direction is the same and whose intensity changes periodically, and the output vibrator (cantilever) is driven by the excitation electrode 1608. ) The electrostatic force exerted on 1601 is always a constant force. As a result, the output vibrator (cantilever) 1601 vibrates in the vicinity of the excitation electrode 1607 as a belly while the tip vibrates freely. That is, this periodic force generates a secondary mode vibration having two antinodes and one node.

In this case, since the resonance frequency of the output vibrator (cantilever) 1601 is about 6.3 times the resonance frequency in the primary mode, the frequency of the AC voltage source 1801 must also be set to about 6.3 times. There is.
By applying the above-described DC bias voltage to the vibrator 1600 having the above-described configuration, an oscillation frequency that is half the resonance frequency of the output vibrator (cantilever) 1601 is obtained in the primary mode. In the secondary mode, an oscillation frequency about 6.3 times that can be obtained.

  With the configuration described above, this oscillator can be formed by integrating all the components on the same substrate. Further, for example, other integrated circuits that perform various signal processing using the oscillation signal of the present oscillation circuit can be formed on the same substrate.

As mentioned above, although embodiment of this invention was explained in full detail, the concrete structure is not restricted to this embodiment, The design change etc. of the range which does not deviate from the summary of this invention are included.
For example, the number of excitation electrodes is not limited to the above-described example, and the configuration of the oscillation circuit is not limited to the configuration illustrated in FIG.

It is a block diagram of the oscillator concerning the embodiment of the present invention. It is a perspective view which shows the 1st structural example of a vibrator | oscillator same as the above. It is a principle figure showing a vibrator same as the above. It is a figure explaining the application state of the voltage to each electrode of a vibrator | oscillator same as the above, and the electrostatic force which acts on a vibrator | oscillator. It is explanatory drawing of the natural vibration mode of a vibrator | oscillator same as the above. It is a connection diagram of a vibrator same as the above. It is a schematic diagram showing the natural vibration mode of the vibrator same as the above It is a figure explaining the application state of the voltage to the electrode of a vibrator | oscillator same as the above, and the electrostatic force which acts on a vibrator | oscillator. It is a connection diagram of a vibrator same as the above. It is a schematic diagram showing the natural vibration mode of a vibrator | oscillator same as the above. It is a circuit diagram of an oscillation circuit same as the above. It is a perspective view which shows the 2nd structural example of a vibrator | oscillator same as the above. It is a figure explaining the application state of the voltage to the electrode of a vibrator | oscillator same as the above, and the electrostatic force which acts on a vibrator | oscillator. It is a connection diagram of a vibrator same as the above. It is a schematic diagram showing the natural vibration mode of a vibrator | oscillator same as the above. It is a perspective view which shows the 3rd structural example of a vibrator | oscillator same as the above. It is a figure explaining the application state of the voltage to the electrode of a vibrator | oscillator same as the above, and the electrostatic force which acts on a vibrator | oscillator. It is a connection diagram of a vibrator same as the above. It is a schematic diagram showing the natural vibration mode of a vibrator | oscillator same as the above.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100; Output vibrator, 101; DC bias voltage application circuit, 102; Fundamental frequency selection circuit, 103; Output oscillation circuit, 201; Output vibrator (cantilever), 202, 203; Output vibrator electrode pad, 204-206; Excitation electrode pad, 207-209; Excitation electrode, 210; Support layer, 211-215; Insulating layer, 216, 217; Fixing part, 301; Spring, 302; Weight, 303; Substrate, 304; Excitation electrode, 305; Electrode, 306; AC power supply, 307; DC power supply, 400 to 402; DC bias voltage source, 500; Output vibrator, 501; Support point, 600; DC bias voltage source, 601; 602 to 604; switch 605; terminal (1), 606; terminal (2), 700; position of output vibrator (cantilever), 701; output Position at which the moving element (cantilever) vibrates closest to the excitation electrode 208, 702; Position at which the output vibrator (cantilever) vibrates most away from the excitation electrode 208, 703; Output vibrator (cantilever) ); 901; AC voltage source, 910; AC voltage source waveform, 1001; Position where the output vibrator (cantilever) vibrates closest to the excitation electrode 208, 1002; Output vibrator ( The position where the cantilever oscillates most away from the excitation electrode 208, 1003; the vibration center position of the output vibrator (cantilever), 1004; 1005; position where the output vibrator (cantilever) vibrates and the antinode is closest to the excitation electrode 209, 1100; Child, 1101; switches, 1102 and 1103; the DC component cutting capacitor, 1104 and 1105; load capacity, 1108; load resistors, 1110, 1111; inverter (amplifier), 1120; oscillation signal output terminal.

Claims (6)

An output vibrator provided so as to vibrate mechanically;
A DC voltage application unit for applying a DC voltage to the output vibrator;
A plurality of excitation electrodes arranged along the longitudinal direction of the output vibrator, which are arranged in the vicinity of the vibration abdomen of the output vibrator, and an electric field is generated between the output vibrator and the output vibrator. A plurality of excitation electrodes interacting with each other,
An oscillation circuit that is electrically connected to the plurality of excitation electrodes and oscillates at a resonance frequency of the output vibrator and outputs an oscillation signal ;
An oscillator comprising: a fundamental frequency selection circuit that changes a natural vibration mode of the output vibrator by selecting an electrical connection path from the oscillation circuit to each of the excitation electrodes . The output vibrator is disposed to face a support layer that is a semiconductor substrate, at least a part of which is fixed to an insulating layer on the support layer,
2. The oscillator according to claim 1 , wherein the plurality of excitation electrodes are arranged to face the support layer, and the entirety thereof is fixed to the insulating layer on the support layer. 3. The oscillator according to claim 2 , wherein the plurality of excitation electrodes are arranged on one side of the output vibrator along a long side direction of the output vibrator. The oscillator according to claim 2 , wherein the plurality of excitation electrodes are arranged on both sides of the output vibrator along a long side direction of the output vibrator. Wherein the output transducer positive voltage of the DC is applied, the oscillator according to any one of the preceding claims 2, wherein the supporting layer is characterized in that the grounded. The oscillator according to claim 2 or 3 , wherein the output vibrator is grounded, and a negative DC voltage is applied to the support layer.

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