Vibration device and oscillator

A vibration device includes a quartz substrate including a first vibration section, a second vibration section, and a third vibration section, a pair of first excitation electrodes formed at two principal surfaces of the quartz substrate, a pair of second excitation electrodes so formed as to sandwich the second vibration section in the thickness direction of the quartz substrate, and a pair of third excitation electrodes so formed as to sandwich the third vibration section in the thickness direction of the quartz substrate. At least one of the pair of second excitation electrodes is formed at a first inclining surface that inclines with respect to the two principal surfaces. At least one of the pair of third excitation electrodes is formed at a second inclining surface that inclines with respect to the two principal surfaces. The second inclining surface inclines with respect to the first inclining surface.

The present application is based on, and claims priority from JP Application Serial Number 2020-087260, filed May 19, 2020, the disclosure of which is hereby incorporated by reference herein in its entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to a vibration device and an oscillator.

2. Related Art

To generate a frequency signal that is stable over a wide temperature range, a temperature compensated crystal oscillator (TCXO) including a temperature detection device and a temperature compensation circuit is widely used. However, a TCXO, in which the vibration device made of quartz and the temperature detection device are separately configured and the temperature detected by the temperature detection device and there is therefore a discrepancy due to a detection error between the temperature of the vibration device, has a difficulty performing temperature compensation with high precision.

To eliminate the difficulty, a vibration device in which a first vibration section for oscillation signal output and a second vibration section for temperature detection are provided on a common piezoelectric plate is disclosed, as shown in JP-A-2013-98841. Since the two vibration sections are formed on the common piezoelectric plate, heat transfer is quickly performed between the first and second vibration sections. Therefore, the detection error between the temperature detected by the second vibration section for temperature detection and the temperature of the first vibration section for oscillation signal output is smaller than the detection error when the vibration device and the temperature detection device are separately configured, whereby the temperature compensation can be performed with higher precision.

In the vibration device described in JP-A-2013-98841, however, a vibration excitation electrode for oscillation signal output and a vibration excitation electrode for temperature detection are formed on surfaces of the piezoelectric plate that have been cut at the same cutting angle, and the first vibration section for oscillation signal output and the second vibration section for temperature detection have the same frequency-temperature characteristic. The first vibration section for oscillation signal output is cut at a cutting angle so set that a frequency change is small with respect to a temperature change, and the second vibration section for temperature detecting therefore also has a frequency-temperature characteristic providing a small frequency change with respect to a temperature change, resulting in low resolution of a temperature change with respect to a frequency change and hence a problem of imprecise temperature detection.

SUMMARY

A vibration device includes a quartz substrate including a first vibration section, a second vibration section, and a third vibration section, a pair of first excitation electrodes formed at two principal surfaces of the quartz substrate in the first vibration section, a pair of second excitation electrodes so formed in the second vibration section as to sandwich the second vibration section in a thickness direction of the quartz substrate, and a pair of third excitation electrodes so formed in the third vibration section as to sandwich the third vibration section in the thickness direction of the quartz substrate. At least one of the pair of second excitation electrodes is formed at a first inclining surface that inclines with respect to the two principal surfaces. At least one of the pair of third excitation electrodes is formed at a second inclining surface that inclines with respect to the two principal surfaces. The second inclining surface inclines with respect to the first inclining surface.

An oscillator includes the vibration device described above, a first oscillation circuit that is electrically coupled to the first excitation electrodes and outputs a first oscillation signal, a second oscillation circuit that is electrically coupled to the second excitation electrodes and outputs a second oscillation signal, a third oscillation circuit that is electrically coupled to the third excitation electrodes and outputs a third oscillation signal, and a control signal output circuit to which at least one of the second oscillation signal and the third oscillation signal is inputted and which outputs a control signal that controls an oscillation frequency of the first oscillation signal based on the inputted signal.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

1. First Embodiment

A schematic configuration of a vibration device1according to a first embodiment will be described with reference toFIGS.1and2.

Out of axes X, Y, and Z perpendicular to one another, axes Y′ and Z′ inFIGS.1and2are the axes Y and Z rotated around the axis X by a predetermined angle.

The vibration device1according to the first embodiment includes a quartz substrate2, first excitation electrodes4, which are formed at a first vibration section3, second excitation electrodes6, which are formed at a second vibration section4, third excitation electrodes8, which are formed at a third vibration section7, terminals10,11, and12, which are formed at fixing sections9, lead electrodes13, which couple the first excitation electrodes4to the terminals10in an electrically conductive manner, lead electrodes14, which couple the second excitation electrodes6to the terminals11in an electrically conductive manner, and lead electrodes15, which couple the third excitation electrodes8to the terminals12in an electrically conductive manner.

The vibration device1includes a first vibration device X1, a second vibration device X2, and a third vibration device X3. The first vibration device X1includes the first vibration section3, at which a pair of first excitation electrodes4are formed. The second vibration device X2includes the second vibration section5, at which a pair of second excitation electrodes6are formed. The third vibration device X3includes the third vibration section7, at which a pair of third excitation electrodes8are formed. The first vibration device X1, the second vibration device X2, and the third vibration device X3share the quartz substrate2and therefore each have a structure that is likely to allow external heat to be uniformly transferred among them.

The quartz substrate2includes the first vibration section3, the second vibration section5, the third vibration section7, and the fixing sections9, which fix the quartz substrate2to a package that is not shown. The quartz substrate2is a flat plate so configured that the surface XZ′ is a principal surface and the direction along the axis Y′ is the thickness direction.

The first vibration section3, the second vibration section5, and the third vibration section7are juxtaposed with each other in the direction along the axis Z′ and arranged in the order of the third vibration section7, the first vibration section3, and the second vibration section5toward the positive side of the axis Z′. The fixing sections9are so disposed as to be shifted in the direction along the axis X, which is perpendicular to the axis Z′, from the first vibration section3, the second vibration section5, the third vibration section7.

The first vibration section3has a first principal surface16aand a second principal surface16bof the quartz substrate2, and the second principal surface16bis parallel to the first principal surface16a. The pair of first excitation electrodes4are so formed on the first principal surface16aand the second principal surface16bof the first vibration section3as to sandwich the first vibration section3in the thickness direction of the quartz substrate2. The first excitation electrode4on the first principal surface16aand the first excitation electrode4on the second principal surface16bare so disposed as to coincide with each other in the plan view in the direction along the axis Y′. The first principal surface16aand the second principal surface16bcorrespond to two principal surfaces.

The second vibration section5has a first inclining surface17and the second principal surface16bof the quartz substrate2. The pair of second excitation electrodes6are so formed on the first inclining surface17and the second principal surface16bof the second vibration section5as to sandwich the second vibration section5in the thickness direction of the quartz substrate2. The second excitation electrode6on the first inclining surface17and the second excitation electrode6on the second principal surface16bare so disposed as to coincide with each other in the plan view in the direction along the axis Y′.

The first inclining surface17is an inclining surface that inclines by a predetermined inclination angle with respect to the first principal surface16a, and the first inclining surface17inclines in the first embodiment in such a way that the thickness of the second vibration section5decreases as the distance from the first vibration section3increases.

The third vibration section7has a second inclining surface18and the second principal surface16bof the quartz substrate2. The pair of third excitation electrodes8are so formed on the second inclining surface18and the second principal surface16bof the third vibration section7as to sandwich the third vibration section7in the thickness direction of the quartz substrate2. The third excitation electrode8on the second inclining surface18and the third excitation electrode8on the second principal surface16bare so disposed as to coincide with each other in the plan view in the direction along the axis Y′.

The second inclining surface18is an inclining surface that inclines by a predetermined inclination angle with respect to the first principal surface16a, and the second inclining surface18inclines in the first embodiment in such a way that the thickness of the third vibration section7decreases as the distance from the first vibration section3increases.

The first vibration device X1includes the first vibration section3, the first excitation electrodes4, which are formed at the first vibration section3, the terminals10, which are formed at the fixing section9, and the lead electrodes13, which couple the first excitation electrodes4to the terminals10in an electrically conductive manner.

On the first principal surface16aof the first vibration device X1are formed the first excitation electrode4, the terminal10, which electrically couples the first vibration device X1to an oscillation circuit that is not shown, and the lead electrode13, which electrically couples the first excitation electrode4to the terminal10. Further, on the second principal surface16bof the first vibration device X1are formed the first excitation electrode4, the terminal10, which electrically couples the first vibration device X1to the oscillation circuit that is not shown, and the lead electrode13, which electrically couples the first excitation electrode4to the terminal10.

The second vibration device X2includes the second vibration section5, the second excitation electrodes6, which are formed at the second vibration section5, the terminals11, which are formed at the fixing section9, and the lead electrodes14, which couple the second excitation electrodes6to the terminals11in an electrically conductive manner.

On the first inclining surface17of the second vibration device X2are formed the second excitation electrode6, the terminal11, which electrically couples the second vibration device X2to the oscillation circuit that is not shown, and the lead electrode14, which electrically couples the second excitation electrode6to the terminal11. Further, on the second principal surface16bof the second vibration device X2are formed the second excitation electrode6, the terminal11, which electrically couples the second vibration device X2to the oscillation circuit that is not shown, and the lead electrode14, which electrically couples the second excitation electrode6to the terminal11.

The third vibration device X3includes the third vibration section7, the third excitation electrodes8, which are formed at the third vibration section7, the terminals12, which are formed at the fixing section9, and the lead electrodes15, which couple the third excitation electrodes8to the terminals12in an electrically conductive manner.

On the second inclining surface18of the third vibration device X3are formed the third excitation electrode8, the terminal12, which electrically couples the third vibration device X3to the oscillation circuit that is not shown, and the lead electrode15, which electrically couples the third excitation electrode8to the terminal12. Further, on the second principal surface16bof the third vibration device X3are formed the third excitation electrode8, the terminal12, which electrically couples the third vibration device X3to the oscillation circuit that is not shown, and the lead electrode15, which electrically couples the third excitation electrode8to the terminal12.

Since the first vibration device X1has the pair of first excitation electrodes4formed on the two principal surfaces16aand16bof the first vibration section3, applying voltage to the terminals10allows the first vibration section3to vibrate.

Since the second vibration device X2has the pair of second excitation electrodes6so formed on the first inclining surface17and the second principal surface16bof the second vibration section5as to sandwich the second vibration device X2in the thickness direction of the quartz substrate2, applying voltage to the terminals11allows the second vibration section5to vibrate.

Since the third vibration device X3has the pair of third excitation electrodes8so formed on the second inclining surface18and the second principal surface16bof the third vibration section7as to sandwich the third vibration device X3in the thickness direction of the quartz substrate2, applying voltage to the terminals12allows the third vibration section7to vibrate.

A first through hole19, a second through hole20, and a third through hole21are provided between the first vibration section3and the fixing section9, between the second vibration section5and the fixing section9, and between the third vibration section7and the fixing section9, respectively. Providing the first through hole19, the second through hole20, and the third through hole21allows suppression of transmission of stress induced when the vibration device1is fixed to the package, which is not shown, via a bonding member, such as an adhesive or bumps, from the fixing sections9to the first vibration section3, the second vibration section5, and the third vibration section7.

Small-width sections22a,22b,22c, and22dare provided between the first vibration section3and the fixing section9, between the second vibration section5and the fixing section9, and between the third vibration section7and the fixing section9, respectively. The small-width sections are portions of the quartz substrate2that are the portion that couples the first vibration section3to the fixing section9, the portion that couples the second vibration section5to the fixing section9, and the portion that couples the third vibration section7to the fixing section9and each have a length in the direction along the axis Z′ shorter than the overall length of the quartz substrate2in the direction along the axis Z′. Providing the small-width sections22a,22b,22c, and22dallows suppression of transmission of the stress induced when the vibration device1is fixed to the package, which is not shown, via the bonding member, such as an adhesive or bumps, from the fixing sections to the first vibration section3, the second vibration section5, and the third vibration section7.

In the first embodiment, the small-width sections22a,22b,22c, and22dare formed by providing the first through hole19, the second through hole20, and the third through hole21, but not necessarily, and may instead be formed by providing the quartz substrate2with cutouts formed by cutting in the direction along the axis Z′ part of edges of the quartz substrate2that are the edges parallel to the direction along the axis X in the plan view in the direction along the axis Y′.

The cutting angle of the quartz substrate2in the present embodiment will next be described with reference toFIG.3.

A piezoelectric material, such as quartz, belongs to a trigonal system and has crystal axes X, Y, and Z perpendicular to one another, as shown inFIG.3. The axes X, Y, and Z are called an electrical axis, a mechanical axis, and an optical axis, respectively.

For example, as the piezoelectric substrate, a flat plate formed of what is called a rotated-Y-cut quartz substrate, which is produced by cutting a quartz block along a rotated plane XZ rotated around the axis X by a predetermined angle θ1, is used as the quartz substrate2. The angle θ1 is also called a cutting angle of the rotated-Y-cut quartz substrate.

The rotation direction in which the plane XZ is rotated around the axis X is indicated by the arrow B; the counterclockwise rotation when viewed from the positive side of the axis X, which is the axis of rotation, is called a positive rotation, and the clockwise rotation is called a negative rotation.

Assuming that the axis Y′ is a coordinate axis that is the rotated axis Y rotated by the angle θ1 around the axis X and the axis Z′ is a coordinate axis that is the rotated axis Z rotated by the angle θ1 around the axis X, the rotated-Y-cut quartz substrate can be expressed by crystal axes X, Y′, and Z′ perpendicular to one another. The rotated-Y-cut quartz substrate has a thickness direction along the axis Y′ and has a principal surface that is the plane XZ′ containing the axes X and Z′ perpendicular to the axis Y′, and a thickness slip vibration is excited as primary vibration at the principal surface.

A rotated-Y-cut quartz substrate having an angle θ1 of about 35° 15′ is called an AT-cut quartz substrate and has an excellent frequency-temperature characteristic. The following description of the present embodiment will be made by using the AT-cut quartz substrate as an example of the quartz substrate2, but not necessarily, and the quartz substrate2may be, for example, a BT-cut quartz substrate that allows excitation of thickness slip vibration. When the AT-cut quartz substrate is used as the quartz substrate2, the angle θ1 may be about 35° 15′ or may instead, for example, be 35° 17′.

In the present embodiment, the angle θ1 of the quartz substrate2is 35° 15′. The cutting angle of the two principal surfaces16aand16bof the quartz substrate2is therefore θ1, that is, 35° 15′.

The first inclining surface17of the quartz substrate2inclines by an angle θ2 with respect to the first principal surface16a. That is, since the first inclining surface17of the quartz substrate2is rotated from the axis Z′ in the positive direction around the axis X, the cutting angle of the first inclining surface17is θ1+θ2, that is, 35° 15′+θ2.

The second inclining surface18of the quartz substrate2inclines by an angle θ3 with respect to the first principal surface16a. That is, since the second inclining surface18of the quartz substrate2is rotated from the axis Z′ in the negative direction around the axis X, the cutting angle of the second inclining surface18is θ1−θ3, that is, 35° 15′−θ3.

In the present embodiment, the cutting angle of the first inclining surface17is θ1+θ2, and the cutting angle of the second inclining surface18is θ1−θ3, so that the cutting angle of the first inclining surface17differs from the cutting angle of the second inclining surface18.

The state in which the cutting angle of the first inclining surface17differs from the cutting angle of the second inclining surface18also refers to a state in which the second inclining surface18inclines with respect to the first inclining surface17.

The relationship between the cutting angle and the frequency-temperature characteristic of the quartz substrate2will next be described with reference toFIGS.4and5.FIG.4shows the relationship of the frequency-temperature characteristic with the cutting angle of a rotated-Y-cut quartz substrate with the cutting angle changed by an increment of 2′ with respect to an AT-cut quartz substrate having the cutting angle of 35° 15′. For example, inFIG.4, the curve labeled with +10 represents the frequency-temperature characteristic of the rotated-Y-cut quartz substrate having a cutting angle of 35° 15′+10′, that is, a cutting angle of 35° 25′. Changing the cutting angle as described above allows adjustment of the amount of frequency change Δf/f with respect to a temperature change.

In the present embodiment, one of the pair of second excitation electrodes6, which excite the second vibration section5, is provided on the first inclining surface17, and the other second excitation electrode6is provided on the second principal surface16b, so that the frequency-temperature characteristic of the second vibration device X2in the present embodiment is somewhere between the frequency-temperature characteristic corresponding to the cutting angle θ1+θ2=35° 15′+θ2 of the first inclining surface17and the frequency-temperature characteristic corresponding to the cutting angle θ1=35° 15′ of the second principal surface16b. Specifically, the amount of change Δf/f in the frequency of the second vibration device X2with respect to a change in the temperature thereof is the amount of frequency change Δf/f with respect to a temperature change when the cutting angle is ((θ1+θ2)+θ1)/2=(2θ1+θ2)/2, that is, θ1+θ2/2=35° 15′+θ2/2.

One of the pair of third excitation electrodes8, which excite the third vibration section7, is provided on the second inclining surface18, and the other third excitation electrode8is provided on the second principal surface16b, so that the frequency-temperature characteristic of the third vibration device X3in the present embodiment is somewhere between the frequency-temperature characteristic corresponding to the cutting angle of 35° 15′−θ3 of the second inclining surface18and the frequency-temperature characteristic corresponding to the cutting angle of 35° 15′ of the second principal surface16b. Specifically, the amount of change Δf/f in the frequency of the third vibration device X3with respect to a change in the temperature thereof is the amount of frequency change Δf/f with respect to a temperature change when the cutting angle is 35° 15′−θ3/2.

InFIG.5showing an example of the frequency-temperature characteristic of the vibration device1according to the present embodiment, AT1represents the frequency-temperature characteristic of the first vibration device X1, AT2represents the frequency-temperature characteristic of the second vibration device X2, and AT3represents the frequency-temperature characteristic of the third vibration device X3.

Since the angle θ1 of the first vibration section3is 35° 15′, and the At-cut quartz substrate is used as it is, the amount of change Δf/f in the frequency of the first vibration device X1with respect to a change in the temperature thereof is small. Using the first vibration device X1as a vibration device for oscillation signal output therefore allows generation of a relatively stable oscillation signal with respect to a temperature change.

The amount of change Δf/f in the frequency of the second vibration section5with respect to a change in the temperature thereof can be so adjusted as to increase by changing the angle θ2 of the first inclining surface17, so can the amount of change Δf/f in the frequency the third vibration section7with respect to a change in the temperature thereof by changing the angle θ3 of the second inclining surface18. A large amount of change Δf/f in the frequency of the second vibration device X2and the third vibration device X3with respect to a change in the temperature thereof means that the resolution of a temperature change with respect to a frequency change is high and precise temperature detection can therefore be performed. Using the second vibration device X2and the third vibration device X3as vibration devices for temperature detection therefore allows precise temperature detection.

In the present embodiment, the cutting angle of the first inclining surface17of the second vibration section5is θ1+θ2, that is, 35° 15′+θ2, where θ1 is the cutting angle of the two principal surfaces16aand16b, and the cutting angle of the first inclining surface17of the second vibration section5is greater than the cutting angle θ1 of the two principal surfaces16aand16b. The cutting angle of the second inclining surface18of the third vibration section7is θ1−θ3, that is, 35° 15′−θ3 and is smaller than the cutting angle θ1 of the two principal surfaces16aand16b. Setting the cutting angle of the first inclining surface17of the second vibration section5and the cutting angle of the second inclining surface18of the third vibration section7differ from each other allows the frequency-temperature characteristics of the second vibration device X2and the third vibration device X3for temperature detection to differ from each other.

The configuration in which the frequency-temperature characteristics of the second vibration device X2and the third vibration device X3for temperature detection differ from each other allows, for example, temperature detection based on the second vibration device X2over a temperature range where the second vibration device X2has higher resolution of a temperature change with respect to a frequency change than the third vibration device X3and can therefore perform precise temperature detection and temperature detection based on the third vibration device X3over a temperature range where the third vibration device X3has higher resolution of a temperature change with respect to a frequency change than the second vibration device X2and can therefore perform precise temperature detection. More precise temperature detection can thus be performed.

For example, in a temperature range where the temperature T ranges from −10 to 60° C. inFIG.5, since the second vibration device X2has higher resolution of a temperature change with respect to a frequency change than the third vibration device X3, the temperature detection may be performed based on the second vibration device X2. On the other hand, in a temperature range where the temperature T is lower than −10° C. or higher than 60° C., the second vibration device X2has low resolution of a temperature change with respect to a frequency change, and further, a change in the frequency of the second vibration device X2does not show a monotonous increase or decrease with respect to a change in the temperature of the second vibration device X2. Therefore, in the temperature range where the temperature T is lower than −10° C. or higher than 60° C., the temperature detection may be performed based on the third vibration device X3, which has higher resolution of a temperature change with respect to a frequency change than the second vibration device X2.

The temperature range over which the second vibration device X2is used to perform the temperature detection and the temperature range over which the third vibration device X3is used to perform the temperature detection are not limited to the temperature ranges described above and can be arbitrarily set based on the frequency-temperature characteristics of the second vibration section5and the third vibration section7.

Further, since the first vibration device X1, the second vibration device X2, and the third vibration device X3are formed on the common quartz substrate2, heat transfer is quickly performed among the first vibration device X1, the second vibration device X2, and the third vibration device X3. The temperature of the first vibration device X1can therefore be quickly and precisely detected by the second vibration device X2and the third vibration device X3for temperature detection, whereby the temperature of the first vibration device X1can be quickly and precisely compensated.

A method for manufacturing the vibration device1will be described below with reference toFIGS.6to11. The method for manufacturing the vibration device1includes a quartz substrate preparation step, a resist application step, a dry etching step, an individualization step, and an electrode formation step.

1.1 Quartz Substrate Preparation Step

A large quartz substrate80, which allows a plurality of vibration devices1to be manufactured in a batch process method in consideration of the mass productivity and manufacturing cost of the vibration device1, as shown inFIG.6. The large quartz substrate80is produced by cutting a quartz raw material at the predetermined cutting angle θ1 and lapping, polishing, and otherwise processing the cut quartz material into a desired thickness. In the first embodiment, the cutting angle θ1 is 35° 15′.

1.2 Resist Application Step

A resist82is applied onto each of the two principal surfaces16aand16bof the large quartz substrate80, as shown inFIG.7. A method for applying the resist82onto the first principal surface16aincludes filling a die having a recess corresponding to the shape of the first inclining surface17, where the second excitation electrode6is formed, and the second inclining surface18, where the third excitation electrode8is formed, with the resist82, transferring the resist82with which the die has been filled onto the first principal surface16a, and curing the resist82.

1.3 Dry Etching Step

A dry etching method along, for example, with a plasma etcher is then used to perform dry etching on the first principal surface16afrom above, as indicated by the arrows inFIG.8.

FIG.9shows the state in which the resist82has been removed by the dry etching. The shape of the resist82that is formed inFIG.7and conforms to the shape of the first principal surface16aincluding the inclining surfaces is exactly transferred onto the large quartz substrate80, which is thinned accordingly. The first inclining surface17and the second inclining surface18are thus formed on the large quartz substrate80.

InFIG.9, since a plurality of quartz pieces are linked to each other to form the large quartz substrate80, the large quartz substrate80is individualized. The large quartz substrate80is individualized by dicing or wet etching along imaginary lines L inFIG.9.FIG.10shows individualized quartz substrates2.

1.5 Electrode Formation Step

The first excitation electrodes4, the second excitation electrodes6, the third excitation electrodes8, and other components are formed on each of the individualized quartz substrates2by deposition or sputtering to form the vibration device1, as shown inFIG.11.

The first inclining surface17and the second inclining surface18may be formed by a method other than the method described above. For example, as a method for forming the resist82part of which is thinned, grayscale light exposure in which the resist82is exposed to light under different light intensity distribution conditions may be used.

Still instead, before individualizing the large quartz substrate80, the first excitation electrodes4, the second excitation electrodes6, the third excitation electrodes8, and other components may be collectively formed on the large quartz substrate80, and the resultant structure may then be individualized into the vibration devices1.

The first vibration device X1, the second vibration device X2, and the third vibration device X3are formed on the common quartz substrate2, whereby heat transfer is quickly performed among the first vibration device X1, the second vibration device X2, and the third vibration device X3. Since the first inclining surface17and the second inclining surface18can be formed in a manufacturing method in which the burden on the quartz substrate is small, such as a dry etching method, a decrease in mechanical strength and chronological degradation of the quartz substrate2are unlikely to occur.

In the present embodiment, the first vibration section3is excited by the pair of first excitation electrodes formed on the two principal surfaces16aand16bof the quartz substrate2, and the second vibration section5and the third vibration section7are so configured that one of the pair of second excitation electrodes6and one of the pair of third excitation electrodes8are formed on the first inclining surface17and the second inclining surface18, which incline with respect to the two principal surfaces16aand16bby the angles θ2 and θ3, respectively, whereby the frequency-temperature characteristic of the first vibration device X1including the first vibration section3can differ from the frequency-temperature characteristic of the second vibration device X2including the second vibration section5and the frequency-temperature characteristic of the third vibration device X3including the third vibration section7.

The configuration in which the first vibration section3is produced at a cutting angle that achieves a frequency-temperature characteristic providing a small amount of frequency change and the first inclining surface17of the second vibration section5and the second inclining surface18of the third vibration section7are produced at cutting angles that achieve frequency-temperature characteristics each providing a large amount of frequency change allows the first vibration device X1to be used for oscillation signal output and the second vibration device X2and the third vibration device X3to be used for temperature detection.

The second inclining surface18inclines with respect to the first inclining surface17. That is, setting the cutting angle of the first inclining surface17and the cutting angle of the second inclining surface18differ from each other allows the frequency-temperature characteristic of the second vibration device X2and the frequency-temperature characteristic of the third vibration device X3to differ from each other.

Therefore, for example, the configuration in which the temperature detection is performed based on the second vibration device X2over the temperature range where the second vibration device X2has higher resolution of a temperature change with respect to a frequency change than the third vibration device X3and can therefore perform precise temperature detection and the temperature detection is performed based on the third vibration device X3over the temperature range where the third vibration device X3has higher resolution of a temperature change with respect to a frequency change than the second vibration device X2and can therefore perform precise temperature detection allows more precise temperature detection to be performed.

In the present embodiment, since the first inclining surface17and the second inclining surface18incline in such a way that the thickness of each of the second vibration section5and the third vibration section7decreases as the distance from the first vibration section3increases, the frequency-temperature characteristic of the first vibration section3can differ from the frequency-temperature characteristics of the second vibration section5and the third vibration section7. Therefore, the frequency-temperature characteristic of the first vibration device X1can be suitable for oscillation signal output, while the frequency-temperature characteristics of the second vibration detection X2and the third vibration device X3can be suitable for temperature detection.

Further, since the first vibration device X1, the second vibration device X2, and the third vibration device X3are formed on the common quartz substrate2, heat transfer is quickly performed among the first vibration device X1, the second vibration device X2, and the third vibration device X3. The temperature of the first vibration device X1can therefore be quickly and precisely detected by the second vibration device X2and the third vibration device X3for temperature detection, whereby the temperature of the first vibration device X1can be quickly and precisely compensated.

In the first embodiment, the first vibration section3, the second vibration section5, and the third vibration section7are arranged along the positive direction of the axis Z′ in the order of the third vibration section7, the first vibration section3, and the second vibration section5, but the first vibration section3, the second vibration section5, and the third vibration section7are not necessarily arranged as described above.

The first inclining surface17is formed as part of the first principal surface16aof the quartz substrate2in the present embodiment and may instead be formed as part of the second principal surface16bor may still instead be formed as part of both the principal surfaces16aand16b.

The second inclining surface18is formed as part of the first principal surface16aof the quartz substrate2in the present embodiment and may instead be formed as part of the second principal surface16bor may still instead be formed as part of both the principal surfaces16aand16b.

When an AT-cut quartz substrate is used as the quartz substrate2, and one of the first inclining surface17and the second inclining surface18of the quartz substrate2that is the inclining surface cut at a larger cutting angle is cut at a cutting angle θa and the other inclining surface is cut at a cutting angle θb, θb is preferably greater than or equal to θa−5′ but smaller than or equal to θa−20°. When the cutting angle θb is greater than or equal to θa−5′, the difference between the cutting angle of the first inclining surface17of the quartz substrate2and the cutting angle of the second inclining surface18of the quartz substrate2is sufficiently large, whereby the frequency-temperature characteristics of the second vibration device X2and the third vibration device X3for temperature detection can sufficiently differ from each other and precise temperature detection can therefore performed. When the cutting angle θb increases, it is difficult to form the inclining surface, and cutting angle θb is therefore preferably smaller than or equal to θa−20°. In the present embodiment, the cutting angle θ1+θ2 of the first inclining surface17corresponds to ea, and the cutting angle θ1−θ3 of the second inclining surface18corresponds to θb.

2. Second Embodiment

A schematic configuration of a vibration device1aaccording to a second embodiment will be described with reference toFIGS.12and13. The same configurations as those in the first embodiment have the same reference characters, and no redundant description of the same configurations will be made.

In the second embodiment, the first vibration section3, a second vibration section5a, and a third vibration section7aare arranged along the positive direction of the axis Z′ in the order of the third vibration section7a, the first vibration section3, and the second vibration section5a, as shown inFIGS.12and13.

In the second embodiment, a quartz substrate2ais so configured that a first inclining surface17aprovided at the second vibration section5aand a second inclining surface18aprovided at the third vibration section7aincline in such a way that the thickness of each of the second vibration section5aand the third vibration section7adecreases as the distance to the first vibration section3decreases.

The first inclining surface17aof the quartz substrate2ais rotated from the axis Z′ by the angle θ2 in the negative direction around the axis X. That is, the cutting angle of the first inclining surface17ais θ1−θ2, that is, 35° 15′−θ2, where the cutting angle of the two principal surfaces16aand16bis 01, and is therefore smaller than the cutting angle θ1 of the two principal surfaces16aand16b. The second inclining surface18aof the quartz substrate2ais rotated from the axis Z′ by the angle θ3 in the positive direction around the axis X. That is, the cutting angle of the second inclining surface18ais θ1+θ3, that is, 35° 15′+θ3 and is therefore greater than the cutting angle θ1 of the two principal surfaces16aand16b. As described above, the cutting angle of the first inclining surface17ais θ1−θ2, and the cutting angle of the second inclining surface18ais θ1+θ3, so that the cutting angle of the first inclining surface17adiffers from the cutting angle of the second inclining surface18a.

Further, the first vibration section3has steps24at the end surfaces of the first vibration section3, and the first vibration section3is so shaped as to protrude in the positive direction of the axis Y′ with respect to the first inclining surface17aof the second vibration section5aand the second inclining surface18aof the third vibration section7a.

According to the present embodiment, the frequency-temperature characteristics of a second vibration device X2aincluding the second vibration section5aand a third vibration device X3aincluding the third vibration section7aallow an increase in the amount of frequency change as compared with the frequency-temperature characteristic of the first vibration device X1including the first vibration section3, whereby when the second vibration device X2aand the third vibration device X3aare used to perform the temperature detection the second vibration device X2aand the third vibration device X3ahave a high resolution of temperature change with respect to a frequency change and can therefore perform, which is one of the same effects provided by the first embodiment.

Further, the present embodiment can provide the following effects in addition to the effects provided by the first embodiment.

The first inclining surface17ainclines in such a way that the thickness of the second vibration section5aincreases as the distance from the first vibration section3increases. Therefore, since the vibration of the second vibration section5ashifts toward a thicker portion of the quartz substrate2a, the vibration area of the second vibration section5ais away from the first vibration section3. The effect of the vibration of the second vibration section5aon the first vibration section3can therefore be reduced.

Since the second inclining surface18aalso inclines in such a way that the thickness of the third vibration section7aincreases as the distance from the first vibration section3increases, the effect of the vibration of the third vibration section7aon the first vibration section3can be reduced.

The end surfaces of the first vibration section3are provided with the steps24. The step24can confine the energy of the vibration of the first vibration section3in the first vibration section3to reduce vibration leakage, whereby the vibration of the first vibration section3can be stabilized.

A schematic configuration of a vibration device1baccording to a third embodiment will be described with reference toFIGS.14and15. The same configurations as those in the first embodiment have the same reference characters, and no redundant description of the same configurations will be made.

In the third embodiment, the first vibration section3, the second vibration section5, and a third vibration section7bare arranged along the positive direction of the axis Z′ in the order of the third vibration section7b, the first vibration section3, and the second vibration section5, as shown inFIGS.14and15.

In the third embodiment, a quartz substrate2bis so configured that the first inclining surface17provided at the second vibration section5inclines in such a way that the thickness of the second vibration section5decreases as the distance from the first vibration section3increases, and that a second inclining surface18bprovided at the third vibration section7binclines in such a way that the thickness of the third vibration section7bdecreases as the distance to the first vibration section3decreases.

The second inclining surface18bof the quartz substrate2bis rotated from the axis Z′ by the angle θ3 in the positive direction around the axis X. That is, the cutting angle of the second inclining surface18bis θ1+θ3, that is, 35° 15′+θ3.

In the third embodiment, the first inclining surface17of the quartz substrate2band the second inclining surface18bof the quartz substrate2bare each an inclining surface rotated from the axis Z′ in the positive direction around the axis X, with the cutting angle of the first inclining surface17being θ1+θ2, and the cutting angle of the second inclining surface18bbeing θ1+θ3. However, since the angle θ2 of the first inclining surface17differs from the angle θ3 of the second inclining surface18b, the cutting angle of the first inclining surface17differs from the cutting angle of the second inclining surface18b.

In the present embodiment, the third vibration section7bis so configured that one of the pair of third excitation electrodes8is formed on the second inclining surface18b, which inclines with respect to the two principal surfaces16aand16b, whereby the frequency-temperature characteristic of the first vibration section3can differ from the frequency-temperature characteristic of the third vibration section7b, as in the first embodiment.

Further, in the present embodiment, the cutting angle of the first inclining surface17differs from the cutting angle of the second inclining surface18b. That is, since the second inclining surface18bincline with respect to the first inclining surface17, the frequency-temperature characteristic of the second vibration device X2including the second vibration section5can differ from the frequency-temperature characteristic of a third vibration device X3binclining the third vibration section7b.

Since the first inclining surface17of the quartz substrate2band the second inclining surface18bof the quartz substrate2bare each rotated by angles θ2 and θ3, respectively, from the axis Z′ in the positive direction around the axis X that is, in the same direction, the frequency-temperature characteristic of the second vibration device X2and the frequency-temperature characteristic of the third vibration device X3are expressed by the same cubic curve. The between the second vibration device X2and the third vibration device X3ballows high resolution of a temperature change with respect to a frequency change, whereby the temperature of the first vibration device X1can be quickly and precisely detected.

A schematic configuration of a vibration device1caccording to a fourth embodiment will be described with reference toFIGS.16and17. The same configurations as those in the first embodiment have the same reference characters, and no redundant description of the same configurations will be made.

In the fourth embodiment, a protrusion25is formed at each of the two principal surfaces16aand16bin a first vibration section3c, as shown inFIGS.16and17. The first vibration section3cincluding the protrusion25has the pair of first excitation electrodes4, which sandwich the first vibration section3cin the thickness direction of a quartz substrate2c.

The present embodiment can provide the following effects in addition to the effects provided by the first embodiment. Since an area of the first vibration section3cthat is the area including the protrusions25is excited by the first excitation electrodes4in a first vibration device X1c, the energy of the vibration of the first vibration section3cis confined in the area including the protrusions25, so that leakage of the vibration to areas other than the area including the protrusions25can be reduced, whereby the vibration of the first vibration device X1cis stabilized. Further, the impedance of the first vibration device X1ccan be lowered, so that the Q value thereof increases, whereby the thus configured first vibration device X1cas an oscillator can be used to achieve a precise oscillator having an excellent carrier wave to noise ratio.

The protrusions25are formed at the two principal surfaces16aand16bof the first vibration section3cin the present embodiment, and a protrusion may instead be formed at one of the two principal surfaces16aand16bof the first vibration section3c.

The protrusions25have a mesa shape protruding from the two principal surfaces16aand16bof the first vibration section3cin the direction along the axis Y′ in the present embodiment, and the protrusions25may instead each have a spherical shape.

A schematic configuration of a vibration device1daccording to a fifth embodiment will be described with reference toFIGS.18and19. The same configurations as those in the first embodiment have the same reference characters, and no redundant description of the same configurations will be made.

In the fifth embodiment, a quartz substrate2dhas through holes26between the first vibration section3and the second vibration section5and between the first vibration section3and the third vibration section7, as shown inFIGS.18and19.

The present embodiment can provide the following effect in addition to the effects provided by the first embodiment. Providing the through holes26between the first vibration section3and the second vibration section5and between the first vibration section3and the third vibration section7can suppress the effect of the vibration of the first vibration section3and the vibration of the second vibration section5and the third vibration section7on each other.

A schematic configuration of a vibration device1eaccording to a sixth embodiment will be described with reference toFIGS.20and21. The same configurations as those in the first embodiment have the same reference characters, and no redundant description of the same configurations will be made.

In the sixth embodiment, a quartz substrate2ehas recesses27, which open toward the second principal surface16b, between the first vibration section3and the second vibration section5and between the first vibration section3and the third vibration section7, as shown inFIGS.20and21. That is, thin sections28are formed between the first vibration section3and the second vibration section5and between the first vibration section3and the third vibration section7, as shown inFIG.21.

The present embodiment can provide the following effect in addition to the effects provided by the first embodiment. Providing the thin sections28between the first vibration section3and the second vibration section5and between the first vibration section3and the third vibration section7can suppress the effect of the vibration of the first vibration section3and the vibration of the second vibration section5and the third vibration section7on each other.

The recesses27may be formed at the first inclining surface17, the second inclining surface18, and the first principal surface16a.

A schematic configuration of an oscillator100according to a seventh embodiment will be described with reference toFIGS.22to24. In the oscillator100according to the seventh embodiment, any of the vibration devices1,1a,1b,1c,1d, and1edescribed above can be used, and the following description will be made of a case where the vibration device1described in the first embodiment is used.

The oscillator100includes a vibrator40, which accommodates the vibration device1, an IC chip60, which includes oscillation circuits61a,61b, and61c, which drive the vibration device1, and a control signal output circuit63, a package main body50, which accommodates the vibrator40and the IC chip60, and a lid member57, which is made, for example, of glass, ceramic, or metal, as shown inFIG.22.

The package main body50is formed by layering an implementation terminal45, a first substrate51, a second substrate52, and a seal ring53on each other, as shown inFIGS.22and23. The package main body50has a cavity58, which opens upward. The interior of the cavity58, which accommodates the vibrator40and the IC chip60, is hermetically sealed with a reduced pressured atmosphere or an inert gas atmosphere, such as nitrogen, by bonding the lid member57to the package main body50via the seal ring53.

The implementation terminal45are actually formed of a plurality of implementation terminals45at the outer bottom surface of the first substrate51. The implementation terminals45are electrically coupled to connection electrodes and connection terminals44, which are provided on the upper side of the first substrate51, via through electrodes and interlayer wiring that are not shown.

The cavity58in the package main body50accommodates the vibrator40and the IC chip60. The vibrator40is fixed to the connection electrodes43provided on the first substrate51via solder or an electrically conductive adhesive. The IC chip60is fixed to the upper side of the first substrate51via a bonding member55, such as an adhesive. The plurality of connection terminals44is provided in the cavity58. The connection terminals44are electrically coupled to connection terminals46provided on the upper side of the IC chip60via bonding wires56.

The IC chip60includes the first oscillation circuit61a, which causes the first vibration device X1to oscillate and output a first oscillation signal, the second oscillation circuit61b, which causes the second vibration device X2to oscillate and output a second oscillation signal, the third oscillation circuit61c, which causes the third vibration device X3to oscillate and output a third oscillation signal, and the control signal output circuit63, which outputs a control signal that controls the oscillation frequency of the first oscillation signal based on the second and third oscillation signals.

The circuit configuration of the oscillator100will next be described. The following description will be made with reference to a TCXO as an example of the oscillator100.

The control signal output circuit63is a circuit that outputs a set frequency f0via an output end65irrespective of a change in the temperature outside the oscillator100or with the effect of a change in the outside temperature suppressed. The set frequency f0is an output frequency produced when reference voltage V0is applied to the first oscillation circuit61aat a reference temperature T0.

The first oscillation circuit61ais electrically coupled to the pair of first excitation electrodes4of the first vibration device X1via the terminal10. Similarly, the second oscillation circuit61bintended for temperature detection is electrically coupled to the pair of second excitation electrodes6of the second vibration device X2via the terminal11. The third oscillation circuit61cintended for temperature detection is electrically coupled to the pair of third excitation electrodes8of the third vibration device X3via the terminal12.

An output selection circuit90, which selects a frequency f to be outputted to the control signal output circuit63, and the control signal output circuit63, which estimates the temperature of the first vibration device X1based on the frequency f, which is an output signal outputted from the output selection circuit90, and computes control voltage VC(VC=V0−ΔV), which causes the first oscillation circuit61ato produce the set frequency f0as the first oscillation signal at the estimated temperature, are provided between the first oscillation circuit61aand the combination of the second oscillation circuit61band the third oscillation circuit61c.

The output selection circuit90includes a selection controller91and an output selector92. The selection controller91is electrically coupled to the output selector92, a temperature sensor93, and a temperature estimator68. The temperature sensor93detects the temperature outside the vibration device1. The selection controller91selects, based on the temperature detected with the temperature sensor93, the frequency f to be outputted to the control signal output circuit63from an oscillation frequency f2as the second oscillation signal outputted from the second oscillation circuit61band an oscillation frequency f3as the third oscillation signal outputted from the third oscillation circuit61c. Further, the selection control91controls the output selector92in such a way that the frequency f, which is the output signal outputted from the output selection circuit90, is switched. The output selector92outputs one of the oscillation frequency f2outputted from the second oscillation circuit61band the oscillation frequency f3outputted from the third oscillation circuit61cas the frequency f, which is an output signal outputted from the output selection circuit90, based on the selection made by the selection control91to the control signal output circuit63.

Reference voltage V10is inputted to the second oscillation circuit61bvia an input end64bof the second oscillation circuit61b, reference voltage V11is inputted to the third oscillation circuit61cvia an input end64cof the third oscillation circuit61c, and the set frequency f0is outputted via the output end65. The reference voltage V10and V11and control voltage VCinputted to the first oscillation circuit61a, the second oscillation circuit61b, and the third oscillation circuit61care stabilized by varicap diodes66in advance.

The second vibration device X2and the third vibration device X3are each used as a temperature detector. The oscillation frequency f2as the second oscillation signal outputted from the second oscillation circuit61b, which drives the second vibration device X2, is an output according to the temperature T of the second vibration device X2based on the frequency-temperature characteristic of the second vibration device X2. The oscillation frequency f3as the third oscillation signal outputted from the third oscillation circuit61c, which drives the third vibration device X3, is an output according to the temperature T of the third vibration device X3based on the frequency-temperature characteristic of the third vibration device X3. The temperature T of the second vibration device X2and the temperature T of the third vibration device X3can thus be determined.

The first vibration device X1is provided on the quartz substrate2shared by the second vibration device X2and the third vibration device X3as well as the first vibration device X1, and the first vibration device X1is coupled to the second vibration device X2and the third vibration device X3, so that no heat transfer period difference occurs, whereby the temperature T of the first vibration device X1can be accurately estimated from the temperature T of the second vibration device X2and the temperature T of the third vibration device X3.

Since the cutting angle of the second vibration section5differs from the cutting angle of the third vibration section7, the frequency-temperature characteristic of the second vibration device X2differs from the frequency-temperature characteristic of the third vibration device X3. In view of the fact described above, for example, the temperature T of the first vibration device X1is estimated based on the temperature T of the second vibration device X2over the temperature range where the second vibration device X2has higher resolution of a temperature change with respect to a frequency change than the third vibration device X3and can therefore perform precise temperature detection, and the temperature T of the first vibration device X1is estimated based on the temperature T of the third vibration device X3over the temperature range where the third vibration device X3has higher resolution of a temperature change with respect to a frequency change than the second vibration device X2and can therefore perform precise temperature detection. The temperature T of the first vibration device X1can thus be more precisely estimated.

The control signal output circuit63computes the control voltage VC(VC=V0−ΔV), which causes the first oscillation circuit61ato output the set frequency f0as the first oscillation signal, based on the temperature T of the vibration device having a frequency-temperature characteristic that provides a larger amount of frequency change out of the frequency-temperature characteristic of the second vibration device X2and the frequency-temperature characteristic of the third vibration device X3.

Specifically, the control signal output circuit63includes a frequency detector67, which is formed, for example, of a frequency counter that measures the frequency f outputted from the output selection circuit90, the temperature estimator68, which estimates the temperature T based on the frequency f measured by the frequency detector67, a compensation voltage computation section69, which computes compensation voltage ΔV based on the temperature T estimated by the temperature estimator68, and an adder70, which outputs the control voltage VC, which is the result of subtraction of the compensation voltage ΔV computed by the compensation voltage computation section69from the reference voltage V0, to the first oscillation circuit61a.

The temperature estimator68stores the frequency-temperature characteristic of the second oscillation circuit61bshown by Expression (1) below and the frequency-temperature characteristic of the third oscillation circuit61cshown by Expression (2) below.

When the output selector92selects the oscillation frequency f2outputted from the second oscillation circuit61bas the frequency f to be outputted to the control signal output circuit63, the temperature estimator68can determine the temperature T of the second vibration device X2based on the frequency-temperature characteristic shown by Expression (1) and the oscillation frequency f2outputted from the second oscillation circuit61band estimate the temperature T of the first vibration device X1from the temperature T of the second vibration device X2.

When the output selector92selects the oscillation frequency f3outputted from the third oscillation circuit61cas the frequency f to be outputted to the control signal output circuit63, the temperature estimator68can determine the temperature T of the third vibration device X3based on the frequency-temperature characteristic shown by Expression (2) and the oscillation frequency f3outputted from the third oscillation circuit61cand estimate the temperature T of the first vibration device X1from the temperature T of the third vibration device X3.
f1=f10{1+α2(T−T10)3+β2(T−T10)+γ2}  (1)
f2=f11{1+α3(T−T11)3+β3(T−T11)+γ2}  (2)

The compensation voltage computation section69includes, for example, a generator that generates a cubic function that is the temperature characteristic of the first oscillation circuit61aand is configured to determine the compensation voltage ΔV based on Expressions (3) to (5) below and the temperature T.
ΔV=V0(Δf/f0)  (3)
Δf/f0=α1(T−T0)3+β1(T−T0)+γ1(4)
ΔV=V0{α1(T−T0)3+β1(T−T0)+γ1}  (5)

The symbols α1, β1, and γ1, α2, β2, and γ2, and α3, β3, and γ3 are constants specific to the first oscillation circuit61a, the second oscillation circuit61b, and the third oscillation circuit61c, respectively, and are determined by measuring the output frequency with the temperature and the reference voltage variously changed. It is also noted that Δf=f−f0, that f10is the output frequency produced when the reference voltage V10is applied at the reference temperature T10in the second oscillation circuit61b, and that f11is the output frequency produced when the reference voltage V11is applied at the reference temperature T11in the third oscillation circuit61c.

When the control voltage V10is inputted to the input end64bof the second oscillation circuit61b, the second oscillation circuit61boscillates in the form of thickness slip vibration of the basic wave at the oscillation frequency f1determined by Expression (1) described above based on the temperature T of the second oscillation device X2. When the control voltage V11is inputted to the input end64cof the third oscillation circuit61c, the third oscillation circuit61coscillates in the form of wave thickness slip vibration of the basic wave at the oscillation frequency f2determined by Expression (2) described above based on the temperature T of the third oscillation device X3.

The output selection circuit90outputs as the frequency f, which is the output signal outputted from the output selection circuit90, one of the oscillation frequency f2as the second oscillation signal outputted from the second oscillation circuit61band the oscillation frequency f3as the third oscillation signal outputted from the third oscillation circuit61cbased on the temperature detected with the temperature sensor93to the control signal output circuit63.

The frequency f is inputted to the temperature estimator68via the frequency detector67. The temperature estimator68determines the temperature T of the second vibration device X2or the temperature T of the third vibration device X3based on the selection made by the output selector of the output selection circuit90and estimates the temperature T of the first vibration device X1. The compensation voltage computation section69then computes the compensation voltage ΔV based on the temperature T provided by the temperature estimator68and applies the control voltage VCto the first oscillation circuit61avia the adder70. The first oscillation circuit61avibrates in the form of thickness slip vibration at the frequency that is the first oscillation signal according to the temperature T of the first vibration device X1and the control voltage VC, that is, the set frequency f0.

That is, at the temperature T, the oscillation frequency of the first oscillation circuit61atends to deviate from the set frequency f0by the difference (T−T0) from the reference temperature To along the frequency-temperature characteristic of the first oscillation circuit61a. However, since the control voltage VC, which is lower or higher than the reference voltage V0by the amount corresponding to the difference described above, is applied to the first oscillation circuit61a, the output frequency that reflects the cancelation of the difference, that is, the set frequency f0can be produced.

The oscillator100according to the present embodiment can adjust the frequency-temperature characteristic of the second vibration device X2and the frequency-temperature characteristic of the third vibration device X3to characteristics suitable for the temperature detection while allowing the frequency-temperature characteristic of the first vibration device X1to be suitable for the oscillation signal output can therefore quickly and precisely compensate the set frequency f0outputted from the first vibration device X1in terms of temperature based on the oscillation frequency f2of the second vibration device X2and the oscillation frequency f3of the third vibration device X3. A high-precision oscillator100that oscillates at a stable set frequency f0can therefore be provided.

Further, under the condition that the frequency-temperature characteristic of the second vibration device X2and the frequency-temperature characteristic of the third vibration device X3differ from each other, estimating the temperature T of the first vibration device X1based on the temperature T of the vibration device having a frequency-temperature characteristic that provides a larger amount of frequency change at the temperature detected with the temperature sensor93out of the frequency-temperature characteristic of the second vibration device X2and the frequency-temperature characteristic of the third vibration device X3allows more precise estimation of the temperature T of the first vibration device X1. A high-precision oscillator100that oscillates at a further stabler set frequency f0can therefore be provided.

The circuit configuration of an oscillator100aaccording to an eighth embodiment will be described with reference toFIG.25. The same configurations as those in the seventh embodiment have the same reference characters, and no redundant description of the same configurations will be made.

The eighth embodiment is a form in which the sum of the oscillation frequency f2of the second oscillation device X2and the oscillation frequency f3of the third vibration device X3or the difference therebetween is determined and the thus computed frequency f is used as a temperature detection signal.

A control signal output circuit63bis provided between the first oscillation circuit61aand the combination of the second oscillation circuit61band the third oscillation circuit61c, and the control signal output circuit63bestimates the temperature of the first vibration device X1based on the oscillation frequency f2as the second oscillation signal outputted from the second oscillation circuit61bof the second vibration device X2and the oscillation frequency f3as the third oscillation signal outputted from the third oscillation circuit61cof the third vibration device X3and computes the control voltage VC(VC=V0−ΔV), which provides the set frequency f0as the first oscillation signal in the first oscillation circuit61aat the estimated temperature.

The control signal output circuit63bincludes frequency detectors67band67c, a temperature estimator68b, the compensation voltage computation section69, and the adder70.

The oscillation frequency f2outputted from the second oscillation circuit61bis inputted to the temperature estimator68bvia the frequency detector67b. The oscillation frequency f3outputted from the third oscillation circuit61cis inputted to the temperature estimator68bvia the frequency detector67c.

The temperature estimator68bcomputes the difference between the oscillation frequencies f2and f3(f2−f3) and estimates the temperature T of the first vibration device X1based on the computed frequency difference (f2−f3) and data on the relationship between the frequency difference (f2−f3) and the temperature T.

FIG.26shows an example of the data on the relationship between the frequency difference (f2−f3) and the temperature T and is the result of subtraction of the cubic curve that is the frequency-temperature characteristic of the third vibration device X3from the cubic curve that is the frequency-temperature characteristic of the second vibration device X2. The computed frequency difference (f2−f3) is substantially proportional to the temperature T, as seen fromFIG.26.

The temperature estimator68bincludes a storage that stores the data on the relationship between the frequency difference (f2−f3) and the temperature T, a computation section that computes the difference between the oscillation frequencies f2and f3(f2−f3), and a reader that reads the temperature T corresponding to the frequency difference (f2−f3) from the relationship data in the storage, which is not shown.

In place of computing the difference between the oscillation frequencies f2and f3(f2−f3), the sum of the oscillation frequencies f2and f3(f2+f3) may be determined, and the temperature T may be determined by referring to data on the relationship between the sum of the oscillation frequencies (f2+f3) and the temperature T. Still instead, in place of computing the difference between the oscillation frequencies f2and f3, the difference between V2, which is the result of conversion of the oscillation frequency f2into voltage, and V3, which is the result of conversion of the oscillation frequency f3into voltage, may be determined, and the temperature T may be determined by referring to data on the relationship between the voltage difference (V2−V3) and the temperature T.

The oscillator100aaccording to the present embodiment can adjust the frequency-temperature characteristic of the second vibration device X2and the frequency-temperature characteristic of the third vibration device X3to characteristics suitable for the temperature detection while allowing the frequency-temperature characteristic of the first vibration device X1to be suitable for the oscillation signal output can therefore quickly and precisely compensate the set frequency f0outputted from the first vibration device X1in terms of temperature based on the oscillation frequency f2of the second vibration device X2and the oscillation frequency f3of the third vibration device X3. A high-precision oscillator100athat oscillates at a stable set frequency f0can therefore be provided.

Further, under the condition that the frequency-temperature characteristic of the second vibration device X2and the frequency-temperature characteristic of the third vibration device X3differ from each other, estimating the temperature T of the first vibration device X1based on the sum of the oscillation frequency f2of the second oscillation device X2and the oscillation frequency f3of the third vibration device X3or the difference therebetween allows more precise estimation of the temperature T of the first vibration device X1. A high-precision oscillator100athat oscillates at a further stabler set frequency f0can therefore be provided.