JP2011120199A - Oscillation circuit system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oscillation circuit system of a piezoelectric oscillator that can perform temperature compensation with high precision without increasing the number of measurement temperatures when temperature characteristic information is generated. <P>SOLUTION: The oscillation circuit system is configured to calculate a first approximation formula for approximating temperature characteristics of an oscillation frequency of a piezoelectric vibrator from temperature characteristic information 76 showing temperature characteristics of the oscillation frequency of the piezoelectric vibrator 12 and to perform temperature compensation on an oscillation signal 58 by a frequency correction circuit 42 with the first approximation formula and a temperature compensation amount 80 corresponding to the detection voltage 66 of a temperature sensor 16. The temperature characteristic information is generated on the basis of information generated by adding interpolation temperature characteristic information to discrete temperature characteristic information discretely showing the relation between the temperature and oscillation frequency of the piezoelectric vibrator, the interpolation temperature characteristic information is calculated on the basis of the discrete temperature characteristic information so that the first approximation formula can be calculated from the information, and is extracted from a second approximation formula of lower order than the first approximation formula. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to temperature compensation of a piezoelectric oscillator that performs position measurement based on a positioning signal from a GPS (Global Positioning System) satellite, and particularly to a TSXO (Temperature Sensor Xtal Oscillator) that is a piezoelectric oscillator that entrusts a temperature compensation function to the outside. The present invention relates to temperature compensation of a piezoelectric oscillator that is mounted and used for an external temperature compensation circuit.

  A receiving device such as a mobile phone equipped with a GPS function, a mobile phone equipped with a GPS receiving function, and the like measure a current position by demodulating and analyzing positioning signals transmitted from a plurality of GPS satellites. As a reference oscillator used in these receiving apparatuses, a temperature compensated piezoelectric oscillator TCXO (Temperature Compensated Xtal Oscillator) having a small frequency change due to temperature is widely used. The reason is that the higher the frequency accuracy of the oscillator built in the receiving device, the narrower the search range for capturing the positioning signal transmitted from the GPS satellite, resulting in shortening the search time, that is, Positioning can be performed in a short time by shortening the time for capturing the positioning signal of the GPS satellite.

  On the other hand, the temperature of the above-mentioned receiving device etc. rises in a short time when the device is turned on, or when the mobile phone etc. moves from outdoor to indoor, or from indoor to outdoor. Has a problem that the temperature compensation becomes unstable until the temperature in the oscillator is stabilized. In order to solve this problem, a temperature compensation circuit that can respond to temperature changes at high speed on the user's side is uniquely constructed, and the frequency-temperature characteristics of the cubic curve specific to the piezoelectric vibrator mounted on the oscillator from the oscillator side. There has been a demand for obtaining temperature characteristic information to perform temperature compensation appropriately. Therefore, in order to cope with this, TSXO that does not require a temperature compensation circuit is applied on the oscillation circuit side. The TSXO includes a temperature sensor that outputs the current temperature of the mounted piezoelectric vibrator to the user side, and a mounted piezoelectric sensor. A memory circuit that stores the frequency temperature information (temperature coefficient) of the vibrator and outputs the frequency temperature information to the user side is mounted (see Patent Document 1).

  When using a crystal resonator using thickness shear vibration, the oscillation signal output from the oscillator has a temperature dependency that draws a positive cubic curve. However, the above-described TSXO is mounted and connected to the TSXO on the user side. In a GPS system or the like having a temperature compensation circuit, temperature compensation is performed in the temperature compensation circuit so that the frequency is constant at any temperature based on the current temperature obtained from the temperature sensor and the temperature characteristic information obtained from the memory circuit. The amount is calculated and frequency correction is applied.

  Here, since the temperature characteristic information stored in the memory circuit is acquired at the time of the manufacturing inspection process, from the viewpoint of the throughput at the time of manufacturing, when one of the temperature changes at the time of temperature rise or temperature fall Generally, the temperature characteristic information is acquired and stored in a storage circuit. On the other hand, on the temperature compensation circuit side, based on this temperature characteristic information, an approximate expression of a frequency deviation that continuously changes with respect to a temperature change is calculated based on the oscillation frequency at the reference temperature of the crystal resonator. The temperature compensation amount is calculated from the temperature.

By the way, in the field of high-precision electronic devices such as mobile phone terminals equipped with the GPS function described above, the allowable range of frequency deviation (Δf / f ₀ ) is very narrow, for example, a temperature of −30 ° C. to 85 ° C. In the range, the frequency deviation (Δf / f ₀ ) is required to be within 0.5 ppm. If this condition is not satisfied, there is a problem that the search time becomes long, resulting in a positioning error or a malfunction in synchronization with the GPS satellite. For this reason, it is conceivable to perform temperature compensation by calculating an approximate expression with high accuracy by increasing the number of pieces of temperature characteristic information.

JP 2003-324318 A

  Here, when acquiring temperature characteristic information, the crystal unit was sequentially immersed in a plurality of thermostats set to different set temperatures, and the temperature of the crystal unit became the set temperature of the thermostat bath in which it was immersed. By the way, the oscillation frequency is measured. However, increasing the number of pieces of temperature characteristic information increases the number of constant temperature baths as it is, and there is a problem that it takes work time and cost.

  Therefore, the present invention pays attention to the above-mentioned problems, generates temperature characteristic information necessary for the temperature compensation circuit without increasing the number of measurement temperatures when generating the temperature characteristic information, and stores the frequency deviation information in the temperature compensation circuit. An object of the present invention is to provide a piezoelectric oscillator temperature compensation method and a piezoelectric oscillator capable of calculating an approximate expression with high accuracy and performing temperature compensation with high accuracy.

SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms and application examples.
An oscillation circuit system according to a first embodiment includes a piezoelectric vibrator, an oscillation circuit that oscillates the piezoelectric vibrator and outputs an oscillation signal, and temperature detection means that outputs a detection voltage corresponding to the temperature of the piezoelectric vibrator. And a storage circuit that outputs temperature characteristic information indicating the temperature characteristic of the oscillation frequency of the piezoelectric vibrator, and a temperature circuit for approximating the temperature characteristic of the oscillation frequency of the piezoelectric vibrator from the temperature characteristic information A CPU that calculates a first approximate expression and outputs a temperature compensation amount using the first approximate expression and the detected voltage, and a frequency correction circuit that performs temperature compensation of the oscillation signal in accordance with the temperature compensation amount The temperature characteristic information is interpolated into discrete temperature characteristic information discretely indicating the relationship between the temperature of the piezoelectric vibrator and the oscillation frequency. Temperature characteristics The interpolation temperature characteristic information is generated based on the discrete temperature characteristic information so that the first approximate expression can be calculated from the information. An oscillation circuit system, wherein the oscillation circuit system is extracted from a second approximate expression lower in order than the first approximate expression.

  With the above configuration, the temperature characteristic information includes discrete temperature characteristic information generated by actual measurement and interpolation temperature characteristic information obtained from the discrete temperature characteristic information via the second approximate expression. Therefore, since the temperature characteristic information has a component obtained by the second approximate expression, it seems that the accuracy of approximation is deteriorated as compared with the case where all of the temperature characteristic information is configured based on actually measured data. However, in the temperature compensation circuit, since the first approximate expression is performed based on temperature characteristic information having a larger number of information than the number of coefficients of the first approximate expression, the coefficient of the first approximate expression and the temperature characteristic information As a result, the accuracy of the first approximate expression is improved, and the temperature characteristic information configured based on actually measured data is calculated. It is not inferior to the case of using. Therefore, it is not necessary to increase the number of thermostats for obtaining the actual measurement data, and the oscillation circuit system is capable of suppressing work time and cost and allowing the temperature compensation circuit to perform highly accurate temperature compensation.

[Application Example 1]
A first approximate expression for approximating the temperature characteristic of the oscillation frequency of the piezoelectric vibrator is calculated based on the temperature characteristic information of the piezoelectric vibrator, and corresponds to the temperature of the first approximate expression and the piezoelectric vibrator. A temperature compensation method for a piezoelectric oscillator that outputs an oscillation signal and the temperature characteristic information to a temperature compensation circuit capable of calculating a temperature compensation amount using information, wherein the relationship between the temperature of the piezoelectric vibrator and the oscillation frequency is expressed as follows: Discrete temperature characteristic information shown discretely is generated, a second approximate expression lower than the first approximate expression is calculated based on the discrete temperature characteristic information, and the second approximate expression is calculated from the second approximate expression. 1. A method of manufacturing a piezoelectric oscillator, comprising: extracting interpolated temperature characteristic information capable of calculating one approximate expression; and generating information obtained by adding the interpolated temperature characteristic information to the discrete temperature characteristic information as the temperature characteristic information .

  By the above method, the temperature characteristic information is constituted by discrete temperature characteristic information generated by actual measurement and interpolation temperature characteristic information obtained from the discrete temperature characteristic information through the second approximate expression. Therefore, in the temperature compensation circuit, the first approximate expression is calculated based on the temperature characteristic information having the number of information equal to or greater than the number of coefficients of the first approximate expression, and therefore the coefficient that falls within a certain approximate error range is calculated. Will do. For this reason, the accuracy of temperature compensation when the first approximate expression is used is improved as compared with the case where temperature compensation is performed using the second approximate expression. Therefore, it is not necessary to increase the number of thermostats for obtaining actually measured data, and the working time and cost can be suppressed and the temperature compensation circuit can perform highly accurate temperature compensation.

[Application Example 2]
2. The piezoelectric device according to application example 1, wherein the temperature characteristic information is generated by temperature information and information on an oscillation frequency corresponding to the temperature or frequency deviation from a reference frequency corresponding to the temperature. A method for manufacturing an oscillator.

  According to the above method, the calculation of the temperature coefficient is not required on the piezoelectric oscillator side, so that the work burden when forming the piezoelectric oscillator can be suppressed and the cost can be suppressed. In this case, the temperature coefficient is calculated from the first approximate expression corresponding to the temperature characteristic information on the user side, but the user side can calculate an accurate temperature coefficient uniquely.

[Application Example 3]
The temperature characteristic information is extracted from the first approximate expression obtained from the temperature information and the oscillation frequency information corresponding to the temperature or the frequency deviation information from the reference frequency corresponding to the temperature. The method for manufacturing a piezoelectric oscillator according to Application Example 1, wherein the piezoelectric oscillator is generated by a temperature coefficient.

  According to the above method, the temperature compensation circuit does not require an operation for calculating the temperature coefficient, so that it is possible to reduce the burden on the user side and easily construct a system equipped with a piezoelectric oscillator.

[Application Example 4]
Temperature detecting means for outputting a detection voltage corresponding to the temperature of the piezoelectric vibrator is disposed adjacent to the piezoelectric vibrator, and the first approximate expression, the second approximate expression, and the temperature characteristic information are: Generated as information associated with the detection voltage, calculates the first approximate expression based on the temperature characteristic information, and uses the first approximate expression and the detection voltage input from the temperature detection means. 4. The method of manufacturing a piezoelectric oscillator according to any one of application examples 1 to 3, wherein the oscillation signal is output to a temperature compensation circuit capable of calculating a temperature compensation amount.

  By the above method, the temperature detecting means can suppress the measurement error of the temperature of the piezoelectric vibrator and output the detection voltage corresponding to the temperature of the piezoelectric vibrator. Therefore, the discrete temperature characteristic information is calculated with high accuracy, The second approximate expression and the interpolated temperature characteristic information can be calculated with high accuracy, whereby the first approximate expression and the temperature characteristic information can be calculated with high accuracy. Furthermore, since the current temperature of the piezoelectric vibrator can be measured in real time with high accuracy, correction errors in the temperature compensation circuit can be suppressed and temperature compensation can be performed with high accuracy.

[Application Example 5]
A method for manufacturing a piezoelectric oscillator, wherein the temperature compensation circuit is incorporated in a piezoelectric oscillator formed by the method for manufacturing a piezoelectric oscillator according to any one of Application Examples 1 to 4.
By the above method, it is possible to output an oscillation signal that has been subjected to temperature compensation with high accuracy without increasing the number of thermostats for generating temperature characteristic information.

[Application Example 6]
A first approximate expression for oscillating the piezoelectric vibrator and the piezoelectric vibrator and approximating the temperature characteristic of the oscillation frequency of the piezoelectric vibrator is calculated based on the temperature characteristic information of the piezoelectric vibrator, An oscillation circuit that outputs an oscillation signal to a temperature compensation circuit that calculates a temperature compensation amount using the first approximate expression and information corresponding to the temperature of the piezoelectric vibrator; and a storage circuit that stores the temperature characteristic information; The temperature characteristic information generates discrete temperature characteristic information discretely indicating a relationship between the temperature of the piezoelectric vibrator and the oscillation frequency, and the first temperature characteristic information is generated based on the discrete temperature characteristic information. A second approximate expression lower than the approximate expression is calculated, interpolation temperature characteristic information that enables calculation of the first approximate expression is extracted from the second approximate expression, and the interpolation is performed on the discrete temperature characteristic information. The temperature information is added to the temperature information. Piezoelectric oscillator, characterized in that stored in the storage circuit as the characteristic information.

  With the above configuration, the temperature characteristic information includes discrete temperature characteristic information generated by actual measurement and interpolation temperature characteristic information obtained from the discrete temperature characteristic information via the second approximate expression. Therefore, since the temperature characteristic information has a component obtained by the second approximate expression, it seems that the accuracy of approximation is deteriorated as compared with the case where all of the temperature characteristic information is configured based on actually measured data. However, in the temperature compensation circuit, since the first approximate expression is performed based on temperature characteristic information having a larger number of information than the number of coefficients of the first approximate expression, the coefficient of the first approximate expression and the temperature characteristic information As a result, the accuracy of the first approximate expression is improved, and the temperature characteristic information configured based on actually measured data is calculated. It is not inferior to the case of using. Therefore, it is not necessary to increase the number of thermostats for obtaining actually measured data, and it becomes a piezoelectric oscillator capable of suppressing the working time and cost and allowing the temperature compensation circuit to perform highly accurate temperature compensation.

[Application Example 7]
The temperature characteristic information includes temperature information and oscillation frequency information corresponding to the temperature, or frequency deviation information from a reference frequency corresponding to the temperature. Piezoelectric oscillator.

  With the above configuration, since it is not necessary to calculate the temperature coefficient on the piezoelectric oscillator side, it is possible to suppress the work burden when forming the piezoelectric oscillator and to reduce the cost. In this case, the temperature coefficient is calculated from the first approximate expression corresponding to the temperature characteristic information on the user side, but the piezoelectric oscillator is capable of calculating an accurate temperature coefficient uniquely on the user side.

[Application Example 8]
The temperature characteristic information is a temperature extracted from the first approximate expression obtained from temperature information and oscillation frequency information corresponding to the temperature or frequency deviation information from a reference frequency corresponding to the temperature. The piezoelectric oscillator according to Application Example 6, which is a coefficient.

  With the above configuration, the temperature compensation circuit does not require an operation for calculating the temperature coefficient. Therefore, it is possible to easily build a system equipped with a piezoelectric oscillator while reducing the burden on the user side.

[Application Example 9]
Temperature detection means for outputting a detection voltage corresponding to the temperature of the piezoelectric vibrator is provided adjacent to the piezoelectric vibrator, and the first approximate expression, the second approximate expression, and the temperature characteristic information are: The oscillation circuit calculates the first approximate expression based on the temperature characteristic information, and is input from the first approximate expression and the temperature detection means. 9. The piezoelectric oscillator according to any one of application examples 6 to 8, wherein the oscillation signal is output to a temperature compensation circuit capable of calculating a temperature compensation amount using a detection voltage.

  With the above configuration, the temperature detector can measure the measurement error of the temperature of the piezoelectric vibrator and output a detection voltage corresponding to the temperature of the piezoelectric vibrator. Therefore, the discrete temperature characteristic information can be calculated with high accuracy. Thus, the second approximate expression and the interpolated temperature characteristic information can be calculated with high accuracy, whereby the first approximate expression and the temperature characteristic information can be calculated with high accuracy. Furthermore, since the current temperature of the piezoelectric vibrator can be measured in real time with high accuracy, a correction error in the temperature compensation circuit can be suppressed and a piezoelectric oscillator capable of performing temperature compensation with high accuracy can be obtained.

[Application Example 10]
A piezoelectric oscillator characterized by being formed by incorporating the temperature compensation circuit into the piezoelectric oscillator according to any one of Application Examples 6 to 9.
With the above configuration, a temperature compensated oscillator that can output an oscillation signal that has been subjected to temperature compensation with high accuracy without increasing the temperature chamber for generating temperature characteristic information is provided.

It is a schematic diagram of the oscillation circuit system provided with the piezoelectric oscillator of this embodiment connected to the temperature compensation circuit. It is a connection diagram of the piezoelectric oscillator of this embodiment and a measuring instrument. It is a flowchart which calculates the 2nd approximate expression and temperature characteristic information of this embodiment. It is a flowchart which acquires the coefficient of the temperature variation per unit voltage added to temperature characteristic information, and the value of the voltage in reference | standard temperature. It is a flowchart of the temperature compensation in a temperature compensation circuit. It is a figure which shows the 2nd approximate expression calculated corresponding to discrete temperature characteristic information and discrete temperature characteristic information. It is a figure which shows the 1st approximate expression calculated corresponding to the temperature characteristic information produced | generated by adding the interpolation temperature characteristic information extracted from the 2nd approximate expression, and discrete temperature characteristic information and interpolation temperature characteristic information. . It is a figure which shows the comparison of the temperature compensation at the time of using the 1st approximate expression and the 2nd approximate expression.

  Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. However, the components, types, combinations, shapes, relative arrangements, and the like described in this embodiment are merely illustrative examples and not intended to limit the scope of the present invention only unless otherwise specified. .

  FIG. 1 shows an oscillation circuit system including a piezoelectric oscillator according to this embodiment connected to a temperature compensation circuit. The piezoelectric oscillator 10 according to the present embodiment oscillates the piezoelectric vibrator 12 and the piezoelectric vibrator 12, and a first approximate expression 70 for approximating the temperature characteristics of the oscillation frequency of the piezoelectric vibrator 12 (FIG. 7) based on the temperature characteristic information 76 of the piezoelectric vibrator 12, and using the first approximate expression 70 and information corresponding to the temperature of the piezoelectric vibrator 12 (detection voltage 66), the temperature is calculated. The oscillation circuit 14 that outputs the oscillation signal 58 to the temperature compensation circuit 40 that calculates the compensation amount 80, and the storage circuit 20 that stores the temperature characteristic information 76, the temperature characteristic information 76 being the piezoelectric vibrator Discrete temperature characteristic information 74 indicating discretely the relationship between the temperature of 12 and the oscillation frequency is generated, and a second approximation lower than the first approximate expression 70 based on the discrete temperature characteristic information 74 Equation 72 (see FIG. 6) Information obtained by extracting the interpolation temperature characteristic information 78 from which the first approximate expression 70 can be calculated from the second approximate expression 72, and adding the interpolation temperature characteristic information 78 to the discrete temperature characteristic information 74. Is stored in the storage circuit 20 as the temperature characteristic information 76.

  Therefore, in the temperature compensation method of the piezoelectric oscillator 10 using the above configuration, the first approximate expression 70 for approximating the temperature characteristic of the oscillation frequency of the piezoelectric vibrator 12 is based on the temperature characteristic information 76 of the piezoelectric vibrator 12. The temperature compensation circuit 40 capable of calculating and calculating the temperature compensation amount 80 using the first approximate expression 76 and information (detection voltage 66) corresponding to the temperature of the piezoelectric vibrator 12 is supplied to the oscillation signal 58 and the temperature. A temperature compensation method for the piezoelectric oscillator 10 that outputs the characteristic information 76, wherein discrete temperature characteristic information 74 that discretely indicates a relationship between the temperature of the piezoelectric vibrator 12 and the oscillation frequency is generated, and the discrete temperature characteristic is generated. Based on the information 74, a second approximate expression 72 that is lower than the first approximate expression 70 is calculated, and the interpolation temperature characteristic that allows the first approximate expression 70 to be calculated from the second approximate expression 72. Extract information 78 And is information obtained by adding the interpolated temperature characteristic information 78 in the discrete temperature characteristic information 74 that is generated as the temperature characteristic information 76.

  The piezoelectric oscillator 10 of this embodiment is a TSXO that does not include the temperature compensation circuit 40. By patterning on a semiconductor substrate (not shown), the oscillation circuit 14, the temperature sensor 16, the buffer 18, the storage circuit 20, the serial interface circuit 22, the power supply terminal 36, the ground terminal 38, and the like are formed. The piezoelectric vibrator 12 is connected. Further, as shown in FIG. 1, the temperature compensation circuit 40 to be connected to the piezoelectric oscillator 10 includes a frequency correction circuit 42, a CPU 44, a memory 46, and an A / D converter 48. When calculating the temperature characteristic information 76, as shown in FIG. 2, the piezoelectric oscillator 10 is connected to a measuring device 50, and the measuring device 50 includes a frequency counter 52, a PC 54, and a voltage multimeter 56.

  The piezoelectric vibrator 12 is a piezoelectric material such as quartz, lithium niobate, lithium tantalate, etc. If it is quartz, it is formed by AT-cutting, receives an AC voltage from the oscillation circuit 14, and receives a predetermined amount by thickness shear vibration. It can oscillate at the resonance frequency. The resonance frequency of the crystal resonator using the thickness shear vibration due to the AT cut has a temperature characteristic that becomes a positive cubic curve centering on the reference temperature (25 ° C.).

  The oscillation circuit 14 is, for example, a Colpitts oscillation circuit using the piezoelectric vibrator 12 as an oscillation source, and outputs an oscillation signal 58 to the temperature compensation circuit 40 or the measuring device 50 via the oscillation frequency output terminal 24.

  The temperature sensor 16 has a diode structure, allows a forward current to flow, and outputs a detection voltage 66 that varies depending on the temperature from the temperature sensor voltage output terminal 34 to the temperature compensation circuit 40 or the measuring device 50 via the buffer 18. Is. Here, the detection voltage 66 decreases in a linear function as the temperature rises, and the output detection voltage 66 corresponds to the measured temperature. The temperature sensor 16 is desirably disposed adjacent to the piezoelectric vibrator 12. As a result, the temperature of the piezoelectric vibrator 12 can be accurately measured, and the correspondence between temperature and frequency or frequency displacement can be accurately determined in the discrete temperature characteristic information 74, the second approximate expression 72, and the interpolation temperature characteristic information 78 described later. The first approximate expression 70 and the temperature characteristic information 76 can be calculated with high accuracy. As described above, in this embodiment, the temperature of the piezoelectric vibrator corresponds to the detection voltage 66 from the temperature sensor 16, and the temperature compensation circuit 40 and the measuring device 50 described later are also discrete as information associated with the detection voltage 66. Temperature characteristic information 74, interpolation temperature characteristic information 78, temperature characteristic information 76, first approximate expression 70, and second approximate expression 72 are calculated.

  The serial interface circuit 22 receives a command from the outside, stores the temperature characteristic information 76 in the storage circuit 20, and outputs the detected voltage 66 output from the temperature sensor 16 and the temperature characteristic information 76 stored in the storage circuit 20 to the outside. Is output. The serial interface circuit 22 is connected to the memory circuit 20 and the temperature sensor 16 and has a data input / output terminal 26, a first control clock input terminal 28, and a second control clock input terminal 30.

  When the first control clock 60 is input to the first control clock input terminal 28, the serialized temperature characteristic information 76 input to the data input / output terminal 26 is triggered by the first control clock 60 (the first control clock 60). It can be stored (written) in the storage circuit 20 in synchronization with the control clock 60. When the second control clock 62 is input to the second control clock input terminal 30, the temperature characteristic information 76 stored in the storage circuit 20 is converted into serial data using the second control clock 62 as a trigger via the data input / output terminal 26. Can be output.

  The memory circuit 20 is formed of an EEPROM or the like, and the temperature characteristic information 76 is stored (written) through the serial interface circuit 22 or the temperature characteristic information 76 can be output. The temperature characteristic information 76 is composed of a finite number of data, and addresses that can be commonly recognized by the PC 54 in the measuring instrument 50 and the CPU 44 in the temperature compensation circuit 40 are provided.

FIG. 2 shows a connection diagram between the piezoelectric oscillator 10 and the measuring instrument 50. The measuring device 50 writes temperature characteristic information 76 required by the temperature compensation circuit 40 to the storage circuit 20.
That is, the measuring instrument 50 generates the discrete temperature characteristic information 74 having a smaller number of information than the temperature characteristic information 76 from the temperature characteristic of the oscillation frequency of the piezoelectric vibrator 12 mounted in the oscillation circuit 14, and the first temperature is obtained from the discrete temperature characteristic information 74. The second approximate expression 72 lower than the approximate expression 70 is calculated, the interpolation temperature characteristic information 78 that allows the first approximate expression 70 to be calculated in the second approximate expression 72 is extracted, and the discrete temperature characteristic information 74 is extracted. And interpolation temperature characteristic information 78 are added to generate temperature characteristic information 76 used in the temperature compensation circuit 40 and write it into the storage circuit 20.

  The measuring device 50 includes a frequency counter 52, a PC (personal computer) 54, and a voltage multimeter 56. The frequency counter 52 is connected to the oscillation circuit 14 and can measure the frequency of the oscillation signal 58 output from the oscillation circuit 14 at every predetermined time interval and output it to the PC 54. The voltage multimeter 56 can convert the detection voltage 66 from the temperature sensor 16 into digital data and output it to the PC 54.

  The PC 54 can start the frequency counter 52 and the voltage multimeter 56 by a key operation or the like, and can input a detection voltage 66 (current temperature) from the temperature sensor 16 and store it in a storage area attached to the PC. .

  The temperature characteristic information 76 is generated based on the discrete temperature characteristic information 74 and the interpolation temperature characteristic information 78. The discrete temperature characteristic information 74 is obtained by sequentially immersing the piezoelectric oscillator 10 in a plurality of thermostats having different set temperatures, and the piezoelectric vibrator 12 when the temperature of the piezoelectric oscillator 10 is stabilized in accordance with the set temperature in each thermostat. This is discrete data showing the relationship between the temperature and the frequency deviation obtained by measuring the oscillation frequency. The interpolation temperature characteristic information 78 calculates a later-described second approximate expression 72 of the frequency deviation information of the piezoelectric vibrator 12 on the basis of the discrete temperature characteristic information 74, and calculates a later-described first approximate expression 72 from the curve of the second approximate expression 72. This is data extracted at a temperature at which the approximate expression 70 can be calculated. Therefore, the interpolation temperature characteristic information 78 is extracted from a position on the second approximate expression 72 where the temperature does not overlap with the discrete temperature characteristic information 74.

  As the contents of the temperature characteristic information 76, the discrete temperature characteristic information 74 and the interpolated temperature characteristic information 78 are added and used as they are, that is, a plurality of temperatures arbitrarily selected from the operating temperature range (the temperature of the thermostat described later). And information on the frequency corresponding to each temperature in the plurality of temperatures or information on the frequency deviation from the reference frequency can be used. Alternatively, a combination of a temperature coefficient calculated based on this combination and an offset coefficient that is a part of the temperature coefficient can be used. Among these, the combination of the information on the plurality of temperatures and the information on the frequency deviation from the reference frequency corresponding to each temperature in the plurality of temperatures has a smaller number of digits than the case where the absolute value of the oscillation frequency is used. Therefore, the capacity of the temperature characteristic information 76 becomes the smallest. Further, when the temperature coefficient is stored as the temperature characteristic information 76, it is not necessary to store the temperature information itself, so that the capacity of the temperature characteristic information 76 can be reduced. In addition, when the temperature characteristic information 76 is a combination of the above-described plurality of temperature information and frequency information corresponding to each temperature, the reference temperature and the frequency information at the reference temperature are acquired and the combination. It is necessary to attach an address that allows the PC 54 and the CPU 44 to distinguish from other information.

  In the above-described temperature characteristic information 76, which type is used is determined by what type of temperature characteristic information is used by the temperature compensation circuit 40. Therefore, the temperature required by the temperature compensation circuit 40 in the PC 54 is determined. Assume that it is appropriately calculated according to the format of the characteristic information and written in the storage circuit 20.

  In this embodiment, five thermostats (not shown) having different set temperatures are used, the piezoelectric oscillator 10 is immersed in each thermostat, and the temperature of the piezoelectric vibrator 12 is set to the set temperature of the thermostat, and the PC 54 is piezoelectric. A detection voltage 66 (temperature information) is input from the temperature sensor 16 when the vibrator 12 is stabilized at a predetermined temperature, and the oscillation frequency of the piezoelectric vibrator 12 at that time is input via the frequency counter 52. Discrete temperature characteristic information 74 is generated from the relationship between the temperature of the point and the oscillation frequency at each temperature.

Assuming that the reference frequency at the reference temperature T ₀ is f for the oscillation frequency of the piezoelectric vibrator using the thickness shear vibration, the frequency deviation information of the oscillation frequency at an arbitrary temperature T has the orders up to the fourth order as shown below. It can be expressed by the second approximate expression 72 (Δf _B / f) having five coefficients.

Here, B _{1 to} B ₄ are temperature coefficients for determining the frequency deviation information, and B ₀ is an offset coefficient for determining the offset of the frequency deviation information, and belongs to the temperature coefficient. Therefore, the PC 54 can approximately calculate each coefficient of Formula 1 by substituting the discrete temperature characteristic information 74 into Formula 1 and using polynomial and polynomial approximation using 5 coefficients.

On the other hand, in the temperature compensation performed by the temperature compensation circuit 40 based on the temperature characteristic information 76, as shown below, the first approximate expression 70 (Δf _A / f) having orders up to the fifth order and six coefficients. ) Is used.

Here, A _{1 to} A ₅ are temperature coefficients that determine the frequency deviation information, and A ₀ is an offset coefficient that determines the offset of the frequency deviation information, and belongs to the temperature coefficient. Thus, since there are six coefficients in Expression 2, it is not sufficient to use only the discrete temperature characteristic information 74 in calculating the coefficients satisfying Expression 2. Therefore, it can be calculated by extracting one point of the interpolation temperature characteristic information 78 that can be calculated by the first approximate expression 70 from Expression 1 and adding this to the discrete temperature characteristic information 74 to generate the temperature characteristic information 76. However, in order to obtain an approximate function that can accurately represent the actual frequency deviation information, the method of calculating an unknown coefficient using only the same number of temperature and frequency deviation information as the number of coefficients that determine the function, and converting it into a function. Inaccurate accuracy. When performing the fifth-order approximation as in the present embodiment, if only the information on the temperature and frequency deviation at the six points actually used passes on the curve of the fifth-order approximation, this is the ideal fifth-order approximation. Therefore, it is necessary to consider that the error between the frequency deviation at an arbitrary temperature point other than 6 points and the fifth-order approximation is as small as possible. Therefore, in this embodiment, in order to obtain the first approximate expression 70, the temperature characteristic information 76 needs to have the number of information more than the number of coefficients of the first approximate expression 70. When the temperature characteristic information 76 is temperature information and frequency deviation information corresponding to the temperature, seven (or more) information pieces are prepared, and an approximate function that best matches using the least square method is prepared. calculate. The least squares method is a method of estimating the best approximation value based on the relationship between multiple pairs of data. The square of the error between the actual data and the theoretical value on the approximation function is calculated for each discrete data. The coefficients are derived so that the sum when all are added is minimized. That is, given n (n = 7) data (t ₁ , f ₁ )... (T _n , f _n ),

The sum S of squares of errors between the theoretical value of this equation shown below and the original measurement data (combination of the discrete temperature characteristic information 74 and the interpolated temperature characteristic information 78) is the smallest. Coefficients a _{5 to} a ₀ are determined.

In order to minimize the square sum S, the values obtained by partial differentiation of the square sum S by the coefficients a _{5 to} a ₀ are all zero as shown below.

となるａ_ｊ（ｊ＝０〜５）を求める。ここで、Ａ_ｊｋは正規方程式の係数行列、Ｆ_ｊは正規方程式の定数ベクトルで、

となる。さらに数式６は、

であるが、これを

に示すように数式９の左辺のＡ_ｉｊの部分が単位行列となるように変形し、これによりａ_５＝Ｆ_５’，・・・ａ_０＝Ｆ_０’となるようにして各近似係数ａ_５〜ａ_０の値を求める。ＰＣ５４は上述の演算を行なって各近似係数（温度係数）を求め、これを温度特性情報７６として生成し記憶回路２０に記憶する。また上述の演算は温度補償回路４０においても可能であるので、その場合ＰＣ５４は、離散温度特性情報７４に補間温度特性情報７８を付加したものを温度特性情報７６として生成し記憶回路２０に記憶する。 Then, by solving the simultaneous 6-element linear equation derived based on Equation 5 using the Gauss-Jordan elimination method, the values of the approximate coefficients a _{5 to} a ₀ are obtained. That is,

A _j (j = 0 to 5) is obtained. Where A _jk is the coefficient matrix of the normal equation, F _j is the constant vector of the normal equation,

It becomes. Furthermore, Formula 6 becomes

But this

As shown in FIG. 4, the portion of _{Aij on} the left side of Equation 9 is transformed to be a unit matrix, whereby each approximation coefficient a is set so that a ₅ = F ₅ ′,... A ₀ = F ₀ ′. The value of _{5 to} a ₀ is obtained. The PC 54 performs the above calculation to obtain each approximate coefficient (temperature coefficient), generates this as temperature characteristic information 76, and stores it in the storage circuit 20. Since the above-described calculation can be performed in the temperature compensation circuit 40, the PC 54 generates the temperature characteristic information 76 obtained by adding the interpolated temperature characteristic information 78 to the discrete temperature characteristic information 74 and stores it in the storage circuit 20. .

  As described above, the temperature characteristic information 76 includes information obtained by adding the interpolated temperature characteristic information 78 to the discrete temperature characteristic information 74, and information obtained by calculating the temperature coefficient of Formula 2 from this addition using the least square method. When the temperature characteristic information 76 is a temperature coefficient, not only can the temperature information be omitted, but the number of pieces of information is reduced by one. Therefore, the capacity of the temperature characteristic information 76 can be reduced, and the memory circuit 20 can be downsized. Can be reduced in size and cost.

  After constructing the temperature characteristic information 76 in the PC 54 as described above, the PC 54 outputs the first control clock 60 to the first control clock input terminal 28 and serializes it in synchronization with the first control clock 60. The temperature characteristic information 76 is output to the data input / output terminal 26, and the temperature characteristic information 76 is stored in the storage circuit 20 via the serial interface circuit 22.

  As described above, the measuring instrument 50 generates the discrete temperature characteristic information 74, the second approximate expression 72, the interpolated temperature characteristic information 78, and the temperature characteristic information 76 as information associated with the detection voltage 66 from the temperature sensor 16. . On the other hand, the temperature compensation circuit 40 also uses the temperature characteristic information 76 to calculate the first approximate expression 70 using the detected voltage 66 as a domain, but calculates the first approximate expression 70 using the actual temperature value as the domain. In this case, the temperature characteristic information 76 needs to correspond to this.

As described above, the detection voltage 66 output from the temperature sensor 16 changes in a linear function with respect to the temperature change. Here, if the value of the detection voltage 66 at the reference temperature (25 ° C.) is V ₂₅ , the detection voltage 66 (V _read ) output from the temperature sensor 16 and the temperature T at that time can be expressed as follows.

Here, A is a coefficient of the temperature change amount per 1 V, and A can be obtained as follows.

Here, V ₈₅ is a value of the detection voltage 66 at the set maximum temperature, and V ₍₋₂₅₎ is a value of the detection voltage 66 at the set minimum temperature. Therefore, the PC 54 measures each value (V ₍₋₃₀₎ , V ₂₅ , V ₈₅ ) of the detection voltage 66 at the set minimum temperature (−30 ° C.), the reference temperature (25 ° C.), and the set maximum temperature (85 ° C.). Then, the coefficient A is obtained, and an address that can be recognized by the CPU 44 is added to the coefficient A and the value V ₂₅ of the detection voltage 66 at the reference temperature (25 ° C.), and then added to the temperature characteristic information 76.

  As shown in FIG. 1, the temperature compensation circuit 40 is a part of an external system separated from the piezoelectric oscillator 10. The temperature compensation circuit 40 calculates the first approximate expression 70 using the temperature characteristic information 76 input from the PC 54 to the storage circuit 20, and the detection voltage 66 constantly input from the first approximate expression 70 and the temperature sensor 16. The temperature compensation amount 80 is calculated based on (temperature information), and includes a frequency correction circuit 42, a CPU 44, a memory 46, and the like. The frequency correction circuit 42 is a circuit that varies the frequency of the output signal in accordance with the temperature compensation amount 80 output from the CPU 44. The frequency correction circuit 42 is connected to the oscillation circuit 14 and receives the oscillation signal 58. And an oscillation signal 68 subjected to temperature compensation.

  The CPU 44 is the core of the temperature compensation circuit 40, and calculates a first approximate expression 70 as frequency deviation information from the temperature characteristic information 76 input from the storage circuit 20, and the first approximate expression 70 and the temperature are calculated. The temperature compensation amount 80 is calculated based on the detection voltage 66 (temperature information) input from the sensor 16 and is output to the frequency correction circuit 42.

  The CPU 44 is connected to the data input / output terminal 26, the second control clock input terminal 30, the frequency correction circuit 42, and the temperature sensor 16 via an A / D converter 48. At startup, the CPU 44 inputs the second control clock 62 to the second control clock input terminal 30 by a program, and synchronizes the second control clock 62 with the temperature characteristic information 76 in the storage circuit 20 in the serial interface circuit 22. And stored in a memory 46 attached to the CPU 44.

  When the temperature characteristic information 76 stored in the storage circuit 20 is a combination of information on a plurality of temperatures in the operating temperature range of the piezoelectric vibrator 12 and information on frequency deviation corresponding to each temperature in the plurality of temperatures, The CPU 44 uses the temperature characteristic information 76 and Equations 2 to 8 to calculate the temperature coefficient and the offset coefficient by the above-described method and use a configuration that can be stored in the attached memory 46. When the temperature characteristic information 76 is the above-described information on the plurality of temperatures and the frequency (absolute value) information corresponding to each temperature, the CPU 44 uses the reference temperature information in the temperature characteristic information 76 and the frequency measured at the reference temperature. The information address can be identified, and the temperature characteristic information 76 and the mathematical expressions 2 to 8 are used to calculate the temperature coefficient and the offset coefficient by the above-described method, and the information can be stored in the attached memory 46. Use. If the temperature characteristic information 76 stored in the storage circuit 20 is a temperature coefficient and an offset coefficient, the CPU 44 uses the one having a configuration for storing it in the attached memory 46 as it is.

Further, the CPU 44 digitizes and inputs the detection voltage 66 (temperature information) from the temperature sensor 16 through the A / D converter 48 every predetermined time by a program and stores it in the attached memory 46. Then, the temperature coefficient and the offset coefficient are read from the memory 46 to calculate the first approximate expression 70, and the detection voltage 66 (voltage information) from the temperature sensor 16 is further read from the memory 46 to obtain the first approximate expression 70 and A temperature compensation amount 80 is calculated from the detection voltage 66, and the temperature compensation amount 80 is output to the frequency correction circuit 42. Therefore, the CPU 44 calculates the temperature compensation amount 80 every predetermined time and outputs it to the frequency correction circuit 42. As a result, the frequency correction circuit 42 outputs an oscillation signal 68 subjected to temperature compensation every predetermined time. When the CPU 44 calculates the first approximate expression 70 using the actual temperature as a domain, the CPU 44 is configured to convert the detection voltage 66 (current voltage) input based on Expression 9 into a temperature. . In response to this, the PC 54 adds coefficients A and V ₂₅ to the temperature characteristic information 76 as described above.

A procedure for writing temperature characteristic information of the piezoelectric oscillator 10 according to the present embodiment will be described.
FIG. 3 shows a flow diagram for calculating the second approximate expression and temperature characteristic information, and FIG. 4 shows a flow for obtaining a coefficient of temperature change per unit voltage to be added to the temperature characteristic information and a voltage value at the reference temperature. The figure is shown.

  First, as shown in FIG. 2, the measuring device 50 is connected to the piezoelectric oscillator 10, the set temperatures of five thermostats (not shown) in which the piezoelectric oscillator 10 is immersed are set to different values, and the piezoelectric oscillators are set in the thermostat. Immerse sequentially. When the temperature of the piezoelectric oscillator 10 is stabilized, the PC 54 acquires the detection voltage 66 (temperature information) and the oscillation frequency, generates discrete temperature characteristic information 74, and stores it in a storage area (not shown) of the PC 54. Then, a second approximate expression 72 having a fourth order is calculated using polynomial approximation. Then, two points on the second approximate expression 72 that do not overlap with the discrete temperature characteristic information 74 are extracted to generate the interpolation temperature characteristic information 78, and the discrete temperature characteristic information 74 read from the storage area is added to the interpolation temperature characteristic information 78. This information is used as temperature characteristic information 76, which is stored in a storage area (not shown).

When the temperature coefficient is output to the temperature compensation circuit 40, the first approximate expression 70 having the fifth order is calculated using the temperature characteristic information 76 read from the storage area of the PC 54 using the least square method. Then, the obtained temperature coefficient is overwritten in the storage area of the PC 54 as new temperature characteristic information 76. Next, as shown in FIG. The temperatures (−30 ° C., 80 ° C.) at both ends of the low temperature side and the constant temperature side of the discrete temperature characteristic information 74 and the values V ₍₋₃₀₎ , V _{80 of} the detection voltage 66 output from the temperature sensor 16 at that temperature The value V ₂₅ of the detection voltage 66 at the reference temperature (25 ° C.) is extracted, the coefficient A of the temperature change amount per unit voltage is calculated according to Equation 9, and the coefficients A and V ₂₅ are read from the storage area of the PC 54 It is added to the characteristic information 76, and the added temperature characteristic information 76 is overwritten in the storage area.

  Next, a temperature compensation procedure in the temperature compensation circuit 40 will be described. In the present embodiment, a GPS device including the piezoelectric oscillator 10 and the temperature compensation circuit 40 is assumed. FIG. 5 shows a flow chart of temperature compensation in the temperature compensation circuit.

As shown in FIG. 1, a temperature compensation circuit 40 is connected to the piezoelectric oscillator 10 and an oscillation signal 58 is output to a frequency correction circuit 42. Then, the GPS device that has received the oscillation signal 68 output from the frequency correction circuit 42 starts the operation of capturing the positioning signal from the GPS satellite within a certain search range. At this time, the CPU 44 acquires the temperature characteristic information 76 stored in the storage circuit and calculates the first approximate expression. Here, when the temperature characteristic information 76 is the sum of the discrete temperature characteristic information 74 and the interpolation temperature characteristic information 78, the coefficient of the first approximate expression 70 is calculated using the above-mentioned least square method. If the temperature characteristic information 76 has already been converted into a temperature coefficient in the PC 54, it is directly substituted for the coefficient corresponding to the first approximate expression 70. Then, the detection voltage 66 (V _read ) is obtained from the temperature sensor 16 to obtain the frequency deviation. At this time, when the temperature compensation circuit 40 calculates the frequency deviation using the actual temperature value instead of the detection voltage 66 as a domain, the temperature compensation circuit 40 uses the temperature characteristic information 76 generated by using the temperature as a definer. A first approximate expression 70 having a domain defined as F is calculated, the coefficient A and the voltage value V ₂₅ at the reference temperature are extracted from the acquired temperature characteristic information 76, and the current temperature is calculated from the detected voltage 66 input according to Expression 9. Calculate the value. Then, the value of the current temperature on the first approximate expression 70 is extracted to calculate a frequency deviation, and the temperature compensation amount 80 is output from the frequency deviation to the frequency correction circuit 42 to generate a new temperature compensated oscillation signal. 68 is output to the GPS device, and the search range of the positioning signal is offset. As a result, the positioning signal can be captured in a short time.

The effect of temperature compensation using the piezoelectric oscillator of this embodiment will be described.
FIG. 6 is a schematic diagram of the discrete temperature characteristic information 74 obtained by measurement and the second approximate expression 72 calculated corresponding to the discrete temperature characteristic information 74. FIG. 7 shows the discrete temperature characteristic information 74 and the points extracted on the second approximate expression 72 and extracted at a temperature at which the first approximate expression 70 can be calculated (the temperature does not overlap with the discrete temperature characteristic information 74). A schematic diagram of the first approximate expression 70 generated based on the interpolated temperature characteristic information 78, the discrete temperature characteristic information 74, and the interpolated temperature characteristic information 78 is shown.

  In FIG. 6, the discrete temperature characteristic information 74 is measured at -30 ° C, 0 ° C, 25 ° C, 55 ° C, and 85 ° C. Since the second approximate expression 72 is calculated based on the discrete temperature characteristic information 74, the second approximate expression 72 passes on the plot of the discrete temperature characteristic information 74, and the second approximate expression 72 is better than the discrete temperature characteristic information 74. It is an approximate curve. However, in order to reduce the error of the approximate curve from the actual frequency deviation at other temperatures, higher order approximation is required. Therefore, in the present embodiment, as shown in FIG. 3, the interpolation temperature characteristic information 78 is generated by extracting points on the second approximate expression 72 at −15 ° C. and 75 ° C. Then, as shown in FIG. 7, a first approximate expression 70 having a fifth order is calculated using the least square method based on the discrete temperature characteristic information 74 and the interpolation temperature characteristic information 78.

  FIG. 8 shows the result of comparing the temperature compensation characteristic (thin line) when temperature compensation is performed with the second approximate expression 72 and the temperature compensation characteristic (thick line) when temperature compensation is performed with the first approximate expression 70. Is shown. As shown in FIG. 8, when temperature compensation is performed using the second approximate expression 72 having the fourth order (thin line), a temperature compensation error exceeding 0.2 ppm occurs at around 45 ° C. Yes. On the other hand, when temperature compensation is performed using the first approximate expression 70 having the fifth order (thick line), the error in the vicinity of 45 ° C. is improved to about 1.5 ppm, and in other temperature regions, it is almost It is suppressed to about 0.1 ppm. Therefore, it can be understood that the accuracy of temperature compensation is improved in the fifth-order approximate expression over the fourth-order approximate expression even when the actually measured data based on the five set temperatures is used in common.

  Originally, it is preferable to have actual measurement data based on seven set temperatures in order to accurately calculate a fifth-order approximation using the least square method. However, in this embodiment, it is based on the discrete temperature characteristic information 74 that is actually measured data based on the five set temperatures. Therefore, in consideration of the approximation error of the approximate expression, it is preferable to calculate a fourth-order approximate expression having five coefficients when the actually measured data is five points. Therefore, in this embodiment, the interpolated temperature characteristic information 78 generated by extracting two points on the second approximate expression 72 having the fourth order calculated based on the above-described discrete temperature characteristic information 74 is represented by the discrete temperature. Temperature characteristic information 76 is generated by adding to the characteristic information 74, and based on this, the first approximate expression 70 having the fifth order is calculated using the least square method, and temperature compensation is performed based on this. ing. It can be seen that by using such a temperature compensation method, it is possible to improve the accuracy of temperature compensation as compared with the case where temperature compensation is performed using a fourth-order approximation as shown in FIG.

  In the present embodiment, the piezoelectric vibrator 12 has been described on the assumption of a thickness-shear vibrator. However, the present invention is not limited to this, and the present invention may be applied to a double tuning fork type piezoelectric vibrator, a single beam type piezoelectric vibrator, a SAW resonator, and the like. Applicable. In the present embodiment, the piezoelectric oscillator 10 has been described on the premise of TSXO. However, by incorporating the temperature compensation circuit 40, a temperature compensated oscillator (TCXO) can be formed, and an oscillation signal 68 subjected to highly accurate temperature compensation is obtained. Needless to say, output is possible.

  As described above, according to the piezoelectric oscillator 10 and the manufacturing method of the piezoelectric oscillator 10 according to the present embodiment, first, the temperature characteristic information 76 includes the discrete temperature characteristic information 74 generated by actual measurement, the discrete temperature characteristic information, and the like. Interpolated temperature characteristic information 78 obtained from the information 74 through the second approximate expression 72 is configured. Therefore, in the temperature compensation circuit 40, since the first approximate expression 70 is calculated based on the temperature characteristic information 76 having the number of information equal to or greater than the number of coefficients of the first approximate expression 70, the first approximate expression 70 falls within a certain approximate error range. The coefficient that falls is calculated. For this reason, the accuracy of temperature compensation when the first approximate expression 70 is used is improved as compared with the case where temperature compensation is performed using the second approximate expression 72. Therefore, it is not necessary to increase the number of thermostats for obtaining actually measured data, and the working time and cost can be suppressed, and the temperature compensation circuit 40 can perform highly accurate temperature compensation.

  Second, the temperature characteristic information 76 is generated based on the information on the temperature of the piezoelectric vibrator and the information on the oscillation frequency corresponding to the temperature of the piezoelectric vibrator or the information on the frequency deviation from the reference frequency. Since the calculation of the temperature coefficient is unnecessary on the 10 side, the work burden when forming the piezoelectric oscillator 10 can be suppressed and the cost can be reduced. In this case, the temperature coefficient is calculated from the first approximate expression 70 corresponding to the temperature characteristic information 76 on the user side, but the user can calculate the exact temperature coefficient uniquely.

  Third, the temperature characteristic information 76 is obtained by applying the first approximate expression 70 to the information on the temperature of the piezoelectric vibrator, the information on the oscillation frequency corresponding to the temperature of the piezoelectric vibrator, or the information on the frequency deviation from the reference frequency. Since the temperature compensation circuit 40 does not need to calculate the temperature coefficient because it is generated by matching and extracting the temperature coefficient, the burden on the user side is reduced and the piezoelectric oscillator 10 is mounted. Easy to build.

  Fourth, a temperature sensor 16 that outputs a detection voltage 66 corresponding to the temperature is disposed adjacent to the piezoelectric vibrator 12, and the first approximate expression 70, the second approximate expression 72, and the temperature characteristic information 76 are The first approximate expression 70 is generated based on the temperature characteristic information 76, and the temperature information input from the first approximate expression 70 and the temperature sensor 16 (detection voltage) is generated as information associated with the detection voltage 66. 66), the temperature sensor 16 can measure the temperature of the piezoelectric vibrator 12 while suppressing the measurement error by outputting the oscillation signal 58 to the temperature compensation circuit 40 that can calculate the temperature compensation amount 80. The discrete temperature characteristic information 74 is calculated with high accuracy, and the second approximate expression 72 and the interpolated temperature characteristic information 78 are calculated with high accuracy, whereby the first approximate expression 70 and the temperature characteristic information 76 are calculated with high accuracy. Can be calculated . Furthermore, since the current temperature of the piezoelectric vibrator 12 can be measured in real time and with high accuracy, a correction error in the temperature compensation circuit 40 can be suppressed and temperature compensation can be performed with high accuracy.

  Further, according to the temperature compensated oscillator and the manufacturing method thereof according to the present embodiment, the temperature compensation circuit 40 is formed in the piezoelectric oscillator 10 described above, thereby increasing the number of thermostats for generating the temperature characteristic information 76. Therefore, it is possible to output the oscillation signal 68 subjected to temperature compensation with high accuracy.

10 ......... Piezoelectric oscillator, 12 ......... Piezoelectric vibrator, 14 ......... Oscillation circuit, 16 ......... Temperature sensor, 18 ......... Buffer, 20 ......... Storage circuit, 22 ......... Serial interface circuit, 24... Oscillation frequency output terminal 26... Data input / output terminal 28... First control clock input terminal 30 30 Second control clock input terminal 34 34 Temperature sensor voltage output terminal 36... Power supply terminal 38... Ground terminal 40 40 Temperature compensation circuit 42 Frequency correction circuit 44 CPU 46 Memory 48 A / D conversion 50 ......... Measurement instrument 52 ......... Frequency counter 54 ......... PC 56 ......... Voltage multimeter 58 ......... Oscillation signal 60 ......... First control clock 62 ... ... second control clock, 66 ... Detected voltage 68... Oscillation signal 70... First approximate expression 72... Second approximate expression 74 74 Discrete temperature characteristic information 76 76 Temperature characteristic information 78 ......... Interpolated temperature characteristic information, 80 ......... Temperature compensation amount.

Claims (1)

A piezoelectric vibrator; an oscillation circuit that oscillates the piezoelectric vibrator and outputs an oscillation signal; temperature detection means that outputs a detection voltage corresponding to the temperature of the piezoelectric vibrator; and a temperature at an oscillation frequency of the piezoelectric vibrator. A piezoelectric circuit having a storage circuit that outputs temperature characteristic information indicating characteristics;
A CPU that calculates a first approximate expression for approximating the temperature characteristic of the oscillation frequency of the piezoelectric vibrator from the temperature characteristic information, and outputs a temperature compensation amount using the first approximate expression and the detected voltage; A temperature correction circuit having a frequency correction circuit for performing temperature compensation of the oscillation signal corresponding to the temperature compensation amount, and an oscillation circuit system comprising:
The temperature characteristic information is
It is generated based on information obtained by adding interpolation temperature characteristic information to discrete temperature characteristic information discretely indicating the relationship between the temperature of the piezoelectric vibrator and the oscillation frequency, and
The interpolation temperature characteristic information is
It is calculated based on the discrete temperature characteristic information and extracted from the second approximate expression lower than the first approximate expression so that the first approximate expression can be calculated from the information. A featured oscillation circuit system.

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