JP2011114860A - Oscillation circuit system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oscillation circuit system capable of reducing the influence of a hysteresis characteristic of an oscillation frequency of a piezoelectric vibrator and oscillating the vibrator at a stable oscillation frequency. <P>SOLUTION: The oscillation circuit system includes: a piezoelectric oscillator 10 provided with the piezoelectric vibrator 12 having a frequency temperature characteristic with the hysteresis characteristic, an oscillation circuit 14 for oscillating the piezoelectric vibrator 12 and outputting an oscillation signal 58, a temperature sensor 16 for outputting a detection voltage 66 corresponding to the ambient temperature of the piezoelectric vibrator 12, and a storage circuit 20 for outputting frequency temperature information 76 indicating the temperature characteristic of the oscillation frequency of the piezoelectric vibrator 12; and a temperature compensation circuit 40 provided with a CPU 44 for calculating a temperature compensation quantity 80 using the frequency temperature information 76 and the detection voltage 66, and a frequency correction circuit 42 for executing the temperature compensation of the oscillation signal 58 on the basis of the temperature compensation quantity 80. The frequency temperature information 76 indicates the frequency temperature characteristic in an area surrounded by two frequency temperature characteristics (an elevated-temperature frequency temperature characteristic 77a and a lowered-temperature frequency temperature characteristic 77b) of the oscillation signal appearing under the influence of the hysteresis characteristic. <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. 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 side is uniquely constructed, and temperature information of the piezoelectric vibrator mounted on the oscillator is obtained from the oscillator side. There has been a demand for appropriate compensation. 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 temperature of the mounted piezoelectric vibrator to the user side, and a mounted piezoelectric vibration. A memory circuit that stores the frequency temperature information (temperature coefficient) of the child 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 temperature information obtained from the temperature sensor and the frequency temperature information obtained from the storage circuit. The amount is calculated and frequency correction is applied.

  Here, since the frequency temperature 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 In general, the frequency temperature information is acquired and stored in a storage circuit.

JP 2003-324318 A

  By the way, the frequency-temperature characteristic of the crystal resonator has a hysteresis characteristic. Having a hysteresis characteristic means that the temperature dependence of the crystal resonator is different when the temperature rises and when it falls. This is due to the fact that the change in strain stress of the crystal resonator with respect to the temperature change cannot follow the actual temperature change, and the thermal strain change of the support structure, adhesive, welding alloy, electrode, etc. in the oscillator. It becomes more prominent as the size of the vibrator becomes smaller.

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.

  Therefore, the conventional method of acquiring frequency temperature information at the time of temperature change at the time of temperature rise or at the time of temperature fall and storing it in the storage circuit stores only frequency temperature information in one direction. Therefore, if the temperature changes in the opposite direction to when acquiring the frequency temperature information, the difference in oscillation frequency resulting from the hysteresis characteristic remains as a correction error even if frequency correction is performed as a system. Therefore, due to this, there has been a problem that it takes a long time for positioning, resulting in a positioning error or a malfunction in synchronization with the GPS satellite.

  Accordingly, the present invention focuses on the above-described problems, and an object thereof is to provide an oscillation circuit system capable of oscillating at a stable oscillation frequency by reducing the influence of hysteresis characteristics of the oscillation frequency of a piezoelectric vibrator.

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 corresponds to a piezoelectric vibrator having a hysteresis characteristic in frequency temperature characteristics, an oscillation circuit that oscillates the piezoelectric vibrator and outputs an oscillation signal, and an ambient temperature of the piezoelectric vibrator A piezoelectric oscillator having a temperature detection means for outputting the detected voltage and a storage circuit for outputting frequency temperature information indicating a temperature characteristic of the oscillation frequency of the piezoelectric vibrator, and using the frequency temperature information and the detection voltage. An oscillation circuit system comprising: a CPU that calculates a temperature compensation amount; and a temperature compensation circuit that includes a frequency correction circuit that performs temperature compensation of the oscillation frequency based on the temperature compensation amount, wherein the frequency temperature The information indicates the frequency temperature characteristic in the region surrounded by the two frequency temperature characteristics of the oscillation signal that appears under the influence of the hysteresis characteristic. Oscillation circuit system comprising.

  The two frequency temperature characteristics are a frequency temperature characteristic when the temperature of the piezoelectric vibrator is increased and a frequency temperature characteristic when the temperature is decreased. In the above configuration, the temperature compensation circuit uses the frequency temperature information in the region surrounded by the two frequency temperature characteristics of the piezoelectric vibrator and the temperature information of the piezoelectric vibrator at the time of oscillation of the piezoelectric vibrator, as a reference frequency. Thus, the temperature compensation amount is calculated. Therefore, the oscillation circuit system can suppress the correction error caused by the hysteresis characteristic of the piezoelectric vibrator to a certain range regardless of whether the ambient temperature is rising or falling. Furthermore, since it is not necessary to store the temperature rise frequency temperature information, the temperature fall frequency temperature information, or the temperature information extracted from these in the memory circuit, an increase in the capacity burden on the memory circuit can be avoided.

  [Application Example 1] A piezoelectric vibrator having a hysteresis characteristic in frequency temperature characteristics, and an oscillation circuit that oscillates the piezoelectric vibrator and outputs an oscillation signal, and shows temperature characteristics of the oscillation frequency of the piezoelectric vibrator. A piezoelectric oscillator that outputs the oscillation signal and the frequency temperature information to a temperature compensation circuit capable of calculating a temperature compensation amount using frequency temperature information and temperature information of the piezoelectric vibrator at the time of oscillation of the oscillation signal. A temperature compensation method, wherein the temperature rise frequency temperature information of the piezoelectric vibrator generated when the ambient temperature of the piezoelectric vibrator is increased, and the piezoelectric vibration generated when the ambient temperature is lowered A temperature compensation method for a piezoelectric oscillator, wherein an intermediate value between the temperature drop frequency temperature information of the child is calculated as the frequency temperature information.

  By the above method, in the temperature compensation circuit, an intermediate value between the temperature increase frequency temperature information generated when the ambient temperature of the piezoelectric vibrator is increased and the temperature decrease frequency temperature information when the ambient temperature is decreased is obtained. Frequency temperature information is input, and a frequency deviation from the reference frequency is calculated using the frequency temperature information and the temperature information of the piezoelectric vibrator at the time of oscillation of the piezoelectric vibrator, thereby calculating a temperature compensation amount. Therefore, the correction error caused by the hysteresis characteristic of the piezoelectric vibrator can be suppressed to a certain range regardless of whether the ambient temperature is rising or falling.

  Application Example 2 The frequency temperature information is calculated from the temperature rising frequency temperature information, calculated from first approximate curve information indicating a continuous temperature characteristic of the oscillation frequency, and the temperature decreasing frequency temperature information, The temperature compensation of the piezoelectric oscillator according to Application Example 1, wherein the temperature information is extracted from second approximate curve information indicating a continuous temperature characteristic of the oscillation frequency and third approximate curve information calculated as an intermediate value. Method.

  By the above method, the frequency temperature information is extracted from the intermediate approximate curve information that continuously changes with respect to the temperature change. On the other hand, the temperature compensation circuit forms an approximate curve of the oscillation frequency that continuously changes with respect to the temperature change based on the frequency temperature information. Accordingly, since the approximate curve calculated by the temperature compensation circuit is the third approximate curve, temperature compensation can be performed with high accuracy. Further, since it is not necessary to measure the temperature rising frequency temperature information and the temperature falling frequency information at the same temperature position, it is possible to increase the yield of generating the frequency temperature information and to suppress the cost.

  Application Example 3 The frequency temperature information is generated from temperature information and oscillation frequency information corresponding to the temperature information or frequency deviation information from a reference frequency corresponding to the temperature information. A temperature compensation method for a piezoelectric oscillator according to Example 1 or 2.

  This eliminates the need to generate a temperature coefficient on the piezoelectric oscillator side, thereby reducing the work burden when forming the piezoelectric oscillator and reducing the cost. In this case, the temperature compensation amount is calculated by calculating the temperature coefficient of the series that should overlap the temperature information plot on the user side, but the user can calculate the exact temperature coefficient independently.

  [Application Example 4] The temperature compensation method for a piezoelectric oscillator according to Application Example 2, wherein the frequency temperature information is generated based on temperature coefficient information extracted from the third approximate curve information.

  This eliminates the need for calculation for calculating the temperature coefficient in the temperature compensation circuit, thereby reducing the burden on the user side and easily constructing a system equipped with a piezoelectric oscillator.

  Application Example 5 The temperature increase frequency temperature information is approximately calculated using the temperature decrease frequency temperature information and temperature and frequency information measured by raising the ambient temperature to a reference temperature region. The temperature compensation method for a piezoelectric oscillator according to any one of Application Examples 1 to 4.

  When the difference between the frequency components of the temperature increase frequency temperature information and the temperature decrease frequency temperature information is taken, the difference becomes the largest in the reference temperature region, and decreases as the distance from the reference temperature increases. Therefore, the temperature increase frequency temperature information can be approximately calculated using the temperature decrease frequency temperature information and the temperature and frequency information measured by raising the ambient temperature of the piezoelectric vibrator to the reference temperature region. Therefore, information on the temperature and frequency at the time of temperature rise need only be acquired in the reference temperature region, and a step of raising the temperature to a high temperature region higher than the reference temperature becomes unnecessary. Therefore, since the acquisition time of temperature rising frequency temperature information can be shortened, the work burden can be reduced and the cost can be suppressed.

  Application Example 6 The temperature drop frequency temperature information is approximately calculated using the temperature rise frequency temperature information and temperature and frequency information measured by lowering the ambient temperature to a reference temperature region. The temperature compensation method for a piezoelectric oscillator according to any one of Application Examples 1 to 4.

  For the same reason as in application example 5, the temperature decrease frequency temperature information is approximately calculated using the temperature increase frequency temperature information and the temperature and frequency information measured by lowering the ambient temperature of the piezoelectric vibrator to the reference temperature region. be able to. Further, it is only necessary to measure the reference temperature region when the temperature falls, and it is not necessary to measure a low temperature region lower than the reference temperature. Therefore, since the acquisition time of temperature fall frequency temperature information can be shortened, a work burden can be reduced and cost can be suppressed.

  Application Example 7 A temperature detection unit that outputs a detection voltage corresponding to the ambient temperature is disposed adjacent to the piezoelectric vibrator, and the temperature increase frequency temperature information and the temperature decrease frequency temperature information are stored in the detection voltage. Temperature compensation that is generated as a function, and the frequency temperature information is calculated based on the temperature rising frequency temperature information and the temperature falling frequency temperature information, and a temperature compensation amount can be calculated based on the frequency temperature information and the detected voltage The temperature compensation method for a piezoelectric oscillator according to any one of Application Examples 1 to 6, wherein the oscillation signal is output to a circuit, and the detection voltage is output from the temperature detection unit to the temperature compensation circuit.

  By the above method, the temperature detecting means can measure the ambient temperature of the piezoelectric vibrator while suppressing measurement error, so that the temperature temperature information and the temperature decreasing frequency temperature information are generated with high accuracy, and the frequency temperature information is obtained. It can be calculated with high accuracy. Furthermore, since temperature information of the piezoelectric vibrator can be measured in real time and with high accuracy, correction errors in the temperature compensation circuit can be suppressed and temperature compensation can be performed with high accuracy.

  Application Example 8 A piezoelectric vibrator having hysteresis characteristics in frequency temperature characteristics, an oscillation circuit that oscillates the piezoelectric vibrator and outputs an oscillation signal, and a storage circuit, and the storage circuit includes A piezoelectric oscillator characterized by storing frequency temperature information indicating a frequency temperature characteristic in a region surrounded by two frequency temperature characteristics of the oscillation signal that appears under the influence of a hysteresis characteristic.

  The two frequency temperature characteristics are a frequency temperature characteristic when the temperature of the piezoelectric vibrator is increased and a frequency temperature characteristic when the temperature is decreased. In the above configuration, when the piezoelectric oscillator is connected to the temperature compensation circuit, the temperature compensation circuit uses the frequency temperature information in the region surrounded by the two frequency temperature characteristics of the piezoelectric vibrator and the piezoelectric at the time of oscillation of the piezoelectric vibrator. The frequency deviation from the reference frequency is calculated using the temperature information of the vibrator, thereby calculating the temperature compensation amount. Therefore, it becomes a piezoelectric oscillator capable of suppressing the correction error caused by the hysteresis characteristic of the piezoelectric vibrator to a certain range regardless of whether the ambient temperature is rising or falling. Furthermore, since it is not necessary to store the temperature rise frequency temperature information, the temperature fall frequency temperature information, or the temperature information extracted from these in the memory circuit, an increase in the capacity burden on the memory circuit can be avoided.

  Application Example 9 The frequency temperature information is generated from temperature information and oscillation frequency information corresponding to the temperature information or frequency deviation information from a reference frequency corresponding to the temperature information. The piezoelectric oscillator according to Application Example 8.

  This eliminates the need for a calculation to generate a temperature coefficient on the piezoelectric oscillator side, so that the work load at the time of forming the piezoelectric oscillator can be suppressed and the piezoelectric oscillator can be reduced in cost. In particular, when the frequency deviation is stored, since the digit becomes small, the data capacity can be reduced, and the memory circuit can be reduced in size and the cost can be reduced.

  [Application Example 10] The piezoelectric oscillator according to Application Example 8, wherein the frequency temperature information is a temperature coefficient extracted from approximate curve information by a power series corresponding to the frequency temperature characteristic.

  As a result, when a piezoelectric oscillator is connected to a temperature compensation circuit, the temperature compensation circuit does not require computation to generate a temperature coefficient, thus reducing the burden on the user and making it easy to build a system with an oscillation circuit. It becomes a piezoelectric oscillator that can be performed.

  Application Example 11 A temperature detection unit that outputs a detection voltage corresponding to the ambient temperature is provided adjacent to the piezoelectric vibrator, and the frequency temperature information is expressed as a function of the detection voltage. Based on the frequency temperature information and the temperature decrease frequency temperature information and calculated and stored in the storage circuit, the oscillation circuit generates an oscillation signal to a temperature compensation circuit that calculates a temperature compensation amount using the frequency temperature information and the detected voltage. The piezoelectric oscillator according to any one of Application Examples 8 to 10, wherein the temperature detection unit outputs the detection voltage to the temperature compensation circuit.

  With the above configuration, the temperature detecting unit can measure the ambient temperature of the piezoelectric vibrator while suppressing measurement errors, and therefore, the temperature temperature information is calculated with high accuracy by calculating the temperature rise frequency temperature information and the temperature fall frequency temperature information. It can be obtained with high accuracy. Furthermore, since temperature information of the piezoelectric vibrator can be measured in real time and with high accuracy, a piezoelectric oscillator capable of performing temperature compensation with high accuracy by suppressing a correction error in the temperature compensation circuit.

It is a schematic diagram of 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 figure which shows the hysteresis characteristic of the oscillation frequency of the piezoelectric vibrator of this embodiment. It is a figure which shows the frequency deviation at the time of performing temperature compensation using the temperature coefficient measured at the time of temperature rise and temperature fall, respectively. It is a figure which shows the frequency deviation at the time of performing temperature compensation using the temperature coefficient which concerns on this embodiment. It is a figure which shows the approximate calculation method of the temperature fall frequency temperature information of this embodiment. It is a table | surface which compares the capacity | capacitance of the frequency temperature information memorize | stored in a memory | storage circuit.

  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 and a piezoelectric oscillator according to this embodiment connected to a temperature compensation circuit. The piezoelectric oscillator 10 according to this embodiment includes a piezoelectric vibrator 12 having a hysteresis characteristic in frequency temperature characteristics, an oscillation circuit 14 that oscillates the piezoelectric vibrator 12 and outputs an oscillation signal 58, and a storage circuit 20. The memory circuit 20 stores frequency temperature information 76 indicating frequency temperature characteristics in a region surrounded by two frequency temperature characteristics of the oscillation signal that appears under the influence of the hysteresis characteristics. It is. Here, the two frequency temperature characteristics are a frequency temperature characteristic when the temperature of the piezoelectric vibrator 12 is increased and a frequency temperature characteristic when the temperature is decreased, and a region surrounded by two characteristic curves centering on the reference temperature. appear. The piezoelectric oscillator 10 is connected to the temperature compensation circuit 40 during operation.

  Accordingly, the piezoelectric oscillator 10 according to the present embodiment will be described in more detail. The piezoelectric vibrator 12 having a hysteresis characteristic in frequency temperature characteristics, the piezoelectric vibrator 12 is oscillated and the oscillation signal 58 is output, and the piezoelectric oscillator A temperature compensation circuit 40 capable of calculating a temperature compensation amount 80 using frequency temperature information 76 indicating temperature characteristics of the oscillation frequency of the vibrator 12 and temperature information of the piezoelectric vibrator 12 when the oscillation signal 58 is oscillated. The oscillation circuit 14 that outputs the oscillation signal 58 at the same time, the temperature rise frequency temperature information 77a of the piezoelectric vibrator 12 that is generated when the ambient temperature of the piezoelectric vibrator 12 is raised, and the ambient temperature is lowered. An intermediate value between the temperature drop frequency temperature information 77b of the piezoelectric vibrator 12 generated in the case of the piezoelectric vibrator 12 is stored as the frequency temperature information 76, and the frequency temperature is stored in the temperature compensation circuit 40. A storage circuit 20 for outputting a broadcast 76, and has a.

  Further, temperature detecting means (temperature sensor 16) for outputting a detection voltage 66 corresponding to the ambient temperature is provided adjacent to the piezoelectric vibrator 12, and the frequency temperature information 76 is a function of the detection voltage 66. Based on the temperature increase frequency temperature information 77a and the temperature decrease frequency temperature information 77b represented and stored in the storage circuit 20, the oscillation circuit 14 uses the frequency temperature information 76 and the detection voltage 66 to compensate the temperature. The oscillation signal 58 is output to the temperature compensation circuit 40 that calculates the amount 80, and the temperature detection means outputs the detection voltage 66 to the temperature compensation circuit 40.

  Therefore, the temperature compensation method of the piezoelectric oscillator 10 using the above configuration includes the piezoelectric vibrator 12 having a hysteresis characteristic in frequency temperature characteristics, and the oscillation circuit 14 that oscillates the piezoelectric vibrator 12 and outputs an oscillation signal 58. A temperature compensation amount 80 can be calculated using frequency temperature information 76 indicating temperature characteristics of the oscillation frequency of the piezoelectric vibrator 12 and temperature information of the piezoelectric vibrator 12 when the oscillation signal 58 is oscillated. A temperature compensation method of the piezoelectric oscillator 10 that outputs the oscillation signal 58 and the frequency temperature information 76 to the temperature compensation circuit 40, and the piezoelectric vibration generated when the ambient temperature of the piezoelectric vibrator 12 is raised. An intermediate value between the temperature increase frequency temperature information 77a of the child 12 and the temperature decrease frequency temperature information 77b of the piezoelectric vibrator 12 generated when the ambient temperature is decreased is the intermediate value. And it calculates a wavenumber temperature information 76.

  Further, a temperature detecting means (temperature sensor 16) for outputting a detection voltage 66 corresponding to the ambient temperature is disposed adjacent to the piezoelectric vibrator 12, and the temperature increase frequency temperature information 77a and the temperature decrease frequency temperature information 77b are disposed. Is generated as a function of the detection voltage 66, the frequency temperature information 76 is calculated based on the temperature increase frequency temperature information 77a and the temperature decrease frequency temperature information 77b, and the frequency temperature information 76 and the detection voltage 66 are calculated. The oscillation signal 58 is output to the temperature compensation circuit 40 that can calculate the temperature compensation amount 80 based on the above, and the detection voltage 66 is output from the temperature detection means to the temperature compensation circuit 40.

  Before describing the configuration of the piezoelectric oscillator according to the present embodiment, a method for temperature compensation of the piezoelectric oscillator 10 according to the present embodiment will be described with reference to the drawings. The frequency temperature information 76 is data related to a frequency temperature characteristic that is an intermediate value between two frequency temperature characteristics that appear in the oscillation signal 58 of the oscillation circuit 14 with a hysteresis characteristic. That is, FIG. 5 is a diagram for explaining the frequency temperature information 76.

  The temperature increase frequency temperature information 77a shown in FIG. 5 is from −30 ° C. to + 85 ° C. so that the ambient temperature of the piezoelectric vibrator 12 that is an AT-cut crystal vibrator straddles the reference temperature (for example, 25 ° C.) of the piezoelectric vibrator 12. Is a plot of the frequency of the oscillation signal 58 of the oscillation circuit 14 for each predetermined temperature during the increase. The temperature decrease frequency temperature information 77b is a plot of the frequency of the oscillation signal 58 of the oscillation circuit 14 for each predetermined temperature while the ambient temperature of the piezoelectric vibrator 12 is lowered from + 85 ° C. to −30 ° C.

The first approximate curve information 70 is generated by calculating a temperature coefficient of Equation 1 described later corresponding to the temperature increase frequency temperature information 77a, and the frequency can be calculated continuously with respect to the temperature change. It is a curve. The second approximate curve information 72 is generated by calculating a temperature coefficient of Equation 1 described later corresponding to the temperature decrease frequency temperature information 77b, and the frequency can be continuously calculated with respect to the temperature change. It is a curve. The third approximate curve information 74 is generated as an intermediate value between the first approximate curve information 70 and the second approximate curve information 72. Therefore, the frequency temperature information 76 can be generated by extracting the temperature information necessary for the frequency temperature information 76 and the frequency in the temperature information from the third approximate curve information 74. Here, the intermediate value is at one temperature position of two frequency temperature characteristics, that is, first approximate curve information 70 and second approximate curve information 72 (temperature increase frequency temperature information 77a, temperature decrease frequency temperature information 77b). In addition to the intermediate value in the frequency direction obtained by addition averaging or the like, the value displaced in the frequency direction within the region surrounded by the hysteresis characteristic is also included.
The frequency temperature information 76 generated in this way is used when an approximate calculation of a parameter (coefficient) of a temperature compensation polynomial (formula 1) described later is obtained.

  The temperature compensation circuit 40 calculates a coefficient necessary for forming a polynomial for frequency temperature compensation by an approximate calculation using the frequency temperature information 76, and determines a polynomial for frequency temperature compensation. Further, the temperature compensation circuit 40 uses the frequency temperature compensation polynomial and the temperature information detected by the temperature sensor 16 (detection voltage 66) for the oscillation frequency of the oscillation signal 58 of the oscillation circuit 14 to determine the temperature. The frequency is corrected according to the compensation amount 80 (frequency correction amount), and the temperature-compensated oscillation signal 68 is output.

  Therefore, in the temperature compensation method of the oscillation circuit system including the piezoelectric oscillator 10 according to the present embodiment, the frequency temperature characteristic information having continuous frequency temperature characteristics with respect to the temperature change based on the frequency temperature information 76 or the frequency temperature characteristic information is obtained. A coefficient necessary for the frequency temperature compensation polynomial to be corrected (third approximated curve information 74) is calculated. Based on the information obtained by calculating the temperature compensation amount 80 using the polynomial determined by the frequency temperature characteristic information or coefficient and the temperature information detected by the temperature sensor 16 (detection voltage 66), the oscillation circuit 14 The oscillation signal 58 is subjected to frequency control such as frequency division, and an oscillation signal 68 subjected to temperature compensation is output. In order to realize such a temperature compensation method, the piezoelectric oscillator 10 needs to include at least the piezoelectric vibrator 12, the oscillation circuit 14, the temperature sensor 16, and the storage circuit 20.

Next, a generation process of the temperature increase frequency temperature information 77a and the temperature decrease frequency temperature information 77b will be described.
For example, after the piezoelectric oscillator 10 (piezoelectric vibrator 12) of the present embodiment is housed in a chamber (not shown) in which temperature can be set, the ambient temperature of the piezoelectric oscillator 10 (piezoelectric vibrator 12) is changed from a low temperature to a high temperature. A first temperature test is performed in which the frequency of the oscillation signal 58 of the oscillation circuit 14 at a plurality of temperature points is measured during the temperature change.

  That is, in the first temperature test, the case where the piezoelectric vibrator 12 is an AT-cut crystal vibrator will be described as an example. The ambient temperature of the piezoelectric vibrator 12 is increased from, for example, −30 ° C. to + 85 ° C. The temperature rise frequency temperature information 77a is generated by measuring the frequency of the oscillation signal 58 of the oscillation circuit 14 at a plurality of temperature points. For example, in the example shown in FIG. 5A, as the plurality of temperature points, information on a curve of −30 ° C. (minimum set temperature), + 85 ° C. (maximum set temperature) and frequency temperature characteristics, which is the temperature at the end of the set temperature range. In addition to + 25 ° C. (reference temperature) near the inflection point (similar to the third approximate curve information 74), a temperature point near the maximum or minimum value of the curve or the temperature between the extreme value and the end And seven temperature points (temperature increase frequency temperature information 77a) including temperature points between the extreme values and the reference temperature. Here, the temperature rising frequency temperature information 77a is composed of information on the set temperature (or measurement temperature) of the piezoelectric oscillator 10 and information on the frequency of the oscillation signal 58 of the oscillation circuit 14 at the set temperature (or measurement temperature). Yes.

  After the first temperature test, the ambient temperature of the piezoelectric oscillator 10 (piezoelectric vibrator 12) is changed from a high temperature to a low temperature so that the temperature changes in a direction opposite to the test, and a plurality of temperature changes occur during the temperature change. A second temperature test is performed to measure the frequency of the oscillation signal 58 of the oscillation circuit 14 at the temperature point.

  In the second temperature test as well, the case where the piezoelectric vibrator 12 is an AT-cut crystal vibrator will be described as an example. The ambient temperature of the piezoelectric oscillator 10 (piezoelectric vibrator 12) is lowered from + 85 ° C. to −35 ° C. At the same time, the temperature drop frequency temperature information 77b is generated by measuring the frequency of the oscillation signal 58 of the oscillation circuit 14 at a plurality of temperature points.

  As the plurality of temperature points, for example, in the example shown in FIG. 5A, the temperature of the end of the variable temperature range is −30 ° C. (set minimum temperature), + 85 ° C. (set maximum temperature), and frequency temperature characteristic information curves. In addition to + 25 ° C. (reference temperature) near the inflection point (similar to the third approximate curve information 74), a temperature point near the maximum or minimum value of the curve or the temperature between the extreme value and the end And seven temperature points (temperature-decreasing frequency temperature information 77b) including temperature points between the extreme values and the reference temperature. Here, the temperature-decreasing frequency temperature information 77b includes information on the set temperature (or measurement temperature) of the piezoelectric oscillator 10 and information on the frequency of the oscillation signal 58 of the oscillation circuit 14 at the set temperature (or measurement temperature). .

  Then, first approximate curve information 70 corresponding to the temperature increase frequency temperature information 77a and second approximate curve information 72 corresponding to the temperature decrease frequency temperature information 77b are calculated, and the first approximate curve information 70 and the second approximation curve information are calculated. The third approximate curve information 74 is generated by the temperature coefficient that is an intermediate value generated by the addition average of the temperature coefficients of the curve information 72 or the like. The frequency temperature information 76 is generated by extracting the temperature information required by the frequency temperature information 76 and the frequency corresponding to the temperature information from the third approximate curve information 74. The frequency temperature information 76 obtained in this way is stored in the storage circuit 20.

  In this case, in the example shown in FIG. 5A, the temperature point indicated by the frequency temperature information 76 is −35 ° C., + 85 ° C., which is the temperature at the end of the variable temperature range, the first approximate curve information 70 and the second + 25 ° C. (reference temperature) near the inflection point of the approximate curve information 72, the temperature point near the extreme value that becomes the maximum value or minimum value of the first approximate curve information 70 and the second approximate curve information 72, or this extreme point Seven temperature points including a temperature point between the value and the end temperature or between the extreme value and the reference temperature are set.

  The set minimum temperature and the set maximum temperature may be determined from at least the operable temperature range required for the piezoelectric oscillator 10, and a curve that is information on frequency temperature characteristics is also approximated at a temperature point that is a measurement point. Any position where frequency information that can be obtained by calculation can be obtained.

  Further, at a temperature point where the frequency values indicated by the temperature increase frequency temperature information 77a and the temperature decrease frequency temperature information 77b are relatively close, such as a temperature point at the end of the variable temperature range, information related to the frequency of the frequency temperature information 76 is increased. The information related to the frequency of the temperature frequency temperature information 77a or the temperature decrease frequency temperature information 77b may be the same. That is, at the above-described temperature point, the frequency information of the temperature increase frequency temperature information 77a or the temperature decrease frequency temperature information 77b may be taken in as it is as the frequency information of the frequency temperature information 76.

  Next, a specific configuration of the present embodiment will be described. The specific configuration of the piezoelectric oscillator 10 according to the present embodiment includes an oscillation circuit 14, a temperature sensor 16, a buffer 18, a storage circuit 20, a serial interface circuit 22, a power supply terminal 36, a ground terminal by patterning on a silicon substrate (not shown). The semiconductor circuit board is formed with terminals such as 38, and the oscillation circuit 14 and the piezoelectric vibrator 12 are connected to each other. 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 as an arithmetic processing circuit, a memory 46 as a storage device, and an A / A as an analog / digital converter. The D converter 48 is included, and an integrated circuit is formed on the above-described silicon substrate or another silicon substrate. When calculating the frequency temperature information 76, as shown in FIG. 2, the piezoelectric oscillator 10 is connected to a measuring device 50. The measuring device 50 includes a frequency counter 52, a PC (personal computer) 54, and a voltage multimeter 56. Have.

  The piezoelectric vibrator 12 is made of a piezoelectric material such as quartz, lithium niobate, lithium tantalate, etc., and uses an AT-cut quartz vibrator that has relatively excellent frequency temperature characteristics and can suppress the temperature compensation amount of the frequency. Is preferred. The resonance frequency of the piezoelectric vibrator using the thickness shear vibration by the AT cut is a positive cubic curve centering on the reference temperature (25 ° C.), or lower than the reference temperature as shown in FIG. It has temperature dependence represented by a polynomial function having a maximum value and a minimum value on the high temperature side.

  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 detects a detection voltage 66 that is a potential between the terminals of the diode that varies depending on the temperature from the temperature sensor voltage output terminal 34 via the buffer 18. 40 or the measuring device 50. The temperature sensor 16 always outputs the detection voltage 66 as long as power is supplied from the power supply voltage (V _DD ). 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. It is desirable that the temperature sensor 16 be disposed adjacent to the piezoelectric vibrator 12, so that the ambient temperature of the piezoelectric vibrator 12 can be accurately measured. In the information 77b, the first approximate curve information 70, the second approximate curve information 72, the third approximate curve information 74, and the frequency temperature information 76, the correspondence between temperature and frequency or frequency deviation can be accurately performed. .

  The serial interface circuit 22 receives a command from the outside, stores the frequency temperature information 76 in the storage circuit 20, and outputs the frequency temperature information 76 stored in the storage circuit 20 to the outside. 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 frequency temperature 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 frequency temperature information 76 stored in the storage circuit 20 is serialized using the second control clock 62 as a trigger via the data input / output terminal 26. Can be output.

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

  As the frequency temperature information 76, a combination of a temperature coefficient and an offset coefficient, which will be described later, or a plurality of temperature information arbitrarily selected from the operating temperature range of the piezoelectric vibrator 12 and a frequency corresponding to each of the plurality of temperature information. Information or a combination with frequency deviation information from a reference frequency corresponding to the plurality of temperature information can be used. Among these, the combination of the plurality of temperature information and the information of the frequency deviation from the reference frequency corresponding to each of the plurality of temperature information reduces the number of digits of information compared to the case where the absolute value of the oscillation frequency is used. Therefore, the capacity of the frequency temperature information 76 is the smallest. When the temperature coefficient is stored as the frequency temperature information 76, it is not necessary to store the temperature itself, so that the capacity of the frequency temperature information 76 can be reduced. When the frequency temperature information 76 is a combination of the above-described plurality of temperature information and frequency information corresponding to each of the plurality of temperature information, the reference temperature and the frequency information at the reference temperature are acquired. At the same time, it is necessary to attach an address that allows the PC 54 and the CPU 44 to be distinguished from other information.

  FIG. 2 shows a connection diagram between the piezoelectric oscillator 10 and the measuring instrument 50. The measuring device 50 calculates the frequency temperature information 76 used in the temperature compensation circuit 40 from the temperature characteristics of the oscillation frequency of the piezoelectric vibrator 12 mounted on the oscillation circuit 14 and writes the frequency temperature information 76 in the storage circuit 20. , PC 54 and 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 is connected to the data input / output terminal 26, the first control clock input terminal 28, the frequency counter 52, and the voltage multimeter 56. The PC 54 can start the frequency counter 52 and the voltage multimeter 56 by a key operation or the like, and always inputs a detection voltage 66 (ambient temperature information) from the temperature sensor 16 via the voltage multimeter 56. Further, the PC 54 inputs a frequency from the frequency counter 52 for each predetermined temperature according to the installed program, and stores the detection voltage 66 (ambient temperature information) and the frequency in a storage area (not shown) in the PC.

With respect to the resonance frequency of the piezoelectric vibrator using the thickness shear vibration, if the reference frequency at the reference temperature T ₀ is f, the frequency temperature information Δf / f at an arbitrary temperature T can be approximately expressed by the following power series. .

  Here, A, B, C, and D are temperature coefficients that determine an approximate curve of frequency temperature information, E is an offset coefficient that determines an offset of frequency temperature information, and belongs to the temperature coefficient. In the temperature compensation circuit 40, it is necessary to calculate frequency temperature information that continuously changes with respect to a temperature change as shown in Formula 1.

  By the way, since there are five variables in Equation 1, for example, as the frequency temperature information 76, information on the measured ambient temperature (detection voltage 66) and information on the frequency deviation from the reference frequency corresponding to the information on the ambient temperature. If there are at least five combinations with the above, each of them is substituted into Equation 1, and all the variables in Equation 1 can be calculated by solving the simultaneous quinary linear equation, and approximate curve information can be calculated. Furthermore, it is possible to generate a more accurate approximate curve by calculating the temperature coefficient satisfying Equation 1 by the least square method or the like based on the frequency information at the seven temperature points as described above. However, since the piezoelectric vibrator has hysteresis characteristics, it is necessary to consider temperature information when the temperature rises and temperature information when the temperature falls.

  Therefore, during the period from when the ambient temperature of the piezoelectric vibrator 12 is increased from the set minimum temperature (−30 ° C.) to the reference maximum temperature (+ 25 ° C.) until the set maximum temperature (+ 85 ° C.) is reached, the PC 54 is programmed. The frequency is measured at a predetermined temperature interval (temperature increase frequency temperature information 77a), and then the frequency is measured at a predetermined temperature interval until the reference temperature is lowered from the set maximum temperature to reach the set minimum temperature (temperature decrease frequency temperature information). 77b).

  Then, the PC 54 uses the temperature rising frequency temperature information 77a (for example, the temperature at 7 points and the frequency deviation corresponding to the temperature) generated at the time of temperature rise and the first approximate curve information 70 (see FIG. 5) using Equation 1. And the second approximate curve information 72 (see FIG. 5) using the temperature-decreasing frequency temperature information 77b (for example, the seven temperatures and the frequency deviation corresponding to the temperature) generated when the temperature is lowered calculate.

  Next, for example, a calculation is performed to obtain an average of the frequency components of the first approximate curve information 70 and the second approximate curve information 72, and the frequency components of the first approximate curve information 70 and the second approximate curve information 72 are calculated. The third approximate curve information 74 (see FIG. 5), which is an intermediate value of, is calculated. Similarly, this is performed for other temperatures (for example, an arbitrary temperature of -30 ° C to + 85 ° C). Then, from the third approximate curve information 74, a plurality of temperature information for which the temperature compensation circuit 40 can easily calculate the third approximate curve information 74 and a combination of frequencies corresponding to the temperature information are appropriately extracted. The frequency temperature information 76 is generated with an address that the CPU 44 can recognize.

  After the frequency temperature information 76 is constructed 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 converts it into serial data in synchronization with the first control clock 60. The frequency temperature information 76 is output to the data input / output terminal 26, and the frequency temperature information 76 is stored in the storage circuit 20 via the serial interface circuit 22.

  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 uses the frequency temperature information 76 input from the PC 54 to the storage circuit 20, and approximate curve information (third approximate curve information 74) corresponding to a continuous temperature change in the oscillation frequency of the piezoelectric vibrator 12. The temperature compensation amount 80 is calculated based on the approximate curve information and the detected voltage 66 (information on the ambient temperature) that is always input from the temperature sensor 16, and the frequency correction circuit 42, CPU 44, memory 46 and the like. The frequency correction circuit 42 is a circuit that varies the frequency of the oscillation signal 58 corresponding to 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. The oscillation signal 68 subjected to temperature compensation is output.

  The CPU 44 is the core of the temperature compensation circuit 40, calculates approximate curve information (same as the third approximate curve information 74) from the frequency temperature information 76 input from the storage circuit 20, and calculates approximate curve information and temperature. A temperature compensation amount 80 is calculated based on the detection voltage 66 (information on ambient temperature) input from the sensor 16 and is output to the frequency correction circuit 42. If the temperature increase frequency temperature information 77a is stored in the storage circuit 20, the CPU 44 calculates approximate curve information similar to the first approximate curve information 70, and if the temperature decrease frequency temperature information 77b is stored, the CPU 44 The approximate curve information similar to the approximate curve information 72 of 2 is calculated.

  The CPU 44 is connected to the data input / output terminal 26, the second control clock input terminal 30, and the frequency correction circuit 42, and is further connected to 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 frequency / temperature information 76 in the storage circuit 20 as a serial interface circuit. The data is output from the data input / output terminal 26 via 22 and stored in the memory 46 attached to the CPU 44.

  When the frequency temperature information 76 stored in the storage circuit 20 is a combination of a plurality of temperature information in the operating temperature range of the piezoelectric vibrator 12 and a frequency deviation corresponding to each of the plurality of temperature information, the CPU 44 Using the temperature information 76 and Equation 1, the temperature coefficient and the offset coefficient in Equation 1 are calculated by the above-described method, and those having a configuration that can be stored in the attached memory 46 are used. Further, when the frequency temperature information 76 is information of the above-described plurality of temperature information and the frequency (absolute value) corresponding to each temperature information, the CPU 44 uses the reference temperature information in the frequency temperature information 76 and the frequency measured at the reference temperature. The address of the above information can be identified, and the temperature coefficient and the offset coefficient in Formula 1 are calculated by the above-described method using the frequency temperature information 76 and Formula 1, and have a configuration that can be stored in the attached memory 46. Use. If the frequency temperature 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 in which it is stored in the attached memory 46 as it is.

  Further, the CPU 44 digitizes and inputs the detection voltage 66 (information on the ambient temperature) from the temperature sensor 16 through the A / D converter 48 every predetermined time by a program or the like, and stores it in the attached memory 46. Then, the temperature coefficient and the offset coefficient are read out from the memory 46 to calculate an approximate curve (third approximate curve information 74), and the detected voltage 66 from the temperature sensor 16 is read out from the memory 46 to obtain an approximate curve (third approximate curve). A temperature compensation amount 80 is calculated from the curve information 74) and 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.

  In the above embodiment, when the temperature information at the time of frequency measurement in the temperature rise frequency temperature information 77a and the temperature drop frequency temperature information 77b is different from each other, or the temperature information required in the frequency temperature information 76 is the temperature rise frequency temperature information 77a and the temperature drop. In the case where the temperature information is different from the temperature information of the frequency temperature information 77b, it has been described on the premise that the frequency temperature information 76 is generated using a plurality of pieces of approximate curve information expressed by Formula 1.

  However, if the temperature information of the temperature increase frequency temperature information 77a and the temperature decrease frequency temperature information 77b match each other and match the temperature information requested by the frequency temperature information 76, the PC 54 determines that the temperature increase frequency temperature information 77a and the temperature decrease frequency In the temperature information 77b, information on an intermediate frequency value is calculated by, for example, addition averaging of frequency information corresponding to the same temperature information, and frequency temperature information 76 is generated by a combination of the temperature information and the intermediate value information. It becomes possible. In this case, the PC 54 does not need to calculate the first approximate curve information 70 and the second approximate curve information 72, and the manufacturing process of the piezoelectric oscillator 10 can be simplified, so that the cost can be suppressed.

  In the present embodiment, the frequency temperature information 76 is information for approximating the temperature characteristic of the frequency of the piezoelectric vibrator 12 (or the oscillation circuit 14). However, the present invention is not limited to this, and for example, As the information relating to the difference between the target frequency to be output by the frequency correction circuit 42 and the frequency of the piezoelectric vibrator 12 (or the oscillation circuit 14), the difference information or the information on the target frequency is added to the difference information. The information may be stored in the storage circuit 20 and the temperature compensation amount 80 may be calculated by the CPU 44 based on this information. At this time, the information stored in the storage circuit 20 includes information on the difference between the target frequency and the frequency of the piezoelectric vibrator 12 (or the oscillation circuit 14), and information on the temperature. Information (temperature coefficient and offset coefficient) of an approximate expression for approximating the difference between the frequency of the piezoelectric vibrator 12 (or the oscillation circuit 14) and the frequency of In this way, the calculation of the temperature compensation amount 80 in the CPU 44 can be simplified.

  Next, the effect of the piezoelectric oscillator 10 according to the present embodiment will be described. FIG. 3A shows a hysteresis characteristic of the piezoelectric vibrator, and FIG. 3B shows a partially enlarged view of FIG. FIG. 4A shows the frequency deviation of the oscillation signal output from the temperature compensation circuit when the temperature compensation is performed using the temperature increase frequency temperature information at the time of temperature rise (when the temperature rises and when the temperature falls), FIG. b) shows the frequency deviation (when the temperature rises and when the temperature falls) of the oscillation signal output from the temperature compensation circuit when temperature compensation is performed using the temperature-decreasing frequency temperature information when the temperature falls. 5A is a diagram showing frequency temperature information of the present embodiment, FIG. 5B is a partially enlarged view of FIG. 5A, and FIG. 5C is a temperature using the frequency temperature information of the present embodiment. The frequency deviation of the oscillation signal output from the temperature compensation circuit when compensation is performed is shown.

  As described in the prior art, as shown in FIG. 3, the piezoelectric vibrator does not have the same frequency-temperature characteristic when the temperature rises and falls, but has a hysteresis characteristic. Therefore, as shown in FIGS. 3A and 3B, the temperature compensation circuit 40 calculates an approximate curve (first approximate curve 70) using the temperature rise frequency temperature information 77a at the time of temperature rise, and based on this. When the temperature compensation is performed, as shown in FIG. 4A, the temperature compensation when the temperature of the piezoelectric oscillator 10 is raised is satisfactorily performed, but the temperature compensation when the temperature is lowered is reversed. Is not performed well, and the frequency deviation exceeds 0.5 ppm.

  Further, as shown in FIGS. 3A and 3B, the temperature compensation circuit 40 calculates an approximate curve (second approximate curve information 72) using the temperature decrease frequency temperature information 77b at the time of temperature decrease, and based on this. When the temperature compensation is performed, as shown in FIG. 4B, the temperature compensation when the temperature of the piezoelectric vibrator 12 is lowered is satisfactorily performed, but conversely, the temperature when the temperature is raised. Compensation is not performed well, and the frequency deviation is 0.5 ppm. When such a frequency deviation occurs in a device having a GPS function assumed in the present embodiment, the positioning performance is adversely affected as described in the prior art.

  On the other hand, as shown in FIGS. 5A and 5B, the frequency temperature information 76 of the present embodiment includes first approximate curve information 70 calculated corresponding to the temperature increase frequency temperature information 77a, and the temperature decrease frequency. The second approximate curve information 72 calculated corresponding to the temperature information 77b and the third approximate curve information 74 calculated as an intermediate value in the frequency direction are extracted and formed. Therefore, the temperature compensation circuit 40 calculates the frequency deviation from the reference frequency using the third approximate curve information 74 and the ambient temperature information (detection voltage 66), thereby calculating the temperature compensation amount 80. Become. Therefore, the correction error caused by the hysteresis characteristics of the piezoelectric vibrator 12 can be suppressed within a certain range regardless of whether the ambient temperature is rising or falling. As shown in FIG. 5C, in the present embodiment, the frequency deviation can be suppressed to about 0.3 ppm both when the temperature rises and when the temperature falls, and the piezoelectric vibrator 12 having hysteresis characteristics can be suppressed. It can be seen that good temperature compensation can be performed.

  By the way, the hysteresis characteristic of the piezoelectric vibrator 12 according to the present embodiment appears most prominently near the reference temperature, and decreases as the distance from the reference temperature increases. Are hardly detected. Therefore, it is possible to reduce the time for constructing the frequency temperature information 76 of the present embodiment by calculating approximately after limiting either one of the temperature increase frequency temperature information 77a and the temperature decrease frequency temperature information 77b.

  FIG. 6 shows the difference (hysteresis amount) between the frequency temperature information when the oscillation frequency of the piezoelectric vibrator rises and the frequency temperature information when the temperature drops. As shown in FIG. 6A, frequency temperature information 77a (see the first approximate curve information 70, FIG. 3 etc.) when the oscillation frequency of the piezoelectric vibrator increases, and frequency temperature information 77b (first) when the temperature drops. The difference between the two approximate curve information 72 (see FIG. 3 and the like) has a quadratic shape that is convex upward with the reference temperature as the center. Therefore, in the present invention, the entire hysteresis characteristic is simply calculated from the hysteresis amount at the reference temperature.

  For example, the temperature increase frequency temperature information 77a is generated by combining the temperature information for each predetermined temperature and the frequency information when the ambient temperature of the piezoelectric vibrator 12 is increased across the reference temperature as described above. At this time, the temperature rising frequency temperature information 77a includes low temperature region information 82 (including a set minimum temperature) measured in a temperature region lower than the reference temperature, and first reference temperature region information measured in a reference temperature region including the reference temperature. 84, and high temperature region information 86 (including the set maximum temperature) measured in a high temperature region higher than the reference temperature region. Further, first approximate curve information 70 corresponding to the temperature increase frequency temperature information 77a is calculated.

  Then, second temperature-decreasing frequency temperature information (not shown) that is approximately calculated includes the second reference temperature region information 88 measured in the reference temperature region when the ambient temperature is lowered across the reference temperature, and the first information It can be calculated using the difference from the reference temperature region information 84, the low temperature region information 82, and the high temperature region information 86. Here, by approximating the difference (hysteresis amount) between the temperature increase frequency temperature information 77a and the temperature decrease frequency temperature information 77b to zero in the low temperature region and the high temperature region, hysteresis is obtained from three plot points as shown in FIG. 6B. A quadratic temperature coefficient of a quadratic function approximating the quantity can be calculated. By subtracting the secondary temperature coefficient from the secondary temperature coefficient constituting the first approximate curve information 70, second approximate curve information (not shown) can be calculated. By extracting the temperature information for each predetermined temperature and the frequency information corresponding to the temperature information from the second approximate curve information (not shown), the temperature-decreasing frequency temperature information (not shown) can be generated approximately.

  It should be noted that two or more points are measured in the reference temperature region, and fitting is performed using a power series corresponding thereto, and the temperature coefficient obtained thereby is calculated from the temperature coefficient constituting the corresponding first approximate curve information 70. By subtracting, second approximate curve information (not shown) can be calculated. All the above operations are performed on the PC 54. As shown in FIG. 6C, the difference 73a between the temperature increase frequency temperature characteristic 77a and the temperature decrease frequency temperature characteristic (not shown) approximately calculated is a temperature increase frequency temperature characteristic 77a and a temperature decrease frequency temperature characteristic 77b. It can be seen that it has a hysteresis characteristic that is inferior to the difference 73b. In the present embodiment, the second reference temperature region information 88 may be generated first, and then the temperature increase frequency temperature information 77a may be generated.

  Conversely, when the above approximation is used in the calculation of the temperature increase frequency temperature information 77a, the temperature decrease frequency temperature information 77b is the same as described above for each predetermined temperature when the ambient temperature of the piezoelectric vibrator 12 is decreased with the reference temperature interposed therebetween. A combination of temperature information and frequency information is generated. At this time, the temperature decrease frequency temperature information 77b includes high temperature region information (approximate to be the same as the high temperature region information 86) measured in a temperature region higher than the reference temperature when the ambient temperature is raised across the reference temperature, and the reference temperature. Third reference temperature region information 90 (same as the second reference temperature region information 88) measured in the reference temperature region including the low temperature region information (low temperature region information 82) measured in a low temperature region lower than the reference temperature region. And approximated to be the same. Then, second approximate curve information 72 corresponding to the temperature decrease frequency temperature information 77b is calculated.

  On the other hand, the temperature increase frequency temperature information (not shown) calculated approximately is fourth reference temperature region information 92 (first reference) measured in the reference temperature region when the ambient temperature is raised with the reference temperature interposed therebetween. It can be calculated using the difference between the third reference temperature region information 90, the low temperature region information 82, and the high temperature region information 86. Here, by approximating the difference (hysteresis amount) between the temperature increase frequency temperature information 77a and the temperature decrease frequency temperature information 77b to zero in the low temperature region and the high temperature region, hysteresis is obtained from three plot points as shown in FIG. 6B. A quadratic temperature coefficient of a quadratic function approximating the quantity can be calculated. By subtracting the secondary temperature coefficient from the secondary temperature coefficient constituting the second approximate curve information 72, the first approximate curve information (not shown) can be calculated. By extracting temperature information for each predetermined temperature and frequency information corresponding to the temperature information from the first approximate curve information (not shown), it is possible to approximately generate temperature rising frequency temperature information (not shown). .

  FIG. 7 shows a table for comparing the capacity of the frequency temperature information stored in the storage circuit. As shown in FIG. 7, eleven digits are required to store frequency absolute value information as frequency temperature information, but five digits are sufficient to store frequency deviation information from the reference frequency. About 45 percent. Further, assuming that the capacity when the temperature increase frequency temperature information 77a and the temperature decrease frequency temperature information 77b are configured using information on the absolute value of frequency is 100, the frequency temperature information 76 is configured using information on the absolute value of frequency. When the frequency temperature information 76 is configured using frequency deviation information, the capacity can be reduced by 73%. Note that the required number of digits in the address information stored as frequency temperature information is sufficient if the measured temperature is 7 points, and 3 digits (up to 8 addresses are allowed) are sufficient. The number of digits required for the voltage 66) is determined according to its resolution. Further, when the frequency temperature information is information on the temperature coefficient, the necessary number of digits is determined according to the significant digits for the temperature coefficient, but the temperature information is unnecessary, so the capacity can be reduced.

  As described above, according to the temperature compensation method of the piezoelectric oscillator 10 and the piezoelectric oscillator 10 according to the present embodiment, first, the temperature rise generated when the ambient temperature of the piezoelectric vibrator 12 is increased. Frequency temperature information 76 which is an intermediate value between the frequency temperature information 77a and the temperature decrease frequency temperature information 77b when the ambient temperature is lowered is input, and the frequency temperature information 76 and the piezoelectric vibrator 12 at the time of oscillation of the piezoelectric vibrator 12 are input. The frequency deviation from the reference frequency is calculated using the temperature information, and thereby the temperature compensation amount 80 is calculated. Therefore, the correction error caused by the hysteresis characteristic of the piezoelectric vibrator can be suppressed to a certain range regardless of whether the ambient temperature is rising or falling. Furthermore, since it is not necessary to store the temperature increase frequency temperature information 77a, the temperature decrease frequency temperature information 77b, or the temperature coefficient extracted from these in the storage circuit 20, an increase in capacity burden on the storage circuit 20 can be avoided.

  Secondly, the frequency temperature information 76 is calculated from the temperature rising frequency temperature information 77a, calculated from the first approximate curve information 70 indicating the continuous temperature characteristic of the oscillation frequency, and the temperature decreasing frequency temperature information 77b. The second approximate curve information 72 indicating the continuous temperature characteristics of the frequency and the third approximate curve information 74 calculated as an intermediate value are extracted. Thereby, the frequency temperature information 76 is extracted from the third approximate curve information 74 that continuously changes with respect to the temperature change. On the other hand, the temperature compensation circuit 40 forms an approximate curve of the oscillation frequency that continuously changes with respect to the temperature change based on the frequency temperature information 76. Therefore, since the approximate curve calculated by the temperature compensation circuit 40 is the third approximate curve information 74, temperature compensation can be performed with high accuracy. Further, since it is not necessary to measure the temperature increase frequency temperature information 77a and the temperature decrease frequency temperature information 77b at the same temperature position, the yield of generation of the frequency temperature information 76 can be increased and the cost can be suppressed.

  Third, the frequency temperature information 76 is generated from the temperature information and the information on the oscillation frequency corresponding to the temperature information or the information on the frequency deviation from the reference frequency corresponding to the temperature information. Since the calculation of the temperature coefficient is not required on the side, the work burden at the time of forming the piezoelectric oscillator 10 can be suppressed and the cost can be suppressed. In particular, when frequency deviation information is stored, the number of digits is reduced, so that the data capacity can be reduced, and the memory circuit 20 can be reduced in size and the cost can be reduced. In this case, the user calculates the third approximate curve information 74 by calculating the temperature coefficient of the series that should overlap the plot of the frequency temperature information 76, but the user calculates the exact temperature coefficient uniquely. be able to.

  Fourth, by generating the frequency temperature information 76 based on the temperature coefficient information extracted from the third approximate curve information 74, the temperature compensation circuit 40 calculates the third approximate curve information 74. Since computation is not required, it is possible to easily construct a system equipped with the piezoelectric oscillator 10 while reducing the burden on the user side.

  Fifth, temperature increase frequency temperature information 77a is approximately calculated using temperature decrease frequency temperature information 77b and temperature and frequency information measured by raising the ambient temperature of the piezoelectric vibrator 12 to the reference temperature region. did. When the difference between the frequency components of the temperature increase frequency temperature information 77a and the temperature decrease frequency temperature information 77b is taken, the difference becomes the largest in the reference temperature region, and becomes smaller as the distance from the reference temperature is increased. Therefore, the temperature increase frequency temperature information 77a can be approximately calculated using the temperature decrease frequency temperature information 77b and temperature and frequency information measured by raising the ambient temperature to the reference temperature region. Therefore, information on the temperature and frequency at the time of temperature rise need only be acquired in the reference temperature region, and a step of raising the temperature to a high temperature region higher than the reference temperature becomes unnecessary. Therefore, since the acquisition time of the temperature rising frequency temperature information 77a can be shortened, the work load can be reduced and the cost can be suppressed.

  Sixth, the temperature decrease frequency temperature information 77b is approximately calculated using the temperature increase frequency temperature information 77a and temperature and frequency information measured by lowering the ambient temperature of the piezoelectric vibrator 12 to the reference temperature region. did. For the same reason as described above, the temperature decrease frequency temperature information 77b can be calculated approximately using the temperature increase frequency temperature information 77a and temperature and frequency information measured by lowering the ambient temperature to the reference temperature region. Further, it is only necessary to measure the reference temperature region when the temperature falls, and it is not necessary to measure a low temperature region lower than the reference temperature. Therefore, since the acquisition time of the temperature decrease frequency temperature information 77b can be shortened, the work burden can be reduced and the cost can be suppressed.

  Seventh, a temperature sensor 16 that outputs a detection voltage 66 corresponding to the ambient temperature is disposed adjacent to the piezoelectric vibrator 12, and the temperature increase frequency temperature information 77a and the temperature decrease frequency temperature information 77b are detected. Generated as a function of the voltage 66, the frequency temperature information 76 is calculated based on the temperature rising frequency temperature information 77a and the temperature decreasing frequency temperature information 77b, and the temperature compensation amount 80 is calculated based on the frequency temperature information 76 and the detected voltage 66. The oscillation signal 58 is output to the possible temperature compensation circuit 40, and the detection voltage 66 is output from the temperature sensor 16 to the temperature compensation circuit 40.

  As a result, the temperature sensor 16 can measure the ambient temperature of the piezoelectric vibrator 12 while suppressing measurement errors, so that the temperature rise frequency temperature information 77a and the temperature fall frequency temperature information 77b are generated with high accuracy, and the frequency temperature Information 76 can be calculated with high accuracy. Furthermore, since the temperature information of the piezoelectric vibrator 12 can be measured in real time and with high accuracy, the correction error in the temperature compensation circuit 40 can be suppressed and temperature compensation can be performed with high accuracy.

  In this embodiment, the piezoelectric vibrator has been described on the premise of a thickness-shear vibrator. However, the present invention is not limited to this, and is applicable to a double tuning fork type piezoelectric vibrator, a single beam type piezoelectric vibrator, a SAW resonator, and the like. it can. The temperature rise frequency temperature information 77a, the temperature fall frequency temperature information 77b, the first approximate curve information 70, the second approximate curve information 72, the third approximate curve information 74, and the frequency temperature information 76 are functions of the detected voltage 66, respectively. However, the detection voltage 66 output from the temperature sensor 16 may be converted into an actual temperature value and used. Accordingly, in response to this, the information may be a function of the actual temperature, and the PC 54 and the CPU 44 may be configured to recognize the above information as a function of the temperature.

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 curve information, 72... Second approximate curve information, 74. , 77a ......... Temperature increase frequency temperature information, 77b ......... Temperature decrease frequency temperature information, 78 ......... Temperature coefficient, 80 ......... Temperature compensation amount, 82 ......... Low temperature region information, 84 ......... First Reference temperature region information, 86 ... High temperature region information, 88 ... Second reference temperature region information, 90 ... Third reference temperature region information, 92 ... Fourth reference temperature region information.

Claims (1)

A piezoelectric vibrator having a hysteresis characteristic in frequency temperature characteristics; an oscillation circuit that oscillates the piezoelectric vibrator and outputs an oscillation signal; and a temperature detection means that outputs a detection voltage corresponding to the ambient temperature of the piezoelectric vibrator; A storage circuit for outputting frequency temperature information indicating temperature characteristics of the oscillation frequency of the piezoelectric vibrator, and a piezoelectric oscillator having
A temperature compensation circuit comprising: a CPU that calculates a temperature compensation amount using the frequency temperature information and the detection voltage; and a frequency correction circuit that performs temperature compensation of the oscillation frequency based on the temperature compensation amount. An oscillation circuit system,
The frequency temperature information is
An oscillation circuit system characterized by exhibiting a frequency temperature characteristic in a region surrounded by two frequency temperature characteristics of the oscillation signal that appears under the influence of the hysteresis characteristic.

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