JP5534182B2 - Measuring system and measuring method of frequency temperature characteristic of vibration device - Google Patents

Description

  The present invention relates to a measurement system and a measurement method for frequency temperature characteristics of a piezoelectric oscillator.

  The temperature compensated crystal oscillator (TCXO: Temperature Compensated X'tal Oscillator) achieves high frequency stability by canceling the deviation (frequency deviation) from the desired frequency (nominal frequency) of the oscillation frequency of the crystal resonator in a specified temperature range. Therefore, it is widely used in devices and systems that require highly accurate timing signals, such as mobile phone terminals, base stations, and GPS (Global Positioning System) receivers. Recently, a crystal oscillator (TSXO: Temperature Sensing X'tal Oscillator) with a temperature sensor and an internal ROM that stores the correspondence table of temperature information and oscillation frequency has appeared. A system that realizes temperature compensation according to the output voltage of the temperature sensor by reading out the signal is also developed. In recent years, these systems are required to have extremely high temperature compensation accuracy on the order of ppb, and the purpose is to obtain accurate frequency-temperature characteristics (change in frequency deviation with respect to temperature) of the crystal oscillator after temperature compensation. In order to obtain an accurate frequency temperature characteristic of the crystal resonator in order to calculate an accurate temperature compensation coefficient, it is necessary to measure the frequency of the crystal oscillator (crystal resonator) with a resolution of ppb order. ing.

  In general, in a conventional system that measures the frequency temperature characteristics of a crystal oscillator (crystal oscillator), the temperature of the crystal oscillator is strictly controlled using a thermostatic chamber, etc., and the temperature stabilizes until the temperature fluctuation becomes extremely small. The measurement accuracy was improved by measuring the oscillation frequency after waiting.

JP 2006-126052 A JP 2003-4785 A

For example, as shown in FIG. 10A, when measuring the frequency and temperature (output voltage of the temperature sensor) of the piezoelectric oscillator at two different set temperatures T1 and T2 with the conventional measurement method, first, the ambient temperature performs frequency measured by the measuring time t _f in a state set to T1, performs temperature measurement (voltage measured) after completion of the frequency measurement, the measurement time t _v. After completion of the temperature measurement at the set temperature T1 (voltage measurement), the ambient temperature of the thermostatic chamber is set to T2, waiting for the temperature is sufficiently stable, performs frequency measured by the measuring time t _f, the frequency after completion of the measurement, the temperature measurement (voltage measurement) with the measurement time t _v. FIG. 10B is an enlarged view of a circled portion (measurement at the set temperature T2) in FIG. Strictly speaking, as shown in FIG. 10B, the atmospheric temperature of the thermostatic chamber fluctuates in the vicinity of the set temperature T2. Therefore, the average value of the actual temperature at the measurement time of the frequency t _f = T2a, the average value of the temperature at the measuring time t _v of the temperature (voltage) (measurement temperature) is T2b, at frequency measurement An error occurs between the temperature and the measured temperature. Therefore, in order to further improve the measurement accuracy with the conventional method, it is necessary to perform temperature management more strictly so as to minimize temperature fluctuations. Due to an increase in the temperature stabilization waiting time and the complexity and size of the measurement system, There is a problem of increasing the cost. Furthermore, when measurement with a high frequency resolution on the order of ppb is required, only a temperature error of about several m ° C. may be allowed, and the conventional method has reached its limit.

  The present invention has been made in view of the above problems, and according to some aspects of the present invention, a piezoelectric device capable of measuring frequency temperature characteristics with high accuracy without requiring strict temperature management. It is possible to provide a measurement system and a measurement method for the frequency temperature characteristic of an oscillator.

  (1) The present invention is a measurement system for frequency temperature characteristics of a piezoelectric oscillator that measures frequency temperature characteristics by oscillating a piezoelectric oscillator at a plurality of different temperatures, and includes a temperature adjustment unit that variably adjusts the temperature of the piezoelectric oscillator; A temperature measuring unit that measures the temperature of the piezoelectric oscillator, a frequency measuring unit that measures an oscillation frequency of the piezoelectric oscillator, and a measurement control unit that synchronizes temperature measurement by the temperature measuring unit and frequency measurement by the frequency measuring unit And a frequency temperature characteristic measurement system for a piezoelectric oscillator.

  According to the measurement system of the present invention, instead of measuring the oscillation frequency and temperature of the piezoelectric oscillator asynchronously as in the prior art, these two measurements are performed synchronously, so the actual temperature and temperature measurement at the time of frequency measurement is performed. The difference in results can be reduced. Therefore, the frequency temperature characteristic can be measured with high accuracy without requiring strict temperature control.

  (2) In this measurement system, the measurement control unit may control the temperature measurement unit and the frequency measurement unit so that the temperature measurement and the frequency measurement are simultaneously performed in the same measurement time.

  By doing so, it is possible to eliminate the deviation between the actual temperature at the time of frequency measurement and the temperature measurement result, so that the measurement accuracy of the frequency temperature characteristic can be improved.

  Furthermore, since the temperature fluctuation during the measurement can be reduced as the measurement time is shortened, the measurement accuracy can be maintained without waiting until the temperature becomes strictly constant. In other words, since the measurement waiting time after changing the temperature setting can be shortened (in some cases, there is no need for the measurement waiting time), the total measurement time can be shortened and the cost can be reduced. it can.

  (3) In this measurement system, the measurement time of the frequency measurement unit is such that the fluctuation range of the oscillation frequency of the piezoelectric oscillator caused by temperature fluctuation in the measurement time is within the range of the frequency resolution required for the frequency measurement. It may be time to fit.

  In this way, it is possible to reliably perform frequency measurement with the same accuracy as the required frequency resolution.

  (4) In this measurement system, the measurement control unit transmits one measurement start signal to the temperature measurement unit and the frequency measurement unit at the same time, and the temperature measurement unit receives the measurement start signal, thereby the temperature measurement unit. The measurement may be started, and the frequency measurement unit may start the frequency measurement by receiving the measurement start signal.

  In this way, frequency measurement and temperature measurement can be performed simultaneously with a simple configuration.

  (5) In this measurement system, the measurement time of the temperature measurement unit and the measurement time of the frequency measurement unit may both be an integral multiple of the period of the AC power supply of the measurement system.

  In this way, it is possible to minimize the influence of power supply noise, which is a dominant cause of measurement variation, and thus the measurement accuracy can be increased.

  (6) The measurement system further includes a frequency conversion unit that converts an oscillation signal of the piezoelectric oscillator into an oscillation signal having a frequency lower than the oscillation frequency, and the frequency measurement unit is converted by the frequency conversion unit. The frequency of the oscillation signal may be measured.

  In this way, the frequency resolution can be increased while keeping the frequency measurement time short.

  (7) In this measurement system, the frequency converter includes a direct digital synthesizer that converts an oscillation signal of the piezoelectric oscillator into an oscillation signal having a frequency near the first frequency, and a frequency near the first frequency is included in the passband. A first filter to which the output signal of the direct digital synthesizer is input, a mixer that mixes the output signal of the bandpass filter and a reference clock signal of a second frequency, and the first frequency A frequency near the difference between the first frequency and the second frequency is included in the pass band, and a frequency near the sum of the first frequency and the second frequency is included in the stop band. And a second filter to which the output signal is input.

  In this way, the oscillation signal of the piezoelectric oscillator can be converted into an oscillation signal having a lower frequency while suppressing the deterioration of the S / N ratio.

  (8) The present invention relates to a method for measuring the frequency temperature characteristic of a piezoelectric oscillator that measures the frequency temperature characteristic by oscillating the piezoelectric oscillator at a plurality of different temperatures, and includes a temperature adjustment step for variably adjusting the temperature of the piezoelectric oscillator; A temperature measurement step for measuring the temperature of the piezoelectric oscillator, a frequency measurement step for measuring the oscillation frequency of the piezoelectric oscillator, and a measurement control step for synchronizing the temperature measurement in the temperature measurement step and the frequency measurement in the frequency measurement step. And measuring the frequency temperature characteristics of the piezoelectric oscillator.

  According to the measurement method of the present invention, the measurement of the oscillation frequency of the piezoelectric oscillator and the measurement of the temperature of the piezoelectric oscillator are not performed asynchronously as in the prior art, but these two measurements are performed synchronously. The difference between the actual temperature and the temperature measurement result can be reduced. Therefore, the frequency temperature characteristic can be measured with high accuracy without requiring strict temperature control.

The figure which shows an example of a function structure of the frequency temperature characteristic measuring system of this embodiment. The figure which shows another example of a function structure of the frequency temperature characteristic measurement system of this embodiment. The figure which shows the structural example of the piezoelectric oscillator of a measuring object. The figure which shows an example of the specific structure of the frequency temperature characteristic measuring system of this embodiment. The figure which shows the structural example of a down converter. The figure which shows an example of the timing of the measurement operation | movement of the frequency temperature characteristic measurement system of this embodiment. The figure which shows the example in the case of performing frequency measurement and voltage measurement with two different preset temperature. The figure for demonstrating the relationship between measurement time and a power supply period. The flowchart figure which shows an example of the process sequence of the frequency temperature characteristic measurement system of this embodiment. The figure for demonstrating the measuring method of the conventional frequency temperature characteristic.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. The embodiments described below do not unduly limit the contents of the present invention described in the claims. Also, not all of the configurations described below are essential constituent requirements of the present invention.

1. Functional Configuration of Frequency Temperature Characteristic Measuring System FIGS. 1 and 2 are diagrams showing an example of a functional configuration of a frequency temperature characteristic measuring system (hereinafter simply referred to as “frequency temperature characteristic measuring system”) of the piezoelectric oscillator of the present embodiment. is there.

  The frequency temperature characteristic measurement system 1 of the present embodiment includes a measurement control unit 10, a frequency measurement unit 20, a temperature measurement unit 30, and a temperature adjustment unit 40, and oscillates the piezoelectric oscillator 2 at a plurality of different temperatures. Measure frequency temperature characteristics of

  The temperature adjustment unit 40 variably adjusts the temperature of the piezoelectric oscillator 2. For example, the temperature adjustment unit 40 may have a structure in which a piezoelectric oscillator can be housed, such as a thermostatic chamber, or a structure in which a piezoelectric oscillator is brought into contact, such as a hot plate. The temperature may be adjusted by attaching a Peltier element to the oscillator.

  The temperature measuring unit 30 measures the temperature of the piezoelectric oscillator 2. For example, the temperature measurement unit 30 may measure the output voltage of the temperature sensor 3 provided in or near the piezoelectric oscillator 2. The temperature sensor 3 may be included in the frequency temperature characteristic measurement system 1 or may be outside the frequency temperature characteristic measurement system 1.

  The frequency measuring unit 20 measures the oscillation frequency of the piezoelectric oscillator 2. The measurement time of the oscillation frequency by the frequency measuring unit 20 is such that the fluctuation width of the oscillation frequency of the piezoelectric oscillator 2 due to the temperature fluctuation in the measurement time falls within the frequency resolution range required for frequency measurement. It may be.

  Both the measurement time of the temperature measurement unit 30 and the measurement time of the frequency measurement unit 20 may be an integral multiple of the period of the AC power supply of the frequency temperature characteristic measurement system 1.

  The measurement control unit 10 synchronizes the temperature measurement by the temperature measurement unit 30 and the frequency measurement by the frequency measurement unit 20. For example, the measurement control unit 10 transmits one measurement start signal 12 to the temperature measurement unit 30 and the frequency measurement unit 20 at the same time, and the temperature measurement unit 30 and the frequency measurement unit 20 receive the measurement start signal 12, respectively. By starting frequency measurement, these two measurements may be synchronized. Further, for example, the measurement control unit 10 controls the temperature measurement unit 30 and the frequency measurement unit 20 so that the temperature measurement by the temperature measurement unit 30 and the frequency measurement by the frequency measurement unit 20 are simultaneously performed in the same measurement time. May be.

  Further, as shown in FIG. 2, the frequency temperature characteristic measurement system 1 may further include a frequency conversion unit 50. Then, the frequency conversion unit 50 may convert the oscillation signal of the piezoelectric oscillator 2 into an oscillation signal 52 having a frequency lower than the oscillation frequency, and the frequency measurement unit 20 may measure the frequency of the oscillation signal 52.

  Hereinafter, the frequency temperature characteristic measurement system and the frequency temperature characteristic measurement method of the present embodiment will be described with more specific examples.

2. Configuration of Piezoelectric Oscillator FIGS. 3A and 3B are diagrams showing a configuration example of a piezoelectric oscillator to be measured by the frequency temperature characteristic measurement system of the present embodiment.

  For example, as shown in FIG. 3A, the piezoelectric oscillator 200 to be measured of the present embodiment includes a piezoelectric vibrator 210, a voltage control oscillation circuit 220, a temperature compensated voltage generation circuit 230, a temperature sensor 240, and a nonvolatile memory 250. , A control circuit 260, switch circuits 262, 264, and an interface (I / F) circuit 270.

  The piezoelectric vibrator 210 is a piezoelectric element that vibrates using the inverse piezoelectric effect. For example, a vibration using a single crystal material such as a crystal vibrator, a ceramic vibrator, a lithium niobate vibrator, or a lithium tantalate vibrator. Or a vibrator using a piezoelectric thin film such as a zinc oxide piezoelectric thin film vibrator or an aluminum oxide piezoelectric thin film vibrator.

  In particular, it is known that the frequency-temperature characteristics of an AT-cut crystal resonator exhibit extremely good characteristics of an approximate cubic curve over a wide temperature range, and an AT-cut crystal resonator is used as the piezoelectric vibrator 210. Thus, a temperature compensated crystal oscillator with extremely high frequency stability can be realized.

  The voltage controlled oscillation circuit 220 generates the oscillation signal 201 by causing the piezoelectric vibrator 210 to oscillate at a frequency corresponding to the input voltage by changing the load capacity of the piezoelectric vibrator 210 according to the input voltage, and outputs the oscillation signal 201 to the outside. To do.

  The nonvolatile memory 250 stores frequency adjustment data 252 and temperature compensation data 254.

  The frequency adjustment data 252 is data for adjusting the load capacity of the piezoelectric vibrator 210 so that the frequency (oscillation frequency) of the oscillation signal 201 becomes a desired frequency (nominal frequency) at a reference temperature (for example, 25 ° C.). . For example, in the inspection process of the piezoelectric oscillator 200, the frequency adjustment data 252 is adjusted so that the oscillation frequency of the piezoelectric vibrator 210 at a reference temperature (for example, 25 ° C.) becomes a desired frequency (nominal frequency), and the adjusted frequency The adjustment data 252 is written into the nonvolatile memory 250. As a result, it is possible to absorb frequency variations at the reference temperature (for example, 25 ° C.) of the piezoelectric vibrator 210.

The temperature compensation data 254 is data for compensating the frequency-temperature characteristics of the piezoelectric vibrator 210 so that the frequency of the oscillation signal 201 (oscillation frequency) becomes a substantially constant frequency regardless of the temperature. Specifically, the temperature compensation data 254 is a parameter for specifying a curve representing the frequency temperature characteristic of the piezoelectric vibrator 210. For example, if the piezoelectric vibrator 210 is an AT-cut quartz crystal vibrator, the frequency deviation Δf / f is approximated by a cubic curve, and a cubic function corresponding to the cubic curve is expressed as the following equation (1). be able to. In Expression (1), f is a nominal frequency, Δf is a frequency error, T is a temperature variable, and t ₀ is a reference temperature (for example, 25 ° C.).

Equation (1) is a coefficient _A 3, _{A 1,} it is possible to identify the constants _{A 0} and the reference temperature _{t 0,} and the coefficient _A 3, _{A 1,} temperature compensation data 254 constants _{A 0} and the reference temperature _{t 0} be able to.

  For example, in the inspection process of the piezoelectric oscillator 200 and the like, the frequency temperature characteristic of the piezoelectric vibrator 210 is measured using the frequency temperature characteristic measurement system of the present embodiment, and the temperature compensation data 254 is created from this measurement data to create a nonvolatile memory. Write to 250. Thereby, the variation in the frequency temperature characteristic of the piezoelectric vibrator 210 can be absorbed.

  The temperature sensor 240 is disposed in the vicinity of the piezoelectric vibrator 210 and outputs a voltage 202 corresponding to the temperature. The output voltage 202 of the temperature sensor 240 can be output to the outside. The temperature sensor 50 can be realized by, for example, a thermistor that captures a temperature change as a change in electrical resistance.

  The temperature compensation voltage generation circuit 230 generates a temperature compensation voltage for compensating the frequency temperature characteristic of the piezoelectric vibrator 210 based on the temperature compensation data 254 and the output voltage 202 of the temperature sensor 240.

  The control circuit 260 performs open / close control of the switch circuits 262 and 264 and processing for reading / writing the frequency adjustment data 252 and the temperature compensation data 254 with respect to the nonvolatile memory 250 according to the control data 173 from the external device.

  The switch circuit 262 is disposed between the output of the temperature compensation voltage generation circuit 230 and the input of the voltage controlled oscillation circuit 220. By switching the switch circuit 262, the output voltage (temperature compensation voltage) of the temperature compensation voltage generation circuit 230 is obtained. Can be selected to be supplied to the voltage controlled oscillation circuit 220 or not.

  The switch circuit 264 is disposed between an external voltage supply source and the input of the voltage controlled oscillation circuit 220. By switching the switch circuit 264, a constant control voltage 172 supplied from an external device is applied to the voltage controlled oscillation circuit 220. It is possible to select whether or not to supply to.

  The switch circuit 262 and the switch circuit 264 are opened and closed exclusively, and the voltage controlled oscillation circuit 220 is supplied with the output voltage (temperature compensation voltage) of the temperature compensation voltage generation circuit 230 during normal operation (normal mode). When the frequency temperature characteristic of the piezoelectric vibrator 210 is measured (test mode), the control voltage 172 is supplied.

  Therefore, in the normal mode, the voltage-controlled oscillation circuit 220 generates the oscillation signal 201 having a substantially constant frequency by changing the load capacitance according to the output voltage (temperature compensation voltage) of the temperature compensation voltage generation circuit 230. On the other hand, in the test mode, the voltage controlled oscillation circuit 220 selects a load capacitance corresponding to the constant control voltage 172 and generates an oscillation signal 201 having a frequency corresponding to the frequency temperature characteristic of the piezoelectric vibrator 210.

  The interface (I / F) circuit 270 performs interface processing between the external device and the control circuit 260. For example, the interface (I / F) circuit 270 receives the control data 173 from the external device and transfers the control data 173 to the control circuit 260, or the memory data 203 (frequency adjustment data 252 and the like) read from the nonvolatile memory 250 by the control circuit 260. The temperature compensation data 254) is received and transferred to an external device.

  For example, as shown in FIG. 3B, the piezoelectric oscillator 200 to be measured of the present embodiment includes a piezoelectric vibrator 210, an oscillation circuit 280, a temperature sensor 240, a nonvolatile memory 250, a control circuit 260, an interface ( (I / F) A piezoelectric oscillator including a circuit 270 may be used.

  The piezoelectric vibrator 210 and the temperature sensor 240 in FIG. 3B are the same as those in FIG.

  The oscillation circuit 280 oscillates the piezoelectric vibrator 210 to generate an oscillation signal 201 and outputs it to the outside.

  The nonvolatile memory 250 stores frequency adjustment data 252 and frequency temperature characteristic data 256. The frequency adjustment data 252 is the same as that shown in FIG.

  The frequency-temperature characteristic data 256 is data (correspondence table) representing the correspondence between the temperature value (or the output voltage of the temperature sensor 202) and the oscillation frequency. For example, frequency temperature characteristics are measured in an inspection process or the like of the piezoelectric oscillator 200, and the measurement data is converted into frequency temperature characteristic data 256 and written into the nonvolatile memory 250.

  The control circuit 260 performs a process of reading / writing the frequency adjustment data 252 and the frequency temperature characteristic data 256 with respect to the nonvolatile memory 250 in accordance with the control data 173 from the external device.

  The interface (I / F) circuit 270 performs interface processing between the external device and the control circuit 260. That is, the interface (I / F) circuit 270 receives the control data 173 from the external device and transfers it to the control circuit 260, or the memory data 203 (frequency adjustment data 252 and the like) read from the nonvolatile memory 250 by the control circuit 260. The frequency temperature characteristic data 256) is received and transferred to an external device.

  By reading out the frequency temperature characteristic data 256 stored in the nonvolatile memory 250 from the outside as the memory data 203 with respect to the piezoelectric oscillator 200, each coefficient specifying the curve representing the frequency temperature characteristic of the piezoelectric vibrator 210 is obtained. Can be calculated. Thereby, temperature compensation of the oscillation frequency can be performed outside the piezoelectric oscillator 200.

  The piezoelectric oscillator 200 shown in FIGS. 3A and 3B becomes TCXO and TSXO, respectively, if the piezoelectric vibrator 210 is a crystal vibrator.

3. Specific Configuration of Frequency Temperature Characteristic Measurement System FIG. 4 is a diagram illustrating an example of a specific configuration of the frequency temperature characteristic measurement system of the present embodiment. The frequency temperature characteristic measuring system 100 of this embodiment includes a personal computer (PC) 110, a frequency counter 120, a digital multimeter (DMM) 130, a thermostatic chamber (temperature chamber) 140, a down converter 150, a power supply 160, and an interface circuit 170. It is configured to include.

  The PC 110, the frequency counter 120, the digital multimeter (DMM) 130, and the thermostatic chamber 140 correspond to the measurement control unit 10, the frequency measurement unit 20, the temperature measurement unit 30, and the temperature adjustment unit 40 of FIGS. The down converter 150 corresponds to the frequency conversion unit 50 in FIG.

  The PC 110 is connected to a frequency counter 120 and a digital multimeter (DMM) 130 via a GPIB (General Purpose Interface Bus), and the frequency counter 120 and the digital multimeter (DMM) are connected via a GPIB interface (GPIB-I / F) 111. ) 130 operations can be controlled, and various measurement settings (measurement time settings, etc.) and measurement data acquisition can be performed. Further, the PC 110 and the power supply 160 may be connected by GPIB so that the PC 110 can control the output voltage of the power supply 160 via the GPIB-I / F 111.

  The PC 110 simultaneously transmits a measurement start signal 113 to the frequency counter 120 and the digital multimeter (DMM) 130 via the digital I / O 112, and the frequency measurement and voltage are respectively transmitted to the frequency counter 120 and the digital multimeter (DMM) 130. Instruct the start of measurement.

  Further, the PC 110 transmits control data 114 to the down converter 150 via the digital I / O 112, and performs processing such as frequency setting of the down converter 150.

  In addition, the PC 110 transmits control data 116 to the thermostat 140 via the digital I / O 112, and performs processing such as setting the ambient temperature inside the thermostat 140.

  Note that the PC 110 may be connected to the down converter 150 and the thermostat 140 via GPIB, and the down converter 150 and the thermostat 140 may be controlled via the GPIB-I / F 111.

  In the thermostatic chamber 140, the piezoelectric oscillator 200 to be measured shown in FIG. 3A or 3B is installed. The piezoelectric oscillator 200 is connected to the digital I of the PC 110 via the interface circuit 170. / O 112, power supply 160, frequency counter 120, digital multimeter (DMM) 130, and down converter 150 are connected.

  The interface circuit 170 converts the control data 115 received from the digital I / O 112 of the PC 110 into the control data 173 shown in FIGS. 3A and 3B and transmits the control data 173 to the piezoelectric oscillator 200. For example, by using the control data 173, the switch circuits 262 and 264 inside the piezoelectric oscillator 200 in FIG. Measurement of the frequency temperature characteristic of the previous piezoelectric oscillator 200 is possible. Further, for example, the control data 173 causes the frequency of the piezoelectric oscillator 200 after temperature compensation by switching the switch circuits 262 and 264 inside the piezoelectric oscillator 200 of FIG. Temperature characteristics can be measured.

  The interface circuit 170 supplies the DC power supply voltage 161 and the control voltage 162 generated by the power supply 160 to the piezoelectric oscillator 200 as the DC power supply voltage 171 and the control voltage 172 shown in FIG. The DC power supply voltage 171 is a power supply voltage (not shown in FIGS. 3A and 3B) for operating each circuit of the piezoelectric oscillator 200.

  The interface circuit 170 receives the output voltage 202 of the temperature sensor 240 inside the piezoelectric oscillator 200 and supplies it to the digital multimeter (DMM) 130 as the input voltage 175. The digital multimeter (DMM) 130 receives the measurement start signal 113, measures the average value of the voltage value of the input voltage 175 at the set measurement time, and transmits the measurement data 131 to the PC 110 via GPIB.

  Further, the interface circuit 170 receives the oscillation signal 201 (the oscillation signal 201 shown in FIGS. 3A and 3B) output from the piezoelectric oscillator 200 and transmits the oscillation signal 201 as the oscillation signal 174 to the down converter 150. The down converter 150 down-converts the oscillation signal 174 into an oscillation signal 156 having a frequency corresponding to the set value and transmits the oscillation signal 174 to the frequency counter 120.

  The frequency counter 120 receives the measurement start signal 113, measures the average value of the frequency of the oscillation signal 156 at the set measurement time (gate time), and transmits the measurement data 121 to the PC 110 via GPIB. The frequency counter 120 is configured as a direct counter frequency counter (direct counter) that counts the number of pulses in the measurement time (gate time) with respect to the oscillation signal 156, converts the count result into a frequency, and outputs the frequency. Alternatively, a reciprocal frequency counter (reciprocal counter) that counts and measures a measurement time (gate time) that is an integral multiple of the period of the oscillation signal 156 with an accurate internal clock, calculates the frequency from its reciprocal, and outputs it. It may be configured as.

  Thus, by measuring the frequency after down-converting the oscillation signal 201 output from the piezoelectric oscillator 200, the resolution of frequency measurement can be improved without changing the measurement time (gate time). For example, if the number of measurement digits of the frequency counter 120 is constant, the frequency resolution is 1000 without changing the measurement time (gate time) by measuring the frequency after down-converting the oscillation signal 201 to 1/1000 frequency. Can be doubled.

  FIG. 5A is a diagram illustrating a configuration example of the down converter 150. The down converter 150 includes an OCXO (Oven Control X'tal Oscillator) 151, a direct digital synthesizer (DDS) 152, a filter 153, a mixer 154, and a filter 155.

  The OCXO 151 has an extremely high frequency accuracy by placing an SC cut crystal resonator whose temperature characteristics of the oscillation frequency are flat at a predetermined temperature (for example, 90 ° C.) and heating it to be constant at the predetermined temperature. The reference clock signal is output.

  The DDS 152 generates a signal obtained by frequency-converting the reference clock signal output from the OCXO 151 in accordance with the frequency setting value set by the control data 114 from the PC 110 in FIG. This frequency setting value is changed according to the nominal frequency of the piezoelectric oscillator 200 so that the difference between the frequency of the output signal of the DDS 152 and the nominal frequency of the piezoelectric oscillator 200 is close to the desired frequency.

  The filter 153 is a bandpass filter (BPF) that allows the output signal of the DDS 152 to pass through, and can be realized by a filter using a resonance circuit, an active filter, or the like. Since the frequency of the output signal of the DDS 152 changes according to the nominal frequency of the piezoelectric oscillator 200, it is necessary to widen the pass band of the filter 153 in order to have versatility.

  The mixer 154 mixes (mixes) the output signal of the filter 153 and the oscillation signal 174 of FIG. 4, and generates an oscillation signal (sum signal) having a frequency corresponding to the sum of the frequencies of these two signals and the frequency of these two signals. An oscillation signal (difference signal) having a frequency corresponding to the difference is generated. The mixer 154 can be realized by, for example, a double balanced modulator (DBM). Although the frequency of the sum signal varies depending on the nominal frequency of the piezoelectric oscillator 200, the frequency of the difference signal is substantially constant.

  The filter 155 is a band-pass filter (BPF) or a low-pass filter (LPF: Lowpass Filter) in which the frequency of the difference signal is included in the pass band and the frequency of the sum signal is included in the stop band. It can be realized by a filter, a digital filter or the like. The output signal of this filter 155 becomes the oscillation signal 156 of FIG. In order to improve the S / N ratio of the oscillation signal 156 as much as possible, it is important to attenuate as much as possible spurious noise mixed in a wide band in the mixer 154 as much as possible. Therefore, it is desirable to configure the filter 155 as a bandpass filter with a gorge band as much as possible.

  FIG. 5B is a diagram illustrating another configuration example of the down converter 150. The down converter 150 includes an OCXO 151, a DDS 152, a filter 153, a mixer 154, and a filter 155, as in FIG.

  The DDS 152 generates a signal obtained by frequency-converting the oscillation signal 174 of FIG. 4 according to the frequency setting value set by the control data 114 from the PC 210 of FIG. This frequency setting value is changed according to the nominal frequency of the piezoelectric oscillator 200 so that the frequency of the output signal of the DDS 152 is close to the desired frequency.

  The filter 153 is a band pass filter (BPF) that passes the output signal of the DDS 152. Since the frequency of the output signal of the DDS 152 is always near the desired frequency regardless of the oscillation frequency of the piezoelectric oscillator 200, the pass band of the filter 153 can be narrowed.

  The mixer 154 mixes (mixes) the output signal of the filter 153 and the reference clock signal of the OCXO 151, and the difference between the frequency of the oscillation signal (sum signal) corresponding to the sum of the frequencies of these two signals and the frequency of these two signals. An oscillation signal (difference signal) having a frequency corresponding to is generated. Regardless of the nominal frequency of the piezoelectric oscillator 200, the frequency of the sum signal and the frequency of the difference signal are both substantially constant.

  The filter 155 is a band-pass filter (BPF) or a low-pass filter (LPF) in which the frequency of the difference signal is included in the passband and the frequency of the sum signal is included in the stopband, and the output signal of the filter 155 is the output signal of FIG. Oscillation signal 156.

  In the down converter of FIG. 5B, since the pass band of the filter 153 can be narrowed, spurious noise generated in a wide band inside the DDS 152 can be effectively attenuated by the filter 153. Therefore, the down converter of FIG. 5B can improve the S / N ratio of the oscillation signal 156 as compared with the down converter of FIG.

4). Measurement Operation of Frequency Temperature Characteristic Measurement System Next, the timing of the measurement operation of the frequency temperature characteristic measurement system of the present embodiment will be described with reference to FIG. FIG. 6 is a diagram illustrating an example of the timing of the measurement operation of the frequency temperature characteristic measurement system of the present embodiment.

First, at time t _{1 to} t ₂ , the PC 110 transmits control data 116 to the thermostat 140 via the digital I / O 112 to set the atmospheric temperature inside the thermostat 140. For a while from the time t ₂ is the ambient temperature of the thermostatic chamber 140 is rapidly changed.

After the atmospheric temperature of the thermostatic chamber 140 becomes substantially constant, the PC 110 simultaneously sends a measurement start signal 113 to the frequency counter 120 and the digital multimeter (DMM) 130 via the digital I / O 112 at time t _{3 to} t ₄ . Send.

The frequency counter 120 and the digital multimeter (DMM) 130 receive the measurement start signal 113 and simultaneously measure the frequency of the oscillation signal 156 and the voltage value of the input voltage 175 at times t _{4 to} t ₅ .

At times t _{5 to} t ₆ , the frequency counter 120 transmits the frequency measurement data 121 to the PC 110 via the GPIB, and the PC 110 acquires the frequency measurement data 121.

At times t _{6 to} t ₇ , the digital multimeter (DMM) 130 transmits the voltage measurement data 131 to the PC 110 via the GPIB, and the PC 110 acquires the voltage measurement data 131.

Measuring process at one temperature setting is completed in the period of the time t ₁ ~t _7. A plurality of voltage measurement data 131 and a plurality of frequency measurement data 121 can be obtained by repeating the same measurement process at times t _{1 to} t ₇ at a plurality of different set temperatures. Based on the plurality of voltage measurement data 131 and the plurality of frequency measurement data 121 acquired at a plurality of set temperatures, the correspondence between the temperature of the piezoelectric vibrator 210 and the oscillation frequency is calculated, and the temperature compensation data 254 or the frequency temperature characteristic data 256 is obtained. Can be created. The temperature compensation data 254 or frequency temperature characteristic data 256 is written from the PC 110 to the nonvolatile memory 250 of the piezoelectric oscillator 200 via the interface circuit 170.

As described above, in the frequency temperature characteristic measurement system of this embodiment, the frequency measurement by the frequency counter 120 and the voltage measurement by the digital multimeter (DMM) 130 are synchronized by the measurement start signal 113. Thus, the voltage measurement is simultaneously started at time _{t 4} due to frequency measurement and digital multimeter (DMM) 130 by the frequency counter 120. Further, the frequency temperature characteristics measuring system of the present embodiment is set to a frequency measurement time t _f and the voltage measurement time t _v the same in both time (t 5 _{-t 4).} This frequency measurement time t _f and the voltage measurement time t _v is preferably a possible short.

FIGS. 7 (A) and 7 (B) is set to an extremely short time frequency measuring time t _f and the voltage measurement time t _v, in the case of performing frequency measurement and voltage measurement at two different set temperatures T1 and T2 It is a figure which shows an example. As shown in FIG. 7 (A), is set in a very short time the frequency measuring time t _f and the voltage measurement time t _v, after the set temperature of the constant temperature bath 140 was measured in the T1, setting the constant temperature bath 140 The same measurement is performed by switching the temperature from T1 to T2. FIG. 7B is an enlarged view of a circled portion (measurement at the set temperature T2) in FIG. 7A. As shown in FIG. 7B, the ambient temperature of the thermostatic chamber 140 (the temperature of the piezoelectric oscillator 200) fluctuates in the vicinity of the set temperature T2. However, according to this embodiment, since the frequency measuring time t _f and the voltage measurement time t _v match, it is possible to measure the voltage according to the value T2c of the actual temperature during frequency measurement. Furthermore, since the frequency measuring time t _f and the voltage measurement time t _v is very short, as compared with the conventional technique shown in FIG. 10 (B), the temperature variation while performing frequency measurement and voltage measurement The width can be significantly reduced. The width of this temperature fluctuation can be suppressed to several m ° C., and it can cope with a measurement that requires a frequency resolution of ppb order. Conversely, the variation width of the oscillation frequency of the piezoelectric oscillator 200 (piezoelectric vibrator 210) due to temperature variations in the frequency measurement time t _f is in a range falling within the range of the frequency resolution required to frequency measurement, as much as possible it may be set short frequency measurement time t _f.

  The temperature converted from the voltage measurement value is a temperature T2c that deviates from the set temperature T2, but an accurate temperature compensation coefficient can be calculated as long as the exact temperature at the time of frequency measurement is known. There is no particular problem.

Furthermore, the frequency measurement time _{t f} and the voltage measurement time _{t v} the AC power source (not shown) for driving the power supply 160 (e.g., 50 Hz or 60Hz) is preferably an integral multiple of the period of the. The DC power supply voltage 161 (171) supplied to the piezoelectric oscillator 200 is generated by converting an AC voltage into a DC voltage inside the power supply 160, but this AC voltage signal is slightly DC power supply voltage 161 (171). Is superimposed on. Since the temperature sensor 240 inside the piezoelectric oscillator 200 also operates with this DC power supply voltage 171, an AC voltage signal is also superimposed on the output voltage 202 of the temperature sensor 240. Therefore, as shown in FIG. 8A, the AC voltage signal is also superimposed on the input voltage 175 of the digital multimeter (DMM) 130. By setting the voltage measurement time _tv to N (integer) times the power cycle of the AC power supply, the AC component is integrated and canceled. Incidentally, as shown in FIG. 8 (B), rather than the starting point of the voltage measurement time t _v must match the 0 cross point of the AC component, the voltage measurement time t _v is the power supply cycle of the AC power supply N (integer) It only needs to be doubled.

Similarly, an AC voltage signal is superimposed on the oscillation signal 201 output from the piezoelectric oscillator 200, and an AC voltage signal is also superimposed on the oscillation signal 156 input to the frequency counter 120. By setting the frequency measuring time t _f in N (an integer) times the power supply cycle of the AC power supply, it is possible to perform the frequency measurement by canceling the AC component.

For example, if the power supply period of the AC power supply is 50 Hz, the frequency measurement time _{t f} and the voltage measurement time _{t v} together, it may be an integer multiple of 20ms (= 1 / 50Hz). In particular, by equal to both power supply cycle frequency measurement time t _f and the voltage measurement time t _v, the effect of power source noise in the measurement can be minimized.

5. Processing Procedure of Frequency Temperature Characteristic Measurement System FIG. 9 is a flowchart showing an example of the processing procedure of the frequency temperature characteristic measurement system of the present embodiment.

  First, various initial settings for measuring the frequency temperature characteristics of the piezoelectric oscillator 200 are performed (step S10). That is, initial setting of the power supply 160 is performed, and the DC power supply voltage 161 and the control voltage 162 are generated as necessary. Further, the PC 110 performs initial settings (measurement time (gate time) setting, etc.) of the frequency counter 120 and digital multimeter (DMM) 130 and initial settings of the down converter 150 (frequency setting of the DDS 152, etc.). Further, the piezoelectric oscillator 200 of FIG. 3A is set to either the test mode or the normal mode from the PC 110.

  Next, the atmospheric temperature of the thermostatic chamber 140 is set from the PC 110 to the first temperature to be measured (step S20).

  Next, after a predetermined time has elapsed since the temperature was set in step S20 (in the case of Y in step S30), the measurement start signal 113 is transmitted from the PC 110 (step S40).

  Next, the frequency counter 120 and the digital multimeter 130 receive the measurement start signal 113, and simultaneously start frequency measurement and voltage measurement (step S50).

  Next, after the frequency measurement and the voltage measurement are completed (in the case of Y in step S60), the PC 110 acquires the frequency measurement data 121 from the frequency counter 120 (step S70), and further the voltage measurement data 131 from the digital multimeter 130. Is acquired (step S80). Here, the determination of whether or not the frequency measurement and the voltage measurement have ended may be made based on, for example, whether or not the measurement time (gate time) has elapsed, or the frequency counter 120 and the digital multimeter 130 have ended the measurement. Sometimes, the measurement end signal may be transmitted to the PC 110 to determine whether the PC 110 has received the measurement end signal. The order of step S70 in which the PC 110 acquires the frequency measurement data 121 and step S80 in which the PC 110 acquires the voltage measurement data 131 may be reversed.

  If frequency measurement and voltage measurement at all measurement target temperatures are not yet completed (in the case of N in step S90), the ambient temperature of the thermostat 140 is set from the PC 110 to the next measurement target temperature (step S100), Steps S30 to S80 are performed (frequency measurement and voltage measurement).

  The above processing is repeated until frequency measurement and voltage measurement are completed at all measurement target temperatures, and frequency measurement data and voltage measurement data at each measurement target temperature can be obtained. Then, using these frequency measurement data and voltage measurement data, it is possible to create temperature compensation data 254 and frequency temperature characteristic data 256, or to inspect the frequency temperature characteristic after temperature compensation.

  According to the present embodiment described above, since the measurement of the oscillation frequency of the piezoelectric oscillator and the measurement of the temperature are performed in synchronization, the deviation between the actual temperature and the temperature measurement result at the time of frequency measurement can be reduced. Therefore, the frequency temperature characteristic can be measured with high accuracy without requiring strict temperature control.

  In particular, by performing frequency measurement and voltage measurement (temperature measurement) at the same measurement time at the same time, it is possible to eliminate the deviation between the actual temperature and the temperature measurement result at the time of frequency measurement. Can be increased.

  Furthermore, according to the present embodiment, the frequency fluctuation during measurement and the voltage measurement (temperature measurement) can be performed in a very short time, so that the temperature fluctuation during the measurement can be made very small, so that the temperature becomes strictly constant. Measurement accuracy can be maintained without waiting. In other words, the measurement waiting time after changing the temperature setting can be shortened (in some cases, there is no need for the measurement waiting time), so the total measurement time can be shortened and the cost can be reduced. it can.

  In addition, this invention is not limited to this embodiment, A various deformation | transformation implementation is possible within the range of the summary of this invention.

  For example, the digital multimeter (DMM) 130 is installed in the temperature sensor (for example, inside the thermostatic chamber 140) installed in the vicinity of the piezoelectric oscillator 200 instead of the output voltage of the temperature sensor 240 inside the piezoelectric oscillator 200. The output voltage of the temperature sensor may be measured.

  The present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations that have the same functions, methods, and results, or configurations that have the same objects and effects). In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that exhibits the same operational effects as the configuration described in the embodiment or a configuration that can achieve the same object. Further, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

1 frequency temperature characteristic measurement system, 2 piezoelectric oscillator, 3 temperature sensor, 10 measurement control unit, 12 measurement start signal, 20 frequency measurement unit, 30 temperature measurement unit, 40 temperature adjustment unit, 50 frequency conversion unit, 52 oscillation signal, 100 Frequency temperature characteristic measurement system, 110 personal computer (PC), 111 GPIB-I / F, 112 digital I / O, 113 measurement start signal, 114, 115, 116 control data, 120 frequency counter, 121 frequency measurement data, 130 digital Multimeter, 131 Voltage measurement data, 140 Temperature chamber, 150 Down converter, 151 OCXO, 152 Direct digital synthesizer (DDS), 153 filter, 154 mixer, 155 filter, 156 oscillation signal, 1 0 power supply, 161 DC power supply voltage, 162 control voltage, 170 interface circuit, 171 DC power supply voltage, 172 control voltage, 173 control data, 200 piezoelectric oscillator, 201 oscillation signal, 202 output voltage of temperature sensor, 203 memory data, 210 piezoelectric Resonator, 220 Voltage control oscillation circuit, 230 Temperature compensation voltage generation circuit, 240 Temperature sensor, 250 Non-volatile memory, 252 Frequency adjustment data, 254 Temperature compensation data, 256 Frequency temperature characteristic data, 260 Control circuit, 262, 264 Switch circuit 270 interface (I / F) circuit, 280 oscillator circuit

Claims (11)

A frequency temperature characteristic measurement system for a vibration device that measures frequency temperature characteristics by oscillating a vibration device at a plurality of different temperatures,
A temperature adjusting unit for adjusting the temperature of the vibrating device;
A temperature measuring unit for measuring the temperature of the vibrating device;
A frequency measuring unit for measuring the oscillation frequency of the vibrating device;
A measurement control unit for synchronizing the temperature measurement by the temperature measurement unit and the frequency measurement by the frequency measurement unit;
With
The measurement control unit, the temperature measuring and said frequency measurement to control said frequency measuring unit and the temperature measuring unit as is done in the same measurement time, the measurement system of the frequency temperature characteristic of the vibrating device. Measurement time of the measurement time and the frequency measurement unit of the temperature measuring unit are both an integer multiple of the period of the AC power supply connected to said measuring system, the frequency-temperature characteristics of the vibration device according to claim 1 Measuring system. A frequency temperature characteristic measurement system for a vibration device that measures frequency temperature characteristics by oscillating a vibration device at a plurality of different temperatures,
A temperature adjusting unit for adjusting the temperature of the vibrating device;
A temperature measuring unit for measuring the temperature of the vibrating device;
A frequency measuring unit for measuring the oscillation frequency of the vibrating device;
A measurement control unit for synchronizing the temperature measurement by the temperature measurement unit and the frequency measurement by the frequency measurement unit;
With
Both the measurement time of the temperature measuring unit and the measurement time of the frequency measuring unit are integral multiples of the period of the AC power supply connected to the measurement system, and the frequency temperature characteristic measurement system of the vibration device. The measurement time of the frequency measurement unit, the variation width of the oscillation frequency of the vibration device due to temperature fluctuations in the measurement time is the time to fall within the scope of the frequency resolution required for the frequency measurement, claim 1 The measurement system of the frequency temperature characteristic of the vibration device as described in any one of thru | or 3 . The measurement control unit simultaneously transmits one measurement start signal to the temperature measurement unit and the frequency measurement unit,
The temperature measurement unit starts the temperature measurement by receiving the measurement start signal,
Wherein the frequency measurement unit, the starts frequency measurement by receiving the measurement start signal, the measurement system of the frequency temperature characteristic of the vibration device according to any one of claims 1 to 4. A frequency converter that converts the oscillation signal of the vibration device into an oscillation signal having a frequency lower than the oscillation frequency;
6. The frequency temperature characteristic measurement system for a vibrating device according to claim 1, wherein the frequency measurement unit measures the frequency of the oscillation signal after the frequency conversion unit converts the frequency. The frequency converter is
A direct digital synthesizer that converts an oscillation signal of the vibration device into an oscillation signal having a frequency near a first frequency;
A first filter having a bandpass characteristic in which a frequency in the vicinity of the first frequency is included in a passband, and to which an output signal of the direct digital synthesizer is input;
A mixer for mixing the output signal of the bandpass filter and a reference clock signal of a second frequency;
A frequency near the difference between the first frequency and the second frequency is included in the pass band, and a frequency near the sum of the first frequency and the second frequency is included in the stop band. A second filter to which the output signal of the mixer is input;
The frequency temperature characteristic measurement system for a vibrating device according to claim 6.   The system for measuring frequency temperature characteristics of a vibrating device according to any one of claims 1 to 7, wherein the vibrating device is a crystal oscillator. A method for measuring a frequency temperature characteristic of a vibrating device that oscillates the vibrating device at a plurality of different temperatures and measures a frequency temperature characteristic,
A temperature adjustment step of adjusting the temperature of the vibrating device,
A temperature measuring step for measuring the temperature of the vibrating device;
A frequency measuring step for measuring an oscillation frequency of the vibrating device;
A measurement control step for synchronizing the temperature measurement in the temperature measurement step and the frequency measurement in the frequency measurement step;
Only including,
In the measurement control unit step, the frequency temperature characteristic measurement method of the vibration device is controlled such that the temperature measurement and the frequency measurement are performed in the same measurement time .   A method for measuring a frequency temperature characteristic of a vibrating device that oscillates the vibrating device at a plurality of different temperatures and measures a frequency temperature characteristic,
  A temperature adjusting step for adjusting the temperature of the vibrating device;
  A temperature measuring step for measuring the temperature of the vibrating device;
  A frequency measuring step for measuring an oscillation frequency of the vibrating device;
  A measurement control step for synchronizing the temperature measurement in the temperature measurement step and the frequency measurement in the frequency measurement step;
Including
  Both the measurement time in the temperature measurement step and the measurement time in the frequency measurement step are integer multiples of the period of the AC power source used in the measurement method, and the frequency temperature characteristic measurement method of the vibration device. The method for measuring frequency temperature characteristics of a vibrating device according to claim 9 or 10 , wherein the vibrating device is a crystal oscillator.

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