JPH07321644A - Method for updating temperature versus frequency characteristic data for oscillator - Google Patents

Abstract

PURPOSE:To compensate secular change in an oscillation frequency from a crystal oscillator digitally. CONSTITUTION:Oscillation frequency signal from a crystal oscillator 10 is counted by a frequency counter 26 based on a clock from a satellite positioning device 12 and obtained frequency data are stored in an EEPROM 24 together with temperature data obtained by a temperature sensor 28. The temperature versus frequency characteristic of the crystal oscillator 10 is obtained based on data stored in the EEPROM 24 and the temperature versus frequency characteristic having been stored in the EEPROM 24 as a table are updated by new temperature versus frequency characteristic data prior to shipment. Since the new temperature versus frequency characteristic data reflects on the secular change in the oscillated frequency signal from the crystal oscillator 10, a system reference frequency obtained by a PLL 14 is controlled accurately to an object frequency independently of secular change by setting a frequency division ratio of a frequency divider 22 based on the temperature versus frequency characteristic data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oscillator such as a crystal oscillator whose oscillation frequency changes with temperature and with time, and more particularly to a temperature-frequency characteristic data updating method.

[0002]

2. Description of the Related Art An oscillator such as a crystal oscillator has a characteristic that its oscillation frequency changes with temperature. Therefore,
In a configuration in which a crystal oscillator or the like is used as a reference oscillator and the output of the reference oscillator is supplied to a PLL or the like to obtain the required frequency from the PLL, the temperature-frequency characteristics of the reference oscillator are stored in advance as data, and A configuration (digital temperature compensation of oscillation frequency) for controlling the PLL output to a required frequency by controlling the frequency division ratio in the PLL based on the data is adopted.

[0003]

However, even if the digital temperature compensation of the oscillation frequency is carried out by such a method, it is not possible to cope with the change with time.
That is, since an oscillator such as a crystal oscillator has a characteristic that its oscillation frequency changes with time, the required frequency may not be obtained even if temperature compensation is performed by the above-described method.

The present invention has been made to solve the above problems, and it is an object of the present invention to always obtain a necessary frequency in response to both temperature change and time change. To aim.

[0005]

In order to achieve such an object, the present invention provides temperature-frequency characteristic data of an oscillator whose oscillation frequency changes with temperature and changes with time prior to shipment or start of use. Data is written in a rewritable non-volatile memory, and data related to the oscillation frequency and temperature of the oscillator is collected for a predetermined time after shipment, after starting use, or after a lapse of a predetermined period from the last update, and the collected data Based on the above, new temperature-frequency characteristic data is generated, and the temperature-frequency characteristic data on the nonvolatile memory is updated with the generated new temperature-frequency characteristic data.

Further, according to the present invention, when collecting data concerning the oscillation frequency and temperature of the oscillator, data concerning the collection time of these data are also collected, and the data concerning the oscillation frequency among the collected data are collected for each temperature. Generate a new temperature-frequency characteristic data based on the collected data by calculating the representative value of the oscillation frequency at each temperature by performing the weighted average calculation based on the collection time and applying the curve of the predetermined order to the calculated representative value. It is characterized by doing.

Furthermore, the present invention is characterized in that data relating to the oscillation frequency of the oscillator is collected with reference to the time data obtained by the satellite positioning device.

The present invention is characterized in that the time data obtained by the satellite positioning device is collected as data relating to the collection time.

[0009]

In the present invention, first, the temperature-frequency characteristic data of the oscillator is written in the non-volatile memory before the shipment or the start of use of the oscillator. Therefore, while the oscillation frequency of the oscillator does not change significantly with time, the required frequency can be obtained by controlling the frequency division ratio of the PLL using the temperature-frequency characteristic data written in the nonvolatile memory. . When a certain amount of time has passed since the shipment or use of the oscillator, a change in the oscillation frequency with the passage of this time, that is, a change in the oscillation frequency with time begins to become apparent. In the present invention, data relating to the oscillation frequency and temperature of the oscillator is collected after shipment of the oscillator or after the start of use of the oscillator, and new temperature vs. frequency characteristic data is generated based on the collected data. The temperature-frequency characteristic data on the non-volatile memory is updated by the frequency characteristic data. Therefore, after such an update is performed, the change over time of the oscillation frequency of the oscillator becomes PL.
Since it is reflected in the control of the frequency division ratio of L, etc., it becomes possible to obtain the required frequency regardless of the change over time of the oscillation frequency of the oscillator. Further, the collection of data on the oscillation frequency and the temperature, the generation of new temperature-frequency characteristic data, and the operation of updating the temperature-frequency characteristic data by this are automatically executed every predetermined period, which impairs usability. The above-mentioned change with time is realized without any trouble.

Further, in the present invention, generation of new temperature-frequency characteristic data is realized by curve fitting. That is, for the data relating to the oscillation frequency of the collected data, the weighted average calculation is performed for each temperature at the frequency time, and the representative value of the oscillation frequency at each temperature is obtained. New temperature-frequency characteristic data can be obtained by fitting a curve of a predetermined order representing the temperature-frequency characteristic of the oscillator, such as a cubic curve, to the representative value obtained for each temperature. The data regarding the collection time is
It may be collected at the same time as the data on the oscillation frequency and temperature of the oscillator. With such a method, generation of the above-mentioned new temperature-frequency characteristic data is suitably realized.

Further, in the present invention, the data regarding the oscillation frequency of the oscillator is collected with reference to the time data obtained by the satellite positioning device. Further, in the present invention, the time data obtained by the satellite positioning device is collected as the data regarding the collection time. Since the time data obtained by the satellite positioning device has high accuracy, accurate frequency compensation with respect to changes over time can be realized by generating and updating the temperature-frequency characteristic data using the time data.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the structure of an apparatus according to an embodiment of the present invention. The device shown in this figure is a circuit that causes the PLL 14 to generate a reference frequency of a certain system with the oscillation frequency of the crystal oscillator 10 as a reference. Calibration can be done.

That is, the oscillation output of the crystal oscillator 10 is
It is input as a reference frequency to the phase comparator 16 that constitutes the PLL 14. The PLL 14 is composed of a phase comparator 16, a loop filter 18, a VCO 20 and a frequency divider 22. The oscillation output of the crystal oscillator 10 input to the phase comparator 16 is phase-compared with the frequency-divided output of the frequency divider 22, and the resulting signal is smoothed by the loop filter 18. The signal smoothed by the loop filter 18 and having the high frequency component removed is supplied to the VCO 20. VCO
20 oscillates at a frequency according to the voltage value of the signal output from the loop filter 18, and the resulting frequency can be used as the accurate reference frequency of the system. The frequency divider 22 divides the oscillation output of the VCO 20, that is, the generated system reference frequency, and the phase comparator 1
Supply to 6.

The oscillation frequency of the crystal oscillator 10 changes depending on the ambient temperature, as is conventionally known. In this embodiment, the EEP is performed prior to shipment or start of use.
The temperature-frequency characteristics of the crystal oscillator 10 are written in advance on the ROM 24. That is, the characteristics shown by the solid line in FIG.
It is written on the ROM 24. In measuring this characteristic, the oscillation output of the crystal oscillator 10 is counted by the frequency counter 26, the ambient temperature of the crystal oscillator 10 is measured by the temperature sensor 28, and the CPU 30 writes the result in the EEPROM 24.

The CPU 30 determines the frequency divider 2 based on the temperature-frequency characteristic data written in the EEPROM 24.
Control the division ratio of 2. For example, it is assumed that the target frequency of the system reference frequency is 12.8 MHz, and temperature-frequency characteristic data of the crystal oscillator 10 of 10 MHz at 0 ° C. and 10.01 MHz at 70 ° C. is tabulated and written on the EEPROM 24. . In this case, CPU3
0 is 70 even if the ambient temperature of the crystal oscillator 10 is 0 ° C.
Set the frequency division ratio of the frequency divider so that the system reference frequency is 12.8 MHz even in the case of ° C. That is, when the temperature is 0 ° C., the frequency division ratio of the frequency divider 22 is 12.8 / 10 = 1.28.
In the case of 70 ° C., 12.8 / 10.01 = 1.2
787213. In order to realize such control, the frequency divider 22 is capable of dividing the decimal point.

Even if the temperature characteristic of the oscillation frequency of the crystal oscillator 10 is compensated by such a configuration, the influence of the change over time still remains. That is, the oscillation frequency of the crystal oscillator 10 changes not only with changes in the ambient temperature but also with the passage of time. Therefore, in this embodiment, the EEPROM 2
The device is configured so that the temperature-frequency characteristic data on 4 is updated at a predetermined frequency.

That is, the CPU 30 collects the oscillation frequency of the crystal oscillator 10 counted by the frequency counter 26 together with the output of the temperature sensor 28 as oscillation frequency and temperature data, and stores it in the EEPROM 24 together with the collection time as a temporary file. that time,
An accurate clock obtained by the satellite positioning device 12 is used as the reference of the counting timing in the frequency counter 26, and the satellite positioning device 1 is also used as the collection time stored in the temporary file on the EEPROM 24.
The time data (clock) obtained by 2 is used. Since the time data obtained by the satellite positioning device 12 is accurate, with such a configuration, the collection time of the oscillation frequency data and the temperature data can be made highly accurate.

The CPU 30 collects the oscillation frequency data, the temperature data, and the data relating to the collection time thereof in the temporary file for a predetermined time after the shipment or use of the device shown in FIG. CPU30 after collecting
The collected oscillation frequency data is grouped for each temperature, weighted by the collection time, and then the average value of the oscillation frequency is obtained. That is, the oscillation frequency data as indicated by the black circles in FIG. 2 are weighted and averaged according to the collection time, and a representative value as indicated by the cross in the figure is obtained for each temperature. The temperature step for grouping the oscillation frequencies may be about 20 ° C.

The CPU 30 executes curve fitting for the representative value thus obtained. That is, since the temperature-frequency characteristics of the crystal oscillator 10 are considered to be approximated by a cubic curve, a cubic curve that approximates the representative value for each temperature obtained by the weighted average described above is obtained by curve fitting. The CPU 30 tabulates the curve thus obtained, that is, the curve indicated by the broken line in FIG. 2, and writes it in the EEPROM 24 as the temperature-frequency characteristic after time change. That is, the EEPROM
Update the temperature versus frequency characteristic data on 24.

Therefore, according to the present embodiment, the crystal oscillator 1
Even when the oscillation frequency of 0 changes with time, the influence of this change with time is reflected in the temperature-frequency characteristic data on the EEPROM 24. Therefore, as a result of the frequency division ratio control of the frequency divider 22 by the CPU 30, the system reference frequency is obtained. Is a target frequency, for example, 12.8 MHz. Also, EEPRO
If the update time of the temperature-frequency characteristic data is also written on the M24 and the next update is performed according to the lapse of a predetermined time from this update time, the update process of the temperature-characteristic data is always automatically performed. Since it is performed, not only the temperature compensation but also the change with time can be dealt with without impairing the convenience of the user.

The period for collecting the data regarding the oscillation frequency of the crystal oscillator 10 and the data regarding the ambient temperature may be, for example, about four months. That is, the period may be such that the deviation of the oscillation frequency of the crystal oscillator 10 changes linearly with respect to the elapsed time. Further, if the new temperature-frequency characteristic data obtained by curve fitting does not fall within a proper value, the temperature-frequency characteristic data on the EEPROM 24 may not be updated.

[0023]

As described above, according to the present invention,
After shipment, after the start of use or after the lapse of a predetermined period from the start of the previous update, data concerning the oscillation frequency and temperature of the oscillator is collected, and based on the collected data, new temperature-frequency characteristic data is generated and nonvolatile. Since the temperature-frequency characteristic data on the non-volatile memory is updated, when the oscillation frequency of the oscillator is digitally compensated using the temperature-frequency characteristic data on the non-volatile memory, the oscillation frequency changes with temperature and changes with time. Can be reflected together, and the required frequency can always be obtained regardless of temperature changes and changes over time.

Further, according to the present invention, the representative value of the data related to the oscillation frequency of the collected data is obtained by the weighted average calculation regarding the collection time, and the curve fitting is performed by the obtained representative value. It is possible to preferably obtain new temperature-frequency characteristic data.

Further, according to the present invention, since the satellite positioning device that generally obtains highly accurate time data is used to execute the collecting process of various data, new temperature-frequency characteristic data relating to the update is obtained. The data can be highly accurate.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing the contents of temperature versus frequency characteristic data of a crystal oscillator stored on an EEPROM in this embodiment.

[Explanation of symbols]

 10 Crystal Oscillator 12 Satellite Positioning Device 14 PLL 24 EEPROM 26 Frequency Counter 28 Temperature Sensor 30 CPU

Claims (4)

[Claims] 1. The temperature-frequency characteristic data of an oscillator whose oscillation frequency changes with temperature and changes with time is written in a rewritable nonvolatile memory prior to shipment or start of use, and the product is used after shipment. Data on the oscillation frequency and temperature of the oscillator is collected over a specified time after the start or after a specified period has elapsed since the previous update, new temperature-frequency characteristic data is generated based on the collected data, and the generated new temperature A temperature-frequency characteristic data updating method characterized by updating the temperature-frequency characteristic data on the nonvolatile memory with the frequency-characteristic data. 2. The temperature-frequency characteristic data updating method according to claim 1, wherein when collecting data relating to the oscillation frequency and temperature of the oscillator, the data relating to the collection time of these data are also collected, and the collected data. Of the data related to the oscillation frequency, a weighted average calculation is performed for each temperature based on the collection time to obtain a representative value of the oscillation frequency at each temperature, and a curve of a predetermined order is applied to the obtained representative value, based on the collected data. A method for updating temperature-frequency characteristic data, characterized in that the new temperature-frequency characteristic data is generated. 3. The temperature-frequency characteristic data updating method according to claim 1, wherein data relating to the oscillation frequency of the oscillator is collected with reference to time data obtained by the satellite positioning device. Data update method. 4. The temperature-frequency characteristic data updating method according to claim 2, wherein the time data obtained by the satellite positioning device is collected as data relating to the collection time. .