JPH10256831A - Digital temperature compensation type crystal oscillator and its temperature compensation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use efficiently a memory cell by minimizing points of temperature compensation data. SOLUTION: The crystal oscillator is provided with a D/A converter 4 that divides temperature fluctuation data from a voltage controlled oscillator 5 to be measured or each prescribed frequency deviation and stores the temperature at that time, measures the ambient temperature of the voltage controlled oscillator 5 and generates the control voltage of the voltage controlled oscillator 5 based on the result, and a CPU 7 that predicts and calculates the data in the D/A converter 4 based on the value stored in a memory 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital temperature-compensated crystal oscillating device for digitally compensating for temperature and a method for temperature compensation thereof. It belongs to the temperature compensation method.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing a conventional digital temperature-compensated crystal oscillation device. Referring to FIG. 3, a conventional crystal oscillation device includes a temperature-voltage converter 1 that obtains temperature information as a voltage, an A / D converter 2 that converts the voltage of the temperature-voltage converter 1 into 0/1 data, and 1 data. 3 for storing the temperature correction data with the address as an address, a D / A converter 4 for converting the temperature correction data of the memory 3 into a control voltage, and a VCXO for applying as a control voltage and outputting 6
(Voltage-controlled oscillator) 5.

The temperature correction data is obtained by previously measuring the oscillation frequency-temperature characteristic in an uncompensated state, and having a control voltage as a digital value for each temperature point at a constant interval so as to make the frequency fluctuation value zero. The temperature correction data is generated by the D / A converter 4 and applied to the control voltage of the corresponding oscillating device to correct the oscillating frequency (for example, see Japanese Patent Application Laid-Open No. 1-198807).

[0004]

The above-mentioned conventional crystal oscillation device has a problem in that it is necessary to set temperature points at regular intervals and have the temperature correction data regardless of the magnitude of the temperature correction data value. is there.

The reason is that by increasing the number of correction data points, it is possible to perform fine frequency correction,
There is a problem that the capacity of the memory 3 for holding the correction data increases.

That is, assuming that the number of bits (bits) of the D / A converter 4 is 8 bits, if the number of temperature points is doubled in order to obtain correction data finely, the total memory capacity becomes 2 × 8 = 16, and 16 And the number of memory cells becomes 16 times, which leads to a large increase in chip area.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to reduce the increase in the memory capacity for digital temperature correction by setting a temperature interval at which the correction data difference is made substantially constant without performing a method of having a correction value at a constant temperature interval. It is an object of the present invention to provide a digital temperature-compensated crystal oscillation device that determines a temperature and corrects the temperature at each optimum temperature interval, and a method of compensating the temperature.

[0008]

According to the present invention, there is provided a temperature / voltage converter, an A / D converter for obtaining temperature information as a voltage by the temperature / voltage converter, and an A / D converter for converting the voltage to 0 / D by the A / D converter. A memory for converting the temperature correction data into a control voltage, a memory for storing the temperature correction data using the 0/1 data as an address, and a D / A converter;
A voltage-controlled oscillator for applying the control voltage;
A digital temperature-compensated crystal oscillation device characterized by having a CPU for predicting and calculating the data of the A converter from the value stored in the memory.

Further, according to the present invention, temperature information is obtained as a voltage by a temperature-voltage converter, the voltage is converted to 0/1 data by an A / D converter, and the 0/1 data is used as an address for temperature correction in a memory. Storing the data, converting the temperature data into a control voltage using a D / A converter,
In a temperature compensation method for a crystal oscillator that applies this voltage as a control voltage of a voltage-controlled oscillator, a voltage address where a deviation of a correction data value is constant is determined, and a memory area for storing temperature data is allocated for each address. A temperature compensation method for a digital temperature-compensated crystal oscillation device characterized by performing temperature compensation is obtained.

Further, according to the present invention, the temperature fluctuation data of the voltage controlled oscillator to be measured in advance is separated for each fixed frequency deviation, the temperature at that time is stored, and the ambient temperature where the voltage controlled oscillator is placed is measured. The control voltage of the voltage controlled oscillator is generated by the D / A converter based on the result, and the data of the D / A converter is predicted and calculated by the CPU from the value stored in the memory. The temperature compensation method of the digital temperature compensation type crystal oscillation device described above is obtained.

[0011]

The digital temperature-compensated crystal oscillation device of the present invention,
In the temperature compensation method, first, a frequency variation value is measured at constant temperature intervals, and a temperature at which the variation (inclination value) becomes a constant value is obtained. Then, when actually performing the temperature correction, the correction is performed for each temperature measured in advance.

That is, in order to reduce the increase in the memory requirements, the correction value is not set to 0 at a constant temperature interval, but the temperature fluctuation data of the VCXO to be measured is divided in advance for each constant frequency deviation and the temperature at that time is stored. The ambient temperature where the VCXO is placed is measured, and a control voltage of the VCXO is generated by a D / A converter based on the result. The data of the D / A converter is predicted and calculated on the CPU side from the value stored in the memory described above.

The compensation between the (temperature) points at which the correction values are measured may be estimated by various calculations based on the values at the two points. In addition, as a general method, a linear approximation method, a least square method, or the like can be considered.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A digital temperature-compensated crystal oscillator of the present invention and a method for compensating the temperature will be described in detail with reference to the drawings. FIG. 1 shows an embodiment of a digital temperature compensated crystal oscillation device according to the present invention.

Referring to FIG. 1, a crystal oscillator includes a temperature-voltage converter 1 for obtaining temperature information as a voltage, and an A / D converter 2 for converting the voltage of this temperature-voltage converter 1 into 0/1 data.
A memory 3 for storing temperature correction data with one data as an address, and a memory 3 with one data as an address
A D / A converter 4 for converting the temperature correction data into a control voltage, a VCXO (voltage controlled oscillator) 5 for applying a voltage as a control voltage,
And a CPU for predictively calculating the data of the / A converter 4 from the value stored in the memory 3.

In this crystal oscillator, a voltage address at which the deviation of the correction data value is constant is determined, a memory area for storing temperature data is allocated for each address, and temperature compensation is performed. The data of the D / A converter is predicted and calculated by the CPU 7 based on the value stored in the memory 3.

The temperature compensation method of the digital temperature compensation type crystal oscillation device will be described below. The output 6 of the temperature-voltage converter 1 is applied to the A / D converter 2 and converted into 1/0 digital data. This data is applied to the CPU 7.

On the other hand, address data is added to the D / A converter 4 from the output of the CPU 7. The output of the D / A converter 4 is applied to a voltage controlled oscillator 5. CPU
7 is provided with a memory 3 and is used for storing and storing temperature compensation data.

Here, the temperature-frequency variation of the VCXO 5 is measured in advance. FIG. 2 shows a characteristic example. In FIG. 2, the vertical axis represents the frequency fluctuation temperature ΔF, and the horizontal axis represents the temperature. In the present invention, the temperature at which the frequency variation ΔF is obtained is determined in advance.

The CPU 7 first observes the current temperature, measures a temperature fluctuation value corresponding to the temperature from FIG. 2, generates correction data, and passes the output to a D / A converter.

Here, t ₁ , t ₂ , t ₃ , and t ₁ shown in FIG.
If the current temperature falls between... And the measured point, linear approximation is performed in this case to determine a correction value.

As described above, in the temperature compensation method for the crystal oscillation device, the temperature fluctuation data of the VCXO 5 to be measured in advance is separated for each fixed frequency deviation and the temperature at that time is stored.

Then, the ambient temperature where the VCXO5 is placed is measured, and the control voltage of the VCXO5 is set to D / O based on the result.
Generated by the A converter 4. The data of the D / A converter 4 is obtained from the value stored in the memory 3 by the CPU 7.
Calculate the prediction on the side.

[0024]

As described above, according to the digital temperature compensation type crystal oscillation device and the temperature compensation method thereof, according to the embodiment, the voltage address at which the deviation of the correction data value is constant is obtained, and the address is obtained. Since a memory area for accumulating temperature data is allocated every time and temperature compensation is performed, as a first effect, the storage amount of correction data is reduced, and as a result, the internal memory capacity is significantly reduced.

As a second effect, considering the condition of the same memory capacity, since the memory can be used efficiently, the accuracy of frequency correction can be improved even with the same memory capacity.

Therefore, the points of the temperature compensation data can be minimized, and the memory cell can be used efficiently.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a digital temperature compensated crystal oscillation device according to the present invention.

FIG. 2 shows V of the crystal oscillation device of FIG. 1 in a state without temperature correction.
It is a graph which shows the example of a temperature characteristic of CXO.

FIG. 3 is a block diagram showing a conventional digital temperature compensated crystal oscillation device.

[Description of Signs] 1 Temperature / voltage converter 2 A / D converter 3 Memory 4 D / A converter 5 Voltage controlled oscillator (VCXO) 6 Output 7 CPU

Claims (3)

[Claims] 1. A temperature / voltage converter, an A / D converter for obtaining temperature information as a voltage by the temperature / voltage converter, and converting the voltage into 0/1 data by the A / D converter, and converting the 0/1 data into A memory for storing temperature correction data as an address, a D / A converter for converting the temperature correction data to a control voltage, a voltage controlled oscillator for applying the control voltage, and data for the D / A converter stored in the memory A digital temperature-compensated crystal oscillation device, comprising: a CPU for performing a prediction calculation from a stored value. 2. Temperature information is obtained as a voltage by a temperature-voltage converter, the voltage is converted into 0/1 data by an A / D converter, and the temperature correction data is stored in a memory using the 0/1 data as an address. In a temperature compensation method for a crystal oscillation device in which temperature data is converted into a control voltage using a D / A converter and this voltage is applied as a control voltage of a voltage controlled oscillator, a voltage address at which a deviation of a correction data value is constant is determined. A temperature compensating method for a digital temperature-compensated crystal oscillation device, comprising: allocating a memory area for accumulating temperature data for each address and performing temperature compensation. 3. The temperature compensation method for a digital temperature compensation type crystal oscillation device according to claim 2, wherein temperature fluctuation data of said voltage controlled oscillator to be measured in advance is separated for each constant frequency deviation, and the temperature at that time is stored. The ambient temperature where the voltage controlled oscillator is placed is measured, and based on the result, the control voltage of the voltage controlled oscillator is generated by the D / A converter, and the data of the D / A converter is stored in the memory. A temperature compensation method for a digital temperature compensation type crystal oscillation device, wherein a prediction calculation is performed by a CPU based on a value obtained.