JP2000323926A - Temperature compensation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To compensate the temperature of a frequency with inexpensive constitution. SOLUTION: A first oscillator 11 generates a first oscillation signal. A second oscillator 12 generates a second oscillation signal whose frequency characteristic differs from that of the first oscillation signal. A deviation generation part 13 receives the first and second oscillation signals, obtains a relative change rate against an environment temperature between the first and second oscillation signals and makes it to be a deviation. A programmable frequency divider 15 frequency-divides the first oscillation signal and separates a clock signal. The temperature characteristic of a first oscillation signal frequency against the environment temperature and a relative change rate are previously set in a memory 16. CPU 15 controls the programmable frequency divider based on the content of the memory when the deviation is received and compensates the temperature of a clock signal frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature compensating device, and more particularly to a device for performing temperature compensation of an oscillation frequency.

[0002]

2. Description of the Related Art In general, a temperature-compensated oscillator (TCXO) may be used for a communication device in order to prevent the oscillation frequency from fluctuating with temperature. In particular, a spread spectrum communication device and a communication device requiring synchronization are sometimes used. In such cases, it is necessary to use a temperature-compensated oscillator that is not easily affected by temperature in order to perform synchronization quickly.

[0003]

However, in general, since a temperature-compensated oscillator is expensive, there is a problem in that a communication apparatus using such a temperature-compensated oscillator itself becomes expensive.

An object of the present invention is to provide an apparatus capable of performing temperature compensation of an oscillation frequency at low cost.

[0005]

According to the present invention, there is provided a temperature compensating device for use in generating a clock signal having a predetermined frequency, and for compensating a fluctuation of the frequency with respect to an environmental temperature. A first oscillator that generates a first oscillation signal; a second oscillator that generates a second oscillation signal having a frequency characteristic different from that of the first oscillation signal;
And a deviation generating means for obtaining a relative change rate with respect to the environmental temperature between the second oscillation signal and the second variation signal to obtain a deviation; Frequency dividing means for generating a signal, and control means for controlling the frequency dividing ratio in accordance with the deviation, wherein the temperature characteristic of the first oscillation signal frequency with respect to the environmental temperature and the relative change rate are set in advance. Thus, a temperature compensating device characterized by the following is obtained.

The deviation generating means includes, for example, a first frequency divider that divides the first oscillation signal at a predetermined frequency division ratio and outputs a first frequency-divided signal; A second frequency-divided signal which is divided at a predetermined frequency-division ratio and outputs a second frequency-divided signal;
And a counter, wherein the first frequency-divided signal is supplied to a count input terminal and the second frequency-divided signal is supplied to a setting gate terminal to output a count signal. Used as deviation.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

Referring to FIG. 1, the illustrated oscillating frequency temperature compensator includes, for example, first and second crystal oscillators 11 and 12 having oscillating frequencies different from each other. The frequency change (depending on temperature) of the crystal oscillator is
It is known that, depending on the direction of the cut, it behaves like a quadratic or cubic function with respect to the temperature.

Referring to FIG. 2, the solid line indicates the temperature characteristic of a few MHz oscillator generally called an AT cut (the horizontal axis indicates temperature, and the vertical axis indicates frequency change rate).
The broken line indicates a tuning-fork type oscillator (kHz
z) shows the temperature characteristic. And in the example shown,
For example, a crystal oscillator having a temperature characteristic shown in FIG. 2 is used. That is, an oscillator having a temperature characteristic shown by a solid line in FIG. 2 is used as the first crystal oscillator 11, and an oscillator having a temperature characteristic shown by a broken line in FIG. 2 is used as the second crystal oscillator 12. Can be

Referring again to FIG. 1, the oscillation frequency / temperature compensator further includes a deviation generator 13, a CPU 14, and a programmable frequency divider 15, and a memory 16 is connected to the CPU 14. The memory 16 stores the temperature characteristics shown in FIG. 2 and the functions shown in FIG. The function shown in FIG. 3 is a function indicating a quotient when the temperature characteristic shown by the solid line is divided by the temperature characteristic shown by the broken line when the crystal oscillator having the temperature characteristic shown in FIG. The vertical axis indicates the relative change.

An example in which a clock signal having a predetermined oscillation frequency (for example, a 1 MHz clock signal) is generated irrespective of a change in environmental temperature will be described. An oscillation clock signal output from the first crystal oscillator 11 is a first oscillation clock signal (for example, 10 MHz),
The oscillation clock signal output from the second crystal oscillator 12 is changed to a second oscillation clock signal (for example, 32 kHz).
z). The first oscillation clock signal is supplied to the programmable frequency divider 15 and to the deviation generator 13. On the other hand, the second oscillation clock signal
Only given to 3. The programmable frequency divider 15
Is divided and output as an output clock signal (for example, the frequency of this output clock signal is 1).
MHz). However, depending on the ambient temperature,
When the frequency of the first oscillation clock signal changes, an output clock signal having a desired frequency cannot be obtained. Therefore, in the illustrated example, the output clock signal having a desired frequency (for example, 1 MHz) is obtained by controlling the frequency division ratio of the programmable frequency divider 15 as follows.

Here, referring also to FIG.
Is provided with first and second frequency dividers 13a and 13b and a counter 13c, and the first oscillation clock signal supplied to the first frequency divider 13a is divided by a predetermined frequency. The frequency is divided by the frequency ratio and output as a first frequency-divided clock signal. Similarly, the second oscillation clock signal is supplied to the second frequency divider 13b, where it is frequency-divided at a predetermined frequency division ratio and output as a second frequency-divided clock signal.

The first divided clock signal is supplied to a counter 13
c is input to a clock input terminal (count input terminal) CIN, and the second divided clock signal is applied to a setting gate terminal GT of the counter 13c. Then, the counter 13c outputs a count signal from the output terminal OUT.
This count signal indicates a value obtained by dividing the first frequency-divided clock signal by the second frequency-divided clock signal, and this value changes according to a temperature change. That is, the count signal indicates a frequency deviation (relative rate of change) corresponding to the temperature.

The count signal from the counter 13c is C
PU14. The CPU 14 reads the function shown in FIG. 3 from the memory 16 and knows the temperature at that time as the environmental temperature from the frequency deviation (relative rate of change) indicated by the count signal. Next, the CPU 14 reads the temperature characteristic indicated by the solid line in FIG. 2 from the memory 16 and obtains the frequency change rate from the ambient temperature. Then, the CPU 14 controls the frequency division ratio of the programmable frequency divider 15 according to the frequency change rate to generate an output clock signal having a desired frequency.

As described above, the pair of oscillators is used to compensate for the oscillation frequency of one of the oscillators based on the relative change of these oscillators with respect to the environmental temperature. The temperature compensation of the oscillation frequency can be easily performed only by using the oscillator.

As shown by a broken line in FIG. 1, a comparator 17 is connected to the output of the programmable frequency divider 15 to compare a signal received from the outside with an output clock signal, and to output the signal in accordance with the deviation. The frequency of the clock signal may be further controlled. That is, for example, a GPS signal is given to the comparator 17, and the comparator 17 compares the GPS signal with the output clock signal to obtain a deviation thereof.
This deviation is fed back to the CPU 14 and the CP
In U14, according to this deviation, the programmable frequency divider 15
Is controlled so that the deviation output from the comparator 17 becomes zero.

[0017]

As described above, in the present invention, two oscillators having different frequency characteristics are used, and the oscillation frequency of one of the oscillators is changed based on the relative change of these oscillators with respect to the ambient temperature. Because we actually compensated,
That is, there is an effect that temperature compensation of the oscillation frequency can be easily performed only by using two oscillators.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of an oscillation frequency temperature compensator according to the present invention.

FIG. 2 is a diagram showing an example of a temperature characteristic of an oscillator used in FIG.

FIG. 3 is a diagram showing a relationship between temperature and a relative rate of change of frequency in the oscillator having the temperature characteristics shown in FIG. 2;

FIG. 4 is a block diagram illustrating an example of a deviation generator illustrated in FIG. 1;

[Explanation of symbols]

 11, 12 Oscillator 13 Deviation generator 14 CPU 15 Programmable frequency divider 16 Memory 17 Comparator

Claims (3)

[Claims] 1. A temperature compensating device used for generating a clock signal having a predetermined frequency, for compensating a fluctuation of the frequency with respect to an environmental temperature, wherein the first compensating device generates a first oscillation signal. A second oscillator that generates a second oscillation signal having a frequency characteristic different from that of the first oscillation signal, and a relative to the environmental temperature between the first and second oscillation signals. Deviation generating means for obtaining a target change rate and obtaining a deviation; frequency dividing means for generating a clock signal by dividing a frequency of the first oscillation signal with a variable frequency division ratio; A temperature compensating device comprising: a temperature characteristic of a frequency with respect to an environmental temperature; and a control unit that sets the relative change rate and controls the frequency division ratio according to the deviation. 2. The temperature compensating device according to claim 1, wherein said deviation generating means divides said first oscillation signal by a predetermined dividing ratio and outputs a first divided signal. A first frequency divider; a second frequency divider that divides the second oscillation signal by a predetermined frequency division ratio to output a second frequency-divided signal; and a first frequency-divided signal. A counter which is supplied to a count input terminal and the second frequency-divided signal is supplied to a setting gate terminal and outputs a count signal, wherein the count signal is used as the deviation. Compensator. 3. The temperature compensator according to claim 1, wherein said frequency divider is a programmable frequency divider.