JPH1141032A - Temperature controller for crystal oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the frequency precision by forming a shape which comes into contact with the external wall of a casing, sticking a temperature sensor and a heater on the external surface, and adjusting heating value so that the deviation of the temperature sensor from the set value of the crystal oscillator is zero. SOLUTION: A temperature control member 1 is in contact with the casing of the crystal vibrator 10, and the both are at the same temperature. The measured value of the temperature sensor 3 is inputted as a signal 4 to a heater controller 6 and a current 7 is supplied so as to eliminate the deviation of the measured value of the temperature sensor 3 from the temperature set value, thereby controlling the heating value of an electric heater 5. The temperature sets value is set to, for example, 60 deg.C and the heater controller 6 increases or decreases the output of the heater 5 to control the temperature of the temperature control member 1 to target temperature. Consequently, even when the ambient temperature varies, the temperature of the casing of the crystal oscillator 10 is held constant. A high vacuum is produced in the crystal oscillator and the external surface temperature of the casing is controlled to maintain sufficient precision.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature control device for a crystal oscillator.

[0002]

2. Description of the Related Art A quartz oscillator is a kind of a piezoelectric oscillator made of a plate or a bar-shaped quartz piece cut out from a crystal of a crystal in a certain direction. It is an electronic component that is taken out as a stable electric vibration through. The resonance phenomenon appears as an electrical resonance phenomenon using the piezoelectricity of the quartz plate from the mechanical resonance phenomenon of the quartz plate.

A crystal oscillator using this crystal oscillator in a resonance circuit generates electric vibration of a constant frequency with high accuracy by utilizing elastic resonance. The oscillation frequency is close to the natural frequency of the crystal unit, and a device having a frequency of 1 kHz to 100 MHz can be manufactured. Such a crystal oscillator (signal generation circuit) is used as a high-frequency main oscillator for various communications and broadcasting in almost all electronic circuits. The reason why the crystal oscillator is widely used as a frequency standard is that the frequency-temperature characteristics are superior to other electronic components. The most important items in such an oscillation circuit are the range of the oscillation frequency and the accuracy of the frequency fluctuation.

Conventionally, several temperature correction techniques have been considered. However, in an era when the operating frequency band has a margin and the operating temperature range is narrow, the frequency fluctuation caused by a temperature change is about several ppm. Even if the changes were ignored, most of them had no practical problems. In recent years, the use of mobile communication and the like has increased dramatically, and the frequency band used has become narrower.
In addition, as the operating temperature range of the devices has expanded, the allowable range of the deviation (change) of the frequency of the crystal oscillator has been reduced. On the other hand, with the rapid expansion of the market for portable telephones (PHS) and the like, an inexpensive and reliable technique for compensating for the temperature characteristics of a crystal oscillator is required.

The method of stabilizing the frequency of a crystal oscillator basically involves correcting the temperature characteristics of the crystal oscillator. In general, the temperature characteristic of quartz has a cubic curve characteristic as shown by a curve 31 in FIG. 4, and there is a difference in the temperature characteristic in the cutting direction in the crystal axis direction of the crystal. Temperature characteristics themselves cannot be eliminated. Therefore, the following means is used to prevent the frequency of the crystal oscillator from changing due to the temperature.

(A) A technique for keeping a crystal oscillator at a constant temperature using an oven (OVEN). In the case of a transmitter or the like that requires a particularly stable frequency, the crystal oscillator is placed in a constant temperature bath heated to a constant temperature of about 60 ° C., and the temperature is kept constant, and the characteristic change due to the temperature change is made zero. . This technology is
CXO (Oven Control CrystalO)
This is referred to as a “scilator”. Such a technology has been developed in various ways, for example, Japanese Patent Application Laid-Open No. 7-50523, and is ideal for high-grade applications. Has the disadvantage of being very expensive.

(B) A technique of forming a series and parallel resonance circuit and forming a compensation circuit having a tendency opposite to the temperature characteristic of the crystal oscillator to cancel a frequency change due to temperature. For example, a compensation circuit having a characteristic opposite to that of the curve 31 such as a curve 32 shown in FIG. 4 is added to cancel the frequency change. In response to this, a compensation network using NTC thermistors (or capacitors) and resistors has been developed.
XO (Temperature Compensate)
It is called a “Crystal Oscillator” circuit. The price of this TCXO circuit is about several hundred yen.
-10 ° C to +60 for expensive products upgraded from TCXO
Products with a frequency change rate of 1 ppm or less at ° C. are on the market, but their cost performance is not sufficient.

[0008]

The temperature characteristics of the conventional crystal oscillation circuit are such that the frequency change rate ppm in a temperature range of -10.degree. C. to + 60.degree. C. is substantially as shown in Table 1.

[0009]

[Table 1]

[0010] The present invention provides an inexpensive crystal oscillator which can provide sufficient reliability to a mobile communication device or the like without using an expensive device such as a thermostat and having less frequency variation due to temperature than before. It is an object of the present invention to provide a temperature control device.

[0011]

SUMMARY OF THE INVENTION The present invention relates to a technique for preventing a characteristic change of a crystal oscillator due to a temperature, and basically belongs to a technique for keeping a temperature constant. The technical means includes a temperature adjusting member having a shape which is fitted to and adheres to the outer wall of the casing of the crystal oscillator, a temperature sensor and an electric heater are adhered to the outer surface, and a temperature adjusting member comprising a plate of a good conductor of heat; A temperature control device for controlling the amount of heating of the electric heater so as to make the deviation between the temperature set value of the temperature sensor and the measurement value of the temperature sensor zero. It is.

In the present invention, a simple and inexpensive temperature adjusting member that is in close contact with the crystal oscillator casing is used, and a heater and a temperature sensor are directly attached to the temperature adjusting member to maintain the temperature of the crystal oscillator casing at a constant temperature. Without use, desired frequency accuracy and stability against temperature changes were obtained. For the temperature adjusting member, a material having high thermal conductivity such as copper, aluminum, or an alloy thereof is used. A steel plate or a stainless steel plate may be used. This temperature adjusting member is easily formed by forming a U-shaped or cylindrical cap having an inner surface profile substantially equal to the outer surface of the crystal oscillator casing, applying silicon oil or the like to the inner surface, and covering the inner surface with the crystal oscillator casing. Adhered and hardly any temperature difference between them.

It is preferable that the temperature control member is provided with a heat insulating cover that covers the entire outer surface thereof in a dense manner, so that it is easier to keep the temperature constant. Furthermore, the temperature control device of the recommended oscillator according to the present invention has a less influence of heat radiation from legs than a substrate having a through-hole on a substrate of a type in which the crystal oscillator is formed on a substrate, and has a frequency fluctuation. This has the effect of being smaller.

A particularly effective effect is obtained when the temperature characteristic of the crystal oscillator has a curve having an inflection point near the oven control temperature.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of an embodiment, FIG. 2 is a sectional view of an embodiment, and FIG. 3 is a sectional view of another embodiment. The temperature control device for a crystal oscillator according to the present invention includes a temperature control member 1 and a heater control device 6. The temperature control member 1
It is composed of a good heat conductor 2 formed like a U-shaped or cylindrical cap that fits and adheres to the casing of the crystal resonator 10, and a temperature sensor 3 and an electric heater 5 attached to the outer surface thereof. is there. The temperature sensor 3 is attached using an epoxy resin or the like. Using a thermistor as the temperature sensor 3,
A power transistor was used for the electric heater 5. The electric heater 5 is similarly adhered with an epoxy resin or the like. Note that the electric heater 5 and the temperature sensor 3 can be integrally mounted.

The temperature adjusting member 1 is in close contact with the casing of the crystal oscillator 10, and both are at the same temperature. The measured value of the temperature sensor 3 is input to the heater control device 6 as a signal 4, and the heater control device 6 supplies a current 7 so as to make the deviation between the temperature set value and the measured value of the temperature sensor 3 zero,
The heating amount of the electric heater 5 is operated. The temperature set value is set to, for example, 60 ° C., and the heater control device 6 increases or decreases the output of the electric heater 5 so that the temperature of the temperature adjusting member 1 matches the target temperature (set value of 60 ° C.). As a result, the temperature of the casing of the crystal oscillator 10 is kept constant even when the ambient temperature changes. The inside of the crystal oscillator 10 is under a high vacuum, and by maintaining the outer surface temperature of the casing as described above, it is possible to achieve sufficient precision characteristic retention. The power supply supplies power inputs 21 and 22 to the heater control device 6 and the oscillating circuit 20, the crystal oscillator 10 supplies an output 23 of a constant frequency to the oscillating circuit 20, and the oscillating circuit 20 outputs an oscillation frequency output 24. 1 and 2, the temperature of the crystal oscillator can be maintained at a constant temperature, and a highly accurate output 24 can be obtained.

FIG. 3 shows another embodiment of the present invention, which is provided with a heat insulating cover 8 which covers the entire outer surface of the temperature control member 1 closely, so that it is less affected by the surrounding environment (disturbance).
It is hardly affected by fluctuations in the environmental temperature, and it is easy to precisely maintain a constant temperature. 2 and 3, the crystal oscillator 10 has the legs 12 mounted on a single-sided mounting substrate 11 and is electrically isolated from the bottom surface of the substrate 11 by an insulating plate. The electric insulating plate has a large heat insulating property, is less affected by the heat radiation from the legs 12, has a smaller frequency variation, and is more effective than a substrate having a through hole.

Next, the operation and effect will be further described with reference to specific examples of the embodiment of the present invention. The crystal oscillator of the example was placed in a test thermostat, and the temperature of the test thermostat was set to -10 ° C to +
When the temperature was changed between 60 ° C. and the frequency change rate (ppm / 10 MHz) of the crystal resonator of the example was actually measured, the result shown in FIG. 5 was obtained. As is clear from FIG. 5, the frequency change rate was within ± 0.2 ppm in the example.

[0019]

According to the present invention, a simple and inexpensive structure in which a temperature sensor and an electric heater are adhered to the outer surface of a temperature adjusting member which is fitted to and adheres to the outer wall of the casing, has a temperature of -10.degree.
It is possible to improve the frequency fluctuation at 0 ° C. to 0.1 to 0.2 ppm, and to obtain a crystal oscillator that satisfies the frequency accuracy for mobile communication and other purposes.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment.

FIG. 2 is an operation explanatory view of the embodiment.

FIG. 3 is a cross-sectional view of the temperature control device according to the embodiment.

FIG. 4 is a schematic graph showing an example of a frequency change rate according to a temperature of a crystal oscillator.

FIG. 5 is a graph showing an actually measured value of a frequency change rate depending on the temperature of the crystal oscillator of the example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Temperature control member 2 Good conductor of heat 3 Temperature sensor 4 Signal 5 Electric heater 6 Heater control device 7 Current 8 Insulation coating 10 Crystal oscillator 11 Substrate 12 Leg 20 Oscillation circuit 21 and 22 Power input 23 (Crystal oscillator) output 24 ( Oscillation frequency) output 31 (temperature characteristic) curve 32 (compensation) curve

Claims (3)

[Claims] 1. A temperature adjusting member having a shape which is fitted to and adheres to an outer wall of a casing of a crystal oscillator, a temperature control member comprising a heat conductive plate having a temperature sensor and an electric heater adhered to an outer surface thereof, A temperature control device for a crystal oscillator, comprising: a heater control device that controls a heating amount of the electric heater so that a deviation between a temperature set value and a measurement value of the temperature sensor is set to zero. 2. The temperature control device for a crystal oscillator according to claim 1, wherein the temperature control member includes a heat insulating coating that covers the entire outer surface of the temperature control member. 3. The temperature control device for a crystal oscillator according to claim 1, wherein said crystal oscillator is mounted on a single-sided mounting board.