JP2000183649A - Highly stable piezo-oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce deterioration of an electronic part due to high temperature by setting the temperature of a thermostatic oven low, according to the maximum temperature of an ambient temperature. SOLUTION: The temperature of a thermostatic oven is set according to the maximum temperature of an ambient temperature. In this oscillator, a control part CONT first decides a set temperature in the thermostatic oven OVN based on an ambient temperature from a temperature sensor Tsensor, when power is inputted. For instance, when environment temperature information is 10 deg.C, the set temperature in the thermostatic oven OVN is defined as, e.g. 35 deg.C, and the control part CONT supplies the defines set temperature to a temperature control part Tcont. The part Tcont performs control so as to fix the temperature in the oven OVN to 35 deg.C, based on the supplied set temperature. If it is set to about 15 deg.C which is higher than an ambient maximum temperature in this way, the temperature in the oven keeps almost constant. Then, because the temperature in the oven OVN keeps low when an ambient temperature is low, it is possible to reduce the characteristic deterioration of an electronic component due to high temperature aging.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-stable crystal oscillator, and more particularly to a high-stable crystal oscillator in which the temperature and oscillation frequency of a thermostat of the high-stable crystal oscillator can be set according to the ambient temperature.

[0002]

2. Description of the Related Art A high stability crystal oscillator has excellent frequency accuracy,
Of the components that make up the oscillator in order to satisfy frequency temperature characteristics, frequency aging characteristics, etc., at least peripheral circuits such as the crystal oscillator and the temperature detection circuit are housed in a thermostat and the internal temperature is kept constant. And are used in many fields from mobile radio base stations to measuring instruments. Figure
FIG. 7 is a block diagram showing a configuration of a conventional high-stable crystal oscillator, which includes a crystal oscillator Y, a thermostatic chamber OVN accommodating the same, a temperature control unit Tcont for controlling the temperature of the thermostatic chamber OVN, and an oscillator for oscillation. It consists of an amplifier AMP. FIG. 8A shows an example of the temperature control unit Tcont.
h, composed of a differential amplifier D.AMP, a transistor Tr and a heater H. That is, the resistor R1 side of the series connection circuit of the resistor R1 and the resistor R2 is connected to the power supply Vcc, the other end is grounded, and the middle point is connected to the + input of the differential amplifier D.AMP.
Further, the thermistor Th side of the series connection circuit of the thermistor Th and the resistor R3 is connected to the power supply Vcc, the other end is grounded, and the middle point is connected to the negative input of the differential amplifier D.AMP. The negative input and output terminal of the differential amplifier D.AMP are connected via a feedback resistor R4, and the output of the differential amplifier D.AMP is connected to the base of a transistor Tr with a common emitter.
A heater H is connected between the collector and the power supply Vcc.
Note that at least the thermistor Th is disposed inside the thermostatic oven OVN and close to the crystal oscillator.

The set temperature of the oven OVN for a highly stable crystal oscillator shown in FIG. 7 is generally set to a flat region of the frequency temperature characteristic exhibited by the crystal unit Y, for example, a minimum value thereof. The divided voltage Vr of the power supply voltage Vcc by the resistors R1 and R2 shown in FIG. 8A is used as a reference voltage, the divided voltage Vs by the thermistor Th and the resistor R3 is used as a comparison voltage, and the temperature of the oven is controlled by the temperature of the crystal unit Y. The resistances R1 to R3 are adjusted and set so as to be the same as the minimum temperature of the frequency temperature characteristic. As is well known, the operation of the temperature control unit shown in FIG. 8A is such that when the ambient temperature of the vibrator, that is, the internal temperature of the thermostatic chamber changes from the set temperature, the resistance value of the thermistor Th changes and the comparison voltage Vs and the reference voltage Vs Voltage Vr
And a difference voltage is generated. The output voltage of the differential amplifier D.AMP changes in accordance with the difference voltage.As a result, the current of the heater H changes, and the temperature of the thermistor Th is reduced until the difference between the two input voltages of the differential amplifier becomes zero. Change. That is, if the ambient temperature of the crystal unit increases, the current flowing through the heater H1 is reduced, and if the ambient temperature decreases, the current flowing through the heater H1 is increased so that the temperature in the constant temperature chamber is kept constant. Works like that.

FIG. 8B shows an oscillation amplifier AM shown in FIG.
P is an example of a transistor Tr, resistors r1 to r4, and a capacitor C
11 to C13. That is, the transistor T
A voltage obtained by dividing the power supply voltage Vcc by the resistors r1 and r2 is applied to the base of r as a bias voltage, and the collector is connected to the power supply Vcc via the resistor r3. Further, one end of a parallel circuit of a resistor r4 and a capacitor C12 is connected to the emitter of the transistor Tr, the other end is grounded, and a capacitor C11 is connected in parallel between the base and the emitter. The output is taken out from the collector via the capacitor C13.

FIG. 9 shows a temperature control unit Tcont disclosed by the present inventor in Japanese Patent Application No. 10-125048. The temperature control unit Tcont includes a temperature detection circuit A, a low-pass filter B, an amplification circuit C, and a current drive circuit D. It is configured. The operation of the temperature control unit is as follows. When a constant current generated by the insulated FET (Tr3) of the temperature detection circuit A and the resistor R5 flows through a series circuit composed of the thermistors Th1, Th2 and the resistor R6, the temperature at the point α Is generated and applied to the amplifier circuit C via the low-pass filter B for amplification. The amplified voltage is the transistor Tr1 of the current drive circuit D.
To the heater H1 connected to the collector and connected to the collector.

For example, when the inside of the thermostat is lower than the set temperature, the combined value of the thermistors Th1 and Th2 of the temperature detecting circuit A and the resistor R6 becomes a large value.
, The gate potential applied to the MOSFET (Tr2) becomes large. As the potential between the gate and source of the MOSFET (Tr2) increases, the drain current increases, and the potential at the drain decreases. Therefore, the base current of the power transistor Tr1 becomes large, and the current flows to the heater H1 connected to the collector to operate so as to generate heat. The reverse is true when the temperature is high.

[0007]

In the above-mentioned highly stable crystal oscillator, the temperature of the thermostat is represented by a crystal oscillator, for example.
When using an SC-cut crystal resonator having temperature characteristics as shown in Fig. 2, it is set to maintain any temperature between 60 degrees and 75 degrees, which is higher than the ambient temperature and has less frequency fluctuation due to temperature changes. General. However, at such a high temperature, not only the crystal oscillator in the thermostat, but also the electronic components disposed around it are constantly exposed to high-temperature aging, and the deterioration of the components is accelerated and the characteristics change, Reliability may be reduced.
The present invention has been made in order to solve the above-mentioned problem, and by setting the temperature of a constant temperature bath according to the maximum temperature of the ambient temperature, the temperature of the constant temperature bath is set as low as possible. It is another object of the present invention to provide a highly stable crystal oscillator in which deterioration of electronic components due to high temperature is reduced.

[0008]

According to a first aspect of the present invention, there is provided a high-stability piezoelectric oscillator according to the present invention, comprising: a piezoelectric oscillator including a piezoelectric vibrator and an amplifier; and at least the piezoelectric vibrator. A constant temperature bath for storing the internal temperature at a set temperature, a temperature sensor for detecting an environmental temperature, and a constant temperature bath temperature switching means for controlling the internal temperature of the constant temperature bath to one of a plurality of predetermined set temperatures. A high-stability piezoelectric oscillator characterized in that the environmental temperature region is divided into a plurality of temperature ranges, and the temperature of the constant-temperature bath is controlled so that a set temperature is higher than a maximum temperature by a predetermined temperature for each temperature range. According to a second aspect of the present invention, there is provided a piezoelectric oscillator including a piezoelectric vibrator and an amplifier, a thermostat containing at least the piezoelectric vibrator and maintaining an internal temperature at a set temperature, a temperature sensor for detecting an environmental temperature, and the thermostat. A constant temperature bath temperature switching means for controlling the inside temperature of the bath to one of a plurality of predetermined set temperatures, and a compensation signal memory storing frequency compensation signal information to be supplied to the oscillator at each set temperature of the constant temperature bath. Dividing the environmental temperature region into a plurality of temperature ranges, controlling the temperature of the constant temperature bath so as to be a set temperature higher than the maximum temperature by a predetermined temperature for each temperature range, and storing the compensation signal memory for each constant temperature bath temperature. A high stability piezoelectric oscillator characterized in that a compensation signal is supplied to the oscillator based on stored information. According to a third aspect of the present invention, in the case where the piezoelectric vibrator is an SC-cut quartz crystal vibrator and the valley temperature or the peak temperature is 60 ° C to 75 ° C, and the environmental temperature is 30 ° C or less, the constant temperature is maintained. Temperature set inside the tank is 4
The constant temperature bath set temperature is around 50 ° C. in the range of 0 ° C., 30 ° C. and 40 ° C., and the constant temperature bath set temperature is 60 ° C. or more in the range of 50 ° C. or more. 2. A high stability piezoelectric oscillator according to item 2. The information stored in the compensation signal memory may be such that the difference between the oscillation frequency when the piezoelectric oscillator is at a constant temperature set temperature and the specified oscillation frequency is equal to or less than a desired frequency deviation. 4. The high stability piezoelectric oscillator according to claim 1, wherein the information is information for setting a load capacitance value of the piezoelectric oscillator. According to a fifth aspect of the present invention, the constant temperature bath includes an internal temperature detecting means, and when a set temperature of the constant temperature bath is changed, a compensation signal to be supplied to the piezoelectric oscillator is changed according to the change in the internal temperature. 5. The high-stability piezoelectric oscillator according to claim 1, wherein a frequency deviation in a transient state of the temperature inside the thermostat is reduced. The invention according to claim 6 is characterized in that the constant temperature bath is provided with an internal temperature information detecting means, and when a constant temperature bath set temperature is changed, a compensation signal to be supplied to the piezoelectric oscillator is changed according to the internal temperature change. 2. A digital TCXO function for reducing a frequency deviation in a transient state of the temperature inside the thermostatic chamber by causing the temperature to be reduced.
5. A high-stability piezoelectric oscillator according to any one of claims 1 to 4.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on an embodiment shown in the drawings. FIG. 1 is a block diagram showing the configuration of a high-stable crystal oscillator according to the present invention, in which a crystal oscillator including a crystal oscillator Y and an amplifier AMP, a thermostatic chamber OVN containing the crystal oscillator Y, and a thermostat. A temperature control unit Tcont for controlling the temperature of the tank OVN to be maintained at the set temperature;
A frequency shift unit Fshift that shifts the oscillation frequency to correct the oscillation frequency at the set temperature of the oven OVN to a specified frequency, a temperature sensor Tsensor that detects a temperature around the crystal oscillator, and a temperature from the temperature sensor Tsensor. The temperature control unit Tcont changes a constant-temperature chamber set temperature based on the information, and supplies a frequency shift amount information to the frequency shift unit Fshift.
Although various types of the temperature sensor Tsensor have been proposed, a detailed description thereof will be omitted. However, for example, a temperature and a terminal voltage have a predetermined relationship, such as those using a thermistor or a semiconductor element such as a diode or a transistor. And those using an oscillator whose oscillation frequency has a temperature dependency, and the like. Further, as described later, the temperature control unit Tcont for controlling the temperature of the constant temperature bath includes a temperature detecting element such as a thermistor for controlling the temperature in the constant temperature bath, and the frequency shift unit Fshift is provided during the oscillation loop of the oscillator. The oscillation frequency is adjusted to a desired value by correcting the control voltage to the inserted variable diode.

Various modifications are conceivable for the specific circuit of the configuration example of the present invention shown in FIG. 1 described above. Unlike the case where the temperature is set 15 ° C. to 20 ° C. higher than the compensation temperature range, the temperature set in the thermostatic bath is switched according to the environmental temperature. Hereinafter, representative examples will be described. First, although not shown, the control unit CONT includes a read-only memory (ROM), in which the following information is stored in advance. The temperature range in which the specifications are to be guaranteed, for example, an environment temperature of -20 ° C to 60 ° C is set to 20 ° C or lower (I range), 20 ° C to 30 ° C (II range), 30 ° C to 40 ° C (I
Information on what the set temperature of the constant temperature bath should be at each temperature when the temperature is divided into an area II, 40 ° C. to 50 ° C. (IV area), and 50 ° C. or more (V area). Specifically, a temperature higher by 10 ° C. to 15 ° C. than the maximum temperature for each of the above temperature ranges is set as a constant temperature bath set temperature. That is, 30 ° C. in the I region, 40 ° C. in the II region, 50 ° C. in the III region, 60 ° C. in the IV region,
In the V region, 70 ° C may be appropriate. Frequency compensation signal information to be supplied to the oscillator at each set temperature of the constant temperature bath. That is, in the present invention, since the set temperature of the thermostat is changed, the oscillation frequency at each thermostat temperature is slightly different from the desired frequency. On the other hand, since the deviation of the oscillation frequency from the desired frequency (nominal frequency) at each temperature can be known in advance, compensation signal information for compensating for these frequency deviations and approaching the nominal frequency is recorded in the memory. , Based on this signal. An operation and control example of the high stability piezoelectric oscillator configured as described above will be described. When the power supply is turned on, the control unit CONT first operates based on the ambient temperature from the temperature sensor Tsensor.
Determine the set temperature in VN. For example, if the environmental temperature information is 10
If the temperature is ° C, the temperature is included in the region I described above, so that the set temperature in the thermostatic oven OVN is determined as 35 ° C as another example, and the control unit CONT supplies the determined set temperature to the temperature control unit Tcont. The temperature control unit Tcont controls the temperature in the constant temperature bath OVN to be constant at 35 ° C. based on the set temperature supplied from the control unit CONT.

As described above, if the temperature is set to be higher than the ambient temperature by about 15 ° C., the temperature in the tank is kept almost constant. Therefore,
When the ambient temperature is low, the temperature of the oven OVN is kept low, so that the deterioration of characteristics of the crystal unit Y and other electronic components due to high-temperature aging can be reduced. However, although the temperature characteristic of the SC-cut vibrator is slight as shown in FIG. 2, it changes depending on the temperature. Therefore, if the temperature in the bath is changed according to the ambient temperature, the oscillation frequency will deviate from a desired value. The frequency shift unit Fshift is provided to correct this shift. For example, it is assumed that the frequency temperature characteristics of the crystal unit used are as shown in FIG. 2 and the reference temperature is 65 ° C., and the oscillation frequency at this time is the target nominal frequency f ₀ . The control unit CONT stores information for correcting the frequency deviation amount corresponding to the set temperature of the thermostatic oven OVN calculated based on the graph of FIG. 2, and reads out this information and supplies it to the frequency shift unit Fshift. Wherein the frequency deviation is the difference in frequency at a vessel temperature of definitive frequency and the reference temperature, reference numeral Delta] f ₃₅ when intracisternal As shown in FIG. 2 is 35 ° C.
Is equivalent to That is, the frequency shift unit Fshift is controlled by the control unit CO
It functions to shift the frequency from point A to point B in FIG. 2 based on the frequency deviation from NT. As a result, the circuit of FIG. 1 can realize an oscillator with a small frequency fluctuation while maintaining the temperature in the bath at a relatively low temperature.

Similarly, the thermostat is controlled to a temperature corresponding to the environmental temperature and set to each temperature range. For example, when the ambient temperature is -20 ° C or 0 ° C, the temperature is 35 ° C, when it is 35 ° C, it is 55 ° C, when it is 45 ° C, it is 65 ° C, and when it is 55 ° C, it is 75 ° C. At this time, it is needless to say that it is necessary to appropriately change the correction signal supplied to the frequency shift unit so as to correct the deviation from the nominal frequency (reference frequency) at each temperature of the thermostatic bath as described above. Also, as shown in FIG.
When the temperature is set to be the reference frequency (nominal frequency), the temperature becomes lower than the reference frequency when the temperature of the thermostat is set to 75 ° C., so that a correction signal for increasing the frequency is supplied. Even if the temperature of the constant temperature bath is changed, the inside of the constant temperature bath does not immediately reach the set temperature due to the relation of heat capacity, but gradually reaches the set temperature after a predetermined time. Therefore,
If the frequency is shifted in accordance with the signal supplied to the frequency shift unit simultaneously with the temperature change in the constant temperature bath, a correction error may occur. If this error is undesirably large, the frequency shift may be executed after the required time elapses after the temperature of the thermostat is changed. In addition, a specific countermeasure for a case where it is necessary to perform correction with higher accuracy will be described later.

FIG. 3 is a circuit diagram showing a specific configuration example of the temperature control unit Tcont.
, An amplifier circuit C, and a current drive circuit D. Note that the thermistor Th is housed in a thermostat as in the case described with reference to FIG. Setting circuit A
, A constant current generated by the insulating FET (Tr3) and the resistor R7 flows through the thermistor Th.
The contact a with 3 becomes a voltage corresponding to the temperature of the thermostat, and the voltage is applied to the gate of the FET Tr2 of the amplifier C via the low-pass filter B. The voltage changes the gate-source voltage of the FET Tr2 of the amplifier C, and accordingly, the FET Tr2
Drain current flows. When the drain current flows,
A voltage is generated across the resistor R5 connected to the drain of the FET Tr2, and this voltage is applied to the FET T via the resistor R3 of the current driver D.
The gate voltage becomes r1, and a drain current corresponding to the voltage between the gate and the source flows through the heaters H1 and H2.
Here, the Zener diode ZD used for the amplifier C raises the voltage between the gate and the source of Tr2 and is inserted to compensate for the drift due to the temperature of Tr2.

For example, when the temperature of the constant temperature bath falls below a predetermined temperature, the resistance of the thermistor Th increases, and the voltage at the point a is determined by the current from the constant current source determined by the FET Tr3 and the resistor R7. Goes down. When the voltage at point a decreases, the voltage between the gate and source of the FET Tr2 of the amplifier circuit C increases, the drain current increases, and the voltage across the resistor R5 between the drain and ground increases. This increased voltage is connected to the FET via the resistor R3 of the current drive circuit D.
・ It becomes the gate voltage of Tr1 and increases the voltage between the gate and source. When the voltage increases, the drain current of the FET Tr1 increases, and the current flows through the heaters H1 and H2, so that the temperature of the heaters H1 and H2 increases. When the temperature of the thermostat rises above a predetermined temperature, the above description is reversed.

Here, the digital variable resistor IC (hereinafter, referred to as variable resistor Rv1) used in the setting circuit A of FIG. 3 will be briefly described. FIG. 10 is an internal block diagram of the variable resistor Rv. The variable resistors (R0, R1,..., R63) are changed from a minimum resistance value R0 to a maximum resistance value (R0 + R1 +.
The configuration is such that the value can be switched to 64 levels up to 3). The multiplexer is an up / down counter (Up / Dou) controlled by the inputs of the input signals D, UC, DC and V-.
n) is connected to. For example, switch SW is connected to UC terminal and V
When connected to the-terminal (UC terminal is OR-connected with the D terminal, so the same applies between the D terminal and the V- terminal)
When the switch SW is pressed and goes LOW, one pulse is sent to the internal up / down counter, and the counter increases (or decreases) by +1 (or -1) and the resistance increases by 1/64. (Or decrease). The operation of increasing or decreasing the resistance value will be described later.

In addition, when the ON time of the switch is longer than 1 mS (1 millisecond) and shorter than 1 S, the resistance value increases or decreases by 1/64 step with one input. The resistance value continuously increases or decreases by 1/64 step at a time, and continues until the switch is turned off or the resistance value reaches the maximum value or the minimum value. And the input is 1S
When the above does not occur, or when the resistance value reaches the maximum value or the minimum value, the mode of the up-down counter is inverted. That is, the mode of the up / down counter is inverted when the next pulse is input after 1S or more has elapsed from the previously input pulse. Furthermore, the pulse width of D input is 1S
In the above case, the internal timer automatically increases (or decreases) by one step every 100 ms. When up and down are controlled independently, the UC input can be used as the up input and the DC input can be used as the down input. Further, in the variable resistor IC, the position of the tap of the variable resistor is stored in the E ² PROM (rewritable memory) inside the IC even after the power is cut off.

As shown in FIG. 3, the setting circuit A has a variable resistor Rv1
The operation in the case of using is described. The resistance value of the variable resistor Rv1 is changed by a pulse from the external input terminal P, and a signal corresponding to the set temperature from the control unit CONT is input to the external input terminal P. That is, the control unit CONT
Supplies the information on the set temperature to the external input terminal P, the variable resistor Rv1 sets the resistance value according to the information. The monitor terminal M is a terminal for monitoring whether the set resistance value is appropriate. The control unit CONT
The generation of the thermostatic chamber set temperature signal supplied to the temperature control unit from will be described briefly. That is, as described above, the control unit
Read-only memory (ROM) not shown for CONT
Which is divided into a plurality of temperature regions to be compensated,
Information on what the set temperature of the thermostatic bath is at which temperature at each temperature is stored. Therefore, the temperature sensor Tsensor
When the environmental temperature information is input from the controller, it determines which temperature section the temperature belongs to, and if the temperature is out of the preset temperature range, generates a thermostatic chamber set temperature change instruction and supplies it to the temperature control unit Tcont. I do. As a signal format, a method of generating the number of pulses to be newly supplied in order to change from the already set temperature, or clearing all the already input states, and adding a new required number Various methods are conceivable, such as a method of supplying a pulse, and a method of providing a necessary number of shift registers and storing a pulse train required for temperature setting in the section. Also, in order to more accurately control the temperature inside the thermostat, for example, a means for monitoring the voltage (or the resistance value at both ends) of the temperature detecting element thermistor Th disposed in the thermostat is provided. It may be monitored whether or not the temperature has reached.

FIG. 4 is a circuit diagram showing a specific example of the configuration of a variable frequency oscillation circuit composed of a crystal unit Y, a frequency setting unit α, and an amplifier β. The frequency setting unit α connects one end of a series circuit including the capacitance C _L1 and the variable capacitance diode Cv to the crystal unit Y, and grounds the other end. further,
In order to vary the oscillation frequency, one end of a series circuit including the resistor r1, the variable resistor Rv2, and the resistor r2 is connected to the power supply Vcc, and the other end is connected to the ground, and then the output of the variable resistor Rv2 is connected to the parallel connection capacitor C12. Connected to the cathode side of the variable capacitance diode Cv via the high resistance Rh connected in series. The frequency setting unit α also functions as the frequency shift unit shown in FIG. As a specific example therefor, the same variable resistance Rv2 as the digital variable resistance IC shown in FIG. 10 is used. Control unit CONT
Briefly describing the correction signal supplied to the frequency shift unit Fshift from the above, the control unit CONT is provided with a read-only memory (ROM) (not shown) as described above. Frequency compensation signal information for setting to zero, that is, frequency shift information necessary to correct the set temperature of the thermostatic chamber when the set temperature is changed is slightly different from the desired frequency.

Therefore, when the environmental temperature information is input from the temperature sensor Tsensor, it is determined which temperature section the temperature belongs to, and if necessary, a constant temperature chamber setting temperature change instruction is generated and the temperature control unit Tcont At the same time, a necessary number of pulse signals are supplied to the frequency shift unit in order to correct the oscillation frequency deviation at the newly set constant temperature. At this time, similar to the signal supplied from the control unit CONT to the temperature control unit Tcont, a method of generating the number of pulses necessary for changing from the already set value, or clearing all the values already input Then, various methods can be considered, such as a method of supplying a new required number of pulses, and a method of providing a required number of stages of shift registers and storing a pulse train required for frequency shift in the section. . FIG. 5 shows the resistance value of the variable resistor Rv1 of the temperature control unit Tcont shown in FIG.
It is a diagram showing the relationship between the temperature of OVN and the horizontal axis is the variable resistance Rv1
The vertical axis represents the temperature of the thermostat. Using the relationship between the variable resistor Rv1 and the temperature in the thermostatic chamber shown in FIG. 5, the control unit CONT always controls the ambient temperature of the crystal oscillator by 15 degrees or more.
The temperature of the thermostat can be set to be about 20 degrees higher.

FIG. 6 shows the frequency shift unit Fshift shown in FIG.
For example, the initial resistance setting value of the variable resistor Rv2 is 10 kΩ
The oscillation frequency at₀And the amount of change from this frequency
F ₀Δf divided by (= (f−f₀) / F₀) And the resistance of the variable resistor Rv2
FIG. 4 is a diagram illustrating a relationship between resistance values. Control unit CONT is OVN
Required from the temperature setting and the frequency temperature characteristics of the crystal unit Y.
The shift amount Δf is determined and the resistance of the variable resistor Rv2 is determined based on FIG.
Value to control the frequency shifter Fshift.
You. Thus, the output voltage of the variable resistor Rv2 is
By applying to the diode Cv, the capacitance of the diode
Change the oscillation frequency to the specified value.
You.

As described above, since the temperature of the thermostat is controlled in accordance with the ambient temperature of the highly stable crystal oscillator, the temperature of the thermostat can be kept lower than that of the conventional one, and the crystal oscillator and the thermostat can be maintained. Deterioration due to high-temperature aging of electronic components used in the inside can be largely suppressed. Although the operation of the oscillator using the quartz oscillator has been described above, the present invention is not necessarily limited to the quartz oscillator, and can be similarly applied to an oscillator using another piezoelectric oscillator.

Although the embodiment of the present invention has been described above, the present invention is not limited to this embodiment, and various modifications can be made. For example, the entire region including the minus temperature region of the compensation temperature region is equally divided, and the maximum temperature of each divided region is 10 ° C.
It is also possible to keep the thermostat at a temperature higher by ~ 15 ° C. That is, if the compensation region is from -20 ° C to 60 ° C,
For 0 ° C, set the temperature to 15 ° C, for 0 ° C to 10 ° C, set the temperature to 25 ° C, for 10 ° C to 20 ° C, 35 ° C,
..., it is also possible to set the temperature of the constant temperature bath to 75 ° C. in the range of 50 ° C. to 60 ° C., and according to this method, it is possible to lower the average temperature of the constant temperature bath in a low temperature area. It is possible to save power for heat retention. Conversely, in order to keep the frequency accuracy high, it is also effective to limit the set temperature of the thermostatic chamber to a range in which the frequency temperature deviation of the crystal resonator itself is small. That is, for example, when an SC-cut crystal resonator as shown in FIG. 2 is used as the crystal resonator, the frequency deviation is relatively small between 50 ° C. and 70 ° C. based on the peak temperature of 60 ° C. Selecting a range may eliminate the need for a frequency shift in some cases.

Further, when changing the temperature of the constant temperature bath, it takes a predetermined time for the temperature of the crystal unit to reach the set temperature of the constant temperature bath. Therefore, in order to minimize the frequency deviation during the transition, the transition period is required. May be configured to control the frequency shift amount in accordance with the temperature frequency characteristics of. That is,
If it is assumed that the time from the change of the temperature setting of the thermostat to the actual temperature of the crystal unit being equal to the temperature setting of the thermostat is 10 minutes, the frequency change of the oscillator during that time is measured in advance, and this change is corrected. Control the amount of frequency shift to obtain. Data for this is stored in the memory of the control unit CONT. In order to compensate more accurately, it is preferable to measure the above-mentioned characteristics for each set temperature of the thermostatic chamber and store the data, and a digital TCXO technology conventionally known would be useful as this means. In the case where the digital temperature control corresponds to a temperature change of 10 ° C. to 15 ° C. as in the above-described embodiment, even if the number of bits is about 8 bits, it is possible to perform sufficiently precise high-precision control.
In this case, it is preferable to provide a constant temperature chamber internal temperature detecting means, but it is also possible to use the voltage or resistance value of the thermistor of the constant temperature chamber temperature control circuit as described above.

[0024]

According to the present invention, as described above, the temperature of the thermostat is switched stepwise according to the external temperature of the high-stability crystal oscillator. This makes it possible to lower the temperature, thereby suppressing the deterioration of the crystal unit and the electronic components exposed to high-temperature aging, and significantly improving the reliability and greatly reducing the power consumption.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a highly stable crystal oscillator according to the present invention.

FIG. 2 is a graph showing frequency-temperature characteristics of an SC-cut quartz resonator using a cutting angle as a parameter.

FIG. 3 is a diagram showing a circuit configuration of a temperature control unit of the high stability crystal oscillator of the present invention.

FIG. 4 is a diagram showing a circuit configuration of a frequency setting unit and an oscillation amplifier of the high stability crystal oscillator of the present invention.

FIG. 5 is a diagram showing a relationship between a resistance value of a first digital variable resistor IC of a temperature control unit and a temperature of a constant temperature bath.

FIG. 6 is a second digital variable resistor IC of a frequency setting unit.
FIG. 4 is a diagram showing a relationship between the resistance value of the first embodiment and the amount of change (ppm) from an initial setting frequency.

FIG. 7 is a block diagram showing a configuration of a conventional high stability crystal oscillator.

8A is a diagram illustrating a circuit configuration of a temperature control unit used in a conventional high-stable crystal oscillator, and FIG. 8B is a diagram illustrating a circuit configuration of a conventional oscillation amplifier.

FIG. 9 is a diagram showing a circuit configuration of another temperature control unit of the conventional high stability crystal oscillator.

FIG. 10 is a block diagram showing an internal configuration of a digital variable resistor IC.

[Explanation of symbols]

 Y ・ ・ Crystal oscillator OVN ・ ・ Temperature chamber CONT ・ ・ Control part Tcont ・ ・ Temperature control part Fshift ・ ・ Frequency shift part AMP ・ ・ Amplifier A ・ ・ Setting circuit B ・ ・ Low pass filter C Current drive circuit Vcc Power supply Tr1, Tr2, Tr3 Field effect (FET) transistor R1, R2, R3, R4, R5, R6, R7 Resistance r1, r2, r3, r4, r5, r6 Resistance C1, C2, C3, C4 Capacitance C11, C12, C13, C14, C15 Capacitance Th Thermistor ZD Zener diode Rv1, Rv2 Digital variable resistor IC (variable resistor) P External input Terminal M Monitor

Claims (6)

[Claims] 1. A piezoelectric oscillator including a piezoelectric vibrator and an amplifier, a thermostat containing at least the piezoelectric vibrator and maintaining an internal temperature at a set temperature, a temperature sensor detecting an environmental temperature, and an internal temperature of the thermostat. Constant temperature bath temperature switching means for controlling the temperature to one of a plurality of predetermined set temperatures, dividing the environmental temperature range into a plurality of temperature ranges, and setting each set temperature range to a set temperature higher than the highest temperature by a predetermined temperature. Controlling the temperature of the thermostatic chamber as described above. 2. A piezoelectric oscillator including a piezoelectric vibrator and an amplifier, a thermostat containing at least the piezoelectric vibrator and maintaining an internal temperature at a set temperature, a temperature sensor detecting an environmental temperature, and an internal temperature of the thermostat. And a compensation signal memory for storing frequency compensation signal information to be supplied to the oscillator at each set temperature of the constant temperature bath. The environmental temperature region to be divided into a plurality of temperature ranges, and controlling the temperature of the constant temperature bath so as to be a set temperature higher than the maximum temperature by a predetermined temperature for each temperature range, and in the compensation signal memory for each constant temperature bath temperature. A high-stability piezoelectric oscillator configured to supply a compensation signal to an oscillator based on stored information. 3. The piezoelectric vibrator is an SC cut quartz crystal vibrator, and its valley temperature or peak temperature is 60 ° C. to 75 ° C.
When the ambient temperature is 30 ° C. or less, the temperature set inside the constant temperature bath is around 40 ° C.
In the range of 40 ° C. and 40 ° C., the set temperature of the thermostat is around 50 ° C.
The high stability piezoelectric oscillator according to claim 1 or 2, wherein: 4. The information stored in the compensation signal memory is based on the load capacitance of the piezoelectric oscillator because the difference between the oscillation frequency when the piezoelectric oscillator is at a constant temperature set temperature and the specified oscillation frequency is equal to or less than a desired frequency deviation. 4. The high stability piezoelectric oscillator according to claim 1, wherein the information is information for setting a value. 5. The constant temperature bath is provided with an internal temperature detecting means, and when a set temperature of the constant temperature bath is changed, a compensation signal to be supplied to the piezoelectric oscillator is changed in accordance with the change in the internal temperature, so that the temperature of the constant temperature bath is changed. 5. The high stability piezoelectric oscillator according to claim 1, wherein a frequency deviation in a transient state of the temperature inside the bath is reduced. 6. The constant temperature bath is provided with an internal temperature information detecting means, and when a set temperature of the constant temperature bath is changed, a compensation signal to be supplied to the piezoelectric oscillator is changed according to the internal temperature change. 5. The high stability piezoelectric oscillator according to claim 1, further comprising a digital TCXO function for reducing a frequency deviation in a transient state of the temperature inside the thermostat.