JP2023032468A - Temperature compensation type piezoelectric oscillator - Google Patents

Abstract

To suppress an influence applied to an oscillatory frequency from a noise generated in a temperature sensor as much as possible.SOLUTION: A temperature compensation type piezoelectric oscillator 1 comprises: a piezoelectric transducer 6; a temperature sensor 2 that outputs a detection voltage corresponded to a temperature; and a compensation voltage generation circuit 3 that generates a compensation voltage that compensates a frequency temperature characteristic of the piezoelectric transducer 6 on the basis of the detection voltage of the temperature sensor 2. The temperature compensation type piezoelectric oscillator suppressing an oscillatory frequency on the basis of the compensation voltage, provides a low-pass filter 5 that passes a low region component of the detection voltage of the temperature sensor 2 to between the temperature sensor 2 and the compensation voltage generation circuit 3 to output it to the compensation voltage generation circuit 3.SELECTED DRAWING: Figure 1

Description

The present invention relates to a temperature compensated piezoelectric oscillator.

A temperature-compensated piezoelectric oscillator that compensates for the frequency-temperature characteristic of a piezoelectric vibrator has high frequency stability with respect to temperature changes, and is therefore widely used as a reference signal source for electronic devices and portable communication devices.

As such a temperature-compensated piezoelectric oscillator, there is known one in which a temperature sensor, a temperature-compensating circuit for generating a compensation voltage, and the like are integrated as an integrated circuit element (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 2003-224425 (Fig. 3)

In a temperature-compensated piezoelectric oscillator, a compensation voltage is generated by a compensation voltage generation circuit according to a voltage detected by a temperature sensor, and this compensation voltage is applied to a voltage-controlled oscillator to control the oscillation frequency. The detected voltage of the temperature sensor contains noise generated in the temperature sensor. The noise included in the detected voltage of the temperature sensor is amplified by the compensation voltage generation circuit, and the amplified compensation voltage including the noise is applied to the voltage controlled oscillator to affect the oscillation frequency.

SUMMARY OF THE INVENTION It is an object of the present invention to minimize the influence of noise generated by a temperature sensor on the oscillation frequency.

In order to achieve the above object, the present invention is configured as follows.

That is, the temperature-compensated piezoelectric oscillator of the present invention includes a piezoelectric vibrator, a temperature sensor that outputs a detection voltage corresponding to temperature, and a frequency-temperature characteristic of the piezoelectric vibrator that is compensated based on the detection voltage of the temperature sensor. A temperature-compensated piezoelectric oscillator that controls an oscillation frequency based on the compensation voltage, comprising a compensation voltage generation circuit that generates a compensation voltage that
A low-pass filter is provided between the temperature sensor and the compensation voltage generation circuit for passing low-frequency components of the voltage detected by the temperature sensor and outputting the low-frequency component to the compensation voltage generation circuit.

According to the present invention, a low-pass filter is provided between the temperature sensor and the compensation voltage generation circuit to pass low-frequency components of the voltage detected by the temperature sensor and output the voltage to the compensation voltage generation circuit. The noise contained in the generated detection voltage can be removed by the low-pass filter, and the noise generated by the temperature sensor is amplified by the compensation voltage generation circuit to suppress the influence on the oscillation frequency.

In a preferred embodiment of the present invention, a voltage-controlled oscillation circuit is provided that oscillates the piezoelectric vibrator and controls the oscillation frequency based on the compensation voltage.

According to this embodiment, by applying the compensating voltage as the control voltage of the voltage-controlled oscillation circuit, the oscillation frequency can be controlled to compensate for the frequency-temperature characteristics of the piezoelectric vibrator.

In one embodiment of the invention, the low-pass filter is composed of resistors and capacitors.

According to this embodiment, it is possible to achieve cost reduction with a simple configuration. are integrated in

According to this embodiment, miniaturization and thinning can be achieved.

In a preferred embodiment of the invention, the piezoelectric vibrator is a crystal vibrator.

According to this embodiment, since the piezoelectric oscillator is a crystal oscillator, the frequency stability is excellent.

According to the present invention, a low-pass filter is provided between the temperature sensor and the compensation voltage generation circuit to pass low-frequency components of the voltage detected by the temperature sensor and output the voltage to the compensation voltage generation circuit. Noise contained in the generated detection voltage can be removed by a low-pass filter. As a result, it is possible to suppress the noise generated by the temperature sensor from being amplified by the compensation voltage generation circuit and affecting the oscillation frequency.

FIG. 1 is a block diagram showing the configuration of a temperature-compensated crystal oscillator according to one embodiment of the present invention. FIG. 2 is a diagram showing input/output characteristics of the temperature sensor of FIG. FIG. 3 is a diagram showing temperature characteristics of the compensation voltage of the compensation voltage generation circuit of FIG. FIG. 4 is a diagram showing control voltage (compensation voltage) vs. frequency characteristics of the voltage controlled oscillator of FIG. FIG. 5 is a diagram showing frequency-temperature characteristics of the crystal oscillator of FIG. FIG. 6 is a diagram showing frequency-temperature characteristics of the temperature-compensated crystal oscillator of FIG. FIG. 7 is a cross-sectional view showing a schematic configuration of the temperature-compensated crystal oscillator of FIG. FIG. 8 is a diagram showing the output frequency of a conventional temperature-compensated crystal oscillator that does not have a low-pass filter. FIG. 9 is a diagram showing the output frequency of the temperature-compensated crystal oscillator of FIG.

An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a temperature compensated crystal oscillator (TCXO) according to one embodiment of the present invention.

The temperature-compensated crystal oscillator 1 of this embodiment includes a temperature sensor 2 that outputs a detection voltage corresponding to temperature, a compensation voltage generation circuit 3 that generates a compensation voltage based on the detection voltage of the temperature sensor 2, and a compensation voltage is applied as a control voltage, and a low-frequency component of the voltage detected by the temperature sensor 2 is passed between the temperature sensor 2 and the compensation voltage generation circuit 3 to generate a compensation voltage A low-pass filter 5 is provided for output to the generating circuit 3 .

The voltage controlled oscillator circuit 4 of this embodiment is a voltage controlled crystal oscillator (Voltage Controlled Xtal Oscillator: VCXO), and includes a crystal oscillator 6, a feedback resistor 7, an inverter 8, and variable capacitors 9 and 10. there is

Crystal oscillator 6, inverter 8 and feedback resistor 7 are connected in parallel with each other, and variable capacitors 9 and 10 are connected between one end of each of them and ground GND, respectively.

Variable capacitors 9 and 10 operate as variable capacitance elements for adjusting the oscillation frequency of the output signal according to the applied voltage. Variable capacitance diodes may be used instead of the variable capacitors 9 and 10. FIG.

A compensation voltage of compensation voltage generation circuit 3 is applied to voltage controlled oscillation circuit 4 as a control voltage, and voltage controlled oscillation circuit 4 outputs an oscillation signal having a frequency corresponding to the compensation voltage.

Compensation voltage generation circuit 3 generates a compensation voltage for compensating the frequency-temperature characteristic of crystal oscillator 6 according to the detected voltage corresponding to the temperature from temperature sensor 2 input via low-pass filter 5 . By applying this compensation voltage to the voltage controlled oscillator circuit 4, the voltage controlled oscillator circuit 4 can output an oscillation signal with a stable frequency over a wide temperature range.

In this embodiment, the low-pass filter 5 is provided between the temperature sensor 2 and the compensation voltage generation circuit 3 as described above. The low-pass filter 5 includes a resistor 11 and a capacitor 12 connected between the output side of the resistor 11 and the ground GND.

The low-pass filter 5 passes low-frequency components from the voltage detected by the temperature sensor 2 to remove noise of high-frequency components and outputs the detected voltage to the compensation voltage generation circuit 3 .

In this embodiment, the temperature sensor 2, the resistor 11 of the low-pass filter 5, the compensation voltage generator circuit 3, and the voltage controlled oscillator circuit 4 excluding the crystal oscillator 6 are integrated into a single chip IC 13 as indicated by the phantom line. It is integrated and housed in a package as described below.

A semiconductor temperature sensor suitable for integration into an IC is used as the temperature sensor 2 . FIG. 2 shows an example of input/output characteristics of the temperature sensor 2, where the horizontal axis is temperature and the vertical axis is detected voltage. In this example, the detected voltage has a negative characteristic that decreases linearly as the temperature rises. The temperature sensor 2 outputs a detection voltage corresponding to temperature.

FIG. 3 shows an example of the temperature characteristic of the compensation voltage of the compensation voltage generation circuit 3 to which the voltage detected by the temperature sensor 2 is input through the low-pass filter 5, where the horizontal axis represents temperature and the vertical axis represents compensation voltage. .

The compensation voltage generating circuit 3 has a cubic curve characteristic that has an inflection point near 25.degree. are doing. The compensation voltage at 25° C. is indicated by Va.

FIG. 4 shows an example of the characteristics of the voltage controlled oscillator circuit 4. The horizontal axis represents the control voltage, ie, the compensation voltage, and the vertical axis represents the frequency deviation df/f, ie, the amount of deviation from the reference frequency.

The voltage controlled oscillator circuit 4 of this embodiment has the characteristic that the frequency deviation changes approximately linearly in the negative direction as the compensation voltage applied as the control voltage rises.

In this example, when the compensation voltage Va is input as the control voltage at a temperature of 25° C., the frequency deviation of the output signal of the voltage controlled oscillator circuit 4 becomes "0", and the frequency of the output signal is the desired frequency, which is the reference frequency. match.

FIG. 5 shows an example of frequency-temperature characteristics of the crystal resonator 6, where the horizontal axis is temperature and the vertical axis is frequency deviation df/f. In this example, the crystal oscillator 6 is an AT-cut crystal oscillator and has characteristics of a cubic curve with an inflection point. is designed to be "0".

As shown in FIG. 5, for example, when the temperature is around 50.degree. It is lower than the compensation voltage Va at 25°C. Since the compensation voltage applied as the control voltage is lower than the compensation voltage Va, the frequency deviation is corrected in the positive direction in the voltage controlled oscillator circuit 4 having the characteristics shown in FIG. As shown in the frequency temperature characteristics of the type crystal oscillator 1, the frequency deviation near 50° C. is approximately "0".

Further, as shown in the frequency-temperature characteristics of the crystal oscillator 6 in FIG. , when the temperature is around 0.degree. C., the compensation voltage Va is higher than when the temperature is 25.degree. Since the compensating voltage applied as the control voltage is higher than the compensating voltage Va, the frequency deviation is corrected in the negative direction in the voltage controlled oscillator circuit 4 having the characteristics shown in FIG. , the frequency deviation near 0° C. is approximately “0”.

Thus, in the temperature-compensated crystal oscillator 1 , the compensation voltage generation circuit 3 generates a compensation voltage so as to cancel out the frequency-temperature characteristics of the crystal oscillator 6 , and this compensation voltage is applied to the voltage-controlled oscillation circuit 4 . Therefore, the frequency of the oscillation signal has a smaller frequency deviation than the frequency-temperature characteristic of the crystal oscillator 6 .

FIG. 7 is a cross-sectional view showing a schematic configuration of the temperature-compensated crystal oscillator 1 of this embodiment.

The package 15 of the temperature-compensated crystal oscillator 1 of this embodiment includes a base 18 having first and second storage recesses 16 and 17 on the top and bottom, and a sealing member 19 interposed between the first storage recess 16 of the base 18 and the base 18 . and a lid 20 as a lid which is joined to the opening of the first housing recess 16 to hermetically seal the first housing recess 16 . The package 15 has a substantially rectangular parallelepiped shape and a rectangular shape in plan view.

The base 18 is made of a ceramic material such as alumina. A first frame portion 18b having a rectangular frame shape in plan view and a second frame portion 18b having a rectangular frame shape in plan view projected downward along the outer peripheral portion of the other main surface side (lower side in FIG. 7) of the substrate portion 18a. It has a frame portion 18c and has a substantially H-shaped cross section.

The substrate portion 18a and the first frame portion 18b on the upper side constitute the first recessed storage portion 16, and the substrate portion 18a and the second frame portion 18c on the lower side constitute the second recessed storage portion 17. As shown in FIG.

The crystal oscillator 6 is housed in the first housing recess 16 of the base 18 . A pair of excitation electrodes of the crystal oscillator 6 are bonded to a pair of oscillator mounting electrodes 22 on the inner bottom surface of the first housing recess 16 with a conductive adhesive 23 .

In the second housing recess 17 of the base 18, the temperature sensor 2, the resistor 11 of the low-pass filter 5, the compensation voltage generation circuit 3, and the voltage-controlled oscillation circuit 4 excluding the crystal oscillator 6 are installed as described above. An IC 13 integrated on a chip and a capacitor 12 of the low-pass filter 5 are accommodated. Therefore, a capacitor with a large capacity can be set, and circuit design and adjustment thereof can be easily performed. The IC 13 is flip-chip mounted on the IC mounting electrodes 24 on the inner bottom surface of the second housing recess 17 by bumps 25 , and the second housing recess 17 is filled with an underfill 27 . Note that the capacitor 12 may be separately installed on an external circuit board.

At the four corners of the outer bottom surface of the base 18, surface-mounting external connection terminals 26 are formed for surface-mounting the temperature-compensated crystal oscillator 1 on an external circuit board or the like.

As described above, the detected voltage of the temperature sensor 2 includes noise generated by the temperature sensor 2. If the detected voltage of the temperature sensor 2 is directly input to the compensation voltage generation circuit 3, the compensation voltage generation circuit 3 includes the noise amplified by the compensation voltage generating circuit 3 . When the compensation voltage containing this amplified noise is applied to the voltage controlled oscillator circuit 4, the oscillation frequency is affected by the noise.

In this embodiment, a low-pass filter 5 is provided between the temperature sensor 2 and the compensation voltage generation circuit 3 to remove noise of high frequency components by passing only low frequency components. 2 can be removed. As a result, it is possible to reduce the noise of the compensation voltage generated by the compensation voltage generation circuit 3 and suppress the influence of the noise on the oscillation signal of the temperature compensated crystal oscillator 1 .

FIG. 8 is a diagram showing the output frequency of a conventional temperature-compensated crystal oscillator without the low-pass filter 5 in FIG. 1, and FIG. 2A and 2B are diagrams showing the output frequency of the oscillator 1. In each diagram, the horizontal axis is time, and the vertical axis is the output frequency.

The output frequency of this embodiment, in which noise contained in the detected voltage of the temperature sensor 2 is removed by the low-pass filter 5 shown in FIG. 9, is suppressed in variations due to noise in the output frequency compared to the conventional example of FIG. I understand.

As described above, in this embodiment, the noise contained in the detected voltage of the temperature sensor 2 can be removed by the low-pass filter 5 to suppress the influence of the noise on the oscillation frequency. can improve the phase noise of

The package structure of the temperature-compensated crystal oscillator 1 is not limited to the H-shaped package structure in which the crystal resonator 6 and the IC 13 are housed in separate housing recesses 16 and 17 as shown in FIG. A single package structure in which the resonator 6 and the IC 13 are housed in a common housing recess may be used, or a separate package structure in which the crystal resonator 6 and the IC 13 are individually housed and stacked may be used. Also, the package material may be composed of an insulating material other than ceramics.

Although a CR filter is used as the low-pass filter 5 in the above embodiment, other filters such as an LC filter may be used instead of the CR filter. In the above embodiment, the low-pass filter 5 is provided only between the temperature sensor 2 and the compensation voltage generating circuit 3. However, the low-pass filter may be added to other regions other than this portion. There may be. The present invention is applicable not only to crystal oscillators but also to other temperature compensated piezoelectric oscillators using ceramic oscillators or the like.

REFERENCE SIGNS LIST 1 temperature compensated crystal oscillator 2 temperature sensor 3 compensation voltage generation circuit 4 voltage controlled oscillation circuit 5 low pass filter 6 crystal oscillator 11 resistor 12 capacitor 13 IC

Claims (5)

A piezoelectric vibrator, a temperature sensor that outputs a detection voltage corresponding to temperature, and a compensation voltage generation circuit that generates a compensation voltage that compensates for the frequency-temperature characteristics of the piezoelectric vibrator based on the detection voltage of the temperature sensor. A temperature-compensated piezoelectric oscillator that controls an oscillation frequency based on the compensation voltage,
A low-pass filter is provided between the temperature sensor and the compensation voltage generation circuit to pass low-frequency components of the voltage detected by the temperature sensor and output the voltage to the compensation voltage generation circuit.
A temperature compensated piezoelectric oscillator characterized by: a voltage-controlled oscillation circuit that oscillates the piezoelectric vibrator and controls an oscillation frequency based on the compensation voltage;
2. The temperature compensated piezoelectric oscillator according to claim 1. The low-pass filter is composed of a resistor and a capacitor,
3. The temperature-compensated piezoelectric oscillator according to claim 1. the temperature sensor, the resistor of the low-pass filter, and the compensation voltage generation circuit are integrated in an IC;
4. The temperature compensated piezoelectric oscillator according to claim 3. wherein the piezoelectric vibrator is a quartz crystal vibrator,
5. The temperature-compensated piezoelectric oscillator according to claim 1.

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