JP2013211654A - Oscillator, electronic apparatus and temperature compensation method for oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oscillator that can further reduce phase noise of an oscillation signal while improving accuracy of temperature compensation, and further to provide an electronic apparatus and a temperature compensation method for the oscillator.SOLUTION: An oscillator 1 includes: a crystal oscillator 2; an oscillator circuit 10 that is provided with a variable capacitance element 11 and a variable capacitance element 12 and oscillates the crystal oscillator 2 at a frequency in response to a capacitance value of the variable capacitance element 11 and a capacitance value of the variable capacitance element 12; a temperature detection circuit 20; an analog temperature compensation section 110 for generating a first temperature compensation voltage on the basis of frequency temperature characteristics information 72 and a detection signal of the temperature detection circuit 20; and a digital temperature compensation section 120 for generating a second temperature compensation voltage on the basis of temperature compensation information 74 for correcting an error of an oscillating frequency that is a difference between an oscillating frequency temperature-compensated and an oscillating frequency serving as a reference and the detection signal of the temperature detection circuit 20. The capacitance value of the variable capacitance element 11 varies in response to the first temperature compensation voltage, and the capacitance value of the variable capacitance element 12 varies in response to the second temperature compensation voltage.

Description

  The present invention relates to an oscillator, an electronic device, and a temperature compensation method for the oscillator.

  A temperature-compensated crystal oscillator (TCXO: Temperature Compensated X'tal Oscillator) has a high frequency by canceling the deviation (frequency deviation) from the desired frequency (nominal frequency) of the oscillation frequency of the crystal resonator in a predetermined temperature range. Since stability is obtained, it is widely used in devices and systems that require highly accurate timing signals, such as mobile phone terminals, base stations, and GPS (Global Positioning System) receivers.

  In general, an AT-cut quartz crystal whose frequency temperature characteristic is approximated by a cubic function is used for TCXO, but this cubic function is different for each AT-cut quartz crystal. Therefore, in the final inspection of TCXO, there is a process (temperature compensation process) in which a relationship between four or more temperatures and oscillation frequencies is obtained, each coefficient of this cubic function is calculated, and temperature compensation data is written in the memory inside TCXO. Provided. When the TCXO operates, a voltage (temperature compensation voltage) that compensates the frequency temperature characteristic of the crystal resonator is generated internally based on the temperature compensation data, and the frequency of the output oscillation signal is output. The temperature characteristics are made to approach flat.

  However, since the frequency temperature characteristic of the crystal resonator is not a perfect cubic function, it cannot be made completely flat and a frequency deviation remains. In order to reduce this frequency deviation as much as possible, the frequency temperature characteristics of the crystal unit are approximated by a higher-order function as much as possible, and temperature compensation data with a large amount of data is obtained by acquiring oscillation frequencies at more temperatures in the inspection process. Must be created and written to memory. Further, a complicated circuit for generating a temperature compensation voltage corresponding to a higher-order function using the temperature compensation data is also required. Therefore, when an extremely high-accuracy frequency is required, the area cost and inspection cost of the TCXO are greatly increased, which may not be realistic.

  In order to solve such a problem, in Patent Document 1, the temperature information from the temperature detection circuit is converted into temperature compensation error data that was not previously obtained by the temperature compensated crystal oscillator according to the information of the A / D converter. Voltage-controlled oscillation of the compensation voltage obtained by inputting the output voltage of the stored memory circuit into an analog signal with a D / A converter and the output voltage of the function generation circuit of the temperature-compensated crystal oscillator. A temperature compensated oscillation circuit that compensates by inputting to a circuit has been proposed. According to this oscillation circuit, since the compensation accuracy is further improved by the digital processing of the characteristics compensated for the temperature by the analog processing, the compensation range to be handled digitally is small, and the resolution of the memory used for the digital processing can be reduced. The oscillation circuit itself can be reduced in size, and noise can be significantly suppressed because the digital compensation width is small.

JP 2000-34040 A

  However, when the technique of Patent Document 1 is applied to TCXO, a voltage generated by analog processing and a voltage generated by digital processing are applied to a variable capacitance element having sufficient sensitivity to compensate the frequency temperature characteristics of the crystal resonator. The added compensation voltage is applied. For this reason, noise generated by digital processing is applied to a variable capacitance element having high sensitivity, and there is a possibility that phase noise of an oscillation signal output from the TCXO increases.

  The present invention has been made in view of the above problems, and according to some aspects of the present invention, it is possible to improve the accuracy of temperature compensation and further reduce the phase noise of the oscillation signal. Possible oscillators, electronic devices and oscillator temperature compensation methods can be provided.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following aspects or application examples.

[Application Example 1]
An oscillator according to this application example includes an oscillation element, a first variable capacitance unit, and a second variable capacitance unit, and the oscillation element includes a capacitance value of the first variable capacitance unit and a second variable capacitance unit. Based on the oscillation circuit that oscillates at a frequency according to the capacitance value of the above, a temperature detection unit that detects the temperature around the oscillation element, frequency temperature characteristic information of the oscillation element and the detection signal of the temperature detection unit, A first temperature compensation signal generating unit for generating a first temperature compensation signal for temperature compensation so that the oscillation frequency of the oscillation element approaches a reference oscillation frequency; and the temperature compensated oscillation frequency and the reference A second temperature for temperature compensation of the oscillation frequency of the oscillation element based on temperature compensation information for correcting an error of the oscillation frequency that is a difference from the oscillation frequency to be and a detection signal of the temperature detection unit. Generate compensation signal And a temperature value of the first variable capacitance unit changes according to the first temperature compensation signal, and the second variable capacitance unit includes the second temperature compensation signal generation unit. The capacitance value changes according to the temperature compensation signal.

  According to the oscillator according to this application example, since the error of the oscillation frequency that cannot be compensated for by the first temperature compensation signal is corrected by the second temperature compensation signal, only the temperature compensation by the first temperature compensation signal is performed. Compared with, the accuracy of temperature compensation is improved, and the accuracy of the oscillation frequency can be further increased.

  In addition, according to the oscillator according to this application example, the second variable capacitance unit is provided independently of the first variable capacitance unit for temperature compensation by the second temperature compensation signal. Regardless of the sensitivity of the variable capacitor (the amount of change in the oscillation frequency relative to the size of the first temperature compensation signal), the sensitivity of the second variable capacitor can be set freely. Therefore, for example, the sensitivity of the second variable capacitance section (the magnitude of the change in the oscillation frequency with respect to the magnitude of the second temperature compensation signal) is set to an optimum sensitivity that reduces the phase noise of the oscillation signal. Thus, higher frequency accuracy can be realized.

[Application Example 2]
In the oscillator according to the application example described above, the sensitivity of the second variable capacitance unit may be lower than the sensitivity of the first variable capacitance unit.

  According to the oscillator according to this application example, since the sensitivity of the second variable capacitance unit is lower, one variable capacitance element is used for the temperature compensation by the first temperature compensation signal and the temperature compensation by the second temperature compensation signal. As compared with the case of performing the above, the phase noise of the oscillation signal caused by the noise generated in the second temperature compensation signal generation unit can be reduced, so that higher frequency accuracy can be realized.

[Application Example 3]
In the oscillator according to the application example, the capacitance value of the second variable capacitance unit may change according to a control signal input from the outside.

  According to the oscillator according to this application example, it is possible to adjust the oscillation frequency from the outside while maintaining high frequency accuracy.

[Application Example 4]
In the oscillator according to the application example, the second temperature compensation signal generation unit is configured to perform the second temperature compensation signal based on a control signal input from the outside together with the temperature compensation information and the detection signal of the temperature detection unit. A signal may be generated.

  According to the oscillator according to this application example, the second temperature compensation signal for simultaneously performing the temperature compensation by the second temperature compensation signal and the frequency control is generated based on the processing of the second temperature compensation signal generation unit. Therefore, fine control can be performed in accordance with the sensitivity characteristic of the second variable capacitance element.

[Application Example 5]
In the oscillator according to the application example, the second variable capacitance unit is a capacitor bank including a plurality of variable capacitance elements and a plurality of switch elements, and the second temperature compensation signal generation unit is configured to include the second temperature compensation signal generation unit. As the temperature compensation signal, a signal for controlling the opening / closing of each of the plurality of switch elements may be generated.

  Since the capacitor bank is used for temperature compensation by the second temperature compensation signal (no variable capacitor is used), the phase noise of the oscillation signal can be reduced.

[Application Example 6]
The electronic device according to this application example includes the oscillator according to any one of the application examples described above.

[Application Example 7]
The temperature compensation method for an oscillator according to this application example includes a vibration element, a first variable capacitor unit, and a second variable capacitor unit, and the oscillator device includes a capacitance value of the first variable capacitor unit and a second variable capacitor unit. An oscillation circuit that oscillates at a frequency corresponding to the capacitance value of the variable capacitance portion of the oscillator, and a temperature compensation method for the oscillator that compensates the temperature of the oscillation frequency of the oscillator, the temperature detection detecting the temperature around the oscillation element First temperature compensation for temperature compensation so that the oscillation frequency of the oscillation element approaches a reference oscillation frequency based on the step, the frequency temperature characteristic information of the oscillation element, and the detection result of the temperature detection step A first temperature compensation signal generating step for generating a signal, temperature compensation information for correcting an error in oscillation frequency, which is a difference between the temperature compensated oscillation frequency and the reference oscillation frequency, and the temperature detection. And a second temperature compensation signal generating step for generating a second temperature compensation signal for temperature compensating the oscillation frequency of the oscillation element based on the detection result of the step, the first variable capacitance unit The capacitance value changes according to the first temperature compensation signal, and the capacitance value of the second variable capacitance section changes according to the second temperature compensation signal.

  According to the temperature compensation method of the oscillator according to this application example, the error of the oscillation frequency that cannot be compensated by the first temperature compensation signal is corrected by the second temperature compensation signal. Therefore, the temperature compensation by the first temperature compensation signal is performed. Compared with the case where only the operation is performed, the accuracy of the temperature compensation is improved, and the accuracy of the oscillation frequency can be further increased.

  In addition, according to the temperature compensation method for an oscillator according to this application example, the second variable capacitance unit is provided independently of the first variable capacitance unit for temperature compensation by the second temperature compensation signal. The sensitivity of the second variable capacitor can be freely set regardless of the sensitivity of the first variable capacitor. Therefore, for example, by setting the sensitivity of the second variable capacitance unit to an optimum sensitivity that reduces the phase noise of the oscillation signal, higher frequency accuracy can be realized.

The figure which shows the structural example of the oscillator of 1st Embodiment. The figure which shows the structural example of an oscillation circuit. The figure which shows the equivalent circuit of a crystal oscillator. The figure which shows an example of temperature compensation information. The figure which shows the experimental result for an effect confirmation. The figure which shows an example of the graph of the sensitivity of a variable capacitance element. The figure which shows the other structural example of the oscillator of 1st Embodiment. The figure which shows the structural example of the oscillator of 2nd Embodiment. The figure which shows the other structural example of the oscillator of 2nd Embodiment. The figure which shows the structural example of the oscillator of 3rd Embodiment. The figure which shows the other structural example of the oscillator of 3rd Embodiment. The figure which shows the structural example of the oscillator of 4th Embodiment. The figure which shows the structural example of the oscillation circuit in 4th Embodiment. The figure which shows an example of the temperature compensation information in 4th Embodiment. 1 is a functional block diagram of an electronic apparatus according to an embodiment. 1 is a diagram illustrating an example of an appearance of an electronic apparatus according to an embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. The embodiments described below do not unduly limit the contents of the present invention described in the claims. Also, not all of the configurations described below are essential constituent requirements of the present invention.

1. Oscillator 1-1. First Embodiment FIG. 1 is a diagram illustrating a configuration example of an oscillator according to a first embodiment. As shown in FIG. 1, the oscillator 1 of the first embodiment is a temperature compensated crystal oscillator (TCXO) including a crystal resonator 2 and an integrated circuit (IC) 100.

  The IC 100 includes an oscillation circuit 10, a temperature detection circuit 20, a function generation circuit 30, an A / D conversion circuit 40, a data conversion circuit 50, a D / A conversion circuit 60, and a storage unit 70.

  One end of the crystal unit 2 is connected to the external terminal 101 of the IC 100, and the other end is connected to the external terminal 102 of the IC 100.

  The S1 terminal and S2 terminal of the oscillation circuit 10 are connected to the external terminal 101 and the external terminal 102 of the IC 100, respectively. That is, the oscillation circuit 10 is connected to both ends of the crystal resonator 2 via the external terminal 101 and the external terminal 102 of the IC 100. The oscillation circuit 10 includes a variable capacitance element 11 (an example of a first variable capacitance section) and a variable capacitance element 12 (an example of a second variable capacitance section). The capacitance value of the variable capacitance element 11 and the variable capacitance element The crystal unit 2 is oscillated at a frequency corresponding to the capacitance value of 12. An oscillation signal generated by the oscillation of the crystal unit 2 is output to the outside from the OUT terminal of the oscillation circuit 10 via the external terminal 103.

  FIG. 2 is a diagram illustrating a configuration example of the oscillation circuit 10. As shown in FIG. 2, the oscillation circuit 10 includes a variable capacitance element (variable capacitance diode) 11, a variable capacitance element (variable capacitance diode) 12, a resistor 13, a resistor 14, a capacitor 15, a capacitor 16, a CMOS inverter 17, and a resistor 18. It is comprised including.

  In the CMOS inverter 17, an input terminal (gate terminal) and an output terminal (drain terminal) are connected to both ends of the crystal unit 2 through S 1 terminal and S 2 terminal, respectively, and amplifies the output signal of the crystal unit 2. And function as an amplifying element that inputs to the crystal unit 2. A capacitor 15 and a capacitor 16 that function as a load capacity of the crystal resonator 2 are connected to an input terminal and an output terminal of the CMOS inverter 20. A resistor 18 (feedback resistor) is connected between the input terminal and the output terminal of the CMOS inverter 20. The output terminal of the CMOS inverter 20 is connected to the OUT terminal.

  The variable capacitance element (variable capacitance diode) 11 is connected between the capacitor 15 and the ground, and a resistor 13 (input resistance) is connected between the cathode terminal and the C1 terminal of the oscillation circuit 10.

  Similarly, the variable capacitance element (variable capacitance diode) 12 is connected between the capacitor 16 and the ground, and a resistor 14 (input resistance) is connected between the cathode terminal and the C2 terminal of the oscillation circuit 10. Yes.

  As will be described later, two different temperature compensation voltages are applied to the C1 terminal and the C2 terminal, and the capacitance values of the variable capacitance elements 11 and 12 change according to the two temperature compensation voltages.

The crystal resonator 2 (an example of an oscillation element) is represented by an equivalent circuit (R ₁ is equivalent series resistance, L ₁ is equivalent series inductance, C ₁ is equivalent series capacitance, and C ₀ is parallel capacitance) as shown in FIG. is, the crystal oscillator 2 includes a parallel capacitance _{C 0,} the condenser 15, the condenser 16, the variable capacitance element 11, the combined capacitance (load capacitance) of the variable capacitance element 12 oscillates at a frequency corresponding to the _{C L.}

The capacitance values of the variable capacitance elements 11 and 12 are increased or decreased within a predetermined range by the temperature compensation voltages applied from the C1 terminal and the C2 terminal, respectively, and thereby the combined capacitance _CL is changed, whereby the oscillation frequency of the crystal resonator 2 is changed. Is compensated so as to approach the reference oscillation frequency.

  Returning to FIG. 1, the temperature detection circuit 20 (an example of a temperature detection unit) detects the temperature around the vibrator 2 and outputs a detection voltage (an example of a detection signal) corresponding to the detected temperature.

  The function generation circuit 30 oscillates based on the oscillation frequency of the crystal resonator 2 according to the detection voltage of the temperature detection circuit 20 based on the frequency temperature characteristic information 72 of the crystal resonator 2 stored in the storage unit 70. A temperature compensation voltage (an example of a first temperature compensation signal) for temperature compensation so as to approach the frequency is generated. The frequency temperature characteristic information 72 is information on a function (for example, a cubic function) that approximates the frequency temperature characteristic of the crystal unit 2, and is, for example, information on a coefficient value of the function. The frequency temperature characteristic information 72 is calculated by using a method such as least square approximation from information on the oscillation frequency at a predetermined number of temperatures acquired in the inspection process of the oscillator 1 and is written in the storage unit 70, for example.

  The temperature compensation voltage generated by the function generation circuit 30 is applied to the C1 terminal of the oscillation circuit 10, and the capacitance value of the variable capacitance element 11 is controlled. Thereby, the oscillation frequency of the crystal resonator 2 is controlled, and the first temperature compensation is performed.

  The A / D conversion circuit 40 converts the detection voltage (temperature detection voltage) of the temperature detection circuit 20 into a digital value.

  Based on the temperature compensation information 74 stored in the storage unit 70, the data conversion circuit 50 performs temperature compensation on the digital value (temperature detection voltage value) converted by the A / D conversion circuit 40 on the oscillation frequency of the crystal unit 2. Is converted to a temperature compensated voltage value. The temperature compensation information 74 is information for correcting an error in the oscillation frequency that is the difference between the oscillation frequency temperature-compensated by the function generation circuit 30 and the reference oscillation frequency. Since the temperature compensation information 74 is required to be highly accurate, it is not information on the coefficient value of the function, for example, information defining a correspondence relationship between the temperature detection voltage value and the temperature compensation voltage value as shown in FIG. It is. For example, in the inspection process of the oscillator 1, after the frequency temperature characteristic information 72 is written in the storage unit 70, the temperature at a plurality of temperatures is compensated by the temperature compensation voltage generated by the function generation circuit 30. The temperature compensation information 74 is generated by acquiring information on the detected voltage and the oscillation frequency, and calculating the temperature compensation voltage value necessary for correcting the frequency error at each temperature detection voltage value, and is written in the storage unit 70.

  If the detection voltage (temperature detection voltage) of the temperature detection circuit 20 is a voltage value that is not defined in the temperature compensation information 74, the data conversion circuit 50 calculates the temperature compensation voltage value by complementary calculation. As the data amount of the temperature compensation information is larger, the accuracy of the oscillation frequency of the oscillator 1 is improved, but the area cost is increased. Therefore, it is only necessary to prepare temperature compensation information with a minimum necessary data amount that satisfies the required oscillation frequency accuracy.

  The D / A conversion circuit 60 converts the temperature compensation voltage value converted by the data conversion circuit 50 into an analog signal, that is, a temperature compensation voltage (an example of a second temperature compensation signal).

  The temperature compensation voltage converted by the D / A conversion circuit 60 is applied to the C2 terminal of the oscillation circuit 10, and the capacitance value of the variable capacitance element 12 is controlled. Thereby, the oscillation frequency of the crystal unit 2 is controlled, and the second temperature compensation is performed.

  The function generation circuit 30 functions as an analog temperature compensation unit 110 (an example of a first temperature compensation signal generation unit) that generates a temperature compensation voltage by analog processing based on the temperature detection voltage. In addition, the A / D conversion circuit 40, the data conversion circuit 50, and the D / A conversion circuit generate a temperature compensation voltage mainly by digital processing based on the temperature detection voltage (second temperature compensation). It functions as an example of a signal generation unit. Hereinafter, the temperature compensation voltage generated by the analog temperature compensation unit 110 will be appropriately referred to as “analog compensation voltage”, and the temperature compensation voltage generated by the digital temperature compensation unit 120 will be referred to as “digital compensation voltage”. Further, temperature compensation by the analog temperature compensation unit 110 is referred to as “analog temperature compensation”, and temperature compensation by the digital temperature compensation unit 120 is referred to as “digital temperature compensation”.

  According to the oscillator 1 having such a configuration, analog temperature compensation equivalent to the temperature compensation performed in the conventional TCXO is performed, and furthermore, an error of the oscillation frequency that cannot be compensated by the analog temperature compensation is obtained by digital temperature compensation. It can be corrected. Thereby, compared with the conventional TCXO, the frequency accuracy can be greatly improved. In order to confirm this effect, an existing temperature-controlled crystal oscillator with voltage control function (VC-TCXO: Voltage Controlled Temperature Compensated X'tal Oscillator) is used, and the control voltage input terminal (Vc terminal) for frequency control is used. Figure shows the frequency temperature characteristics obtained when a constant voltage is applied (when only analog temperature compensation is performed) and when ideal digital compensation voltage is applied (when analog temperature compensation and digital temperature compensation are performed). As shown in FIG. In FIG. 5, G1 is a result when a constant voltage is applied to the Vc terminal (when only analog temperature compensation is performed), and G1 is a result when a digital compensation voltage is applied to the Vc terminal (analog temperature compensation and digital temperature compensation are performed). (If you do). The horizontal axis represents temperature, and the vertical axis represents frequency error with respect to a frequency of 25 ° C. According to the result of FIG. 5, when only analog temperature compensation is performed, the frequency error is −30 ppb to +100 ppb in the range of 0 ° C. to 70 ° C., whereas when analog temperature compensation and digital temperature compensation are performed. In the range of 0 ° C. to 70 ° C., the frequency error is −10 ppb to +10 ppb, and the frequency accuracy is greatly improved. However, the digital compensation voltage applied to the Vc terminal is an ideal voltage value that is not subjected to A / D conversion and D / A conversion. However, in the oscillator according to the present embodiment, the digital temperature compensation unit 120 includes the A / D conversion voltage. Since the conversion circuit 40 and the D / A conversion circuit 60 are included, the frequency error increases as the number of these bits decreases. Therefore, it is necessary to appropriately select the number of bits for satisfying the required frequency accuracy.

  By the way, in the oscillator 1 of this embodiment, in the analog temperature compensation, since the temperature compensation is performed on the frequency temperature characteristic of the crystal resonator 2, it is necessary to make the variable range of the oscillation frequency relatively wide. On the other hand, in digital temperature compensation, it is only necessary to correct a frequency error that cannot be compensated for by analog temperature compensation. Therefore, the variable range of the oscillation frequency may be narrower than in the case of analog temperature compensation. Therefore, the sensitivity of the variable capacitance element 12 (the magnitude of change in the oscillation frequency with respect to the temperature compensation voltage) may be lower than the sensitivity of the variable capacitance element 11. FIG. 6A is a diagram illustrating an example of a sensitivity graph of the variable capacitance element 11, and FIG. 6B is a diagram illustrating an example of a sensitivity graph of the variable capacitance element 12. 6A and 6B, the horizontal axis represents the applied voltage, and the vertical axis represents the frequency change amount. In the example of FIG. 6A, the frequency temperature characteristic of the crystal resonator 2 fluctuates within a range of ± 10 ppm with respect to the reference temperature (for example, 25 ° C.), and this is corrected by analog temperature compensation. Changes the oscillation frequency in the range of −10 ppm to +10 ppm with respect to the applied voltage of 0 V to the power supply voltage of 3.3 V. In the example of FIG. 6B, the frequency error is driven to a range of ± 1 ppm by analog temperature compensation, and this is corrected by digital temperature compensation. Therefore, the variable capacitance element 12 has an applied voltage of 0 V to power supply voltage 3.3 V. On the other hand, the oscillation frequency is changed in the range of -1 ppm to +1 ppm. Therefore, in the example of FIGS. 6A and 6B, the sensitivity of the variable capacitance element 12 is 1/10 of the sensitivity of the variable capacitance element 11.

  If there is no variable capacitance element 12 and a voltage obtained by adding an analog compensation voltage and a digital compensation voltage is applied to the variable capacitance element 11 having the sensitivity shown in FIG. 6A, the applied voltage for changing the frequency by 1 ppm is 0.165V. Therefore, the range of the digital compensation voltage is in the range of ± 0.165V centering on 1.65V. On the other hand, like the oscillator 1 of the present embodiment, the analog compensation voltage is applied to the variable capacitor 11 having the sensitivity shown in FIG. 6A, and the digital compensation voltage is applied to the variable capacitor 12 having the sensitivity shown in FIG. In this case, the range of the digital compensation voltage is within a range of ± 1.65V with 1.65V being the center.

  That is, as for the digital compensation voltage, when an analog compensation voltage and a digital compensation voltage are applied to the variable capacitance element 11 and the variable capacitance element 12, respectively, a voltage obtained by adding the analog compensation voltage and the digital compensation voltage is applied to the variable capacitance element 11. 10 times the compensation voltage value. Since the analog compensation voltage is amplified by an amplifier or the like to generate a voltage, when the compensation voltage becomes 10 times, the noise also becomes 10 times. However, the digital compensation voltage is generated by dividing the reference voltage by a resistor or the like. Even if is 10 times, the noise is not 10 times. If the amount of noise is constant even when the digital compensation voltage becomes 10 times, the latter, that is, the ratio of the digital compensation voltage to the noise is 1/10 of the former in the oscillator 1 of the present embodiment. Therefore, the phase noise of the oscillation signal is reduced, and the accuracy of digital temperature compensation is high.

  As described above, according to the oscillator of the first embodiment, the accuracy of the temperature compensation can be improved by correcting the error of the oscillation frequency that cannot be compensated by the analog temperature compensation by the digital temperature compensation. Furthermore, according to the oscillator of the present embodiment, the variable sensitivity element 11 having relatively high sensitivity for analog temperature compensation and the variable capacitance element 12 having relatively low sensitivity for digital temperature compensation are separately provided. The phase noise of the oscillation signal caused by the noise generated in the digital temperature compensation unit 120 can be reduced. Therefore, higher frequency accuracy can be realized as compared with the case where analog temperature compensation and digital temperature compensation are performed using one variable capacitance element.

  1 is a temperature-compensated oscillation circuit including a temperature-compensating variable capacitor 11 and a temperature-compensating variable capacitor 12, but the temperature-compensating variable capacitor 11 and the frequency control element are used for frequency control. A temperature compensated oscillation circuit with a voltage control function including the variable capacitance element 12 may be used. In this case, the C2 terminal of the oscillation circuit 10 is a control voltage input terminal (Vc terminal) for frequency control, and the variable capacitance element 12 is used for digital temperature compensation instead of being used for frequency adjustment. In this way, an existing temperature compensated oscillation circuit with a voltage control function may be used.

  In FIG. 1, an example in which a circuit portion other than the crystal resonator 2 is configured by a single chip IC 100 is described. However, the circuit portion may be divided into a plurality of ICs. For example, as shown in FIG. 7, the digital temperature compensation unit 120 may be mounted on the IC 200 and the other circuit portions may be mounted on the IC 100. In this case, the frequency temperature characteristic information 72 is stored in the storage unit 70 of the IC 100, and the temperature compensation information 74 is stored in the storage unit 71 of the IC 200. The IC 100 is provided with an external terminal 104 for outputting a temperature detection voltage and an external terminal 105 for inputting a digital compensation voltage. The IC 200 is provided with an external terminal 201 for inputting a temperature detection voltage and a digital signal. An external terminal 202 for outputting a compensation voltage is provided, and the external terminal 104 and the external terminal 201, and the external terminal 105 and the external terminal 202 are connected to each other.

  For example, an existing temperature compensated crystal oscillator with a voltage control function (VC-TCXO) may be used as the IC 100. In this case, the variable capacitance element 11 is a temperature compensation variable capacitance element built in the VC-TCXO, and the variable capacitance element 12 is a frequency control variable capacitance element. The external terminal 105 is a control voltage input terminal (Vc terminal) for frequency control, and the digital compensation voltage output from the external terminal 202 of the IC 200 may be input to the Vc terminal. As described above, the frequency control function cannot be used by using the existing temperature-compensated crystal oscillator with voltage control function (VC-TCXO), but frequency accuracy can be improved by performing analog temperature compensation and digital temperature compensation. A high temperature compensated crystal oscillator (TCXO) can be easily realized.

1-2. Second Embodiment FIG. 8 is a diagram illustrating a configuration example of an oscillator according to a second embodiment. In FIG. 8, the same components as those in FIG. As shown in FIG. 8, in the oscillator 1 of the second embodiment, an external terminal 105 and an adder 80 are added to the IC 100 as compared to the first embodiment (FIG. 1).

  The external terminal 105 is a control voltage input terminal (Vc terminal) for frequency control.

  The adder 80 adds the control voltage input from the external terminal 105 and the output voltage (digital compensation voltage) of the D / A conversion circuit, and the output voltage of the adder 80 is variable capacitance via the C2 terminal of the oscillation circuit 10. Applied to the element 12. That is, the variable capacitance element 12 is a variable capacitance element for digital temperature compensation and a variable capacitance element for frequency adjustment.

  The adder 80 may add the control voltage input from the external terminal 105 and the output voltage (digital compensation voltage) of the D / A conversion circuit by weighting (multiplying each by a predetermined coefficient).

  Since the other configuration of the oscillator 1 of the second embodiment is the same as that of the first embodiment, description thereof is omitted.

  As described above, the oscillator 1 of the second embodiment performs temperature compensation of the oscillation frequency of the crystal resonator 2 and can adjust the frequency from the outside, that is, a temperature-compensated crystal oscillator with a voltage control function. (VC-TCXO). According to the oscillator of the second embodiment, the same effect as that of the oscillator of the first embodiment can be obtained, and the oscillation frequency of the crystal unit 2 is adjusted from the outside while maintaining high frequency accuracy. be able to.

  In FIG. 8, an example in which circuit portions other than the crystal unit 2 are configured by one-chip IC 100 is described. However, the circuit portion may be divided into a plurality of ICs. For example, as shown in FIG. 9, the digital temperature compensation unit 120 and the adder 80 may be mounted on the IC 200, and other circuit portions may be mounted on the IC 100. In this case, the frequency temperature characteristic information 72 is stored in the storage unit 70 of the IC 100, and the temperature compensation information 74 is stored in the storage unit 71 of the IC 200. The IC 100 is provided with an external terminal 104 for outputting a temperature detection voltage. The IC 200 has an external terminal 201 for inputting a temperature detection voltage, an external terminal 202 for outputting a digital compensation voltage, and a frequency. An external terminal 203 for inputting a control voltage for control is provided, and the external terminal 104 and the external terminal 201, and the external terminal 105 and the external terminal 202 are connected to each other. For example, an existing temperature compensated crystal oscillator with a voltage control function (VC-TCXO) may be used as the IC 100.

1-3. Third Embodiment FIG. 10 is a diagram illustrating a configuration example of an oscillator according to a third embodiment. 10, the same components as those in FIG. 8 are denoted by the same reference numerals. As shown in FIG. 10, in the oscillator 1 of the third embodiment, the adder 80 is eliminated and the A / D conversion circuit 90 is added in the IC 100 as compared to the second embodiment (FIG. 8).

  The A / D conversion circuit 90 converts the control voltage input from the external terminal 105 into a digital value.

  The data conversion circuit 50 refers to the temperature compensation information 74 stored in the storage unit 70 and extracts a temperature compensation voltage value corresponding to the digital value (temperature detection voltage value) converted by the A / D conversion circuit 40. The data conversion circuit 50 converts the digital value x converted by the A / D conversion circuit 90 with a predetermined function f (x) to generate a control voltage value. This function f is associated with a function that represents the amount of frequency change with the applied voltage of the variable capacitance element 12 as a variable. Then, the data conversion circuit 50 adds the temperature compensation voltage value and the control voltage value to calculate a voltage value to be applied to the variable capacitance element 12.

  The voltage value generated by the data conversion circuit 50 is converted into a voltage by the D / A conversion circuit 60 and applied to the C2 terminal of the oscillation circuit 10. The capacitance value of the variable capacitance element 12 is controlled by this applied voltage, that is, a voltage obtained by adding the digital compensation voltage and the control voltage. Thereby, the oscillation frequency of the crystal unit 2 is controlled, and frequency adjustment is performed together with digital temperature compensation.

  The other configuration of the oscillator 1 according to the third embodiment is the same as that of the first embodiment, and a description thereof will be omitted.

  As described above, the oscillator 1 according to the third embodiment performs temperature compensation of the oscillation frequency of the crystal resonator 2 and can adjust the frequency from the outside, that is, a temperature-compensated crystal oscillator with a voltage control function. (VC-TCXO). According to the oscillator of the third embodiment, the same effect as that of the oscillator of the first embodiment can be obtained, and the oscillation frequency of the crystal resonator 2 can be adjusted from the outside.

  Further, according to the oscillator of the third embodiment, the voltage value to be applied to the variable capacitance element 12 for simultaneously performing digital temperature compensation and frequency control is generated based on the digital processing of the data conversion circuit 50. Fine control in accordance with the sensitivity characteristic of the element 12 can be performed.

  In FIG. 10, an example in which the circuit portion other than the crystal unit 2 is configured by the one-chip IC 100 has been described, but may be configured by being divided into a plurality of ICs. For example, as shown in FIG. 11, the digital temperature compensation unit 120 and the A / D conversion circuit 90 may be mounted on the IC 200, and the other circuit portions may be mounted on the IC 100. In this case, the frequency temperature characteristic information 72 is stored in the storage unit 70 of the IC 100, and the temperature compensation information 74 is stored in the storage unit 71 of the IC 200. The IC 100 is provided with an external terminal 104 for outputting a temperature detection voltage. The IC 200 has an external terminal 201 for inputting a temperature detection voltage, an external terminal 202 for outputting a digital compensation voltage, and a frequency. An external terminal 203 for inputting a control voltage for control is provided, and the external terminal 104 and the external terminal 201, and the external terminal 105 and the external terminal 202 are connected to each other. For example, an existing temperature compensated crystal oscillator with a voltage control function (VC-TCXO) may be used as the IC 100.

1-4. Fourth Embodiment FIG. 12 is a diagram illustrating a configuration example of an oscillator according to a fourth embodiment. 12, the same components as those in FIG. 1 are denoted by the same reference numerals. As shown in FIG. 12, in the oscillator 1 of the fourth embodiment, the variable capacitance element 12 of the oscillation circuit 10 is replaced with a capacitance bank 19 in the IC 100 as compared with the first embodiment (FIG. 1). The / A conversion circuit 60 is eliminated.

FIG. 13 is a diagram illustrating a configuration example of the oscillation circuit 10 according to the fourth embodiment. In FIG. 13, the same components as those in FIG. As shown in FIG. 13, in the oscillation circuit 10 according to the fourth embodiment, the variable capacitance element (variable capacitance diode) 12 is replaced with a capacitance bank 19 and the C2 terminal is B _{1 to} B _n terminals ( n is an integer of 2 or more).

The capacitor bank 19 (an example of the second variable capacitor unit) includes n capacitors C _{1 to} C _n and n switch elements SW _{1 to} SW _n , and the capacitor C _i and the switch element SW _i connected in series. (I = 1, 2,..., N) are connected in parallel between the capacitor 16 and the ground. Control signals are supplied from the B _{1 to} B _n terminals to the switch elements SW _{1 to} SW _n , respectively, and the switch elements SW _{1 to} SW _n are turned on or off in accordance with the control signals. When the switch element SW _i is turned condenser C _i between the condenser 16 and ground is connected, at the load capacitance C _L of the crystal oscillator 2. For _example, when the SW 1 to SW _n are all turned on, the capacitor _C 1 -C _n, condenser 15, a condenser 16, the combined capacitance load capacitance _{C L} next to the variable capacitance element _11, the SW 1 to SW _n are all turned off, the capacitor 15, a condenser 16, the combined capacitance of the variable capacitance element 11 is the load capacitance _{C L.}

As shown in FIG. 12, the data conversion circuit 50 converts the digital value (temperature detection voltage value) converted by the A / D conversion circuit 40 based on the temperature compensation information 74 stored in the storage unit 70 into a crystal resonator. 2 is converted into a control signal of the capacitor bank 19 for temperature compensation. The temperature compensation information 74 in the fourth embodiment includes, for example, a switch control code (A) for controlling the temperature detection voltage value and on / off of the switch elements SW _{1 to} SW _n of the capacitor bank 19 as shown in FIG. _n A _n-1 ... A ₂ A ₁ ) is defined information. Each bit of the switch control code _{A i (i = 1,2, ···} , n) is the control bit of the switch element SW _i, if _A i = 0 the switch element SW _i is turned _{off, A} i = If it is 1, the switch element SW _i is turned on. For example, in the inspection process of the oscillator 1, after the frequency temperature characteristic information 72 is written in the storage unit 70, the temperature at a plurality of temperatures is compensated by the temperature compensation voltage generated by the function generation circuit 30. Information on the detection voltage and the oscillation frequency is acquired, a load capacitance value necessary for correcting the frequency error at each temperature detection voltage value is calculated, and the switch elements SW _{1 to} SW _n closest to the load capacitance value are turned on / off. The temperature compensation information 74 is created by obtaining the off pattern and written in the storage unit 70.

Data conversion circuit 50 refers to the temperature compensation information 74, extracts the switch control code corresponding to the temperature detected voltage value, a voltage value corresponding to bits A ₁ to A _n of the switch control code (0V or the power supply voltage) ( An example of the second temperature compensation signal is applied to the B _{1 to} B _n terminals of the oscillation circuit 10. Thereby, the oscillation frequency of the crystal unit 2 is controlled, and digital temperature compensation is performed.

  Since the other structure of the oscillator 1 of 4th Embodiment is the same as that of 1st Embodiment, the description is abbreviate | omitted.

  As described above, the oscillator 1 according to the fourth embodiment performs temperature compensation of the oscillation frequency of the crystal resonator 2 and can adjust the frequency from the outside, that is, a temperature-compensated crystal oscillator with a voltage control function. (VC-TCXO). According to the oscillator of the fourth embodiment, the same effect as that of the oscillator of the first embodiment can be obtained, and since the capacitor bank 19 is used for digital temperature compensation (no variable capacitor is used), the oscillation signal The phase noise can be reduced.

2. Electronic Device FIG. 15 is a functional block diagram of the electronic device of the present embodiment. FIG. 16 is a diagram illustrating an example of the appearance of a smartphone that is an example of the electronic apparatus of the present embodiment.

  The electronic device 300 according to the present embodiment includes a clock generation unit 310, a CPU (Central Processing Unit) 320, an operation unit 330, a ROM (Read Only Memory) 340, a RAM (Random Access Memory) 350, a communication unit 360, a display unit 370, A sound output unit 380 is included. Note that the electronic device of the present embodiment may have a configuration in which some of the components (each unit) in FIG. 15 are omitted or changed, or other components are added.

  The clock generation unit 310 generates various clock signals using the oscillation signal of the oscillator 312 as the original oscillation clock. The oscillator 312 is, for example, one of the oscillators 1 of the first to fourth embodiments described above.

  The CPU 320 performs various calculation processes and control processes using various clock signals generated by the clock generation unit 310 in accordance with programs stored in the ROM 340 and the like. Specifically, the CPU 320 performs various processes according to operation signals from the operation unit 330, processes for controlling the communication unit 360 to perform data communication with the outside, and displays various types of information on the display unit 370. Processing for transmitting a display signal, processing for causing the sound output unit 380 to output various sounds, and the like are performed.

  The operation unit 330 is an input device including operation keys, button switches, and the like, and outputs an operation signal corresponding to an operation by the user to the CPU 320.

  The ROM 340 stores programs, data, and the like for the CPU 320 to perform various calculation processes and control processes.

  The RAM 350 is used as a work area of the CPU 320, and temporarily stores programs and data read from the ROM 340, data input from the operation unit 330, calculation results executed by the CPU 320 according to various programs, and the like.

  The communication unit 360 performs various controls for establishing data communication between the CPU 320 and an external device.

  The display unit 370 is a display device configured by an LCD (Liquid Crystal Display) or the like, and displays various types of information based on a display signal input from the CPU 320.

  The sound output unit 380 is a device that outputs sound such as a speaker.

  By incorporating the oscillator 1 of this embodiment as the oscillator 312, an electronic device with higher performance can be realized.

  Various electronic devices can be considered as such an electronic device 300. For example, personal computers (for example, mobile personal computers, laptop personal computers, tablet personal computers), mobile terminals such as mobile phones, digital steel Cameras, inkjet discharge devices (for example, inkjet printers), storage area network devices such as routers and switches, local area network devices, TVs, video cameras, video tape recorders, car navigation devices, pagers, electronic notebooks (also with communication functions) Electronic dictionary, calculator, electronic game machine, game controller, word processor, workstation, video phone, security TV monitor, electronic Binoculars, POS terminal, medical equipment (eg, electronic thermometer, blood pressure meter, blood glucose meter, electrocardiogram measuring device, ultrasonic diagnostic device, electronic endoscope), fish detector, various measuring devices, instruments (eg, vehicle, aircraft, Ship instruments), flight simulator, head mounted display, motion trace, motion tracking, motion controller, PDR (pedestrian position measurement), and the like.

3. The present invention is not limited to this embodiment, and various modifications can be made within the scope of the present invention.

  Examples of the oscillation element include a SAW (Surface Acoustic Wave) resonator, an AT cut crystal resonator, an SC cut crystal resonator, a tuning fork crystal resonator, other piezoelectric resonators, and a MEMS (Micro Electro Mechanical Systems) resonator. Can be used.

  As a substrate material of the oscillation element, a piezoelectric single crystal such as crystal, lithium tantalate, or lithium niobate, a piezoelectric material such as piezoelectric ceramics such as lead zirconate titanate, or a silicon semiconductor material can be used.

  As the excitation means of the oscillation element, one using a piezoelectric effect may be used, or electrostatic driving using a Coulomb force may be used.

  In this embodiment, an oscillation circuit using a CMOS inverter as an amplifying element has been described as an example. However, as an amplifying element, a bipolar transistor, a field effect transistor (FET), a metal oxide film type field effect is used. Any type of oscillation circuit using a transistor (MOSFET: Metal Oxide Semiconductor Field Effect Transistor), a thyristor, or the like may be used.

  In this embodiment, the temperature compensated crystal oscillator (TCXO) has been described as an example. However, the oscillator of the present invention is not limited to this, and a piezoelectric oscillator, a SAW oscillator, and a voltage control type having a temperature compensation function. An oscillator, a silicon oscillator, an atomic oscillator, or the like may be used.

  The above-described embodiments and modifications are merely examples, and the present invention is not limited to these. For example, it is possible to appropriately combine each embodiment and each modification.

  The present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations that have the same functions, methods, and results, or configurations that have the same objects and effects). In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that exhibits the same operational effects as the configuration described in the embodiment or a configuration that can achieve the same object. Further, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

DESCRIPTION OF SYMBOLS 1 Oscillator, 2 Crystal oscillator, 10 Oscillator circuit, 11 Variable capacity element, 12 Variable capacity element, 13 Resistance, 14 Resistance, 15 Capacitor, 16 Capacitor, 17 CMOS inverter, 18 Resistance, 19 Capacity bank, 20 Temperature detection circuit, 30 function generation circuit, 40 A / D conversion circuit, 50 data conversion circuit, 60 D / A conversion circuit, 70 storage unit, 80 adder, 90 A / D conversion circuit, 71 storage unit, 72 frequency temperature characteristic information, 74 Temperature compensation information, 100 IC, 101, 102, 103, 104, 105 IC external terminal, 110 analog temperature compensation unit, 120 digital temperature compensation unit, 200 IC, 201, 202, 203 IC external terminal, 300 electronic device, 310 clock generator, 312 oscillator, 320 CPU, 330 operation , 340 ROM, 350 RAM, 360 communication unit, 370 display unit, 380 sound output section

Claims (7)

An oscillation element;
An oscillation circuit comprising a first variable capacitance unit and a second variable capacitance unit, wherein the oscillation element oscillates at a frequency corresponding to a capacitance value of the first variable capacitance unit and a capacitance value of the second variable capacitance unit. When,
A temperature detection unit for detecting a temperature around the oscillation element;
Based on the frequency temperature characteristic information of the oscillation element and the detection signal of the temperature detection unit, a first temperature compensation signal is generated for temperature compensation so that the oscillation frequency of the oscillation element approaches a reference oscillation frequency. A first temperature compensation signal generator that
Based on temperature compensation information for correcting an oscillation frequency error, which is a difference between the temperature compensated oscillation frequency and the reference oscillation frequency, and the detection signal of the temperature detection unit, the oscillation frequency of the oscillation element A second temperature compensation signal generation unit for generating a second temperature compensation signal for temperature compensation,
The first variable capacitance unit is
The capacitance value changes according to the first temperature compensation signal,
The second variable capacitance unit is
An oscillator in which a capacitance value changes according to the second temperature compensation signal. In claim 1,
The sensitivity of the second variable capacitor unit is lower than the sensitivity of the first variable capacitor unit. In claim 1 or 2,
The second variable capacitance unit is
An oscillator whose capacitance value changes in accordance with an externally input control signal. In claim 1 or 2,
The second temperature compensation signal generator is
An oscillator that generates the second temperature compensation signal based on a control signal input from the outside together with the temperature compensation information and a detection signal of the temperature detection unit. In any one of Claims 1 thru | or 4,
The second variable capacitance unit is
A capacitor bank including a plurality of variable capacitor elements and a plurality of switch elements;
The second temperature compensation signal generator is
An oscillator that generates a signal that controls opening and closing of each of the plurality of switch elements as the second temperature compensation signal.   An electronic device comprising the oscillator according to claim 1. An oscillation element; a first variable capacitance unit; and a second variable capacitance unit, the oscillation element having a frequency according to a capacitance value of the first variable capacitance unit and a capacitance value of the second variable capacitance unit. An oscillator temperature compensation method for compensating temperature of an oscillation frequency of an oscillator including an oscillation circuit that oscillates,
A temperature detecting step for detecting a temperature around the oscillation element;
Based on the frequency temperature characteristic information of the oscillation element and the detection result of the temperature detection step, a first temperature compensation signal is generated for temperature compensation so that the oscillation frequency of the oscillation element approaches a reference oscillation frequency. A first temperature compensation signal generating step,
Based on temperature compensation information for correcting an error of the oscillation frequency, which is a difference between the oscillation frequency compensated for the temperature and the reference oscillation frequency, and the detection result of the temperature detection step, the oscillation frequency of the oscillation element Generating a second temperature compensation signal for temperature compensating the temperature compensation signal, and
The first variable capacitance unit is
The capacitance value changes according to the first temperature compensation signal,
The second variable capacitance unit is
An oscillator temperature compensation method in which a capacitance value changes according to the second temperature compensation signal.