JP2016092585A - Oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve series arm characteristics in the vicinity of a series resonance point.SOLUTION: An oscillator 1 includes: a crystal vibrator 10; an inductor 20 having an inductance value, which is resonated in parallel between an equivalent series capacitance 12 of the crystal vibrator 10 in a series resonance frequency of the crystal vibrator 10; and an inductor 30 whose inductance value is smaller than that of the inductor 20. The inductor 20 and the inductor 30 are arranged in parallel to the crystal vibrator 10 and connected in series to each other.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an oscillator having a crystal resonator.

  Conventionally, an equivalent circuit of a crystal resonator is represented by a series arm composed of an equivalent series resistance, an equivalent series capacitance, and an equivalent series inductor, and a parallel arm composed of an equivalent parallel capacitance connected in parallel to the series arm. It is known that In the crystal resonator, since the equivalent parallel capacitance included in the parallel arm affects the characteristics of the series resonance point, it is required to cancel the influence of the equivalent parallel capacitance included in the parallel arm. Patent Document 1 discloses a circuit that cancels the influence of an equivalent parallel capacitance included in a parallel arm by connecting an inductance in parallel with a crystal resonator.

JP 2014-93545 A

  According to the conventional method, by providing an inductor in parallel with the crystal resonator, a parallel resonance point is generated by the inductor and the equivalent parallel capacitance of the parallel arm. As a result, the current flowing through the parallel arm is reduced, and the influence of the equivalent parallel capacity of the parallel arm can be reduced. However, by such a method, the influence of the equivalent parallel capacitance included in the parallel arm can be removed, but the characteristics of the series arm near the series resonance point cannot be improved.

  Accordingly, the present invention has been made in view of these points, and an object thereof is to provide an oscillator capable of improving the characteristics of a series arm in the vicinity of a series resonance point.

  In the first aspect of the present invention, the first resonator having an inductance value that resonates in parallel with the crystal resonator and the equivalent parallel capacitance of the crystal resonator at the series resonance frequency of the crystal resonator, There is provided an oscillator including a second inductor having an inductance value smaller than that of the first inductor, wherein the first inductor and the second inductor are connected in series with each other in parallel with the crystal resonator.

  In a second aspect of the present invention, the first resonator having an inductance value that resonates in parallel with the crystal resonator and the equivalent parallel capacitance of the crystal resonator at the series resonance frequency of the crystal resonator, There is provided an oscillator comprising a second inductor having an inductance value smaller than that of the first inductor, wherein the first inductor and the second inductor are connected in parallel with the crystal resonator.

  In the above oscillator, the second inductor may be an inductor having a variable inductance value.

  The oscillator may further include a control unit that controls an inductance value of the second inductor. For example, the control unit controls the inductance value of the second inductor based on the oscillation frequency of the crystal resonator.

  The control unit may control an inductance value of the second inductor based on a magnitude of a reactance change amount with respect to a frequency change amount at a frequency within a predetermined range from a series resonance frequency of the crystal resonator.

  In a third aspect of the present invention, the first resonator having an inductance value that resonates in parallel with the crystal resonator and the equivalent parallel capacitance of the crystal resonator at the series resonance frequency of the crystal resonator, Preparing a second inductor having an inductance value smaller than that of the first inductor; mounting the crystal resonator, the first inductor, and the second inductor on a substrate; and determining an inductance value of the second inductor. And a step of adjusting. An oscillator manufacturing method is provided.

  According to the present invention, it is possible to improve the characteristics of the series arm in the vicinity of the series resonance point.

It is a figure which shows the structure of the oscillator which concerns on 1st Embodiment. It is a figure which shows the reactance characteristic of an oscillator. It is a figure which shows the structure of the oscillator which concerns on 2nd Embodiment.

<First Embodiment>
FIG. 1A is a diagram illustrating a configuration of the oscillator 1 according to the first embodiment. The oscillator 1 includes a crystal resonator 10, an inductor 20, and an inductor 30.

  FIG. 1B is a diagram showing a configuration of the oscillator 1 showing an internal equivalent circuit of the crystal resonator 10. As shown in FIG. 1B, the crystal resonator 10 includes a series arm composed of an equivalent series resistance 11, an equivalent series capacitance 12, and an equivalent series inductor 13 connected in series to each other, and in parallel with the series arm. And an equivalent parallel capacitor 14 connected thereto.

  The inductor 20 and the inductor 30 are connected in series with each other in parallel with the crystal unit 10. The inductor 20 has an inductance value that resonates in parallel with the equivalent parallel capacitance 14 of the crystal resonator 10 at the series resonance frequency of the crystal resonator 10. That is, the impedance of the parallel circuit constituted by the equivalent parallel capacitor 14 and the inductor 20 is maximized at the series resonance frequency. Since the inductor 20 has such characteristics, the inductor 20 can cancel the influence of the equivalent parallel capacitance 14 at the series resonance frequency.

  The inductor 30 has a smaller inductance value than the inductor 20. For example, the inductance value of the inductor 30 is several hundred nH to several μH, whereas the inductance value of the inductor 30 is several tens of nH. That is, the inductance value of the inductor 30 is 1/10 or less of the inductance value of the inductor 20. Since the inductance value of the inductor 30 is sufficiently smaller than the inductance value of the inductor 20, the characteristics of the series arm in the vicinity of the series resonance frequency are finely adjusted without impairing the effect of canceling the influence of the equivalent parallel capacitance 14 by the inductor 20. can do.

  FIG. 2 is a diagram illustrating reactance characteristics of the oscillator 1. In FIG. 2A, the horizontal axis indicates the frequency, and the vertical axis indicates the value of the imaginary part of the reactance. The reactance increases as the frequency increases and becomes 0 at the series resonance frequency fr. When the frequency further increases, the reactance decreases and the reactance becomes zero at the parallel resonance frequency fa. The parallel resonance frequency fa changes according to the inductance value of the inductor 20 provided in the oscillator 1.

  FIG. 2B is a diagram showing reactance characteristics near the series resonance frequency fr. The alternate long and short dash line indicates the reactance characteristic when the total value of the inductance value of the inductor 20 and the inductance value of the inductor 30 is the first value. A broken line indicates a reactance characteristic when the total value of the inductance value of the inductor 20 and the inductance value of the inductor 30 is a second value larger than the first value. The solid line indicates the reactance characteristic when the total value of the inductance value of the inductor 20 and the inductance value of the inductor 30 is a third value that is larger than the second value.

  Comparing the slopes (phase slopes) in the vicinity of the series resonance frequency fr of the respective curves shown in FIG. 2B, it can be seen that the slope of the reactance characteristic indicated by the alternate long and short dash line is the largest at frequencies higher than fr. In addition, it can be seen that the slope of the reactance characteristic indicated by the broken line is the largest at a frequency lower than fr. In the reactance characteristic shown in FIG. 2B, the Q value of the oscillator 1 tends to increase as the slope of the curve near the series resonance frequency fr increases. Therefore, it can be seen that the Q value at the frequency at which the oscillator 1 is operated can be increased by adjusting the inductance value of the inductor 30 based on whether the frequency at which the oscillator 1 is operated is higher or lower than the series resonance frequency fr. It is known that the phase noise characteristic, which is a main characteristic of the crystal oscillator, is greatly related to the Q value of the crystal oscillator. Therefore, by adjusting the value of the inductor 30 provided in the oscillator 1, the phase noise characteristic of the oscillator 1 is adjusted. Phase noise characteristics can also be improved.

[Manufacturing Method of Oscillator 1]
The oscillator 1 can be manufactured by the following procedure. First, a crystal resonator 10, an inductor 20, and an inductor 30 having a series resonance frequency fr are prepared. Subsequently, the crystal unit 10, the inductor 20, and the inductor 30 are mounted on the substrate so as to be in the connection state shown in FIG. Subsequently, a substrate on which the crystal resonator 10, the inductor 20, and the inductor 30 are mounted is provided in the housing. Subsequently, in a state where a predetermined voltage is applied to the substrate, the inductance value of the inductor 30 is adjusted to oscillate at a desired frequency near the series resonance frequency fr. After confirming that it oscillates at a desired frequency, the substrate is sealed by fixing the lid to the housing. With the above procedure, the oscillator 1 having good phase noise characteristics at a desired frequency can be manufactured.

[Modification]
In the above description, an example in which the inductor 20 and the inductor 30 are connected in series has been described, but the inductor 20 and the inductor 30 may be connected in parallel to each other. That is, each of the inductor 20 and the inductor 30 may be provided in parallel with the crystal unit 10. Even in this case, the Q value near the series resonance frequency can be optimized by finely adjusting the inductance value of the inductor 30.

[Effect in the first embodiment]
As described above, the oscillator 1 includes the inductor 20 for canceling the influence of the equivalent parallel capacitance 14 of the parallel arm on the series resonance frequency, and the characteristics of the series arm connected in series with the inductor 20 in the vicinity of the series resonance frequency. And an inductor 30 for adjusting. Since the inductance value of the inductor 20 is sufficiently smaller than the inductance value of the inductor 30, the reactance characteristic near the series resonance frequency can be adjusted by finely adjusting the inductance value of the inductor 20.

<Second Embodiment>
FIG. 3 is a diagram illustrating a configuration of the oscillator 2 according to the second embodiment. The oscillator 2 has a variable inductor 40 instead of the inductor 30 in the oscillator 1 shown in FIG. The variable inductor 40 is an inductor having a variable inductance value. The oscillator 2 includes a control unit 50 that controls the inductance value of the variable inductor 40. The control unit 50 includes, for example, a CPU and a memory.

  The control unit 50 controls the inductance value of the variable inductor 40 based on the oscillation frequency of the crystal resonator 10. For example, the control unit 50 changes the reactance with respect to the amount of change in frequency at a frequency within a predetermined range from the series resonance frequency of the crystal resonator 10 stored in a memory (not shown) in association with the inductance value of the variable inductor 40. Based on the magnitude of the quantity (that is, the slope of the reactance characteristic), the inductance value of the variable inductor 40 is controlled. The predetermined range is, for example, a range in which the series resonance frequency of the crystal unit 10 can change according to changes in the external environment.

  The control unit 50 may control the inductance value of the variable inductor 40 based on the average value of the slope of the reactance characteristic at a frequency within a predetermined range. By doing in this way, the control part 50 can adjust the inductance value of the variable inductor 40 so that the inclination of the reactance characteristic at the oscillation frequency of the crystal resonator 10 becomes an optimal magnitude.

  The control unit 50 obtains information indicating the slope of the reactance characteristic or the Q value desired by the user of the oscillator 1 from the outside, and the user desires the slope of the reactance characteristic at the oscillation frequency based on the obtained information. The inductance value of the variable inductor 40 may be adjusted so that the reactance characteristic has an inclination.

[Modification]
In the above description, the example in which the inductor 20 and the variable inductor 40 are connected in series has been described. However, the inductor 20 and the variable inductor 40 may be connected in parallel to each other. That is, each of the inductor 20 and the variable inductor 40 may be provided in parallel with the crystal resonator 10. Even in this case, the control unit 50 can finely adjust the inductance value of the variable inductor 40 to optimize the Q value near the series resonance frequency.

[Effects of Second Embodiment]
As described above, the oscillator 2 includes the inductor 20 for canceling the influence of the equivalent parallel capacitance 14 of the parallel arm on the series resonance frequency, and the characteristics of the series arm connected in series with the inductor 20 in the vicinity of the series resonance frequency. And a variable inductor 40 for adjusting. Furthermore, the oscillator 2 includes a control unit 50 for adjusting the inductance value of the variable inductor 40. When the control unit 50 adjusts the inductance value of the variable inductor 40, the oscillator 1 can flexibly adjust the characteristics of the series arm near the series resonance point. In the above description, the control unit 50 is described as a person who adjusts the inductance value of the variable inductor 40. However, the oscillator 1 does not have the control unit 50, and the user of the oscillator 1 sets the inductance value of the variable inductor 40. You may adjust.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Oscillator 2 Oscillator 10 Crystal oscillator 11 Equivalent series resistance 12 Equivalent series capacity 13 Equivalent series inductor 14 Equivalent parallel capacity 20 Inductor 30 Inductor 40 Variable inductor 50 Control part

Claims (7)

A crystal unit,
A first inductor having an inductance value that resonates in parallel with an equivalent parallel capacitance of the crystal resonator at a series resonance frequency of the crystal resonator;
A second inductor having an inductance value smaller than that of the first inductor;
With
An oscillator in which the first inductor and the second inductor are connected in series with each other in parallel with the crystal resonator. A crystal unit,
A first inductor having an inductance value that resonates in parallel with an equivalent parallel capacitance of the crystal resonator at a series resonance frequency of the crystal resonator;
A second inductor having an inductance value smaller than that of the first inductor;
With
An oscillator in which the first inductor and the second inductor are connected in parallel to each other in parallel with the crystal resonator. The second inductor is an inductor having a variable inductance value.
The oscillator according to claim 1 or 2. A controller for controlling an inductance value of the second inductor;
The oscillator according to claim 3. The control unit controls an inductance value of the second inductor based on an oscillation frequency of the crystal resonator.
The oscillator according to claim 4. The control unit controls the inductance value of the second inductor based on the magnitude of the reactance change amount with respect to the frequency change amount at a frequency within a predetermined range from the series resonance frequency of the crystal resonator.
The oscillator according to claim 5. A first inductor having an inductance value that resonates in parallel between the quartz crystal resonator and an equivalent parallel capacitance of the quartz crystal resonator at a series resonance frequency of the quartz crystal resonator, and a first inductor having a smaller inductance value than the first inductor; A step of preparing two inductors;
Mounting the crystal resonator, the first inductor, and the second inductor on a substrate;
Adjusting the inductance value of the second inductor to oscillate the crystal resonator at a frequency different from the series resonance frequency;
A method for manufacturing an oscillator.

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