JPH09139651A - Crystal oscillator for overtone - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the oscillated output of overtone without using any tuner circuit when a crystal oscillator for overtone is used for a crystal transmitter by providing the crystal piece of AT cut, exciting electrodes and basic wave suppressing electrodes for suppressing basic wave vibrations. SOLUTION: A crystal piece 1 of AT cut for exciting thickness-slip vibrations is formed by cutting the crystal of artificial crystal at a prescribed angle to a crystal axis, cutting it out in the shape of plate and forming it into short slip slender in X-axis direction. Then, rectangular exciting electrode 2 are deposited while facing the respective central parts of front and rear sides of the crystal piece. The respective exciting electrodes 2 extend lead electrodes 3 toward mutually opposite terminal parts along the lengthwise direction of the crystal piece 1. Then, basic wave suppressing electrodes 4 are formed outside the respective exciting electrodes 2 in the breadthwise direction of the crystal piece 1. These basic wave suppressing electrodes 4 are provided for suppressing the vibrations of basic waves. Therefore, the film thickness of basic wave suppressing electrodes 4 is made thicker than the exciting electrodes 2 or more mass is provided by depositing the material of much mass.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crystal oscillator for overtone which suppresses vibration of a fundamental wave and facilitates vibration of overtone.

[0002]

2. Description of the Related Art Generally, there are various vibration modes such as bending vibration, flexural vibration, and thickness shear vibration as vibration modes of a crystal resonator. And the resonance frequency is several MHz to several tens of MHz
In the crystal oscillator of (1), a crystal oscillator of thickness shear vibration mode is mainly used. The resonance frequency of the crystal oscillator excited in this thickness shear vibration mode is inversely proportional to the thickness of the crystal piece. For example, the thickness of the crystal piece having a resonance frequency of 10 MHz is about 0.167 mm, and the thickness of the crystal piece having a resonance frequency of 30 MHz is about 0.056 mm.

Therefore, when the resonance frequency is increased, the thickness of the crystal piece becomes thin, and the manufacture becomes extremely difficult due to the strength of the crystal piece and problems in processing. Therefore, when a crystal oscillator having a high resonance frequency is required, the overtone mode is used. In the overtone mode, it resonates at a frequency that is an odd multiple of the resonance frequency of the fundamental wave,
Generally, modes such as third order, fifth order, and seventh order are used.

However, in the oscillation circuit using the ordinary crystal oscillator, the vibration of the fundamental wave is excited more strongly than the vibration of the overtone. For this reason, in the overtone oscillation circuit, a tuning circuit that is substantially tuned to the overtone frequency is provided on the output side to extract the oscillation frequency. However, in the oscillation circuit provided with the tuning circuit, it is necessary to adjust the tuning circuit, and the coil used in the tuning circuit has a large shape. Therefore, in order to make the oscillation circuit unadjusted and downsize, there has been a demand for a crystal resonator that can obtain overtone vibration without adjustment without using a tuning circuit.

In order to obtain overtone vibration without adjustment, the crystal impedance (hereinafter referred to as CI) in the overtone must be smaller than the CI of the fundamental wave. To this end, in order to facilitate the vibration of the overtone, it is conceivable to suppress the vibration of the fundamental wave to relatively reduce the CI of the overtone.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has an overtone C with a simple structure.
To provide a crystal resonator for an overtone, in which I can be made smaller than the CI of a fundamental wave, whereby an oscillation output of an overtone can be obtained without using a tuning circuit when used in a crystal oscillator. The purpose is.

[0007]

According to the present invention, there is provided an AT-cut crystal piece elongated in the X-axis or Z'-axis direction of the crystal.
An excitation electrode formed facing the central portion of the front and back plate surfaces of this crystal piece, and a fundamental wave suppression electrode that suppresses fundamental vibration formed outside the width direction of each excitation electrode of the crystal piece. It is a feature.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will now be described in detail with reference to the plan view of the crystal piece shown in FIG. 1 and the sectional view of FIG. In the figure, 1 is an AT-cut crystal piece that is excited by thickness shear vibration. The crystal piece 1 is obtained by cutting a crystal of artificial quartz at a predetermined angle with respect to a crystal axis, cutting it into a plate shape, and molding it into a strip shape elongated in the X-axis direction. Then, rectangular excitation electrodes 2 are vapor-deposited so as to face the central portions of the front and back plate surfaces of the crystal piece.

Each of the excitation electrodes 2 is arranged so that the extraction electrode 3 extends along the longitudinal direction of the crystal blank 1 to opposite ends. Then, the fundamental wave suppression electrode 4 is formed outside each excitation electrode 2 in the width direction of the crystal piece 1. The fundamental wave suppression electrode 4 is provided to suppress the vibration of the fundamental wave. Therefore, it is desirable that the fundamental wave suppression electrode 4 has a large mass so as to sufficiently suppress the thickness shear vibration at the peripheral portion of the crystal piece 1 in the width direction.

For this reason, the fundamental wave suppression electrode 4 is made thicker than the excitation electrode 2 or a large mass is obtained by vapor deposition of a substance having a large mass. In addition, the crystal piece 1 has an end portion of the extraction electrode 3 led out to the excitation electrode 2,
Of course, it is held by a holding member (not shown) and hermetically sealed in the container, and the excitation electrode 2 is led out to the outside via the holding member.

By the way, as shown in FIG. 3, when the electrode 12 is formed on the crystal piece 11 and thickness shear vibration is excited, the vibration displacement distribution showing the distribution of the vibration energy 13 is as shown in FIG. As shown in (a), it is widely distributed up to the edge of the plate surface of the crystal piece, whereas in the case of overtone, it is ubiquitous in the central part of the plate surface as shown in FIG. 3 (b). ing. Therefore, when the mass is added to the peripheral portion of the crystal piece, the vibration of the fundamental wave is significantly suppressed, while the vibration of the overtone is hardly suppressed.

Therefore, the vibration displacement distribution of the crystal oscillator having the fundamental wave suppression electrode 14 as in the above embodiment is as shown in FIG. That is, in the case of the fundamental wave, FIG.
As shown in (3), the presence of the fundamental wave suppression electrode suppresses the vibration and reduces the displacement. Therefore, CI becomes large and it becomes difficult to vibrate. On the other hand, in the case of overtone vibration, since the vibration displacement is ubiquitous in the central portion of the plate surface as shown in FIG. 4B, the magnitude of the vibration displacement is present even if the fundamental wave suppression electrode is present. Has not changed much.

Therefore, the displacement of the overtone becomes relatively larger than that of the fundamental wave, and the CI of the vibration of the overtone becomes low, so that the vibration easily occurs. Therefore, when this crystal oscillator is connected to, for example, an unadjusted oscillation circuit, it can stably oscillate at an overtone frequency. In the thickness-slipped quartz crystal resonator, the peripheral edge of the main surface is thinly formed or chamfered to confine the vibration energy in the central portion to obtain good vibration characteristics.

However, in the crystal resonator for overtone as in the above-mentioned embodiment, it is desirable that the main surfaces are not processed to be parallel planes having a uniform thickness. By doing so, the fundamental wave vibration in which the vibration energy is widely distributed on the plate surface cannot sufficiently obtain the energy trapping effect, and the CI thereof increases. Therefore, the CI of the overtone becomes relatively small, which makes it easy to vibrate at the frequency of the overtone.

The present invention is not limited to the above-mentioned embodiment, and the fundamental wave suppressing electrode 4 facing the central wave suppressing electrode 4 can be formed as shown in the sectional view of the central portion of the crystal resonator with the thickness being exaggerated as shown in FIG. It may be conducted. By doing so, the excitation energy generated when the thickness shear vibration is excited by the excitation electrode 2 is induced in the fundamental wave suppression electrode 4, but is short-circuited between the fundamental wave suppression electrodes 4 on the front and back plate surfaces. Vibration is suppressed.

However, the action of suppressing the piezoelectric vibration by the fundamental wave suppressing electrode 4 is greatly affected by the vibration of the fundamental wave in which the vibration energy is widely distributed over the entire plate surface, and the vibration energy is in the central portion of the plate surface. It is almost unaffected by the overtone vibration that is ubiquitous. Therefore, by providing the fundamental wave suppression electrode 4, the CI of the vibration of the fundamental wave becomes large and becomes difficult to vibrate, whereas the CI of the vibration of the overtone becomes relatively small and easily vibrates.

Therefore, even if the fundamental wave suppression electrode 4 having such a structure is provided, the vibration of the fundamental wave can be suppressed and the overtone can be easily vibrated as in the above-described embodiment. In addition, in the other embodiments described above, vibration is not suppressed by adding mass, and the induced charges are short-circuited. It is not necessary to add a particularly large mass.

[0018]

As described above in detail, according to the present invention, the vibration of the fundamental wave can be suppressed and the vibration of the overtone can be easily performed. When the crystal oscillator is used, the overtone is not used. It is possible to provide a crystal resonator for overtone that can obtain the oscillation output of.

[Brief description of the drawings]

FIG. 1 is a plan view showing an electrode arrangement of a crystal resonator according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along the line AA of the crystal unit shown in FIG.

FIG. 3 is a diagram showing a vibration displacement of a conventional crystal unit.
FIG. 3A shows a fundamental wave, and FIG. 3B shows an overtone vibration displacement distribution.

FIG. 4 is a diagram showing a vibration displacement of a crystal resonator of the present invention, FIG. 4 (a) shows a fundamental wave, and FIG. 4 (b) shows an overtone vibration displacement distribution.

FIG. 5 is a sectional view of a central portion of a crystal resonator according to another embodiment of the present invention.

[Explanation of symbols]

 1 Quartz piece 2 Excitation electrode 3 Extraction electrode 4 Fundamental wave suppression electrode

Claims (3)

[Claims] 1. An AT-cut crystal piece elongated in the X-axis or Z'-axis direction of the crystal, an excitation electrode formed facing the central portion of the front and back plate surfaces of the crystal piece, and the width of the crystal piece. A quartz resonator for overtone, comprising: a fundamental wave suppressing electrode that suppresses fundamental wave vibration formed outside each excitation electrode in the direction. 2. A crystal resonator for overtone according to claim 1, wherein the fundamental wave suppression electrodes on the front and back plate surfaces of the crystal piece are formed so as to face each other. 3. The crystal resonator for overtone according to claim 1, wherein the fundamental wave suppressing electrodes on the front and back plate surfaces of the crystal piece are formed so as to be electrically connected to each other.