JPH04128422U - overtone crystal oscillator - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a crystal resonator capable of oscillating at an overtone frequency using an unadjusted oscillation circuit. [Configuration] An AT-cut crystal resonator with a rotation angle of 2.0 degrees in the direction rotated by 45 degrees with respect to the Z' axis passing through the center of the plate surface of the crystal piece.
x 10 ^-5 cm to 2.5 x 10 ^-5 cm thick, with a gap smaller than 0.3 times the dimension of the crystal piece in the direction to the periphery of the plate surface, and a surface opposite to the front and back plate surfaces. to form an excitation electrode.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

The present invention is an overtone oscillation system that allows easy overtone oscillation using an unadjusted oscillation circuit. Regarding tone crystal oscillators.

0002

[Conventional technology]

Recently, many electronic devices use piezoelectric vibrators as standards for frequency, time, etc. It uses a lot of crystal oscillators. In particular, crystal oscillators are inexpensive and high quality due to advances in manufacturing technology. It is manufactured and used in large quantities because of its ability. The vibration modes of such crystal resonators include bending vibration, deflection vibration, thickness vibration, etc. There are various vibration modes. In a crystal resonator whose resonance frequency is on the order of MHz, , the thickness-shear vibration mode is mainly used. In this way, the thickness shear vibration mode The resonant frequency of a crystal oscillator excited by a quartz crystal is inversely proportional to the thickness of the crystal piece. therefore , the thickness of the vibrator with a resonant frequency of 10 MHz is approximately 0.167 mm, and the resonant frequency is 3 The thickness of a 0 MHz vibrator is approximately 0.056 mm. That is, opposite to the resonant frequency. The thickness of the crystal piece becomes proportionally thinner, the frequency increases, and the strength and processing of the crystal piece increases. Production becomes extremely difficult due to such problems. If a crystal resonator with a high resonant frequency is required for this purpose, an overtone model is required. The use of a code is being practiced. In overtone mode, it is approximately the same as the fundamental wave. Resonates at a frequency that is an odd multiple of the vibration frequency, and generally uses modes such as 3rd, 5th, and 7th orders. The order is determined by the constants of the oscillator circuit, for example, the constants of the tuned circuit on the output side. It will be done. However, in such an overtone oscillator circuit, the resonance of the fundamental wave cannot be controlled by the circuit. Since a tuned circuit is provided to suppress the shall be. However, it is difficult to downsize the tuned circuit, especially the inductance. However, there were problems that required adjustment.

0003 By the way, in recent years, oscillation circuits have been made smaller and require no adjustment, allowing them to operate at high frequencies for long periods of time. To maintain accuracy, for example, the crystal resonator and integrated circuit can be integrated to generate unadjusted oscillation. Micro-sized oscillators configured with circuits are manufactured and used in large quantities. However, this An oscillator circuit with a configuration like this uses overtone mode because it does not have a tuned circuit. cannot be used. Therefore, the maximum frequency of the oscillation output is the limit due to the processing of the crystal blank. Therefore, the frequency is generally limited to about 30 MHz. Therefore, by suppressing the fundamental vibration mode, it is possible to Several crystal units have been proposed that can oscillate at overtone frequencies. ing. For example, transmitting the vibrational energy of the fundamental wave to the supporting part of the crystal piece and attenuating it. There are some that suppress the fundamental wave vibration mode. However, something like this The frequency adjustment is significant due to variations in the spacing between the support of the crystal piece and the electrode. There are difficult problems. In addition, the electrodes may be unevenly distributed around the periphery of the crystal piece, or the dimensions of the electrode may be approximately the same as the dimensions of the crystal piece. It has also been considered to suppress the fundamental wave vibration mode by making them the same. deer However, there is a problem in that even such a device cannot sufficiently suppress fundamental wave vibration.

0004

[Problem that the idea aims to solve]

The present invention was developed in view of the above circumstances, and uses an unadjusted oscillation circuit to overtone that can oscillate at the overtone frequency without using a The purpose is to provide a crystal resonator.

[0005]

[Means to solve the problem]

The present invention is an AT-cut crystal resonator in which the end of the crystal piece's plate surface in the Z'-axis direction is held by a holding member, and the crystal piece is rotated by 45 degrees with respect to the Z'-axis passing through the center of the plate surface. A gap of 2.0 x 10 ^-5 cm to 2.5 x 10 ^-5 cm in the direction in which the crystal piece is formed, and a gap smaller than 0.3 times the dimension of the crystal piece in that direction with respect to the periphery of the plate surface. The invention is characterized in that excitation electrodes are formed facing oppositely to the front and back plate surfaces.

[0006]

[Embodiment] Hereinafter, a crystal resonator according to an embodiment of the present invention will be described in detail with reference to the side view shown in FIG. 1 with the cover removed. In the figure, reference numeral 1 indicates an AT-cut thick sliding crystal piece, which is formed by cutting a quartz crystal at a predetermined angle with respect to its crystal axis and forming it into a square plate shape. Note that this crystal piece 1 is not chamfered at the peripheral edge in order to suppress the fundamental wave vibration and facilitate the excitation of the overtone vibration. The excitation electrode 2 is formed in a direction rotated by 45 degrees with respect to the Z' axis passing through the center of the crystal piece 1. Further, this excitation electrode is formed in one of the regions divided into four by the Z' axis and the X axis, which are perpendicular to each other at the center of the plate surface of the crystal blank 1. This excitation electrode 2 is made of a conductor such as aluminum or silver by vacuum deposition. It is formed to have a thickness of 0×10 ⁻⁵ cm to 2.5×10 ⁻⁵ cm. Further, the excitation electrode 2 is formed with a gap smaller than 0.3 times the dimension of the crystal piece in this direction from the periphery of the plate surface of the crystal piece 1. Then, the excitation electrode 2 is led out in the Z'-axis direction of the plate surface of the crystal piece, and this lead-out end is held by a holding member 3. This holding member 3 is fixed by soldering, welding, etc. to the tips of a pair of terminals 5 which are implanted in a base 4 insulated from each other. The excitation electrode 2 formed on the plate surface of the crystal blank 1 is led out to the outside via the terminal 5. Note that the base 4 is covered with a cover (not shown) and hermetically sealed by soldering, resistance welding, or the like.

[0007]However, while fundamental wave vibrations are unevenly distributed in the center of the plate surface, overtone vibrations are not concentrated in the center of the plate surface but occur almost over the entire plate surface. Therefore, when the excitation electrode 2 is provided unevenly toward the periphery of the plate surface as in the above embodiment, the fundamental wave vibration is significantly inhibited, but the overtone vibration can be excited with almost no loss. . FIG. 2 shows the ratio of the dimension B of the crystal piece to the distance A from the edge of the excitation electrode 2 to the periphery of the crystal piece, and the crystal impedance of the fundamental wave and third-order overtone (hereinafter referred to as CI) with respect to the thickness of the excitation electrode 2. ). As is clear from this result, the CI of the third overtone is a constant value of about 25Ω, but that of the fundamental wave varies greatly from about 220Ω to 530Ω. Therefore, in order to suppress the vibration of the fundamental wave and reliably excite the overtone, it is desirable that the CI of the fundamental wave take a value as large as possible. Therefore, the smaller the ratio of distance A/dimension B is, the larger the CI of the fundamental wave becomes, which is convenient.Practically speaking, the gap between the excitation electrode and the periphery of the plate surface is set to 0.3 of the dimension of the crystal piece in that direction. A CI ratio of 10 times or more can be obtained by making the value smaller than 1 times. Further, by setting the thickness of the excitation electrode 2 to 2.0×10 ⁻⁵ cm to 2.5×10 ⁻⁵ cm, the CI of the fundamental wave is maximized. Therefore, in the above embodiment, the thickness of the electrode is set to 2.0 x 10 ^-5 cm to 2.5 x 10 ^-5 cm, for example, by vacuum evaporation. With such a configuration, the CI of the fundamental wave is more than 10 times the CI of the third overtone, and even if an unadjusted oscillation circuit is used, the vibration of the fundamental wave can be suppressed and excited with the third overtone. can do. By controlling the position where the excitation electrode is formed and its thickness, a sufficient ratio between the CI of the third overtone and that of the fundamental wave can be obtained, and it is possible to reliably excite in the mode of the third overtone. In the above embodiment, a round excitation electrode was formed on a rectangular crystal piece, but it is also possible to form a rectangular electrode on a strip-shaped crystal piece as shown in FIG. A round excitation electrode may be formed on a round crystal piece as shown in FIG. Further, as the holding member for the crystal piece, a wire clip may be used as shown in Fig. 1, or a slit may be formed in the longitudinal direction of a band-shaped metal piece as shown in Figs. 'The periphery in the axial direction may be fitted and held.

[0008]

[Effect of the idea]

As detailed above, if the crystal resonator of the present invention is used, an unadjusted oscillation circuit can be used. Can perform overtone oscillation, making it possible to use integrated oscillation circuits It is possible to provide a crystal resonator that can be used to construct a compact oscillator. can.

[0009]

[Brief explanation of drawings]

FIG. 1 is a side view showing an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between CI and the position and thickness of an excitation electrode in an embodiment of the present invention.

FIG. 3 is a side view of another embodiment of the present invention.

FIG. 4 is a side view of yet another embodiment of the present invention.

[Explanation of symbols]

1 crystal piece 2 Excitation electrode 3 Holding member

Claims (1)

[Scope of utility model registration request] Claim 1: In an AT-cut crystal resonator, there is provided a holding member that holds the end of the plate surface of the crystal piece in the Z'-axis direction, and a holding member that holds the end part of the plate surface of the crystal piece in the Z'-axis direction. 2.0×10 ^-5 cm to 2.5×10 ^-5 c in the rotated direction
m thickness and an excitation electrode formed facing the front and back plate surfaces with a gap smaller than 0.3 times the dimension of the crystal piece in the direction to the periphery of the plate surface. Overtone crystal oscillator.