JPH11177376A - Sc-cut crystal resonator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an SC-cut crystal resonator with a satisfactory stress sensitivity characteristic to maintain a highly stable oscillation frequency irrespective of the posture of the resonator itself and of a stress from outside by setting the longitudinal direction of a crystal piece to a specified angle from an XX'-axis. SOLUTION: A crystal piece 11 is obtained by rotating a face orthogonal to the Y-axis of artificial rock crystal with an X-axis as a center and cutting it in an oblong form from an SC board rotated from the rotated position by 22 degrees with a Z-axis as its center. Stress sensitivity characteristic of the crystal piece 11 in the oblong form almost continuously changes in accordance with an intra-face rotation angle and the longitudinal direction of the oblong form becomes maximum on a '+' side by 0 degree from the XX-axis and becomes maximum on a '-' side by 90 degrees. Since the stress sensitivity characteristic crosses an original point and it becomes minimum '0' when the longitudinal direction is between 45 degrees and 135 degrees. For making a frequency change by stress from outside or a posture difference to be minimum, it is desirable to set the longitudinal direction to be the direction of ±45 degree from the XX'-axis in the case of an oblong SC-cut crystal piece 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an SC-cut quartz resonator, and more particularly to suppression of B-mode auxiliary vibration.

[0002]

2. Description of the Related Art Recently, attention has been paid to SC-cut quartz resonators having excellent performances such as stress sensitivity, thermal shock characteristics, and phase noise performance. As shown in FIG. 3, such an SC-cut quartz resonator rotates a plane orthogonal to the Y-axis of the crystal of the quartz crystal by about 33 ° about the X-axis, and further rotates the Z-axis from the rotated position. An electrode is formed on a crystal blank 1 cut out from a plane rotated by about 22 °.

[0003] The frequency and temperature characteristics of such an SC-cut quartz resonator have a substantially cubic curve having an inflection point near 80 ° C. On the other hand, as a highly stable crystal oscillator, 80
2. Description of the Related Art A constant temperature oven-type crystal oscillator that operates by heating to a constant temperature of about ° C. is known. Such an oscillator has a heater for heating and a temperature control circuit, and maintains a constant temperature by controlling the amount of heat generated by the heater.

In a constant temperature oven type crystal oscillator, a stable oscillation frequency is obtained by maintaining the crystal oscillator at a constant temperature of about 80.degree. However, since the SC-cut crystal unit has an inflection point around 80 ° C, when used as a thermostatic oven, use it in the temperature range where the rate of change of the oscillation frequency with respect to temperature change is the least. And a more stable oscillation frequency can be obtained.

[0005] However, a high-stability crystal oscillator using such an SC-cut crystal resonator is 10-10 to 1
It is used as a frequency reference source having a stability of about 0-11. For this reason, it is required that the stress sensitivity characteristics be good, that is, the frequency change with respect to external stress be as small as possible.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has a good stress sensitivity characteristic and a high stable oscillation frequency irrespective of the attitude of the oscillator itself and the action of external stress. It is an object of the present invention to provide an SC-cut crystal unit that can be maintained.

[0007]

A first aspect of the present invention is to set a plane orthogonal to the Y axis of a crystal of crystal to about 33 degrees around the X axis.
゜ rotate, and from this rotated position about 2
In a rectangular SC-cut crystal resonator cut out from a 2 ゜ rotated plane, the longitudinal direction of the crystal blank is ±± from the XX ′ axis.
According to a second aspect of the present invention, in the second aspect, the excitation electrode formed to face the front and back plate surfaces of the crystal piece is led to one end in the longitudinal direction of the crystal piece. The crystal piece is held at the leading end of the excitation electrode.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to a plan view of a crystal blank having electrodes shown in FIG. In the figure, reference numeral 11 denotes a crystal blank, for example, as shown in FIG. 3, a plane orthogonal to the Y axis of the crystal of the artificial quartz is rotated by about 33 ° about the X axis, and from this rotated position, about the Z axis. From the SC plate rotated about 22 °.

Here, the longitudinal direction of the strip-shaped crystal piece is represented by X
Eighteen types of samples rotated in the plane by 10 ° from the direction of the X ′ axis were manufactured, and the stress sensitivity characteristics of each sample were measured. The resonance frequency of the sample crystal piece was 11 MHz, and the excitation electrode formed facing the front and back plate surfaces of the crystal piece was led out to one end in the longitudinal direction, and the leading end supported the cantilever. Then, the change in the resonance frequency when the other end in the longitudinal direction of the quartz piece was pressed was measured.

FIG. 2 is a graph showing the measurement results of the stress sensitivity characteristics. As is clear from this graph, the stress sensitivity characteristic of the strip-shaped quartz piece changes substantially continuously according to the in-plane rotation angle, and the longitudinal direction of the strip is 0 ° from the XX ′ axis and reaches the maximum on the + side at 90 °. And the frequency deviation is about 3 ppb / N. XX '
At 45 ° and 135 ° from the axis, the stress sensitivity characteristic becomes minimum 0 because it crosses the origin.

Therefore, in order to minimize a frequency change due to an external stress or a posture difference, a rectangular SC
In the case of a cut crystal blank, the longitudinal direction is 45 ° or 135 ° from the XX ′ axis, that is, the longitudinal direction is ± 45 ° from the XX ′ axis.
It is desirable to make the direction of ゜.

This makes it possible to minimize a change in frequency due to external stress, a difference in attitude, and the like. For example, in the case of a constant temperature oven type oscillator, a high stability of about 10-10, An oscillation output with a very small change in oscillation frequency due to the attitude difference can be obtained.

[0013]

As described in detail above, according to the present invention,
It is possible to provide an SC-cut quartz resonator that has good stress sensitivity characteristics, minimizes a frequency change due to an external stress and a posture difference, and can maintain a resonance frequency with high stability.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a cutout angle of a crystal piece according to an embodiment of the present invention.

FIG. 2 is a graph showing a relationship between a cutout angle of a crystal piece and stress sensitivity.

FIG. 3 is a diagram illustrating a cut-out angle of a crystal piece in an SC cut.

[Explanation of symbols]

 11 ・ ・ Crystal pieces

Claims (2)

[Claims] 1. A rectangular shape obtained by rotating a plane orthogonal to the Y-axis of a crystal of a quartz crystal by about 33 ° about the X-axis, and cutting the plane rotated about 22 ° about the Z-axis from the rotated position. 3. The SC-cut crystal resonator according to claim 1, wherein the longitudinal direction of the crystal piece is set to ± 45 ° from the XX ′ axis. 2. An apparatus according to claim 1, wherein the excitation electrode formed facing the front and back plate surfaces of the crystal blank is led out to one end in the longitudinal direction of the crystal blank, and the leading end of the excitation electrode is connected to the leading end of the excitation electrode. An SC-cut crystal unit characterized by holding a crystal piece.