JPH077363A - SC cut crystal unit - Google Patents

Abstract

PURPOSE:To surely excite main vibration of a C mode by suppressing sub- vibration. CONSTITUTION:A twice rotation crystal oscillator of an SC cut which is cut out of the surface formed by rotating the face being orthogonal to the Y axis of a crystal of quartz about 33 deg. centering around the X axis, and also, rotating its face about 22 deg. centering around the Z axis from this rotated position is obtained. A main electrode 2 is provided so as to be opposed to the plate surface of a crystal piece 1, and by being insulated from this main electrode, a sub-electrode 3 is formed so as to be opposed thereto, and a frequency of main vibration of the sub-electrode is equalized to a resonance frequency of the sub-vibration generated in the main electrode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to SC-cut crystal units, and more particularly to suppression of side vibration.

[0002]

2. Description of the Related Art Generally, a piezoelectric crystal can excite piezoelectric vibration only at a specific cutting angle with respect to a crystal axis. For example, in the case of a crystal resonator that utilizes the piezoelectric characteristics of crystal, piezoelectric vibration can be excited only at a specific cutting angle with respect to the crystal axis. There are a plurality of combinations of these cutting angles, and It exhibits unique vibration characteristics at the cutting angle. For example, an AT-cut crystal resonator most commonly used at a frequency of several MHz to several tens of MHz exhibits a cubic curve-shaped temperature characteristic having an inflection point near 25 ° C. By the way, when the frequency stability is strictly required in a reference oscillator used for measuring equipment, wireless equipment, etc., for example, a thermostat-type oscillator is used. In this constant temperature oven type oscillator, the crystal oscillator is housed in a constant temperature oven heated to a constant temperature of about 80 ° C. to eliminate the frequency change due to the temperature characteristic of the crystal oscillator and stabilize the crystal oscillator. An SC-cut crystal oscillator is known as a crystal oscillator suitable for such an oscillator. This S
The C-cut crystal unit is rotated about 33 degrees about the X axis on the plane perpendicular to the Y axis of the crystal of the crystal, and about 22 degrees about the ZZ 'axis from this rotated position. For example, it is cut into a strip. However, this SC-cut crystal resonator has better thermal shock characteristics than the AT-cut crystal resonator, exhibits a zero temperature coefficient at a relatively high temperature of around 80 ° C., and can obtain a high Q value. Such characteristics are extremely desirable characteristics for a highly stable crystal oscillator that is used by being stored in a constant temperature bath heated to a constant temperature of about 80 ° C., for example. Therefore, for example, the 34th FCS (FREQ.CON) held in May 1980
TROL SYMPOSIUM) Proceedings, pp. 187-193, Fundamental mode SC cut resonator (FUNDAMENTAL MODES
Various reports have been made as disclosed as C-CUT RESONATORS).

By the way, such an SC-cut crystal oscillator produces B-mode and A-mode sub-vibrations near the C-mode resonance, which is the main vibration, and at frequencies on the high frequency side. Here, since the value of the crystal impedance (hereinafter abbreviated as CI) of the vibration of the A mode is larger than that of the C mode, it does not cause any particular problem. On the other hand, B
The CI of the mode is equal to or less than that of the C mode. Therefore, when an oscillator is actually manufactured, there is a problem that the oscillator often oscillates in the B mode of the secondary vibration. Therefore, when the SC-cut crystal oscillator is used, it is necessary to suppress the B-mode vibration and make its CI larger than that of the C-mode in order to reliably excite the C-mode main vibration. For this reason, various modifications have been made to the outer shape of the crystal piece, the holding position, etc. to suppress the B-mode secondary vibration. However, each method has a problem that designing and manufacturing are troublesome and the yield of the actual manufacturing process is lowered.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is an SC which can reliably excite the main vibration of the C mode and can surely suppress the sub vibration. It is intended to provide a cut crystal unit.

[0005]

According to the present invention, a plane perpendicular to the Y axis of a crystal of quartz is rotated about the X axis by about 33 °,
Further, in the SC-cut double-rotation crystal unit cut out from the surface rotated about 22 ° about the Z axis from the rotated position, the main electrode is provided facing the plate surface of the crystal piece.
It is characterized in that it is insulated from this main electrode and a sub-electrode is formed so as to face each other and the frequency of the main vibration of the sub-electrode is made equal to the resonance frequency of the sub-vibration generated in the main electrode.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to a plan view showing an electrode pattern of a crystal piece shown in FIG. In the figure, 1 is an SC-cut crystal piece. This crystal piece 1
Is rotated by about 33 °, eg 33 ° 30 ′ counterclockwise about the X axis on the plane orthogonal to the Y axis of the crystal of quartz, and further about 22 °, eg 22 ° 30 ′ counterclockwise about the ZZ ′ axis. It is a two-rotation SC-cut crystal piece cut out from the flat surface. The crystal piece 1 is polished to a thickness corresponding to a desired resonance frequency, and the main electrode 2 is formed by facing the front and back plate surfaces by vacuum deposition or the like. Then, the sub-electrode 3 is formed so as to be electrically insulated from the main electrode 2 and face the front and back plate surfaces. The sub-electrode 3 has a slightly smaller area so as not to impair the resonance characteristics of the main electrode 2, for example. The mass of the sub-electrode 3 is adjusted so that the main vibration has a frequency equal to the resonance frequency of the sub-vibration generated in the main electrode 2, for example, the frequency of the B-mode sub-vibration by the main electrode 2. Therefore, the frequency of the main vibration in the sub electrode 3 is
It is necessary to make the sub-electrode 3 thinner than the main electrode 2, or the sub-electrode 3 is made of a material having a low specific gravity. The crystal piece 1 is not limited to a rectangular plate-like one as shown in FIG. 1, but is a round plate-like one as shown in FIG.
Of course, it can be applied to a strip type as shown in FIG.

FIG. 4 is a side view showing the electrical electrode arrangement of the SC-cut crystal unit of the above embodiment.
A pair of main electrodes 2 and a pair of sub-electrodes 3 are provided on the plate surface so as to be insulated from each other. For example, the main electrode 2 is used as an oscillator and the sub-electrode 3 is used as a resonator. By doing so, the resonance characteristics of the main electrode 2 such as the resonance characteristics shown in FIG. 5 are the C mode fc, the B mode fb, and the A mode from the lowest frequency.
Appear in the order of mode fa. On the other hand, the resonance characteristic of the sub-electrode is that the frequency fs of the main vibration is B of the main electrode 2
The frequency fb of the mode is matched. Therefore, in the modified Colpitts type oscillation circuit as shown in FIG. 6, if the pair of main electrodes 2 is inserted as an oscillator in the base of the oscillation transistor 4 and the resonator formed of the sub-electrode 3 is inserted in the emitter, the resonator Component of the resonance frequency fs can be removed, the resonance of the B mode of the main electrode 2 can be surely suppressed, and the target C mode can be obtained without causing spurious as in the oscillation output shown in FIG. The oscillation output of can be obtained. Then, the SC of the above embodiment
If a cut crystal oscillator is used, the frequency of the main vibration of the sub-electrode 3 is made to match the frequency of the sub-vibration of the main electrode 2, so that the sub-vibration of the main electrode 2 can be reliably suppressed. It is possible to easily obtain the oscillation output of the target frequency without causing jumps or spurious noises.

[0008]

As described in detail above, according to the present invention, it is possible to provide an SC-cut crystal resonator having good vibration characteristics without causing a frequency jump due to a change in temperature and having no spurious.

[0009]

[Brief description of drawings]

FIG. 1 is a plan view showing an electrode structure of a crystal resonator of the present invention.

FIG. 2 is a plan view showing an electrode structure of a crystal resonator according to another embodiment of the present invention.

FIG. 3 is a plan view showing an electrode structure of a crystal resonator according to still another embodiment of the present invention.

FIG. 4 is a side view showing an electrical electrode arrangement of the crystal unit of the present invention.

FIG. 5 is a resonance characteristic diagram showing the relationship between the resonance output of each electrode of the crystal unit of the present invention and the oscillation output.

[Explanation of symbols]

 1 Quartz piece 2 Main electrode 3 Sub electrode 4 Transistor

[Procedure amendment]

[Submission date] May 12, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Figure 6

[Correction method] Added

[Correction content]

FIG. 6 is a circuit diagram showing an example of an oscillator circuit using the crystal unit of the invention.

Claims (1)

[Claims] 1. A plane perpendicular to the Y-axis of a crystal of quartz is rotated about 33 ° about the X-axis, and Z is rotated from this rotated position.
SC cut out from the surface rotated about 22 ° around the axis
In a cut crystal unit, a main electrode that is provided facing the plate surface of the crystal piece, and a sub-vibration that is formed on the plate surface of the crystal piece, facing and insulated from the main electrode, and generated in the main electrode. An SC-cut crystal resonator, comprising: a sub-electrode having a main vibration at a frequency equal to the resonance frequency of 1.