JPH114138A - Monolithic crystal filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an excellent electric characteristic by obtaining a more excellent attenuation characteristic and also suppressing a spurious vibration (unrequired vibration) mode which occurs in the neighborhood of a main vibration. SOLUTION: An input electrode 21 and an output electrode 22 are adjacently provided by arraying in a Z'-axial direction at a prescribed interval on the surface of a crystal plate 1 and drawing electrodes 211 and 221 are drawn on the end surface of the crystal plate 1 from the respective electrodes. Two shared electrodes 23 and 24 corresponding to the input electrode 21 and the output electrode 22 are provided on a rear surface and a shielding electrode 31 is provided between the input electrode 21 and the output electrode 22 at the prescribed interval from the long side of the output electrode so as to be deviated at an output electrode 22 side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a monolithic crystal filter using thickness vibrations used in communication equipment and the like, which suppresses the influence of spurious (unnecessary) vibrations and obtains a good damping characteristic. It is about filters.

[0002]

2. Description of the Related Art In a monolithic crystal filter, a symmetric mode vibration (fs) and an oblique symmetric mode vibration (fa) are excited by using an input / output electrode and a common electrode portion formed opposite to each other with a quartz plate as a resonance region. , Form a main vibration by being acoustically coupled, and constitute a filter having a predetermined pass band.

[0003] The applicant of the present invention has previously described Japanese Patent Application Laid-Open No. 5-327402.
Discloses a monolithic crystal filter that suppresses spurious and improves the attenuation characteristics. FIGS. 10 and 11 show one configuration disclosed here as a conventional example.
It will be explained together. FIG. 10 is a plan view on the input / output electrode side of the monolithic crystal filter, and FIG. 11 is a plan view on the common electrode side.

The quartz plate 1 is an AT-cut quartz plate, on the surface of which an input electrode 61, an output electrode 62 and lead electrodes 611, 621 for guiding these electrodes to the outer periphery of the quartz plate are provided, and the back surface corresponds to the input / output electrodes. A common electrode 63 and an extraction electrode 631 for guiding these electrodes to the outer periphery of the quartz plate are provided. A linear shield (cut off) at the middle position between the input and output electrodes on the surface
Electrodes 64 are formed and electrically connected to the common electrodes, which are grounded. These electrodes are formed by a thin film forming means such as a vacuum evaporation method.

[0005] By forming such a shield electrode, the electric signal input to the input electrode is directly converted into an electromagnetic wave,
This prevents the direct wave from reaching the adjacent output electrode and improves the attenuation characteristics.

Japanese Unexamined Patent Application Publication No. 5-327402 discloses several examples of configurations other than the configuration shown in the above-mentioned conventional example. The configuration is such that the shield electrode is located exactly at the midpoint of the electrode. However, by forming the electrode at the intermediate point in this way, spurious vibrations may be excited near the main vibration, albeit small, and the required characteristics may not be satisfied depending on the required electric characteristics. Was.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and provides a better damping characteristic and a spurious vibration generated near a main vibration (nominal frequency). An object of the present invention is to provide a monolithic crystal filter capable of suppressing vibration (vibration) mode and obtaining good electric characteristics.

[0008]

According to the present invention, an arrangement of a shield electrode formed between input and output electrodes for preventing a direct wave is provided.
By being formed unevenly at one of the intermediate points rather than at the intermediate point, for example, (1.
1.3) Focusing on the fact that the growth of spurious components such as anharmonic spurious vibration in the mode becomes smaller, it can be solved by the following configuration.

A monolithic quartz filter according to the present invention is characterized in that an input electrode,
An output electrode is formed in close proximity at a predetermined interval, and a common electrode corresponding to the input electrode and the output electrode is provided on the back surface to form a resonance region, and at least one electrode is provided between the input electrode and the output electrode. In a monolithic crystal filter using thickness-based vibration in which two shield electrodes are arranged, the arranged shield electrode is located at a position biased toward one or both electrodes, except for an intermediate portion between the input electrode and the output electrode. It is characterized by being arranged.

With the above arrangement, the shield electrode is formed not on the intermediate portion of the input / output electrode but on one of the electrodes, so that spurious vibration is hardly excited, and the electric signal input to the input electrode is not affected by electromagnetic waves. As a result, the direct wave reaching the output electrode is cut off.

FIG. 12 and FIG. 13 are graphs showing the attenuation characteristics depending on the position where the shield electrode is formed in the monolithic crystal filter. FIG. 12 shows data on a configuration disclosed in a first embodiment described later, and FIG. 13 shows data on a configuration described in a conventional example. In each case, the center frequency is 21 MHz, and the outer dimensions of the quartz plate are 4 mm long and 5 mm wide, and a pair of input / output electrodes (each 2 mm long, 1 mm wide, approximately 2000 mm thick) face the center of the quartz plate. Angstroms, and the distance between the electrodes is 1 mm.)
Are formed, and a shield electrode is formed between the electrodes. The width of the shield electrode is 0.3 mm, and the shield electrode shown in FIG. 12 is formed so as to be biased at a distance of 0.2 mm from the output electrode. The shield electrode in FIG. 13 is formed at a substantially central position between the input and output electrodes. From these characteristics, it can be understood that the spurious S1 in the vicinity of the main vibration is suppressed relatively small in the product of the present invention, and the spurious S2 grows relatively large in the conventional product.

According to a second aspect of the present invention, an input electrode and an output electrode are formed on a front surface of a quartz plate so as to be close to each other at predetermined intervals, and a common electrode corresponding to the input electrode and the output electrode is formed on the back surface. To form a resonance region, and at least 2 between the input electrode and the output electrode.
In a monolithic quartz crystal filter using a thickness system vibration in which two shield electrodes are arranged, the shield electrode has a region overlapping in the arrangement direction of the input electrode and the output electrode, and the input electrode side and the output between the input and output electrodes. It is also possible to adopt a configuration in which the electrodes are biased toward the electrodes and extend to the ends of the quartz plate in directions away from each other.

With the above arrangement, the shield electrode blocks the direct wave that reaches the output electrode by converting the electric signal input to the input electrode into an electromagnetic wave, and does not form an electrode at an intermediate portion between the input and output electrodes. As a result, spurious vibrations are less likely to be excited. Furthermore, since the shield electrodes extend in the directions away from each other, the mass of the entire quartz plate is balanced by electrode formation,
Does not induce spurious vibrations.

According to a third aspect of the present invention, an input electrode and an output electrode are formed on a front surface of a quartz plate so as to be close to each other at a predetermined interval, and a common electrode corresponding to the input electrode and the output electrode is formed on the back surface. To form a resonance region, and at least one between the input electrode and the output electrode.
A monolithic crystal filter using thickness-based vibration in which two shield electrodes are arranged, wherein the shield electrode extends from one end of the crystal plate to one of the input / output electrodes and is biased toward one of the electrodes. At the same time, it may be configured such that it is folded back in the opposite direction and is biased toward the other electrode side between the input and output electrodes.

According to the above configuration, the direct wave is more reliably blocked by the two shield electrodes existing between the input and output electrodes, and since no electrode is formed between the input and output electrodes, spurious vibration is not excited. In addition, since only one shield electrode is led out to the end of the quartz plate, no excitation of spurious vibration due to unnecessary mass addition is not induced.

According to a fourth aspect of the present invention, an input electrode and an output electrode are formed on a front surface of a quartz plate so as to be close to each other at predetermined intervals, and a common electrode corresponding to the input electrode and the output electrode is formed on the back surface. To form a resonance region, and at least one between the input electrode and the output electrode.
A monolithic crystal filter using thickness-based vibration in which three shield electrodes are arranged, and the shield electrode may be configured to have a zigzag shape at least between the input and output electrodes.

According to the above configuration, since the shield electrode has a zigzag configuration between the input and output electrodes, the area of the shield electrode can be increased as a whole, and the above-mentioned direct wave can be more efficiently cut off. In addition, since there is little electrode formation area in the intermediate portion between the input and output electrodes, it is possible to minimize the excitation of spurious vibrations.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a plan view of the front surface of a quartz plate showing a first embodiment of the present invention, FIG. 2 is a plan view of the back surface, and FIG. The quartz plate 1 is an AT-cut quartz plate and is processed into a rectangular shape. An input electrode 21 and an output electrode 22 are provided on the surface in a row in the Z′-axis direction and closely adjacent to each other at a predetermined interval, and extraction electrodes 211 and 221 are extracted from the respective electrodes to the end face of the quartz plate. On the back surface, 2 corresponding to the input and output electrodes 21 and 22 are provided.
Two common electrodes 23 and 24 are provided, these common electrodes are connected in common below the common electrodes, and an extraction electrode 231 is extended to the lower end face of the quartz plate. The arrangement of the input / output electrodes may be arranged in the X-axis direction.

A shield electrode 31 is provided between the input electrode 21 and the output electrode 22 so as to be biased toward the output electrode 22 and to be parallel to the long side 22a of the output electrode at a predetermined interval.
This shield electrode 31 is commonly connected to the common electrode,
Finally connected to ground. Each of these electrodes can be formed by a vacuum deposition method using a masking means, and a material such as aluminum or silver is used as an electrode material. Although not shown, a monolithic crystal filter is completed by mounting on a base having lead terminals and sealing hermetically, or by mounting on a surface mounting base and sealing hermetically.

According to the above configuration, since the shield electrode 31 is formed not on the intermediate portion of the input / output electrode but on one of the electrodes, spurious vibrations are hardly excited, and the electric signal input to the input electrode is suppressed. It blocks electromagnetic waves which directly reach the output electrode.

Next, an example in which a shield electrode 32 is formed on the input electrode 21 and a shield electrode 33 is formed on the output electrode 22 will be described as a second embodiment. FIGS. 4, 5, and 6 show the second embodiment. FIG. 4 is a plan view of the front surface of the quartz plate, FIG.
Is a sectional view taken along the line BB in FIG. The same components as those in the first embodiment will be described with the same reference numerals, and a description thereof will be partially omitted.

The basic configuration is the same as that of the first embodiment.
Input / output electrodes 21 and 22 are attached to a quartz plate 1 made of a T-cut quartz plate.
2 and common electrodes 23 and 24 are formed. The shield electrode 32 extends from the upper part of the quartz plate to the end of the long side in parallel with the long side of the electrode at a certain interval, with the shield electrode 32 being biased toward the input electrode 21 between the input and output electrodes. In addition, the shield electrode 33 extends from the lower part of the quartz plate to the end of the long side in parallel with the long side of the electrode at a certain interval in a state where the shield electrode 33 is biased toward the output electrode 22 among the input and output electrodes.

With this configuration, two shield electrodes are arranged between the input and output electrodes so as to be biased toward the input and output electrodes, and one shield electrode is extended to the upper part of the quartz plate and the other shield electrode is extended to the lower part. Therefore, the load mass on the quartz plate by electrode formation is balanced as a whole. Therefore, spurious vibration based on imbalance of the load mass can be suppressed.

The shield electrodes 34 and 35 extending between the input and output electrodes from above and below the quartz plate are, as shown in FIG.
The length may be such that only a part of the input / output electrodes overlap in the arrangement direction. Thus, by minimizing the overlapping portion of each shield electrode, the load mass due to the electrode formation can be reduced.

A third embodiment will be described with reference to FIG. Shield electrode 36 formed between input / output electrodes 21 and 22
Extends upward from the lower end of the quartz plate along the vicinity of the output electrode 22, and extends near the upper end of the longer side of the output electrode 22.
Side, and then extends downward along the vicinity of the input electrode 21 to reach near the lower end of the long side. As a result, a shield electrode is formed at a portion other than the intermediate portion of the input / output electrode. In addition, it is necessary to lead the shield electrode to the end of the quartz
Therefore, it does not induce the excitation of spurious vibration due to unnecessary mass addition. The bent portion of the shield electrode 36 may be located at a portion protruding from between the input and output electrodes.

A fourth embodiment will be described with reference to FIG. Shield electrode 37 formed between input / output electrodes 21 and 22
Has a zigzag shape having a plurality of bent portions at least in a part between the input and output electrodes, and the electrodes are extended to upper and lower ends of the quartz plate. This zigzag portion may be formed in the middle of the input / output electrodes as shown in FIG. 9, or may be formed biased on any of the electrodes. Also,
The zigzag portion may be a part of the shield electrode or may be formed entirely. With the above configuration, the area of the shield electrode can be increased as a whole, and the above-described direct wave can be more efficiently cut off, and the electrode formation area at the intermediate portion between the input and output electrodes is small, so that the spurious vibration Can be minimized.

Since the electrode formation in each of the above embodiments requires a finer electrode pattern than the electrode formation of a normal quartz oscillator, it is necessary to pay attention to a short circuit accident between adjacent electrodes. Therefore, an electrode may be formed by using a photolithography technique in addition to a vacuum evaporation method using a metal mask which is usually used, and sputtering.

[0028]

According to each aspect of the present invention, since the shield electrode is formed not on the intermediate portion of the input / output electrode but on one of the electrodes, spurious vibration is less likely to be excited. Further, a better attenuation characteristic can be obtained by blocking the direct wave that reaches the output electrode by converting the electric signal input to the input electrode into an electromagnetic wave. Therefore,
Good electrical characteristics as a monolithic crystal filter can be obtained.

According to the second aspect, in addition to the above effects, since the shield electrodes extend in the directions away from each other, the mass of the entire quartz plate is balanced by electrode formation, so that unnecessary spurious noise is obtained. Does not induce vibrational excitation. Therefore, more stable electrical characteristics can be obtained.

According to the third aspect of the present invention, the shield electrode is close to both the input electrode and the output electrode, but only one lead of the shield electrode to the end of the quartz plate is provided. In addition, the shield effect can be improved, and a stable electric characteristic can be obtained without inducing the excitation of spurious vibration due to unnecessary addition of mass.

Furthermore, according to the fourth aspect, the area of the shield electrode can be increased as a whole, and the above-described direct wave can be more efficiently cut off, and the electrode can be formed at an intermediate portion between the input and output electrodes. Since the area is small, excitation of spurious vibration can be suppressed to a minimum. Therefore, more stable electrical characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is a plan view showing an electrode configuration on a surface of a quartz plate according to a first embodiment.

FIG. 2 is a plan view showing an electrode configuration on the back surface of the quartz plate according to the first embodiment.

FIG. 3 is a sectional view taken along line AA of FIG. 1;

FIG. 4 is a plan view showing an electrode configuration on the surface of a quartz plate according to a second embodiment.

FIG. 5 is a plan view showing an electrode configuration on the back surface of a quartz plate according to a second embodiment.

FIG. 6 is a sectional view taken along line BB of FIG. 4;

FIG. 7 is a plan view showing an electrode configuration on the surface of a quartz plate according to another example of the second embodiment.

FIG. 8 is a plan view showing an electrode configuration on the surface of a quartz plate according to a third embodiment.

FIG. 9 is a plan view showing an electrode configuration on the surface of a quartz plate according to a fourth embodiment.

FIG. 10 is a diagram showing a conventional example.

FIG. 11 shows a conventional example.

FIG. 12 shows comparison data.

FIG. 13 shows comparison data.

[Explanation of symbols]

1 Quartz plate 21, 61 Input electrode 22, 62 Output electrode 23, 63 Common electrode 31, 32, 33, 34, 35, 36, 37, 64 Shield electrode

Claims (4)

[Claims] 1. A resonance region is formed by forming an input electrode and an output electrode close to each other at a predetermined interval on a front surface of a quartz plate and providing common electrodes respectively corresponding to the input electrode and the output electrode on the back surface. And a monolithic crystal filter using thickness-based vibration in which at least one shield electrode is disposed between the input electrode and the output electrode, wherein the disposed shield electrode excludes an intermediate portion between the input electrode and the output electrode A monolithic crystal filter, wherein the monolithic crystal filter is arranged at a position biased toward one or both electrodes. 2. A resonance region is formed by forming an input electrode and an output electrode close to each other at a predetermined interval on a front surface of a quartz plate and providing common electrodes respectively corresponding to the input electrode and the output electrode on the back surface. And a monolithic crystal filter using a thickness-based vibration in which at least two shield electrodes are arranged between the input electrode and the output electrode, wherein the shield electrode has a region overlapping in the arrangement direction of the input electrode and the output electrode. A monolithic crystal filter, wherein the monolithic crystal filter is arranged so as to be biased toward the input electrode side and the output electrode side between the input and output electrodes, and extends to the ends of the crystal plate in directions away from each other. 3. A resonance region is formed by forming an input electrode and an output electrode close to each other at a predetermined interval on a front surface of a quartz plate and providing common electrodes respectively corresponding to the input electrode and the output electrode on the back surface. And a monolithic crystal filter using a thickness system vibration in which at least one shield electrode is arranged between the input electrode and the output electrode, wherein the shield electrode is any one of an end portion of the quartz plate and a portion between the input and output electrodes. While extending to one of the electrode side,
A monolithic crystal filter characterized by being folded in the opposite direction and extending between input and output electrodes so as to be biased toward the other electrode. 4. A resonance region is formed by forming an input electrode and an output electrode close to each other on a front surface of a quartz plate at predetermined intervals and providing common electrodes respectively corresponding to the input electrode and the output electrode on the back surface. And a monolithic quartz crystal filter using a thickness vibration in which at least one shield electrode is arranged between the input electrode and the output electrode, wherein the shield electrode has a zigzag shape at least between the input and output electrodes. Monolithic crystal filter.