JP3141696B2 - Ladder type filter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ladder filter in which at least one series resonator and at least one parallel resonator are connected like a ladder, and more particularly, to a series resonator and a parallel resonator. The present invention relates to a ladder filter having an improved resonator structure.

[0002]

2. Description of the Related Art FIG. 1 shows an example of the structure of a conventional ladder filter. This ladder-type filter is configured by using a plurality of piezoelectric resonators utilizing a spread vibration mode of a square plate. That is, a four-element two-stage ladder filter shown in the circuit diagram of FIG. 2 is configured by using the rectangular plate-shaped series resonators 1 and 2 and the rectangular plate-shaped parallel resonators 3 and 4.

In FIG. 1, reference numeral 2a denotes an electrode formed on one main surface of the series resonator, and a similar electrode is formed on the other main surface of the series resonator 2. Similar electrodes are formed on both main surfaces of the series resonator 1.
On the other hand, the parallel resonators 3 and 4 have electrodes 3
a, 4a are formed.

[0004] Reference numerals 5 to 11 denote metal terminals, which are used to electrically connect the series resonators 1 and 2 and the parallel resonators 3 and 4 to each other as shown in FIG. The metal terminals 5 to 11 are housed together with the series resonators 1 and 2 and the parallel resonators 3 and 4 in a case member 12 made of an insulating material. Further, the upper opening 12a of the case member 12 is closed by a lid member (not shown) to form a ladder-type filter component. In this case, the metal terminals 9 to 11 are drawn out of the case and used as connection terminals with the outside.

When the ladder-type filter is driven, it is necessary that the series resonators 1 and 2 and the parallel resonators 3 and 4 can vibrate in a desired manner while being housed in a case. That is, in the state stored in the case,
The vibration of each resonator 1-4 must not be disturbed. Therefore, a so-called spring terminal having a spring property is used as the metal terminal 11 located at the end.

In the ladder-type filter shown in FIG. 1, since a spring terminal is used as the metal terminal 11 so as not to hinder the vibration of the resonators 1 to 4 housed in the case, a considerable unnecessary space is formed. Therefore, the size of the entire ladder-type filter tends to be considerably large. For example, in the illustrated two-stage ladder-type filter with four built-in elements, the dimensions when configured as a final ladder-type filter component are 7.0 mm × 8.0 mm × 8.0 mm in thickness.
It was about the size.

In recent years, like other electronic components, there has been a demand for a ladder-type filter configured as a surface-mounted electronic component. Therefore, Japanese Patent Application Laid-Open No. 4-284
01 5 No. can be the overall shape small,
A ladder-type filter that can be configured as a surface-mounted electronic component has been proposed. In this ladder-type filter, the series resonator and the parallel resonator are each formed of a tuning-fork type piezoelectric resonator having a tuning-fork-shaped vibrating portion at one edge of the piezoelectric plate. Then, a plurality of tuning-fork type piezoelectric resonators constituting the series resonator and the parallel resonator are stacked and integrally formed via a cavity forming material for securing a cavity for not hindering the vibration of the tuning-fork vibrating portions. Has been

[0008]

The ladder-type filter using the tuning-fork type piezoelectric resonator described above can simplify the assembling process, reduce the size, and achieve surface mounting. However, since the tuning fork type piezoelectric resonator is used,
There is a problem that a sufficient bandwidth cannot be secured.

An object of the present invention is to provide a ladder-type filter capable of not only simplifying the manufacturing process, reducing the size and realizing surface mounting, but also securing a sufficient bandwidth.

[0010]

The present invention comprises at least one series resonator forming a series arm and at least one parallel resonator forming a parallel arm. among children, at least one resonator, a piezoelectric plate, and a resonance part using and shear mode and a pair of excitation electrodes formed to face each other in the outer surface of the piezoelectric plate, the resonant Vibration leaking from the part
Resonates more in bending mode and reduces the vibration due to dynamic vibration absorption
A damping dynamic damper, and a damper between the resonance part and the dynamic damper.
And a supporting part connected to the dynamic vibration absorbing part, and a connecting part connected between the dynamic vibration absorbing part and the holding part.
An energy trapping type of the dynamic vibration reducer unit built-in piezoelectric resonator and a coupling portion disposed in a ladder-type filter.

In the above-described piezoelectric resonator having a built-in dynamic vibration absorbing portion of the energy trapping type utilizing the slip mode, the piezoelectric plate, the dynamic vibration absorbing portion and the holding portion are integrally formed of a piezoelectric material. It may be constituted by a piezoelectric substrate, or may be prepared by a separate member, connected to each other and integrated as described in claim 3.

The piezoelectric plate may be made of a piezoelectric material. Examples of such a piezoelectric material include piezoelectric ceramics and piezoelectric single crystals. Further, the piezoelectric plate does not necessarily need to be formed entirely of a piezoelectric material, but may be formed by forming a piezoelectric thin film on a metal plate or a semiconductor plate.

In the above-described piezoelectric resonator having a built-in dynamic vibration absorbing portion, the dynamic vibration absorbing portion and the holding portion are connected to at least one side of the resonance portion. The dynamic vibration absorbing part and the holding part are connected to both sides of the resonance part. By connecting the dynamic vibration absorbing portion and the holding portion to both sides, the resonance portion can be stably held, and the vibration leaking from the resonance portion can be more effectively suppressed by the dynamic vibration absorbing portions on both sides.

In the present invention, the positions at which the pair of excitation electrodes are formed in the energy-trapping type piezoelectric resonator with a built-in dynamic vibration absorbing portion are not particularly limited. Can be variously changed. That is, the pair of excitation electrodes may be formed on a pair of side surfaces of the piezoelectric plate, as described in claim 6, and formed separately on both main surfaces of the piezoelectric plate as described in claim 7. Alternatively, the piezoelectric plate may be formed so as to face one main surface of the piezoelectric plate with a predetermined distance therebetween. When a pair of excitation electrodes are formed on one main surface of the piezoelectric plate, preferably, a pair of excitation electrodes are formed along a pair of opposed side edges of the piezoelectric plate, thereby forming the piezoelectric plate. Can be effectively used to configure the resonance section in the slip mode.

[0015]

The ladder-type filter of the present invention has the following features.
At least one of the series resonators and the parallel resonators is constituted by the above-mentioned resonator with a built-in dynamic vibration absorbing unit using the slip vibration mode. The resonator with a built-in dynamic vibration absorbing section has a dynamic vibration absorbing section that attenuates vibration leaked from the resonance section due to a dynamic vibration absorbing phenomenon. The details of this dynamic vibration absorption phenomenon
For example, it is described in Osamu Taniguchi, "Vibration Engineering", pp. 113-116 (Corona). Simply put, the dynamic vibration absorption phenomenon means that the vibration of the main vibrating body is suppressed by connecting the sub-vibrating body to the main vibrating body to be prevented from vibration and selecting the natural frequency of the sub-vibrating body appropriately. It is a phenomenon that is done.

The above-mentioned dynamic vibration absorbing portion of the ladder type filter according to the present invention corresponds to a sub vibrator in a dynamic vibration absorbing phenomenon, and a holding portion outside the resonance portion corresponds to a main vibrating body. According to the present invention, in the above-described resonator with a built-in dynamic vibration absorbing portion, the vibration energy is effectively confined to a portion up to the dynamic vibration absorbing portion, so that the resonance portion can be configured in a slip vibration mode. I have. Therefore, the band of the ladder-type filter can be easily expanded.

In addition, since the vibration energy is confined in the portion up to the dynamic vibration absorbing portion, a plurality of resonators with a built-in dynamic vibration absorbing portion can be easily combined. That is, it is easy to connect a plurality of series resonators and / or parallel resonators in the lateral direction and to stack them in the thickness direction. Therefore, the manufacturing process of the ladder-type filter can be simplified and downsized easily, and it can be easily configured as a surface-mounted electronic component.

Further, since the above-described resonator having a built-in dynamic vibration absorbing portion has a dynamic vibration absorbing portion, it has excellent energy confinement efficiency. Therefore, it is smaller in size than a conventional energy confining type piezoelectric resonator utilizing a sliding vibration mode. Can be configured. Therefore, the ladder-type filter can be downsized.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be clarified by describing non-limiting embodiments of the present invention.

First Embodiment FIG. 3 is an exploded perspective view of a ladder-type filter according to a first embodiment, and FIG. 4 is a perspective view showing an appearance of the ladder-type filter.

The ladder type filter 20 has a structure in which a case substrate 21, a first resonance plate 22, a separating spacer 23, a second resonance plate 24, and a case substrate 25 shown in FIG.

The first resonance plate 22 is composed of piezoelectric resonators 26 and 27 with a built-in dynamic vibration absorbing portion using a sliding vibration mode.
And a piezo-resonator 28 with a built-in dynamic vibration absorbing portion using a width vibration mode, which are integrated with each other.
It has a structure in which 9, 30 are joined using an adhesive. The spacer plates 29 and 30 are made of an insulating material having a certain degree of strength, such as insulating ceramics such as alumina or a synthetic resin, and the piezoelectric resonator 2.
Notch 29 for preventing vibration of vibrating parts 6, 27
a and 30a.

The piezoelectric resonator 26 with a built-in dynamic vibration absorber is shown in FIG.
As shown in (a), the piezoelectric substrate is configured by using an elongated rectangular plate-shaped piezoelectric ceramic plate 26a which is uniformly polarized in a direction indicated by an arrow P. An excitation electrode 26b is formed on one side surface of the piezoelectric ceramic plate 26a from one end of the piezoelectric ceramic plate 26a toward the other end. The end of the excitation electrode 26b ends at a portion reaching the concave portion 26c formed by notching the side surface. Also, a concave portion 26d is formed at a predetermined distance from the concave portion 26c, and thereby a dynamic vibration absorbing portion 26e is formed between the concave portions 26c and 26d.

Similarly, on the other side surface of the piezoelectric ceramic plate 26a, an excitation electrode 26f is formed so as to extend from the other end of the piezoelectric ceramic plate 26a to the one end. Further, by forming two recesses 26g and 26h in the same manner as the side on which the excitation electrode 26b is formed,
The dynamic vibration absorbing portion 26i is configured.

In other words, a piezoelectric ceramic plate 26a having a rectangular planar shape is prepared, two grooves are formed on each side surface, and the concave portions 26c, 26d, 26g, and 26h are formed. Dynamic vibration absorbing portions 26e and 26i are respectively formed between the grooves.

In the piezoelectric resonator 26, the excitation electrode 26b
The portion where the and the excitation electrode 26f overlap constitutes a resonating portion, the portion between the resonating portion and the dynamic vibration absorbing portions 26e and 26i constitutes a supporting portion, and the portion where the concave portions 26d and 26h are formed. Also, the piezoelectric ceramic plate portion at the outer end forms a holding portion, and a relatively narrow piezoelectric ceramic portion between the holding portion and the dynamic vibration absorbing portions 26e and 26i forms a connecting portion.

In the piezoelectric resonator 26 with a built-in dynamic vibration absorbing portion, by applying an AC voltage from the excitation electrodes 26b and 26f, the region where the excitation electrodes 26b and 26f overlap resonates in a slip vibration mode, and operates as a piezoelectric resonator. I do.

The vibration generated in the region where the excitation electrodes 26b and 26f overlap each other is caused by the dynamic vibration absorbers 26e and 26i.
Trapped in the part up to. That is, even if the resonance in the slip vibration mode leaks from the portion where the excitation electrodes 26b and 26f overlap, that is, from the resonance portion, the dynamic vibration absorbing portions 26e and 26i resonate due to the leaked vibration and are attenuated by the dynamic vibration absorbing phenomenon. You. Therefore, the dynamic vibration absorbing portions 26e,
Vibration is hardly transmitted to the piezoelectric ceramic plate portion outside of 26i. Therefore, in the piezoelectric resonator 26 with a built-in dynamic vibration absorbing portion, the piezoelectric ceramic plate portion outside the dynamic vibration absorbing portions 26e and 26i is connected to another member, so that the piezoelectric resonator 26 can be formed without obstructing the resonance of the resonance portion. It is possible to hold it mechanically.

Returning to FIG. 3, the piezoelectric resonator 28 with a built-in dynamic vibration absorber used for the first resonance plate 22 is
This will be described with reference to FIG. The dynamic vibration absorbing section built-in type piezoelectric resonator 28 is configured by using a piezoelectric ceramic plate 28a having a planar shape shown in FIG. In this piezoelectric ceramic plate 28a, a resonance portion 28b having a rectangular planar shape is formed at the center of the piezoelectric ceramic plate. Resonant part 28b
In the figure, the polarization processing is performed in the direction of the arrow P shown in the figure, and the excitation electrodes 28c are formed on both main surfaces (the excitation electrodes on the lower surface are not shown). By applying an AC voltage from the excitation electrodes 28c on both main surfaces of the resonance section 28b, the resonance section 28b resonates in the width vibration mode.

On the other hand, elongated rod-shaped support portions 28d and 28e are connected to the center of the opposing side surfaces of the resonance portion 28b, and the dynamic vibration absorbing portions 28f and 28g are respectively connected to the outer ends of the support portions 28d and 28e. Is configured. The dynamic vibration absorbing portions 28f and 28g are configured to vibrate in a bending mode, and are configured to resonate by the vibration transmitted from the resonance portion 28b. Therefore, the resonance unit 28
The resonance at b is confined in the portion up to the dynamic vibration absorbing portions 28f and 28g.

Connecting portions 28h and 28i are connected to the outside of the dynamic vibration absorbing portions 28f and 28g, and holding portions 28j and 28k are connected to outer ends of the connecting portions 28h and 28i. The holding portions 28j and 28k are connected to the piezoelectric resonator 28.
Is provided as a part for connecting to other members or mechanically holding the same, and has a relatively large area as shown in the figure.

The piezoelectric resonator 28 with a built-in dynamic vibration absorber shown in FIG. 5B may be formed by machining a single piezoelectric ceramic plate as described above. They may be formed separately and connected to each other by an adhesive or the like. For example, instead of the piezoelectric ceramic plate 28a shown in FIG. 5B, the supporting portions 28d, 28e,
The members constituting the dynamic vibration absorbing portions 28f and 28g, the connecting portions 28h and 28i, and the holding portions 28j and 28k may be integrated by bonding with an adhesive or the like. In a piezoelectric resonator with a built-in dynamic vibration absorber used in the following embodiments, the piezoelectric ceramic plate for forming each piezoelectric resonator is the same as that of the present embodiment. It should be pointed out that this may be formed by machining or by connecting a plurality of members.

The excitation electrode 28c is connected to the connection conductive portion 28.
electrode 28m formed on the upper surface of the holding portion 28k via
Is electrically connected to Similarly, the excitation electrode formed on the lower surface of the resonance portion 28b is also electrically connected to the electrode formed on the lower surface of the holding portion 28j via the connection conductive portion.

Returning to FIG. 3, a piezoelectric resonator 27 with a built-in dynamic vibration absorber having the same structure as the piezoelectric resonator 26 with a built-in dynamic vibration absorber, and the piezoelectric resonators 26 and 28 with a built-in dynamic vibration absorber are mutually connected. The side surfaces of the holding portion are integrated by bonding with an insulating adhesive, and the spacer plates 29, 30 described above are integrated.
Are further joined laterally to form the first resonance plate 22.

In the resonance plate 22, on the upper surface side,
Electrodes 22a to 22c for electrically connecting the piezoelectric resonators 26 to 28 so as to form a ladder-type filter as described later.
22d are formed. The electrode 22a is electrically connected to the above-described excitation electrode 26f of the piezoelectric resonator 26 (see FIG. 5A). Similarly, the electrode 22c is electrically connected to the excitation electrode 26b, and the electrodes 22b and 22d are electrically connected to one excitation electrode formed on the side surface of the piezoelectric resonator 27, respectively. Further, in the piezoelectric resonator 28, an electrode 28m connected to one of the excitation electrodes 28c is formed so as to reach the edge of the resonance plate 22 as shown in the drawing.
Similarly, an electrode electrically connected to the excitation electrode on the lower surface side is also formed so as to reach the opposite edge on the lower surface of the resonance plate 22.

In the second resonance plate 24, the same as the piezoelectric resonator 28 with a built-in dynamic vibration absorbing section is provided on both sides of a piezoelectric resonator 31 with a built-in dynamic vibration absorbing section utilizing the sliding vibration mode having the same structure as the piezoelectric resonator 26. The piezoelectric resonators 32 and 33 with a built-in dynamic vibration absorbing portion using the width vibration mode are bonded. Further, spacers 34 and 35 made of an insulating material having an appropriate degree of strength such as insulating ceramics or synthetic resin having the same thickness as those of the piezoelectric resonators 31 to 33 are provided on the side of the piezoelectric resonators 32 and 33. Glued to the side. As shown in the figure, the spacers 34 and 35 are provided with substantially U-shaped cutouts 34 at the edges on the piezoelectric resonators 32 and 33 side.
a, 35a. The cutouts 34a and 35a are provided to secure a space that does not hinder the vibration of the resonance portions and the dynamic resonance portions of the piezoelectric resonators 32 and 33.

The piezoelectric resonator 31 and the piezoelectric resonator 3
The structures of the piezoelectric resonators 2 and 33 are the same as those of the piezoelectric resonator 26 and the piezoelectric resonator 28 described above, and a detailed description thereof will be omitted. In the second resonance plate 24, electrodes 24a and 24b are formed on the upper surface so as to reach different edges. The electrodes 24a and 24b are respectively connected to the piezoelectric resonator 3
1 is electrically connected to one of the excitation electrodes formed on both side surfaces. In the piezoelectric resonators 32 and 33, the electrodes 32c and 33d on the holding portion electrically connected to the excitation electrodes 32a and 33a formed on the upper surface are formed so as to reach different edges of the resonance plate 24. I have. Further, the excitation electrodes formed on the lower surfaces of the resonance portions of the piezoelectric resonators 32 and 33 are electrically connected to electrodes reaching the opposite edge on the lower surfaces.

The case substrates 21 and 25 have concave portions 21a and 25a respectively on the lower surface and the upper surface. Recesses 21a,
The reference numeral 25a is provided so as not to hinder the vibration of the resonance part and the dynamic vibration absorbing part of the adjacent piezoelectric resonators when they are stacked. Also, in the separation spacer 23, the concave portion 23a is formed on the upper surface.
Although not clearly shown in FIG. 3, a concave portion having the same shape as the concave portion 23a is formed on the lower surface side. These recesses are provided so as not to hinder the vibration of the resonance part and the dynamic vibration absorbing part of the piezoelectric resonators arranged vertically.

However, the recesses 21a, 23a,
Instead of providing the 25a, a flat case substrate 21, a separating spacer 23, and the case substrate 25 may be used. In that case, in order not to hinder the vibration of the resonance part and the dynamic vibration absorbing part,
A similar space needs to be formed by interposing a rectangular frame-shaped spacer having a thickness corresponding to the depth of the concave portions 21a, 23a, and 25a, or by applying an insulating adhesive to the rectangular frame. .

The case substrates 21 and 25 and the separating spacer 23 can be made of an insulating material having a certain strength, for example, an insulating ceramic such as alumina or a synthetic resin.

In this embodiment, the case substrate 21 described above is used.
The first resonance plate 22, the separation spacers 23, the second resonance plate 24, and the case substrate 25 are laminated and bonded with an insulating adhesive, thereby being integrated as a ladder-type filter having a laminated structure. This will be described with reference to FIG.

As is clear from FIG. 4, the ladder filter 20 of this embodiment has a structure in which a plurality of rectangular plate-like members are laminated, and the terminal electrodes 20a to 20l extend from the side surface to the upper surface and the lower surface. Are formed. Terminal electrode 20a
２０20 l can be formed by applying and baking a conductive paste, or by vapor deposition, plating or sputtering. As shown in FIG. 3, a plurality of electrodes 21b are previously formed on the upper surface of the case substrate 21, and a plurality of terminal electrode portions are similarly formed on the lower surface of the case substrate 25. Thereafter, as shown in FIG. 4, by applying an electrode material to the side surface of the laminate, the terminal electrodes 20a to 20l extending from the side surface to the upper surface and the lower surface may be formed.

In the ladder-type filter obtained as described above, as shown in FIG. 6, the terminal electrodes 20a to 20l are connected, the terminal electrode 20a is used as an input terminal, and the terminal electrode 20a is used.
k, 20j as output terminals, and terminal electrodes 201, 20f, 2
By connecting 0b to the ground potential, it is possible to operate as a ladder filter shown in the circuit diagram of FIG.

In the ladder-type filter 20 of the present embodiment, a series resonator and a parallel resonator are constituted by using the piezoelectric resonators 26 to 28 and 31 to 33 with a built-in dynamic vibration absorber using the slip vibration mode and the width vibration mode. Have been. Therefore, the pass band width can be easily expanded as compared with a ladder type filter using a tuning fork type piezoelectric resonator.

Further, in each of the resonators with a built-in dynamic vibration absorbing portion, the vibration energy is confined in the portion up to the dynamic vibration absorbing portion. And can be integrated.

Second Embodiment FIG. 8 is an exploded perspective view of a so-called T-type connection filter in the circuit configuration used for the ladder-type filter according to the second embodiment, and FIG. It is a perspective view showing the appearance of a filter.

The T-type filter 70 includes a case substrate 71,
It is configured by laminating a resonance plate 72 and a case substrate 73. The case substrates 71 and 73 are
It is configured similarly to the case substrates 21 and 25 of the embodiment. That is, a concave portion 73 a is formed on the upper surface of the case substrate 73, and a similar concave portion is formed on the lower surface of the case substrate 71, although not particularly shown.

On the other hand, the resonance plate 72 has substantially the same configuration as the resonance plate 22 used in the first embodiment. That is, the piezoelectric resonator 28 with a built-in dynamic vibration absorbing portion using a width mode is arranged at the center, the piezoelectric resonators 26 and 27 with a built-in dynamic vibration absorbing portion using a sliding mode are adhered to the side, and a spacer is further provided outside. It has a structure in which 29 and 30 are bonded. However, in the present embodiment, on the upper surface of the piezoelectric resonator 28, the electrode 28m connected to the excitation electrode 28c
The electrodes 72a and 72b connected to one of the excitation electrodes of the piezoelectric resonators 26 and 27 are also drawn out from the edge from which the is drawn out.

Also, as shown by the broken line on the right side in FIG. 8, the electrode 28o electrically connected to the excitation electrode 28n is also electrically connected to the other excitation electrode of the piezoelectric resonators 26 and 27 also on the lower surface side. The electrodes 72c and 72d are drawn to the same edge side.

As is apparent from FIG. 9, in the ladder-type filter 70 obtained by laminating the above members, the electrode 2
8m, depending on the position where 72a to 72d are formed,
Terminal electrodes 70a to 70f are formed. Therefore, by connecting the terminal electrode 70c to the input terminal, connecting the terminal electrode 70b to the ground potential, setting the terminal electrode 70a to the output terminal, and connecting the terminal electrodes 70d to 70f in common, FIG.
The filter for so-called T-type connection shown in FIG.

The filter 70 is connected to a π-type connection filter shown with reference to FIGS. 11 and 12, and forms a three-stage ladder-type filter. The π-type connection filter will be described with reference to FIGS.

The so-called π-type connection filter 80 in the circuit configuration of the ladder filter has a structure in which a case substrate 81, a resonance plate 82 and a case substrate 83 are laminated. The case substrates 81 and 83 have the same configuration as the case substrates 71 and 73 shown in FIG. That is, a concave portion is formed on the lower surface of the case substrate 81, and a concave portion 83a is formed on the upper surface of the case substrate 83.

On the other hand, the resonance plate 82 has substantially the same configuration as the resonance plate 24 of the first embodiment. The difference is that the excitation electrodes 32a, 33a on the upper surfaces of the dynamic vibration absorbing section built-in type piezoelectric resonators 32, 33 using the width mode are all drawn out to one end side of the resonance plate 82, and are indicated by broken lines in FIG. As shown on the right side, all of the excitation electrodes on the lower surface are drawn out to the other end side of the resonance plate 82. The other points are the same as those of the resonance plate 24 of FIG. 3, and the corresponding parts are denoted by the same reference numerals and the description thereof will be omitted.

As shown in FIG. 12, in the π-type connection filter 80, terminal electrodes 80a to 80f are formed on the side surfaces, the terminal electrodes 80a and 80b are commonly connected, the output terminals are provided, and the terminal electrodes 80c and 80d are connected. The π-type filter shown in FIG. 13 is configured by connecting to the ground potential and commonly connecting the terminal electrodes 80e and 80f to be an input terminal.

Therefore, by connecting the output terminal of the T-type connection filter 70 and the input terminal of the π-type filter 80, a three-stage ladder-type filter is formed. In other words, the T-type connection filter 70 and the π-type connection filter 80
By connecting to the ladder-type filter, a ladder-type filter having the same number of stages as the ladder-type filter of the first embodiment can be configured.

Third Embodiment FIG. 14 is an exploded perspective view showing a one-stage ladder-type filter according to a third embodiment, and FIG. 15 is a perspective view showing its appearance.

In the ladder type filter 110 of this embodiment,
Case substrate 111, resonance plate 112, cavity forming spacer 113, resonance plate 114, and case substrate 11
5 are stacked.

A recess 115 a is formed on the upper surface of the case substrate 115.
However, a similar concave portion is formed on the lower surface of the case substrate 111, and a space for preventing the vibration of the vibrating portion of the laminated resonance plate is secured.
Further, by interposing the cavity forming spacer 113 therebetween, a space is formed so as not to hinder the vibration of the vibration portions of the resonance plates 112 and 114.

Since the details of the case substrates 111 and 115 and the cavity forming spacer 113 are the same as those of the case substrate and the cavity forming spacer used in the first embodiment, detailed description thereof is omitted. .

The resonance plate 112 has spacers 11 on both sides of the piezoelectric resonator 26 with a built-in dynamic vibration absorbing portion shown in FIG.
6,117 are attached. Spacer 11
6, 117 are cutouts 116 on the side face on the piezoelectric resonator 26 side.
a, 117a so that the vibration of the vibrating portion of the piezoelectric resonator 26 is not hindered.

On the other hand, the resonance plate 114 is the same as the piezoelectric resonator 28 shown in FIG. 5B, except that the positions of the electrodes where the excitation electrodes are drawn out are slightly different. It is configured by bonding spacers 118 and 119 to the sides of the. Spacer 11
8, 119 have cutouts 118a, 119a on the piezoelectric resonator 28 side, similarly to the spacers 116, 117.

Although not clearly shown in FIG. 14, in the piezoelectric resonator 28, an excitation electrode is also formed on the lower surface of the resonance portion 28b, and an electrode electrically connected to the excitation electrode is connected to the resonance plate. 114 are formed to reach the edge 114a side.

In the ladder-type filter 110 of this embodiment,
Each of the above members is laminated, and as shown in FIG.
It is completed by forming 0a, 110b, 110c on the side surface. That is, the terminal electrode 110a is connected to the ground potential, the terminal electrode 110b is the input terminal, the terminal electrode 110c
Is used as an output terminal, a one-stage ladder-type filter can be configured as shown in FIG. By laminating two or more resonance plates 112 and 114, a ladder filter having two or more stages can be easily formed.

[0064] The ladder filter 120 of the fourth embodiment The fourth embodiment will be described with reference to FIGS. 17 and 18.

In the third embodiment, the piezoelectric resonator 26 with a built-in dynamic vibration absorber using a slip mode and the piezoelectric resonator with a built-in dynamic vibration absorber 28 using a width mode are formed on different resonance plates 112 and 114. However, in this embodiment,
Both piezoelectric resonators 26 and 28 are integrated as one resonance plate 121. That is, the piezoelectric resonators 26 and 2
8 is bonded via a spacer 122, and a spacer 123 is provided on the side of the piezoelectric resonator 28 with the piezoelectric resonator 26.
A spacer 124 is joined to the outside of the substrate to form a resonance plate 121. On the other hand, the resonance plate 121
Are sandwiched between the case substrates 125 and 126 from above and below to obtain a laminate as shown in FIG.

A terminal electrode 120a is provided on the opposite end face of the laminate.
By forming ~ 120d, a one-stage ladder-type filter is formed. That is, the terminal electrode 120a is connected to the ground potential, the terminal electrode 120b is used as an input terminal, and the terminal electrodes 120c and 120d are commonly connected and used as an output terminal, thereby forming a one-stage ladder-type filter as shown in FIG. Is done. Further, by stacking a plurality of the resonance plates 121 via a cavity forming spacer therebetween,
A ladder-type filter having more than two stages can be easily formed.

Fifth Embodiment FIG. 20 is an exploded perspective view for explaining a ladder filter according to a fifth embodiment, and FIG. 21 is a perspective view showing an appearance of the ladder filter.

Referring to FIG. 20, first resonance plate 1
Numeral 61 denotes a piezoelectric resonator 162 with a built-in dynamic vibration absorbing portion using a sliding mode and a piezoelectric resonator 163 with a built-in dynamic vibration absorbing portion using a width mode, which are integrated by bonding their holding portions. Spacers 164 and 165 are attached outside the piezoelectric resonators 162 and 163.

The piezoelectric resonator 162 is a piezoelectric resonator 26 using the slip mode used in the first embodiment (FIG. 5A).
). This piezoelectric resonator 162
The excitation electrode formed on one side of the
1 is electrically connected to an electrode 161a formed along one edge. On the other hand, the excitation electrode formed on the other side surface is electrically connected to an electrode 161b formed along the other end of the resonance plate 161.

Further, the piezoelectric resonator 163 with a built-in dynamic vibration absorber using the width mode has substantially the same configuration as the piezoelectric resonator 28 used in the first embodiment. This piezoelectric resonator 16
The excitation electrode 163a on the upper surface of No. 3 is electrically connected to the electrode 161c. The electrode 161c is formed along the same edge as the electrode 161b.

On the other hand, as shown by a broken line on the right side of FIG.
On the lower surface side of the resonance plate 161, the piezoelectric resonator 1
The excitation electrode 163b formed on the lower surface of the electrode 63 is connected to the electrode 16 formed along one edge of the resonance plate 161.
1d.

The second resonance plate 166 corresponds to a structure in which the first resonance plate 161 is inverted. That is, the piezoelectric resonator 167 with a built-in dynamic vibration absorbing unit using the slip mode and the piezoelectric resonator 168 with a built-in dynamic vibration absorbing unit using the width mode are integrated by bonding the holding parts together, and the spacers 169a and 169b are provided on the outside. It has a laminated structure.

Since the first resonance plate 161 corresponds to an inverted one, the shape of the electrodes formed on both main surfaces is upside down with respect to the first resonance plate 161. Each of the above members was laminated, and the resulting laminate was provided with terminal electrodes 160a.
By forming を 160f, the ladder filter 160 shown in FIG. 21 is obtained. In this embodiment, the terminal electrodes 160a and 160d are used as output terminals,
By using 0c as an input terminal, connecting the terminal electrode 160b to the ground potential, and connecting the terminal electrodes 160e and 160f in common, it is possible to operate as a two-stage ladder filter.

Sixth Embodiment In the above-described first to fifth embodiments, a laminated ladder filter is formed by laminating piezoelectric resonators with a built-in dynamic vibration absorber in the thickness direction. However, the ladder-type filter of the present invention may have a structure in which all the piezoelectric resonators are stacked in the horizontal direction. The sixth embodiment is an example having a structure in which a plurality of piezoelectric resonators are horizontally stacked.

Referring to FIG. 22, ladder type filter 17
In FIG. 5A, the piezoelectric resonator 26 with a built-in dynamic vibration absorbing portion using the slip vibration mode shown in FIG. 5A and the piezoelectric resonator 171 with a built-in dynamic vibration absorbing portion also using the sliding vibration mode have spacers 172. And spacers 173 and 174 are attached to both outer sides.

The piezoelectric resonator 171 with a built-in dynamic vibration absorbing portion is configured using a rectangular parallelepiped piezoelectric substrate 171a. This increases the thickness of the piezoelectric ceramic plate 26a of the piezoelectric resonator 26 with a built-in dynamic vibration absorbing portion. It is equivalent to what was done. That is, in the piezoelectric resonator 26 with the built-in dynamic vibration absorbing portion, the excitation electrode 26
b, 26f, the piezoelectric ceramic plate 26a
Of the piezoelectric resonator 171 with a built-in dynamic vibration absorbing section, the distance between the excitation electrode 171f on the upper surface side and the excitation electrode (not shown) on the lower surface side and the piezoelectric ceramic plate 171a Are substantially equal to the horizontal dimension. In other respects, the piezoelectric resonator 171 is configured in the same manner as the piezoelectric resonator 26, so that the description thereof will be omitted by attaching the corresponding reference numerals.

Therefore, in the present embodiment, not only the piezoelectric resonator 26 with a built-in dynamic vibration absorber but also the piezoelectric resonator 1 with a built-in dynamic vibration absorber is used.
Reference numeral 71 also denotes an energy trap type piezoelectric resonator having a dynamic vibration absorbing portion and utilizing a sliding vibration mode. Further, in the piezoelectric resonator 171 with a built-in dynamic vibration absorber, the facing area between the excitation electrodes is larger than that of the piezoelectric resonator 26 with a built-in dynamic vibration absorber, so that a larger capacitance can be obtained.
Therefore, in the ladder-type filter of the present embodiment, the piezoelectric resonator 171 is used as a parallel resonator of the ladder-type filter.

The spacers 172 to 174 are respectively provided on the piezoelectric resonator side as shown in the drawing so as not to hinder the vibration of the adjacent piezoelectric resonator 26 or the piezoelectric resonator 171, that is, the resonance section and the dynamic vibration absorbing section. Notches 172a-174
a. Each of the spacers 172 to 174 is made of an insulating material having an appropriate degree of strength, such as an insulating ceramic such as alumina or a synthetic resin. Further, the spacer plates 172 to 174 are fixed to the holding portions of the piezoelectric resonators 26 and 172 with a built-in dynamic vibration absorbing portion using an insulating adhesive.

Further, case substrates 175 and 176 are attached to the upper and lower sides of a resonance plate formed by fixing the piezoelectric resonators 26 and 171 and the spacers 172 to 174 using an insulating adhesive.

The case substrates 175 and 176 have the same configuration as the case substrates 71 and 73 used in the second embodiment. That is, the concave portion 17 is formed on the upper surface of the case substrate 176.
6a, a similar concave portion is formed on the lower surface of the case substrate 175. Also, a plurality of electrodes 175a to 175d are formed on the upper surface of the case substrate 175. Similarly, the lower surface of the case substrate 176 is formed at a position opposed to the upper surface and the lower surface of the multilayer body after being laminated with the electrodes 175a to 175d. Electrodes are formed.

By bonding the case substrates 175 and 176 to the above-described resonance plate, and further forming internal electrodes on the end surfaces of the obtained laminate, the structure shown in FIG.
3 is obtained. This filter 17
FIG. 24 shows an equivalent circuit of 0.

That is, in the filter 170 of this embodiment, a one-stage ladder-type filter is formed as shown in FIG. Also in the sixth embodiment, the piezoelectric resonator 2 with a built-in dynamic vibration absorbing portion using the slip vibration mode as described above.
6,171, the bandwidth can be increased and the ladder filter can be downsized.

Seventh Embodiment In the above-described embodiment, a ladder filter is constituted by using a plurality of piezoelectric resonators having a dynamic vibration absorbing portion.
In the ladder-type filter of the present invention, it is only required that at least one piezoelectric resonator is constituted by a piezoelectric resonator with a built-in dynamic vibration absorber. Such an embodiment will be described with reference to FIGS.

Ladder type filter 18 according to the seventh embodiment
0, the case substrate 18 above and below the resonance plate 181
2,183 are stacked. Case substrates 182, 183
Has the same configuration as the case substrate used in the first embodiment described above.

In the resonance plate 181, the piezoelectric resonators 184 and 185 with a built-in dynamic vibration absorbing part and the piezoelectric resonators 186 and 187 in the thickness shear vibration mode using a normal TS mode having no dynamic vibration absorbing part are formed. Spacer 188,
The layers are stacked in the horizontal direction via 189 and 190. The spacers 188 to 190 are made of insulating ceramics or synthetic resin, and are bonded near both ends of each piezoelectric resonator. Further, spacers 191 and 192 are attached to the outermost portion, thereby forming a resonance plate 181. The spacers 191 and 192 can also be made of insulating ceramics or synthetic resin, and are adhered to the vicinity of both ends on one main surface side of the piezoelectric resonators 181 and 187.

As shown in FIG. 26, the piezoelectric resonator 184 with a built-in dynamic vibration absorbing portion utilizing the sliding vibration mode has a structure in which an excitation electrode 184b is formed on one main surface of a rectangular ceramic piezoelectric plate 184a. Have. Excitation electrode 1
84b is electrically connected to an electrode 184c formed near one end of the piezoelectric ceramic plate 184a on the illustrated side main surface. In this embodiment, two laterally extending grooves 184d and 184e are formed in the piezoelectric ceramic plate 184a.
The electrode 184f is located between the groove 184e and the other end of the piezoelectric ceramic plate 184a.
h is formed. This structure corresponds to the piezoelectric ceramic plate 1
84a, the electrodes 184c, 1 having the same area at both ends
After forming 84h and forming an elongated electrode so as to connect them, the grooves 184d and 184e are formed by dicing or the like.

On the other hand, the same applies to the other end face of the piezoelectric ceramic plate 184a, except that the grooves 184d and 184e are
By forming two grooves 184i and 184j on opposite sides of the piezoelectric ceramic plate 184a at the center in the length direction, excitation electrodes and electrodes connected to the excitation electrodes are formed.

Therefore, the portion where the excitation electrodes overlap on both sides via the piezoelectric ceramic plate 184a, that is, the groove 184
The portion sandwiched between d and 184i is configured as a resonance portion that resonates in the slip vibration mode.

The piezoelectric ceramic portion between the grooves 184d and 184e and the piezoelectric ceramic portion between the grooves 184i and 184j constitute dynamic vibration absorbing portions. The known piezoelectric resonators 186 and 187 in the slip vibration mode using the TS mode have a well-known electrode structure in which a pair of excitation electrodes overlapping each other via a piezoelectric ceramic plate are formed at the center of a rectangular piezoelectric ceramic plate. It is comprised so that it may have. However, the excitation electrodes on both main surfaces are drawn to different ends.

The ladder-type filter 180 of this embodiment is provided above and below the resonance plate 181 with case substrates 182 and 18.
3 are bonded to each other, and a predetermined terminal electrode is formed on the opposite end face of the obtained laminated body, whereby a ladder-type filter using the dynamic vibration absorbing section built-in type piezoelectric resonator is formed in the same manner as in the above-described embodiment. Can be configured. Also in this embodiment, the ladder-type filter is configured using the piezoelectric resonator with a built-in dynamic vibration absorber, so that the bandwidth can be increased as compared with the ladder-type filter using the piezoelectric tuning fork-type resonator. .

The energy confinement type motion used in the present invention
Other Examples of Piezoelectric Resonator with Built- in Vibration Absorber The piezoelectric resonator with a built-in energy absorption type using a slip mode, which is used in the present invention, is not limited to the one described above. Various modifications can be made as described with reference to FIG.

FIG. 27 is a plan view showing a modification of the energy trap type piezoelectric resonator. In the piezoelectric resonator 381, the dynamic vibration absorbing portions 391 to 394 are formed by forming the grooves 383 to 386 on one side surface and forming the grooves 387 to 390 on the other side surface. Also, the grooves 384, 3
The portion of the piezoelectric substrate between 85 is the resonance portion 395 of the present invention.
Is composed. Further, holding portions 396 and 397 are formed outside the grooves 383 and 386, respectively. The supporting portions are a piezoelectric substrate portion sandwiched between the grooves 384 and 388 and a piezoelectric substrate portion sandwiched between the grooves 385 and 389. The piezoelectric substrate portion between the grooves 383 and 387 and the thin piezoelectric substrate portion between the grooves 386 and 390 constitute a connecting portion.

The piezoelectric resonator 395 is polarized so as to extend along the direction of the arrow P in the figure, that is, along the length of the piezoelectric substrate 382. On the other hand, the excitation electrodes 398 and 399 are formed on the upper surface of the piezoelectric substrate 382 in parallel with the polarization direction P.

Therefore, by applying an AC voltage from the excitation electrodes 398 and 399, the resonance section 395 resonates in a slip mode, and the resonance energy is effectively confined in the resonance section 395. Further, the dynamic vibration absorbing portions 391 to 394
However, the slight vibration that has leaked is suppressed by the dynamic vibration absorption phenomenon. Therefore, in the piezoelectric resonator 381, the dynamic vibration absorbing portion 391
Vibration energy is reliably confined to the portion where .about.394 is provided.

Note that lead electrodes 400 and 401 are formed on the holding portions 396 and 397. FIG.
28 is a modification of the piezoelectric resonator 381 shown in FIG. The difference from the piezoelectric resonator 381 is that, in the piezoelectric resonator 411, the resonance section 395 is polarized in the direction indicated by the arrow P, that is, in the width direction of the piezoelectric substrate 382, and the excitation electrodes 398, 399 Are formed so as to extend in the width direction.

FIG. 29 shows the piezoelectric resonator 38 shown in FIG.
It is a perspective view which shows the further another modification of 1. In the piezoelectric resonator 421, the resonance section 395 is polarized in a direction indicated by an arrow P, that is, parallel to the length direction of the piezoelectric substrate 382. The difference from the piezoelectric resonator 381 is the position where the electrodes are formed.

That is, in the piezoelectric resonator 421, the excitation electrodes 398 and 399 are formed on both sides of the piezoelectric substrate 382 in the resonance section 395. Also, the piezoelectric resonator 4
21, the extraction electrodes 400 and 401 are respectively
The holding portions 396 and 397 are formed on the side surfaces of the piezoelectric substrate 382. Also, the extraction electrodes 400 and 401
A connection conductive portion for electrically connecting the excitation electrodes 398 and 399 is also formed along the side surface of the piezoelectric substrate 382.

As is clear from the piezoelectric resonator 421, the pair of excitation electrodes may be formed not only on the upper and lower surfaces of the piezoelectric plate constituting the resonance part but also on the side surfaces. Further, for example, in the piezoelectric resonator 381 shown in FIG.
One excitation electrode 399 may be formed on the lower surface of the piezoelectric substrate 382, or, in the piezoelectric resonator 421, one excitation electrode 398 or 399 may be
82 may be formed on one main surface side.

Further, these piezoelectric resonators 381, 41
Also in 1,421, the resonance unit, the dynamic vibration absorbing unit, and the holding unit may be configured by machining a single piezoelectric substrate, or may be configured by separate members.

For example, as shown in FIG. 30, by joining insulating plates 432 and 433 of the same thickness to a rectangular piezoelectric plate 431 for forming a resonance section, a substrate 434 is formed.
May be formed. Using the substrate 434, the above-described piezoelectric resonator can be formed. Note that, in the substrate 434 shown in FIG.
Although 35 and 436 and the holding portions 437 and 438 are formed integrally, each of these portions may be formed of a separate member.

Further, as shown in FIG.
Outside the portions 35 and 436, substrate portions 439 and 44 of the same width are provided.
0 may be formed. In this case, the substrate portion 439,
The reference numeral 440 also serves as a connecting portion and a holding portion.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view for explaining a conventional ladder-type filter.

FIG. 2 is a diagram showing a circuit configuration of a conventional ladder-type filter.

FIG. 3 is an exploded perspective view of the ladder-type filter according to the first embodiment.

FIG. 4 is a perspective view showing the appearance of the ladder filter according to the first embodiment.

FIGS. 5A and 5B are perspective views illustrating a piezoelectric resonator with a built-in dynamic vibration absorber used in the first embodiment.

FIG. 6 is a schematic plan view for explaining a connection state of terminal electrodes in the first embodiment.

FIG. 7 is a diagram illustrating a circuit configuration of a ladder-type filter according to the first embodiment.

FIG. 8 is an exploded perspective view of a T-type filter used to configure the ladder-type filter according to the second embodiment.

FIG. 9 is a perspective view showing a T-type filter.

FIG. 10 is a diagram showing a circuit configuration of a T-type filter.

FIG. 11 is an exploded perspective view for explaining a π-type filter used in the second embodiment.

FIG. 12 is a perspective view showing the appearance of the π-type filter shown in FIG. 11;

FIG. 13 is a diagram showing a circuit configuration of a π-type filter.

FIG. 14 is an exploded perspective view showing a ladder-type filter according to a third embodiment.

FIG. 15 is a perspective view of a ladder-type filter according to a third embodiment.

FIG. 16 is a diagram illustrating a circuit configuration of a ladder-type filter according to a third embodiment.

FIG. 17 is an exploded perspective view for explaining a ladder-type filter according to a fourth embodiment.

FIG. 18 is a perspective view showing a ladder-type filter according to a fourth embodiment.

FIG. 19 is a diagram illustrating a circuit configuration of a ladder-type filter according to a fourth embodiment.

FIG. 20 is an exploded perspective view for explaining a ladder-type filter according to a fifth embodiment.

FIG. 21 is a perspective view showing the appearance of a ladder-type filter according to a fifth embodiment.

FIG. 22 is an exploded perspective view illustrating a ladder-type filter according to a sixth embodiment.

FIG. 23 is a perspective view showing a ladder-type filter according to a sixth embodiment.

FIG. 24 is a diagram illustrating a circuit configuration of a ladder-type filter according to a sixth embodiment.

FIG. 25 is an exploded perspective view for explaining a ladder-type filter according to a seventh embodiment.

FIG. 26 is a perspective view showing a piezoelectric resonator with a built-in dynamic vibration absorber used in the seventh embodiment.

FIG. 27 is a plan view showing a modification of the energy trapping type piezoelectric resonator with a built-in dynamic vibration absorbing portion used in the ladder-type filter of the present invention.

FIG. 28 is a plan view showing a modification of the piezoelectric resonator with a built-in dynamic vibration absorber shown in FIG. 27;

FIG. 29 is a perspective view for explaining still another modification of the piezoelectric resonator with a built-in dynamic vibration absorbing portion.

FIG. 30 is a perspective view showing an example of a substrate used for a piezoelectric resonator with a built-in dynamic vibration absorbing portion.

FIG. 31 is a perspective view showing another example of the substrate used for the piezoelectric resonator with a built-in dynamic vibration absorber.

[Explanation of symbols]

20: Ladder type filter 22, 23 ... Resonance plate 26, 27, 31 ... Piezoelectric resonator with built-in dynamic vibration absorbing part using slip mode 28, 32, 33 ... Piezoelectric resonator with built-in dynamic vibration absorbing part using width mode 28a ... Piezoelectric ceramic plate 28 b. Resonant parts 28 d and 28 e. Support parts 28 f and 28 g. Resonant parts 52b, 52c Support parts 52d, 52e Dynamic vibration absorbing parts 52f Connection parts 52g, 52h Holding parts 61 ... Piezoelectric resonator with built-in dynamic vibration absorbing parts

Continuation of the front page (56) References JP-A-4-67762 (JP, A) JP-A-4-17560 (JP, A) JP-A-2-260191 (JP, A) JP-A-4-282911 (JP) , A) Japanese Utility Model 2-100335 (JP, U) Japanese Utility Model 60-174325 (JP, U) Japanese Utility Model 60-172425 (JP, U) Japanese Utility Model 59-108330 (JP, U) Japanese Utility Model 53-25245 (JP, U) Jikken Sho 59-12811 (JP, Y2) (58) Fields investigated (Int. Cl. ⁷ , DB name) H03H 9/00-9/215 H03H 9/54-9 / 60

Claims (9)

(57) [Claims] 1. At least one series resonator constituting a series arm and at least one parallel resonator constituting a parallel arm, wherein at least one of the series resonator and the parallel resonator is provided. resonators, piezoelectric plate and the resonating part utilizing a and shear mode and a pair of excitation electrodes formed to face each other in the outer surface of the piezoelectric plate, leakage from the resonating portion
Resonates in the bending mode due to the vibration that has occurred and absorbs the vibration dynamically
A dynamic vibration-absorbing section that attenuates due to a vibration phenomenon ;
A support portion provided between the dynamic vibration absorbing portion and the holding portion connected to the dynamic vibration absorbing portion;
And a connecting portion arranged to connect the energy-trapping type dynamic vibration absorbing portion built-in type piezoelectric resonator,
Ladder type filter. 2. The ladder-type filter according to claim 1, wherein the piezoelectric plate, the dynamic vibration absorbing section, and the holding section are configured using an integrated piezoelectric substrate. 3. The piezoelectric plate, the dynamic vibration absorbing portion, and the holding portion are integrated by connecting different members.
The ladder-type filter according to 1. 4. The ladder-type filter according to claim 1, wherein the piezoelectric plate is made of a piezoelectric material. 5. The ladder-type filter according to claim 1, wherein said dynamic vibration absorbing section and said holding section are formed on both sides of said resonance section. 6. The pair of excitation electrodes are formed on a pair of opposing side surfaces of a piezoelectric plate, respectively.
6. The ladder-type filter according to any one of items 1 to 5, 7. The ladder-type filter according to claim 1, wherein the pair of excitation electrodes are formed by being dispersed on both main surfaces of the piezoelectric plate. 8. The ladder filter according to claim 1, wherein said pair of excitation electrodes are formed at a predetermined distance on one main surface of said piezoelectric plate. 9. The ladder-type filter according to claim 2, wherein the dynamic vibration absorbing portion is a portion of the piezoelectric substrate formed between the grooves by processing two grooves in the piezoelectric substrate.