JP2002252549A - Multimode piezoelectric filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To evade the adverse influence of external noise by actualizing a 4-pole MCF which is usable as a balanced type. SOLUTION: A 4-pole type multimode piezoelectric filter has a piezoelectric substrate 1 and a package body 8 which contains it and the package body is constituted into a balanced type characterized by that connection terminals for leading respective electrodes of the piezoelectric substrate out to an external circuit are independently formed, the electrodes are connected to the 1st to the 6th connection terminals, the 1st and 3rd, and 2nd and 4th connection terminals are formed at opposite positions of the package body while the 1st and 4th, and 2nd and 3rd connection terminals are formed at diagonal positions about the center of gravity of the package body, and the 5th and 6th connection terminals are connected in common by the external circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-mode piezoelectric filter used for a radio equipment such as a portable telephone and represented by a crystal filter (MCF). In particular, the present invention relates to an improvement for realizing a balanced 4-pole multimode piezoelectric filter.

[0002]

2. Description of the Related Art Conventionally, the above-mentioned MCF is known as a kind of multi-mode piezoelectric filter (for example, Japanese Patent Application Laid-Open No.
No. 46170). Hereinafter, the configuration of the MCF will be described. FIG. 5 shows a multi-mode piezoelectric filter called a 4-pole MCF. In this filter, a plurality of electrodes 102 to 107 are formed on one main surface S101 (upper surface in FIG. 5) and another main surface S102 (lower surface in FIG. 5) of a quartz substrate 101 serving as a piezoelectric substrate. It is configured. That is, the input electrode 10 is provided on one main surface S101.
2 and the first electrode 103 are formed with a predetermined gap, and the second electrode 104 and the output electrode 105 are formed with a predetermined gap. On the other hand, a first ground electrode 106 is formed on the other main surface S102 so as to face the electrode pair of the input electrode and the first electrode, and a second ground electrode 106 faces the electrode pair of the second electrode and the output electrode. 107 are formed.

The four-pole MCF has four connection terminals 111 to 114 formed on the package 2.
The first connection terminal 111 is connected to the input electrode 102 via a wiring.
However, the output electrode 10 is connected to the second connection terminal 112 via a wiring.
5 are connected. An earth electrode 106 is connected to the third connection terminal 113 via a wiring, and an earth electrode 107 is connected to the fourth connection terminal 114 via a wiring. The third connection terminal 113 and the fourth connection terminal 114 are connected to each other. They are commonly connected via a wiring 115. The first electrode 103 and the second electrode 104 are commonly connected to each other via a wiring in an external circuit.

[0004]

By the way, the general four-pole MCF so far is provided with each of the ground electrodes 106, 10
7 is an unbalanced type commonly connected to the third connection terminal 113 and the fourth connection terminal 114 via wiring. Therefore, the third connection terminal 113 (or the fourth connection terminal 11
When external noise enters from the 4) side, the external noise is transmitted to the fourth connection terminal 114 (or the third connection terminal 113) via the common connection wiring 115, and the external noise is easily affected. There was a defect.

In general, when a balanced device is compared with an unbalanced device, the balanced device can cut off external noise because each terminal is not grounded, and can reduce power consumption. . Further, when the connected components are of the balanced type, there are various advantages such that individual components such as a conversion circuit for matching the balanced component and the unbalanced component are not required.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to realize a 4-pole MCF which can be used as a balanced type, and to avoid the adverse effects of external noise to achieve a high-performance 4-pole MCF. Paul MCF.

[0007]

In order to achieve the above-mentioned object, the present invention provides a piezoelectric substrate and a package for accommodating the piezoelectric substrate. A first electrode pair formed with a predetermined gap between the electrodes, a third electrode opposed to the first electrode pair via a piezoelectric substrate, and an output electrode and a second electrode formed with a predetermined gap. A four-pole multi-mode piezoelectric filter in which a second electrode pair and a fourth electrode opposed to the second electrode pair via a piezoelectric substrate are formed, and the package body includes the electrodes of the piezoelectric substrate. A connection terminal leading to an external circuit is formed independently, an input electrode is connected to the first connection terminal, a fourth electrode is connected to the second connection terminal, and a third electrode is connected to the third connection terminal. The output electrode is connected to the fourth connection terminal and the first connection terminal And a third connection terminal, a second connection terminal and a fourth connection terminal are formed at positions facing each other on the package body, and the first connection terminal and the fourth connection terminal, and the second connection terminal and the third connection terminal are formed. Are formed diagonally to each other with respect to the center of gravity of the package body, the first electrode is connected to the fifth connection terminal, the second electrode is connected to the sixth connection terminal, and the fifth connection terminal And a sixth connection terminal are connected in common in an external circuit, and the common connection terminal connected in common is grounded via a capacitor to form a balanced type.

According to this specific feature, the first connection terminal connected to the input electrode of the piezoelectric substrate, the fourth connection terminal connected to the output electrode of the piezoelectric substrate, and the second connection terminal connected to the fourth electrode of the piezoelectric substrate. And a third connection terminal connected to the third electrode of the piezoelectric substrate. The first connection terminal and the third connection terminal, and the second connection terminal and the fourth connection terminal are located at positions facing each other on the package body. And each of the connection terminals is independently formed and connected to the fifth connection terminal connected to the first electrode and to the second electrode. And the sixth connection terminal is commonly connected in an external circuit, and the common connection terminal connected to the sixth connection terminal is grounded via a capacitor, thereby obtaining a steep filter characteristic unique to a 4-pole MCF. Type multi-mode piezoelectric It has become possible to realize the filter. Therefore, since the fourth electrode connected to the second connection terminal and the third electrode connected to the third connection terminal are separately wired, external noise is transmitted between these terminals. Can be avoided.

According to a second aspect of the present invention, in the first aspect, the package body includes a shield component that electromagnetically shields the piezoelectric substrate and is not connected to the electrodes of the piezoelectric substrate. The shield component is grounded via a ground terminal formed independently of the connection terminals.

According to this specific matter, in addition to the above-mentioned functions and effects, it is possible to realize the EMS countermeasure and the improvement of the guaranteed attenuation characteristic of the balanced multi-mode piezoelectric filter in which the ground terminal is not connected to the electrode of the piezoelectric substrate.

According to a third aspect of the present invention, in the second aspect of the present invention, the package body has a planar rectangular shape, and each of the electrodes of the piezoelectric substrate is connected to a first connection terminal to a sixth connection terminal for leading to an external circuit. A first ground terminal and a second ground terminal for grounding the shield component of the package body, wherein the first connection terminal and the third connection terminal are formed on a first side. The second side facing the side is the second side
A connection terminal and a fourth connection terminal are formed;
The fifth connection terminal and the first ground terminal are formed on a second side adjacent to one of the sides, and the sixth connection terminal and the second ground terminal are formed on a fourth side opposite to the second side. And the first connection terminal and the fourth connection terminal, the second connection terminal and the third connection terminal, the fifth connection terminal and the sixth connection terminal, and the first ground terminal and the second ground terminal, respectively. It is formed at a position diagonal to the center of gravity of the package body.

According to this particular feature, in addition to the above-described functions and effects, the input electrode connection terminal and the output electrode connection terminal are formed to face each other at diagonal positions so as to separate the distance from each other. By preventing the electric field lines from being coupled to each other, and by forming the two ground terminals to face each other at diagonal positions, the electromagnetic wave shielding effect of the package body can be further improved. Therefore, in a miniaturized package for surface mounting, the guaranteed attenuation characteristic of the multi-mode piezoelectric filter can be remarkably improved.

According to a fourth aspect, in the first to third aspects, the first connection terminal is connected to one connection terminal of the input-side balun transformer, and the third connection terminal is connected to the other of the input-side balun transformer. The second connection terminal is connected to one connection terminal of the output-side balun transformer, and the fourth connection terminal is connected to another connection terminal of the output-side balun transformer. .

According to this specific matter, in addition to the above-described functions and effects, when a multi-mode piezoelectric filter configured as a balanced component is connected to an unbalanced component, matching between the two can be achieved by a balun transformer.

[0015]

Next, an embodiment of the present invention will be described. Embodiments 1 and 2 below are cases where a balanced 4-pole MCF is realized by the present invention.

(Embodiment 1) First, Embodiment 1 of the present invention
Will be described with reference to the drawings. FIG. 1 is a plan view showing a balanced 4-pole MCF according to the present embodiment, with a lid removed, and FIG. 2 is a cross-sectional view taken along line AA of FIG. 1 with the lid attached. .

The balanced 4-pole MCF is a piezoelectric substrate 1
And electrodes formed on the outer surface of the piezoelectric substrate 1, that is, an input electrode 2, an output electrode 3, and first to fourth electrodes 4, 5, 6, and 7 as auxiliary electrodes. Piezoelectric substrate 1
On one main surface S1, an input electrode 2 and a first electrode 4 are formed with a predetermined gap, and a second electrode 5 and an output electrode 3 are formed.
Are formed with a predetermined gap. On the other hand, a third electrode 6 is formed on the other main surface S2 of the piezoelectric substrate 1 via the piezoelectric substrate 1 so as to face the electrode pair of the input electrode and the first electrode. Fourth facing the electrode pair
An electrode 7 is formed.

The package body has a planar rectangular shape, and includes, for example, a base substrate 8 in which pits are formed using a ceramic multilayer technique, and a metal lid 9. The base substrate has six connection terminals 1 for leading each electrode of the piezoelectric substrate to an external circuit by a method such as metallization.
1, 12, 13, 14, 15, 16 and the ground terminal 17,
18 are formed independently, a shield electrode 85 is formed on the bottom surface side of the base substrate by the same metallization method, and a Kovar ring CR for seam sealing is provided at a sealing portion with the lid. ing. The metal cover 9 and the shield electrode 85 formed on the bottom surface of the base substrate 8 constitute a shield component for electromagnetically shielding the upper and lower surfaces of the piezoelectric substrate. And are commonly grounded via the ground terminals 17 and 18.

As the arrangement of the connection terminal and the ground terminal in the package, the first connection terminal 11 and the third connection terminal 13 are formed on the first side 81 of the base substrate 8,
The second connection terminal 12 and the fourth connection terminal 14 are formed on a third side 83 facing the first side, and the second connection terminal 12 and the fourth connection terminal 14 are formed on a second side 82 adjacent to one of the first sides. The fifth connection terminal 15 and the first ground terminal 17 are formed, and the sixth connection terminal 16 and the second ground terminal 18 are formed on a fourth side 84 facing the second side. Further, the first connection terminal 11 and the fourth connection terminal 14, the second connection terminal 12 and the third connection terminal 13, the fifth connection terminal 15 and the sixth connection terminal 16,
The ground terminal 17 and the second ground terminal 18 are formed at positions diagonal to each other with respect to the center of gravity of the package body.

The first connection terminal 11 and the input electrode 2 are connected through a conductive bonding material D to the piezoelectric substrate mounted on the base substrate of the package body.
The electrode 7 is connected, the third connection terminal 13 is connected to the third electrode 6, the fourth connection terminal 14 is connected to the output electrode 3, the fifth connection terminal 15 is connected to the second electrode 5, and the sixth connection The terminal 16 and the first electrode 4 are connected. The fifth connection terminal 15 and the sixth connection terminal 16 are commonly connected by a wiring L of an external circuit, and are grounded via an external capacitor C.

When this balanced 4-pole MCF is incorporated in a portable radio device such as a portable telephone, the first connection terminal 11 is connected to the input side balun transformer 2 as shown in FIG.
1, and the third connection terminal 13 is connected to another connection terminal of the input-side balun transformer 21. Also, the second
The connection terminal 12 is connected to one connection terminal of the output-side balun transformer 22, and the fourth connection terminal 14 is connected to the output-side balun transformer 2.
2 Connect to the other connection terminal.

FIG. 1 shows a built-in state in a case where components (such as IC components) connected to the balanced 4-pole MCF are unbalanced components. That is, each balun transformer 2
Parts balanced by 1 and 22 (balanced 4-pole MCF)
And unbalanced parts. Therefore, balanced type 4
If the components connected to the pole MCF are balanced components, the balun transformers 21 and 22 become unnecessary.

As described above, the balanced 4-pole MC of the present embodiment
F is the fourth electrode 7 connected to the second connection terminal 12
And the third electrode 6 connected to the third connection terminal 13 are separately wired. Therefore, for example, it is possible to prevent external noise that has entered the balanced 4-pole MCF from the second connection terminal 12 (or the third connection terminal 13) from being transmitted to the third connection terminal 13 (or the second connection terminal 12).

Further, the balanced 4-pole MCF of the present embodiment
Are the first electrode 4 and the second electrode 5, which are auxiliary electrodes except the input electrode 2 and the output electrode 3, and the third electrode 6 and the fourth electrode 7
Are independently connected to the second connection terminal 12, the third connection terminal 13, the fifth connection terminal 15, or the sixth connection terminal 16, respectively. Therefore, the third connection terminal 13 is connected to the other connection terminal of the input-side balun transformer 21 and the second connection terminal 12 is connected to one connection terminal of the output-side balun transformer 22 to be used as a balanced 4-pole MCF. Can be.

In this way, since the 4-pole MCF can be made balanced, external noise can be cut off as described above.
High performance of the MCF can be achieved. In addition, it is possible to reduce power consumption, which is a characteristic feature of the balanced component. In addition, when the connected components are of a balanced type, a balun transformer is not required, and the installation space of the MCF when incorporated in a portable wireless device can be reduced, thereby contributing to the miniaturization of the portable wireless device. can do.

(Embodiment 2) Next, Embodiment 2 of the present invention
Will be described with reference to the drawings.

FIG. 3 shows a balanced 4-pole MC according to this embodiment.
FIG. 7F is a plan view showing a state where a lid is removed. The balanced four-pole MCF of the present embodiment is different from the balanced four-pole MCF of the first embodiment in that the piezoelectric substrate is formed by a first electrode pair of the input electrode 2, the first electrode 4, and the third electrode 6. , And a second opposing area formed by the electrode pair of the second electrode 5 and the output electrode 3 and the fourth electrode 7 separately constitute a piezoelectric substrate, and the first piezoelectric substrate 1A and the second piezoelectric The only difference is that a substrate 1B is provided, so that acoustic coupling in regions facing each other is more easily prevented. The other parts are the same as those of the balanced four-pole MCF in the first embodiment described above, and thus detailed description is omitted.

This balanced 4-pole MCF is also connected to the fourth electrode 7 connected to the second connection terminal 12 and the third connection terminal 13, similarly to the balanced 4-pole MCF in the first embodiment. And the third connection terminal 12 (or the third connection terminal 1).
External noise that enters the balanced 4-pole MCF from 3) can be prevented from being transmitted to the third connection terminal 13 (or the second connection terminal 12).

(Other Embodiments) In each of the above-described embodiments, the arrangement direction of the vibrating regions forming the respective opposing regions and the arrangement direction of the electrode pairs in the respective opposing regions have been described. However, the present invention is not limited to this. As shown in FIG. 4, (a) the arrangement direction of the vibration region forming each opposed region may be orthogonal to the arrangement direction of the electrode pair of each opposed region, or (b) the arrangement direction of each opposed region. The arrangement directions of the electrode pairs may be orthogonal.

[0030]

As described above, according to the present invention,
Of the electrodes constituting the four-pole multi-mode piezoelectric filter, the third electrode and the fourth electrode except for the input electrode and the output electrode, and the first electrode and the second electrode, which commonly connect the respective regions, are divided into two, and two connections are made. Since it is independently connected to the terminal, it is possible to provide a multi-mode piezoelectric filter that can be used as a balanced filter that can cut off external noise and obtain a steep filter characteristic unique to a 4-pole MCF. For this reason,
It is possible to improve the performance of the filter due to blocking of external noise. In addition, it is possible to reduce power consumption, which is an inherent feature of the balanced component.

According to the second aspect of the present invention, in addition to the above-described functions and effects, it is possible to realize an EMS countermeasure and an improvement in a guaranteed attenuation characteristic in a balanced multimode piezoelectric filter in which a ground terminal is not connected to the electrode of the piezoelectric substrate.

According to the third aspect, in addition to the above-described functions and effects, the input electrode connection terminal and the output electrode connection terminal are formed to face each other at diagonal positions so that a distance between the input electrode connection terminal and the output electrode connection terminal can be separated. By preventing the coupling of the lines of electric force between the electrodes and by forming the two ground terminals to face each other at diagonal positions, the electromagnetic wave shielding effect of the package can be further improved. Therefore, in a miniaturized package for surface mounting, the guaranteed attenuation characteristic of the multi-mode piezoelectric filter can be remarkably improved.

According to the fourth aspect of the present invention, in addition to the above-described functions and effects, when a balun transformer is connected to each terminal of the filter, a multi-mode piezoelectric filter configured as a balanced component is connected to an unbalanced component. In addition, the balun transformer can achieve matching between the two, and the application range of the multi-mode piezoelectric filter can be expanded.

[Brief description of the drawings]

FIG. 1 is a plan view showing a balanced 4-pole MCF according to a first embodiment.

FIG. 2 is a sectional view showing a balanced 4-pole MCF according to the first embodiment.

FIG. 3 is a plan view showing a balanced 4-pole MCF according to a second embodiment.

FIG. 4 is a plan view showing a balanced 4-pole MCF according to another embodiment.

FIG. 5 is a schematic view showing an example of a conventional 4-pole MCF.

[Explanation of symbols]

 1, 1A, 1B, 101 Piezoelectric substrate (quartz substrate) 2 input electrode 3 output electrode 4 first electrode 5 second electrode 6 third electrode (input side electrode vs. counter electrode) 7 fourth electrode (output side electrode vs. counter electrode) 8) Base board of package body 9 Cover of package body 11 First connection terminal 12 Second connection terminal 13 Third connection terminal 14 Fourth connection terminal 15 Fifth connection terminal 16 Sixth connection terminal 17 First ground terminal 18 Second Ground terminal 21 Input-side balun transformer 22 Output-side balun transformer S1 One main surface S2 Other main surface

Claims (4)

[Claims] 1. A first electrode pair comprising a piezoelectric substrate and a package for accommodating the piezoelectric substrate, wherein a main electrode of the piezoelectric substrate has a first electrode pair formed with an input electrode and a first electrode with a predetermined gap. A third electrode facing the first electrode pair via a piezoelectric substrate, a second electrode pair formed by forming a predetermined gap between an output electrode and a second electrode, and a second electrode pair via a piezoelectric substrate. A four-pole type multi-mode piezoelectric filter in which a fourth electrode facing the first electrode is formed, and connection terminals for leading each of the electrodes of the piezoelectric substrate to an external circuit are independently formed in the package body; The input electrode is connected to the first connection terminal, the fourth electrode is connected to the second connection terminal, the third electrode is connected to the third connection terminal, and the output electrode is connected to the fourth connection terminal.
A first connection terminal and a third connection terminal, and a second connection terminal and a fourth connection terminal are formed at positions facing each other on the package body;
The first connection terminal and the fourth connection terminal, the second connection terminal and the third connection terminal are formed at positions diagonal to each other with respect to the center of gravity of the package body, and the first electrode is connected to the fifth connection terminal. The second electrode is connected to the sixth connection terminal, the fifth connection terminal and the sixth connection terminal are commonly connected by an external circuit, and the commonly connected common connection terminal is grounded via a capacitor to be balanced. A multi-mode piezoelectric filter characterized by being configured in a mold. 2. The multi-mode piezoelectric filter according to claim 1, wherein the package body electromagnetically shields the piezoelectric substrate,
And a shield component not connected to each of the electrodes of the piezoelectric substrate, wherein the shield component is grounded via a ground terminal formed independently of the connection terminals. Multimode piezoelectric filter. 3. The multi-mode piezoelectric filter according to claim 2, wherein the package body has a planar rectangular shape, and the first to sixth connection terminals for leading the electrodes of the piezoelectric substrate to an external circuit; First grounding shield component of package
An earth terminal and a second earth terminal, wherein the first connection terminal and the third connection terminal are formed on a first side, and the second side is formed on a third side opposite to the first side. A connection terminal and a fourth connection terminal are formed, the fifth connection terminal and a first ground terminal are formed on a second side adjacent to one of the first sides, and the second side is connected to the second side. A sixth connection terminal and a second ground terminal are formed on the opposing fourth side, and the first connection terminal and the fourth connection terminal, and the second connection terminal and the third connection terminal.
The multiplexing method, wherein the connection terminal, the fifth connection terminal and the sixth connection terminal, and the first ground terminal and the second ground terminal are formed at positions diagonal to each other with respect to the center of gravity of the package body. Mode piezoelectric filter. 4. The multi-mode piezoelectric filter according to claim 1, wherein the first connection terminal is connected to one connection terminal of the input-side balun transformer, and the third connection terminal is connected to the input side. The other connection terminal of the balun transformer is connected, the second connection terminal is connected to one connection terminal of the output balun transformer, and the fourth connection terminal is connected to another connection terminal of the output balun transformer. A multimode piezoelectric filter characterized by the above-mentioned.