WO2008038498A1

WO2008038498A1 - Balanced acoustic wave filter device

Info

Publication number: WO2008038498A1
Application number: PCT/JP2007/067185
Authority: WO
Inventors: Kazumasa Haruta
Original assignee: Murata Manufacturing Co., Ltd.
Priority date: 2006-09-28
Filing date: 2007-09-04
Publication date: 2008-04-03
Also published as: JPWO2008038498A1; JP4873010B2

Abstract

A balanced acoustic wave filter device with improved balancing is provided. The balanced acoustic wave filter device (1) having a longitudinally coupled resonator type acoustic wave filter (18) formed on a piezoelectric body (2) comprises an unbalanced terminal (11), first and second balanced terminals (12, 13), and an input signal line (31) connecting the unbalanced terminal (11) and the longitudinally coupled resonator type acoustic wave filter (18). The balanced acoustic wave filter device further comprises a shield pattern (32) connected to earth potential and provided between the input signal line (31) and the second balanced terminal (13) so as to insolate the input signal line (31) from the second balanced terminal (13).

Description

Specification

Balanced elastic wave filter device

Technical field

The present invention relates to an elastic wave filter device using an elastic wave such as a boundary acoustic wave or a surface acoustic wave, and more specifically, a balanced elastic wave filter having a balance-unbalance conversion function. Relates to the device.

Background art

Conventionally, a surface acoustic wave filter device has been widely used for a band filter of an RF stage of a mobile phone. In recent years, various boundary acoustic wave filter devices using boundary acoustic waves have been proposed in place of surface acoustic wave filter devices.

[0003] By the way, for example, in an RF stage bandpass filter of a mobile phone, an input end is connected to an antenna terminal. An amplifier circuit having a balanced input is connected to the subsequent stage of the bandpass filter. Therefore, in order to omit a component called a balun having a balance-unbalance conversion function, the bandpass filter itself is required to have a balance-unbalance conversion function.

[0004] An example of a surface acoustic wave filter device having a balance-unbalance conversion function used for such applications is disclosed in Patent Document 1 below. As shown in FIG. 14, a surface acoustic wave filter device 1001 described in Patent Document 1 has an unbalanced terminal 1002 and first and second balanced terminals 1003 and 1004. A longitudinally coupled resonator-type surface acoustic wave filter unit 1007 is connected to the unbalanced terminal 1002 through 1-port inertial surface acoustic wave resonators 1005 and 1006. In the longitudinally coupled resonator-type surface acoustic wave filter unit 1007, the second and third IDTs 1009 and 1010 are provided on both sides J of the first IDT 1008 disposed in the center. Further, reflectors 1011 and 1012 are arranged on both sides of the surface wave propagation direction in the region where the first to third IDTs 1008 to 1010 are provided.

[0005] One ends of the second and third IDTs 1009 and 1010 are connected in common and connected to the unbalanced terminal 1002 via surface acoustic wave resonators 1005 and 1006. The other ends of IDT1009 and 1010 are connected to the ground potential!

[0006] One end of the first IDT 1008 is connected to the first balanced terminal 1003, and the other end is connected to the second Connected to balanced terminal 1004. The polarity of the third IDT 1010 is inverted with respect to the polarity of the second IDT 1009. The number of electrode fingers of the first IDT 1008 is an even number. Therefore, a balanced-unbalanced conversion function is realized.

[0007] By the way, in a surface acoustic wave filter device having a balance-unbalance conversion function, it is strongly required that the phase balance and the amplitude balance of signals taken out from the first and second balanced terminals are good. In the surface acoustic wave filter device 1001 described in Patent Document 1, a ground pattern 1013 is provided in order to improve the balance. Although this ground pattern 1013 is shown in a floating state in FIG. 14, specifically, in the space occupying the input side of the longitudinally coupled resonator-type surface acoustic wave filter unit 1007, the unbalanced terminal 1002 and the second It is provided in a region between the input signal line 1014 connecting the IDTs 1009 and 1010 of 2 and 3 and the first balanced terminal 1003. In Patent Document 1, the earth line 1013 is formed in a U-shape or the like so as to surround the balance terminal 1003 formed on the electrode pad. You will be shown! /!

Patent Document 1: Japanese Patent No. 3384403

Disclosure of the invention

In the surface acoustic wave filter device described in Patent Document 1, the ground line 1013 is provided between the input signal line 1014 and the first balanced terminal 1003 in a configuration having a balance-unbalance conversion function. As a result, the phase balance and the amplitude balance were supposed to be improved. However, even if the ground line 1013 is simply provided, the phase balance and the amplitude balance are still not sufficient and further improvement is strongly demanded. On the other hand, a longitudinally coupled resonator type surface acoustic wave filter device and boundary acoustic wave filter device having a balanced-unbalanced conversion function that is not a float type but a midpoint grounding type are also known. There is also a strong demand for improving the balance of the grounded-point type elastic wave filter device.

[0009] Then, as described in Patent Document 1, a configuration in which an earth line is provided between the input signal line and the first balanced terminal has a center-grounded longitudinally coupled resonator type acoustic wave filter. It can be applied to equipment. However, in the float type longitudinally coupled resonator type surface acoustic wave filter 1001 as described in Patent Document 1, the first and second balanced terminals 1003 and 1004 are connected to both ends of the central first IDT. Was connected. Therefore, the unbalanced end located on the input side It is only necessary to provide the ground line 1013 between the first balanced terminal 1003 and the unbalanced terminal 1002 arranged on the same side as the child 1002. On the other hand, in the longitudinally coupled resonator type acoustic wave filter device of the middle-point grounding type, the first and second balances from the first and second IDTs located on both sides of the center first IDT are balanced. Since it is connected to the terminal, the above earth line 10 13 could not be applied as it is.

An object of the present invention is a longitudinally coupled resonator-type elastic wave filter device having a balance-unbalance conversion function in view of the above-described current state of the prior art, in which the degree of balance is further improved. An object of the present invention is to provide a resonator type acoustic wave filter device.

[0011] According to the present invention, there is provided a balanced filter device having a balance-unbalance conversion function, comprising: a piezoelectric body; and an electrode structure provided on the piezoelectric body. The IDT and the first IDT are disposed on both sides of the elastic wave propagation direction of the first IDT, the first and second IDTs disposed on both sides of the elastic wave propagation direction, and the first to third IDTs. , 2 reflectors, thereby forming a longitudinally coupled resonator type acoustic wave filter section, the electrode structure comprising an unbalanced terminal, first and second balanced terminals, And further comprising an input signal line connected to the unbalanced terminal and the longitudinally coupled resonator type acoustic wave filter unit, and one end of the first IDT is connected to the unbalanced terminal by the input signal line. One end of each of the second and third IDTs is connected to the first and second balanced terminals, respectively. The structure further includes a shield pattern disposed between the input signal line and the second balanced terminal, and connected to a ground potential. The first IDT and the third IDT are connected to each other. There is provided a balanced elastic wave filter device characterized in that the polarities of outermost electrode fingers adjacent to each other at different locations are different polarities.

In the balanced elastic wave filter device according to the present invention, the fourth and fifth IDTs may be further arranged on both sides of the elastic wave propagation direction where the first to third IDTs are provided. In that case, the first and second reflectors are arranged on both sides of the portion where the first to fifth IDTs are provided, and the balance is further improved according to the present invention. A balanced type acoustic wave filter device including a 5IDT type longitudinally coupled resonator type acoustic wave filter unit can be provided. In this case, one end of the fourth and fifth IDTs connected only by the first IDT is connected to the unbalanced terminal by the input signal line, and the third IDT and the first IDT The polarities of the outermost electrode fingers that are adjacent to each other at the positions adjacent to each other and the polarities of the outermost electrode fingers that are adjacent to each other at the positions where the third IDT and the fifth IDT are adjacent to each other are different.

In the elastic wave filter device according to the present invention, a dielectric laminated on a piezoelectric body may be further provided. In that case, an elastic boundary wave may be used as the elastic wave. A boundary acoustic wave filter device can be provided.

[0014] The balanced acoustic wave filter device according to the present invention preferably further includes an earth line provided on the dielectric. The earth line is opposed to the shield pattern. In this case, since the ground line is further provided, the balance can be further improved.

[0015] Preferably, the ground line is electrically connected to the shield pattern by a via-hole conductor provided so as to penetrate the dielectric, whereby the shield pattern can be reliably electrically connected to the ground potential. It is possible to further improve the balance.

[0016] The balanced elastic wave filter device according to the present invention may use a surface acoustic wave as the elastic wave, and in that case, according to the present invention, the balanced elastic wave with improved balance is provided. A filter device can be provided.

(The invention's effect)

In the balanced acoustic wave filter device according to the present invention, the first IDT is connected to the unbalanced terminal, and the second and third IDT forces are connected to the first and second balanced terminals, respectively. The balance-unbalance conversion function is realized. Since the shield pattern is provided between the input signal line and the second balanced terminal, as will be apparent from the embodiment described later, the first balanced signal taken out from the first balanced terminal; It is possible to effectively improve the degree of balance with the second balanced signal extracted from the second balanced terminal.

Therefore, according to the present invention, it is possible to provide an elastic wave filter device having a balance-unbalance conversion function suitable for, for example, a bandpass filter used in an RF stage of a mobile phone, etc.

FIG. 1 is a plan view of a boundary acoustic wave filter device according to a first embodiment of the present invention. It is a top view which shows typically the position of the bump formed on a terminal in order to connect with an electrode structure and the exterior.

FIG. 2 is a schematic front sectional view for explaining the boundary acoustic wave filter device of the first embodiment.

FIG. 3 is a schematic plan view showing an electrode structure of the boundary acoustic wave filter device of the first embodiment.

FIG. 4 is a diagram showing amplitude balance characteristics of the boundary acoustic wave filter devices of the first embodiment and the first comparative example.

FIG. 5 is a diagram showing phase balance characteristics of the boundary acoustic wave filter devices of the first embodiment and the first comparative example.

[Fig. 6] Fig. 6 is a diagram showing a common-mode attenuation-one-frequency characteristic of the boundary acoustic wave filter devices of the first embodiment and the first comparative example.

FIG. 7 is a diagram showing amplitude balance characteristics of the boundary acoustic wave filter devices of the first embodiment and the second comparative example.

FIG. 8 is a diagram showing phase balance characteristics of the boundary acoustic wave filter devices of the first embodiment and the second comparative example.

FIG. 9 is a diagram showing a common-mode attenuation amount-one-frequency characteristic of the boundary acoustic wave filter devices of the first embodiment and the second comparative example.

FIG. 10 is a front sectional view schematically showing a boundary acoustic wave filter device according to a second embodiment.

FIG. 11 is a diagram showing the amplitude balance characteristics of the boundary acoustic wave filter devices of the second embodiment and the first comparative example.

FIG. 12 is a diagram showing the phase balance characteristics of the boundary acoustic wave filter devices of the second embodiment and the first comparative example.

FIG. 13 is a schematic plan view showing an electrode structure of a boundary acoustic wave filter device of a second comparative example.

FIG. 14 is a schematic plan view showing an electrode structure of a conventional surface acoustic wave filter device. Explanation of symbols

1 ... boundary acoustic wave filter device

2 ... Piezoelectric body

3 · Dielectric

3a, 3b… Opening

4 ... Electrode structure

5a, 5b ... electrode pads

7a, 7b ... conductive pattern

8… Resin layer

9a, 9b… Conductive bonding material

10a, 10b… Bump

11 ... Unbalanced terminal

12, 13 ... 1st and 2nd balanced terminals

14 ~; 16 ... Earth terminal

17 .... boundary acoustic wave resonator

18 • • Longitudinal coupled resonator type boundary acoustic wave filter

19 ·-Inertial boundary wave resonator

20 ... Additional capacity

21-25 "'10th 1st-5th

26, 27… Reflector

31 ... Input signal line

32 Shield pattern

33, 34 ... Output signal line

41 '' boundary acoustic wave filter device

42 ··· Earth line

-Via hole conductor

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described by describing specific embodiments of the present invention with reference to the drawings. Reveal the light.

With reference to FIGS. 1 to 3, a balanced boundary acoustic wave filter device according to an embodiment of the present invention will be described.

As shown in FIG. 2, the balanced boundary acoustic wave filter device 1 of the present embodiment has a structure in which a dielectric 3 is laminated on a piezoelectric 2. LiNbO is used as the piezoelectric body 2

Three

. As the dielectric 3, SiO is used. At the boundary between piezoelectric 2 and dielectric 3

2

The electrode structure 4 is formed. A plurality of openings 3a, 3b are formed in the dielectric 3

In order to electrically connect the electrode structure 4 to the outside, a plurality of electrode pads 5 a and 5 b connected to the electrode structure 4 are formed on the piezoelectric body 2. The openings 3a and 3b are formed so as to expose the electrode pads 5a and 5b. Conductive patterns 7a and 7b are formed so as to reach the top surface of the dielectric 3 outside the openings 3a and 3b and the openings 3a and 3b.

A resin layer 8 is provided so as to cover the dielectric 3. The resin layer 8 is made of an appropriate synthetic resin such as silicon resin or epoxy resin, and absorbs sound when the boundary acoustic wave generated at the boundary between the piezoelectric body 2 and the dielectric body 3 leaks to the upper surface side. Works. As a result, it is possible to suppress unwanted and spurious noises!

[0026] The resin layer 8 is provided with openings that are continuous with the openings 3a and 3b. The openings are filled with conductive bonding materials 9a and 9b made of Cu, and metal bumps 10a and 10b made of solder are passed through the conductive patterns 7a and 7b by the conductive bonding materials 9a and 9b. Electrically connected to 5a and 5b. That is, since the boundary acoustic wave filter device 1 has the bumps 10a and 10b as described above, it can be surface-mounted on the printed circuit board or the like from the bumps 10a and 10b side.

In order to show the details of the electrode structure of the boundary acoustic wave filter device 1, in FIG. 1, the dielectric 3, the resin layer 8, etc. are removed from the structure shown in FIG. FIG. 3 is a plan view schematically showing the electrode structure and the electrode pad, and FIG. 3 is a schematic plan view for clarifying the electrical connection of the electrode structure.

As shown in FIG. 3, the boundary acoustic wave filter device 1 of the present embodiment includes an unbalanced terminal 11, first and second balanced terminals 12 and 13, and first to third ground terminals 14. ~; Imbalance The terminal 11 and the first and second balanced terminals 12 and 13 and the first to third ground terminals 14 to 16 correspond to the portion that electrically connects the electrode structure to the outside, and the electrode shown in FIG. It is configured to have a pad 5a.

A longitudinally coupled resonator type boundary acoustic wave filter unit 18 is connected to an unbalanced terminal 11 as an input terminal via a one-port type boundary acoustic wave resonator 17. The 1-port boundary acoustic wave resonator 17 includes an IDT and reflectors disposed on both sides of the IDT in the boundary wave propagation direction.

[0030] The longitudinally coupled resonator-type boundary acoustic wave filter unit 18 includes a first IDT 21 disposed in the center and second and third IDTs 22, 23 disposed on both sides of the first IDT 21 in the boundary wave propagation direction. And fourth and fifth IDTs 24 and 25 and reflectors 26 and 27 arranged on both sides of the boundary wave propagation direction of the portion where the first to third IDTs are provided. That is, the longitudinally coupled resonator type boundary acoustic wave filter unit 18 is a 5IDT type longitudinally coupled resonator type boundary acoustic wave filter.

[0031] One end of each of the first IDT 21, the fourth IDT 24, and the fifth IDT 25 is commonly connected, and is connected to the unbalanced terminal 11 via the one-port boundary acoustic wave resonator 17! . The other ends of the first ID T21, the fourth IDT 24, and the fifth IDT 25 are connected in common on the dielectric 3, and are electrically connected to the third ground terminal 16.

On the other hand, one end of the second IDT 22 is connected to the first ground terminal 14, and the other end is connected to the first balanced terminal 12.

[0033] Further, one end of the third IDT 23 is commonly connected to one end of the second IDT 22 on the dielectric, and is connected to the first ground terminal 14, and the other end of the third IDT 23 is It is electrically connected to the second balanced terminal 13.

[0034] The polarity of the third IDT 23 is inverted with respect to the polarity of the second IDT 22. Accordingly, the phase of the signal flowing from the second IDT 22 to the first balanced terminal 12 and the third IDT 22 The IDT23 force and the phase of the signal flowing through the second balanced terminal 13 are 180 ° different from each other. Thereby, the balance-unbalance conversion function is realized.

On the other hand, a 1-port boundary acoustic wave resonator 19 is connected between the first and second balanced terminals 12 and 13. An additional capacitor 20 is connected between the first balanced terminal 12 and the third ground terminal 16.

[0036] In the boundary acoustic wave filter device 1 of the present embodiment, the unbalanced terminal 11 side serves as an input terminal. Therefore, on the input side of the longitudinally coupled resonator type boundary acoustic wave filter unit 18, the unbalanced terminal 11 is connected to one end of the first, fourth and fifth IDTs 21, 21 and 24, 25. The input signal lines 31 constitute the signal lines that are present. That is, the input signal line 31 includes a portion connecting the unbalanced terminal 11 and the boundary acoustic wave resonator 17, and the boundary acoustic wave resonator 17, the first IDT 21, the fourth IDT 24, and the fifth boundary. Including the signal line part connecting IDT25. The feature of this embodiment is that the input signal line 31 is connected to the ground potential between the second balanced terminal 13 provided at the subsequent stage of the longitudinally coupled resonator-type boundary acoustic wave filter unit 18. The shield pattern 32 is provided. As shown in FIG. 3, the shield pattern 32 is electrically connected to the first and second ground terminals 14 and 15.

More specifically, as shown in FIG. 1, the piezoelectric body 2 has a rectangular planar shape having a pair of long sides 2a, 2b and a pair of short sides 2c, 2d. The first and _second ground terminals ₁₄ and 15 are arranged at the corner portions located on both sides of the one long side 2a, and the first and _second ground terminals ₁₄ and 15 are disposed at the corner portions on both sides of the other long side 2b. The balanced terminals 12 and 13 are arranged. The unbalanced terminal 11 is arranged in the vicinity of the long side 2a and in the central part in the length direction of the long side 2a, and the third ground terminal 16 is arranged in the vicinity of the central part of the other long side 2b. It has been done. In FIG. 1, the unbalanced terminal 11 and the first and second balanced terminals 12, 13 and the first to third ground terminals 14 to 16 are indicated by circles. This corresponds to the bumps 10a and 10b shown in Fig. 2. That is, taking the unbalanced terminal 11 as an example, the unbalanced terminal 11 is a portion that is electrically connected to the outside, and is therefore disposed below as shown by the bump 10a shown in FIG. By providing a bump on the electrode pad via a conductive bonding material, the electrode pad can be electrically connected to the outside.

In FIG. 1, the terminal portion electrically connected to the outside is originally formed above, and the shape of the bump (not shown) and the electrode pad positioned below the bump are schematically shown. Show. That is, in practice, circular bumps are formed on the dielectric 3 and the resin layer 8, in order to facilitate understanding of the force, in FIG. 1, the bumps on each terminal are indicated by circles. To do.

As apparent from FIG. 1, an electrode pad to which the bump is bonded is formed below each bump. 1 port on the side of the longitudinally coupled resonator type boundary acoustic wave filter 18 Type boundary acoustic wave resonator 17 is arranged, and the input signal line 31 on the input side of the longitudinally coupled resonator type boundary acoustic wave filter unit 18 is connected to the longitudinally coupled resonator type boundary acoustic wave filter unit 18 and the unbalanced terminal 11. It is considered to be a conductive pattern to connect with!

On the other hand, on the output side of the boundary acoustic wave filter unit 18, output signal lines 33 and 34 are formed of a conductive pattern. The output signal lines 33 and 34 are electrically connected to the first and second balanced terminals 12 and 13, respectively.

As is apparent from FIG. 1, the ground terminal of each IDT of the boundary acoustic wave filter unit 18 is connected to a rectangular ground electrode pad! The dielectric 3 on the ground electrode pad is removed to form an opening 3a! Five ground electrode pads are connected in common by the conductive pattern 7a through the opening 3a, and are connected to the ground terminal 14 by the conductive pattern 7a. The conductive bonding material 9a and the bump 10a are not formed on the ground electrode pad.

In the present embodiment, the shield pattern 32 is provided so as to be positioned between the input signal line 31 and the second balanced terminal 13. In other words, the output signal line 34 connecting the input end of the longitudinally coupled resonator-type boundary acoustic wave filter unit 18 and the second balanced terminal 13 and the input signal line 31 are electrically separated by the shield pattern 32. For this purpose, a shield pattern 32 is provided. This makes it possible to further improve the balance. This will be described based on a specific experimental example.

[0043] The longitudinally coupled resonator type boundary acoustic wave filter unit 18 was designed with the following specifications.

[0044] First 10 electrode finger cross width = 110 111, number of electrode fingers = 15.

[0045] The electrode finger crossing width of the second and third ten pieces = 110 111, the number of electrode fingers = 16. However, the polarities of the second IDT and the third IDT are inverted.

[0046] Crossing width of electrode fingers of fourth and fifth IDTs = 110 111, number of electrode fingers = 29.

[0047] Wavelength of the first to fifth IDTs = 3.5 m.

[0048] Number of electrode fingers of reflectors on both sides = 22.

[0049] Specifications of 1-port inertial boundary wave resonator 17

IDT electrode finger crossing width = 168 m, number of electrode fingers = 81.

[0050] Number of electrode fingers of reflectors on both sides = 20.

[0051] Specifications of 1-port inertial boundary wave resonator 19 IDT electrode finger crossing width = 75 μm, number of electrode fingers = 41.

[0052] Number of electrode fingers of reflectors on both sides = 20.

Note that the longitudinally coupled resonator type boundary acoustic wave filter unit 18 and the 1-port type boundary acoustic wave resonator

The electrode structures 17 and 19 were formed by depositing a metal made of Au to a thickness of 120 nm.

[0054] Further, the additional capacitor 20 is composed of a pair of interdigital electrodes, and the capacitance is 0.05 pF. In addition, the comb electrode constituting the additional capacitor 20 was formed using the same material at the same time when the electrode structure such as the longitudinally coupled resonator type boundary acoustic wave filter unit 18 was formed.

[0055] The shield pattern 32 was formed of the same material as that of the electrodes constituting the longitudinally coupled resonator-type boundary acoustic wave filter unit 18 at the same time.

[0056] Further, the input signal line 31, the output signal lines 33, 34, and the like were also formed by patterning using the same electrode material when forming the longitudinally coupled resonator type boundary acoustic wave filter unit 18. .

[0057] In addition, the electrode pads 5a and 5b formed in the portion electrically connected to the outside such as the unbalanced terminal 11 were formed by separately forming A1 with a thickness of 1600 nm.

[0058] The thickness of the dielectric 3 made of SiO force is 6 m, and the resin layer 8 is made of 6 μm of polyimide resin.

2

The film was formed to a thickness of m.

[0059] For comparison with the boundary acoustic wave filter device of the present embodiment obtained in this way, the shield pattern 32 is provided! /, NA! /, Except that! / In the same way

The boundary acoustic wave filter device of 1 comparative example was produced.

FIG. 4 and FIG. 5 show the amplitude balance characteristics and phase balance characteristics of the boundary acoustic wave filter devices of the embodiment and the first comparative example obtained as described above. Fig. 6 shows the frequency characteristics of the common mode attenuation of the boundary acoustic wave filter device of this embodiment and the first comparative example.

As is apparent from FIGS. 4 to 6, by providing the shield pattern 32, the boundary acoustic wave filter device of the present embodiment reduces the influence of the direct wave and reduces the common mode. As a result, the amplitude balance and the phase balance are compared with those in the first comparative example. The power that can be greatly improved.

[0062] Next, for comparison, in the longitudinally coupled resonator-type boundary acoustic wave filter unit 18, the polarities of the second and third IDTs are reversed, and the first balanced terminal 12 and the second balanced terminal A boundary acoustic wave filter device of a second comparative example formed in the same manner as in the above embodiment was manufactured except that the position with respect to 13 was reversed from the state shown in FIG. FIG. 13 is a schematic plan view showing the electrode structure of the elastic boundary wave filter device of the second comparative example. As is clear from FIG. 13, in the boundary acoustic wave filter device 101 of the second comparative example, the shield pattern 102 is an output signal line 33 connecting the first balanced terminal and the longitudinally coupled resonator boundary acoustic wave filter section 33. And the input signal line 31.

[0063] The amplitude balance characteristic, phase balance characteristic, and attenuation frequency characteristic of the longitudinally coupled resonator type boundary acoustic wave filter device of the second comparative example prepared in this way are shown by solid lines in Figs. It shows with. In FIGS. 7 to 9, for ease of comparison, the amplitude balance characteristic, the phase balance characteristic, and the attenuation-one frequency characteristic of the boundary acoustic wave filter device of the first comparative example are shown together with a broken line. Show.

As is apparent from FIGS. 7 to 9, even if the shield pattern 32 is provided, the first and second balanced terminals are reversed from those in the above embodiment! /, The second comparative example It can be seen that the decrease in common mode is slight and the effect of improving the balance is small.

Therefore, it can be seen that the shield pattern 31 is preferably provided between the input signal line 31 and the second balanced terminal 13.

[0066] By providing the shield pattern 32 only on the output signal line side on the second balanced terminal side, a capacitance is generated between the output signal line 34 on the second balanced terminal side and the ground potential. As a result, the balance may be slightly deteriorated. However, the capacitance generated between the output signal line 34 and the ground potential can be canceled by the additional capacitor 20 between the output signal line 33 on the first balancing terminal 12 side and the ground line. Therefore, the provision of the additional capacitor 20 is desirable because the deterioration of the balance can be further suppressed.

[0067] The shield pattern 32 is three-dimensionally electrically connected to a bump disposed above and opposed to a ground pattern provided above the dielectric 3, thereby The yield effect can be further enhanced and the balance can be improved.

FIG. 10 is a schematic front cross-sectional view for explaining a main part of the boundary acoustic wave filter device 41 according to the second embodiment of the present invention.

In FIG. 10, an earth line 42 is provided on the dielectric 3 made of SiO. This

2

The source line 42 is opposed to the shield pattern 32 which is positioned below the dielectric 3! Thus, by providing the earth line 42 so as to face the shield pattern 32 with the dielectric 3 interposed therebetween, the balance can be further improved.

In addition, as shown in FIG. 10, the ground line 42 is electrically connected to the shield pattern 32 positioned below and the via-hole conductor 43, and the ground line 42 is electrically connected to the ground potential. Connected. Therefore, it is possible to strengthen the ground by the shield pattern 32, thereby further reducing the influence of the direct wave and further improving the balance. This will be described with reference to FIGS. 11 and 12 based on specific experimental results.

[0071] Except for the provision of the via-hole conductor and the ground line, the amplitude balance and the phase balance of the boundary acoustic wave filter device of the second embodiment manufactured in the same manner as the first embodiment Was measured. The results are shown in FIG. 11 and FIG. In FIGS. 11 and 12, the solid line shows the result of the second embodiment, and the broken line shows the result of the first comparative example. As is apparent from FIGS. 11 and 12, according to the second embodiment having a structure in which the via hole conductor is electrically connected to the ground line, the amplitude balance and the phase balance are further improved. The ability to gain S

[0072] It should be noted that another silicon oxide may be used instead of SiO. In addition, the dielectric is oxidized

2

For example, other dielectric materials such as nitride nitride may be used. Similarly, the piezoelectric body may be formed of a piezoelectric single crystal other than LiNbO.

Three

[0073] In the first and second embodiments, the force S described for the 5IDT type longitudinally coupled resonator type boundary acoustic wave filter device having the first to fifth IDTs, The present invention can also be applied to a 3IDT type longitudinally coupled resonator type acoustic wave filter device in which only the third IDT is provided. Furthermore, the present invention can be applied not only to a boundary acoustic wave filter device but also to a surface acoustic wave filter device using a surface acoustic wave.

Claims

The scope of the claims

[1] A balanced filter device having a balance-unbalance conversion function,

A piezoelectric body;

An electrode structure provided on the piezoelectric body,

The electrode structure includes the first IDT and the second IDT arranged on both sides of the first IDT in the elastic wave propagation direction, and the elastic wave propagation in the portion where the first to third IDTs are provided. First and second reflectors arranged on both sides of the direction, thereby forming a longitudinally coupled resonator type acoustic wave filter section,

The electrode structure further comprises an unbalanced terminal, first and second balanced terminals, and an input signal line connected to the unbalanced terminal and the longitudinally coupled resonator type acoustic wave filter unit, One end of the IDT of 1 is connected to the unbalanced terminal by the input signal line,

One ends of the second and third IDTs are respectively connected to the first and second balanced terminals, and the electrode structure is disposed between the input signal line and the second balanced terminal. , Further comprising a shield pattern connected to the ground potential, wherein the first IDT and the third IDT are adjacent to each other, and the outermost electrode fingers adjacent to each other have different polarities, Balance type elastic wave filter device.

[2] The apparatus further includes fourth and fifth IDTs arranged on both sides of the elastic wave propagation direction of the portion where the first to third IDTs are provided, and the first and second reflectors are the first and second IDTs, respectively. The first to fifth IDTs are arranged on both sides of the part, and thereby a 5IDT type longitudinally coupled resonator type acoustic wave filter unit is formed, and the input signal line One end of each of the fourth and fifth IDTs connected to only the first IDT is connected to the unbalanced terminal, and the third IDT and the first IDT are adjacent to each other at adjacent locations. 2. The balanced elastic wave filter device according to claim 1, wherein the polarities of the fingers and the polarities of the outermost electrode fingers adjacent to each other at a position where the third IDT and the fifth IDT are adjacent are different.

[3] The balanced acoustic wave filter device according to [1] or [2], further comprising a dielectric laminated on the piezoelectric body, wherein boundary acoustic waves are used as the elastic waves.

[4] An earth line provided on the dielectric is further provided, and the earth line includes the sheet. 4. The balanced acoustic wave filter device according to claim 3, wherein the balanced acoustic wave filter device is opposed to the gold pattern through a dielectric.

5. The balanced elastic wave filter device according to claim 4, further comprising a via-hole conductor provided so as to penetrate the dielectric so as to electrically connect the shield pattern and the earth line. .

6. The balanced elastic wave filter device according to claim 1, wherein a surface acoustic wave is used as the elastic wave.