Elastic wave device

Abstract

Provided is an elastic wave device that can be miniaturized and is less likely to have characteristics deteriorated. The elastic wave device comprises: a piezoelectric substrate (2); a first elastic wave element (15) disposed on the piezoelectric substrate and having at least one first IDT electrode (12A) and a first reflector (13A) disposed on one side of a region in a first direction where the first IDT electrode is disposed; and a second elastic wave element (16) disposed on the piezoelectric substrate and having at least one second IDT electrode (12B) and a second reflector (14A) disposed on one side of a region in a first direction where the second IDT electrode is disposed, wherein the first and second reflectors are arranged along a first direction, and the elastic wave device further comprises a reflective member (17) disposed between the first and second reflectors, wherein the planar shape of the reflective member has a curve or has a side inclined relative to the first direction, and is arranged in a row along a direction intersecting the first direction.

Description

[0001] This application is a divisional application of an invention patent application with an application date of November 21, 2016, application number 201680069468.3, and invention name “Elastic Wave Device”. Technical Field

[0002] The present invention relates to an elastic wave device used for a resonator, a band filter, etc. Background Art

[0003] Conventionally, elastic wave devices have been widely used as resonators and band filters.

[0004] Patent document 1 below discloses an elastic wave device as a surface acoustic wave filter having a plurality of longitudinally coupled surface acoustic wave filters. The plurality of longitudinally coupled surface acoustic wave filters are arranged in the propagation direction of the surface acoustic wave, and each of the plurality of IDT electrodes and grating reflectors provided on both sides of the IDT electrodes in the propagation direction of the surface acoustic wave. The grating reflectors are shared by mutually adjacent longitudinally coupled surface acoustic wave filters.

[0005] Prior Art Literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2006-186433 Summary of the invention

[0008] -Problems to be solved by the invention-

[0009] However, when a reflector is shared between two adjacent elastic wave elements as in the elastic wave device of Patent Document 1, ripples are likely to occur in the passband if the number of electrode fingers of the reflector is reduced. Also, even when two elastic wave elements are adjacent to each other without sharing a reflector, ripples are likely to occur in the passband if the distance between the adjacent reflectors is reduced. In either case, there is a problem in achieving miniaturization of the elastic wave device.

[0010] An object of the present invention is to provide an elastic wave device that can be miniaturized and is less likely to suffer from degradation in characteristics.

[0011] -Methods for solving the problem-

[0012] The elastic wave device involved in the present invention comprises: a piezoelectric substrate; a first elastic wave element, which is arranged on the piezoelectric substrate and has at least one first IDT electrode and a first reflector arranged on one side of the elastic wave propagation direction of the region where the first IDT electrode is arranged; and a second elastic wave element, which is arranged on the piezoelectric substrate and has at least one second IDT electrode and a second reflector arranged on one side of the elastic wave propagation direction of the region where the second IDT electrode is arranged, wherein the first reflector and the second reflector are arranged along the elastic wave propagation direction, and the elastic wave device further comprises a reflecting component, which is arranged between the first and second reflectors and reflects the elastic wave in at least a direction different from the elastic wave propagation direction.

[0013] In a specific aspect of the elastic wave device according to the present invention, the plurality of reflecting members are arranged so that there is no portion without the reflecting members in the propagation direction of the elastic wave. In this case, the characteristics of the elastic wave device can be further less likely to deteriorate.

[0014] In another specific aspect of the elastic wave device according to the present invention, the plurality of reflective components are arranged in a row along a direction intersecting the elastic wave propagation direction. Preferably, the direction intersecting the elastic wave propagation direction is a direction orthogonal to the elastic wave propagation direction. In this case, the elastic wave device can be further miniaturized.

[0015] In another specific aspect of the elastic wave device according to the present invention, the planar shape of the reflective component has a curved line. The planar shape of the reflective component may be circular or elliptical. In this case, since the excited elastic wave can be scattered in various directions different from the propagation direction of the elastic wave, it is further difficult to cause degradation of the characteristics.

[0016] In another specific aspect of the elastic wave device according to the present invention, the reflective member has a rectangular planar shape. In this case, the excited elastic wave can be more reliably reflected in a direction different from the elastic wave propagation direction, and thus the characteristics are less likely to deteriorate.

[0017] In another specific aspect of the elastic wave device of the present invention, in a plan view, the direction along the long axis of the elliptical reflecting member or the long side of the rectangular reflecting member is inclined at 45 degrees ± 25 degrees with respect to the propagation direction of the elastic wave. In this case, since the excited elastic wave can be more reliably reflected in a direction different from the propagation direction of the elastic wave, it is further difficult to cause degradation of the characteristics.

[0018] -Effects of the Invention-

[0019] According to the present invention, it is possible to provide an elastic wave device that can be miniaturized and is less likely to suffer from degradation in characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic plan view showing an elastic wave device according to one embodiment of the present invention.

[0021] Figure 2 , (a) is a circuit diagram of an elastic wave device according to one embodiment of the present invention, and (b) is a schematic plan view showing an electrode structure of a one-port elastic wave resonator.

[0022] Figure 3 Yes Figure 1 FIG. 1 is a schematic plan view showing an enlarged view of a portion where the first and second elastic wave elements are provided.

[0023] Figure 4 This is a schematic plan view showing an enlarged view of a portion where first and second elastic wave elements are provided in a first modification of the elastic wave device according to the embodiment of the present invention.

[0024] Figure 5 It is a schematic plan view showing an enlarged view of a portion where the first and second elastic wave elements are provided in a second modification of the elastic wave device according to the embodiment of the present invention.

[0025] Figure 6 This is a schematic plan view showing an enlarged view of a portion where the first and second elastic wave elements are provided in a third modified example of the elastic wave device according to the embodiment of the present invention.

[0026] -Explanation of symbols-

[0027] 1...Elastic wave device

[0028] 2...Piezoelectric substrate

[0029] 3...Antenna terminal

[0030] 4...Common terminal

[0031] 5...Receiving terminal

[0032] 6...Sending terminal

[0033] 7...Receive filter

[0034] 8...Transmit filter

[0035] 9...1 port elastic wave resonator

[0036] 10, 11...Longitudinal coupled resonator type elastic wave filter section

[0037] 12...IDT electrode

[0038] 12A, 12B...1st and 2nd IDT electrodes

[0039] 13, 14...Reflector

[0040] 13A, 14A...1st and 2nd reflectors

[0041] 15...1st elastic wave element

[0042] 16...Second elastic wave element

[0043] 17, 17A~17D...Reflective components

[0044] L...Inductor

[0045] P1~P3...Parallel arm resonator

[0046] S1~S4b...series arm resonator. DETAILED DESCRIPTION

[0047] Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings in order to make the present invention clear.

[0048] In addition, it should be pointed out that the various embodiments described in this specification are exemplary, and partial replacement or combination of structures can be performed between different embodiments.

[0049] Figure 1 It is a schematic plan view showing an elastic wave device according to one embodiment of the present invention. Figure 2 (a) is a circuit diagram of an elastic wave device according to one embodiment of the present invention.

[0050] like Figure 1 As shown, elastic wave device 1 includes piezoelectric substrate 2. Piezoelectric substrate 2 is formed of a piezoelectric single crystal substrate such as LiTaO3 or LiNbO3 or a piezoelectric ceramic substrate. In the present embodiment, piezoelectric substrate 2 includes a rectangular plate-shaped piezoelectric single crystal substrate.

[0051] In this embodiment, a duplexer is formed by forming a plurality of elastic wave elements on the piezoelectric substrate 2. In this embodiment, a duplexer of Band 8 (Tx passband: 880 to 915 MHz, Rx passband: 925 to 960 MHz) is formed in which the transmission filter (Tx) is formed by a ladder filter and the reception filter (Rx) is formed by a longitudinal coupling filter. More specifically, Figure 2A duplexer of the circuit structure shown in (a).

[0052] In addition, if Figure 2 As shown in (a), elastic wave device 1 has common terminal 4 connected to antenna terminal 3. An impedance matching inductor L is connected between antenna terminal 3 and ground potential. A reception filter 7 is formed between common terminal 4 and reception terminal 5. A transmission filter 8 is formed between common terminal 4 and transmission terminal 6.

[0053] In the receiving filter 7, a 1-port elastic wave resonator 9 as a notch filter is connected to the common terminal 4. In addition, 3IDT-type longitudinally coupled resonator-type elastic wave filter units 10 and 11 are provided between the 1-port elastic wave resonator 9 and the receiving terminal 5. The longitudinally coupled resonator-type elastic wave filter units 10 and 11 are connected in cascade to each other. The longitudinally coupled resonator-type elastic wave filter units 10 and 11 are arranged to form a plurality of IDT electrodes in the propagation direction of the surface acoustic wave propagating on the surface of the piezoelectric substrate 2, respectively, and reflectors are provided on both sides of the plurality of IDT electrode groups. For example, as a structure having an odd number of IDT electrode groups of more than 3, a structure having 5 IDT electrodes in the longitudinally coupled resonator-type elastic wave filter unit may be provided.

[0054] Return to Figure 1 , the shape of X surrounded by a frame schematically indicates that the parts of the one-port elastic wave resonator 9 and the longitudinally coupled resonator-type elastic wave filter parts 10 and 11 are formed on the piezoelectric substrate 2. In the reception filter 7, the parts forming the one-port elastic wave resonator 9 and the longitudinally coupled resonator-type elastic wave filter parts 10 and 11 are elastic wave elements.

[0055] like Figure 2 As shown in (a), the transmission filter 8 has a ladder-type circuit structure. That is, it has series arm resonators S1, S2a, S2b, S3a, S3b, S4a, and S4b, each of which includes an elastic wave resonator, and parallel arm resonators P1 to P3. The series arm resonators S1 to S4b and the parallel arm resonators P1 to P3 include a 1-port type elastic wave resonator.

[0056] The 1-port elastic wave resonator has Figure 2 The electrode structure shown in (b) of FIG. 1 is shown in FIG. 2. The IDT electrode 12 and the reflectors 13 and 14 arranged on both sides of the IDT electrode 12 in the elastic wave propagation direction are formed on the piezoelectric substrate 2. Thus, a one-port elastic wave resonator is formed.

[0057] Return to Figure 1On the piezoelectric substrate 2, a rectangular frame enclosing an X symbol schematically indicates a portion that includes the series arm resonators S1 to S4b and the parallel arm resonators P1 to P3. That is, the portion that includes the series arm resonators S1 to S4b and the parallel arm resonators P1 to P3 is an elastic wave element. In the present embodiment, the parallel arm resonator P3 is a first elastic wave element, and the series arm resonator S4b is a second elastic wave element.

[0058] In addition, the IDT electrodes, reflectors, and connecting wirings in each of the elastic wave elements described above can be formed of appropriate metals such as Al, Ti, Ag, Cu, Pt, and W, or alloys thereof.

[0059] Figure 3 Yes Figure 1 FIG. 1 is a schematic plan view showing an enlarged view of a portion where the first and second elastic wave elements are provided.

[0060] like Figure 3 As shown in FIG. 1 , first elastic wave element 15 includes first IDT electrode 12A and first reflector 13A. First reflector 13A is provided on one side of a region where first IDT electrode 12A is provided in the propagation direction of the elastic wave excited by first IDT electrode 12A. Although not shown in the figure, a reflector is also provided on the opposite side of first IDT electrode 12A in the propagation direction of the elastic wave.

[0061] The second elastic wave element 16 is arranged with the first elastic wave element 15 in the above-mentioned elastic wave propagation direction. The second elastic wave element 16 includes a second IDT electrode 12B and a second reflector 14A. The second reflector 14A is provided on one side of the region where the second IDT electrode 12B is provided in the propagation direction of the elastic wave excited by the second IDT electrode 12B. The second reflector 14A is arranged with the first reflector 13A in the elastic wave propagation direction. In addition, although not shown in the figure, a reflector is also provided on the opposite side of the second IDT electrode 12B in the above-mentioned elastic wave propagation direction.

[0062] In the present embodiment, a reflecting component 17 is provided between the first reflector 13A and the second reflector 14A. The reflecting component 17 is a reflecting component for reflecting elastic waves at least in a direction different from the elastic wave propagation direction. The planar shape of the reflecting component 17 is circular. In the present embodiment, a plurality of reflecting components 17 of the same shape and size are provided in two rows so as to be along a direction orthogonal to the elastic wave propagation direction. Specifically, the reflecting components 17 arranged in the row on the first reflector 13A side and the reflecting components 17 arranged in the row on the second reflector 14A side are alternately arranged in a direction orthogonal to the elastic wave propagation direction.

[0063] The plurality of reflecting components 17 are arranged so that the region overlaps with the intersection region of one elastic wave element in the direction of propagation of the elastic wave, and there is no portion where the reflecting component 17 is not provided. In addition, the plurality of reflecting components 17 are arranged so that the region overlaps with the intersection region of another elastic wave element in the direction of propagation of the elastic wave, and there is no portion where the reflecting component 17 is not provided.

[0064] Specifically, in the present embodiment, when viewed from the direction of propagation of the elastic wave, the reflection components 17 of the column on the first reflector 13A side and the reflection components 17 of the column on the second reflector 14A side are arranged to be in contact with each other. In addition, the reflection components 17 of the column on the first reflector 13A side and the reflection components 17 of the column on the second reflector 14A side may be arranged to overlap with each other when viewed from the direction of propagation of the elastic wave, or may be arranged not to overlap with each other. Furthermore, from the viewpoint of further reducing unnecessary arrival of the leaked elastic wave to the elastic wave element, it is preferred that the reflection components 17 of the column on the first reflector 13A side and the reflection components 17 of the column on the second reflector 14A side are in contact with each other or at least partially overlap with each other when viewed from the direction of propagation of the elastic wave.

[0065] Thus, in the elastic wave device 1, the reflecting member 17 for reflecting the elastic wave at least in a direction different from the propagation direction of the elastic wave is provided between the first reflector 13A and the second reflector 14A. Therefore, in the elastic wave device 1, it is possible to achieve a compact size and suppress degradation of characteristics. This aspect will be described in detail below.

[0066] In the past, when two elastic wave elements were arranged adjacent to each other in the direction of elastic wave propagation, the mechanical vibration of one elastic wave element might leak to the other elastic wave element, causing fluctuations in the passband of the other elastic wave element. In addition, the mechanical vibration of one elastic wave element might be reflected by the reflector of the other elastic wave element, causing fluctuations in the passband of one elastic wave element due to the reflected mechanical vibration. In order to prevent the degradation of the characteristics of such elastic wave elements, it is necessary to increase the distance between the two elastic wave elements. Therefore, in the conventional elastic wave device, when the two elastic wave elements are arranged adjacent to each other, it is difficult to achieve miniaturization while maintaining the characteristics of the elastic wave elements.

[0067] In contrast, in the elastic wave device 1 of the present embodiment, as described above, the reflecting member 17 is provided between the first and second elastic wave elements 15 and 16 adjacent to each other. The reflecting member 17 can reflect the elastic wave excited by the first and second IDT electrodes 12A and 12B in at least a direction different from the propagation direction of the elastic wave. That is, in the elastic wave device 1, since the component of the mechanical vibration of one elastic wave element reaching the other elastic wave element is reduced, the characteristics of the other elastic wave element are unlikely to deteriorate. In addition, the mechanical vibration of one elastic wave element is reflected by the reflecting member 17 before reaching the reflector on the other side. Therefore, the component of the reflected mechanical vibration returning to the one elastic wave element is suppressed, and the characteristics of the one elastic wave element are unlikely to deteriorate. Therefore, in the elastic wave device 1, even if the distance between the first and second elastic wave elements 15 and 16 is reduced, the characteristics are unlikely to deteriorate. Therefore, in the elastic wave device 1, miniaturization can be achieved and the characteristics are unlikely to deteriorate.

[0068] Furthermore, in the elastic wave device 1, as described above, it is configured such that there is no portion in the direction of propagation of the elastic wave where the plurality of reflection components 17 are not provided. That is, the plurality of reflection components 17 are arranged in the direction of propagation of the elastic wave to prevent the leaked elastic wave from reaching the path of the elastic wave element, and in the elastic wave device 1, it is further difficult to cause degradation of characteristics.

[0069] In addition, in the present embodiment, since the planar shape of the reflective member 17 is circular, it is possible to scatter the propagating elastic waves in various directions. In addition, in the present invention, various shapes may be adopted as in the modified examples described below.

[0070] In addition, the reflective member 17 can be formed of a suitable metal or alloy such as Al, Ti, Ag, Cu, Pt, W, etc. In addition, the reflective member 17 can be formed by a lift-off process or an etching process simultaneously with the first and second IDT electrodes 12A and 12B. In addition, the reflective member 17 can also be manufactured by a process different from that of the first and second IDT electrodes 12A and 12B.

[0071] (First Modification)

[0072] Figure 4 This is a schematic plan view showing an enlarged view of a portion where first and second elastic wave elements are provided in a first modification of the elastic wave device according to the embodiment of the present invention.

[0073] like Figure 4As shown, in the elastic wave device of the first variant, a reflective component 17A is provided between the first and second reflectors 13A and 14A. More specifically, between the first and second reflectors 13A and 14A, a plurality of reflective components 17A are provided in a row along a direction orthogonal to the propagation direction of the elastic wave. In addition, the planar shape of the reflective component 17A is a rectangular shape. When the reflective component 17A is viewed from above, the direction along the long side of the rectangular reflective component 17A is inclined at approximately 45 degrees relative to the propagation direction of the elastic wave. Other aspects are the same as those of the elastic wave device 1 described above.

[0074] In the elastic wave device of the first modification, multiple reflective members 17A can also reflect the elastic wave excited by the IDT electrode in at least a direction different from the propagation direction of the elastic wave. Therefore, the elastic wave device of the first modification can also be miniaturized and is less likely to deteriorate in characteristics.

[0075] In particular, in the elastic wave device of the present modification, since the plurality of reflecting components 17A are arranged in a row along a direction orthogonal to the elastic wave propagation direction between the first and second reflectors 13A and 14A, further miniaturization can be achieved. Therefore, in the elastic wave device of the present invention, it is preferred that the plurality of reflecting components are arranged in a row along a direction orthogonal to the elastic wave propagation direction between the first and second reflectors. Furthermore, the plurality of reflecting components 17A may be arranged in a direction intersecting the elastic wave propagation direction, or may be arranged in a plurality of rows.

[0076] Furthermore, in this modification, since the direction along the long side of the rectangular reflective member 17A is set to be inclined at about 45 degrees relative to the elastic wave propagation direction when viewed from above, the excited elastic wave can be more reliably reflected in a direction different from the elastic wave propagation direction. Therefore, in the elastic wave device of this modification, it is difficult for the reflected elastic wave to return to the direction of the first or second elastic wave element 15, 16, and it is further difficult to cause degradation of the characteristics. From this point of view, it is preferable that the direction along the long side of the rectangular reflective member 17A is inclined at 45 degrees ± 25 degrees relative to the elastic wave propagation direction.

[0077] (Second Modification)

[0078] Figure 5 This is a schematic plan view showing an enlarged view of a portion where the first and second elastic wave elements are provided in a second modification of the elastic wave device according to the embodiment of the present invention.

[0079] like Figure 5As shown, in the elastic wave device of the second modified example, the plane shape of the reflective member 17B is an ellipse. In addition, in the elastic wave device of the second modified example, a plurality of reflective members 17B are arranged in a row along a direction orthogonal to the elastic wave propagation direction between the first and second reflectors 13A and 14A. When the reflective members 17B are viewed from above, the direction along the major axis of the elliptical reflective member 17B is inclined at about 45 degrees with respect to the elastic wave propagation direction. Other aspects are the same as those of the elastic wave device 1 described above.

[0080] In the elastic wave device of the second modification, the elastic waves excited by the IDT electrodes 12A and 12B can be reflected at least in a direction different from the propagation direction of the elastic waves by the plurality of reflection members 17B. Therefore, in the elastic wave device of the second modification, miniaturization can be achieved, and degradation of characteristics is unlikely to occur. In addition, between the first and second reflectors 13A and 14A, the plurality of reflection members 17B are arranged in a row along a direction orthogonal to the propagation direction of the elastic waves. Therefore, further miniaturization can be achieved.

[0081] In this modification, since the direction along the major axis of the elliptical reflector 17B is inclined at about 45 degrees relative to the elastic wave propagation direction when viewed from above, the excited elastic wave can be more reliably reflected in a direction different from the elastic wave propagation direction. Therefore, in the elastic wave device of this modification, the reflected elastic wave is less likely to return to the first or second elastic wave element 15, 16, and the degradation of the characteristics can be further less likely to occur. From this point of view, it is preferable that the direction along the major axis of the elliptical reflector 17B is inclined at 45 degrees ± 25 degrees relative to the elastic wave propagation direction.

[0082] In addition, in the elastic wave device of this modification, similarly to elastic wave device 1, since the outer shape of the planar shape has a curved line, the propagating elastic waves can be scattered in various directions.

[0083] In the elastic wave device 1, the reflecting member 17 of the same size and shape is used, but it is also possible to Figure 6 As shown in the third modification, different-sized reflective members 17C and 17D may be combined. In addition, different-shaped reflective members not shown in the figure may be combined. In these cases, the effects of the present invention can be obtained, which can achieve miniaturization of the elastic wave device and reduce the degradation of characteristics.

[0084] In the above embodiment, the case where the resonators of the ladder-type filter are adjacent to each other is described, but the present invention can be widely applied to elastic wave devices having various structures as long as the reflector of the first elastic wave element is adjacent to the reflector of the second elastic wave element. For example, the present invention can also be applied to the case where the reflector of a longitudinally coupled resonator-type elastic wave filter is adjacent to the reflector of another resonator.

Claims

1. An elastic wave device comprising: Piezoelectric substrate; a first elastic wave element provided on the piezoelectric substrate and including at least one first IDT electrode and a first reflector provided on one side in a first direction of a region where the first IDT electrode is provided; and a second elastic wave element provided on the piezoelectric substrate and including at least one second IDT electrode and a second reflector provided on one side in the first direction of a region where the second IDT electrode is provided; The first reflector and the second reflector are arranged along the first direction, The elastic wave device further includes a reflecting member, the reflecting member is provided between the first reflector and the second reflector, and the planar shape of the reflecting member has a curved line or at least two sides inclined with respect to the first direction. The plurality of reflective members having the same shape and the same size are arranged in at least one row along a direction perpendicular to the first direction.

2. The elastic wave device according to claim 1, wherein: The first IDT electrode has a plurality of electrode fingers extending in a direction orthogonal to the first direction.

3. The elastic wave device according to claim 1 or 2, wherein: The plurality of reflecting members are arranged so that there is no portion in the first direction where the reflecting members are not provided.

4. The elastic wave device according to claim 1 or 2, wherein: The plane shape of the reflecting component is circular.

5. The elastic wave device according to claim 1 or 2, wherein: The plane shape of the reflecting component is elliptical.

6. The elastic wave device according to claim 1 or 2, wherein: The plane shape of the reflective component is a rectangular shape.

7. The elastic wave device according to claim 5, wherein: In a plan view, the direction along the major axis of the elliptical reflecting member is inclined at 45 degrees ±25 degrees with respect to the first direction.

8. The elastic wave device according to claim 6, wherein: In a plan view, a direction along a long side of the rectangular reflecting member is inclined at 45 degrees ±25 degrees with respect to the first direction.

9. The elastic wave device according to claim 1 or 2, wherein: A plurality of the reflecting members having the same shape and the same size are arranged in at least one row in a direction perpendicular to the first direction, and a plurality of rows are provided.

10. The elastic wave device according to claim 1 or 2, wherein: The reflective member includes metal or alloy.

11. The elastic wave device according to claim 1 or 2, wherein: The elastic wave device has a ladder-type circuit structure, The first elastic wave element is a parallel arm resonator, and the second elastic wave element is a series arm resonator.

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