Longitudinal coupling resonator type elastic wave filter

Abstract

Provided is a longitudinal coupling resonator type elastic wave filter that is less likely to degrade in attenuation characteristics. A longitudinal coupling resonator type elastic wave filter (1) in which a first IDT electrode (13) and a second IDT electrode (14) are provided on a piezoelectric substrate (2), the direction in which electrode fingers (13c, 13d, 14c, 14d) of the IDT electrodes (13, 14) extend is set as a first direction, the direction orthogonal to the first direction is set as a second direction, a ground side bus bar (13b) of the first IDT electrode (13) and a signal side bus bar (14a) of the second IDT electrode (14) face each other in the second direction, and the longitudinal coupling resonator type elastic wave filter is provided with a protrusion (13b1) that is connected to the ground side bus bar (13b) of the first IDT electrode (13) and extends toward the second IDT electrode (14) in the second direction compared to the intersection area of the first IDT electrode (13).

Description

Technical Field

[0001] The present invention relates to a longitudinally coupled resonator type elastic wave filter having multiple IDT electrodes arranged along the propagation direction of the elastic wave. Background Technology

[0002] Patent Document 1 discloses a longitudinally coupled resonator type elastic wave filter having multiple IDT electrodes. In two adjacent IDT electrodes, the signal side busbar of one IDT electrode and the ground side busbar of the other IDT electrode are arranged in the elastic wave propagation direction. Furthermore, the ground side busbar of one IDT electrode and the signal side busbar of the other IDT electrode are arranged in the elastic wave propagation direction.

[0003] Prior art literature

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent No. 3391346 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] In the above-mentioned longitudinally coupled resonator type elastic wave filter, there is a problem that unwanted electromagnetic field coupling occurs between the signal side busbar of one IDT electrode and the signal side busbar of another IDT electrode, thus degrading the attenuation characteristics.

[0008] The purpose of this invention is to provide a longitudinally coupled resonator type elastic wave filter that is less prone to attenuation degradation.

[0009] Technical solutions for solving the problem

[0010] The longitudinally coupled resonator type elastic wave filter of the present invention comprises: a piezoelectric substrate; a first IDT electrode disposed on the piezoelectric substrate; and a second IDT electrode disposed on the piezoelectric substrate adjacent to the first IDT electrode. The first IDT electrode has: a signal-side busbar connected to a signal-side potential; a ground-side busbar connected to a ground-side potential; multiple first electrode fingers connected to the signal-side busbar; and multiple second electrode fingers connected to the ground-side busbar. The second IDT electrode has: a signal-side busbar connected to a signal-side potential; a ground-side busbar connected to a ground-side potential; multiple third electrode fingers connected to the signal-side busbar; and multiple fourth electrode fingers connected to the ground-side busbar. The direction in which the first electrode fingers to the fourth electrode fingers extend is defined as a first direction, and the direction orthogonal to the first direction is defined as... In the second direction, the regions where the multiple first electrode fingers and multiple second electrode fingers of the first IDT electrode overlap in the second direction, and the regions where the multiple third electrode fingers and multiple fourth electrode fingers of the second IDT electrode overlap in the second direction, are respectively designated as intersection regions. At this time, the ground-side busbar of the first IDT electrode and the signal-side busbar of the second IDT electrode are opposite each other in the second direction, and the signal-side busbar of the first IDT electrode and the ground-side busbar of the second IDT electrode are opposite each other in the second direction. The longitudinally coupled resonator type elastic wave filter is provided with a protrusion, which is connected to the ground-side busbar of the first IDT electrode and extends towards the second IDT electrode side in the second direction compared with the intersection region of the first IDT electrode.

[0011] Invention Effects

[0012] According to the present invention, a longitudinally coupled resonator type elastic wave filter that is less prone to attenuation degradation can be provided. Attached Figure Description

[0013] Figure 1 This is a top view of the longitudinally coupled resonator type elastic wave filter according to the first embodiment of the present invention.

[0014] Figure 2 This is a circuit diagram of a receiving filter having the longitudinally coupled resonator type elastic wave filter according to the first embodiment of the present invention.

[0015] Figure 3 This is a schematic top view showing the main parts of the longitudinally coupled resonator type elastic wave filter according to the first embodiment of the present invention.

[0016] Figure 4This is a top view showing the electrode configuration of a longitudinally coupled resonator type elastic wave filter, which is a comparative example.

[0017] Figure 5 This is a graph showing the attenuation-frequency characteristics of the receiving filter of the embodiment and the receiving filter of the comparative example.

[0018] Figure 6(a) is a top view showing the main part of the electrode structure of the longitudinally coupled resonator type elastic wave filter according to the second embodiment of the present invention, Figure 6(b) is an enlarged cross-sectional view of the portion along line A-A in Figure 6(a), and Figure 6(c) is an enlarged cross-sectional view showing a modified example of the portion along line A-A in Figure 6(a).

[0019] Figure 7 This is a top view showing the main parts of the electrode structure of the longitudinally coupled resonator type elastic wave filter according to the third embodiment of the present invention.

[0020] Figure 8 This is a top view showing the main parts of the electrode structure of the longitudinally coupled resonator type elastic wave filter according to the fourth embodiment of the present invention.

[0021] Figure 9 This is a top view showing the main parts of the electrode structure of the longitudinally coupled resonator type elastic wave filter according to the fifth embodiment of the present invention.

[0022] Figure 10 This is a top view showing the main parts of the electrode structure of the longitudinally coupled resonator type elastic wave filter according to the sixth embodiment of the present invention. Detailed Implementation

[0023] Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings, thereby clarifying the present invention.

[0024] In addition, it should be noted that the embodiments described in this specification are illustrative and that partial substitutions or combinations of structures can be made between different embodiments.

[0025] Figure 1 This is a top view of a longitudinally coupled resonator type elastic wave filter according to the first embodiment of the present invention. The longitudinally coupled resonator type elastic wave filter 1 has a piezoelectric substrate 2. The piezoelectric substrate 2 contains a suitable piezoelectric material such as LiTaO3 or LiNbO3.

[0026] IDT electrodes 11 to 15 are disposed on the piezoelectric substrate 2 along the direction of elastic wave propagation. Reflectors 16 and 17 are disposed on both sides of the region where the IDT electrodes 11 to 15 are disposed. This constitutes a 5IDT type longitudinally coupled resonator type surface acoustic wave filter. Alternatively, a film containing a dielectric material can be disposed on the piezoelectric substrate 2 to cover the IDT electrodes 11 to 15.

[0027] This longitudinally coupled resonator type elastic wave filter 1 is used as the receiving filter for Band66.

[0028] Figure 2 This is the circuit diagram of the receiving filter. The receiving filter 18 has an antenna terminal 18a and a receiving terminal 18b. A series resonator 19a, a longitudinally coupled resonator type elastic wave filter 1, and a series resonator 19b are connected between the antenna terminal 18a and the receiving terminal 18b. The series resonators 19a and 19b are not particularly limited and are composed of elastic wave resonators.

[0029] Figure 3 This is a schematic top view showing the main parts of the longitudinally coupled resonator type elastic wave filter 1 enlarged. Figure 3 The image shows the portion where IDT electrode 13, IDT electrode 14 and IDT electrode 15 are provided.

[0030] When IDT electrode 13 and IDT electrode 15 are considered equivalent to the first IDT electrode in this invention, IDT electrode 14 is considered equivalent to the second IDT electrode. IDT electrode 13 has a signal-side busbar 13a and a ground-side busbar 13b. In this specification, the signal-side busbar is a busbar connected to the signal-side potential. The ground-side busbar is a busbar connected to the ground-side potential. Multiple electrode fingers 13c, serving as multiple first electrode fingers, are connected to the signal-side busbar 13a. Multiple electrode fingers 13d, serving as multiple second electrode fingers, are connected to the ground-side busbar 13b. The multiple electrode fingers 13c and 13d are interleaved and interlocked.

[0031] Furthermore, in this specification, the direction in which the multiple electrodes extend (points 13c and 13d) is designated as the first direction. Additionally, on the piezoelectric substrate 2, the direction orthogonal to the first direction is designated as the second direction. The second direction is the direction of elastic wave propagation.

[0032] The IDT electrode 14 also has a signal-side busbar 14a and a ground-side busbar 14b. A connection wiring 21 is connected to the signal-side busbar 14a. Multiple electrode fingers 14c, serving as multiple third electrode fingers, are connected to the signal-side busbar 14a. Multiple electrode fingers 14d, serving as multiple fourth electrode fingers, are connected to the ground-side busbar 14b. (The text repeats itself here.) Figure 1 as well as Figure 2As shown, the connection wiring 21 and the connection wiring 22 connected to the IDT electrode 12 are connected together.

[0033] In addition, the signal side busbar 13a of the IDT electrode 13 is connected to the connection wiring 23.

[0034] like Figure 3 As shown, the ground side bus 13b of IDT electrode 13 and the signal side bus 14a of IDT electrode 14 are arranged in the second direction. Similarly, the signal side bus 13a of IDT electrode 13 and the ground side bus 14b of IDT electrode 14 are arranged in the second direction.

[0035] The ground-side busbar 13b has a protrusion 13b1. The protrusion 13b1 extends from the ground-side busbar 13b toward the signal-side busbar 14a, which serves as the second IDT electrode 14, i.e., it extends in the second direction. In this embodiment, the protrusion 13b1 extends to a position where it overlaps with the signal-side busbar 14a in the first direction. That is, the end 14a1 beyond the IDT electrode 13 side of the signal-side busbar 14a extends toward the IDT electrode 14 side. Here, the boundary between the ground-side busbar 13b and the protrusion 13b1 is shown by the dashed line X. The ground-side busbar 13b refers to the portion extending in the second direction in the region overlapping with the intersecting region when viewed from the first direction, where the area where multiple electrode fingers 13c and multiple electrode fingers 13d intersect is defined as an intersecting region. The protrusion 13b1 is the portion that extends outward in the second direction compared to the aforementioned intersecting region.

[0036] like Figure 3 As shown, a protrusion 14b1 is also provided on the ground side busbar 14b of the IDT electrode 14, and the protrusion 14b1 is provided on the side of the IDT electrode 13. The protrusion 14b1 extends beyond the end 13a1 of the signal side busbar 13a toward the side of the IDT electrode 13, which serves as the first IDT electrode.

[0037] In the longitudinally coupled resonator type elastic wave filter 1, the aforementioned protrusions 13b1 and 14b1 are provided, thereby suppressing electromagnetic field coupling between the signal-side bus 13a and the signal-side bus 14a. Specifically, because the protrusion 13b1, connected to the ground-side bus 13b, is located near the signal-side bus 14a, the electromagnetic field is guided from the signal-side bus 14a to the protrusion 13b1 side. Similarly, because the protrusion 14b1 is located near the signal-side bus 13a, the electromagnetic field is guided from the signal-side bus 13a to the protrusion 14b1 side. Therefore, the electromagnetic field coupling between the signal-side bus 13a and the signal-side bus 14a is reduced. This improves the attenuation.

[0038] This is made clear by illustrating the characteristics of the following embodiments and comparative examples.

[0039] As an example 1, it constitutes Figure 2 The receiving filter 18 is shown. In Embodiment 1, each IDT electrode 11-15 has a main body portion and a narrow-pitch portion. The electrode finger spacing in the narrow-pitch portion is narrower than the electrode finger spacing in the main body portion. The electrode finger spacing refers to the center-to-center distance between adjacent electrode fingers. The narrow-pitch portion is located in the portion adjacent to other IDT electrodes. Furthermore, Embodiment 1 is an example, and the electrode finger spacing of each IDT electrode 11-15 can also be fixed. Moreover, in Embodiment 1, a structure is provided in which a film containing a dielectric is provided on the piezoelectric substrate 2, covering the IDT electrodes 11-15.

[0040] Here, the design parameters for the longitudinally coupled resonator type elastic wave filter 1 are set as follows. The wavelength specified by the electrode finger spacing is set as λ. When the electrode finger spacing is not fixed, the average value of the electrode finger spacing can also be used when specifying the wavelength λ. The dimension of the cross region along the first direction is set as the cross width. The "electrode" in the design parameters includes IDT electrodes 11-15 and reflectors 16 and 17.

[0041] [Table 1]

[0042]

[0043] [Table 2]

[0044]

[0045] Average distance between electrode fingers: 1.805 μm (λ = 3.61 μm)

[0046] Utilization pattern: LN Rayleigh

[0047] Cross width: 27μm (7.5λ)

[0048] Electrode materials: From side 2 of the piezoelectric substrate, Nicr / Pt / Ti / AlCu / Ti

[0049] Materials containing dielectric films: SiO2

[0050] Electrode film thickness: For each layer, from side 2 of the piezoelectric substrate, it is 10nm / 35nm / 10nm / 130nm / 10nm.

[0051] Film thickness including dielectric: 500 nm

[0052] The series resonator 19a is composed of the following elastic wave resonator.

[0053] Utilization pattern: LN Rayleigh

[0054] Electrode finger spacing (reflector / IDT electrode / reflector): 1.718μm / 1.652μm / 1.718μm

[0055] Cross width: 27.7μm

[0056] Number of electrode pairs (reflector / IDT electrode / reflector): 10 pairs / 92.5 pairs / 10 pairs

[0057] Electrode materials: From side 2 of the piezoelectric substrate, Nicr / Pt / Ti / AlCu / Ti

[0058] Materials containing dielectric films: SiO2

[0059] Electrode film thickness: For each layer, from side 2 of the piezoelectric substrate, it is 10nm / 35nm / 10nm / 130nm / 10nm.

[0060] Film thickness including dielectric: 500 nm

[0061] The series resonator 19b is composed of the following elastic wave resonator.

[0062] Utilization pattern: LN Rayleigh

[0063] Electrode finger spacing (reflector / IDT electrode / reflector): 1.712μm / 1.646μm / 1.712μm

[0064] Cross width: 28.5μm

[0065] Electrode pairs (reflector / IDT electrode / reflector): 10 pairs / 121 pairs / 10 pairs

[0066] Electrode materials: From side 2 of the piezoelectric substrate, Nicr / Pt / Ti / AlCu / Ti

[0067] Materials containing dielectric films: SiO2

[0068] Electrode film thickness: For each layer, from side 2 of the piezoelectric substrate, it is 10nm / 35nm / 10nm / 130nm / 10nm.

[0069] Film thickness including dielectric: 500 nm

[0070] For comparison, in addition to using Figure 4Except for the longitudinally coupled resonator type elastic wave filter 101 shown, the comparative example receiving filter is constructed in the same manner as in Embodiment 1. In the longitudinally coupled resonator type elastic wave filter 101, no protrusion is provided on the ground side busbar of the IDT electrodes 111-115, and the width of the ground side busbar, that is, the dimension along the first direction, is set to be the same as the width of the signal side busbar. With other structures the same as in the embodiment, the comparative example receiving filter is constructed.

[0071] Figure 5 This is a graph showing the attenuation-frequency characteristics of the receiving filters in the embodiments and comparative examples. The solid line shows the results of the embodiments, and the dashed line shows the results of the comparative examples.

[0072] according to Figure 5 It is clear that, compared to the comparative example, in this embodiment, the attenuation in the attenuation band above 2250MHz and below 2480MHz, which is higher than the passband, is greater. That is, in the longitudinally coupled resonator type elastic wave filter 1, the attenuation characteristics are improved compared to the comparative example. This is believed to be because, as mentioned above, by providing protrusions 13b1 and 14b1 between adjacent IDT electrodes 13 and 14, electromagnetic field coupling between adjacent signal-side busbars 13a and 14a is suppressed.

[0073] In addition, such as Figure 3 As shown, in the portion adjacent to IDT electrode 14 and IDT electrode 15, a protrusion 15b1 is also connected to the ground-side busbar 15b of IDT electrode 15. Furthermore, a protrusion 14b2 extending towards IDT electrode 15 is also provided in the ground-side busbar 14b. Therefore, electromagnetic field coupling between signal-side busbar 14a and signal-side busbar 15a can be suppressed between IDT electrodes 14 and 15. In the longitudinally coupled resonator type elastic wave filter 1, protrusions are also connected to the ground-side busbar in the portions adjacent to IDT electrode 14 and IDT electrode 13, and in the portions adjacent to IDT electrode 14 and IDT electrode 15, as well as in the portions adjacent to IDT electrode 11 and IDT electrode 12, and in the portions adjacent to IDT electrode 12 and IDT electrode 13. This allows for improvement in attenuation characteristics.

[0074] However, in this invention, the aforementioned protrusion is sufficient as long as the structure of this invention is provided in at least one location where the IDT electrodes are adjacent to each other in a longitudinally coupled resonator type elastic wave filter having multiple IDT electrodes. Preferably, protrusions are provided on the ground-side busbar in all locations where the IDT electrodes are adjacent to each other, as in the above embodiment. This allows for more effective improvement in attenuation characteristics.

[0075] Refer to Figures 6(a) to 6(c) and Figures 7-10The second to sixth embodiments of the present invention will be described below. Figures 6(a) to 6(c) and... Figures 7-10 In the image, only the portions of the IDT electrodes that are adjacent to each other are shown in magnification.

[0076] Figure 6(a) is a top view showing the main part of the electrode structure of the longitudinally coupled resonator type elastic wave filter according to the second embodiment of the present invention.

[0077] In the longitudinally coupled resonator type elastic wave filter 31, IDT electrodes 32 and 33 are adjacent in the elastic wave propagation direction, that is, adjacent in the second direction. IDT electrode 32 has a signal-side busbar 32a and a ground-side busbar 32b. A protrusion 32b1 is connected to the ground-side busbar 32b. Multiple electrode fingers 32c, serving as multiple first electrode fingers, are connected to the signal-side busbar 32a. Multiple electrode fingers 32d, serving as multiple second electrode fingers, are connected to the ground-side busbar 32b. A connecting wire 34 is connected to the signal-side busbar 32a. The connecting wire 34 has a first wiring portion 34a and a second wiring portion 34b, with the first wiring portion 34a connected to the signal-side busbar 32a and the second wiring portion 34b connected to the first wiring portion 34a, and extending in the second direction.

[0078] In the IDT electrode 33, multiple electrode fingers 33c are connected to the signal-side busbar 33a. Multiple electrode fingers 33d are connected to the ground-side busbar 33b. A protrusion 33b1 is connected to the ground-side busbar 33b.

[0079] The protrusion 32b1 extends beyond the IDT electrode 32-side end 33a1 of the signal-side busbar 33a in the second direction toward the IDT electrode 33 side. Similarly, the protrusion 33b1 extends beyond the IDT electrode 33-side end 32a1 of the signal-side busbar 32a in the second direction.

[0080] A connecting wire 35 is connected to the signal-side busbar 33a. Specifically, the first wiring portion 35a of the connecting wire 35 is connected to the signal-side busbar 33a. The first wiring portion 35a extends in a first direction. Furthermore, a second wiring portion 35b extending in a second direction is connected to the first wiring portion 35a. Therefore, the protrusion 32b1 is configured to reach the area surrounded by the signal-side busbar 33a, the first wiring portion 35a, and the second wiring portion 35b of the connecting wire 35. Similarly, the protrusion 33b1 also extends into the area surrounded by the signal-side busbar 32a, the first wiring portion 34a, and the second wiring portion 34b.

[0081] Therefore, the electromagnetic field is guided from the signal-side busbar 33a to the protrusion 32b1 side, and from the signal-side busbar 32a side to the protrusion 33b1 side. Consequently, electromagnetic field coupling between the signal-side busbar 32a and the signal-side busbar 33a can be effectively suppressed, and attenuation characteristics can be improved.

[0082] Preferably, when the distance between the intersection area edge of the protrusion 32b1 and the signal-side busbar 33a is set as d1, and the opposing distance between the signal-side busbar 33a and the ground-side busbar 33b is set as d2, d1 < d2. In this case, the electromagnetic field can be guided more effectively to the protrusion 32b1 side, and the attenuation characteristics can be further improved.

[0083] Figure 6(b) is an enlarged cross-sectional view of the portion along line A-A in Figure 6(a). In this embodiment, the height of the protrusion 32b1 is set to be lower than the height of the connecting wiring 35. In this case, since the protrusion 32b1 is provided closer to the piezoelectric substrate 2, the electromagnetic field passing through the piezoelectric substrate 2 can be guided to the protrusion 32b1 side more effectively.

[0084] However, as shown in FIG6(c), the height of the protrusion 32b1 can be made higher than that of the connecting wiring 35, which serves as the signal side wiring portion. In this case, the protrusion 32b1 is provided at a position away from the piezoelectric substrate with a relatively high dielectric constant, thereby reducing the useless capacitance between it and the signal side busbar 33a.

[0085] Figure 7 This is a top view showing the main parts of the electrode structure of the longitudinally coupled resonator type elastic wave filter 41 according to the third embodiment. In the longitudinally coupled resonator type elastic wave filter 41, the signal-side busbars 32a and 33a in the IDT electrodes 32 and 33 are designed with a width that tapers from the center towards both sides in the second direction. Furthermore, the width of the signal-side busbars 32a and 33a is a dimension along the first direction. Regarding other structures, the longitudinally coupled resonator type elastic wave filter 41 is the same as the longitudinally coupled resonator type elastic wave filter 31.

[0086] In this embodiment, similar to the second embodiment, the attenuation characteristics are improved by providing protrusions 32b1 and 33b1. Furthermore, the width of the signal-side busbars 32a and 33a tapers towards both ends in the second direction. Therefore, by increasing the width of the signal-side busbars 32a and 33a at the center of the second direction where the current distribution is large, and by thinning the ends on the second direction side where the current distribution is small and the contribution to coupling is large, losses in the passband can be effectively suppressed. That is, the attenuation characteristics can be improved while suppressing the impact on losses in the passband.

[0087] Figure 8 This is a top view showing the main part of the electrode structure of the longitudinally coupled resonator type elastic wave filter 51 according to the fourth embodiment of the present invention.

[0088] Here, IDT electrodes 32 and 33 are configured in the same way as the longitudinally coupled resonator type elastic wave filter 31 shown in FIG. 6(a). Therefore, the same reference numerals are used for the same parts, and their descriptions are omitted.

[0089] However, on the opposite side of IDT electrode 32 to IDT electrode 33, there is also an adjacent IDT electrode 52. If IDT electrode 32 corresponds to the first IDT electrode in this invention and IDT electrode 33 corresponds to the second IDT electrode, then IDT electrode 52 corresponds to the third IDT electrode. IDT electrode 52 has a ground-side busbar 52b and a signal-side busbar. In IDT electrode 52, the ground-side busbar 52b is arranged with the signal-side busbar 33a of IDT electrode 33 in the elastic wave propagation direction, i.e., the second direction. Furthermore, the protrusions 32b1 of IDT electrode 32 and IDT electrode 52 are connected. Thus, in a structure where three IDT electrodes 32, 33, and 52 are arranged along the elastic wave propagation direction, the protrusions 32b1 and 52b1 of IDT electrodes 32 and 52 on both sides can also be connected. Furthermore, if the protrusion 32b1 of the IDT electrode 32 is equivalent to the first protrusion, then the protrusion 52b1 of the IDT electrode 52 is equivalent to the second protrusion in this invention.

[0090] exist Figure 8 As shown by the dashed lines, protrusions 32b1 and 52b1 are connected. Furthermore, a dielectric film 53 is laminated between the first wiring portion 35a of the connecting wiring 35 and the aforementioned protrusions 32b1 and 52b1. This prevents short circuits between the connecting wiring 35 and the ground-side busbars 32b and 52b. The dielectric film 53 can contain a suitable dielectric. In this embodiment, the dielectric constant of the dielectric film 53 is lower than that of the piezoelectric substrate.

[0091] Through such Figure 8 The dielectric film 53 is provided in a three-dimensional wiring structure, thereby reducing the contact area between the signal-side connection wiring 35 and the piezoelectric substrate with a relatively high dielectric constant. Therefore, the degradation of attenuation characteristics can be suppressed more effectively.

[0092] Figure 9 This is a top view showing the main parts of the electrode structure of the longitudinally coupled resonator type elastic wave filter 61 according to the fifth embodiment of the present invention. In the longitudinally coupled resonator type elastic wave filter 61, protrusions 32b1 and 33b1 extend toward the IDT electrode 33 side and the IDT electrode 32 side, respectively. However, as Figure 9 As shown, the front ends of protrusions 32b1 and 33b1 do not reach the portions that overlap with the signal-side busbar 33a of IDT electrode 33 and the signal-side busbar 32a of IDT electrode 32 in the first direction. In this way, the lengths of protrusions 32b1 and 33b1 can also be set to the lengths that do not overlap with adjacent busbars in the first direction.

[0093] Figure 10 This is a top view showing the main parts of the electrode structure of the longitudinally coupled resonator type elastic wave filter 71 according to the sixth embodiment of the present invention. In the longitudinally coupled resonator type elastic wave filter 71, protrusions 32b1 and 33b1 extend toward the signal side busbar 33a side of IDT electrode 33 and the signal side busbar 32a side of IDT electrode 32, respectively. However, protrusions 32b1 and 33b1 extend from the intersection region side end of ground side busbars 32b and 33b, respectively, in a first direction. In this way, the protrusions can protrude from any position at the end of the connected ground side busbar in the first direction.

[0094] Explanation of reference numerals in the attached figures

[0095] 1: Longitudinal coupled resonator type elastic wave filter;

[0096] 2: Piezoelectric substrate;

[0097] 11-15: IDT electrodes;

[0098] 13a, 14a, 15a: Signal side busbars;

[0099] 13b, 14b, 15b: Grounding side busbar;

[0100] 13a1, 14a1: end;

[0101] 13b1, 14b1, 14b2, 15b1: Protrusions;

[0102] 13c, 13d, 14c, 14d: Electrode indices;

[0103] 16, 17: Reflectors;

[0104] 18: Receiver filter;

[0105] 18a: Antenna terminal;

[0106] 18b: Receive terminal;

[0107] 19a, 19b: Series resonators;

[0108] 21-23: Connection wiring;

[0109] 31: Longitudinal Coupled Resonator Type Elastic Wave Filter;

[0110] 32, 33: IDT electrodes;

[0111] 32a, 33a: Signal side busbars;

[0112] 32a1, 33a1: End;

[0113] 32b, 33b: Grounding side busbar;

[0114] 32b1, 33b1: Protrusions;

[0115] 32c, 32d, 33c, 33d: Electrode references;

[0116] 34: Connection wiring;

[0117] 34a, 34b: First wiring section, second wiring section;

[0118] 35: Connection wiring;

[0119] 35a, 35b: First wiring section, second wiring section;

[0120] 41, 51: Longitudinal coupled resonator type elastic wave filter;

[0121] 52: IDT electrode;

[0122] 52b: Grounding side busbar;

[0123] 52b1: Protrusion;

[0124] 53: Dielectric film;

[0125] 61, 71: Longitudinal coupled resonator type elastic wave filter.

Claims

1. A longitudinally coupled resonator type elastic wave filter, comprising: Piezoelectric substrate; A first IDT electrode is disposed on the piezoelectric substrate; and The second IDT electrode is disposed on the piezoelectric substrate adjacent to the first IDT electrode. The first IDT electrode has: The signal-side busbar is connected to the signal-side potential. The grounding side busbar is connected to the grounding side potential. Multiple first electrode fingers are connected to the signal-side busbar; as well as Multiple second electrode fingers are connected to the grounding side busbar. The second IDT electrode has: The signal-side busbar is connected to the signal-side potential. The grounding side busbar is connected to the grounding side potential. Multiple third electrode fingers are connected to the signal-side busbar; as well as Multiple fourth electrode fingers are connected to the grounding side busbar. The direction in which the first to fourth electrode fingers extend is defined as the first direction, and the direction orthogonal to the first direction is defined as the second direction. The areas where the multiple first and second electrode fingers of the first IDT electrode overlap in the second direction, and the areas where the multiple third and fourth electrode fingers of the second IDT electrode overlap in the second direction, are respectively defined as intersection areas. In this case, the ground-side busbar of the first IDT electrode and the signal-side busbar of the second IDT electrode are opposite each other in the second direction, and the signal-side busbar of the first IDT electrode and the ground-side busbar of the second IDT electrode are opposite each other in the second direction. The longitudinally coupled resonator type elastic wave filter is provided with a protrusion that is connected to the ground side busbar of the first IDT electrode and extends towards the second IDT electrode in the second direction compared to the intersection region of the first IDT electrode. The protrusion extends toward the second IDT electrode side in the second direction compared to the first IDT electrode side end of the signal side busbar of the second IDT electrode.

2. The longitudinally coupled resonator type elastic wave filter according to claim 1, wherein, In the region opposite to the intersection region of the second IDT electrode in the signal-side busbar of the second IDT electrode, the protrusion extends in the second direction.

3. The longitudinally coupled resonator type elastic wave filter according to claim 1 or 2, wherein, The width of the signal-side busbar of the second IDT electrode, as a dimension along the first direction, decreases as it moves from the center of the signal-side busbar of the second IDT electrode toward both ends in the second direction.

4. The longitudinally coupled resonator type elastic wave filter according to claim 1 or 2, wherein, Let d1 be the distance between the end of the second IDT electrode on the cross region side of the protrusion and the end edge of the signal side busbar of the second IDT electrode connected to the plurality of third electrode fingers, and let d2 be the distance between the signal side busbar and the ground side busbar in the second IDT electrode. In this case, d1 < d2.

5. The longitudinally coupled resonator type elastic wave filter according to claim 1 or 2, wherein, It also includes: connecting wiring, connected to the end edge of the signal-side busbar of the second IDT electrode on the opposite side of the intersection region of the second IDT electrode. The connection wiring has: The first wiring section is connected to the signal-side busbar of the second IDT electrode; and The second wiring section is connected to the end of the first wiring section opposite to the portion connected to the signal-side busbar, and extends in the second direction.

6. The longitudinally coupled resonator type elastic wave filter according to claim 5, wherein, The protrusion extends into the area surrounded by the signal-side busbar of the second IDT electrode, the first wiring portion, and the second wiring portion.

7. The longitudinally coupled resonator type elastic wave filter according to claim 5, wherein, The height of the protrusion is lower than the height of the signal-side busbar of the second IDT electrode and the height of the connecting wiring.

8. The longitudinally coupled resonator type elastic wave filter according to claim 5, wherein, The height of the protrusion is greater than the height of the signal-side busbar of the second IDT electrode and the height of the connecting wiring.

9. The longitudinally coupled resonator type elastic wave filter according to claim 5, wherein, The protrusion extends to reach below the first wiring portion of the connecting wiring. The longitudinally coupled resonator type elastic wave filter has the following characteristics: A dielectric film is disposed between the protrusion and the first wiring portion.

10. The longitudinally coupled resonator type elastic wave filter according to claim 9, wherein, The dielectric constant of the dielectric film is lower than that of the piezoelectric substrate.

11. The longitudinally coupled resonator type elastic wave filter according to claim 1 or 2, wherein, It also includes: a third IDT electrode, disposed in the second direction on the side of the second IDT electrode opposite to the first IDT electrode. The third IDT electrode has: The grounding side busbar is connected to the grounding side potential. The signal-side busbar is connected to the signal-side potential. The second protrusion, connected to the grounding-side busbar, extends in the second direction toward the second IDT electrode side. The second protrusion of the third IDT electrode is connected to the protrusion of the first IDT electrode.

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