Elastic wave filter

Abstract

An elastic wave filter includes at least three split resonators (Sa, Sb, Sc, Sd) connected in series with each other, the at least three split resonators (Sa, Sb, Sc, Sd) each having an IDT (Inter Digital Transducer) electrode and arranged in a direction intersecting a propagation direction of an elastic wave, and a center of an elastic wave propagation direction of the IDT electrode of a first split resonator (Sb) and a second split resonator (Sa) adjacent to each other among the at least three split resonators (Sa, Sb, Sc, Sd) is offset from each other as viewed in a direction orthogonal to the propagation direction of the elastic wave.

Description

Technical Field

[0001] This invention relates to elastic wave filters equipped with split resonators. Background Technology

[0002] Previously, it was known to construct a resonator group by connecting multiple elastic wave resonators in series, that is, to divide the elastic wave resonator into multiple segmented resonators connected in series (for example, Patent Document 1). By dividing the elastic wave resonator in this way, the power consumption per unit area can be reduced, and the power tolerance of the elastic wave filter can be improved.

[0003] Prior art literature

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2001-156588 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] However, when the elastic wave resonator is divided into three or more segmented resonators connected in series, there will be segmented resonators that are configured to be sandwiched between other segmented resonators. Moreover, due to the interaction between this segmented resonator and the adjacent segmented resonators sandwiching it, the temperature of the elastic wave filter becomes prone to rise, resulting in a decrease in the power tolerance of the elastic wave filter.

[0008] Therefore, the object of the present invention is to provide an elastic wave filter that can effectively improve power tolerance.

[0009] Methods for solving problems

[0010] One aspect of the present invention relates to an elastic wave filter comprising at least three segmented resonators connected in series, each of the at least three segmented resonators having an IDT (Interdigital Transducer) electrode and arranged in a direction intersecting the propagation direction of the elastic wave. When viewed from a direction orthogonal to the propagation direction of the elastic wave, the IDT electrodes of adjacent first and second segmented resonators among the at least three segmented resonators are centrally offset in the direction of elastic wave propagation.

[0011] Invention Effects

[0012] According to the present invention, an elastic wave filter that can effectively improve power tolerance can be provided. Attached Figure Description

[0013] Figure 1This is a circuit diagram of the filter involved in the implementation method.

[0014] Figure 2 This is a top view showing an example of the layout of the segmented resonator group involved in the embodiment.

[0015] Figure 3 This is the circuit diagram of the filter involved in the comparative example.

[0016] Figure 4 This is a top view showing an example layout of the segmented resonator group involved in the comparative example.

[0017] Figure 5A This is a diagram showing the temperature distribution of the piezoelectric substrate in which the filter involved in the comparative example is formed.

[0018] Figure 5B This is a diagram showing the temperature distribution of the piezoelectric substrate forming the filter according to the embodiment.

[0019] Figure 6 This is a graph showing the power tolerance of the filter according to the embodiment and the filter according to the comparative example.

[0020] Figure 7A This is a diagram illustrating an example of the layout and circuit structure of a segmented resonator array involved in other embodiments.

[0021] Figure 7B This is a diagram illustrating an example of the layout and circuit structure of a segmented resonator array involved in other embodiments.

[0022] Figure 7C This is a diagram illustrating an example of the layout and circuit structure of a segmented resonator array involved in other embodiments.

[0023] Figure 7D This is a diagram illustrating an example of the layout and circuit structure of a segmented resonator array involved in other embodiments.

[0024] Figure 7E This is a diagram illustrating an example of the layout and circuit structure of a segmented resonator array involved in other embodiments. Detailed Implementation

[0025] Hereinafter, embodiments of the present invention will be described in detail using the accompanying drawings. Furthermore, the embodiments described below are either general or specific examples. The numerical values, shapes, materials, constituent elements, arrangements of constituent elements, and connection methods shown in the following embodiments are examples only and are not intended to limit the present invention. Constituent elements in the following embodiments not described in the independent claims are described as arbitrary constituent elements. In addition, in the figures, substantially identical structures are labeled with the same reference numerals, and sometimes repeated descriptions are omitted or simplified. Furthermore, in the following embodiments, the term "connection" includes not only direct connections but also electrical connections via other elements.

[0026] (Implementation Method)

[0027] use Figure 1 The structure of the elastic wave filter involved in the implementation method will be described.

[0028] Figure 1 This is a circuit structure diagram of the filter 10 according to the implementation method. Figure 1 The diagram also illustrates the antenna ANT, inductors L2 and L3 connected to filter 10. The antenna ANT is a multi-band antenna for transmitting and receiving high-frequency signals, such as those conforming to communication standards like LTE (Long Term Evolution). Inductor L2 is a matching circuit used to achieve impedance matching between filter 10 and antenna ANT, and inductor L3 is a matching circuit used to achieve impedance matching between filter 10 and circuits connected to terminal 20 (e.g., amplifier circuits, switches, or RFICs).

[0029] Filter 10 is an elastic wave filter that includes elastic wave resonators. Each elastic wave resonator constituting filter 10 can be a surface acoustic wave (SAW) resonator or an SAW (bulk acoustic wave) resonator. Furthermore, SAW includes, for example, surface waves, Love waves, leaky waves, Rayleigh waves, boundary waves, leaky SAWs, pseudo-SAWs, and plate waves.

[0030] Filter 10 includes series arm resonators 11, 12, 13, 14, and 15, parallel arm resonators 16, 17, 18, and 19, and inductor L1. The series arm resonators 11, 12, 13, 14, and 15, and the parallel arm resonators 16, 17, 18, and 19 form the passband of filter 10. Inductor L1 is used to adjust the passband of filter 10. Alternatively, filter 10 may not include inductor L1. Furthermore, filter 10 may also include other impedance elements (inductors or capacitors, etc.) to achieve a desired passband.

[0031] Series arm resonators 11, 12, 13, 14, and 15 are connected in series with each other on the path connecting the antenna ANT and terminal 20. Parallel arm resonator 16 is connected between a node on the aforementioned path between series arm resonators 11 and 12, and ground. Parallel arm resonator 17 is connected between a node on the aforementioned path between series arm resonators 12 and 13, and ground. Parallel arm resonator 18 is connected between a node on the aforementioned path between series arm resonators 13 and 14, and ground. Parallel arm resonator 19 is connected between a node on the aforementioned path between series arm resonators 14 and 15, and ground.

[0032] According to the above structure of filter 10, series arm resonators 11, 12, 13, 14 and 15 composed of elastic wave resonators are arranged in the series arm path, and parallel arm resonators 16, 17, 18 and 19 composed of elastic wave resonators are arranged in the parallel arm path. Therefore, an elastic wave filter with a low-loss passband and a steep transition band from the passband to the stopband can be realized.

[0033] The series arm resonators 11, 12, 13, 14, and 15, and the parallel arm resonators 16, 17, 18, and 19, are each a segmented resonator group composed of multiple segmented resonators connected in series. A segmented resonator group refers to an elastic wave resonator where the connection nodes between adjacent series-connected segmented resonators forming the group are not connected except to that adjacent segmented resonator. For example, no other components are connected between adjacent segmented resonators, and the connection nodes between adjacent segmented resonators are not connected to ground. By segmenting the elastic wave resonators in this way, the power consumption per unit area can be reduced, and the power tolerance of the filter 10 can be improved.

[0034] However, when the elastic wave resonator is divided into three or more segmented resonators connected in series, there will be segmented resonators that are configured to be sandwiched between other segmented resonators. Moreover, due to the interaction between this segmented resonator and the adjacent segmented resonators sandwiching it, the temperature of the elastic wave filter becomes prone to rise, resulting in a decrease in the power tolerance of the elastic wave filter.

[0035] The following description focuses on the application of the series arm resonator 11 of the present invention in order to solve such problems.

[0036] The filter 10 has at least three split resonators connected in series as series arm resonators 11. Here, the at least three split resonators are split resonators Sa, Sb, Sc, and Sd connected in series. Two adjacent split resonators among the at least three are referred to as the first split resonator and the second split resonator. Here, the first split resonator is composed of at least two split resonators connected in parallel. In other words, the first split resonator is divided into two split resonators in parallel. For example, considering split resonators Sa and Sb, split resonator Sb becomes the first split resonator, and split resonator Sa becomes the second split resonator. For example, considering split resonators Sb and Sc, split resonator Sb becomes the first split resonator, and split resonator Sc becomes the second split resonator. For example, considering split resonators Sc and Sd, split resonator Sd becomes the first split resonator, and split resonator Sc becomes the second split resonator.

[0037] At this point, the number of segmented resonators constituting the first segmented resonator is different from the number constituting the second segmented resonator. For example, the first segmented resonator is composed of at least two segmented resonators, while the second segmented resonator is composed of one segmented resonator. Specifically, the number of segmented resonators Sa constituting the second segmented resonator is one, the number of segmented resonators Sb constituting the first segmented resonator is two, the number of segmented resonators Sc constituting the second segmented resonator is one, and the number of segmented resonators Sd constituting the first segmented resonator is two.

[0038] That is, a segmented resonator Sa consists of one segmented resonator, which is called the segmented resonator Sa. A segmented resonator Sb consists of two segmented resonators Pb1 and Pb2 connected in parallel, and the set of segmented resonators Pb1 and Pb2 is called the segmented resonator Sb. A segmented resonator Sc consists of one segmented resonator, which is called the segmented resonator Sc. A segmented resonator Sd consists of two segmented resonators Pd1 and Pd2 connected in parallel, and the set of segmented resonators Pd1 and Pd2 is called the segmented resonator Sd.

[0039] Secondly, use Figure 2 The layout of the series arm resonator 11 is described.

[0040] Figure 2 This is a top view illustrating an example of the layout of the segmented resonator group (series arm resonator 11) according to an embodiment. For example, at least three segmented resonators (specifically, segmented resonators Sa, Sb, Sc, and Sd constituting the series arm resonator 11) each have IDT (Interdigital Transducer) electrodes and are arranged in a direction intersecting the propagation direction of the elastic wave. Figure 2 In the diagram, IDT electrodes are represented by squares, and illustrations of reflectors, etc., are omitted.

[0041] The direction of propagation of elastic waves is Figure 2 The direction that intersects the direction of elastic wave propagation in the left-right direction of the paper is, for example, the direction that is orthogonal to the direction of elastic wave propagation. Figure 2 The direction from top to bottom on the paper. Additionally, the direction intersecting the direction of elastic wave propagation doesn't necessarily have to be orthogonal to the direction of elastic wave propagation; it can also be determined from... Figure 2 The vertical direction of the paper is deviated.

[0042] At least two segmented resonators in the first segmented resonator (segmented resonators Sb and Sd) (segmented resonators Pb1 and Pb2 for segmented resonator Sb, and segmented resonators Pd1 and Pd2 for segmented resonator Sd) are arranged in the direction of elastic wave propagation. For example, segmented resonators Pb1 and Pb2, and segmented resonators Pd1 and Pd2 are arranged in the same direction as segmented resonators Sa, Sb, Sc, and Sd ( Figure 2 The direction perpendicular to the top and bottom of the paper (the direction perpendicular to the top and bottom of the paper) Figure 2 Arranged on the left and right sides of the paper.

[0043] The segmented resonators Sb and Sd can also be segmented in parallel, making the area of ​​the IDT electrode portion the same as when they are not segmented in parallel. For example, it is possible to make the area of ​​the IDT electrode portion of the segmented resonator Sb the same as the area of ​​the IDT electrode portion of the segmented resonator Sa when the segmented resonator Sb is not segmented in parallel. Moreover, it is possible to make the sum of the areas of the IDT electrodes of the segmented resonator Pb1 and the IDT electrodes of the segmented resonator Pb2 ​​the same as the area of ​​the IDT electrodes of the segmented resonator Sa when the segmented resonator Sb is segmented in parallel. That is, the first segmented resonator can be segmented in parallel without increasing the area. In this case, the power withstand capability can be improved without changing the capacitance. In addition, the statement that the area is the same as when it is not segmented in parallel also includes the case where the area is slightly increased compared to when it is not segmented in parallel, that is, the amount corresponding to the spacing between the segmented resonators segmented in parallel and the amount of reflectors provided between the segmented resonators segmented in parallel.

[0044] exist Figure 2 In the diagram, a cross-shaped mark is made at the point where the elastic wave excited by each IDT electrode reaches its maximum amplitude. The point of maximum amplitude at each IDT electrode represents the center of the propagation direction of the elastic wave at that IDT electrode. This is because the two ends of the IDT electrode become nodes of the elastic wave's vibration, and the nodes at both ends and the center of those nodes become antinodes of the elastic wave's vibration. Furthermore, the point of maximum amplitude of the elastic wave excited by the IDT electrode can be interpreted as the center of the propagation direction of the elastic wave at the IDT electrode.

[0045] like Figure 2As shown, when viewed from a direction orthogonal to the propagation direction of the elastic wave, the maximum amplitude points of the elastic waves excited by the IDT electrodes of adjacent first and second segmented resonators (Sa, Sb, Sc, and Sd) in a direction intersecting the propagation direction of the elastic wave are staggered. For example, considering the adjacent first and second segmented resonators, if we focus on segmented resonators Sb and Sa, when viewed from a direction orthogonal to the propagation direction of the elastic wave, the maximum amplitude points of the elastic waves excited by the IDT electrodes of segmented resonator Sb (specifically, the maximum amplitude points of the elastic waves excited by the IDT electrodes of segmented resonators Pb1 and Pb2) and the maximum amplitude points of the elastic waves excited by the IDT electrodes of segmented resonator Sa are staggered. For example, considering the adjacent first and second segmented resonators, if we focus on the segmented resonators Sb and Sc, when viewed from a direction orthogonal to the propagation direction of the elastic wave, the maximum amplitude point of the elastic wave excited by the IDT electrode of the segmented resonator Sb (specifically the maximum amplitude point of the elastic wave excited by the IDT electrode of the segmented resonator Pb1 and the maximum amplitude point of the elastic wave excited by the IDT electrode of the segmented resonator Pb2) is offset from the maximum amplitude point of the elastic wave excited by the IDT electrode of the segmented resonator Sc. For example, considering the first and second adjacent segmented resonators, if we focus on the segmented resonators Sd and Sc, when viewed from a direction orthogonal to the propagation direction of the elastic wave, the point of maximum amplitude of the elastic wave excited by the IDT electrode of the segmented resonator Sd (specifically, the point of maximum amplitude of the elastic wave excited by the IDT electrode of the segmented resonator Pd1 and the point of maximum amplitude of the elastic wave excited by the IDT electrode of the segmented resonator Pd2) is offset from the point of maximum amplitude of the elastic wave excited by the IDT electrode of the segmented resonator Sc.

[0046] As a result, the amplitude maximum points of the adjacent first and second segmented resonators become farther apart, meaning that the adjacent first and second segmented resonators become less likely to interact, thus suppressing localized temperature rises. While comparing with a comparative example, it will be explained to what extent temperature rises can be suppressed and to what extent power tolerance can be improved by observing from a direction orthogonal to the propagation direction of the elastic wave that the amplitude maximum points of the elastic waves excited by the IDT electrodes of the adjacent first and second segmented resonators are offset.

[0047] Figure 3 This is a circuit diagram of the filter 10a involved in the comparative example.

[0048] The filter 10a in the comparative example differs from the filter 10 in the embodiment in that it has a series arm resonator 11a instead of a series arm resonator 11. Other aspects are the same as the structure in the filter 10 in the embodiment, and therefore description is omitted.

[0049] The series arm resonator 11a is a group of segmented resonators consisting of multiple segmented resonators connected in series. Here, the series arm resonator 11a has segmented resonators Saa, Sba, Sca, and Sda connected in series.

[0050] Figure 4 This is a top view showing an example layout of the segmented resonator group (series arm resonator 11a) involved in the comparative example. The segmented resonators Saa, Sba, Sca, and Sda constituting the series arm resonator 11a each have IDT electrodes and are arranged in a direction orthogonal to the propagation direction of the elastic wave. Figure 4 In the diagram, IDT electrodes are represented by squares, and illustrations of reflectors, etc., are omitted.

[0051] The direction of propagation of elastic waves is Figure 4 The direction perpendicular to the direction of elastic wave propagation is the left-right direction of the paper. Figure 4 The top and bottom direction on the paper.

[0052] exist Figure 4 In the diagram, a cross-shaped mark is made at the point where the amplitude of the elastic wave excited by each IDT electrode is maximum. The point of maximum amplitude at each IDT electrode becomes the center of the propagation direction of the elastic wave at that IDT electrode. Figure 3 as well as Figure 4 As shown, in the comparative example, the series arm resonator 11a does not have a parallel segmented resonator. When viewed from a direction orthogonal to the propagation direction of the elastic wave, the points of maximum amplitude of the elastic wave excited by the IDT electrodes of the segmented resonators Saa, Sba, Sca and Sda overlap.

[0053] Figure 5A This is a diagram showing the temperature distribution of the piezoelectric substrate in which the filter 10a of the comparative example is formed. For example, the filter 10a is formed from a piezoelectric substrate, in... Figure 5A The temperature distribution of the piezoelectric substrate around the series arm resonator 11a in filter 10a is shown in the figure.

[0054] Viewed from a direction orthogonal to the propagation direction of the elastic wave, the points of maximum amplitude of the elastic waves excited by the IDT electrodes of the segmented resonators Saa, Sba, Sca, and Sda constituting the series arm resonator 11a overlap. Therefore, the temperature around the series arm resonator 11a increases, and the piezoelectric substrate forming the filter 10a... Figure 5A The maximum temperature at the shown section is 148°C.

[0055] Figure 5B This is a diagram showing the temperature distribution of the piezoelectric substrate forming the filter 10 according to the embodiment. For example, the filter 10 is formed from a piezoelectric substrate, in... Figure 5B The temperature distribution of the piezoelectric substrate around the series arm resonator 11 in the filter 10 is shown in the figure.

[0056] Viewed from a direction orthogonal to the propagation direction of the elastic wave, the maximum amplitude points of the elastic waves excited by the IDT electrodes of adjacent first and second segmented resonators among the segmented resonators Sa, Sb, Sc, and Sd constituting the series arm resonator 11 are offset. Therefore, the temperature around the series arm resonator 11 decreases, and the piezoelectric substrate forming the filter 10... Figure 5B The maximum temperature at the part shown is 121℃.

[0057] In this way, the maximum amplitude points of adjacent first and second segmented resonators become far apart, and adjacent first and second segmented resonators become less likely to interact, thus suppressing local temperature rise.

[0058] Figure 6 This is a graph showing the power handling capability of the filter 10 according to the embodiment and the filter 10a according to the comparative example. The horizontal axis shows the input power to each filter, and the vertical axis shows the output power relative to the input power. It shows that the higher the output power, the higher the power handling capability.

[0059] In the filter 10 described in the implementation, since the point of maximum amplitude is dispersed, localized temperature rise can be suppressed, as can the degradation of insertion loss and frequency shift. Thus, as... Figure 6 As shown, the output power can be improved, and the power handling capability of the filter 10 according to the embodiment is improved compared to that of the filter 10a involved in the comparative example. Furthermore, as described above, the parallel-segmented resonators (first segmented resonators) can be parallel-segmented while maintaining the area of ​​the IDT electrode portion, thus effectively improving the power handling capability while suppressing the enlargement of the filter 10.

[0060] As described above, the filter 10 has at least three segmented resonators connected in series with each other. Each of the at least three segmented resonators has an IDT electrode and is arranged in a direction that intersects the propagation direction of the elastic wave. When viewed from a direction orthogonal to the propagation direction of the elastic wave, the IDT electrodes of adjacent first segmented resonators (e.g., segmented resonator Sb) and second segmented resonators (e.g., segmented resonator Sa) are centrally offset in the propagation direction of the elastic wave.

[0061] For each segmented resonator, the excitation at the center of the elastic wave propagation direction of the IDT electrode (i.e., the point of maximum amplitude of the elastic wave excited by the IDT electrode) is strong and prone to heating. If such maximum amplitude points overlap when viewed from a direction orthogonal to the elastic wave propagation direction, the maximum amplitude points of adjacent segmented resonators will be located close to each other. Due to the interaction between adjacent segmented resonators, the temperature is prone to localized rise, and the power withstand capability of the elastic wave filter decreases. In contrast, according to this method, for the first and second segmented resonators adjacent in a direction intersecting the elastic wave propagation direction, when viewed from a direction orthogonal to the elastic wave propagation direction, the center of the elastic wave propagation direction of the IDT electrode (i.e., the point of maximum amplitude of the elastic wave excited by the IDT electrode) is offset. Therefore, the maximum amplitude points of adjacent first and second segmented resonators become farther apart, and adjacent first and second segmented resonators become less likely to interact, thus suppressing localized temperature rise. Therefore, the power withstand capability can be effectively improved.

[0062] Alternatively, the first segmented resonator can be configured to consist of at least two segmented resonators connected in parallel, with the at least two segmented resonators in the first segmented resonator arranged in the direction of elastic wave propagation.

[0063] In this way, by dividing the first segmented resonator into at least two segmented resonators in parallel, the point of maximum amplitude of the first segmented resonator can be offset from the center of the first segmented resonator (the center of the set of at least two segmented resonators) to the center of each of the at least two segmented resonators after being divided, when viewed from a direction orthogonal to the direction of propagation of the elastic wave. In other words, the point of maximum amplitude of the first segmented resonator can be dispersed from the center of the set of at least two segmented resonators to both ends of the set. Thus, when viewed from a direction orthogonal to the direction of propagation of the elastic wave, the points of maximum amplitude of adjacent first and second segmented resonators can be offset.

[0064] Alternatively, the number of segmented resonators constituting the first segmented resonator can be different from the number of segmented resonators constituting the second segmented resonator. For example, the second segmented resonator can be configured to consist of a single segmented resonator.

[0065] In this way, by making the number of segmented resonators constituting the first segmented resonator different from the number of segmented resonators constituting the second segmented resonator, the points of maximum amplitude of the segmented resonators in the first segmented resonator and the second segmented resonator become easily offset when viewed from a direction orthogonal to the propagation direction of the elastic wave. For example, by having the first segmented resonator composed of at least two segmented resonators and the second segmented resonator composed of one segmented resonator, the points of maximum amplitude in the first segmented resonator are dispersed from the center of the elastic wave propagation direction of the first segmented resonator towards both ends, while the points of maximum amplitude in the second segmented resonator are located at the center of the elastic wave propagation direction of the second segmented resonator. Therefore, when viewed from a direction orthogonal to the propagation direction of the elastic wave, the points of maximum amplitude of the adjacent first and second segmented resonators can be offset.

[0066] (Other implementation methods)

[0067] The above description illustrates the elastic wave filter of the present invention through examples, but the present invention is not limited to the above-described embodiments. Other embodiments implemented by combining any of the constituent elements in the above embodiments, variations of the above embodiments that can be conceived by those skilled in the art through various modifications without departing from the spirit of the present invention, and various devices incorporating the elastic wave filter of the present invention are also included in the present invention.

[0068] For example, the elastic wave filter of the present invention has at least three segmented resonators connected in series. When viewed from a direction orthogonal to the propagation direction of the elastic wave, the maximum amplitude points of the elastic waves excited by the IDT electrodes of the adjacent first and second segmented resonators among the at least three segmented resonators are staggered, but the staggered manner of the maximum amplitude points is not particularly limited.

[0069] For example, it can also be like Figures 7A to 7E As shown, the points of maximum amplitude are offset.

[0070] Figures 7A to 7E This is a diagram illustrating an example of the layout and circuit structure of a segmented resonator group according to other embodiments. The layout of the segmented resonator group is shown on the left side of each diagram, and the circuit structure of the segmented resonator group is shown on the right side. Here, an example of a segmented resonator group consisting of three segmented resonators Sa, Sb, and Sc connected in series in the order of segmented resonators Sa, Sb, and Sc is shown. Figures 7A to 7E .exist Figure 7A , Figure 7B , Figure 7D as well as Figure 7EIn this context, for adjacent segmented resonators Sa and Sb, segmented resonator Sa is designated as the second segmented resonator, and segmented resonator Sb as the first segmented resonator. Similarly, for adjacent segmented resonators Sb and Sc, segmented resonator Sb is designated as the first segmented resonator, and segmented resonator Sc as the second segmented resonator. Figure 7C In this context, for adjacent segmented resonators Sa and Sb, segmented resonator Sa is designated as the first segmented resonator, and segmented resonator Sb as the second segmented resonator. Similarly, for adjacent segmented resonators Sb and Sc, segmented resonator Sb is designated as the second segmented resonator, and segmented resonator Sc as the first segmented resonator. Figures 7A to 7E On the left, the IDT electrode is represented by a square, and illustrations of reflectors, etc., are omitted. Furthermore, in Figures 7A to 7E On the left side, a cross-shaped mark is marked at the point where the amplitude of the elastic wave excited by each IDT electrode is maximum. The point where the amplitude of each IDT electrode is maximum is the center of the propagation direction of the elastic wave of each IDT electrode.

[0071] like Figure 7A As shown, among the three segmented resonators Sa, Sb, and Sc, the segmented resonator Sb sandwiched between segmented resonators Sa and Sc can also be segmented in parallel and composed of segmented resonators Pb1 and Pb2 connected in parallel. That is, in the segmented resonator group, the segmented resonators can also be connected in series in the following order: a second segmented resonator composed of one segmented resonator, a first segmented resonator composed of two segmented resonators connected in parallel, and a second segmented resonator composed of one segmented resonator.

[0072] like Figure 7B As shown, among the three segmented resonators Sa, Sb, and Sc, adjacent segmented resonators Sb and Sc can also be segmented in parallel and constructed from segmented resonators connected in parallel (segmented resonators Pb1 and Pb2 for segmented resonator Sb, and segmented resonators Pc1 and Pc2 for segmented resonator Sc). That is, in the segmented resonator group, the segmented resonators can also be connected in series in the following order: a second segmented resonator composed of one segmented resonator, a first segmented resonator composed of two segmented resonators connected in parallel, and a second segmented resonator composed of two segmented resonators connected in parallel.

[0073] In addition, such as Figure 7BAs shown, the IDT electrodes of the segmented resonators Pb1 and Pb2 in the first segmented resonator Sb, and the segmented resonators Pc1 and Pc2 in the second segmented resonator Sc, can also be arranged in the direction of elastic wave propagation. Furthermore, the ratio of the lengths of the IDT electrodes of the segmented resonators Pb1 and Pb2 in the first segmented resonator Sb, and the ratio of the lengths of the IDT electrodes of the segmented resonators Pc1 and Pc2 in the second segmented resonator Sc, in the direction of elastic wave propagation, can also be different. For example, the ratio of the lengths of the IDT electrodes of the segmented resonators Pb1 and Pb2 in the direction of elastic wave propagation in the segmented resonator Sb can be 1:1, and the ratio of the lengths of the IDT electrodes of the segmented resonators Pc1 and Pc2 in the direction of elastic wave propagation in the segmented resonator Sc can be 1:2.

[0074] like Figure 7C As shown, among the three segmented resonators Sa, Sb, and Sc, the segmented resonators Sa and Sc, which sandwich the segmented resonator Sb, can also be segmented in parallel and constructed from segmented resonators connected in parallel (segmented resonators Pa1 and Pa2 for segmented resonator Sa, and segmented resonators Pc1 and Pc2 for segmented resonator Sc). That is, in the segmented resonator group, the segmented resonators can also be connected in series in the following order: a first segmented resonator composed of two segmented resonators connected in parallel, a second segmented resonator composed of one segmented resonator, and a third segmented resonator composed of two segmented resonators connected in parallel.

[0075] like Figure 7D As shown, among the three segmented resonators Sa, Sb, and Sc, adjacent segmented resonators Sa and Sb can also be segmented in parallel and constructed from segmented resonators connected in parallel (segmented resonators Pa1 and Pa2 for segmented resonator Sa, and segmented resonators Pb1 and Pb2 for segmented resonator Sb). That is, in the segmented resonator group, the segmented resonators can also be connected in series in the following order: a second segmented resonator composed of two segmented resonators connected in parallel, a first segmented resonator composed of two segmented resonators connected in parallel, and a second segmented resonator composed of one segmented resonator.

[0076] In addition, such as Figure 7DAs shown, the IDT electrodes of the segmented resonators Pa1 and Pa2 in the segmented resonator Sa (as the second segmented resonator) and the segmented resonators Pb1 and Pb2 in the segmented resonator Sb (as the first segmented resonator) can also be arranged in the direction of elastic wave propagation. Furthermore, the ratio of the lengths of the IDT electrodes of the segmented resonators Pa1 and Pa2 in the direction of elastic wave propagation in the segmented resonator Sa to that of the segmented resonators Pb1 and Pb2 in the direction of elastic wave propagation in the segmented resonator Sb can also be different. For example, the ratio of the lengths of the IDT electrodes of the segmented resonators Pa1 and Pa2 in the direction of elastic wave propagation in the segmented resonator Sa can be 1:2, and the ratio of the lengths of the IDT electrodes of the segmented resonators Pb1 and Pb2 in the direction of elastic wave propagation in the segmented resonator Sb can be 1:1.

[0077] like Figure 7E As shown, all three segmented resonators Sa, Sb, and Sc can also be segmented in parallel and constructed from mutually connected segmented resonators (Pa1 and Pa2 for segmented resonator Sa, Pb1 and Pb2 for segmented resonator Sb, and Pc1 and Pc2 for segmented resonator Sc). That is, in the segmented resonator group, the segmented resonators can also be connected in series in the following order: a second segmented resonator composed of two mutually connected segmented resonators, a first segmented resonator composed of two mutually connected segmented resonators, and a second segmented resonator composed of two mutually connected segmented resonators.

[0078] In addition, such as Figure 7EAs shown, the IDT electrodes of the segmented resonators Pa1 and Pa2 in the segmented resonator Sa (as the second segmented resonator), Pb1 and Pb2 in the segmented resonator Sb (as the first segmented resonator), and Pc1 and Pc2 in the segmented resonator Sc (as the second segmented resonator) can also be arranged in the direction of elastic wave propagation. Furthermore, the ratio of the lengths of the IDT electrodes of Pa1 and Pa2 in the direction of elastic wave propagation of the segmented resonators Sa (as the second segmented resonator) and the ratio of the lengths of the IDT electrodes of Pb1 and Pb2 in the direction of elastic wave propagation of the segmented resonators Sb (as the first segmented resonator) can also be different. For example, the ratio of the lengths of the IDT electrodes of Pa1 and Pa2 in the direction of elastic wave propagation of the segmented resonators Sa (as the second segmented resonator) can be 1:1, and the ratio of the lengths of the IDT electrodes of Pb1 and Pb2 in the direction of elastic wave propagation of the segmented resonators Sb (as the first segmented resonator) can be 1:2.

[0079] Furthermore, the ratio of the lengths of the elastic waves in the propagation direction of the IDT electrodes of the segmented resonators Pb1 and Pb2 in the segmented resonator Sb (which is the first segmented resonator) and the ratio of the lengths of the elastic waves in the propagation direction of the IDT electrodes of the segmented resonators Pc1 and Pc2 in the segmented resonator Sc (which is the second segmented resonator) can also be different. For example, the ratio of the lengths of the elastic waves in the propagation direction of the IDT electrodes of the segmented resonators Pb1 and Pb2 in the segmented resonator Sb is 1:2, and the ratio of the lengths of the elastic waves in the propagation direction of the IDT electrodes of the segmented resonators Pc1 and Pc2 in the segmented resonator Sc is 2:1. Here, we assume that 1:2 and 2:1 are different.

[0080] like Figure 7B , Figure 7D as well as Figure 7E As shown, the second segmented resonator may not consist of a single segmented resonator, but may consist of at least two segmented resonators connected in parallel. Alternatively, the at least two segmented resonators in the second segmented resonator may be arranged in the direction of elastic wave propagation, and the ratio of the lengths of the IDT electrodes of the at least two segmented resonators in the first segmented resonator in the direction of elastic wave propagation may differ from the ratio of the lengths of the IDT electrodes of the at least two segmented resonators in the second segmented resonator in the direction of elastic wave propagation.

[0081] Accordingly, for the first and second segmented resonators, by making the length ratio of the IDT electrodes of each segmented resonator different in the direction of elastic wave propagation, the maximum amplitude points of the segmented resonators in the first and second segmented resonators become easily offset when viewed from a direction orthogonal to the direction of elastic wave propagation. In particular, the number of segmented resonators constituting the first and second segmented resonators can be the same; even in this case, the maximum amplitude points can still be offset by the aforementioned difference in length ratio.

[0082] Furthermore, for example, to offset the points of maximum amplitude, the segmented resonator may not be composed of at least two segmented resonators connected in parallel. For instance, in an elastic wave filter, the first and second adjacent segmented resonators of at least three interconnected segmented resonators may each be composed of a single segmented resonator, and the lengths of the elastic waves propagating in the IDT electrodes may differ for each segmented resonator. This is because by making the lengths of the elastic waves propagating in the IDT electrodes different in the first and second segmented resonators, the points of maximum amplitude (i.e., the center of the elastic waves propagating in the respective IDT electrodes) become offset when viewed from a direction orthogonal to the propagation direction of the elastic waves.

[0083] Furthermore, for example, the elastic wave filter can have at least three segmented resonators, as long as there are more than three, without any particular limitation.

[0084] Furthermore, for the first and second segmented resonators, when they are composed of at least two segmented resonators connected in parallel, they are not limited to two segmented resonators connected in parallel, but can also be composed of three or more segmented resonators connected in parallel.

[0085] Industrial availability

[0086] This invention can be widely used in communication devices such as portable telephones that have elastic wave filters with segmented resonators.

[0087] Explanation of reference numerals in the attached figures

[0088] 10, 10a filters;

[0089] Series arm harmonic oscillators 11, 11a, 12, 13, 14, 15;

[0090] Parallel arm harmonic oscillators 16, 17, 18, and 19;

[0091] 20 terminals;

[0092] ANT antenna;

[0093] L1, L2, L3 inductors;

[0094] Pa1, Pa2, Pb1, Pb2, Pc1, Pc2, Pd1, Pd2 divide the resonator;

[0095] Sa, Sb, Sc, Sd, Saa, Sba, Sca, Sda are segmented resonators.

Claims

1. An elastic wave filter comprising at least three segmented resonators connected in series. The at least three segmented resonators each have interdigitated transducer (IDT) electrodes and are arranged in a direction intersecting the propagation direction of the elastic wave. Viewed from a direction orthogonal to the propagation direction of the elastic wave, the centers of the IDT electrodes of the adjacent first and second segmented resonators among the at least three segmented resonators are offset in the direction of elastic wave propagation. The first segmented resonator is composed of at least two segmented resonators connected in parallel. The at least two segmented resonators in the first segmented resonator are arranged in the direction of elastic wave propagation. The number of segmented resonators constituting the first segmented resonator is different from the number of segmented resonators constituting the second segmented resonator.

2. The elastic wave filter according to claim 1, wherein, The second segmented resonator consists of a single segmented resonator.

3. An elastic wave filter comprising at least three segmented resonators connected in series. The at least three segmented resonators each have interdigitated transducer (IDT) electrodes and are arranged in a direction intersecting the propagation direction of the elastic wave. Viewed from a direction orthogonal to the propagation direction of the elastic wave, the centers of the IDT electrodes of the adjacent first and second segmented resonators among the at least three segmented resonators are offset in the direction of elastic wave propagation. The first segmented resonator is composed of at least two segmented resonators connected in parallel. The at least two segmented resonators in the first segmented resonator are arranged in the direction of elastic wave propagation. The second segmented resonator is composed of at least two segmented resonators connected in parallel. The at least two segmented resonators in the second segmented resonator are arranged in the direction of elastic wave propagation. The ratio of the lengths of the elastic waves of the IDT electrodes of the at least two segmented resonators in the first segmented resonator along the direction of propagation is different from the ratio of the lengths of the elastic waves of the IDT electrodes of the at least two segmented resonators in the second segmented resonator along the direction of propagation.

Images