Elastic wave filter and multiplexer

Abstract

The elastic wave filter (40) includes a longitudinal coupling resonator (1) having a plurality of IDT electrodes and reflectors. [i] The distance between electrode fingers (Fe(k)) and electrode fingers (Fe(k+1)) is defined as the k-th electrode finger pitch (P(k)). [ii] Among three adjacent electrode fingers, namely electrode finger (Fe(k-1)), electrode finger (Fe(k)), and electrode finger (Fe(k+1)), the value obtained by dividing the difference between the electrode finger pitch (P(k)) and the interval average electrode finger pitch by the overall average electrode finger pitch is defined as the pitch deviation rate. [iii] The distribution obtained by calculating the pitch deviation rate for all electrode fingers of the IDT electrode or the reflector is defined as the histogram of the pitch deviation rate. In this case, the standard deviation of the pitch deviation rate in the histogram of at least one of the plurality of IDT electrodes or reflectors is 1.4% or more.

Description

Technical Field

[0001] The present invention relates to an elastic wave filter and a multiplexer including the elastic wave filter. Background Art

[0002] Patent Document 1 discloses the following elastic wave filter. In a longitudinal coupling resonator in which a plurality of IDT (InterDigital Transducer) electrodes and reflectors are arranged in the elastic wave propagation direction, a sub-excitation region in which the electrode finger pitch changes stepwise is arranged between the main excitation regions of the IDT electrodes or between the main excitation region and the reflector. Thereby, the low loss property of the elastic wave filter is improved.

[0003] Prior Art Documents

[0004] Patent Document

[0005] Patent Document 1: WO 2003 / 003574 Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] However, in an elastic wave filter including a longitudinal coupling resonator having a sub-excitation region in which the distribution of the electrode finger pitch changes regularly as in Patent Document 1, there are the following problems: useless acoustic waves are excited, and thus sufficient attenuation characteristics cannot be obtained. In addition, there is a problem that the isolation characteristic of a multiplexer including the above elastic wave filter deteriorates.

[0008] Therefore, the present invention has been made to solve the above problems, and an object thereof is to provide an elastic wave filter with improved attenuation characteristics and a multiplexer with improved isolation characteristics.

[0009] Means for Solving the Problems

[0010] In order to achieve the above object, a surface acoustic wave filter according to one aspect of the present invention includes longitudinal coupling resonators, the longitudinal coupling resonators having: a substrate having piezoelectricity; a plurality of IDT electrodes provided on the substrate and arranged in the surface acoustic wave propagation direction; and reflectors arranged adjacent to the plurality of IDT electrodes in the surface acoustic wave propagation direction. Among them, each of the plurality of IDT electrodes and the reflectors includes a plurality of electrode fingers, the plurality of electrode fingers extending in a direction crossing the surface acoustic wave propagation direction and arranged parallel to each other. (1) The distance between the k-th (k is an integer of 2 or more) electrode finger and the (k + 1)-th electrode finger in the surface acoustic wave propagation direction is defined as the k-th electrode finger pitch. (2) Among the adjacent three electrode fingers of the (k - 1)-th electrode finger, the k-th electrode finger, and the (k + 1)-th electrode finger, the value obtained by dividing the difference between the k-th electrode finger pitch and the interval average electrode finger pitch by the overall average electrode finger pitch is defined as the pitch deviation rate of the k-th electrode finger. The interval average electrode finger pitch is the average of the (k - 1)-th electrode finger pitch and the (k + 1)-th electrode finger pitch, and the overall average electrode finger pitch is the average pitch of all the electrode fingers of the IDT electrode or the reflector including the adjacent three electrode fingers. (3) The distribution of the pitch deviation rates obtained by calculating the pitch deviation rate of the k-th electrode finger for all the electrode fingers of the IDT electrode or the reflector including the adjacent three electrode fingers is defined as the histogram of the pitch deviation rate. In this case, the standard deviation of the pitch deviation rate in the histogram of at least one of the plurality of IDT electrodes and the reflectors is 1.4% or more.

[0011] Effect of the Invention

[0012] According to the present invention, a surface acoustic wave filter with improved attenuation characteristics and a multiplexer with improved isolation characteristics can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a circuit structure diagram of the surface acoustic wave filter according to the embodiment.

[0014] Figure 2 is a schematic top view showing the electrode structure of the longitudinal coupling resonator according to the embodiment.

[0015] Figure 3 is a graph showing the distribution of the electrode finger pitches of the longitudinal coupling resonator according to the embodiment.

[0016] Figure 4 is a graph showing the distribution of the electrode finger pitches of the longitudinal coupling resonator according to the comparative example.

[0017] Figure 5It is a diagram showing the effect of the irregular electrode finger pitch distribution of the longitudinal coupling resonator involved in the embodiment.

[0018] Figure 6 It is a diagram showing the pitch deviation rate and its standard deviation in the irregular electrode finger pitch distribution of the longitudinal coupling resonator involved in the embodiment.

[0019] Figure 7 It is a structural diagram of the multiplexer and its peripheral circuit involved in Embodiment 1.

[0020] Figure 8 It is a chart comparing the passing characteristics and isolation characteristics of the multiplexers involved in Embodiment 1 and Comparative Example 1.

[0021] Figure 9 It is a chart comparing the voltage standing wave ratios of the multiplexers involved in Embodiment 1 and Comparative Example 1.

[0022] Figure 10 It is a chart showing the relationship between the standard deviation of the pitch deviation rate of the longitudinal coupling resonator and the isolation of the multiplexer.

[0023] Figure 11A It is a circuit structural diagram of the surface acoustic wave filter involved in Embodiment 2.

[0024] Figure 11B It is a chart comparing the passing characteristics of the surface acoustic wave filters involved in Embodiment 2 and Comparative Example 2.

[0025] Figure 12A It is a chart showing the electrode finger configuration structure and the distribution of the electrode finger pitch of the longitudinal coupling resonator included in the surface acoustic wave filter involved in Embodiment 3.

[0026] Figure 12B It is a chart comparing the passing characteristics and isolation characteristics of the multiplexers involved in Embodiment 3 and Comparative Example 3.

[0027] Figure 13 It is a structural diagram of the multiplexer and its peripheral circuit involved in Embodiment 4.

[0028] Figure 14 It is a chart comparing the passing characteristics of the surface acoustic wave filters involved in Embodiment 4, Comparative Example 4, and Comparative Example 5. Detailed Embodiments

[0029] Hereinafter, embodiments of the present invention will be described in detail with reference to the embodiments and the drawings. In addition, all the embodiments described below show general or specific examples. The numerical values, shapes, materials, components, arrangements of components, connection manners, etc. shown in the following embodiments are merely examples, and the gist thereof is not intended to limit the present invention. Among the components in the following embodiments, the components not described in the independent claims are described as optional components. In addition, the sizes or size ratios of the components shown in the drawings are not necessarily precise.

[0030] (Embodiment)

[0031] [1. Structure of the surface acoustic wave filter 40 according to the embodiment]

[0032] Figure 1 is a circuit structure diagram of the surface acoustic wave filter 40 according to the embodiment. In addition, Figure 2 is a schematic top view showing the electrode structure of the longitudinal coupling resonator 1 according to the embodiment. In Figure 2 shows the planar layout structure of the IDT electrodes and reflectors constituting the longitudinal coupling resonator 1 and the electrical connection state between the IDT electrodes. In addition, Figure 2 the longitudinal coupling resonator 1 shown is used to illustrate a typical planar layout structure of the IDT electrodes, and the number of electrode fingers, length, electrode finger pitch, etc. of the IDT electrodes constituting the same are not limited thereto.

[0033] As Figure 1 shown, the surface acoustic wave filter 40 includes a longitudinal coupling resonator 1, series arm resonators 31s and 32s, parallel arm resonators 31p and 32p, and input / output terminals 110 and 120.

[0034] The series arm resonators 31s and 32s are surface acoustic wave resonators connected in series on the path connecting the input / output terminal 110 and the input / output terminal 120. The parallel arm resonators 31p and 32p are surface acoustic wave resonators respectively connected between the nodes on the above path and the ground.

[0035] In addition, as Figure 2As shown, the longitudinal coupling resonator 1 includes longitudinally coupled resonators 10 and 20 connected in parallel, and is disposed between the terminal 130 and the input / output terminal 120. The longitudinally coupled resonator 10 has: five IDT (InterDigital Transducer) electrodes 11, 12, 13, 14, and 15 arranged in the elastic wave propagation direction on a piezoelectric substrate; and reflectors 19A and 19B arranged adjacent to the five IDT electrodes in the elastic wave propagation direction. The longitudinally coupled resonator 20 has: five IDT electrodes 21, 22, 23, 24, and 25 arranged in the elastic wave propagation direction on a piezoelectric substrate; and reflectors 29A and 29B arranged adjacent to the five IDT electrodes in the elastic wave propagation direction.

[0036] The IDT electrodes 11 to 15, 21 to 25, reflectors 19A, 19B, 29A, and 29B are formed on a piezoelectric substrate, and each of the IDT electrodes 11 to 15 and 21 to 25 and the piezoelectric substrate constitute a surface acoustic wave resonator.

[0037] Each of the IDT electrodes 11 to 15, 21 to 25, and reflectors 19A, 19B, 29A, and 29B includes a plurality of electrode fingers that extend in a direction intersecting the elastic wave propagation direction and are arranged parallel to each other.

[0038] The IDT electrode 11 includes comb-shaped electrodes 11a and 11b. The comb-shaped electrode 11a is an example of the first comb-shaped electrode, including electrode fingers that are part of the multiple electrode fingers constituting the IDT electrode 11 and a bus bar electrode that connects one ends of the part of the electrode fingers to each other, and is connected to the input / output terminal 120. The comb-shaped electrode 11b is an example of the second comb-shaped electrode, including electrode fingers that are another part of the multiple electrode fingers constituting the IDT electrode 11 and a bus bar electrode that connects the other ends of the other part of the electrode fingers to each other, and is connected to the ground. The electrode fingers constituting the comb-shaped electrode 11a and the electrode fingers constituting the comb-shaped electrode 11b are interlaced with each other. The IDT electrode 13 includes comb-shaped electrodes 13a (the first comb-shaped electrode) and 13b (the second comb-shaped electrode). The comb-shaped electrode 13a is connected to the input / output terminal 120, and the comb-shaped electrode 13b is connected to the ground. The IDT electrode 15 includes comb-shaped electrodes 15a (the first comb-shaped electrode) and 15b (the second comb-shaped electrode). The comb-shaped electrode 15a is connected to the input / output terminal 120, and the comb-shaped electrode 15b is connected to the ground. The IDT electrode 21 includes comb-shaped electrodes 21a (the first comb-shaped electrode) and 21b (the second comb-shaped electrode). The comb-shaped electrode 21a is connected to the input / output terminal 120, and the comb-shaped electrode 21b is connected to the ground. The IDT electrode 23 includes comb-shaped electrodes 23a (the first comb-shaped electrode) and 23b (the second comb-shaped electrode). The comb-shaped electrode 23a is connected to the input / output terminal 120, and the comb-shaped electrode 23b is connected to the ground. The IDT electrode 25 includes comb-shaped electrodes 25a (the first comb-shaped electrode) and 25b (the second comb-shaped electrode). The comb-shaped electrode 25a is connected to the input / output terminal 120, and the comb-shaped electrode 25b is connected to the ground.

[0039] The IDT electrode 12 includes comb-shaped electrodes 12a and 12b. The comb-shaped electrode 12b is an example of the first comb-shaped electrode, and includes electrode fingers that are a part of the plurality of electrode fingers constituting the IDT electrode 12 and a bus bar electrode that connects one ends of the part of the electrode fingers to each other, and is connected to the terminal 130. The comb-shaped electrode 12a is an example of the second comb-shaped electrode, and includes electrode fingers that are another part of the plurality of electrode fingers constituting the IDT electrode 12 and a bus bar electrode that connects the other ends of the other part of the electrode fingers to each other, and is connected to the ground. The electrode fingers constituting the comb-shaped electrode 12a and the electrode fingers constituting the comb-shaped electrode 12b are interdigitated with each other. The IDT electrode 14 includes comb-shaped electrodes 14b (the first comb-shaped electrode) and 14a (the second comb-shaped electrode). The comb-shaped electrode 14b is connected to the terminal 130, and the comb-shaped electrode 14a is connected to the ground. The IDT electrode 22 includes comb-shaped electrodes 22b (the first comb-shaped electrode) and 22a (the second comb-shaped electrode). The comb-shaped electrode 22b is connected to the terminal 130, and the comb-shaped electrode 22a is connected to the ground. The IDT electrode 24 includes comb-shaped electrodes 24b (the first comb-shaped electrode) and 24a (the second comb-shaped electrode). The comb-shaped electrode 24b is connected to the terminal 130, and the comb-shaped electrode 24a is connected to the ground.

[0040] In addition, the number of IDT electrodes constituting the longitudinal coupling resonator section 10 may be two or more, and the number of IDT electrodes constituting the longitudinal coupling resonator section 20 may also be two or more. Further, the number of reflectors constituting the longitudinal coupling resonator section 10 may be one or more, and the number of reflectors constituting the longitudinal coupling resonator section 20 may also be one or more.

[0041] In addition, in the surface acoustic wave filter 40 according to the present embodiment, the number of longitudinal coupling resonator sections constituting the longitudinal coupling resonator 1 is arbitrary, and the longitudinal coupling resonator 1 may also include only any one of the longitudinal coupling resonator sections 10 and 20.

[0042] In addition, in the surface acoustic wave filter 40 according to the present embodiment, the number of series arm resonators and the number of shunt arm resonators are arbitrary, and the series arm resonators 31s and 32s and the shunt arm resonators 31p and 32p may not be provided.

[0043] In addition, in the surface acoustic wave filter 40 according to the present embodiment, Figure 1 other circuit elements, wirings, etc. may be inserted between the paths connecting the surface acoustic wave resonator, the input / output terminals, and the ground that are disclosed.

[0044] [2. Electrode Finger Pitch and Pitch Deviation Rate]

[0045] As Figure 2As shown, the IDT electrodes 11 to 15, 21 to 25, the reflectors 19A, 19B, 29A, and 29B each include a plurality of electrode fingers Fe, and the plurality of electrode fingers Fe extend in a direction intersecting the elastic wave propagation direction and are arranged parallel to each other.

[0046] The elastic wave filter 40 according to the present embodiment is characterized by the distribution of the electrode finger pitch P, which is the distance between adjacent electrode fingers Fe (the distance between the center lines of the electrode fingers Fe in the elastic wave propagation direction). Here, as Figure 2 shown, in one IDT electrode or one reflector (for example, the IDT electrode 11), the distance between the first electrode finger Fe(1) and the second electrode finger Fe(2) in the elastic wave propagation direction (the distance between the center line of the electrode finger Fe(1) in the elastic wave propagation direction and the center line of the electrode finger Fe(2) in the elastic wave propagation direction) is defined as the electrode finger pitch P(1) of the electrode finger Fe(1). Thereafter, similarly, the electrode finger pitch P(2) of the electrode finger Fe(2), the electrode finger pitch P(3) of the electrode finger Fe(3), and the electrode finger pitch P(4) of the electrode finger Fe(4) are defined. That is, the distance between the electrode finger Fe(k) and the electrode finger Fe(k + 1) (the distance between the center line of the electrode finger Fe(k) in the elastic wave propagation direction and the center line of the electrode finger Fe(k + 1) in the elastic wave propagation direction) is defined as the electrode finger pitch P(k) of the k-th electrode finger Fe(k) in the elastic wave propagation direction (k is a natural number).

[0047] Figure 3 is a graph showing the distribution of the electrode finger pitch P(k) of the longitudinal coupling resonator 1 according to the embodiment. In the same figure, the electrode finger pitch P(k) of the longitudinal coupling section 10 constituting the longitudinal coupling resonator 1 is shown. The positions of the electrode fingers Fe(1) to Fe(200) constituting the longitudinal coupling section 10 are shown on the horizontal axis, and the electrode finger pitch P(k) of the electrode finger Fe(k) is shown on the vertical axis.

[0048] As Figure 3 shown, in the longitudinal coupling section 10 according to the present embodiment, the electrode finger pitch P(k) has electrode finger intervals arranged irregularly.

[0049] Figure 4 is a graph showing the distribution of the electrode finger pitch P(k) of the longitudinal coupling section included in the elastic wave filter according to the comparative example. The elastic wave filter according to the comparative example is the same as the elastic wave filter 40 according to the embodiment in that it has an elastic wave resonator in which two elastic wave resonance sections are connected in parallel, but the distribution of the electrode finger pitch P(k) of the two elastic wave resonance sections is different. In Figure 4 the electrode finger pitch P(k) of the longitudinal coupling section according to the comparative example is shown.

[0050] As Figure 4 shown, in the longitudinal coupling resonator section involved in the comparative example, the electrode finger pitch P(k) is regularly arranged. Specifically, in the longitudinal coupling resonator section involved in the comparative example, there is an interval in the same IDT electrode or reflector, that is, there is a fixed electrode finger pitch P between three or more adjacent electrode fingers Fe. In addition, as an example of the regular arrangement of the electrode finger pitch P(k), in addition to the example shown in Figure 4 , the following cases can also be cited, that is, with respect to the progression of the electrode finger Fe, the electrode finger pitch P(k) increases or decreases at a fixed ratio (the so-called tapered pitch where the electrode finger pitch P(k) has a fixed slope).

[0051] In contrast, in the longitudinal coupling resonator section 10 according to the present embodiment, there is an IDT electrode or reflector in which there is no fixed electrode finger pitch P between three or more adjacent electrode fingers Fe, and the electrode finger pitch P(k) does not have a fixed slope between three or more adjacent electrode fingers Fe.

[0052] In addition, although in the longitudinal coupling resonator section 10 according to the present embodiment shown in Figure 3 , the electrode finger pitch P(k) is irregularly arranged in all of the IDT electrodes 11 to 15 and the reflectors 19A and 19B, the longitudinal coupling resonator of the surface acoustic wave filter according to the present invention is not limited thereto. That is, with respect to the surface acoustic wave filter according to the present invention, it is sufficient that there is an electrode finger interval in at least one of the IDT electrodes 11 to 15, the reflectors 19A, and 19B in which the electrode finger pitch P(k) is irregularly arranged between three or more adjacent electrode fingers Fe.

[0053] In addition, with respect to the electrode finger pitch P(k) of the longitudinal coupling resonator section 20 constituting the longitudinal coupling resonator 1, it may have an irregular distribution in the same manner as the electrode finger pitch P(k) of the longitudinal coupling resonator section 10. In addition, the distributions of the electrode finger pitch P(k) of the longitudinal coupling resonator section 10 and the longitudinal coupling resonator section 20 may be the same or different.

[0054] Figure 5 is a diagram for explaining the effect of the irregular distribution of the electrode finger pitch P(k) of the longitudinal coupling resonator 1 according to the embodiment. In the figure, a schematic cross-sectional view of a piezoelectric substrate 60 and electrode fingers Fe(k) to Fe(k + 4) formed on the substrate 60 is shown. Figure 5 The shown electrode fingers Fe(k) to Fe(k + 4) have irregular electrode finger pitches P(k) to P(k + 4).

[0055] First, assume Figure 5The electrode fingers Fe(k) to Fe(k + 4) shown are electrode fingers arranged within the same IDT electrode (Function 1). Here, electrode fingers Fe(k), Fe(k + 2), and Fe(k + 4) form the first comb-shaped electrode to which a signal potential (HOT) is applied. In addition, electrode fingers Fe(k + 1) and Fe(k + 3) form the second comb-shaped electrode connected to ground (GND). Here, the electrode finger pitches P(k), P(k + 1), P(k + 2), and P(k + 3) have an irregular electrode finger pitch distribution.

[0056] At this time, in the wavelength (the wavelength of the sound wave of HOT2) of the sound wave (solid line in Figure 5 ) excited by electrode finger Fe(k + 2) as the HOT electrode and the phase of the sound wave ( Figure 5 ) excited by electrode finger Fe(k) as the HOT electrode, an offset occurs. In addition, in the wavelength (the wavelength of the sound wave of HOT2) of the sound wave (solid line in Figure 5 ) excited by electrode finger Fe(k + 2) as the HOT electrode and the phase of the sound wave ( Figure 5 ) excited by electrode finger Fe(k + 4) as the HOT electrode, an offset occurs. Therefore, an acoustic impedance mismatch is likely to occur between electrode fingers Fe(k), Fe(k + 2), and Fe(k + 4) as the HOT electrode.

[0057] Next, assume that Figure 5 the electrode fingers Fe(k) to Fe(k + 3) shown belong to the input-side IDT electrode in the longitudinal coupling resonator 1, and the electrode finger Fe(k + 4) belongs to the output-side IDT electrode in the longitudinal coupling resonator 1 (Function 2). Here, electrode fingers Fe(k), Fe(k + 2), and Fe(k + 4) form the first comb-shaped electrode to which a signal potential (HOT) is applied. In addition, electrode fingers Fe(k + 1) and Fe(k + 3) form the second comb-shaped electrode connected to ground (GND). Here, the electrode finger pitches P(k), P(k + 1), P(k + 2), and P(k + 3) have an irregular electrode finger pitch distribution.

[0058] At this time, when electrode finger Fe(k + 4) in the output-side IDT electrode picks up the sound waves excited by electrode finger Fe(k) and electrode finger Fe(k + 2) in the input-side IDT electrode, since the phases of the sound waves of electrode finger Fe(k) and electrode finger Fe(k + 2) are offset, electrode finger Fe(k + 4) cannot pick them up efficiently.

[0059] As a method for improving the attenuation characteristics of a longitudinal coupling resonator, examples include suppressing the excitation of signals having frequencies in the attenuation band in electrode fingers serving as HOT electrodes, and preventing signals having frequencies in the attenuation band from propagating from the input-side IDT electrode to the output-side IDT electrode.

[0060] In the case of a conventional longitudinal coupling resonator having a structure in which the electrode finger pitch P(k) increases or decreases (tapered pitch) at a fixed ratio with respect to the shift of the electrode fingers Fe, although it is possible to eliminate the phase difference and prevent signals having frequencies in the attenuation band from propagating from the input-side IDT electrode to the output-side IDT electrode, the ability to suppress the excitation of signals having frequencies in the attenuation band itself in the electrode fingers serving as HOT electrodes is low, and a sufficient attenuation improvement effect cannot be obtained.

[0061] In contrast, in the surface acoustic wave filter 40 according to the present embodiment, by applying a distribution of the electrode finger pitch P having irregularities such as Figure 5 to the IDT electrode or reflector having an electrode finger pitch P corresponding to the frequency of the attenuation band, it is possible to suppress the excitation of unnecessary acoustic waves itself by the above-described action 1, and in addition, it is possible to suppress the pickup of the excited acoustic waves by the above-described action 2. As a result, the attenuation characteristics of the surface acoustic wave filter 40 can be improved.

[0062] Next, the pitch deviation rate D and the standard deviation SD defined in the surface acoustic wave filter 40 according to the present embodiment will be described.

[0063] Figure 6 FIG. is a diagram for explaining the pitch deviation rate D and the standard deviation SD in the irregular electrode finger pitch distribution of the longitudinal coupling resonator 1 according to the embodiment.

[0064] In Figure 6 FIG. (a) shows an example of the distribution of the electrode finger pitch P(k) of the IDT electrode or reflector constituting the longitudinal coupling resonator. The horizontal axis shows the position of the electrode finger Fe(k) constituting the IDT electrode or reflector, and the vertical axis shows the electrode finger pitch P(k) of the electrode finger Fe(k).

[0065] As described above, first, (1) the distance between the k-th (k is an integer of 2 or more) electrode finger Fe(k) and the (k + 1)-th electrode finger Fe(k + 1) in the elastic wave propagation direction (the distance between the center lines in the elastic wave propagation direction of the electrode finger Fe(k) and the electrode finger Fe(k + 1)) is defined as the k-th electrode finger pitch P(k).

[0066] Next, (2) among three adjacent electrode fingers, namely electrode finger Fe(k-1), electrode finger Fe(k), and electrode finger Fe(k+1), the average of electrode finger pitch P(k-1) and electrode finger pitch P(k+1) is defined as the interval average electrode finger pitch PM(k) [= {P(k-1) + P(k+1)} / 2]. At this time, the difference between electrode finger pitch P(k) and interval average electrode finger pitch PM(k) [= P(k) - PM(k)] is divided by the value of the overall average electrode finger pitch PT, which is the average pitch of all electrode fingers of the IDT electrode or reflector including electrode fingers Fe(k-1), Fe(k), and Fe(k+1), to define the pitch deviation rate D(k) of electrode finger Fe(k) [= {P(k) - PM(k)} / PT].

[0067] Next, (3) for all electrode fingers Fe of the IDT electrode or reflector including electrode fingers Fe(k-1), Fe(k), and Fe(k+1), the pitch deviation rate D(k) of electrode finger Fe(k) is calculated, and the histogram of the pitch deviation rate D(k) in this IDT electrode or reflector is calculated.

[0068] In Figure 6 (b) shows an example of the distribution of the pitch deviation rate D(k) of the IDT electrode or reflector constituting the longitudinal coupling resonator. The horizontal axis shows the position of electrode finger Fe(k) constituting the IDT electrode or reflector, and the vertical axis shows the pitch deviation rate D(k).

[0069] In addition, in Figure 6 (c) shows an example of the histogram of the pitch deviation rate D(k) of the IDT electrode or reflector constituting the longitudinal coupling resonator.

[0070] Finally, based on the histogram of the pitch deviation rate D(k), the standard deviation SD of the pitch deviation rate D(k) of the IDT electrode or reflector constituting the longitudinal coupling resonator is calculated.

[0071] According to the above definition, the stronger the regularity of electrode finger pitch P(k), the smaller the standard deviation SD of pitch deviation rate D(k), and the stronger the irregularity of electrode finger pitch P(k), the larger the standard deviation SD of pitch deviation rate D(k).

[0072] In the longitudinal coupling resonator 1 of the surface acoustic wave filter 40 according to the present embodiment, the standard deviation of the pitch deviation rate D(k) of each of the IDT electrodes 11 to 15, reflectors 19A and 19B constituting the longitudinal coupling section 10 is 1.4% or more. In addition, in each of the IDT electrodes 21 to 25, reflectors 29A and 29B constituting the longitudinal coupling section 20, the standard deviation of the pitch deviation rate D(k) in the above histogram is 1.4% or more.

[0073] Thus, when acoustic waves corresponding to the frequencies in the attenuation band of the elastic wave filter propagate on the substrate, for example, the phases of the acoustic waves excited by the electrode fingers Fe(k) and the phases of the acoustic waves excited by the electrode fingers Fe(k + 2) are liable to shift, and acoustic impedance mismatches are liable to occur. Therefore, the excitation of acoustic waves corresponding to the frequencies in the attenuation band of the elastic wave filter can be suppressed. Furthermore, when the acoustic waves excited by the electrode fingers Fe(k) and the acoustic waves excited by the electrode fingers Fe(k + 2) in the input-side IDT electrode are picked up by the output-side IDT electrode, since the phases of both acoustic waves are shifted, they cannot be picked up efficiently. Therefore, the attenuation characteristics of the elastic wave filter 40 can be improved.

[0074] In addition, in Figure 4 the longitudinal coupling resonator section in the comparative example shown, in each of the IDT electrode and the reflector, the regularity of the electrode finger pitch P(k) is strong, and thus the standard deviation SD in the above histogram is less than 1.4%. Further, in each of the IDT electrode and the reflector having an electrode finger structure in which the electrode finger pitch P(k) increases or decreases at a fixed ratio with respect to the shift of the electrode finger Fe (a so-called tapered pitch in which the electrode finger pitch P(k) has a fixed slope), the regularity of the electrode finger pitch P(k) is also strong, and thus the standard deviation SD in the above histogram is less than 1.4%.

[0075] In addition, in the longitudinal coupling resonator 1 according to the present embodiment, it is sufficient that at least one of the IDT electrodes 11 to 15, the reflectors 19A and 19B constituting the longitudinal coupling resonator section 10 and the IDT electrodes 21 to 25, the reflectors 29A and 29B constituting the longitudinal coupling resonator section 20 has a standard deviation SD of 1.4% or more in the above histogram.

[0076] Thus, by making the standard deviation SD in the above histogram 1.4% or more for the IDT electrode or the reflector that has a great influence on the attenuation characteristics, the attenuation characteristics of the elastic wave filter 40 can be effectively improved.

[0077] In addition, it may be that in the longitudinal coupling resonator 1 according to the present embodiment, at least one of the IDT electrodes 11 to 15 constituting the longitudinal coupling resonator section 10 and the IDT electrodes 21 to 25 constituting the longitudinal coupling resonator section 20 has a standard deviation SD of 1.4% or more in the above histogram, and each of the reflectors 19A, 19B, 29A, and 29B has a standard deviation SD of less than 1.4% in the above histogram.

[0078] Thus, by applying an irregular electrode finger pitch P(k) to the IDT electrode that has a large influence on the attenuation characteristics, the attenuation characteristics of the surface acoustic wave filter 40 can be improved, and the manufacturing deviation of the electrode finger pitch P(k) in the reflector can be suppressed. Therefore, the attenuation outside the passband defined by the resonance operation of the reflector can be made stable.

[0079] In addition, it may be that, in the longitudinal coupling resonator 1 according to the present embodiment, the standard deviation SD of one of the IDT electrodes 11 to 15 and 21 to 25 in the above histogram is 1.4% or more, and the standard deviation SD of the other IDT electrodes among the IDT electrodes 11 to 15 and 21 to 25 in the above histogram is less than 1.4%.

[0080] Thus, for one IDT electrode that has a large influence on the attenuation characteristics, the attenuation characteristics of the surface acoustic wave filter 40 can be improved, and the manufacturing deviation in the other IDT electrodes can be suppressed. Therefore, characteristic degradation can be suppressed.

[0081] In addition, it may be that, in the longitudinal coupling resonator 1 according to the present embodiment, the standard deviation SD of at least one of the reflectors 19A, 19B that constitute the longitudinal coupling resonator section 10 and the reflectors 29A and 29B that constitute the longitudinal coupling resonator section 20 in the above histogram is 1.4% or more, and the standard deviation SD of each of the IDT electrodes 11 to 15 and 21 to 25 in the above histogram is less than 1.4%.

[0082] Thus, by applying an irregular electrode finger pitch P(k) to the reflector that has a large influence on the attenuation characteristics, the attenuation characteristics of the surface acoustic wave filter 40 can be improved, and the manufacturing deviation of the electrode finger pitch P(k) in the IDT electrode can be suppressed. Therefore, the insertion loss in the passband can be made stable.

[0083] [3. Structure and characteristics of the multiplexer 100 according to Embodiment 1]

[0084] Figure 7 It is a structural diagram of the multiplexer 100 according to Embodiment 1 and its peripheral circuit. As shown in the figure, the multiplexer 100 includes a surface acoustic wave filter 40, a filter 50, and a common terminal 160. The multiplexer 100 is connected to the antenna 2 at the common terminal 160. An inductor 3 for impedance matching is connected between the connection path of the common terminal 160 and the antenna 2 and the ground. In addition, the inductor 3 may be connected in series between the common terminal 160 and the antenna 2. In addition, the inductor 3 may be configured to be included in the multiplexer 100, or may be a structure external to the multiplexer 100. In addition, the inductor 3 may be a capacitor, or may be a synthetic circuit including an inductor and a capacitor.

[0085] The filter 50 is an example of the first filter and is applied to the transmit filter (transmission frequency band: 824 - 849 MHz) of Band 26 of LTE (Long Term Evolution).

[0086] The surface acoustic wave filter 40 is applied to the receive filter (receive frequency band: 859 - 894 MHz) of Band 26 of LTE.

[0087] The input / output terminal 140 of the filter 50 and the input / output terminal 110 of the surface acoustic wave filter 40 are connected to the common terminal 160, and the multiplexer 100 related to this embodiment is applied to the duplexer of Band 26 of LTE.

[0088] The filter 50 has an input / output terminal 140 (the third input / output terminal) and an input / output terminal 150 (the fourth input / output terminal), and is a ladder-type surface acoustic wave filter composed of a plurality of surface acoustic wave resonators. The filter 50 includes series-arm resonators 51s, 52s, 53s, and 54s and shunt-arm resonators 51p, 52p, and 53p. The series-arm resonators 51s, 52s, 53s, and 54s are serially arranged on the path connecting the input / output terminal 140 and the input / output terminal 150. The shunt-arm resonators 51p, 52p, and 53p are respectively connected between the nodes on the above path and the ground. With this structure, the filter 50 constitutes a band-pass filter having the transmission frequency band of Band 26 of LTE as the passband.

[0089] The surface acoustic wave filter 40 has the same circuit structure as the surface acoustic wave filter 40 related to the embodiment, and uses Love wave as the surface acoustic wave. The five IDT electrodes 11 - 15, reflectors 19A and 19B of the longitudinal coupling resonator 10 and the five IDT electrodes 21 - 25, reflectors 29A and 29B of the longitudinal coupling resonator 20 have Figure 3 the shown distribution of the electrode finger pitch P(k), and the standard deviation SD of the pitch deviation rate D(k) of the longitudinal coupling resonators 10 and 20 respectively becomes 2.92%.

[0090] Figure 8 It is a graph comparing the pass characteristics and isolation characteristics of the multiplexers related to Example 1 and Comparative Example 1. In addition, Figure 9 It is a graph comparing the voltage standing wave ratios of the multiplexers related to Example 1 and Comparative Example 1.

[0091] In addition, the circuit structure of the multiplexer related to Comparative Example 1 is the same as Figure 7The circuit structure of the multiplexer 100 involved in the shown Embodiment 1 is the same. However, compared with the multiplexer 100 involved in Embodiment 1, the difference lies in that the electrode finger pitch P(k) of the longitudinal coupling resonator section constituting the receiving filter (surface acoustic wave filter 40) is regularly distributed. That is, the standard deviation SD of the pitch deviation rate D(k) of the longitudinal coupling resonator section constituting the receiving filter involved in Comparative Example 1 is less than 1.4%.

[0092] As Figure 8 shown in (a) of, regarding the passing characteristics of the transmitting filter (filter 50), no difference was seen between Embodiment 1 and Comparative Example 1. This is due to the fact that the transmitting filter involved in Embodiment 1 and the transmitting filter involved in Comparative Example 1 have the same circuit structure and the same electrode finger structure.

[0093] On the other hand, as Figure 8 shown in (b) of, regarding the passing characteristics of the receiving filter, the attenuation characteristics in the transmission band (inside the dotted circle in the figure) were improved in Embodiment 1 compared with Comparative Example 1.

[0094] Furthermore, as Figure 8 shown in (c) of, regarding the isolation characteristics between the transmitting filter and the receiving filter, due to the improvement of the attenuation characteristics of the receiving filter, the isolation characteristics in the transmission band (inside the dotted circle in the figure) were improved in Embodiment 1 compared with Comparative Example 1.

[0095] In addition, although not shown in Figure 8 , regarding the passing characteristics of the receiving filter, the passing characteristics of the transmitting filter, and the isolation characteristics between the transmitting filter and the receiving filter (surface acoustic wave filter 40) in the attenuation band on the low-frequency side of the transmission band of Band 26 and in the attenuation band on the high-frequency side of the receiving band of Band 26, no difference was seen between Embodiment 1 and Comparative Example 1.

[0096] Furthermore, as Figure 9 shown in (a) and (c) of, the voltage standing wave ratios on the input side and the output side in the receiving band of the receiving filter involved in Embodiment 1 are smaller than those of the receiving filter involved in Comparative Example 1 in the receiving band, so the impedance characteristics of the receiving filter were also improved.

[0097] Regarding the improvement of the attenuation characteristics, the improvement of the impedance characteristics, and the improvement of the isolation characteristics between the receiving filter and the transmitting filter in Embodiment 1, it can be interpreted that, in Embodiment 1, by making the electrode finger pitch P(k) of the longitudinal coupling resonator portion irregularly distributed and increasing the standard deviation SD of the pitch deviation rate D(k), it is possible to impede the excitation of useless acoustic waves and suppress the propagation of useless signals.

[0098] Figure 10 It is a graph showing the relationship between the standard deviation SD of the pitch deviation rate D(k) of the longitudinal coupling resonator 1 and the isolation of the multiplexer 100. In the same figure, the correlation between the standard deviation SD of the pitch deviation rate D(k) of the longitudinal coupling resonator 1 included in the elastic wave filter 40 in Multiplexer 100 related to Embodiment 1 and the isolation in the transmission band is shown. According to Figure 10 , by making the standard deviation SD of the pitch deviation rate D(k) 1.4% or more, an improvement effect (1 dB or more) of the isolation in the transmission band was obtained. Further, within the range where the standard deviation SD is 1.4% to 3.0%, as the standard deviation SD becomes larger, the isolation in the transmission band increases.

[0099] [4. Structure and characteristics of the elastic wave filter 40A related to Embodiment 2]

[0100] Figure 11A It is a circuit structure diagram of the elastic wave filter 40A related to Embodiment 2. As shown in the same figure, the elastic wave filter 40A includes a longitudinal coupling resonator portion 10A, series arm resonators 33s and 34s, parallel arm resonators 33p and 34p, and input / output terminals 110 and 120. Compared with the elastic wave filter 40 related to the embodiment, the structure of the longitudinal coupling resonator portion 10A is mainly different. Hereinafter, regarding the elastic wave filter 40A related to Embodiment 2, the description of the same structure as that of the elastic wave filter 40 related to the embodiment will be omitted, and the description will be centered on the different structure.

[0101] The series arm resonators 33s and 34s are elastic wave resonators connected in series on the path connecting the input / output terminal 110 and the input / output terminal 120. The parallel arm resonators 33p and 34p are elastic wave resonators respectively connected between the nodes on the above path and the ground.

[0102] The longitudinal coupling resonator section 10A includes: seven IDT electrodes arranged in the elastic wave propagation direction on a piezoelectric substrate; and two reflectors arranged adjacent to the seven IDT electrodes in the elastic wave propagation direction. Each of the seven IDT electrodes and the two reflectors forms a surface acoustic wave resonator together with the piezoelectric substrate. Each of the seven IDT electrodes and the two reflectors includes a plurality of electrode fingers Fe that extend in a direction crossing the elastic wave propagation direction and are arranged parallel to each other.

[0103] The elastic wave filter 40A uses a Rayleigh wave with a low sound velocity as the elastic wave and forms a band-pass filter having the reception frequency band (925 - 960 MHz) of LTE Band8 as the passband.

[0104] The seven IDT electrodes and the two reflectors included in the longitudinal coupling resonator section 10A have a distribution of irregular electrode finger pitches P(k), and the standard deviation SD of the pitch deviation rate D(k) of the longitudinal coupling resonator section 10A becomes 1.5%.

[0105] Figure 11B It is a graph comparing the passing characteristics of the elastic wave filters related to Example 2 and Comparative Example 2.

[0106] In addition, the circuit structure of the elastic wave filter related to Comparative Example 2 is the same as the circuit structure of the elastic wave filter 40A related to Example 2 shown in Figure 11A However, compared with the elastic wave filter 40A related to Example 2, the difference is that the electrode finger pitches P(k) of the longitudinal coupling resonator section 10A are regularly distributed. That is, the standard deviation SD of the pitch deviation rate D(k) of the longitudinal coupling resonator section 10A constituting the elastic wave filter related to Comparative Example 2 is less than 1.4%.

[0107] As Figure 11B shown, compared with the elastic wave filter related to Comparative Example 2, the elastic wave filter 40A related to Example 2 has improved attenuation characteristics in the transmission frequency band (880 - 915 MHz) and reduced ripple in the passband.

[0108] Therefore, it can be interpreted that in Example 2, by making the electrode finger pitches P(k) of the longitudinal coupling resonator section 10A irregularly distributed and increasing the standard deviation SD of the pitch deviation rate D(k), not only the excitation of useless acoustic waves generated in the attenuation band is blocked, but also the excitation of useless acoustic waves generated in the passband is blocked, thereby reducing the ripple in the passband.

[0109] [5. Structure and Characteristics of the Multiplexer Related to Example 3]

[0110] The multiplexer related to Example 3 is the same asFigure 7 The circuit structure of the multiplexer 100 involved in the shown Embodiment 1 is the same, but compared with the multiplexer 100 involved in Embodiment 1, the distribution pattern of the electrode finger pitch P(k) of the longitudinal coupling resonator portion constituting the receiving filter is different.

[0111] Figure 12A It is a diagram showing the electrode finger arrangement structure and the distribution of the electrode finger pitch of the longitudinal coupling resonator portion 10 included in the receiving filter (surface acoustic wave filter 40) involved in Embodiment 3. In Figure 12A the lower part, an enlarged electrode layout of a part of the IDT electrode 11 constituting the longitudinal coupling resonator portion 10 is shown. The IDT electrode 11 includes comb-shaped electrodes 11a and 11b. The comb-shaped electrode 11a is an example of a first comb-shaped electrode to which a signal potential (HOT) is applied, and the comb-shaped electrode 11b is an example of a second comb-shaped electrode connected to ground. The electrode fingers Fe(1), Fe(3), Fe(5), and Fe(7) constituting the comb-shaped electrode 11a and the electrode fingers Fe(2G), Fe(4G), and Fe(6G) constituting the comb-shaped electrode 11b are interlaced with each other.

[0112] Here, the electrode finger pitches of adjacent electrode fingers among the electrode fingers Fe(1), Fe(3), Fe(5), Fe(7),... constituting the comb-shaped electrode 11a are irregularly distributed. On the other hand, the electrode finger pitches of adjacent electrode fingers among the electrode fingers Fe(2G), Fe(4G), Fe(6G),... constituting the comb-shaped electrode 11b are equal throughout the comb-shaped electrode 11b. In addition, in the IDT electrode 11, due to the irregularity of the electrode finger pitch in the comb-shaped electrode 11a and the regularity of the electrode finger pitch in the comb-shaped electrode 11b, the standard deviation SD of the pitch deviation rate D(k) as the IDT electrode 11 as a whole becomes 1.4% or more.

[0113] That is, as Figure 12A shown, for example, based on the condition that {P(2G)+P(3)} and {P(4G)+P(5)} are equal, through the distribution of P(1), P(2G), P(3), P(4G), P(5), P(6G), P(7),..., the standard deviation SD of the pitch deviation rate D(k) becomes 1.4% or more.

[0114] In addition, in the multiplexer involved in this embodiment, as Figure 12A shown in the upper part, the IDT electrodes 12 to 15, the reflectors 19A and 19B constituting the longitudinal coupling resonator portion 10 of the receiving filter (surface acoustic wave filter 40) have the same distribution pattern of the electrode finger pitch P(k) as the above-described IDT electrode 11.

[0115] Figure 12BIt is a graph comparing the pass characteristics and isolation characteristics of the multiplexers related to Example 3 and Comparative Example 3.

[0116] In addition, the circuit structure of the multiplexer related to Comparative Example 3 is the same as that of the multiplexer related to Example 3. However, compared with the multiplexer related to Example 3, the difference is that the electrode finger pitch P(k) of the longitudinal coupling resonator portion constituting the receiving filter (surface acoustic wave filter 40) is regularly distributed. That is, the standard deviation SD of the pitch deviation rate D(k) of the longitudinal coupling resonator portion constituting the receiving filter related to Comparative Example 3 is less than 1.4%.

[0117] As Figure 12B shown in (a) of [], regarding the pass characteristics of the transmitting filter (filter 50), no difference was seen between Example 3 and Comparative Example 3. This is because the transmitting filter related to Example 3 and the transmitting filter related to Comparative Example 3 have the same circuit structure and the same electrode finger structure.

[0118] On the other hand, as Figure 12B shown in (b) of [], regarding the pass characteristics of the receiving filter, the attenuation characteristics in the transmission band (inside the dotted circle in the figure) were improved in Example 3 compared with Comparative Example 3.

[0119] Furthermore, as Figure 12B shown in (c) of [], regarding the isolation characteristics between the transmitting filter and the receiving filter, due to the improvement of the attenuation characteristics of the receiving filter, the isolation characteristics in the transmission band (inside the dotted circle in the figure) were improved in Example 3 compared with Comparative Example 3.

[0120] Regarding the improvement of the attenuation characteristics of the receiving filter related to Example 3 and the improvement of the isolation characteristics between the receiving filter and the transmitting filter, it can be explained that in Example 3, by making the electrode finger pitch P(k) of the longitudinal coupling resonator portion irregularly distributed and increasing the standard deviation SD of the pitch deviation rate D(k), it is possible to hinder the excitation of useless acoustic waves and suppress the propagation of useless signals.

[0121] In addition, when the electrode finger pitch P(k) is not fixed, it is conceivable that the manufacturing deviation of the electrode finger pitch P(k) between the IDT electrodes becomes large, and due to this, the pass characteristics deteriorate. In contrast, according to the above structure, the electrode finger pitch P(k) of the comb-shaped electrode 11b connected to the ground among the pair of comb-shaped electrodes constituting the IDT electrode 11 is fixed, so at least the electrode finger pitch P(k) of the comb-shaped electrode 11b can be manufactured with high precision. Thereby, the manufacturing deviation of the electrode finger pitch P(k) between the IDT electrodes can be reduced, and thus the deterioration of the pass characteristics can be suppressed.

[0122] In addition, in the multiplexer according to this embodiment, as the configuration structure of the IDT electrodes and the electrode fingers of the reflector that are the longitudinal coupling resonance parts of the receiving filter, by the irregularity of the electrode finger pitch P(k) in the first comb-shaped electrode to which the signal potential (HOT) is applied, and the regularity (equal pitch) of the electrode finger pitch P(k) in the second comb-shaped electrode connected to the ground, the standard deviation SD of the pitch deviation rate D(k) in the above IDT electrodes and the reflector is 1.4% or more, but it is not limited thereto. For example, as the configuration structure of the IDT electrodes and the electrode fingers of the reflector that are the longitudinal coupling resonance parts, it is also possible to make the standard deviation SD of the pitch deviation rate D(k) in the above IDT electrodes and the reflector 1.4% or more by the irregularity of the electrode finger pitch P(k) in the second comb-shaped electrode connected to the ground, and the regularity (equal pitch) of the electrode finger pitch P(k) in the first comb-shaped electrode to which the signal potential (HOT) is applied. Thereby, it is also possible to reduce the manufacturing deviation of the electrode finger pitch P(k) between the IDT electrodes, and thus it is possible to suppress the deterioration of the passing characteristics.

[0123] [Structure and characteristics of the multiplexer according to Embodiment 4]

[0124] Figure 13 FIG. is a structural diagram of the multiplexer 200 according to Embodiment 4 and its peripheral circuits. As shown in the figure, the multiplexer 200 includes a surface acoustic wave filter 41, a filter 51, and a common terminal 160. The multiplexer 200 is connected to the antenna 2 at the common terminal 160. In addition, an impedance matching circuit may be connected in the path connecting the common terminal 160 and the antenna 2.

[0125] The filter 51 is, for example, a receiving filter applied to Band 26 of LTE. The filter structure of the filter 51 is arbitrary.

[0126] The surface acoustic wave filter 41 is, for example, a transmitting filter applied to Band 26 of LTE.

[0127] The input / output terminals 140 of the filter 51 and the input / output terminals 110 of the surface acoustic wave filter 41 are connected to the common terminal 160, and the multiplexer 200 according to this embodiment is applied as a duplexer for Band 26 of LTE.

[0128] The surface acoustic wave filter 41 includes a filter circuit 43 and a longitudinal coupling resonator 42.

[0129] The filter circuit 43 is provided on a piezoelectric substrate 60. The filter circuit 43 is connected to the input / output terminals 110 and 120, includes one or more surface acoustic wave resonators, and has a first frequency band as a passband. The first frequency band is, for example, the transmission frequency band of Band 26 of LTE.

[0130] The longitudinal coupling resonator 42 is an additional circuit that is disposed on the substrate 60 and has IDT electrodes 42a and 42b arranged in the elastic wave propagation direction. It is connected to the input / output terminal 110 and a node on the path connecting the input / output terminals 110 and 120, and generates a signal whose phase is opposite to the signal component of a given frequency band other than the first frequency band passing through the filter circuit 43. The longitudinal coupling resonator 42 is a longitudinal coupling type surface acoustic wave resonator including a surface acoustic wave resonator having the IDT electrode 42a and a surface acoustic wave resonator having the IDT electrode 42b. One end (IDT electrode 42a) of the longitudinal coupling resonator 42 is connected to the input / output terminal 110, and the other end (IDT electrode 42b) is connected to the series arm of the filter circuit 43. Additionally, as long as one end and the other end of the longitudinal coupling resonator 42 are connected to a node on the series arm path of the filter circuit 43 that connects the input / output terminals 110 and 120. Furthermore, the longitudinal coupling resonator 42 may include reflectors arranged adjacent to the IDT electrodes 42a and 42b in the elastic wave propagation direction. Moreover, the number of IDT electrodes included in the longitudinal coupling resonator 42 may be three or more. Additionally, the longitudinal coupling resonator 42 may be a surface acoustic wave filter, a lateral resonator, or a lateral filter composed of surface acoustic wave resonators having IDT electrodes.

[0131] With the above structure, in the surface acoustic wave filter 41, when the signal component of a given frequency band generated in the longitudinal coupling resonator 42 and the signal component to be eliminated (e.g., the reception frequency band of Band 26 of LTE) in the signal transmitted through the filter circuit 43 are added together, the amplitude of the added signal can be made smaller than the amplitude of the original signal component to be eliminated. More preferably, the cancellation signal component generated by the longitudinal coupling resonator 42 is a signal whose phase is opposite and amplitude is the same with respect to the signal component to be eliminated after passing through the filter circuit 43.

[0132] Here, the standard deviation SD of the pitch deviation rate D(k) in the above histogram for at least one of the IDT electrodes 42a, 42b, and the reflectors is 1.4% or more.

[0133] Thus, when the acoustic wave corresponding to the given frequency band of the longitudinal coupling resonator 42 propagates on the substrate 60, for example, the phase of the acoustic wave excited by the electrode finger Fe(k) and the phase of the acoustic wave excited by the electrode finger Fe(k + 2) are likely to shift, and the acoustic impedance is likely to become mismatched. Therefore, the excitation of the acoustic wave corresponding to the above given frequency band can be suppressed.

[0134] Figure 14It is a graph comparing the pass characteristics of the surface acoustic wave filters related to Example 4, Comparative Example 4, and Comparative Example 5. The standard deviation SD of the pitch deviation rate D(k) of the surface acoustic wave filter 41 related to Example 4 is 1.5%. In addition, compared with the circuit structure of the surface acoustic wave filter related to Example 4, the surface acoustic wave filter related to Comparative Example 4 is different only in that the standard deviation SD of the pitch deviation rate D(k) is 1.1%. In addition, compared with the circuit structure of the surface acoustic wave filter 41 related to Example 4, the surface acoustic wave filter related to Comparative Example 5 is different only in that it does not have the longitudinal coupling resonator 42.

[0135] In Figure 14 Among the pass characteristics of the surface acoustic wave filters shown, compared with the surface acoustic wave filters related to Comparative Example 4 and Comparative Example 5, the attenuation amount in the attenuation band (receiving band) on the high-frequency side of the pass band (transmission band) of the surface acoustic wave filter 41 related to Example 4 becomes larger, and the frequency band in which the attenuation amount in the attenuation band (receiving band) becomes larger becomes wider.

[0136] The reason why the attenuation amount in the attenuation band (receiving band) of the surface acoustic wave filter 41 related to Example 4 becomes larger can be explained as being due to the out-of-band excitation suppression effect generated by the random pitch in the longitudinal coupling resonator 42, thereby improving the ripple caused by the longitudinal coupling resonator 42 that reduces the attenuation amount in the high-frequency region of the attenuation band (receiving band). In addition, the reason why the frequency band in which the attenuation amount in the attenuation band (receiving band) of the surface acoustic wave filter 41 related to Example 4 becomes larger becomes wider can be explained as being due to the optimization of the propagation characteristics between the IDT electrodes 42a and 42b of the longitudinal coupling resonator 42 by the above-mentioned random pitch.

[0137] In addition, through the above improvement of the attenuation band (receiving band) in the surface acoustic wave filter 41, a multiplexer 200 with improved isolation characteristics of the surface acoustic wave filter 41 and the filter 51 can be provided.

[0138] [7. Effects, etc.]

[0139] As described above, the surface acoustic wave filter 40 according to the present embodiment includes the longitudinal coupling resonator 1. The longitudinal coupling resonator 1 includes: a substrate 60 having piezoelectricity; a plurality of IDT electrodes provided on the substrate 60 and arranged in the surface acoustic wave propagation direction; and reflectors arranged adjacent to the plurality of IDT electrodes in the surface acoustic wave propagation direction. Each of the plurality of IDT electrodes and the reflectors includes a plurality of electrode fingers Fe. The plurality of electrode fingers Fe extend in a direction crossing the surface acoustic wave propagation direction and are arranged parallel to each other. (1) The distance between the electrode finger Fe(k) (k is an integer of 2 or more) and the electrode finger Fe(k + 1) is defined as the k-th electrode finger pitch P(k). (2) Among the three adjacent electrode fingers of the electrode finger Fe(k - 1), the electrode finger Fe(k), and the electrode finger Fe(k + 1), the value obtained by dividing the difference between the electrode finger pitch P(k) and the interval average electrode finger pitch PM(k) by the overall average electrode finger pitch PT is defined as the pitch deviation rate D(k) of the k-th electrode finger. The interval average electrode finger pitch PM(k) is the average of the electrode finger pitches P(k - 1) and P(k + 1). The overall average electrode finger pitch PT is the average pitch of all the electrode fingers included in the IDT electrode or the reflector including the three adjacent electrode fingers. (3) The distribution of the pitch deviation rate D(k) obtained by calculating the pitch deviation rate D(k) of the k-th electrode finger for all the electrode fingers included in the IDT electrode or the reflector including the three adjacent electrode fingers is defined as the histogram of the pitch deviation rate D(k). In this case, the standard deviation SD of the pitch deviation rate D(k) in the histogram of at least one of the plurality of IDT electrodes and the reflectors is 1.4% or more.

[0140] Accordingly, when the acoustic wave corresponding to the frequency band outside the passband of the surface acoustic wave filter 40 propagates on the substrate 60, for example, the phases of the acoustic waves excited by the electrode finger Fe(k) and the acoustic waves excited by the electrode finger Fe(k + 2) are likely to shift, and the acoustic impedance is likely to be mismatched. Therefore, the excitation of the acoustic wave corresponding to the frequency band outside the passband of the surface acoustic wave filter 40 can be suppressed. Further, when the acoustic waves excited by the electrode finger Fe(k) and the acoustic waves excited by the electrode finger Fe(k + 2) in the input side IDT electrode are picked up by the output side IDT electrode, since the phases of both acoustic waves are shifted, they cannot be picked up efficiently. Therefore, the attenuation characteristics of the surface acoustic wave filter 40 can be improved.

[0141] In addition, it may also be that each of the above-mentioned multiple IDT electrodes has: a first comb-shaped electrode including electrode fingers that are a part of a plurality of electrode fingers Fe and a bus bar electrode that connects one ends of the part of the electrode fingers to each other; and a second comb-shaped electrode including electrode fingers that are another part of the above-mentioned plurality of electrode fingers and a bus bar electrode that connects the other ends of the other part of the electrode fingers to each other and is connected to the ground. Here, the electrode fingers constituting the first comb-shaped electrode and the electrode fingers constituting the second comb-shaped electrode are interlaced with each other, and the standard deviation SD of the pitch deviation rate D(k) in the above-mentioned histogram of at least one of the above-mentioned multiple IDT electrodes is 1.4% or more, and the electrode finger pitch of adjacent electrode fingers Fe in the electrode fingers Fe constituting the second comb-shaped electrode is equal throughout the second comb-shaped electrode.

[0142] When the electrode finger pitch P(k) is not fixed, it is conceivable that the manufacturing deviation of the electrode finger pitch between the IDT electrodes becomes large, and in particular, the characteristics deteriorate. In contrast, according to the above structure, among the first comb-shaped electrode and the second comb-shaped electrode constituting the IDT electrode, the electrode finger pitch P(k) of the second comb-shaped electrode connected to the ground is fixed, so the electrode finger pitch P(k) of the second comb-shaped electrode can be manufactured with high precision, and thus the deterioration of the through characteristics can be suppressed.

[0143] In addition, it may also be that the standard deviation SD of the pitch deviation rate D(k) in the above-mentioned histogram of at least one of the above-mentioned multiple IDT electrodes is 1.4% or more, and the electrode finger pitch P(k) of adjacent electrode fingers in the electrode fingers constituting the first comb-shaped electrode is equal throughout the first comb-shaped electrode.

[0144] According to the above structure, among the first comb-shaped electrode and the second comb-shaped electrode constituting the IDT electrode, the electrode finger pitch P(k) of the first comb-shaped electrode to which the signal potential (HOT) is applied is fixed, so the electrode finger pitch P(k) of the first comb-shaped electrode can be manufactured with high precision, and thus the deterioration of the through characteristics can be suppressed.

[0145] In addition, it may also be that the standard deviation SD of the pitch deviation rate D(k) in the above-mentioned histogram of at least one of the multiple IDT electrodes is 1.4% or more, and the standard deviation SD of the pitch deviation rate D(k) of the reflector in the above-mentioned histogram is less than 1.4%.

[0146] Thereby, the manufacturing deviation of the electrode finger pitch P(k) in the reflector can be suppressed, and thus the attenuation outside the passband defined by the resonant operation of the reflector can be made extremely stable.

[0147] In addition, it is also possible that the standard deviation SD of the pitch deviation rate D(k) of one IDT electrode among the multiple IDT electrodes in the above histogram is 1.4% or more, and the standard deviation of the pitch deviation rate D(k) of the other IDT electrodes among the multiple IDT electrodes in the above histogram is less than 1.4%.

[0148] Thus, by making only the IDT electrode that has a large influence on the attenuation characteristics have an irregular pitch, the attenuation characteristics can be improved, and by making the other IDT electrodes have a regular pitch, deterioration of characteristics due to manufacturing deviations can be suppressed.

[0149] In addition, it is also possible that the standard deviation SD of the pitch deviation rate D(k) of each of the multiple IDT electrodes in the above histogram is less than 1.4%, and the standard deviation of the pitch deviation rate D(k) of the reflector in the above histogram is 1.4% or more.

[0150] Thus, manufacturing deviations in the electrode finger pitch in the IDT electrodes can be suppressed, and therefore the insertion loss in the passband can be stabilized.

[0151] In addition, it is also possible that the surface acoustic wave filter 41 includes: a substrate 60 having piezoelectricity; a filter circuit 43 provided on the substrate 60, connected to the input / output terminals 110 and 120, including surface acoustic wave resonators, and having a first frequency band as a passband; and a longitudinal coupling resonator 42 provided on the substrate 60, having a plurality of IDT electrodes 42a and 42b arranged in the surface acoustic wave propagation direction, connected to at least any one of the input / output terminal 110, the input / output terminal 120, and a path connecting the input / output terminal 110 and the input / output terminal 120, and generating a signal having a phase different from that of a signal component in a given frequency band other than the first frequency band passing through the filter circuit 43. The IDT electrodes 42a and 42b include a plurality of electrode fingers that extend in a direction intersecting the surface acoustic wave propagation direction and are arranged parallel to each other, and the standard deviation of the pitch deviation rate D(k) of at least one of the IDT electrodes 42a and 42b in the above histogram is 1.4% or more.

[0152] Thus, the attenuation amount in a given attenuation frequency band in the filter circuit 43 can be increased, and the frequency band in which the attenuation amount becomes larger in the attenuation frequency band can be broadened.

[0153] In addition, the multiplexer 100 according to the present embodiment includes: a common terminal 160; a surface acoustic wave filter 40 having input / output terminals 110 and 120; and a filter 50 having input / output terminals 140 and 150, with a passband different from that of the surface acoustic wave filter 40, and the common terminal 160 is connected to the input / output terminal 110 and the input / output terminal 140.

[0154] Accordingly, a multiplexer 100 can be provided that improves the isolation characteristics of the elastic wave filter 40 and the filter 50.

[0155] (Other modification examples, etc.)

[0156] As described above, the elastic wave filter and the multiplexer according to the present invention have been described by way of embodiments and examples. However, the elastic wave filter and the multiplexer of the present invention are not limited to the above-described embodiments and examples. Other embodiments achieved by combining any of the constituent elements in the above-described embodiments and examples, modification examples obtained by applying various modifications conceivable by those skilled in the art to the above-described embodiments and examples without departing from the gist of the present invention, and various devices incorporating the elastic wave filter and the multiplexer in the above-described embodiments and examples are also included in the present invention.

[0157] For example, in the above-described embodiments and examples, as the multiplexer, a duplexer applied to Band 26 of LTE is exemplified, and as the elastic wave filter, a receiving filter applied to Band 8 of LTE is exemplified. However, the present invention can also be applied to communication frequency bands other than Band 8 and Band 26 of LTE. In addition, the above-described multiplexer can be applied not only to a duplexer, but also to a triplexer in which three filters are commonly connected to an antenna, a multiplexer in which three duplexers are commonly connected at a common terminal, etc. That is, the above-described multiplexer only needs to include two or more filters.

[0158] In addition, the multiplexer according to the present invention is not limited to a structure including both a transmitting filter and a receiving filter, and may also be a structure including only a plurality of transmitting filters or only a plurality of receiving filters.

[0159] In addition, in the elastic wave filter and the multiplexer in the above-described embodiments and examples, other circuit elements, wirings, etc. may be inserted between the paths connecting the respective circuit elements (and components) and signal paths disclosed in the drawings.

[0160] Industrial Applicability

[0161] The present invention can be widely used as a transceiver filter and a multiplexer used in the front end of a wireless communication terminal that requires low loss in the passband and high attenuation outside the passband.

[0162] Explanation of Reference Numerals

[0163] 1: Longitudinal coupling resonator;

[0164] 2: Antenna;

[0165] 3: Inductor;

[0166] 10, 10A, 20: Longitudinal coupling resonator;

[0167] 11, 12, 13, 14, 15, 21, 22, 23, 24, 25, 42a, 42b: IDT electrode;

[0168] 11a, 11b, 12a, 12b, 13a, 13b, 14a, 14b, 15a, 15b, 21a, 21b, 22a, 22b, 23a, 23b, 24a, 24b, 25a, 25b: Comb electrode;

[0169] 19A, 19B, 29A, 29B: Reflector;

[0170] 31s, 32s, 33s, 34s, 51s, 52s, 53s, 54s: Series arm resonator;

[0171] 31p, 32p, 33p, 34p, 51p, 52p, 53p: Shunt arm resonator;

[0172] 40, 40A, 41: Surface acoustic wave filter;

[0173] 42: Longitudinal coupling resonator;

[0174] 43: Filter circuit;

[0175] 50, 51: Filter;

[0176] 60: Substrate;

[0177] 100, 200: Multiplexer;

[0178] 110, 120, 140, 150: Input / output terminal;

[0179] 130: Terminal;

[0180] 160: Common terminal;

[0181] D: Spacing deviation rate;

[0182] Fe: Electrode finger;

[0183] P: Electrode finger spacing;

[0184] PM: Interval average electrode finger spacing;

[0185] PT: Overall average electrode finger spacing;

[0186] SD: Standard deviation.

Claims

1. An elastic wave filter includes a longitudinal coupling resonator, and the longitudinal coupling resonator has: a substrate having piezoelectricity; a plurality of IDT electrodes, i.e., interdigital transducer electrodes, disposed on the substrate and arranged in the elastic wave propagation direction; and a reflector configured to be adjacent to the plurality of IDT electrodes in the elastic wave propagation direction, wherein each of the plurality of IDT electrodes and the reflector includes a plurality of electrode fingers that extend in a direction crossing the elastic wave propagation direction and are configured to be parallel to each other, (1) The distance between the k-th electrode finger and the (k + 1)-th electrode finger in the elastic wave propagation direction is defined as the k-th electrode finger pitch, where k is an integer of 2 or more, (2) Among the adjacent three electrode fingers of the (k - 1)-th electrode finger, the k-th electrode finger, and the (k + 1)-th electrode finger, the value obtained by dividing the difference between the k-th electrode finger pitch and the interval average electrode finger pitch by the overall average electrode finger pitch is defined as the pitch deviation rate of the k-th electrode finger. The interval average electrode finger pitch is the average of the (k - 1)-th electrode finger pitch and the (k + 1)-th electrode finger pitch, and the overall average electrode finger pitch is the average pitch of all the electrode fingers of the IDT electrode or the reflector including the adjacent three electrode fingers, (3) The distribution of the pitch deviation rates obtained by calculating the pitch deviation rate of the k-th electrode finger for all the electrode fingers of the IDT electrode or the reflector including the adjacent three electrode fingers is defined as the histogram of the pitch deviation rates, The standard deviation of the pitch deviation rates in the histogram of at least one of the plurality of IDT electrodes and the reflector is 1.4% or more.

2. The elastic wave filter according to claim 1, wherein each of the plurality of IDT electrodes has: a first comb-shaped electrode including a part of the plurality of electrode fingers and a bus bar electrode connecting one ends of the part of the electrode fingers to each other; and a second comb-shaped electrode including another part of the plurality of electrode fingers and a bus bar electrode connecting the other ends of the other part of the electrode fingers to each other and connected to ground, the electrode fingers constituting the first comb-shaped electrode and the electrode fingers constituting the second comb-shaped electrode are interlaced with each other, The standard deviation of the pitch deviation rates in the histogram of at least one of the plurality of IDT electrodes is 1.4% or more, and the electrode finger pitches of adjacent electrode fingers among the electrode fingers of the second comb-shaped electrode constituting the at least one IDT electrode are equal throughout the second comb-shaped electrode.

3. The elastic wave filter according to claim 1, wherein each of the plurality of IDT electrodes has: a first comb-shaped electrode including a part of the plurality of electrode fingers and a bus bar electrode connecting one ends of the part of the electrode fingers to each other; and a second comb-shaped electrode including another part of the plurality of electrode fingers and a bus bar electrode connecting the other ends of the other part of the electrode fingers to each other and connected to ground, The electrode fingers forming the first comb-shaped electrode and the electrode fingers forming the second comb-shaped electrode are interlaced with each other. The standard deviation of the pitch deviation rate of at least one of the plurality of IDT electrodes in the histogram is 1.4% or more, and the electrode finger pitch between adjacent electrode fingers among the electrode fingers of the first comb-shaped electrode forming the at least one IDT electrode is equal throughout the first comb-shaped electrode.

4. The surface acoustic wave filter according to any one of claims 1 to 3, wherein the standard deviation of the pitch deviation rate of at least one of the plurality of IDT electrodes in the histogram is 1.4% or more, the standard deviation of the pitch deviation rate of the reflector in the histogram is less than 1.4%.

5. The surface acoustic wave filter according to any one of claims 1 to 3, wherein the standard deviation of the pitch deviation rate of one IDT electrode among the plurality of IDT electrodes in the histogram is 1.4% or more, the standard deviation of the pitch deviation rate of the other IDT electrodes among the plurality of IDT electrodes in the histogram is less than 1.4%.

6. The surface acoustic wave filter according to claim 4, wherein the standard deviation of the pitch deviation rate of one IDT electrode among the plurality of IDT electrodes in the histogram is 1.4% or more, the standard deviation of the pitch deviation rate of the other IDT electrodes among the plurality of IDT electrodes in the histogram is less than 1.4%.

7. The surface acoustic wave filter according to claim 1, wherein the standard deviation of the pitch deviation rate of each of the plurality of IDT electrodes in the histogram is less than 1.4%, the standard deviation of the pitch deviation rate of the reflector in the histogram is 1.4% or more.

8. A surface acoustic wave filter comprising: a substrate having piezoelectricity; a filter circuit provided on the substrate, connected to a first input / output terminal and a second input / output terminal, including a surface acoustic wave resonator, and having a first frequency band as a passband; and a longitudinal coupling resonator provided on the substrate, having a plurality of IDT electrodes arranged in the surface acoustic wave propagation direction, and connected to at least any one of the first input / output terminal, the second input / output terminal, and a path connecting the first input / output terminal and the second input / output terminal, and generating a signal having a phase different from that of a signal component in a given frequency band other than the first frequency band passing through the filter circuit, the plurality of IDT electrodes include a plurality of electrode fingers, the plurality of electrode fingers extend in a direction crossing the surface acoustic wave propagation direction, and are arranged parallel to each other, (1) Define the distance between the k-th electrode finger and the (k+1)-th electrode finger in the elastic wave propagation direction as the k-th electrode finger pitch, where, k is an integer of 2 or more. (2) Among the three adjacent electrode fingers, namely the (k - 1)-th electrode finger, the k-th electrode finger, and the (k + 1)-th electrode finger, the value obtained by dividing the difference between the k-th electrode finger pitch and the interval average electrode finger pitch by the overall average electrode finger pitch is defined as the pitch deviation rate of the k-th electrode finger. The interval average electrode finger pitch is the average of the (k - 1)-th electrode finger pitch and the (k + 1)-th electrode finger pitch, and the overall average electrode finger pitch is the average pitch of all the electrode fingers of the IDT electrode including the three adjacent electrode fingers. (3) The distribution of the pitch deviation rates obtained by calculating the pitch deviation rate of the k-th electrode finger for all the electrode fingers of the IDT electrode including the three adjacent electrode fingers is defined as the histogram of the pitch deviation rate. The standard deviation of the pitch deviation rate in the histogram of at least one of the plurality of IDT electrodes is 1.4% or more.

9. A multiplexer, comprising: A common terminal; An elastic wave filter according to any one of claims 1 to 8, having a first input / output terminal and a second input / output terminal; and A first filter, having a third input / output terminal and a fourth input / output terminal, with a passband different from that of the elastic wave filter. The common terminal is connected to the first input / output terminal and the third input / output terminal.

Images