Elastic wave filter and communication device

Abstract

The performance of an elastic wave filter is improved. An elastic wave element in an elastic wave filter includes: a piezoelectric layer; an IDT electrode on the piezoelectric body layer; a low sound velocity film having a sound velocity lower than that of the piezoelectric layer; and a support substrate having a higher acoustic velocity than the piezoelectric body. When the wavelength of an elastic wave excited by the IDT electrode is represented by lambda, the thickness of the piezoelectric layer is lambda or less. The elastic wave filter includes: a transmission filter including a first elastic wave element group among the plurality of elastic wave elements; and a reception filter including a second elastic wave element group different from the first elastic wave element group among the plurality of elastic wave elements. A passband of the transmission filter is located on a higher-frequency side than a passband of the reception filter, and a width of the passband of the transmission filter is wider than a width of the passband of the reception filter.

Description

Technical Field

[0001] One aspect of the present disclosure relates to an elastic wave filter. Background Art

[0002] Patent Document 1 listed below discloses a configuration example of a multiplexer as an example of an elastic wave filter.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2021-5742 Summary of the Invention

[0006] An elastic wave filter according to one aspect of the present disclosure is an elastic wave filter having a plurality of elastic wave elements, each of the elastic wave elements comprising: a piezoelectric layer; an IDT electrode located on the piezoelectric layer; a low-acoustic-velocity membrane having a lower acoustic velocity than that of the piezoelectric layer; and a supporting substrate having a higher acoustic velocity than that of the piezoelectric layer. When the wavelength of an elastic wave excited by the IDT electrode is represented by λ, the thickness of the piezoelectric layer is less than λ. The elastic wave filter comprises: a transmitting filter including a first elastic wave element group among the plurality of elastic wave elements; and a receiving filter including a second elastic wave element group, different from the first elastic wave element group, among the plurality of elastic wave elements. The passband of the transmitting filter is located on the higher-frequency side than the passband of the receiving filter, and the width of the passband of the transmitting filter is wider than the width of the passband of the receiving filter.

[0007] In addition, an elastic wave filter according to one aspect of the present disclosure is an elastic wave filter having a plurality of elastic wave elements, wherein the elastic wave element comprises: a piezoelectric layer; an IDT electrode located on the piezoelectric layer; a low-acoustic-velocity membrane having an acoustic velocity lower than that of the piezoelectric layer; and a supporting substrate having an acoustic velocity higher than that of the piezoelectric layer. When the wavelength of the elastic wave excited by the IDT electrode is represented by λ, the thickness of the piezoelectric layer is less than λ. The elastic wave filter comprises: a transmitting filter comprising a first elastic wave element group among the plurality of elastic wave elements; and a receiving filter comprising a second elastic wave element group, different from the first elastic wave element group, among the plurality of elastic wave elements. The passband of the transmitting filter is spaced apart from the passband of the receiving filter by at least 50 MHz, and the passband width of the transmitting filter is wider than the passband width of the receiving filter. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 A configuration example of an elastic wave element in the elastic wave filter according to the first embodiment is shown.

[0009] Figure 2A configuration example of the elastic wave filter according to the first embodiment is shown.

[0010] Figure 3 Examples of frequency characteristics of elastic wave filters in comparative examples and embodiments are schematically shown.

[0011] Figure 4 Examples of frequency characteristics of one elastic wave element in a comparative example and an embodiment are schematically shown.

[0012] Figure 5 Examples of frequency characteristics of the elastic wave filters in Examples 1 and 2 are shown.

[0013] Figure 6 Examples of power consumption characteristics of each series resonator in Embodiment 1 and Embodiment 2 are shown.

[0014] Figure 7 A schematic configuration of a communication device in a third embodiment is illustrated. DETAILED DESCRIPTION

[0015] [Implementation Method 1]

[0016] The following describes the elastic wave filter 100 according to Embodiment 1. For ease of explanation, components (constituent elements) having the same functions as those described in Embodiment 1 are denoted by the same reference numerals in the subsequent embodiments, and their descriptions are not repeated. For the sake of simplicity, descriptions of known technical matters are omitted as appropriate. The components, materials, and numerical values described herein are merely examples, unless otherwise specified. Therefore, unless otherwise specified, the positional and connection relationships of the components, for example, are not limited to the examples in the figures. Furthermore, the figures are not necessarily drawn to scale.

[0017] (One structural example of an elastic wave element)

[0018] Figure 1 FIG. 1 shows an example of the structure of elastic wave element 1 in elastic wave filter 100. Elastic wave element 1 is also called an elastic wave resonator. Figure 1 In FIG, the stacked structure of the elastic wave element 1 is schematically shown. Figure 1 FIG. 1 shows a portion of an elastic wave element 1. As will be described later Figure 2 As shown, elastic wave filter 100 may include a plurality of elastic wave elements 1. Specifically, as described later, elastic wave filter 100 may include series resonators 1S and parallel resonators 1P as elastic wave elements 1.

[0019] In this manual, for the sake of convenience, Figure 1The orthogonal coordinate system (D1, D2, D3 coordinate system) shown in FIG. The D1 direction in the example of the first embodiment is the propagation direction of the elastic wave propagating in the piezoelectric layer 2 of the elastic wave element 1. Figure 1 As shown, multiple electrode fingers 32 of acoustic wave element 1 can be arranged along direction D1. Direction D2 is an example of a direction intersecting direction D1. Electrode fingers 32 can extend along direction D2. Direction D3 is the thickness direction of each portion of acoustic wave element 1. In this specification, the positive direction of direction D3 is considered upward. Therefore, the negative direction of direction D3 is considered downward.

[0020] An acoustic wave element 1 may include (i) a piezoelectric layer 2, (ii) an IDT (interdigital transducer) electrode 3 located on the piezoelectric layer 2, (iii) a low-acoustic-velocity film 5, and (iv) a supporting substrate 6. The supporting substrate 6, low-acoustic-velocity film 5, and piezoelectric layer 2 may be common to multiple acoustic wave elements 1. Alternatively, each of the multiple acoustic wave elements 1 may have a separate IDT electrode 3. The IDT electrode 3 is also called an excitation electrode.

[0021] Support substrate 6 supports various parts of acoustic wave element 1. Therefore, support substrate 6 can be located below low-acoustic-velocity film 5. Support substrate 6 can have a higher acoustic velocity than piezoelectric layer 2. Therefore, support substrate 6 can contain Si, for example.

[0022] The piezoelectric layer 2 can be made of a single crystal material exhibiting piezoelectricity. The piezoelectric layer 2 can include lithium tantalate (LiTaO3, also referred to as LT) as a material. The cut angle of the LT can be appropriately set. As an example, the piezoelectric layer 2 can include Y-cut, X-propagating LT with a cut angle of 40° or less (see Example 1, described below). As another example, the piezoelectric layer 2 can include Y-cut, X-propagating LT with a cut angle of 25°±3° (see Example 2, described below).

[0023] The X-axis and Y-axis are the crystal orientation axes of the piezoelectric layer 2, respectively. For example, "Y-cut X-propagation LT with a cutting angle of 40°" means "LT obtained by cutting a surface with the X-axis as the center axis and the axis rotated 40° from the Y-axis as the normal, when the X-axis direction is the propagation direction of the elastic wave." The X-axis and Y-axis can also be associated with the D1-D3 directions. For example, the direction of the X-axis can also be consistent with the D1 direction. However, the X-axis and Y-axis do not have to be associated with the D1-D3 directions.

[0024] The IDT electrode 3 may include a first bus bar and a second bus bar (not shown) facing each other in the direction D2. The IDT electrode 3 may include (i) a plurality of first electrode fingers 32a connected to the first bus bar and (ii) a plurality of second electrode fingers 32b connected to the second bus bar. In this specification, the first electrode fingers 32a and the second electrode fingers 32b are collectively referred to as electrode fingers 32.

[0025] The first electrode fingers 32a can extend in the D2 direction from the first bus bar toward the second bus bar. The second electrode fingers 32b can extend in the D2 direction from the second bus bar toward the first bus bar. Therefore, the second electrode fingers 32b can be staggered with the plurality of first electrode fingers 32a in the D2 direction.

[0026] The plurality of electrode fingers 32 can be alternately and repeatedly arranged on the piezoelectric layer 2 so as to have a substantially constant spacing in the D1 direction. In this specification, the pitch of the electrode fingers 32 is denoted as p. p is also referred to as the electrode finger pitch of the IDT electrode 3. For example, p can be the spacing (repeating spacing) in the D1 direction between the centers of two adjacent electrode fingers 32.

[0027] In this specification, the wavelength λ of the elastic wave excited by the IDT electrode 3 is represented by λ. As an example, p can be set equal to half λ (λ / 2). In this case, λ can be defined as twice the length of p. Therefore, in Embodiment 1, the case of λ=2p is illustrated.

[0028] In this specification, the length of electrode finger 32 in the direction D1 is referred to as width w of electrode finger 32. w can be appropriately set based on, for example, the electrical characteristics required of acoustic wave device 1. For example, w can be set based on p. In this specification, the ratio of w to p (w / p) is referred to as the duty cycle of electrode finger 32.

[0029] As one example, the frequency characteristics of acoustic wave element 1 can be controlled by changing the duty cycle. As another example, the frequency characteristics of acoustic wave element 1 can be controlled by maintaining a constant duty cycle and varying either w or p. In this way, by varying the design of IDT electrode 3 in each of multiple acoustic wave elements 1, the frequency characteristics of each of the multiple acoustic wave elements 1 can be controlled. As described above, by varying the design of IDT electrode 3, the frequency characteristics of acoustic wave filter 100 can be controlled.

[0030] In this specification, the thickness of the piezoelectric layer 2 is represented as T. In Embodiment 1, the piezoelectric layer 2 is sufficiently thin, that is, T is sufficiently small. As an example, T can be less than λ. In this case, the IDT electrode 3 can excite plate waves (Lamb waves) as elastic waves. As an example, the IDT electrode 3 can excite Al Lamb waves as plate waves.

[0031] The low-acoustic-velocity film 5 is an example of a dielectric layer located between the piezoelectric layer 2 and the supporting substrate 6. The low-acoustic-velocity film 5 may be located below the piezoelectric layer 2. The low-acoustic-velocity film 5 may have a lower acoustic velocity than the piezoelectric layer 2. Therefore, for example, the low-acoustic-velocity film 5 may contain SiO2 as a material.

[0032] The acoustic wave element 1 may further include a dielectric layer separate from the low-acoustic-velocity film 5. For example, the acoustic wave element 1 may include an acoustic reflective film as the separate dielectric layer between the piezoelectric layer 2 and the supporting substrate 6. The acoustic reflective film may be a multilayer reflective film formed by alternating layers of (i) a low-acoustic-impedance layer having a lower acoustic impedance than the piezoelectric layer 2 and (ii) a high-acoustic-impedance layer having a higher acoustic impedance than the piezoelectric layer 2.

[0033] The multilayer reflective film can be a stacked unit composed of a low-acoustic impedance layer and a high-acoustic impedance layer. For example, the acoustic wave element 1 can have four stacked units. For example, the low-acoustic impedance layer can contain SiO2. For example, the high-acoustic impedance layer can contain HfO2.

[0034] (One Configuration Example of an Elastic Wave Filter)

[0035] Figure 2 A configuration example of elastic wave filter 100 is shown. In Embodiment 1, elastic wave filter 100 is exemplified as a multiplexer (demultiplexer). In Embodiment 1, elastic wave filter 100 is exemplified as a duplexer for clarity of description.

[0036] The elastic wave filter 100 may include a transmission filter 109T and a reception filter 111R. Figure 2 , a transmission filter 109T and a reception filter 111R are shown as ladder filters. The transmission filter 109T and the reception filter 111R can be connected to the antenna 159 via the antenna terminal ANT (also refer to the antenna terminal 159 described later). Figure 7 ).

[0037] Transmit filter 109T and receive filter 111R may each include multiple elastic wave elements 1. In this specification, for convenience, among the multiple elastic wave elements 1, those belonging to transmit filter 109T are denoted by T, and those belonging to receive filter 111R are denoted by R.

[0038] In this specification, the group of elastic wave elements 1 belonging to transmit filter 109T is referred to as the first elastic wave element group. Meanwhile, the group of elastic wave elements 1 belonging to receive filter 111R is referred to as the second elastic wave element group. The second elastic wave element group is different from the first elastic wave element group. By making the second elastic wave element group different from the first elastic wave element group, the transmission frequency band and the reception frequency band, described later, can be made different. Furthermore, by excluding common elastic wave elements 1 from the first and second elastic wave element groups, the transmission frequency band and the reception frequency band can be easily separated.

[0039] The transmission filter 109T may have four series resonators 1S located on the series arms of the transmission filter 109T. Figure 2 In the example of FIG, the four series resonators 1S in the transmission filter 109T are referred to as series resonators 1S-1T to 1S-4T, respectively. The series resonators 1S-1T to 1S-4T may also be collectively referred to as series resonator 1S-T.

[0040] The series arm of the transmit filter 109T can be connected to the transmit terminal TX and the antenna terminal ANT. Figure 2 In the example of FIG, the series resonator 1S-1T is the series resonator closest to the transmission terminal TX. On the other hand, the series resonator 1S-4T is the series resonator closest to the antenna terminal ANT.

[0041] The transmission filter 109T may include four parallel resonators 1P located on the parallel arms of the transmission filter 109T. Figure 2 In the example of FIG, the four parallel resonators 1P in the transmission filter 109T are respectively referred to as parallel resonators 1P-1T to 1P-4T. The parallel resonators 1P-1T to 1P-4T may also be collectively referred to as parallel resonators 1P-T. The parallel resonators 1P-T may be grounded.

[0042] exist Figure 2 In the example shown in FIG. 1 , the parallel resonator 1P-1T is the parallel resonator closest to the transmit terminal TX. The parallel resonator 1P-1T can be located on a parallel arm extending between the series resonator 1S-1T and the transmit terminal TX. On the other hand, the parallel resonator 1P-4T is the parallel resonator closest to the antenna terminal ANT. The parallel resonator 1P-4T can be located on a parallel arm extending between the series resonator 1S-4T and the series resonator 1S-3T.

[0043] The reception filter 111R may have four series resonators 1S located on the series arms of the reception filter 111R. Figure 2 In the example of FIG, the four series resonators 1S in the reception filter 111R are respectively referred to as series resonators 1S-1R to 1S-4R. The series resonators 1S-1R to 1S-4R in the reception filter 111R may also be collectively referred to as series resonators 1S-R.

[0044] The series arm of the reception filter 111R can be connected to the reception terminal RX and the antenna terminal ANT. Figure 2 In the example of FIG. 5 , the series resonator 1S-1R is the series resonator closest to the antenna terminal ANT. On the other hand, the series resonator 1S-4R is the series resonator closest to the reception terminal RX.

[0045] The reception filter 111R may have three parallel resonators 1P located on the parallel arms of the reception filter 111R. Figure 2 In the example of FIG, the three parallel resonators 1P in the receive filter 111R are referred to as parallel resonators 1P-1R to 1P-3R. The parallel resonators 1P-1R to 1P-3R may also be collectively referred to as parallel resonators 1P-R. The parallel resonators 1P-R may be grounded.

[0046] exist Figure 2 In the example shown in FIG. 1 , the parallel resonator 1P-1R is the parallel resonator closest to the antenna terminal ANT. The parallel resonator 1P-1R can be located on a parallel arm extending between the series resonator 1S-1R and the series resonator 1S-2R. On the other hand, the parallel resonator 1P-3R is the parallel resonator closest to the receive terminal RX. The parallel resonator 1P-3R can be located on a parallel arm extending between the series resonator 1S-3R and the series resonator 1S-4R.

[0047] Transmit filter 109T may include a series resonator 1S-T and a parallel resonator 1P-T as a first elastic wave element group, while receive filter 111R may include a series resonator 1S-R and a parallel resonator 1P-R as a second elastic wave element group.

[0048] (Schematic Example of Frequency Characteristics of an Elastic Wave Filter)

[0049] Figure 3 The frequency characteristics (specifically, attenuation characteristics) of an elastic wave filter of a comparative example (e.g., a conventional elastic wave filter) and an elastic wave filter of an embodiment (e.g., the elastic wave filter 100) are schematically shown. Figure 3, reference numeral 300A denotes an example of attenuation characteristics in a comparative example, and reference numeral 300B denotes an example of attenuation characteristics in an embodiment.

[0050] exist Figure 3 In the graph, the horizontal axis represents frequency (unit: Hz), and the vertical axis (Transmission) represents attenuation (unit: dB). Attenuation can also be understood as insertion loss. In the following description, the transmit filter passband is referred to as the transmit frequency band, and the receive filter passband is referred to as the receive frequency band.

[0051] exist Figure 3 In the specification, the transmission band and passband, which are enclosed in square brackets, represent the transmission band and reception band, respectively, specified by the standard. In this specification, the transmission band specified by the standard is referred to as the specified transmission band. Furthermore, the reception band specified by the standard is referred to as the specified reception band.

[0052] The actual transmission frequency band of the transmission filter can be determined, for example, as the frequency band from the low-frequency cutoff frequency to the high-frequency cutoff frequency in the transmission filter. As known to those skilled in the art, in the attenuation characteristics of a frequency filter, relative to the peak frequency representing the frequency at minimum attenuation, there are -3dB attenuation points (points where the attenuation is -3dB) on both the low-frequency side and the high-frequency side.

[0053] The transmit filter's high-frequency cutoff frequency (for convenience, fcut1_T) is the frequency at which the peak frequency in the transmit filter is attenuated at -3 dB on the high-frequency side. The transmit filter's low-frequency cutoff frequency (for convenience, fcut2_T) is the frequency at which the peak frequency in the transmit filter is attenuated at -3 dB on the low-frequency side.

[0054] Therefore, the transmission band in this specification can be defined as the frequency band from fcut2_T to fcut1_T. As described above, the transmission bandwidth (the width of the transmission band) can be determined by the width from the -3dB attenuation point on the low-frequency side to the -3dB attenuation point on the high-frequency side in the attenuation characteristics of the transmission filter. In this case, fcut2_T is the frequency at the low-frequency end of the transmission band, and fcut1_T is the frequency at the high-frequency end of the transmission band.

[0055] The actual receive frequency band of the receive filter can be determined, for example, as the frequency band from the low-frequency cutoff frequency to the high-frequency cutoff frequency of the receive filter. The high-frequency cutoff frequency of the receive filter (for convenience, referred to as fcut1_R) is the frequency at which the peak frequency in the receive filter is at a -3dB attenuation point on the high-frequency side. The low-frequency cutoff frequency of the receive filter (for convenience, referred to as fcut2_R) is the frequency at which the peak frequency in the receive filter is at a -3dB attenuation point on the low-frequency side.

[0056] Therefore, the reception band in this specification can be defined as the frequency band from fcut2_R to fcut1_R. As described above, the reception bandwidth (the width of the reception band) can be determined by the width from the -3dB attenuation point on the low-frequency side to the -3dB attenuation point on the high-frequency side in the attenuation characteristics of the reception filter. In this case, fcut2_R is the frequency at the low-frequency end of the reception band, and fcut1_R is the frequency at the high-frequency end of the reception band.

[0057] Unless otherwise specified, the transmit frequency band referred to in this specification should be understood to refer to the frequency band determined by the -3dB attenuation point in the transmit filter's attenuation characteristics. Furthermore, the receive frequency band referred to in this specification should be understood to refer to the frequency band determined by the -3dB attenuation point in the receive filter's attenuation characteristics.

[0058] The transmit filters in both the comparative example and the embodiment are designed so that the transmit frequency band includes a specified transmit frequency band. Furthermore, the receive filters in both the comparative example and the embodiment are designed so that the receive frequency band includes a specified receive frequency band. As known to those skilled in the art, the transmit and receive frequency bands can differ depending on the standards to which the elastic wave filter complies.

[0059] like Figure 3 As shown in FIG300A, in conventional elastic wave filters, the transmission band may be positioned at a lower frequency than the reception band, for example, due to standard requirements (see, for example, Patent Document 1). Therefore, in the comparative example, the frequency characteristics of the transmission filter and the reception filter are set so that the transmission band is positioned at a lower frequency than the reception band.

[0060] In contrast, Figure 3 As shown in reference numeral 300B, in the embodiment, the transmission band is located at a lower frequency side than the reception band. Therefore, in the embodiment, the frequency characteristics of the transmission filter and the reception filter are set so that the transmission band is located at a higher frequency side than the reception band.

[0061] (Schematic Example of Frequency Characteristics of an Elastic Wave Element)

[0062] Figure 4 An example of the frequency characteristics of an elastic wave element in the comparative example and the embodiment is schematically shown. Figure 4 , reference numeral 400A denotes an example of the impedance characteristics of the elastic wave element, and reference numeral 400B denotes an example of the power consumption characteristics of the elastic wave element.

[0063] exist Figure 4 In the example of FIG, for the sake of simplicity, the transmission frequency band in the comparative example and the transmission frequency band in the embodiment are shown at the same position. However, in reality, Figure 3As shown, in the comparative example, the transmission frequency band is located on the low frequency side compared with the reception frequency band, and in the embodiment, the transmission frequency band is located on the high frequency side compared with the reception frequency band.

[0064] Figure 4 The horizontal axis in reference numerals 400A and 400B represents frequency. The vertical axis in reference numeral 400A represents the magnitude (absolute value) of the acoustic wave element's impedance. In the following description, the magnitude of impedance will be referred to simply as impedance unless otherwise specified. The vertical axis in reference numeral 400B represents the power consumption of the acoustic wave element.

[0065] In this specification, the resonant frequency (for convenience, referred to as fr) of an elastic wave element is defined as the frequency at which impedance is minimum, whereas the antiresonant frequency (for convenience, referred to as fa) of an elastic wave element is defined as the frequency at which impedance is maximum.

[0066] Generally, power dissipation increases with increasing impedance. Figure 4 As shown, power consumption is minimum near fr. Ideally, power consumption is minimum at fr. On the other hand, power consumption is maximum near fa. Ideally, power consumption is maximum at fa.

[0067] exist Figure 4 In the example, fr<fa. Figure 4 In the example of , it is assumed that fr in the comparative example and the embodiment are equal. Figure 4 In the example, fr belongs to the transmission band. Figure 4 In the example, the maximum values of the impedances in the comparative example and the embodiment are equal. Figure 4 In the example of , the maximum values of power consumption in the comparative example and the embodiment are also equal.

[0068] However, in Figure 4 In the example, fa is different between the comparative example and the embodiment. Figure 4 In the example, fa in the embodiment is higher than fa in the comparative example. The frequency bandwidth of the elastic wave element can be determined as Δf = |fa-fr|. Therefore, in Figure 4 In the examples, Δf in the embodiment is larger than Δf in the comparative example.

[0069] Generally speaking, the temperature of an elastic wave element increases as its power consumption increases. Furthermore, the shoulder on the low-frequency side of the transmission band of an elastic wave filter shifts toward the lower frequency side as the temperature of the elastic wave element increases. To compensate for this shift in the low-frequency shoulder of the transmission band, for example, one approach is to design the elastic wave filter so that the shoulder on the high-frequency side of the transmission band shifts toward the higher frequency side.

[0070] However, in typical multiplexers, the transmission band and the reception band must be separated. Therefore, in a comparative example where the transmission band is located at a lower frequency than the reception band, the separation between the transmission band and the reception band can sometimes make it difficult to shift the high-frequency shoulder of the transmission band to the higher frequency side.

[0071] Based on this, in the above Figure 3 In the comparative example, the case where the transmission bandwidth is the same as the reception bandwidth is illustrated. Figure 4 As shown, near the end of the high-frequency side of the transmission band, the increase in power consumption becomes significant as the frequency increases.

[0072] On the other hand, in the embodiment, since the transmission band is located on the higher frequency side than the reception band, the gap between the transmission band and the reception band can be maintained even if the shoulder on the higher frequency side of the transmission band is shifted to the higher frequency side.

[0073] Based on this, in the above Figure 3 The embodiments of the present disclosure illustrate a case where the transmit bandwidth is wider than the receive bandwidth. As an example, in an elastic wave filter according to one aspect of the present disclosure, the transmit bandwidth can be at least 2 MHz wider than the receive bandwidth. As another example, the transmit bandwidth can be at least 4 MHz wider than the receive bandwidth.

[0074] Therefore, in the embodiment, the degree of freedom of frequency selection on the high-frequency side of the transmission band is increased compared to the comparative example. Therefore, in the embodiment, it is easier to set fa higher than in the comparative example. In other words, in the embodiment, it is easier to set Δf larger than in the comparative example. Figure 4 As shown, within the range from the high-frequency end of the transmission band to fa, power consumption increases approximately monotonically with increasing frequency. However, in the embodiment, since Δf can be set larger than in the comparative example, the increase in power consumption with increasing frequency can be more gradual than in the comparative example.

[0075] As a result, the embodiment can reduce fluctuations in power consumption of each elastic wave element within the frequency filter compared to the comparative example. Therefore, the embodiment can achieve a frequency filter with higher power handling than the comparative example. Consequently, the embodiment can achieve, for example, a frequency filter with excellent mass production capabilities.

[0076] As described above, elastic wave filter 100 can achieve, for example, a wider transmission band and improved power handling. Thus, elastic wave filter 100 can improve elastic wave filter performance compared to conventional methods.

[0077] (Further Study on Frequency Characteristics of the Elastic Wave Filter of the Example)

[0078] The inventors of the present application further studied the examples through simulations. Specifically, the inventors simulated Examples 1 and 2 described below.

[0079] In the simulation of Example 1, the inventors set the design conditions of the elastic wave element 1 as follows:

[0080] Piezoelectric layer: LT (thickness T = 0.35λ)

[0081] Low acoustic velocity film: SiO2 (thickness: 0.1λ)

[0082] Support substrate: Si (thickness: 40λ)

[0083] IDT electrode thickness: 0.09λ

[0084] Cutting angle of LT: 40°.

[0085] Meanwhile, the inventors set the design conditions for acoustic wave element 1 in Example 2 by changing the LT cut angle, among the design conditions for acoustic wave element 1 in Example 1, to 26°. All design conditions for acoustic wave element 1, except the LT cut angle, were the same in Examples 1 and 2.

[0086] The inventors derived the frequency characteristics of the elastic wave filters of each of Examples 1 and 2 through simulation. Figure 5 Examples of frequency characteristics of elastic wave filters in Examples 1 and 2 derived by the inventors are shown. Figure 5 Corresponding to the above Figure 3 Example of reference numeral 300B in FIG. Figure 5 As shown, in Example 2, the transmission bandwidth can be further widened toward the high frequency side compared to Example 1. Therefore, according to Example 2, compared to Example 1, power consumption on the high frequency side can be further reduced.

[0087] As can be seen from the above description, setting the LT cut angle to 40° or less can improve the performance of the elastic wave filter compared to conventional methods. Furthermore, setting the LT cut angle to 25°±3° can further improve the performance of the elastic wave filter.

[0088] (Further Study on Power Consumption Characteristics of the Series Resonator of the Example)

[0089] Next, the inventors conducted simulations to derive the frequency characteristics of power consumption in the acoustic wave devices of Examples 1 and 2. Specifically, the inventors derived the frequency characteristics of power consumption in the series resonators 1S-1T to 1S-4 for Examples 1 and 2, respectively.

[0090] Figure 6 An example of power consumption characteristics of each series resonator in Embodiment 1 and Embodiment 2 derived by the inventor is shown. Figure 6 , reference numeral 600A denotes an example of power consumption characteristics in Embodiment 1, and reference numeral 600B denotes an example of power consumption characteristics in Embodiment 2.

[0091] Figure 6 The transmission band shown is the designated transmission band. Figure 6 The transmission frequency band described in the example refers to a designated transmission frequency band. Figure 6 The horizontal axis of the graph represents the frequency on a normalized frequency scale. Normalized frequency is the quantity obtained by dividing the frequency by the center frequency of the transmission band. Figure 6 In the example of , the frequency corresponding to the value "1" on the horizontal axis is equal to the center frequency of the transmission band.

[0092] In Examples 1 and 2, the series resonators 1S-1T to 1S-4 have power consumption peaks on the low-frequency side and the high-frequency side with respect to the transmission frequency band. Figure 6 In the example of , attention is paid to the peak power consumption on the high-frequency side relative to the transmission band. In this specification, the frequency at which power consumption reaches its peak is referred to as the peak frequency of power consumption (power consumption peak frequency).

[0093] like Figure 6 As shown, in Example 1 and Example 2, at least one power consumption peak frequency of the series resonators 1S-1T to 1S-4 is located in a range of 1.035 or more on the horizontal axis (for example, referring to Figure 6 1S-2T series resonator in FIG).

[0094] As described above, in one aspect of the elastic wave filter disclosed herein, the series resonator's power consumption peak frequency can be at least 1.035 times the normalized frequency. In this case, the series resonator's power consumption peak frequency can be sufficiently separated from the transmission band on the high-frequency side. This effectively reduces the power consumption of the series resonator during elastic wave filter operation.

[0095] Furthermore, as can be understood from the above descriptions, according to Example 2, Δf can be set larger than that of Example 1. Thus, in the elastic wave filter of one aspect of the present disclosure, a larger Δf can be obtained by appropriately setting the cut angle of LT. Therefore, Figure 6 As shown, according to the second embodiment, the power consumption peak frequency of the series resonator can be increased compared with the first embodiment. As a result, according to the second embodiment, the power consumption can be reduced more effectively than the first embodiment.

[0096] [Implementation Method 2]

[0097] In Embodiment 1, the transmission band of the elastic wave filter according to one aspect of the present disclosure is illustrated as being located higher in frequency than the reception band. However, the transmission band of the elastic wave filter according to one aspect of the present disclosure does not necessarily need to be located higher in frequency than the reception band. For example, if the transmission band and the reception band are sufficiently separated, even if the transmission band is located lower in frequency than the reception band, the transmission bandwidth may be wider than the reception bandwidth.

[0098] As an example, in the elastic wave filter of one aspect of the present disclosure, the interval between the transmission band and the reception band may be 50 MHz or more. As another example, the interval between the transmission band and the reception band may be 300 MHz or more.

[0099] [Implementation Method 3]

[0100] Figure 7 The schematic configuration of a communication device 151 in Embodiment 3 is illustrated. The communication device 151 performs wireless communication using radio waves. The communication device 151 may include an elastic wave filter (eg, elastic wave filter 100 ) according to one aspect of the present disclosure.

[0101] In communication device 151, a transmission information signal (TIS) containing the information to be transmitted is modulated and frequency-upgraded (converted to a high-frequency signal with a carrier frequency) by RF-IC (Radio Frequency-Integrated Circuit) 153, and then converted into a transmission signal (TS). Bandpass filter 155 removes unnecessary components outside the transmission passband from TS. The TS, after being amplified by amplifier 157, is then input to transmit filter 109T.

[0102] The transmission filter 109T can receive signals from the transmission terminal TX ( Figure 7 The transmission filter 109T can remove unnecessary components other than the transmission passband from the transmission signal TS input by the antenna terminal ANT (not shown). Figure 7 (not shown) the TS after removing unnecessary components is output to the antenna 159. The antenna 159 can convert the TS as an electrical signal input to itself into an electric wave as a wireless signal and transmit the electric wave to the outside of the communication device 151.

[0103] In addition, the antenna 159 can convert the received external radio waves into an electric signal, namely, a reception signal RS. The antenna 159 can input RS to the reception filter 111R via the antenna terminal ANT. The reception filter 111R can remove unnecessary components outside the passband for reception from the input RS. The reception filter 111R can receive the RS via the reception terminal RX ( Figure 7 (not shown) The received signal RS, from which unnecessary components have been removed, is output to amplifier 161. The output RS is amplified by amplifier 161. Bandpass filter 163 removes unnecessary components outside the reception passband from the amplified RS. The RS, from which unnecessary components have been removed, is frequency-reduced and demodulated by RF-IC 153 and converted into a received information signal RIS.

[0104] The TIS and RIS can be low-frequency signals (baseband signals) containing appropriate information. For example, the TIS and RIS can be analog audio signals or digitized audio signals. The passband of the wireless signal can be appropriately set and can comply with various well-known standards.

[0105] 〔Summarize〕

[0106] An elastic wave filter according to aspect 1 of the present disclosure is an elastic wave filter having a plurality of elastic wave elements, wherein the elastic wave elements include: a piezoelectric layer; an IDT electrode located on the piezoelectric layer; a low-acoustic-velocity membrane having an acoustic velocity lower than that of the piezoelectric layer; and a supporting substrate having an acoustic velocity higher than that of the piezoelectric layer. When the wavelength of the elastic wave excited by the IDT electrode is represented by λ, the thickness of the piezoelectric layer is less than λ. The elastic wave filter includes: a transmitting filter including a first elastic wave element group among the plurality of elastic wave elements; and a receiving filter including a second elastic wave element group different from the first elastic wave element group among the plurality of elastic wave elements. The passband of the transmitting filter is located on the high-frequency side compared to the passband of the receiving filter, and the width of the passband of the transmitting filter is wider than the width of the passband of the receiving filter.

[0107] The elastic wave filter of aspect 2 of the present disclosure is an elastic wave filter having a plurality of elastic wave elements, wherein the elastic wave element comprises: a piezoelectric layer; an IDT electrode located on the piezoelectric layer; a low-acoustic-velocity membrane having an acoustic velocity lower than that of the piezoelectric layer; and a supporting substrate having an acoustic velocity higher than that of the piezoelectric layer. When the wavelength of the elastic wave excited by the IDT electrode is represented as λ, the thickness of the piezoelectric layer is less than λ. The elastic wave filter comprises: a transmitting filter comprising a first elastic wave element group among the plurality of elastic wave elements; and a receiving filter comprising a second elastic wave element group among the plurality of elastic wave elements that is different from the first elastic wave element group. The passband of the transmitting filter is spaced apart from the passband of the receiving filter by more than 50 MHz, and the width of the passband of the transmitting filter is wider than the width of the passband of the receiving filter.

[0108] In the elastic wave filter according to aspect 3 of the present disclosure, in aspect 2 above, a passband of the transmission filter may be spaced apart from a passband of the reception filter by 300 MHz or more.

[0109] In the elastic wave filter of aspect 4 of the present disclosure, in any one of aspects 1 to 3 above, when the width of the passband of the transmitting filter is determined based on the width from the -3dB attenuation point on the low-frequency side to the -3dB attenuation point on the high-frequency side in the attenuation characteristics of the transmitting filter, and the width of the passband of the receiving filter is determined based on the width from the -3dB attenuation point on the low-frequency side to the -3dB attenuation point on the high-frequency side in the attenuation characteristics of the receiving filter, the width of the passband of the transmitting filter is wider than the width of the passband of the transmitting filter by more than 2 MHz.

[0110] In the elastic wave filter of aspect 5 of the present disclosure, in any one of aspects 1 to 4 above, when the width of the passband of the transmitting filter is determined based on the width from the -3dB attenuation point on the low-frequency side to the -3dB attenuation point on the high-frequency side in the attenuation characteristics of the transmitting filter, and the width of the passband of the receiving filter is determined based on the width from the -3dB attenuation point on the low-frequency side to the -3dB attenuation point on the high-frequency side in the attenuation characteristics of the receiving filter, the width of the passband of the transmitting filter is wider than the width of the passband of the transmitting filter by more than 4 MHz.

[0111] In the elastic wave filter of aspect 6 of the present disclosure, in any of aspects 1 to 5 above, the piezoelectric layer may contain Y-cut X-propagation LT with a cutting angle of less than 40° as a material, the low acoustic velocity film may contain SiO2 as a material, and the supporting substrate may contain Si as a material.

[0112] In the elastic wave filter of aspect 7 of the present disclosure, in any of aspects 1 to 6 above, the piezoelectric layer may contain Y-cut X-propagation LT with a cutting angle of 25°±3° as a material, wherein the low acoustic velocity film may contain SiO2 as a material, and the supporting substrate may contain Si as a material.

[0113] In the elastic wave filter of aspect 8 of the present disclosure, in any one of aspects 1 to 7 above, the transmitting filter may have a series resonator as the elastic wave element, and the peak frequency of the power consumption of the series resonator on the high-frequency side of the passband of the transmitting filter may be more than 1.035 times the center frequency of the passband of the transmitting filter.

[0114] The communication device according to aspect 9 of the present disclosure may include the elastic wave filter according to any one of aspects 1 to 8.

[0115] [Additional Notes]

[0116] The invention of the present disclosure has been described above based on the accompanying drawings and embodiments. However, the invention of the present disclosure is not limited to the above-mentioned embodiments. That is, the invention of the present disclosure can be variously modified within the scope shown in the present disclosure, and the embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the invention of the present disclosure. In other words, those skilled in the art should note that various deformations or corrections can be easily made based on the present disclosure. It should also be noted that these variations or modifications are included in the scope of the present disclosure.

[0117] Captions

[0118] 1: Elastic wave element

[0119] 1S: Series Resonator

[0120] 1S-1T to 1S-4T: Series resonators in the transmission filter (series resonators belonging to the first elastic wave element group)

[0121] 1S-1R to 1S-4R: Series resonators in the receive filter (series resonators belonging to the second elastic wave element group)

[0122] 2: Piezoelectric layer

[0123] 3: IDT electrode

[0124] 5: Low sound velocity membrane

[0125] 6: Support substrate

[0126] 100: Elastic Wave Filter

[0127] 109T: Transmit filter

[0128] 111R: Receive filter

[0129] 151: Communication device

Claims

1. An elastic wave filter comprising a plurality of elastic wave elements, wherein: The elastic wave element has: piezoelectric layer; An IDT electrode is located on the piezoelectric layer; a low-acoustic-velocity film having an acoustic velocity lower than that of the piezoelectric layer; as well as A supporting substrate having a higher acoustic velocity than that of the piezoelectric layer, When the wavelength of the elastic wave excited by the IDT electrode is represented by λ, the thickness of the piezoelectric layer is less than λ. The elastic wave filter has: a transmission filter including a first elastic wave element group among the plurality of elastic wave elements; and a receiving filter including a second elastic wave element group different from the first elastic wave element group among the plurality of elastic wave elements; The passband of the transmission filter is located on the higher frequency side than the passband of the reception filter. The width of the passband of the transmission filter is wider than the width of the passband of the reception filter.

2. An elastic wave filter comprising a plurality of elastic wave elements, The elastic wave element has: piezoelectric layer; An IDT electrode is located on the piezoelectric layer; a low-acoustic-velocity film having an acoustic velocity lower than that of the piezoelectric layer; as well as A supporting substrate having a higher acoustic velocity than that of the piezoelectric layer, When the wavelength of the elastic wave excited by the IDT electrode is represented by λ, the thickness of the piezoelectric layer is less than λ. The elastic wave filter has: a transmission filter including a first elastic wave element group among the plurality of elastic wave elements; and a receiving filter including a second elastic wave element group different from the first elastic wave element group among the plurality of elastic wave elements; The passband of the transmitting filter and the passband of the receiving filter are separated by more than 50 MHz. The width of the passband of the transmission filter is wider than the width of the passband of the reception filter.

3. The elastic wave filter according to claim 2, wherein The passband of the transmitting filter and the passband of the receiving filter are separated by more than 300 MHz.

4. The elastic wave filter according to any one of claims 1 to 3, wherein When the width of the passband of the transmission filter is determined based on the width from the -3dB attenuation point on the low frequency side to the -3dB attenuation point on the high frequency side in the attenuation characteristic of the transmission filter, and the width of the passband of the reception filter is determined based on the width from the -3dB attenuation point on the low frequency side to the -3dB attenuation point on the high frequency side in the attenuation characteristic of the reception filter, The passband width of the transmission filter is greater than or equal to 2 MHz than the passband width of the reception filter.

5. The elastic wave filter according to any one of claims 1 to 4, wherein When the width of the passband of the transmission filter is determined based on the width from the -3dB attenuation point on the low frequency side to the -3dB attenuation point on the high frequency side in the attenuation characteristic of the transmission filter, and the width of the passband of the reception filter is determined based on the width from the -3dB attenuation point on the low frequency side to the -3dB attenuation point on the high frequency side in the attenuation characteristic of the reception filter, The passband width of the transmission filter is greater than or equal to 4 MHz than the passband width of the reception filter.

6. The elastic wave filter according to any one of claims 1 to 5, wherein The piezoelectric layer contains Y-cut X-propagation LT with a cut angle of 40° or less as a material, The low acoustic velocity film contains SiO2 as a material, The supporting substrate contains Si as a material.

7. The elastic wave filter according to any one of claims 1 to 6, wherein The piezoelectric layer contains Y-cut X-propagation LT with a cutting angle of 25°±3° as a material, The low acoustic velocity film contains SiO2 as a material, The supporting substrate contains Si as a material.

8. The elastic wave filter according to any one of claims 1 to 7, wherein The transmission filter includes a series resonator as the elastic wave element. A peak frequency of power consumption of the series resonator on the high-frequency side of the pass band of the transmission filter is 1.035 times or more the center frequency of the pass band of the transmission filter.

9. A communication device, wherein: A method comprising the elastic wave filter according to any one of claims 1 to 8.

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