Multiplexer

Abstract

This device provides a multiplexer that enables simultaneous communication of signals from multiple frequency bands with low loss. [Solution] The multiplexer 100 comprises an elastic wave filter 200 having a first passband and a filter 230 having a second passband, wherein the center frequency fc2 of the second passband is 1.35 times or more the center frequency fc1 of the first passband, and the first elastic wave resonator in the elastic wave filter 200 that is closest to the common terminal 101 comprises a piezoelectric substrate 50, an IDT electrode 10 having a plurality of electrode fingers 11a and 11b, and an insulating layer 60 arranged to embed the IDT electrode 10, where λ is the wavelength of the IDT electrode 10 and t is the thickness of the insulating layer 60, then (t / λ) × 100 ≤ 20.124 × (fc2 / fc1) 2 The following relationship is satisfied: -92.823 × (fc2 / fc1) + 119.41.

Description

Technical Field

[0001] The present invention relates to a multiplexer.

Background Art

[0002] Patent Document 1 discloses a demultiplexer (multiplexer) that includes a first filter connected to a common contact and having a Surface Acoustic Wave (SAW) filter and a SAW resonator, and a second filter connected to the common contact. It states that by making the thickness of the dielectric film covering the SAW filter larger than the thickness of the dielectric film covering the SAW resonator, spurious signals generated in the passband of the second filter can be reduced.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] With the progress of larger capacity and multi-band in mobile communication, there is a demand for a multiplexer that can perform simultaneous communication with low loss for signals of multiple bands whose frequencies are further apart.

[0005] Accordingly, the present invention has been made to solve the above problems, and its object is to provide a multiplexer that can perform simultaneous communication with low loss for signals of a plurality of bands with separated frequencies.

Means for Solving the Problems

[0006] A multiplexer according to one aspect of the present invention comprises a common terminal, an elastic wave filter connected to the common terminal and having a first passband including at least a portion of a first band, and a first filter connected to the common terminal and having a second passband including at least a portion of a second band, wherein the center frequency of the second passband is 1.35 times or more the center frequency of the first passband, the elastic wave filter includes a plurality of elastic wave resonators, and the first elastic wave resonator among the plurality of elastic wave resonators that is closest to the common terminal has a first main surface and comprises a piezoelectric substrate containing lithium niobate, and arranged on the first main surface and having a plurality of first electrode fingers, a plurality of second electrode fingers, a first busbar electrode connecting one end of the plurality of first electrode fingers, and a second busbar electrode connecting one end of the plurality of second electrode fingers. The first elastic wave resonator comprises a transducer electrode and an insulating layer arranged on the first main surface to embed the IDT electrode. In the first elastic wave resonator, if the wavelength of the IDT electrode defined by a plurality of first electrode fingers or a plurality of second electrode fingers is λ, the thickness of the insulating layer in the region between adjacent electrode fingers among the plurality of first electrode fingers and the plurality of second electrode fingers is t, the center frequency of the first passband is fc1, and the center frequency of the second passband is fc2, then (t / λ) × 100 ≤ 20.124 × (fc2 / fc1) 2 The following relationship is satisfied: -92.823 × (fc2 / fc1) + 119.41. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a multiplexer that can simultaneously communicate signals from multiple bands with far apart frequencies with low loss. [Brief explanation of the drawing]

[0008] [Figure 1] This is a circuit diagram of a multiplexer according to an embodiment. [Figure 2] This diagram shows the frequency relationships of each filter constituting the multiplexer according to the embodiment. [Figure 3] These are a plan view and a cross-sectional view of the first elastic wave resonator according to an embodiment. [Figure 4]This is a cross-sectional view of a first elastic wave resonator according to a modified embodiment. [Figure 5] This is a graph showing the reflection characteristics of the elastic wave filter according to the embodiment. [Figure 6] This graph shows the relationship between the center frequency ratio of the multiplexer according to the embodiment and the film thickness wavelength ratio of the first elastic wave resonator. [Modes for carrying out the invention]

[0009] The embodiments of this disclosure will be described in detail below with reference to the drawings. The embodiments described below are all general or specific examples. The numerical values, shapes, materials, components, arrangement of components, and connection configurations shown in the following embodiments are examples only and are not intended to limit the present invention.

[0010] The figures are schematic diagrams that have been appropriately emphasized, omitted, or had their proportions adjusted to illustrate the present invention, and are not necessarily strictly accurate representations. Actual shapes, positional relationships, and proportions may differ. In each figure, substantially identical components are denoted by the same reference numerals, and redundant explanations may be omitted or simplified.

[0011] Furthermore, terms indicating relationships between elements, such as "parallel" and "perpendicular," terms indicating the shape of elements, such as "rectangle," and numerical ranges do not represent only strict meanings, but also include substantially equivalent ranges, such as errors of a few percent.

[0012] Furthermore, in this disclosure, the passband of an elastic wave device or elastic wave filter is defined as the frequency band between two frequencies that are 3 dB greater than the minimum insertion loss within the passband.

[0013] Further, in the resonance characteristics of the acoustic wave device of the present disclosure, the resonance frequency and the anti-resonance frequency are derived, for example, by bringing an RF probe into contact with two input and output terminals of the acoustic wave device in a state where the acoustic wave device is not connected to other circuit elements, and measuring the reflection characteristic (impedance characteristic) with a network analyzer or the like.

[0014] Further, in the present disclosure, the "main component of a material" refers to a component whose proportion in the material exceeds 50% by weight. The main component may exist in any state of single crystal, polycrystal, and amorphous, or in a state where these are mixed.

[0015] Further, in the present disclosure, "band" means at least one of an uplink operation band and a downlink operation band of a frequency band predefined by a standardization organization (for example, 3GPP (registered trademark), IEEE (Institute of Electrical and Electronics Engineers), etc.) for a communication system constructed using a radio access technology (RAT). In the present embodiment, as the communication system, for example, an LTE (Long Term Evolution) system, a 5G (5th Generation)-NR (New Radio) system, a WLAN (Wireless Local Area Network) system, and the like can be used, but the present invention is not limited to these. The uplink operation band of a frequency band means a frequency range designated for uplink in the frequency band. The downlink operation band of a frequency band means a frequency range designated for downlink in the frequency band.

[0016] (Embodiment) [1 Circuit Configuration of Multiplexer 100] A circuit configuration example of the multiplexer 100 according to the embodiment will be described. FIG. 1 is a circuit configuration diagram of the multiplexer 100 according to the embodiment. As shown in the figure, the multiplexer 100 includes an acoustic wave filter 200, filters 210, 220 and 230, a common terminal 101, and input / output terminals 102, 103, 104 and 105. The common terminal 101 is connected to, for example, an antenna.

[0017] The acoustic wave filter 200 is connected between the common terminal 101 and the input / output terminal 102, and has a first passband including at least a part of band A (first band). The first passband includes, for example, the reception band (A-Rx) of band A. The acoustic wave filter 200 is a ladder-type band-pass filter including series arm resonators 211, 212, 213 and 214, parallel arm resonators 221, 222 and 223, and input / output terminals 201 and 202. Each of the series arm resonators 211 to 214 and the parallel arm resonators 221 to 223 is an acoustic wave resonator. The detailed structures of the series arm resonators 211 to 214 and the parallel arm resonators 221 to 223 will be described later. The acoustic wave filter 200 does not have to be a ladder-type band-pass filter, and may be, for example, an acoustic wave filter having a longitudinally coupled resonator.

[0018] The series arm resonators 211 to 214 are arranged in series in the series arm path connecting the input / output terminal 201 and the input / output terminal 202 in the order of the series arm resonators 211, 212, 213 and 214 from the input / output terminal 201 toward the input / output terminal 202. The series arm resonator 211 is an example of a first acoustic wave resonator, and is connected closest to the common terminal 101 among the plurality of acoustic wave resonators constituting the acoustic wave filter 200. The parallel arm resonator 221 is connected between the connection node of the series arm resonators 211 and 212 and the ground. The parallel arm resonator 222 is connected between the connection node of the series arm resonators 212 and 213 and the ground. The parallel arm resonator 223 is connected between the connection node of the series arm resonators 213 and 214 and the ground.

[0019] The elastic wave filter 200 is not limited to a ladder-type filter comprising four series-arm resonators and three parallel-arm resonators. The elastic wave filter 200 may also be a ladder-type filter comprising one or more series-arm resonators and one or more parallel-arm resonators. Furthermore, the first elastic wave resonator among the multiple elastic wave resonators constituting the elastic wave filter 200 that is closest to the common terminal 101 may be a parallel-arm resonator.

[0020] The filter 210 is connected between the common terminal 101 and the input / output terminal 103 and has a third passband that includes at least a portion of band B. The third passband includes, for example, the receiving band (B-Rx) of band B. The filter 210 may be an elastic wave filter, or it may be an LC filter, a dielectric filter, etc., and the filter structure is arbitrary.

[0021] The filter 220 is connected between the common terminal 101 and the input / output terminal 104 and has a fourth passband that includes at least a portion of band C. The fourth passband includes, for example, the receiving band (C-Rx) of band C. The filter 220 may be an elastic wave filter, or it may be an LC filter, a dielectric filter, etc., and the filter structure is arbitrary.

[0022] Filter 230 is an example of a first filter, connected between the common terminal 101 and the input / output terminal 105, and has a second passband that includes, for example, at least a portion of band D (second band). The second passband includes, for example, the receiving band (D-Rx) of band D. Filter 230 may be an elastic wave filter, or it may be an LC filter, a dielectric filter, etc., and the filter structure is arbitrary.

[0023] Filters 210 and 220 do not necessarily have to be included in the multiplexer 100, and the number of filters constituting the multiplexer 100, including the elastic wave filter 200 and filter 230, must be two or more.

[0024] Furthermore, at least one of the elastic wave filter 200 and filters 210-230 may be a transmission filter having a passband that includes the transmission bandwidth.

[0025] Figure 2 is a diagram showing the frequency relationships of each filter constituting the multiplexer 100 according to the embodiment. With respect to the center frequency fc200 of the first passband of the elastic wave filter 200, the center frequency fc220 of the fourth passband of filter 220 and the center frequency fc230 of the second passband of filter 230 are each located in a frequency range of 1.35 times or more and 2 times or less. Furthermore, with respect to the center frequency fc200 of the first passband, it is desirable that the center frequency fc220 of the fourth passband and the center frequency fc230 of the second passband are each located in a frequency range greater than 1.4 times. Note that the center frequency fc220 does not necessarily have to be located in a frequency range of 1.35 times or more and 2 times or less of the center frequency fc200.

[0026] In this embodiment, Band A (first band) is a composite band including, for example, bands n75 and n76 for 5G-NR. Band B (second band) is, for example, band B3 for LTE or band n3 for 5G-NR. Band C is, for example, band B1 for LTE or band n1 for 5G-NR. Band D is, for example, band B7 for LTE or band n7 for 5G-NR.

[0027] [2 Structure of the elastic wave filter 200] The structure of the series arm resonators 211-214 and parallel arm resonators 221-223 that constitute the elastic wave filter 200 will be described.

[0028] Figure 3 is a plan view and a cross-sectional view of a series arm resonator 211 according to an embodiment. Figure 3(a) is a plan view (through the insulating layer 60) of the main surface 50a of the piezoelectric substrate 50 from the positive z-axis side. Figure 3(b) is a cross-sectional view taken along line III-III in Figure 3(a). As shown in Figure 3, the series arm resonator 211 comprises an IDT electrode 10, reflective electrodes 20A and 20B, a piezoelectric substrate 50, an insulating layer 60, and a dielectric layer 70.

[0029] The IDT electrode 10 is positioned on the main surface 50a of the piezoelectric substrate 50. As shown in Figure 3(a), the IDT electrode 10 has a plurality of electrode fingers 11a and a plurality of electrode fingers 11b, and busbar electrodes 12a and 12b.

[0030] Multiple electrode fingers 11a are examples of multiple first electrode fingers and are arranged parallel to each other. Multiple electrode fingers 11b are examples of multiple second electrode fingers and are arranged parallel to each other. Multiple electrode fingers 11a and multiple electrode fingers 11b are arranged parallel to each other so as to intersect each other. Busbar electrode 12a is an example of a first busbar electrode and is arranged to connect one end of multiple electrode fingers 11a. Busbar electrode 12a extends in a direction (x-axis direction) that intersects the extension direction (y-axis direction) of multiple electrode fingers 11a. Busbar electrode 12b is an example of a second busbar electrode and is arranged to connect one end of multiple electrode fingers 11b. Busbar electrode 12b extends in a direction (x-axis direction) that intersects the extension direction (y-axis direction) of multiple electrode fingers 11b. Busbar electrode 12a and busbar electrode 12b are arranged opposite each other, with multiple electrode fingers 11a and multiple electrode fingers 11b in between. The other end of each of the multiple electrode fingers 11a faces the busbar electrode 12b, and the other end of each of the multiple electrode fingers 11b faces the busbar electrode 12a.

[0031] The reflective electrodes 20A and 20B are positioned on both sides of the IDT electrode 10, adjacent to it, in a direction perpendicular to the extension direction of the electrode fingers 11a and 11b (x-axis direction). However, it is not necessary for at least one of the reflective electrodes 20A and 20B to be positioned on both sides of the IDT electrode 10.

[0032] Each of the IDT electrode 10 and the reflective electrodes 20A and 20B may be composed of a metal or alloy such as Ti, Al, Cu, Pt, Au, Ag, or Pd, or it may be composed of multiple laminates made of the above metals or alloys.

[0033] Here, we will explain the wavelength λ of the IDT electrode 10. The wavelength λ of the IDT electrode 10 is a unit of length defined by the repetition period of the electrode fingers 11a or 11b. The electrode finger pitch p of the IDT electrode 10 is half the wavelength λ. Note that if the distance between adjacent electrode fingers of the IDT electrode 10 is not constant, the wavelength λ of the IDT electrode 10 is the average wavelength λ of the IDT electrode 10. AVE Defined by the average wavelength λ of the IDT electrode 10. AVE The formula is defined as 2 × Di / (Ni-1), where Ni is the total number of electrode fingers 11a and 11b included in the IDT electrode 10, and Di is the distance between the centers of the electrode fingers located at one end and the electrode fingers located at the other end of the IDT electrode 10 in the direction of elastic wave propagation.

[0034] Furthermore, if the IDT electrode 10 includes so-called thinned electrodes, the average wavelength λ AVE In calculating the total number of electrode fingers Ni, the number of thinned electrodes is excluded, and the center-to-center distance Di excludes the line width L of the thinned electrode and one of the two spaces adjacent to the thinned electrode (space width S). ​​Thinned electrodes include floating thinned electrodes, polarity reversal electrodes, and filled electrodes. A floating thinned electrode is an electrode finger that is not connected to either of the two opposing busbar electrodes and is positioned parallel to the electrode finger that is connected to one of the two busbar electrodes. A polarity reversal electrode is an electrode finger that is connected to the same busbar electrode to which both adjacent electrode fingers are connected and is positioned parallel to both adjacent electrode fingers. A filled electrode is an electrode finger that has an electrode finger width of at least twice the average electrode finger width of the electrode fingers excluding the filled electrode and is positioned parallel to the electrode fingers excluding the filled electrode.

[0035] The wavelength λ of the IDT electrode 10 can be measured by measuring the line width and space width by viewing the main surface 50a of the piezoelectric substrate 50 on which the IDT electrode 10 is formed in plan view using a scanning electron microscope (SEM), scanning transmission electron microscope (STEM), or transmission electron microscope (TEM), and / or by viewing the cross-section perpendicular to the extension direction of the electrode fingers 11a and 11b.

[0036] The piezoelectric substrate 50 is an example of a piezoelectric substrate, having a main surface 50a (first main surface), and is made of a piezoelectric single crystal. The piezoelectric substrate 50 is, for example, a single-crystal piezoelectric substrate made of lithium niobate. The piezoelectric substrate 50 may also be a single-crystal piezoelectric substrate made of lithium tantalate, quartz, or potassium nitride.

[0037] The insulating layer 60 is positioned on the main surface 50a and embedded in the IDT electrode 10. More specifically, the insulating layer 60 covers the upper surfaces of the electrode fingers 11a and 11b of the IDT electrode 10 and is positioned on the main surface 50a such that the thickness t60 of the insulating layer 60 is 90% or more of the thickness t11 of the electrode fingers 11a and 11b in the region between the electrode fingers 11a and 11b. The insulating layer 60 is, for example, a layer mainly composed of silicon dioxide (SiO2). By adjusting the thickness t60 of the insulating layer 60, spurious emissions generated on the low-frequency and high-frequency sides of the resonance band of the series arm resonator 211 can be reduced.

[0038] Furthermore, it is desirable that the thickness t60 of the insulating layer 60 be arranged on the main surface 50a such that the thickness t11 of the electrode fingers 11a and 11b in the region between the electrode fingers 11a and 11b is equal to or greater than the thickness t11 of the electrode fingers 11a and 11b.

[0039] The dielectric layer 70 is arranged to cover the insulating layer 60. The dielectric layer 70 is preferably a layer in which the speed of sound of the bulk wave propagating through the piezoelectric substrate 50 is faster than the speed of sound of the bulk wave propagating through the dielectric layer 70. For example, silicon nitride (SiN) or a material mainly composed of silicon nitride can be used.

[0040] Furthermore, each of the series arm resonators 212-214 and the parallel arm resonators 221-223 may have a structure similar to that of the series arm resonator 211 described above, except for the electrode parameters of the IDT electrode 10 (wavelength λ, number of electrode finger pairs, electrode finger duty cycle, crossover width, etc.) and the film thickness t60 of the insulating layer 60. In this case, the series arm resonators 211-214 and the parallel arm resonators 221-223 may be formed on a common piezoelectric substrate 50.

[0041] In addition, in the series arm resonators 211 to 214 and the parallel arm resonators 221 to 223, the piezoelectric substrate 50 may have a laminated structure consisting of a piezoelectric layer, an intermediate layer, and a support substrate. Figure 4 is a cross-sectional view of a modified series arm resonator 211 according to the embodiment. The series arm resonator 211 according to this modified embodiment includes an IDT electrode 10 (shown in Figure 4 as electrode fingers 11a and 11b), reflective electrodes 20A and 20B (not shown in Figure 4), a piezoelectric substrate 50A, an insulating layer 60, and a dielectric layer 70. The series arm resonator 211 according to this modified embodiment differs from the series arm resonator 211 according to the embodiment only in the structure of the piezoelectric substrate 50A. In the following, the series arm resonator 211 according to this modified embodiment will be described in detail, omitting the explanation of the same components as the series arm resonator 211 according to the embodiment, and focusing on the piezoelectric substrate 50A, which has a different configuration.

[0042] As shown in Figure 4, the piezoelectric substrate 50A has piezoelectric properties and comprises a piezoelectric layer 51, a low-sonic-velocity layer 52, a high-sonic-velocity layer 53, and a support substrate 54.

[0043] The piezoelectric layer 51 has two opposing main surfaces 51a (first main surface) and 51b. The IDT electrode 10 and the reflective electrodes 20A and 20B are arranged on the main surface 51a. The piezoelectric layer 51 can be made of, for example, lithium niobate or a material mainly composed of the above material. Alternatively, the piezoelectric layer 51 may be mainly composed of lithium tantalate, quartz, or potassium nitride.

[0044] The support substrate 54 is a support substrate positioned on the main surface 51b side of the piezoelectric layer 51, and is a substrate that supports the piezoelectric layer 51, the IDT electrode 10, and the reflective electrodes 20A and 20B. The support substrate 54 is made of, for example, a non-oxide material, and can be silicon (Si), silicon carbide (SiC), or a material mainly composed of these materials. Since silicon and silicon carbide have high thermal conductivity, using these materials as the support substrate 54 can improve the heat dissipation of the series arm resonator 211.

[0045] The low-sound-velocity layer 52 is positioned between the piezoelectric layer 51 and the support substrate 54, and is a layer in which the speed of sound of the bulk waves propagating is slower than that of the bulk waves propagating through the piezoelectric layer 51. The low-sound-velocity layer 52 can be made of, for example, silicon oxide (e.g., silicon dioxide) or a material mainly composed of silicon oxide.

[0046] Furthermore, as the material for the low-sound velocity layer 52, for example, dielectric materials such as glass, silicon oxide, silicon oxynitride, lithium oxide, tantalum oxide, or compounds of silicon oxide to which fluorine, carbon, or boron have been added, or materials mainly composed of the above materials can also be used.

[0047] The high-speed layer 53 is positioned between the low-speed layer 52 and the support substrate 54, and is a layer in which the speed of sound of the bulk waves propagating is faster than that of the bulk waves propagating through the piezoelectric layer 51. For example, silicon nitride (SiN) or a material mainly composed of silicon nitride can be used for the high-speed layer 53.

[0048] Furthermore, as the material for the high-speed layer 53, for example, ceramics such as aluminum nitride (AlN), silicon nitride (SiN), zirconia, cordierite, mullite, steatite, forsterite, spinel, and sialon, dielectrics such as aluminum oxide, silicon oxynitride, DLC (diamond-like carbon), and diamond, or materials mainly composed of the above materials can be used. The spinel mentioned above includes aluminum compounds containing one or more elements selected from Mg, Fe, Zn, Mn, etc., and oxygen. Examples of the spinel mentioned above include MgAl2O4, FeAl2O4, ZnAl2O4, and MnAl2O4.

[0049] According to the modified series arm resonator 211, it is possible to increase the Q factor at the resonant frequency and anti-resonant frequency compared to an elastic wave resonator using a single layer of piezoelectric substrate. In other words, since an elastic wave resonator with a high Q factor can be constructed, it is possible to construct a filter with low insertion loss using this elastic wave resonator.

[0050] Furthermore, each of the series arm resonators 212-214 and the parallel arm resonators 221-223 may have a structure similar to that of the modified series arm resonator 211, except for the electrode parameters of the IDT electrode 10 (wavelength λ, number of electrode finger pairs, electrode finger duty cycle, crossover width, etc.) and the thickness of the insulating layer 60. In this case, the series arm resonators 211-214 and the parallel arm resonators 221-223 may be formed on a common piezoelectric substrate 50A.

[0051] [3. Film thickness range of the insulating layer 60 that reduces reflection loss] Next, the film thickness range of the insulating layer 60 that reduces reflection loss in the second and fourth passbands of the elastic wave filter 200 will be described.

[0052] Figure 5 is a graph showing the reflection characteristics of the elastic wave filter 200 according to the embodiment. The vertical axis of the figure shows the reflection loss at the input / output terminal 201 of the elastic wave filter 200 alone. The film thickness wavelength ratio (%) shown in the figure is the ratio of the film thickness t60 of the insulating layer 60 to the wavelength λ of the series arm resonator 211 ((t60 / λ) × 100).

[0053] As shown in Figure 5, the reflection loss increases in the frequency band above the center frequency fc200 of the elastic wave filter 200. When the film thickness wavelength ratio is 28.3%, the frequency ratio (frequency relative to fc200) of point M1 where the reflection loss is 1.5 dB is 1.42. When the film thickness wavelength ratio is 24.0%, the frequency ratio of point M2 where the reflection loss is 1.5 dB is 1.53. When the film thickness wavelength ratio is 19.7%, the frequency ratio of point M3 where the reflection loss is 1.5 dB is 1.71. When the film thickness wavelength ratio is 15.4%, the frequency ratio of point M4 where the reflection loss is 1.5 dB is 1.92. In other words, the frequency band where the reflection loss is 1.5 dB or less extends to higher frequencies as the film thickness wavelength ratio decreases.

[0054] In filters 220 and 230, which have a center frequency 1.35 to 2 times that of fc200, approximately 1 / 3 of the reflection loss (dB) of the elastic wave filter 200 in fc220 and fc230 is added to the passband insertion loss of filters 220 and 230. From this perspective, when receiving simultaneously with the elastic wave filter 200 and at least one of filters 220 and 230, the passband insertion loss of that filter is required to be 0.5 dB or less compared to when receiving with that filter alone. In other words, the reflection loss (maximum value) of the elastic wave filter 200 in fc220 and fc230 is required to be 1.5 dB or less.

[0055] As shown in Figure 5, for a filter that receives simultaneously with the elastic wave filter 200, it is desirable that the film thickness wavelength ratio of the elastic wave filter 200 be small as its center frequency moves further away from the fc200 on the higher frequency side.

[0056] Figure 6 is a graph showing the relationship between the center frequency ratio x of the multiplexer 100 according to the embodiment and the film thickness wavelength ratio y (%) of the series arm resonator 211. More specifically, the horizontal axis shows the center frequency ratio x (1.35 to 2.0) of the filters that receive simultaneously with the elastic wave filter 200, and includes, for example, the center frequency ratio of filter 220 and the elastic wave filter 200 (fc220 / fc200 = 1.45), and the center frequency ratio of filter 230 and the elastic wave filter 200 (fc230 / fc200 = 1.80). The vertical axis shows the film thickness wavelength ratio y (%) at which the reflection loss of the elastic wave filter 200 is 1.5 dB. In Figure 6, the relationship between the center frequency ratio x and the film thickness wavelength ratio (%) y obtained from the reflection characteristics of the series arm resonator 211 shown in Figure 5 is plotted (black circles). The approximate formula for these plotted points is shown in Equation 1.

[0057] y = 20.124 × x 2 -92.823×x+119.41 (1.35≦x≦2.0) (Formula 1)

[0058] Equation 1 shows the film thickness wavelength ratio (%) at which the reflection loss of the elastic wave filter 200 is 1.5 dB, when the center frequency ratio x is in the range of 1.35 or more and 2.0 or less. From this, the film thickness wavelength ratio (%) y (= (t60 / λ) × 100) at which the reflection loss of the elastic wave filter 200 is 1.5 dB or less is given by the following Equation 2, where fc1 is the center frequency of the elastic wave filter 200 and fc2 is the center frequency of the filter that receives simultaneously with the elastic wave filter 200.

[0059] (t60 / λ)×100≦20.124×(fc2 / fc1) 2 -92.823×(fc2 / fc1)+119.41 (Formula 2)

[0060] According to this, by defining the film thickness t60 of the insulating layer 60 of the first elastic wave resonator most closely connected to the common terminal 101 of the elastic wave filter 200 according to the above formula 2, a multiplexer 100 can be provided that can simultaneously communicate with the elastic wave filter 200 and at least one of filters 220 and 230 whose frequencies are further apart on the higher frequency side than the elastic wave filter 200 with low loss.

[0061] The reflection characteristics of the first elastic wave resonator, which is closest to the common terminal 101, have the greatest influence on the transmission characteristics of filters 210, 220, and 230 among the multiple elastic wave resonators in the elastic wave filter 200. Therefore, by defining the film thickness t60 of the insulating layer 60 of the first elastic wave resonator according to the above equation 2, the degradation of the insertion loss of at least one of filters 220 and 230 can be suppressed more effectively.

[0062] Furthermore, in the series arm resonator 211, it is desirable that the film thickness t60 of the insulating layer 60 is greater than the film thickness t11 of the electrode fingers 11a and 11b. This allows for broad suppression of spurious signals at both the lower and higher frequency sides of the first passband of the elastic wave filter 200.

[0063] Furthermore, the relational expression in Equation 2 may be satisfied not only for the series arm resonator 211, but also for each of the elastic wave resonators (series arm resonators 211-214 and parallel arm resonators 221-223) of the elastic wave filter 200.

[0064] According to this, it becomes possible to further reduce the reflection loss in the bandwidth of the elastic wave filter 200 in the range of center frequency ratios of 1.35 to 2.0.

[0065] In this case, it is desirable that the film thickness t60 of the insulating layer 60 is greater than the film thickness t11 of the electrode fingers 11a and 11b in each of the elastic wave resonators (series arm resonators 211-214 and parallel arm resonators 221-223) of the elastic wave filter 200. This allows for broader suppression of spurious signals at lower and higher frequencies than the first passband of the elastic wave filter 200.

[0066] [4 Effects, etc.] As described above, the multiplexer 100 according to the embodiment comprises a common terminal 101, an elastic wave filter 200 connected to the common terminal 101 and having a first passband including at least a portion of the first band, and a filter 230 connected to the common terminal 101 and having a second passband including at least a portion of the second band, wherein the center frequency fc2 of the second passband is 1.35 times or more the center frequency fc1 of the first passband, the elastic wave filter 200 includes a plurality of elastic wave resonators, and the first elastic wave resonator among the plurality of elastic wave resonators that is closest to the common terminal 101 has a main surface 50a and contains lithium niobate. The first elastic wave resonator comprises a piezoelectric substrate 50, an IDT electrode 10 arranged on the main surface 50a and having a plurality of electrode fingers 11a, a plurality of electrode fingers 11b, a busbar electrode 12a connecting one end of the plurality of electrode fingers 11a, and a busbar electrode 12b connecting one end of the plurality of electrode fingers 11b, and an insulating layer 60 arranged on the main surface 50a and positioned to embed the IDT electrode 10, wherein in the first elastic wave resonator, when the wavelength of the IDT electrode 10 defined by the plurality of electrode fingers 11a or the plurality of electrode fingers 11b is λ, and the thickness of the insulating layer 60 in the region between adjacent electrode fingers among the plurality of electrode fingers 11a and the plurality of electrode fingers 11b is t, (t / λ)×100≦20.124×(fc2 / fc1) 2 -92.823×(fc2 / fc1)+119.41 (Equation 3) The following relationship is satisfied.

[0067] According to this, by defining the film thickness t of the insulating layer 60 according to the above formula 3, a multiplexer 100 can be provided that enables simultaneous communication with low loss between an elastic wave filter 200 and a filter 230 whose frequency is 1.35 times or more higher on the center frequency side than the elastic wave filter 200.

[0068] For example, in the multiplexer 100, in the first elastic wave resonator, the thickness t of the insulating layer 60 in the region between adjacent electrode fingers among the plurality of electrode fingers 11a and plurality of electrode fingers 11b is greater than the thickness t11 of the plurality of electrode fingers 11a and plurality of electrode fingers 11b.

[0069] According to this, spurious signals can be broadly suppressed at frequencies lower and higher than the first passband of the elastic wave filter 200.

[0070] For example, in the multiplexer 100, each of the multiple elastic wave resonators of the elastic wave filter 200 comprises a piezoelectric substrate 50 having a main surface 50a and containing lithium niobate, an IDT electrode 10 arranged on the main surface 50a and having a plurality of electrode fingers 11a, a plurality of electrode fingers 11b, a busbar electrode 12a connecting one end of the plurality of electrode fingers 11a, and a busbar electrode 12b connecting one end of the plurality of electrode fingers 11b, and an insulating layer 60 arranged on the main surface 50a and positioned to embed the IDT electrode 10, wherein in each of the plurality of elastic wave resonators, if the wavelength of the IDT electrode 10 defined by the plurality of electrode fingers 11a or the plurality of electrode fingers 11b is λ, and the thickness of the insulating layer 60 in the region between adjacent electrode fingers among the plurality of electrode fingers 11a and the plurality of electrode fingers 11b is t, then the relational expression Equation 3 is satisfied.

[0071] According to this, it becomes possible to further reduce the reflection loss in the bandwidth of the elastic wave filter 200 at a center frequency ratio of 1.35 or higher.

[0072] For example, in the multiplexer 100, in each of the multiple elastic wave resonators, the thickness t of the insulating layer 60 in the region between adjacent electrode fingers among the multiple electrode fingers 11a and the multiple electrode fingers 11b is greater than the thickness t11 of the multiple electrode fingers 11a and the multiple electrode fingers 11b.

[0073] According to this, spurious signals in the lower and higher frequency ranges beyond the first passband of the elastic wave filter 200 can be suppressed over a wider area.

[0074] For example, in the multiplexer 100, the center frequency fc2 of the second passband is less than or equal to twice the center frequency fc1 of the first passband.

[0075] According to this, by defining the film thickness t of the insulating layer 60 according to Equation 3, it becomes possible to reduce the reflection loss in the bandwidth between a center frequency ratio of 1.35 and 2.

[0076] For example, in the multiplexer 100, the piezoelectric substrate 50 is a single-crystal piezoelectric substrate made of lithium niobate.

[0077] According to this, by adjusting the film thickness t of the insulating layer 60, spurious emissions on the low-frequency and high-frequency sides of the resonance band of the first elastic wave resonator can be reduced, and the frequency-temperature characteristics of the first elastic wave resonator can be improved.

[0078] Furthermore, for example, in a modified multiplexer, the piezoelectric substrate 50A comprises a piezoelectric layer 51 having opposing main surfaces 51a and 51b, a support substrate 54 disposed on the main surface 51b side of the piezoelectric layer 51, a low-sonic layer 52 disposed between the piezoelectric layer 51 and the support substrate 54 and having a bulk wave velocity lower than the bulk wave velocity of the piezoelectric layer 51 and the support substrate 54, and a high-sonic layer 53 disposed between the low-sonic layer 52 and the support substrate 54 and having a bulk wave velocity higher than the bulk wave velocity of the low-sonic layer 52.

[0079] According to this, it is possible to increase the Q factor at the resonant and anti-resonant frequencies compared to elastic wave resonators using a single layer of piezoelectric substrate. In other words, since it is possible to construct a first elastic wave resonator with a high Q factor, it becomes possible to construct a filter with low insertion loss using the first elastic wave resonator.

[0080] For example, in the multiplexer 100, the first band includes at least one of band n75 and band n76 for 5G-NR.

[0081] For example, in the multiplexer 100, the second band is band B1, band B3, or band B7 for LTE, or band n1, n3, or n7 for 5G-NR.

[0082] (Other embodiments) Although embodiments and modifications of the multiplexer according to the present invention have been described above, the present invention is not limited to the above embodiments and modifications. The present invention also includes other embodiments realized by combining any of the components in the above embodiments and modifications, and modifications obtained by applying various modifications to the above embodiments and modifications that a person skilled in the art can conceive of without departing from the spirit of the present invention. [Industrial applicability]

[0083] This invention can be widely used in communication devices such as mobile phones as a multiplexer positioned in the front end. [Explanation of Symbols]

[0084] 10 IDT electrodes 11a, 11b electrode fingers 12a, 12b busbar electrodes 20A, 20B reflective electrode 50 Piezoelectric substrate 50a, 51a, 51b main surface 50A Piezoelectric Substrate 51 Piezoelectric layer 52 Low sound speed layer 53 High-sonic layer 54 Support substrate 60 Insulating layer 70 Dielectric layer 100 Multiplexer 101 Common terminal 102, 103, 104, 105, 201, 202 input / output terminals 200 Elastic wave filters 210, 220, 230 filters 211, 212, 213, 214 Series Arm Resonators 221, 222, 223 Parallel Arm Resonators

Claims

1. Common terminal and An elastic wave filter connected to the common terminal and having a first passband including at least a portion of the first band, The system comprises a first filter connected to the common terminal and having a second passband that includes at least a portion of the second band, The center frequency of the second passband is 1.35 times or more the center frequency of the first passband. The aforementioned elastic wave filter includes a plurality of elastic wave resonators, Of the plurality of elastic wave resonators, the first elastic wave resonator connected closest to the common terminal is, A piezoelectric substrate having a first main surface and containing lithium niobate, An IDT (InterDigital Transducer) electrode is arranged on the first main surface and has a plurality of first electrode fingers, a plurality of second electrode fingers, a first busbar electrode connecting one end of the plurality of first electrode fingers, and a second busbar electrode connecting one end of the plurality of second electrode fingers, The first main surface is provided with an insulating layer arranged to embed the IDT electrode, In the first elastic wave resonator, when the wavelength of the IDT electrode defined by the plurality of first electrode fingers or the plurality of second electrode fingers is λ, the thickness of the insulating layer in the region between adjacent electrode fingers among the plurality of first electrode fingers and the plurality of second electrode fingers is t, the center frequency of the first passband is fc1, and the center frequency of the second passband is fc2, (t / λ)×100≦20.124×(crcq / ccq) ２ -92.823×(fc2 / fc1)+119.41 Satisfying the following relationship, Multiplexer.

2. In the first elastic wave resonator, the thickness of the insulating layer in the region between adjacent electrode fingers among the plurality of first electrode fingers and the plurality of second electrode fingers is greater than the thickness of the plurality of first electrode fingers and the plurality of second electrode fingers. The multiplexer according to claim 1.

3. Each of the aforementioned multiple elastic wave resonators is A piezoelectric substrate having a first main surface and containing lithium niobate, An IDT electrode is arranged on the first main surface and has a plurality of first electrode fingers, a plurality of second electrode fingers, a first busbar electrode connecting one end of the plurality of first electrode fingers, and a second busbar electrode connecting one end of the plurality of second electrode fingers, The first main surface is provided with an insulating layer arranged to embed the IDT electrode, In each of the plurality of elastic wave resonators, if the wavelength of the IDT electrode defined by the plurality of first electrode fingers or the plurality of second electrode fingers is λ, and the thickness of the insulating layer in the region between adjacent electrode fingers among the plurality of first electrode fingers and the plurality of second electrode fingers is t, (t / λ)×100≦20.124×(crcq / ccq) ２ -92.823×(fc2 / fc1)+119.41 Satisfying the following relationship, The multiplexer according to claim 1.

4. In each of the plurality of elastic wave resonators, the thickness of the insulating layer in the region between adjacent electrode fingers among the plurality of first electrode fingers and the plurality of second electrode fingers is greater than the thickness of the plurality of first electrode fingers and the plurality of second electrode fingers. The multiplexer according to claim 3.

5. The center frequency of the second passband is less than or equal to twice the center frequency of the first passband. A multiplexer according to any one of claims 1 to 4.

6. The piezoelectric substrate is a single-crystal piezoelectric substrate made of lithium niobate. A multiplexer according to any one of claims 1 to 5.

7. The piezoelectric substrate is A piezoelectric layer having the first main surface and the second main surface facing each other, A support substrate disposed on the second main surface side of the piezoelectric layer, A low-sound-velocity layer is disposed between the piezoelectric layer and the support substrate, and has a bulk-wave sound velocity lower than the bulk-wave sound velocity of the piezoelectric layer and the support substrate. The system comprises a high-speed layer disposed between the low-speed layer and the support substrate, having a bulk wave velocity higher than the bulk wave velocity of the low-speed layer. A multiplexer according to any one of claims 1 to 5.

8. The first band includes at least one of band n75 and band n76 for 5G-NR. A multiplexer according to any one of claims 1 to 7.

9. The second band is band B1, band B3, or band B7 for LTE, or band n1, n3, or n7 for 5G-NR. A multiplexer according to any one of claims 1 to 8.

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