JP2017225109A - Multiplexer and high frequency front end module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress reduction in pass characteristics of other filters constituting the same multiplexer when using an acoustic wave filter in the multiplexer.SOLUTION: A multiplexer comprises: a first filter 11 which is disposed between a common terminal 15 and a first terminal 16; and a second filter 12 which is disposed between the common terminal 15 and a second terminal 17 and has a higher pass band frequency than that of the first filter 11. The second filter 12 includes multiple IDT parts 211-215 that are disposed to be longitudinally coupled. Among multiple IDT electrodes constituting the IDT parts 211-215, IDT electrodes 212b and 214b at one side are connected to a side of the common terminal 15, and IDT electrodes 211b, 213b and 215b at the other side are connected to a side of the second terminal 17. Between the IDT electrodes at one side and the IDT electrodes at the other side, main pitches λm of multiple electrode fingers are different and in at least one of the IDT electrodes at the other side, the main pitch λm of the electrode fingers is maximum.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a multiplexer having a plurality of filters and a high-frequency front-end module including the multiplexer.

  Recent mobile phones are required to support a plurality of frequency bands and a plurality of wireless systems, so-called multiband and multimode, in one terminal. In order to cope with this, a multiplexer for demultiplexing a high-frequency signal having a plurality of radio carrier frequencies is arranged immediately below one antenna. As the plurality of band pass filters constituting the multiplexer, an elastic wave filter or the like characterized by low loss in the pass band and steep pass characteristics around the pass band is used.

  As an example of this elastic wave filter, Patent Document 1 discloses a longitudinally coupled elastic wave filter having five IDT (Inter Digital Transducer) sections. In this elastic wave filter, five IDT portions are arranged on the piezoelectric substrate along the propagation direction of the elastic wave.

International Publication No. 2013/069225

  In the elastic wave filter disclosed in Patent Document 1, the first IDT electrode, the third IDT electrode, and the fifth IDT electrode of the five IDT portions are common to one input side terminal (unbalanced terminal). The second IDT electrode and the fourth IDT electrode are connected to different terminals on the other output side (balanced terminals). In the description of paragraph [0025] of Patent Document 1, the pitch of electrode fingers of the first and fifth IDT electrodes is 1.0582 μm, and the pitch of electrode fingers of the second and fourth IDT electrodes is 1.0569 μm. The pitch of the electrode fingers of the third IDT electrode is 1.0612 μm. That is, the IDT electrode having the maximum electrode finger pitch (in the case of Patent Document 1, the third IDT electrode) is connected to the input side terminal.

  In order to cope with the above-described multibanding or the like, a multiplexer having a plurality of filters is used. In this regard, the inventor has noticed that when an acoustic wave filter having the electrode finger pitch as shown above is used as a multiplexer filter, the pass characteristics of other filters constituting the same multiplexer may be reduced. .

  In view of the above, an object of the present invention is to suppress degradation of the pass characteristics of other filters constituting the same multiplexer when an elastic wave filter is used in the multiplexer.

  To achieve the above object, a multiplexer according to an aspect of the present invention includes a common filter, a first terminal, a second terminal, and a first filter disposed on a path connecting the common terminal and the first terminal. And a second filter disposed on a path connecting the common terminal and the second terminal and having a higher passband frequency than the first filter, and the second filter is an acoustic wave filter, , Having a plurality of IDT portions arranged along the propagation direction of the elastic wave, each of the plurality of IDT portions being composed of a pair of IDT electrodes facing each other, and a plurality of constituting the plurality of IDT portions Of the IDT electrodes, one IDT electrode is connected to the common terminal side of the common terminal and the second terminal, and the other IDT electrode is the second of the common terminal and the second terminal. Each of the one IDT electrode and the other IDT electrode is formed on the surface of the piezoelectric substrate and has a plurality of electrode fingers arranged in the propagation direction of the elastic wave, and the one IDT electrode And the other IDT electrode have different main pitches of the electrode fingers, and at least one of the other IDT electrodes has a maximum main pitch of the electrode fingers among the plurality of IDT electrodes.

  In this way, for at least one of the other IDT electrodes, by making the main pitch of the electrode fingers maximum, an unnecessary wave that increases the return loss of the second filter that occurs in the frequency passband of the first filter. Can be moved out of the pass band of the first filter. Thereby, when an elastic wave filter is used in a multiplexer, it can suppress that the pass characteristic of the other filter which comprises the same multiplexer falls.

  Further, at least one of the one IDT electrodes may have a minimum main pitch of the electrode fingers among the plurality of IDT electrodes.

  In this way, for at least one of the IDT electrodes, the main pitch of the electrode fingers is minimized, so that the return loss of the second filter that occurs in the pass band of the first filter increases. The position can be moved to a higher frequency side than the pass band of the first filter and into a low frequency side stop band of the second filter. Thereby, when an elastic wave filter is used in a multiplexer, it can suppress that the pass characteristic of the other filter which comprises the same multiplexer falls.

  In addition, a multiplexer according to another aspect of the present invention includes a common terminal, a first terminal, a second terminal, a first filter disposed on a path connecting the common terminal and the first terminal, and the common A second filter disposed on a path connecting the terminal and the second terminal and having a passband frequency higher than that of the first filter, the second filter being an acoustic wave filter, A plurality of IDT portions arranged along a propagation direction, each of the plurality of IDT portions being composed of a pair of IDT electrodes facing each other, and the plurality of IDT electrodes constituting the plurality of IDT portions One IDT electrode is connected to the common terminal side of the common terminal and the second terminal, and the other IDT electrode is connected to the second terminal side of the common terminal and the second terminal. Is Each of the one IDT electrode and the other IDT electrode has a plurality of electrode fingers formed on the surface of the piezoelectric substrate and arranged in the propagation direction of the elastic wave, and the one IDT electrode and the other IDT electrode The main pitch of the electrode fingers is different, and the total average pitch of the electrode fingers of the one IDT electrode is smaller than the total average pitch of the electrode fingers of the other IDT electrode.

  Thus, by making the total average of the pitches of the electrode fingers possessed by one IDT electrode smaller than the total average of the pitches of the electrode fingers possessed by the other IDT electrode, the first frequency generated in the frequency passband of the first filter. It becomes possible to move the position of the unnecessary wave where the return loss of the two filters becomes large outside the pass band of the first filter. Thereby, when an elastic wave filter is used in a multiplexer, it can suppress that the pass characteristic of the other filter which comprises the same multiplexer falls.

  In addition, a multiplexer according to another aspect of the present invention includes a common terminal, a first terminal, a second terminal, a first filter disposed on a path connecting the common terminal and the first terminal, and the common A second filter disposed on a path connecting the terminal and the second terminal and having a passband frequency higher than that of the first filter, the second filter being an acoustic wave filter, A plurality of IDT portions arranged along a propagation direction, each of the plurality of IDT portions being composed of a pair of IDT electrodes facing each other, and the plurality of IDT electrodes constituting the plurality of IDT portions One IDT electrode is connected to the common terminal side of the common terminal and the second terminal, and the other IDT electrode is connected to the second terminal side of the common terminal and the second terminal. Is Each of the one IDT electrode and the other IDT electrode has a plurality of electrode fingers formed on the surface of the piezoelectric substrate and arranged in the propagation direction of the elastic wave, and the one IDT electrode and the other IDT electrode The main pitch of the electrode fingers is different, and when the average value of the pitch of the electrode fingers is obtained for each of the IDT electrodes, the IDT electrode having the maximum average value exists in the other IDT electrode To do.

  Thus, when the average value of the pitch of the electrode finger is obtained in each IDT electrode, the IDT electrode having the maximum average value is present in the other IDT electrode, so that the frequency pass band of the first filter is obtained. It becomes possible to move the position of the unnecessary wave where the return loss of the generated second filter becomes large outside the pass band of the first filter. Thereby, when an elastic wave filter is used in a multiplexer, it can suppress that the pass characteristic of the other filter which comprises the same multiplexer falls.

  Moreover, when the average value of the pitch of the electrode fingers is obtained for each of the IDT electrodes, an IDT electrode having the minimum average value may be present in the one IDT electrode.

  As described above, since the IDT electrode having the minimum average value is present in one IDT electrode, the position of the unnecessary wave at which the return loss of the second filter generated in the pass band of the first filter becomes large is determined as the first. It is possible to move to a higher frequency side than the pass band of the filter and within a low frequency side stop band of the second filter. Thereby, when an elastic wave filter is used in a multiplexer, it can suppress that the pass characteristic of the other filter which comprises the same multiplexer falls.

  A circuit element different from the second filter may be connected between the one IDT electrode and the common terminal.

  Thus, even when a circuit element different from the second filter is connected between the one IDT electrode and the common terminal, the return loss of the second filter that occurs in the frequency passband of the first filter. It becomes possible to move the position of the unnecessary wave where the frequency becomes large outside the pass band of the first filter. Thereby, it can suppress that the pass characteristic of the other filter which comprises the same multiplexer falls.

  The second filter may include an odd number of IDT portions of 3 or more, and the number of the one IDT electrodes may be smaller than the number of the other IDT electrodes.

  According to this, the position of the unnecessary wave where the return loss of the second filter generated in the pass band of the first filter becomes large can be easily moved to the high frequency side, and when the elastic wave filter is used in the multiplexer. Decreasing the pass characteristics of other filters constituting the same multiplexer can be suppressed.

  The second filter may include five or more IDT portions.

  According to this, the frequency pass band of each of the first filter and the second filter can be expanded.

  The first filter and the second filter may be reception filters.

  According to this, when an elastic wave filter is used, it is possible to provide a multiplexer composed of a plurality of reception filters that can suppress the deterioration of the pass characteristics of other filters constituting the same multiplexer.

  In addition, when the first filter is connected to the common terminal, the second filter may be connected to the common terminal.

  According to this, even when an unnecessary wave in which the return loss of the second filter becomes large is generated in the pass band of the first filter, the unnecessary wave can be moved out of the pass band of the first filter. Become. Thereby, when an elastic wave filter is used in a multiplexer, it can suppress that the pass characteristic of the other filter which comprises the same multiplexer falls.

  A high frequency front end module according to another aspect of the present invention includes the multiplexer.

  Thus, in the multiplexer of the high-frequency front-end module, at least one of the other IDT electrodes has the main pitch of the electrode fingers maximized, so that the second filter generated in the frequency passband of the first filter It is possible to move the position of the unwanted wave where the return loss increases outside the pass band of the first filter. Thereby, when an elastic wave filter is used in a high frequency front end module, it can control that the passage characteristic of other filters which constitute the same multiplexer falls.

  According to the present invention, when an elastic wave filter is used in a multiplexer or a high-frequency front-end module, it is possible to suppress a decrease in pass characteristics of other filters constituting the same multiplexer or high-frequency front-end module.

It is a circuit block diagram of the communication apparatus containing the multiplexer which concerns on embodiment. It is a schematic diagram which shows the insertion loss (passage characteristic) of the multiplexer which concerns on embodiment. It is a circuit block diagram which is the multiplexer which concerns on embodiment, Comprising: The multiplexer which has a 1st filter and a 2nd filter. FIG. 3 is a schematic plan view showing a second filter of the multiplexer shown in FIG. 2. It is a figure which represents typically the IDT part of the 2nd filter shown in FIG. 2, (a) is a top view, (b) is sectional drawing. It is a typical top view which shows the 2nd filter of the multiplexer concerning a comparative example. It is a figure which shows the insertion loss in the frequency pass band of a 1st filter. It is a figure which shows the return loss of a 2nd filter in the frequency pass band of a 1st filter. It is a circuit block diagram of the high frequency front end module containing the multiplexer which concerns on embodiment. It is a schematic plan view which shows the structure by the side of the 2nd filter of the multiplexer which concerns on another form.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the embodiments and the drawings. It should be noted that each of the embodiments described below shows a comprehensive or specific example. Numerical values, shapes, materials, constituent elements, arrangement of constituent elements, connection forms, and the like shown in the following embodiments are merely examples, and are not intended to limit the present invention. Among the constituent elements in the following embodiments, constituent elements not described in the independent claims are described as optional constituent elements. In addition, the size or size ratio of the components shown in the drawings is not necessarily strict.

(Embodiment)
[1. Overall configuration of multiplexer]
FIG. 1A is a circuit configuration diagram of a communication device 9 including a multiplexer 1 according to an embodiment. FIG. 1B is a schematic diagram illustrating insertion loss (passage characteristics) of the multiplexer 1 according to the embodiment.

  As illustrated in FIG. 1A, the communication device 9 includes a multiplexer 1 and a radio frequency integrated circuit (RFIC) 4 that is a high-frequency signal processing circuit. The multiplexer 1 is connected to the antenna element 2 via the common terminal 15.

  FIG. 1A shows, as an example of the multiplexer 1, Band 25 (transmission pass band: 1850-1915 MHz, reception pass band: 1930-1995 MHz) and Band 66 (transmission pass band: 1710-1780 MHz, reception) of LTE (Long Term Evolution) standard. The quadplexer applied to a passband: 2110-2200 MHz is shown.

  The multiplexer 1 includes transmission side filters 101 and 103, reception side filters 102 and 104, a common terminal 15, transmission input terminals 106 and 108, and reception output terminals 107 and 109. The transmission-side filters 101 and 103 and the reception-side filters 102 and 104 are connected to the common terminal 15 by bundling respective lead wires.

  Each of the transmission-side filters 101 and 103 receives the transmission wave generated by the RFIC 4 via the respective transmission input terminals 106 and 108, and filters the respective transmission pass bands to output to the common terminal 15. It is a filter.

  Each of the reception-side filters 102 and 104 is a band-pass filter that receives a reception wave input from the common terminal 15, filters it in each reception pass band, and outputs it to the respective reception output terminals 107 and 109.

  Here, in order to grasp the gist of the multiplexer 1 of the present embodiment, attention is paid to arbitrary two filters included in the multiplexer 1 of FIG. 1A. Then, each of the focused two filters is referred to as a first filter 11 and a second filter 12.

  FIG. 2 is a circuit configuration diagram showing a multiplexer 1 </ b> A including the first filter 11 and the second filter 12.

  As shown in FIG. 2, the first filter 11 is disposed on a path connecting the common terminal 15 and the first terminal 16. The second filter 12 is disposed on a path connecting the common terminal 15 and the second terminal 17. At least when the first filter 11 is connected to the common terminal 15 for filtering, the second filter 12 is connected to the common terminal 15.

  The second filter 12 has a passband frequency higher than that of the first filter 11. In this embodiment, as an example, the first filter 11 is described as a Band 25 reception passband (Band25Rx) filter, and the second filter 12 is described as a Band66 reception passband (Band66Rx) filter.

[2. Structure of IDT part of second filter]
FIG. 3 is a schematic plan view showing the second filter 12 of the multiplexer 1A.

  The second filter 12 is a longitudinally coupled elastic wave filter and includes a plurality of IDT portions 211, 212, 213, 214 and 215. The first filter 11 may be a ladder type filter having a series resonator and a parallel resonator, or may be a longitudinally coupled elastic wave filter.

  Before describing the second filter 12, the structure of the IDT units 211 to 215 constituting the second filter 12 will be described using the IDT unit 22 common to the IDT units 211 to 215.

  4A and 4B are diagrams schematically showing the IDT portion 22, where FIG. 4A is a plan view and FIG. 4B is a cross-sectional view. The IDT section 22 is for explaining a typical structure of the acoustic wave filter, and the number and length of electrode fingers constituting the electrode are not limited to this.

  The IDT section 22 is configured by IDT (Inter Digital Transducer) electrodes 22a and 22b having a comb shape.

  As shown in FIG. 4A, a pair of IDT electrodes 22a and 22b facing each other are formed on the piezoelectric substrate 326. The IDT electrode 22a includes a plurality of electrode fingers 222a that are parallel to each other and a bus bar electrode 221a that connects the plurality of electrode fingers 222a. The IDT electrode 22b includes a plurality of electrode fingers 222b that are parallel to each other and a bus bar electrode 221b that connects the plurality of electrode fingers 222b. The plurality of electrode fingers 222a and 222b are formed along a direction orthogonal to the propagation direction of the elastic wave. That is, the electrode fingers 222a and 222b are formed side by side in the propagation direction of the elastic wave.

  Further, the IDT electrodes 22a and 22b including the plurality of electrode fingers 222a and 222b and the bus bar electrodes 221a and 221b are formed by stacking the adhesion layer 323 and the main electrode layer 324 as shown in FIG. It has a structure.

  The adhesion layer 323 is a layer for improving the adhesion between the piezoelectric substrate 326 and the main electrode layer 324, and for example, Ti is used as a material. The film thickness of the adhesion layer 323 is, for example, 12 nm.

  The main electrode layer 324 is made of, for example, Al containing 1% Cu. The film thickness of the main electrode layer 324 is, for example, 162 nm.

  The protective layer 325 is formed so as to cover the IDT electrodes 22a and 22b. The protective layer 325 is a layer for the purpose of protecting the main electrode layer 324 from the external environment, adjusting frequency temperature characteristics, and improving moisture resistance, and is, for example, a film mainly composed of silicon dioxide. .

The piezoelectric substrate 326 is made of, for example, LiTaO ₃ piezoelectric single crystal, LiNbO ₃ piezoelectric single crystal, or piezoelectric ceramic having a predetermined cut angle.

  Here, the design parameters of the IDT unit 22 will be described. The wavelength of the surface acoustic wave resonator is defined by the repetition pitch λ of the plurality of electrode fingers 222a and 222b constituting the IDT 22 shown in FIG. Further, as shown in FIG. 4A, the IDT electrode crossing width L overlaps when the electrode finger 222a of the IDT electrode 22a and the electrode finger 222b of the IDT electrode 22b are viewed from the propagation direction of the elastic wave. The electrode finger length. The duty ratio D is the line width occupation ratio of the plurality of electrode fingers 222a and 222b, and is the ratio of the line width to the sum of the line width and the space width of the plurality of electrode fingers 222a and 222b. More specifically, the duty ratio is set when the line width of the electrode fingers 222a and 222b constituting the IDT electrodes 22a and 22b is W, and the space width between the adjacent electrode fingers 222a and 222b is S. , W / (W + S).

[3. Configuration of Second Filter in Embodiment]
As described above, the second filter 12 is a longitudinally coupled elastic wave filter, and includes a plurality of IDT portions 211 to 215 as shown in FIG. The second filter 12 includes reflectors 220 and 221, a first port 230 and a second port 240. The first port 230 is provided on the common terminal 15 side when viewed from the plurality of IDT portions 211 to 215 among the common terminal 15 and the second terminal 17. The second port 240 is provided on the second terminal 17 side of the common terminal 15 and the second terminal 17 when viewed from the plurality of IDT portions 211 to 215.

  In the second filter 12, for example, when a high-frequency signal is input from the common terminal 15, a potential difference is generated between the common terminal 15 and the reference terminal (ground). A wave is generated. Here, by making the pitch λ of each electrode finger of the IDT sections 211 to 215 substantially coincide with the wavelength of the pass band, the second filter 12 is used to generate a high-frequency signal having a frequency component to be passed. Can be passed.

  The IDT section 211 of the second filter 12 has a pair of IDT electrodes 211a and 211b facing each other. Similarly, each of the IDT portions 212 to 215 includes a pair of IDT electrodes 212a and 212b, 213a and 213b, 214a and 214b, and 215a and 215b that face each other. The IDT parts 211 to 215 are sequentially arranged along the propagation direction of the elastic wave so as to be vertically coupled. That is, the IDT units 212 and 214 are arranged so as to sandwich the IDT unit 213 in the propagation direction, and the IDT units 211 and 215 are arranged so as to sandwich the IDT units 212 to 214 in the propagation direction. Reflectors 220 and 221 are arranged so as to sandwich IDT portions 211 to 215 in the propagation direction.

  The IDT units 212 and 214 are connected in parallel between the first port 230 and a reference terminal (ground). Specifically, the IDT electrodes 212a and 214a are connected to the reference terminal. The IDT electrodes 212 b and 214 b are connected to the common terminal 15 side of the common terminal 15 and the second terminal 17 via the first port 230.

  The IDT units 211, 213, and 215 are connected in parallel between the second port 240 and the reference terminal. Specifically, the IDT electrodes 211a, 213a, and 215a are connected to the reference terminal. The IDT electrodes 211 b, 213 b and 215 b are connected to the second terminal 17 side of the common terminal 15 and the second terminal 17 via the second port 240.

  As described above, in the second filter 12, among the plurality of IDT portions 211 to 215, one IDT electrode 212b and 214b is connected to the common terminal 15 side, and the other IDT electrode 211b, 213b and 215b is the second terminal 17 side. It is connected to the. That is, the connection destination of one IDT electrode 212b and 214b is the common terminal 15, and the connection destination of the other IDT electrodes 211b, 213b and 215b is the second terminal 17.

  Here, Table 1 shows design parameters (main pitch λm of electrode fingers, crossing width L, IDT logarithm N, duty ratio D) of the IDT portions 211 to 215.

  The pitch of the electrode fingers of the reflectors 220 and 221 is 1.855 μm, which is larger than the main pitch λ1 to λ5 of the electrode fingers of the IDT portions 211 to 215.

  Moreover, the main pitch λm of the electrode fingers shown in Table 1 is the pitch of the electrode fingers at the center of each IDT electrode 211b to 215b. The main pitch λm is a pitch formed by electrode fingers that occupy 50% or more of all the electrode fingers of the IDT electrode 211b, taking the IDT electrode 211b as an example. In the longitudinally coupled elastic wave filter, the pitch of the electrode fingers at both ends of the IDT electrode 211b may be made smaller than that at the central portion in order to adjust the degree of coupling with the adjacent IDT electrode 212b. For this reason, the pitch λ of the electrode fingers is different between the central portion and both end portions of the IDT electrode 211b in the elastic wave propagation direction when viewed from the whole IDT electrode 211b. Therefore, in this embodiment, when comparing the pitch λ of the electrode fingers of the IDT electrodes 211b to 215b, the comparison may be made at the main pitch λm.

  In the present embodiment, as shown in Table 1, the main pitch λm of each electrode finger has the following relationship.

  (Λ2 = λ4) <(λ1 = λ5) <λ3

  That is, the main pitches λ2, λ4 of the electrode fingers of one IDT electrode 212b, 214b connected to the common terminal 15 and the electrode fingers of the other IDT electrodes 211b, 213b, 215b connected to the second terminal 17 are connected. The main pitches λ1, λ3, and λ5 are different.

  Of the main pitches λ1 to λ5 of each of the plurality of IDT electrodes 211b to 215b, the main pitch λ3 of the electrode finger of the other IDT electrode 213b connected to the second terminal 17 is the maximum. Of the main pitches λ1 to λ5, the main pitches λ2 and λ4 of the IDT electrodes 212b and 214b connected to the common terminal 15 are the smallest.

  In the present embodiment, the total average of the pitch λ of the plurality of electrode fingers included in one IDT electrode 212b, 214b is the total average of the pitch λ of the plurality of electrode fingers included in the other IDT electrode 211b, 213b, 215b. Smaller than. The total average of the pitches λ of the plurality of electrode fingers can be obtained by weighted averaging the pitches λ of the electrode fingers including the center and end portions of the IDT electrode. In this embodiment, the total average pitch of electrode fingers of one IDT electrode 212b, 214b is 1.789 μm, and the total average pitch of electrode fingers of the other IDT electrodes 211b, 213b, 215b is 1. 819 μm.

  Further, in the present embodiment, when the average value of the pitch λ of the plurality of electrode fingers is obtained for each IDT electrode 211b to 215b, the IDT electrode having the maximum average value is the other IDT electrode 211b, 213b. 215b. The average value of the pitches λ of the plurality of electrode fingers is a value obtained by calculating a weighted average of the pitches λ of the electrode fingers including the center and end portions of the IDT electrodes for each IDT electrode. In the present embodiment, the IDT electrode having the maximum average value is the IDT electrode 213b, and the IDT electrodes having the minimum average value are the IDT electrodes 212b and 214b.

[4. Configuration of second filter in comparative example]
FIG. 5 is a schematic plan view showing the second filter 552 of the multiplexer according to the comparative example.

  As shown in FIG. 5, the second filter 552 includes a plurality of IDT units 511 to 515, reflectors 220 and 221, a first port 230 and a second port 240.

  The IDT portion 511 has a pair of IDT electrodes 511a and 511b facing each other. Similarly, each of the IDT portions 512 to 515 has a pair of IDT electrodes 512a and 512b, 513a and 513b, 514a and 514b, and 515a and 515b facing each other. The IDT portions 511 to 515 are sequentially arranged along the propagation direction of the elastic wave so as to be vertically coupled.

  The IDT portions 511, 513, and 515 are connected in parallel between the first port 230 and a reference terminal (ground). Specifically, the IDT electrodes 511a, 513a, and 515a are connected to the reference terminal. The IDT electrodes 511b, 513b, and 515b are connected to the common terminal 15 via the first port 230.

  The IDT parts 512 and 514 are connected in parallel between the second port 240 and the reference terminal. Specifically, the IDT electrodes 512a and 514a are connected to the reference terminal. The IDT electrodes 512b and 514b are connected to the second terminal 17 via the second port 240.

  Thus, in the second filter 552 of the comparative example, among the plurality of IDT portions 511 to 515, one IDT electrode 511b, 513b and 515b is connected to the common terminal 15, and the other IDT electrode 512b and 514b is the second. It is connected to the terminal 17.

  Here, Table 2 shows design parameters of the IDT portions 511 to 515 of the comparative example.

  The pitch of the electrode fingers of the reflectors 220 and 221 is 1.861 μm, which is larger than the main pitch λ1 of the electrode fingers of the IDT portion 511 and smaller than the main pitch λ3 of the electrode fingers of the IDT portion 513.

  In the comparative example, as shown in Table 2, the main pitch λm of the electrode fingers has the following relationship.

  (Λ2 = λ4) <(λ1 = λ5) <λ3

  The magnitude relationship of the main pitch λm of the electrode fingers in the comparative example is the same as in the embodiment. However, the comparative example is different from the present embodiment in that the IDT electrodes 511b, 513b, and 515b are connected to the common terminal 15 and the IDT electrodes 512b and 514b are connected to the second terminal 17.

[5. Frequency characteristics of embodiment and comparative example]
Hereinafter, the frequency characteristics of the multiplexers in the present embodiment and the comparative example will be described.

  FIG. 6 is a diagram illustrating the insertion loss in the frequency pass band of the first filter 11. As an evaluation circuit corresponding to the embodiment, as shown in FIG. 6A, a circuit in which one lead of the first filter 11 and the second filter 12 is bundled is used. As an evaluation circuit corresponding to the comparative example, a circuit obtained by replacing the second filter 12 of the embodiment with the second filter 552 of the comparative example was used.

  FIG. 6B is a diagram illustrating the insertion loss (passage characteristics) of the embodiment and the comparative example from 1850 MHz to 2050 MHz. As shown in FIG. 6B, in the comparative example, the insertion loss is large in the vicinity of 1975 MHz, which is within the Band25Rx band. On the other hand, in the embodiment, the insertion loss near 1975 MHz is smaller than that of the comparative example. This difference will be described with reference to FIG.

  FIG. 7 is a diagram showing the return loss of the second filter 12 (or 552) in the frequency pass band of the first filter 11. As shown in FIG. As an evaluation circuit corresponding to the embodiment, as shown in FIG. 7A, a circuit composed only of the second filter 12 is used by releasing the bundle of the first filter 11 and the second filter 12. . As an evaluation circuit corresponding to the comparative example, a circuit including only the second filter 552 of the comparative example was used.

  (B) of FIG. 7 is a figure which shows each return loss of embodiment and a comparative example in 1850 MHz to 2050 MHz. As shown in FIG. 7B, in the comparative example, an unnecessary wave with a large return loss occurs in the vicinity of 1975 MHz within the Band 25Rx band. This indicates that the second filter 552 of the comparative example absorbs a part of the signal input at 1975 MHz without being sufficiently reflected. In the comparative example, since this unnecessary wave exists in the vicinity of 1975 Mz, it is considered that the insertion loss in the vicinity of 1975 MHz is large as shown in FIG.

  On the other hand, in the embodiment, the return loss is small in the Band25Rx band. This is because by changing the pitch λ of the electrode fingers of the IDT electrodes 211b to 215b, it passes the position of the unnecessary wave where the return loss of the second filter 12 generated in the frequency pass band (Band25Rx) of the first filter 11 becomes large. This is because they are moved out of band. Specifically, the main pitch λm of the electrode fingers of the IDT electrodes 211b, 213b, and 215b connected to the second terminal 17 is increased, or the main pitch of the electrode fingers of the IDT electrodes 212b and 214b connected to the common terminal 15 This is because by reducing λm, the position of the unnecessary wave can be moved to the higher frequency side than the pass band of the first filter 11. Thereby, in the multiplexer 1A using the second filter 12 of the embodiment, it is possible to suppress an increase in insertion loss in the pass band of the first filter 11.

[6. Summary]
As described above, the multiplexer 1A according to the present embodiment includes the common terminal 15, the first terminal 16, the second terminal 17, and the first filter 11 disposed on the path connecting the common terminal 15 and the first terminal 16. A second filter 12 is disposed on a path connecting the common terminal 15 and the second terminal 17 and has a higher passband frequency than the first filter 11.

  The 2nd filter 12 is an elastic wave filter, Comprising: It has several IDT parts 211-215 arrange | positioned along the propagation direction of an elastic wave. Each of the plurality of IDT portions 211 to 215 is composed of a pair of IDT electrodes facing each other, and one of the plurality of IDT electrodes constituting the plurality of IDT portions 211 to 215 is common to one IDT electrode 212b, 214b. The terminal 15 and the second terminal 17 are connected to the common terminal 15 side, and the other IDT electrodes 211b, 213b, and 215b are connected to the common terminal 15 and the second terminal 17 on the second terminal 17 side. . Each of the IDT electrodes 212b and 214b and the other IDT electrodes 211b, 213b, and 215b has a plurality of electrode fingers formed on the surface of the piezoelectric substrate 326 and arranged in the propagation direction of the elastic wave. One IDT electrode 212b, 214b and the other IDT electrode 211b, 213b, 215b have different main pitches λm of a plurality of electrode fingers arranged in the propagation direction of the elastic wave, and at least one of the other IDT electrodes 211b, 213b, 215b. One of the plurality of IDT electrodes 211b to 215b has the largest main pitch λm of electrode fingers.

  According to this configuration, it is possible to move the position of the unnecessary wave where the return loss of the second filter 12 generated in the frequency pass band of the first filter 11 becomes large outside the pass band of the first filter 11. Thereby, when an elastic wave filter is used in the multiplexer 1A, it is possible to suppress a decrease in pass characteristics of other filters constituting the same multiplexer.

  Further, at least one of the one IDT electrodes 212b and 214b may have a minimum main pitch λm of electrode fingers among the plurality of IDT electrodes 211b to 215b.

  According to this, the position of the unwanted wave where the return loss of the second filter 12 generated in the pass band of the first filter 11 becomes larger than the pass band of the first filter 11 is higher than the second filter 12. It is possible to move within the low frequency side stop band. Thereby, when an elastic wave filter is used in the multiplexer 1A, it is possible to suppress a decrease in pass characteristics of other filters constituting the same multiplexer.

  Further, in the multiplexer 1A according to the present embodiment, the total average of the electrode finger pitch λ of one IDT electrode 212b, 214b is the total average of the electrode finger pitch λ of the other IDT electrode 211b, 213b, 215b. Smaller than.

  Further, in the multiplexer 1A according to the present embodiment, when the average value of the pitch λ of the electrode fingers is obtained in each of the IDT electrodes 211b to 215b, the IDT electrode having the maximum average value is the other IDT electrode 211b, 213b. 215b.

  According to this configuration, it is possible to move the position of the unnecessary wave where the return loss of the second filter 12 generated in the frequency pass band of the first filter 11 becomes large outside the pass band of the first filter 11. Thereby, when an elastic wave filter is used in the multiplexer 1A, it is possible to suppress a decrease in pass characteristics of other filters constituting the same multiplexer.

(Other forms etc.)
Although the multiplexers 1 and 1A according to the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. For example, an aspect in which the following embodiment is modified as follows can be included in the present invention.

  FIG. 8 is a circuit configuration diagram showing the high-frequency front-end module 8 including the multiplexer 1B. In the high frequency front end module 8 shown in FIG. 8, in order to amplify an input signal, an LNA (Low Noise Amplifier) 3 is provided between the first terminal 16 and the RFIC 4 and between the second terminal 17 and the RFIC 4. Is provided. In order to switch the connection state with the antenna element 2, the multiport switch 5 is provided between the first filter 11 and the common terminal 15 and between the second filter 12 and the common terminal 15. The multi-port switch 5 is a switch that can be turned ON / OFF at the same time. When the first filter 11 is connected to the common terminal 15, that is, when the first filter 11 performs signal processing, The two filters 12 can also be connected to the common terminal 15.

  Also in the high-frequency front end module 8 having such a circuit configuration, when an elastic wave filter is used as a part of the multiplexer 1A, the pass characteristics of other filters constituting the same multiplexer are reduced, as in the above embodiment. Can be suppressed.

  In the present embodiment, the example in which both the first filter 11 and the second filter 12 of the multiplexer 1A are reception filters has been described. However, the present invention is not limited to this, and both may be transmission filters. The reception filter and the other may be a transmission filter. Specifically, the Band 66 Rx band-pass filter may be the second filter 12, and either the Band 25 Tx or Band 66 Tx band-pass filter may be the first filter 11. Alternatively, the Band 25 Rx band pass filter may be the second filter 12, and either the Band 66 Tx or Band 25 Tx band pass filter may be the first filter 11. Further, the Band 25 Tx pass band filter may be the second filter 12, and the Band 66 Tx band pass filter may be the first filter 11.

  In addition, for example, an aspect in which the following embodiment is modified as described below may be included in the present invention.

  FIG. 9 is a schematic plan view showing the configuration of the multiplexer according to another embodiment on the second filter 12 side.

  In the multiplexer according to this embodiment, the circuit element 350 is connected between the IDT electrodes 212 b and 214 b of the second filter 12 and the common terminal 15. Specifically, a circuit element 350 different from the second filter 12 is connected in series between the first port 230 and the common terminal 15. The circuit element 350 is, for example, an inductor, a capacitor, a switch, an LC resonator, or an acoustic wave resonator. For example, the LC resonator and the acoustic wave resonator may be a series resonator, a parallel resonator, or a resonator including both a series resonator and a parallel resonator. . The circuit element 350 may be provided for frequency trapping or impedance matching.

  In the present invention, even when the circuit element 350 is connected between the one IDT electrode 212b, 214b and the common terminal 15 as described above, the second generated in the frequency pass band of the first filter 11. It is possible to move the position of the unnecessary wave where the return loss of the filter 12 becomes large outside the pass band of the first filter 11. Thereby, when an elastic wave filter is used in the multiplexer 1A, it is possible to suppress a decrease in pass characteristics of other filters constituting the same multiplexer.

  Moreover, in the said embodiment, the surface acoustic wave filter which has an IDT electrode was illustrated as the multiplexer 1, 1A, and the high frequency front end module 8. FIG. However, the filters constituting the multiplexers 1 and 1A and the high-frequency front-end module 8 according to the present invention may be elastic wave filters using boundary acoustic waves. This also produces the same effect as the effect of the multiplexer according to the above embodiment.

Further, the piezoelectric substrate 326 constituting the surface acoustic wave filter may have a laminated structure in which a high acoustic velocity support substrate, a low acoustic velocity film, and a piezoelectric film are laminated in this order. The piezoelectric film may be, for example, a 50 ° Y-cut X-propagating LiTaO ₃ piezoelectric single crystal or a piezoelectric ceramic (a lithium tantalate single crystal cut along a plane whose axis is rotated by 50 ° from the Y axis with the X axis as the central axis, Alternatively, it is made of ceramic and is made of a single crystal or ceramic in which surface acoustic waves propagate in the X-axis direction. The piezoelectric film has a thickness of 600 nm, for example. The high sound velocity support substrate is a substrate that supports the low sound velocity film, the piezoelectric film, and the IDT electrode. The high-sonic support substrate is a substrate in which the acoustic velocity of the bulk wave in the high-sonic support substrate is higher than that of the surface wave or boundary wave that propagates through the piezoelectric film. It functions in such a way that it is confined in the portion where the sonic film is laminated and does not leak below the high sonic support substrate. The high sound speed support substrate is, for example, a silicon substrate, and has a thickness of, for example, 200 μm. The low acoustic velocity film is a membrane in which the acoustic velocity of the bulk wave in the low acoustic velocity film is lower than the bulk wave propagating through the piezoelectric membrane, and is disposed between the piezoelectric membrane and the high acoustic velocity support substrate. Due to this structure and the property that energy is concentrated in a medium where acoustic waves are essentially low in sound velocity, leakage of surface acoustic wave energy to the outside of the IDT electrode is suppressed. The low acoustic velocity film is, for example, a film mainly composed of silicon dioxide and has a thickness of, for example, 670 nm. According to this laminated structure, the Q value at the resonance frequency and the anti-resonance frequency can be greatly increased as compared with a structure in which the piezoelectric substrate 326 is used as a single layer. That is, since a surface acoustic wave resonator having a high Q value can be configured, a filter with a small insertion loss can be configured using the surface acoustic wave resonator.

  INDUSTRIAL APPLICABILITY The present invention can be widely used in communication devices such as mobile phones as a low-loss multiplexer and a high-frequency front-end module that can be applied to multiband and multimode frequency standards.

1, 1A, 1B Multiplexer 2 Antenna element 3 LNA
4 RFIC (High Frequency Signal Processing Circuit)
DESCRIPTION OF SYMBOLS 5 Multiport switch 8 High frequency front end module 9 Communication apparatus 11 1st filter 12 2nd filter 15 Common terminal 16 1st terminal 17 2nd terminal 22 IDT part 22a, 22b IDT electrode 101,103 Transmission side filter 102,104 Reception side Filter 106, 108 Transmission input terminal 107, 109 Reception output terminal 211, 212, 213, 214, 215 IDT part 211b, 213b, 215b Other IDT electrode 212b, 214b One IDT electrode 220, 221 Reflector 221a, 221b Bus bar electrode 222a, 222b Electrode finger 230 1st port 240 2nd port 326 Piezoelectric substrate 350 Circuit element 511, 512, 513, 514, 515 IDT part (comparative example)
511b, 513b, 515b One IDT electrode (comparative example)
512b, 514b The other IDT electrode (comparative example)
552 Second Filter (Comparative Example)
λ Pitch of electrode fingers λm, λ1, λ2, λ3, λ4, λ5 Main pitch of electrode fingers

Claims (11)

A common terminal, a first terminal and a second terminal;
A first filter disposed on a path connecting the common terminal and the first terminal;
A second filter disposed on a path connecting the common terminal and the second terminal and having a higher passband frequency than the first filter;
The second filter is an elastic wave filter, and has a plurality of IDT portions arranged along the propagation direction of the elastic wave,
Each of the plurality of IDT portions is composed of a pair of IDT electrodes facing each other,
Of the plurality of IDT electrodes constituting the plurality of IDT portions, one IDT electrode is connected to the common terminal side of the common terminal and the second terminal, and the other IDT electrode is the common terminal and the Connected to the second terminal of the second terminals,
Each of the one IDT electrode and the other IDT electrode has a plurality of electrode fingers formed on the surface of the piezoelectric substrate and arranged in the propagation direction of the elastic wave,
The main pitch of the electrode fingers is different between the one IDT electrode and the other IDT electrode,
At least one of the other IDT electrodes has a maximum main pitch of the electrode fingers among the plurality of IDT electrodes. The multiplexer according to claim 1, wherein at least one of the one IDT electrodes has a minimum main pitch of the electrode fingers among the plurality of IDT electrodes. A common terminal, a first terminal and a second terminal;
A first filter disposed on a path connecting the common terminal and the first terminal;
A second filter disposed on a path connecting the common terminal and the second terminal and having a higher passband frequency than the first filter;
The second filter is an elastic wave filter, and has a plurality of IDT portions arranged along the propagation direction of the elastic wave,
Each of the plurality of IDT portions is composed of a pair of IDT electrodes facing each other,
Of the plurality of IDT electrodes constituting the plurality of IDT portions, one IDT electrode is connected to the common terminal side of the common terminal and the second terminal, and the other IDT electrode is the common terminal and the Connected to the second terminal of the second terminals,
Each of the one IDT electrode and the other IDT electrode has a plurality of electrode fingers formed on the surface of the piezoelectric substrate and arranged in the propagation direction of the elastic wave,
The main pitch of the electrode fingers is different between the one IDT electrode and the other IDT electrode,
The total average pitch of the electrode fingers of the one IDT electrode is smaller than the total average pitch of the electrode fingers of the other IDT electrode. Multiplexer. A common terminal, a first terminal and a second terminal;
A first filter disposed on a path connecting the common terminal and the first terminal;
A second filter disposed on a path connecting the common terminal and the second terminal and having a higher passband frequency than the first filter;
The second filter is an elastic wave filter, and has a plurality of IDT portions arranged along the propagation direction of the elastic wave,
Each of the plurality of IDT portions is composed of a pair of IDT electrodes facing each other,
Of the plurality of IDT electrodes constituting the plurality of IDT portions, one IDT electrode is connected to the common terminal side of the common terminal and the second terminal, and the other IDT electrode is the common terminal and the Connected to the second terminal of the second terminals,
Each of the one IDT electrode and the other IDT electrode has a plurality of electrode fingers formed on the surface of the piezoelectric substrate and arranged in the propagation direction of the elastic wave,
The main pitch of the electrode fingers is different between the one IDT electrode and the other IDT electrode,
The multiplexer in which the IDT electrode having the maximum average value exists in the other IDT electrode when the average value of the pitches of the electrode fingers is obtained in each of the IDT electrodes. The multiplexer according to claim 4, wherein an IDT electrode having the minimum average value exists in the one IDT electrode when an average value of pitches of the electrode fingers is obtained in each of the IDT electrodes. The multiplexer according to any one of claims 1 to 5, wherein a circuit element different from the second filter is connected between the one IDT electrode and the common terminal. The second filter has an odd number of IDT portions of 3 or more,
The multiplexer according to claim 1, wherein the number of the one IDT electrode is smaller than the number of the other IDT electrode. The multiplexer according to claim 1, wherein the second filter includes five or more IDT units. The multiplexer according to any one of claims 1 to 8, wherein the first filter and the second filter are reception filters. The multiplexer according to any one of claims 1 to 9, wherein the second filter is connected to the common terminal when the first filter is connected to the common terminal.   A high frequency front end module comprising the multiplexer according to claim 1.

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