WO2022019072A1 - Acoustic wave filter, and multiplexer - Google Patents

Acoustic wave filter, and multiplexer Download PDF

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Publication number
WO2022019072A1
WO2022019072A1 PCT/JP2021/024758 JP2021024758W WO2022019072A1 WO 2022019072 A1 WO2022019072 A1 WO 2022019072A1 JP 2021024758 W JP2021024758 W JP 2021024758W WO 2022019072 A1 WO2022019072 A1 WO 2022019072A1
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WIPO (PCT)
Prior art keywords
elastic wave
electrode
idt
electrode fingers
signal terminal
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PCT/JP2021/024758
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French (fr)
Japanese (ja)
Inventor
明 野口
Original Assignee
株式会社村田製作所
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Application filed by 株式会社村田製作所 filed Critical 株式会社村田製作所
Priority to CN202190000716.5U priority Critical patent/CN219592382U/en
Publication of WO2022019072A1 publication Critical patent/WO2022019072A1/en

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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/125—Driving means, e.g. electrodes, coils
    • H03H9/145—Driving means, e.g. electrodes, coils for networks using surface acoustic waves
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/46—Filters
    • H03H9/64—Filters using surface acoustic waves
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/70—Multiple-port networks for connecting several sources or loads, working on different frequencies or frequency bands, to a common load or source
    • H03H9/72—Networks using surface acoustic waves

Definitions

  • the present invention relates to an elastic wave filter and a multiplexer.
  • Patent Document 1 discloses an elastic wave filter including a filter circuit having a predetermined frequency band as a pass band and a cancel line connected in parallel to the filter circuit.
  • an unnecessary wave outside the pass band is subjected to an antiphase by using a cancel line to cancel the unnecessary wave and increase the attenuation amount outside the pass band.
  • the resonance Q of the cancel line becomes higher than necessary, unnecessary waves such as spurious are generated outside the pass band, and the amount of attenuation outside the pass band may not be sufficiently secured.
  • the present invention has been made to solve the above problems, and an object of the present invention is to provide an elastic wave filter or the like that can secure an amount of attenuation outside the frequency passband.
  • the elastic wave filter has a predetermined frequency band as a passing band and is arranged on a first path connecting the first signal terminal and the second signal terminal.
  • a first filter circuit and an additional circuit connected in parallel to at least a part of the first filter circuit are provided, and the additional circuit comprises a plurality of IDT electrodes arranged along an elastic wave propagation direction.
  • the ratio of the number of electrode fingers of the plurality of reflectors having the IDT electrode group and located on both outer sides of the IDT electrode group in the direction of propagation of the elastic wave is the number of electrode fingers of the plurality of IDT electrodes and the plurality of electrode fingers. It is 11% or less of the total number of electrode fingers of the reflector.
  • the multiplexer has a pass band of the elastic wave filter, the first signal terminal, the second signal terminal and the third signal terminal, and a frequency band different from that of the first filter circuit.
  • a second filter circuit arranged on a third path connecting the second signal terminal and the third signal terminal is provided.
  • the elastic wave filter or the like according to the present invention, it is possible to secure the amount of attenuation outside the frequency passband.
  • FIG. 1 is a circuit configuration diagram of a multiplexer including an elastic wave filter according to the first embodiment.
  • FIG. 2 is a schematic diagram showing a group of IDT electrodes included in the additional circuit of the elastic wave filter according to the first embodiment.
  • FIG. 3 is a plan view and a cross-sectional view schematically showing the structure of the IDT electrode group shown in FIG.
  • FIG. 4 is a diagram showing the passing characteristics of the elastic wave filter according to the first embodiment.
  • FIG. 5 is a diagram showing the isolation characteristics of the multiplexer according to the first embodiment.
  • FIG. 6 is a diagram showing the relationship between the ratio of the number of electrode fingers of the reflector and the peak level of unnecessary waves.
  • FIG. 7 is a circuit configuration diagram of a multiplexer including an elastic wave filter according to the second embodiment.
  • FIG. 8 is a schematic diagram showing a group of IDT electrodes included in the additional circuit of the elastic wave filter according to the second embodiment.
  • FIG. 9 is a plan view schematically showing the structure of the IDT electrode group shown in FIG.
  • FIG. 10 is a diagram showing the passage characteristics of the elastic wave filter according to the second embodiment.
  • FIG. 11 is a diagram showing the relationship between the ratio of the number of electrode fingers of the reflector and the peak level of unnecessary waves.
  • FIG. 1 is a circuit configuration diagram of a multiplexer 5 including the elastic wave filter 1 according to the first embodiment. Note that FIG. 1 also shows the antenna element 9.
  • the multiplexer 5 is a demultiplexer or combiner including a plurality of filters having different frequency pass bands. As shown in FIG. 1, the multiplexer 5 includes an elastic wave filter 1 having a first filter circuit 10 and an additional circuit 20, and a second filter circuit 50. Further, the multiplexer 5 includes a first signal terminal T1, a second signal terminal T2, and a third signal terminal T3.
  • the first signal terminal T1 is connected to the elastic wave filter 1. Further, the first signal terminal T1 is connected to an RF signal processing circuit (not shown) via an amplifier circuit or the like (not shown) outside the multiplexer 5.
  • the second signal terminal T2 is a common terminal connected to each of the elastic wave filter 1 and the second filter circuit 50. Specifically, the second signal terminal T2 is connected to the elastic wave filter 1 via the node n0 between the elastic wave filter 1 and the second signal terminal T2, and is also connected to the elastic wave filter 1 via the node n0. It is connected to 50. Further, the second signal terminal T2 is connected to the antenna element 9 outside the multiplexer 5. The second signal terminal T2 is also an antenna terminal of the multiplexer 5.
  • the third signal terminal T3 is connected to the second filter circuit 50. Further, the third signal terminal T3 is connected to an RF signal processing circuit (not shown) via an amplifier circuit or the like (not shown) outside the multiplexer 5.
  • the elastic wave filter 1 is arranged on the first path r1 connecting the first signal terminal T1 and the second signal terminal T2.
  • the elastic wave filter 1 is, for example, a transmission filter having an uplink frequency band (transmission band) as a pass band, and is set so that the frequency pass band is lower than that of the second filter circuit 50.
  • the elastic wave filter 1 includes a first filter circuit 10 and an additional circuit 20 additionally connected to the first filter circuit 10.
  • the additional circuit 20 is a circuit for canceling unnecessary waves outside the frequency pass band of the first filter circuit 10. The additional circuit 20 will be described later.
  • the second filter circuit 50 is arranged on the third path r3 connecting the second signal terminal T2 and the third signal terminal T3.
  • the second filter circuit 50 is, for example, a reception filter having a downlink frequency band (reception band) as a pass band.
  • the second filter circuit 50 is composed of, for example, a series arm resonator RS1, a parallel arm resonator RP1, a series arm resonator RS2, a vertically coupled elastic wave resonator 60, and a parallel arm resonator RP2. ..
  • Each of the elastic wave filter 1 and the second filter circuit 50 is required to have a characteristic of passing through a predetermined frequency band and attenuating a band outside the frequency band.
  • the elastic wave filter 1 includes a first filter circuit 10 and an additional circuit 20.
  • the first filter circuit 10 includes series arm resonators S1, S2, S3, S4 and parallel arm resonators P1, P2, P3, which are elastic wave resonators.
  • the series arm resonators S1 to S4 are arranged on the first path (series arm) r1 connecting the first signal terminal T1 and the second signal terminal T2.
  • the series arm resonators S1 to S4 are connected in series from the first signal terminal T1 toward the second signal terminal T2 in this order.
  • the parallel arm resonators P1 to P3 are paths (parallel arms) connecting the nodes n1, n2, n3 between the adjacent series arm resonators S1 to S4 on the first path r1 and the reference terminal (ground). They are connected in parallel to each other on top. Specifically, among the parallel arm resonators P1 to P3, the parallel arm resonator P1 closest to the first signal terminal T1 has one end connected to the node n1 between the series arm resonators S1 and S2, and the other. The end is connected to the reference terminal via the inductor L1.
  • One end of the parallel arm resonator P2 is connected to the node n2 between the series arm resonators S2 and S3, and the other end is connected to the reference terminal via the inductor L2.
  • One end of the parallel arm resonator P3 is connected to the node n3 between the series arm resonators S3 and S4, and the other end is connected to the reference terminal via the inductor L2.
  • the capacitive element C11 is connected in parallel to the circuit composed of the series arm resonators S1 and S2 and the parallel arm resonators P1 and P2, and the capacitive element C12 is connected in parallel to the series arm resonator S3.
  • the first filter circuit 10 is arranged on the four series arm resonators S1 to S4 arranged on the first path r1 and the path connecting the first path r1 and the reference terminal 3. It has a T-shaped ladder filter structure composed of two parallel arm resonators P1 to P3.
  • the number of series arm resonators and parallel arm resonators constituting the first filter circuit 10 is not limited to four or three, and there are two or more series arm resonators and one or more parallel arm resonators. It should be. Further, the parallel arm resonator may be connected to the reference terminal without using an inductor. Further, in FIG. 1, a part of the reference terminals to which the parallel arm resonators are connected is shared, but whether the reference terminals are shared or individualized depends on, for example, the mounting layout of the first filter circuit 10. It can be appropriately selected due to restrictions and the like.
  • the additional circuit 20 is a circuit that suppresses the output of unnecessary waves from the elastic wave filter 1 by applying an antiphase to unnecessary waves outside the frequency passband generated by the first filter circuit 10.
  • the additional circuit 20 is connected to a plurality of different nodes on the first path r1 so as to be connected in parallel to at least a part of the first filter circuit 10.
  • the additional circuit 20 includes a first terminal 21 that is a connection node on one end side of the additional circuit 20, a second terminal 22 that is a connection node on the other end side, and a second terminal that connects the first terminal 21 and the second terminal 22. It has an IDT (InterDigital Transducer) electrode group 25 arranged on the path r2 of the above.
  • the terminal here means an inlet or an outlet of a high frequency signal.
  • the first terminal 21 is electrically connected to the IDT electrode group 25.
  • the second terminal 22 is connected to the IDT electrode group 25 via the capacitive element C22.
  • the first terminal 21 and the second terminal 22 are acoustically connected via the IDT electrode group 25.
  • each of the first terminal 21 and the second terminal 22 is connected to a different node on the first path r1.
  • the first terminal 21 is connected to the node n1 between the series arm resonators S1 and S2
  • the second terminal 22 is the node n4 between the series arm resonator S4 and the second signal terminal T2. It is connected to the.
  • FIG. 2 is a schematic diagram showing an IDT electrode group 25 included in the additional circuit 20 of the elastic wave filter 1.
  • the electrodes and the wiring are shown by solid lines.
  • the IDT electrode group 25 is an elastic wave resonator group composed of a plurality of IDT electrodes 31 and 32.
  • the IDT electrode group 25 is, for example, a vertically coupled resonator.
  • the plurality of IDT electrodes 31 and 32 are arranged adjacent to each other along the elastic wave propagation direction D1.
  • the electrode parameters of the plurality of IDT electrodes 31 and 32 are different from each other.
  • the additional circuit 20 has a plurality of reflectors 41 and 42.
  • the plurality of reflectors 41 and 42 are located on both outer sides of the IDT electrode group 25 so as to sandwich the IDT electrode group 25 in the elastic wave propagation direction D1.
  • FIG. 2 illustrates an additional circuit 20 with two reflectors 41, 42. The structures of the reflectors 41 and 42 will be described in detail later.
  • the plurality of IDT electrodes 31 and 32 have a plurality of first comb-shaped electrodes 31a and 32a and a plurality of second comb-shaped electrodes 31b and 32b.
  • one of the IDT electrodes 31 is composed of a pair of a first comb-shaped electrode 31a and a second comb-shaped electrode 31b.
  • the other IDT electrode 32 is composed of a pair of a first comb-shaped electrode 32a and a second comb-shaped electrode 32b.
  • the first comb-shaped electrode 31a and the second comb-shaped electrode 31b face each other.
  • the first comb-shaped electrode 32a and the second comb-shaped electrode 32b face each other.
  • the first comb-shaped electrodes 31a and 32a are arranged in opposite directions to each other, and the second comb-shaped electrodes 31b are arranged.
  • 32b are also arranged in opposite directions to each other.
  • the first comb-shaped electrode 31a and the second comb-shaped electrode 32b are arranged in the same direction.
  • the plurality of first comb-shaped electrodes 31a and 32a are electrically connected to a plurality of different nodes on the first path r1. Specifically, the first comb-shaped electrode 31a is connected to the node n1 by the first terminal 21, and the first comb-shaped electrode 32a is connected to the node n4 by the second terminal 22. On the other hand, each of the second comb-shaped electrodes 31b and 32b is connected to the ground.
  • first terminal 21 of the additional circuit 20 is connected to the node n1 and the second terminal 22 is connected to the node n4, but the present invention is not limited to this.
  • Each of the first terminal 21 and the second terminal 22 may be connected to the outer nodes of two or more series arm resonators adjacent to each other on the first path r1.
  • the first terminal 21 may be connected to a node on the first path r1 connecting the first signal terminal T1 and the series arm resonator S1, or may be connected to the node n2.
  • the second terminal 22 may be connected to the node n3.
  • the additional circuit 20 does not have to include the capacitive element C22.
  • the IDT electrode group 25 may be connected to the second terminal 22 by wiring without a capacitive element as long as the unnecessary wave can be appropriately suppressed.
  • the IDT electrode group 25 is composed of, for example, a plurality of surface acoustic wave (SAW) resonators.
  • SAW surface acoustic wave
  • FIG. 3 is a plan view and a cross-sectional view schematically showing the structure of the IDT electrode group 25.
  • the IDT electrode group 25 shown in FIG. 3 is for explaining a typical structure of the resonator, and the number and length of the electrode fingers included in the IDT electrode and the reflector are the same. Not limited to.
  • the IDT electrode group 25 is composed of a substrate 320 having piezoelectricity and a plurality of IDT electrodes 31 and 32 formed on the substrate 320.
  • a plurality of reflectors 41 and 42 are provided on both outer sides of the IDT electrode group 25 in the elastic wave propagation direction D1.
  • the IDT electrode group 25 and the plurality of reflectors 41 and 42 include a substrate 320, each IDT electrode 31, 32 and an electrode layer 325 constituting the plurality of reflectors 41 and 42. It is formed by a dielectric layer 326 provided on the substrate 320 so as to cover each IDT electrode 31, 32 and each reflector 41, 42.
  • the substrate 320 is, for example, a LiNbO 3 substrate (lithium niobate substrate) having a cut angle of 127.5 °.
  • the cut angle of the substrate 320 is preferably 120 ° ⁇ 20 ° or 300 ° ⁇ 20 °.
  • the electrode layer 325 has a structure in which a plurality of metal layers are laminated.
  • the electrode layer 325 is formed by, for example, laminating a Ti layer, an Al layer, a Ti layer, a Pt layer, and a NiCr layer in order from the top.
  • the dielectric layer 326 is, for example, a film containing silicon dioxide (SiO 2 ) as a main component.
  • the dielectric layer 326 is provided for the purpose of adjusting the frequency temperature characteristics of the IDT electrode group 25, protecting the electrode layer 325 from the external environment, or enhancing the moisture resistance.
  • the IDT electrode 31 has a pair of first comb-shaped electrodes 31a and second comb-shaped electrodes 31b facing each other.
  • the IDT electrode 32 has a pair of first comb-shaped electrodes 32a and second comb-shaped electrodes 32b facing each other.
  • Each of the first comb-shaped electrodes 31a and 32a has a comb-shaped shape and is composed of a plurality of electrode fingers 36a parallel to each other and a bus bar electrode 37a connecting one ends of the plurality of electrode fingers 36a to each other.
  • Each of the second comb-shaped electrodes 31b and 32b has a comb-tooth shape and is composed of a plurality of electrode fingers 36b parallel to each other and a bus bar electrode 37b connecting one ends of the plurality of electrode fingers 36b to each other.
  • the bus bar electrodes 37a and 37b are formed so as to extend along the elastic wave propagation direction D1.
  • the plurality of electrode fingers 36a and 36b are formed so as to extend in the orthogonal direction D2 of the elastic wave propagation direction D1, intersperse with each other in the orthogonal direction D2, and face the elastic wave propagation direction D1.
  • the pitches (distances between the center lines) of the plurality of electrode fingers 36a in the elastic wave propagation direction D1 are different between the IDT electrode 31 and the IDT electrode 32. Further, the pitches (distances between the center lines) of the plurality of electrode fingers 36b in the elastic wave propagation direction D1 are different between the IDT electrode 31 and the IDT electrode 32.
  • the first comb-toothed electrode 31a is connected to the first terminal 21 via the lead-out wiring d1a.
  • the first comb-shaped electrode 32a is connected to the second terminal 22 via the lead-out wiring d2a and the capacitive element C22.
  • the second comb-shaped electrode 31b is connected to the ground via the lead-out wiring d1b.
  • the second comb-toothed electrode 32b is connected to the ground via the lead-out wiring d2b.
  • the ground may be a ground connection electrode (not shown) provided on the substrate of the multiplexer 5.
  • the plurality of reflectors 41 and 42 are arranged so as to sandwich the IDT electrodes 31 and 32 in the elastic wave propagation direction D1.
  • the reflectors 41 and 42 are independent electrodes that are not connected to each other.
  • the reflectors 41 and 42 shown in FIG. 3 are not connected to the ground and are in an open state.
  • the reflectors 41 and 42 may be connected to the ground or may be connected to a hot terminal (signal terminal).
  • Each of the reflectors 41 and 42 is composed of a plurality of electrode fingers 46 parallel to each other and a plurality of bus bars 47 connecting both ends of the plurality of electrode fingers 46.
  • Each electrode finger 46 is formed so as to extend in the orthogonal direction D2 of the elastic wave propagation direction D1.
  • Each bus bar 47 is formed so as to extend in the elastic wave propagation direction D1.
  • the number of the electrode fingers 46 of the reflectors 41 and 42 is two or more, and the ratio R is 0 ⁇ (the number of the electrode fingers 46 / (the number of the electrode fingers 36a and 36b + the number of the electrode fingers 46)). It is desirable to have a relationship of ⁇ 100.
  • the duty of the reflectors 41 and 42 is smaller than the duty of the IDT electrodes 31 and 32, respectively.
  • the duty of each reflector 41, 42 is 0.3 or more and less than 0.5.
  • the duties of the reflectors 41 and 42 may be the same or different.
  • the duty of the reflector in the present embodiment is a value obtained by dividing the width of the electrode fingers 46 by the distance between the electrode fingers 46 adjacent to each other in the elastic wave propagation direction D1 (the distance between the center lines of the adjacent electrode fingers). Is.
  • the duty of the IDT electrodes 31 and 32 means that the width of the electrode fingers 36a (or 36b) of the IDT electrodes 31 and 32 is the distance between the electrode fingers 36a and the electrode fingers 36b adjacent to each other in the elastic wave propagation direction D1 (adjacent electrode fingers). It is the value divided by the distance between the center lines of.
  • the ratio R of the number of electrode fingers 46 of the reflectors 41 and 42 is 11% or less of the total number of electrode fingers 36a, 36b and 46. According to this, it is possible to secure the amount of attenuation of the elastic wave filter 1 outside the frequency passband.
  • the effects of the first embodiment will be specifically described.
  • FIG. 4 is a diagram showing the passing characteristics of the elastic wave filter 1.
  • FIG. 5 is a diagram showing the isolation characteristics of the multiplexer 5.
  • the elastic wave filter is used as a transmission filter
  • the second filter circuit 50 is used as a receive filter
  • the frequency passband of the elastic wave filter is 880 MHz-915 MHz
  • the frequency passband of the second filter circuit 50 is 925 MHz.
  • An example of -960 MHz is shown.
  • FIG. 4 shows an insertion loss between the first signal terminal T1 and the second signal terminal T2
  • FIG. 5 shows the insertion loss between the first signal terminal T1 and the third signal terminal T3. There is.
  • the number of the electrode fingers 36a and 36b of the IDT electrode is 70
  • the number of the electrode fingers 46 of the reflectors 41 and 42 (total number) is 7
  • the number of the electrode fingers 46 is 7.
  • the ratio R of the number is 9.1%.
  • the elastic wave filter of the comparative example has 70 electrode fingers 36a and 36b of the IDT electrode, 11 electrode fingers 46 of the reflectors 41 and 42 (total number), and is a ratio of the number of electrode fingers 46. R is 13.6%.
  • FIG. 6 is a diagram showing the relationship between the ratio R of the number of electrode fingers 46 of the reflectors 41 and 42 and the peak level of unnecessary waves.
  • the horizontal axis of FIG. 6 is the ratio R of the number of electrode fingers 46, and the vertical axis is the peak level of the largest unnecessary wave in the isolation characteristic of the multiplexer.
  • the peak level of unwanted waves is represented by insertion loss.
  • the ratio R of the number of electrode fingers 46 of the reflectors 41 and 42 was set according to the conditions shown in Table 1. Specifically, the number of each of the electrode fingers of the IDT electrodes 31 and 32 is 35, and the number of each of the electrode fingers 46 of the reflectors 41 and 42 is changed between 0 and 17 or less. The ratio R of the number of fingers 46 was changed.
  • the duty of the IDT electrodes 31 and 32 and the duty of the reflectors 41 and 42 are as shown in Table 1.
  • the ratio R of the number of electrode fingers 46 of the reflectors 41 and 42 is larger than 11%, the peak level of unnecessary waves is not so large even if the ratio R of the number of electrode fingers 46 is reduced. Does not decrease.
  • FIG. 7 is a circuit configuration diagram of a multiplexer 5 including the elastic wave filter 1 according to the second embodiment. Note that FIG. 7 also shows the antenna element 9.
  • the multiplexer 5 includes an elastic wave filter 1 having a first filter circuit 10 and an additional circuit 20A, and a second filter circuit 50. Further, the multiplexer 5 includes a first signal terminal T1, a second signal terminal T2, and a third signal terminal T3.
  • the elastic wave filter 1 of the second embodiment includes a first filter circuit 10 and an additional circuit 20A.
  • the first filter circuit 10 is the same as that of the first embodiment. That is, the first filter circuit 10 is arranged on the four series arm resonators S1 to S4 arranged on the first path r1 and on the path connecting the first path r1 and the reference terminal. It has a T-shaped ladder filter structure composed of three parallel arm resonators P1 to P3.
  • the additional circuit 20A is connected to a plurality of different nodes on the first path r1 so as to be connected in parallel to at least a part of the first filter circuit 10.
  • the additional circuit 20A includes first terminals 21 and 21a as connection nodes on one end side of the additional circuit 20A, second terminals 22 and 22a as connection nodes on the other end side, and first terminals 21 and 21a and second terminals. It has an IDT electrode group 25A arranged on the second path r2, r2a connecting 22 and 22a.
  • the first terminals 21 and 21a are electrically connected to the IDT electrode group 25A.
  • the second terminal 22 is connected to the IDT electrode group 25A via the capacitive element C22, and the second terminal 22a is connected to the IDT electrode group 25A via the capacitive element C22a.
  • each of the first terminals 21, 21a and the second terminals 22, 22a is connected to different nodes on the first path r1.
  • the first terminal 21 is connected to the node n1 between the series arm resonators S1 and S2
  • the first terminal 21a is connected to the node n2
  • the second terminal 22 is the series arm resonator S4.
  • the second terminal 22a is connected to the node n4a between the series arm resonator S4 and the second signal terminal T2.
  • FIG. 8 is a schematic diagram showing the IDT electrode group 25A included in the additional circuit 20A of the elastic wave filter 1. Also in FIG. 8, the electrodes and wiring are shown by solid lines.
  • the IDT electrode group 25A is composed of a plurality of IDT electrodes 31, 32, 33, 34.
  • the IDT electrode group 25A is, for example, a vertically coupled resonator.
  • the plurality of IDT electrodes 31, 32, 33, 34 are arranged adjacent to each other along the elastic wave propagation direction D1 in this order.
  • the additional circuit 20 has a plurality of reflectors 41 and 42.
  • the plurality of reflectors 41 and 42 are located on both outer sides of the IDT electrode group 25A so as to sandwich the IDT electrode group 25A in the elastic wave propagation direction D1.
  • FIG. 7 illustrates an IDT electrode group 25A including two reflectors 41 and 42.
  • the plurality of IDT electrodes 31 to 34 have a plurality of first comb-shaped electrodes 31a, 32a, 33a, 34a and a plurality of second comb-shaped electrodes 31b, 32b, 33b, 34b.
  • the IDT electrode 31 is composed of a pair of a first comb-shaped electrode 31a and a second comb-shaped electrode 31b.
  • the IDT electrode 32 is composed of a pair of a first comb-shaped electrode 32a and a second comb-shaped electrode 32b.
  • the IDT electrode 33 is composed of a pair of a first comb-shaped electrode 33a and a second comb-shaped electrode 33b.
  • the IDT electrode 34 is composed of a pair of a first comb-shaped electrode 34a and a second comb-shaped electrode 34b.
  • the first comb-shaped electrode and the second comb-shaped electrode face each other.
  • the first comb-shaped electrodes 31a and 33a and the first comb-shaped electrodes 32a and 34a are arranged in opposite directions to each other.
  • the second comb-shaped electrodes 31b and 33b and the second comb-shaped electrodes 32b and 34b are arranged in opposite directions to each other.
  • the first comb-shaped electrodes 31a and 33a and the second comb-shaped electrodes 32b and 34b are arranged in the same direction.
  • the plurality of first comb-shaped electrodes 31a to 34a are electrically connected to a plurality of nodes on the first path r1. Specifically, the first comb-shaped electrode 31a is connected to the node n1 by the first terminal 21, the first comb-shaped electrode 33a is connected to the node n2 by the first terminal 21a, and the first comb-shaped electrode is formed. The electrode 33a is connected to the node n4 by the second terminal 22, and the first comb-shaped electrode 34a is connected to the node n4a by the second terminal 22a. On the other hand, each of the second comb-shaped electrodes 31b to 34b is connected to the ground.
  • the first terminals 21, 21a and the second terminals 22, 22a may be connected to the outer nodes of two or more series arm resonators adjacent to each other on the first path r1.
  • the first terminal 21 may be connected to a node on the first path r1 connecting the first signal terminal T1 and the series arm resonator S1, or may be connected to the node n2.
  • the first terminal 21a may be connected to the node n1.
  • the second terminals 22 and 22a may be connected to the node n3.
  • the additional circuit 20A does not have to include the capacitive elements C22 and C22a.
  • the IDT electrode group 25A may be connected to the second terminals 22 and 22a by wiring without using a capacitive element as long as the unnecessary wave can be appropriately suppressed.
  • FIG. 9 is a plan view schematically showing the structure of the IDT electrode group 25A shown in FIG.
  • each of the first comb-shaped electrodes 31a to 34a is composed of a plurality of electrode fingers 36a parallel to each other and a bus bar electrode 37a connecting one ends of the plurality of electrode fingers 36a to each other.
  • Each of the second comb-shaped electrodes 31b to 34b is composed of a plurality of electrode fingers 36b parallel to each other and a bus bar electrode 37b connecting one ends of the plurality of electrode fingers 36b to each other.
  • the plurality of electrode fingers 36a and 36b are formed so as to extend in the orthogonal direction D2 of the elastic wave propagation direction D1, intersperse with each other in the orthogonal direction D2, and face the elastic wave propagation direction D1.
  • the bus bar electrodes 37a and 37b are formed so as to extend along the elastic wave propagation direction D1.
  • the plurality of reflectors 41 and 42 are arranged so as to sandwich the plurality of IDT electrodes 31 to 34 in the elastic wave propagation direction D1.
  • the reflectors 41 and 42 are independent electrodes that are not connected to each other.
  • Each of the reflectors 41 and 42 has a plurality of electrode fingers 46 parallel to each other and a plurality of bus bars 47 connecting both ends of the plurality of electrode fingers 46. And, it is composed of.
  • Each electrode finger 46 is formed so as to extend in the orthogonal direction D2 of the elastic wave propagation direction D1.
  • Each bus bar 47 is formed so as to extend in the elastic wave propagation direction D1.
  • the number of the electrode fingers 46 is two or more, and the ratio R may have a relationship of 0 ⁇ (the number of the electrode fingers 46 / (the number of the electrode fingers 36a and 36b + the number of the electrode fingers 46)) ⁇ 100. desirable.
  • the duty of each of the reflectors 41 and 42 is smaller than the duty of the IDT electrodes 31 to 34.
  • the duty of each reflector 41, 42 is 0.1 or more and less than 0.5.
  • the duties of the reflectors 41 and 42 may be the same or different.
  • the ratio R of the number of the electrode fingers 46 of the reflectors 41 and 42 is set to 11% or less of the total number of the electrode fingers 36a, 36b and 46. According to this, it is possible to secure the amount of attenuation of the elastic wave filter 1 outside the frequency passband.
  • the effects of the second embodiment will be specifically described.
  • FIG. 10 is a diagram showing the passing characteristics of the elastic wave filter 1 of the second embodiment.
  • the elastic wave filter is used as a transmission filter
  • the second filter circuit 50 is used as a reception filter
  • the frequency pass band of the elastic wave filter is 880 MHz-915 MHz
  • the frequency pass band of the second filter circuit 50 is 925 MHz-960 MHz.
  • An example is shown.
  • FIG. 10 shows an insertion loss between the first signal terminal T1 and the second signal terminal T2.
  • the number of the electrode fingers 36a and 36b of the IDT electrode is 74, the number of the electrode fingers 46 of the reflectors 41 and 42 (total number) is 7, and the number of the electrode fingers 46 is 7.
  • the ratio R of the number is 8.6%.
  • the elastic wave filter of the comparative example has 74 electrode fingers 36a and 36b of the IDT electrode and 11 electrode fingers 46 (total number) of the reflectors 41 and 42, and is a ratio of the number of electrode fingers 46. R is 12.9%.
  • FIG. 11 is a diagram showing the relationship between the ratio R of the number of electrode fingers 46 of the reflectors 41 and 42 and the peak level of unnecessary waves.
  • the horizontal axis of FIG. 11 is the ratio R of the number of electrode fingers 46, and the vertical axis is the peak level of the largest unnecessary wave.
  • the peak level of unwanted waves is expressed as insertion loss.
  • the ratio R of the number of electrode fingers 46 was set according to the conditions shown in Table 2. Specifically, the number of electrode fingers of the IDT electrodes 31, 32, 33, and 34 is 19, 23, 11, and 23, respectively, and the number of electrode fingers 46 of the reflector 41 is 0 or more and 17 or less. In addition, by changing the number of the electrode fingers 46 of the reflector 41 between 0 and more and 21 or less, the ratio R of the number of the electrode fingers 46 was changed.
  • the duty of the IDT electrodes 31 to 34 and the duty of the reflectors 41 and 42 are as shown in Table 2.
  • the ratio R of the number of electrode fingers 46 when the ratio R of the number of electrode fingers 46 is larger than 11.9%, the peak level of unnecessary waves does not decrease so much even if the ratio R of the number of electrode fingers 46 is reduced.
  • the elastic wave filter 1 has a predetermined frequency band as a pass band and is arranged on the first path r1 connecting the first signal terminal T1 and the second signal terminal T2.
  • a first filter circuit 10 and an additional circuit 20 connected in parallel to at least a part of the first filter circuit 10 are provided.
  • the additional circuit 20 has an IDT electrode group 25 composed of a plurality of IDT electrodes arranged along the elastic wave propagation direction D1.
  • the ratio R of the number of the electrode fingers 46 of the plurality of reflectors 41 and 42 located on both outer sides of the IDT electrode group 25 in the elastic wave propagation direction D is the number of the electrode fingers 36a and 36b of the plurality of IDT electrodes and the plurality of reflections. It is 11% or less of the total number of electrode fingers 46 of the vessels 41 and 42.
  • the resonance Q of the additional circuit 20 is required by setting the ratio R of the number of the electrode fingers 46 of the reflectors 41 and 42 in the additional circuit 20 to 11% or less of the total number of the electrode fingers 36a, 36b and 46. It is possible to suppress the increase above. As a result, it is possible to suppress the generation of unnecessary waves outside the frequency passband of the elastic wave filter 1 and secure the amount of attenuation outside the frequency passband.
  • the IDT electrode group 25 may be composed of two or more IDT electrodes 31 and 32.
  • the additional circuit 20 having two or more IDT electrodes 31 and 32, by setting the ratio R to 11% or less, it is possible to suppress the resonance Q of the additional circuit 20 from becoming higher than necessary. As a result, it is possible to suppress the generation of unnecessary waves outside the frequency passband of the elastic wave filter 1 and secure the amount of attenuation outside the frequency passband.
  • the IDT electrode group 25 may be composed of four IDT electrodes 31, 32, 33, 34.
  • the additional circuit 20 having four IDT electrodes 31 to 34 by setting the ratio R to 11% or less of the total number, it is possible to suppress that the resonance Q of the additional circuit 20 becomes higher than necessary. .. Further, as compared with the case where the plurality of IDT electrodes are composed of two IDT electrodes, the adjustment range of the ratio R can be widened, and it is possible to easily suppress that the resonance Q of the additional circuit 20 becomes higher than necessary. As a result, it is possible to suppress the generation of unnecessary waves outside the frequency passband of the elastic wave filter 1 and secure the amount of attenuation outside the frequency passband.
  • the duty of the reflectors 41 and 42 may be smaller than the duty of the IDT electrodes 31 and 32.
  • the multiplexer 5 has a pass band different from that of the elastic wave filter 1, the first signal terminal T1, the second signal terminal T2, the third signal terminal T3, and the first filter circuit 10.
  • a second filter circuit 50 arranged on a third path r3 connecting the second signal terminal T2 and the third signal terminal T3 is provided.
  • the elastic wave filter is provided with two or four IDT electrodes, but the number of IDT electrodes is not limited to this, and the number of IDT electrodes may be three or five or more.
  • the frequency passband of the elastic wave filter 1 is set to be lower than the frequency passband of the second filter circuit 50, but the present invention is not limited to this, and the frequency passband of the elastic wave filter 1 is not limited to this. May be set to be higher than the frequency passband of the second filter circuit 50.
  • the elastic wave filter 1 is a transmission filter
  • the present invention is not limited to this, and the elastic wave filter 1 may be a reception filter.
  • the multiplexer 5 is not limited to the configuration including both the transmission filter and the reception filter, and may be configured to include only the transmission filter or only the reception filter.
  • a multiplexer including two filters has been described as an example, but in the present invention, for example, a triplexer having common antenna terminals of three filters and a hexaplexer having common antenna terminals of six filters have been described. Can also be applied to. That is, the multiplexer need only have two or more filters.
  • first signal terminal T1 and the second signal terminal T2 may be either an input terminal or an output terminal.
  • first signal terminal T1 when the first signal terminal T1 is an input terminal, the second signal terminal T2 becomes an output terminal, and when the second signal terminal T2 is an input terminal, the first signal terminal T1 becomes an output terminal.
  • the second filter circuit 50 is not limited to the above-mentioned filter configuration, and can be appropriately designed according to the required filter characteristics and the like.
  • the second filter circuit 50 may have a vertically coupled filter structure or a ladder type filter structure.
  • each resonator constituting the second filter circuit 50 is not limited to the SAW resonator, and may be, for example, a BAW (Bulk Acoustic Wave) resonator.
  • the second filter circuit 50 may be configured without using a resonator, and may be, for example, an LC resonance filter or a dielectric filter.
  • the materials constituting the electrode layers 325 and the dielectric layer 326 of the IDT electrodes 31 and 32 and the reflectors 41 and 42 are not limited to the above-mentioned materials. Further, the IDT electrodes 31 and 32 do not have to have the above-mentioned laminated structure.
  • the IDT electrodes 31 and 32 may be made of, for example, a metal or alloy such as Ti, Al, Cu, Pt, Au, Ag, Pd, or from a plurality of laminates made of the above metal or alloy. It may be configured.
  • a substrate having piezoelectricity is shown as the substrate 320, but the substrate may be a piezoelectric substrate composed of a single layer of a piezoelectric layer.
  • the piezoelectric substrate in this case is composed of, for example, a piezoelectric single crystal of LiTaO 3 or another piezoelectric single crystal such as LiNbO 3.
  • the substrate 320 on which the IDT electrodes 31 and 32 are formed may be entirely composed of a piezoelectric layer or may have a structure in which the piezoelectric layer is laminated on the support substrate, as long as the substrate 320 has piezoelectricity.
  • the cut angle of the substrate 320 according to the first embodiment is not limited.
  • the laminated structure, material, and thickness may be appropriately changed according to the required passing characteristics of the surface acoustic wave filter, and the LiTaO 3 piezoelectric substrate having a cut angle other than the cut angle shown in the first embodiment may be used. Even an elastic surface acoustic wave filter using a LiNbO 3 piezoelectric substrate or the like can achieve the same effect.
  • the present invention can be widely used in communication equipment such as mobile phones as a multiplexer having an elastic wave filter, a front-end circuit, and a communication device.

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  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)

Abstract

An acoustic wave filter (1) is provided with: a first filter circuit (10) which has a prescribed frequency band as a passband, and which is disposed on a first pathway (r1) linking a first signal terminal (T1) and a second signal terminal (T2); and an additional circuit (20) connected in parallel with at least a portion of the first filter circuit (10). The additional circuit (20) includes an IDT electrode group (25) comprising a plurality of IDT electrodes (31, 32) disposed in an acoustic wave propagation direction (D1). The proportion (R) of the number of electrode fingers (46) in a plurality of reflectors (41, 42) positioned on both outer sides of the IDT electrode group (25) in the acoustic wave propagation direction (D1) is at most equal to 11% of a total number obtained by summing the number of electrode fingers (36a, 36b) in the plurality of IDT electrodes (31, 32) and the number of electrode fingers (46) in the plurality of reflectors (41, 42).

Description

弾性波フィルタおよびマルチプレクサSAW filter and multiplexer
　本発明は、弾性波フィルタおよびマルチプレクサに関する。 The present invention relates to an elastic wave filter and a multiplexer.
　従来、直列腕共振子および並列腕共振子を備えるラダー型の弾性波フィルタが知られている。この種の弾性波フィルタの一例として、特許文献１には、所定の周波数帯域を通過帯域とするフィルタ回路と、フィルタ回路に並列接続されたキャンセル線路とを備える弾性波フィルタが開示されている。 Conventionally, a ladder type elastic wave filter including a series arm resonator and a parallel arm resonator is known. As an example of this type of elastic wave filter, Patent Document 1 discloses an elastic wave filter including a filter circuit having a predetermined frequency band as a pass band and a cancel line connected in parallel to the filter circuit.
特開２０１７－２０４７４３号公報Japanese Unexamined Patent Publication No. 2017-204743
　特許文献１に開示された弾性波フィルタでは、キャンセル線路を用いて通過帯域外の不要波に逆位相をかけ、不要波をキャンセルし、通過帯域外における減衰量を大きくしている。しかしながら、この弾性波フィルタでは、キャンセル線路の共振Ｑが必要以上に高くなって通過帯域外にスプリアスなどの不要波が発生し、通過帯域外における減衰量を十分に確保できないことがある。 In the elastic wave filter disclosed in Patent Document 1, an unnecessary wave outside the pass band is subjected to an antiphase by using a cancel line to cancel the unnecessary wave and increase the attenuation amount outside the pass band. However, in this elastic wave filter, the resonance Q of the cancel line becomes higher than necessary, unnecessary waves such as spurious are generated outside the pass band, and the amount of attenuation outside the pass band may not be sufficiently secured.
　本発明は、上記課題を解決するためになされたものであり、周波数通過帯域外における減衰量を確保することができる弾性波フィルタ等を提供することを目的とする。 The present invention has been made to solve the above problems, and an object of the present invention is to provide an elastic wave filter or the like that can secure an amount of attenuation outside the frequency passband.
　上記目的を達成するために、本発明の一態様に係る弾性波フィルタは、所定の周波数帯域を通過帯域とし、第１信号端子と第２信号端子とを結ぶ第１の経路上に配置された第１フィルタ回路と、前記第１フィルタ回路の少なくとも一部に対し並列に接続される付加回路と、を備え、前記付加回路は、弾性波伝搬方向に沿って配置された複数のＩＤＴ電極からなるＩＤＴ電極群を有し、前記弾性波伝搬方向において前記ＩＤＴ電極群の両外側に位置する複数の反射器の電極指の本数の割合は、前記複数のＩＤＴ電極の電極指の本数および前記複数の反射器の電極指の本数を合計した総本数の１１％以下である。 In order to achieve the above object, the elastic wave filter according to one aspect of the present invention has a predetermined frequency band as a passing band and is arranged on a first path connecting the first signal terminal and the second signal terminal. A first filter circuit and an additional circuit connected in parallel to at least a part of the first filter circuit are provided, and the additional circuit comprises a plurality of IDT electrodes arranged along an elastic wave propagation direction. The ratio of the number of electrode fingers of the plurality of reflectors having the IDT electrode group and located on both outer sides of the IDT electrode group in the direction of propagation of the elastic wave is the number of electrode fingers of the plurality of IDT electrodes and the plurality of electrode fingers. It is 11% or less of the total number of electrode fingers of the reflector.
　また、本発明の一態様に係るマルチプレクサは、上記弾性波フィルタと、前記第１信号端子、前記第２信号端子および第３信号端子と、前記第１フィルタ回路とは異なる周波数帯域を通過帯域とし、前記第２信号端子と前記第３信号端子とを結ぶ第３の経路上に配置された第２フィルタ回路とを備える。 Further, the multiplexer according to one aspect of the present invention has a pass band of the elastic wave filter, the first signal terminal, the second signal terminal and the third signal terminal, and a frequency band different from that of the first filter circuit. , A second filter circuit arranged on a third path connecting the second signal terminal and the third signal terminal is provided.
　本発明に係る弾性波フィルタ等によれば、周波数通過帯域外における減衰量を確保することができる。 According to the elastic wave filter or the like according to the present invention, it is possible to secure the amount of attenuation outside the frequency passband.
図１は、実施の形態１に係る弾性波フィルタを備えるマルチプレクサの回路構成図である。FIG. 1 is a circuit configuration diagram of a multiplexer including an elastic wave filter according to the first embodiment. 図２は、実施の形態１に係る弾性波フィルタの付加回路に含まれるＩＤＴ電極群を示す模式図である。FIG. 2 is a schematic diagram showing a group of IDT electrodes included in the additional circuit of the elastic wave filter according to the first embodiment. 図３は、図２に示すＩＤＴ電極群の構造を模式的に示す平面図および断面図である。FIG. 3 is a plan view and a cross-sectional view schematically showing the structure of the IDT electrode group shown in FIG. 図４は、実施の形態１に係る弾性波フィルタの通過特性を示す図である。FIG. 4 is a diagram showing the passing characteristics of the elastic wave filter according to the first embodiment. 図５は、実施の形態１に係るマルチプレクサのアイソレーション特性を示す図である。FIG. 5 is a diagram showing the isolation characteristics of the multiplexer according to the first embodiment. 図６は、反射器の電極指の本数の割合および不要波のピークレベルの関係を示す図である。FIG. 6 is a diagram showing the relationship between the ratio of the number of electrode fingers of the reflector and the peak level of unnecessary waves. 図７は、実施の形態２に係る弾性波フィルタを備えるマルチプレクサの回路構成図である。FIG. 7 is a circuit configuration diagram of a multiplexer including an elastic wave filter according to the second embodiment. 図８は、実施の形態２に係る弾性波フィルタの付加回路に含まれるＩＤＴ電極群を示す模式図である。FIG. 8 is a schematic diagram showing a group of IDT electrodes included in the additional circuit of the elastic wave filter according to the second embodiment. 図９は、図８に示すＩＤＴ電極群の構造を模式的に示す平面図である。FIG. 9 is a plan view schematically showing the structure of the IDT electrode group shown in FIG. 図１０は、実施の形態２に係る弾性波フィルタの通過特性を示す図である。FIG. 10 is a diagram showing the passage characteristics of the elastic wave filter according to the second embodiment. 図１１は、反射器の電極指の本数の割合および不要波のピークレベルの関係を示す図である。FIG. 11 is a diagram showing the relationship between the ratio of the number of electrode fingers of the reflector and the peak level of unnecessary waves.
　以下、本発明の実施の形態について、実施の形態および図面を用いて詳細に説明する。なお、以下で説明する実施の形態は、いずれも包括的または具体的な例を示すものである。以下の実施の形態で示される数値、形状、材料、構成要素、構成要素の配置および接続形態などは、一例であり、本発明を限定する主旨ではない。以下の実施の形態における構成要素のうち、独立請求項に記載されていない構成要素については、任意の構成要素として説明される。また、図面に示される構成要素の大きさ、または大きさの比は、必ずしも厳密ではない。また、各図において、実質的に同一の構成に対しては同一の符号を付しており、重複する説明は省略または簡略化する場合がある。また、以下の実施の形態において、「接続される」とは、直接接続される場合だけでなく、他の素子等を介して電気的に接続される場合も含まれる。 Hereinafter, embodiments of the present invention will be described in detail with reference to embodiments and drawings. It should be noted that all of the embodiments described below are comprehensive or specific examples. The numerical values, shapes, materials, components, arrangement of components, connection modes, etc. shown in the following embodiments are examples, and are not intended to limit the present invention. Among the components in the following embodiments, the components not described in the independent claims are described as arbitrary components. Also, the sizes of the components shown in the drawings, or the ratio of sizes, are not always exact. Further, in each figure, the same reference numerals are given to substantially the same configurations, and duplicate explanations may be omitted or simplified. Further, in the following embodiments, "connected" includes not only the case of being directly connected but also the case of being electrically connected via another element or the like.
　（実施の形態１）
　［１－１．マルチプレクサの構成］
　実施の形態１に係る弾性波フィルタを備えるマルチプレクサの構成について、図１を参照しながら説明する。 (Embodiment 1)
[1-1. Multiplexer configuration]
The configuration of the multiplexer including the elastic wave filter according to the first embodiment will be described with reference to FIG.
　図１は、実施の形態１に係る弾性波フィルタ１を備えるマルチプレクサ５の回路構成図である。なお、図１にはアンテナ素子９も示されている。 FIG. 1 is a circuit configuration diagram of a multiplexer 5 including the elastic wave filter 1 according to the first embodiment. Note that FIG. 1 also shows the antenna element 9.
　マルチプレクサ５は、周波数通過帯域が異なる複数のフィルタを備える分波器または合波器である。図１に示すように、マルチプレクサ５は、第１フィルタ回路１０および付加回路２０を有する弾性波フィルタ１と、第２フィルタ回路５０とを備えている。また、マルチプレクサ５は、第１信号端子Ｔ１、第２信号端子Ｔ２および第３信号端子Ｔ３を備えている。 The multiplexer 5 is a demultiplexer or combiner including a plurality of filters having different frequency pass bands. As shown in FIG. 1, the multiplexer 5 includes an elastic wave filter 1 having a first filter circuit 10 and an additional circuit 20, and a second filter circuit 50. Further, the multiplexer 5 includes a first signal terminal T1, a second signal terminal T2, and a third signal terminal T3.
　第１信号端子Ｔ１は、弾性波フィルタ１に接続されている。また、第１信号端子Ｔ１は、マルチプレクサ５の外部において、増幅回路等（図示せず）を介してＲＦ信号処理回路（図示せず）に接続される。 The first signal terminal T1 is connected to the elastic wave filter 1. Further, the first signal terminal T1 is connected to an RF signal processing circuit (not shown) via an amplifier circuit or the like (not shown) outside the multiplexer 5.
　第２信号端子Ｔ２は、弾性波フィルタ１および第２フィルタ回路５０のそれぞれに接続される共通端子である。具体的には、第２信号端子Ｔ２は、弾性波フィルタ１と第２信号端子Ｔ２との間のノードｎ０を介して弾性波フィルタ１に接続され、また、ノードｎ０を介して第２フィルタ回路５０に接続されている。また、第２信号端子Ｔ２は、マルチプレクサ５の外部でアンテナ素子９に接続される。第２信号端子Ｔ２は、マルチプレクサ５のアンテナ端子でもある。 The second signal terminal T2 is a common terminal connected to each of the elastic wave filter 1 and the second filter circuit 50. Specifically, the second signal terminal T2 is connected to the elastic wave filter 1 via the node n0 between the elastic wave filter 1 and the second signal terminal T2, and is also connected to the elastic wave filter 1 via the node n0. It is connected to 50. Further, the second signal terminal T2 is connected to the antenna element 9 outside the multiplexer 5. The second signal terminal T2 is also an antenna terminal of the multiplexer 5.
　第３信号端子Ｔ３は、第２フィルタ回路５０に接続されている。また、第３信号端子Ｔ３は、マルチプレクサ５の外部において、増幅回路等（図示せず）を介してＲＦ信号処理回路（図示せず）に接続される。 The third signal terminal T3 is connected to the second filter circuit 50. Further, the third signal terminal T3 is connected to an RF signal processing circuit (not shown) via an amplifier circuit or the like (not shown) outside the multiplexer 5.
　弾性波フィルタ１は、第１信号端子Ｔ１と第２信号端子Ｔ２とを結ぶ第１の経路ｒ１上に配置されている。弾性波フィルタ１は、例えば、上り周波数帯（送信帯域）を通過帯域とする送信フィルタであり、第２フィルタ回路５０よりも周波数通過帯域が低くなるように設定される。弾性波フィルタ１は、第１フィルタ回路１０と、第１フィルタ回路１０に付加接続された付加回路２０とを備える。付加回路２０は、第１フィルタ回路１０の周波数通過帯域外の不要波をキャンセルするための回路である。付加回路２０については後述する。 The elastic wave filter 1 is arranged on the first path r1 connecting the first signal terminal T1 and the second signal terminal T2. The elastic wave filter 1 is, for example, a transmission filter having an uplink frequency band (transmission band) as a pass band, and is set so that the frequency pass band is lower than that of the second filter circuit 50. The elastic wave filter 1 includes a first filter circuit 10 and an additional circuit 20 additionally connected to the first filter circuit 10. The additional circuit 20 is a circuit for canceling unnecessary waves outside the frequency pass band of the first filter circuit 10. The additional circuit 20 will be described later.
　第２フィルタ回路５０は、第２信号端子Ｔ２と第３信号端子Ｔ３とを結ぶ第３の経路ｒ３上に配置されている。第２フィルタ回路５０は、例えば、下り周波数帯（受信帯域）を通過帯域とする受信フィルタである。第２フィルタ回路５０は、例えば、直列腕共振子ＲＳ１と、並列腕共振子ＲＰ１と、直列腕共振子ＲＳ２と、縦結合型弾性波共振器６０と、並列腕共振子ＲＰ２とによって構成される。 The second filter circuit 50 is arranged on the third path r3 connecting the second signal terminal T2 and the third signal terminal T3. The second filter circuit 50 is, for example, a reception filter having a downlink frequency band (reception band) as a pass band. The second filter circuit 50 is composed of, for example, a series arm resonator RS1, a parallel arm resonator RP1, a series arm resonator RS2, a vertically coupled elastic wave resonator 60, and a parallel arm resonator RP2. ..
　弾性波フィルタ１および第２フィルタ回路５０のそれぞれには、予め決められた周波数帯域を通過させ、当該周波数帯域外の帯域を減衰させるような特性が求められる。 Each of the elastic wave filter 1 and the second filter circuit 50 is required to have a characteristic of passing through a predetermined frequency band and attenuating a band outside the frequency band.
　［１－２．弾性波フィルタの構成］
　次に、弾性波フィルタ１の構成について、図１および図２を参照しながら説明する。 [1-2. Structure of elastic wave filter]
Next, the configuration of the elastic wave filter 1 will be described with reference to FIGS. 1 and 2.
　図１に示すように、弾性波フィルタ１は、第１フィルタ回路１０と付加回路２０とを備えている。 As shown in FIG. 1, the elastic wave filter 1 includes a first filter circuit 10 and an additional circuit 20.
　第１フィルタ回路１０は、弾性波共振子である直列腕共振子Ｓ１、Ｓ２、Ｓ３、Ｓ４および並列腕共振子Ｐ１、Ｐ２、Ｐ３を備えている。 The first filter circuit 10 includes series arm resonators S1, S2, S3, S4 and parallel arm resonators P1, P2, P3, which are elastic wave resonators.
　直列腕共振子Ｓ１～Ｓ４は、第１信号端子Ｔ１と第２信号端子Ｔ２とを結ぶ第１の経路（直列腕）ｒ１上に配置されている。直列腕共振子Ｓ１～Ｓ４は、第１信号端子Ｔ１から第２信号端子Ｔ２に向かって、この順で直列に接続されている。 The series arm resonators S1 to S4 are arranged on the first path (series arm) r1 connecting the first signal terminal T1 and the second signal terminal T2. The series arm resonators S1 to S4 are connected in series from the first signal terminal T1 toward the second signal terminal T2 in this order.
　並列腕共振子Ｐ１～Ｐ３は、第１の経路ｒ１上にて隣り合う直列腕共振子Ｓ１～Ｓ４の間の各ノードｎ１、ｎ２、ｎ３と基準端子（グランド）とを結ぶ経路（並列腕）上に互いに並列に接続されている。具体的には、並列腕共振子Ｐ１～Ｐ３のうち、第１信号端子Ｔ１に最も近い並列腕共振子Ｐ１は、一端が直列腕共振子Ｓ１とＳ２との間のノードｎ１に接続され、他端がインダクタＬ１を介して基準端子に接続されている。並列腕共振子Ｐ２は、一端が直列腕共振子Ｓ２とＳ３との間のノードｎ２に接続され、他端がインダクタＬ２を介して基準端子に接続されている。並列腕共振子Ｐ３は、一端が直列腕共振子Ｓ３とＳ４との間のノードｎ３に接続され、他端がインダクタＬ２を介して基準端子に接続されている。なお、直列腕共振子Ｓ１、Ｓ２および並列腕共振子Ｐ１、Ｐ２で構成される回路には容量素子Ｃ１１が並列接続され、直列腕共振子Ｓ３には容量素子Ｃ１２が並列接続されている。 The parallel arm resonators P1 to P3 are paths (parallel arms) connecting the nodes n1, n2, n3 between the adjacent series arm resonators S1 to S4 on the first path r1 and the reference terminal (ground). They are connected in parallel to each other on top. Specifically, among the parallel arm resonators P1 to P3, the parallel arm resonator P1 closest to the first signal terminal T1 has one end connected to the node n1 between the series arm resonators S1 and S2, and the other. The end is connected to the reference terminal via the inductor L1. One end of the parallel arm resonator P2 is connected to the node n2 between the series arm resonators S2 and S3, and the other end is connected to the reference terminal via the inductor L2. One end of the parallel arm resonator P3 is connected to the node n3 between the series arm resonators S3 and S4, and the other end is connected to the reference terminal via the inductor L2. The capacitive element C11 is connected in parallel to the circuit composed of the series arm resonators S1 and S2 and the parallel arm resonators P1 and P2, and the capacitive element C12 is connected in parallel to the series arm resonator S3.
　このように第１フィルタ回路１０は、第１の経路ｒ１上に配置された４つの直列腕共振子Ｓ１～Ｓ４、および、第１の経路ｒ１と基準端子とを結ぶ経路上に配置された３つの並列腕共振子Ｐ１～Ｐ３で構成されるＴ型のラダーフィルタ構造を有している。 As described above, the first filter circuit 10 is arranged on the four series arm resonators S1 to S4 arranged on the first path r1 and the path connecting the first path r1 and the reference terminal 3. It has a T-shaped ladder filter structure composed of two parallel arm resonators P1 to P3.
　なお、第１フィルタ回路１０を構成する直列腕共振子および並列腕共振子の数は、４つまたは３つに限定されず、直列腕共振子が２つ以上かつ並列腕共振子が１つ以上であればよい。また、並列腕共振子は、インダクタを介さずに、基準端子に接続されていてもよい。また図１では、並列腕共振子が接続される基準端子の一部が共通化されているが、基準端子を共通化するか個別化するかは、例えば、第１フィルタ回路１０の実装レイアウトの制約等によって適宜選択され得る。 The number of series arm resonators and parallel arm resonators constituting the first filter circuit 10 is not limited to four or three, and there are two or more series arm resonators and one or more parallel arm resonators. It should be. Further, the parallel arm resonator may be connected to the reference terminal without using an inductor. Further, in FIG. 1, a part of the reference terminals to which the parallel arm resonators are connected is shared, but whether the reference terminals are shared or individualized depends on, for example, the mounting layout of the first filter circuit 10. It can be appropriately selected due to restrictions and the like.
　次に、弾性波フィルタ１の付加回路２０について説明する。付加回路２０は、第１フィルタ回路１０で発生する周波数通過帯域外の不要波に逆位相をかけることで、弾性波フィルタ１から不要波が出力されることを抑制する回路である。 Next, the additional circuit 20 of the elastic wave filter 1 will be described. The additional circuit 20 is a circuit that suppresses the output of unnecessary waves from the elastic wave filter 1 by applying an antiphase to unnecessary waves outside the frequency passband generated by the first filter circuit 10.
　付加回路２０は、第１フィルタ回路１０の少なくとも一部に対し並列に接続されるように、第１の経路ｒ１上の異なる複数のノードに接続される。付加回路２０は、付加回路２０の一端側の接続ノードとなる第１端子２１、他端側の接続ノードとなる第２端子２２、および、第１端子２１と第２端子２２とを結ぶ第２の経路ｒ２上に配置されたＩＤＴ（ＩｎｔｅｒＤｉｇｉｔａｌ　Ｔｒａｎｓｄｕｃｅｒ）電極群２５を有している。なお、ここでいう端子は、高周波信号の入口または出口を意味する。 The additional circuit 20 is connected to a plurality of different nodes on the first path r1 so as to be connected in parallel to at least a part of the first filter circuit 10. The additional circuit 20 includes a first terminal 21 that is a connection node on one end side of the additional circuit 20, a second terminal 22 that is a connection node on the other end side, and a second terminal that connects the first terminal 21 and the second terminal 22. It has an IDT (InterDigital Transducer) electrode group 25 arranged on the path r2 of the above. The terminal here means an inlet or an outlet of a high frequency signal.
　第１端子２１は、ＩＤＴ電極群２５に電気的に接続されている。第２端子２２は、容量素子Ｃ２２を介してＩＤＴ電極群２５に接続されている。第１端子２１および第２端子２２は、ＩＤＴ電極群２５を介して音響的接続されている。 The first terminal 21 is electrically connected to the IDT electrode group 25. The second terminal 22 is connected to the IDT electrode group 25 via the capacitive element C22. The first terminal 21 and the second terminal 22 are acoustically connected via the IDT electrode group 25.
　また、第１端子２１および第２端子２２のそれぞれは、第１の経路ｒ１上の異なるノードに接続される。図１では、第１端子２１は、直列腕共振子Ｓ１とＳ２との間のノードｎ１に接続され、第２端子２２は、直列腕共振子Ｓ４と第２信号端子Ｔ２との間のノードｎ４に接続されている。 Further, each of the first terminal 21 and the second terminal 22 is connected to a different node on the first path r1. In FIG. 1, the first terminal 21 is connected to the node n1 between the series arm resonators S1 and S2, and the second terminal 22 is the node n4 between the series arm resonator S4 and the second signal terminal T2. It is connected to the.
　図２は、弾性波フィルタ１の付加回路２０に含まれるＩＤＴ電極群２５を示す模式図である。なお図２では、電極および配線が実線で示されている。 FIG. 2 is a schematic diagram showing an IDT electrode group 25 included in the additional circuit 20 of the elastic wave filter 1. In FIG. 2, the electrodes and the wiring are shown by solid lines.
　ＩＤＴ電極群２５は、複数のＩＤＴ電極３１および３２からなる弾性波共振子群である。ＩＤＴ電極群２５は、例えば、縦結合型共振器である。複数のＩＤＴ電極３１、３２は、弾性波伝搬方向Ｄ１に沿って隣り合って配置されている。複数のＩＤＴ電極３１、３２の電極パラメータは、互いに異なっている。 The IDT electrode group 25 is an elastic wave resonator group composed of a plurality of IDT electrodes 31 and 32. The IDT electrode group 25 is, for example, a vertically coupled resonator. The plurality of IDT electrodes 31 and 32 are arranged adjacent to each other along the elastic wave propagation direction D1. The electrode parameters of the plurality of IDT electrodes 31 and 32 are different from each other.
　なお、付加回路２０は、複数の反射器４１、４２を有している。複数の反射器４１、４２は、弾性波伝搬方向Ｄ１において、ＩＤＴ電極群２５を挟み込むように、ＩＤＴ電極群２５の両外側に位置している。図２には、２つの反射器４１、４２を備える付加回路２０が例示されている。反射器４１、４２の構造については後で詳しく説明する。 The additional circuit 20 has a plurality of reflectors 41 and 42. The plurality of reflectors 41 and 42 are located on both outer sides of the IDT electrode group 25 so as to sandwich the IDT electrode group 25 in the elastic wave propagation direction D1. FIG. 2 illustrates an additional circuit 20 with two reflectors 41, 42. The structures of the reflectors 41 and 42 will be described in detail later.
　複数のＩＤＴ電極３１、３２は、複数の第１櫛歯状電極３１ａ、３２ａおよび複数の第２櫛歯状電極３１ｂ、３２ｂを有している。複数のＩＤＴ電極３１、３２のうち、一方のＩＤＴ電極３１は、一対となる第１櫛歯状電極３１ａおよび第２櫛歯状電極３１ｂによって構成されている。他方のＩＤＴ電極３２は、一対となる第１櫛歯状電極３２ａおよび第２櫛歯状電極３２ｂによって構成されている。 The plurality of IDT electrodes 31 and 32 have a plurality of first comb-shaped electrodes 31a and 32a and a plurality of second comb-shaped electrodes 31b and 32b. Of the plurality of IDT electrodes 31 and 32, one of the IDT electrodes 31 is composed of a pair of a first comb-shaped electrode 31a and a second comb-shaped electrode 31b. The other IDT electrode 32 is composed of a pair of a first comb-shaped electrode 32a and a second comb-shaped electrode 32b.
　第１櫛歯状電極３１ａおよび第２櫛歯状電極３１ｂは、互いに対向している。第１櫛歯状電極３２ａおよび第２櫛歯状電極３２ｂは、互いに対向している。ＩＤＴ電極３１、３２を基板３２０（図３参照）に垂直な方向から見た場合に、第１櫛歯状電極３１ａ、３２ａは、互いに逆向きで配置され、また、第２櫛歯状電極３１ｂ、３２ｂも、互いに逆向きで、配置されている。第１櫛歯状電極３１ａおよび第２櫛歯状電極３２ｂは同じ向きで配置されている。 The first comb-shaped electrode 31a and the second comb-shaped electrode 31b face each other. The first comb-shaped electrode 32a and the second comb-shaped electrode 32b face each other. When the IDT electrodes 31 and 32 are viewed from a direction perpendicular to the substrate 320 (see FIG. 3), the first comb-shaped electrodes 31a and 32a are arranged in opposite directions to each other, and the second comb-shaped electrodes 31b are arranged. , 32b are also arranged in opposite directions to each other. The first comb-shaped electrode 31a and the second comb-shaped electrode 32b are arranged in the same direction.
　複数の第１櫛歯状電極３１ａ、３２ａは、第１の経路ｒ１上の異なる複数のノードに電気的に接続される。具体的には、第１櫛歯状電極３１ａが、第１端子２１によってノードｎ１に接続され、第１櫛歯状電極３２ａが、第２端子２２によってノードｎ４に接続される。一方、第２櫛歯状電極３１ｂ、３２ｂのそれぞれは、グランドに接続されている。 The plurality of first comb-shaped electrodes 31a and 32a are electrically connected to a plurality of different nodes on the first path r1. Specifically, the first comb-shaped electrode 31a is connected to the node n1 by the first terminal 21, and the first comb-shaped electrode 32a is connected to the node n4 by the second terminal 22. On the other hand, each of the second comb-shaped electrodes 31b and 32b is connected to the ground.
　なお、上記では、付加回路２０の第１端子２１がノードｎ１に接続され、第２端子２２がノードｎ４に接続されている例を示したが、それに限られない。第１端子２１および第２端子２２のそれぞれは、第１の経路ｒ１上にて隣り合う２以上の直列腕共振子の両外側のノードに接続されていればよい。例えば、第１端子２１は、第１信号端子Ｔ１と直列腕共振子Ｓ１とを結ぶ第１の経路ｒ１上のノードに接続されていてもよいし、ノードｎ２に接続されていてもよい。例えば、第２端子２２は、ノードｎ３に接続されていてもよい。 Note that the above shows an example in which the first terminal 21 of the additional circuit 20 is connected to the node n1 and the second terminal 22 is connected to the node n4, but the present invention is not limited to this. Each of the first terminal 21 and the second terminal 22 may be connected to the outer nodes of two or more series arm resonators adjacent to each other on the first path r1. For example, the first terminal 21 may be connected to a node on the first path r1 connecting the first signal terminal T1 and the series arm resonator S1, or may be connected to the node n2. For example, the second terminal 22 may be connected to the node n3.
　また、付加回路２０は、容量素子Ｃ２２を備えていなくてもよい。不要波を適度に抑制できるのであれば、ＩＤＴ電極群２５は、第２端子２２に、容量素子を介さずに配線接続されていてもよい。 Further, the additional circuit 20 does not have to include the capacitive element C22. The IDT electrode group 25 may be connected to the second terminal 22 by wiring without a capacitive element as long as the unnecessary wave can be appropriately suppressed.
　［１－３．ＩＤＴ電極群の構造］
　次に、付加回路２０に含まれるＩＤＴ電極群２５の構造について説明する。ＩＤＴ電極群２５は、例えば、複数の弾性表面波（ＳＡＷ：Ｓｕｒｆａｃｅ　Ａｃｏｕｓｔｉｃ　Ｗａｖｅ）共振子によって構成されている。 [1-3. Structure of IDT electrode group]
Next, the structure of the IDT electrode group 25 included in the additional circuit 20 will be described. The IDT electrode group 25 is composed of, for example, a plurality of surface acoustic wave (SAW) resonators.
　図３は、ＩＤＴ電極群２５の構造を模式的に示す平面図および断面図である。なお、図３に示されたＩＤＴ電極群２５は、共振子の典型的な構造を説明するためのものであって、ＩＤＴ電極および反射器に含まれる電極指の本数や長さなどは、これに限定されない。 FIG. 3 is a plan view and a cross-sectional view schematically showing the structure of the IDT electrode group 25. The IDT electrode group 25 shown in FIG. 3 is for explaining a typical structure of the resonator, and the number and length of the electrode fingers included in the IDT electrode and the reflector are the same. Not limited to.
　ＩＤＴ電極群２５は、圧電性を有する基板３２０と、基板３２０上に形成された複数のＩＤＴ電極３１、３２とによって構成される。弾性波伝搬方向Ｄ１におけるＩＤＴ電極群２５の両外側には、複数の反射器４１、４２が設けられている。 The IDT electrode group 25 is composed of a substrate 320 having piezoelectricity and a plurality of IDT electrodes 31 and 32 formed on the substrate 320. A plurality of reflectors 41 and 42 are provided on both outer sides of the IDT electrode group 25 in the elastic wave propagation direction D1.
　図３の断面図に示すように、ＩＤＴ電極群２５および複数の反射器４１、４２は、基板３２０と、各ＩＤＴ電極３１、３２および複数の反射器４１、４２を構成する電極層３２５と、各ＩＤＴ電極３１、３２および各反射器４１、４２を覆うように基板３２０上に設けられた誘電体層３２６とによって形成される。 As shown in the cross-sectional view of FIG. 3, the IDT electrode group 25 and the plurality of reflectors 41 and 42 include a substrate 320, each IDT electrode 31, 32 and an electrode layer 325 constituting the plurality of reflectors 41 and 42. It is formed by a dielectric layer 326 provided on the substrate 320 so as to cover each IDT electrode 31, 32 and each reflector 41, 42.
　基板３２０は、例えば、カット角１２７．５°のＬｉＮｂＯ３基板（ニオブ酸リチウム基板）ある。基板３２０内を伝搬する弾性波としてレイリー波が使用される場合、基板３２０のカット角は、１２０°±２０°、または、３００°±２０°であることが望ましい。 The substrate 320 is, for example, a LiNbO 3 substrate (lithium niobate substrate) having a cut angle of 127.5 °. When a Rayleigh wave is used as an elastic wave propagating in the substrate 320, the cut angle of the substrate 320 is preferably 120 ° ± 20 ° or 300 ° ± 20 °.
　電極層３２５は、複数の金属層が積層された構造を有している。電極層３２５は、例えば、上から順に、Ｔｉ層、Ａｌ層、Ｔｉ層、Ｐｔ層、ＮｉＣｒ層が積層されることで形成されている。 The electrode layer 325 has a structure in which a plurality of metal layers are laminated. The electrode layer 325 is formed by, for example, laminating a Ti layer, an Al layer, a Ti layer, a Pt layer, and a NiCr layer in order from the top.
　誘電体層３２６は、例えば、二酸化ケイ素（ＳｉＯ２）を主成分とする膜である。誘電体層３２６は、ＩＤＴ電極群２５の周波数温度特性を調整すること、電極層３２５を外部環境から保護すること、または、耐湿性を高めることなどを目的として設けられている。 The dielectric layer 326 is, for example, a film containing silicon dioxide (SiO 2 ) as a main component. The dielectric layer 326 is provided for the purpose of adjusting the frequency temperature characteristics of the IDT electrode group 25, protecting the electrode layer 325 from the external environment, or enhancing the moisture resistance.
　図３の平面図に示すように、ＩＤＴ電極３１は、互いに対向する一対の第１櫛歯状電極３１ａおよび第２櫛歯状電極３１ｂを有している。ＩＤＴ電極３２は、互いに対向する一対の第１櫛歯状電極３２ａおよび第２櫛歯状電極３２ｂを有している。 As shown in the plan view of FIG. 3, the IDT electrode 31 has a pair of first comb-shaped electrodes 31a and second comb-shaped electrodes 31b facing each other. The IDT electrode 32 has a pair of first comb-shaped electrodes 32a and second comb-shaped electrodes 32b facing each other.
　各第１櫛歯状電極３１ａ、３２ａは、櫛歯状の形状を有し、互いに平行な複数の電極指３６ａと、複数の電極指３６ａのそれぞれの一端同士を接続するバスバー電極３７ａとで構成されている。各第２櫛歯状電極３１ｂ、３２ｂは、櫛歯の形状を有し、互いに平行な複数の電極指３６ｂと、複数の電極指３６ｂのそれぞれの一端同士を接続するバスバー電極３７ｂとで構成されている。各バスバー電極３７ａおよび３７ｂは、弾性波伝搬方向Ｄ１に沿って延びるように形成されている。 Each of the first comb-shaped electrodes 31a and 32a has a comb-shaped shape and is composed of a plurality of electrode fingers 36a parallel to each other and a bus bar electrode 37a connecting one ends of the plurality of electrode fingers 36a to each other. Has been done. Each of the second comb-shaped electrodes 31b and 32b has a comb-tooth shape and is composed of a plurality of electrode fingers 36b parallel to each other and a bus bar electrode 37b connecting one ends of the plurality of electrode fingers 36b to each other. ing. The bus bar electrodes 37a and 37b are formed so as to extend along the elastic wave propagation direction D1.
　複数の電極指３６ａおよび３６ｂは、弾性波伝搬方向Ｄ１の直交方向Ｄ２に延びるように形成され、直交方向Ｄ２に互いに間挿し合い、弾性波伝搬方向Ｄ１に対向している。弾性波伝搬方向Ｄ１における複数の電極指３６ａのピッチ（中心線同士の距離）は、ＩＤＴ電極３１とＩＤＴ電極３２とで異なっている。また、弾性波伝搬方向Ｄ１における複数の電極指３６ｂのピッチ（中心線同士の距離）は、ＩＤＴ電極３１とＩＤＴ電極３２とで異なっている。 The plurality of electrode fingers 36a and 36b are formed so as to extend in the orthogonal direction D2 of the elastic wave propagation direction D1, intersperse with each other in the orthogonal direction D2, and face the elastic wave propagation direction D1. The pitches (distances between the center lines) of the plurality of electrode fingers 36a in the elastic wave propagation direction D1 are different between the IDT electrode 31 and the IDT electrode 32. Further, the pitches (distances between the center lines) of the plurality of electrode fingers 36b in the elastic wave propagation direction D1 are different between the IDT electrode 31 and the IDT electrode 32.
　第１櫛歯状電極３１ａは、引き出し配線ｄ１ａを介して第１端子２１に接続される。第１櫛歯状電極３２ａは、引き出し配線ｄ２ａおよび容量素子Ｃ２２を介して第２端子２２に接続される。第２櫛歯状電極３１ｂは、引き出し配線ｄ１ｂを介してグランドに接続される。第２櫛歯状電極３２ｂは、引き出し配線ｄ２ｂを介してグランドに接続される。なお、グランドは、マルチプレクサ５の基板等に設けられたグランド接続用電極（図示省略）であってもよい。 The first comb-toothed electrode 31a is connected to the first terminal 21 via the lead-out wiring d1a. The first comb-shaped electrode 32a is connected to the second terminal 22 via the lead-out wiring d2a and the capacitive element C22. The second comb-shaped electrode 31b is connected to the ground via the lead-out wiring d1b. The second comb-toothed electrode 32b is connected to the ground via the lead-out wiring d2b. The ground may be a ground connection electrode (not shown) provided on the substrate of the multiplexer 5.
　複数の反射器４１、４２は、弾性波伝搬方向Ｄ１において、ＩＤＴ電極３１、３２を挟むように配置されている。反射器４１、４２は、互いに接続されていない独立した電極である。図３に示す反射器４１、４２は、グランドに接続されずオープン状態となっている。なお、反射器４１、４２は、グランドに接続されてもよいし、ホット端子（信号端子）に接続されてもよい。 The plurality of reflectors 41 and 42 are arranged so as to sandwich the IDT electrodes 31 and 32 in the elastic wave propagation direction D1. The reflectors 41 and 42 are independent electrodes that are not connected to each other. The reflectors 41 and 42 shown in FIG. 3 are not connected to the ground and are in an open state. The reflectors 41 and 42 may be connected to the ground or may be connected to a hot terminal (signal terminal).
　各反射器４１、４２は、互いに平行な複数の電極指４６と、複数の電極指４６の両端同士を接続する複数のバスバー４７と、で構成されている。各電極指４６は、弾性波伝搬方向Ｄ１の直交方向Ｄ２に延びるように形成されている。各バスバー４７は弾性波伝搬方向Ｄ１に延びるように形成されている。 Each of the reflectors 41 and 42 is composed of a plurality of electrode fingers 46 parallel to each other and a plurality of bus bars 47 connecting both ends of the plurality of electrode fingers 46. Each electrode finger 46 is formed so as to extend in the orthogonal direction D2 of the elastic wave propagation direction D1. Each bus bar 47 is formed so as to extend in the elastic wave propagation direction D1.
　複数の反射器４１、４２の電極指４６の本数の割合Ｒは、複数のＩＤＴ電極３１、３２の電極指３６ａ、３６ｂの本数および複数の反射器４１、４２の電極指４６の本数を合計した総本数の１１％以下である。すなわち、電極指４６の本数の割合Ｒ（％）＝（電極指４６の本数／（電極指３６ａ、３６ｂの本数＋電極指４６の本数））×１００≦１１である。なお、反射器４１、４２のそれぞれは、１本以上の電極指４６を有していることが望ましい。すなわち、反射器４１、４２の電極指４６の本数は２本以上であり、上記割合Ｒは、０＜（電極指４６の本数／（電極指３６ａ、３６ｂの本数＋電極指４６の本数））×１００の関係を有することが望ましい。 The ratio R of the number of the electrode fingers 46 of the plurality of reflectors 41 and 42 is the sum of the number of the electrode fingers 36a and 36b of the plurality of IDT electrodes 31 and 32 and the number of the electrode fingers 46 of the plurality of reflectors 41 and 42. It is 11% or less of the total number. That is, the ratio R (%) of the number of the electrode fingers 46 = (the number of the electrode fingers 46 / (the number of the electrode fingers 36a and 36b + the number of the electrode fingers 46)) × 100 ≦ 11. It is desirable that each of the reflectors 41 and 42 has one or more electrode fingers 46. That is, the number of the electrode fingers 46 of the reflectors 41 and 42 is two or more, and the ratio R is 0 <(the number of the electrode fingers 46 / (the number of the electrode fingers 36a and 36b + the number of the electrode fingers 46)). It is desirable to have a relationship of × 100.
　また、反射器４１、４２のそれぞれのデューティは、ＩＤＴ電極３１、３２のデューティよりも小さい。例えば、各反射器４１、４２のデューティは、０．３以上０．５未満である。反射器４１、４２のデューティは、同じであってもよいし、異なっていてもよい。なお、本実施の形態における反射器のデューティとは、電極指４６の幅を、弾性波伝搬方向Ｄ１に隣り合う電極指４６の距離（隣り合う電極指の中心線同士の距離）で割った値である。ＩＤＴ電極３１、３２のデューティとは、ＩＤＴ電極３１、３２の電極指３６ａ（または３６ｂ）の幅を、弾性波伝搬方向Ｄ１に隣り合う電極指３６ａと電極指３６ｂとの距離（隣り合う電極指の中心線同士の距離）で割った値である。 Further, the duty of the reflectors 41 and 42 is smaller than the duty of the IDT electrodes 31 and 32, respectively. For example, the duty of each reflector 41, 42 is 0.3 or more and less than 0.5. The duties of the reflectors 41 and 42 may be the same or different. The duty of the reflector in the present embodiment is a value obtained by dividing the width of the electrode fingers 46 by the distance between the electrode fingers 46 adjacent to each other in the elastic wave propagation direction D1 (the distance between the center lines of the adjacent electrode fingers). Is. The duty of the IDT electrodes 31 and 32 means that the width of the electrode fingers 36a (or 36b) of the IDT electrodes 31 and 32 is the distance between the electrode fingers 36a and the electrode fingers 36b adjacent to each other in the elastic wave propagation direction D1 (adjacent electrode fingers). It is the value divided by the distance between the center lines of.
　本実施の形態では、反射器４１、４２の電極指４６の本数の割合Ｒを、電極指３６ａ、３６ｂ、４６の総本数の１１％以下としている。これによれば、弾性波フィルタ１の周波数通過帯域外における減衰量を確保することができる。以下、実施の形態１の効果について具体的に説明する。 In the present embodiment, the ratio R of the number of electrode fingers 46 of the reflectors 41 and 42 is 11% or less of the total number of electrode fingers 36a, 36b and 46. According to this, it is possible to secure the amount of attenuation of the elastic wave filter 1 outside the frequency passband. Hereinafter, the effects of the first embodiment will be specifically described.
　［１－４．効果等］
　本実施の形態の弾性波フィルタ１の通過特性、および、マルチプレクサ５のアイソレーション特性について、比較例と比べながら説明する。 [1-4. Effect, etc.]
The pass characteristics of the elastic wave filter 1 and the isolation characteristics of the multiplexer 5 of the present embodiment will be described with reference to comparative examples.
　図４は、弾性波フィルタ１の通過特性を示す図である。図５は、マルチプレクサ５のアイソレーション特性を示す図である。 FIG. 4 is a diagram showing the passing characteristics of the elastic wave filter 1. FIG. 5 is a diagram showing the isolation characteristics of the multiplexer 5.
　図４および図５には、弾性波フィルタを送信フィルタとし、第２フィルタ回路５０を受信フィルタとし、弾性波フィルタの周波数通過帯域を８８０ＭＨｚ－９１５ＭＨｚとし、第２フィルタ回路５０の周波数通過帯域を９２５ＭＨｚ－９６０ＭＨｚとした例が示されている。また、図４には、第１信号端子Ｔ１－第２信号端子Ｔ２間の挿入損失が示され、図５には、第１信号端子Ｔ１－第３信号端子Ｔ３間の挿入損失が示されている。 In FIGS. 4 and 5, the elastic wave filter is used as a transmission filter, the second filter circuit 50 is used as a receive filter, the frequency passband of the elastic wave filter is 880 MHz-915 MHz, and the frequency passband of the second filter circuit 50 is 925 MHz. An example of -960 MHz is shown. Further, FIG. 4 shows an insertion loss between the first signal terminal T1 and the second signal terminal T2, and FIG. 5 shows the insertion loss between the first signal terminal T1 and the third signal terminal T3. There is.
　実施の形態１の弾性波フィルタ１は、ＩＤＴ電極の電極指３６ａおよび３６ｂの本数が７０本、反射器４１、４２の電極指４６の本数（合計本数）が７本であり、電極指４６の本数の割合Ｒは９．１％である。比較例の弾性波フィルタは、ＩＤＴ電極の電極指３６ａおよび３６ｂの本数が７０本、反射器４１、４２の電極指４６の本数（合計本数）が１１本であり、電極指４６の本数の割合Ｒは１３．６％である。 In the elastic wave filter 1 of the first embodiment, the number of the electrode fingers 36a and 36b of the IDT electrode is 70, the number of the electrode fingers 46 of the reflectors 41 and 42 (total number) is 7, and the number of the electrode fingers 46 is 7. The ratio R of the number is 9.1%. The elastic wave filter of the comparative example has 70 electrode fingers 36a and 36b of the IDT electrode, 11 electrode fingers 46 of the reflectors 41 and 42 (total number), and is a ratio of the number of electrode fingers 46. R is 13.6%.
　図４および図５に示すように、比較例（Ｒ＝１３．６％）では、弾性波フィルタの周波数通過帯域外において３つの大きな不要波ａ、ｂ、ｃが発生している。それに対し、実施の形態１（Ｒ＝９．１％）では、不要波ａ、ｂ、ｃのピークレベルが抑えられ、減衰量が大きくなっている。 As shown in FIGS. 4 and 5, in the comparative example (R = 13.6%), three large unnecessary waves a, b, and c are generated outside the frequency passband of the elastic wave filter. On the other hand, in the first embodiment (R = 9.1%), the peak levels of the unnecessary waves a, b, and c are suppressed, and the amount of attenuation is large.
　ここで、反射器４１、４２の電極指４６の本数の割合Ｒを変えた場合の不要波のピークレベルについて説明する。 Here, the peak level of unnecessary waves when the ratio R of the number of electrode fingers 46 of the reflectors 41 and 42 is changed will be described.
　図６は、反射器４１、４２の電極指４６の本数の割合Ｒおよび不要波のピークレベルの関係を示す図である。図６の横軸は、電極指４６の本数の割合Ｒであり、縦軸は、マルチプレクサのアイソレーション特性における最も大きな不要波のピークレベルである。不要波のピークレベルは挿入損失で表されている。 FIG. 6 is a diagram showing the relationship between the ratio R of the number of electrode fingers 46 of the reflectors 41 and 42 and the peak level of unnecessary waves. The horizontal axis of FIG. 6 is the ratio R of the number of electrode fingers 46, and the vertical axis is the peak level of the largest unnecessary wave in the isolation characteristic of the multiplexer. The peak level of unwanted waves is represented by insertion loss.
　反射器４１、４２の電極指４６の本数の割合Ｒは、表１に示す条件により設定した。具体的には、ＩＤＴ電極３１、３２の電極指のそれぞれの本数を３５本とし、反射器４１、４２の電極指４６のそれぞれの本数を、０以上１７本以下の間で変えることで、電極指４６の本数の割合Ｒを変えた。なお、ＩＤＴ電極３１、３２のデューティ、および、反射器４１、４２のデューティは表１に示すとおりとした。 The ratio R of the number of electrode fingers 46 of the reflectors 41 and 42 was set according to the conditions shown in Table 1. Specifically, the number of each of the electrode fingers of the IDT electrodes 31 and 32 is 35, and the number of each of the electrode fingers 46 of the reflectors 41 and 42 is changed between 0 and 17 or less. The ratio R of the number of fingers 46 was changed. The duty of the IDT electrodes 31 and 32 and the duty of the reflectors 41 and 42 are as shown in Table 1.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　図６に示すように、反射器４１、４２の電極指４６の本数の割合Ｒが１１％よりも大きい場合、電極指４６の本数の割合Ｒを小さくしても、不要波のピークレベルがそれほど低下しない。それに対し、電極指４６の本数の割合Ｒが１１％以下である場合、電極指４６の本数の割合Ｒを小さくすると、不要波のピークレベルが極端に低下する。すなわち、不要波のピークレベルの低下率（傾き）が、割合Ｒ＝１１％を境に急に大きくなっている。このように、反射器４１、４２の電極指４６の本数の割合Ｒを、電極指３６ａ、３６ｂ、４６の総本数の１１％以下とすることで、周波数通過帯域外における不要波のピークレベルを低下させることができる。 As shown in FIG. 6, when the ratio R of the number of electrode fingers 46 of the reflectors 41 and 42 is larger than 11%, the peak level of unnecessary waves is not so large even if the ratio R of the number of electrode fingers 46 is reduced. Does not decrease. On the other hand, when the ratio R of the number of the electrode fingers 46 is 11% or less, if the ratio R of the number of the electrode fingers 46 is reduced, the peak level of the unnecessary wave is extremely lowered. That is, the rate of decrease (slope) of the peak level of the unwanted wave suddenly increases at the ratio R = 11%. In this way, by setting the ratio R of the number of electrode fingers 46 of the reflectors 41 and 42 to 11% or less of the total number of electrode fingers 36a, 36b, 46, the peak level of unnecessary waves outside the frequency pass band can be set. Can be reduced.
　（実施の形態２）
　［２－１．マルチプレクサの構成］
　実施の形態２に係る弾性波フィルタ１を備えるマルチプレクサ５の構成について、図１を参照しながら説明する。実施の形態２では、付加回路２０ＡのＩＤＴ電極群２５Ａが４つのＩＤＴ電極で構成されている例について説明する。 (Embodiment 2)
[2-1. Multiplexer configuration]
The configuration of the multiplexer 5 including the elastic wave filter 1 according to the second embodiment will be described with reference to FIG. In the second embodiment, an example in which the IDT electrode group 25A of the additional circuit 20A is composed of four IDT electrodes will be described.
　図７は、実施の形態２に係る弾性波フィルタ１を備えるマルチプレクサ５の回路構成図である。なお、図７にはアンテナ素子９も示されている。 FIG. 7 is a circuit configuration diagram of a multiplexer 5 including the elastic wave filter 1 according to the second embodiment. Note that FIG. 7 also shows the antenna element 9.
　マルチプレクサ５は、第１フィルタ回路１０および付加回路２０Ａを有する弾性波フィルタ１と、第２フィルタ回路５０とを備えている。また、マルチプレクサ５は、第１信号端子Ｔ１、第２信号端子Ｔ２および第３信号端子Ｔ３を備えている。 The multiplexer 5 includes an elastic wave filter 1 having a first filter circuit 10 and an additional circuit 20A, and a second filter circuit 50. Further, the multiplexer 5 includes a first signal terminal T1, a second signal terminal T2, and a third signal terminal T3.
　［２－２．弾性波フィルタの構成］
　図７に示すように、実施の形態２の弾性波フィルタ１は、第１フィルタ回路１０と付加回路２０Ａとを備えている。 [2-2. Structure of elastic wave filter]
As shown in FIG. 7, the elastic wave filter 1 of the second embodiment includes a first filter circuit 10 and an additional circuit 20A.
　第１フィルタ回路１０は、実施の形態１と同じである。すわなち、第１フィルタ回路１０は、第１の経路ｒ１上に配置された４つの直列腕共振子Ｓ１～Ｓ４、および、第１の経路ｒ１と基準端子とを結ぶ経路上に配置された３つの並列腕共振子Ｐ１～Ｐ３で構成されるＴ型のラダーフィルタ構造を有している。 The first filter circuit 10 is the same as that of the first embodiment. That is, the first filter circuit 10 is arranged on the four series arm resonators S1 to S4 arranged on the first path r1 and on the path connecting the first path r1 and the reference terminal. It has a T-shaped ladder filter structure composed of three parallel arm resonators P1 to P3.
　付加回路２０Ａは、第１フィルタ回路１０の少なくとも一部に対し並列に接続されるように、第１の経路ｒ１上の異なる複数のノードに接続される。付加回路２０Ａは、付加回路２０Ａの一端側の接続ノードとなる第１端子２１、２１ａ、他端側の接続ノードとなる第２端子２２、２２ａ、および、第１端子２１、２１ａと第２端子２２、２２ａとを結ぶ第２の経路ｒ２、ｒ２ａ上に配置されたＩＤＴ電極群２５Ａを有している。 The additional circuit 20A is connected to a plurality of different nodes on the first path r1 so as to be connected in parallel to at least a part of the first filter circuit 10. The additional circuit 20A includes first terminals 21 and 21a as connection nodes on one end side of the additional circuit 20A, second terminals 22 and 22a as connection nodes on the other end side, and first terminals 21 and 21a and second terminals. It has an IDT electrode group 25A arranged on the second path r2, r2a connecting 22 and 22a.
　第１端子２１、２１ａは、ＩＤＴ電極群２５Ａに電気的に接続されている。第２端子２２は、容量素子Ｃ２２を介してＩＤＴ電極群２５Ａに接続され、第２端子２２ａは、容量素子Ｃ２２ａを介してＩＤＴ電極群２５Ａに接続されている。 The first terminals 21 and 21a are electrically connected to the IDT electrode group 25A. The second terminal 22 is connected to the IDT electrode group 25A via the capacitive element C22, and the second terminal 22a is connected to the IDT electrode group 25A via the capacitive element C22a.
　また、第１端子２１、２１ａおよび第２端子２２、２２ａのそれぞれは、第１の経路ｒ１上の異なるノードに接続される。図７では、第１端子２１は、直列腕共振子Ｓ１とＳ２との間のノードｎ１に接続され、第１端子２１ａは、ノードｎ２に接続され、第２端子２２は、直列腕共振子Ｓ４と第２信号端子Ｔ２との間のノードｎ４に接続され、第２端子２２ａは、直列腕共振子Ｓ４と第２信号端子Ｔ２との間のノードｎ４ａに接続されている。 Further, each of the first terminals 21, 21a and the second terminals 22, 22a is connected to different nodes on the first path r1. In FIG. 7, the first terminal 21 is connected to the node n1 between the series arm resonators S1 and S2, the first terminal 21a is connected to the node n2, and the second terminal 22 is the series arm resonator S4. The second terminal 22a is connected to the node n4a between the series arm resonator S4 and the second signal terminal T2.
　図８は、弾性波フィルタ１の付加回路２０Ａに含まれるＩＤＴ電極群２５Ａを示す模式図である。なお図８でも、電極および配線が実線で示されている。 FIG. 8 is a schematic diagram showing the IDT electrode group 25A included in the additional circuit 20A of the elastic wave filter 1. Also in FIG. 8, the electrodes and wiring are shown by solid lines.
　ＩＤＴ電極群２５Ａは、複数のＩＤＴ電極３１、３２、３３、３４からなる。ＩＤＴ電極群２５Ａは、例えば、縦結合型共振器である。複数のＩＤＴ電極３１、３２、３３、３４は、弾性波伝搬方向Ｄ１に沿って隣り合って、この順で配置されている。 The IDT electrode group 25A is composed of a plurality of IDT electrodes 31, 32, 33, 34. The IDT electrode group 25A is, for example, a vertically coupled resonator. The plurality of IDT electrodes 31, 32, 33, 34 are arranged adjacent to each other along the elastic wave propagation direction D1 in this order.
　また、付加回路２０は、複数の反射器４１、４２を有している。複数の反射器４１、４２は、弾性波伝搬方向Ｄ１において、ＩＤＴ電極群２５Ａを挟み込むように、ＩＤＴ電極群２５Ａの両外側に位置している。図７には、２つの反射器４１、４２を備えるＩＤＴ電極群２５Ａが例示されている。 Further, the additional circuit 20 has a plurality of reflectors 41 and 42. The plurality of reflectors 41 and 42 are located on both outer sides of the IDT electrode group 25A so as to sandwich the IDT electrode group 25A in the elastic wave propagation direction D1. FIG. 7 illustrates an IDT electrode group 25A including two reflectors 41 and 42.
　複数のＩＤＴ電極３１～３４は、複数の第１櫛歯状電極３１ａ、３２ａ、３３ａ、３４ａおよび複数の第２櫛歯状電極３１ｂ、３２ｂ、３３ｂ、３４ｂを有している。ＩＤＴ電極３１は、一対となる第１櫛歯状電極３１ａおよび第２櫛歯状電極３１ｂによって構成されている。ＩＤＴ電極３２は、一対となる第１櫛歯状電極３２ａおよび第２櫛歯状電極３２ｂによって構成されている。ＩＤＴ電極３３は、一対となる第１櫛歯状電極３３ａおよび第２櫛歯状電極３３ｂによって構成されている。ＩＤＴ電極３４は、一対となる第１櫛歯状電極３４ａおよび第２櫛歯状電極３４ｂによって構成されている。 The plurality of IDT electrodes 31 to 34 have a plurality of first comb-shaped electrodes 31a, 32a, 33a, 34a and a plurality of second comb-shaped electrodes 31b, 32b, 33b, 34b. The IDT electrode 31 is composed of a pair of a first comb-shaped electrode 31a and a second comb-shaped electrode 31b. The IDT electrode 32 is composed of a pair of a first comb-shaped electrode 32a and a second comb-shaped electrode 32b. The IDT electrode 33 is composed of a pair of a first comb-shaped electrode 33a and a second comb-shaped electrode 33b. The IDT electrode 34 is composed of a pair of a first comb-shaped electrode 34a and a second comb-shaped electrode 34b.
　第１櫛歯状電極および第２櫛歯状電極は、互いに対向している。 The first comb-shaped electrode and the second comb-shaped electrode face each other.
　ＩＤＴ電極３１～３４を基板３２０に垂直な方向から見た場合に、第１櫛歯状電極３１ａ、３３ａと第１櫛歯状電極３２ａ、３４ａとは、互いに逆向きで配置されている。また、第２櫛歯状電極３１ｂ、３３ｂと第２櫛歯状電極３２ｂ、３４ｂとは、互いに逆向きで配置されている。第１櫛歯状電極３１ａ、３３ａおよび第２櫛歯状電極３２ｂ、３４ｂは同じ向きで配置されている。 When the IDT electrodes 31 to 34 are viewed from the direction perpendicular to the substrate 320, the first comb-shaped electrodes 31a and 33a and the first comb-shaped electrodes 32a and 34a are arranged in opposite directions to each other. Further, the second comb-shaped electrodes 31b and 33b and the second comb-shaped electrodes 32b and 34b are arranged in opposite directions to each other. The first comb-shaped electrodes 31a and 33a and the second comb-shaped electrodes 32b and 34b are arranged in the same direction.
　複数の第１櫛歯状電極３１ａ～３４ａは、第１の経路ｒ１上の複数のノードに電気的に接続される。具体的には、第１櫛歯状電極３１ａが、第１端子２１によってノードｎ１に接続され、第１櫛歯状電極３３ａが、第１端子２１ａによってノードｎ２に接続され、第１櫛歯状電極３３ａが、第２端子２２によってノードｎ４に接続され、第１櫛歯状電極３４ａが、第２端子２２ａによってノードｎ４ａに接続される。一方、第２櫛歯状電極３１ｂ～３４ｂのそれぞれは、グランドに接続されている。 The plurality of first comb-shaped electrodes 31a to 34a are electrically connected to a plurality of nodes on the first path r1. Specifically, the first comb-shaped electrode 31a is connected to the node n1 by the first terminal 21, the first comb-shaped electrode 33a is connected to the node n2 by the first terminal 21a, and the first comb-shaped electrode is formed. The electrode 33a is connected to the node n4 by the second terminal 22, and the first comb-shaped electrode 34a is connected to the node n4a by the second terminal 22a. On the other hand, each of the second comb-shaped electrodes 31b to 34b is connected to the ground.
　なお、第１端子２１、２１ａおよび第２端子２２、２２ａは、第１の経路ｒ１上にて隣り合う２以上の直列腕共振子の両外側のノードに接続されていればよい。例えば、第１端子２１は、第１信号端子Ｔ１と直列腕共振子Ｓ１とを結ぶ第１の経路ｒ１上のノードに接続されていてもよいし、ノードｎ２に接続されていてもよい。例えば、第１端子２１ａは、ノードｎ１に接続されていてもよい。例えば、第２端子２２、２２ａは、ノードｎ３に接続されていてもよい。 The first terminals 21, 21a and the second terminals 22, 22a may be connected to the outer nodes of two or more series arm resonators adjacent to each other on the first path r1. For example, the first terminal 21 may be connected to a node on the first path r1 connecting the first signal terminal T1 and the series arm resonator S1, or may be connected to the node n2. For example, the first terminal 21a may be connected to the node n1. For example, the second terminals 22 and 22a may be connected to the node n3.
　また、付加回路２０Ａは、容量素子Ｃ２２、Ｃ２２ａを備えていなくてもよい。不要波を適度に抑制できるのであれば、ＩＤＴ電極群２５Ａは、第２端子２２、２２ａに、容量素子を介さずに配線接続されていてもよい。 Further, the additional circuit 20A does not have to include the capacitive elements C22 and C22a. The IDT electrode group 25A may be connected to the second terminals 22 and 22a by wiring without using a capacitive element as long as the unnecessary wave can be appropriately suppressed.
　［２－３．ＩＤＴ電極群の構造］
　次に、付加回路２０Ａに含まれるＩＤＴ電極群２５Ａの構造について説明する。 [2-3. Structure of IDT electrode group]
Next, the structure of the IDT electrode group 25A included in the additional circuit 20A will be described.
　図９は、図８に示すＩＤＴ電極群２５Ａの構造を模式的に示す平面図である。 FIG. 9 is a plan view schematically showing the structure of the IDT electrode group 25A shown in FIG.
　図９に示すように、各第１櫛歯状電極３１ａ～３４ａは、互いに平行な複数の電極指３６ａと、複数の電極指３６ａのそれぞれの一端同士を接続するバスバー電極３７ａとで構成されている。各第２櫛歯状電極３１ｂ～３４ｂは、互いに平行な複数の電極指３６ｂと、複数の電極指３６ｂのそれぞれの一端同士を接続するバスバー電極３７ｂとで構成されている。複数の電極指３６ａおよび３６ｂは、弾性波伝搬方向Ｄ１の直交方向Ｄ２に延びるように形成され、直交方向Ｄ２に互いに間挿し合い、弾性波伝搬方向Ｄ１に対向している。各バスバー電極３７ａおよび３７ｂは、弾性波伝搬方向Ｄ１に沿って延びるように形成されている。 As shown in FIG. 9, each of the first comb-shaped electrodes 31a to 34a is composed of a plurality of electrode fingers 36a parallel to each other and a bus bar electrode 37a connecting one ends of the plurality of electrode fingers 36a to each other. There is. Each of the second comb-shaped electrodes 31b to 34b is composed of a plurality of electrode fingers 36b parallel to each other and a bus bar electrode 37b connecting one ends of the plurality of electrode fingers 36b to each other. The plurality of electrode fingers 36a and 36b are formed so as to extend in the orthogonal direction D2 of the elastic wave propagation direction D1, intersperse with each other in the orthogonal direction D2, and face the elastic wave propagation direction D1. The bus bar electrodes 37a and 37b are formed so as to extend along the elastic wave propagation direction D1.
　複数の反射器４１、４２は、弾性波伝搬方向Ｄ１において、複数のＩＤＴ電極３１～３４を挟むように配置されている。反射器４１、４２は、互いに接続されていない独立した電極である各反射器４１、４２は、互いに平行な複数の電極指４６と、複数の電極指４６の両端同士を接続する複数のバスバー４７と、で構成されている。各電極指４６は、弾性波伝搬方向Ｄ１の直交方向Ｄ２に延びるように形成されている。各バスバー４７は弾性波伝搬方向Ｄ１に延びるように形成されている。 The plurality of reflectors 41 and 42 are arranged so as to sandwich the plurality of IDT electrodes 31 to 34 in the elastic wave propagation direction D1. The reflectors 41 and 42 are independent electrodes that are not connected to each other. Each of the reflectors 41 and 42 has a plurality of electrode fingers 46 parallel to each other and a plurality of bus bars 47 connecting both ends of the plurality of electrode fingers 46. And, it is composed of. Each electrode finger 46 is formed so as to extend in the orthogonal direction D2 of the elastic wave propagation direction D1. Each bus bar 47 is formed so as to extend in the elastic wave propagation direction D1.
　実施の形態２において、複数の反射器４１、４２の電極指４６の本数の割合Ｒは、複数のＩＤＴ電極３１～３４の電極指３６ａ、３６ｂの本数および複数の反射器４１、４２の電極指４６の本数を合計した総本数の１１％以下である。すなわち、電極指４６の本数の割合Ｒ（％）＝（電極指４６の本数／（電極指３６ａ、３６ｂの本数＋電極指４６の本数））×１００≦１１である。電極指４６の本数は２本以上であり、上記割合Ｒは、０＜（電極指４６の本数／（電極指３６ａ、３６ｂの本数＋電極指４６の本数））×１００の関係を有することが望ましい。 In the second embodiment, the ratio R of the number of the electrode fingers 46 of the plurality of reflectors 41 and 42 is the number of the electrode fingers 36a and 36b of the plurality of IDT electrodes 31 to 34 and the electrode fingers of the plurality of reflectors 41 and 42. It is 11% or less of the total number of 46 pieces. That is, the ratio R (%) of the number of the electrode fingers 46 = (the number of the electrode fingers 46 / (the number of the electrode fingers 36a and 36b + the number of the electrode fingers 46)) × 100 ≦ 11. The number of the electrode fingers 46 is two or more, and the ratio R may have a relationship of 0 <(the number of the electrode fingers 46 / (the number of the electrode fingers 36a and 36b + the number of the electrode fingers 46)) × 100. desirable.
　また、反射器４１、４２のそれぞれのデューティは、ＩＤＴ電極３１～３４のデューティよりも小さい。例えば、各反射器４１、４２のデューティは、０．１以上０．５未満である。反射器４１、４２のデューティは、同じであってもよいし、異なっていてもよい。 Further, the duty of each of the reflectors 41 and 42 is smaller than the duty of the IDT electrodes 31 to 34. For example, the duty of each reflector 41, 42 is 0.1 or more and less than 0.5. The duties of the reflectors 41 and 42 may be the same or different.
　実施の形態２でも、反射器４１、４２の電極指４６の本数の割合Ｒを、電極指３６ａ、３６ｂ、４６の総本数の１１％以下としている。これによれば、弾性波フィルタ１の周波数通過帯域外における減衰量を確保することができる。以下、実施の形態２の効果について具体的に説明する。 Also in the second embodiment, the ratio R of the number of the electrode fingers 46 of the reflectors 41 and 42 is set to 11% or less of the total number of the electrode fingers 36a, 36b and 46. According to this, it is possible to secure the amount of attenuation of the elastic wave filter 1 outside the frequency passband. Hereinafter, the effects of the second embodiment will be specifically described.
　［２－４．効果等］
　本実施の形態の弾性波フィルタ１の通過特性について、比較例と比べながら説明する。 [2-4. Effect, etc.]
The passing characteristics of the elastic wave filter 1 of the present embodiment will be described with reference to comparative examples.
　図１０は、実施の形態２の弾性波フィルタ１の通過特性を示す図である。 FIG. 10 is a diagram showing the passing characteristics of the elastic wave filter 1 of the second embodiment.
　図１０には、弾性波フィルタを送信フィルタとし、第２フィルタ回路５０を受信フィルタとし、弾性波フィルタの周波数通過帯域を８８０ＭＨｚ－９１５ＭＨｚとし、第２フィルタ回路５０の周波数通過帯域を９２５ＭＨｚ－９６０ＭＨｚとした例が示されている。また、図１０には、第１信号端子Ｔ１－第２信号端子Ｔ２間の挿入損失が示されている。 In FIG. 10, the elastic wave filter is used as a transmission filter, the second filter circuit 50 is used as a reception filter, the frequency pass band of the elastic wave filter is 880 MHz-915 MHz, and the frequency pass band of the second filter circuit 50 is 925 MHz-960 MHz. An example is shown. Further, FIG. 10 shows an insertion loss between the first signal terminal T1 and the second signal terminal T2.
　実施の形態２の弾性波フィルタ１は、ＩＤＴ電極の電極指３６ａ、３６ｂの本数が７４本、反射器４１、４２の電極指４６の本数（合計本数）が７本であり、電極指４６の本数の割合Ｒは８．６％である。比較例の弾性波フィルタは、ＩＤＴ電極の電極指３６ａ、３６ｂの本数が７４本、反射器４１、４２の電極指４６の本数（合計本数）が１１本であり、電極指４６の本数の割合Ｒは１２．９％である。 In the elastic wave filter 1 of the second embodiment, the number of the electrode fingers 36a and 36b of the IDT electrode is 74, the number of the electrode fingers 46 of the reflectors 41 and 42 (total number) is 7, and the number of the electrode fingers 46 is 7. The ratio R of the number is 8.6%. The elastic wave filter of the comparative example has 74 electrode fingers 36a and 36b of the IDT electrode and 11 electrode fingers 46 (total number) of the reflectors 41 and 42, and is a ratio of the number of electrode fingers 46. R is 12.9%.
　図１０に示すように、比較例（Ｒ＝１２．９％）では、弾性波フィルタの周波数通過帯域外において３つの大きな不要波ａ１、ｂ１、ｃ１が発生している。それに対し、実施の形態２（Ｒ＝８．６％）では、不要波ａ１、ｂ１、ｃ１のピークレベルが抑えられ、減衰量が大きくなっている。 As shown in FIG. 10, in the comparative example (R = 12.9%), three large unnecessary waves a1, b1 and c1 are generated outside the frequency passband of the elastic wave filter. On the other hand, in the second embodiment (R = 8.6%), the peak levels of the unnecessary waves a1, b1 and c1 are suppressed, and the attenuation is large.
　ここで、反射器４１、４２の電極指４６の本数の割合Ｒを変えた場合の不要波のピークレベルについて説明する。 Here, the peak level of unnecessary waves when the ratio R of the number of electrode fingers 46 of the reflectors 41 and 42 is changed will be described.
　図１１は、反射器４１、４２の電極指４６の本数の割合Ｒおよび不要波のピークレベルの関係を示す図である。図１１の横軸は、電極指４６の本数の割合Ｒであり、縦軸は、最も大きな不要波のピークレベルである。不要波のピークレベルは挿入損失として表されている。 FIG. 11 is a diagram showing the relationship between the ratio R of the number of electrode fingers 46 of the reflectors 41 and 42 and the peak level of unnecessary waves. The horizontal axis of FIG. 11 is the ratio R of the number of electrode fingers 46, and the vertical axis is the peak level of the largest unnecessary wave. The peak level of unwanted waves is expressed as insertion loss.
　電極指４６の本数の割合Ｒは、表２に示す条件により設定した。具体的には、ＩＤＴ電極３１、３２、３３、３４の電極指のそれぞれの本数を１９本、２３本、１１本、２３本とし、反射器４１の電極指４６の本数を０以上１７本以下の間で、また、反射器４１の電極指４６の本数を０以上２１本以下の間で変えることで、電極指４６の本数の割合Ｒを変えた。なお、ＩＤＴ電極３１～３４のデューティ、および、反射器４１、４２のデューティは表２に示すとおりとした。 The ratio R of the number of electrode fingers 46 was set according to the conditions shown in Table 2. Specifically, the number of electrode fingers of the IDT electrodes 31, 32, 33, and 34 is 19, 23, 11, and 23, respectively, and the number of electrode fingers 46 of the reflector 41 is 0 or more and 17 or less. In addition, by changing the number of the electrode fingers 46 of the reflector 41 between 0 and more and 21 or less, the ratio R of the number of the electrode fingers 46 was changed. The duty of the IDT electrodes 31 to 34 and the duty of the reflectors 41 and 42 are as shown in Table 2.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　図１１に示すように、電極指４６の本数の割合Ｒが１１．９％よりも大きい場合、電極指４６の本数の割合Ｒを小さくしても、不要波のピークレベルがそれほど低下しない。それに対し、電極指４６の本数の割合Ｒが１１．９％以下である場合、電極指４６の本数の割合Ｒを小さくすると、不要波のピークレベルが極端に低下する。すなわち、不要波のピークレベルの低下率（傾き）が、割合Ｒ＝１１．９％を境に急に大きくなっている。このように、反射器４１、４２の電極指４６の本数の割合Ｒを、電極指３６ａ、３６ｂ、４６の総本数の１１．９％以下とすることで、周波数通過帯域外における不要波のピークレベルを低下させることができる。 As shown in FIG. 11, when the ratio R of the number of electrode fingers 46 is larger than 11.9%, the peak level of unnecessary waves does not decrease so much even if the ratio R of the number of electrode fingers 46 is reduced. On the other hand, when the ratio R of the number of the electrode fingers 46 is 11.9% or less, if the ratio R of the number of the electrode fingers 46 is reduced, the peak level of the unnecessary wave is extremely lowered. That is, the rate of decrease (slope) of the peak level of the unwanted wave suddenly increases at the ratio R = 11.9%. In this way, by setting the ratio R of the number of electrode fingers 46 of the reflectors 41 and 42 to 11.9% or less of the total number of electrode fingers 36a, 36b, 46, the peak of unnecessary waves outside the frequency pass band The level can be lowered.
　（まとめ）
　以上説明したように、本実施の形態に係る弾性波フィルタ１は、所定の周波数帯域を通過帯域とし、第１信号端子Ｔ１と第２信号端子Ｔ２とを結ぶ第１の経路ｒ１上に配置された第１フィルタ回路１０と、第１フィルタ回路１０の少なくとも一部に対し並列に接続される付加回路２０と、を備える。付加回路２０は、弾性波伝搬方向Ｄ１に沿って配置された複数のＩＤＴ電極からなるＩＤＴ電極群２５を有する。弾性波伝搬方向Ｄ１においてＩＤＴ電極群２５の両外側に位置する複数の反射器４１、４２の電極指４６の本数の割合Ｒは、複数のＩＤＴ電極の電極指３６ａ、３６ｂの本数および複数の反射器４１、４２の電極指４６の本数を合計した総本数の１１％以下である。 (summary)
As described above, the elastic wave filter 1 according to the present embodiment has a predetermined frequency band as a pass band and is arranged on the first path r1 connecting the first signal terminal T1 and the second signal terminal T2. A first filter circuit 10 and an additional circuit 20 connected in parallel to at least a part of the first filter circuit 10 are provided. The additional circuit 20 has an IDT electrode group 25 composed of a plurality of IDT electrodes arranged along the elastic wave propagation direction D1. The ratio R of the number of the electrode fingers 46 of the plurality of reflectors 41 and 42 located on both outer sides of the IDT electrode group 25 in the elastic wave propagation direction D is the number of the electrode fingers 36a and 36b of the plurality of IDT electrodes and the plurality of reflections. It is 11% or less of the total number of electrode fingers 46 of the vessels 41 and 42.
　このように、付加回路２０における反射器４１、４２の電極指４６の本数の割合Ｒを電極指３６ａ、３６ｂ、４６の総本数の１１％以下とすることで、付加回路２０の共振Ｑが必要以上に高くなることを抑制できる。これにより、弾性波フィルタ１の周波数通過帯域外に不要波が発生することを抑止し、周波数通過帯域外における減衰量を確保することができる。 As described above, the resonance Q of the additional circuit 20 is required by setting the ratio R of the number of the electrode fingers 46 of the reflectors 41 and 42 in the additional circuit 20 to 11% or less of the total number of the electrode fingers 36a, 36b and 46. It is possible to suppress the increase above. As a result, it is possible to suppress the generation of unnecessary waves outside the frequency passband of the elastic wave filter 1 and secure the amount of attenuation outside the frequency passband.
　また、ＩＤＴ電極群２５は、２つ以上のＩＤＴ電極３１、３２で構成されていてもよい。 Further, the IDT electrode group 25 may be composed of two or more IDT electrodes 31 and 32.
　これによれば、２つ以上のＩＤＴ電極３１、３２を有する付加回路２０において、上記割合Ｒを１１％以下とすることで、付加回路２０の共振Ｑが必要以上に高くなることを抑制できる。これにより、弾性波フィルタ１の周波数通過帯域外に不要波が発生することを抑止し、周波数通過帯域外における減衰量を確保することができる。 According to this, in the additional circuit 20 having two or more IDT electrodes 31 and 32, by setting the ratio R to 11% or less, it is possible to suppress the resonance Q of the additional circuit 20 from becoming higher than necessary. As a result, it is possible to suppress the generation of unnecessary waves outside the frequency passband of the elastic wave filter 1 and secure the amount of attenuation outside the frequency passband.
　また、ＩＤＴ電極群２５は、４つのＩＤＴ電極３１、３２、３３、３４で構成されていてもよい。 Further, the IDT electrode group 25 may be composed of four IDT electrodes 31, 32, 33, 34.
　これによれば、４つのＩＤＴ電極３１～３４を有する付加回路２０において、上記割合Ｒを総本数の１１％以下とすることで、付加回路２０の共振Ｑが必要以上に高くなることを抑制できる。また、複数のＩＤＴ電極を２つのＩＤＴ電極で構成する場合に比べて、割合Ｒの調整幅を広げることができ、付加回路２０の共振Ｑが必要以上に高くなることを簡易に抑制できる。これにより、弾性波フィルタ１の周波数通過帯域外に不要波が発生することを抑止し、周波数通過帯域外における減衰量を確保することができる。 According to this, in the additional circuit 20 having four IDT electrodes 31 to 34, by setting the ratio R to 11% or less of the total number, it is possible to suppress that the resonance Q of the additional circuit 20 becomes higher than necessary. .. Further, as compared with the case where the plurality of IDT electrodes are composed of two IDT electrodes, the adjustment range of the ratio R can be widened, and it is possible to easily suppress that the resonance Q of the additional circuit 20 becomes higher than necessary. As a result, it is possible to suppress the generation of unnecessary waves outside the frequency passband of the elastic wave filter 1 and secure the amount of attenuation outside the frequency passband.
　また、反射器４１、４２のデューティは、ＩＤＴ電極３１、３２のデューティよりも小さくてもよい。 Further, the duty of the reflectors 41 and 42 may be smaller than the duty of the IDT electrodes 31 and 32.
　これによれば、付加回路２０の共振Ｑが必要以上に高くなることを抑制できる。これにより、弾性波フィルタ１の周波数通過帯域外に不要波が発生することを抑止し、周波数通過帯域外における減衰量を確保することができる。 According to this, it is possible to prevent the resonance Q of the additional circuit 20 from becoming higher than necessary. As a result, it is possible to suppress the generation of unnecessary waves outside the frequency passband of the elastic wave filter 1 and secure the amount of attenuation outside the frequency passband.
　本実施の形態に係るマルチプレクサ５は、上記弾性波フィルタ１と、第１信号端子Ｔ１、第２信号端子Ｔ２および第３信号端子Ｔ３と、第１フィルタ回路１０とは異なる周波数帯域を通過帯域とし、第２信号端子Ｔ２と第３信号端子Ｔ３とを結ぶ第３の経路ｒ３上に配置された第２フィルタ回路５０とを備える。 The multiplexer 5 according to the present embodiment has a pass band different from that of the elastic wave filter 1, the first signal terminal T1, the second signal terminal T2, the third signal terminal T3, and the first filter circuit 10. , A second filter circuit 50 arranged on a third path r3 connecting the second signal terminal T2 and the third signal terminal T3 is provided.
　これによれば、周波数通過帯域外における減衰量が確保された弾性波フィルタ１を備えるマルチプレクサ５を提供することができる。 According to this, it is possible to provide a multiplexer 5 provided with an elastic wave filter 1 in which an attenuation amount outside the frequency pass band is secured.
　（その他の実施の形態）
　以上、本発明の実施の形態に係る弾性波フィルタおよびマルチプレクサについて、実施の形態１、２を挙げて説明したが、本発明は、上記実施の形態における任意の構成要素を組み合わせて実現される別の実施の形態や、上記実施の形態に対して本発明の主旨を逸脱しない範囲で当業者が思いつく各種変形を施して得られる変形例や、本発明に係る弾性波フィルタまたはマルチプレクサを含む高周波フロントエンド回路および通信装置も本発明に含まれる。 (Other embodiments)
Although the elastic wave filter and the multiplexer according to the embodiment of the present invention have been described with reference to the first and second embodiments, the present invention can be realized by combining arbitrary components according to the above embodiment. A high-frequency front including an elastic wave filter or a multiplexer according to the present invention, examples of modifications obtained by subjecting various modifications to the above embodiments to the extent that those skilled in the art can think of. End circuits and communication devices are also included in the present invention.
　上記では、弾性波フィルタが２つまたは４つのＩＤＴ電極を備えている例を示したが、それに限られず、ＩＤＴ電極の数は、３つでもよいし、５つ以上であってもよい。 In the above, the example in which the elastic wave filter is provided with two or four IDT electrodes is shown, but the number of IDT electrodes is not limited to this, and the number of IDT electrodes may be three or five or more.
　上記では、弾性波フィルタ１の周波数通過帯域が、第２フィルタ回路５０の周波数通過帯域よりも低くなるように設定されている例を示したが、それに限られず、弾性波フィルタ１の周波数通過帯域は、第２フィルタ回路５０の周波数通過帯域よりも高くなるように設定されていてもよい。 In the above, an example is shown in which the frequency passband of the elastic wave filter 1 is set to be lower than the frequency passband of the second filter circuit 50, but the present invention is not limited to this, and the frequency passband of the elastic wave filter 1 is not limited to this. May be set to be higher than the frequency passband of the second filter circuit 50.
　上記では、弾性波フィルタ１が送信フィルタである例を示したが、それに限られず、弾性波フィルタ１は受信フィルタであってもよい。また、マルチプレクサ５は、送信フィルタおよび受信フィルタの双方を備える構成に限られず、送信フィルタのみ、または、受信フィルタのみを備える構成であってもよい。 In the above, the example in which the elastic wave filter 1 is a transmission filter is shown, but the present invention is not limited to this, and the elastic wave filter 1 may be a reception filter. Further, the multiplexer 5 is not limited to the configuration including both the transmission filter and the reception filter, and may be configured to include only the transmission filter or only the reception filter.
　また、上記では、２つのフィルタを含むマルチプレクサを例に説明したが、本発明は、例えば、３つのフィルタのアンテナ端子が共通化されたトリプレクサや、６つのフィルタのアンテナ端子が共通化されたヘキサプレクサについても適用することができる。つまり、マルチプレクサは、２以上のフィルタを備えていればよい。 Further, in the above description, a multiplexer including two filters has been described as an example, but in the present invention, for example, a triplexer having common antenna terminals of three filters and a hexaplexer having common antenna terminals of six filters have been described. Can also be applied to. That is, the multiplexer need only have two or more filters.
　また、第１信号端子Ｔ１および第２信号端子Ｔ２は、入力端子および出力端子のいずれかであってもよい。例えば、第１信号端子Ｔ１が入力端子である場合は、第２信号端子Ｔ２が出力端子となり、第２信号端子Ｔ２が入力端子である場合は、第１信号端子Ｔ１が出力端子となる。 Further, the first signal terminal T1 and the second signal terminal T2 may be either an input terminal or an output terminal. For example, when the first signal terminal T1 is an input terminal, the second signal terminal T2 becomes an output terminal, and when the second signal terminal T2 is an input terminal, the first signal terminal T1 becomes an output terminal.
　また、第２フィルタ回路５０は、前述したフィルタの構成に限定されず、要求されるフィルタ特性等に応じて適宜設計され得る。具体的には、第２フィルタ回路５０は、縦結合型のフィルタ構造であってもよいし、ラダー型のフィルタ構造であってもよい。また、第２フィルタ回路５０を構成する各共振子は、ＳＡＷ共振子に限らず、例えば、ＢＡＷ（Ｂｕｌｋ　Ａｃｏｕｓｔｉｃ　Ｗａｖｅ）共振子であってもよい。さらには、第２フィルタ回路５０は、共振子を用いずに構成されていてもよく、例えば、ＬＣ共振フィルタあるいは誘電体フィルタであってもよい。 Further, the second filter circuit 50 is not limited to the above-mentioned filter configuration, and can be appropriately designed according to the required filter characteristics and the like. Specifically, the second filter circuit 50 may have a vertically coupled filter structure or a ladder type filter structure. Further, each resonator constituting the second filter circuit 50 is not limited to the SAW resonator, and may be, for example, a BAW (Bulk Acoustic Wave) resonator. Further, the second filter circuit 50 may be configured without using a resonator, and may be, for example, an LC resonance filter or a dielectric filter.
　また、ＩＤＴ電極３１、３２および反射器４１、４２の電極層３２５および誘電体層３２６を構成する材料は、前述した材料に限定されない。また、ＩＤＴ電極３１、３２は、上記積層構造でなくてもよい。ＩＤＴ電極３１、３２は、例えば、Ｔｉ、Ａｌ、Ｃｕ、Ｐｔ、Ａｕ、Ａｇ、Ｐｄなどの金属または合金から構成されてもよく、また、上記の金属または合金から構成される複数の積層体から構成されてもよい。 Further, the materials constituting the electrode layers 325 and the dielectric layer 326 of the IDT electrodes 31 and 32 and the reflectors 41 and 42 are not limited to the above-mentioned materials. Further, the IDT electrodes 31 and 32 do not have to have the above-mentioned laminated structure. The IDT electrodes 31 and 32 may be made of, for example, a metal or alloy such as Ti, Al, Cu, Pt, Au, Ag, Pd, or from a plurality of laminates made of the above metal or alloy. It may be configured.
　また、実施の形態１では、基板３２０として圧電性を有する基板を示したが、当該基板は、圧電体層の単層からなる圧電基板であってもよい。この場合の圧電基板は、例えば、ＬｉＴａＯ３の圧電単結晶、または、ＬｉＮｂＯ３などの他の圧電単結晶で構成される。また、ＩＤＴ電極３１、３２が形成される基板３２０は、圧電性を有する限り、全体が圧電体層からなるものの他、支持基板上に圧電体層が積層されている構造を用いてもよい。また、上記実施の形態１に係る基板３２０のカット角は限定されない。つまり、弾性波フィルタの要求通過特性などに応じて、適宜、積層構造、材料、および厚みを変更してもよく、上記実施の形態１に示すカット角以外のカット角を有するＬｉＴａＯ３圧電基板またはＬｉＮｂＯ３圧電基板などを用いた弾性表面波フィルタであっても、同様の効果を奏することが可能となる。 Further, in the first embodiment, a substrate having piezoelectricity is shown as the substrate 320, but the substrate may be a piezoelectric substrate composed of a single layer of a piezoelectric layer. The piezoelectric substrate in this case is composed of, for example, a piezoelectric single crystal of LiTaO 3 or another piezoelectric single crystal such as LiNbO 3. Further, the substrate 320 on which the IDT electrodes 31 and 32 are formed may be entirely composed of a piezoelectric layer or may have a structure in which the piezoelectric layer is laminated on the support substrate, as long as the substrate 320 has piezoelectricity. Further, the cut angle of the substrate 320 according to the first embodiment is not limited. That is, the laminated structure, material, and thickness may be appropriately changed according to the required passing characteristics of the surface acoustic wave filter, and the LiTaO 3 piezoelectric substrate having a cut angle other than the cut angle shown in the first embodiment may be used. Even an elastic surface acoustic wave filter using a LiNbO 3 piezoelectric substrate or the like can achieve the same effect.
　本発明は、弾性波フィルタを有するマルチプレクサ、フロントエンド回路および通信装置として、携帯電話などの通信機器に広く利用できる。 The present invention can be widely used in communication equipment such as mobile phones as a multiplexer having an elastic wave filter, a front-end circuit, and a communication device.
　１　　弾性波フィルタ
　５　　マルチプレクサ
　９　　アンテナ素子
　１０　第１フィルタ回路
　２０、２０Ａ　付加回路
　２１、２１ａ　第１端子
　２２、２２ａ　第２端子
　２５、２５Ａ　ＩＤＴ電極群
　３１、３２、３３、３４　ＩＤＴ電極
　３１ａ、３２ａ、３３ａ、３４ａ　第１櫛歯状電極
　３１ｂ、３２ｂ、３３ｂ、３４ｂ　第２櫛歯状電極
　３６ａ、３６ｂ　電極指
　３７ａ、３７ｂ　バスバー電極
　４１、４２　反射器
　４６　電極指
　４７　バスバー
　５０　第２フィルタ回路
　６０　縦結合型弾性波共振器
　３２０　基板
　３２５　電極層
　３２６　誘電体層
　Ｃ１１、Ｃ１２、Ｃ２２、Ｃ２２ａ　容量素子
　Ｄ１　弾性波伝搬方向
　Ｄ２　直交方向
　ｄ１ａ、ｄ１ｂ、ｄ２ａ、ｄ２ｂ　引き出し配線
　Ｌ１、Ｌ２　インダクタ
　ｎ０、ｎ１、ｎ２、ｎ３、ｎ４、ｎ４ａ　ノード
　Ｐ１、Ｐ２、Ｐ３、ＲＰ１、ＲＰ２　並列腕共振子
　ｒ１、ｒ２、ｒ２ａ、ｒ３　経路
　Ｓ１、Ｓ２、Ｓ３、Ｓ４、ＲＳ１、ＲＳ２　直列腕共振子
　Ｔ１　第１信号端子
　Ｔ２　第２信号端子
　Ｔ３　第３信号端子 1 Elastic wave filter 5 Dielectric 9 Antenna element 10 1st filter circuit 20, 20A Additional circuit 21, 21a 1st terminal 22, 22a 2nd terminal 25, 25A IDT electrode group 31, 32, 33, 34 IDT electrode 31a, 32a, 33a, 34a 1st comb tooth electrode 31b, 32b, 33b, 34b 2nd comb tooth electrode 36a, 36b Electrode finger 37a, 37b Bus bar electrode 41, 42 Reflector 46 Electrode finger 47 Bus bar 50 Second filter circuit 60 Vertical coupling Type elastic wave resonator 320 substrate 325 electrode layer 326 dielectric layer C11, C12, C22, C22a capacitive element D1 elastic wave propagation direction D2 orthogonal direction d1a, d1b, d2a, d2b lead-out wiring L1, L2 inductor n0, n1, n2, n3, n4, n4a node P1, P2, P3, RP1, RP2 Parallel arm resonator r1, r2, r2a, r3 Path S1, S2, S3, S4, RS1, RS2 Series arm resonator T1 1st signal terminal T2 2nd Signal terminal T3 3rd signal terminal

Claims (5)

  1. 　所定の周波数帯域を通過帯域とし、第１信号端子と第２信号端子とを結ぶ第１の経路上に配置された第１フィルタ回路と、
    　前記第１フィルタ回路の少なくとも一部に対し並列に接続される付加回路と、
    　を備え、
    　前記付加回路は、弾性波伝搬方向に沿って配置された複数のＩＤＴ電極からなるＩＤＴ電極群を有し、
    　前記弾性波伝搬方向において前記ＩＤＴ電極群の両外側に位置する複数の反射器の電極指の本数の割合は、前記複数のＩＤＴ電極の電極指の本数および前記複数の反射器の電極指の本数を合計した総本数の１１％以下である
    　弾性波フィルタ。     A first filter circuit arranged on a first path connecting a first signal terminal and a second signal terminal with a predetermined frequency band as a pass band,
    An additional circuit connected in parallel to at least a part of the first filter circuit,
    Equipped with
    The additional circuit has an IDT electrode group composed of a plurality of IDT electrodes arranged along the elastic wave propagation direction.
    The ratio of the number of electrode fingers of the plurality of reflectors located on both outer sides of the IDT electrode group in the direction of propagation of the elastic wave is the number of electrode fingers of the plurality of IDT electrodes and the number of electrode fingers of the plurality of reflectors. An elastic wave filter that is 11% or less of the total number of filters.
  2. 　前記ＩＤＴ電極群は、２つ以上のＩＤＴ電極で構成されている
    　請求項１に記載の弾性波フィルタ。     The elastic wave filter according to claim 1, wherein the IDT electrode group is composed of two or more IDT electrodes.
  3. 　前記ＩＤＴ電極群は、４つのＩＤＴ電極で構成されている
    　請求項１または２に記載の弾性波フィルタ。     The elastic wave filter according to claim 1 or 2, wherein the IDT electrode group is composed of four IDT electrodes.
  4. 　前記反射器のデューティは、前記ＩＤＴ電極のデューティよりも小さい
    　請求項１～３のいずれか１項に記載の弾性波フィルタ。     The elastic wave filter according to any one of claims 1 to 3, wherein the duty of the reflector is smaller than the duty of the IDT electrode.
  5. 　請求項１～４のいずれか１項に記載の弾性波フィルタと、
    　前記第１信号端子、前記第２信号端子および第３信号端子と、
    　前記第１フィルタ回路とは異なる周波数帯域を通過帯域とし、前記第２信号端子と前記第３信号端子とを結ぶ第３の経路上に配置された第２フィルタ回路と
    　を備えるマルチプレクサ。     The elastic wave filter according to any one of claims 1 to 4.
    The first signal terminal, the second signal terminal, and the third signal terminal,
    A multiplexer having a frequency band different from that of the first filter circuit as a pass band, and a second filter circuit arranged on a third path connecting the second signal terminal and the third signal terminal.
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