WO2022019072A1 - Filtre à ondes acoustiques et multiplexeur - Google Patents

Filtre à ondes acoustiques et multiplexeur 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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Prior art keywords
elastic wave
electrode
idt
electrode fingers
signal terminal
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PCT/JP2021/024758
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English (en)
Japanese (ja)
Inventor
明 野口
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株式会社村田製作所
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Priority to CN202190000716.5U priority Critical patent/CN219592382U/zh
Publication of WO2022019072A1 publication Critical patent/WO2022019072A1/fr

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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.

Landscapes

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

Abstract

La présente invention concerne un filtre à ondes acoustiques (1) qui est pourvu : d'un premier circuit de filtre (10) qui a une bande de fréquence prescrite en tant que bande passante, et qui est disposé sur un premier trajet (r1) reliant une première borne de signal (T1) et une deuxième borne de signal (T2) ; et d'un circuit supplémentaire (20) connecté en parallèle avec au moins une partie du premier circuit de filtre (10). Le circuit supplémentaire (20) comprend un groupe d'électrodes IDT (25) comprenant une pluralité d'électrodes IDT (31, 32) disposées dans une direction de propagation d'ondes acoustiques (D1). La proportion (R) du nombre de doigts d'électrode (46) dans une pluralité de réflecteurs (41, 42) positionnés sur les deux côtés extérieurs du groupe d'électrodes IDT (25) dans la direction de propagation des ondes acoustiques (D1) est au plus égale à 11 % d'un nombre total obtenu par addition du nombre de doigts d'électrode (36a, 36b) dans la pluralité d'électrodes IDT (31, 32) et du nombre de doigts d'électrode (46) dans la pluralité de réflecteurs (41, 42).
PCT/JP2021/024758 2020-07-20 2021-06-30 Filtre à ondes acoustiques et multiplexeur WO2022019072A1 (fr)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2024029610A1 (fr) * 2022-08-03 2024-02-08 株式会社村田製作所 Dispositif à ondes élastiques

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH10322161A (ja) * 1997-05-14 1998-12-04 Toyo Commun Equip Co Ltd 縦結合３重モードｓａｗフィルタ
JP2000312126A (ja) * 1999-04-28 2000-11-07 Kyocera Corp 弾性表面波装置
JP2004343637A (ja) * 2003-05-19 2004-12-02 Murata Mfg Co Ltd 弾性表面波装置
JP2008124703A (ja) * 2006-11-10 2008-05-29 Epson Toyocom Corp 弾性表面波フィルタ
JP2018078489A (ja) * 2016-11-10 2018-05-17 太陽誘電株式会社 フィルタおよびマルチプレクサ
JP2020088846A (ja) * 2018-11-20 2020-06-04 株式会社村田製作所 フィルタおよびマルチプレクサ

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH10322161A (ja) * 1997-05-14 1998-12-04 Toyo Commun Equip Co Ltd 縦結合３重モードｓａｗフィルタ
JP2000312126A (ja) * 1999-04-28 2000-11-07 Kyocera Corp 弾性表面波装置
JP2004343637A (ja) * 2003-05-19 2004-12-02 Murata Mfg Co Ltd 弾性表面波装置
JP2008124703A (ja) * 2006-11-10 2008-05-29 Epson Toyocom Corp 弾性表面波フィルタ
JP2018078489A (ja) * 2016-11-10 2018-05-17 太陽誘電株式会社 フィルタおよびマルチプレクサ
JP2020088846A (ja) * 2018-11-20 2020-06-04 株式会社村田製作所 フィルタおよびマルチプレクサ

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2024029610A1 (fr) * 2022-08-03 2024-02-08 株式会社村田製作所 Dispositif à ondes élastiques

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