Filters and multiplexers

Abstract

To provide a filter capable of suppressing reduction in attenuation amount.SOLUTION: A filter 100 comprises: capacitors C2 and C3 connected in series between an input terminal Tin and an output terminal Tout sequentially from the input terminal side; an acoustic wave resonator R1 connected in parallel to the capacitors C2 and C3, between the input terminal and the output terminal; an inductor L1 whose one end is connected with a node N1 between the capacitor C2 and the capacitor C3 and whose the other end is connected with a ground terminal Tg; an inductor L2 and an acoustic wave resonator R2 connected in series between a node N2 between the input terminal Tin and the capacitor C2, and the ground terminal Tg; an inductor L3 and an acoustic wave resonator R3 connected in series between a node N3 between the output terminal Tout and the capacitor C3, and the ground terminal Tg; and a capacitor C5 whose one end is connected with a node N4 between the inductor L2 and the acoustic wave resonator R2 and whose the other end is connected with a node N5 between the inductor L3 and the acoustic wave resonator R3.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a filter and a multiplexer.

Background Art

[0002] As a high-frequency filter, a filter combining an inductor and an elastic-wave resonator is known (for example, Patent Document 1). Also, it is known that by connecting an elastic-wave resonator in parallel to the capacitor of a T-type CLC filter, a filter having an attenuation pole near the passband can be obtained (for example, Patent Document 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a filter having an attenuation pole near the passband, it is desired to widen the bandwidth of the attenuation band. However, when attempting to widen the bandwidth of the attenuation band, the attenuation amount of the attenuation pole near the passband may decrease.

[0005] The present invention has been made in view of the above problems, and an object thereof is to suppress a decrease in the attenuation amount.

Means for Solving the Problems

[0006] The present invention relates to an input terminal, an output terminal, one or more ground terminals, a first capacitor and a second capacitor connected in series between the input terminal and the output terminal in order from the input terminal side, a first elastic wave resonator connected in parallel with the first capacitor and the second capacitor between the input terminal and the output terminal, a first inductor with one end connected to a first node between the first capacitor and the second capacitor and the other end connected to one of the one or more ground terminals, a second inductor and a third capacitor or second elastic wave resonator connected in series between the second node between the input terminal and the first capacitor and one of the one or more ground terminals, a third inductor and a fourth capacitor or third elastic wave resonator connected in series between the third node between the output terminal and the second capacitor and one of the one or more ground terminals, and a third inductor with one end connected to a fourth node between the second inductor and the third capacitor or second elastic wave resonator and the other end connected to a fifth node between the third inductor and the fourth capacitor or third elastic wave resonator. , having a capacitance smaller than the capacitance of the first elastic wave resonator This is a filter that includes a fifth capacitor.

[0007] In the above configuration, at least The first capacitor, the second capacitor, the first inductor, and the first elastic wave resonator by The passband and the first minimum of the first attenuation pole at frequencies lower than the passband but formation So , at least The first elastic wave resonator by The second minimum of the second attenuation pole is located between the first minimum and the passband. but formation It will be done It can be configured as follows.

[0009] The present invention includes an input terminal, an output terminal, one or more ground terminals, and a first capacitor, a first inductor, and a first elastic wave resonator connected between the input terminal and the output terminal. at least The first capacitor, the first inductor, and the first elastic wave resonator byThe passband and the first minimum of the first attenuation pole at frequencies lower than the passband but formation So , at least The first elastic wave resonator by The second minimum of the second attenuation pole is located between the first minimum and the passband. but formation It will be done A filter circuit, a second inductor and a second capacitor or a second elastic wave resonator connected in series between the input terminal and the filter circuit and one of the one or more ground terminals, a third inductor and a third capacitor or a third elastic wave resonator connected in series between the output terminal and the filter circuit and one of the one or more ground terminals, one end of which is connected to the third node between the second inductor and the second capacitor or the second elastic wave resonator, and the other end of which is connected to the fourth node between the third inductor and the third capacitor or the third elastic wave resonator. , having a capacitance smaller than the capacitance of the first elastic wave resonator This is a filter that includes a fourth capacitor.

[0010] In the above configuration, the second elastic wave resonator is connected in series with the second inductor, or the third elastic wave resonator is connected in series with the third inductor. at least The second elastic wave resonator or the third elastic wave resonator by The third minimum of the third attenuation pole occurs at a frequency lower than the aforementioned second minimum. but formation to be done, It can be configured as follows.

[0011] In the above configuration, the second elastic wave resonator is connected in series with the second inductor, and the third elastic wave resonator is connected in series with the third inductor. at least The second elastic wave resonator by The third minimum of the third attenuation pole occurs at a frequency lower than the aforementioned second minimum. but formation So , at least The third elastic wave resonator by The fourth minimum of the fourth attenuation pole occurs at a frequency lower than the second minimum. but formation It will be done It can be configured as follows.

[0013] In the above configuration, the shortest distance between the second inductor and the third inductor can be set to 2 mm or less.

[0014] In the above configuration, the second inductor and the third capacitor or the second surface acoustic wave resonator, and the third inductor and the fourth capacitor or the third surface acoustic wave resonator can be connected to a common one of the one or more ground terminals.

[0015] In the above configuration, the third capacitor can be connected in series to the second inductor, and the fourth capacitor can be connected in series to the third inductor.

[0016] The present invention is a multiplexer including the filter described above.

Advantages of the Invention

[0017] According to the present invention, it is possible to suppress a decrease in the attenuation amount.

Brief Description of the Drawings

[0018] [Figure 1] FIG. 1 is a circuit diagram of a filter according to Embodiment 1. [Figure 2] FIG. 2(a) is a plan view showing an example of a surface acoustic wave resonator in Embodiment 1, and FIG. 2(b) is a cross-sectional view showing another example of the surface acoustic wave resonator in Embodiment 1. [Figure 3] FIG. 3 is a cross-sectional view of a laminate mounted on a substrate in Embodiment 1. [Figure 4] FIGS. 4(a) to 4(f) are plan views of a dielectric layer in Embodiment 1. [Figure 5] FIG. 5(a) is a circuit diagram of a filter according to Comparative Example 1, and FIG. 5(b) is a diagram showing a simulation result of a passing characteristic. [Figure 6]Figure 6(a) is a circuit diagram of the filter according to Comparative Example 1 when parasitic inductance is formed, and Figure 6(b) is a diagram showing the simulation results of the transmission characteristics. [Figure 7] Figure 7(a) is a circuit diagram showing the case where magnetic coupling occurs in the filter according to Comparative Example 1, and Figure 7(b) is a diagram showing the simulation results of the transmission characteristics. [Figure 8] Figure 8(a) is a circuit diagram of the filter according to Example 1 when parasitic inductance is formed, and Figure 8(b) is a diagram showing the simulation results of the transmission characteristics. [Figure 9] Figure 9(a) is a circuit diagram showing the case where magnetic coupling occurs in the filter according to Example 1, and Figure 9(b) is a diagram showing the simulation results of the transmission characteristics. [Figure 10] Figure 10(a) is a circuit diagram showing the case where magnetic coupling occurs in the filter according to Comparative Example 2, and Figure 10(b) is a diagram showing the simulation results of the transmission characteristics. [Figure 11] Figure 11(a) is a circuit diagram of a filter according to Modification 1 of Example 1, and Figure 11(b) is a circuit diagram of a filter according to Modification 2 of Example 1. [Figure 12] Figure 12(a) is a circuit diagram of the filter according to Comparative Example 3, Figure 12(b) is a circuit diagram when parasitic inductance is formed in the filter according to Comparative Example 3, Figure 12(c) is a circuit diagram when parasitic inductance is formed in the filter according to Modification 1 of Example 1, and Figures 12(d) to 12(f) are diagrams showing the simulation results of the pass characteristics of the filters in Figures 12(a) to 12(c). [Figure 13] Figure 13(a) is a circuit diagram of the filter according to Comparative Example 3, Figure 13(b) is a circuit diagram of the filter according to Comparative Example 3 when magnetic coupling M occurs, Figure 13(c) is a circuit diagram of the filter according to Modification 1 of Example 1 when magnetic coupling M occurs, and Figures 13(d) to 13(f) are diagrams showing the simulation results of the pass characteristics of the filters in Figures 13(a) to 13(c). [Figure 14]Figure 14(a) is a circuit diagram of the filter according to Modification 3 of Example 1, Figure 14(b) is a circuit diagram of the filter according to Modification 4 of Example 1, and Figure 14(c) is a circuit diagram of the filter according to Modification 5 of Example 1. [Figure 15] Figure 15(a) is a circuit diagram of the filter according to Comparative Example 4, Figure 15(b) is a circuit diagram when parasitic inductance is formed in the filter according to Comparative Example 4, Figure 15(c) is a circuit diagram when parasitic inductance Lg is formed in the filter according to Modification 3 of Example 1, and Figures 15(d) to 15(f) show the simulation results of the pass characteristics of the filters in Figures 15(a) to 15(c). [Figure 16] Figure 16(a) is a circuit diagram of the filter according to Comparative Example 4, Figure 16(b) is a circuit diagram of the filter according to Comparative Example 4 when magnetic coupling occurs, Figure 16(c) is a circuit diagram of the filter according to Modification 3 of Example 1 when magnetic coupling occurs, and Figures 16(d) to 16(f) show the simulation results of the pass characteristics of the filters in Figures 16(a) to 16(c). [Figure 17] Figure 17(a) is a circuit diagram of the filter according to Modification 6 of Example 1, Figure 17(b) is a circuit diagram of the filter according to Modification 7 of Example 1, and Figure 17(c) is a circuit diagram of the filter according to Modification 8 of Example 1. [Figure 18] Figure 18(a) is a circuit diagram of the filter according to Comparative Example 5, Figure 18(b) is a circuit diagram when parasitic inductance is formed in the filter according to Comparative Example 5, Figure 18(c) is a circuit diagram when parasitic inductance is formed in the filter according to Modification 6 of Example 1, and Figures 18(d) to 18(f) show the simulation results of the pass characteristics of the filters in Figures 18(a) to 18(c). [Figure 19]Figure 19(a) is the circuit diagram of the filter according to Comparative Example 5, Figure 19(b) is the circuit diagram when magnetic coupling occurs in the filter according to Comparative Example 5, Figure 19(c) is the circuit diagram when magnetic coupling occurs in the filter according to Modification 6 of Example 1, and Figures 19(d) to 19(f) show the simulation results of the pass characteristics of the filters in Figures 19(a) to 19(c). [Figure 20] Figures 20(a) to 20(c) are circuit diagrams of filters relating to modified examples 9 to 11 of Example 1. [Figure 21] Figure 21 is a circuit diagram of the triplexer according to Example 2. [Modes for carrying out the invention]

[0019] The embodiments of the present invention will be described below with reference to the drawings. [Examples]

[0020] Figure 1 is a circuit diagram of the filter 100 according to Embodiment 1. As shown in Figure 1, in the filter 100 according to Embodiment 1, capacitors C1, C2, C3, and C4 are connected in series from the input terminal Tin side between the input terminal Tin and the output terminal Tout. An elastic wave resonator R1 is connected in parallel to capacitors C2 and C3 between the input terminal Tin and the output terminal Tout. One end of the elastic wave resonator R1 is connected to node N6 between capacitors C1 and C2, and the other end is connected to node N7 between capacitors C3 and C4. An inductor L1 is connected between node N1 between capacitors C2 and C3 and the ground terminal Tg. One end of the inductor L1 is connected to node N1, and the other end is connected to the ground terminal Tg. The ground terminal Tg is connected to ground. As a result, a filter circuit 50 including capacitors C2 and C3, inductor L1, and elastic wave resonator R1 is connected between the input terminal Tin and the output terminal Tout. The filter circuit 50 is a high-pass filter that allows signals within the passband of the high-frequency signal input to the input terminal Tin to pass through to the output terminal Tout, while suppressing signals in other frequency bands.

[0021] An inductor L2 and an elastic wave resonator R2 are connected in series between node N2, which is between the input terminal Tin and capacitor C1, and the ground terminal Tg. Inductor L2 is connected to the input terminal Tin side of elastic wave resonator R2, and elastic wave resonator R2 is connected to the ground terminal Tg side of inductor L2. An inductor L3 and an elastic wave resonator R3 are connected in series between node N3, which is between the output terminal Tout and capacitor C4, and the ground terminal Tg. Inductor L3 is connected to the output terminal Tout side of elastic wave resonator R3, and elastic wave resonator R3 is connected to the ground terminal Tg side of inductor L3. Ground terminal Tg is connected to ground. The inductor L2 and elastic wave resonator R2, and the inductor L3 and elastic wave resonator R3 are provided to broaden the bandwidth of the attenuation region in the pass-through characteristics. Capacitor C1 and inductor L2, and capacitor C4 and inductor L3 function as matching circuits that match the impedance seen from the input terminal Tin and output terminal Tout to the filter circuit 50 to a reference impedance (e.g., 50Ω), respectively.

[0022] A capacitor C5 is connected between node N4, which is between inductor L2 and elastic wave resonator R2, and node N5, which is between inductor L3 and elastic wave resonator R3. One end of capacitor C5 is connected to node N4, and the other end is connected to node N5.

[0023] Figure 2(a) is a plan view showing an example of elastic wave resonators R1 to R3 in Example 1, and Figure 2(b) is a cross-sectional view showing another example of elastic wave resonators R1 to R3 in Example 1. In the example in Figure 2(a), elastic wave resonators R1 to R3 are surface acoustic wave resonators. As shown in Figure 2(a), an IDT (Interdigital Transducer) 12 and a reflector 13 are provided on the upper surface of the substrate 10. The IDT 12 has a pair of comb-shaped electrodes 12a facing each other. The comb-shaped electrodes 12a have a plurality of electrode fingers 12b and a busbar 12c connecting the plurality of electrode fingers 12b. The reflector 13 is provided on both sides of the IDT 12. The IDT 12 excites surface acoustic waves in the substrate 10. The substrate 10 is a piezoelectric substrate such as a lithium tantalate substrate, a lithium niobate substrate, or a quartz substrate. The substrate 10 may be a composite substrate in which a piezoelectric substrate is bonded to a support substrate such as a sapphire substrate, spinel substrate, alumina substrate, quartz substrate, or silicon substrate. The IDT 12 and reflector 13 are formed from, for example, an aluminum film or a copper film. A protective film or temperature compensation film may be provided on the substrate 10 so as to cover the IDT 12 and reflector 13.

[0024] In the example shown in Figure 2(b), elastic wave resonators R1 to R3 are piezoelectric thin-film resonators. As shown in Figure 2(b), a piezoelectric film 16 is provided on a substrate 10. A lower electrode 14 and an upper electrode 18 are provided so as to sandwich the piezoelectric film 16. A gap 15 is formed between the lower electrode 14 and the substrate 10. The region where the lower electrode 14 and the upper electrode 18 face each other, with at least a portion of the piezoelectric film 16 in between, is the resonance region 17. The lower electrode 14 and the upper electrode 18 within the resonance region 17 excite elastic waves of thickness longitudinal vibration mode within the piezoelectric film 16. The substrate 10 is, for example, a sapphire substrate, spinel substrate, alumina substrate, glass substrate, quartz substrate, or silicon substrate. The lower electrode 14 and the upper electrode 18 are, for example, metal films such as ruthenium films. The piezoelectric film 16 is, for example, an aluminum nitride film. An acoustic reflective film may be provided instead of the gap 15.

[0025] Figure 3 is a cross-sectional view of the laminate 20 in Example 1 mounted on a substrate 30. As shown in Figure 3, the laminate 20 comprises a plurality of dielectric layers 21a to 21d. Terminals 24 are provided on the lower surface of the laminate 20. Terminals 32 are provided on the substrate 30. Terminals 24 and 32 are joined by a bonding material 34. The substrate 30 is, for example, a circuit board. When mounting the laminate 20 on the substrate 30, solder, for example, is used as the bonding material 34.

[0026] Figures 4(a) to 4(f) are plan views of the dielectric layers 21a to 21d in Example 1. Figures 4(a) to 4(e) are plan views of the dielectric layers 21a to 21d viewed from above. Figure 4(a) also shows the chip component mounted on the upper surface of the dielectric layer 21a. Figure 4(f) is a plan view of the terminal 24 seen through the dielectric layer 21d.

[0027] As shown in Figures 4(a) to 4(f), conductive patterns 22a to 22c are provided on dielectric layers 21a to 21c, and via wirings 23a to 23d are provided on dielectric layers 21a to 21d, penetrating the dielectric layers 21a to 21d. As shown in Figure 4(a), a chip component 2 for elastic wave resonator R1, a chip component 3 for elastic wave resonator R2, a chip component 4 for elastic wave resonator R3, a chip component 5 for capacitor C1, a chip component 6 for capacitor C4, and an integrated chip component 7 for capacitor C2, inductor L1, and capacitor C3 are mounted on the conductive pattern 22a provided on dielectric layer 21a.

[0028] As shown in Figure 4(b), the conductive pattern 22a provided on the dielectric layer 21a forms transmission lines L2a and L3a. As shown in Figure 4(c), the conductive pattern 22b provided on the dielectric layer 21b forms transmission lines L2b and L3b. Transmission lines L3a and L3b are electrically connected by via wiring 23a to form inductor L3. As shown in Figure 4(d), the conductive pattern 22c provided on the dielectric layer 21c forms transmission line L2c. Transmission lines L2a, L2b, and L2c are electrically connected by via wirings 23a and 23b to form inductor L2. The shortest distance X between inductor L2 and inductor L3 is, for example, 2 mm or less.

[0029] As shown in Figure 4(c), the conductive pattern 22b provided on the dielectric layer 21b forms the upper electrode C5a of the capacitor C5. As shown in Figure 4(d), the conductive pattern 22c provided on the dielectric layer 21c forms the lower electrode C5b of the capacitor C5. Electrodes C5a and C5b, sandwiching the dielectric layer 21b, form the capacitor C5. As shown in Figure 4(f), the terminal 24 provided on the lower surface of the dielectric layer 21d forms the input terminal Tin, the output terminal Tout, and the ground terminal Tg.

[0030] The dielectric layers 21a to 21d are made of, for example, a ceramic material and mainly contain oxides of Si, Ca, and Mg (for example, CaMgSi2O6, which is a diopside crystal). The main components of the dielectric layers 21a to 21d may also be oxides other than Si, Ca, and / or Mg. Furthermore, the dielectric layers 21a to 21d may contain at least one oxide of Ti, Zr, and Al as an insulating material. The dielectric layers 21a to 21d may also be resins such as glass epoxy resin, or ceramics such as LTCC (Low Temperature Co-fired Ceramics) or HTCC (High Temperature Co-fired Ceramics). The upper part of the conductive patterns 22a to 22c, via wirings 23a to 23d, and terminals 24 is a non-magnetic metal layer mainly composed of, for example, Ag, Pd, Pt, Cu, Ni, Au, Au-Pd alloy, or Ag-Pd alloy. The upper part of terminal 24 may include nonconductive materials such as TiO2, ZrO2, or Al2O3 in addition to the above-mentioned metallic material. The lower part of terminal 24 may be, for example, a Ni film and a Sn film.

[0031] [Comparative Example 1] Figure 5(a) is a circuit diagram of the filter 500 according to Comparative Example 1. As shown in Figure 5(a), in the filter 500 according to Comparative Example 1, capacitor C5 is not connected between the wiring between inductor L2 and elastic wave resonator R2, and between inductor L3 and elastic wave resonator R3. The other configurations are the same as in Example 1, so their explanation is omitted.

[0032] The pass-through characteristics of filter 500 related to Comparative Example 1 were simulated. The simulation is a circuit simulation (the simulations shown below are also circuit simulations). Table 1 shows the capacitances of capacitors C1 to C4, the inductances of inductors L1 to L3, and the resonant frequencies, anti-resonant frequencies, and capacitances of elastic wave resonators R1 to R3 in the simulation. The capacitances of elastic wave resonators R1 to R3 are the damping capacitances in the LC equivalent circuit (referred to as the Butterworth Van Dyke: BVD model) (the same applies below). In the case of a surface acoustic wave resonator, the damping capacitance corresponds to the capacitance between the pair of comb-shaped electrodes 12a, and in the case of a piezoelectric thin-film resonator, it corresponds to the capacitance between the lower electrode 14 and the upper electrode 18. [Table 1]

[0033] As shown in Table 1, the capacitances of capacitors C1 to C4 were set to 1.5pF, 0.24pF, 0.24pF, and 1.5pF, respectively. The inductances of inductors L1 to L3 were set to 1.79nH, 2.7nH, and 2.7nH, respectively. The resonant frequencies of elastic wave resonators R1 to R3 were set to 5077MHz, 4468MHz, and 4668MHz, respectively, and their anti-resonant frequencies were set to 5271MHz, 4622MHz, and 4822MHz, respectively, with capacitances of 0.20pF, 0.86pF, and 1.10pF, respectively.

[0034] Figure 5(b) shows the simulation results of the passband characteristics of filter 500 according to Comparative Example 1. As shown in Figure 5(b), the filter circuit 50 is a high-pass filter, and the passband Pass is approximately 5.15 GHz or higher. By adding the elastic wave resonator R1, an attenuation pole A1 with a minimum at a frequency lower than the passband Pass is formed by the capacitances of capacitors C2 and C3, inductor L1, and elastic wave resonator R1. If node N1 is directly connected to elastic wave resonator R1, the attenuation pole A1 is not formed. Therefore, there are only two paths connecting node N1 and elastic wave resonator R1: one from node N1 to elastic wave resonator R1 via capacitor C2, and the other from node N1 to elastic wave resonator R1 via capacitor C3. In this way, the attenuation pole A1 is formed when elastic wave resonator R1 is connected to node N1 via only two paths: one via capacitor C2 and the other via capacitor C3. Furthermore, mainly due to the resonant frequency of elastic wave resonator R1, a damping pole A4 is formed with a minimum between the minimum of damping pole A1 and the passband Pass. Damping pole A4 improves the steepness of the attenuation between the passband Pass and the attenuation region. Moreover, mainly due to the anti-resonant frequency of elastic wave resonator R2, a damping pole A2 is formed with a minimum between the minimum of damping pole A1 and the minimum of damping pole A4, and mainly due to the anti-resonant frequency of elastic wave resonator R3, a damping pole A3 is formed with a minimum between the minimum of damping pole A1 and the minimum of damping pole A4.

[0035] In the filter 500 according to Comparative Example 1, as shown in Figure 5(b), the attenuation pole A2 is formed by the elastic wave resonator R2 and the attenuation pole A3 is formed by the elastic wave resonator R3, thereby widening the bandwidth of the attenuation region. However, the filter 500 according to Comparative Example 1 is an ideal circuit, and in real devices, parasitic inductance and / or magnetic coupling between elements occur. For example, as shown in Figure 3, when the laminate 20 is mounted on the substrate 30, the path from terminal 24 to terminal 32 via the bonding material 34 forms parasitic inductance. As shown in Figures 4(b) to 4(d), inductors L2 and L3 are formed in the dielectric layers 21a to 21c by the conductive patterns 22a to 22c, resulting in magnetic coupling between inductor L2 and inductor L3. Therefore, the case where parasitic inductance or magnetic coupling is considered in the filter 500 according to Comparative Example 1 is shown below.

[0036] Figure 6(a) is a circuit diagram of the filter 500 according to Comparative Example 1 when a parasitic inductance Lg is formed. As shown in Figure 6(a), the ground terminal Tg is connected to ground via the parasitic inductance Lg. The parasitic inductance Lg is formed by the path from terminal 24 to terminal 32 via bonding material 34 when the laminate 20 in Figure 3 is mounted on the substrate 30. The other configurations are the same as in Figure 5(a).

[0037] The pass-through characteristics of filter 500 in Figure 6(a) were simulated. Table 2 shows the capacitances of capacitors C1 to C4, the inductances of inductors L1 to L3, the resonant frequencies, anti-resonant frequencies, capacitances, and parasitic inductance Lg of elastic wave resonators R1 to R3 in the simulation. [Table 2]

[0038] As shown in Table 2, the capacitances of capacitors C1 to C4, the inductances of inductors L1 to L3, and the resonant frequencies, anti-resonant frequencies, and capacitances of elastic wave resonators R1 to R3 were the same values ​​as in Table 1. The parasitic inductance Lg was set to 0.02 nH.

[0039] Figure 6(b) shows the simulation results of the transmission characteristics when a parasitic inductance Lg is formed in filter 500 according to Comparative Example 1. As shown in Figure 6(b), the ground terminal Tg is connected to ground via the parasitic inductance Lg, resulting in a deterioration of the attenuation amount at the attenuation pole A4.

[0040] Figure 7(a) is a circuit diagram of the filter 500 according to Comparative Example 1 when magnetic coupling occurs. As shown in Figure 7(a), it is assumed that magnetic coupling M occurs between inductors L2 and L3, and this magnetic coupling M is represented by connecting an inductor Lt between inductors L2 and L3. The other configurations are the same as in Figure 5(a).

[0041] The pass-through characteristics of filter 500 in Figure 7(a) were simulated. Table 3 shows the capacitances of capacitors C1 to C4, the inductances of inductors L1 to L3, the resonant frequencies, anti-resonant frequencies, capacitances, and inductor Lt of elastic wave resonators R1 to R3 in the simulation. [Table 3]

[0042] As shown in Table 3, the capacitances of capacitors C1 to C4, the inductances of inductors L1 to L3, and the resonant frequencies, anti-resonant frequencies, and capacitances of elastic wave resonators R1 to R3 were the same as those in Table 1. The inductor Lt was set to 150 nH.

[0043] Figure 7(b) shows the simulation results of the transmission characteristics when magnetic coupling occurs in filter 500 according to Comparative Example 1. As shown in Figure 7(b), the magnetic coupling M that occurs between inductor L2 and inductor L3 resulted in a deterioration of the attenuation amount at damping pole A4. In addition, damping poles A2 and A3 became one and the attenuation amount deteriorated.

[0044] As shown in Figures 5(a) and 5(b), even when sufficient attenuation is obtained at the attenuation pole A4 in an ideal circuit, it was found that the attenuation at the attenuation pole A4 deteriorates due to the formation of parasitic inductance Lg or the occurrence of magnetic coupling M between inductor L2 and inductor L3, as shown in Figures 6(a) to 7(b).

[0045] Even after adjusting the capacitances of capacitors C1-C4, the inductances of inductors L1-L3, and the resonant frequencies, anti-resonant frequencies, and capacitances of elastic wave resonators R1-R3 in an attempt to improve the degradation of the attenuation, the degradation of the attenuation could not be improved.

[0046] [Simulation of Example 1] Figure 8(a) is a circuit diagram of the filter 100 according to Example 1 when a parasitic inductance Lg is formed. As shown in Figure 8(a), the ground terminal Tg is connected to ground via the parasitic inductance Lg. The other configurations are the same as in Figure 1.

[0047] The pass-through characteristics of filter 100 in Figure 8(a) were simulated. Table 4 shows the capacitances of capacitors C1 to C5, the inductances of inductors L1 to L3, the resonant frequencies, anti-resonant frequencies, capacitances, and parasitic inductance Lg of elastic wave resonators R1 to R3 in the simulation. [Table 4]

[0048] As shown in Table 4, the capacitances of capacitors C1 to C5 were set to 1.5pF, 0.239pF, 0.239pF, 1.5pF, and 0.004pF, respectively. The inductances of inductors L1 to L3 were set to 1.79nH, 2.7nH, and 2.7nH, respectively. The resonant frequencies of elastic wave resonators R1 to R3 were set to 5077MHz, 4518MHz, and 4668MHz, respectively, and their anti-resonant frequencies were set to 5271MHz, 4672MHz, and 4822MHz, respectively, with capacitances of 0.20pF, 0.85pF, and 1.10pF, respectively. The parasitic inductance Lg was set to 0.02nH.

[0049] Figure 8(b) shows the simulation results of the transmission characteristics when a parasitic inductance Lg is formed in the filter 100 according to Example 1. As shown in Figure 8(b), even when the ground terminal Tg is connected to ground via the parasitic inductance Lg, connecting the capacitor C5 between node N4 and node N5 suppresses the degradation of the attenuation amount at the attenuation pole A4.

[0050] Figure 9(a) is a circuit diagram of the filter 100 according to Example 1 when magnetic coupling occurs. As shown in Figure 9(a), it is assumed that magnetic coupling M occurs between inductor L2 and inductor L3, and this magnetic coupling M is represented by connecting inductor Lt between inductor L2 and inductor L3. The other configurations are the same as in Figure 1.

[0051] The pass-through characteristics of filter 100 in Figure 9(a) were simulated. Table 5 shows the capacitances of capacitors C1 to C5, the inductances of inductors L1 to L3, the resonant frequencies, anti-resonant frequencies, capacitances, and inductor Lt of elastic wave resonators R1 to R3 in the simulation. [Table 5]

[0052] As shown in Table 5, the capacitances of capacitors C1 to C5 were set to 1.5pF, 0.24pF, 0.24pF, 1.5pF, and 0.004pF, respectively. The inductances of inductors L1 to L3 were set to 1.79nH, 2.7nH, and 2.7nH, respectively. The resonant frequencies of elastic wave resonators R1 to R3 were set to 5077MHz, 4468MHz, and 4718MHz, respectively, and their anti-resonant frequencies were set to 5271MHz, 4622MHz, and 4872MHz, respectively, with capacitances of 0.20pF, 0.86pF, and 1.09pF, respectively. The inductor Lt was set to 150nH.

[0053] Figure 9(b) shows the simulation results of the transmission characteristics when magnetic coupling occurs in the filter 100 according to Example 1. As shown in Figure 9(b), even when magnetic coupling M occurs between inductor L2 and inductor L3, connecting capacitor C5 between node N4 and node N5 suppresses the degradation of the attenuation amount at the attenuation pole A4. This is thought to be because the balance between the magnetic coupling M between inductor L2 and inductor L3 and the electric field coupling between inductor L2 and inductor L3 due to the connection of capacitor C5 was adjusted, thereby suppressing the degradation of the attenuation amount.

[0054] [Comparative Example 2] Figure 10(a) is a circuit diagram of the filter 600 according to Comparative Example 2 when magnetic coupling occurs. As shown in Figure 10(a), in the filter 600 according to Comparative Example 2, capacitor C5 is connected between node N4 between inductor L2 and elastic wave resonator R2, and node N8 between node N3 and inductor L3. The other configurations are the same as in Example 1, so their explanation is omitted. Assuming that magnetic coupling M occurs between inductor L2 and inductor L3, this magnetic coupling M is represented by connecting inductor Lt between inductor L2 and inductor L3.

[0055] The pass-through characteristics of filter 600 in Figure 10(a) were simulated. Table 6 shows the capacitances of capacitors C1 to C5, the inductances of inductors L1 to L3, and the resonant frequencies, anti-resonant frequencies, capacitances, and inductor Lt of elastic wave resonators R1 to R3 in the simulation. [Table 6]

[0056] As shown in Table 6, the capacitances of capacitors C1 to C5, the inductances of inductors L1 to L3, and the resonant frequencies, anti-resonant frequencies, capacitances, and inductor Lt of elastic wave resonators R1 to R3 were set to the same values ​​as in Table 5.

[0057] Figure 10(b) shows the simulation results of the transmission characteristics when magnetic coupling occurs in the filter 600 according to Comparative Example 2. As shown in Figure 10(b), when magnetic coupling M occurs between inductor L2 and inductor L3, connecting capacitor C5 between node N4 and node N8 does not improve the attenuation at attenuation pole A4, but rather it deteriorates.

[0058] From this, it was found that in order to suppress the degradation of the attenuation amount at the damping pole A4, it is preferable to connect a capacitor C5 between node N4 between inductor L2 and elastic wave resonator R2, and between node N5 between inductor L3 and elastic wave resonator R3.

[0059] As described above, according to Embodiment 1, an inductor L2 and an elastic wave resonator R2 are connected in series between node N2, which is between the input terminal Tin and capacitor C2, and the ground terminal Tg. An inductor L3 and an elastic wave resonator R3 are connected in series between node N3, which is between the output terminal Tout and capacitor C3, and the ground terminal Tg. This allows the bandwidth of the attenuation region to be widened, as shown in Figures 8(b) and 9(b). A capacitor C5 is provided with one end connected to node N4, which is between inductor L2 and elastic wave resonator R2, and the other end connected to node N5, which is between inductor L3 and elastic wave resonator R3. This suppresses deterioration of the attenuation amount at the attenuation pole A4, even when a parasitic inductance Lg is formed or when magnetic coupling M occurs between inductor L2 and inductor L3, as shown in Figures 8(b) and 9(b).

[0060] Furthermore, according to Example 1, as shown in Figures 8(b) and 9(b), a filter circuit 50 including capacitors C2 and C3, inductor L1, and elastic wave resonator R1 forms a minimum of attenuation pole A1 at a frequency lower than the passband Pass. Elastic wave resonator R1 forms a minimum of attenuation pole A4 between the minimum of attenuation pole A1 and the passband Pass. In such a case, if inductors L2 and L3 and elastic wave resonators R2 and R3 are added to widen the bandwidth of the attenuation region, the amount of attenuation at attenuation pole A4 deteriorates. Therefore, it is preferable to add capacitor C5 to suppress the deterioration of the amount of attenuation.

[0061] Furthermore, according to Example 1, as shown in Tables 4 and 5, the capacitance of capacitor C5 is smaller than the capacitance of elastic wave resonator R1. This suppresses the deterioration of the attenuation at the damping pole A4, as shown in Figures 8(b) and 9(b). To suppress the deterioration of the attenuation, the capacitance of capacitor C5 is preferably 1 / 10 or less of the capacitance of elastic wave resonator R1, more preferably 1 / 20 or less, even more preferably 1 / 30 or less, and even more preferably 1 / 50 or less. Also, to suppress the deterioration of the attenuation, the capacitance of capacitor C5 is preferably 1 / 1000 or more of the capacitance of elastic wave resonator R1, more preferably 1 / 500 or more, even more preferably 1 / 100 or more, and even more preferably 1 / 80 or more. Furthermore, in order to suppress the degradation of attenuation, the capacitance of capacitor C5 is preferably smaller than the capacitance of the smaller of the elastic wave resonators R1 and R2, preferably 1 / 30 or less, more preferably 1 / 50 or less, and even more preferably 1 / 100 or less. Furthermore, in order to suppress the degradation of attenuation, the capacitance of capacitor C5 is preferably 1 / 1000 or more of the capacitance of the smaller of the elastic wave resonators R1 and R2, more preferably 1 / 750 or more, and even more preferably 1 / 500 or more.

[0062] Furthermore, according to Example 1, as shown in Figures 8(b) and 9(b), the elastic wave resonator R2 forms a minimum of attenuation pole A2 at a frequency lower than the minimum of attenuation pole A4. This allows the bandwidth of the attenuation region to be widened. In addition, the elastic wave resonator R3 forms a minimum of attenuation pole A3 at a frequency lower than the minimum of attenuation pole A4. This allows the bandwidth of the attenuation region to be widened even further.

[0063] Furthermore, according to Example 1, the shortest distance X between inductors L2 and L3 formed on the laminate 20 is 2 mm or less. In this case, magnetic coupling M occurs between inductors L2 and L3. Therefore, in such cases, it is preferable to connect a capacitor C5 between node N4 and node N5 in order to suppress the deterioration of attenuation. To suppress the deterioration of attenuation, it is preferable to provide a capacitor C5 when the shortest distance X between inductors L2 and L3 is 1.5 mm or less, more preferable to provide a capacitor C5 when it is 1.3 mm or less, and even more preferable to provide a capacitor C5 when it is 1 mm or less. Note that electric field coupling between inductors L2 and L3 hardly occurs when the shortest distance X between inductors L2 and L3 is 2 mm or more.

[0064] Furthermore, according to Example 1, as shown in Figures 4(a) to 4(f), the inductor L2 and elastic wave resonator R2, and the inductor L3 and elastic wave resonator R3 are connected to a common ground terminal Tg. In such a case, since the attenuation at the damping pole A4 deteriorates because the ground terminal Tg is connected to ground via parasitic inductance Lg, it is preferable to connect a capacitor C5 between node N4 and node N5.

[0065] In Example 1, as shown in Figure 4(f), a case where one ground terminal Tg is provided is shown as an example. However, it is also possible to have multiple ground terminals Tg, where the inductor L1, elastic wave resonators R2 and R3 are each connected to separate ground terminals Tg.

[0066] In Example 1, as shown in Figures 4(c) and 4(d), a capacitor C5 is formed within the laminate 20 by an electrode C5a formed by the conductive pattern 22b of the dielectric layer 21b and an electrode C5b formed by the conductive pattern 22c of the dielectric layer 21c. However, the capacitor C5 is not limited to being formed by the conductive pattern of the dielectric layer, and may be formed in other cases, such as within one of the chip components of the elastic wave resonator R1 to R3.

[0067] [Modifications 1 and 2] Figure 11(a) is a circuit diagram of filter 110 according to Modification 1 of Example 1, and Figure 11(b) is a circuit diagram of filter 120 according to Modification 2 of Example 1. As shown in Figure 11(a), in filter 110 according to Modification 1 of Example 1, the elastic wave resonator R2 is connected to the input terminal Tin side from inductor L2, and inductor L2 is connected to the ground terminal Tg side from elastic wave resonator R2. Elastic wave resonator R3 is connected to the output terminal Tout side from inductor L3, and inductor L3 is connected to the ground terminal Tg side from elastic wave resonator R3. The other configurations are the same as in Figure 1 of Example 1, so their explanation is omitted.

[0068] As shown in Figure 11(b), in the filter 120 according to the modified example 2 of Example 1, the elastic wave resonator R2 is connected to the input terminal Tin side from the inductor L2, and the inductor L2 is connected to the ground terminal Tg side from the elastic wave resonator R2. Inductor L3 and elastic wave resonator R3 are the same as in Example 1, with inductor L3 connected to the output terminal Tout side from the elastic wave resonator R3, and elastic wave resonator R3 connected to the ground terminal Tg side from the inductor L3. The other configurations are the same as in Figure 1 of Example 1, so their explanation is omitted.

[0069] [simulation] Figure 12(a) is a circuit diagram of the filter 700 according to Comparative Example 3, Figure 12(b) is a circuit diagram of the filter 700 according to Comparative Example 3 when parasitic inductance Lg is formed, and Figure 12(c) is a circuit diagram of the filter 110 according to Modification 1 of Example 1 when parasitic inductance Lg is formed. As shown in Figure 12(a), in the filter 700 according to Comparative Example 3, capacitor C5 is not connected between the wiring between inductor L2 and elastic wave resonator R2, and between inductor L3 and elastic wave resonator R3. The other configurations are the same as those of the filter 110 according to Modification 1 of Example 1, so their explanation is omitted.

[0070] The pass characteristics of filters 700 and 110 in Figures 12(a) to 12(c) were simulated. Table 7 shows the capacitances of capacitors C1 to C5, the inductances of inductors L1 to L3, the resonant frequencies, anti-resonant frequencies, capacitances, and parasitic inductance Lg of elastic wave resonators R1 to R3 in the simulation. [Table 7]

[0071] As shown in Table 7, the capacitances of capacitors C1 to C5 were set to 1.5pF, 0.24pF, 0.24pF, 1.5pF, and 0.003pF, respectively. The inductances of inductors L1 to L3 were set to 1.79nH, 2.7nH, and 2.7nH, respectively. The resonant frequencies of elastic wave resonators R1 to R3 were set to 5077MHz, 4468MHz, and 4668MHz, respectively, and their anti-resonant frequencies were set to 5271MHz, 4622MHz, and 4822MHz, respectively, with capacitances of 0.20pF, 0.86pF, and 1.10pF, respectively. The parasitic inductance Lg was set to 0.02nH.

[0072] Figures 12(d) to 12(f) show the simulation results of the pass characteristics of filters 700 and 110 in Figures 12(a) to 12(c). As shown in Figures 12(d) and 12(e), even when elastic wave resonator R2 is connected to the input terminal Tin side of inductor L2 and elastic wave resonator R3 is connected to the output terminal Tout side of inductor L3, if capacitor C5 is not connected, the ground terminal Tg is connected to ground via parasitic inductance Lg, resulting in a deterioration of the attenuation at the attenuation pole A4. In this case as well, as shown in Figure 12(f), connecting capacitor C5 between node N4 and node N5 suppresses the deterioration of the attenuation at the attenuation pole A4.

[0073] Figure 13(a) is the circuit diagram of filter 700 according to Comparative Example 3, Figure 13(b) is the circuit diagram of filter 700 according to Comparative Example 3 when magnetic coupling M occurs, and Figure 13(c) is the circuit diagram of filter 110 according to Modification 1 of Example 1 when magnetic coupling M occurs. The pass characteristics of filters 700 and 110 in Figures 13(a) to 13(c) were simulated. Table 8 shows the capacitances of capacitors C1 to C5, the inductances of inductors L1 to L3, the resonant frequencies, anti-resonant frequencies, capacitances, and inductor Lt of elastic wave resonators R1 to R3 in the simulation. [Table 8]

[0074] As shown in Table 8, the capacitances of capacitors C1 to C4, the inductances of inductors L1 to L3, and the resonant frequencies, anti-resonant frequencies, and capacitances of elastic wave resonators R1 to R3 were the same values ​​as in Table 7. The capacitance of capacitor C5 was set to 0.007 pF, and the inductor Lt was set to 150 nH.

[0075] Figures 13(d) to 13(f) show the simulation results of the pass characteristics of filters 700 and 110 in Figures 13(a) to 13(c). As shown in Figures 13(d) and 13(e), even when elastic wave resonator R2 is connected to the input terminal Tin side from inductor L2 and elastic wave resonator R3 is connected to the output terminal Tout side from inductor L3, if capacitor C5 is not connected, magnetic coupling M occurs between inductor L2 and inductor L3, resulting in a deterioration of the attenuation at the attenuation pole A4. In this case as well, as shown in Figure 13(f), connecting capacitor C5 between node N4 and node N5 suppresses the deterioration of the attenuation at the attenuation pole A4.

[0076] From this, it can be seen that regardless of the connection order of inductor L2 and elastic wave resonator R2, and the connection order of inductor L3 and elastic wave resonator R3, the amount of attenuation at the damping pole A4 deteriorates when parasitic inductance Lg and / or magnetic coupling M occur, but the deterioration of the amount of attenuation can be suppressed by connecting capacitor C5 between node N4 and node N5. Therefore, in both the filter 110 according to modified example 1 of Embodiment 1 shown in Figure 11(a) and the filter 120 according to modified example 2 of Embodiment 1 shown in Figure 11(b), the deterioration of the amount of attenuation at the damping pole A4 can be suppressed.

[0077] [Modifications 3, 4, 5] Figure 14(a) is a circuit diagram of filter 130 according to modification 3 of Example 1, Figure 14(b) is a circuit diagram of filter 140 according to modification 4 of Example 1, and Figure 14(c) is a circuit diagram of filter 150 according to modification 5 of Example 1. As shown in Figure 14(a), in filter 130 according to modification 3 of Example 1, a capacitor C6 is connected instead of the elastic wave resonator R2. The other configurations are the same as in Figure 1 of Example 1, so their explanation is omitted.

[0078] As shown in Figure 14(b), in the filter 140 according to Modification 4 of Example 1, a capacitor C6 is connected instead of the elastic wave resonator R2, and the capacitor C6 is connected to the input terminal Tin side from the inductor L2. The other configurations are the same as in Figure 1 of Example 1, so their explanation is omitted.

[0079] As shown in Figure 14(c), in the filter 150 according to Modification 5 of Example 1, a capacitor C6 is connected instead of the elastic wave resonator R2, and the capacitor C6 is connected to the input terminal Tin side from the inductor L2. Also, the elastic wave resonator R3 is connected to the output terminal Tout side from the inductor L3. The other configurations are the same as in Figure 1 of Example 1, so their explanation is omitted.

[0080] [simulation] Figure 15(a) is a circuit diagram of filter 800 according to Comparative Example 4, Figure 15(b) is a circuit diagram of filter 800 according to Comparative Example 4 when parasitic inductance Lg is formed, and Figure 15(c) is a circuit diagram of filter 130 according to Modification 3 of Example 1 when parasitic inductance Lg is formed. As shown in Figure 15(a), in filter 800 according to Comparative Example 4, capacitor C5 is not connected between the wiring between inductor L2 and capacitor C6, and between the wiring between inductor L3 and elastic wave resonator R3. The other configurations are the same as those of filter 130 according to Modification 3 of Example 1, so their explanation is omitted.

[0081] The pass characteristics of filters 800 and 130 in Figures 15(a) to 15(c) were simulated. Table 9 shows the capacitances of capacitors C1-C4 and C6, the inductances of inductors L1-L3, the resonant frequencies, anti-resonant frequencies, capacitances, and parasitic inductance Lg of elastic wave resonators R1 and R3 in the simulation for filter 800 in Figures 15(a) and 15(b). [Table 9]

[0082] As shown in Table 9, the capacitances of capacitors C1-C4 and C6 were set to 1.5pF, 0.236pF, 0.236pF, 1.5pF, and 0.9pF, respectively. The inductances of inductors L1-L3 were set to 1.79nH, 2.7nH, and 2.7nH, respectively. The resonant frequencies of elastic wave resonators R1 and R3 were set to 5077MHz and 4588MHz, respectively, and their anti-resonant frequencies were set to 5271MHz and 4742MHz, respectively, with capacitances of 0.20pF and 1.12pF, respectively. The parasitic inductance Lg was set to 0.05nH.

[0083] Table 10 shows the capacitances of capacitors C1 to C6, the inductances of inductors L1 to L3, the resonant frequencies, anti-resonant frequencies, capacitances, and parasitic inductances Lg of elastic wave resonators R1 and R3 in the simulation for filter 130 in Figure 15(c). [Table 10]

[0084] As shown in Table 10, the capacitances of capacitors C1 to C6 were set to 1.5pF, 0.232pF, 0.232pF, 1.5pF, 0.015pF, and 0.9pF, respectively. The inductances of inductors L1 to L3 were set to 1.79nH, 2.7nH, and 2.7nH, respectively. The resonant frequencies of elastic wave resonators R1 and R3 were set to 5077MHz and 4588MHz, respectively, and their anti-resonant frequencies were set to 5271MHz and 4742MHz, respectively, with capacitances of 0.20pF and 1.12pF, respectively. The parasitic inductance Lg was set to 0.05nH.

[0085] Figures 15(d) to 15(f) show the simulation results of the pass characteristics of filters 800 and 130 in Figures 15(a) to 15(c). As shown in Figures 15(d) and 15(e), even when capacitor C6 was connected instead of elastic wave resonator R2, if capacitor C5 was not connected, the ground terminal Tg was connected to ground via parasitic inductance Lg, resulting in a deterioration of the attenuation at the attenuation pole A4. In this case as well, as shown in Figure 15(f), connecting capacitor C5 between node N4 and node N5 suppressed the deterioration of the attenuation at the attenuation pole A4.

[0086] Figure 16(a) is the circuit diagram of filter 800 according to Comparative Example 4, Figure 16(b) is the circuit diagram of filter 800 according to Comparative Example 4 when magnetic coupling M occurs, and Figure 16(c) is the circuit diagram of filter 130 according to Modification 3 of Example 1 when magnetic coupling M occurs. The pass characteristics of filters 800 and 130 in Figures 16(a) to 16(c) were simulated. Table 11 shows the capacitances of capacitors C1 to C4 and C6, the inductances of inductors L1 to L3, the resonant frequencies, anti-resonant frequencies, capacitances, and inductor Lt of elastic wave resonators R1 and R3 in the simulation for filter 800 in Figures 16(a) and 16(b). [Table 11]

[0087] As shown in Table 11, the capacitances of capacitors C1-C4 and C6, the inductances of inductors L1-L3, and the resonant frequencies, anti-resonant frequencies, and capacitances of elastic wave resonators R1 and R3 were set to the same values ​​as in Table 9. The inductor Lt was set to 75 nH.

[0088] Table 12 shows the capacitances of capacitors C1 to C6, the inductances of inductors L1 to L3, the resonant frequencies, anti-resonant frequencies, capacitances, and inductor Lt of elastic wave resonators R1 and R3 in the simulation for filter 130 in Figure 16(c). [Table 12]

[0089] As shown in Table 12, the capacitances of capacitors C1 to C6, the inductances of inductors L1 to L3, and the resonant frequencies, anti-resonant frequencies, and capacitances of elastic wave resonators R1 and R3 were set to the same values ​​as in Table 10. The inductor Lt was set to 75 nH.

[0090] Figures 16(d) to 16(f) show the simulation results of the pass characteristics of filters 800 and 130 in Figures 16(a) to 16(c). As shown in Figures 16(d) and 16(e), even when capacitor C6 was connected instead of elastic wave resonator R2, when capacitor C5 was not connected, magnetic coupling M occurred between inductor L2 and inductor L3, resulting in a deterioration of the attenuation at the damping pole A4. In this case as well, as shown in Figure 16(f), connecting capacitor C5 between node N4 and node N5 suppressed the deterioration of the attenuation at the damping pole A4.

[0091] From this, it can be seen that even if either of the elastic wave resonators R2 or R3 is replaced with a capacitor C6, the attenuation at the damping pole A4 deteriorates when parasitic inductance Lg or magnetic coupling M occurs, but the deterioration of the attenuation can be suppressed by connecting capacitor C5 between node N4 and node N5. Therefore, in any of the cases of filter 130 according to modified example 130 shown in Figure 14(a), filter 140 according to modified example 14(b) shown in Figure 14(b), and filter 150 according to modified example 150 shown in Figure 14(c), the deterioration of the attenuation at the damping pole A4 can be suppressed.

[0092] [Modifications 6, 7, 8] Figure 17(a) is a circuit diagram of filter 160 according to modification 6 of Example 1, Figure 17(b) is a circuit diagram of filter 170 according to modification 7 of Example 1, and Figure 17(c) is a circuit diagram of filter 180 according to modification 8 of Example 1. As shown in Figure 17(a), in filter 160 according to modification 6 of Example 1, a capacitor C6 is connected instead of elastic wave resonator R2, and a capacitor C7 is connected instead of elastic wave resonator R3. The other configurations are the same as in Figure 1 of Example 1, so their explanation is omitted.

[0093] As shown in Figure 17(b), in the filter 170 according to the modified example 7 of Example 1, capacitors C6 and C7 are connected instead of elastic wave resonators R2 and R3, and capacitor C6 is connected to the input terminal Tin side of inductor L2. The other configurations are the same as in Figure 1 of Example 1, so their explanation is omitted.

[0094] As shown in Figure 17(c), in the filter 180 according to the modified example 8 of Example 1, capacitors C6 and C7 are connected instead of elastic wave resonators R2 and R3. Capacitor C6 is connected to the input terminal Tin side from inductor L2, and capacitor C7 is connected to the output terminal Tout side from inductor L3. The other configurations are the same as in Figure 1 of Example 1, so their explanation is omitted.

[0095] [simulation] Figure 18(a) is a circuit diagram of the filter 900 according to Comparative Example 5, Figure 18(b) is a circuit diagram of the filter 900 according to Comparative Example 5 when parasitic inductance Lg is formed, and Figure 18(c) is a circuit diagram of the filter 160 according to Modification 6 of Example 1 when parasitic inductance Lg is formed. As shown in Figure 18(a), in the filter 900 according to Comparative Example 5, capacitor C5 is not connected between the wiring between inductor L2 and capacitor C6, and between the wiring between inductor L3 and capacitor C7. The other configurations are the same as those of the filter 160 according to Modification 6 of Example 1, so their explanation is omitted.

[0096] The pass characteristics of filters 900 and 160 in Figures 18(a) to 18(c) were simulated. Table 13 shows the capacitances of capacitors C1-C4, C6, and C7, the inductances of inductors L1-L3, the resonant frequency, anti-resonant frequency, capacitance, and parasitic inductance Lg of the elastic wave resonator R1 in the simulation for filter 900 in Figures 18(a) and 18(b). [Table 13]

[0097] As shown in Table 13, the capacitances of capacitors C1-C4, C6, and C7 were set to 2pF, 0.233pF, 0.233pF, 2pF, 0.9pF, and 0.9pF, respectively. The inductances of inductors L1-L3 were set to 1.79nH, 2.5nH, and 2.5nH, respectively. The resonant frequency of elastic wave resonator R1 was set to 5077MHz, the anti-resonant frequency to 5271MHz, and its capacitance to 0.20pF. The parasitic inductance Lg was set to 0.05nH.

[0098] Table 14 shows the capacitances of capacitors C1 to C7, the inductances of inductors L1 to L3, the resonant frequency, anti-resonant frequency, capacitance, and parasitic inductance Lg of the elastic wave resonator R1 in the simulation for filter 160 in Figure 18(c). [Table 14]

[0099] As shown in Table 14, the capacitances of capacitors C1 to C7 were set to 2pF, 0.228pF, 0.228pF, 2pF, 0.015pF, 0.9pF, and 0.9pF, respectively. The inductances of inductors L1 to L3 were set to 1.79nH, 2.5nH, and 2.5nH, respectively. The resonant frequency of elastic wave resonator R1 was set to 5077MHz, the anti-resonant frequency to 5271MHz, and its capacitance to 0.20pF. The parasitic inductance Lg was set to 0.05nH.

[0100] Figures 18(d) to 18(f) show the simulation results of the pass characteristics of filters 900 and 160 in Figures 18(a) to 18(c). As shown in Figures 18(d) and 18(e), even when capacitors C6 and C7 were connected instead of elastic wave resonators R2 and R3, the attenuation at the damping pole A4 deteriorated because the ground terminal Tg was connected to ground via parasitic inductance Lg. In this case as well, as shown in Figure 18(f), connecting capacitor C5 between node N4 and node N5 suppressed the deterioration of the attenuation at the damping pole A4.

[0101] Figure 19(a) is the circuit diagram of filter 900 according to Comparative Example 5, Figure 19(b) is the circuit diagram of filter 900 according to Comparative Example 5 when magnetic coupling M occurs, and Figure 19(c) is the circuit diagram of filter 160 according to Modification 6 of Example 1 when magnetic coupling M occurs. The pass characteristics of filters 900 and 160 in Figures 19(a) to 19(c) were simulated. Table 15 shows the capacitances of capacitors C1 to C4, C6, and C7, the inductances of inductors L1 to L3, the resonant frequency, anti-resonant frequency, capacitance, and inductor Lt of elastic wave resonator R1 in the simulation for filter 900 in Figures 19(a) and 19(b). [Table 15]

[0102] As shown in Table 15, the capacitances of capacitors C1-C4, C6, and C7, the inductances of inductors L1-L3, and the resonant frequency, anti-resonant frequency, and capacitance of elastic wave resonator R1 were set to the same values ​​as in Table 13. The inductor Lt was set to 50 nH.

[0103] Table 16 shows the capacitances of capacitors C1 to C7, the inductances of inductors L1 to L3, the resonant frequency, anti-resonant frequency, capacitance, and inductor Lt of the elastic wave resonator R1 in the simulation for filter 160 in Figure 19(c). [Table 16]

[0104] As shown in Table 16, the capacitances of capacitors C1-C4, C6, and C7, the inductances of inductors L1-L3, and the resonant frequency, anti-resonant frequency, and capacitance of elastic wave resonator R1 were the same values ​​as in Table 14. The capacitance of capacitor C5 was set to 0.02 pF, and the inductor Lt was set to 50 nH.

[0105] Figures 19(d) to 19(f) show the simulation results of the pass characteristics of filters 900 and 160 in Figures 19(a) to 19(c). As shown in Figures 19(d) and 19(e), even when capacitors C6 and C7 were connected instead of elastic wave resonators R2 and R3, if capacitor C5 was not connected, a magnetic coupling M occurred between inductors L2 and L3, resulting in a deterioration of the attenuation at the damping pole A4. In this case as well, as shown in Figure 19(f), connecting capacitor C5 between nodes N4 and N5 suppressed the deterioration of the attenuation at the damping pole A4.

[0106] From this, it can be seen that even when both elastic wave resonators R2 and R3 are replaced with capacitors C6 and C7, the attenuation at the damping pole A4 deteriorates when parasitic inductance Lg or magnetic coupling M occurs, but the deterioration of the attenuation can be suppressed by connecting capacitor C5 between node N4 and node N5. Therefore, in any of the cases of filter 160 according to modified example 6 of Example 1 shown in Figure 17(a), filter 170 according to modified example 7 of Example 1 shown in Figure 17(b), and filter 180 according to modified example 8 of Example 1 shown in Figure 17(c), the deterioration of the attenuation at the damping pole A4 can be suppressed.

[0107] As described above, the element connected in series with inductor L2 may be either an elastic wave resonator R2 or a capacitor C6. Similarly, the element connected in series with inductor L3 may be either an elastic wave resonator R3 or a capacitor C7. In either case, connecting capacitor C5 can suppress the degradation of the attenuation at the damping pole A4.

[0108] As shown in Figures 14(a) to 14(c) and Figures 17(a) to 17(c), from filter 130 in Modification 3 of Example 1 to filter 180 in Modification 8 of Example 1, at least one of the elastic wave resonators R2 and R3 may be replaced with capacitors C6 and C7. Even when capacitors C6 and C7 are used, the bandwidth of the attenuation range can be widened.

[0109] [Variations 9-11] Figures 20(a) to 20(c) are circuit diagrams of filters 190 to 210 according to modified examples 9 to 11 of Embodiment 1. As shown in filter 190 according to modified example 9 of Embodiment 1 in Figure 20(a), inductors L11 and L12 are connected in series between node N3 and output terminal Tout, capacitors C11 and C12 are connected in parallel to inductors L11 and L12 respectively, and capacitor C13 may be connected between the node between inductors L11 and L12 and the ground terminal Tg. As shown in filter 200 according to modified example 10 of Embodiment 1 in Figure 20(b), in addition to inductors L11 and L12 and capacitors C11 to C13, capacitor C14 may be connected between the node between inductor L12 and output terminal Tout and the ground terminal Tg. As shown in the filter 210 in modified example 11 of Embodiment 1 in Figure 20(c), in addition to inductors L11, L12 and capacitors C11 to C14, a capacitor C15 may be connected between node N3 and inductor L11. In this way, a low-pass filter may be connected between node N3 and the output terminal Tout.

[0110] In the above embodiment 1 and its modified examples, the case is shown where two groups of inductors and elastic wave resonators or capacitors connected in series are connected between a node on the path connecting the input terminal Tin and the output terminal Tout and the ground terminal Tg. However, three or more groups may be connected. In this case, it is sufficient that a capacitor C5 is connected between the nodes of the inductors and elastic wave resonators or capacitors of any two of the three or more groups. [Examples]

[0111] Example 2 is an example of a multiplexer using Example 1 and its modifications. Figure 21 is a circuit diagram of a triplexer 40 according to Example 2. As shown in Figure 21, the triplexer 40 according to Example 2 includes filters 42, 44, and 46. Filter 42 is connected between the common terminal Ant and terminal LB, filter 44 is connected between the common terminal Ant and terminal MB, and filter 46 is connected between the common terminal Ant and terminal HB. Antenna 48 is connected to the common terminal Ant. Filter 42 is, for example, a low-pass filter, which allows low-band high-frequency signals to pass through and suppresses signals of other frequencies. Filter 44 is, for example, a band-pass filter, which allows middle-band high-frequency signals with frequencies higher than the low-band to pass through and suppresses signals of other frequencies. Filter 46 is, for example, a high-pass filter, which allows high-band high-frequency signals with frequencies higher than the middle-band to pass through and suppresses signals of other frequencies. Filters 100 to 180 from Example 1 and modifications 1 to 8 of Example 1 can be used as filter 46. As filter 44, filters 190 to 210 from modified examples 9 to 11 of Example 1 can be used. Although a triplexer was shown as an example of a multiplexer, the multiplexer may also be a diplexer, duplexer, or quadplexer.

[0112] Although embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention as described in the claims. [Explanation of symbols]

[0113] 20 Laminate 21a~21d Dielectric layer 22a~22c Conductive Pattern Via wiring 23a~23d 24 terminals 30 circuit boards 32 terminals 34 Bonding material 40 Triplexa 42, 44, 46 filters 48 Antennas 50 Filter Circuits A1~A4 Attenuation poles C1~C8 Capacitors L1~L3 Inductors L2a~L2c, L3a, L3b tracks Lg parasitic inductance Inductor designed for Lt magnetic coupling R1~R3 ​​Elastic wave resonator Nodes N1-N7 Tin input terminal Tout output terminal Tg Ground terminal Ant Common Terminal LB, MB, HB terminals 100-210, 500-900 filters

Claims

1. Input terminals, Output terminals, One or more ground terminals, A first capacitor and a second capacitor are connected in series between the input terminal and the output terminal, starting from the input terminal side. A first elastic wave resonator is connected in parallel with the first capacitor and the second capacitor between the input terminal and the output terminal, A first inductor, one end of which is connected to a first node between the first capacitor and the second capacitor, and the other end of which is connected to one of the one or more ground terminals, A second inductor and a third capacitor or a second elastic wave resonator are connected in series between the second node between the input terminal and the first capacitor and one of the one or more ground terminals, A third inductor and a fourth capacitor or a third elastic wave resonator are connected in series between the third node between the output terminal and the second capacitor and one of the one or more ground terminals, A filter comprising: a fifth capacitor having one end connected to a fourth node between the second inductor and the third capacitor or the second elastic wave resonator, and the other end connected to a fifth node between the third inductor and the fourth capacitor or the third elastic wave resonator, and having a capacitance smaller than the capacitance of the first elastic wave resonator.

2. At least the first capacitor, the second capacitor, the first inductor, and the first elastic wave resonator form a passband and a first minimum of the first attenuation pole at a frequency lower than the passband, The filter according to claim 1, wherein at least the first elastic wave resonator forms a second minimum of the second attenuation pole between the first minimum and the passband.

3. Input terminals, Output terminals, One or more ground terminals, A filter circuit connected between the input terminal and the output terminal, comprising a first capacitor, a first inductor and a first elastic wave resonator, wherein at least the first capacitor, the first inductor and the first elastic wave resonator form a passband and a first minimum of a first attenuation pole at a frequency lower than the passband, and at least the first elastic wave resonator forms a second minimum of a second attenuation pole between the first minimum and the passband, A second inductor and a second capacitor or a second elastic wave resonator are connected in series between the first node between the input terminal and the filter circuit and one of the one or more ground terminals, A third inductor and a third capacitor or a third elastic wave resonator are connected in series between the second node between the output terminal and the filter circuit and one of the one or more ground terminals, A filter comprising: a fourth capacitor having one end connected to a third node between the second inductor and the second capacitor or the second elastic wave resonator, and the other end connected to a fourth node between the third inductor and the third capacitor or the third elastic wave resonator, and having a capacitance smaller than the capacitance of the first elastic wave resonator.

4. The second elastic wave resonator is connected in series with the second inductor, or the third elastic wave resonator is connected in series with the third inductor. The filter according to claim 2 or 3, wherein at least the second elastic wave resonator or the third elastic wave resonator forms a third minimum of the third attenuation pole at a frequency lower than the second minimum.

5. The second elastic wave resonator is connected in series with the second inductor, and the third elastic wave resonator is connected in series with the third inductor. At least the second elastic wave resonator forms a third minimum of the third attenuation pole at a frequency lower than the second minimum, The filter according to claim 2 or 3, wherein at least the third elastic wave resonator forms a fourth minimum of the fourth attenuation pole at a frequency lower than the second minimum.

6. The filter according to claim 1 or 3, wherein the shortest distance between the second inductor and the third inductor is 2 mm or less.

7. The filter according to claim 1, wherein the second inductor and the third capacitor or the second elastic wave resonator, and the third inductor and the fourth capacitor or the third elastic wave resonator are connected to a common ground terminal among the one or more ground terminals.

8. The filter according to claim 1, wherein the third capacitor is connected in series with the second inductor, and the fourth capacitor is connected in series with the third inductor.

9. A multiplexer comprising the filter according to claim 1 or 3.

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