Duplexer

Abstract

Duplexer (1), comprising: an antenna connection (11), a transmission connection (12), a receiving connection (13), a transmission filter connected between the antenna connection (11) and the transmission connection (12), a receiving filter connected between the antenna terminal (11) and the receiving terminal (13), and an inductance component (4) connected at one end to the antenna terminal (11) and connected at another end to a ground potential, wherein the transmission filter comprises an elastic wave filter having a ladder circuit configuration, the elastic wave filter including a piezoelectric substrate (5), a series arm resonator (51, 52, 53, 54) and a plurality of shunt arm resonators (P1 - P4), the series arm resonator (51, 52, 53, 54) comprising an elastic wave resonator formed on the piezoelectric substrate and the shunt arm resonators (P1 - P4) each comprising an elastic wave resonator formed on the piezoelectric substrate (5), and wherein one of the shunt arm resonators provided in a shunt arm arranged closest to the transmission terminal in the ladder circuit configuration comprises a transmission-side shunt arm resonator (P1), and the transmission-side shunt arm resonator (P1) is arranged closer to one side of the piezoelectric substrate (5) than a rest of the shunt arm resonators (P2 - P4), the one side (5a) extending in a direction parallel to a propagation direction of an elastic wave in the transmission-side shunt arm resonator (P1), characterized in that the inductance component (4) is arranged outside one side of the piezoelectric substrate such that the electromagnetic coupling between the inductance component (4) and the transmitting-side shunt arm resonator (P1) with its own ground connection is stronger than the electromagnetic coupling between the inductance component (4) and the rest of the shunt arm resonators (P2 - P4).

Description

TECHNICAL FIELD

[0001] The present invention relates to a duplexer having a transmitting filter and a receiving filter, in particular to a duplexer having a transmitting filter including a ladder filter for elastic waves. STATE OF THE ART

[0002] Duplexers with a ladder elastic wave filter are widely used in applications such as mobile phones. For example, WO 2010 / 013778 A1 discloses an example of this type of duplexer. The duplexer described therein comprises a transmission filter and a reception filter connected to an antenna terminal. The transmission filter is formed by a ladder elastic wave filter having multiple elastic wave resonators. An electromagnetic coupling device for electromagnetically coupling to the antenna terminal is provided between a shunt arm resonator of the ladder elastic wave filter and a ground terminal. The electromagnetic coupling device consists of multiple wound patterns connected to each other by a through-hole electrode.

[0003] WO 2014 / 168162 A1 shows a duplexer according to the preamble of claim 1. SUMMARY OF THE INVENTIONTechnical Problem

[0004] According to WO 2010 / 013778 A1, the electromagnetic coupling device consists of multiple wound patterns connected by a through-hole electrode. Therefore, a large space must be provided in the piezoelectric substrate to form the electromagnetic coupling device. This complicates miniaturization.

[0005] It is an object of the present invention to provide a duplexer capable of miniaturization and providing improved isolation. Solution to the problem

[0006] In general terms, the present invention provides a duplexer according to claim 1, including an antenna terminal, a transmit terminal, a receive terminal, a transmit filter connected between the antenna terminal and the transmit terminal, a receive filter connected between the antenna terminal and the receive terminal, and an inductance component connected at one end to the antenna terminal and connected at another end to a ground potential.The transmission filter comprises an elastic wave filter having a ladder circuit configuration, the elastic wave filter including a piezoelectric substrate, a longitudinal arm resonator, and a plurality of shunt arm resonators, the longitudinal arm resonator being formed by an elastic wave resonator formed on the piezoelectric substrate, and the shunt arm resonators each being formed by an elastic wave resonator formed on the piezoelectric substrate.One of the shunt resonators provided in the shunt arm closest to the transmitting terminal in the ladder circuit configuration forms a transmitting-side shunt resonator. The transmitting-side shunt resonator is positioned closer to one side of the piezoelectric substrate than the rest of the shunt resonators, and the one side extends in a direction parallel to the propagation direction of an elastic wave in the transmitting-side shunt resonator. The inductance component is arranged outside one side of the piezoelectric substrate such that the electromagnetic coupling between the inductance component and the transmitting-side shunt resonator with its own ground terminal is stronger than the electromagnetic coupling between the inductance component and the rest of the shunt resonators.

[0007] In a particular embodiment of the duplexer according to the present invention, the inductance component is arranged outside one side of the piezoelectric substrate such that the longitudinal direction of the inductance component extends parallel to that side. In this case, the resulting electromagnetic coupling effectively improves the isolation in the passband of the receiving filter.

[0008] In another particular embodiment of the duplexer according to the present invention, the inductance component includes a coil winding, wherein the coil winding has an axial direction perpendicular to the mounting surface of the inductance component. In this case, the electromagnetic coupling is improved, thereby further improving the isolation properties in the passband of the receive filter.

[0009] In another particular embodiment of the duplexer according to the present invention, the transmitting-side shunt arm resonator and the one side are spaced apart by a distance shorter than the distance between each remainder of the shunt arm resonators and the one side and the distance between the longitudinal arm resonator and the one side. In this case, the electromagnetic coupling is improved, thereby further improving the isolation properties in the passband of the receiving filter.

[0010] In another particular embodiment of the duplexer according to the present invention, no other electronic component element is present between the inductance component and one side of the piezoelectric substrate. In this case, the electromagnetic coupling between the inductance component and the transmitting-side shunt resonator is improved.

[0011] This allows the isolation properties in the passband of the receiving filter to be improved even more effectively.

[0012] In another particular embodiment of the duplexer according to the present invention, the transmitting-side shunt arm resonator and the transmitting port are spaced apart by a distance that is shorter than the distance between the longitudinal arm resonator closest to the antenna port and the transmitting port. In this case, the isolation characteristics in the passband of the receiving filter can be further effectively improved.

[0013] In another particular embodiment of the duplexer according to the present invention, no inductance is connected between the transmitting-side shunt resonator and a ground potential. In this case, the absence of an inductance between the transmitting-side shunt resonator and the ground potential enables further miniaturization.

[0014] In another particular embodiment of the duplexer according to the present invention, one side of the piezoelectric substrate is different from the side of the piezoelectric substrate that is closest to the antenna terminal. In this case, the design freedom of the device incorporating the duplexer can be increased.

[0015] In yet another specific embodiment of the duplexer according to the present invention, the receiving filter is also formed on the piezoelectric substrate, and the piezoelectric substrate forms a duplexer chip. In this case, further miniaturization can be achieved.

[0016] In yet another particular embodiment of the duplexer according to the present invention, the duplexer further includes a module substrate and the inductance component is mounted on the module substrate. Advantageous effects of the invention

[0017] In the duplexer according to the present invention, the inductance component is arranged outside one side of the piezoelectric substrate, adjacent to which the transmitting-side shunt resonator is positioned so that the inductance component extends parallel to that side. This configuration enables the miniaturization of the duplexer. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a plan view of a duplexer according to a first embodiment of the present invention. Fig. 2 is a circuit diagram of the duplexer according to the first embodiment of the present invention. Fig. 3 is a plan view of a duplexer according to a second embodiment of the present invention. Fig. 4(a) and Fig. 4(b) are plan views of the structures of electrodes on the first and second layers under the top surface of the module substrate of the duplexer according to the second embodiment, respectively. Fig. 5(a) and Fig. 5(b) are plan views of the structures of electrodes on the third and fifth layers under the top surface of the module substrate of the duplexer according to the second embodiment, respectively. Fig. 6 is a schematic plan view of the structure of electrodes on the bottom surface of the module substrate of the duplexer according to the second embodiment. Fig. 7 is a plan view of a duplexer according to a comparative example. Fig. 8(a) to Fig. 8(b) are plan views of the structures of electrodes on the first, second, third, and fifth layers under the top surface of the module substrate of the duplexer according to the comparative example, respectively. Fig. 9 is a schematic plan view of the structure of electrodes on the bottom surface of the piezoelectric substrate of the duplexer according to the comparative example. Fig. 10 illustrates the respective insulation characteristics of the first embodiment, the second embodiment, and the comparative example. DESCRIPTION OF EMBODIMENTS

[0018] The present invention will be further explained by the following description of specific embodiments of the invention with reference to the drawings.

[0019] It should be noted that the embodiments described herein are intended to be illustrative and that in various embodiments, some of their features may be substituted or combined with one another.

[0020] Fig. 1 is a plan view of a duplexer according to a first embodiment of the present invention. The duplexer 1 includes a module substrate 2. A duplexer chip 3 is mounted on the module substrate 2. An inductance component 4 is mounted on the module substrate 2. The inductance component 4, formed by a chip-like coil component, has a longitudinal direction.

[0021] The duplexer chip 3 has a piezoelectric substrate 5. A transmit filter Tx and a receive filter Rx are formed on the piezoelectric substrate 5.

[0022] More specifically, the piezoelectric substrate 5 consists of a piezoelectric single crystal such as LiTaO3 or LiNbO3.

[0023] The Fig. The electrode structure shown in Figure 1 is formed on the piezoelectric substrate 5 to form the transmitting filter Tx and the receiving filter Rx. The piezoelectric substrate 5 has a rectangular shape with a pair of short sides 5a and 5b and a pair of long sides 5c and 5d. The transmitting filter Tx is positioned near the short side 5a. The receiving filter Rx is positioned near the short side 5b.

[0024] The configurations of the transmit filter Tx and the receive filter Rx are described below with reference to the circuit diagram of Fig. 2 described.

[0025] The duplexer 1 has an antenna port 11, a transmit port 12, and a receive port 13. The antenna port 11 is connected to an antenna ANT located outside the duplexer 1.

[0026] The inductance component 4 for impedance matching is connected between the antenna terminal 11 and the ground potential. The transmit filter Tx is connected between the antenna terminal 11 and the transmit terminal 12.

[0027] The transmission filter Tx, which has a ladder circuit configuration, includes a plurality of series-arm resonators S1 to S4 and a plurality of shunt-arm resonators P1 to P4. The series-arm resonator S1, the series-arm resonator S2, the series-arm resonator S3, and the series-arm resonator S4 are connected to the transmission terminal 12 in order of decreasing proximity. Of the shunt-arm resonators P1 to P4, the shunt-arm resonator in the sub-arm closest to the transmission terminal 12 will be referred to as the transmission-side shunt-arm resonator P1, as appropriate.

[0028] Both the longitudinal arm resonators S1 to S4 and the shunt arm resonators P1 to P4 are formed by surface acoustic wave resonators. Specifically, each elastic wave resonator includes an interdigital transducer (IDT) electrode disposed on the piezoelectric substrate 5 and having an elongated shape, with reflectors located on both sides of the IDT electrode with respect to the direction of elastic wave propagation. Fig. 1, an “X” enclosed by a rectangular box is used to schematically represent an area in which an elastic wave resonator is formed. As shown in Fig. 1, the long side 5c is the side closest to the antenna terminal 11. The antenna terminal 11 is positioned in the center of the long side 5c. The transmitting terminal 12 is located near the corner part between the long side 5d, which is opposite to the long side 5c, and the short side 5a, which connects the long side 5c and the long side 5d. The receiving terminal 13 is located near the corner part between the long side 5d and the short side 5b, which is opposite to the short side 5a. In other words, the transmitting port 12 is positioned on the same side as the long side 5d and near the short side 5a, and the receiving port 13 is positioned on the same side as the long side 5d and near the short side 5b.

[0029] With further reference to Fig. 2, the transmitting-side shunt resonator P1 is connected to the ground potential. That is, no inductance is connected between the transmitting-side shunt resonator and the ground potential. An inductance L1 is connected between the ground-side end portion of each of the shunt resonators P2 to P4 and the ground potential. The inductance L1 is provided to adjust the frequency characteristics of an attenuation pole generated at a harmonic frequency of the transmitting filter Tx.

[0030] The inductance L1 may be formed by providing an inductance component on the piezoelectric substrate 5 by wiring or other methods. Alternatively, the inductance L1 may be formed on the module substrate 2, outside the piezoelectric substrate 5. Further, the inductance L1 may be provided by attaching an external inductance component to the module substrate 2.

[0031] An inductance can be provided between the ground potential end section of the transmitting side shunt resonator P1 and the ground potential.

[0032] Characteristic features of the duplexer 1 according to the first embodiment include that the inductance component 4 for impedance matching is arranged to be electromagnetically coupled to the transmitting-side shunt arm resonator P1, and that the inductance component 4 is formed by an inductance component externally added to the duplexer chip 3.

[0033] Duplexer 1 uses inductance component 4, thus eliminating the need for a large area between duplexer chip 3 and module substrate 2. In the duplexer described in Patent Document 1, multiple wound patterns are provided within the module substrate and connected by a through-hole electrode to form an inductance. This configuration inevitably leads to an increase in the area of ​​the module substrate. Furthermore, a large inductance value is required to achieve electromagnetic coupling.

[0034] In contrast, in the first embodiment, a coiled wiring pattern with a large area, which is composed of a multi-layer structure including components such as conductor lines, vias, and ground electrodes, need not be provided within the module substrate 2. This allows the area of ​​the module substrate 2 to be reduced. The duplexer 1 thus enables effective miniaturization. Even if the inductance L1 formed by a coiled wiring pattern is provided within the module substrate 2 of a multi-layer structure to adjust the frequency characteristics of an attenuation pole generated at a harmonic frequency of the transmission filter Tx, electromagnetic coupling is utilized, so that a small inductance value is sufficient to adjust the frequency characteristics of an attenuation pole at a harmonic frequency.As a result, the frequency characteristics of an attenuation pole at a harmonic frequency can be adjusted without increasing the physical size of the module substrate 2.

[0035] The inductance component 4, which is a chip component with a substantially rectangular parallelepiped shape, is arranged with its longitudinal direction parallel to the direction in which the short side 5a extends. When the inductance component 4 is arranged with its transverse direction parallel to the direction in which the short side 5a extends, the fixing electrode part (outer electrode) of the inductance component, which has electrical conductivity, is arranged opposite to the short side 5a. This means that the fixing electrode part is located between the inductance included in the inductance component 4 and the transmitting-side shunt arm resonator P1, making it difficult for electromagnetic coupling to occur.

[0036] The absence of any other electronic component between the inductance component 4 and the short side 5a also enables miniaturization.

[0037] One end of the inductance component 4 is connected to the antenna terminal 11 by wiring (not shown). The inductance component 4 is located near the short side 5a of the piezoelectric substrate 5. The short side 5a is the side of the piezoelectric substrate 5 that is the least far from the transmission-side shunt arm resonator P1. More specifically, the transmission filter Tx includes the shunt arm resonators P1 to P4 and the series arm resonators S1 to S4. Of these resonators, the transmission-side shunt arm resonator P1 and the short side 5a are spaced apart by a distance shorter than the distance between each of the remaining resonators, such as the series arm resonators S1 to S4 and the shunt arm resonators P2 to P4, and the short side 5a.Therefore, arranging the inductance component 4 outside the short side 5a effectively improves the electromagnetic coupling between the inductance component 4 and the capacitance of the transmitting-side shunt resonator P1. This configuration of the duplexer 1 effectively improves the isolation characteristics of the transmitting filter Tx in the passband of the receiving filter Rx. This will be described in more detail later with reference to specific experimental examples.

[0038] The distance between the transmitting side shunt arm resonator P1 and the transmitting terminal 12 is shorter than the distance between the longitudinal arm resonator S4, which is the least far from the antenna terminal 11, and the transmitting terminal 12. This configuration also enables the above-mentioned electromagnetic coupling to be effectively improved.

[0039] The short side 5a is a side different from the long side 5c located near the antenna terminal 11. This ensures improved design freedom regarding the relative positioning of the antenna terminal 11 and the inductance component 4. However, it should be noted that the inductance component 4 can be positioned adjacent to the same side as the antenna terminal 11.

[0040] Alternatively, the inductance component 4 may be positioned adjacent to the long side 5d opposite to the long side 5c. That is, there are no particular restrictions on the side of the piezoelectric substrate 5 to which the inductance component 4 is positioned adjacent, as long as the inductance component 4 is positioned adjacent to the transmitting-side shunt resonator P1.

[0041] In the first embodiment, the axial direction of the coil winding of the inductance component 4 is perpendicular to the mounting surface of the inductance component. As a result, viewed in the axial direction of the coil winding, the central cavity of the coil contained in the inductance component 4 has a large inner diameter in the longitudinal direction of the inductance component 4 and a small inner diameter in the transverse direction of the inductance component 4. This results in an elongated shape in the longitudinal direction of the inductance component 4 as viewed in the axial direction of the coil winding. The longitudinal direction of the inductance component 4 is parallel to the propagation direction of the surface acoustic wave in the transmitting-side shunt arm resonator P1.This configuration allows a larger portion of the magnetic flux generated by the central cavity of the elongated coil to penetrate the transmitting-side shunt arm resonator P1, in which the electrode fingers of a comb-shaped electrode are arranged in the propagation direction of the surface acoustic wave. This improves the electromagnetic coupling between the inductance component 4 and the transmitting-side shunt arm resonator P1. However, it should be noted that the axial direction of the coil winding of the inductance component 4 is not limited to the above-mentioned direction.

[0042] The reception filter Rx has a circuit configuration with a cascade connection of longitudinally coupled resonator-type 3-IDT surface acoustic wave filters 21 and 22. An elastic wave resonator 23 is connected between the longitudinally coupled resonator-type surface acoustic wave filter 21 and the antenna terminal 11. The reception filter Rx is not limited to a filter using the aforementioned longitudinally coupled resonator-type surface acoustic wave filters 21 and 22, but may be configured as a ladder-type elastic wave filter. Each of the longitudinally coupled resonator-type 3-IDT surface acoustic wave filters 21 and 22 may be partially replaced by a longitudinally coupled resonator-type 5-IDT surface acoustic wave filter, which is an extension of a longitudinally coupled resonator-type 3-IDT surface acoustic wave filter.

[0043] Although both the transmitting filter Tx and the receiving filter Rx are formed on the piezoelectric substrate 5 in the first embodiment, only the transmitting filter Tx may be provided on the piezoelectric substrate 5. That is, the receiving filter Rx may be formed on another piezoelectric substrate and mounted on the module substrate 2. Furthermore, the receiving filter Rx may be formed directly on the module substrate 2.

[0044] Fig. 3 is a plan view of a duplexer 31 according to a second embodiment of the present invention. In the duplexer 31, the distance between the longitudinal arm resonator S1 and the transmission port 12 is shorter than the distance between the transmission-side shunt arm resonator P1 and the transmission port 12. Otherwise, the second embodiment has the same configuration as the first embodiment. As in the duplexer 31, according to the present invention, at least one longitudinal arm resonator may be physically positioned closer to the inductance component 4 or the transmission port 12 than the transmission-side shunt arm resonator P1.

[0045] Next, the structure of the electrodes within the module substrate 2 of the duplexer 31 will be described with reference to the Fig. 4(a), Fig. 4(b), Fig. 5(a), Fig. 5(b) and Fig. 6 described. Fig. 4(a) and Fig. 4(b) are schematic plan views of the electrode structures of the first and second layers under the top surface of the module substrate 2, respectively. Fig. 5(a) and Fig. 5(b) are schematic plan views of the electrode structures of the third and fifth layers under the top surface of the module substrate 2, respectively. Fig. 6 is a schematic plan view of the electrode structure of the bottom surface of the module substrate 2. The electrode structure of the fourth layer is the same as that of the third layer and will therefore not be described.

[0046] As in Fig. As shown in Fig. 4(a), the first layer below the top surface of the module substrate 2 is provided with an electrode pad 11a connected to the antenna terminal 11, an electrode pad 35a connected to the ground-side end portion of the transmitting-side shunt-arm resonator P1, an electrode pad 12a connected to the transmitting terminal 12, and an electrode pad 13a connected to the receiving terminal 13. Further, a wound wiring pattern 33 is provided to form the inductor L1 connected between each of the shunt-arm resonators P2 to P4 and the ground potential. An electrode pad 36 connected to the ground potential is arranged below the inductor L1, and the shunt-arm resonators and series resonators of the transmitting filter Tx are arranged above the inductor L1.

[0047] The antenna connection 11 is connected by a through-hole electrode with a Fig. 4(b) shown electrode connection surface 11b, one in Fig. 5(a) and an electrode connection surface 11c shown in Fig. 5(b) shown. The electrode pad 11d is electrically connected to the electrode pad 11d by a through-hole electrode with the Fig. 6 shown connection electrode 11A.

[0048] The transmitting terminal 12 is connected by a through-hole electrode to the Fig. 4(a) shown electrode connection surface 12a, with a Fig. 4(b) shown electrode connection surface 12b, with a Fig. 5(a) and an electrode connection surface 12c shown in Fig. 5(b) shown. The electrode pad 12d is electrically connected to the electrode pad 12d by a through-hole electrode with the Fig. 6 shown connection electrode 12A.

[0049] The inductance component 4 is connected to each of the Fig. 4(a) are electrically connected to the electrode pads 34a and 34d. The electrode pad 34a is formed by a through-hole electrode having a Fig. 4(b) shown electrode pad 34b. The electrode pad is connected by a through-hole electrode each having a Fig. 5(a) and the electrode pad 34c shown in Fig. 5(b). Thus, one end of the inductance component 4 is electrically connected to the antenna terminal 11.

[0050] The Fig. The electrode pad 34d shown in Fig. 4(a) is formed by a through-hole electrode having a Fig. 4(b) is electrically connected to the electrode pad 34e shown in Fig. 4(b). The electrode pad 34e is connected to the electrode pad 34e by a through-hole electrode shown in Fig. 5(a). The electrode pad 36 is an electrode pad connected to the ground potential.

[0051] The receiving terminal 13 is connected by a through-hole electrode to the Fig. 4(a) or Fig. 4(b) and an electrode pad 13b, and with an electrode pad 13a shown in Fig. 5(a) or Fig. 5(b) and an electrode pad 13d. Furthermore, the electrode pad 13d is electrically connected to the electrode pad 13c shown in Fig. 6 shown connection electrode 13A.

[0052] Fig. 7 is a plan view of a duplexer according to a comparative example. In a duplexer 101 according to the comparative example, a duplexer chip 103 and an inductance component 104, which is an external component, are mounted on a module substrate 102. The duplexer chip 103 is configured in substantially the same manner as the duplexer chip according to the second embodiment. However, it should be noted that the inductance component 104 is arranged outside a long side 105c of a piezoelectric substrate 105 having an elongated shape. That is, the distance between the inductance component 104 and the antenna terminal is shorter than the distance between the inductance component 104 and the transmission terminal. Fig. 8(a) to Fig. 8(b) are schematic plan views of the electrode structures of the first layer, the second layer, the third and fourth layers, and the fifth layer under the top surface of the module substrate 102 of the duplexer 101 according to the comparative example, respectively. Fig. Fig. 9 is a schematic plan view of the electrode structure of the bottom side of the module substrate 102. The electrode pads 11f, 11g, 11h and 11i, which are respectively Fig. 8(a) to Fig. 8(d) are connected to each other by a through-hole electrode. The electrode pad 11i is connected to the through-hole electrode shown in Fig. 9. The electrode pads 12f and 12g are electrically connected to each other by a through-hole electrode and are connected to the Fig. 9. Furthermore, the electrode pads 13f to 13i are electrically connected to each other by a through-hole electrode. The electrode pad 13i is connected to the Fig. 9 shown antenna connection 13.

[0053] Duplexer 1 according to the above-mentioned first embodiment was manufactured in the same manner as duplexer 31 according to the second embodiment. Duplexers 1, 31, and 101 are each configured as a Band28B duplexer. In this case, the passband of the transmit filter Tx is in the range of 718 MHz to 748 MHz, and the passband of the receive filter Rx is in the range of 773 MHz to 803 MHz. The isolation characteristics of the duplexers according to the first and second embodiments and the duplexer according to the comparative example were achieved. Fig. 10 presents the results.

[0054] Out of Fig.10 shows that, compared to the comparative example, the first and second embodiments offer improved isolation in the frequency range from 773 MHz to 803 MHz, which is the passband of the receiving filter Rx. It is also evident that the comparative example has an isolation of 45.1 dB at the frequency corresponding to the lowest isolation in the passband of the receiving filter Rx, while the first and second embodiments have significantly improved values ​​of 53.8 dB and 51.1 dB, respectively. This is presumably due to the better electromagnetic coupling between the inductance component 4 and the transmitting-side shunt resonator P1.

[0055] A characteristic feature of the present invention is that, as described above, the duplexer includes the transmission filter Tx formed by a ladder elastic wave filter, and the reception filter Rx is configured such that the inductance component 4, which is an external component, is disposed outside a side of the piezoelectric substrate 5 close to the transmission-side shunt arm resonator P1, so that the electromagnetic coupling between the inductance component 4 and the transmission-side shunt arm resonator P1 is stronger than the electromagnetic coupling between the inductance component 4 and the remaining shunt arm resonators P2 to P4. Thus, there are no particular restrictions on the number of stages or circuit configurations in the transmission filter Tx formed by a ladder elastic wave filter.Thus, the number of stages of shunt arm resonators and series arm resonators is not particularly limited. It is not absolutely necessary to connect an inductor between the transmitting-side shunt arm resonator and the ground potential, nor is it absolutely necessary to connect an inductor with a relatively large inductance value between the transmitting-side shunt arm resonator and the ground potential. In the related art, an antenna matching inductor is commonly used as a matching circuit to provide matching between an antenna and a duplexer. The present invention utilizes electromagnetic coupling between an antenna matching inductor and a transmitting-side shunt arm resonator, which includes an IDT electrode provided on a piezoelectric substrate forming part of a ladder transmission filter.The use of such electromagnetics for duplexer applications makes it possible to provide a duplexer that not only provides matching between the antenna and the duplexer, but also improves the isolation between the transmit filter and the receive filter, which has a passband outside the passband of the transmit filter at higher frequencies. Furthermore, the present invention enables the use of a configuration in which no inductance is connected between the transmitting-side shunt resonator P1 and the ground potential, or a configuration in which an inductance with a relatively small inductance value is connected between the transmitting-side shunt resonator P1 and the ground potential. This effectively makes it possible to reduce the area of ​​the inductance arranged in the duplexer.

[0056] Furthermore, although a chip-type coil component is used as the inductance component 4 in the above description, other chip-type inductance components may also be used. LIST OF REFERENCE SYMBOLS 1 duplexer 2 Module substrate 3 Duplexer chip 4 Inductance component 5 Piezoelectric substrate 5a, 5b Short side 5c, 5d Long side 11 Antenna connection 11A connection electrode 11a to 11d Electrode connection surface 12 Transmission connection 12A connection electrode 12a to 12d Electrode connection surface 13 Reception connection 13A connection electrode 13a to 13d Electrode connection surface 21, 22 Longitudinally coupled resonator-type surface acoustic wave filter 23 Resonator for elastic waves 31 duplexers 33 Coiled wiring pattern 34a to 34e, 35a, 36 Electrode connection surface L1 inductance P1 to P4 shunt arm resonator S1 to S4 longitudinal arm resonator

Claims

A duplexer (1) comprising: an antenna terminal (11), a transmission terminal (12), a reception terminal (13), a transmission filter connected between the antenna terminal (11) and the transmission terminal (12), a reception filter connected between the antenna terminal (11) and the reception terminal (13), and an inductance component (4) connected at one end to the antenna terminal (11) and connected at another end to a ground potential, wherein the transmission filter comprises an elastic wave filter having a ladder circuit configuration, the elastic wave filter including a piezoelectric substrate (5), a series arm resonator (51, 52, 53, 54), and a plurality of shunt arm resonators (P1-P4), wherein the series arm resonator (51, 52, 53,54) comprises an elastic wave resonator formed on the piezoelectric substrate, and the shunt arm resonators (P1 - P4) each comprise an elastic wave resonator formed on the piezoelectric substrate (5), and wherein one of the shunt arm resonators provided in a shunt arm located closest to the transmission terminal in the ladder circuit configuration comprises a transmission-side shunt arm resonator (P1), and the transmission-side shunt arm resonator (P1) is located closer to one side of the piezoelectric substrate (5) than a rest of the shunt arm resonators (P2 - P4), the one side (5a) extending in a direction parallel to a propagation direction of an elastic wave in the transmission-side shunt arm resonator (P1), characterized in that the inductance component (4) is arranged outside the one side of the piezoelectric substrate so thatthat the electromagnetic coupling between the inductance component (4) and the transmitting-side shunt resonator (P1) with its own earth connection is stronger than the electromagnetic coupling between the inductance component (4) and the rest of the shunt resonators (P2 - P4)., Duplexer (1) according to claim 1, wherein the inductance component (4) is arranged outside the one side of the piezoelectric substrate (5) such that a longitudinal direction of the inductance component (4) extends parallel to the one side (5a). Duplexer (1) according to claim 1 or 2, wherein the inductance component (4) includes a coil winding and the coil winding has an axial direction perpendicular to a mounting surface of the inductance component (4). Duplexer (1) according to one of claims 1 to 3, wherein the transmitting-side shunt arm resonator (P1) and the one side (5a) have a distance from each other which is shorter than a distance between each remainder of the shunt arm resonators (P2 - P4) and the one side and a distance between the longitudinal arm resonator (51, 52, 53, 54) and the one side (5a). Duplexer (1) according to one of claims 1 to 4, wherein no other electronic component element is present between the inductance component (4) and the one side of the piezoelectric substrate (5). Duplexer (1) according to one of claims 1 to 5, wherein the transmitting-side shunt arm resonator (P1) and the transmitting port (12) are spaced apart by a distance that is shorter than a distance between the longitudinal arm resonator (54) closest to the antenna port and the transmitting port (12). Duplexer (1) according to one of claims 1 to 6, wherein no inductance is connected between the transmitting-side shunt resonator (P1) and a ground potential. Duplexer (1) according to one of claims 1 to 7, wherein the one side (5a) of the piezoelectric substrate differs from a side (5c) of the piezoelectric substrate which is the least far away from the antenna terminal (11). Duplexer (1) according to one of claims 1 to 8, wherein the receiving filter (13) is also formed on the piezoelectric substrate and the piezoelectric substrate (5) forms a duplexer chip. Duplexer (1) according to one of claims 1 to 9, further comprising a module substrate (2), wherein the inductance component (4) is mounted on the module substrate (2).

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