Filter device, antenna device, and antenna module

Abstract

A filter device (100) comprises: an insulator (10) including a first external electrode (11) and a second external electrode (12); an inductor (L1) connected to the first external electrode; a resonance circuit (RS) including an inductor (L2) and a capacitor (C1); and an inductor (L3). The inductor (L1) is connected to the second external electrode (12) and is connected to the resonance circuit (RS). The inductor (L3) includes an inductor (L3a) connected to both ends of the resonance circuit (RS). The inductor (L1) and the inductor (L2) are magnetically coupled with demagnetizing polarity.

Description

FILTER DEVICE, ANTENNA DEVICE, AND ANTENNA MODULE

[0001] The present disclosure relates to a filter device, an antenna device, and an antenna module.

[0002] Conventionally, filter devices that pass high-frequency signals in a specific first frequency band while attenuating high-frequency signals in a specific second frequency band have been known. For example, International Publication No. 2023 / 080009 (Patent Document 1) discloses a filter device having a pass band in a first frequency band and an attenuation band in a second frequency band lower than the first frequency band.

[0003] International Publication No. 2023 / 080009

[0004] The filter device disclosed in WO 2023 / 080009 includes a first inductor and a resonant circuit including a second inductor and a capacitor connected to the first inductor. By forming a parallel resonator using the mutual inductance generated when the first inductor and the second inductor are magnetically coupled, high-frequency signals in the second frequency band can be attenuated by parallel resonance and high-frequency signals in the first frequency band can be passed by series resonance.

[0005] In the filter device described above, there is a demand for it to be compact and yet be able to attenuate high frequency signals better by using parallel resonance.

[0006] The present disclosure has been made to solve such problems, and its object is to provide a filter device that is small and can obtain good attenuation and pass characteristics.

[0007] A filter device according to an aspect of the present disclosure includes an insulator including a first external electrode and a second external electrode, a first inductor connected to the first external electrode, a resonant circuit including a second inductor and a capacitor, and a third inductor. The first inductor is connected to the second external electrode and to the resonant circuit. The third inductor includes a resonant inductor connected to both ends of the resonant circuit. The first inductor and the second inductor are magnetically coupled with each other in a depolarized manner.

[0008] An antenna device according to another aspect of the present disclosure includes a radiating element that radiates a high-frequency signal in a first frequency band as radio waves, a power feed circuit that supplies the high-frequency signal in the first frequency band to the radiating element, and the above-mentioned filter device provided between the radiating element and the power feed circuit.

[0009] According to another aspect of the present disclosure, there is provided an antenna module including a first antenna device that emits a high-frequency signal in a first frequency band as a radio wave, and a second antenna device that emits a high-frequency signal in a second frequency band as a radio wave. The first antenna device is the antenna device described above.

[0010] According to the present disclosure, by configuring a parallel resonator using the mutual inductance that occurs when a first inductor and a second inductor are magnetically coupled in a depolarized manner, high-frequency signals can be attenuated more effectively by parallel resonance, and further, the amount of attenuation of high-frequency signals by parallel resonance can be increased by a resonant inductor connected to a resonant circuit. As a result, the present disclosure can provide a filter device that is small in size and has good attenuation and pass characteristics.

[0011] 1 is a diagram illustrating a configuration of an antenna device according to a first embodiment. FIG. 2 is a graph illustrating frequency characteristics of reactance of the filter device according to the first embodiment. FIG. 3 is a diagram illustrating a configuration of an antenna module according to the first embodiment. FIG. 4 is a circuit diagram of a filter device according to the first embodiment. FIG. 5 is a circuit diagram of a filter device according to a comparative example. FIG. 6 is a diagram illustrating an example of insertion loss of a filter device according to a comparative example. FIG. 7 is a diagram illustrating an example of insertion loss of a filter device according to the first embodiment. FIG. 8 is an external view of a filter device according to the first embodiment. FIG. 9 is a perspective view illustrating a layered structure of a filter device according to the first embodiment. FIG. 10 is an exploded plan view illustrating the layered structure of a filter device according to the first embodiment. FIG. 11 is an exploded plan view illustrating the layered structure of a filter device according to the first embodiment. FIG. 12 is a diagram illustrating a comparative example of insertion loss due to differences in inductance in the filter device according to the first embodiment. FIG. 13 is a circuit diagram of a filter device according to a second embodiment. FIG. 14 is a perspective view illustrating the layered structure of a filter device according to the second embodiment. FIG. 15 is an exploded plan view illustrating the layered structure of a filter device according to the second embodiment. FIG. 16 is an exploded plan view illustrating the layered structure of a filter device according to the second embodiment.

[0012] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

[0013] First Embodiment A filter device 100 according to a first embodiment will be described with reference to FIGS. 1 to 13. FIG.

[0014] 1 is a diagram showing the configuration of an antenna device 1 according to embodiment 1. The antenna device 1 can be mounted on a communication device capable of transmitting and receiving radio waves, such as a mobile phone, a smartphone, a tablet terminal, or a smartwatch, or a personal computer (PC) with a communication function.

[0015] As shown in FIG. 1 , antenna device 1 is an example of a "first antenna device" and includes a feed circuit RF1, a radiating element 50, and a filter device 100. The feed circuit RF1 supplies a high-frequency signal in a specific first frequency band to the radiating element 50. In the first embodiment, the first frequency band is referred to as the f1 band. The radiating element 50 is, for example, a monopole antenna, and radiates the high-frequency signal in the f1 band supplied from the feed circuit RF1 into the air as radio waves. Note that the radiating element 50 is not limited to a monopole antenna, and may be a dipole antenna, an inverted-F antenna, a loop antenna, or the like.

[0016] The filter device 100 is disposed between the radiating element 50 and the feed circuit RF1. The filter device 100 is configured to attenuate high-frequency signals in a second frequency band while passing high-frequency signals in a first frequency band (f1 band). In the first embodiment, the second frequency band is referred to as the f2 band. The f2 band is a frequency band lower than the first frequency band (f1 band) and close to the f1 band. For example, if the f1 band is the 5 GHz band (5.15-5.85 GHz) used by Wi-Fi (registered trademark), the f2 band is n79 (4.4-5.0 GHz). Such a filter device 100 is particularly useful when the antenna device 1 is used near an antenna that transmits and receives radio waves in the f2 band.

[0017] Fig. 2 is a graph illustrating the frequency characteristics of the reactance of the filter device 100 according to the first embodiment. In Fig. 2, the frequency characteristics of the reactance of the filter device 100 are shown in a graph with frequency on the horizontal axis and reactance on the vertical axis. As shown in Fig. 2, in the filter device 100, the attenuation band due to parallel resonance is the f2 band, and the pass band due to series resonance is the f1 band.

[0018] 3 is a diagram showing the configuration of the antenna module 3 according to embodiment 1. The antenna module 3 can be mounted on a communication device capable of transmitting and receiving radio waves, such as a mobile phone, a smartphone, a tablet terminal, or a smart watch, or a PC with a communication function.

[0019] As shown in Fig. 3, the antenna module 3 includes the antenna device 1 according to the first embodiment described above and an antenna device 2. The antenna device 2 is an example of a "second antenna device" and includes a feed circuit RF2 and a radiating element 60. The feed circuit RF2 supplies a high-frequency signal in a specific second frequency band (f2 band) to the radiating element 60. The radiating element 60 is, for example, a monopole antenna, and radiates the high-frequency signal in the f2 band supplied from the feed circuit RF2 into the air as radio waves. Note that the radiating element 60 is not limited to a monopole antenna, and may also be a dipole antenna, an inverted-F antenna, a loop antenna, or the like.

[0020] The radiating element 60 is provided on the same substrate 70 as the radiating element 50 of the antenna device 1. In the example of Fig. 3, the radiating elements 50 and 60 are provided on the same substrate 70, but they may be provided on different substrates as long as they are provided within the same antenna module 3.

[0021] The high-frequency signal in the f2 band radiated from the antenna device 2 is absorbed by the antenna device 1 located in the vicinity of the antenna device 1, resulting in a deterioration in the radiation efficiency of the antenna device 2. For this reason, the filter device 100 is configured to attenuate the high-frequency signal in the f2 band radiated from the antenna device 2. That is, the filter device 100 is configured to pass the high-frequency signal in the f1 band supplied from the feed circuit RF1 to the radiating element 50, while not passing the high-frequency signal in the f2 band radiated from the antenna device 2, thereby suppressing deterioration in the radiation efficiency of the antenna device 2. This makes it possible to place multiple antennas close to each other and reduce the size of the antenna module while suppressing deterioration in antenna characteristics.

[0022] [Configuration of Filter Device] The filter device 100 according to the first embodiment will be described in detail with reference to Fig. 4 to Fig. 13. Fig. 4 is a circuit diagram of the filter device 100 according to the first embodiment. The filter device 100 is a trap filter that attenuates high-frequency signals in a specific frequency band (f2 band) by preventing their passage, and may also be a band-elimination filter.

[0023] 4, the filter device 100 includes a first terminal P1, a second terminal P2, an inductor L1, a resonant circuit RS including an inductor L2 and a capacitor C1, an inductor L3, and an inductor L4. The inductor L3 includes an inductor L3a and an inductor L3b. The filter device 100 can be connected to a transmission line on the feed circuit RF1 side via the first terminal P1. The filter device 100 can be connected to a transmission line on the radiating element 50 side via the second terminal P2.

[0024] When a radio frequency signal supplied from the feed circuit RF1 is supplied to the radiating element 50 via the filter device 100, the first terminal P1 becomes an input terminal and the second terminal P2 becomes an output terminal. When a radio frequency signal received by the radiating element 50 is supplied to a circuit on the feed circuit RF1 side via the filter device 100, the first terminal P1 becomes an output terminal and the second terminal P2 becomes an input terminal. Here, an example has been shown in which the feed circuit RF1 is connected to the first terminal P1 and the radiating element 50 is connected to the second terminal P2, but it is also possible to connect the radiating element 50 to the first terminal P1 and the feed circuit RF1 to the second terminal P2. Either connection will produce the same effect.

[0025] Inductor L1 is an example of a "first inductor." Inductor L2 is an example of a "second inductor." Inductor L3 is an example of a "third inductor." Inductor L4 is an example of a "fourth inductor." Inductor L3a is an example of a "resonating inductor." Inductor L3b is an example of an "other inductor."

[0026] One end of the inductor L4 is connected to the first terminal P1. The other end of the inductor L4 is connected to one end of the inductor L1. That is, one end of the inductor L1 is connected to the first terminal P1 via the inductor L4. The other end of the inductor L1 is connected to the second terminal P2 via a second path TL2, which is a short-circuit path, and is also connected to one end of the inductor L3b. The other end of the inductor L3b is connected to the resonant circuit RS and one end of the inductor L3a. That is, the other end of the inductor L1 is connected to the resonant circuit RS and one end of the inductor L3a via the inductor L3b. One end of the resonant circuit RS is connected to the other end of the inductor L3b and one end of the inductor L3a. The other end of the resonant circuit RS is connected to the other end of the inductor L3a. That is, the inductor L3a is connected to both ends of the resonant circuit RS. In this way, a loop-shaped first path TL1 passing through the inductor L3 and the resonant circuit RS, and a short-circuited second path TL2 are provided between the inductor L1 and the second terminal P2.

[0027] The resonant circuit RS is configured by connecting an inductor L2 and a capacitor C1 in series between one end of the inductor L3a and the other end of the inductor L3a. The inductor L3a is connected in parallel to the resonant circuit RS.

[0028] When a current flows from the first terminal P1 to inductor L1, the direction of the current flowing to the inductor pattern of inductor L1 is different from the direction of the current flowing to the inductor pattern of inductor L2 when a current flows from inductor L1 to inductor L2. Therefore, inductors L1 and L2 generate magnetic fields in directions in which the magnetic fluxes passing through them weaken each other, resulting in magnetic coupling. That is, inductors L1 and L2 are magnetically coupled by depolarization (hereinafter also referred to as "depolarization coupling"). This generates a mutual inductance -M between inductors L1 and L2. The generated mutual inductance -M generates a mutual inductance +M in each of inductors L3a and L3b included in inductor L3. As a result, a parallel resonator is formed by the mutual inductance -M generated between inductors L1 and L2 and the mutual inductance +M generated in inductor L3.

[0029] The series resonant frequency f0 of the resonant circuit RS is expressed as f0 = 1 / 2π√(L2 × C1). At the series resonant frequency f0, the combined reactance X of the inductor L2 and the capacitor C1 becomes 0 (zero) (X = 0). At such a series resonant frequency f0, the filter device 100 functions as a parallel resonator with mutual inductance +M and mutual inductance -M. The resonant frequency of such a parallel resonator coincides with the series resonant frequency f0 of the resonant circuit RS, and becomes the parallel resonant frequency in the attenuation band (f2 band) of the filter device 100.

[0030] In the filter device 100 according to the first embodiment, a designer can design the parallel resonant frequency of the attenuation band simply by determining the values ​​of the inductor L2 and the capacitor C1 that constitute the resonant circuit RS. In this way, the filter device 100 has a configuration that is extremely advantageous in terms of structural design.

[0031] Furthermore, by changing the coupling coefficient k between the inductors L1 and L2, the designer can change the series resonance frequency of the pass band (f1 band) and bring the pass band (f1 band) due to series resonance closer to the attenuation band (f2 band) due to parallel resonance. In other words, the designer can configure the filter device 100 having a narrow band in which the attenuation characteristics change sharply near the parallel resonance frequency of the attenuation band (f2 band).

[0032] The coupling coefficient k between the inductors L1 and L2 also affects the amount and width of attenuation of high-frequency signals in the attenuation band (f2 band). The larger the coupling coefficient k, the larger the mutual inductance that occurs, so the high-frequency signals are attenuated more sharply in the attenuation band (f2 band), resulting in good attenuation characteristics.

[0033] In order to increase the coupling coefficient k, it is conceivable to increase the inductance of inductor L1 or inductor L2. However, since inductor L1 affects the pass characteristics of high-frequency signals in the pass band (f1 band), it is preferable to minimize the inductance of inductor L1 in order to obtain good pass characteristics without attenuating high-frequency signals in the pass band (f1 band). Furthermore, if the number of turns of inductor L2 is increased or the opening area of ​​inductor L2 is increased in order to increase the inductance of inductor L2, the entire filter device 100 becomes larger, making it difficult to miniaturize the filter device 100. Therefore, it is difficult to increase the inductance of inductor L1 or inductor L2 while miniaturizing the filter device 100.

[0034] Here, a filter device 100A according to a comparative example will be described with reference to Fig. 5. Fig. 5 is a circuit diagram of the filter device 100A according to the comparative example. As shown in Fig. 5, the filter device 100A according to the comparative example has a circuit configuration similar to that of the filter device 100 according to the first embodiment, but includes inductors L1A and L2A instead of inductors L1 and L2, respectively.

[0035] In the filter device 100A, when viewed along the path connecting inductor L1A to inductor L2, the winding direction of the inductor pattern constituting inductor L1A is the same as the winding direction of the inductor pattern constituting inductor L2. Therefore, the direction of current flow in inductor L1A is the same as the direction of current flow in inductor L2A. That is, inductors L1A and L2A are magnetically coupled with additive polarity (hereinafter also referred to as "additive polarity coupling"). As a result, a mutual inductance +M is generated between inductors L1A and L2A. The generated mutual inductance +M generates a mutual inductance -M in each of inductors L3a and L3b included in inductor L3. As a result, a parallel resonator is formed by the mutual inductance +M generated between inductors L1 and L2 and the mutual inductance -M generated in inductor L3.

[0036] As described above, in order to obtain good attenuation characteristics while miniaturizing the filter device 100A, it is sufficient to generate a larger mutual inductance. However, as shown in FIG. 5 , in the filter device 100A, wiring inductance ESL (parasitic inductance) exists in paths such as the inductor pattern connecting the inductor and capacitor. As in the filter device 100A according to the comparative example, when a mutual inductance −M occurs in inductor L3 due to additive coupling between inductors L1A and L2A, the wiring inductance ESL and the mutual inductance −M cancel each other out, reducing the inductance in the parallel resonance. As a result, it becomes difficult to increase the attenuation of high-frequency signals through parallel resonance in the filter device 100A.

[0037] For example, Fig. 6 is a graph showing an example of the insertion loss of the filter device 100A according to the comparative example. Fig. 6 shows the frequency characteristics of the insertion loss of the filter device 100A in a graph with frequency on the horizontal axis and insertion loss on the vertical axis. In the example shown in Fig. 6, the inductance of the inductor L1 is 0.5 nH, the inductance of the inductor L2 is 0.9 nH, the inductance of the inductor L4 is 0.01 nH, the inductance of the capacitor C1 is 0.9 pF, and the coupling coefficient k is 0.45 (additive polarity).

[0038] As shown in FIG. 6, the filter device 100A attenuates high-frequency signals in the attenuation band by parallel resonance, but is unable to effectively attenuate high-frequency signals sharply and significantly.

[0039] In contrast, as described above, in the filter device 100 according to the first embodiment, the inductor L1 and the inductor L2 are depolarized, causing a mutual inductance +M in the inductor L3. Therefore, the mutual inductance +M is added to the wiring inductance ESL, thereby increasing the inductance in the parallel resonance. As a result, the filter device 100 can increase the amount of attenuation of high-frequency signals due to the parallel resonance.

[0040] For example, Fig. 7 is a diagram showing an example of the insertion loss of the filter device 100 according to the first embodiment. In Fig. 7, a graph with frequency on the horizontal axis and insertion loss on the vertical axis shows the frequency characteristics of the insertion loss of the filter device 100. In the example of Fig. 7, the inductance of the inductor L1 is 0.5 nH, the inductance of the inductor L1 is 0.9 nH, the inductance of the inductor L4 is 0.01 nH, the inductance of the capacitor C1 is 0.9 pF, and the coupling coefficient k is 0.45 (depolarization).

[0041] As shown in FIG. 7, the filter device 100 in which the inductors L1 and L2 are depolarly coupled can attenuate high-frequency signals in the attenuation band more sharply and to a greater extent through parallel resonance than the filter device 100A in which the inductors L1A and L2A are additively coupled, and can pass high-frequency signals in the pass band with as little attenuation as possible through series resonance.

[0042] In this way, the filter device 100 can achieve good attenuation and passing characteristics while being miniaturized.

[0043] As will be described in detail later, in the filter device 100 according to the first embodiment, the inductors L3a and L3b are configured as part of the second external electrode 12. For this reason, the wiring inductance ESL shown in Fig. 4 can also be considered to be the same as the inductance of each of the inductors L3a and L3b.

[0044] FIG. 8 is an external view of a filter device 100 according to the first embodiment. The filter device 100 is formed, for example, as an integrated chip component, and includes an inductor and a capacitor disposed within an insulator 10 (housing) in which multiple dielectric layers are stacked. In FIG. 8 , the longitudinal direction of the filter device 100 (insulator 10) is designated the X direction, the lateral direction is designated the Y direction, and the height direction is designated the Z direction, with the stacking direction of the dielectric layers corresponding to the Z direction. The bottom surface (X-Y plane) of the filter device 100 is the mounting surface that is placed on a mounting substrate, and when the filter device 100 is mounted on the mounting substrate, the bottom surface faces the mounting substrate.

[0045] 8, the filter device 100 includes a first external electrode 11 and a second external electrode 12 that are electrically connected to an inductor pattern or an electrode pattern provided inside the insulator 10. The first external electrode 11 corresponds to the first terminal P1 described above. The second external electrode 12 corresponds to the second terminal P2 described above.

[0046] The first external electrode 11 has a U-shape and includes an external electrode 11a provided on the bottom surface (X-Y plane) of the insulator 10, an external electrode 11b provided on one side surface (X-Z plane) of the insulator 10, and an external electrode 11c provided on the other side surface (X-Z plane) of the insulator 10. The external electrode 11b faces the external electrode 11c, and the ends of the external electrodes 11b and 11c are connected to the ends of the external electrode 11a.

[0047] The second external electrode 12 is disposed at a predetermined distance from the first external electrode 11 along the longitudinal direction (X direction) of the filter device 100 (insulator 10). The second external electrode 12 has a U-shape and includes an external electrode 12a provided on the bottom surface (X-Y plane) of the insulator 10, an external electrode 12b provided on one side surface (X-Z plane) of the insulator 10, and an external electrode 12c provided on the other side surface (X-Z plane) of the insulator 10. The external electrode 12b faces the external electrode 12c, and the ends of the external electrodes 12b and 12c are connected to the ends of the external electrode 12a.

[0048] Fig. 9 is a perspective view showing the layered structure of the filter device 100 according to the first embodiment. Note that in Fig. 9, the outline of the insulator 10 is omitted to make it easier to understand the filter device 100. Figs. 10 and 11 are exploded plan views showing the layered structure of the filter device 100 according to the first embodiment.

[0049] 9 to 11 , the filter device 100 is formed by stacking a plurality of dielectric layers Ly1 to Ly8 in a stacking direction (Z direction) through a lamination process. Each of the dielectric layers Ly1 to Ly8 is a ceramic green sheet, and each electrode pattern and each inductor pattern are formed by printing a conductive paste (for example, Ni paste) on each of the dielectric layers Ly1 to Ly8 through a screen printing method.

[0050] The capacitor C1 is composed of electrode patterns r1 to r3 formed on the dielectric layers Ly1 to Ly3, respectively.

[0051] An electrode pattern r1 that constitutes a part of the capacitor C1 is formed on the dielectric layer Ly1. One end of the electrode pattern r1 is electrically connected to the second terminal P2 (the outer electrode 12b of the second outer electrode 12). The other end of the electrode pattern r1 is electrically connected to the second terminal P2 (the outer electrode 12c of the second outer electrode 12).

[0052] An electrode pattern r2 that constitutes a part of the capacitor C1 is formed on the dielectric layer Ly2. The electrode pattern r2 is electrically connected to neither the first terminal P1 nor the second terminal P2, and is also not electrically connected to any other electrode patterns.

[0053] An electrode pattern r3 that constitutes a part of the capacitor C1 is formed on the dielectric layer Ly3. The electrode pattern r3 is electrically connected to an end of the inductor pattern r4 on the dielectric layer Ly4 through a via conductor.

[0054] In this way, the capacitor C1 is constructed by utilizing the space formed between the electrode pattern r1 formed on the dielectric layer Ly1 and the electrode pattern r2 formed on the dielectric layer Ly2, and the space formed between the electrode pattern r2 formed on the dielectric layer Ly2 and the electrode pattern r3 formed on the dielectric layer Ly3.

[0055] The inductor L2 is composed of inductor patterns r4, r5, and r6 formed on the dielectric layers Ly4 to Ly6, respectively.

[0056] An inductor pattern r4 constituting a part of the inductor L2 is formed on the dielectric layer Ly4. The inductor pattern r4 is wound around the stacking direction as a winding axis, and is formed so as to make approximately one full turn clockwise on the dielectric layer Ly4. One end of the inductor pattern r4 is electrically connected to the electrode pattern r3 on the dielectric layer Ly3 via a via conductor. The other end of the inductor pattern r4 is electrically connected to a mid-path portion of the inductor pattern r5 on the dielectric layer Ly5 via a via conductor. The mid-path portion of the inductor pattern r4 is electrically connected to an end of the inductor pattern r5 on the dielectric layer Ly5 via a via conductor.

[0057] An inductor pattern r5 constituting a part of the inductor L2 is formed on the dielectric layer Ly5. The inductor pattern r5 is wound around the lamination direction as a winding axis, and is formed so as to make approximately one full turn clockwise on the dielectric layer Ly5. One end of the inductor pattern r5 is electrically connected to a mid-path portion of the inductor pattern r4 on the dielectric layer Ly4 via a via conductor. The other end of the inductor pattern r5 is electrically connected to an end of the inductor pattern r6 on the dielectric layer Ly6 via a via conductor. The mid-path portion of the inductor pattern r5 is electrically connected to an end of the inductor pattern r4 on the dielectric layer Ly4 via a via conductor.

[0058] An inductor pattern r6 constituting a part of the inductor L2 is formed on the dielectric layer Ly6. The inductor pattern r6 is wound around the stacking direction as a winding axis, and is formed on the dielectric layer Ly6 so as to make approximately one full turn clockwise in the drawing. One end of the inductor pattern r6 is electrically connected to the second terminal P2 (the external electrode 12c of the second external electrode 12). The other end of the inductor pattern r6 is electrically connected to an end of the inductor pattern r5 on the dielectric layer Ly5 through a via conductor.

[0059] In this way, in the inductor L2, when the insulator 10 is viewed from the stacking direction, the inductor pattern r4 of the dielectric layer Ly4, the inductor pattern r5 of the dielectric layer Ly5, and the inductor pattern r6 of the dielectric layer Ly6 are each configured to have a winding shape wound around the stacking direction as the winding axis.

[0060] The inductor L1 is composed of inductor patterns r7 and r8 formed on dielectric layers Ly7 and Ly8, respectively.

[0061] An inductor pattern r7 constituting a part of the inductor L1 is formed on the dielectric layer Ly7. The inductor pattern r7 is wound around the lamination direction as a winding axis, and is formed on the dielectric layer Ly7 so as to make approximately one full turn counterclockwise in the figure. One end of the inductor pattern r7 is electrically connected to the second terminal P2 (the external electrode 12c of the second external electrode 12). The other end of the inductor pattern r7 is electrically connected to a mid-path portion of the inductor pattern r8 on the dielectric layer Ly8 via a via conductor. The mid-path portion of the inductor pattern r7 is electrically connected to an end of the inductor pattern r8 on the dielectric layer Ly8 via a via conductor.

[0062] An inductor pattern r8 constituting a part of the inductor L1 is formed on the dielectric layer Ly8. The inductor pattern r8 is wound around the lamination direction as a winding axis, and is formed on the dielectric layer Ly8 so as to make approximately one full turn counterclockwise in the figure. One end of the inductor pattern r8 is electrically connected to a mid-path portion of the inductor pattern r7 on the dielectric layer Ly7 via a via conductor. The other end of the inductor pattern r8 is electrically connected to the first terminal P1 (the external electrode 11c of the first external electrode 11). The mid-path portion of the inductor pattern r8 is electrically connected to an end of the inductor pattern r7 on the dielectric layer Ly7 via a via conductor.

[0063] In this way, in the inductor L1, when the insulator 10 is viewed from the stacking direction, the inductor pattern r7 of the dielectric layer Ly7 and the inductor pattern r8 of the dielectric layer Ly8 are each configured to have a winding shape wound around the stacking direction as the winding axis.

[0064] In the filter device 100 configured as described above, the inductors L1 and L2 are arranged to face each other in the stacking direction, and at least a portion of the opening of the inductor L1 overlaps with the opening of the inductor L2 when the insulator 10 is viewed from the stacking direction. The larger the overlapping area between the openings of the inductors L1 and L2, the larger the coupling coefficient k between the inductors L1 and L2, and the larger the mutual inductance due to magnetic coupling.

[0065] Furthermore, as shown in FIG. 9, the inductor L3 (inductor L3a, inductor L3b) is formed by a part of the second external electrode 12 (external electrode 12c).

[0066] Specifically, a wiring inductance ESL exists in a part of the external electrode 12c between the end of the electrode pattern r1 connected to the external electrode 12c and the end of the inductor pattern r6 connected to the external electrode 12c. The wiring inductance ESL existing in the part of the external electrode 12c between the electrode pattern r1 and the inductor pattern r6 corresponds to the inductor L3a.

[0067] Furthermore, a wiring inductance ESL exists in a part of the external electrode 12c between the end of the inductor pattern r6 connected to the external electrode 12c and the end of the inductor pattern r7 connected to the external electrode 12c. This wiring inductance ESL existing in the part of the external electrode 12c between the inductor pattern r6 and the inductor pattern r7 corresponds to inductor L3b.

[0068] The electrical length of inductor L3a is longer than the electrical length of inductor L3b. For example, the linear distance between the end of electrode pattern r1, which corresponds to the electrical length of inductor L3a, and the end of inductor pattern r6 is longer than the linear distance between the end of inductor pattern r6 and the end of inductor pattern r7.

[0069] Furthermore, the electrical length of inductor L3 (the combined electrical length of inductors L3a and L3b) is shorter than the electrical length of inductor L1. For example, the linear distance between the end of electrode pattern r1 and the end of inductor pattern r7, which corresponds to the electrical length of inductor L3, is shorter than the combined length of inductor patterns r7 and r8, which corresponds to the electrical length of inductor L1. Furthermore, the electrical length of inductor L3 (the combined electrical length of inductors L3a and L3b) is shorter than the electrical length of inductor L2. For example, the linear distance between the end of electrode pattern r1 and the end of inductor pattern r7, which corresponds to the electrical length of inductor L3, is shorter than the combined length of inductor patterns r4 to r6, which correspond to the electrical length of inductor L2.

[0070] Furthermore, as shown in FIG. 9, the inductor L4 is formed by a part of the first external electrode 11 (external electrode 11c).

[0071] Specifically, a wiring inductance ESL exists in a part of the external electrode 11c between the end of the inductor pattern r8 connected to the external electrode 11c and the connection between the external electrode 11c and the external electrode 11a. This wiring inductance ESL existing in the part of the external electrode 11c extending from the end of the inductor pattern r8 to the external electrode 11a corresponds to the inductor L4.

[0072] The electrical length of inductor L3 (the combined electrical length of inductors L3a and L3b) is longer than the electrical length of inductor L4. For example, the linear distance between the end of electrode pattern r1 and the end of inductor pattern r7, which corresponds to the electrical length of inductor L3, is longer than the linear distance from the end of inductor pattern r8, which corresponds to the electrical length of inductor L4, to the external electrode 11a.

[0073] In the filter device 100 configured as described above, the depolarizing coupling between the inductor L1 and the inductor L2 generates a mutual inductance +M in the inductor L3 formed by a part of the external electrode 12c. As a result, the mutual inductance +M is further added to the inductor L3, which increases the inductance in parallel resonance, and the filter device 100 can increase the amount of attenuation of high-frequency signals due to parallel resonance.

[0074] The electrical length of inductor L3a is longer than the electrical length of inductor L3b, and therefore the inductance of inductor L3a is greater than the inductance of inductor L3b. In this way, the filter device 100 can increase the attenuation of high-frequency signals in the attenuation band due to parallel resonance by relatively increasing the inductance of inductor L3a, which performs parallel resonance with the resonant circuit RS, among the inductors L3.

[0075] For example, Fig. 12 is a diagram illustrating a comparative example of insertion loss due to differences in inductance in the filter device 100 according to the first embodiment. In Fig. 12, a graph with frequency on the horizontal axis and insertion loss on the vertical axis shows the frequency characteristics of insertion loss when the inductances of inductors L3a and L3b are the same (dotted line in the figure) and when the inductance of inductor L3a is greater than the inductance of inductor L3b (solid line in the figure). In the example of Fig. 12, the inductance of inductor L1 is 0.5 nH, the inductance of inductor L1 is 0.9 nH, the inductance of inductor L4 is 0.01 nH, the inductance of capacitor C1 is 0.9 pF, and the coupling coefficient k is 0.45 (depolarization). Furthermore, in the example where the inductances of inductors L3a and L3b are the same, the inductance of inductor L3a is 0.05 nH and the inductance of inductor L3b is 0.05 nH. On the other hand, in an example where the inductance of the inductor L3a is larger than the inductance of the inductor L3b, the inductance of the inductor L3a is 0.08 nH and the inductance of the inductor L3b is 0.02 nH.

[0076] As shown in FIG. 12, when the inductance of inductor L3a is larger than the inductance of inductor L3b (solid line in the figure), as in the filter device 100 according to embodiment 1, high-frequency signals can be attenuated more sharply and significantly in the attenuation band by parallel resonance than when the inductances of inductor L3a and inductor L3b are the same (dotted line in the figure).

[0077] The electrical length of inductor L3 (the combined electrical length of inductor L3a and inductor L3b) is longer than the electrical length of inductor L4, and therefore the inductance of inductor L3 is greater than the inductance of inductor L4. In this way, by increasing the inductance of inductor L3 that performs parallel resonance, the filter device 100 can increase the amount of attenuation of high-frequency signals in the attenuation band due to parallel resonance.

[0078] For example, Figure 13 is a diagram showing a comparative example of insertion loss due to differences in inductance in the filter device according to embodiment 1. In Figure 13, a graph with frequency on the horizontal axis and insertion loss on the vertical axis shows the frequency characteristics of insertion loss when the inductance of inductor L3 is smaller than a predetermined value (dotted line in the figure) and when the inductance of inductor L3 is larger than a predetermined value (solid line in the figure). Note that in the example of Figure 13, similar to the example of Figure 12, the inductance of inductor L1 is 0.5 nH, the inductance of inductor L1 is 0.9 nH, the inductance of inductor L4 is 0.01 nH, the inductance of capacitor C1 is 0.9 pF, and the coupling coefficient k is 0.45 (passive). Furthermore, in the example where the inductance of inductor L3 is smaller than a predetermined value, the inductance of inductor L3a is 0.05 nH, the inductance of inductor L3b is 0.05 nH, and the inductance of inductor L3 is 0.1 nH. On the other hand, in an example where the inductance of the inductor L3 is larger than the predetermined value, the inductance of the inductor L3a is 0.1 nH, the inductance of the inductor L3b is 0.1 nH, and the inductance of L3 is 0.2 nH.

[0079] As shown in FIG. 13, when the inductance of inductor L3 is large (solid line in the figure), as in the filter device 100 according to embodiment 1, high-frequency signals can be attenuated more sharply and significantly in the attenuation band by parallel resonance than when the inductance of inductor L3 is small (dotted line in the figure).

[0080] Furthermore, since the electrical length of inductor L4 is shorter than the electrical length of inductor L3 (the combined electrical length of inductors L3a and L3b), it can also be said that the inductance of inductor L4 is smaller than the inductance of inductor L3. In this way, by making the inductance of inductor L4, which can affect the attenuation of high-frequency signals in the pass band (f1 band), relatively small, the filter device 100 can obtain good pass characteristics without attenuating high-frequency signals in the pass band as much as possible.

[0081] As described above, the filter device 100 can achieve good attenuation and pass characteristics while being miniaturized.

[0082] 14 to 18, a filter device 200 according to a second embodiment will be described. Only the parts of the filter device 200 according to the second embodiment that are different from the filter device 100 according to the first embodiment will be described below.

[0083] 14 is a circuit diagram of a filter device 200 according to a second embodiment. As shown in FIG. 14, the filter device 200 according to the second embodiment includes a plurality of inductors as the inductor L1, and the number of inductors included in the inductor L1 is greater than the number of inductors included in the inductor L2. For example, the inductor L1 includes an inductor L1a and an inductor L1b connected in parallel between the inductor L4 and the resonant circuit RS. The inductors L1a and L1b are examples of a "first sub-inductor." The inductor L2 is an example of a "second sub-inductor."

[0084] One end of each of the parallel-connected inductors L1a and L1b is connected to inductor L4. The other end of each of the inductors L1a and L1b is connected to the second terminal P2 via a short-circuit path and to one end of inductor L3b. Each of the inductors L1a and L1b is connected to inductor L3b in series at the same potential. In the example of Fig. 14, each of the inductors L1a and L1b is depolarly coupled to inductor L2, generating a coupling coefficient k.

[0085] Furthermore, in the filter device 200 according to the second embodiment, the inductors (inductors L1a and L1b) included in the inductor L1 and the inductor L2 are stacked alternately one by one.

[0086] Fig. 15 is a perspective view showing the layered structure of filter device 200 according to embodiment 2. Note that in Fig. 15, the outline of insulator 10 is omitted to make it easier to understand filter device 200. Figs. 16 to 18 are exploded plan views showing the layered structure of filter device 200 according to embodiment 2.

[0087] 15 to 18, the filter device 200 is formed by stacking a plurality of dielectric layers Ly11 to Ly24 in the stacking direction (Z direction) through a lamination process. Each of the dielectric layers Ly11 to Ly24 is a ceramic green sheet, and each electrode pattern and each inductor pattern are formed by printing a conductive paste (for example, Ni paste) on each of the dielectric layers Ly11 to Ly24 through a screen printing method.

[0088] The capacitor C1 is composed of electrode patterns r11 to r13 formed on the dielectric layers Ly11 to Ly13, respectively.

[0089] An electrode pattern r11 that constitutes a part of the capacitor C1 is formed on the dielectric layer Ly11. One end of the electrode pattern r11 is electrically connected to the second terminal P2 (the outer electrode 12b of the second outer electrode 12). The other end of the electrode pattern r11 is electrically connected to the second terminal P2 (the outer electrode 12c of the second outer electrode 12).

[0090] An electrode pattern r12 that forms part of the capacitor C1 is formed on the dielectric layer Ly12. The electrode pattern r12 is electrically connected to neither the first terminal P1 nor the second terminal P2, and is also not electrically connected to any other electrode patterns.

[0091] An electrode pattern r13 that constitutes a part of the capacitor C1 is formed on the dielectric layer Ly13. The electrode pattern r13 is electrically connected to an end of the inductor pattern r14 on the dielectric layer Ly14 through a via conductor.

[0092] In this way, the capacitor C1 is constructed by utilizing the space formed between the electrode pattern r11 formed on the dielectric layer Ly11 and the electrode pattern r12 formed on the dielectric layer Ly12, and the space formed between the electrode pattern r12 formed on the dielectric layer Ly12 and the electrode pattern r13 formed on the dielectric layer Ly13.

[0093] The inductor L2 is composed of inductor patterns r14, r15, r16, r18, and r20 formed on the dielectric layers Ly14 to Ly18, respectively.

[0094] An inductor pattern r14 constituting a part of the inductor L2 is formed on the dielectric layer Ly14. The inductor pattern r14 is wound around the stacking direction as a winding axis, and is formed on the dielectric layer Ly14 so as to make approximately one full turn clockwise in the figure. One end of the inductor pattern r14 is electrically connected to the electrode pattern r13 on the dielectric layer Ly13 via a via conductor. The other end of the inductor pattern r14 is electrically connected to a mid-path portion of the inductor pattern r15 on the dielectric layer Ly15 via a via conductor. The mid-path portion of the inductor pattern r14 is electrically connected to an end of the inductor pattern r15 on the dielectric layer Ly15 via a via conductor.

[0095] An inductor pattern r15 constituting a part of the inductor L2 is formed on the dielectric layer Ly15. The inductor pattern r15 is wound around the lamination direction as a winding axis, and is formed so as to make approximately one full turn clockwise on the dielectric layer Ly15 in the figure. One end of the inductor pattern r15 is electrically connected to a mid-path portion of the inductor pattern r14 on the dielectric layer Ly14 via a via conductor. The other end of the inductor pattern r15 is electrically connected to the inductor pattern r16 on the dielectric layer Ly16 via a via conductor. The mid-path portion of the inductor pattern r15 is electrically connected to an end of the inductor pattern r14 on the dielectric layer Ly14 via a via conductor.

[0096] The inductor L1b is composed of inductor patterns r17 and r19 formed on the dielectric layers Ly16 and Ly17, respectively.

[0097] An inductor pattern r16 constituting a part of the inductor L2 is formed on the dielectric layer Ly16. The inductor pattern r16 is electrically connected to an end of the inductor pattern r15 on the dielectric layer Ly15 through a via conductor. Furthermore, the inductor pattern r16 is electrically connected to an end of the inductor pattern r18 on the dielectric layer Ly17 through a via conductor.

[0098] Furthermore, an inductor pattern r17 constituting a part of the inductor L1b is formed on the dielectric layer Ly16. The inductor pattern r17 is wound around the lamination direction as a winding axis, and is formed on the dielectric layer Ly16 so as to make approximately one full turn counterclockwise in the figure. One end of the inductor pattern r17 is electrically connected to the second terminal P2 (the external electrode 12c of the second external electrode 12). The other end of the inductor pattern r17 is electrically connected to a mid-path portion of the inductor pattern r19 on the dielectric layer Ly17 via a via conductor. The mid-path portion of the inductor pattern r17 is electrically connected to an end of the inductor pattern r19 on the dielectric layer Ly17 via a via conductor.

[0099] An inductor pattern r18 constituting a part of the inductor L2 is formed on the dielectric layer Ly17. One end of the inductor pattern r18 is electrically connected to the inductor pattern r16 on the dielectric layer Ly16 through a via conductor. Furthermore, the other end of the inductor pattern r18 is electrically connected to an end of the inductor pattern r20 on the dielectric layer Ly18 through a via conductor.

[0100] Furthermore, an inductor pattern r19 constituting a part of the inductor L1b is formed on the dielectric layer Ly17. The inductor pattern r19 is wound around the stacking direction as a winding axis, and is formed on the dielectric layer Ly17 so as to make approximately one full turn counterclockwise in the figure. One end of the inductor pattern r19 is electrically connected to a mid-path portion of the inductor pattern r17 on the dielectric layer Ly16 via a via conductor. The other end of the inductor pattern r19 is electrically connected to the first terminal P1 (the external electrode 11c of the first external electrode 11). The mid-path portion of the inductor pattern r19 is electrically connected to an end of the inductor pattern r17 on the dielectric layer Ly16 via a via conductor.

[0101] In this way, in the inductor L1b, when the insulator 10 is viewed from the stacking direction, the inductor pattern r17 of the dielectric layer Ly16 and the inductor pattern r19 of the dielectric layer Ly17 are each configured to have a winding shape wound around the stacking direction as the winding axis.

[0102] An inductor pattern r20 constituting a part of the inductor L2 is formed on the dielectric layer Ly18. The inductor pattern r20 is wound around the stacking direction as a winding axis, and is formed on the dielectric layer Ly18 so as to make approximately one full turn clockwise in the drawing. One end of the inductor pattern r20 is electrically connected to an end of the inductor pattern r18 on the dielectric layer Ly17 via a via conductor. The other end of the inductor pattern r20 is electrically connected to the second terminal P2 (the external electrode 12c of the second external electrode 12).

[0103] In this way, in inductor L2, when the insulator 10 is viewed from the stacking direction, the inductor pattern r14 of the dielectric layer Ly14, the inductor pattern r15 of the dielectric layer Ly15, and the inductor pattern r20 of the dielectric layer Ly18 are each configured to have a winding shape wound around the stacking direction as the winding axis.

[0104] The inductor L1a is composed of inductor patterns r21 and r22 formed on the dielectric layers Ly19 and Ly20, respectively.

[0105] An inductor pattern r21 constituting a part of the inductor L1a is formed on the dielectric layer Ly19. The inductor pattern r21 is wound around the lamination direction as a winding axis, and is formed on the dielectric layer Ly19 so as to make approximately one full turn counterclockwise in the figure. One end of the inductor pattern r21 is electrically connected to the second terminal P2 (the external electrode 12c of the second external electrode 12). The other end of the inductor pattern r21 is electrically connected to a mid-path portion of the inductor pattern r22 on the dielectric layer Ly20 via a via conductor. The mid-path portion of the inductor pattern r21 is electrically connected to an end of the inductor pattern r22 on the dielectric layer Ly20 via a via conductor.

[0106] An inductor pattern r22 constituting a part of the inductor L1a is formed on the dielectric layer Ly20. The inductor pattern r22 is wound around the stacking direction as a winding axis, and is formed on the dielectric layer Ly20 so as to make approximately one full turn counterclockwise in the figure. One end of the inductor pattern r22 is electrically connected to a mid-path portion of the inductor pattern r21 on the dielectric layer Ly19 via a via conductor. The other end of the inductor pattern r22 is electrically connected to the first terminal P1 (the external electrode 11c of the first external electrode 11). The mid-path portion of the inductor pattern r22 is electrically connected to an end of the inductor pattern r21 on the dielectric layer Ly19 via a via conductor.

[0107] In this way, in the inductor L1a, when the insulator 10 is viewed from the stacking direction, the inductor pattern r21 of the dielectric layer Ly19 and the inductor pattern r22 of the dielectric layer Ly20 are each configured to have a winding shape wound around the stacking direction as the winding axis.

[0108] An electrode pattern r23 is formed on the dielectric layer Ly21. One end of the electrode pattern r23 is electrically connected to the second terminal P2 (the external electrode 12b of the second external electrode 12), and the other end of the electrode pattern r23 is electrically connected to the second terminal P2 (the external electrode 12c of the second external electrode 12). A mid-path portion of the electrode pattern r23 is electrically connected to the electrode pattern r25 of the dielectric layer Ly22 through a via conductor.

[0109] Furthermore, an electrode pattern r24 is formed on the dielectric layer Ly21. One end of the electrode pattern r24 is electrically connected to the first terminal P1 (the external electrode 11b of the first external electrode 11), and the other end of the electrode pattern r24 is electrically connected to the first terminal P1 (the external electrode 11c of the first external electrode 11). A mid-path portion of the electrode pattern r24 is electrically connected to the electrode pattern r26 of the dielectric layer Ly22 through a via conductor.

[0110] An electrode pattern r25 is formed on the dielectric layer Ly22. The electrode pattern r25 is electrically connected to a mid-path portion of the electrode pattern r23 on the dielectric layer Ly21 through a via conductor. The electrode pattern r25 is also electrically connected to an electrode pattern r27 on the dielectric layer Ly23 through a via conductor.

[0111] Furthermore, an electrode pattern r26 is formed on the dielectric layer Ly22. The electrode pattern r26 is electrically connected to a mid-path portion of the electrode pattern r24 on the dielectric layer Ly21 through a via conductor. The electrode pattern r26 is also electrically connected to an electrode pattern r28 on the dielectric layer Ly23 through a via conductor.

[0112] An electrode pattern r27 is formed on the dielectric layer Ly23. The electrode pattern r27 is electrically connected to the electrode pattern r25 on the dielectric layer Ly22 through a via conductor. The electrode pattern r27 is also electrically connected to the second terminal P2 (the external electrode 12a of the second external electrode 12) through the via conductor.

[0113] Furthermore, an electrode pattern r28 is formed on the dielectric layer Ly23. The electrode pattern r28 is electrically connected to the electrode pattern r26 on the dielectric layer Ly22 through a via conductor. The electrode pattern r28 is also electrically connected to the first terminal P1 (the external electrode 11a of the first external electrode 11) through the via conductor.

[0114] Furthermore, as shown in FIG. 15, the inductor L3 (inductor L3a, inductor L3b) is formed by a part of the second external electrode 12 (external electrode 12c).

[0115] Specifically, a wiring inductance ESL exists in a part of the external electrode 12c between the end of the electrode pattern r11 connected to the external electrode 12c and the end of the inductor pattern r20 connected to the external electrode 12c. This wiring inductance ESL existing in the part of the external electrode 12c between the electrode pattern r11 and the inductor pattern r20 corresponds to the inductor L3a.

[0116] Furthermore, a wiring inductance ESL exists in a part of the external electrode 12c between the end of the inductor pattern r20 connected to the external electrode 12c and the end of the inductor pattern r21 connected to the external electrode 12c. This wiring inductance ESL existing in the part of the external electrode 12c between the inductor pattern r20 and the inductor pattern r21 corresponds to inductor L3b.

[0117] The electrical length of inductor L3a is longer than the electrical length of inductor L3b. For example, the linear distance between the end of electrode pattern r11, which corresponds to the electrical length of inductor L3a, and the end of inductor pattern r20 is longer than the linear distance between the end of inductor pattern r20, which corresponds to the electrical length of inductor L3b, and the end of inductor pattern r21.

[0118] Furthermore, the electrical length of inductor L3 (the combined electrical length of inductors L3a and L3b) is shorter than the electrical length of inductor L1 (the combined electrical length of inductors L1a and L1b). For example, the linear distance between the end of electrode pattern r11, which corresponds to the electrical length of inductor L3, and the end of inductor pattern r21 is shorter than the combined length of inductor patterns r17, r19, r21, and r22, which correspond to the electrical length of inductor L1. Furthermore, the electrical length of inductor L3 (the combined electrical length of inductors L3a and L3b) is shorter than the electrical length of inductor L2. For example, the linear distance between the end of electrode pattern r21, which corresponds to the electrical length of inductor L3, and the end of inductor pattern r21 is shorter than the combined length of inductor patterns r14, r15, r16, r18, and r20, which correspond to the electrical length of inductor L2.

[0119] Furthermore, as shown in FIG. 15, the inductor L4 is formed by a part of the first external electrode 11 (external electrode 11c).

[0120] Specifically, a wiring inductance ESL exists in a part of the external electrode 11c between the end of the inductor pattern r22 connected to the external electrode 11c and the connection between the external electrode 11c and the external electrode 11a. This wiring inductance ESL existing in the part of the external electrode 11c extending from the end of the inductor pattern r22 to the external electrode 11a corresponds to inductor L4.

[0121] The electrical length of inductor L3 (the combined electrical length of inductors L3a and L3b) is longer than the electrical length of inductor L4. For example, the linear distance between the end of electrode pattern r11 and the end of inductor pattern r21, which corresponds to the electrical length of inductor L3, is longer than the linear distance from the end of inductor pattern r22, which corresponds to the electrical length of inductor L4, to the external electrode 11a.

[0122] In the filter device 200 configured as described above, the depolarizing coupling between the inductor L1 and the inductor L2 generates a mutual inductance +M in the inductor L3 formed by a part of the external electrode 12c. As a result, the mutual inductance +M is further added to the inductor L3, which increases the inductance in parallel resonance, and the filter device 100 can increase the amount of attenuation of high-frequency signals due to parallel resonance.

[0123] Furthermore, in the filter device 200, the inductors L1a, L1b, and L2 are arranged to face each other in the stacking direction, and at least a portion of the openings of the inductors L1a and L1b overlaps with the opening of the inductor L2 when the insulator 10 is viewed in the stacking direction. The larger the area where the openings of the inductors L1a and L1b overlap with the opening of the inductor L2, the larger the coupling coefficient k between the inductors L1 (inductors L1a and L1b) and the inductor L2, and the larger the mutual inductance due to magnetic coupling.

[0124] Furthermore, in the filter device 200, the inductors L1 and L2 are arranged alternately in the stacking direction and are magnetically coupled. Specifically, as shown in Figures 15 to 18, the inductors L1a and L1b included in the inductor L1 and the inductor L2 are arranged alternately in the stacking direction.

[0125] For example, in the filter device 200, from the bottom surface on which the external electrodes 11a and 12a are provided toward the top surface, inductor patterns r21 and r22 constituting the inductor L1a (inductor L1), inductor pattern r20 constituting part of the inductor L2, inductor patterns r17 and r19 constituting the inductor L1b (inductor L1), and inductor patterns r14 and r15 constituting part of the inductor L2 are arranged in this order along the stacking direction.

[0126] In other words, the inductor pattern r20 constituting a part of the inductor L2 is arranged so as to be sandwiched in the stacking direction between the inductor patterns r21 and r22 constituting the inductor L1a (inductor L1) and the inductor patterns r17 and r19 constituting the inductor L1b (inductor L1). Moreover, the inductor patterns r17 and r19 constituting the inductor L1b (inductor L1) are arranged so as to be sandwiched in the stacking direction between the inductor pattern r20 constituting a part of the inductor L2 and the inductor patterns r14 and r15 constituting a part of the inductor L2.

[0127] According to the filter device 200 configured as described above, the coupling coefficient k between the inductor L1 (inductors L1a, L1b) and the inductor L2 can be increased by arranging the inductor L2 close to the multiple inductors L1a, L1b constituting the inductor L1, without increasing the number of turns of the inductor L2 or increasing the opening area of ​​the inductor L2. As a result, the filter device 200 can attenuate high-frequency signals more significantly through parallel resonance while being miniaturized, and can achieve good attenuation and pass characteristics.

[0128] <Modifications> The present disclosure is not limited to the above-described embodiment, and various modifications and applications are possible. Modifications that can be applied to the present disclosure will be described below.

[0129] The inductor L3 is not limited to being formed from a part of the external electrode 12c, but may be formed from a part of the external electrode 12a or 12b. The inductor L3 may be formed from at least one of the external electrodes 12a, 12b, and 12c, or may be formed from a combination of these two or more external electrodes. The inductor L3 is not limited to being formed from the second external electrode 12, but may be formed from a part of the first external electrode 11. Furthermore, the inductor L3 may be formed from an inductor pattern or an interlayer conductor formed in a dielectric layer within the insulator 10.

[0130] The inductor L4 is not limited to being formed from a part of the external electrode 11c, but may also be formed from a part of the external electrode 11a or 11b. The inductor L4 may be formed from at least one of the external electrodes 11a, 11b, and 11c, or may be formed from a combination of these two or more external electrodes. The inductor L4 is not limited to being formed from the first external electrode 11, but may also be formed from a part of the second external electrode 12. Furthermore, the inductor L4 may be formed from an inductor pattern or an interlayer conductor formed in a dielectric layer within the insulator 10.

[0131] The number of inductors included in inductor L1 may be one or more, and the number of inductors included in inductor L2 may be one or more. In the filter device of the present disclosure, at least one of inductor L1 and inductor L2 may include a plurality of inductors, and inductor L1 and inductor L2 may be arranged alternately in the stacking direction and magnetically coupled.

[0132] For example, the filter device may include one inductor L1 and a plurality of inductors L2, and the inductors may be arranged in the stacking direction such that the inductor L1 is sandwiched between the plurality of inductors L2.

[0133] For example, the filter device may include a plurality of inductors L1 and one inductor L2, and the inductors may be arranged in the stacking direction such that the inductors L1 sandwich the inductor L2.

[0134] For example, the filter device may include a plurality of inductors L1 and a plurality of inductors L2, with one inductor L1 and one inductor L2 alternately arranged in the stacking direction. Alternatively, the inductors may be arranged such that the plurality of inductors L1 sandwich the plurality of inductors L2 in the stacking direction. Furthermore, the inductors may be arranged such that the plurality of inductors L2 sandwich the plurality of inductors L1 in the stacking direction.

[0135] <Aspects> (Item 1) A filter device (100, 200) according to one aspect includes an insulator (10) including a first external electrode (11) and a second external electrode (12), a first inductor (L1) connected to the first external electrode, a resonant circuit (RS) including a second inductor (L2) and a capacitor (C1), and a third inductor (L3). The first inductor is connected to the second external electrode and also to the resonant circuit. The third inductor includes a resonant inductor (L3a) connected to both ends of the resonant circuit. The first inductor and the second inductor are magnetically coupled in a depolarized manner.

[0136] (Clause 2) The filter device described in clause 1 is a two-terminal filter consisting of a first external electrode and a second external electrode, which passes high-frequency signals in a first frequency band and attenuates high-frequency signals in a second frequency band lower than the first frequency band.

[0137] (Item 3) In the filter device according to item 1 or 2, the third inductor is formed by a part of the second external electrode.

[0138] (4) In the filter device according to any one of the first to third paragraphs, the electrical length of the third inductor is shorter than the electrical length of each of the first inductor and the second inductor.

[0139] (Item 5) In the filter device according to any one of items 1 to 4, the third inductor includes another inductor (L3b) provided between the first inductor and the resonant circuit, and the electrical length of the resonant inductor is longer than the electrical length of the other inductor.

[0140] (Item 6) The filter device according to any one of items 1 to 5, further comprising a fourth inductor (L4) provided between the first external electrode and the first inductor. The electrical length of the third inductor is longer than the electrical length of the fourth inductor.

[0141] (Item 7) In the filter device according to item 6, the fourth inductor is formed by a part of the first external electrode.

[0142] (Item 8) In the filter device according to any one of Items 1 to 7, the first inductor and the second inductor are stacked within an insulator. At least one of the first inductor and the second inductor includes a plurality of inductor patterns. The first inductors and the second inductors are alternately arranged in the stacking direction and are magnetically coupled.

[0143] (Item 9) In the filter device according to any one of items 1 to 8, the first inductor includes a plurality of first sub-inductors (L1a, L1b). The second inductor includes at least one second sub-inductor (L2). The at least one second sub-inductor is sandwiched between the plurality of first sub-inductors in the stacking direction.

[0144] (Item 10) An antenna device (1) according to one aspect includes a radiating element (50) that radiates a high-frequency signal in a first frequency band as radio waves, a power feeding circuit (RF1) that supplies the high-frequency signal in the first frequency band to the radiating element, and a filter device (100, 200) that is provided between the radiating element and the power feeding circuit.

[0145] (Item 11) An antenna module (3) according to one aspect includes a first antenna device (1) that emits a high-frequency signal in a first frequency band as a radio wave, and a second antenna device (2) that emits a high-frequency signal in a second frequency band as a radio wave. The first antenna device is the antenna device (1) described in item 10.

[0146] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not by the description of the above embodiments, and is intended to include all modifications within the meaning and scope of the claims.

[0147] 1, 2 Antenna device, 3 Antenna module, 10 Insulator, 11 First external electrode, 11a, 11b, 11c, 12a, 12b, 12c External electrode, 12 Second external electrode, 50, 60 Radiating element, 70 Substrate, 100, 100A, 200 Filter device, C1 Capacitor, ESL Wiring inductance, L1a, L1b, L1, L1A, L2A, L2, L3b, L3, L3a, L4 Inductor, P1 First terminal, P2 Second terminal, RF1, RF2 Power supply circuit, RS Resonant circuit, TL1 First path, TL2 Second path.

Claims

1. A filter device comprising: an insulator including a first external electrode and a second external electrode; a first inductor connected to the first external electrode; a resonant circuit including a second inductor and a capacitor; and a third inductor, wherein the first inductor is connected to the second external electrode and also to the resonant circuit, and the third inductor includes a resonant inductor connected to both ends of the resonant circuit, and the first inductor and the second inductor are magnetically coupled in a depolarized manner.

2. The filter device according to claim 1, which is a two-terminal filter consisting of the first external electrode and the second external electrode, passes high-frequency signals in a first frequency band and attenuates high-frequency signals in a second frequency band lower than the first frequency band.

3. A filter device according to claim 1 or 2, wherein the third inductor is formed of a part of the second external electrode.

4. A filter device according to any one of claims 1 to 3, wherein the electrical length of the third inductor is shorter than the electrical length of each of the first inductor and the second inductor.

5. A filter device as described in any one of claims 1 to 4, wherein the third inductor includes another inductor provided between the first inductor and the resonant circuit, and the electrical length of the resonant inductor is longer than the electrical length of the other inductor.

6. A filter device as described in any one of claims 1 to 5, further comprising a fourth inductor provided between the first external electrode and the first inductor, wherein the electrical length of the third inductor is longer than the electrical length of the fourth inductor.

7. The filter device according to claim 6, wherein the fourth inductor is formed as a part of the first external electrode.

8. A filter device as described in any one of claims 1 to 7, wherein the first inductor and the second inductor are stacked within the insulator, at least one of the first inductor and the second inductor includes a plurality of inductor patterns, and the first inductor and the second inductor are arranged alternately in the stacking direction and are magnetically coupled.

9. A filter device described in any one of claims 1 to 8, wherein the first inductor includes a plurality of first sub-inductors, the second inductor includes at least one second sub-inductor, and the at least one second sub-inductor is sandwiched between the plurality of first sub-inductors in the stacking direction.

10. An antenna device comprising: a radiating element that radiates a high-frequency signal in the first frequency band as radio waves; a power supply circuit that supplies the high-frequency signal in the first frequency band to the radiating element; and the filter device according to claim 2 that is provided between the radiating element and the power supply circuit.

11. An antenna module comprising: a first antenna device that radiates a high-frequency signal in the first frequency band as radio waves; and a second antenna device that radiates a high-frequency signal in the second frequency band as radio waves, wherein the first antenna device is the antenna device described in claim 10.

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