Filter device

Abstract

To improve attenuation characteristics in non-pass bands for a filter device having a plurality of resonators.SOLUTION: A filter device 100 includes: a laminate 110, an input terminal T1, an output terminal T2, a filter part 61 including resonators RC1 to RC4, and a filter part 62 including resonators RC5 to RC8. In the filter part 61, a signal from the input terminal T1 is transferred to the filter part 62 through the resonator RC1, the resonator RC2, the resonator RC3, and the resonator RC4 in this order. In the filter part 62, a signal from the filter part 61 is transferred to the output terminal T2 through the resonator RC5, the resonator RC6, the resonator RC7, and the resonator RC8 in this order. A cross coupling is formed between the resonator RC3 and the resonator RC6. Main coupling of one of a coupling between the resonator RC4 and the resonator RC5 and a coupling between the resonator RC3 and the resonator RC6 is magnetic coupling and main coupling of the other is electric field coupling.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a filter device, and more particularly to a technique for improving the attenuation characteristics of non-pass bands in a bandpass filter. [Background technology]

[0002] Japanese Patent No. 7111214 (Patent Document 1) and Japanese Patent Laid-Open No. 2020-198482 (Patent Document 2) disclose bandpass filters having a multistage configuration of multiple LC parallel resonators between an input terminal and an output terminal. In these documents, a sub-path including cross-coupling that bypasses some of the resonators is formed in a main path along which a signal is transmitted sequentially through multiple resonators from the input terminal to the output terminal. By forming such a sub-path including cross-coupling, an attenuation pole is added in the non-passband, thereby improving the attenuation characteristics in the non-passband compared to a case without a sub-path. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7111214 [Patent Document 2] Japanese Patent Publication No. 2020-198482 Summary of the Invention [Problem to be solved by the invention]

[0004] In the configuration of Japanese Patent No. 7111214 (Patent Document 1), cross-coupling is formed in the first-stage resonator closest to the input terminal and the final-stage resonator closest to the output terminal, and the resonators in the intermediate stages are arranged in order from the input terminal to the output terminal. In such a configuration, as the number of resonator stages increases, the spacing between the resonators becomes narrower, which may limit the adjustment range of the coupling degree in the intermediate-stage resonators and the degree of freedom in designing the cross-coupling.

[0005] In addition, in the case of JP 2020-198482 A (Patent Document 2), the resonators are arranged so that the direction of the main signal transmission path reverses midway. Therefore, compared to the configuration of JP 7111214 A (Patent Document 1), the degree of freedom in designing the cross-coupling in the intermediate stage is reduced. However, because the input terminal and output terminal are arranged adjacent to each other, the isolation between the input and output terminals is likely to decrease, which may lead to a decrease in attenuation characteristics.

[0006] The present disclosure has been made to solve such problems, and its purpose is to improve the attenuation characteristics of non-passbands in a filter device including a plurality of resonators. [Means for solving the problem]

[0007] A filter device according to an aspect of the present disclosure includes a dielectric substrate including a first main surface and a second main surface, an input terminal and an output terminal disposed on the second main surface, a first filter section, and a second filter section. The first filter section includes a first resonator, a second resonator, a third resonator, and a fourth resonator disposed within the dielectric substrate. The second filter section includes a fifth resonator, a sixth resonator, a seventh resonator, and an eighth resonator disposed within the dielectric substrate. In the first filter section, a signal transmitted from the input terminal is transmitted to the second filter section via the first resonator, the second resonator, the third resonator, and the fourth resonator in this order. In the second filter section, a signal transmitted from the first filter section is transmitted to the output terminal via the fifth resonator, the sixth resonator, the seventh resonator, and the eighth resonator in this order. A cross-coupling is formed between the third resonator and the sixth resonator. Of the coupling between the fourth resonator and the fifth resonator and the coupling between the third resonator and the sixth resonator, one of them is mainly magnetic coupling, and the other is mainly electric field coupling.

[0008] A filter device according to another aspect of the present disclosure includes an input terminal, an output terminal, first to fourth inductor circuits, first to third capacitor circuits, a first capacitor, and a second capacitor. The first capacitor is connected between the input terminal and a ground potential. The second capacitor is connected between the output terminal and a ground potential. The first inductor circuit is connected between the input terminal and the first capacitor circuit. The second inductor circuit is connected between the first capacitor circuit and the second capacitor circuit. The second inductor circuit is connected between the second capacitor circuit and the third capacitor circuit. The fourth inductor circuit is connected between the third capacitor circuit and the output terminal. The first inductor circuit and the second inductor circuit, the second inductor circuit and the third inductor circuit, and the third inductor circuit and the fourth inductor circuit are magnetically coupled. [Effects of the Invention]

[0009] According to the filter device according to the present disclosure, in a filter device including a plurality of resonators, it is possible to improve the attenuation characteristics of non-pass bands. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a block diagram of a communication device having a high-frequency front-end circuit to which a filter device according to a first embodiment is applied. [Figure 2] FIG. 2 is a diagram illustrating the topology of the filter device according to the first embodiment. [Figure 3] 1 is an equivalent circuit diagram of a filter device according to a first embodiment. [Figure 4] 1 is an external perspective view of a filter device according to a first embodiment. [Figure 5] FIG. 5 is an exploded perspective view showing an example of a layered structure of the filter device of FIG. 4. [Figure 6] FIG. 5 is a top view of the filter device of FIG. [Figure 7] FIG. 10 is a diagram for explaining the topology of a filter device of a comparative example. [Figure 8]5A and 5B are diagrams for explaining the filter characteristics of the filter devices of the first embodiment and the comparative example. [Figure 9] FIG. 10 is a diagram illustrating an example of a configuration for adjusting magnetic coupling between resonators. [Figure 10] 10A and 10B are diagrams illustrating a first example of adjusting magnetic coupling between resonators using ground vias. [Figure 11] FIG. 10 is a diagram showing a second example of adjusting magnetic coupling between resonators using ground vias. [Figure 12] FIG. 10 is a diagram showing a third example of adjusting magnetic coupling between resonators using ground vias. [Figure 13] FIG. 10 is a diagram illustrating an example of a configuration for adjusting electric field coupling between resonators. [Figure 14] FIG. 10 is an equivalent circuit diagram of a filter device according to a first modified example. [Figure 15] 10 is a diagram illustrating the configuration of a resonator in a filter device according to a second modification. FIG. [Figure 16] FIG. 10 is a diagram illustrating the topology of a filter device according to a second embodiment. [Figure 17] FIG. 10 is a diagram illustrating the topology of a filter device according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] 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.

[0012] [Embodiment 1] (Basic configuration of communication equipment) 1 is a block diagram of a communication device 10 having a high-frequency front-end circuit 20 to which a filter device 100 according to the first embodiment is applied. The communication device 10 is, for example, a mobile terminal such as a smartphone, or a mobile phone base station.

[0013] 1, a communication device 10 includes an antenna 12, a high-frequency front-end circuit 20, a mixer 30, a local oscillator 32, a D / A converter (DAC) 40, and an RF circuit 50. The high-frequency front-end circuit 20 also includes band-pass filters 22 and 28, an amplifier 24, and an attenuator 26. Although the description of FIG. 1 illustrates a case in which the high-frequency front-end circuit 20 includes a transmission circuit that transmits a high-frequency signal from the antenna 12, the high-frequency front-end circuit 20 may also include a reception circuit that receives a high-frequency signal via the antenna 12.

[0014] The communication device 10 upconverts a transmission signal transmitted from the RF circuit 50 to a high-frequency signal and radiates it from the antenna 12. The modulated digital signal output from the RF circuit 50, which is the transmission signal, is converted to an analog signal by the D / A converter 40. The mixer 30 upconverts the transmission signal, converted from digital to analog by the D / A converter 40, to a high-frequency signal by mixing it with an oscillation signal from the local oscillator 32. The bandpass filter 28 removes unwanted waves generated by the upconversion and extracts only the transmission signal in the desired frequency band. The attenuator 26 adjusts the intensity of the transmission signal. The amplifier 24 power-amplifies the transmission signal that has passed through the attenuator 26 to a predetermined level. The bandpass filter 22 removes unwanted waves generated during the amplification process and passes only signal components in the frequency band specified by the communication standard. The transmission signal that has passed through the bandpass filter 22 is radiated from the antenna 12.

[0015] A filter device according to the present disclosure can be employed as the bandpass filters 22, 28 in the communication device 10 described above.

[0016] (Configuration of filter device) Next, the configuration of the filter device 100 according to the first embodiment will be described with reference to FIGS.

[0017] (1) Topology of the filter device. Fig. 2 is a diagram illustrating a topology showing a coupling state between resonators in the filter device 100. Referring to Fig. 2, the filter device 100 according to the first embodiment has a configuration in which two filter sections 61 and 62 are cascade-connected between an input terminal T1 and an output terminal T2.

[0018] Each of the filter sections 61 and 62 is a bandpass filter including four resonators. That is, the filter device 100 is an eight-stage filter device including eight resonators. In FIG. 2, nodes indicated by numbers correspond to the respective resonators. The numbers indicated on the nodes indicate the order of the main signal transmission path (hereinafter also referred to as the "main path") from the input terminal T1 to the output terminal T2. In the following description, the numbers of each node may be used to express the "first-stage resonator" and the "second-stage resonator", etc.

[0019] In the filter sections 61 and 62, the resonators are electromagnetically coupled to each other along the main path. In reality, the resonators are coupled by both magnetic coupling and electric field coupling, but in this specification, the coupling state in which the strength is relatively strong will be referred to as the coupling state between the resonators.

[0020] In the filter units 61 and 62, in addition to a main path indicated by a solid line, there is a sub-path in which two resonators are coupled so as to bypass the series path of the main path. Specifically, in the filter unit 61, the couplings R12 between the first-stage resonator and the second-stage resonator, the coupling R23 between the second-stage resonator and the third-stage resonator, and the coupling R34 between the third-stage resonator and the fourth-stage resonator are the main paths, and the coupling R14 between the first-stage resonator and the fourth-stage resonator indicated by a dashed line is the sub-path. Similarly, in the filter unit 62, the couplings R56 between the fifth-stage resonator and the sixth-stage resonator, the coupling R67 between the sixth-stage resonator and the seventh-stage resonator, and the coupling R78 between the seventh-stage resonator and the eighth-stage resonator are the main paths, and the coupling R58 between the fifth-stage resonator and the eighth-stage resonator indicated by a dashed line is the sub-path.

[0021] Coupling through such a sub-path is generally called a “cross-coupling.” It is known that forming a “cross-coupling” can add an attenuation pole to a filter device.

[0022] In the filter device 100, the filter unit 61 and the filter unit 62 are configured to be coupled by two paths. One coupling is a coupling R45 between the fourth-stage resonator and the fifth-stage resonator, and the other coupling is a coupling R36 between the third-stage resonator and the sixth-stage resonator. The coupling R45 corresponds to the coupling of the main path, and the coupling R36 corresponds to the coupling of the sub-path, i.e., a "cross-coupling."

[0023] In the filter device 100 of the first embodiment, two filter sections are coupled via two paths, a main path and a sub-path, to form cross-coupling. This allows for the addition of attenuation poles in the non-pass band on the higher frequency side and the non-pass band on the lower frequency side of the pass band, compared to coupling via only the main path. Furthermore, in the filter device 100, one of the main path and the sub-path is coupled magnetically, and the other is coupled electric-field. This coupling state allows for a phase difference to occur between the paths. Therefore, using a topology like that of the filter device 100 allows for improved attenuation characteristics in the non-pass band.

[0024] (2) Equivalent circuit. Fig. 3 is an example of an equivalent circuit diagram of the filter device 100. In the equivalent circuit of Fig. 3, the filter device 100 includes four inductor circuits LC1 to LC4, three capacitor circuits CC1 to CC3, and capacitors C01 and C02.

[0025] Each of the inductor circuits LC1 to LC4 is a T-type circuit having three inductors. Specifically, the inductor circuit LC1 includes inductors L11 to L13, and the inductor L13 is connected between a connection node N1 of the series-connected inductors L11 and L12 and the ground potential GND.

[0026] Similarly, inductor circuit LC2 includes inductors L31-L33, with inductor L33 connected between connection node N3 of series-connected inductors L31 and L32 and ground potential GND. Inductor circuit LC3 includes inductors L51-L53, with inductor L53 connected between connection node N5 of series-connected inductors L51 and L52 and ground potential GND. Inductor circuit LC4 includes inductors L71-L73, with inductor L73 connected between connection node N7 of series-connected inductors L71 and L72 and ground potential GND.

[0027] Each of the capacitor circuits CC1 to CC3 is a T-type circuit having three capacitors. Specifically, the capacitor circuit CC1 includes capacitors C21 to C23, and the capacitor C23 is connected between a connection node N2 of the series-connected capacitors C21 and C22 and the ground potential GND.

[0028] Similarly, the capacitor circuit CC2 includes capacitors C41 to C43, with the capacitor C43 connected between a connection node N4 of the series-connected capacitors C41 and C42 and the ground potential GND. The capacitor circuit CC3 includes capacitors C61 to C63, with the capacitor C63 connected between a connection node N6 of the series-connected capacitors C61 and C62 and the ground potential GND.

[0029] The filter device 100 has a configuration in which inductor circuits and capacitor circuits are alternately connected between the input terminal T1 and the output terminal T2. Specifically, the inductor L11 in the inductor circuit LC1 is connected to the input terminal T1. The inductor L12 in the inductor circuit LC1 is connected to the capacitor C21 in the capacitor circuit CC1. The capacitor C22 in the capacitor circuit CC1 is connected to the inductor L31 in the inductor circuit LC2. The inductor L32 in the inductor circuit LC2 is connected to the capacitor C41 in the capacitor circuit CC2.

[0030] Capacitor C42 of capacitor circuit CC2 is connected to inductor L51 of inductor circuit LC3. Inductor L52 of inductor circuit LC3 is connected to capacitor C61 of capacitor circuit CC3. Capacitor C62 of capacitor circuit CC3 is connected to inductor L71 of inductor circuit LC4. Inductor L72 of inductor circuit LC4 is connected to output terminal T2.

[0031] Furthermore, the inductor L11 is connected to the ground terminal GND via a capacitor C01, and the inductor L72 of the inductor circuit LC4 is connected to the ground potential GND via a capacitor C02. Note that the inductor L11 may be connected to the input terminal T1 via a capacitor (not shown). Furthermore, the inductor L72 may be connected to the output terminal T2 via a capacitor (not shown).

[0032] 3, a first-stage resonator RC1 is formed by the capacitor C01 and the inductors L11 and L13 of the inductor circuit LC1. A second-stage resonator RC2 is formed by the inductors L12 and L13 of the inductor circuit LC1 and the capacitors C21 and C23 of the capacitor circuit CC1. A third-stage resonator RC3 is formed by the capacitors C22 and C23 of the capacitor circuit CC1 and the inductors L31 and L33 of the inductor circuit LC2.

[0033] A fourth-stage resonator RC4 is formed by the inductors L32 and L33 of the inductor circuit LC2 and the capacitors C41 and C43 of the capacitor circuit CC2. A fifth-stage resonator RC5 is formed by the capacitors C42 and C43 of the capacitor circuit CC2 and the inductors L51 and L53 of the inductor circuit LC3.

[0034] The sixth-stage resonator RC6 is formed by the inductors L52 and L53 of the inductor circuit LC3 and the capacitors C61 and C63 of the capacitor circuit CC3. The seventh-stage resonator RC7 is formed by the capacitors C62 and C63 of the capacitor circuit CC3 and the inductors L71 and L73 of the inductor circuit LC4. The eighth-stage resonator RC8 is formed by the inductors L72 and L73 of the inductor circuit LC4 and the capacitor C02.

[0035] Inductor L11 in inductor circuit LC1 and inductor L32 in inductor circuit LC2 are magnetically coupled (M14), and inductor L31 in inductor circuit LC2 and inductor L52 in inductor circuit LC3 are magnetically coupled (M36). Furthermore, inductor L51 in inductor circuit LC3 and inductor L72 in inductor circuit LC4 are magnetically coupled (M58). These magnetic couplings form cross-couplings between resonators RC1 and RC4, between resonators RC3 and RC6, and between resonators RC5 and RC8.

[0036] (3) Detailed configuration. Next, the detailed configuration of the filter device 100 will be described with reference to Fig. 4 to Fig. 6. Fig. 4 is an external perspective view of the filter device 100. Fig. 5 is an exploded perspective view showing an example of the layered structure of the filter device 100. Fig. 6 is a top view of the filter device 100.

[0037] 4 to 6, the filter device 100 includes a rectangular or approximately rectangular parallelepiped laminate 110 (dielectric substrate) in which a plurality of dielectric layers LY1 to LY8 are stacked in a stacking direction. The dielectric layers LY1 to LY8 are formed of ceramics such as low-temperature co-fired ceramics (LTCC) or resin. Inside the laminate 110, a plurality of electrodes provided on each dielectric layer and a plurality of vias provided between the dielectric layers form inductors and capacitors of an LC parallel resonator. In this specification, the term "via" refers to a conductor provided in a dielectric layer to connect electrodes provided on different dielectric layers. The vias are formed, for example, by conductive paste, plating, and / or metal pins.

[0038] In the following description, the stacking direction of the dielectric layers LY1 to LY8 in the laminate 110 is referred to as the "Z-axis direction," the direction perpendicular to the Z-axis direction and along the long side of the laminate 110 is referred to as the "X-axis direction," and the direction along the short side of the laminate 110 is referred to as the "Y-axis direction." In the following, the positive direction of the Z-axis in each drawing may be referred to as the upper side, and the negative direction may be referred to as the lower side.

[0039] A directionality mark DM for identifying the orientation of the filter device 100 is arranged on an upper surface 111 (dielectric layer LY1) of the laminate 110. External terminals (an input terminal T1, an output terminal T2, and a plurality of ground terminals GND) for connecting the filter device 100 to external devices are arranged on a lower surface 112 (dielectric layer LY8) of the laminate 110. The input terminal T1, the output terminal T2, and the ground terminal GND are each a flat electrode, and are LGA (Land Grid Array) terminals regularly arranged on the lower surface 112 of the laminate 110.

[0040] As described with reference to FIGS. 2 and 3, the filter device 100 has eight resonators RC1 to RC8, which are LC parallel resonators. More specifically, the resonator RC1 includes a via V1 and a capacitor electrode PC1. The resonator RC2 includes a via V2 and a capacitor electrode PC2. The resonator RC3 includes a via V3 and a capacitor electrode PC3. The resonator RC4 includes a via V4 and a capacitor electrode PC4. The resonator RC5 includes a via V5 and a capacitor electrode PC5. The resonator RC6 includes a via V6 and a capacitor electrode PC6. The resonator RC7 includes a via V7 and a capacitor electrode PC7. The resonator RC8 includes a via V8 and a capacitor electrode PC8.

[0041] Ground electrodes PG1 and PG2 are disposed on the dielectric layers LY2 and LY7 of the laminate 110, respectively, and are arranged over almost the entire surfaces of the dielectric layers. The ground electrodes PG1 and PG2 are connected to each other by a plurality of ground vias VG1. The ground electrode PG2 is connected to the ground terminal GND of the dielectric layer LY8 by a plurality of ground vias VG5.

[0042] The via V1 that defines the resonator RC1 passes from the input terminal T1 through the ground electrode PG2 disposed on the dielectric layer LY7 and is connected to the ground electrode PG1 disposed on the dielectric layer LY2. The via V1 is also connected to the capacitor electrode PC1 disposed on the dielectric layer LY4. The via V1 corresponds to the inductors L11 and L13 in FIG. 3.

[0043] The capacitor electrode PC1 is a flat plate electrode having a substantially rectangular shape. When viewed from a plane normal to the upper surface 111 of the laminate 110 (i.e., the Z-axis direction), at least a portion of the capacitor electrode PC1 overlaps with the ground electrode PG2. The capacitor electrode PC1 and the ground electrode PG2 define the capacitor C01 in FIG. 3. Therefore, the via V1 and the capacitor electrode PC1 form a one-sided open-circuit LC resonator.

[0044] The via V2 that defines the resonator RC2 has one end connected to the capacitor electrode PC2 disposed on the dielectric layer LY4 and the other end connected to the ground electrode PG1. The via V2 corresponds to the inductors L12 and L13 in FIG.

[0045] The capacitor electrode PC2 is disposed on the dielectric layer LY4 so as to be spaced apart from the capacitor electrode PC1 in the positive direction of the Y-axis. In addition, when viewed in a plan view from the Z-axis direction, at least a portion of the capacitor electrode PC2 overlaps with the capacitor electrode PC23 disposed on the dielectric layer LY5.

[0046] The capacitor electrode PC23 is a flat electrode having a substantially rectangular shape with its long sides extending in the X-axis direction. When viewed from above in the Z-axis direction, the capacitor electrode PC23 overlaps with the ground electrode PG2 of the dielectric layer LY7. The capacitor electrodes PC2 and PC23 define the capacitor C21 in FIG. 3. The capacitor electrode PC23 and the ground electrode PG2 define the capacitor C23 in FIG. 3. Therefore, the via V2 and the capacitor electrodes PC2 and PC23 form a one-sided open-circuit LC resonator.

[0047] The via V1 included in the resonator RC1 and the via V2 included in the resonator RC2 are connected to each other by a plate electrode PL12 disposed on the dielectric layer LY3. The plate electrode PL12 is a strip-shaped electrode extending in the Y-axis direction, with one end connected to the via V1 and the other end connected to the via V2. The plate electrode PL12 provides magnetic coupling as the main coupling between the resonators RC1 and RC2.

[0048] The via V3 that defines the resonator RC3 has one end connected to the capacitor electrode PC3 disposed on the dielectric layer LY4 and the other end connected to the ground electrode PG1. The via V3 corresponds to the inductors L31 and L33 in FIG.

[0049] Capacitor electrode PC3 is disposed on dielectric layer LY4 at a distance from capacitor electrode PC2 in the positive direction of the X-axis. In addition, when viewed from above in the Z-axis direction, at least a portion of capacitor electrode PC3 overlaps with capacitor electrode PC23 disposed on dielectric layer LY5. Capacitor electrode PC3 and capacitor electrode PC23 define capacitor C22 in FIG. 3. Therefore, via V3 and capacitor electrodes PC3 and PC23 form a one-sided open-circuit LC resonator.

[0050] Here, the capacitor electrode PC2 included in the resonator RC2 and the capacitor electrode PC3 included in the resonator RC3 share the capacitor electrode PC23, so that the main coupling between the resonators RC2 and RC3 is electric field coupling.

[0051] The via V4 that defines the resonator RC4 has one end connected to a capacitor electrode PC4 disposed on the dielectric layer LY4 and the other end connected to the ground electrode PG1. The via V4 corresponds to the inductors L32 and L33 in FIG.

[0052] The capacitor electrode PC4 is disposed on the dielectric layer LY4 so as to be spaced apart from the capacitor electrode PC3 in the negative direction of the Y-axis and spaced apart from the capacitor electrode PC1 in the positive direction of the X-axis. When viewed in a plan view from the Z-axis direction, at least a portion of the capacitor electrode PC4 overlaps with the capacitor electrode PC45 disposed on the dielectric layer LY5.

[0053] The capacitor electrode PC45 is a flat electrode having a substantially rectangular shape with its long sides extending in the X-axis direction. When viewed from above in the Z-axis direction, the capacitor electrode PC45 overlaps with the ground electrode PG2 of the dielectric layer LY7. The capacitor electrodes PC4 and PC45 define the capacitor C41 in FIG. 3. Alternatively, the capacitor electrode PC45 and the ground electrode PG2 define the capacitor C43 in FIG. 3. Therefore, the via V4 and the capacitor electrodes PC4 and PC45 form a one-sided open-circuit LC resonator.

[0054] The via V3 included in the resonator RC3 and the via V4 included in the resonator RC4 are connected to each other by a plate electrode PL34 disposed on the dielectric layer LY3. The plate electrode PL34 is a strip-shaped electrode extending in the Y-axis direction, with one end connected to the via V3 and the other end connected to the via V4. The plate electrode PL34 provides magnetic coupling as the main coupling between the resonators RC3 and RC4.

[0055] Since resonator RC4 is disposed adjacent to resonator RC1 in the X-axis direction, there is considerable coupling between resonator RC4 and resonator RC1. Specifically, magnetic coupling occurs between via V1 and via V4, and electric field coupling occurs between capacitor electrodes PC1 and PC4. The main coupling between resonators RC1 and RC4 is determined by the coupling strength between the vias and the coupling strength between the capacitor electrodes. This results in cross-coupling between resonators RC3 and RC4.

[0056] The via V5 that defines the resonator RC5 has one end connected to a capacitor electrode PC5 disposed on the dielectric layer LY4 and the other end connected to the ground electrode PG1. The via V5 corresponds to the inductors L51 and L53 in FIG.

[0057] The capacitor electrode PC5 is disposed on the dielectric layer LY4 so as to be spaced apart from the capacitor electrode PC4 in the positive direction of the X-axis. Furthermore, when viewed in a plan view from the Z-axis direction, at least a portion of the capacitor electrode PC5 overlaps with the capacitor electrode PC45 disposed on the dielectric layer LY5. The capacitor electrodes PC5 and PC45 define the capacitor C42 in FIG. 3. Therefore, the via V5 and the capacitor electrodes PC5 and PC45 form a one-sided open-circuit LC resonator.

[0058] Here, the capacitor electrode PC4 included in the resonator RC4 and the capacitor electrode PC5 included in the resonator RC5 share the capacitor electrode PC45, so that the main coupling between the resonators RC4 and RC5 is electric field coupling.

[0059] The via V6 that defines the resonator RC6 has one end connected to a capacitor electrode PC6 disposed on the dielectric layer LY4 and the other end connected to the ground electrode PG1. The via V6 corresponds to the inductors L52 and L53 in FIG.

[0060] Capacitor electrode PC6 is disposed on dielectric layer LY4 so as to be spaced apart from capacitor electrode PC4 in the positive direction of the Y-axis and spaced apart from capacitor electrode PC3 in the positive direction of the X-axis. In addition, when viewed in a plan view from the Z-axis direction, at least a portion of capacitor electrode PC6 overlaps with capacitor electrode PC67 disposed on dielectric layer LY5.

[0061] The capacitor electrode PC67 is a flat electrode having a substantially rectangular shape with its long sides extending in the X-axis direction, and is disposed apart from the capacitor electrode PC23 in the positive direction of the X-axis. The capacitor electrode PC67 overlaps with the ground electrode PG2 of the dielectric layer LY7 when viewed from above in the Z-axis direction. The capacitor electrodes PC6 and PC67 define the capacitor C61 in FIG. 3. The capacitor electrode PC67 and the ground electrode PG2 define the capacitor C63 in FIG. 3. Therefore, the via V6 and the capacitor electrodes PC6 and PC67 form a one-sided open-circuit LC resonator.

[0062] The via V5 included in the resonator RC5 and the via V6 included in the resonator RC6 are connected to each other by a plate electrode PL56 disposed on the dielectric layer LY3. The plate electrode PL56 is a strip-shaped electrode extending in the Y-axis direction, with one end connected to the via V5 and the other end connected to the via V6. The plate electrode PL56 provides magnetic coupling as the main coupling between the resonators RC5 and RC6.

[0063] Between the via V3 of the resonator RC3 and the via V6 of the resonator RC6, ground vias VG2, VG3, and VG4 are arranged, one end of which is connected to the ground electrode PG1 and the other end of which is connected to the ground electrode PG2. The ground vias VG2, VG3, and VG4 are arranged side by side in the Y-axis direction. The ground vias VG2, VG3, and VG4 are connected to each other by a plate electrode PL1 arranged on the dielectric layer LY5 and a plate electrode PL2 arranged on the dielectric layer LY6.

[0064] Because resonator RC6 is adjacent to resonator RC3 in the X-axis direction, there is a considerable degree of coupling between resonator RC6 and resonator RC3, forming cross-coupling. Ground vias VG2, VG3, and VG4 are adjustment vias for adjusting the degree of coupling between resonators RC3 and RC6. In the filter device 100, the placement of ground vias VG2, VG3, and VG4 allows the design to reduce magnetic coupling compared to a case where ground vias VG2, VG3, and VG4 are not present. The degree of magnetic coupling is adjusted by changing the number and spacing of the ground vias. The electric field components of the resonators in the filter device 100, including resonators RC3 and RC6, are concentrated near the capacitor electrodes, so the main coupling between resonators RC3 and RC6 is magnetic coupling.

[0065] The via V7 that defines the resonator RC7 has one end connected to the capacitor electrode PC7 arranged on the dielectric layer LY4 and the other end connected to the ground electrode PG1. The via V7 corresponds to the inductors L71 and L73 in FIG.

[0066] The capacitor electrode PC7 is disposed on the dielectric layer LY4 at a distance from the capacitor electrode PC6 in the positive direction of the X-axis. When viewed from above in the Z-axis direction, at least a portion of the capacitor electrode PC7 overlaps with the capacitor electrode PC67 disposed on the dielectric layer LY5. The capacitor electrodes PC6 and PC67 define the capacitor C62 in FIG. 3. Therefore, the via V7 and the capacitor electrodes PC7 and PC67 form a one-sided open-circuit LC resonator.

[0067] Here, the capacitor electrode PC6 included in the resonator RC6 and the capacitor electrode PC7 included in the resonator RC7 share the capacitor electrode PC67, so that the main coupling between the resonators RC6 and RC7 is electric field coupling.

[0068] The via V8 that defines the resonator RC8 has one end connected to the ground electrode PG1 and the other end passing through the ground electrode PG2 and connected to the output terminal T2 disposed on the dielectric layer LY8. The via V8 is also connected to the capacitor electrode PC8 disposed on the dielectric layer LY4. The via V8 corresponds to the inductors L72 and L73 in FIG. 3.

[0069] The capacitor electrode PC8 is a flat plate electrode having a substantially rectangular shape. When viewed from above in the Z-axis direction, at least a portion of the capacitor electrode PC8 overlaps with the ground electrode PG2. The capacitor electrode PC8 and the ground electrode PG2 define the capacitor C02 in FIG. 3. Therefore, the via V8 and the capacitor electrode PC8 form a one-sided open-circuit LC resonator.

[0070] The via V7 included in the resonator RC7 and the via V8 included in the resonator RC8 are connected to each other by a plate electrode PL78 disposed on the dielectric layer LY3. The plate electrode PL78 is a strip-shaped electrode extending in the Y-axis direction, with one end connected to the via V7 and the other end connected to the via V8. The plate electrode PL78 provides magnetic coupling as the main coupling between the resonators RC7 and RC8.

[0071] Since resonator RC8 is adjacent to resonator RC5 in the X-axis direction, there is some coupling between resonator RC8 and resonator RC5. Specifically, magnetic coupling occurs between via V5 and via V8, and electric field coupling occurs between capacitor electrodes PC5 and PC8. The main coupling between resonator RC5 and resonator RC8 is determined by the coupling strength between the vias and the coupling strength between the capacitor electrodes. This results in cross-coupling between resonators RC5 and RC8.

[0072] In the filter device 100 of the first embodiment, the resonators RC1 to RC4 define a four-stage bandpass filter (first filter section) having a cross-coupling between the resonators RC1 and RC4, and the resonators RC5 to RC8 define a four-stage bandpass filter (second filter section) having a cross-coupling between the resonators RC5 and RC8. These two bandpass filters are coupled by electric field coupling between the resonators RC4 and RC5 and magnetic coupling corresponding to the cross-coupling between the resonators RC3 and RC6. By coupling the two bandpass filters in two coupling states with different polarities and configuring one coupling as a cross-coupling, as described with reference to FIG. 2, it is possible to add attenuation poles to each of the non-passbands located higher and lower than the passband. This increases the degree of freedom in designing the attenuation poles, thereby improving the attenuation characteristics of the non-passbands in an eight-stage bandpass filter.

[0073] 6, the elements arranged in the laminate 110 are arranged symmetrically with respect to an imaginary line that passes through the center of the laminate 110 and is aligned along the Y axis. The symmetrical structure also makes the filter characteristics symmetrical, making it easier to adjust the degree of coupling between the resonators compared to a filter device with an asymmetrical structure. This increases the degree of freedom in design and makes it easier to achieve desired characteristics.

[0074] Furthermore, the input terminal T1 and the output terminal T2 are arranged at opposite ends of the long side of the laminate 110 (i.e., at the end in the positive direction and the end in the negative direction of the X-axis), and a ground terminal GND is arranged between the input terminal T1 and the output terminal T2, thereby improving the isolation between the input terminal T1 and the output terminal T2.

[0075] (4) Filter characteristics. Next, the filter characteristics of the filter device 100 according to the first embodiment will be described together with a comparative example with reference to Fig. 7 and Fig. 8. Fig. 7 is a diagram for explaining the topology of the filter device 100X according to the comparative example. Fig. 8 is a diagram for explaining the filter characteristics of the filter devices according to the first embodiment and the comparative example.

[0076] 7, the filter device 100X corresponds to the eight-stage filter device in the above-mentioned Patent Document 1 (Japanese Patent No. 7111214). Specifically, in the filter device 100X, cross-coupling is formed between the first-stage resonator and the third-stage resonator, and between the sixth-stage resonator and the eighth-stage resonator.

[0077] 8, the horizontal axis represents frequency, and the vertical axis represents the insertion loss of the filter device 100 (solid line LN10) and the insertion loss of the filter device 100X (dashed line LN11). The right diagram (B) of FIG. 8 is an enlarged view of the vertical axis in the left diagram (A).

[0078] As shown in the right diagram (B) of Fig. 8, the fractional bandwidth where the insertion loss is 3 dB is larger in the filter device 100 of the first embodiment than in the filter device 100X of the comparative example, and a wideband insertion characteristic is obtained. In the example of Fig. 8, the fractional bandwidth where the insertion loss is 3 dB is 54.4% in the filter device 100 and 51.5% in the filter device 100X.

[0079] On the other hand, as shown in the left diagram (A) of Fig. 8, the fractional bandwidth where the insertion loss is 25 dB is smaller in the filter device 100 of the first embodiment than in the filter device 100X of the comparative example. That is, the filter device 100 has a steeper attenuation characteristic than the filter device 100X. In the example of Fig. 8, the fractional bandwidth where the insertion loss is 25 dB is 59.3% in the filter device 100 and 60.1% in the filter device 100X.

[0080] As described above, the filter device 100 according to the first embodiment has a wider band and steeper attenuation characteristics than the filter device 100X according to the comparative example, and the attenuation characteristics in the non-pass bands are improved.

[0081] (5) Adjustment of coupling between resonators. 9 to 13, an example of a method for adjusting the degree of coupling between resonators in a filter device will be described. For ease of explanation, coupling between two resonators RC1 and RC2 will be described as an example in FIGS. 9 and 13.

[0082] First, a method for adjusting the magnetic coupling between resonators will be described with reference to Fig. 9. As described in Fig. 5, each resonator is an open-ended LC resonator in which one end is short-circuited to ground potential and the other end is opened by a capacitor.

[0083] In the case of one-sided open-circuit resonators, magnetic coupling between the resonators is achieved through coupling via the common ground electrode PG1 and coupling between the vias. Therefore, if you want to strengthen the magnetic coupling between two resonators, you can adjust it by connecting the two vias V1 and V2 with a common plate electrode PL12 as in the first example of Figure 9, or by shortening the distance L1 between the two vias V1 and V2 as in the second example.

[0084] Conversely, if it is desired to weaken the magnetic coupling, this can be adjusted by increasing the distance L1 between vias V1 and V2, or by forming a slit between vias V1 and V2 on the common ground electrode PG1, thereby effectively lengthening the distance between vias V1 and V2 on the ground electrode PG1.

[0085] Furthermore, as shown in Figures 10 to 12, the magnetic coupling can be adjusted by adjusting the number and / or position of ground vias placed between two resonators. Ground vias essentially function as a shield against magnetic coupling. Therefore, increasing the number of ground vias between resonators weakens the magnetic coupling between the resonators. The degree of magnetic coupling can also be adjusted by adjusting the position of the ground vias from the shortest path connecting the vias of the two resonators.

[0086] 10, the filter device 100A has a configuration in which the ground vias VG3 and VG4 between the resonators RC3 and RC6 in the filter device 100 shown in FIG. 6 are removed, and only the ground via VG2 is provided. In this case, the degree of magnetic coupling between the resonators RC3 and RC6 is stronger than in the filter device 100.

[0087] 11, in addition to the configuration of the filter device 100 shown in Fig. 6, ground vias VG6 are added between the resonators RC1 and RC4 and between the resonators RC5 and RC8. In this case, the magnetic coupling between the resonators RC1 and RC4 and between the resonators RC5 and RC8 is weakened compared to the filter device 100.

[0088] In the example of the filter device 100C in Fig. 12, in addition to the configuration in Fig. 11, ground vias VG7 are further added near the centers of the first filter section and the second filter section. In this case, it is possible to weaken the magnetic coupling between the resonators RC1 and RC3, between the resonators RC2 and RC4, between the resonators RC5 and RC7, and between the resonators RC6 and RC8. The ground vias VG7 eliminate unwanted magnetic coupling between the resonators, thereby suppressing unintended degradation of the filter characteristics.

[0089] Next, a method for adjusting the electric field coupling between resonators will be described with reference to Fig. 13. In the case of a one-sided open-type resonator, the electric field coupling between the resonators is realized by the coupling between the two capacitor electrodes PC1 and PC2. Therefore, if you want to strengthen the electric field coupling between two resonators, you can adjust it by shortening the adjacent distance between the two capacitor electrodes PC1 and PC2, as in the first example.

[0090] 5, the degree of coupling can also be adjusted by providing a capacitor electrode PC12, which is commonly coupled to both capacitor electrodes PC1 and PC2, between the capacitor electrodes PC1 and PC2 and the ground electrode PG2, as in the second example. In this case, the degree of coupling can be adjusted by adjusting the distance between the capacitor electrodes PC1 and PC2 and the capacitor electrode PC12 and / or the opposing area between the capacitor electrodes PC1 and PC2 and the capacitor electrode PC12.

[0091] Furthermore, as in the third example, by disposing a dielectric layer DL1 having a relatively high dielectric constant between the capacitor electrodes PC1, PC2 and the capacitor electrode PC12, the degree of electric field coupling can be further strengthened.

[0092] The capacitor electrode commonly coupled to the two resonators can be arranged on the upper side of the capacitor electrodes PC1 and PC2, i.e., on the ground electrode PG1 side, like the capacitor electrode PC12A in the fourth example. By arranging like the capacitor electrode PC12A, the distance from the ground electrode PG2 can be made larger than in the case of the capacitor electrode PC12 in the second example. This makes it possible to relatively increase the capacitance between the resonators, thereby strengthening the electric field coupling between the resonators.

[0093] (6) Variations. (Variation 1) In Modification 1, a different configuration of the capacitor circuit of the equivalent circuit shown in FIG. 3 will be described.

[0094] 14 is an equivalent circuit diagram of a filter device 100D of Modification 1. In the filter device 100D, capacitor circuits CC1A to CC3A of π-type circuits are arranged instead of the capacitor circuits CC1 to CC3 of T-type circuits in the filter device 100 of FIG.

[0095] Each of the capacitor circuits CC1A to CC3A includes three capacitors connected in series between the ground potential GND, and each connection node of the capacitors is connected to an adjacent inductor circuit. Specifically, the capacitor circuit CC1A includes capacitors C21A, C22A, and C23A. One end of the capacitor C23A is connected to the ground potential GND via the capacitor C21A, and the other end is connected to the ground potential GND via the capacitor C22A. A connection node N2A between the capacitors C21A and C23A is connected to the inductor L12 of the inductor circuit LC1. Furthermore, a connection node N2B between the capacitors C22A and C23A is connected to the inductor L31 of the inductor circuit LC2.

[0096] The capacitor circuit CC2A includes capacitors C41A, C42A, and C43A. One end of the capacitor C43A is connected to the ground potential GND via the capacitor C41A, and the other end is connected to the ground potential GND via the capacitor C42A. A connection node N4A between the capacitors C41A and C43A is connected to the inductor L32 of the inductor circuit LC3. A connection node N4B between the capacitors C42A and C43A is connected to the inductor L51 of the inductor circuit LC3.

[0097] The capacitor circuit CC3A includes capacitors C61A, C62A, and C63A. One end of the capacitor C63A is connected to the ground potential GND via the capacitor C61A, and the other end is connected to the ground potential GND via the capacitor C62A. A connection node N6A between the capacitors C61A and C63A is connected to the inductor L52 of the inductor circuit LC3. A connection node N6B between the capacitors C62A and C63A is connected to the inductor L71 of the inductor circuit LC4.

[0098] In this way, even in a configuration that employs a π-type capacitor circuit, by coupling two bandpass filters in a four-stage configuration using magnetic coupling and electric field coupling, and using cross-coupling coupling for one of the filters, it is possible to improve the attenuation characteristics in the non-passbands.

[0099] (Variation 2) In the second modification, a configuration in which a resonator of a different type from that in the first embodiment is used will be described.

[0100] Fig. 15 is a diagram for explaining the configuration of the resonators in the filter device of Modification 2. In Fig. 15, for ease of explanation, only the configurations of the resonators RC1 and RC2 are shown.

[0101] 15, in the filter device of Modification 2, each resonator is an open-ended resonator in which flat-plate-shaped capacitor electrodes are connected to both ends of a via. More specifically, resonator RC1 includes a via V1 and capacitor electrodes PC1A and PC1B. Capacitor electrode PC1A is connected to the end of via V1 on the ground electrode PG1 side and faces the ground electrode PG1. Capacitor electrode PC1B is connected to the end of via V1 on the ground electrode PG2 side and faces the ground electrode PG2. Resonator RC1 functions as a resonator due to the inductance component of via V1 and the capacitance components of capacitors formed by the capacitor electrode PC1A and the ground electrode PG1, and the capacitor electrode PC1B and the ground electrode PG2.

[0102] Similarly, in resonator RC2, a capacitor electrode PC2A is connected to the end of via V2 on the ground electrode PG1 side, and a capacitor electrode PC2B is connected to the end of via V2 on the ground electrode PG2 side. The other resonators RC3 to RC8 have the same configuration.

[0103] In this way, even when open-ended resonators are used as each resonator, the attenuation characteristics in the non-pass bands can be improved by coupling two band-pass filters in a four-stage configuration using magnetic coupling and electric field coupling, with one of the filters being cross-coupled.

[0104] When open-ended resonators are used, if it is desired to strengthen the magnetic coupling between the resonators, connecting adjacent resonators with a plate electrode as in embodiment 1 may result in the two resonators appearing as a single resonator, which may result in the resonators resonating in different modes. Therefore, it is preferable to adjust the magnetic coupling between the resonators by adjusting the distance between the vias of the resonators.

[0105] [Embodiment 2] In the second embodiment, a configuration in which the features of the present disclosure are applied to a 10-stage filter device will be described.

[0106] 16 is a diagram illustrating the topology of a filter device 100E according to the second embodiment. The filter device 100E is roughly configured such that one resonator is added between the first-stage resonator RC1 and the input terminal T1 and between the last-stage resonator RC8 and the output terminal T2 in the filter device 100 according to the first embodiment. That is, a filter unit 61A formed of second- to fifth-stage resonators corresponds to the filter unit 61 formed of the resonators RC1 to RC4 in the first embodiment, and a filter unit 62A formed of sixth- to ninth-stage resonators corresponds to the filter unit 62 formed of the resonators RC5 to RC8 in the first embodiment.

[0107] In the filter device 100E, the filter section 61A and the filter section 62A are coupled between the fifth-stage resonator and the sixth-stage resonator, and form a cross-coupling between the fourth-stage resonator and the seventh-stage resonator, with one coupling being a magnetic coupling and the other being an electric field coupling, thereby improving the attenuation characteristics in the non-pass bands, as in the filter device 100 of embodiment 1.

[0108] It is possible to configure the two additional resonators so that they are placed only on the input terminal T1 side or the output terminal T2 side. However, from the viewpoint of structural symmetry, it is preferable to place the resonators on the input terminal T1 side and the output terminal T2 side, as shown in FIG. 16.

[0109] [Embodiment 3] In the third embodiment, a configuration in which the features of the present disclosure are applied to a 12-stage filter device will be described.

[0110] Fig. 17 is a diagram for explaining the topology of the filter device of embodiment 3. The filter device 100F1 shown in the upper part (A) of Fig. 17 and the filter device 100F2 shown in the lower part (B) basically have the same configuration, but can be considered as follows in comparison with the configuration of embodiment 1.

[0111] 17A can be considered to have a configuration in which two resonators are added between the first-stage resonator RC1 and the input terminal T1 and between the final-stage resonator RC8 and the output terminal T2 in the filter device 100 of the first embodiment. In this case, a filter unit 61B constituted by the third-stage to sixth-stage resonators corresponds to the filter unit 61 of the first embodiment, and a filter unit 62B constituted by the seventh-stage to tenth-stage resonators corresponds to the filter unit 62 of the first embodiment.

[0112] Therefore, in the filter device 100F1, two four-stage filter sections are coupled by two paths, one of which is a cross-coupling, as in the case of the second embodiment. Therefore, the attenuation characteristics in the non-pass bands can also be improved in the filter device 100F1.

[0113] 17B, ​​the filter device 100F2 can be considered to have a four-stage configuration in which filter units 61C, 62C, and 63C are cascade-connected between the input terminal T1 and the output terminal T2. In this case, the pair of filter unit 61C and filter unit 62C and / or the pair of filter unit 62C and filter unit 63C correspond to the filter units 61 and 62 in the first embodiment.

[0114] Therefore, in the pair of filter unit 61C and filter unit 62C and the pair of filter unit 62C and filter unit 63C, two four-stage filter units are coupled by two paths, one of which is a cross-coupling. Therefore, the attenuation characteristics in the non-pass bands can be improved in the filter device 100F2 as well.

[0115] [Aspect] It will be appreciated by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

[0116] (Item 1) A filter device according to one aspect includes a dielectric substrate including a first main surface and a second main surface, an input terminal and an output terminal arranged on the second main surface, a first filter section, and a second filter section. The first filter section includes a first resonator, a second resonator, a third resonator, and a fourth resonator arranged in the dielectric substrate. The second filter section includes a fifth resonator, a sixth resonator, a seventh resonator, and an eighth resonator arranged in the dielectric substrate. In the first filter section, a signal transmitted from the input terminal is transmitted to the second filter section via the first resonator, the second resonator, the third resonator, and the fourth resonator in this order. In the second filter section, a signal transmitted from the first filter section is transmitted to the output terminal via the fifth resonator, the sixth resonator, the seventh resonator, and the eighth resonator in this order. A cross-coupling is formed between the third resonator and the sixth resonator. Of the coupling between the fourth resonator and the fifth resonator and the coupling between the third resonator and the sixth resonator, one of them is mainly magnetic coupling, and the other is mainly electric field coupling.

[0117] (Item 2) In the filter device described in item 1, a cross coupling is formed between the first resonator and the fourth resonator in the first filter section, and between the fifth resonator and the eighth resonator in the second filter section.

[0118] (Item 3) In the filter device according to item 2, the main coupling of the cross coupling between the first resonator and the fourth resonator and the cross coupling between the fifth resonator and the eighth resonator is magnetic coupling.

[0119] (Item 4) In the filter device according to item 2, the main coupling of the cross coupling between the first resonator and the fourth resonator and the cross coupling between the fifth resonator and the eighth resonator is electric field coupling.

[0120] (Item 5) The filter device according to any one of items 1 to 4 further includes a first ground electrode arranged opposite to the first principal surface, and a second ground electrode arranged between the first ground electrode and the second principal surface opposite to the second principal surface. Each resonator is arranged between the first ground electrode and the second ground electrode.

[0121] (Item 6) In the filter device described in item 5, each resonator includes a via having one end connected to the first ground electrode, and a flat electrode connected to the other end of the via and arranged opposite the second ground electrode.

[0122] (Item 7) The filter device according to item 6 further includes, in each of the first filter section and the second filter section, an inductor electrode that connects the vias of the two resonators whose main coupling is magnetic coupling.

[0123] (Item 8) In each of the first filter section and the second filter section of the filter device described in item 6, the distance between the vias of two resonators whose main coupling is magnetic coupling is shorter than the distance between the vias of two resonators whose main coupling is electric field coupling.

[0124] (Item 9) The first filter section and the second filter section of the filter device according to item 6 each further include capacitor electrodes arranged opposite the plate electrodes of the two resonators whose main coupling is electric field coupling.

[0125] (Item 10) In the filter device described in item 9, the dielectric substrate has a multilayer structure in which a plurality of dielectric layers are stacked. The dielectric constant of the dielectric layer disposed between the capacitor electrode and the plate electrode in the dielectric substrate is greater than the dielectric constant of the dielectric layers disposed in the other layers.

[0126] (Item 11) In each of the first filter section and the second filter section of the filter device described in item 6, the distance between the plate electrodes of two resonators whose main coupling is electric field coupling is shorter than the distance between the plate electrodes of two resonators whose main coupling is magnetic coupling.

[0127] (Clause 12) The filter device described in clause 6 further includes first to fourth inductor electrodes and first to third capacitor electrodes. The first inductor electrode connects the vias of the first and second resonators. The second inductor electrode connects the vias of the third and fourth resonators. The third inductor electrode connects the vias of the fifth and sixth resonators. The fourth inductor electrode connects the vias of the seventh and eighth resonators. The first capacitor electrode is arranged to face the plate electrodes of the second and third resonators. The second capacitor electrode is arranged to face the plate electrodes of the fourth and fifth resonators. The third capacitor electrode is arranged to face the plate electrodes of the sixth and seventh resonators.

[0128] (Item 13) In the filter device according to item 12, each of the first capacitor electrode, the second capacitor electrode, and the third capacitor electrode is disposed between the plate electrode and the second ground electrode of the corresponding resonator.

[0129] (Item 14) In the filter device according to item 12, each of the first capacitor electrode, the second capacitor electrode, and the third capacitor electrode is disposed between the plate electrode and the first ground electrode of the corresponding resonator.

[0130] (Item 15) In the filter device described in item 5, each resonator includes a first plate electrode, a second plate electrode, and a via. The first plate electrode is disposed opposite the first ground electrode. The second plate electrode is disposed opposite the second ground electrode. One end of the via is connected to the first plate electrode and the other end is connected to the second plate electrode.

[0131] (Item 16) A filter device according to one aspect includes an input terminal, an output terminal, first to fourth inductor circuits, first to third capacitor circuits, a first capacitor, and a second capacitor. The first capacitor is connected between the input terminal and a ground potential. The second capacitor is connected between the output terminal and a ground potential. The first inductor circuit is connected between the input terminal and the first capacitor circuit. The second inductor circuit is connected between the first capacitor circuit and the second capacitor circuit. The second inductor circuit is connected between the second capacitor circuit and the third capacitor circuit. The fourth inductor circuit is connected between the third capacitor circuit and the output terminal. The first inductor circuit and the second inductor circuit, the second inductor circuit and the third inductor circuit, and the third inductor circuit and the fourth inductor circuit are magnetically coupled.

[0132] (Item 17) In the filter device described in item 16, each inductor circuit includes a first terminal, a second terminal, and first to third inductors. The first inductor and the second inductor are connected in series between the first terminal and the second terminal. The third inductor is connected between a connection node of the first inductor and the second inductor and ground potential.

[0133] (Item 18) In the filter device according to item 16 or 17, each capacitor circuit includes a third terminal, a fourth terminal, and third to fifth capacitors. The third and fourth capacitors are connected in series between the third and fourth terminals. The fifth capacitor is connected between a connection node of the third and fourth capacitors and ground potential.

[0134] (Item 19) In the filter device according to item 16 or 17, each capacitor circuit includes a fifth terminal, a sixth terminal, and sixth to eighth capacitors. The sixth capacitor is connected between the fifth terminal and a ground potential. The seventh capacitor is connected between the sixth terminal and a ground potential. The eighth capacitor is connected between the fifth terminal and the sixth terminal.

[0135] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention 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. [Explanation of symbols]

[0136] 10 communication device, 12 antenna, 20 high frequency front end circuit, 22, 28 band pass filter, 24 amplifier, 26 attenuator, 30 mixer, 32 local oscillator, 40 D / A converter, 50 RF circuit, 61, 62, 61A to 61C, 62A to 62C, 63C filter section, 100, 100A to 100E, 100F1, 100F2, 100X filter device, 110 laminate, 111 upper surface, 112 lower surface, C01, C02, C21 to C23, C21A to C23A, C41 to C43, C41A to C43A, C61 to C63, C61A to C63A capacitor, CC1 to CC3, CC1A to CC3A capacitor circuit, DM direction mark, GND Ground terminals, L11 to L13, L31 to L33, L51 to L53, L71 to L73 Inductors, LC1 to LC4 Inductor circuit, DL1, LY1 to LY8 Dielectric layers, N1 to N7, N2A, N2B, N4A, N4B, N6A, N6B Connection nodes, PC1 to PC8, PC12, PC12A, PC1A, PC1B, PC23, PC2A, PC2B, PC45, PC67 Capacitor electrodes, PG1, PG2 Ground electrodes, PL1, PL2, PL12, PL34, PL56, PL78 Plate electrodes, R12, R14, R23, R34, R36, R45, R56, R58, R67, R78 Coupling, RC1 to RC8 Resonators, T1 input terminal, T2 output terminal, V1 to V8 Vias, VG1~VG7 ground vias.

Claims

1. a dielectric substrate including a first major surface and a second major surface; an input terminal and an output terminal disposed on the second main surface; a first filter section including a first resonator, a second resonator, a third resonator, and a fourth resonator arranged in the dielectric substrate; a second filter section including a fifth resonator, a sixth resonator, a seventh resonator, and an eighth resonator arranged in the dielectric substrate, in the first filter section, a signal transmitted from the input terminal is transmitted to the second filter section via the first resonator, the second resonator, the third resonator, and the fourth resonator in this order; in the second filter section, the signal transmitted from the first filter section is transmitted to the output terminal via the fifth resonator, the sixth resonator, the seventh resonator, and the eighth resonator in this order; a cross coupling is formed between the third resonator and the sixth resonator; a filter device, wherein one of the couplings between the fourth resonator and the fifth resonator and the coupling between the third resonator and the sixth resonator is a primary magnetic coupling, and the other of the couplings is a primary electric field coupling.

2. 2. The filter device according to claim 1, wherein a cross coupling is formed between the first resonator and the fourth resonator in the first filter section, and between the fifth resonator and the eighth resonator in the second filter section.

3. 3. The filter device according to claim 2, wherein a main coupling of the cross coupling between the first resonator and the fourth resonator and the cross coupling between the fifth resonator and the eighth resonator is magnetic coupling.

4. 3. The filter device according to claim 2, wherein a main coupling of the cross coupling between the first resonator and the fourth resonator and a main coupling of the cross coupling between the fifth resonator and the eighth resonator is electric field coupling.

5. a first ground electrode disposed opposite the first main surface; a second ground electrode disposed between the first ground electrode and the second main surface so as to face the second main surface, 5. The filter device according to claim 1, wherein each resonator is disposed between the first ground electrode and the second ground electrode.

6. Each resonator is a via having one end connected to the first ground electrode; The filter device according to claim 5 , further comprising: a plate electrode connected to the other end of the via and disposed opposite the second ground electrode.

7. 7. The filter device according to claim 6, further comprising an inductor electrode that connects vias of two resonators, the two resonators being primarily coupled by magnetic coupling, in each of the first filter section and the second filter section.

8. 7. The filter device according to claim 6, wherein in each of the first filter section and the second filter section, the distance between the vias of two resonators whose main coupling is magnetic coupling is shorter than the distance between the vias of two resonators whose main coupling is electric field coupling.

9. 7. The filter device according to claim 6, further comprising: capacitor electrodes disposed opposite to the plate electrodes of the two resonators, the main coupling of which is electric field coupling, in each of the first filter section and the second filter section.

10. the dielectric substrate has a multilayer structure in which a plurality of dielectric layers are stacked, 10. The filter device according to claim 9, wherein the dielectric layer disposed between the capacitor electrode and the plate electrode on the dielectric substrate has a dielectric constant greater than the dielectric constants of the dielectric layers disposed on other layers.

11. 7. The filter device according to claim 6, wherein in each of the first filter section and the second filter section, the distance between the plate electrodes of two resonators whose main coupling is electric field coupling is shorter than the distance between the plate electrodes of two resonators whose main coupling is magnetic coupling.

12. a first inductor electrode connecting the vias of the first resonator and the second resonator; a second inductor electrode connecting the vias of the third resonator and the fourth resonator; a third inductor electrode connecting the vias of the fifth resonator and the sixth resonator; a fourth inductor electrode connecting the vias of the seventh resonator and the eighth resonator; a first capacitor electrode disposed to face the plate electrode of the second resonator and the plate electrode of the third resonator; a second capacitor electrode disposed to face the plate electrode of the fourth resonator and the plate electrode of the fifth resonator; 7. The filter device according to claim 6, further comprising: a third capacitor electrode disposed so as to face the plate electrode of the sixth resonator and the plate electrode of the seventh resonator.

13. 13. The filter device according to claim 12, wherein each of the first capacitor electrode, the second capacitor electrode, and the third capacitor electrode is disposed between a plate electrode of a corresponding resonator and the second ground electrode.

14. 13. The filter device according to claim 12, wherein each of the first capacitor electrode, the second capacitor electrode, and the third capacitor electrode is disposed between a plate electrode of a corresponding resonator and the first ground electrode.

15. Each resonator is a first flat plate electrode disposed opposite the first ground electrode; a second plate electrode disposed opposite the second ground electrode; 6. The filter device according to claim 5, further comprising a via having one end connected to the first plate electrode and the other end connected to the second plate electrode.

16. input terminals and output terminals; a first inductor circuit, a second inductor circuit, a third inductor circuit, and a fourth inductor circuit; a first capacitor circuit, a second capacitor circuit, and a third capacitor circuit; a first capacitor connected between the input terminal and a ground potential; a second capacitor connected between the output terminal and the ground potential; the first inductor circuit is connected between the input terminal and the first capacitor circuit; the second inductor circuit is connected between the first capacitor circuit and the second capacitor circuit; the second inductor circuit is connected between the second capacitor circuit and the third capacitor circuit; the fourth inductor circuit is connected between the third capacitor circuit and the output terminal; The filter device, wherein the first inductor circuit and the second inductor circuit, the second inductor circuit and the third inductor circuit, and the third inductor circuit and the fourth inductor circuit are magnetically coupled.

17. Each inductor circuit is a first terminal and a second terminal; a first inductor and a second inductor connected in series between the first terminal and the second terminal; 17. The filter device according to claim 16, further comprising: a third inductor connected between a connection node of the first inductor and the second inductor and the ground potential.

18. Each capacitor circuit is a third terminal and a fourth terminal; a third capacitor and a fourth capacitor connected in series between the third terminal and the fourth terminal; 18. The filter device according to claim 16, further comprising: a fifth capacitor connected between a connection node of the third capacitor and the fourth capacitor and the ground potential.

19. Each capacitor circuit is a fifth terminal and a sixth terminal; a sixth capacitor connected between the fifth terminal and the ground potential; a seventh capacitor connected between the sixth terminal and the ground potential; 18. The filter device according to claim 16 or 17, further comprising an eighth capacitor connected between the fifth terminal and the sixth terminal.

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