Filter device and high frequency front-end circuit

Abstract

To provide a filter device including multi-stage resonators, the filter device being capable of preventing a reduction of attenuation characteristics caused by capacitive coupling between the resonators, and a radio-frequency front-end circuit including the filter device.SOLUTION: A filter device 100 includes: a stacked body; an input terminal, an output terminal T2, and a ground terminal GND; a ground electrode PG1; two resonators disposed in a signal transmission path between the input terminal and the output terminal, in a layer between an upper surface and the ground electrode; and a coupling electrode PC45 coupling the two resonators via capacitive coupling. The resonators respectively include capacitor electrodes PC40, PC50 defining capacitors with the ground electrode. The coupling electrode is connected to the capacitor electrode PC40 and defines a capacitor with the capacitor electrode PC50. The coupling electrode includes electrodes P1, P2 which each have a first end and a second end. The first end of the electrode P1 and the first end of the electrode P2 are connected to each other, and the second end of the electrode P1 and the second end of the electrode P2 are connected to the capacitor electrode PC40.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a filter device and a high-frequency front-end circuit, and more particularly to a technique for improving the attenuation characteristics of a filter device. [Background technology]

[0002] International Publication No. 2021 / 079737 (Patent Document 1) discloses a filter device including multiple stages of LC parallel resonators. In the filter device disclosed in Patent Document 1, adjacent resonators are electromagnetically coupled to each other and are also capacitively coupled using capacitors, thereby transmitting a signal in a desired frequency band from an input terminal to an output terminal. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2021 / 079737 Summary of the Invention [Problem to be solved by the invention]

[0004] In a filter device such as that disclosed in Patent Document 1, capacitive coupling between adjacent resonators is achieved by a capacitor formed by a plate electrode extending from one resonator and a plate electrode included in the other resonator.

[0005] In this case, the plate electrode extending from one of the resonators actually has a certain length and therefore functions as an inductor with a certain inductance value. As a result, the plate electrode constituting the capacitor itself becomes a distributed parameter LC parallel resonator, which may result in an unintended decrease in attenuation characteristics near the resonant frequency of the plate electrode.

[0006] In recent years, communications have been conducted based on multiple communication standards using different frequency bands. If the attenuation characteristics of a filter device in a frequency band other than the pass band (i.e., a non-pass band) targeted by the filter device are degraded, it may adversely affect other communication devices that use the non-pass band. Furthermore, in the filter device, signals in the frequency band with degraded attenuation characteristics may appear as noise.

[0007] The present disclosure has been made to solve such problems, and its purpose is to suppress the deterioration of attenuation characteristics caused by capacitive coupling between resonators in a filter device including multiple stages of resonators. [Means for solving the problem]

[0008] A filter device according to the present disclosure includes a laminate including a plurality of dielectric layers stacked together, an input terminal, an output terminal, and a ground terminal, a ground electrode connected to the ground terminal, a first resonator, a second resonator, and a coupling electrode. The laminate has a first surface and a second surface. The input terminal, the output terminal, and the ground terminal are disposed on the second surface of the laminate. The ground electrode is disposed inside the laminate. The first resonator and the second resonator are disposed on a signal transmission path from the input terminal to the output terminal in a layer between the first surface and the ground electrode. The coupling electrode capacitively couples the first resonator and the second resonator. The first resonator and the second resonator each include a first capacitor electrode and a second capacitor electrode that form a capacitor with the ground electrode. The coupling electrode is connected to the second capacitor electrode and forms a capacitor with the first capacitor electrode. The coupling electrode includes a first electrode and a second electrode, each having a first end and a second end. The first end of the first electrode is connected to the first end of the second electrode. A second end of the first electrode and a second end of the second electrode are connected to a second capacitor electrode. [Effects of the Invention]

[0009] In a filter device according to the present disclosure, a coupling electrode for forming capacitive coupling between adjacent resonators includes two electrodes, with one end of each electrode electrically connected to the other and the other end electrically connected to the other. That is, the coupling electrode is configured with two paths connected in parallel to each other. This allows the inductance value of the coupling electrode to be reduced compared to when the coupling electrode is configured with a single path, thereby increasing the resonant frequency of the coupling electrode. Therefore, by appropriately adjusting the configuration of the coupling electrode and setting the resonant frequency of the coupling electrode higher than the non-pass band defined by the specifications, it is possible to suppress a decrease in attenuation characteristics in the non-pass band. [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 an embodiment of the present invention is applied. [Figure 2] 1 is an equivalent circuit diagram of a filter device according to an embodiment of the present invention; [Figure 3] 1 is an external perspective view of a filter device according to an embodiment; [Figure 4] FIG. 4 is an exploded perspective view showing an example of a layered structure of the filter device of FIG. 3. [Figure 5] 5 is a partially enlarged perspective view of the filter device of FIG. 4. FIG. [Figure 6] FIG. 6 is an enlarged partial plan view of the filter device of FIG. 5. [Figure 7] 10A and 10B are diagrams illustrating coupling electrodes in a filter device according to an embodiment and a filter device according to a comparative example. [Figure 8] 10A and 10B are diagrams for explaining filter characteristics in the filter devices of the embodiment and the comparative example. [Figure 9] FIG. 10 is a partially enlarged perspective view of a filter device according to a first modified example. [Figure 10] FIG. 10 is a partially enlarged perspective view of a filter device according to a second modification. [Figure 11] FIG. 11 is a partially enlarged perspective view of a filter device according to a third modified example. [Figure 12] FIG. 10 is a partially enlarged perspective view of a filter device according to a fourth modified example. [Figure 13] FIG. 13 is a partially enlarged perspective view of a filter device according to a fifth modified example. 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 Mode] (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 according to an 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 detailed configuration of the filter device 100 according to the embodiment will be described with reference to FIGS.

[0017] (1) Equivalent circuit Fig. 2 is an equivalent circuit diagram of the filter device 100. Referring to Fig. 2, the filter device 100 includes an input terminal T1, an output terminal T2, and resonators RC1 to RC5. Each of the resonators RC1 to RC5 is an LC parallel resonator in which an inductor and a capacitor are connected in parallel.

[0018] The resonator RC1 is connected to the input terminal T1 via the capacitor C0. The resonator RC1 includes inductors L1, L12, L6 and a capacitor C1. The inductors L1, L12, L6 are connected in series between a connection node N1A with the capacitor C0 and the ground terminal GND. The capacitor C1 is also connected between the connection node N1A and the ground terminal GND. In other words, the resonator RC1 is an LC parallel resonator in which the composite inductor formed by the series-connected inductors L1, L12, L6 and the capacitor C1 are connected in parallel.

[0019] The resonator RC2 includes inductors L2, L12, and L6 and a capacitor C2. One end of the inductor L2 is connected to a connection node N2B between the inductors L1 and L12. The other end of the inductor L2 is connected to the ground terminal GND via the capacitor C2. In other words, the resonator RC2 is an LC parallel resonator in which the composite inductor formed by the series-connected inductors L2, L12, and L6 is connected in parallel with the capacitor C2.

[0020] A connection node N2A between the inductor L2 and the capacitor C2 is connected to a connection node N1A in the resonator RC1 via the capacitor C12, that is, the resonator RC2 is capacitively coupled to the resonator RC1 by the capacitor C12.

[0021] The resonator RC3 includes inductors L3 and L6 and a capacitor C3. One end of the inductor L3 is connected to a connection node N3B between the inductors L12 and L6. The other end of the inductor L3 is connected to the ground terminal GND via the capacitor C3. That is, the resonator RC3 is an LC parallel resonator in which the composite inductor formed by the series-connected inductors L3 and L6 and the capacitor C3 are connected in parallel.

[0022] A connection node N3A between the inductor L3 and the capacitor C3 is connected to a connection node N2A in the resonator RC2 via the capacitor C23, that is, the resonator RC3 is capacitively coupled to the resonator RC2 by the capacitor C23.

[0023] The resonator RC4 includes inductors L4, L45, and L6 and a capacitor C4. One end of the inductor L4 is connected to one end of the inductor L45. The other end of the inductor L4 is connected to the ground terminal GND via the capacitor C4. The other end of the inductor L45 is connected to a connection node N3B between the inductors L3 and L6 in the resonator RC3. In other words, the resonator RC4 is an LC parallel resonator in which the composite inductor formed by the series-connected inductors L4, L45, and L6 is connected in parallel with the capacitor C4.

[0024] A connection node N4A between the inductor L4 and the capacitor C4 is connected to a connection node N3A in the resonator RC3 via the capacitor C34, that is, the resonator RC4 is capacitively coupled to the resonator RC3 by the capacitor C34.

[0025] The resonator RC5 includes inductors L5, L45, and L6 and a capacitor C5. One end of the inductor L5 is connected to a connection node N4B between the inductors L4 and L45 in the resonator RC4. The other end of the inductor L5 is connected to the ground terminal GND via the capacitor C5. That is, the resonator RC5 is an LC parallel resonator in which the composite inductor formed by the series-connected inductors L5, L45, and L6 is connected in parallel with the capacitor C5.

[0026] A connection node N5A between the inductor L5 and the capacitor C5 is connected to a connection node N4A in the resonator RC4 via a capacitor C45. That is, the resonator RC5 is capacitively coupled to the resonator RC4 via the capacitor C45. The connection node N5A in the resonator RC5 is connected to the output terminal T2 via a capacitor C6. Furthermore, a capacitor C15 is connected between the connection node N5A in the resonator RC5 and the connection node N1A in the resonator RC1.

[0027] As described above, the inductor L12 is shared by the resonators RC1 and RC2. Similarly, the inductor L45 is shared by the resonators RC4 and RC5. Furthermore, the inductor L6 is shared by the resonators RC1 to RC5.

[0028] The resonators are magnetically coupled to one another. Thus, the filter device 100 has a configuration in which five stages of resonators, which are magnetically and capacitively coupled to one another, are arranged in a signal transmission path between the input terminal T1 and the output terminal T2. By adjusting the resonant frequency of each resonator, the filter device 100 functions as a bandpass filter that passes signals in a desired frequency band. Note that the number of resonators included in the filter device is merely an example, and the features of the present disclosure are applicable to filter devices including two or more resonators.

[0029] (2)Detailed structure Next, the structure of the filter device 100 will be described with reference to Figures 3 and 4. Figure 3 is an external perspective view of the filter device 100, and Figure 4 is an exploded perspective view showing an example of the layered structure of the filter device 100.

[0030] 3 and 4, the filter device 100 includes a rectangular or approximately rectangular parallelepiped laminate 110 in which a plurality of dielectric layers LY1 to LY10 are stacked in a stacking direction. The dielectric layers LY1 to LY10 are formed of ceramics such as low-temperature co-fired ceramics (LTCC) or resin. Inside the laminate 110, inductors and capacitors of an LC parallel resonator are formed by a plurality of electrodes provided on each dielectric layer and a plurality of vias provided between the dielectric layers. 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 by, for example, conductive paste, plating, and / or metal pins.

[0031] In the following description, the stacking direction of the dielectric layers LY1 to LY10 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.

[0032] 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 LY10) 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.

[0033] As described in FIG. 2, the filter device 100 has five resonators RC1 to RC5, which are LC parallel resonators. More specifically, the resonator RC1 includes a via V10, a capacitor electrode PC10, and a plate electrode PL12. The resonator RC2 includes vias V20 and V21, a capacitor electrode PC20, and a plate electrode PL12. The resonator RC3 includes a via V30 and a capacitor electrode PC30. The resonator RC4 includes vias V40 and V41, a capacitor electrode PC40, and a plate electrode PL45. The resonator RC5 includes a via V50, a capacitor electrode PC50, and a plate electrode PL45.

[0034] The input terminal T1 is connected to a capacitor electrode PC01 disposed on the dielectric layer LY7 by vias V01 and V02, which are offset in the dielectric layer LY9.

[0035] The capacitor electrode PC10 of the resonator RC1 is disposed on the dielectric layer LY6. A portion of the capacitor electrode PC10 overlaps with the capacitor electrode PC01 on the dielectric layer LY7 when viewed in a plan view from the stacking direction (Z-axis direction) of the laminate 110. The capacitor electrode PC10 and the capacitor electrode PC01 form the capacitor C0 in FIG.

[0036] Furthermore, another part of the capacitor electrode PC10 overlaps with the ground electrode PG1 disposed on the dielectric layer LY8 when viewed in a plan view from the stacking direction of the laminate 110. The ground electrode PG1 is connected to the ground terminal GND on the lower surface 112 by a plurality of vias VG4 and a plurality of vias VG5. That is, the capacitor electrode PC10 and the ground electrode PG1 form the capacitor C1 in FIG. 2.

[0037] The capacitor electrode PC10 is connected to a plate electrode PL12 arranged on the dielectric layer LY2 by a via V10. The plate electrode PL12 is a strip-like electrode having a substantially U-shape, and the via V10 is connected to one end of the plate electrode PL12. A via VG11 is connected near the middle of the plate electrode PL12. The via VG11 is connected to a ground electrode PG2 arranged on the dielectric layer LY3. The ground electrode PG2 is connected to a ground electrode PG1 on the dielectric layer LY8 by vias VG12 and VG22.

[0038] The portion of the plate electrode PL12 from the connection point of the via V10 to the connection point of the via VG11, and the via V10, form inductor L1 in Fig. 2. The via VG11 forms inductor L12 in Fig. 2. The vias VG12, VG22, VG4, and VG5 form inductor L6 in Fig. 2.

[0039] A via V20 is connected to the other end of the plate electrode PL12. The via V20 is connected to a capacitor electrode PC20 disposed on the dielectric layer LY6. The capacitor electrode PC20 is disposed adjacent to the capacitor electrode PC10 on the dielectric layer LY6. When viewed from above in the stacking direction of the laminate 110, the capacitor electrode PC20 overlaps with the ground electrode PG1 on the dielectric layer LY8. That is, the capacitor electrode PC20 and the ground electrode PG1 form the capacitor C2 in FIG. 2.

[0040] The via V20 is also connected to the capacitor electrode PC12 disposed on the dielectric layer LY5. The capacitor electrode PC12 is also connected to the capacitor electrode PC20 by a via V21. The capacitor electrode PC12 has a substantially Y-shape, with a first end connected to the via V20 and a second end connected to the via V21. A third end of the capacitor electrode PC12 overlaps with the capacitor electrode PC10 of the resonator RC1 when viewed from above in the stacking direction of the laminate 110. That is, the capacitor C12 in FIG. 2 is composed of the capacitor electrode PC12 and the capacitor electrode PC10.

[0041] The inductor L2 in FIG. 2 is formed by the portion of the plate electrode PL12 from the connection point of the via V20 to the connection point of the via VG11, and the via V20.

[0042] The output terminal T2 is connected to the capacitor electrode PC02 disposed on the dielectric layer LY7 by vias V03 and V04, which are offset in the dielectric layer LY9.

[0043] The capacitor electrode PC50 of the resonator RC5 is disposed on the dielectric layer LY6. A portion of the capacitor electrode PC50 overlaps with the capacitor electrode PC02 on the dielectric layer LY7 when viewed from above in the stacking direction of the laminate 110. The capacitor electrode PC50 and the capacitor electrode PC02 form the capacitor C6 in FIG.

[0044] Furthermore, another portion of the capacitor electrode PC50 overlaps with the ground electrode PG1 disposed on the dielectric layer LY8 when viewed in a plan view from the stacking direction of the laminate 110. That is, the capacitor electrode PC50 and the ground electrode PG1 form the capacitor C5 in FIG.

[0045] The capacitor electrode PC50 is connected to a plate electrode PL45 arranged on the dielectric layer LY2 by a via V50. The plate electrode PL45 is a strip-like electrode having a substantially U-shape, and the via V50 is connected to one end of the plate electrode PL45. A via VG21 is connected near the middle of the plate electrode PL45. The via VG21 is connected to a ground electrode PG2 arranged on the dielectric layer LY3.

[0046] The portion of the plate electrode PL45 from the connection point of the via V50 to the connection point of the via VG21, and the via V50 form the inductor L5 in Fig. 2. The via VG21 forms the inductor L45 in Fig. 2.

[0047] A via V40 is connected to the other end of the plate electrode PL45. The via V40 is connected to a capacitor electrode PC40 disposed on the dielectric layer LY6. The capacitor electrode PC40 is disposed adjacent to the capacitor electrode PC50 on the dielectric layer LY6. When viewed from above in the stacking direction of the laminate 110, the capacitor electrode PC40 overlaps with the ground electrode PG1 on the dielectric layer LY8. That is, the capacitor electrode PC40 and the ground electrode PG1 form the capacitor C4 in FIG. 2.

[0048] The via V40 is also connected to the capacitor electrode PC45 disposed on the dielectric layer LY5. The capacitor electrode PC45 is connected to the capacitor electrode PC40 by a via V41. The capacitor electrode PC45 has a substantially Y-shape, with a first end connected to the via V40 and a second end connected to the via V41. A third end of the capacitor electrode PC45 overlaps with the capacitor electrode PC50 of the resonator RC5 when viewed from above in the stacking direction of the laminate 110. That is, the capacitor C45 in FIG. 2 is composed of the capacitor electrodes PC45 and PC50.

[0049] The inductor L4 in FIG. 2 is formed by the portion of the plate electrode PL45 from the connection point of the via V40 to the connection point of the via VG21, and the via V40.

[0050] On the dielectric layer LY6, a capacitor electrode PC30 is disposed between the capacitor electrode PC20 of the resonator RC2 and the capacitor electrode PC40 of the resonator RC4. The capacitor electrode PC30 overlaps with the ground electrode PG1 of the dielectric layer LY8 when viewed in a plan view from the stacking direction of the laminate 110. That is, the capacitor electrode PC30 and the ground electrode PG1 form the capacitor PC3 in FIG. 2 .

[0051] The capacitor electrode PC30 is connected to a plate electrode PL30 disposed on the dielectric layer LY2 by a via V30. The plate electrode PL30 is a strip-shaped electrode extending in the Y-axis direction. One end of the plate electrode PL30 is connected to the via V30, and the other end is connected to a via VG3. The via VG3 is connected to the ground electrode PG2 on the dielectric layer LY3. The vias V30, VG3, and the plate electrode PL30 form the inductor L3 in FIG. 2.

[0052] The via V30 is also connected to a capacitor electrode PC31 disposed on the dielectric layer LY4. The capacitor electrode PC31 is a generally T-shaped flat electrode. When viewed from above in the stacking direction of the laminate 110, a portion of the capacitor electrode PC31 overlaps with a capacitor electrode PC12 on the dielectric layer LY5. That is, the capacitor electrodes PC31 and PC12 form the capacitor C23 in FIG. 2. When viewed from above in the stacking direction of the laminate 110, another portion of the capacitor electrode PC31 overlaps with a capacitor electrode PC45 on the dielectric layer LY5. That is, the capacitor electrodes PC31 and PC45 form the capacitor C45 in FIG. 2.

[0053] A strip-shaped capacitor electrode PC15 extending in the X-axis direction is disposed on the dielectric layer LY9. When viewed from above in the stacking direction of the laminate 110, one end of the capacitor electrode PC15 overlaps with the capacitor electrode PC10 of the resonator RC1, and the other end of the capacitor electrode PC15 overlaps with the capacitor electrode PC50 of the resonator RC5. That is, the capacitor electrodes PC10, PC15, and PC50 form the capacitor C15 in FIG. 2.

[0054] (Effect of coupling electrode shape on attenuation characteristics) 4, in the filter device 100, adjacent resonators are capacitively coupled via a capacitor. The capacitor coupling the resonators is realized by arranging a plate electrode extending from one resonator and an electrode for a capacitor constituting an LC parallel resonator in the other resonator so as to face each other.

[0055] In this case, the plate electrode (hereinafter also referred to as "coupling electrode") extending from one of the resonators actually has a certain length, and therefore also functions as an inductor with a predetermined inductance value. Therefore, the coupling electrode constituting the capacitor itself becomes a distributed constant LC parallel resonator, which may cause an unintended decrease in attenuation characteristics near the resonance frequency of the coupling electrode.

[0056] Recent communication devices may communicate using radio waves based on multiple communication standards with different frequency bands, such as Wi-Fi, 4G, and 5G. In such cases, if the attenuation characteristics of a frequency band other than the passband (non-passband) targeted by the filter device are reduced, it may adversely affect other communication devices that use the non-passband frequency band as their passband. Furthermore, when the filter device is used in a receiving circuit, signals corresponding to the frequency band with reduced attenuation characteristics may appear as noise in the received signal.

[0057] Therefore, in the filter device 100 of this embodiment, the capacitors provided between resonators RC1 and RC2, which are located closest to the input terminal T1, and between resonators RC5 and RC4, which are located closest to the output terminal T2, are configured using electrodes with two parallel paths as coupling electrodes. By configuring the coupling electrodes in parallel in this way, the effective inductance value of the coupling electrodes can be reduced, allowing the resonant frequency of the coupling electrodes to be set higher than in the case of a coupling electrode with a single path. This makes it possible to suppress deterioration in attenuation characteristics in a predetermined frequency band.

[0058] 5 and 6 are diagrams illustrating the detailed structure of the coupling electrode in the filter device 100 according to the embodiment. In FIGS. 5 and 6, the capacitor electrode PC45 corresponding to the coupling electrode between the resonators RC4 and RC5 is used as an example. FIG. 5 is an enlarged perspective view of the capacitor electrode PC45. FIG. 6 is an enlarged plan view of the capacitor electrode PC45. The same applies to the capacitor electrode PC12 corresponding to the coupling electrode between the resonators RC1 and RC2.

[0059] 5 and 6, the capacitor electrode PC45 includes strip-shaped electrodes P1, P2, and P3. The electrodes P1 and P2 have a substantially L-shape. A first end of the electrode P1 is connected to a first end of the electrode P2 at a node NA in FIG. 5. A second end of the electrode P1 is connected to the capacitor electrode PC40 through a via V40. A second end of the electrode P2 is connected to the capacitor electrode PC40 through a via V41. A first end of the electrode P3 is also connected to the node NA. The second end of the electrode P3 is an open end.

[0060] That is, between the node NA and the capacitor electrode PC40, a ring-shaped structure is formed by the first path of the electrode P1 and the second path of the electrode P2, as shown by the dashed line LN10 in Fig. 6. This ring-shaped structure reduces the inductance value of the capacitor electrode PC45.

[0061] The shapes of the electrodes P1, P2, and P3 constituting the capacitor electrode PC45 are not necessarily limited to the elongated strip shapes shown in the examples of Figures 5 and 6. The electrodes P1 and P2 may be rectangular with a wider line width, or may have a line width that varies along the signal transmission path, as long as they can form a ring-shaped structure together with the capacitor electrode PC40. The electrode P3 is also not limited to the rectangular shape shown in Figures 5 and 6, but may have a line width that varies along the way, or may have a bent shape along the way.

[0062] (filter characteristics) Next, with reference to FIGS. 7 and 8, a description will be given of simulation results of the pass characteristics of the filter device 100 of the present embodiment and the filter device 100X of the comparative example.

[0063] 7 is a diagram showing the shapes of the capacitor electrode PC45 of the filter device 100 and the capacitor electrode PC45X of the filter device 100X of the comparative example. Referring to FIG. 7, in the capacitor electrode PC45, as described above, the electrodes P1 and P2 form a ring structure. In contrast, the capacitor electrode PC45X of the comparative example is formed of a single strip-shaped electrode.

[0064] Here, it is desirable that the sum of the line width W1 of the electrode P1 and the line width W2 of the electrode P2 of the capacitor electrode PC45 be approximately equal to the line width W3 of the electrode P3. By setting them in this manner, even if the capacitor electrode PC45 of the resonator RC5 is misaligned in the X-axis direction relative to the capacitor electrode PC50 of the resonator RC5 during manufacturing, it is possible to reduce fluctuations in the overlapping area between the capacitor electrodes PC50 and PC45. Therefore, it is possible to suppress fluctuations in the capacitive coupling between the resonators RC4 and RC5 due to misalignment.

[0065] Note that the above term "substantially the same" allows for an error of about ±20%. In other words, it is desirable that the sum of the line width W1 of electrode P1 and the line width W2 of electrode P2 be 0.8 to 1.2 times the line width W3 of electrode P3.

[0066] Fig. 8 is a diagram illustrating the filter characteristics of the filter devices of the embodiment and the comparative example. In Fig. 8, the horizontal axis represents frequency, and the vertical axis represents insertion loss. In the example of Fig. 8, the pass band of the filter device 100 is 6 GHz to 7 GHz, and the required attenuation characteristics of the non-pass band (stop band) are a1 [dB] in the range of 0 to 4.5 GHz and 9.0 GHz to 35 GHz. In Fig. 8, the solid line LN20 represents the filter device 100 of the embodiment, and the dashed line LN21 represents the filter device 100X of the comparative example.

[0067] 8, in the comparative example, the resonant frequency of the coupling electrode appears near 24 GHz in the non-pass band, and the insertion loss decreases at that frequency and its vicinity, so the required attenuation characteristics are not achieved.

[0068] In contrast, in the filter device 100 according to the embodiment, the resonant frequency of the coupling electrode is around 37 GHz, which is outside the non-pass band range where attenuation characteristics are required, and therefore the attenuation characteristics in the non-pass band satisfy the required level.

[0069] As described above, in a filter device including a plurality of resonators, a ring-shaped structure is formed using coupling electrodes for capacitively coupling adjacent resonators, and the resonant frequency of the coupling electrodes is set higher, thereby making it possible to suppress the deterioration of attenuation characteristics in non-pass bands.

[0070] In the above-described filter device 100, a configuration has been described in which a ring structure is formed by a capacitor electrode that is a coupling electrode and a capacitor electrode of a resonator connected to the coupling electrode. However, the ring structure may be formed by the coupling electrode alone, and the ring structure may be connected to the capacitor electrode of the resonator by a via or a wiring pattern.

[0071] In the arrangement of the filter device 100 of the embodiment, the coupling electrodes of the resonators close to the input terminal and the output terminal tend to be relatively long, and therefore attention is focused on the capacitive coupling between the resonators RC1 and RC2 and the capacitive coupling between the resonators RC4 and RC5. However, in a filter device with a different structure, instead of or in addition to this, a configuration having a ring structure as in the embodiment may be applied to the coupling electrode between the resonators RC2 and RC3 and / or the coupling electrode between the resonators RC3 and RC4.

[0072] A via may penetrate through the opening of the annular structure of the coupling electrode.

[0073] Each of the "resonators RC1" and "resonators RC5" in the embodiments corresponds to a "first resonator" in the present disclosure, and each of the "resonators RC2" and "resonators RC4" in the embodiments corresponds to a "second resonator" in the present disclosure. Each of the "capacitor electrodes PC12" and "capacitor electrodes PC45" in the embodiments corresponds to a "coupling electrode" in the present disclosure. Each of the "capacitor electrodes PC10" and "capacitor electrodes PC50" in the embodiments corresponds to a "first capacitor electrode" in the present disclosure, and each of the "capacitor electrodes PC20" and "capacitor electrodes PC40" in the embodiments corresponds to a "second capacitor electrode" in the present disclosure. Each of the "capacitor electrodes PC01" and "capacitor electrodes PC02" in the embodiments corresponds to a "third capacitor electrode" and a "fourth capacitor electrode" in the present disclosure, respectively. A "ground electrode PG1" in the embodiments corresponds to a "ground electrode" in the present disclosure. "Electrode P1," "electrode P2," and "electrode P3" in the embodiments correspond to "first electrode," "second electrode," and "third electrode," respectively, in the present disclosure.

[0074] [Variations] Modified examples of coupling electrodes for forming capacitive coupling between resonators will be described below with reference to Fig. 9 to Fig. 13. Note that, although the modified examples in Fig. 9 to Fig. 13 describe the coupling electrode between resonators RC4 and RC5, the configurations of the modified examples can also be applied to the coupling electrode between resonators RC1 and RC2.

[0075] (Variation 1) In the first modification, a configuration will be described in which a coupling electrode and a capacitor electrode of a resonator connected to the coupling electrode are arranged on the same dielectric layer.

[0076] Fig. 9 is a partially enlarged perspective view of a filter device 100A of Modification 1. In Fig. 9, the capacitor electrode PC40 of the resonator RC4 and the capacitor electrode PC45 serving as the coupling electrode in Fig. 5 described in the above embodiment are replaced with a capacitor electrode PC45A. In Fig. 9 and Figs. 10 to 13 described later, description of elements that overlap with Fig. 5 will not be repeated.

[0077] 9, the capacitor electrode PC45A includes, in addition to the electrodes P1, P2, and P3 of the capacitor electrode PC45 in FIG. 5, an electrode P4 corresponding to a portion of the capacitor electrode PC40. The electrode P4 is connected to the ends of the electrodes P1 and P2 in FIG. 5 to which the vias V40 and V41 were connected. That is, a ring structure is formed by the electrodes P1, P2, and P4. The via V40 of the resonator RC4 is connected to the capacitor electrode PC45A.

[0078] For ease of explanation, the electrodes P1 to P4 of the capacitor electrode PC45A have been described as separate elements, but in reality, the electrodes P1 to P4 are formed as electrodes of an integral structure arranged on the same dielectric layer.

[0079] In this way, even in a configuration in which the coupling electrode for capacitively coupling between resonators and the capacitor electrode of the resonator to which the coupling electrode is connected are arranged on the same dielectric layer, by making the electrode formed by the coupling electrode and the capacitor electrode into a ring structure, the resonant frequency of the coupling electrode can be set higher, thereby suppressing the deterioration of attenuation characteristics in the non-pass band.

[0080] (Variation 2) In the second modification, a configuration in which the protruding portion (electrode P3) of the coupling electrode is removed will be described.

[0081] Fig. 10 is a partially enlarged perspective view of a filter device 100B of Modification 2. In Fig. 10, the capacitor electrode PC45 in Fig. 5 described in the above embodiment is replaced with a capacitor electrode PC45B.

[0082] 10, the capacitor electrode PC45B has a configuration in which the electrode P3 (the portion LN30 indicated by the broken line in FIG. 6) protruding in the X-axis direction from the node NA in the capacitor electrode PC45 in FIG. 5 is removed. In other words, the capacitor electrode PC45B includes only the electrodes P1 and P2.

[0083] Even in such a configuration, a ring structure is formed by electrodes P1 and P2 of capacitor electrode PC45B and capacitor electrode PC40 of resonator RC4, so that the resonant frequency of the coupling electrode can be set higher to suppress a decrease in attenuation characteristics in the non-pass band.

[0084] Since the area of ​​capacitor electrode PC45B overlapping with capacitor electrode PC50 of resonator RC5 is smaller than that of capacitor electrode PC45, the degree of capacitive coupling may be slightly weaker than in the case of Fig. 5. Therefore, the configuration of Modification 2 can be adopted when the required degree of capacitive coupling is relatively low. Alternatively, the line width of electrodes P1 and P2 may be widened to ensure a degree of coupling equivalent to that of capacitor electrode PC45.

[0085] (Variation 3) In the third modification, a configuration will be described in which the order of arrangement in the lamination direction of the coupling electrodes and the capacitor electrodes of the resonators to which the coupling electrodes are connected is different.

[0086] Fig. 11 is a partially enlarged perspective view of a filter device 100C of Modification 3. In Fig. 11, the capacitor electrode PC40 of the resonator RC4 is arranged closer to the upper surface 111 than the capacitor electrode PC45, which is a coupling electrode. In other words, the capacitor electrode PC45 is arranged on the dielectric layer between the capacitor electrode PC40 and the ground electrode PG1.

[0087] This arrangement can shorten the distance in the stacking direction between the capacitor electrode PC45 and the ground electrode PG1 compared to the case of Fig. 5, thereby strengthening the degree of capacitive coupling between the resonators RC4 and RC5. Furthermore, the capacitor electrodes PC45 and PC40 form a ring-shaped structure, which can suppress deterioration in attenuation characteristics in non-pass bands.

[0088] (Variation 4) In the fourth modification, a configuration will be described in which the coupling electrode is formed by electrodes arranged on a plurality of dielectric layers.

[0089] Fig. 12 is a partially enlarged perspective view of a filter device 100D of Modification 4. In Fig. 12, the capacitor electrode PC45 in Fig. 11 is replaced with a capacitor electrode PC45D.

[0090] Capacitor electrode PC45D includes electrodes P1D and P2D arranged on the same dielectric layer, electrode P3D arranged on a dielectric layer closer to upper surface 111 than electrodes P1D and P2D, and via V45 for connecting electrodes P1D, P2D and electrode P3D. In other words, capacitor electrode PC45D corresponds to a configuration in which the protruding portion (electrode P3) of capacitor electrode PC45 is arranged on a dielectric layer different from electrodes P1 and P2, and is connected to electrodes P1 and P2 at node NA by via V45.

[0091] Even in such a configuration, the electrodes P1D, P2D and the capacitor electrode PC40 of the resonator RC4 form a ring structure, so that it is possible to suppress a decrease in attenuation characteristics in the non-pass bands.

[0092] In the example of Figure 12, the protruding electrode P3D is arranged on the dielectric layer closer to the upper surface 111 than the electrodes P1D and P2D, but the protruding electrode P3D may also be arranged on the dielectric layer closer to the ground electrode PG1 than the electrodes P1D and P2D.

[0093] (Variation 5) In the fifth modification, a configuration will be described in which the arrangement of the coupling electrode and the capacitor electrode that forms the capacitor with the coupling electrode in the stacking direction is different.

[0094] Fig. 13 is a partially enlarged perspective view of a filter device 100E of Modification 5. In Fig. 13, the capacitor electrode PC50 of the resonator RC5 in Fig. 11 is arranged closer to the upper surface 111 than the capacitor electrode PC45, which is the coupling electrode. In other words, the capacitor electrode PC45 is arranged on the dielectric layer between the capacitor electrode PC50 of the resonator RC5 and the ground electrode PG1.

[0095] Even in such an arrangement, the electrodes P1 and P2 of the capacitor electrode PC45 and the capacitor electrode PC40 of the resonator RC4 form a ring structure, so that it is possible to suppress a decrease in attenuation characteristics in the non-pass bands.

[0096] [Aspect] It will be appreciated by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

[0097] (Item 1) A filter device according to one aspect includes a laminate including a plurality of dielectric layers stacked together, an input terminal, an output terminal, and a ground terminal, a ground electrode connected to the ground terminal, a first resonator, a second resonator, and a coupling electrode. The laminate has a first surface and a second surface. The input terminal, the output terminal, and the ground terminal are disposed on the second surface of the laminate. The ground electrode is disposed inside the laminate. The first resonator and the second resonator are disposed on a signal transmission path from the input terminal to the output terminal in a layer between the first surface and the ground electrode. The coupling electrode couples the first resonator and the second resonator via capacitive coupling. The first resonator and the second resonator each include a first capacitor electrode and a second capacitor electrode that form a capacitor with the ground electrode. The coupling electrode is connected to the second capacitor electrode and forms a capacitor with the first capacitor electrode. The coupling electrode includes a first electrode and a second electrode, each having a first end and a second end. The first end of the first electrode and the first end of the second electrode are connected. A second end of the first electrode and a second end of the second electrode are connected to a second capacitor electrode.

[0098] (Item 2) In the filter device described in item 1, the first electrode and the second electrode form a ring-shaped structure.

[0099] (Item 3) In the filter device according to item 1, the first electrode, the second electrode, and the second capacitor electrode form a ring-shaped structure.

[0100] (Item 4) In the filter device according to item 2 or 3, the annular structures are arranged on the same dielectric layer.

[0101] (Item 5) In the filter device according to item 2 or 3, the annular structure is disposed across a plurality of dielectric layers.

[0102] (Item 6) In the filter device according to item 5, the coupling electrode is disposed on the dielectric layer between the second capacitor electrode and the ground electrode.

[0103] (Item 7) In the filter device according to item 5, the second capacitor electrode is disposed on the dielectric layer between the coupling electrode and the ground electrode.

[0104] (Item 8) In the filter device according to any one of items 1 to 7, the coupling electrode further includes a third electrode protruding from first ends of the first electrode and the second electrode.

[0105] (Item 9) In the filter device according to item 8, the first electrode and the second electrode are disposed on a dielectric layer between the third electrode and the ground electrode.

[0106] (Item 10) In the filter device according to item 8 or 9, the sum of the line width of the first electrode and the line width of the second electrode is 0.8 to 1.2 times the line width of the third electrode.

[0107] (Item 11) In the filter device according to any one of items 1 to 10, the first resonator is a resonator disposed closest to the input terminal or the output terminal in the signal transmission path.

[0108] (Item 12) The filter device according to item 11 further includes a third capacitor electrode connected to the input terminal and constituting a capacitor between itself and the first capacitor electrode.

[0109] (Item 13) The filter device according to item 11 further includes a fourth capacitor electrode connected to the output terminal and constituting a capacitor between itself and the first capacitor electrode.

[0110] (14) The filter device according to any one of paragraphs 1 to 10 further includes a third resonator disposed in the signal transmission path between the input terminal and the first resonator.

[0111] (Item 15) The filter device according to item 14 further includes a fourth resonator provided in the signal transmission path between the output terminal and the second resonator.

[0112] (16) The filter device according to any one of paragraphs 1 to 10 further includes a fourth resonator provided in the signal transmission path between the output terminal and the second resonator.

[0113] (Item 17) A high-frequency front-end circuit according to one aspect includes the filter device according to any one of items 1 to 16.

[0114] 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]

[0115] 10 communication device, 12 antenna, 20 high frequency front-end circuit, 22, 28 band pass filter, C0 to C6, C12, C15, C23, C34, C45 capacitor, 24 amplifier, 26 attenuator, 30 mixer, 32 local oscillator, 40 D / A converter, 50 RF circuit, 100, 100A to 100E, 100X filter device, 110 laminate, 111 upper surface, 112 lower surface, PC01, PC02, PC10, PC12, PC15, PC20, PC30, PC31, PC40, PC45, PC45A, PC45B, PC45D, PC45X, PC50 capacitor electrode, DM direction mark, GND ground terminal, L1 to L6, L12, L45 inductor, Y1 to LY10 Dielectric layer, N1A to N5A, N2B to N4B connection nodes, NA node, P1 to P4, P1D to P3D electrodes, PG1, PG2 ground electrodes, PL12, PL30, PL45 plate electrodes, RC1 to RC5 resonators, T1 input terminal, T2 output terminal, V01 to V04, V10 to V50, V21, V41, V45, VG3 to VG5, VG11, VG12, VG21, VG22 vias.

Claims

1. 1. A filter device, comprising: a laminate having a first surface and a second surface and including a plurality of dielectric layers stacked on top of one another; an input terminal, an output terminal, and a ground terminal disposed on the second surface of the laminate; a ground electrode disposed inside the laminate and connected to the ground terminal; a first resonator and a second resonator disposed in a layer between the first surface and the ground electrode on a signal transmission path from the input terminal to the output terminal; a coupling electrode for coupling the first resonator and the second resonator via capacitive coupling; the first resonator and the second resonator each include a first capacitor electrode and a second capacitor electrode that form a capacitor between the first resonator and the ground electrode; the coupling electrode is connected to the second capacitor electrode and forms a capacitor between the coupling electrode and the first capacitor electrode; the coupling electrodes include a first electrode and a second electrode each having a first end and a second end; a first end of the first electrode and a first end of the second electrode are connected to each other; The second end of the first electrode and the second end of the second electrode are connected to the second capacitor electrode.

2. The filter device according to claim 1 , wherein the first electrode and the second electrode form an annular structure.

3. The filter device according to claim 1 , wherein the first electrode, the second electrode, and the second capacitor electrode form a ring-shaped structure.

4. 4. The filter device according to claim 2, wherein the annular structures are arranged on the same dielectric layer.

5. The filter device according to claim 2 or 3, wherein the annular structure is disposed across a plurality of dielectric layers.

6. The filter device according to claim 5 , wherein the coupling electrode is disposed on a dielectric layer between the second capacitor electrode and the ground electrode.

7. The filter device according to claim 5 , wherein the second capacitor electrode is disposed on a dielectric layer between the coupling electrode and the ground electrode.

8. The filter device of claim 1 , wherein the coupling electrode further includes a third electrode protruding from first ends of the first electrode and the second electrode.

9. The filter device of claim 8 , wherein the first electrode and the second electrode are disposed on a dielectric layer between the third electrode and the ground electrode.

10. 10. The filter device according to claim 8, wherein the sum of the line width of the first electrode and the line width of the second electrode is 0.8 to 1.2 times the line width of the third electrode.

11. 2. The filter device according to claim 1, wherein the first resonator is a resonator disposed closest to the input terminal or the output terminal in the signal transmission path.

12. The filter device according to claim 11 , further comprising a third capacitor electrode connected to the input terminal and forming a capacitor between the first capacitor electrode and the third capacitor electrode.

13. The filter device according to claim 11 , further comprising a fourth capacitor electrode connected to the output terminal and forming a capacitor between the fourth capacitor electrode and the first capacitor electrode.

14. The filter device according to claim 1 , further comprising a third resonator disposed in the signal transmission path between the input terminal and the first resonator.

15. 15. The filter device according to claim 14, further comprising a fourth resonator provided in the signal transmission path between the input terminal and the third resonator.

16. The filter device according to claim 1 , further comprising a fifth resonator provided in the signal transmission path between the output terminal and the second resonator.

17. A filter device as described in Claim 16, further comprising a sixth resonator arranged between the output terminal and the fifth resonator in the signal transmission path.

18. A high-frequency front-end circuit comprising the filter device according to claim 1.

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