Filter device and high-frequency front end circuit

Abstract

To improve filter characteristics of a filter device including a plurality of resonance circuits.SOLUTION: The filter device 100 includes a dielectric substrate 110, terminals T1 and T2 disposed on the outer surfaces of the dielectric substrate 110, resonant circuits RC1 and RC2, and ground electrodes PG1 and PG2. The resonant circuit RC1 is connected to the terminals T1. The resonant circuit RC2 is connected to the terminals T2. The ground terminal PG1 is connected to the resonance circuit RC1. The ground electrodes PG2 are connected to the resonance circuit RC2 and are separated from the ground electrodes PG1.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a filter device and a high-frequency front-end circuit incorporating the same, and more particularly to a technique for improving the filter characteristics of a filter device including a plurality of LC resonant circuits. [Background technology]

[0002] WO 2022 / 071191 (Patent Document 1) discloses a filter device in which a plurality of LC resonant circuits are arranged in a dielectric substrate on which a plurality of dielectric layers are stacked. In the filter device of Patent Document 1, some of the resonant circuits have a common configuration in which a portion of the path connected to the ground terminal is shared. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2022 / 071191 Summary of the Invention [Problem to be solved by the invention]

[0004] In a filter device including a plurality of resonant circuits as described above, the resonant circuits may be configured to be connected to a common ground electrode, which has the advantage that fluctuations in the ground potential between the resonant circuits can be reduced and stabilized because the common ground electrode is used.

[0005] On the other hand, because current distribution also occurs in the ground electrode, if a common ground electrode is used, current may flow between the resonant circuits via the ground electrode, which may result in strong magnetic coupling between the resonant circuits. If magnetic coupling occurs between the resonant circuits that was not intended at the time of design, the desired filter characteristics may not be obtained.

[0006] The present disclosure has been made to solve such problems, and its purpose is to suppress degradation of filter characteristics in a filter device including a plurality of resonant circuits. [Means for solving the problem]

[0007] A filter device according to the present disclosure includes a dielectric substrate, a first terminal and a second terminal arranged on an outer surface of the dielectric substrate, a first resonant circuit, a second resonant circuit, a first ground electrode, and a second ground electrode. The first resonant circuit is connected to the first terminal. The second resonant circuit is connected to the second terminal. The first ground electrode is connected to the first resonant circuit. The second ground electrode is connected to the second resonant circuit and is separated from the first ground electrode. [Effects of the Invention]

[0008] In the filter device according to the present disclosure, the ground electrodes connected to the two resonant circuits are separated. This prevents current from flowing between the resonant circuits via the ground electrodes, thereby suppressing unintended magnetic coupling between the resonant circuits. Therefore, in a filter device including multiple resonant circuits, it is possible to suppress degradation of filter characteristics due to unintended magnetic coupling between the resonant circuits. [Brief explanation of the drawings]

[0009] [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] 1 is an equivalent circuit diagram of a filter device according to a first embodiment. [Figure 3] 1 is an external perspective view of a filter device according to a first 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] FIG. 10 is an exploded perspective view showing a laminated structure of a filter device of a comparative example. [Figure 6] 5A and 5B are diagrams for explaining filter characteristics in the filter devices of the first embodiment and the comparative example. [Figure 7] FIG. 10 is an equivalent circuit diagram of a filter device according to a first modified example. [Figure 8] FIG. 10 is an exploded perspective view showing an example of a laminated structure of a filter device according to a first modified example. [Figure 9] FIG. 10 is an equivalent circuit diagram of a filter device according to a second embodiment. [Figure 10] FIG. 10 is an external perspective view of a filter device according to a second embodiment. [Figure 11] 11 is an exploded perspective view showing an example of a layered structure of the filter device of FIG. 10. FIG. [Figure 12] FIG. 10 is an equivalent circuit diagram of a filter device according to a second modification. [Figure 13] FIG. 10 is an exploded perspective view showing an example of a laminated structure of a filter device according to a second modification. [Figure 14] FIG. 11 is an equivalent circuit diagram of a filter device according to a third modification. [Figure 15] FIG. 11 is an exploded perspective view showing an example of a laminated structure of a filter device according to a third modification. DETAILED DESCRIPTION OF THE INVENTION

[0010] 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.

[0011] [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 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.

[0012] 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.

[0013] 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.

[0014] A filter device according to the present disclosure can be employed as the bandpass filters 22, 28 in the communication device 10 described above.

[0015] (Configuration of filter device) Next, the detailed configuration of the filter device 100 according to the first embodiment will be described with reference to FIGS.

[0016] (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 resonant circuits RC1 to RC4. Each of the resonant circuits RC1 to RC4 is an LC parallel resonant circuit in which an inductor and a capacitor are connected in parallel.

[0017] The resonant circuit RC1 is connected to the input terminal T1 via an inductor L1. The resonant circuit RC1 includes inductors L2, L3, L10, and L11 and a capacitor C1. The inductors L2, L3, L10, and L11 are connected in series, in this order, between a connection node N1 with the inductor L1 and the ground terminal GND. The capacitor C1 is also connected between the connection node N1 and the ground terminal GND. In other words, the resonant circuit RC1 is an LC parallel resonant circuit in which the composite inductor formed by the series-connected inductors L2, L3, L10, and L11 is connected in parallel with the capacitor C1.

[0018] The resonant circuit RC2 is connected to the output terminal T2 via an inductor L6. The resonant circuit RC2 includes inductors L4, L5, L10, and L12 and a capacitor C4. The inductors L5, L4, L10, and L12 are connected in series, in this order, between a connection node N5 with the inductor L6 and the ground terminal GND. The capacitor C4 is also connected between the connection node N5 and the ground terminal GND. In other words, the resonant circuit RC2 is an LC parallel resonant circuit in which a composite inductor formed by the series-connected inductors L4, L5, L10, and L12 is connected in parallel with the capacitor C2.

[0019] The resonant circuit RC3 includes inductors L3, L10, and L11 and a capacitor C2. The capacitor C2 is connected between a connection node N2 between the inductors L2 and L3 and the ground terminal GND. The inductors L3, L10, and L11 are part of the inductors that make up the resonant circuit RC1, and are connected in series between the connection node N2 and the ground terminal GND. That is, the resonant circuit RC3 is an LC parallel resonant circuit in which the composite inductor formed by the series-connected inductors L3, L10, and L11 is connected in parallel with the capacitor C2.

[0020] The resonant circuit RC4 includes inductors L4, L10, and L12 and a capacitor C3. The capacitor C3 is connected between a connection node N3 between the inductors L4 and L5 and the ground terminal GND. The inductors L4, L10, and L12 are part of the inductors that make up the resonant circuit RC2, and are connected in series between the connection node N4 and the ground terminal GND. In other words, the resonant circuit RC4 is an LC parallel resonant circuit in which the composite inductor formed by the series-connected inductors L4, L10, and L12 is connected in parallel with the capacitor C3.

[0021] As described above, inductors L3, L10, and L11 are shared by resonant circuits RC1 and RC3. Therefore, resonant circuits RC1 and RC3 are magnetically coupled to each other. In addition, inductors L4, L10, and L12 are shared by resonant circuits RC2 and RC4. Therefore, resonant circuits RC2 and RC4 are magnetically coupled to each other.

[0022] Inductor L10 is connected between a connection node N3 between inductors L3 and L4 and a connection node N6 between inductors L11 and L12, and is shared by resonant circuits RC1 to RC4, so that resonant circuits RC1 to RC4 are magnetically coupled to one another by inductor L10.

[0023] A capacitor C13 is connected in parallel to the inductor L2. This causes the resonant circuits RC1 and RC3 to be capacitively coupled to each other. Furthermore, a capacitor C24 is connected in parallel to the inductor L5. This causes the resonant circuits RC2 and RC4 to be capacitively coupled to each other. Furthermore, a capacitor C12 is connected between the connection node N1 and the connection node N5. This causes the resonant circuits RC1 and RC2 to be capacitively coupled to each other.

[0024] As described above, the filter device 100 has a configuration in which four resonant circuits that are magnetically and capacitively coupled to each other 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 resonant circuits included in the filter device is an example, and the features of the present disclosure are applicable to filter devices that include two or more resonators.

[0025] (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.

[0026] 3 and 4, the filter device 100 includes a rectangular or approximately rectangular parallelepiped dielectric substrate 110 on which a plurality of dielectric layers LY1 to LY11 are stacked in a stacking direction. The dielectric layers LY1 to LY11 are formed of ceramics such as low-temperature co-fired ceramics (LTCC) or resin. Inside the dielectric substrate 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 resonant circuit. 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.

[0027] In the following description, the stacking direction of the dielectric layers LY1 to LY11 in the dielectric substrate 110 is referred to as the "Z-axis direction," the direction perpendicular to the Z-axis direction and along one side of the dielectric substrate 110 is referred to as the "X-axis direction," and the direction along the other side of the dielectric substrate 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.

[0028] A directionality mark DM for identifying the orientation of the filter device 100 is arranged on the upper surface 111 (dielectric layer LY1) of the dielectric substrate 110. Ground terminals GND1 and GND2 are arranged from a side surface 115 in the positive direction of the X axis of the dielectric substrate 110 to a lower surface 112 (dielectric layer LY11). The ground terminal GND1 is arranged on the side surface 115, on the side surface 113 side in the negative direction of the Y axis. The ground terminal GND2 is arranged on the side surface 115, on the side surface 114 side in the positive direction of the Y axis.

[0029] An input terminal T1 and an output terminal T2 are arranged from a side surface 116 in the negative direction of the X axis of the dielectric substrate 110 to a bottom surface 112. The input terminal T1 is arranged on the side surface 115, closer to the side surface 113. The output terminal T2 is arranged on the side surface 115, closer to the side surface 114.

[0030] The input terminal T1, output terminal T2, and ground terminals GND1 and GND2 are flat plate electrodes with portions bent into a generally L-shape. The input terminal T1, output terminal T2, and ground terminals GND1 and GND2 are used as external terminals for connection to external devices.

[0031] The input terminal T1 is connected at its side surface 116 to a plate electrode PL10 disposed on the dielectric layer LY3. The plate electrode PL10 is a strip-shaped electrode having an arc shape, and a first end thereof is connected to the input terminal T1. A second end of the plate electrode PL10 is connected by a via V10 to a plate electrode PL11 disposed on the dielectric layer LY4.

[0032] The plate electrode PL11 is a strip-like electrode having a substantially L-shape, and a first end thereof is connected to a via V10. A second end of the plate electrode PL11 is connected by a via V11 to a plate electrode PL12 disposed on the dielectric layer LY5.

[0033] The plate electrode PL12 is a strip-shaped electrode having an arc shape similar to the plate electrode PL10, and a via V11 is connected to a first end of the plate electrode PL12. A second end of the plate electrode PL12 is connected by a via V12 to a plate electrode PL13 disposed on the dielectric layer LY6.

[0034] The plate electrode PL13 is a linear electrode extending in the Y-axis direction, and a via V12 is connected to a first end of the plate electrode PL13. A second end of the plate electrode PL13 is connected by the via V13 to the capacitor electrode PC1 arranged on the dielectric layer LY8 and the capacitor electrode PC2 arranged on the dielectric layer LY9.

[0035] The plate electrodes PL10, PL11, PL12, and PL13 and the vias V10, V11, V12, and V13 form the inductor L1 in FIG.

[0036] The capacitor electrode PC2 is a linear electrode extending in the X-axis direction, and at least a portion of it overlaps with the ground electrode PG1 arranged on the dielectric layer LY10 when viewed in a plan view from the normal direction of the dielectric substrate 110. The ground electrode PG1 is a flat electrode having a substantially rectangular shape, and is connected to the ground terminal GND1 on the side surface 115 of the dielectric substrate 110. The capacitor electrode PC2 and the ground terminal GND1 form the capacitor C1 in FIG. 2.

[0037] Furthermore, the capacitor electrode PC2 is connected to a plate electrode PL20 disposed on the dielectric layer LY2 by a via V20. The plate electrode PL20 is an electrode having a substantially M-shape. In addition to the via V20, vias V30, V40, V50, and VG1 are connected to the plate electrode PL20. The via V20 is connected to a first end of the plate electrode PL20, and the via V50 is connected to a second end of the plate electrode PL20. The vias V30, VG1, and V40 are connected in this order along a path from the first end to the second end of the plate electrode PL20. The "plate electrode PL20" in the first embodiment corresponds to the "common electrode" in this disclosure.

[0038] The via V30 is connected to the plate electrode PL20 and a capacitor electrode PC3 disposed on the dielectric layer LY9. The capacitor electrode PC3 is a substantially L-shaped plate electrode and is disposed spaced apart from the capacitor electrode PC2. When viewed from above in the normal direction of the dielectric substrate 110, at least a portion of the capacitor electrode PC3 overlaps with the ground electrode PG1 on the dielectric layer LY10.

[0039] The vias V20 and V30 and the path from the via V20 to the via V30 of the plate electrode PL20 form the inductor L2 in Fig. 2. The capacitor electrode PC3 and the ground electrode PG1 form the capacitor C2 in Fig. 2.

[0040] The capacitor electrode PC1 connected to the via V13 on the dielectric layer LY8 is a substantially L-shaped flat plate electrode. When viewed from above in the normal direction of the dielectric substrate 110, at least a portion of the capacitor electrode PC1 overlaps with the capacitor electrode PC3. The capacitor electrodes PC1 and PC3 together form the capacitor C13 in FIG. 2.

[0041] The via VG1 is connected to approximately the midpoint of the path from the first end to the second end of the plate electrode PL20. In the plate electrode PL20, the path from the via V30 to the via VG1 forms the inductor L3 in FIG. 2. In addition, in the plate electrode PL20, the path from the via V40 to the via VG1 forms the inductor L4 in FIG. 2. The via VG1 is connected to the plate electrode PL50 disposed on the dielectric layer LY4.

[0042] The plate electrode PL50 is a linear electrode extending in the Y-axis direction, and a via VG1 is connected to its middle portion. A first end of the plate electrode PL50 is connected to the ground electrode PG1 on the dielectric layer LY10 by a via VG2. A second end of the plate electrode PL50 is connected to the ground electrode PG2 arranged on the dielectric layer LY10 by a via VG3.

[0043] The ground electrode PG2 is a flat plate electrode having a shape symmetrical to that of the ground electrode PG1, and is arranged in the positive direction of the Y axis relative to the ground electrode PG1 and separated from the ground electrode PG1. The ground electrode PG2 is connected to the ground terminal GND2 on the side surface 115 of the dielectric substrate 110.

[0044] The via VG1 constitutes the inductor L10 in Fig. 2. The vias VG2 and VG3 constitute the inductors L11 and L12 in Fig. 2, respectively.

[0045] The via V40 is connected to the plate electrode PL20 and a capacitor electrode PC7 disposed on the dielectric layer LY9. The capacitor electrode PC7 is a substantially L-shaped plate electrode, and has a shape symmetrical to the capacitor electrode PC3. The capacitor electrode PC7 is disposed apart from the capacitor electrode PC3. When viewed from above in the normal direction of the dielectric substrate 110, at least a portion of the capacitor electrode PC7 overlaps with the ground electrode PG2 on the dielectric layer LY10. The capacitor electrode PC7 and the ground electrode PG2 form the capacitor C3 in FIG. 2.

[0046] The via V50 connected to the second end of the plate electrode PL20 is connected to a capacitor electrode PC6 arranged on the dielectric layer LY9. Like the capacitor electrode PC2, the capacitor electrode PC6 is a linear plate electrode extending in the X-axis direction and is arranged spaced apart from the capacitor electrode PC7. When viewed from above in the normal direction of the dielectric substrate 110, at least a portion of the capacitor electrode PC6 overlaps with the ground electrode PG2 arranged on the dielectric layer LY10.

[0047] The vias V40 and V50 and the path from the via V40 to the via V50 of the plate electrode PL20 form the inductor L5 in Fig. 2. The capacitor electrode PC6 and the ground electrode PG2 form the capacitor C4 in Fig. 2.

[0048] The capacitor electrode PC6 is connected by a via V60 to the capacitor electrode PC5 disposed on the dielectric layer LY8 and to the plate electrode PL30 disposed on the dielectric layer LY6.

[0049] Capacitor electrode PC5 is a generally L-shaped flat plate electrode symmetrical to capacitor electrode PC1. When viewed from above in the normal direction of dielectric substrate 110, capacitor electrode PC5 partially overlaps capacitor electrode PC7 on dielectric layer LY9. Capacitor electrode PC5 and capacitor electrode PC7 form capacitor C24 in FIG. 2.

[0050] In addition, when viewed from above in the normal direction of the dielectric substrate 110, the capacitor electrodes PC1 and PC5 of the dielectric layer LY8 partially overlap with the capacitor electrode PC4 disposed on the dielectric layer LY7. The capacitor electrodes PC1, PC4, and PC5 form the capacitor C12 in FIG.

[0051] The plate electrode PL30 is a linear electrode extending in the Y-axis direction, and a first end thereof is connected to a via V30. A second end of the plate electrode PL30 is connected by a via V61 to a plate electrode PL31 disposed on the dielectric layer LY5.

[0052] The plate electrode PL31 has an arc shape symmetrical to the plate electrode PL12, and a via V61 is connected to a first end of the plate electrode PL31. A second end of the plate electrode PL31 is connected by a via V62 to the plate electrode PL32 disposed on the dielectric layer LY4.

[0053] The plate electrode PL32 has a generally L-shape symmetrical to the plate electrode PL11, and a via V62 is connected to a first end of the plate electrode PL32. A second end of the plate electrode PL32 is connected by a via V63 to the plate electrode PL33 disposed on the dielectric layer LY3.

[0054] The plate electrode PL33 has an arc shape symmetrical to the plate electrode PL10, and a via V63 is connected to a first end of the plate electrode PL33. A second end of the plate electrode PL33 is connected to the output terminal T2 on the side surface 116.

[0055] The vias V60, V61, V62, and V63 and the plate electrodes PL30, PL31, PL32, and PL33 form the inductor L6 in FIG.

[0056] (3) Filter characteristics In a filter device including a plurality of resonant circuits as described above, the resonant circuits are generally connected to a common ground electrode, which has the advantage that fluctuations in the ground potential between the resonant circuits can be reduced and stabilized because the common ground electrode is used.

[0057] On the other hand, if a common ground electrode is used, current may flow between the resonant circuits via the ground electrode, which may result in strong magnetic coupling between the resonant circuits. If magnetic coupling between the resonant circuits occurs that was not intended at the time of design, the desired filter characteristics may not be achieved. To avoid this coupling, the spacing between the vias can be increased, but this increases the size of the filter device itself, which may hinder miniaturization.

[0058] Therefore, in the filter device 100 of the first embodiment, the ground electrodes connected to some of the resonant circuits are arranged separately from the ground electrodes connected to the other resonant circuits. Specifically, the ground electrode PG1 connected to the resonant circuits RC1 and RC3 is arranged separately from the ground electrode PG2 connected to the resonant circuits RC2 and RC4. With this configuration, no current flows between the ground electrodes PG1 and PG2, which prevents the overall size of the filter device from increasing and prevents magnetic coupling between the resonant circuits RC1 and RC3 and the resonant circuits RC2 and RC4 due to the current flowing through the ground electrodes.

[0059] 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 FIGS.

[0060] Fig. 5 is an exploded perspective view showing the layered structure of a filter device 100X of a comparative example. In the filter device 100X, the electrode arrangement of the dielectric layer LY10 in the filter device 100 of the first embodiment shown in Fig. 4 is different. Specifically, in the dielectric layer LY10 in the filter device 100X, the ground electrodes PG1 and PG2 in the filter device 100 are integrated into a ground electrode PG1A. Vias VG2 and VG3 are connected to the ground electrode PG1A. In other words, the ground electrodes are common to the resonant circuits RC1 to RC4.

[0061] Fig. 6 is a diagram illustrating the filter characteristics of filter device 100 according to the first embodiment and filter device 100X according to the comparative example. In Fig. 6, the horizontal axis represents frequency, and the vertical axis represents insertion loss. In Fig. 6, a solid line LN10 represents the filter characteristics of filter device 100 according to the first embodiment, and a dashed line LN11 represents the filter characteristics of filter device 100X according to the comparative example.

[0062] 6, in the filter device 100, attenuation poles occur near 8.5 GHz and 10.2 Hz in the stop band, which is higher in frequency than the pass band. On the other hand, in the filter device 100X of the comparative example, attenuation poles occur only near 10 GHz. As a result, in the filter device 100, the pass band on the higher frequency side is expanded compared to the filter device 100X, and the attenuation near the pass band is also steeper.

[0063] In the filter device 100X, the ground electrodes are shared, so the magnetic coupling between the resonant circuits RC1, RC3 and the resonant circuits RC2, RC4 is stronger than in the filter device 100, making the inductance appear smaller, and it is thought that this is why the frequency of the attenuation pole corresponding to around 8.5 GHz in the filter device 100 is higher.

[0064] In this way, in a filter device composed of multiple resonant circuits, separating the ground electrodes connected to the resonant circuits suppresses unintended magnetic coupling between the resonant circuits caused by the current flowing through the ground electrodes, which allows the attenuation pole frequencies to be positioned as designed, thereby preventing degradation of the filter characteristics.

[0065] Furthermore, in the filter device 100, the grounding vias VG1 to VG3 extending from the plate electrode PL20 to the ground electrodes PG1 and PG2 are shared by multiple resonant circuits, thereby reducing the area occupied by the vias in the dielectric substrate, thereby enabling the filter device to be made more compact, improving design flexibility, and reducing coupling between the vias.

[0066] The coupling strength can be adjusted by setting the via diameters of the vias VG2 and VG3 that are individually connected to the ground electrodes to different values. In the filter device 100, the ground electrode PG1 is shared by the resonant circuits RC1 and RC3, and the ground electrode PG2 is shared by the resonant circuits RC2 and RC4. However, each resonant circuit may be provided with its own individual ground electrode.

[0067] The "resonant circuits RC1 to RC4" in the first embodiment correspond to the "first resonant circuit" to the "fourth resonant circuit" in the present disclosure, respectively. The "input terminal T1" and the "output terminal T2" in the first embodiment correspond to the "first terminal" and the "second terminal" in the present disclosure, respectively. The "ground electrode PG1" and the "ground electrode PG2" in the first embodiment correspond to the "first ground electrode" and the "second ground electrode" in the present disclosure, respectively. The "via VG2" and the "via VG3" in the first embodiment correspond to the "first via" and the "second via" in the present disclosure, respectively. The "ground terminal GND1" and the "ground terminal GND2" in the first embodiment correspond to the "first ground terminal" and the "second ground terminal" in the present disclosure, respectively.

[0068] (Variation 1) In the first modification, a configuration will be described in which the coupling mode between the resonant circuits RC1 and RC3 and the resonant circuits RC2 and RC4 is different from that in the first embodiment.

[0069] Fig. 7 is an equivalent circuit diagram of a filter device 100A of Modification 1. Compared with the equivalent circuit of filter device 100 of Embodiment 1 shown in Fig. 2, filter device 100A is provided with inductors L11A, L11B, L12A, L12B, and L13 instead of inductors L10, L11, and L12. The other configuration in Fig. 7 is the same as Fig. 2, and description of overlapping elements will not be repeated.

[0070] In the filter device 100A, the inductor L3 and the inductor L4 are separated from each other. The inductors L3, L11A, and L11B are connected in series between the connection node N2 and the ground terminal GND. The inductors L4, L12A, and L12B are connected in series between the connection node N4 and the ground terminal GND.

[0071] In the filter device 100A, a resonant circuit RC3 is formed by series-connected inductors L3, L11A, and L11B and a capacitor C2 connected in parallel thereto. Similarly, a resonant circuit RC4 is formed by series-connected inductors L4, L12A, and L12B and a capacitor C3 connected in parallel thereto.

[0072] Inductor L13 is connected between connection node N6 between inductors L11A and L11B and connection node N7 between inductors L12A and L12B. In other words, resonant circuits RC1 and RC3 and resonant circuits RC2 and RC4 are magnetically coupled by inductor L13.

[0073] Fig. 8 is an exploded perspective view showing an example of the layered structure of a filter device 100A of Modification 1. Referring to Fig. 8, in the filter device 100A, plate electrodes PL20A and PL20B are provided in place of the plate electrode PL20 on the dielectric layer LY2 of the filter device 100 shown in Fig. 4, and vias VG1A and VG1B are provided in place of the vias VG1 to VG3. The other configuration in Fig. 8 is the same as in Fig. 4, and description of overlapping elements will not be repeated.

[0074] Each of the plate electrodes PL20A and PL20B is a strip-shaped electrode having a substantially U-shape. A via V20 is connected to a first end of the plate electrode PL20A, and a via VG1A is connected to a second end of the plate electrode PL20A. A via V30 is connected to the intermediate portion of the path from the via V20 of the plate electrode PL20A to the via VG1A.

[0075] A via V50 is connected to a first end of the plate electrode PL20B, and a via VG1B is connected to a second end of the plate electrode PL20B. A via V40 is connected to the middle of the path from the via V50 of the plate electrode PL20B to the via VG1B.

[0076] That is, the plate electrode PL20A is shared by the resonant circuits RC1 and RC3, and the plate electrode PL20B is shared by the resonant circuits RC2 and RC4.

[0077] The via VG1A is connected to the ground electrode PG1 on the dielectric layer LY10. The via VG1B is connected to the ground electrode PG2 on the dielectric layer LY10. The vias VG1A and VG1B are connected by a plate electrode PL50 disposed on the dielectric layer LY4.

[0078] The via VG1A forms the inductors L11A and L11B in Fig. 7. The via VG1B forms the inductors L12A and L12B in Fig. 7. The plate electrode PL50 forms the inductor L13 in Fig. 7.

[0079] In the filter device 100A, the ground electrode PG1 connected to the resonant circuits RC1 and RC3 and the ground electrode PG2 connected to the resonant circuits RC2 and RC4 are also separated, which prevents unintended magnetic coupling between the resonant circuits due to the current flowing through the ground electrodes, thereby preventing degradation of the filter characteristics.

[0080] In the filter device 100A of the first modification, the coupling between the resonant circuits RC1 and RC3 and the resonant circuits RC2 and RC4 is realized by the inductor L13, and therefore the coupling between the resonant circuits can be easily adjusted by adjusting the inductance of the inductor L13.

[0081] The "plate electrode PL20A" and the "plate electrode PL20B" in Modification 1 correspond to the "first common electrode" and the "second common electrode" in the present disclosure, respectively.

[0082] [Embodiment 2] In the first embodiment and the first modification, a filter device including four resonant circuits has been described. In the second embodiment and the second and third modifications, a filter device including two resonant circuits will be described.

[0083] 9 is an equivalent circuit diagram of a filter device 100B according to Embodiment 2. The filter device 100B includes a resonant circuit RC1A connected to an input terminal T1 and a resonant circuit RC2A connected to an output terminal T2.

[0084] The resonant circuit RC1A includes inductors L21A and L21B and a capacitor C21, while the resonant circuit RC2A includes inductors L22A and L22B and a capacitor C22.

[0085] In the resonant circuit RC1A, the capacitor C21 is connected between the input terminal T1 and the ground terminal GND. In addition, the inductors L21A and L21B are connected in series between the input terminal T1 and the ground terminal GND. That is, the series-connected inductors L21A and L21B and the capacitor C21 connected in parallel therewith form an LC parallel resonant circuit.

[0086] Similarly, capacitor C22 in resonant circuit RC2A is connected between output terminal T2 and ground terminal GND. In addition, inductors L22A and L22B are connected in series between output terminal T2 and ground terminal GND. That is, an LC parallel resonant circuit is formed by the series-connected inductors L22A and L22B and the capacitor C22 connected in parallel therewith.

[0087] An inductor L23 is connected between a connection node N21 between the inductor L21A and the inductor L21B and a connection node N22 between the inductor L22A and the inductor L22B.

[0088] Next, the structure of filter device 100B will be described with reference to Figures 10 and 11. Figure 10 is an external perspective view of filter device 100B, and Figure 11 is an exploded perspective view showing an example of the layered structure of filter device 100B.

[0089] 3, the filter device 100B differs from the filter device 100 of the first embodiment shown in Fig. 3 in the arrangement of terminals arranged on the outer surface of the dielectric substrate 110. Specifically, as shown in Fig. 10, the input terminal T1 and the output terminal T2 are arranged from the side surface 115 to the bottom surface 112 of the dielectric substrate 110, and the ground terminals GND1 and GND2 are arranged from the side surface 116 to the bottom surface 112.

[0090] Referring to FIG. 11, a dielectric substrate 110 in a filter device 100B includes dielectric layers LY21 to LY27.

[0091] The input terminal T1 is connected to a plate electrode PL70 arranged on the dielectric layer LY24 at the side surface 115. The plate electrode PL70 is a strip-shaped electrode having a substantially L-shape, and a first end thereof is connected to the input terminal T1 at the side surface 115. A second end of the plate electrode PL70 is connected by a via V70 to a plate electrode PL71 arranged on the dielectric layer LY21 and a capacitor electrode PC70 arranged on the dielectric layer LY25.

[0092] The capacitor electrode PC70 is a linear plate electrode extending in the X-axis direction. When viewed from above in the normal direction of the dielectric substrate 110, at least a portion of the capacitor electrode PC70 overlaps with the ground electrode PG1 arranged on the dielectric layer LY26. The ground electrode PG1 is a substantially rectangular plate electrode similar to the filter device 100 of the first embodiment, and is connected to the ground terminal GND1 at the side surface 116. The capacitor electrode PC70 and the ground electrode PG1 form the capacitor C21 in FIG. 9.

[0093] The plate electrode PL71 is a linear electrode extending in the X-axis direction, and a via V70 is connected to a first end thereof. A second end of the plate electrode PL71 is connected to the ground electrode PG1 by the via V71. The vias V70 and V71 and the plate electrode PL71 form inductors L21A and L21B in FIG. 9.

[0094] The output terminal T2 is connected at its side surface 115 to a plate electrode PL80 arranged on the dielectric layer LY24. The plate electrode PL80 is a strip-shaped electrode having a generally L-shape that is symmetrical to the plate electrode PL70. A first end of the plate electrode PL80 is connected to the output terminal T2 at the side surface 115. A second end of the plate electrode PL80 is connected by a via V80 to a plate electrode PL81 arranged on the dielectric layer LY21 and a capacitor electrode PC80 arranged on the dielectric layer LY25.

[0095] The capacitor electrode PC80 is a linear flat plate electrode extending in the X-axis direction. When viewed from above in the normal direction of the dielectric substrate 110, at least a portion of the capacitor electrode PC80 overlaps with the ground electrode PG2 arranged on the dielectric layer LY26. The ground electrode PG2 is a flat plate electrode having a substantially rectangular shape that is symmetrical to the ground electrode PG1, and is arranged further in the positive direction of the Y-axis than the ground electrode PG1 and separated from the ground electrode PG1. The ground electrode PG2 is connected to the ground terminal GND2 at the side surface 116. The capacitor electrode PC80 and the ground electrode PG2 form the capacitor C22 in FIG. 9.

[0096] The plate electrode PL81 is a linear electrode extending in the X-axis direction, and a first end thereof is connected to the via V80. A second end of the plate electrode PL81 is connected to the ground electrode PG2 by the via V81. The vias V80 and V81 and the plate electrode PL81 form the inductors L22A and L22B in FIG. 9.

[0097] The vias V71 and V81 are connected to each other by a plate electrode PL90 disposed on the dielectric layer LY23. The plate electrode PL90 is a linear electrode extending in the Y-axis direction. A first end of the plate electrode PL90 is connected to the via V71, and a second end of the plate electrode PL90 is connected to the via V81. The plate electrode PL90 constitutes the inductor L23 in FIG. 9.

[0098] In the filter device 100B according to the second embodiment, the two resonant circuits RC1A and RC2A are also connected to separate ground electrodes PG1 and PG2. This prevents unintended magnetic coupling between the resonant circuits caused by current flowing through the ground electrodes. This prevents degradation of the filter characteristics.

[0099] The "resonant circuit RC1A" and the "resonant circuit RC2A" in the second embodiment correspond to the "first resonant circuit" and the "second resonant circuit" in the present disclosure, respectively.

[0100] (Variation 2) In the second modification, a configuration in which two resonant circuits are further capacitively coupled in addition to the configuration of the filter device of the second embodiment will be described.

[0101] Fig. 12 is an equivalent circuit diagram of a filter device 100C according to Modification 2. In filter device 100C, a capacitor C23 is further provided in addition to the configuration of filter device 100B according to Embodiment 2 shown in Fig. 9. In Fig. 12, the description of elements that overlap with those in Fig. 9 will not be repeated.

[0102] Capacitor C23 is connected between input terminal T1 and output terminal T2. As a result, resonant circuits RC1A and RC2A are magnetically coupled by inductor L23 and capacitively coupled by capacitor C23. The magnetic coupling by inductor L23 can be weakened by the capacitive coupling of capacitor C23, so the degree of coupling between the resonant circuits can be adjusted by adjusting the capacitance of capacitor C23.

[0103] Fig. 13 is an exploded perspective view showing an example of a layered structure of a filter device 100C of Modification 2. Referring to Fig. 13, in addition to the filter device 100B shown in Fig. 11, a dielectric layer LY24A on which a capacitor electrode PC85 is arranged is provided between a dielectric layer LY24 and a dielectric layer LY25. In Fig. 13, descriptions of elements that overlap with those in Fig. 11 will not be repeated.

[0104] The capacitor electrode PC85 disposed on the dielectric layer LY24A is a linear plate electrode extending in the Y-axis direction. When viewed from above in the normal direction of the dielectric substrate 110, the capacitor electrode PC85 partially overlaps with each of the capacitor electrodes PC70 and PC80 on the dielectric layer LY25. The capacitor electrodes PC70, PC80, and PC85 form the capacitor C23 in FIG. 12.

[0105] In the filter device 100C of the second modification, the two resonant circuits RC1A and RC2A are also connected to separate ground electrodes PG1 and PG2. This prevents unintended magnetic coupling between the resonant circuits caused by current flowing through the ground electrodes. This prevents degradation of the filter characteristics.

[0106] (Variation 3) In the third modification, a configuration in which two resonant circuits are capacitively coupled via a ground electrode will be described.

[0107] Fig. 14 is an equivalent circuit diagram of a filter device 100D according to Modification 3. In filter device 100D, a capacitor C23A is further provided in addition to the configuration of filter device 100B according to Embodiment 2 shown in Fig. 9. Description of elements in Fig. 14 that overlap with those in Fig. 9 will not be repeated.

[0108] The capacitor C23A is connected between the ground terminal GND to which the resonant circuit RC1A is connected and the ground terminal GND to which the resonant circuit RC2A is connected. The resonant circuits RC1A and RC2A are magnetically coupled by the inductor L23 and capacitively coupled by the capacitor C23A. Therefore, the degree of coupling between the resonant circuits can be adjusted by adjusting the capacitance of the capacitor C23A. Furthermore, the capacitive coupling between the resonant circuits RC1A and RC2A via the ground electrodes PG1 and PG2 allows the capacitor C23A to be placed on the same dielectric layer as the capacitors C21 and C22 of the resonant circuits RC1A and RC2A. This reduces the number of layers in the dielectric substrate 110 compared to the filter device 100C of the second modification.

[0109] Fig. 15 is an exploded perspective view showing an example of a layered structure of a filter device 100D of Modification 3. Referring to Fig. 15, in filter device 100D, in addition to filter device 100B shown in Fig. 11, a capacitor electrode PC86 is further arranged on dielectric layer LY25. In Fig. 15, descriptions of elements that overlap with those in Fig. 11 will not be repeated.

[0110] Capacitor electrode PC86 is a linear flat electrode extending in the Y-axis direction and is disposed further in the positive direction of the X-axis than capacitor electrodes PC70 and PC80, and is spaced apart from capacitor electrodes PC70 and PC80. When viewed from above in the normal direction of dielectric substrate 110, capacitor electrode PC86 partially overlaps with ground electrodes PG1 and PG2 of dielectric layer LY26. Capacitor electrode PC86 and ground electrodes PG1 and PG2 form capacitor C23A in FIG. 14.

[0111] In the filter device 100D of the third modification, the two resonant circuits RC1A and RC2A are also connected to separate ground electrodes PG1 and PG2. This prevents unintended magnetic coupling between the resonant circuits caused by current flowing through the ground electrodes. This prevents degradation of the filter characteristics. [Aspect] It will be appreciated by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

[0112] (Item 1) A filter device according to one aspect includes a dielectric substrate, a first terminal and a second terminal arranged on an outer surface of the dielectric substrate, a first resonant circuit, a second resonant circuit, a first ground electrode, and a second ground electrode. The first resonant circuit is connected to the first terminal. The second resonant circuit is connected to the second terminal. The first ground electrode is connected to the first resonant circuit. The second ground electrode is connected to the second resonant circuit and is separated from the first ground electrode.

[0113] (Item 2) In the filter device according to item 1, each of the first resonant circuit and the second resonant circuit is an LC resonant circuit including an inductor and a capacitor.

[0114] (Item 3) In the filter device according to item 2, a part of the inductor included in the first resonant circuit is shared with an inductor included in the second resonant circuit.

[0115] (4) In the filter device according to any one of paragraphs 1 to 3, the first resonant circuit is capacitively coupled to the second resonant circuit.

[0116] (Item 5) In the filter device described in item 1, the first resonant circuit includes a first via connected to the first ground electrode. The second resonant circuit includes a second via connected to the second ground electrode. The first via is connected to the second via.

[0117] (Item 6) The filter device according to item 1 further includes a capacitor electrode that partially overlaps both the first ground electrode and the second ground electrode when viewed in a plan view from the normal direction of the dielectric substrate.

[0118] (7) The filter device according to 5 or 6 further includes a first ground terminal and a second ground terminal arranged on an outer surface of the dielectric substrate. The first ground electrode and the second ground electrode are arranged on an inner layer of the dielectric substrate. The first ground electrode is connected to the first ground terminal. The second ground electrode is connected to the second ground terminal.

[0119] (Item 8) The filter device according to item 1 further includes a third resonant circuit that is electromagnetically coupled to the first resonant circuit, and a fourth resonant circuit that is electromagnetically coupled to the second resonant circuit.

[0120] (Item 9) The filter device according to item 8 further includes a common electrode connected to the first to fourth resonant circuits.

[0121] (Item 10) The filter device described in item 8 further includes a first common electrode connected to the first resonant circuit and the third resonant circuit, and a second common electrode connected to the second resonant circuit and the fourth resonant circuit.

[0122] (Item 11) In the filter device described in item 8, each of the first to fourth resonant circuits is an LC resonant circuit including an inductor and a capacitor.

[0123] (Item 12) In the filter device according to item 11, a part of the inductor included in the first resonant circuit is shared with an inductor included in the third resonant circuit, and a part of the inductor included in the second resonant circuit is shared with an inductor included in the fourth resonant circuit.

[0124] (Item 13) In the filter device according to item 11, some of the inductors included in the first to fourth resonant circuits are shared with one another.

[0125] (14) A high-frequency front-end circuit equipped with the filter device according to any one of the first to thirteenth aspects.

[0126] 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]

[0127] 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, 100, 100A to 100D, 100X filter device, 110 dielectric substrate, 111 top surface, 112 bottom surface, 113 to 116 side surface, C1 to C4 capacitor, C12, C13, C21 to C24, C23A capacitor, DM direction mark, GND, GND1, GND2 ground terminal, L1 to L6, L10 to L12, L11A, L11B, L12, L12A, L12B, L13, L21A, L21B, L22A, L22B, L23 Inductors, LY1 to LY11, LY21 to LY27 dielectric layers, N1 to N7, N21, N22 connection nodes, PC1 to PC7, PC70, PC80, PC85, PC86 capacitor electrodes, PG1, PG1A, PG2 ground electrodes, PL10 to PL13, PL20, PL20A, PL20B, PL30 to PL33, PL50, PL70, PL71, PL80, PL81, PL90 plate electrodes, RC1 to RC4, RC1A, RC2A resonant circuit, T1 input terminal, T2 output terminal, V10 to V13 vias, V20, V30, V40, V50, V60 to V63, V70, V71, V80, V81, VG1 to VG3, VG1A, VG1B vias.

Claims

1. a dielectric substrate; a first terminal and a second terminal disposed on an outer surface of the dielectric substrate; a first resonant circuit connected to the first terminal; a second resonant circuit connected to the second terminal; a first ground electrode connected to the first resonant circuit; a second ground electrode connected to the second resonant circuit and separated from the first ground electrode;

2. 2. The filter device according to claim 1, wherein each of the first resonant circuit and the second resonant circuit is an LC resonant circuit including an inductor and a capacitor.

3. 3. The filter device according to claim 2, wherein a part of an inductor included in the first resonant circuit is shared with an inductor included in the second resonant circuit.

4. 4. The filter device according to claim 1, wherein the first resonant circuit is capacitively coupled to the second resonant circuit.

5. the first resonant circuit includes a first via connected to the first ground electrode; the second resonant circuit includes a second via connected to the second ground electrode; The filter device of claim 1 , wherein the first via is connected to the second via.

6. The filter device according to claim 1 , further comprising a capacitor electrode that partially overlaps both the first ground electrode and the second ground electrode when viewed in a plan view from a normal direction of the dielectric substrate.

7. a first ground terminal and a second ground terminal disposed on an outer surface of the dielectric substrate; the first ground electrode and the second ground electrode are disposed on an inner layer of the dielectric substrate, the first ground electrode is connected to the first ground terminal; 7. The filter device according to claim 5, wherein the second ground electrode is connected to the second ground terminal.

8. a third resonant circuit electromagnetically coupled to the first resonant circuit; The filter device according to claim 1 , further comprising a fourth resonant circuit that is electromagnetically coupled to the second resonant circuit.

9. 9. The filter device according to claim 8, further comprising a common electrode connected to the first resonant circuit to the fourth resonant circuit.

10. a first common electrode connected to the first resonant circuit and the third resonant circuit; The filter device according to claim 8 , further comprising: a second common electrode connected to the second resonant circuit and the fourth resonant circuit.

11. 9. The filter device according to claim 8, wherein each of the first to fourth resonant circuits is an LC resonant circuit including an inductor and a capacitor.

12. a part of an inductor included in the first resonant circuit is shared with an inductor included in the third resonant circuit; The filter device according to claim 11 , wherein a part of an inductor included in the second resonant circuit is shared with an inductor included in the fourth resonant circuit.

13. 12. The filter device according to claim 11, wherein some of the inductors included in the first resonant circuit to the fourth resonant circuit are shared with one another.

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

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