FILTER DEVICE AND HIGH-FREQUENCY FRONT-END CIRCUIT INCLUDING THE SAME

Abstract

A filter device (100) comprises a dielectric substrate (110), an input terminal (T1), an output terminal (T2), a ground terminal (GND), a common electrode (PC), and resonators (RC1 to RC4). Each resonator is connected to the common electrode and the ground terminal. The resonators (RC3 and RC4) are disposed between the resonators (RC1 and RC2). Each resonator includes a capacitor, and a first via and a second via that are connected to the common electrode. The first via is connected to the ground terminal via the capacitor, and the second via is directly connected to the ground terminal. In the common electrode, a direction from the first via to the second via of the resonator (RC1) is opposite to a direction from the first via to the second via of the resonator (RC2). With regard to the resonators (RC3, RC4), a shortest path along the common electrode between the first vias intersects a shortest path along the common electrode between the second vias.

Description

[Technical field]

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

[0002] WO 2019 / 097774 (Patent Document 1) discloses a stacked bandpass filter in which four stages of LC parallel resonators are arranged between an input terminal and an output terminal. In the bandpass filter of WO 2019 / 097774 (Patent Document 1), two capacitors (first capacitor, second capacitor) connected in series are formed between the resonator connected to the input terminal and the resonator connected to the output terminal, and a third capacitor is formed between the connection node of the two capacitors and a ground point. With this configuration, it is possible to change the frequency of the attenuation pole on the higher frequency side than the passband without changing the frequency of the attenuation pole on the lower frequency side than the passband. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2019 / 097774 Summary of the Invention [Problem to be solved by the invention]

[0004] In general, a filter device is required to have a low insertion loss in the pass band and a large attenuation in the non-pass band. In a filter device configured with a plurality of resonators as described above, the insertion loss and the attenuation can be adjusted by adjusting the coupling state between the resonators. However, in general, there is a trade-off between the insertion loss and the attenuation, and it may be difficult to improve both characteristics.

[0005] The present disclosure has been made to solve such problems, and its purpose is to reduce the insertion loss in the passband and improve the attenuation characteristics in non-passbands in a filter device composed of multiple resonators. [Means for solving the problem]

[0006] The filter device according to the present disclosure includes a dielectric substrate having a first surface and a second surface, an input terminal, an output terminal, and a ground terminal disposed on the second surface of the dielectric substrate, a common electrode disposed inside the dielectric substrate, and first to fourth resonators. Each of the first to fourth resonators is connected to the common electrode and the ground terminal. The first resonator is connected to the input terminal, and the second resonator is connected to the output terminal. The third resonator and the fourth resonator are disposed between the first resonator and the second resonator. Each of the first to fourth resonators includes a capacitor, a first via, and a second via. One end of the first via is connected to the common electrode, and the other end is connected to the ground terminal via the capacitor. One end of the second via is connected to the common electrode, and the other end is connected to the ground terminal without the capacitor. In the common electrode, the direction from the first via to the second via of the first resonator is opposite to the direction from the first via to the second via of the second resonator. The shortest path along the common electrode from the first via of the third resonator to the first via of the fourth resonator intersects with the shortest path along the common electrode from the second via of the third resonator to the second via of the fourth resonator. Effect of the Invention

[0007] According to the filter device of the present disclosure, in a filter device including four resonators, each resonator is connected to a common electrode, which reduces the resistance between the resonators compared to a case where the resonators are not connected to each other, thereby reducing the insertion loss in the passband.

[0008] In addition, in the first stage resonator (first resonator) and the fourth stage resonator (second resonator), the vias are arranged in an inverse manner to each other, which weakens the magnetic coupling between the resonators and increases the attenuation at frequencies lower than the passband. Furthermore, in the second stage resonator (third resonator) and the third stage resonator (fourth resonator), the shortest path between the first vias along the common electrode intersects with the shortest path between the second vias along the common electrode. This makes it possible to realize a resonator with a small inductance value and a large capacitance value.

[0009] Therefore, in the filter device according to the present disclosure, in a filter device including a plurality of resonators, it is possible to reduce the insertion loss in the passband and improve the attenuation characteristics in the non-passbands. [Brief description of the drawings]

[0010] [Figure 1] 1 is a block diagram of a communication device having a high-frequency front-end circuit to which a filter device according to a first embodiment is applied. [Diagram 2] 2 is an equivalent circuit diagram of the filter device according to the first embodiment. [Diagram 3] 1 is an external perspective view of a filter device according to a first embodiment. [Figure 4] FIG. 2 is an exploded perspective view showing an example of a laminated structure of the filter device according to the first embodiment. [Diagram 5] 4 is a plan view of a common electrode in the filter device according to the first embodiment. FIG. [Figure 6] 10A and 10B are diagrams for explaining the arrangement of resonators in a filter device of a comparative example. [Figure 7] 4 is a diagram showing the pass characteristic of the filter device according to the first embodiment. FIG. [Figure 8] 13 is a plan view of a common electrode in the filter device of Modification 1. FIG. [Figure 9] 13 is a plan view of a common electrode in a filter device according to a second modified example. FIG. [Figure 10] 13 is a plan view of a common electrode in a filter device according to a third modified example. FIG. [Figure 11] 13 is a plan view of a common electrode in a filter device according to a fourth modified example. FIG. [Figure 12] FIG. 13 is a perspective view of a common electrode in a filter device according to a fifth modified example. [Figure 13] FIG. 23 is a perspective view of a common electrode in a filter device according to a sixth modified example. [Figure 14] 13 is a perspective view of a shield electrode in a filter device according to a seventh modified example. FIG. [Figure 15] 11 is a plan view of a common electrode in a filter device according to a second embodiment. FIG. [Figure 16] 13 is a plan view of a common electrode in a filter device according to a third embodiment. FIG. [Figure 17] 13 is a plan view of a common electrode in a filter device according to a fourth embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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 characters and their description will not be repeated.

[0012] [Embodiment 1] (Basic configuration of communication device) 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 1 is applied. The communication device 10 is, for example, 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 digital-to-analog 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. Note that, although 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 will be described with reference to FIG. 1, 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 up-converts a transmission signal transmitted from the RF circuit 50 into a high-frequency signal and radiates the signal from the antenna 12. The modulated digital signal, which is the transmission signal output from the RF circuit 50, is converted into an analog signal by the D / A converter 40. The mixer 30 mixes the transmission signal, which has been converted from a digital signal to an analog signal by the D / A converter 40, with an oscillation signal from the local oscillator 32, and up-converts the signal into a high-frequency signal. The bandpass filter 28 removes unnecessary waves generated by the up-conversion and extracts only the transmission signal in a desired frequency band. The attenuator 26 adjusts the intensity of the transmission signal. The amplifier 24 amplifies the power of the transmission signal that has passed through the attenuator 26 to a predetermined level. The bandpass filter 22 removes unnecessary waves generated during the amplification process and passes only signal components in a frequency band defined by the communication standard. The transmission signal that has passed through the bandpass filter 22 is radiated from the antenna 12.

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

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

[0017] 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 RC4. Each of the resonators RC1 to RC4 is an LC parallel resonator in which an inductor and a capacitor are connected in parallel.

[0018] The resonator RC1 includes inductors L1A and L1B connected in series between the input terminal T1 and the ground terminal GND, and a capacitor C1 connected in parallel to the inductors L1A and L1B. A connection node N1A between the inductor L1A and the capacitor C1 is connected to the input terminal T1. A connection node N1B between the inductor L1B and the capacitor C1 is connected to the ground terminal GND.

[0019] The resonator RC2 includes inductors L2A and L2B connected in series between the output terminal T2 and the ground terminal GND, and a capacitor C2 connected in parallel to the inductors L2A and L2B. A connection node N2A between the inductor L2A and the capacitor C2 is connected to the output terminal T2. A connection node N2B between the inductor L2B and the capacitor C2 is connected to the ground terminal GND.

[0020] The resonator RC3 includes inductors L3A and L3B connected in series, and a capacitor C3 connected in parallel to the inductors L3A and L3B. A connection node N3A between the inductor L3A and the capacitor C3 is connected to a connection node N1A (i.e., the input terminal T1) of the resonator RC1 via a capacitor C13. A connection node N3B between the inductor L3B and the capacitor C3 is connected to the ground terminal GND.

[0021] The resonator RC4 includes inductors L4A and L4B connected in series, and a capacitor C4 connected in parallel to the inductors L4A and L4B. A connection node N4A between the inductor L4A and the capacitor C4 is connected to a connection node N2A (i.e., the output terminal T2) of the resonator RC2 via a capacitor C24. A connection node N4B between the inductor L4B and the capacitor C4 is connected to the ground terminal GND.

[0022] Moreover, a connection node N1A (input terminal T1) of the resonator RC1 and a connection node N2A (output terminal T2) of the resonator RC2 are connected via a capacitor C12. Furthermore, the connection nodes of the two inductors in each resonator are connected to each other. The part where the resonators are commonly connected corresponds to a common electrode PC described later with reference to FIG. 4 etc.

[0023] The resonators are magnetically coupled to each other. In this manner, the filter device 100 has a configuration in which four stages of resonators that are magnetically coupled to each other are arranged between the input terminal T1 and the output terminal T2. By adjusting the resonance frequency of each resonator, the filter device 100 functions as a bandpass filter that passes signals in a desired frequency band.

[0024] FIG. 3 is an external perspective view of the filter device 100, and FIG. 4 is an exploded perspective view showing an example of a layered structure of the filter device 100. As shown in FIG.

[0025] 3 and 4, the filter device 100 includes a rectangular or substantially rectangular parallelepiped dielectric substrate 110 in which a plurality of dielectric layers LY1 to LY8 are stacked in a stacking direction. The dielectric layers LY1 to LY8 are formed of ceramics such as low temperature co-fired ceramics (LTCC) or resin. Inside the dielectric substrate 110, the inductors and capacitors of the LC parallel resonator are configured 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.

[0026] In the following description, the stacking direction of the dielectric layers LY1 to LY8 in the dielectric substrate 110 is referred to as the "Z-axis direction", the direction perpendicular to the Z-axis direction and along the long side of the dielectric substrate 110 is referred to as the "X-axis direction", and the direction along the short side of the dielectric substrate 110 is referred to as the "Y-axis direction". In the following description, the positive direction of the Z-axis in each drawing may be referred to as the upper side, and the negative direction as the lower side.

[0027] A directionality mark DM for identifying the direction of the filter device 100 is arranged on an upper surface 111 (dielectric layer LY1) of the dielectric substrate 110. External terminals (an input terminal T1, an output terminal T2, and a ground terminal GND) for connecting the filter device 100 to an external device are arranged on a lower surface 112 (dielectric layer LY8) of the dielectric substrate 110. Each of the input terminal T1, the output terminal T2, and the ground terminal GND is a flat electrode, and is a Land Grid Array (LGA) terminal regularly arranged on the lower surface 112 of the dielectric substrate 110. The "upper surface 111" and the "lower surface 112" of the first embodiment correspond to the "first surface" and the "second surface" in this disclosure, respectively.

[0028] As described in FIG. 2, the filter device 100 has a four-stage LC parallel resonator. More specifically, the resonator RC1 includes vias V1A, V1B and a capacitor electrode P1, a resonator RC2 includes vias V2A, V2B and a capacitor electrode P3, a resonator RC3 includes vias V3A, V3B and a capacitor electrode P5, and a resonator RC4 includes vias V4A, V4B and a capacitor electrode P6. Each of the vias V1A, V1B, V2A, V2B, V3A, V3B, V4A, and V4B is connected to a common electrode PC disposed on a dielectric layer LY2. The vias V1B, V2B, V3B, and V4B are also connected to a ground electrode PG1 disposed on a dielectric layer LY6. The ground electrode PG1 is connected to a ground electrode PG2 disposed on a dielectric layer LY7 by a plurality of vias VG1. The ground electrode PG2 is connected to a ground terminal GND of the dielectric layer LY8 by a plurality of vias VG2. The capacitor electrodes P1, P3, P5, and P6 are disposed on the dielectric layer LY5.

[0029] The input terminal T1 is connected to a plate electrode P0 arranged on a dielectric layer LY7 by a via V0. The plate electrode P0 is connected to a common electrode PC arranged on a dielectric layer LY2 by a via V1A. The via V1A is also connected to a capacitor electrode P1 arranged on a dielectric layer LY5 and a capacitor electrode P2 arranged on a dielectric layer LY4. As described above, the common electrode PC is connected to a ground electrode PG1 of the dielectric layer LY6 by a via V1B.

[0030] When the dielectric substrate 110 is viewed in a plan view from the lamination direction (Z-axis direction), a portion of the capacitor electrode P1 overlaps with the ground electrode PG1 of the dielectric layer LY6. The capacitor electrode P1 and the ground electrode PG1 form the capacitor C1 in Fig. 2. The vias V1A and V1B and the common electrode PC form the inductors L1A and L1B in Fig. 2. That is, the capacitor electrode P1, the ground electrode PG1, the vias V1A and V1B, and the common electrode PC form a resonator RC1.

[0031] The output terminal T2 is connected to a plate electrode P8 arranged on the dielectric layer LY7 by a via V5. The plate electrode P8 is connected to a common electrode PC on the dielectric layer LY2 by a via V2A. The via V2A is also connected to a capacitor electrode P3 arranged on the dielectric layer LY5 and a capacitor electrode P4 arranged on the dielectric layer LY4. As described above, the common electrode PC is connected to a ground electrode PG1 on the dielectric layer LY6 by a via V2B.

[0032] When the dielectric substrate 110 is viewed from above, a portion of the capacitor electrode P3 overlaps with the ground electrode PG1 of the dielectric layer LY6. The capacitor electrode P3 and the ground electrode PG1 form the capacitor C2 in Fig. 2. The vias V2A, V2B and the common electrode PC form the inductors L2A, L2B in Fig. 2. That is, the capacitor electrode P3, the ground electrode PG1, the vias V2A, V2B and the common electrode PC form the resonator RC2.

[0033] The capacitor electrode P2 arranged on the dielectric layer LY4 partially overlaps with the capacitor electrode P5 arranged on the dielectric layer LY5 when viewed in a plan view of the dielectric substrate 110. The capacitor electrode P2 and the capacitor electrode P5 form the capacitor C13 in FIG.

[0034] A portion of the capacitor electrode P5 overlaps with the ground electrode PG1 of the dielectric layer LY6 when the dielectric substrate 110 is viewed in plan. The capacitor electrode P5 and the ground electrode PG1 form the capacitor C3 in FIG. 2. The capacitor electrode P5 is connected to the common electrode PC of the dielectric layer LY2 by the via V3A. As described above, the common electrode PC is connected to the ground electrode PG1 by the via V3B. That is, the vias V3A and V3B and the common electrode PC form the inductors L3A and L3B in FIG. 2. That is, the capacitor electrode P5, the ground electrode PG1, the vias V3A and V3B and the common electrode PC form the resonator RC3.

[0035] The capacitor electrode P4 arranged on the dielectric layer LY4 partially overlaps with the capacitor electrode P6 arranged on the dielectric layer LY5 when viewed in a plan view of the dielectric substrate 110. The capacitor electrode P4 and the capacitor electrode P6 form the capacitor C24 in FIG.

[0036] A portion of the capacitor electrode P6 overlaps with the ground electrode PG1 of the dielectric layer LY6 when the dielectric substrate 110 is viewed in plan. The capacitor electrode P6 and the ground electrode PG1 form the capacitor C4 in FIG. 2. The capacitor electrode P6 is connected to the common electrode PC of the dielectric layer LY2 by the via V4A. As described above, the common electrode PC is connected to the ground electrode PG1 by the via V4B. That is, the vias V4A and V4B and the common electrode PC form the inductors L4A and L4B in FIG. 2. That is, the capacitor electrode P6, the ground electrode PG1, the vias V4A and V4B, and the common electrode PC form the resonator RC4.

[0037] Each of the capacitor electrodes P2 and P4 on the dielectric layer LY4 partially overlaps with the capacitor electrode P7 disposed on the dielectric layer LY3 when viewed in a plan view of the dielectric substrate 110. The capacitor electrodes P2, P4, and P7 form the capacitor C12 in FIG.

[0038] In the following description, the vias V1A, V2A, V3A, and V4A connected to the ground terminal GND through a capacitor in each resonator are referred to as "first vias." Also, the vias V1B, V2B, V3B, and V4B connected to the ground terminal GND without a capacitor in each resonator are referred to as "second vias."

[0039] 5 is a plan view of the common electrode PC disposed on the dielectric layer LY2 in the filter device 100. When viewed in a plan view from the normal direction (Z-axis direction), the dielectric substrate 110 has a rectangular shape including long sides LL1, LL2 and short sides SL1, SL2. The long sides LL1, LL2 are sides along the X-axis, and the short sides SL1, SL2 are sides along the Y-axis. The long sides LL1, LL2 correspond to the "first long side" and "second long side" in this disclosure, respectively. The short sides SL1, SL2 correspond to the "first short side" and "second short side" in this disclosure, respectively.

[0040] The common electrode PC includes a plate electrode PT1 to which the vias V1A and V1B constituting the resonator RC1 are connected, a plate electrode PT2 to which the vias V2A and V2B constituting the resonator RC2 are connected, and a plate electrode PT3 to which the vias V3A, V3B, V4A, and V4B constituting the resonators RC3 and RC4 are connected. The plate electrodes PT1 and PT2 are strip-shaped electrodes extending along the short sides SL1 and SL2, respectively. The plate electrode PT3 is disposed between the plate electrodes PT1 and PT2 and has a substantially rectangular shape.

[0041] The plate electrode PT1 is connected to the plate electrode PT3 by the plate electrode PT4. The plate electrode PT4 extends from the end of the plate electrode PT1 in the negative direction of the Y axis along the long side LL1. The plate electrode PT2 is connected to the plate electrode PT3 by the plate electrode PT5. The plate electrode PT5 extends from the end of the plate electrode PT2 in the positive direction of the Y axis along the long side LL2. That is, the common electrode PC is substantially S-shaped and connects the vias V1A, V1B, V2A, V2B, V3A, V3B, V4A, and V4B to each other. In this way, the common electrode PC connects the four resonators RC1 to RC4 to each other.

[0042] A via V1A, which is the first via of the resonator RC1, is connected to the open end of the plate electrode PT1, i.e., the end in the positive direction of the Y axis. A via V1B, which is the second via of the resonator RC1, is connected to the end in the negative direction of the Y axis of the plate electrode PT1. A via V2A, which is the first via of the resonator RC2, is connected to the open end of the plate electrode PT2, i.e., the end in the negative direction of the Y axis. A via V2B, which is the second via of the resonator RC2, is connected to the end in the positive direction of the Y axis of the plate electrode PT2.

[0043] The plate electrode PT3 has a protrusion B1 that protrudes from the end in the positive direction of the Y axis on the side facing the plate electrode PT1 toward the plate electrode PT1, and a protrusion B2 that protrudes from the end in the negative direction of the Y axis on the side facing the plate electrode PT2 toward the plate electrode PT1. PT2 and a protrusion B2 protruding toward the plate electrode PT3. In the plate electrode PT3, a via V3A which is a first via of the resonator RC3 is connected to a connection portion with the plate electrode PT4, and a via V3B which is a second via of the resonator RC3 is connected to the protrusion B1. In addition, in the plate electrode PT3, a via V4A which is a first via of the resonator RC4 is connected to a connection portion with the plate electrode PT5, and a via V4B which is a second via of the resonator RC4 is connected to the protrusion B2. That is, in the plate electrode PT3, the shortest path LN1 from the via V3A to the via V4A and the shortest path LN2 from the via V3B to the via V4B intersect.

[0044] In this way, by reversing the arrangement of the vias of the resonators RC3 and RC4 in the plate electrode PT3, the direction of the electromagnetic field generated in the resonators RC3 and RC4 becomes opposite, so that the magnetic coupling between the resonators RC3 and RC4 becomes weaker than when the vias of both resonators are arranged in the same way. As a result, the electric field coupling between the resonators RC1 and RC2 becomes dominant.

[0045] Generally, in a filter device having four resonators, the coupling between the first resonator and the fourth resonator is related to the occurrence of an attenuation pole in a non-passband at a frequency lower than the passband, and when the electric field coupling between the resonators becomes dominant over the magnetic coupling, the attenuation at the attenuation pole tends to become larger (deeper). Therefore, by reversing the arrangement of the vias of the resonator RC3 to that of the resonator RC4 as in the filter device 100, the attenuation on the lower frequency side than the passband can be made larger than when the arrangement of the vias of the resonator RC3 and the resonator RC4 are the same.

[0046] On the other hand, in a filter device having four resonators, the coupling between the first resonator and the third resonator and the coupling between the second resonator and the fourth resonator are related to the occurrence of attenuation poles in non-pass bands on the higher frequency side than the pass band, and the attenuation at the attenuation poles tends to increase as the magnetic coupling between the resonators increases. In the filter device 100, the arrangement of the vias in the resonator RC1 is the same as that of the resonator RC4, and the arrangement of the vias in the resonator RC2 is the same as that of the resonator RC3. This makes the magnetic coupling dominant over the electric field coupling in the coupling between the resonators RC1 and RC4 and the coupling between the resonators RC2 and RC3. Therefore, the attenuation of the attenuation poles in the non-pass bands on the higher frequency side than the pass band can be increased.

[0047] Furthermore, in the filter device 100, for the resonators RC3 and RC4, the shortest path LN1 from the via V3A of the resonator RC3 to the via V4A of the resonator RC4 intersects with the shortest path LN2 from the via V3B of the resonator RC3 to the via V4B of the resonator RC4. That is, the arrangement of the vias of the resonator RC3 is reversed to that of the resonator RC4. This allows the resonators RC3 and RC4 to have a small inductance value and a large capacitance value. Furthermore, the ratio of the inductance value to the capacitance value can be adjusted without changing the air-core diameter of the inductors L3A and L3B formed by the vias V3A and V3B and the common electrode PC, and the inductors L4A and L4B formed by the vias V4A and V4B and the common electrode PC, and an inductor with a high Q value can be configured.

[0048] It is known that the coupling between the second and third resonators is related to the bandwidth in the passband, and the stronger the magnetic coupling between the resonators, the wider the bandwidth in the passband. In the filter device 100, the arrangement of the vias in the resonator RC3 is opposite to that of the resonator RC4, and as such, the electromagnetic fields generated by the resonators are offset, weakening the magnetic coupling. However, in the filter device 100, the second vias V3B and V4B are arranged on the protruding parts B1 and B2, respectively, and therefore the length of the shortest path LN2 between the second vias is longer than the length of the shortest path LN1 between the first vias. With this configuration, the magnetic coupling is dominant over the electric field coupling between the resonators RC3 and RC4, and therefore the decrease in the bandwidth in the passband can be suppressed.

[0049] (Filter characteristics) Next, the filter characteristics of the filter device 100 of the first embodiment will be described with reference to a comparative example. Fig. 6 is a diagram showing the arrangement of resonators in a filter device 100X of the comparative example. The filter device 100X differs from the filter device 100 in that it does not include a common electrode PC on the dielectric layer LY2, but is otherwise similar to the filter device 100.

[0050] More specifically, since the filter device 100X does not have a common electrode, the resonator RC1 connected to the input terminal T1 and the resonator RC2 connected to the output terminal T2 are not connected to the resonators RC3 and RC4 and are arranged separately. In other words, the plate electrodes PT4 and PT5 are removed from the common electrode PC of the filter device 100. Furthermore, in the filter device 100X, the plate electrode PT3X connected to the resonators RC3 and RC4 does not have the protrusions B1 and B2 like the plate electrode PT3 of the filter device 100, and the distance between the vias V3A and V4A is approximately the same as the distance between the vias V3B and V4B.

[0051] Fig. 7 is a diagram illustrating the pass characteristic of filter device 100 according to the first embodiment. Fig. 7 shows the insertion loss of filter device 100 according to the first embodiment and filter device 100X as a comparative example. In Fig. 7, a solid line LN10 indicates the insertion loss of filter device 100, and a dashed line LN11 indicates the insertion loss of filter device 100X as a comparative example.

[0052] 7, in the filter device 100 of the first embodiment, the frequency bandwidth in which an insertion loss of 3 dB or less can be achieved is wider than that of the filter device 100X. Also, in the filter device 100 of the first embodiment, the attenuation of the attenuation pole on the higher frequency side than the pass band is larger than that of the comparative example. This improves the attenuation characteristics on the higher frequency side than the pass band.

[0053] Furthermore, regarding the attenuation characteristics on the lower frequency side of the passband, the frequencies of the two attenuation poles are closer to the passband side than in the comparative example, which improves the steepness of the attenuation.

[0054] In this manner, the configuration of the filter device 100 of the first embodiment can improve the insertion loss and bandwidth in the passband and improve the attenuation characteristics in the non-passbands, as compared with the filter device 100X of the comparative example.

[0055] (Modification) Modifications of the filter device 100 according to the first embodiment will be described with reference to FIGS.

[0056] (1) Variation 1 In the first modification, a configuration for further expanding the bandwidth of the passband will be described.

[0057] 8 is a plan view of a common electrode PC1 in a filter device 100A of Modification 1. In filter device 100A, the common electrode PC of filter device 100 is replaced with a common electrode PC1. In filter device 100A, descriptions of elements that overlap with those of filter device 100 will not be repeated.

[0058] 8, the common electrode PC1 of the filter device 100A has a plate electrode PT3A to which vias V3A, V3B, V4A, and V4B constituting the resonators RC3 and RC4 are connected, the shape of which is different from that of the plate electrode PT3 of the filter device 100. More specifically, the protrusions B1A and B2A of the plate electrode PT3A have a substantially L-shape. The protrusion B1A protrudes from an end of the side of the plate electrode PT3A facing the plate electrode PT1 in the positive direction of the Y axis toward the plate electrode PT1, and is further bent in the negative direction of the Y axis. The via V3B of the resonator RC3 is connected to the open end of the bent protrusion B1A.

[0059] Similarly, the protrusion B2A protrudes from the end of the plate electrode PT3A in the negative direction of the Y axis on the side facing the plate electrode PT2 toward the plate electrode PT2, and is further bent in the positive direction of the Y axis. The via V4B of the resonator RC4 is connected to the open end of the bent protrusion B2A.

[0060] With this configuration, the length of the shortest path along the plate electrode PT3A connecting the via V3B of the resonator RC3 and the via V4B of the resonator RC4 can be made longer than that of the filter device 100. This makes it possible to further strengthen the magnetic coupling between the resonators RC3 and RC4 compared to the filter device 100, thereby expanding the bandwidth of the passband.

[0061] (2) Variation 2 In the second modification, adjustment of the degree of coupling between the resonators RC1 and RC2 by adjusting the common electrode will be described.

[0062] 9 is a plan view of a common electrode PC2 in a filter device 100B of Modification 2. In filter device 100B, the common electrode PC of filter device 100 is replaced with a common electrode PC2. In filter device 100B, descriptions of elements that overlap with those in filter device 100 will not be repeated.

[0063] 9, in the common electrode PC2 in the filter device 100B, the line width W1 of the plate electrode PT4 and the line width W2 of the plate electrode PT5 are made wider than those of the common electrode PC in the filter device 100. In this manner, by increasing the line width W1 of the plate electrode PT4 and / or the line width W2 of the plate electrode PT5, the shortest distance (arrow AR1) between the via V1A connected to the input terminal T1 and the via V2A connected to the output terminal T2 can be made shorter than that in the filter device 100. That is, the magnetic coupling of the resonators RC1 and RC2 can be strengthened to adjust the attenuation pole on the lower frequency side than the pass band.

[0064] As described above, in the configuration of embodiment 1, the vias of resonator RC1 are arranged in the opposite direction to the vias of resonator RC2, thereby reducing magnetic coupling. However, if it is desired to reduce the degree of magnetic coupling, the line width W1 of the plate electrode PT4 and / or the line width W2 of the plate electrode PT5 can be enlarged to adjust the desired magnetic coupling.

[0065] Furthermore, when the line width W1 of the plate electrode PT4 and / or the line width W2 of the plate electrode PT5 are increased, the inductance value of the path from the input terminal T1 to the output terminal T2 decreases, making it possible to adjust the return loss in the passband.

[0066] In order to ensure symmetry of the filter characteristics, it is preferable that the line width W1 of the plate electrode PT4 and the line width W2 of the plate electrode PT5 are the same (W1=W2). In addition, when it is desired to weaken the magnetic coupling, the line width W1 of the plate electrode PT4 and / or the line width W2 of the plate electrode PT5 may be narrower than that of the filter device 100.

[0067] (3) Variation 3 In Modification 2, a configuration for adjusting the line width of the plate electrode PT4 and / or the line width of the plate electrode PT5 has been described. In Modification 3, a configuration for changing the connection position of the plate electrode PT4 and / or the plate electrode PT5 in addition to the line width of the plate electrode PT4 and / or the line width of the plate electrode PT5 will be described.

[0068] 10 is a plan view of a common electrode PC3 in a filter device 100C of Modification 3. In filter device 100C, the common electrode PC of filter device 100 is replaced with a common electrode PC3. In filter device 100B, descriptions of elements that overlap with those of filter device 100 will not be repeated.

[0069] Referring to FIG. 10, in the common electrode PC3 in the filter device 100C, in addition to the line widths of the plate electrodes PT4 and PT5, the connection position of the plate electrode PT4 from the end of the plate electrode PT1 in the negative direction of the Y axis and / or the connection position of the plate electrode PT5 from the end of the plate electrode PT2 in the positive direction of the Y axis are changed.

[0070] In this way, by changing the line width and connection position of the plate electrodes PT4 and PT5, it is possible to individually adjust the magnetic coupling between the resonators RC1 and RC2 and the inductance value of the path from the input terminal T1 to the output terminal T2, and therefore it is possible to adjust the reflection characteristics in the pass band and the attenuation pole on the lower frequency side of the pass band.

[0071] (4) Variation 4 In the fourth modification, a configuration for adjusting the distance between the vias in the resonators RC3 and RC4 will be described.

[0072] 11 is a plan view of a common electrode PC4 in a filter device 100D of Modification 4. In filter device 100D, the common electrode PC of filter device 100 is replaced with a common electrode PC4. In filter device 100D, descriptions of elements that overlap with those in filter device 100 will not be repeated.

[0073] 11, in the common electrode PC4 of the filter device 100D, the plate electrode PT3D connected to the resonators RC3 and RC4 has cutouts NC1-NC4 in portions along each side of the dielectric substrate 110. More specifically, the cutout NC1 is provided between the via V3A and the via V4B in a portion of the plate electrode PT3D along the long side LL1. Also, the cutout NC2 is provided between the via V3B and the via V4A in a portion of the plate electrode PT3D along the long side LL2.

[0074] Similarly, a notch NC3 is provided between the vias V3A and V3B in a portion along the short side SL1 of the plate electrode PT3D, and a notch NC4 is provided between the vias V4A and V4B in a portion along the short side SL2.

[0075] By providing such a cutout, the path length between the vias of the resonators RC3 and RC4 in the plate electrode PT3D can be adjusted to adjust the inductance between the paths and the magnetic coupling between the resonators, and therefore the bandwidth of the passband and / or the attenuation characteristics in the non-passband can be adjusted.

[0076] (5) Variation 5 In the fifth modification, an example in which the common electrode is configured by flat electrodes arranged on a plurality of dielectric layers will be described.

[0077] Fig. 12 is a perspective view of a common electrode PC5 portion in a filter device 100E of Modification 5. Note that in Fig. 12, the dielectric of the dielectric substrate 110 is omitted.

[0078] 12, the common electrode PC5 in the filter device 100E includes an electrode PC53 arranged in a first layer and electrodes PC51 and PC52 arranged in a second layer. The electrode PC51 corresponds to the plate electrodes PT1 and PT4 in the common electrode PC of the filter device 100. The electrode PC52 corresponds to the plate electrodes PT2 and PT5 in the common electrode PC. The electrode PC53 corresponds to the plate electrode PT3 in the common electrode PC.

[0079] The electrodes PC51 and PC53 are connected by a via V3A of the resonator RC3, and the electrodes PC52 and PC53 are connected by a via V4A of the resonator RC4.

[0080] With this configuration, the path between resonators RC1 and RC2 is lengthened by the length of the vias between electrodes PC51 and PC53, and between electrodes PC52 and PC53, thereby weakening the magnetic coupling between resonators RC1 and RC2, between resonators RC1 and RC4, and between resonators RC2 and RC3.

[0081] (6) Variation 6 In Modification 6, another example in which the common electrode is configured by plate electrodes arranged on a plurality of dielectric layers will be described.

[0082] Fig. 13 is a perspective view of a portion of a common electrode PC6 in a filter device 100F of Modification 6. Note that in Fig. 13, the dielectric of the dielectric substrate 110 is omitted.

[0083] 13, the common electrode PC6 in the filter device 100F includes an electrode PC61 arranged on a first layer and electrodes PC62 and PC63 arranged on a second layer. The electrode PC61 corresponds to a portion of the common electrode PC excluding the protruding portions B1 and B2. The electrode PC62 corresponds to the portion of the common electrode PC corresponding to the protruding portion B1, and the electrode PC63 corresponds to the portion of the common electrode PC corresponding to the protruding portion B2.

[0084] One end of electrode PC62 is connected to electrode PC61 by a via V3B1. The other end of electrode PC62 is connected to ground terminal GND by a via V3B2. One end of electrode PC63 is connected to electrode PC61 by a via V4B1. The other end of electrode PC63 is connected to ground terminal GND by a via V4B2.

[0085] With this configuration, the path length from the connection point between the resonator RC3 and the ground terminal GND to the connection point between the resonator RC4 and the ground terminal GND is increased, and the magnetic coupling between the resonators RC3 and RC4 is strengthened, thereby expanding the bandwidth of the passband.

[0086] (7) Variation 7 In the seventh modification, a configuration will be described in which a shield electrode is disposed on the upper surface side of the common electrode to reduce the influence of other devices disposed outside the filter device.

[0087] Fig. 14 is a perspective view of a portion of a shield electrode PG3 in a filter device 100G of Modification 7. Note that in Fig. 14, the dielectric of the dielectric substrate 110 is omitted.

[0088] 14, in the filter device 100G, a shield electrode PG3 is arranged on the upper surface 111 side of the dielectric layer LY2 on which the common electrode PC is arranged. The shield electrode PG3 has a rectangular shape and overlaps with the common electrode PC when viewed in a plan view from the normal direction of the dielectric substrate 110. Vias V1B, V2B, V3B, and V4B are connected to the shield electrode PG3. That is, the shield electrode PG3 has the same potential as the ground terminal GND and the ground electrode PG1.

[0089] If the shield electrode PG3 is not provided, the current flowing through the common electrode PC may propagate through the shield of an external device or component, causing noise in the signal passing through the filter device. By providing the shield electrode PG3, coupling between the common electrode PC and external devices is prevented, thereby suppressing the generation of noise.

[0090] [Embodiment 2] In the second embodiment, a configuration will be described in which the arrangement of the first and second vias in the resonators RC3 and RC4 is reversed from that of the filter device 100 in the first embodiment.

[0091] 15 is a plan view of a common electrode PC in a filter device 100H according to Embodiment 2. The common electrode PC in filter device 100H has the same shape as the common electrode of filter device 100.

[0092] In the filter device 100H, the via V3A of the resonator RC3 is disposed in the protruding portion B1, and the via V3B of the resonator RC3 is disposed in the connection portion of the plate electrode PT3 with the plate electrode PT4. Also, the via V4A of the resonator RC4 is disposed in the protruding portion B2, and the via V4B of the resonator RC4 is disposed in the connection portion of the plate electrode PT3 with the plate electrode PT5.

[0093] In the filter device 100H, the shortest path from the via V3A to the via V4A and the shortest path from the via V3B to the via V4B also intersect, but in the arrangement of the vias of the resonators RC3 and RC4 in FIG. 15, the shortest path from the via V3A to the via V4A is longer than the shortest path from the via V3B to the via V4B. This makes the magnetic coupling between the resonators RC3 and RC4 stronger than that of the filter device 100. When it is necessary to weaken the magnetic coupling between the resonators RC3 and RC4, the via V3B is moved to a position toward the resonator RC1 along the plate electrode PT4, and the via V4B is moved to a position toward the resonator RC2 along the plate electrode PT5. By adjusting the positions of the vias V3B and V4B in this way, the magnetic coupling between the resonators RC3 and RC4 can be adjusted.

[0094] Since the via V1B of the resonator RC1 and the via V3B of the resonator RC3 are adjacently disposed along the plate electrode, the via V1B and the via V3B may be shared as the via V13B indicated by the dashed line in Fig. 15. By moving the via V1B toward the plate electrode PT3, the inductance value of the resonator RC1 can be increased. Similarly, the via V2B of the resonator RC2 and the via V4B of the resonator RC4 may be shared as the via V24B indicated by the dashed line.

[0095] In the filter device 100H, the arrangements of the vias in the resonators RC1 and RC4 are reversed, and the arrangements of the vias in the resonators RC2 and RC3 are reversed, so that the magnetic coupling between the resonators RC1 and RC4 and between the resonators RC2 and RC3 are weaker than those in the filter device 100 of the first embodiment.

[0096] In the filter device 100H, the resonators RC1 and RC3 have the same via arrangement, and the resonators RC2 and RC4 have the same via arrangement. Therefore, the magnetic coupling between the resonators RC1 and RC3 and between the resonators RC2 and RC4 is stronger than that of the filter device 100 of the first embodiment. In general, the magnetic coupling between the first-stage resonators and the second-stage resonators and the magnetic coupling between the third-stage resonators and the fourth-stage resonators relate to the steepness of attenuation on the low-frequency side of the pass band, so the configuration of the filter device 100H is suitable for a case where a steepness of attenuation is desired to be high near the low-frequency side of the pass band.

[0097] [Embodiment 3] In the third embodiment, a configuration will be described in which the arrangement of the first and second vias in the resonators RC1 and RC2 in the filter device 100 of the first embodiment is reversed.

[0098] 16 is a plan view of a common electrode PC in a filter device 100J according to Embodiment 3. The common electrode PC in the filter device 100J has the same shape as the common electrode of the filter device 100.

[0099] In the filter device 100J, the via V1B of the resonator RC1 is disposed on the open end side of the plate electrode PT1, and the via V1A of the resonator RC1 is disposed at the connection portion with the plate electrode PT4. Also, the via V2B of the resonator RC2 is disposed on the open end side of the plate electrode PT2, and the via V2A of the resonator RC2 is disposed at the connection portion with the plate electrode PT5.

[0100] In the configuration of the filter device 100J, the configuration of the resonators RC3 and RC4 is the same as that of the filter device 100 of the first embodiment, so that the filter device 100J can achieve the same effect as the filter device 100 in terms of the passband bandwidth. Also, the via V1A connected to the input terminal T1 and the via V2A connected to the output terminal T2 are disposed at the ends opposite to the open ends of the plate electrodes PT1 and PT2, so that the length of the path from the input terminal T1 to the output terminal T2 is shorter than that of the filter device 100. Therefore, the insertion loss in the passband can be reduced more than that of the filter device 100.

[0101] In the filter device 100J, the arrangement of the vias in the resonators RC1 and RC4 and the arrangement of the vias in the resonators RC2 and RC3 are reversed to each other, as in the filter device 100H of the second embodiment. The arrangement of the vias in the resonators RC1 and RC3 and the arrangement of the vias in the resonators RC2 and RC4 are the same. Therefore, compared with the filter device 100 of the first embodiment, the magnetic coupling between the resonators RC1 and RC4 and the magnetic coupling between the resonators RC2 and RC3 are weaker, but the magnetic coupling between the resonators RC1 and RC3 and the magnetic coupling between the resonators RC2 and RC4 are stronger than those in the filter device 100 of the first embodiment. The configuration of the filter device 100J is more suitable for a case where a steeper degree of attenuation is desired in the vicinity of the low frequency side of the pass band than that of the filter device 100H of the third embodiment.

[0102] [Embodiment 4] In the fourth embodiment, a configuration will be described in which no protrusion is provided on the plate electrode of the common electrode to which the vias V3A, V3B, V4A, and V4B constituting the resonators RC3 and RC4 are connected.

[0103] 17 is a plan view of a common electrode PC7 in a filter device 100K according to Embodiment 4. In the common electrode PC7 of the filter device 100K, a plate electrode PT3K connected to the resonators RC3 and RC4 has a rectangular shape, and is not provided with the protrusions B1 and B2 as in the filter device 100 of the first embodiment.

[0104] In the common electrode PC7, the via V3B is disposed at the end in the positive direction of the Y axis of the side along the short side SL1 of the dielectric substrate 110, and the via V4B is disposed at the end in the negative direction of the Y axis of the side along the short side SL2 of the dielectric substrate 110. In the filter device 100K, too, the shortest path LN1K from the via V3A to the via V4A and the shortest path LN2K from the via V3B to the via V4B intersect along the plate electrode PT3K.

[0105] In the filter device 100K, since no protrusion is provided on the plate electrode PT3K, the shortest path LN2K from the via V3B to the via V4B is shorter than the shortest path LN2 from the via V3B to the via V4B in the filter device 100. Therefore, compared to the filter device 100, the magnetic coupling between the resonators RC3 and RC4 is stronger, and the bandwidth of the passband is slightly narrower; however, since no protrusion is provided, the insertion loss of the passband can be reduced.

[0106] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not by the description of the embodiments described above, and is intended to include all modifications within the scope and meaning equivalent to the claims. [Explanation of symbols]

[0107] 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 100H, 100J, 100K, 100X filter device, 110 dielectric substrate, 111 upper surface, 112 lower surface, B1, B1A, B2, B2A protrusion, C1 to C4, C12, C13, C24 capacitor, DM directional mark, GND ground terminal, L1A to L4A, L1B to L4B inductor, LL1, LL2 long side, LY1 to LY8 dielectric layer, N1A to N4A, N1B to N4B connection node, NC1 to NC4 Notch, P0, P8, PT1 to PT5, PT3A, PT3D, PT3K, PT3X plate electrodes, P1 to P7 capacitor electrodes, PC, PC1 to PC7 common electrodes, PC51 to PC53, PC61 to PC63 electrodes, PG1, PG2 ground electrodes, PG3 shield electrode, RC1 to RC4 resonators, SL1, SL2 short sides, T1 input terminal, T2 output terminal, V0, V1A to V4A, V1B to V4B, V3B1, V3B2, V3A, V3B1, V13B, V24B, VG1, VG2 vias.

Claims

1. a dielectric substrate having a first surface and a second surface; an input terminal, an output terminal, and a ground terminal disposed on the second surface of the dielectric substrate; a common electrode provided inside the dielectric substrate; a first resonator, a second resonator, a third resonator and a fourth resonator; the first resonator is connected to the input terminal; the second resonator is connected to the output terminal; the third resonator and the fourth resonator are disposed between the first resonator and the second resonator, the first resonator, the second resonator, the third resonator, and the fourth resonator are magnetically coupled to each other, Each of the first resonator, the second resonator, the third resonator, and the fourth resonator is A capacitor; a first via having one end connected to the common electrode and the other end connected to the ground terminal via the capacitor; a second via having one end connected to the common electrode and the other end connected to the ground terminal without passing through the capacitor; a direction of the common electrode from the first via to the second via of the first resonator is opposite to a direction of the common electrode from the first via to the second via of the second resonator; A filter device, wherein the shortest path along the common electrode from a first via of the third resonator to a first via of the fourth resonator intersects with the shortest path along the common electrode from a second via of the third resonator to a second via of the fourth resonator.

2. The common electrode is a first electrode to which a first via and a second via of the first resonator are connected; a second electrode to which the first via and the second via of the second resonator are connected; a third electrode to which the first vias and the second vias of the third resonator and the fourth resonator are connected; a fourth electrode connecting the first electrode and the third electrode; a fifth electrode connecting the second electrode and the third electrode; The third electrode is a first protrusion protruding toward the first electrode; a second protrusion protruding toward the second electrode, a second via of the third resonator is connected to the first protrusion; The filter device according to claim 1 , wherein a second via of the fourth resonator is connected to the second protrusion.

3. 3. The filter device of claim 2, wherein a shortest path along the common electrode from a first via of the third resonator to a first via of the fourth resonator is shorter than a shortest path along the common electrode from a second via of the third resonator to a second via of the fourth resonator.

4. The common electrode is a first electrode to which a first via and a second via of the first resonator are connected; a second electrode to which the first via and the second via of the second resonator are connected; a third electrode to which the first vias and the second vias of the third resonator and the fourth resonator are connected; a fourth electrode connecting the first electrode and the third electrode; a fifth electrode connecting the second electrode and the third electrode; The third electrode is a first protrusion protruding toward the first electrode; a second protrusion protruding toward the second electrode, a first via of the third resonator is connected to the first protrusion; The filter device according to claim 1 , wherein a first via of the fourth resonator is connected to the second protrusion.

5. The filter device according to any one of claims 2 to 4, wherein the first protrusion and the second protrusion are substantially L-shaped.

6. 5. The filter device according to claim 2, wherein the fourth electrode is connected to the first electrode at a position between the first via and the second via of the first resonator.

7. the dielectric substrate has a rectangular shape including a first short side, a second short side, a first long side, and a second long side when viewed in a plan view from the first surface, the first electrode is a strip-shaped electrode disposed along the first short side, the second electrode is a strip-shaped electrode disposed along the second short side, the fourth electrode extends along the first long side and is connected to an end of the first electrode on the first long side; 5. The filter device according to claim 2, wherein the fifth electrode extends along the second long side and is connected to an end of the second electrode on the second long side.

8. The filter device according to claim 7 , wherein the third electrode has a notch formed in at least one of portions along the first short side, the second short side, the first long side, and the second long side.

9. A filter device according to any one of claims 2 to 4, wherein the third electrode is arranged at a position different from the first electrode, the second electrode, the fourth electrode and the fifth electrode in the extension direction of each via in the dielectric substrate.

10. A filter device according to any one of claims 2 to 4, wherein the first protrusion and the second protrusion are positioned at a different position from other parts of the third electrode in the extension direction of each via in the dielectric substrate.

11. a shield electrode disposed on the first surface side of the dielectric substrate relative to the common electrode and connected to the ground terminal; The filter device according to claim 1 , wherein the shield electrode overlaps with the common electrode when viewed in a plan view from the first surface of the dielectric substrate.

12. The filter device of claim 1 , wherein the filter device is a bandpass filter.

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

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