Low-pass filter and duplexer having the same

Abstract

In a low-pass filter, attenuation characteristics are improved without increasing the size of the device. The low-pass filter includes a laminate in which a plurality of dielectric layers are stacked in a stacking direction; an antenna terminal, a terminal, and a ground terminal disposed in the laminate; resonators; capacitors; and an adjustment circuit. The resonators are connected to the input terminal. The resonators are connected between the resonators and the output terminal. The capacitors are connected between a connection node between the resonators and the ground terminal. The adjustment circuit adjusts coupling between the resonators. Each resonator is an LC parallel resonant circuit including a capacitor and an inductor having a via extending in the stacking direction. The adjustment circuit includes a via connected at one end to the ground terminal. In a case where the laminate is viewed from above in the stacking direction, the via is disposed along the via in a region between the via of the resonator and the via of the resonator.

Description

Technical Field

[0001] This disclosure relates to low-pass filters and duplexers having the low-pass filters, and more particularly, to techniques for improving the attenuation characteristics in low-pass filters. Background Technology

[0002] International Publication No. 2018 / 066339 (Patent Document 1) discloses the following configuration: In a 5-stage LC filter (bandpass filter) comprising 5 resonators, a magnetic coupling inductor is connected in parallel to the inductors of each resonator of the first stage resonator on the input terminal side and the fifth stage resonator on the output terminal side.

[0003] In the LC filter disclosed in International Publication No. 2018 / 066339 (Patent Document 1), the desired frequency characteristics are achieved by adjusting the coupling between the magnetic coupling inductor and the adjacent resonator.

[0004] Prior art literature

[0005] Patent documents

[0006] Patent Document 1: International Publication No. 2018 / 066339 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] Typically, it is known that a path is used as the inductor configuration of the resonator in a low-pass filter to improve the Q value and frequency response. However, in such a configuration, since the resonators are coupled to each other through the path via magnetic and / or electric fields, it is sometimes impossible to ensure sufficient isolation between the resonators, and the required attenuation level cannot be achieved.

[0009] To address this issue, increasing the distance between the paths of the resonators is considered. However, this would require increasing the size of the filter device, making it unsuitable for filter devices consisting of multiple resonators to achieve greater attenuation, or for applications requiring miniaturization.

[0010] This disclosure was made to solve the above-mentioned problems, and its purpose is to improve the attenuation characteristics in low-pass filters without increasing the device size.

[0011] Methods for solving problems

[0012] The low-pass filter disclosed herein comprises: a stack having multiple dielectric layers stacked in a stacking direction; an input terminal, an output terminal, and a ground terminal disposed within the stack; a first resonator; a second resonator; a first capacitor; and a first adjustment circuit. The first resonator is connected to the input terminal. The second resonator is connected between the first resonator and the output terminal. The first capacitor is connected between a connection node between the first and second resonators and the ground terminal. The first adjustment circuit adjusts the coupling between the first and second resonators. The first and second resonators are respectively LC parallel resonant circuits comprising a capacitor and an inductor having a path extending in the stacking direction. The first adjustment circuit includes a path connected at one end to the ground terminal. Viewed from above in the stacking direction, the path of the first adjustment circuit is disposed along the path of the first and second resonators in the region between the path of the first and second resonators.

[0013] The effects of the invention

[0014] In the low-pass filter of this invention, a first adjustment circuit having a path arranged along these paths is provided in the region between the first resonator and the second resonator, which are connected in series in the signal transmission path. One end of the path of the first adjustment circuit is connected to a ground terminal, and the coupling between the first resonator and the second resonator can be adjusted (reduced) by the first adjustment circuit. This ensures isolation between the resonators, thus improving the attenuation characteristics in the low-pass filter without increasing the device size. Attached Figure Description

[0015] Figure 1 This is a block diagram of a communication device that includes a low-pass filter and a duplexer for application implementation.

[0016] Figure 2 This is the equivalent circuit diagram of the low-pass filter involved in the implementation method.

[0017] Figure 3 This diagram illustrates the principle of improving attenuation characteristics through a coupling adjustment circuit.

[0018] Figure 4 It means Figure 3 The example shows the throughput characteristics after adjusting for return loss.

[0019] Figure 5 This is an outline diagram of the low-pass filter involved in the implementation method.

[0020] Figure 6 This is an exploded perspective view showing an example of the detailed construction of the low-pass filter involved in the implementation method.

[0021] Figure 7 This is a top view illustrating the configuration of the coupling adjustment circuit in the low-pass filter of Modified Example 1.

[0022] Figure 8 This is a diagram used to illustrate the changes in throughput characteristics caused by the configuration of the coupling adjustment circuit.

[0023] Figure 9 This is a diagram used to illustrate the structure and pass characteristics of the low-pass filter in Modified Example 2.

[0024] Figure 10 This is the equivalent circuit diagram of the low-pass filter involved in Variation Example 3. Detailed Implementation

[0025] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Furthermore, the same or equivalent parts in the drawings will be labeled with the same reference numerals, and their descriptions will not be repeated.

[0026] (Basic components of a communication device)

[0027] Figure 1 This is a block diagram of a high-frequency front-end circuit 20 that includes a duplexer 40 with a low-pass filter 100 applied according to an embodiment, and a communication device 10 equipped with the high-frequency front-end circuit 20. The high-frequency front-end circuit 20 divides the high-frequency signal received by the antenna device ANT into multiple predetermined frequency bands and transmits them to subsequent processing circuits. The high-frequency front-end circuit 20 is used, for example, in mobile terminals such as mobile phones, smartphones or tablets, and communication devices such as personal computers with communication functions.

[0028] Reference Figure 1 The communication device 10 includes a high-frequency front-end circuit 20 containing a duplexer 40 and an RF signal processing circuit (hereinafter also referred to as "RFIC") 30. Figure 1 The high-frequency front-end circuit 20 shown is a receiver-type front-end circuit. The high-frequency front-end circuit 20 includes a duplexer 40 and amplifier circuits LNA1 and LNA2.

[0029] The duplexer 40 includes a filter 100 (FLT1) and a filter 200 (FLT2) that use different frequency ranges as passbands.

[0030] Filter 100 is connected between antenna terminal TA and terminal T1, which serve as common terminals. Filter 100 is a low-pass filter that sets the frequency range of the low-frequency band (LB) group as the passband and the frequency range of the high-frequency band (HB) group as the non-passband. Filter 200 is connected between antenna terminal TA and terminal T2. Filter 200 is a high-pass filter that sets the frequency range of the high-frequency band group as the passband and the frequency range of the low-frequency band group as the non-passband. Furthermore, in the following description, filter 100 is sometimes referred to as "low-pass filter 100" and filter 200 is sometimes referred to as "high-pass filter 200".

[0031] Filters 100 and 200 allow the high-frequency signals from the high-frequency signals received by the antenna device ANT, corresponding to the passbands of each filter, to pass through. This splits the received signal from the antenna device ANT into signals with multiple predefined frequency bands.

[0032] Amplifier circuits LNA1 and LNA2 are each a so-called low-noise amplifier. Amplifier circuits LNA1 and LNA2 utilize low noise to amplify the high-frequency signal after passing through the corresponding filter and transmit it to RFIC 30.

[0033] RFIC 30 is an RF signal processing circuit that processes the high-frequency signals transmitted and received by the antenna device ANT. Specifically, RFIC 30 processes the high-frequency signals input from the antenna device ANT via the receiving-side signal path of the high-frequency front-end circuit 20 through down-conversion and other means, and outputs the received signal generated by the signal processing to the baseband signal processing circuit (not shown).

[0034] In such Figure 1 When the high-frequency front-end circuit 20 is used as a receiving circuit, in the duplexer 40, the antenna terminal TA becomes the input terminal IN, and terminals T1 and T2 become the first output terminal OUT1 and the second output terminal OUT2, respectively. Alternatively, the high-frequency front-end circuit can also be used as a transmitting circuit. In this case, terminals T1 and T2 of the duplexer 40 become input terminals, and the antenna terminal TA becomes a common output terminal. In this case, a power amplifier is used instead of a low-noise amplifier as the amplifier included in the amplification circuit.

[0035] (The structure of a duplexer)

[0036] Figure 2 It means Figure 1 A diagram showing an example of the equivalent circuit of the duplexer 40. (See diagram for example.) Figure 1 As shown in the description, the low-pass filter 100 is connected between antenna terminal TA and terminal T1. Additionally, the high-pass filter 200 is connected between antenna terminal TA and terminal T2.

[0037] Furthermore, as described later, this disclosure aims to improve the pass characteristics of the low-pass filter 100 in the duplexer 40. Therefore, in Figure 2 The equivalent circuit of the low-pass filter 100 is shown only, while the equivalent circuit of the high-pass filter 200 is omitted.

[0038] Reference Figure 2 The low-pass filter 100 includes a filter circuit 110 and a coupling adjustment circuit 120.

[0039] The filter circuit 110 is the actual signal transmission path through which the high-frequency signal input from the antenna terminal TA actually passes. The filter circuit 110 includes: three resonators RC1, RC3, and RC5, which are connected in series between the antenna terminal TA and terminal T1; and two resonators RC2 and RC4, which are connected between the junction of the resonators and the ground terminal GND. That is, the filter circuit 110 is a so-called fifth-order low-pass filter.

[0040] Resonators RC1, RC3, and RC5 are LC parallel resonators with inductors and capacitors connected in parallel. Resonator RC1 includes inductor L11 and capacitor C11. Resonator RC3 includes inductor L31 and capacitor C31. Resonator RC5 includes inductor L51 and capacitor C51.

[0041] One end of inductor L11 is connected to antenna terminal TA. One end of inductor L51 is connected to terminal T1. Inductor L31 is connected between the other ends of inductor L11 and inductor L51. That is, inductors L11, L31, and L51 are connected in series between antenna terminal TA and terminal T1.

[0042] Capacitor C11 is connected in parallel with inductor L11. Capacitor C31 is connected in parallel with inductor L31. Capacitor C51 is connected in series with inductor L51.

[0043] Resonators RC2 and RC4 are LC series resonators formed by connecting an inductor and a capacitor in series. Resonator RC2 includes capacitor C21 and inductor L24. Resonator RC4 includes capacitor C41 and inductor L24. In addition, inductor L24 is shared by resonators RC2 and RC4.

[0044] One end of capacitor C21 of resonator RC2 is connected to the connection node N1 of resonators RC1 and RC3. The other end of capacitor C21 is connected to the ground terminal GND via inductor L24.

[0045] One end of capacitor C41 of resonator RC4 is connected to the connection node N2 of resonators RC3 and RC5. The other end of capacitor C41 is connected to the ground terminal GND via inductor L24.

[0046] In filter circuit 110, signals in a frequency band lower than the cutoff frequency determined by the resonant frequencies of resonators RC1, RC3, and RC5 are transmitted from antenna terminal TA through terminal T1. On the other hand, signals in a frequency band higher than the cutoff frequency are transmitted to ground through resonators RC2 and / or RC4.

[0047] The coupling adjustment circuit 120 is a circuit used to adjust the coupling state between resonators RC1 and RC3, and between resonators RC3 and RC5. The coupling adjustment circuit 120 includes: adjustment circuit AC1 for adjusting the coupling state between resonators RC1 and RC3; and adjustment circuit AC2 for adjusting the coupling state between resonators RC3 and RC5.

[0048] Adjustment circuit AC1 includes inductors L61 and L67, and capacitors C61 and C62. Adjustment circuit AC2 includes inductors L71 and L67, and capacitors C71 and C72. Furthermore, inductor L67 is shared by both adjustment circuits AC1 and AC2.

[0049] In the adjustment circuit AC1, capacitors C61 and C62 are connected in series between the antenna terminal TA and the connection node N2. One end of inductor L61 is connected to the connection node N3 between capacitors C61 and C62. The other end of inductor L61 is connected to the ground terminal GND via inductor L67.

[0050] In the adjustment circuit AC2, capacitors C71 and C72 are connected in series between terminal T1 and connection node N1. One end of inductor L71 is connected to connection node N4 between capacitors C71 and C72. The other end of inductor L71 is connected to the ground terminal GND via inductor L67.

[0051] In addition, in the actual method, capacitors C61 and C62 in the adjustment circuit AC1 are parasitic capacitances generated between the paths of inductors L11 and L31 in the resonators RC1 and RC3, respectively, and the path of inductor L61 in the adjustment circuit AC1.

[0052] Similarly, in the actual implementation, capacitors C71 and C72 in the adjustment circuit AC2 are parasitic capacitances generated between the paths of inductors L31 and L51 in the resonators RC3 and RC5, respectively, and the path of inductor L71 in the adjustment circuit AC2.

[0053] (The effect of the coupling adjustment circuit)

[0054] use Figure 3 This explains the principle that the attenuation characteristics of a low-pass filter can be improved by using such a coupling adjustment circuit. Furthermore, in Figure 3 For ease of explanation, we will use a third-order low-pass filter as an example. Figure 2 In the filter circuit 110, the two sets of resonators RC1, RC2, RC3 and RC3, RC4, RC5 constitute the third-order low-pass filter.

[0055] exist Figure 3 In the diagram, the configuration of an ideal third-order low-pass filter is shown as the left figure (A), the configuration of an actual low-pass filter is shown as the middle figure (B), and the configuration of a low-pass filter according to the embodiment is shown as the right figure (C). The schematic circuit is shown at the top, and the simulated curve of the pass characteristics of the circuit is shown at the bottom.

[0056] In each graph, the solid lines (LN11, LN13, LN15) represent insertion loss, and the dashed lines (LN12, LN14, LN16) represent return loss. Additionally, in the middle graph (B) and the right graph (C), the graph in the left graph (A) is shown with thin lines for comparison.

[0057] The low-pass filter in the left figure (A) has the same characteristics as... Figure 2 The filter circuit 110 shown is a substantially identical ideal (theoretical) low-pass filter. This low-pass filter includes a resonator RCA connected to the input terminal Tin, a resonator RCB connected to the output terminal Tout, and a capacitor CA3 connected between the connection node NA of the resonators RCA and RCB and the ground terminal GND. The resonator RCA includes an inductor LA1 and a capacitor CA1 connected in parallel between the input terminal Tin and the connection node NA. The resonator RCB includes an inductor LA2 and a capacitor CA2 connected in parallel between the connection node NA and the output terminal Tout.

[0058] In this low-pass filter, as shown by line LN11 in the curve diagram below, an attenuation pole is generated near 5.2 GHz in the non-pass band. By obtaining a relatively steep attenuation characteristic, the desired attenuation amount can be obtained.

[0059] However, when the circuit is implemented within a dielectric stack, the distance between resonators cannot be adequately ensured due to device size constraints. Therefore, as shown in Figure (B), a certain degree of capacitive coupling due to parasitic capacitance SC occurs between adjacent resonators. Additionally, inductive coupling M can occur between inductors LA1 and LA3.

[0060] In the case shown in Figure (B), in the signal transmission path from the input terminal Tin to the output terminal Tout, in addition to the path through the series-connected resonators RCA and RCB, a path is also generated through the parasitic capacitance SC and the inductive coupling M. Through this additional path, the signal on the relatively high-frequency side of the input high-frequency signal is transmitted to the output terminal Tout, which may result in a decrease in attenuation at the attenuation poles and a deterioration in the attenuation characteristics in the non-passband, as shown by the solid line LN13.

[0061] In the low-pass filter of the right figure (C) corresponding to the implementation method, the inductor LG (with) is configured with a shunt connection. Figure 2 The inductors L61, L71, and L67 correspond to this, thus creating parasitic capacitance SC between the resonators, which in turn forms parasitic capacitances SC1 and SC2 between the inductor LG and the resonator LG. These parasitic capacitances SC1 and SC2 are connected to the ground terminal GND. In other words, a high-pass filter with a shunt connection is essentially formed through the parasitic capacitances SC1 and SC2 and the inductor LG.

[0062] With this configuration, the high-frequency signal flowing into the path formed by parasitic capacitances SC1 and SC2 is transmitted to ground through inductor LG, but not to terminal T1. Since a portion of inductor LG is positioned between inductors LA1 and LA3, the inductive coupling M generated between inductors LA1 and LA3 includes both the inductive coupling between inductors LA1 and LG and the inductive coupling between inductors LA3 and LG. Therefore, the amount of inductive coupling generated between inductors LA1 and LA3 becomes smaller than that in the middle diagram (B), thus also reducing the isolation degradation between resonators. Therefore, as shown by solid line LN15, even with parasitic capacitance and inductive coupling between resonators, the attenuation characteristics in the non-passband can be improved to the same level as in the left diagram (A).

[0063] Furthermore, in the low-pass filter shown in the right figure (C), the return loss is worse than that in the left figure (A). This can be improved by adjusting the capacitance of capacitor CA2. Figure 4 In the diagram, the insertion loss after capacitor CA2 adjustment is represented by the solid line KN17, and the return loss is represented by the dashed line LN18. For example... Figure 4 As shown, by adjusting the capacitance of capacitor CA2, the return loss in the 0-4 GHz band can be improved to a level comparable to that of capacitor CA2. Figure 3 The situation is similar to that in the left figure (A).

[0064] As mentioned above, in Figure 2 In the filter circuit 110, the resonators RC1, RC2, RC3 and RC3, RC4, RC5 constitute... Figure 3Such a third-order low-pass filter. Therefore, in the filter circuit 110, it is also possible to suppress the reduction in attenuation characteristics associated with parasitic capacitance and inductive coupling between resonators, which is inevitably caused by the size constraints of the device.

[0065] (Detailed structure of a low-pass filter)

[0066] Next, use Figure 5 and Figure 6 This section will explain the detailed configuration of the low-pass filter 100 according to the implementation method. Furthermore, in... Figure 5 and Figure 6 For ease of understanding, the example given is a discrete device, where the low-pass filter 100 is disposed separately within the dielectric stack. However, the low-pass filter 100 may also be configured as part of the duplexer 40 and disposed together with the high-pass filter 200 within a single stack.

[0067] Reference Figure 5 and Figure 6 The low-pass filter 100 includes a cuboid or approximately cuboid stack 130 formed by stacking multiple dielectric layers LY1 to LY16 along a predetermined direction. In the stack 130, the direction in which the multiple dielectric layers LY1 to LY16 are stacked is defined as the stacking direction. Each dielectric layer of the stack 130 is formed, for example, of a ceramic such as low-temperature co-fired ceramics (LTCC) or a resin.

[0068] Inside the stack 130, inductors and capacitors for constituting the low-pass filter 100 are formed by multiple electrodes disposed in each dielectric layer and multiple channels disposed between the dielectric layers. Furthermore, in the following description, for ease of explanation, the case where the stack 130 has a multilayer structure as described above will be used as an example, but the stack 130 may also have a single-layer structure.

[0069] In this specification, "path" refers to a conductor formed in a dielectric layer for connecting electrodes disposed in different dielectric layers. Paths are formed, for example, through conductive paste, plating, and / or metal leads. Furthermore, in the following description, the stacking direction of dielectric layers LY1 to LY16 in the laminate 130 is referred to as the "Z-axis direction," the direction perpendicular to the Z-axis direction and along the long side of the laminate 130 is referred to as the "X-axis direction," and the direction along the short side of the laminate 130 is referred to as the "Y-axis direction." Additionally, the positive direction of the Z-axis in each figure is sometimes referred to as the upper side, and the negative direction as the lower side.

[0070] The stack 130 includes an upper surface 131 (first main surface) and a lower surface 132 (second main surface). A directional marker DM for determining the orientation of the low-pass filter 100 is disposed on the upper surface 131 (dielectric layer LY1) of the stack 130. Figure 5 As shown, on the lower surface 132 (dielectric layer LY16) of the laminate 130, antenna terminal TA, terminal T1, and ground terminal GND are configured as external terminals for connecting the low-pass filter 100 and external devices. Each external terminal is a flat electrode, which is an LGA (Land Grid Array) terminal regularly arranged on the lower surface 132 of the laminate 130.

[0071] The antenna terminal TA of the dielectric layer LY16 disposed on the lower surface 132 is connected to the planar electrode PL10 disposed on the dielectric layer LY15 via the passage V1. The planar electrode PL10 is a strip electrode with an approximate L-shape, with the end connected to the passage VL11 in the positive Y-axis direction and the end connected to the passage VL14 in the negative Y-axis direction.

[0072] The passage VL11 is connected to the planar electrode PL11 disposed on the dielectric layer LY3. The planar electrode PL11 is a straight electrode extending along the Y-axis, with the passage VL11 connected to its end in the positive Y-axis direction. The planar electrode PL11 is connected to one end of the strip-shaped planar electrode PL12 disposed on the dielectric layer LY11 through the passage VL12 disposed at its end in the negative Y-axis direction.

[0073] The passage VL14 connected to the planar electrode PL10 is connected to the capacitor electrode PC10 disposed on the dielectric layer LY8. In addition, the capacitor electrode PC10 is also connected to the capacitor electrode PC11 disposed on the dielectric layer LY6 and the capacitor electrode PC12 disposed on the dielectric layer LY4 through the passage VL13.

[0074] Capacitor electrodes PC10, PC11, and PC12 are all planar electrodes with a generally rectangular shape. When viewed from above in the stacking direction, at least a portion of each of capacitor electrodes PC10 and PC11 overlaps with capacitor electrode PC13 disposed on dielectric layer LY7. Furthermore, when viewed from above in the stacking direction, at least a portion of each of capacitor electrodes PC11 and PC12 overlaps with capacitor electrode PC14 disposed on dielectric layer LY5.

[0075] Capacitor electrodes PC13 and PC14 have a portion that protrudes from a rectangular planar electrode in the X-axis direction, and a passage VL15 is connected to this protruding portion. The passage VL15 is connected to the middle portion of the planar electrode PL12 of the dielectric layer LY11. In addition, the passage VL15 is also connected to capacitor electrode PC30 disposed in dielectric layer LY6 and capacitor electrode PC31 disposed in dielectric layer LY8.

[0076] Composed of capacitor electrodes PC10~PC14 Figure 2 The capacitor C11 is located within the capacitor. Additionally, it is composed of planar electrodes PL10 and PL11, and vias VL11 to VL14. Figure 2 The inductor L11 in the circuit. That is, the resonator RC1 is composed of capacitor electrodes PC10~PC14, plate electrodes PL10, PL11 and the circuit VL11~VL14.

[0077] The other end of the planar electrode PL12 of dielectric layer LY11 is connected to the passage VL30. Passage VL30 is connected to the capacitor electrode PC20 disposed in dielectric layer LY13, and to the planar electrode PL31 disposed in dielectric layer LY3.

[0078] The planar electrode PL31 is a straight electrode that extends along the Y-axis, just like the planar electrode PL11, and its end in the positive Y-axis direction is connected to the passage VL30. The end of the planar electrode PL31 in the negative Y-axis direction is connected to one end of the strip-shaped planar electrode PL32 disposed in the dielectric layer LY10 via the passage VL31.

[0079] A passage VL32 is connected to the other end of the planar electrode PL32. The passage VL32 is connected to the planar electrode PL33 disposed on the dielectric layer LY3. The planar electrode PL33 is a straight electrode disposed parallel to the planar electrode PL31, and the end in the positive Y-axis direction is connected to the passage VL32. The end of the planar electrode PL31 in the negative Y-axis direction is connected to one end of the strip-shaped planar electrode PL34 disposed on the dielectric layer LY11 via the passage VL33, and is connected to the capacitor electrode PC40 disposed on the dielectric layer LY13.

[0080] A passage VL34 is connected to the middle of the flat plate electrode PL34, but... Figure 6 The plate electrode PL34 is obscured by the passage VL33 and is difficult to see. The plate electrode PL34 is connected to the capacitor electrode PC32 disposed on the dielectric layer LY7 and the capacitor electrode PC33 disposed on the dielectric layer LY5 through the passage VL34.

[0081] Capacitor electrodes PC30 to PC33 are all roughly rectangular flat plates, and when viewed from above in the stacking direction, at least a portion of them overlap. The structure consists of capacitor electrodes PC30 to PC33. Figure 2 The capacitor C31 is located within the capacitor. Additionally, it is composed of planar electrodes PL31~PL33 and vias VL30~VL33. Figure 2 The inductor L31 in the circuit. That is, the resonator RC3 is composed of capacitor electrodes PC30~PC33, plate electrodes PL31~PL33, and the circuits VL15, VL30~VL34.

[0082] The other end of the flat plate electrode PL34 is connected to a passage VL50, but... Figure 6 The middle part is obscured by the channel VL70 and is difficult to see. The channel VL50 is connected to the planar electrode PL50 disposed on the dielectric layer LY3.

[0083] The planar electrode PL50 is a straight electrode extending along the Y-axis, with a passage VL50 connected to its end in the positive Y-axis direction. The planar electrode PL50 is connected to one end of the planar electrode PL51 disposed in the dielectric layer LY15 through the passage VL51 disposed at its end in the negative Y-axis direction.

[0084] The planar electrode PL51 is a strip electrode in a roughly L-shape, with a passage VL51 connected to its end in the negative Y-axis direction and a passage VL52 connected to its end in the positive Y-axis direction. Furthermore, the planar electrode PL51 is connected to terminal T1 disposed on the dielectric layer LY16 via passage V2.

[0085] The passage VL52 is connected to the capacitor electrode PC52 disposed on the dielectric layer LY8. In addition, the capacitor electrode PC52 is also connected to the capacitor electrode PC51 disposed on the dielectric layer LY6 and the capacitor electrode PC50 disposed on the dielectric layer LY4 via the passage VL53.

[0086] Capacitor electrodes PC50, PC51, and PC52 are all planar electrodes with a generally rectangular shape. When viewed from above in the stacking direction, at least a portion of each of capacitor electrodes PC50 and PC51 overlaps with capacitor electrode PC33 disposed on the dielectric layer LY5. Furthermore, when viewed from above in the stacking direction, at least a portion of each of capacitor electrodes PC51 and PC52 overlaps with capacitor electrode PC32 disposed on the dielectric layer LY5.

[0087] Composed of capacitor electrodes PC50~PC52 Figure 2 The capacitor C51 is located within the capacitor. Additionally, it consists of planar electrodes PL50 and PL51, and vias VL50 to VL53. Figure 2The inductor L51 in the circuit. That is, the resonator RC5 is composed of capacitor electrodes PC50~PC52, plate electrodes PL50, PL51 and the circuit VL50~VL53.

[0088] The capacitor electrodes PC20 and PC40 disposed in the dielectric layer LY13 are generally rectangular planar electrodes extending along the X-axis. Viewed from above in the stacking direction, capacitor electrodes PC20 and PC40 overlap with capacitor electrode PG1 disposed in the dielectric layer LY14. Furthermore, viewed from above in the stacking direction, at least a portion of each of capacitor electrodes PC20 and PC40 also overlaps with capacitor electrode PC80 disposed in the dielectric layer LY12.

[0089] Capacitor electrode PC80 is connected to capacitor electrode PG1 of dielectric layer LY14 via passage VG3. Capacitor electrode PG1 is connected to ground terminal GND of dielectric layer LY16 via passage VG1, plate electrode PL1 disposed on dielectric layer LY15, and passage VG2.

[0090] It consists of capacitor electrode PC20 and capacitor electrodes PG1 and PC80. Figure 2 The capacitor C21 is located within the capacitor. Additionally, it is composed of capacitor electrode PC40 and capacitor electrodes PG1 and PC80. Figure 2 The capacitor C41 is located within the circuit. Furthermore, it is composed of the pathways VG1 and VG2 and the plate electrode PL1. Figure 2 Inductor L24 in the middle.

[0091] That is, it consists of capacitor electrodes PC20, PG1, PC80, and circuits VG1, VG2, as well as plate electrode PL1. Figure 2 The resonator RC2 in the circuit is similarly composed of capacitor electrodes PC40, PG1, PC80, circuits VG1, VG2, and plate electrode PL1. Figure 2 The resonator RC4 in the middle.

[0092] The capacitor electrode PG1 is also connected to vias VL60 and VL70. Via VL60 is connected to a planar electrode PL60 disposed in the dielectric layer LY2. The planar electrode PL60 is a straight electrode extending along the Y-axis, with via VL60 connected to its end in the positive Y-axis direction. Via VL61 is connected to the end of the planar electrode PL60 in the negative Y-axis direction. The other end of via VL61 extends to the dielectric layer LY9, and its end becomes an open terminal.

[0093] It consists of a flat plate electrode PL60 and a through-pass VL60. Figure 2 The inductor L61 in the above-mentioned inductor L24. Additionally, the circuits VG1 and VG2 and the plate electrode PL1 constituting the aforementioned inductor L24 also serve as... Figure 2 The inductor L67 in the middle plays its role.

[0094] Viewed from above in the stacking direction, path VL60 is positioned along path VL11 and path VL30 in the region between path VL11 in resonator RC1 and path VL30 in resonator RC3. Thus, path VL60 and path VL11 are capacitively coupled through parasitic capacitance, and path VL60 and path VL30 are capacitively coupled through parasitic capacitance.

[0095] Therefore, through the capacitive coupling between path VL60 and path VL11, a Figure 2 Capacitor C61. Similarly, through the capacitive coupling between path VL60 and path VL30, a [structure / structure] is formed. Figure 2 The capacitor C62 is composed of the circuits VL60, VG1, VG2, and the plate electrodes PL1 and PL60. Figure 2 The adjustment circuit AC1 in the middle.

[0096] Additionally, the path VL61 functions as an open-circuit stub to adjust the frequency of the attenuation poles generated by the coupling between resonators RC1 and RC3. Therefore, depending on the frequency of the generated attenuation poles, there may be cases where the path VL61 is not provided. Alternatively, the other end of the path VL61 can be connected to the ground terminal GND to serve as a short-circuit stub.

[0097] Passage VL70 is connected to the planar electrode PL62 disposed in dielectric layer LY3. Planar electrode PL62 is a straight electrode extending along the Y-axis, with passage VL70 connected to its negative Y-axis end. Passage VL71 is connected to the positive Y-axis end of planar electrode PL62. The other end of passage VL71 extends into dielectric layer LY9, its end being an open end. Additionally, in dielectric layer LY2, planar electrode PL62 is connected to planar electrode PL60 via planar electrode PL61. Furthermore, like passage VL61, passage VL71 functions as a stub for adjusting the frequency of the attenuation poles caused by the coupling between resonators RC3 and RC5.

[0098] It consists of a flat plate electrode PL62 and a circuit VL70. Figure 2 The inductor L71 is included. Additionally, as mentioned above, the pathways VG1, VG2, and the planar electrode PL1 also serve as... Figure 2 The inductor L67 in the middle plays its role.

[0099] Viewed from above in the stacking direction, path VL70 is positioned along path VL30 and path VL50 in the region between resonator RC3 and resonator RC5. Thus, path VL70 is capacitively coupled to path VL30 via parasitic capacitance, and path VL70 is capacitively coupled to path VL50 via parasitic capacitance.

[0100] Thus, through the capacitive coupling between path VL70 and path VL30, a Figure 2 Capacitor C71. Similarly, through the capacitive coupling between path VL70 and path VL50, a configuration is formed. Figure 2 The capacitor C72 is composed of the circuits VL62, VG1, VG2, and the plate electrodes PL1 and PL70. Figure 2 The adjustment circuit AC2 in the middle.

[0101] As described above, by configuring electrodes and pathways in the laminate 130, the following can be achieved: Figure 2 The low-pass filter 100 shown.

[0102] (Variation Example 1)

[0103] In the above description, in the dielectric layer LY2, the plate electrode PL60 included in the adjustment circuit AC1 and the plate electrode PL62 included in the adjustment circuit AC2 are connected by the plate electrode PL61, but the plate electrode PL61 is not a necessary component.

[0104] Figure 7 This is a top view of portions of the dielectric layers LY2 and LY3 in the low-pass filter 100A of Modified Example 1, viewed from the stacking direction. Figure 7 As shown, in the low-pass filter 100A of Modified Example 1, the planar electrode PL62 in the dielectric layer LY2 is not configured.

[0105] Even with the configuration of Modification 1, the inclusion of adjustment circuit AC1 (containing a planar electrode PL60) and adjustment circuit AC2 (containing a planar electrode PL62) improves the attenuation characteristics in the non-passband. As described in the embodiment, by directly connecting adjustment circuit AC1 and adjustment circuit AC2 using the planar electrode PL61 to increase the magnetic coupling between adjustment circuit AC1 and adjustment circuit AC2, the magnetic field coupling between inductor L11 and inductor L51 can be adjusted, thus allowing adjustment of the attenuation near the passband of the low-pass filter 100. Therefore, compared to Modification 1, the attenuation characteristics can be further improved.

[0106] Figure 8This is a diagram illustrating the pass-through characteristics of the low-pass filter 100 of the embodiment, the low-pass filter 100A of Modified Example 1, and the low-pass filter 100X of the comparative example without the coupling adjustment circuit 120. Figure 8 The upper part shows a schematic configuration of the coupling adjustment circuit in the low-pass filter of each example, and the lower part shows a graph of the pass characteristics (return loss, insertion loss) of each example.

[0107] In the low-pass filter 100X in the comparative example, no adjustment circuits AC1 and AC2 are provided between resonators RC1 and RC3, and between resonators RC3 and RC5.

[0108] exist Figure 8 In the lower part of the graph, solid lines LN20, LN30, and LN40 represent insertion loss, and dashed lines LN25, LN35, and LN45 represent return loss. Furthermore, lines LN20 and LN25 represent the low-pass filter 100 of the embodiment, and lines LN30 and LN35 represent the low-pass filter 100A of Modified Example 1. Lines LN40 and LN45 represent the low-pass filter 100X of the comparative example.

[0109] like Figure 8 As shown in the graph, in Modification 1, the attenuation characteristics in the non-passband are improved compared to the comparative example, although the attenuation at the attenuation poles near the passband is only about 40 dB. On the other hand, in the case of the low-pass filter 100 of the embodiment, an attenuation of about 65 dB is obtained at the attenuation poles near the passband, and in the 5 GHz to 9 GHz region in the non-passband, more attenuation is ensured compared to the comparative example and Modification 1.

[0110] As described above, even in the low-pass filter 100A of Modified Example 1, which does not have the planar electrode PL62 connecting the adjustment circuits AC1 and AC2, the attenuation characteristics in the non-passband can be improved compared to the case where the coupling adjustment circuit 120 is not provided. Furthermore, as with the low-pass filter 100 of the embodiment, by connecting the adjustment circuits AC1 and AC2 using the planar electrode PL62, the attenuation characteristics can be further improved.

[0111] In the embodiments, "resonator RC1," "resonator RC3," and "resonator RC5" correspond to the "first resonator," "second resonator," and "third resonator" in this disclosure, respectively. In the embodiments, "capacitor C21" and "capacitor C41" correspond to the "first capacitor" and "second capacitor" in this disclosure, respectively. In the embodiments, "adjustment circuit AC1" and "adjustment circuit AC2" correspond to the "first adjustment circuit" and "second adjustment circuit" in this disclosure, respectively. In the embodiments, "planar electrode PL62" corresponds to the "connection electrode" in this disclosure. In the embodiments, "inductor L24" corresponds to the "grounding inductor" in this disclosure. In the embodiments, "antenna terminal TA" corresponds to the "input terminal" in this disclosure.

[0112] (Variation Example 2)

[0113] In Modification 2, the application of the features of this disclosure to a third-order low-pass filter will be described. Furthermore, in Modification 2, the first-order resonator and the third-order resonator connected in series between the input and output terminals are configured differently.

[0114] Figure 9 This is a diagram illustrating the structure and pass-through characteristics of the low-pass filter in Modification Example 2. Figure 9 The upper part shows the equivalent circuits of the third-order low-pass filter 150 corresponding to the embodiment and the low-pass filter 150A of variant 2. Figure 9 The lower part shows the pass characteristics (return loss, insertion loss) of low-pass filter 150 and low-pass filter 150A.

[0115] Furthermore, in the equivalent circuit, only a portion of the filter circuit is shown, omitting the coupling adjustment circuit. As the coupling adjustment circuit, the application... Figure 2 The adjustment circuit shown is configured like AC1.

[0116] In the low-pass filter 150, resonators RC1 and RC3 are connected in series between antenna terminal TA and terminal T1. Resonator RC1 includes an inductor L1 and a capacitor C1 connected in parallel between terminals T10 and T11. Resonator RC3 includes an inductor L3 and a capacitor C3 connected in parallel between terminals T12 and T13. A capacitor C2 is connected between the connection node between resonators RC1 and RC3 and the ground terminal GND.

[0117] On the other hand, in the low-pass filter 150A, resonators RC1A and RC3A are respectively provided instead of resonators RC1 and RC3 in the low-pass filter 150. Resonator RC1A includes inductors L1A and L2A and capacitor C1. In addition, resonator RC3A includes inductors L3A and L4A and capacitor C3.

[0118] In resonator RC1A, an inductor L1A and an inductor L2A connected in parallel and a capacitor C1 connected in series are connected between terminals T10 and T11. Similarly, in resonator RC2A, an inductor L3A and an inductor L4A connected in parallel and a capacitor C3 connected in series are connected between terminals T12 and T13.

[0119] The combined inductance of inductors L1A and L2A is the same as the inductance of inductor L1, and the combined inductance of inductors L3A and L4A is the same as the inductance of inductor L3. Therefore, the resonant frequency of resonator RC1A is the same as the resonant frequency of resonator RC1, and the resonant frequency of resonator RC2A is the same as the resonant frequency of resonator RC2. Consequently, the frequency of the attenuation pole generated in low-pass filter 150A is the same as the frequency of the attenuation pole generated in low-pass filter 150.

[0120] However, in the low-pass filter 150A of Modified Example 2, the inductance value in the signal transmission path from antenna terminal TA to terminal T1 is reduced (L1+L3 > L1A+L3A). Therefore, compared with the case of low-pass filter 150, the loss generated in the signal transmission path in low-pass filter 150A is reduced. Thus, by adopting the resonator configuration of Modified Example 2, the transmission characteristics can be improved.

[0121] exist Figure 9 In the lower part of the graph, solid lines LN50 and LN51 show the insertion loss and return loss in the low-pass filter 150A of Modified Example 2, respectively. Additionally, dashed lines LN55 and LN56 show the insertion loss and return loss in the low-pass filter 150 corresponding to the embodiment, respectively.

[0122] like Figure 9 As shown in the graph, with low-pass filter 150A, the attenuation characteristics near the passband in the non-passband are steeper compared to low-pass filter 150. Furthermore, although the attenuation at the attenuation poles is slightly reduced compared to low-pass filter 150, an attenuation of approximately 60 dB is still achieved.

[0123] As described above, by dividing the inductors in each resonator connected in series in the signal transmission path from the input terminal to the output terminal, a configuration is formed by connecting a first circuit consisting of a portion of the inductors and a second circuit consisting of a series resonant circuit of the remaining inductors and capacitors in parallel, thereby improving the steepness of the attenuation characteristics.

[0124] In Modification 2, "inductor L1" and "inductor L3" correspond to the "first circuit" and "first coil" in this disclosure, respectively. In Modification 2, "resonator RC11" and "resonator RC12" correspond to the "second circuit" in this disclosure, respectively. In Modification 2, "terminal T10" and "terminal T12" correspond to the "first terminal" in this disclosure, respectively. In Modification 2, "terminal T11" and "terminal T13" correspond to the "second terminal" in this disclosure, respectively.

[0125] (Variation Example 3)

[0126] In Variation 3, examples of other configurations of a resonator connected in series between the input and output terminals are described.

[0127] Figure 10 This is a diagram illustrating an example of the equivalent circuit of the duplexer 40A for the low-pass filter 100B involved in Modified Example 3. Figure 10 In, also with Figure 2 Similarly, only the equivalent circuit of the low-pass filter 100B is shown, while the equivalent circuit of the high-pass filter 200 is omitted.

[0128] Reference Figure 10 The low-pass filter 100B includes a filter circuit 110B and a coupling adjustment circuit 120. In the filter circuit 110B, with... Figure 2 Compared to the low-pass filter 100, the resonators RC1, RC3, and RC5 have different configurations, while the other configurations are the same as those of the low-pass filter 100. Furthermore, the coupling adjustment circuit 120 is different from... Figure 2 The same applies to the case of low-pass filter 100.

[0129] The resonators RC1, RC3, and RC5 in the filter circuit 110B are roughly the same as in variant example 2, consisting of an inductor and an LC series resonator connected in parallel.

[0130] Resonator RC1 includes inductor L11B and resonator RC15. Resonator RC15 includes inductors L12B and L13B and capacitor C11. In resonator RC15, capacitor C11 is connected between one end of inductor L12B and one end of inductor L13B. Furthermore, the other end of inductor L12B is connected to one end of inductor L11B and the antenna terminal TA. The other end of inductor L13B is connected to the other end of inductor L11B and resonator RC3.

[0131] Resonator RC3 includes inductor L31B and resonator RC35. Resonator RC35 includes inductors L32B and L33B and capacitor C31. In resonator RC35, capacitor C31 is connected between one end of inductor L32B and one end of inductor L33B. The other end of inductor L32B is connected to one end of inductor L31B and resonator RC1. The other end of inductor L33B is connected to the other end of inductor L31B and resonator RC5.

[0132] Resonator RC5 includes inductor L51B and resonator RC55. Resonator RC55 includes inductors L52B and L53B and capacitor C51. In resonator RC55, capacitor C51 is connected between one end of inductor L52B and one end of inductor L53B. The other end of inductor L52B is connected to one end of inductor L51B and resonator RC3. The other end of inductor L53B is connected to the other end of inductor L51B and terminal T1.

[0133] In this configuration, the attenuation characteristics in the non-passband can also be improved by providing the coupling adjustment circuit 120. Furthermore, by dividing the inductors in each resonator connected in series in the signal transmission path from the input terminal to the output terminal, a configuration is formed in which a first circuit consisting of a portion of the inductors and a second circuit consisting of a series resonant circuit of the remaining inductors and capacitors are connected in parallel, thereby improving the steepness of the attenuation characteristics.

[0134] In Modification 3, "inductor L11B", "inductor L31B" and "inductor L51B" correspond to the "first circuit" and "first coil" in this disclosure, respectively. In Modification 3, "resonator RC21", "resonator RC31" and "resonator RC41" correspond to the "second circuit" in this disclosure, respectively.

[0135] The embodiments disclosed herein should be considered illustrative rather than restrictive in all respects. The scope of the invention is not shown by the description of the embodiments above, but is set forth by the claims, which are intended to include all modifications in the same sense and scope as the claims.

[0136] Explanation of reference numerals in the attached figures

[0137] 10 Communication devices; 20 High-frequency front-end circuits; 30 RFICs; 40, 40A duplexers; 100, 100A, 100B, 100X, 150, 150A low-pass filters; 110, 110B filter circuits; 120 Coupling adjustment circuits; 130 Laminates; 131 Upper surface; 132 Lower surface; 200 High-pass filters; AC1, AC2 adjustment circuits; ANT antenna devices; C1~C3, C11, C21, C31, C41, C51, C61, C62, C71, C72, CA1~CA3 capacitors; DM directional marker; GND ground terminal; IN, Tin Input terminals; L1, L3, L1A~L4A, L11, L11B~L13B, L24, L31, L31B~L33, BL51, L51B~L53B, L61, L67, L71, LA1, LA2, LG; Inductors; LNA1, LNA2; Amplifier circuit; LY1~LY16; Multiple dielectric layers; N1~N4, NA; Connection nodes; PC10~PC14, PC20, PC30~PC33, PC40, PC50~PC52, PC80, PG1; Capacitor electrodes; PL1, PL10~PL12, PL31~PL34, PL50, PL51, PL60~PL62, PL70 Planar electrodes; RC1~RC5, RC1A, RC2A, RC3A, RC11, RC12, RC15, RC21, RC31, RC35, RC41, RC51, RC55, RCA, RCB resonators; SC1, SC2 parasitic capacitances; T1, T2, T10~T13 terminals; TA antenna terminal; Tout output terminal; V1, V2, VG1~VG3, VL11~VL15, VL30~VL34, VL50~VL53, VL60~VL62, VL70, VL71 pathways.

Claims

1. A low-pass filter, comprising: A laminate, in which multiple dielectric layers are stacked in the stacking direction; The input terminals, output terminals, and grounding terminals are configured on the laminate. The first resonator is connected to the input terminal; A second resonator is connected between the first resonator and the output terminal; A first capacitor is connected between the connection node between the first resonator and the second resonator and the ground terminal; as well as The first adjustment circuit adjusts the coupling between the first resonator and the second resonator. The first resonator and the second resonator are respectively LC parallel resonant circuits comprising a capacitor and an inductor having a path extending in the stacking direction. The first adjustment circuit includes a path connected at one end to the ground terminal. When viewed from above in the stacking direction, the path of the first adjustment circuit is configured along the path of the first resonator and the path of the second resonator in the region between the path of the first resonator and the path of the second resonator.

2. The low-pass filter according to claim 1, wherein, The path of the first adjustment circuit is capacitively coupled to the path of the first resonator and the path of the second resonator.

3. The low-pass filter according to claim 1 or 2, wherein, The low-pass filter has the following features: A third resonator is connected between the second resonator and the output terminal; The second capacitor is connected between the connection node between the second resonator and the third resonator and the ground terminal; as well as The second adjustment circuit adjusts the coupling between the second resonator and the third resonator. The third resonator is an LC parallel resonant circuit comprising a capacitor and an inductor having a path extending in the stacking direction. The second adjustment circuit includes a path connected at one end to the ground terminal. When viewed from above in the stacking direction, the path of the second adjustment circuit is configured along the path of the second resonator and the path of the third resonator in the region between the path of the second resonator and the path of the third resonator.

4. The low-pass filter according to claim 3, wherein, The path of the second adjustment circuit is capacitively coupled to the path of the second resonator and the path of the third resonator.

5. The low-pass filter according to claim 3 or 4, wherein, It also includes a connection electrode that connects the path of the first adjustment circuit to the path of the second adjustment circuit.

6. The low-pass filter according to claim 5, wherein, The laminate has a first principal surface and a second principal surface orthogonal to the lamination direction. The input terminal, the output terminal, and the grounding terminal are disposed on the second main surface. The connecting electrodes are disposed on the dielectric layer located on the first main surface side compared to the paths of each resonator.

7. The low-pass filter according to any one of claims 3 to 6, wherein, It also includes a grounding inductor, one end of which is connected to the first capacitor and the second capacitor, and the other end is connected to the grounding terminal.

8. The low-pass filter according to any one of claims 1 to 7, wherein, It also has a short wire that connects to the other end of the path of each adjustment circuit.

9. The low-pass filter according to any one of claims 1 to 8, wherein, Each resonator includes: First terminal and second terminal; and The first circuit and the second circuit are connected in parallel between each other between the first terminal and the second terminal. In each resonator, The inductor includes a first coil and a second coil. The first circuit includes the first coil. The second circuit includes a capacitor connected in series and the second coil.

10. A duplexer, It comprises a low-pass filter as described in any one of claims 1 to 9, and A high-pass filter connected to the input terminal.

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