Filter and communication equipment comprising same

Abstract

The present disclosure relates to a filter and a communication device, the filter comprising: an input terminal, an output terminal, a filter network disposed between the input terminal and the output terminal and comprising a series branch and a parallel branch, a first matching unit disposed between the input terminal and the filter network, and a second matching unit disposed between the input terminal and the filter network, the second matching unit is arranged between the filter network and the output terminal; the series branches comprise resonance units, one end of each parallel branch is connected to a node between the series branches, and the other end of each parallel branch is grounded; at least two parallel branches are provided with at least one common inductor, and other parallel branches, the first matching unit and the second matching unit are provided with inductors connected to the ground; at least one common inductor in the at least two parallel branches is decoupled from one of the inductors, connected to the ground, in the other parallel branches except the at least two parallel branches and the first matching unit or the second matching unit in an adjacent mode.

Description

Technical Field

[0001] The present disclosure relates to a filter, and more particularly, to a radio frequency filter and a communication device including the radio frequency filter. Background Art

[0002] Portable communication devices, such as mobile phones, notebooks or personal digital assistants, need to acquire and transmit signals. Different signals correspond to different communication methods and frequency ranges; for example, cellular-based communication methods, WIFI-based communication methods and GPS-based communication methods are used to acquire and transmit different signals. In order to meet the needs of signal acquisition and transmission of portable communication devices, RF filters came into being. With the increase in 5G commercial use, the demand for RF filters is also increasing.

[0003] See also Figure 1 , Figure 1 The schematic diagram of the radio frequency filter in the prior art is shown, and the radio frequency filter includes an input terminal IN, an output terminal OUT, a matching network and a filtering network. The filtering network is connected between the input terminal IN and the output terminal OUT, and the filtering network includes a series branch and a parallel branch, wherein the boxes on the series branch and the parallel branch represent a resonance unit, and the resonance unit can be a resonance unit composed of LC lumped elements, or a resonance unit composed of an acoustic wave resonator, or a resonance unit composed of different types of devices, such as a resonance unit composed of an LC lumped element and an SMR acoustic wave resonator, or a resonance unit composed of an SMR acoustic wave resonator and an FBAR acoustic wave resonator. Each parallel branch may also include an inductor, wherein one or more inductors are used to generate an out-of-band suppression point to meet the out-of-band suppression of a specific frequency band.

[0004] In the prior art, the inductance in each parallel branch is usually formed by winding on the printed circuit board (PCB), and the winding inductance on the printed circuit board (PCB) has different degrees of coupling, so designers usually need a certain way to eliminate the coupling. However, when it is necessary to strongly suppress a certain frequency band, especially a low frequency band, coupling of different branches is required to achieve strong suppression of the required frequency band; this technical operation usually leads to a weakening of suppression in certain frequency bands, especially high frequency bands. Summary of the invention

[0005] In response to the above technical problems, the present invention has carefully designed a radio frequency filter, avoided the above technical problems of existing filters, and successfully developed a high-performance radio frequency filter that can utilize coupling to enhance the suppression of special frequency bands while ensuring the suppression of high frequency bands.

[0006] A brief overview of the disclosure will be given below in order to provide a basic understanding of certain aspects of the disclosure. It should be understood that this overview is not an exhaustive overview of the disclosure. It is not intended to identify key or important parts of the disclosure, nor is it intended to limit the scope of the disclosure. Its purpose is simply to give certain concepts in a simplified form as a prelude to a more detailed description discussed later.

[0007] According to one aspect of the present disclosure, a filter is provided, comprising: an input terminal, an output terminal, a filter network, a first matching unit, and a second matching unit. The filter network is arranged between the input terminal and the output terminal and comprises a series branch and a parallel branch. The first matching unit is arranged between the input terminal and the filter network, and the second matching unit is arranged between the filter network and the output terminal; the series branch comprises a resonance unit, one end of each parallel branch is connected to a node between the series branches, and the other end of each parallel branch is grounded; at least two parallel branches have at least one common inductor, and other parallel branches, the first matching unit, and the second matching unit have inductors connected to the ground; at least one common inductor in at least two parallel branches is decoupled from one of the inductors connected to the ground in other parallel branches other than the at least two parallel branches, the first matching unit, or the second matching unit by being arranged in proximity.

[0008] Furthermore, the first matching unit and / or the second matching unit has a passive device unit composed of passive devices.

[0009] Furthermore, the decoupling by arranging two inductors in proximity to each other realizes negative coupling by arranging the two inductors in proximity to each other in terms of physical distance on the printed circuit board and setting the currents of the adjacent inductor coil parts to be opposite.

[0010] Furthermore, the physical proximity of two inductors on a printed circuit board refers to the physical proximity of the two inductors on the same metal layer of the printed circuit board in the horizontal direction, or refers to the physical proximity of the two inductors on different metal layers of the printed circuit board in the vertical direction.

[0011] Further, when the physical distance between the two inductors on the printed circuit board is close, the distance between the closest inductor coil parts of the two inductors is set to be greater than twice the line width of the two inductors.

[0012] Further, one of the inductors connected to the ground in the first matching unit or the second matching unit is decoupled through the shared inductor of the second parallel branch and the third parallel branch.

[0013] Furthermore, the decoupling in the manner of arranging the two inductors adjacent to each other is achieved by arranging the two inductors adjacent to each other in the topological distance of the filter circuit and setting the current flow directions of the two inductors opposite to each other when they are working.

[0014] Furthermore, the first matching unit has a series and a parallel inductor network, the series inductor is farther away from one of the common inductors in the first to third parallel branches in circuit topology than the parallel inductor, and the parallel inductor is decoupled by one of the common inductors in the first to third parallel branches.

[0015] Further, when both the fourth parallel branch and the fifth parallel branch have an inductor connected to the ground, the inductor in the fourth parallel branch is decoupled through the shared inductor of the second parallel branch and the third parallel branch.

[0016] According to another aspect of the present disclosure, a communication device is provided, the communication device comprising any one of the above filters. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The specific contents of the present disclosure are described below with reference to the accompanying drawings, which will help to more easily understand the above and other purposes, features and advantages of the present disclosure. The accompanying drawings are only for illustrating the principles of the present disclosure. The sizes and relative positions of the units in the accompanying drawings need not be drawn to scale.

[0018] Figure 1 It is a block diagram of the architecture of a radio frequency filter in the prior art;

[0019] Figure 2 A structural block diagram of the first embodiment of the filter disclosed in the present invention is shown;

[0020] Figure 3-Figure 5 A structural block diagram of a second embodiment of the filter disclosed in the present invention is shown;

[0021] Figure 6 A schematic diagram showing the physical structure of the second embodiment of the filter disclosed in the present invention is adjacent to the PCB board;

[0022] Figure 7 The impedance curves of the embodiment of the present disclosure and the comparative example are shown;

[0023] Figure 8 Show Figure 4 A wiring diagram of the first passive device unit in the filter circuit structure shown on a PCB board;

[0024] Fig. 9 Show Figure 5 A wiring diagram of the first passive device unit in the filter circuit structure shown on a PCB board;

[0025] Fig.10 Shown as Figure 8 and Fig. 9 Impedance curve comparison diagram of the specific example shown in;

[0026] Fig.11A structural block diagram of the third embodiment of the filter disclosed in the present invention is shown. DETAILED DESCRIPTION

[0027] Below, exemplary disclosures of the present disclosure will be described in conjunction with the accompanying drawings. For the sake of clarity and conciseness, not all features of implementing the present disclosure are described in the specification. However, it should be understood that many decisions specific to the present disclosure may be made in the process of developing any such implementation of the present disclosure in order to achieve the developer's specific goals, and these decisions may vary from one disclosure to another.

[0028] It should also be noted that, in order to avoid obscuring the present disclosure due to unnecessary details, only device structures closely related to the solutions according to the present disclosure are shown in the drawings, while other details that are not closely related to the present disclosure are omitted.

[0029] It should be understood that the present disclosure is not limited to the described implementation forms due to the following description with reference to the accompanying drawings. In the present disclosure, features between different embodiments may be replaced or borrowed, and one or more features may be omitted in one embodiment, if feasible.

[0030] First embodiment

[0031] See also Figure 2 , Figure 2 The structural block diagram of the first embodiment of the filter disclosed in the present invention is shown, and the filter includes an input terminal IN, an output terminal OUT and a filter network 100. The filter network 100 is connected between the input port IN and the output port OUT, and the filter network 100 includes a series branch and a parallel branch, wherein the boxes on the series branch and the parallel branch represent a resonance unit. The resonance unit can be a resonance unit composed of LC lumped elements; it can be a resonance unit composed of one or more acoustic wave resonators; it can be a resonance unit composed of different types of devices, such as a resonance unit composed of an LC lumped element and an SMR acoustic wave resonator, or a resonance unit composed of an SMR acoustic wave resonator and an FBAR acoustic wave resonator; each parallel branch of the filter can include an inductor connected to the ground.

[0032] like Figure 2 As shown, a filter network 100 provided in this embodiment has at least N parallel branches, for example, N is a natural number greater than or equal to 4. Five parallel branches are schematically arranged in the filter network 100. An inductor L1 is arranged on the first parallel branch, an inductor L2 is arranged on the second parallel branch, an inductor L3 is arranged on the third parallel branch, an inductor L6 is arranged on the fourth parallel branch, and an inductor L7 is arranged on the fifth parallel branch.

[0033] The first end of the inductor L2 on the second parallel branch is connected to the resonant unit on the second parallel branch, the first end of the inductor L3 on the third parallel branch is connected to the resonant unit on the third parallel branch, the second end of the inductor L2 is connected to the second end of the inductor L3 and then connected to the first end of the common inductor L4, forming a T-type inductive coupling.

[0034] The first end of the inductor L1 on the first parallel branch is connected to the resonant unit on the first parallel branch, the second end of the inductor L1 is connected to the second end of the inductor L4 and then connected to the first end of the shared inductor L5, and the second end of the shared inductor L5 is grounded. That is, the T-type inductor coupling formed by the inductor L2, the inductor L3 and the shared inductor L4 is further coupled with the L1 inductor of the first branch through the shared inductor L5. In a variation of the present embodiment, one or more of the inductor L1, the inductor L2 and the inductor L3 may not exist. In another variation of the present embodiment, the shared inductor L4 may also be the shared inductor between the first parallel branch and the third parallel branch, or the shared inductor L4 may also be the shared inductor between the first parallel branch and the second parallel branch.

[0035] The first end of the inductor L6 on the fourth parallel branch is connected to the resonant unit on the fourth parallel branch, and the second end of the inductor L6 is grounded. The first end of the inductor L7 on the fifth parallel branch is connected to the resonant unit on the fifth parallel branch, and the second end of the inductor L7 is grounded.

[0036] Then, the inductor L6 on the fourth parallel branch or the inductor L7 on the fifth parallel branch is decoupled through one of the shared inductor L4 and the shared inductor L5, so that relatively high suppression can be achieved in both the high frequency band and the low frequency band of the filter.

[0037] Specifically, in the present disclosure, the decoupling of the inductor L6 on the fourth parallel branch or the inductor L7 on the fifth parallel branch through one of the shared inductor L4 and the shared inductor L5 can be achieved by arranging the inductor L6 or the inductor L7 adjacent to one of the shared inductor L4 and the shared inductor L5. This is because the principle of inductor decoupling is to make the two related inductors close to each other to form a combined transformer structure, thereby generating a high-precision, stable negative mutual inductance (-M) in the middle part of the inductor coil. Then, the negative mutual inductance (-M) is used to offset the equivalent series inductance in the high-frequency circuit of the filter, thereby reducing noise.

[0038] It should be pointed out that in the present disclosure, the inductor L6 or the inductor L7 is set to be adjacent to the shared inductor L4 or the shared inductor L5. In a specific implementation, the inductor L6 or the inductor L7 can be adjacent to one of the shared inductor L4 and the shared inductor L5 at a specific physical distance on the PCB board, and then the currents of the adjacent inductor coil parts of the two can be set to be opposite.

[0039] Specifically, physical proximity can be achieved by setting the inductor L6 or L7 on the same metal layer of the printed circuit board to be physically adjacent to one of the shared inductor L4 or shared inductor L5 in the horizontal direction, and then setting the currents of the adjacent inductor coil parts to be opposite. It can also be achieved by setting the inductor L6 or L7 on different metal layers of the printed circuit board to be physically adjacent to one of the shared inductor L4 or shared inductor L5 in the vertical direction, and then setting the currents of the adjacent inductor coil parts to be opposite.

[0040] In the present disclosure, the inductor L6 or the inductor L7 is arranged to be adjacent to one of the shared inductor L4 and the shared inductor L5. In another specific implementation, the inductor L6 or the inductor L7 can be arranged to be adjacent to one of the shared inductor L4 and the shared inductor L5 through the proximity of the circuit topology distance, so that the voltage and current are adjacent during operation and the current flows of the two are arranged to be opposite.

[0041] Specifically, when the inductor L6 or the inductor L7 is arranged to be adjacent to the common inductor L4 and the common inductor L5 in terms of voltage and current during operation, since in the present disclosure, Figure 2 As shown, the fourth parallel branch is closer to the first parallel branch, the second parallel branch and the third parallel branch than the fifth parallel branch in the circuit topology structure. Therefore, the inductor L6 on the fourth parallel branch can be specifically selected to be arranged adjacent to one of the common inductor L4 and the common inductor L5 to obtain a better decoupling effect than when the inductor L7 on the fifth parallel branch is arranged adjacent to one of the common inductor L4 and the common inductor L5.

[0042] Through the design of the filter in this embodiment, not only the near-stopband suppression is enhanced, but the suppression of frequency bands lower than the passband is also significantly enhanced, and the suppression of specific frequency bands on the right side of the passband, such as the suppression at about 100 MHz higher than the right edge frequency of the passband, is significantly enhanced, and the entire out-of-band suppression is also significantly improved.

[0043] Furthermore, the filter further comprises a first matching unit arranged between the input port IN and the filter network; and a second matching unit arranged between the filter network and the output port OUT. Figure 2 As shown in FIG, the first matching unit includes an inductor Lin connected in parallel to the ground, and the second matching unit includes an inductor Lout connected in parallel to the ground. It should be noted that although the first matching unit and the second matching unit are Figure 2In the circuit structure, there is a single inductor connected in parallel to the ground, but the first matching unit and the second matching unit inductor can also be a single lumped element (such as an inductor) connected in series in the series branch, or the first matching unit can also be a resonance unit composed of a resonator with capacitance or inductance connected in series in the series branch; the first matching unit can also be other lumped elements connected in parallel to the ground, such as a capacitor or a resonance unit with capacitance or inductance, and the first matching unit can have a hybrid resonance unit composed of a resonator and a passive device; the first matching unit can also be a resonance unit with more degrees of freedom. The first matching unit and the second matching unit are not further limited in the present disclosure.

[0044] Second embodiment

[0045] See also Figure 3-Figure 5 , Figure 3-Figure 5 A structural block diagram of a second embodiment of the filter disclosed in the present invention is shown;

[0046] The first matching unit of the filter in the second embodiment includes a first passive device unit, and the second matching unit includes a second passive device unit. The first passive device unit includes an inductor connected in parallel to the ground, and the second passive device unit includes an inductor connected in parallel to the ground. Exemplarily, the first passive device unit and the second passive device can be set as a single inductor connected in parallel to the ground, a single inductor connected in series, or an inductor unit with one series and one parallel, or an inductor unit with one parallel and one series, or an inductor unit with one series, one parallel and one series, or a resonance unit composed of a series, one parallel and one series inductor and a capacitor, or a resonance unit composed of a series, one parallel and one series inductor and a capacitor, etc.

[0047] like Figure 3 In the example shown in , the first passive device unit is a single inductor Lin connected in parallel to the ground; the second passive device unit is a single inductor Lout connected in parallel to the ground. Figure 4 As shown in the example, the first passive device unit is a parallel and series inductor unit, wherein the inductor Lin is connected in parallel between the input port IN and the ground, the inductor Lsin is connected in series between the input port IN and the filter network, the inductor Lin is closer to the input port than the inductor Lsin, and the second passive device unit is a single inductor Lout connected in parallel to the ground. Or as Figure 5 In the example shown in the figure, the first passive device unit is a series-parallel inductor unit, wherein the first end of the inductor Lsin is connected in series to the input port IN, the second end of the inductor Lsin is connected in series to the input end of the filter network, and Lin is connected in parallel between the second end of the inductor Lsin and the ground, and the inductor Lsin is closer to the input port than the inductor Lin; the second passive device unit is a single inductor Lout connected in parallel to the ground. The setting method of the filter network in the second embodiment is the same as that in the first embodiment, and will not be repeated here.

[0048] The inductor Lin in the first passive device unit or the inductor Lout in the second passive device unit is decoupled from one of the shared inductor L4 and the shared inductor L5, so that relatively high suppression can be achieved in a specific frequency band in the high frequency band and the low frequency band of the filter.

[0049] Specifically, in the present disclosure, decoupling the inductor Lin in the first passive device unit or the inductor Lout in the second passive device unit through the shared inductor L4 and the shared inductor L5 on the parallel branch of the filter network can be achieved by arranging the inductor Lin or the inductor Lout adjacent to one of the shared inductor L4 and the shared inductor L5.

[0050] It should be noted that in the present disclosure, the inductor Lin or the inductor Lout is arranged adjacent to one of the shared inductor L4 and the shared inductor L5. In a specific implementation, it can be as follows: Figure 3 As shown, the inductor Lin or the inductor Lout is placed adjacent to one of the shared inductor L4 and the shared inductor L5 in terms of a specific physical distance on the PCB board, and then the currents of the adjacent inductor coil parts are set to be opposite.

[0051] For details, please refer to Figure 6 , Figure 6 FIG. 2 is a schematic diagram showing the physical structure of the second embodiment of the filter disclosed in the present invention in the block diagram of the circuit board. Figure 6 As shown, in a preferred manner of physical proximity, the inductor Lin and the shared inductor L4 are selected to be adjacent to each other on the same metal layer of the PCB board, and at the same time, the currents of the inductor coil parts closest to the two are set to flow in opposite directions, and the distance between the inductor coil parts closest to each other is set to be greater than twice the line width of the inductor Lin and the shared inductor L4.

[0052] See also Figure 7 , Figure 7 The impedance curves of the embodiment of the present disclosure and the comparative example are shown. Figure 7 As shown, curve 1 is the impedance curve without inductor Lin; curve 2 is the case where inductor Lin and shared inductor L4 are adjacent, and the current directions of the closest inductor coil parts are the same; curve 3 is the case where inductor Lin and shared inductor L4 are adjacent, and the current directions of the closest inductor coil parts are opposite. Figure 7 It can be seen that compared with curve 1 and curve 2, curve 3 not only has enhanced near-stopband suppression, but also significantly enhanced suppression in frequency bands lower than the passband, and significantly enhanced suppression in specific frequency bands on the right side of the passband, such as the suppression at about 100MHz above the right edge frequency of the passband, and the entire out-of-band suppression is also significantly improved.

[0053] In the present disclosure, the inductor Lin or the inductor Lout is arranged to be adjacent to one of the shared inductor L4 and the shared inductor L5. In another specific implementation, the inductor Lin or the inductor Lout is arranged to be adjacent to one of the shared inductor L4 and the shared inductor L5 in terms of circuit topology distance, and the current flow directions of the two when working are arranged to be opposite.

[0054] For example, see Figure 4-Figure 5 ,Depend on Figure 4-Figure 5 It can be seen that in the topological distance of the filter circuit, Figure 4 The distance ratio between the inductor Lin and the shared inductor L4 in the topology of the filter is Figure 5 In the topology of the filter, the distance between the inductor Lin and the shared inductor L4 is far. Therefore, it is possible to choose a topology with a closer distance, such as Figure 5 The inductor Lin in the topology of the filter shown is decoupled by the shared inductor L4, and a current flows in opposite directions between the two.

[0055] See also Figure 8-Figure 9 ,in Figure 8 for Figure 4 The wiring diagram of the first passive device unit in the filter circuit structure shown on the PCB board, Fig. 9 for Figure 5 The wiring diagram of the first passive component unit in the filter circuit structure shown on the PCB board.

[0056] Figure 8 In the figure, A is a pad directly connected to the filter, B is a through hole connected to the input port IN of the filter, between B and C is the inductor Lin, and between A and B is the inductor Lsin. Fig. 9 A is a pad directly connected to the filter, B is a through hole connected to the input port IN of the filter, between A and C is the inductor Lin, and between A and B is the inductor Lsin. That is, in the specific implementation method where the circuit topology distance is set to be adjacent, different topological structures can be selected according to the degree of coupling to improve the suppression. Figure 5 The topology of the first passive device unit in Fig. 9 The physical implementation is done using the PCB layout method in.

[0057] See also Fig.10 , Fig.10 Indicates Figure 8 and Fig. 9 The impedance curve comparison diagram of the specific example shown in FIG. Fig.10 As shown, curve 4 is Figure 8The impedance curve is when the inductance Lin and the shared inductance L4 are close and the current direction of the inductance coil is opposite, but the topological structure between the inductance Lin and the shared inductance L4 is far away. Curve 5 is Fig. 9 The impedance curve is when the inductance Lin and the shared inductance L4 are close and the current direction of the inductance coil is opposite, but the topological structure between the inductance Lin and the shared inductance L4 is close. Fig.10 It can be seen that the overall suppression effect of curve 5 is significantly improved compared with that of curve 4. It can be seen that the similarity of circuit topology will improve the decoupling effect.

[0058] Third embodiment

[0059] The circuit structure of the filter in the third embodiment is different from the circuit structure of the filter in the first embodiment and the second embodiment in that: the first matching unit includes a first hybrid resonance unit. The first hybrid resonance unit includes a resonance unit and an inductance unit, the resonance unit is a resonance unit composed of a resonator, and the inductance unit can be composed of a series-parallel inductance or a series-parallel-series inductance, etc., or composed of inductances with more degrees of freedom. One end of the inductance unit is connected to the resonance unit, and the other end is connected to the ground.

[0060] See also Fig.11 , Fig.11 FIG. 4 is a block diagram showing a third embodiment of the filter disclosed in the present invention. Fig.11 As shown in the example, the box in the first matching unit represents the resonant unit in the first hybrid resonant unit, and the inductor unit is composed of a single inductor Lin. The second matching unit is a single inductor Lout connected in parallel to the ground. The setting method of the filter network and the second matching unit is the same as that of the first embodiment, and will not be repeated here.

[0061] The inductor Lin in the inductor unit is decoupled through one of the shared inductor L4 and the shared inductor L5, so that relatively high suppression can be achieved in a specific frequency band in both the high frequency band and the low frequency band of the filter.

[0062] Specifically, in the present disclosure, the inductor Lin in the first matching unit is decoupled through one of the common inductors L4 and L5 of the parallel branch of the filter network. The decoupling can be implemented according to the implementation method of the inductor Lin decoupling specifically described in the second embodiment, which will not be repeated here.

[0063] The radio frequency filter provided by the present disclosure not only has enhanced suppression in the near-stopband, but also significantly enhanced suppression in the frequency band lower than the passband, and significantly enhanced suppression in a specific frequency band on the right side of the passband (passband center frequency + about 100 MHz), and the entire out-of-band suppression is also significantly improved.

[0064] The filter of the embodiment of the present disclosure can further be widely used in communication devices, exemplified by mobile phones, personal digital assistants, electronic game devices, wearable terminals, etc.

[0065] The present disclosure is described above in conjunction with specific implementation schemes, but it should be clear to those skilled in the art that these descriptions are exemplary and are not intended to limit the scope of protection of the present disclosure. Those skilled in the art can make various modifications and variations to the present disclosure based on the spirit and principles of the present disclosure, and these modifications and variations are also within the scope of the present disclosure.

Claims

1. A filter, characterized in that: include: An input terminal, an output terminal, a filter network, a first matching unit and a second matching unit, wherein the filter network is arranged between the input terminal and the output terminal and comprises a series branch and a parallel branch, the first matching unit is arranged between the input terminal and the filter network, and the second matching unit is arranged between the filter network and the output terminal; The series branch includes a resonant unit, one end of each parallel branch is connected to a node between the series branches, and the other end of each parallel branch is grounded; at least two parallel branches have at least one common inductor, and the other parallel branches, the first matching unit, and the second matching unit have inductors connected to the ground; At least one common inductor in at least two parallel branches is decoupled from other parallel branches other than the at least two parallel branches, one of the inductors connected to the ground in the first matching unit or the second matching unit by being arranged adjacent to each other.

2. The filter according to claim 1, characterized in that: The first matching unit and / or the second matching unit has a passive device unit composed of passive devices.

3. The filter according to claim 1 or 2, characterized in that: The decoupling by arranging two inductors in close proximity achieves negative coupling by arranging the two inductors in close physical proximity on the printed circuit board and arranging the currents of the adjacent inductor coil parts to be opposite.

4. The filter according to claim 3, characterized in that: The physical proximity of two inductors on a printed circuit board refers to the physical proximity of the two inductors in the horizontal direction on the same metal layer of the printed circuit board, or refers to the physical proximity of the two inductors in the vertical direction on different metal layers of the printed circuit board.

5. The filter according to claim 4, characterized in that: When the physical distance between the two inductors is close on the printed circuit board, the distance between the closest inductor coil parts of the two inductors is set to be greater than twice the line width of the two inductors.

6. The filter according to claim 4 or 5, characterized in that: One of the inductors connected to the ground in the first matching unit or the second matching unit is decoupled by the shared inductor of the second parallel branch and the third parallel branch.

7. The filter according to any one of claims 1 or 2, characterized in that: The decoupling is achieved by arranging the two inductors adjacent to each other in the topological distance of the filter circuit and setting the current flow directions of the two inductors opposite to each other when they are working.

8. The filter according to any one of claims 7, characterized in that: The first matching unit has a series and a parallel inductor network. The series inductor is farther away from one of the shared inductors in the first to third parallel branches in circuit topology than the parallel inductor. The parallel inductor is decoupled by one of the shared inductors in the first to third parallel branches.

9. The filter according to claim 7, characterized in that: When both the fourth parallel branch and the fifth parallel branch have an inductance connected to the ground, the inductance in the fourth parallel branch is decoupled through the shared inductance of the second parallel branch and the third parallel branch.

10. A communication device, characterized in that: The communication device comprises the filter according to any one of claims 1-9.

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