A filter, duplexer, and multiplexer

Abstract

This invention provides a filter, comprising: an input port, an output port, two first resonant units, N second resonant units, and a first matching unit; the two first resonant units are respectively connected between the input port and ground and between the output port and ground, each first resonant unit including at least one first resonator; the N second resonant units are sequentially connected between the input port and the output port, each second resonant unit including at least one second resonator and at least one third resonator, wherein the second resonator is connected in series between the input port and the output port, and the third resonator is connected in parallel between the input port and the output port; the two ends of the first matching unit are respectively connected to the input ports of the two first resonant units. This invention also provides a duplexer and a multiplexer. Implementing this invention helps reduce the manufacturing difficulty of the device.

Description

Technical Field

[0001] This invention relates to the field of electronic communication device technology, and in particular to a filter, a duplexer, and a multiplexer. Background Technology

[0002] A filter is a frequency-selective device that is widely used in fields such as wireless communication. Existing filters mainly consist of a series path and multiple parallel branches. The series path includes an input port, an output port, and multiple series resonators connected in series between the input and output ports. The multiple parallel branches are connected in parallel between the series path and ground, and these parallel branches typically consist of parallel resonators and a grounding inductor.

[0003] The structure of a common existing filter is illustrated with a specific embodiment. Figure 1 As shown, the filter includes an input port 10a, an output port 10b, series resonators 11 to 13, and parallel branches A to C. Series resonators 11 to 13 are connected in series between the input port 10a and the output port 10b. Parallel branch A includes a parallel resonator 14 and a grounding inductor 17. One end of the parallel resonator 14 is connected to the node between series resonators 11 and 12, and the other end is connected to ground through the grounding inductor 17. Parallel branch B includes a parallel resonator 15 and a grounding inductor 18. One end of the parallel resonator 15 is connected to the node between series resonators 12 and 13, and the other end is connected to ground through the grounding inductor 18. Parallel branch C includes a parallel resonator 16 and a grounding inductor 19. One end of the parallel resonator 16 is connected to the node between the series resonator 13 and the output port 10b, and the other end is connected to ground through the grounding inductor 19.

[0004] The shortcomings of the existing filters mentioned above include: (1) In the prior art, the fast roll-off of the filter is achieved by forming a frequency difference between the series resonator and the parallel resonator. As is known to those skilled in the art, the frequency of the resonator is determined by the material and thickness of each layer (i.e., the upper electrode, the piezoelectric layer, and the lower electrode) in the stacked structure. Considering that in the actual production of the filter, all resonators use the same material for the corresponding layers in their stacked structure (i.e., the upper electrode material, the piezoelectric layer material, and the lower electrode material are the same for all resonators), the frequency of the resonator mainly depends on the thickness of each layer in the stacked structure. Based on this, in order to achieve the frequency difference between the series resonator and the parallel resonator, at least one of the upper electrode, the piezoelectric layer, and the lower electrode of the series resonator is usually designed to have a different thickness than the corresponding layer in the parallel resonator. This leads to the inconsistency of the stacked structure of the series resonator and the parallel resonator, which in turn increases the difficulty of the filter manufacturing process. (2) In addition to the inductors in the parallel branches, existing filters often have ground inductors connected in parallel at the input and output ports. The ground inductors are usually implemented using external surface-mount inductors or built-in spiral coil inductors. When there are many inductors, the manufacturing process of the filter will be more difficult to a certain extent. Summary of the Invention

[0005] To overcome the aforementioned deficiencies in the prior art, the present invention provides a filter, specifically a band-stop filter, which includes:

[0006] The system includes an input port, an output port, two first resonant units, N second resonant units, one first matching unit, and N-1 second matching units, where N is an integer greater than or equal to 2.

[0007] The two first resonant units are respectively connected between the input port and ground, and between the output port and ground, and each first resonant unit includes at least one first resonator;

[0008] N second resonant units are connected sequentially between the input port and the output port. Each second resonant unit includes at least one second resonator and at least one third resonator, wherein the second resonator is connected in series between the input port and the output port, and the third resonator is connected in parallel between the input port and the output port.

[0009] The two ends of the first matching unit are respectively connected to the input ports of the two first resonant units.

[0010] According to one aspect of the invention, the filter further includes at least one second matching unit, each of the second matching units being connected between a node between two adjacent second resonant units and ground.

[0011] According to another aspect of the invention, the filter further includes a third matching unit, one end of which is connected to a node between the first resonant unit and an adjacent second resonant unit, and the other end is grounded.

[0012] According to another aspect of the invention, in the filter, the first resonator, the second resonator, and the third resonator have the same resonator frequency.

[0013] According to another aspect of the invention, in the filter, the first resonator, the second resonator, and the third resonator are all bulk acoustic wave resonators, and the first resonator, the second resonator, and the third resonator have the same upper electrode thickness, the same piezoelectric layer thickness, and the same lower electrode thickness.

[0014] According to another aspect of the invention, in the filter, the first resonant unit includes only a first resonator; or the first resonant unit is a combination circuit of a first resonator and a capacitor; or the first resonant unit is a combination circuit of a first resonator and an inductor; or the first resonant unit is a combination circuit of a first resonator, an inductor, and a capacitor.

[0015] According to another aspect of the invention, in the filter, when the first resonant unit comprises only a first resonator, the first resonators are connected in parallel when the number of first resonators is two or more; when the first resonant unit is a combination circuit of a first resonator and a capacitor, the first resonant unit comprises a first resonator and a capacitor, which are connected in parallel; when the first resonant unit is a combination circuit of a first resonator and an inductor, the first resonant unit comprises a first resonator and an inductor. The first resonator and inductor are connected in parallel or in series; or the first resonant unit includes a first resonator and two inductors, the first resonator and one of the inductors are connected in parallel and then in series with the other inductor; or the first resonant unit includes a first resonator and two inductors, the first resonator and one of the inductors are connected in series and then in parallel with the other inductor; in the case where the first resonant unit is a combination circuit of a first resonator, an inductor and a capacitor, the first resonant unit includes a first resonator, an inductor and a capacitor, the first resonator and the inductor are connected in parallel and then in series with the capacitor, or the first resonator and the inductor are connected in series and then in parallel with the capacitor.

[0016] According to another aspect of the invention, in the filter, the second resonant unit includes a second resonator and a third resonator, the third resonator being connected between one end of the second resonator and ground; or the second resonant unit includes two second resonators and a third resonator, the third resonator being connected between a node between the two second resonators and ground; or the second resonant unit includes a second resonator and two third resonators, the two third resonators being respectively connected between the two ends of the second resonator and ground.

[0017] According to another aspect of the invention, in the filter, the first matching unit comprises only an inductor, or a combination circuit of an inductor and a capacitor.

[0018] According to another aspect of the invention, in the filter, for the case where the first matching unit includes only an inductor, the first matching unit includes only one inductor; for the case where the first matching unit is a combination circuit of an inductor and a capacitor, the first matching unit includes one inductor and one capacitor, which are connected in series or in parallel; or the first matching unit includes two inductors and one capacitor, where one inductor and the capacitor are connected in parallel and then connected in series with the other inductor; or the first matching unit includes one inductor and two capacitors, where the inductor and one capacitor are connected in parallel and then connected in series with the other capacitor; or the first matching unit includes one inductor and two capacitors, where the inductor and one capacitor are connected in series and then connected in parallel with the other capacitor.

[0019] According to another aspect of the invention, in the filter, the number of the second matching units is N-1, and the N-1 second matching units are respectively connected between N-1 nodes between the second resonant units and ground.

[0020] According to another aspect of the invention, in the filter, the second matching unit comprises only an inductor, or a combination circuit of an inductor and a capacitor.

[0021] According to another aspect of the invention, in the filter, for the case where the second matching unit includes only an inductor, the second matching unit includes only one inductor; for the case where the second matching unit is a combination circuit of an inductor and a capacitor, the second matching unit includes one inductor and one capacitor, which are connected in series or in parallel; or the second matching unit includes two inductors and one capacitor, where one inductor and the capacitor are connected in parallel and then connected in series with the other inductor; or the second matching unit includes one inductor and two capacitors, where the inductor and one capacitor are connected in parallel and then connected in series with the other capacitor; or the second matching unit includes one inductor and two capacitors, where the inductor and one capacitor are connected in series and then connected in parallel with the other capacitor.

[0022] According to another aspect of the invention, in the filter, the third matching unit includes only an inductor, or only a capacitor, or a combination of an inductor and a capacitor.

[0023] According to another aspect of the invention, in the filter, for the case where the third matching unit includes only an inductor, the third matching unit includes only one inductor; for the case where the third matching unit includes only a capacitor, the third matching unit includes only one capacitor; for the case where the third matching unit is a combination circuit of an inductor and a capacitor, the third matching unit includes one inductor and one capacitor, which are connected in series or in parallel; or the third matching unit includes two inductors and one capacitor, where one inductor and the capacitor are connected in parallel and then connected in series with the other inductor; or the third matching unit includes one inductor and two capacitors, where the inductor and one capacitor are connected in parallel and then connected in series with the other capacitor; or the third matching unit includes one inductor and two capacitors, where the inductor and one capacitor are connected in series and then connected in parallel with the other capacitor.

[0024] According to yet another aspect of the claim, in this filter, N equals 2.

[0025] The present invention also includes a duplexer comprising a transmit filter and a receive filter, wherein the transmit filter and / or the receive filter are implemented using the aforementioned filters.

[0026] The present invention also includes a multiplexer comprising the aforementioned filter.

[0027] The filter provided by this invention, through the design of the first resonant unit, the second resonant unit, and the first matching unit, facilitates ensuring filter performance while maintaining consistent layer thicknesses in the stacked structure of all resonators (i.e., all resonators have the same upper electrode thickness, piezoelectric layer thickness, and lower electrode thickness). Compared to existing filters, firstly, the consistent stacked structure of all resonators in the filter effectively reduces the number of steps in the filter manufacturing process, thereby lowering the difficulty of filter manufacturing; secondly, the second resonant unit does not involve the use of inductors at all, while only the first resonant unit and the first matching unit involve a small number of inductors, thus effectively reducing the number of inductors used, and further effectively lowering the difficulty of filter manufacturing. Attached Figure Description

[0028] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0029] Figure 1 This is a circuit diagram of a common existing filter;

[0030] Figure 2 This is a circuit diagram of a filter according to a specific embodiment of the present invention;

[0031] Figures 3(a) to 3(i) This is a circuit diagram of the first resonant unit according to nine specific embodiments of the present invention;

[0032] Figures 4(a) to 4(c) This is a circuit diagram of the second resonant unit according to three specific embodiments of the present invention;

[0033] Figures 5(a) to 5(f) This is a circuit diagram of the first matching unit according to six specific embodiments of the present invention;

[0034] Figure 6 This is a circuit diagram of a filter according to another specific embodiment of the present invention;

[0035] Figures 7 to 10 These are circuit diagrams of filters according to four preferred embodiments of the present invention;

[0036] Figure 11 This is a circuit diagram of a filter according to yet another specific embodiment of the present invention;

[0037] Figure 12 This is a circuit diagram of a filter according to yet another preferred embodiment of the present invention;

[0038] Figures 13(a) and 13(b) are Figure 7 The small-signal S-parameter simulation curve of the filter is shown below;

[0039] Figures 14(a) and 14(b) are Figure 8 The small-signal S-parameter simulation curve of the filter is shown below;

[0040] Figures 15(a) and 15(b) are Figure 10 The small-signal S-parameter simulation curve of the filter is shown below;

[0041] Figures 16(a) and 16(b) are Figure 12 The small-signal S-parameter simulation curve of the filter is shown.

[0042] The same or similar reference numerals in the accompanying drawings represent the same or similar parts. Detailed Implementation

[0043] To better understand and explain the present invention, a further detailed description of the invention will be provided below in conjunction with the accompanying drawings.

[0044] This invention provides a filter, specifically a stopband filter, which includes:

[0045] The system includes an input port, an output port, two first resonant units, N second resonant units, and a first matching unit, where N is an integer greater than or equal to 2.

[0046] The two first resonant units are respectively connected between the input port and ground, and between the output port and ground, and each first resonant unit includes at least one first resonator;

[0047] N second resonant units are connected sequentially between the input port and the output port. Each second resonant unit includes at least one second resonator and at least one third resonator, wherein the second resonator is connected in series between the input port and the output port, and the third resonator is connected in parallel between the input port and the output port.

[0048] The two ends of the first matching unit are respectively connected to the input ports of the two first resonant units.

[0049] Below, we will combine Figure 2 The components of the above-mentioned filter will be described in detail.

[0050] Specifically, such as Figure 2 As shown, the filter provided by this invention includes an input port P. in and output port P out , where input port P in The input signal to be filtered is used; the output port is P. out Used to output a signal of a specific frequency obtained after filtering.

[0051] like Figure 2 As shown, the filter provided by this invention further includes two first resonant units (represented by reference numerals 101-1 and 101-2 in the figure, respectively). In this embodiment, the first resonant unit 101-1 and the first resonant unit 101-2 are respectively disposed at the input port P. in and output port P out The first resonant unit 101-1 is located at the input port P. in The first resonant unit 101-1 is connected to the input port P between itself and ground. in The other end is grounded; the first resonant unit 101-2 is located at the output port P. out The first resonant unit 101-2 is connected to the output port P between itself and ground. out The other end is grounded.

[0052] Each first resonant unit includes at least one first resonator. The first resonant unit may consist only of a first resonator; or it may be a combination circuit of a first resonator and a capacitor; or it may be a combination circuit of a first resonator and an inductor; or it may be a combination circuit of a first resonator, an inductor, and a capacitor.

[0053] For the case where the first resonant unit includes only a first resonator. In one specific embodiment, as shown in FIG3(a), the first resonant unit includes only one first resonator. This is configured at the input port P. in For the first resonant unit, when the first resonant unit includes only one first resonator, one end of the first resonator is connected to the input port P. in The other end is grounded. In another specific embodiment, as shown in Figure 3(b), the first resonant unit includes two or more first resonators, and the two or more first resonators are connected in parallel. Still assuming it is located at the input port P... in For the first resonant unit, when the first resonant unit includes two or more first resonators, one end of each of the two or more first resonators in the first resonant unit is connected to the input port P. in Both ends are grounded. In this embodiment, as... Figure 2 As shown, the first resonant unit 101-1 includes only one first resonator P. A1 The first resonator P A1 One end is connected to the input port P in The other end is grounded; the first resonant unit 101-2 also includes only one first resonator P. B1 The first resonator P B1 One end is connected to the output port P out The other end is grounded.

[0054] This addresses the case where the first resonant unit is a combination circuit of a first resonator and a capacitor. In one specific embodiment, as shown in FIG3(c), the first resonant unit includes a first resonator and a capacitor, which are connected in parallel. Still assuming it is located at input port P... in In the case of the first resonant unit, when the first resonant unit includes a first resonator and a capacitor, one end of the first resonator and one end of the capacitor are both connected to the input port P. in Both ends are grounded.

[0055] This addresses the case where the first resonant unit is a combination circuit of a first resonator and an inductor. In one specific embodiment, as shown in FIG3(d), the first resonant unit includes a first resonator and an inductor, which are connected in series. Still assuming it is located at input port P... in For the first resonant unit, when the first resonant unit includes a first resonator and an inductor, one end of the first resonator is connected to the input port P. in The other end is grounded through an inductor. In one specific embodiment, as shown in Figure 3(e), the first resonant unit includes a first resonator and an inductor, which are connected in parallel. Still assuming it is located at the input port P... in For the first resonant unit, when the first resonant unit includes a first resonator and an inductor, one end of both the first resonator and the inductor is connected to the input port P. in Both ends are grounded. In another specific embodiment, as shown in Figure 3(f), the first resonant unit includes a first resonator and two inductors. The first resonator and one of the inductors are connected in parallel and then connected in series with the other inductor. It is still set at the input port P. in For the first resonant unit, when the first resonant unit includes a first resonator and two inductors, one end of the first resonator is connected to the input port P. in The other end is grounded through one of the inductors, and one end of the other inductor is connected to the input port P. in The other end is grounded. In another specific embodiment, as shown in Figure 3(g), the first resonant unit includes a first resonator and two inductors. The first resonator and one of the inductors are connected in series and then connected in parallel with the other inductor. It is still set at the input port P. in For the first resonant unit, when the first resonant unit includes a first resonator and two inductors, one end of the first resonator is connected to the input port P. in The other end is grounded through one of the inductors, and one end of the other inductor is connected to the input port P. in The other end is grounded.

[0056] This addresses the case where the first resonant unit is a combination circuit of a first resonator, an inductor, and a capacitor. In a specific embodiment, as shown in Figure 3(h), the first resonant unit includes a first resonator, an inductor, and a capacitor, with the first resonator and inductor connected in parallel and then connected in series with the capacitor. It is still set at the input port P. in For the first resonant unit, when the first resonant unit includes a first resonator, an inductor, and a capacitor, one end of the first resonator and one end of the inductor are both connected to the input port P. inThe other ends of the first resonator and the inductor are both grounded through capacitors. In another specific embodiment, as shown in Figure 3(i), the first resonant unit includes a first resonator, an inductor, and a capacitor, with the first resonator and inductor connected in series and then connected in parallel with the capacitor. Still assuming it is set at the input port P... in For the first resonant unit, when the first resonant unit includes a first resonator, an inductor, and a capacitor, one end of the first resonator is connected to the input port P. in The other end is grounded through an inductor, and one end of the capacitor is connected to the input port P. in The other end is grounded.

[0057] It should be noted that, Figure 2 In the structure shown, the two first resonant units are identical, each consisting of a single first resonator. However, in other embodiments, the structures of the two first resonant units can differ. For example, the first resonant unit 101-1 on the input side may consist of a single first resonator, while the first resonant unit 101-2 on the output side may consist of multiple first resonators connected in parallel. Alternatively, the first resonant unit 101-1 on the input side may consist of multiple first resonators connected in parallel, while the first resonant unit 101-2 on the output side may consist of a first resonator connected in parallel and a capacitor. The specific structures of the two first resonant units can be tailored to actual design requirements. For simplicity, all possible structures of the two first resonant units will not be listed here.

[0058] like Figure 2 As shown, the filter provided by this invention further includes N second resonant units (represented by reference numerals 102-1, 102-2, ..., 102-N from the input port side to the output port side in the figure), and these N second resonant units are sequentially connected to the input port P. in and output port P out The range is between 2 and 2, where N is an integer greater than or equal to 2. In a preferred embodiment, N = 2. Each second resonant unit includes at least one second resonator and at least one third resonator. The second resonators of the N second resonant units are connected in series at the input port P. in and output port P out Between; the third resonator in each of the N second resonant units is connected in parallel at the input port P. in and output port P out Between, that is, any third resonator is connected between the second resonator in its second resonator unit and ground. In other words, for any third resonator, one end is connected to one end of the second resonator in its second resonator unit and the other end is grounded.

[0059] The structure of the second resonant unit is described below using the second resonant unit 102-1 as an example. It should be noted that the structure of the second resonant unit 102-i (i = 2, ... N) can be referred to the structure of the second resonant unit 102-1. For the sake of simplicity, the structure of the second resonant unit 102-i (i = 2, ... N) will not be described in detail here.

[0060] In this embodiment, as Figure 2 As shown, the second resonant unit 102-1 includes a second resonator S. 11 And a third resonator P 11 Among them, the second resonator S 11 Serial connected to input port P in and output port P out Between, the third resonator P 11 One end is connected to the second resonator S 11 The output terminal is connected in parallel to P with the other end grounded. in and output port P out Between. Those skilled in the art will understand that the structure of the second resonant unit 102-1 is not limited to... Figure 2 The structure is shown. In another specific embodiment, as shown in FIG4(a), the second resonant unit 102-1 includes a second resonator S. 11 And a third resonator P 12 Among them, the second resonator S 11 Serial connected to input port P in and output port P out Between, the third resonator P 12 One end is connected to the second resonator S 11 The input terminal is connected in parallel to P with the other end grounded. in and output port P out In another specific embodiment, as shown in FIG4(b), the second resonant unit 102-1 includes two second resonators (i.e., second resonators S). 11 Second resonator S 12 ), and a third resonator P 11 Among them, the second resonator S 11 Second resonator S 12 Serial connected to input port P in and output port P out Between, the third resonator P 11 One end is connected to the second resonator S 11 Second resonator S 12 The nodes between them are connected in parallel to P, with the other end grounded. in and output port P outIn another specific embodiment, as shown in FIG4(c), the second resonant unit 102-1 includes a second resonator S. 11 And two third resonators (i.e., third resonator P) 11 and the third resonator P 12 ), where the second resonator S 11 Serial connected to input port P in and output port P out Between, the third resonator P 12 One end is connected to the second resonator S 11 The input terminal is connected in parallel to P with the other end grounded. in and output port P out Between, the third resonator P 11 One end is connected to the second resonator S 11 The output terminal is connected in parallel to P with the other end grounded. in and output port P out between.

[0061] In addition, it should be noted that (1) Figure 2 , Figures 4(a) to 4(c) The structure shown is only a preferred embodiment of the second resonant unit and should not be taken as a limitation on the structure of the second resonant unit; (2) N second resonant units can have the same structure, for example Figure 2 The N second resonant units in the structure shown are each composed of a second resonator and a third resonator, with the third resonator connected to the output terminal of the second resonator. Alternatively, all N second resonant units can be implemented using the structures shown in Figure 4(a), 4(b), or 4(c). Those skilled in the art will understand that the structures of the N second resonant units can differ in other embodiments. Here, "different structures of the N second resonant units" means that at least two of the N second resonant units have different structures. For example, some of the N second resonant units may be implemented using the structure shown in Figure 4(b), while the remaining second resonant units may be implemented using the structure shown in Figure 4(c); or, for example, some of the N second resonant units may be implemented using... Figure 2 The structure shown in Figure 4(a) is used to implement one part of the second resonant units, another part of the second resonant units is used to implement the structure shown in Figure 4(b), and the remaining second resonant units are all used to implement the structure shown in Figure 4(c). The specific structure of the N second resonant units can be determined according to the actual design requirements. For the sake of simplicity, the possible structures of the N second resonant units will not be listed here.

[0062] like Figure 2As shown, the filter provided by the present invention further includes a first matching unit 103, the two ends of which are respectively connected to the input ports of two first resonant units, that is, one end of the first matching unit 103 is connected to the input port of the first resonant unit 101-1 and the other end is connected to the input port of the first resonator 101-2. The first matching unit 103 may consist only of an inductor, or the first matching unit 103 may be a combination circuit of an inductor and a capacitor.

[0063] For the case where the first matching unit consists only of an inductor. In one specific embodiment, as shown in FIG5(a), the first matching unit 103 includes only one inductor, the two ends of which are respectively connected to the input ports of the two first resonant units.

[0064] For cases where the first matching unit is a combination circuit of an inductor and a capacitor. In one specific embodiment, as shown in FIG5(b), the first matching unit 103 includes an inductor and a capacitor, which are connected in parallel to form a combination circuit. In another specific embodiment, as shown in FIG5(c), the first matching unit 103 includes an inductor and a capacitor, which are connected in series to form a combination circuit. In yet another specific embodiment, as shown in FIG5(d), the first matching unit 103 includes two inductors and a capacitor, one of which is connected in parallel and then connected in series with the other inductor to form a combination circuit. In yet another specific embodiment, as shown in FIG5(e), the first matching unit 103 includes an inductor and two capacitors, the inductor and one of which are connected in parallel and then connected in series with the other capacitor to form a combination circuit. In yet another specific embodiment, as shown in FIG5(f), the first matching unit 103 includes an inductor and two capacitors, the inductor and one of which are connected in series and then connected in parallel with the other capacitor to form a combination circuit. In the case where the first matching unit is a combination circuit of inductor and capacitor, the two ends of the combination circuit are respectively connected to the input ports of the two first resonant units.

[0065] The filter provided by this invention includes two first resonant units, N second resonant units, and a first matching unit. The first matching unit is primarily used to achieve impedance matching and thus filtering. Through proper design of the first resonant units, second resonant units, and first matching unit, all resonators in the filter (including those in the first and second resonant units) can have the same resonant frequency while ensuring excellent filter performance. In this embodiment, all resonators in the filter are bulk acoustic wave resonators, meaning each resonator includes a stacked structure composed of an upper electrode, a piezoelectric layer, and a lower electrode. All resonators have the same resonant frequency, meaning all resonators have the same stacked structure (all resonators have the same upper electrode material and thickness, all resonators have the same piezoelectric layer material and thickness, and all resonators have the same lower electrode material and thickness). Therefore, compared to existing filters that require additional steps to create frequency differences by making the stacked structures of series and parallel resonators inconsistent, the filter provided by this invention has a consistent stacked structure for all resonators. Thus, all resonators in the filter can be formed simultaneously without any additional steps, greatly reducing the difficulty of the filter manufacturing process. Furthermore, since the filter provided by this invention does not include any inductor in its second resonant unit, but only the first resonant unit and the first matching unit may include a small amount of inductor, compared with existing filters that need to set ground inductors in parallel branches and ground inductors at input / output ports, implementing the filter provided by this invention can reduce the amount of inductors used and further reduce the manufacturing difficulty of the filter.

[0066] Preferably, the filter provided by the present invention further includes at least one second matching unit, wherein each second matching unit is disposed between two adjacent second resonant units, that is, one end of each second matching unit is connected to the node between two adjacent second resonant units, and the other end is grounded. In a specific embodiment, such as Figure 6As shown, the number of second matching units is N-1 (represented by reference numerals 104-1, 104-2, ..., 104-N-1 from the input port side to the output port side in the figure). These N-1 second matching units are connected in parallel between the N-1 nodes between the N second resonant units and ground. That is, there is a one-to-one correspondence between the N-1 second matching units and the N-1 nodes between the N second resonant units. One end of each second matching unit is connected to the corresponding node between the two second resonant units, and the other end is grounded. Taking a filter consisting of two second resonant units and one second matching unit (i.e., N=2) as an example, one end of the second matching unit is connected to the node between the two second resonant units, and the other end is grounded. Taking a filter consisting of three second resonant units and two second matching units (i.e., N=3) as an example, there are two nodes between the three second resonant units. One end of each of the two second matching units is connected to these two nodes, and the other end is grounded. The second matching units are mainly used to achieve impedance matching and thus filtering.

[0067] The structure of the second matching unit is explained below using the second matching unit 104-1 as an example. It should be noted that the structure of the second matching unit 104-j (j=2, ...N-1) can be referred to the structure of the second matching unit 104-1. For the sake of simplicity, the structure of the second matching unit 104-j (j=2, ...N-1) will not be described in detail here.

[0068] In one scenario, the second matching unit 104-1 consists solely of an inductor. In one specific embodiment, the second matching unit 104-1 comprises only one inductor, one end of which is connected to a corresponding node (for the second matching unit 104-1, the corresponding node is the node between the second resonant unit 102-1 and the second resonant unit 102-2), and the other end is grounded.

[0069] Another scenario is that the second matching unit is a combination circuit of an inductor and a capacitor. In one specific embodiment, the second matching unit 104-1 includes an inductor and a capacitor, which are connected in parallel to form a combination circuit. In another specific embodiment, the second matching unit 104-1 includes an inductor and a capacitor, which are connected in series to form a combination circuit. In yet another specific embodiment, the second matching unit 104-1 includes two inductors and a capacitor, with one inductor and the capacitor connected in parallel and then connected in series with the other inductor to form a combination circuit. In yet another specific embodiment, the second matching unit 104-1 includes an inductor and two capacitors, with the inductor and one of the capacitors connected in parallel and then connected in series with the other capacitor to form a combination circuit. In yet another specific embodiment, the second matching unit 104-1 includes an inductor and two capacitors, with the inductor and one of the capacitors connected in series and then connected in parallel with the other capacitor to form a combination circuit. In the case where the second matching unit 104-1 is a combination circuit of inductor and capacitor, one end of the combination circuit is connected to the node between the second resonant unit 102-1 and the second resonant unit 102-2, and the other end is grounded.

[0070] It should be noted that (1) the above examples are only preferred embodiments of the second matching unit and should not be considered as limitations on the structure of the second matching unit; (2) all second matching units may have the same structure or different structures. Here, "all second matching units may have different structures" means that at least two of the second matching units have different structures. For example, Figure 6 In the N-1 second matching units of the filter shown, some second matching units are composed only of inductors, while others are implemented by a combination circuit of inductors and capacitors. The specific structure of each second matching unit can be customized according to actual design requirements. For the sake of simplicity, all possible structures of the second matching units will not be listed here.

[0071] The filter provided by the present invention will be described below with reference to four preferred embodiments.

[0072] In a preferred embodiment, such as Figure 7 As shown, the filter includes an input port P. in Output port P out The system comprises a first resonant unit 101-1, a first resonant unit 101-2, a second resonant unit 102-1, a second resonant unit 102-2, a first matching unit 103, and a second matching unit 104-1. The first resonant unit 101-1 includes only one first resonator P. A1 The first resonator P A1 One end is connected to the input port P inThe other end is grounded. The first resonant unit 101-2 includes only one first resonator P. B1 The first resonator P B1 One end is connected to the output port P out The other end is grounded. The second resonant unit 102-1 and the second resonant unit 102-2 are connected sequentially to the input port P. in and output port P out Between. The second resonant unit 102-1 includes a second resonator S. 11 Second resonator S 12 and the third resonator P 11 Among them, the second resonator S 11 Second resonator S 12 Serial connected to input port P in Between the second resonant unit 102-2, the third resonator P 11 One end is connected to the second resonator S 11 Second resonator S 12 The second resonant unit 102-2 includes a second resonator S at one end and grounded at the other. 21 Second resonator S 22 and the third resonator P 21 Among them, the second resonator S 21 Second resonator S 22 Connected in series with the second resonant unit 102-1 and the output port P out Between, the third resonator P 21 One end is connected to the second resonator S 21 Second resonator S 22 One end of the inductor is connected to the node between the two resonant units 101-1, and the other end is grounded. The first matching circuit 103 includes an inductor L1, one end of which is connected to the input port of the first resonant unit 101-1, and the other end is connected to the input port of the first resonant unit 101-2. The second matching unit 104-1 includes an inductor L2, one end of which is connected to the node between the second resonant unit 102-1 and the second resonant unit 102-2, and the other end is grounded. Figure 7 All resonators in the filter shown (i.e., the second resonator S) 11 Second resonator S 12 Second resonator S 21 Second resonator S 22 Third resonator P 11 Third resonator P 21 First resonator P A1 and the first resonator P B1All of them are bulk acoustic wave resonators and have a consistent stacked structure, that is, the upper electrode of all resonators has the same material and thickness, the piezoelectric layer of all resonators has the same material and thickness, and the lower electrode of all resonators has the same material and thickness, and correspondingly, the stacked structure of all resonators has the same thickness.

[0073] In another preferred embodiment, such as Figure 8 As shown, Figure 8 The structure shown is Figure 7 The difference shown lies in the structure of the second resonant unit 102-1 and the second resonant unit 102-2. The second resonant unit 102-1 includes a second resonator S. 11 Third resonator P 11 and the third resonator P 12 The second resonator S 11 Serial connected to input port P in Between the second resonant unit 102-2, the third resonator P 11 One end is connected to the second resonator S 11 The output terminal is connected to ground, and the third resonator P... 12 One end is connected to the second resonator S 11 The input terminal is connected to ground, and the other end is connected to ground. The second resonant unit 102-2 includes a second resonator S. 21 Third resonator P 21 and the third resonator P 22 The second resonator S 21 Connected in series with the second resonant unit 102-1 and the output port P out Between and, the third resonator P 21 One end is connected to the second resonator S 21 The output terminal is connected to ground, and the third resonator P... 22 One end is connected to the second resonator S 21 The input terminal is connected to ground at the other end. Figure 8 All resonators in the filter shown (i.e., the second resonator S) 11 Second resonator S 21 Third resonator P 11 Third resonator P 12 Third resonator P 21 Third resonator P 22 First resonator P A1 and the first resonator P B1All of them are bulk acoustic wave resonators and have a consistent stacked structure, that is, the upper electrode of all resonators has the same material and thickness, the piezoelectric layer of all resonators has the same material and thickness, and the lower electrode of all resonators has the same material and thickness, and correspondingly, the stacked structure of all resonators has the same thickness.

[0074] In yet another preferred embodiment, such as Figure 9 As shown, Figure 9 The structure shown is Figure 7 The difference shown lies in the structure of the second resonant unit 102-1. The second resonant unit 102-1 includes a second resonator S. 11 Third resonator P 11 and the third resonator P 12 The second resonator S 11 Serial connected to input port P in Between the second resonant unit 102-2, the third resonator P 11 One end is connected to the second resonator S 11 The output terminal is connected to ground, and the third resonator P... 12 One end is connected to the second resonator S 11 The input terminal is connected to ground at the other end. Figure 9 All resonators in the filter shown (i.e., the second resonator S) 11 Second resonator S 21 Second resonator S 22 Third resonator P 11 Third resonator P 12 Third resonator P 21 First resonator P A1 and the first resonator P B1 All of them are bulk acoustic wave resonators and have a consistent stacked structure, that is, the upper electrode of all resonators has the same material and thickness, the piezoelectric layer of all resonators has the same material and thickness, and the lower electrode of all resonators has the same material and thickness, and correspondingly, the stacked structure of all resonators has the same thickness.

[0075] In yet another preferred embodiment, such as Figure 10 As shown, Figure 10 The structure shown is Figure 7 The difference in the structure shown lies in the structure of the first matching unit 103 and the second matching unit 104-1. The first matching unit 103 includes an inductor L1 and a capacitor C1 connected in parallel. The second matching unit 104-1 includes an inductor L2 and a capacitor C2 connected in parallel. Figure 10 All resonators in the filter shown (i.e., the second resonator S) 11 Second resonator S12 Second resonator S 21 Second resonator S 22 Third resonator P 11 Third resonator P 21 First resonator P A1 and the first resonator P B1 All of them are bulk acoustic wave resonators and have a consistent stacked structure, that is, the upper electrode of all resonators has the same material and thickness, the piezoelectric layer of all resonators has the same material and thickness, and the lower electrode of all resonators has the same material and thickness, and correspondingly, the stacked structure of all resonators has the same thickness.

[0076] Preferably, the filter provided by the present invention further includes a third matching unit, one end of which is connected to the node between the adjacent first resonant unit and the second resonant unit, and the other end is grounded. In this embodiment, as... Figure 11 As shown, the filter includes two third matching units (denoted by reference numerals 105-1 and 105-2 in the figure). The third matching unit 105-1 is located between the first resonant unit 101-1 and the second resonant unit 102-1 on the input port side. Specifically, one end of the third matching unit 105-1 is connected to the node between the first resonant unit 101-1 and the second resonant unit 102-1, and the other end is grounded. The third matching unit 105-2 is located between the first resonant unit 101-2 and the second resonant unit 102-N on the output port side. Specifically, one end of the third matching unit 105-2 is connected to the node between the first resonant unit 101-2 and the second resonant unit 102-N, and the other end is grounded. The third matching units are mainly used to achieve impedance matching, thereby achieving filtering.

[0077] The structure of the third matching unit will be described below using the third matching unit 105-1 as an example. It should be noted that the structure of the third matching unit 105-2 can refer to the structure of the third matching unit 105-1. For the sake of simplicity, the structure of the third matching unit 105-2 will not be described in detail here.

[0078] In one scenario, the third matching unit 105-1 consists solely of an inductor. In one specific embodiment, the third matching unit 105-1 comprises only one inductor, one end of which is connected to a corresponding node (for the third matching unit 105-1, the corresponding node is the node between the first resonant unit 101-1 and the second resonant unit 102-1 located on the input port side), and the other end is grounded.

[0079] Another scenario is that the third matching unit 105-1 consists of only a capacitor. In one specific embodiment, the third matching unit 105-1 includes only one capacitor, one end of which is connected to the node between the first resonant unit 101-1 and the second resonant unit 102-1 located on the input port side, and the other end is grounded.

[0080] In another embodiment, the third matching unit 105-1 is a combination circuit of an inductor and a capacitor. In one specific embodiment, the third matching unit 105-1 includes an inductor and a capacitor, which are connected in parallel to form a combination circuit. In another specific embodiment, the third matching unit 105-1 includes an inductor and a capacitor, which are connected in series to form a combination circuit. In yet another specific embodiment, the third matching unit 105-1 includes two inductors and a capacitor, with one inductor and the capacitor connected in parallel and then connected in series with the other inductor to form a combination circuit. In yet another specific embodiment, the third matching unit 105-1 includes an inductor and two capacitors, with the inductor and one of the capacitors connected in parallel and then connected in series with the other capacitor to form a combination circuit. In yet another specific embodiment, the third matching unit 105-1 includes an inductor and two capacitors, with the inductor and one of the capacitors connected in series and then connected in parallel with the other capacitor to form a combination circuit. In the case where the third matching unit 105-1 is a combination circuit of inductor and capacitor, one end of the combination circuit is connected to the node between the first resonant unit 101-1 and the second resonant unit 102-1, and the other end is grounded.

[0081] It should be noted that (1) the above examples are only preferred embodiments of the third matching unit and should not be considered as limitations on the structure of the third matching unit; (2) the two third matching units can have the same structure or different structures. For example, Figure 11 The third matching unit 105-1 in the filter shown is composed of only an inductor, while the third matching unit 105-2 is implemented by a combination circuit of an inductor and a capacitor. The specific structure of each third matching unit can be determined according to the actual design requirements. For the sake of simplicity, all possible structures of the third matching units will not be listed here. (3) In other embodiments, according to the actual design requirements, the filter may also include only the third matching unit 105-1 or only the third matching unit 105-2.

[0082] The following description uses preferred embodiments. Figure 12 As shown, Figure 12 The structure shown is Figure 7The difference in the structure shown is that the filter also includes two third matching units (denoted by reference numerals 105-1 and 105-2 in the figure, respectively). Third matching unit 105-1 is positioned between the first resonant unit 101-1 and the second resonant unit 102-1, while third matching unit 105-2 is positioned between the second resonant unit 102-2 and the first resonant unit 101-2. Specifically, the third matching unit 105-1 includes a parallel inductor L. 31 and capacitor C 31 Inductor L 31 and inductor C 31 The input terminals of all units are connected to the node between the first resonant unit 101-1 and the second resonant unit 102-1, and the output terminals are all grounded. The third matching unit 105-2 includes a parallel inductor L. 32 and capacitor C 32 Inductor L 32 and inductor C 32 The input terminals are all connected to the node between the second resonant unit 102-2 and the first resonant unit 101-2, and the output terminals are all grounded. Figure 12 All resonators in the filter shown (i.e., the second resonator S) 11 Second resonator S 12 Second resonator S 21 Second resonator S 22 Third resonator P 11 Third resonator P 21 First resonator P A1 and the first resonator P B1 All of them are bulk acoustic wave resonators and have a consistent stacked structure, that is, the upper electrode of all resonators has the same material and thickness, the piezoelectric layer of all resonators has the same material and thickness, and the lower electrode of all resonators has the same material and thickness, and correspondingly, the stacked structure of all resonators has the same thickness.

[0083] The following is based on Figure 7 , Figure 8 , Figure 10 as well as Figure 12 The performance of the filter provided by this invention will be explained using the filter shown as an example. Figure 7 , Figure 8 , Figure 10 as well as Figure 12 All resonators in the filter shown have the same material and thickness for their upper electrodes, piezoelectric layers, and lower electrodes. For the sake of simplicity, the process parameters of each resonator in the filter will not be described individually below, but will be collectively referred to as resonators.

[0084] Figure 7 The parameters of each component in the filter shown are as follows: the thickness of the upper electrode of the resonator ranges from 185nm to 205nm, the thickness of the piezoelectric layer ranges from 240nm to 260nm, the thickness of the lower electrode ranges from 210nm to 230nm, and the area of ​​the effective working region (i.e., the overlapping area of ​​the upper electrode, piezoelectric layer, and lower electrode in the thickness direction of the device) ranges from 100μm. 2 ~10000μm 2 The inductance value of inductor L1 ranges from 1nH to 2nH, and the inductance value of inductor L2 ranges from 0.5nH to 1nH. Figures 13(a) and 13(b) are... Figure 7 The small-signal S-parameter simulation curves of the filter shown are illustrated in Figure 13(a), which specifically represent the small-signal S-parameter simulation curves of the filter. Figure 7 The filter shown has a passband insertion loss of 1.6 dB at a low frequency of 4.131 GHz and a high frequency of 0.6 dB at 4.446 GHz; Figure 13(b) characterizes... Figure 7 The filter shown has a stopband performance of 54MHz at 30dB. This can be seen from Figures 13(a) and 13(b). Figure 7 The filter shown maintains excellent filtering performance even with all resonator stack-up structures being identical.

[0085] Figure 8 The parameters of each component in the filter shown are as follows: the thickness of the upper electrode of the resonator ranges from 185nm to 205nm, the thickness of the piezoelectric layer ranges from 240nm to 260nm, the thickness of the lower electrode ranges from 210nm to 230nm, and the area of ​​the effective working region (i.e., the overlapping area of ​​the upper electrode, piezoelectric layer, and lower electrode in the thickness direction of the device) ranges from 100μm. 2 ~10000μm 2 The inductance value of inductor L1 ranges from 0.5nH to 1.5nH, and the inductance value of inductor L2 ranges from 1nH to 2nH. Figures 14(a) and 14(b) are... Figure 8 The small-signal S-parameter simulation curves of the filter shown are illustrated in Figure 14(a), which specifically represent the small-signal S-parameter simulation curves of the filter. Figure 8 The filter shown has a passband insertion loss of 1.8 dB at a low frequency of 4.131 GHz and a high frequency of 0.6 dB at 4.446 GHz; Figure 14(b) characterizes... Figure 8 The filter shown has a stopband performance of 35MHz at 30dB. This can be seen from Figures 14(a) and 14(b). Figure 8 The filter shown maintains excellent filtering performance even with all resonator stack-up structures being identical.

[0086] Figure 10The parameters of each component in the filter shown are as follows: the thickness of the upper electrode of the resonator ranges from 185nm to 205nm, the thickness of the piezoelectric layer ranges from 240nm to 260nm, the thickness of the lower electrode ranges from 210nm to 230nm, and the area of ​​the effective working region (i.e., the overlapping area of ​​the upper electrode, piezoelectric layer, and lower electrode in the thickness direction of the device) ranges from 100μm. 2 ~10000μm 2 The inductance of inductor L1 ranges from 1nH to 2nH, the capacitance of capacitor C1 ranges from 0.05pF to 0.15pF, the inductance of inductor L2 ranges from 0.5nH to 1nH, and the capacitance of capacitor C2 ranges from 0.05pF to 0.15pF. Figures 15(a) and 15(b) are... Figure 10 The small-signal S-parameter simulation curves of the filter shown are illustrated in Figure 15(a), which specifically represent the small-signal S-parameter simulation curves of the filter. Figure 10 The filter shown is the passband insertion loss, with an insertion loss of 1.7 dB at a low frequency of 4.131 GHz and 0.5 dB at a high frequency of 4.446 GHz; Figure 15(b) characterizes... Figure 10 The filter shown has a stopband performance of 57MHz at 30dB. This can be seen from Figures 15(a) and 15(b). Figure 10 The filter shown maintains excellent filtering performance even with all resonator stack-up structures being identical.

[0087] Figure 12 The parameters of each component in the filter shown are as follows: the thickness of the upper electrode of the resonator ranges from 185nm to 205nm, the thickness of the piezoelectric layer ranges from 240nm to 260nm, the thickness of the lower electrode ranges from 210nm to 230nm, and the area of ​​the effective working region (i.e., the overlapping area of ​​the upper electrode, piezoelectric layer, and lower electrode in the thickness direction of the device) ranges from 100μm. 2 ~10000μm 2 The inductance value of inductor L1 ranges from 0.5nH to 1.5nH, and the inductance value of inductor L2 ranges from 0.2nH to 1.5nH. 31 The inductance range is 1nH to 2nH, and the capacitance C is... 31 The capacitance value ranges from 0.2pF to 1.5pF, and the inductance L... 32 The inductance range is 1nH to 2nH, and the capacitance C is... 32 The capacitance range is 0.2pF to 1.5pF. Figures 16(a) and 16(b) are... Figure 12 The small-signal S-parameter simulation curves of the filter shown are illustrated in Figure 16(a), which specifically represent the small-signal S-parameter simulation curves of the filter. Figure 12The filter shown has a passband insertion loss of 2.7 dB at a low frequency of 4.131 GHz and a high frequency of 0.9 dB at 4.446 GHz; Figure 16(b) characterizes... Figure 12 The filter shown has a stopband performance of 53MHz at 30dB. This can be seen from Figures 16(a) and 16(b). Figure 12 The filter shown maintains excellent filtering performance even with all resonator stack-up structures being identical.

[0088] Accordingly, the present invention also provides a duplexer, which includes a transmit filter and a receive filter, wherein the transmit filter and / or the receive filter is implemented using the aforementioned filters.

[0089] Specifically, the duplexer includes a transmit filter and a receive filter. The transmit filter is connected between a common port and a transmit port, and the receive filter is connected between a common port and a receive port. In one specific embodiment, both the transmit filter and the receive filter are implemented using the filters described above in this invention. In another specific embodiment, the transmit filter is implemented using the filters described above in this invention, and the receive filter is implemented using existing conventional filters. In yet another specific embodiment, the receive filter is implemented using the filters described above in this invention, and the transmit filter is implemented using existing conventional filters. For the case where the transmit filter and / or the receive filter is implemented using the filters described above in this invention, the filter structure can be referred to the corresponding sections above, and for the sake of brevity, it will not be repeated here.

[0090] Since the filter provided by this invention has the characteristic of simple manufacturing process, the duplexer implemented based on the filter also has the characteristic of simple manufacturing process.

[0091] Accordingly, the present invention also provides a multiplexer that includes the aforementioned filter. Typically, the multiplexer includes three or more filters, such as a tripartite (including three filters), a quadrupleter (including four filters), a quintet (including five filters), etc. At least one filter in the multiplexer is implemented using the aforementioned filter of the present invention. For the case where the filter is implemented using the aforementioned filter of the present invention, the filter structure can be referred to the corresponding section above, and will not be repeated here for the sake of brevity. Since the filter provided by the present invention has the characteristic of simple manufacturing process, the multiplexer implemented based on this filter also has the characteristic of simple manufacturing process.

[0092] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be embraced within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims. Furthermore, it is clear that the word "comprising" does not exclude other components, units, or steps, and the singular does not exclude the plural. Multiple components, units, or devices recited in the system claims may also be implemented by a single component, unit, or device in software or hardware.

[0093] The filter provided by this invention, through the design of the first resonant unit, the second resonant unit, and the first matching unit, facilitates ensuring filter performance while maintaining consistent layer thicknesses in the stacked structure of all resonators (i.e., all resonators have the same upper electrode thickness, piezoelectric layer thickness, and lower electrode thickness). Compared to existing filters, firstly, the consistent stacked structure of all resonators in the filter effectively reduces the number of steps in the filter manufacturing process, thereby lowering the difficulty of filter manufacturing; secondly, the second resonant unit does not involve the use of inductors at all, while only the first resonant unit and the first matching unit involve a small number of inductors, thus effectively reducing the number of inductors used, and further effectively lowering the difficulty of filter manufacturing.

[0094] The above-disclosed embodiments are merely some preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, any equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A filter, characterized in that, The filter includes: The system includes an input port, an output port, two first resonant units, N second resonant units, one first matching unit, and N-1 second matching units, where N is an integer greater than or equal to 2. The two first resonant units are respectively connected between the input port and ground, and between the output port and ground, and each first resonant unit includes at least one first resonator; N second resonant units are sequentially connected between the input port and the output port. Each second resonant unit includes at least two second resonators and at least one third resonator. The at least two second resonators are connected in series between the input port and the output port, and the third resonator is connected between the node between the at least two second resonators and ground. The two ends of the first matching unit are respectively connected to the input ports of the two first resonant units; The N-1 second matching units are respectively connected between the N-1 nodes between the adjacent second resonant units and the ground; The first resonator, the second resonator, and the third resonator are all bulk acoustic wave resonators and have the same resonant frequency; the first resonator, the second resonator, and the third resonator have the same upper electrode thickness, the same piezoelectric layer thickness, and the same lower electrode thickness; no inductor is provided in the second resonant unit.

2. The filter according to claim 1, characterized in that, The filter also includes: At least one second matching unit, each of which is connected between a node between two adjacent second resonant units and ground.

3. The filter according to claim 2, characterized in that, The filter also includes: The third matching unit has one end connected to the node between the first resonant unit and the adjacent second resonant unit, and the other end grounded.

4. The filter according to claim 3, characterized in that, in: The first resonator, the second resonator, and the third resonator have the same resonator frequency.

5. The filter according to any one of claims 1 to 3, characterized in that, in: The first resonant unit includes only the first resonator; or The first resonant unit is a combination circuit of a first resonator and a capacitor; or The first resonant unit is a combination circuit of a first resonator and an inductor; or The first resonant unit is a combination circuit of a first resonator, an inductor, and a capacitor.

6. The filter according to claim 4, characterized in that, in: When the first resonant unit only includes the first resonator, and the number of the first resonators is two or more, the first resonators are connected in parallel. In the case where the first resonant unit is a combination circuit of a first resonator and a capacitor, the first resonant unit includes a first resonator and a capacitor, which are connected in parallel. In the case where the first resonant unit is a combination circuit of a first resonator and an inductor, the first resonant unit includes a first resonator and an inductor, which are connected in parallel or in series; or the first resonant unit includes a first resonator and two inductors, which are connected in parallel with one of the inductors and then in series with the other inductor; or the first resonant unit includes a first resonator and two inductors, which are connected in series with one of the inductors and then in parallel with the other inductor. In the case where the first resonant unit is a combination circuit of a first resonator, an inductor, and a capacitor, the first resonant unit includes a first resonator, an inductor, and a capacitor. The first resonator and the inductor are connected in parallel and then connected in series with the capacitor, or the first resonator and the inductor are connected in series and then connected in parallel with the capacitor.

7. The filter according to any one of claims 1 to 3, characterized in that, in: The second resonant unit includes two second resonators and one third resonator. The two second resonators are connected in series between the input port and the output port, and the third resonator is connected between the node between the second resonators and ground.

8. The filter according to any one of claims 1 to 3, characterized in that, in: The first matching unit includes only an inductor, or a combination circuit of an inductor and a capacitor.

9. The filter according to claim 8, characterized in that, in: In the case where the first matching unit only includes an inductor, the first matching unit includes only one inductor; For cases where the first matching unit is a combination circuit of an inductor and a capacitor, the first matching unit includes one inductor and one capacitor, which are connected in series or in parallel; or the first matching unit includes two inductors and one capacitor, where one inductor and the capacitor are connected in parallel and then connected in series with the other inductor; or the first matching unit includes one inductor and two capacitors, where the inductor and one capacitor are connected in parallel and then connected in series with the other capacitor; or the first matching unit includes one inductor and two capacitors, where the inductor and one capacitor are connected in series and then connected in parallel with the other capacitor.

10. The filter according to claim 2, characterized in that, in: The second matching unit includes only an inductor, or a combination of an inductor and a capacitor.

11. The filter according to claim 10, characterized in that, in: In the case where the second matching unit only includes an inductor, the second matching unit includes only one inductor; For cases where the second matching unit is a combination circuit of an inductor and a capacitor, the second matching unit includes one inductor and one capacitor, which are connected in series or in parallel; or the second matching unit includes two inductors and one capacitor, where one inductor and the capacitor are connected in parallel and then connected in series with the other inductor; or the second matching unit includes one inductor and two capacitors, where the inductor and one capacitor are connected in parallel and then connected in series with the other capacitor; or the second matching unit includes one inductor and two capacitors, where the inductor and one capacitor are connected in series and then connected in parallel with the other capacitor.

12. The filter according to claim 3, characterized in that, in: The third matching unit may consist of only an inductor, only a capacitor, or a combination of an inductor and a capacitor.

13. The filter according to claim 12, characterized in that, in: In the case where the third matching unit only includes an inductor, the third matching unit includes only one inductor; In the case where the third matching unit consists only of a capacitor, the third matching unit consists of only one capacitor; In the case where the third matching unit is a combination circuit of an inductor and a capacitor, the third matching unit includes one inductor and one capacitor, which are connected in series or in parallel; or the third matching unit includes two inductors and one capacitor, with one inductor and the capacitor connected in parallel and then connected in series with the other inductor; or the third matching unit includes one inductor and two capacitors, with the inductor and one capacitor connected in parallel and then connected in series with the other capacitor; or the third matching unit includes one inductor and two capacitors, with the inductor and one capacitor connected in series and then connected in parallel with the other capacitor.

14. The filter according to any one of claims 1 to 3, characterized in that, in, N equals 2.

15. A duplexer, characterized in that, The duplexer includes: A transmit filter and a receive filter, wherein the transmit filter and / or the receive filter are implemented using any one of claims 1 to 14.

16. A multiplexer, characterized in that, The multiplexer includes a filter as described in any one of claims 1 to 14.

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