Filter and duplexer

Abstract

The utility model provides a filter. The filter comprises an input port and an output port, the series path comprises series resonance units which are sequentially connected between the two ports; a parallel resonance unit provided between a node of the series path and ground; the first series resonance unit at least located on the output port side in the series resonance units is a first equivalent structure obtained by splitting a single series resonator, and the first equivalent structure comprises two or more split sub units which are connected in series. Each split sub-unit comprises two or more first split resonators obtained through anti-parallel splitting; at least the first parallel resonance unit located on the output port side in the parallel resonance units is a second equivalent structure obtained by splitting a single parallel resonator, and the second equivalent structure comprises two second split resonators obtained by anti-parallel splitting. The utility model also provides a duplexer. According to the utility model, non-linear behaviors of the filter and the duplexer can be suppressed.

Description

Technical Field

[0001] The utility model relates to the technical field of electronic communication devices, in particular to a filter and a duplexer. Background Art

[0002] The core component of existing filters is the resonator. When the input power gradually changes from a small signal to a high one, the resonator's operating state begins to exhibit nonlinear behavior, causing the filter to exhibit nonlinear behaviors such as harmonic distortion and intermodulation distortion, which in turn affects the performance of the filter and the entire RF circuit. Utility Model Content

[0003] In order to overcome the above-mentioned defects in the prior art, the present invention provides a filter, which includes:

[0004] Input ports and output ports;

[0005] a series path, the series path comprising at least one series resonant unit sequentially connected between the input port and the output port;

[0006] at least one parallel resonant unit, one end of each parallel resonant unit being connected to a node of the series path and the other end being directly grounded or grounded through an inductor;

[0007] Among them, at least the first series resonant unit located on the output port side of the series resonant unit is a first equivalent structure obtained by splitting a single series resonator, and the first equivalent structure includes two or more split sub-units connected in series, and each of the split sub-units includes two or more first split resonators obtained by anti-parallel splitting; at least the first parallel resonant unit located on the output port side of the parallel resonant unit is a second equivalent structure obtained by splitting a single parallel resonator, and the second equivalent structure includes two second split resonators obtained by anti-parallel splitting.

[0008] According to one aspect of the present invention, in the filter, the first split resonator in the first series resonant unit located at the output port side and the second split resonator in the first parallel resonant unit located at the output port side have the same resonance area.

[0009] According to another aspect of the present invention, in the filter, the split sub-units located in the same first equivalent structure all include the same number of the first split resonators, and the first split resonators all have the same resonance area; the two second split resonators located in the same second equivalent structure have the same resonance area.

[0010] According to another aspect of the present invention, in the filter, the first equivalent structure includes three split sub-units connected in series, each of the split sub-units includes two first split resonators obtained by anti-parallel splitting; or the first equivalent structure includes two split sub-units connected in series, each of the split sub-units includes three first split resonators obtained by anti-parallel splitting.

[0011] According to another aspect of the present invention, in the filter, all resonators in the filter are bulk acoustic wave resonators.

[0012] The utility model also provides a duplexer, which includes an antenna port, a receiving port, a transmitting port, a receiving filter arranged between the antenna port and the receiving port, and a transmitting filter arranged between the transmitting port and the antenna port, wherein the transmitting filter is implemented using the aforementioned filter.

[0013] The filter provided by the present invention comprises an input port, an output port, a series path, and at least one parallel resonant unit. The series path includes at least one series resonant unit sequentially connected between the input port and the output port, with one end of each parallel resonant unit connected to a node of the series path and the other end directly grounded or grounded via an inductor. Among the series resonant units, at least the first series resonant unit located on the output port side is a first equivalent structure obtained by splitting a single series resonator, the first equivalent structure comprising two or more split sub-units connected in series, each split sub-unit comprising two or more first split resonators obtained by anti-parallel splitting. At least the first parallel resonant unit located on the output port side of the parallel resonant unit is a second equivalent structure obtained by splitting a single parallel resonator, the second equivalent structure comprising two second split resonators obtained by anti-parallel splitting. Implementing the present invention can effectively suppress the nonlinear behavior of the filter under large signals. The present invention also provides a duplexer. Because the transmit filter in the duplexer is implemented using the above-mentioned filter, the nonlinear characteristics of the duplexer are also improved accordingly. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Other features, objects and advantages of the present invention will become more apparent from the detailed description of the non-limiting embodiments made with reference to the following drawings:

[0015] Figure 1 This is the circuit diagram of the filter without splitting;

[0016] Figure 2(a) to Figure 2(d) According to four specific embodiments of the present invention Figure 1 The circuit diagram of the structure obtained after the filter is decomposed;

[0017] FIG3( a ) and FIG3 ( b ) are circuit diagrams of duplexers according to two specific embodiments of the present invention.

[0018] The same or similar reference numerals in the drawings represent the same or similar components. DETAILED DESCRIPTION

[0019] In order to better understand and illustrate the present invention, the present invention will be described in further detail below with reference to the accompanying drawings.

[0020] The utility model provides a filter, which includes:

[0021] Input ports and output ports;

[0022] a series path, the series path comprising at least one series resonant unit sequentially connected between the input port and the output port;

[0023] at least one parallel resonant unit, one end of each parallel resonant unit being connected to a node of the series path and the other end being directly grounded or grounded through an inductor;

[0024] Among them, at least the first series resonant unit located on the output port side of the series resonant unit is a first equivalent structure obtained by splitting a single series resonator, and the first equivalent structure includes two or more split sub-units connected in series, and each of the split sub-units includes two or more first split resonators obtained by anti-parallel splitting; at least the first parallel resonant unit located on the output port side of the parallel resonant unit is a second equivalent structure obtained by splitting a single parallel resonator, and the second equivalent structure includes two second split resonators obtained by anti-parallel splitting.

[0025] Below, each component of the above filter will be described in detail.

[0026] Specifically, the filter provided by the present invention includes an input port and an output port. The input port is used to input a signal to be filtered, and the output port is used to output a signal of a specific frequency obtained after filtering.

[0027] The filter provided by the present invention further includes a series path, the series path including at least one series resonant unit, and all the series resonant units are connected in series between the input port and the output port. Specifically, in the case where the series path includes only one series resonant unit, the series resonant unit connected in series between the input port and the output port means that one end of the series resonant unit is connected to the input port and the other end is connected to the output port.

[0028] The filter provided by the present invention also includes at least one parallel resonance unit, which is connected in parallel between the series path and the ground. Specifically, for each parallel resonance unit, one end is connected to a node of the series path, and the other end is directly grounded or grounded through an inductor. When the series path includes only one series resonance unit, the nodes of the series path include the node between the input port and the series resonance unit, and the node between the series resonance unit and the output port. When the series path includes two or more series resonance units, the nodes of the series path include the node between the input port and its adjacent series resonance unit, the node between two adjacent series resonance units, and the node between the output port and its adjacent series resonance unit. It should be noted here that, more typically, the number of parallel resonance units is the same as the number of nodes of the series path, and the two correspond one to one, that is, one end of each parallel resonance unit is connected to the node corresponding to it on the series path, and the other end is grounded. In other application scenarios, the parallel resonance unit may not correspond one to one with the nodes on the series path. The present invention does not impose any restrictions on this, and can be formulated accordingly according to actual design requirements. In addition, it should be noted that, for the parallel resonant unit grounded through inductance, the parallel resonant unit can be grounded through an independent inductor, a common inductor, or a coupled inductor, and the present invention does not impose any limitation on this.

[0029] For the series resonant units on the series path, at least the last-order series resonant unit is an equivalent structure obtained by splitting a single series resonator (hereinafter referred to as the first equivalent structure). The last-order series resonant unit here refers to the first series resonant unit located on the output port side of the filter. In this embodiment, the first equivalent structure includes two or more split sub-units, and the two split sub-units are connected in series. Each split sub-unit further includes two or more split resonators obtained by anti-parallel splitting (hereinafter referred to as the first split resonator). In specific implementation, the single series resonator can be first split into two or more sub-series resonators connected in series, and then each sub-series resonator can be split in anti-parallel into two or more first split resonators, thereby obtaining a first equivalent structure. It should be noted here that anti-parallel splitting refers to splitting the target resonator to be split into two groups of split resonators of the same number or as close as possible, and connecting the two groups of split resonators in parallel in a current reverse setting. Specifically, for the case where the target resonator to be split is split in anti-parallel into 2M (M is an integer greater than or equal to 1) split resonators (each split resonator includes a first electrode and a second electrode, and the current direction flows from the first electrode to the second electrode, and the same is true for all split resonators hereinafter. For the sake of simplicity, the current direction of other split resonators that appear later will not be explained), the two groups of split resonators have the same number (i.e., both are M), and the first electrode of the split resonator in one group (represented by group 1) is connected to the second electrode of the split resonator in the other group (represented by group 2), and the second electrode of the split resonator in group 1 is connected to the first electrode of the split resonator in group 2. For the case where the target resonator to be split is split in anti-parallel into 2M+1 (M is an integer greater than or equal to 1) split resonators, the number of the two groups of split resonators is as close as possible (that is, one group is M split resonators and the other group is M+1 split resonators), and the first electrode of the split resonator in one group (represented by group 1) is connected to the second electrode of the split resonator in the other group (represented by group 2), and the second electrode of the split resonator in group 1 is connected to the first electrode of the split resonator in group 2.

[0030] It should be noted here that (1) for the case where the number of series resonant units is greater than or equal to 2, some of the series resonant units (including the last-order series resonant unit) may be the first equivalent structure obtained by splitting a single series resonator, while the other series resonant units are unsplit series resonators, or all series resonant units may be the first equivalent structure obtained by splitting a single series resonator. The present invention does not impose any restrictions on this, and needs to be formulated according to actual design requirements. (2) The present invention does not impose any restrictions on the type of resonator in the series path (including unsplit series resonators and the first split resonators obtained by splitting), preferably a common bulk acoustic wave resonator (BAW). It can be understood by those skilled in the art that the above-mentioned bulk acoustic wave resonator is only a preferred embodiment. In other embodiments, the resonator in the series path can also be a surface acoustic wave resonator (Saw resonator), a transversely excited bulk acoustic wave resonator (XBAR resonator), an LC lumped circuit resonator, etc. For the case where the first split resonator is implemented by a bulk acoustic wave resonator, the first electrode of the first split resonator is one of the top electrode and the bottom electrode, and the second electrode is the other of the top electrode and the bottom electrode. (3) For all split sub-units located in the same first equivalent structure, preferably, all split sub-units include the same number of first split resonators, and all first split resonators have the same resonance area. It should be noted here that the resonance area refers to the effective working area of ​​the resonator. Specifically for the bulk acoustic wave resonator, its resonance area refers to the area of ​​the overlapping area of ​​the top electrode, the piezoelectric layer and the bottom electrode in the thickness direction of the device. Among them, all first split resonators located in the same first equivalent structure can be manufactured to have the same structure and size so that they have the same resonance area. It can be understood by those skilled in the art that in other embodiments, according to actual design requirements, the number of first split resonators in each split sub-unit in the same first equivalent structure may also be different, and the resonance area of ​​each first split resonator may also be different. The present invention does not impose any restrictions on this. (4) The resonance area of ​​a single series resonator before splitting is represented by A. The first equivalent structure obtained after splitting includes L (L is an integer greater than or equal to 2) split sub-units (represented by split sub-unit 1 to split sub-unit L respectively), and the sum of the resonance areas of all first split resonators in split sub-unit i is A i , i = 1, 2, ..., L, wherein the resonant areas of the single series resonator before splitting and the first split resonator after splitting conform to the following formula: 1 / A = 1 / A1 + 1 / A2 + ... + 1 / A L .

[0031] For all parallel resonant units, at least the last-order parallel resonant unit is an equivalent structure obtained by splitting a single parallel resonator (hereinafter referred to as the second equivalent structure). The last-order parallel resonant unit here refers to the first parallel resonant unit located on the output port side of the filter. In this embodiment, the second equivalent structure includes two split resonators obtained by anti-parallel splitting (hereinafter referred to as second split resonators). Specifically, the two second split resonators (hereinafter referred to as second split resonator 1 and second split resonator 2, respectively) are connected in parallel, and the currents of the two are set in reverse (that is, the first electrode of the second split resonator 1 is connected to the second electrode of the second split resonator 2, and the second electrode of the second split resonator 1 is connected to the first electrode of the second split resonator 2).

[0032] It should be noted here that (1) for the case where the number of parallel resonant units is greater than or equal to 2, some of the parallel resonant units (including the last-order parallel resonant unit) may be the second equivalent structure obtained by splitting a single parallel resonator, while the other parallel resonant units are unsplit parallel resonators, or all parallel resonant units may be the second equivalent structure obtained by splitting a single parallel resonator. The present invention does not impose any restrictions on this, and it needs to be formulated according to actual design requirements. (2) The present invention does not impose any restrictions on the type of resonator in all parallel resonant units (including unsplit parallel resonators and second split resonators obtained by splitting), for example, it can be a common bulk acoustic wave resonator. For the case where the second split resonator is implemented using a bulk acoustic wave resonator, the first electrode of the second split resonator is one of the top electrode and the bottom electrode, and the second electrode is the other of the top electrode and the bottom electrode. (3) For two second split resonators located in the same second equivalent structure, preferably, the two second split resonators have the same resonance area. Among them, the two second split resonators located in the same second equivalent structure can be manufactured to have the same structure and size so that they have the same resonance area. It can be understood by those skilled in the art that, in other embodiments, according to actual design requirements, the resonance areas of the two second split resonators in the same second equivalent structure may also be different, and the present invention does not impose any restrictions on this. (4) The resonance area of ​​the single parallel resonator before splitting is represented by B. The second equivalent structure obtained after splitting includes two second split resonators, and the resonance areas of the two second split resonators are represented by B1 and B2 respectively, wherein the resonance areas of the single parallel resonator before splitting and the second split resonator after splitting meet the following formula: B=B1+B2.

[0033] The filter provided by the present invention, on the one hand, for the split sub-unit in the first equivalent structure, since it is formed by anti-parallel splitting, that is, it includes two groups of first split resonators of the same number or as close as possible and the two groups of first split resonators are connected in parallel in a current-reversing manner, so that the resonant signals passing through the two groups of first split resonators can cancel each other out to the greatest extent. The same is true for the second equivalent structure (that is, the resonant signals passing through the two second split resonators can cancel each other out). The mutual cancellation of the resonant signals between the split resonators is beneficial to the suppression of the nonlinear behavior of the filter. On the other hand, the last-order series resonant unit and the last-order parallel resonant unit of the filter are both formed by splitting a single resonator, which can significantly suppress the generation of the second harmonic of the filter, and thus suppress the nonlinear behavior of the filter. On the other hand, the split sub-unit in the first equivalent structure and the splitting method of the second equivalent structure are the same, both of which are formed by anti-parallel splitting. The consistency of this splitting is also beneficial to the suppression of the nonlinear behavior of the filter to a certain extent. Based on this, the filter provided by the present invention has good nonlinear characteristics.

[0034] For the first split resonator in the last-order series resonance unit and the second split resonator in the last-order parallel resonance unit, it is preferred that, through splitting, the resonance areas of all the first split resonators and the second split resonators are made as close as possible or even equal, which is conducive to further improving the suppression effect of the second harmonic of the filter.

[0035] The following will be combined Figure 1 、 Figure 2(a) to Figure 2(d) The filter provided by the present invention is described with four specific embodiments. Figure 1 This is a circuit diagram of a filter that has not been split in the prior art. Figure 2(a) to Figure 2(d) According to four specific embodiments of the present invention Figure 1 Circuit diagram of the structure obtained after the filter shown is decomposed.

[0036] like Figure 1As shown, the filter includes an input port Term_in, an output port Term_out, four series resonant units, and four parallel resonant units. Each series resonant unit is a single unsplit series resonator, and the four series resonators are series resonator S1, series resonator S2, series resonator S3, and series resonator S4 in the direction from the input port Term_in to the output port Term_out. Each parallel resonant unit is a single unsplit parallel resonator, and the four parallel resonators are parallel resonator P1, parallel resonator P2, parallel resonator P3, and parallel resonator P4 in the direction from the input port Term_in to the output port Term_out, wherein one end of the parallel resonator P1 is connected to the node between the input port Term_in and the series resonator S1, and the other end is grounded through the inductor L1, one end of the parallel resonator P2 is connected to the node between the series resonator S1 and the series resonator S2, and the other end is grounded through the inductor L2, one end of the parallel resonator P3 is connected to the node between the series resonator S2 and the series resonator S3, and the other end is grounded through the inductor L3, and one end of the parallel resonator P4 is connected to the node between the series resonator S3 and the series resonator S4, and the other end is grounded through the inductor L4.

[0037] The filter shown in Figure 2(a) is a Figure 1 The filter shown is obtained by splitting the series resonant unit (i.e., series resonator S4) and the parallel resonant unit (i.e., parallel resonator P4) at the last order. In this embodiment, as shown in FIG2(a), the series resonator S4 is split into two split sub-units connected in series. The two split sub-units are represented by split sub-unit 1 and split sub-unit 2 in the direction from the input port Term_in to the output port Term_out, wherein the split sub-unit 1 includes a first split resonator S connected in parallel and with current reversed. 411 and the first split resonator S 412 , the split subunit 2 includes a first split resonator S connected in parallel and with current reversed 421 and the first split resonator S 422 In addition, for the filter shown in FIG2(a), the first split resonator S in the split subunit 1 is 411 and the first split resonator S in the split subunit 2 421 Correspondingly, the first split resonator S in the split subunit 1 412 and the first split resonator S in the split subunit 2 422 In this embodiment, the first split resonator S 411 and the first split resonator S 421 The currents of the two are set in opposite directions (ie, the first electrodes of the two are connected), and the first split resonator S412 and the first split resonator S 422 The currents of the two are set in opposite directions (ie, the second electrodes of the two are connected). It can be understood by those skilled in the art that, in other embodiments, the first split resonator S 411 and the first split resonator S 421 The two currents are set in opposite directions, or the first split resonator S 412 and the first split resonator S 422 The parallel resonator P4 is split into a second split resonator P connected in parallel and with currents reversed. 41 and the second split resonator P 42 It should be noted here that, considering that when the currents of the two split resonators are set in reverse, the current directions of the two split resonators are correspondingly opposite, so the figure represents the reverse setting of the split resonator currents by the opposite current directions of the split resonators, wherein the current directions of the split resonators are represented by arrows in the figure.

[0038] The filter shown in Figure 2(b) is a Figure 1 The filter shown is obtained by splitting the series resonant unit (i.e., series resonator S4) and the parallel resonant unit (i.e., parallel resonator P4) at the last order. In this embodiment, as shown in FIG2(b), the series resonator S4 is split into two split sub-units connected in series. The two split sub-units are represented by split sub-unit 1 and split sub-unit 2 in the direction from the input port Term_in to the output port Term_out, wherein the split sub-unit 1 includes a first split resonator S connected in parallel. 411 , the first split resonator S 412 and the first split resonator S 413 , the first split resonator S 411 and the first split resonator S 413 The currents of the two are set in the same direction, and the first split resonator S 412 With the first split resonator S 411 and the first split resonator S 413 The current reverse setting; the split sub-unit 2 includes a first split resonator S connected in parallel 421 , the first split resonator S 422 and the first split resonator S 423 , the first split resonator S 421 and the first split resonator S 423 The currents of the two are set in the same direction, and the first split resonator S 422 With the first split resonator S 421 and the first split resonator S 423 In addition, for the filter shown in FIG2( b ), the first split resonator S in the split subunit 1 is411 and the first split resonator S in the split subunit 2 421 Correspondingly, the first split resonator S in the split subunit 1 412 and the first split resonator S in the split subunit 2 422 Correspondingly, the first split resonator S in the split subunit 1 413 and the first split resonator S in the split subunit 2 423 In this embodiment, the first split resonator S 411 and the first split resonator S 421 The currents of the two are set in opposite directions (ie, the first electrodes of the two are connected), and the first split resonator S 412 and the first split resonator S 422 The currents of the two are set in opposite directions (ie, the second electrodes of the two are connected), and the first split resonator S 413 and the first split resonator S 423 The currents of the two are set in opposite directions (ie, the second electrodes of the two are connected). It can be understood by those skilled in the art that, in other embodiments, the first split resonator S 411 and the first split resonator S 421 , the first split resonator S 412 and the first split resonator S 422 , the first split resonator S 413 and the first split resonator S 423 The parallel resonator P4 is split into second split resonators P connected in parallel and with current reversed. 41 and the second split resonator P 42 .

[0039] The filter shown in Figure 2(c) is a Figure 1 The filter shown is obtained by splitting the series resonant unit (i.e., series resonator S4) and the parallel resonant unit (i.e., parallel resonator P4) at the last order. In this embodiment, as shown in FIG2(c), the series resonator S4 is split into three split sub-units connected in series. The three split sub-units are represented by split sub-unit 1, split sub-unit 2, and split sub-unit 3 in the direction from the input port Term_in to the output port Term_out, wherein the split sub-unit 1 includes a first split resonator S connected in parallel and with current reversed. 411 and the first split resonator S 412 , the split subunit 2 includes a first split resonator S connected in parallel and with current reversed 421 and the first split resonator S 422 , the split subunit 3 includes a first split resonator S connected in parallel and with current reversed 431and the first split resonator S 432 In addition, for the filter shown in FIG2(c), the first split resonator S in the split subunit 1 is 411 , the first split resonator S in the split subunit 2 421 and the first split resonator S in the split subunit 3 431 Correspondingly, the first split resonator S in the split subunit 1 412 , the first split resonator S in the split subunit 2 422 and the first split resonator S in the split subunit 3 432 In this embodiment, the first split resonator S 411 , the first split resonator S 421 and the first split resonator S 431 The current is reversed in sequence (ie the first split resonator S 411 and the first split resonator S 421 The first electrodes of the two are connected, and the first split resonator S 421 and the first split resonator S 431 The second electrodes of the two are connected), the first split resonator S 412 , the first split resonator S 422 and the first split resonator S 432 The current is reversed in sequence (ie the first split resonator S 412 and the first split resonator S 422 The second electrodes of the two are connected, and the first split resonator S 422 and the first split resonator S 432 The first electrodes of the two are connected). Those skilled in the art will appreciate that, in other embodiments, the first split resonator S may also be 411 , the first split resonator S 421 and the first split resonator S 431 Sequentially current reverse setting, or first split resonator S 412 , the first split resonator S 422 and the first split resonator S 432 The parallel resonator P4 is split into a second split resonator P connected in parallel and with a current reversed setting. 41 and the second split resonator P 42 .

[0040] The filter shown in Figure 2(d) is a Figure 1The filter is obtained by splitting multiple series resonant units (i.e., series resonator S2, series resonator S3, and series resonator S4) and multiple parallel resonant units (i.e., parallel resonator P2, parallel resonator P3, and parallel resonator P4). In this embodiment, as shown in FIG2(d), the series resonator S i It is split into two split sub-units in series, one of which includes a first split resonator S connected in parallel and with current reversed. i11 and the first split resonator S i12 , the other split sub-unit includes a first split resonator S connected in parallel and with current reversed setting i21 and the first split resonator S i22 , where i = 2, 3, 4. Parallel resonator P i The second split resonator P is split into a parallel connection and a current reverse setting. j1 and the second split resonator P j2 , where j = 2, 3, 4.

[0041] Those skilled in the art will appreciate that the above filters are merely illustrative examples and should not be considered as limitations on the filter structure provided by the present invention. The splitting method may be selected according to actual design requirements.

[0042] The utility model also provides a duplexer, which includes an antenna port, a receiving port, a transmitting port, a receiving filter arranged between the antenna port and the receiving port, and a transmitting filter arranged between the transmitting port and the antenna port, wherein the transmitting filter is implemented using the aforementioned filter.

[0043] Specifically, the duplexer provided by the present invention includes an antenna port, a transmitting port, a receiving port, a receiving filter, and a transmitting filter.

[0044] In this embodiment, the transmit filter is implemented using the aforementioned filter. For the sake of simplicity, the structure of the aforementioned filter is not repeated here. The transmit filter is arranged between the transmit port and the antenna port, wherein the input port of the transmit filter is connected to the transmit port of the duplexer, and the output port of the transmit filter is connected to the antenna port of the duplexer.

[0045] In this embodiment, the receive filter includes an input port, an output port, a series path, and at least one parallel resonant unit, wherein the series path includes at least one series resonant unit sequentially connected between the input port and the output port of the receive filter, one end of each of the parallel resonant units is connected to a node of the series path of the receive filter, and the other end is directly grounded or grounded through an inductor. The receive filter is arranged between the antenna port and the receive port, wherein the input port of the receive filter is connected to the antenna port of the duplexer, and the output port of the receive filter is connected to the receive port of the duplexer. In a specific embodiment, all series resonant units and all parallel resonant units in the receive filter are unsplit resonators. In another specific embodiment, at least one series resonant unit in the receive filter (preferably the first series resonant unit located at the antenna port of the receive filter) is an equivalent structure obtained by splitting a single series resonator (hereinafter referred to as a third equivalent structure), and / or at least one parallel resonant unit in the receive filter (preferably the first parallel resonant unit located at the antenna port of the receive filter) is an equivalent structure obtained by splitting a single parallel resonator (hereinafter referred to as a fourth equivalent structure). The third equivalent structure includes two or more split subunits connected in series, each of which includes two or more third split resonators obtained by anti-parallel splitting. The fourth equivalent structure includes two fourth split resonators obtained by anti-parallel splitting. Whether the resonant unit in the receive filter is split is determined by actual design requirements and is not limited in this invention.

[0046] The transmit filter in the duplexer provided by the present invention is implemented using the aforementioned filter. Since the aforementioned filter has excellent nonlinear characteristics, the duplexer provided by the present invention also has correspondingly excellent nonlinear characteristics. When the series resonant unit and / or parallel resonant unit in the receive filter are also equivalent structures obtained by splitting a single resonator, the nonlinear characteristics of the duplexer are further improved.

[0047] The duplexer provided by the present invention is described below with reference to two specific embodiments.

[0048] In one specific embodiment, as shown in FIG3(a), the duplexer includes an antenna port ANT, a transmit port TX, a receive port RX, a transmit filter disposed between the transmit port TX and the antenna port ANT, and a receive filter disposed between the antenna port ANT and the receive port RX. The transmit filter is implemented using the filter shown in FIG2(a). The receive filter is implemented using an existing conventional, unsplit filter. As shown in the figure, the receive filter includes a series resonator S5, a series resonator S6, a series resonator S7, and a series resonator S8, which are sequentially connected in series between the antenna port ANT and the receive port RX. In addition, the receiving filter also includes a parallel resonator P5, a parallel resonator P6 and a parallel resonator P7, wherein one end of the parallel resonator P5 is connected to the node between the series resonator S5 and the series resonator S6, and the other end is grounded through the inductor L5, one end of the parallel resonator P6 is connected to the node between the series resonator S6 and the series resonator S7, and the other end is grounded through the inductor L6, and one end of the parallel resonator P7 is connected to the node between the series resonator S7 and the series resonator S8, and the other end is grounded through the inductor L7.

[0049] In another specific embodiment, as shown in FIG3(b), the duplexer includes an antenna port ANT, a transmitting port TX, a receiving port RX, a transmitting filter arranged between the transmitting port TX and the antenna port ANT, and a receiving filter arranged between the antenna port ANT and the receiving port RX. As for the transmitting filter, it is implemented by the filter shown in FIG2(d). As for the receiving filter, it includes a third equivalent structure S5, a series resonator S6, a series resonator S7 and a series resonator S8 connected in series between the antenna port ANT and the receiving port RX. The third equivalent structure S5 includes two split subunits connected in series, one of which includes a third split resonator S5 connected in parallel and with current reversed. 511 and the third split resonator S 512 , the other split sub-unit includes a third split resonator S connected in parallel and with current reversed setting 521 and the third split resonator S 522 In addition, the receiving filter also includes a fourth equivalent structure P5, a parallel resonator P6 and a parallel resonator P7, wherein one end of the fourth equivalent structure P5 is connected to the node between the series resonator S5 and the series resonator S6, and the other end is grounded through the inductor L5. The fourth equivalent structure P5 includes a fourth split resonator P5 connected in parallel and with current reversed. 51 and the fourth split resonator P 52One end of the parallel resonator P6 is connected to the node between the series resonator S6 and the series resonator S7, and the other end is grounded through the inductor L6. One end of the parallel resonator P7 is connected to the node between the series resonator S7 and the series resonator S8, and the other end is grounded through the inductor L7.

[0050] Those skilled in the art will appreciate that the above-mentioned duplexer is merely an illustrative example and should not be construed as a limitation on the structure of the duplexer provided by the present invention, and the splitting method may be selected accordingly according to actual design requirements.

[0051] It is obvious 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 present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes that fall within the meaning and scope of the equivalent elements of the claims be included in the present invention. Any figure mark in the claims should not be regarded as limiting the claim involved. In addition, it is obvious that the word "comprising" does not exclude other parts, units or steps, and the singular does not exclude the plural. The multiple parts, units or devices stated in the system claim may also be implemented by one part, unit or device through software or hardware.

[0052] The above disclosures are merely some preferred embodiments of the present invention, and certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope covered by the present invention.

Claims

1. A filter, characterized in that: The filter includes: Input ports and output ports; a series path, the series path comprising at least one series resonant unit sequentially connected between the input port and the output port; at least one parallel resonant unit, one end of each parallel resonant unit being connected to a node of the series path and the other end being directly grounded or grounded through an inductor; Among them, at least the first series resonant unit located on the output port side of the series resonant unit is a first equivalent structure obtained by splitting a single series resonator, and the first equivalent structure includes two or more split sub-units connected in series, and each of the split sub-units includes two or more first split resonators obtained by anti-parallel splitting; at least the first parallel resonant unit located on the output port side of the parallel resonant unit is a second equivalent structure obtained by splitting a single parallel resonator, and the second equivalent structure includes two second split resonators obtained by anti-parallel splitting.

2. The filter according to claim 1, wherein: The split subunits located in the same first equivalent structure all include the same number of the first split resonators, and the first split resonators all have the same resonance area; The two second split resonators located in the same second equivalent structure have the same resonance area.

3. The filter according to claim 1, wherein: The first equivalent structure includes three split sub-units connected in series, each of the split sub-units includes two first split resonators obtained by anti-parallel splitting; or The first equivalent structure includes two split sub-units connected in series, and each of the split sub-units includes three first split resonators obtained by anti-parallel splitting.

4. The filter according to claim 1, wherein: The first split resonator in the first series resonance unit located at the output port side and the second split resonator in the first parallel resonance unit located at the output port side both have the same resonance area.

5. The filter according to any one of claims 1 to 4, characterized in that All resonators in the filter are bulk acoustic wave resonators.

6. A duplexer comprising an antenna port, a receiving port, a transmitting port, a receiving filter disposed between the antenna port and the receiving port, and a transmitting filter disposed between the transmitting port and the antenna port, wherein: The transmit filter is implemented by using the filter according to any one of claims 1 to 5.

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