A bandpass filter and a duplexer

Abstract

The present invention provides a bandpass filter, which includes a series path, the series path includes an input port, an output port, and a bandwidth adjustment unit connected in series between the input port and the output port, and N first resonators, wherein the bandwidth adjustment unit is located between two adjacent first resonators, the bandwidth adjustment unit includes a second resonator and a first inductor connected in series, and N is an integer greater than or equal to 2; one or more parallel branches, the one or more parallel branches are connected in parallel between the series path and the ground, and each of the parallel branches includes a third resonator; wherein the resonant frequency of the second resonator is less than the resonant frequency of any of the first resonator and the third resonator. The present invention also provides a duplexer. The bandpass filter provided by the present invention has the characteristics of wide passband, low insertion loss, and high suppression.

Description

Technical Field

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

[0002] A bandpass filter is a filter that can pass frequency components within a certain frequency range but attenuate frequency components in other ranges to a very low level. Currently, bandpass filters are widely used in fields such as wireless communications.

[0003] The existing bandpass filter mainly includes a series path and multiple parallel branches, wherein the series path includes an input port, an output port, and multiple series resonators connected in series between the input port and the output port, and the multiple parallel branches are connected in parallel between the series path and the ground. The structure of the existing common bandpass filter is described with a specific embodiment. Figure 1 As shown, the bandpass filter includes an input port 10a, an output port 10b, series resonators 11 to 14, and parallel branches A to D. The series resonators 11 to 14 are sequentially connected in series between the input port 10a and the output port 10b. The parallel branch A includes a parallel resonator 15 and a grounding inductor 19, one end of which is connected to a node between the series resonator 11 and the series resonator 12, and the other end is connected to the ground through the grounding inductor 19; the parallel branch B includes a parallel resonator 16 and a grounding inductor 20, one end of which is connected to a node between the series resonator 12 and the series resonator 13, and the other end is connected to the ground through the grounding inductor 20; the parallel branch C includes a parallel resonator 17 and a grounding inductor 21, one end of which is connected to a node between the series resonator 13 and the series resonator 14, and the other end is connected to the ground through the grounding inductor 21; the parallel branch D includes a parallel resonator 18 and a grounding inductor 22, one end of which is connected to a node between the series resonator 14 and the output port 10b, and the other end is connected to the ground through the grounding inductor 22.

[0004] The bandwidth of the above existing bandpass filters is generally less than 200M (the bandwidth of a typical bandpass filter is about 160MHz), which can no longer meet the application scenarios that require a wide passband. Therefore, how to make the bandpass filter have a wider passband while ensuring its performance has become a research topic for those skilled in the art. Summary of the invention

[0005] In order to overcome the above defects in the prior art, the present invention provides a bandpass filter, which includes:

[0006] A series path, the series path comprising an input port, an output port, a bandwidth adjustment unit connected in series between the input port and the output port, and N first resonators, wherein the bandwidth adjustment unit is located between two adjacent first resonators, the bandwidth adjustment unit comprises a second resonator and a first inductor connected in series, and N is an integer greater than or equal to 2;

[0007] One or more parallel branches, the one or more parallel branches are connected in parallel between the series path and ground, each of the parallel branches includes a third resonator;

[0008] The resonant frequency of the second resonator is smaller than the resonant frequency of any one of the first resonator and the third resonator.

[0009] According to one aspect of the present invention, in the bandpass filter, one end of each of the parallel branches is connected to a node of the series path and the other end is grounded, wherein the nodes of the series path include a node between the input port and the first resonator adjacent thereto, a node between the bandwidth adjustment unit and N first resonators, and a node between the output port and the first resonator adjacent thereto.

[0010] According to another aspect of the present invention, in the bandpass filter, the resonant frequency of the second resonator is 50 MHz to 10 GHz lower than the resonant frequency of any one of the first resonator and the third resonator.

[0011] According to another aspect of the present invention, in the bandpass filter, at least one of the parallel branches also includes a second inductor, one end of the second inductor is connected to the third resonator in the parallel branch where it is located, and the other end is grounded; wherein the inductance value of the first inductor is greater than the inductance value of the second inductor.

[0012] According to another aspect of the present invention, in the bandpass filter, when the number of the parallel branches is two or more, the third resonators in at least two of the parallel branches are grounded through the same second inductor.

[0013] According to still another aspect of the present invention, in the bandpass filter, the inductance value of the first inductor is 0.5 nH to 10 nH greater than the inductance value of the second inductor.

[0014] According to another aspect of the present invention, the bandpass filter further includes at least one of a third inductor, a fourth inductor and a fifth inductor, wherein one end of the third inductor is connected to the input end of the bandwidth adjustment unit and the other end is grounded, one end of the fourth inductor is connected to the output end of the bandwidth adjustment unit and the other end is grounded, and one end of the fifth inductor is connected to the node between the second resonator and the first inductor and the other end is grounded.

[0015] The present invention also provides a duplexer, which includes a transmitting filter and a receiving filter. The transmitting filter and / or the receiving filter are implemented by the aforementioned bandpass filter.

[0016] The bandpass filter provided by the present invention includes a series path, on which a bandwidth adjustment unit and at least two first resonators are connected in series, wherein the bandwidth adjustment unit is located between two adjacent first resonators, and the bandwidth adjustment unit includes a second resonator and a first inductor connected in series; one or more parallel branches, wherein the one or more parallel branches are connected in parallel between the series path and the ground, and each parallel branch includes a third resonator; wherein the resonant frequency of the second resonator is less than the resonant frequency of any of the first resonator and the third resonator. Compared with the existing bandpass filters, the bandpass filter provided by the present invention has the characteristics of wide passband, low insertion loss and high suppression. Correspondingly, the duplexer formed based on the bandpass filter provided by the present invention also has the characteristics of wide passband, low insertion loss and high suppression. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0018] Figure 1 It is a circuit diagram of a common bandpass filter in the prior art;

[0019] Figure 2 is a circuit diagram of a bandpass filter according to a specific embodiment of the present invention;

[0020] Figure 3 is a circuit diagram of a bandpass filter according to another specific embodiment of the present invention;

[0021] Figure 4 is a circuit diagram of a bandpass filter according to another specific embodiment of the present invention;

[0022] Figure 5 is a circuit diagram of a bandpass filter according to another specific embodiment of the present invention;

[0023] Figure 6 is a circuit diagram of a bandpass filter according to another specific embodiment of the present invention;

[0024] Figure 7 is a circuit diagram of a bandpass filter according to another specific embodiment of the present invention;

[0025] Figure 8 is a circuit diagram of a bandpass filter according to another specific embodiment of the present invention;

[0026] Fig. 9 yes Figure 3 Small signal S parameter simulation curve of the bandpass filter shown;

[0027] Fig.10 yes Figure 5 Small signal S parameter simulation curve of the bandpass filter shown;

[0028] Fig.11 yes Figure 7 Small signal S parameter simulation curve of the bandpass filter shown.

[0029] The same or similar reference numerals in the drawings represent the same or similar components. DETAILED DESCRIPTION

[0030] In order to better understand and illustrate the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0031] The present invention provides a bandpass filter, which includes:

[0032] A series path, the series path comprising an input port, an output port, a bandwidth adjustment unit connected in series between the input port and the output port, and N first resonators, wherein the bandwidth adjustment unit is located between two adjacent first resonators, the bandwidth adjustment unit comprises a second resonator and a first inductor connected in series, and N is an integer greater than or equal to 2;

[0033] One or more parallel branches, the one or more parallel branches are connected in parallel between the series path and ground, each of the parallel branches includes a third resonator;

[0034] The resonant frequency of the second resonator is smaller than the resonant frequency of any one of the first resonator and the third resonator.

[0035] The various components of the above-mentioned bandpass filter are described in detail below.

[0036] Specifically, the filter provided by the present invention is a bandpass filter, which includes a series path. In the present embodiment, the series path includes an input port and an output port, wherein the input port is used to input the signal to be filtered, and the output port is used to output the signal of a specific frequency obtained after filtering. In addition to the input port and the output port, the series path further includes N resonators (hereinafter represented by the first resonator, wherein N is an integer greater than or equal to 2), and a bandwidth adjustment unit, and the N first resonators and the bandwidth adjustment unit are connected in series between the input port and the output port. In the present embodiment, the bandwidth adjustment unit can be arranged between any two adjacent first resonators in the series path. For example, the number of first resonators is equal to 4, and the four first resonators are first resonator A, first resonator B, first resonator C and first resonator D from the input port side to the output port side, wherein the bandwidth adjustment unit can be connected in series between the first resonator A and the first resonator B, or between the first resonator B and the first resonator C, or between the first resonator C and the first resonator D. Further, the bandwidth adjustment unit includes a resonator (hereinafter referred to as the second resonator) and an inductor (hereinafter referred to as the first inductor) connected in series. Since the second resonator and the first inductor are in a series relationship, there is no limitation on the order in which they are arranged. The input end of the second resonator may be connected to the output end of the adjacent first resonator, the input end of the first inductor may be connected to the output end of the second resonator, and the output end may be connected to the input end of the adjacent first resonator. Conversely, the connection order of the second resonator and the first inductor may be reversed.

[0037] The bandpass filter provided by the present invention also includes one or more parallel branches, which are connected in parallel between the series path and the ground. That is to say, one end of each parallel branch is connected to the node of the series path and the other end is grounded, wherein the node of the series path includes the node between the input port and the first resonator adjacent thereto, the node between the bandwidth adjustment unit and the N first resonators, and the node between the output port and the first resonator adjacent thereto. In this embodiment, the number of parallel branches is equal to N+2, and the N+2 parallel branches correspond one-to-one to the N+2 nodes on the above-mentioned series path, wherein one end of each parallel branch is connected to the node corresponding thereto and the other end is grounded. It is still taken as an example that the number of first resonators is equal to 4 (i.e., N=4), and the four first resonators from the input port side to the output port side are first resonator A, first resonator B, first resonator C, and first resonator D, respectively. Assuming that the bandwidth adjustment unit is arranged between the first resonator B and the first resonator C, the number of parallel branches is also 6, which are represented by parallel branch A, parallel branch B, parallel branch C, parallel branch D, parallel branch E and parallel branch F, wherein one end of parallel branch A is connected to the node between the input port and the first resonator A, and the other end is grounded, one end of parallel branch B is connected to the node between the first resonator A and the first resonator B, and the other end is grounded, one end of parallel branch C is connected to the node between the first resonator B and the bandwidth adjustment unit, and the other end is grounded, one end of parallel branch D is connected to the node between the bandwidth adjustment unit and the first resonator C, and the other end is grounded, one end of parallel branch E is connected to the node between the first resonator C and the first resonator D, and the other end is grounded, and one end of parallel branch F is connected between the first resonator D and the output port. It can be understood by those skilled in the art that in the above embodiments, the parallel branches correspond one-to-one to the nodes on the series path. In other embodiments, this one-to-one correspondence may not be adopted, and the present invention does not make any limitation to this.

[0038] In this embodiment, each parallel branch includes a resonator (hereinafter referred to as the third resonator), wherein one end of the third resonator is connected to the node of the series path and the other end is grounded. In other implementations, at least one parallel branch includes an inductor (hereinafter referred to as the second inductor) in series with the third resonator in addition to the third resonator, wherein one end of the third resonator is connected to the node of the series path and the other end is grounded through the second inductor. It should be noted that when there are two or more parallel branches that include the third resonator and the second inductor, the third resonator in each parallel branch can be grounded through an independent second inductor, or the third resonator in two or more parallel branches can be grounded through a common second inductor, and the present invention does not impose any restrictions on this. In addition, preferably, the bandpass filter provided by the present invention also includes a first matching inductor and / or a second matching inductor, wherein the first matching inductor is arranged at the input port, one end of which is connected to the node between the input port and the first resonator adjacent thereto, and the other end is grounded; the second matching port is arranged at the output port, one end of which is connected to the node between the output port and the first resonator adjacent thereto, and the other end is grounded.

[0039] In this embodiment, the resonant frequency of the second resonator in the bandwidth adjustment unit is lower than the resonant frequency of any other resonator in the bandpass filter, that is, the resonant frequency of the second resonator is lower than the resonant frequency of the first resonator and the third resonator. Preferably, the resonant frequency of the second resonator is 50 MHz to 10 GHz less than the resonant frequency of any other resonator in the filter.

[0040] Compared with the existing bandpass filter including only series resonators in the series branch, the bandpass filter provided by the present invention is provided with a bandwidth adjustment unit between two adjacent first resonators in the series path, and the bandwidth adjustment unit includes a second resonator and a first inductor connected in series. By making the resonant frequency of the second resonator smaller than the resonant frequency of the resonator in the series path and the parallel branch of the filter, and using it in conjunction with the first inductor (the first inductor is used to change the series resonant frequency of the second resonator connected in series with it), an impedance minimum point can be formed in the filter passband, thereby changing the impedance distribution of the second resonator to form a passband. In addition, the impedance value of the series path within the passband frequency range can be made smaller than the impedance value of the series path of the existing bandpass filter within the passband frequency range, and the frequency band range of the impedance minimum is effectively expanded, thereby widening the bandwidth (can reach more than 200M), forming a wide passband or even ultra-wideband bandpass filter. In addition, the resonant frequency of the second resonator is lower than the resonant frequency of the resonator in the series path and the parallel branch of the filter, and an additional transmission zero point can be formed at the near stopband on the left and right sides, thereby improving the near stopband suppression on the left and right sides, so that the bandpass filter has the characteristics of high suppression, low insertion loss and fast roll-off. In other words, compared with the existing bandpass filter, the bandpass filter provided by the present invention has excellent performance and a wide passband.

[0041] For the case where the filter parallel branch includes a third resonator and a second inductor, preferably, the inductance value of the first inductor in the bandwidth adjustment unit is greater than the inductance value of the second inductor in all parallel branches, which is conducive to improving the performance of the bandpass filter in the bandwidth range. Typically, the inductance value of the first inductor is 0.5nH to 10nH higher than the inductance value of the second inductor.

[0042] The structure of the bandpass filter provided by the present invention is described below with reference to two specific embodiments.

[0043] Please refer to Figure 2 , Figure 21 is a circuit diagram of a bandpass filter according to a specific embodiment of the present invention. As shown in the figure, the bandpass filter includes an input port 100a and an output port 100b, a first resonator 101, a bandwidth adjustment unit 10 and a first resonator 104 are sequentially connected in series between the input port 100a and the output port 100b, and the bandwidth adjustment unit 10 includes a second resonator 102 and a first inductor 103, wherein the output end of the first resonator 101 is connected to the input end of the second resonator 102, the output end of the second resonator 102 is connected to the input end of the first inductor 103, and the output end of the first inductor 103 is connected to the input end of the first resonator 104. The bandpass filter includes four parallel branches, which are represented by parallel branch A, parallel branch B, parallel branch C and parallel branch D from the input port side to the output port side, respectively, wherein the parallel branch A includes a third resonator 105, one end of which is connected to the node between the input port 100a and the first resonator 101, and the other end is grounded; the parallel branch B includes a third resonator 106, one end of which is connected to the node between the first resonator 101 and the bandwidth adjustment unit 10, and the other end is grounded; the parallel branch C includes a third resonator 107, one end of which is connected to the node between the bandwidth adjustment unit 10 and the first resonator 104, and the other end is grounded; the parallel branch D includes a third resonator 108, one end of which is connected to the node between the first resonator 104 and the output port 100b, and the other end is grounded.

[0044] Please refer to Figure 3 , Figure 32 is a circuit diagram of a bandpass filter according to another specific embodiment of the present invention. As shown in the figure, the bandpass filter includes an input port 200a and an output port 200b, a first resonator 201, a bandwidth adjustment unit 20 and a first resonator 204 are sequentially connected in series between the input port 200a and the output port 200b, the bandwidth adjustment unit 20 includes a second resonator 202 and a first inductor 203, wherein the output end of the first resonator 201 is connected to the input end of the second resonator 202, the output end of the second resonator 202 is connected to the input end of the first inductor 203, and the output end of the first inductor 203 is connected to the input end of the first resonator 204. The bandpass filter includes four parallel branches, which are represented by parallel branch A, parallel branch B, parallel branch C and parallel branch D from the input port side to the output port side, wherein the parallel branch A and the parallel branch B respectively include a third resonator 205 and a third resonator 206, one end of the third resonator 205 is connected to the node between the input port 200a and the first resonator 201, one end of the third resonator 206 is connected to the node between the first resonator 201 and the bandwidth adjustment unit 20, and the third resonator 20 5 and the other end of the third resonator 206 are grounded through the second inductor 211; the parallel branch C includes the third resonator 207 and the second inductor 212, one end of the third resonator 207 is connected to the node between the bandwidth adjustment unit 20 and the first resonator 204, and the other end is grounded through the second inductor 212; the parallel branch D includes the third resonator 208 and the second inductor 213, one end of the third resonator 208 is connected to the node between the first resonator 204 and the output port 200b, and the other end is grounded through the second inductor 213. The bandpass filter also includes a first matching inductor 209 and a second matching inductor 210, wherein one end of the first matching inductor 209 is connected to the node between the input port 200a and the first resonator 201, and the other end is grounded; one end of the second matching inductor 210 is connected to the node between the first resonator 204 and the output port 200b, and the other end is grounded.

[0045] Preferably, the bandpass filter provided by the present invention also includes at least one of a third inductor, a fourth inductor, and a fifth inductor. Among them, one end of the third inductor is connected to the node between the input end of the bandwidth adjustment unit and the first resonator adjacent to it, and the other end is grounded, one end of the fourth inductor is connected to the node between the output end of the bandwidth adjustment unit and the first resonator adjacent to it, and the other end is grounded, and one end of the fifth inductor is connected to the node between the second resonator and the first inductor in the bandwidth adjustment unit, and the other end is grounded. Among them, the third inductor, the fourth inductor and the fifth inductor are mainly used to achieve impedance matching of the filter passband and improve the out-of-band suppression of the filter. The following is an explanation with specific embodiments.

[0046] Please refer to Figure 4 , Figure 41 is a circuit diagram of a bandpass filter according to another specific embodiment of the present invention. As shown in the figure, the bandpass filter includes an input port 300a and an output port 300b, a first resonator 301, a bandwidth adjustment unit 30 and a first resonator 304 are sequentially connected in series between the input port 300a and the output port 300b, the bandwidth adjustment unit 30 includes a second resonator 302 and a first inductor 303, wherein the output end of the first resonator 301 is connected to the input end of the second resonator 302, the output end of the second resonator 302 is connected to the input end of the first inductor 303, and the output end of the first inductor 303 is connected to the input end of the first resonator 304. The bandpass filter includes four parallel branches, which are represented by parallel branch A, parallel branch B, parallel branch C and parallel branch D from the input port side to the output port side, wherein the parallel branch A and the parallel branch B respectively include a third resonator 305 and a third resonator 306, one end of the third resonator 305 is connected to the node between the input port 300a and the first resonator 301, one end of the third resonator 306 is connected to the node between the first resonator 301 and the bandwidth adjustment unit 30, and the third resonator 30 5 and the other end of the third resonator 306 are grounded through the second inductor 311; the parallel branch C includes the third resonator 307 and the second inductor 312, one end of the third resonator 307 is connected to the node between the bandwidth adjustment unit 30 and the first resonator 304, and the other end is grounded through the second inductor 312; the parallel branch D includes the third resonator 308 and the second inductor 313, one end of the third resonator 308 is connected to between the first resonator 304 and the output port 300b, and the other end is grounded through the second inductor 313. The bandpass filter also includes a third inductor 314a, one end of the third inductor 314a is connected to the node between the first resonator 301 and the bandwidth adjustment unit 30, and the other end is grounded. The use of the third inductor 314a can achieve impedance matching of the filter passband. The bandpass filter further includes a first matching inductor 309 and a second matching inductor 310, wherein one end of the first matching inductor 309 is connected to a node between the input port 300a and the first resonator 301, and the other end is grounded; one end of the second matching inductor 310 is connected to a node between the first resonator 304 and the output port 300b, and the other end is grounded.

[0047] Please refer to Figure 5 , Figure 54 is a circuit diagram of a bandpass filter according to another specific embodiment of the present invention. As shown in the figure, the bandpass filter includes an input port 400a and an output port 400b, a first resonator 401, a bandwidth adjustment unit 40 and a first resonator 404 are sequentially connected in series between the input port 400a and the output port 400b, and the bandwidth adjustment unit 40 includes a second resonator 402 and a first inductor 403, wherein the output end of the first resonator 401 is connected to the input end of the second resonator 402, the output end of the second resonator 402 is connected to the input end of the first inductor 403, and the output end of the first inductor 403 is connected to the input end of the first resonator 404. The bandpass filter includes four parallel branches, which are represented by parallel branch A, parallel branch B, parallel branch C and parallel branch D from the input port side to the output port side, wherein the parallel branch A and the parallel branch B respectively include a third resonator 405 and a third resonator 406, one end of the third resonator 405 is connected to the node between the input port 400a and the first resonator 401, one end of the third resonator 406 is connected to the node between the first resonator 401 and the bandwidth adjustment unit 40, and the third resonator 40 5 and the other end of the third resonator 406 are grounded through the second inductor 411; the parallel branch C includes a third resonator 407 and a second inductor 412, one end of the third resonator 407 is connected to the node between the bandwidth adjustment unit 40 and the first resonator 404, and the other end is grounded through the second inductor 412; the parallel branch D includes a third resonator 408 and a second inductor 413, one end of the third resonator 408 is connected to between the first resonator 404 and the output port 400b, and the other end is grounded through the second inductor 413. The bandpass filter also includes a fourth inductor 414b, one end of the fourth inductor 414b is connected to the node between the bandwidth adjustment unit 40 and the first resonator 404, and the other end is grounded. The use of the fourth inductor 414b can achieve impedance matching of the filter passband. The bandpass filter further includes a first matching inductor 409 and a second matching inductor 410, wherein one end of the first matching inductor 409 is connected to a node between the input port 400a and the first resonator 401, and the other end is grounded; one end of the second matching inductor 410 is connected to a node between the first resonator 404 and the output port 400b, and the other end is grounded.

[0048] Please refer to Figure 6 , Figure 61 is a circuit diagram of a bandpass filter according to another specific embodiment of the present invention. As shown in the figure, the bandpass filter includes an input port 500a and an output port 500b, a first resonator 501, a bandwidth adjustment unit 50 and a first resonator 504 are sequentially connected in series between the input port 500a and the output port 500b, and the bandwidth adjustment unit 50 includes a second resonator 502 and a first inductor 503, wherein the output end of the first resonator 501 is connected to the input end of the second resonator 502, the output end of the second resonator 502 is connected to the input end of the first inductor 503, and the output end of the first inductor 503 is connected to the input end of the first resonator 504. The bandpass filter includes four parallel branches, which are represented by parallel branch A, parallel branch B, parallel branch C and parallel branch D from the input port side to the output port side, wherein the parallel branch A and the parallel branch B respectively include a third resonator 505 and a third resonator 506, one end of the third resonator 505 is connected to the node between the input port 500a and the first resonator 501, one end of the third resonator 506 is connected to the node between the first resonator 501 and the bandwidth adjustment unit 50, and the third resonator 50 5 and the other end of the third resonator 506 are grounded through the second inductor 511; the parallel branch C includes a third resonator 507 and a second inductor 512, one end of the third resonator 507 is connected to the node between the bandwidth adjustment unit 50 and the first resonator 504, and the other end is grounded through the second inductor 512; the parallel branch D includes a third resonator 508 and a second inductor 513, one end of the third resonator 508 is connected to between the first resonator 504 and the output port 500b, and the other end is grounded through the second inductor 513. The bandpass filter also includes a fifth inductor 514c, one end of the fifth inductor 514c is connected to the node between the second resonator 502 and the first inductor 503, and the other end is grounded. The use of the fifth inductor 514c can achieve impedance matching of the filter passband. The bandpass filter further includes a first matching inductor 509 and a second matching inductor 510, wherein one end of the first matching inductor 509 is connected to a node between the input port 500a and the first resonator 501, and the other end is grounded; one end of the second matching inductor 510 is connected to a node between the first resonator 504 and the output port 500b, and the other end is grounded.

[0049] Please refer to Figure 7 , Figure 71 is a circuit diagram of a bandpass filter according to another specific embodiment of the present invention. As shown in the figure, the bandpass filter includes an input port 600a and an output port 600b, a first resonator 601, a bandwidth adjustment unit 60 and a first resonator 604 are sequentially connected in series between the input port 600a and the output port 600b, the bandwidth adjustment unit 60 includes a second resonator 602 and a first inductor 603, wherein the output end of the first resonator 601 is connected to the input end of the second resonator 602, the output end of the second resonator 602 is connected to the input end of the first inductor 603, and the output end of the first inductor 603 is connected to the input end of the first resonator 604. The bandpass filter includes four parallel branches, which are represented by parallel branch A, parallel branch B, parallel branch C and parallel branch D from the input port side to the output port side, wherein the parallel branch A and the parallel branch B respectively include a third resonator 605 and a third resonator 606, one end of the third resonator 605 is connected to the node between the input port 600a and the first resonator 601, one end of the third resonator 606 is connected to the node between the first resonator 601 and the bandwidth adjustment unit 60, and the third resonator 60 5 and the other end of the third resonator 606 are grounded through the second inductor 611; the parallel branch C includes the third resonator 607 and the second inductor 612, one end of the third resonator 607 is connected to the node between the bandwidth adjustment unit 60 and the first resonator 604, and the other end is grounded through the second inductor 612; the parallel branch D includes the third resonator 608 and the second inductor 613, one end of the third resonator 608 is connected to between the first resonator 604 and the output port 600b, and the other end is grounded through the second inductor 613. The bandpass filter also includes a third inductor 614a and a fourth inductor 614b, wherein one end of the third inductor 614a is connected to the node between the first resonator 601 and the bandwidth adjustment unit 60, and the other end is grounded, and one end of the fourth inductor 614b is connected to the node between the bandwidth adjustment unit 60 and the first resonator 604, and the other end is grounded. The use of the third inductor 614a and the fourth inductor 614b can not only achieve impedance matching of the filter passband, but also improve the out-of-band suppression of the filter. The bandpass filter also includes a first matching inductor 609 and a second matching inductor 610, wherein one end of the first matching inductor 609 is connected to a node between the input port 600a and the first resonator 601, and the other end is grounded; one end of the second matching inductor 610 is connected to a node between the first resonator 604 and the output port 600b, and the other end is grounded.

[0050] Please refer to Figure 8 , Figure 81 is a circuit diagram of a bandpass filter according to another specific embodiment of the present invention. As shown in the figure, the bandpass filter includes an input port 700a and an output port 700b, a first resonator 701, a bandwidth adjustment unit 70 and a first resonator 704 are sequentially connected in series between the input port 700a and the output port 700b, the bandwidth adjustment unit 70 includes a second resonator 702 and a first inductor 703, wherein the output end of the first resonator 701 is connected to the input end of the second resonator 702, the output end of the second resonator 702 is connected to the input end of the first inductor 703, and the output end of the first inductor 703 is connected to the input end of the first resonator 704. The bandpass filter includes four parallel branches, which are represented by parallel branch A, parallel branch B, parallel branch C and parallel branch D from the input port side to the output port side, wherein the parallel branch A and the parallel branch B respectively include a third resonator 705 and a third resonator 706, one end of the third resonator 705 is connected to the node between the input port 700a and the first resonator 701, one end of the third resonator 706 is connected to the node between the first resonator 701 and the bandwidth adjustment unit 70, and the third resonator 70 5 and the other end of the third resonator 706 are grounded through the second inductor 711; the parallel branch C includes the third resonator 707 and the second inductor 712, one end of the third resonator 707 is connected to the node between the bandwidth adjustment unit 70 and the first resonator 704, and the other end is grounded through the second inductor 712; the parallel branch D includes the third resonator 708 and the second inductor 713, one end of the third resonator 708 is connected to between the first resonator 704 and the output port 700b, and the other end is grounded through the second inductor 713. The bandpass filter also includes a third inductor 714a, a fourth inductor 714b and a fifth inductor 714c, wherein one end of the third inductor 714a is connected to between the first resonator 701 and the bandwidth adjustment unit 70, one end of the fourth inductor 714b is connected to the node between the bandwidth adjustment unit 70 and the first resonator 704, and the other end is grounded, and the fifth inductor 714c is connected to between the second resonator 702 and the first inductor 703, and the other end is grounded. The third inductor 714a, the fourth inductor 714b and the fifth inductor 714c can be used together to achieve impedance matching of the filter passband and improve the out-of-band suppression of the filter. The bandpass filter also includes a first matching inductor 709 and a second matching inductor 710, wherein one end of the first matching inductor 709 is connected to a node between the input port 700a and the first resonator 701 and the other end is grounded; one end of the second matching inductor 710 is connected to a node between the first resonator 704 and the output port 700b and the other end is grounded.

[0051] Below Figure 3 , Figure 5 as well as Figure 7The filter shown is taken as an example to illustrate the performance of the bandpass filter provided by the present invention.

[0052] Figure 3 The parameters of the components of the bandpass filter are as follows: the effective working area of ​​the first resonator 201, the first resonator 204, the second resonator 202, the third resonator 205, the third resonator 206, the third resonator 207 and the third resonator 208 is 3000 μm 2 Up to 20000μm 2 The inductance values ​​of the first inductor 203 , the second inductor 211 , the second inductor 212 , the second inductor 213 , the first matching inductor 209 and the second matching inductor 210 are between 0.1 nH and 5 nH. Fig. 9 yes Figure 3 The small signal S parameter simulation curve of the bandpass filter shown in the figure includes sub-figure (a) and sub-figure (b). Sub-figure (a) represents the passband insertion loss performance, and the icon frequency range is 2.47GHz~2.76GHz; sub-figure (b) represents the near stopband suppression performance, and the icon frequency range is 2.3GHz~3.0GHz. Fig. 9 It can be seen that Figure 3 The bandwidth of the bandpass filter shown can reach 200MHz. The presence of additional transmission zeros near the stopband on the left and right sides improves the near stopband suppression on the left and right sides, and at the same time has the characteristics of low insertion loss and fast roll-off.

[0053] Figure 5 The parameters of the components of the bandpass filter are as follows: the effective working area of ​​the first resonator 401, the first resonator 404, the second resonator 402, the third resonator 405, the third resonator 406, the third resonator 407 and the third resonator 408 is 3000 μm 2 Up to 25000μm 2 The inductance values ​​of the first inductor 403 , the second inductor 411 , the second inductor 412 , the second inductor 413 , the fourth inductor 414 b , the first matching inductor 409 and the second matching inductor 410 are between 0.1 nH and 5 nH. Fig.10 yes Figure 5 The small signal S parameter simulation curve of the bandpass filter shown in the figure includes sub-figure (a) and sub-figure (b). Sub-figure (a) represents the passband insertion loss performance, and the icon frequency range is 2.47GHz~2.76GHz; sub-figure (b) represents the near stopband suppression performance, and the icon frequency range is 2.3GHz~3.0GHz. Fig.10 It can be seen that Figure 5 The bandwidth of the bandpass filter shown can reach 200MHz. The presence of additional transmission zeros near the stopband on the left and right sides improves the near stopband suppression on the left and right sides, and at the same time has the characteristics of low insertion loss and fast roll-off.

[0054] Figure 7 The parameters of the components of the bandpass filter are as follows: the effective working area of ​​the first resonator 601, the first resonator 604, the second resonator 602, the third resonator 605, the third resonator 606, the third resonator 607 and the third resonator 608 is 3000 μm 2 Up to 30000μm 2 The inductance values ​​of the first inductor 603 , the second inductor 611 , the second inductor 612 , the second inductor 613 , the third inductor 614 a , the fourth inductor 614 b , the first matching inductor 609 and the second matching inductor 610 are between 0.1 nH and 5 nH. Fig.11 yes Figure 7 The small signal S parameter simulation curve of the bandpass filter shown in the figure includes sub-figure (a) and sub-figure (b). Sub-figure (a) represents the passband insertion loss performance, and the icon frequency range is 2.47GHz~2.76GHz; sub-figure (b) represents the near stopband suppression performance, and the icon frequency range is 2.3GHz~3.0GHz. Fig.11 It can be seen that Figure 7 The bandwidth of the bandpass filter shown can reach 200MHz. The presence of additional transmission zeros near the stopband on the left and right sides improves the near stopband suppression on the left and right sides, and at the same time has the characteristics of low insertion loss and fast roll-off.

[0055] Correspondingly, the present invention further provides a duplexer, which includes a transmitting filter and a receiving filter, wherein the transmitting filter and / or the receiving filter are implemented by the aforementioned bandpass filter.

[0056] Specifically, the duplexer includes a transmitting filter and a receiving filter. The transmitting filter is connected between the common port and the transmitting port, and the receiving filter is connected between the common port and the receiving port. In a specific embodiment, the transmitting filter and the receiving filter are both implemented by the aforementioned bandpass filter of the present invention. In another specific embodiment, the transmitting filter is implemented by the aforementioned bandpass filter of the present invention, and the receiving filter is implemented by an existing conventional filter. In another specific embodiment, the receiving filter is implemented by the aforementioned bandpass filter of the present invention, and the transmitting filter is implemented by an existing conventional filter. For the case where the transmitting filter and / or the receiving filter are implemented by the aforementioned bandpass filter of the present invention, the structure of the bandpass filter can refer to the content of the corresponding part in the foregoing text, and for the sake of brevity, it will not be repeated here.

[0057] Since the bandpass filter provided by the present invention has the characteristics of broadband, low insertion loss and high suppression, the duplexer realized based on the bandpass filter also has the characteristics of broadband, low insertion loss and high suppression accordingly.

[0058] 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 essential 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 falling within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any figure mark in the claims should not be regarded as limiting the claims involved. In addition, it is obvious 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 stated in the system claim may also be implemented by one component, unit or device through software or hardware.

[0059] The bandpass filter provided by the present invention includes a series path, on which a bandwidth adjustment unit and at least two first resonators are connected in series, wherein the bandwidth adjustment unit is located between two adjacent first resonators, and the bandwidth adjustment unit includes a second resonator and a first inductor connected in series; one or more parallel branches, wherein the one or more parallel branches are connected in parallel between the series path and the ground, and each parallel branch includes a third resonator; wherein the resonant frequency of the second resonator is less than the resonant frequency of any of the first resonator and the third resonator. Compared with the existing bandpass filters, the bandpass filter provided by the present invention has the characteristics of wide passband, low insertion loss and high suppression. Correspondingly, the duplexer formed based on the bandpass filter provided by the present invention also has the characteristics of wide passband, low insertion loss and high suppression.

[0060] The above disclosures are only some preferred embodiments of the present invention, which certainly cannot be used to limit the scope of rights of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A bandpass filter, comprising: A series path, the series path comprising an input port, an output port, a bandwidth adjustment unit connected in series between the input port and the output port, and N first resonators, wherein the bandwidth adjustment unit is located between two adjacent first resonators, the bandwidth adjustment unit comprises a second resonator and a first inductor connected in series, and N is an integer greater than or equal to 2; One or more parallel branches, the one or more parallel branches are connected in parallel between the series path and ground, each of the parallel branches includes a third resonator; The resonant frequency of the second resonator is smaller than the resonant frequency of any one of the first resonator and the third resonator.

2. The bandpass filter according to claim 1, wherein: One end of each of the parallel branches is connected to a node of the series path and the other end is grounded, wherein the nodes of the series path include a node between the input port and the first resonator adjacent thereto, a node between the bandwidth adjustment unit and N first resonators, and a node between the output port and the first resonator adjacent thereto.

3. The bandpass filter according to claim 1, wherein: The resonant frequency of the second resonator is 50 MHz to 10 GHz lower than the resonant frequency of any one of the first resonator and the third resonator.

4. The bandpass filter according to claim 1, wherein: At least one of the parallel branches further comprises a second inductor, one end of the second inductor is connected to the third resonator in the parallel branch where it is located, and the other end of the second inductor is grounded; The inductance value of the first inductor is greater than the inductance value of the second inductor.

5. The bandpass filter according to claim 4, wherein: When the number of the parallel branches is two or more, the third resonators in at least two parallel branches are grounded through the same second inductor.

6. The bandpass filter according to claim 4, wherein: The inductance value of the first inductor is greater than the inductance value of the second inductor by 0.5 nH to 10 nH.

7. The bandpass filter according to any one of claims 1 to 6, further comprising: At least one of a third inductor, a fourth inductor and a fifth inductor, wherein one end of the third inductor is connected to the input end of the bandwidth adjustment unit and the other end is grounded, one end of the fourth inductor is connected to the output end of the bandwidth adjustment unit and the other end is grounded, and one end of the fifth inductor is connected to a node between the second resonator and the first inductor and the other end is grounded.

8. A duplexer, comprising: A transmitting filter and a receiving filter, wherein the transmitting filter and / or the receiving filter is implemented by using the bandpass filter as claimed in any one of claims 1 to 7.

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