Notch resonator, filter and duplexer

Abstract

A notch resonator, a filter, and a duplexer. The notch resonator (100) comprises an interdigital transducer (10); the interdigital transducer (10) comprises M interdigital transducer groups (11), wherein M is a positive integer; each interdigital transducer group (11) comprises four interdigital electrode groups (111); each interdigital electrode group (111) comprises N interdigital electrode pairs (1111), wherein N is a positive integer; in a same interdigital transducer group (11), periods of any two interdigital electrode groups (111) are different, wherein the period of each interdigital electrode group (111) is the sum of the length of one interdigital electrode pair (1111) in the interdigital electrode group (111) and the length of a gap adjacent to the interdigital electrode pair (1111) in a first direction.

Description

Notch resonators, filters, and duplexers

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on December 7, 2023, with application number 202311669155.X. The entire contents of this application are incorporated by reference into this application. Technical Field

[0002] The present application relates to the technical field of notch resonators, for example, to a notch resonator, a filter and a duplexer. Background Art

[0003] In the design of filters, it is sometimes necessary to specially design a notch resonator to achieve the suppression effect of a specific frequency point.

[0004] The existing notch filter design is generally composed of a parallel resonator with a small static capacitance. However, this type of notch filter can only form a single resonance point. If multiple specific frequency points need to be suppressed, a combination of multiple notch filters is required. However, the combination of multiple notch resonators will affect the miniaturization of the filter. Therefore, it is particularly important to design a notch filter with multiple resonance points.

[0005] On the other hand, in surface acoustic wave filters, by connecting the interdigital capacitor in parallel to the required resonator, the distance between the resonant point and the antiresonant point of the resonator can be shortened, thereby achieving a higher passband edge steepness. There are two commonly used solutions. The first solution is to design the resonator without the reflector as an interdigital capacitor, but this solution will form a resonance with a large amplitude, affecting the out-of-band suppression effect. The second solution is to rotate the resonator in the first solution by 90 degrees so as not to stimulate its acoustic effect. Although this solution can suppress the original main resonance, it may generate some new parasitic resonances. Therefore, it is extremely necessary to design a special resonator that takes into account both small resonance effects and good interdigital capacitor performance. Summary of the Invention

[0006] The present application provides a notch resonator, a filter and a duplexer to solve the problem that the existing notch resonator cannot form multiple resonance points.

[0007] In a first aspect, an embodiment of the present application provides a notch resonator, which includes an interdigital transducer; the interdigital transducer includes M interdigital transduction groups, wherein M is a positive integer; the interdigital transduction group includes four interdigital electrode groups; the interdigital electrode group includes N interdigital electrode pairs, wherein N is a positive integer; in the same interdigital transduction group, the periods of any two interdigital electrode groups are different; the period of the interdigital electrode group is the sum of the lengths of one interdigital electrode pair in the interdigital electrode group and the gap adjacent to the interdigital electrode pair in the first direction.

[0008] In one embodiment, in the same interdigital transduction group, the aperture of any two of the interdigital electrode groups is the same; the aperture is the overlapping length of the long finger electrodes connected to different bus bars along the second direction; the second direction intersects with the first direction; in the same interdigital transduction group, the duty cycle of any two of the interdigital electrode groups is the same; the duty cycle is the ratio of the length of one of the interdigital electrode pairs in the interdigital electrode group in the first direction to the period of the interdigital electrode group; in the same interdigital transduction group, the number of interdigital electrode pairs in any two of the interdigital electrode groups is the same.

[0009] In one embodiment, the periods of the four interdigital electrode groups in the same interdigital transduction group are: p, pa, p-2a and p-3a, respectively; wherein p is a positive number, and 5%≤a / p≤10%.

[0010] In one embodiment, the interdigital transduction group includes a first interdigital electrode group, a second interdigital electrode group, a third interdigital electrode group and a fourth interdigital electrode group that are adjacent to each other in sequence along the first direction; the period of the first interdigital electrode group is p; the period of the second interdigital electrode group is p-2a; the period of the third interdigital electrode group is pa; the period of the fourth interdigital electrode group is p-3a; or, the period of the first interdigital electrode group is p; the period of the second interdigital electrode group is p-3a; the period of the third interdigital electrode group is pa; and the period of the fourth interdigital electrode group is p-2a.

[0011] In one embodiment, M≥8; N=1 or 2.

[0012] In one embodiment, the trap resonator further includes a first reflection grating and a second reflection grating; along the first direction, the first reflection grating and the second reflection grating are respectively arranged on two opposite sides of the interdigital transducer.

[0013] In a second aspect, an embodiment of the present application provides a filter, which includes a trap resonator as described in any embodiment of the first aspect.

[0014] In one embodiment, the filter includes an input terminal, an output terminal, at least one first resonator, at least one second resonator and a notch resonator; the first resonator is arranged in series in a loop between the input terminal and the output terminal; one end of the second resonator is connected to the first resonator, and the other end of the second resonator is grounded; the notch resonator includes an interdigital transducer; the notch resonator is connected in parallel with the first resonator; or the notch resonator is connected in parallel with the second resonator.

[0015] In one embodiment, the filter includes an input terminal, an output terminal, at least one first resonator, at least one second resonator and a trap resonator; the first resonator is arranged in series in a loop between the input terminal and the output terminal; one end of the second resonator is connected to the first resonator, and the other end of the second resonator is grounded; the trap resonator includes an interdigital transducer, a first reflection grating and a second reflection grating; along the first direction, the first reflection grating and the second reflection grating are respectively arranged on two opposite sides of the interdigital transducer; one end of the trap resonator is connected to the first resonator, and the other end of the trap resonator is grounded.

[0016] In a third aspect, an embodiment of the present application provides a duplexer comprising an antenna, a receiving filter and a transmitting filter; at least one of the receiving filter and the transmitting filter comprises the filter as described in any embodiment of the second aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG1 is a schematic structural diagram of a trap resonator provided in an embodiment of the present application;

[0018] FIG2 is a schematic structural diagram of an IDT group provided in an embodiment of the present application;

[0019] FIG3 is a schematic structural diagram of another interdigital transduction group provided in an embodiment of the present application;

[0020] FIG4 is a comparison diagram of the admittance characteristic curves of resonators in three different forms;

[0021] FIG5 is a schematic structural diagram of another trap resonator provided in an embodiment of the present application;

[0022] FIG6 is a comparison diagram of the admittance characteristic curves of the notch resonator provided in FIG5 and other resonators;

[0023] FIG7 is a schematic diagram of the structure of a filter provided in an embodiment of the present application;

[0024] FIG8 is a comparison diagram of the performance curves of the filter provided in FIG7 and other filters;

[0025] FIG9 is a schematic diagram of the structure of another filter provided in an embodiment of the present application;

[0026] FIG10 is a schematic structural diagram of a duplexer provided in an embodiment of the present application;

[0027] FIG11 is a performance curve comparison diagram of the duplexer provided in FIG10 and other duplexers. DETAILED DESCRIPTION

[0028] The following will describe the technical solutions in the embodiments of this application in conjunction with the drawings in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of this application.

[0029] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in a sequence other than those illustrated or described herein. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0030] Example 1

[0031] FIG1 is a schematic diagram of the structure of a trap resonator provided in an embodiment of the present application, FIG2 is a schematic diagram of the structure of an interdigital transduction group provided in an embodiment of the present application, and FIG3 is a schematic diagram of the structure of another interdigital transduction group provided in an embodiment of the present application. Referring to FIG1, FIG2, and FIG3, the trap resonator 100 in the embodiment of the present application includes an interdigital transducer 10. The interdigital transducer 10 includes M interdigital transduction groups 11, where M is a positive integer. The interdigital transduction group 11 includes four interdigital electrode groups 111. The interdigital electrode group 111 includes N interdigital electrode pairs 1111, where N is a positive integer. In the same interdigital transduction group 11, the periods of any two interdigital electrode groups 111 differ. The period of an interdigital electrode group 111 is the sum of the lengths, in a first direction, of an interdigital electrode pair 1111 in the interdigital electrode group 111 and the gap adjacent to the interdigital electrode pair 1111.

[0032] As a feasible implementation, M≥8. N=1 or 2. The value of M can be determined according to the electrostatic capacitance required by the notch resonator, and those skilled in the art can set it according to actual needs.

[0033] It should be noted that, in the IDT 10 , the structures of any two IDT groups 11 are the same, so the embodiment of the present application only takes one IDT group 11 as an example for description.

[0034] For example, referring to FIG2 , N=1, the interdigital transduction group 11 includes four interdigital electrode groups 111, each of which includes one interdigital electrode pair 1111. The periods of the four interdigital electrode groups 111 are all different, and the period of an interdigital electrode group 111 refers to the sum T of the lengths in the first direction X of an interdigital electrode pair 1111 in the interdigital electrode group 111 and the gap adjacent to the interdigital electrode pair 1111.

[0035] For example, referring to FIG3 , N=2, the interdigital transduction group 11 includes four interdigital electrode groups 111, each of which includes two interdigital electrode pairs 1111. The periods of the four interdigital electrode groups 111 are all different. The period of an interdigital electrode group 111 refers to the sum of the lengths in the first direction of an interdigital electrode pair 1111 in the interdigital electrode group 111 and the gap adjacent to the interdigital electrode pair 1111 (T1 or T2), where T1=T2.

[0036] The present application sets the periods T of the four interdigital electrode groups 111 in the same interdigital transduction group 11 to be different, so that the notch resonator 100 can form multiple resonance points in a specific frequency band, thereby solving the problem that the notch resonator cannot form multiple resonance points.

[0037] Optionally, in the same IDT group 11, any two IDT groups 111 have the same aperture, which is the overlapping length of long finger electrodes connected to different bus bars along the second direction Y, where the second direction Y intersects the first direction X. In the same IDT group 11, any two IDT groups 111 have the same duty cycle, which is the ratio of the length of an IDT pair 1111 in the first direction X to the period of the IDT group 111. In the same IDT group 11, any two IDT groups 111 have the same number of IDT pairs 1111.

[0038] As a feasible implementation manner, referring to FIG. 2 and FIG. 3 , the first direction X and the second direction Y are perpendicular.

[0039] For example, referring to FIG2 , N=1, the IDT group 11 includes four IDT groups 111 , each of which includes one IDT pair 1111 . The IDT pair 1111 includes a long electrode and a short electrode disposed opposite each other along a second direction Y, with a gap between the long electrode and the short electrode in the second direction Y. The IDT group 11 also includes a first busbar H1 and a second busbar H2 connected to the IDT pair 1111 . The four IDT groups 111 have the same aperture, which refers to the overlapping length W along the second direction Y between the long electrode connected to the first busbar H1 and the long electrode connected to the second busbar H2. The four IDT groups 111 have the same duty cycle, which refers to the ratio Z between the length D of an IDT pair 1111 in the first direction X and the period T of the IDT group 111 , i.e., Z=D / T. The four interdigital electrode groups 111 have the same number of interdigital electrode pairs 1111 , and each interdigital electrode group 111 includes one interdigital electrode pair 1111 .

[0040] For example, referring to FIG3 , N=2, the IDT group 11 includes four IDT groups 111 , each of which includes two IDT electrode pairs 1111 . The IDT pairs 1111 include long finger electrodes and short finger electrodes arranged opposite each other along a second direction Y, with gaps between the long finger electrodes and the short finger electrodes in the second direction Y. The IDT group 11 also includes a first bus bar H1 and a second bus bar H2 connected to the IDT electrode pairs 1111 . The four IDT groups 111 have the same aperture, which refers to the overlapping length W along the second direction Y between the long finger electrodes connected to the first bus bar H1 and the long finger electrodes connected to the second bus bar H2. The four interdigital electrode groups 111 have the same duty cycle. The duty cycle refers to the ratio Z between the length (D1 or D2) of an interdigital electrode pair 1111 in the first direction X and the period (T1 or T2) of the interdigital electrode group 111, i.e., Z = D1 / T1 = D2 / T2, where D1 = D2 and T1 = T2. The four interdigital electrode groups 111 have the same number of interdigital electrode pairs 1111, and each interdigital electrode group 111 includes two interdigital electrode pairs 1111.

[0041] Optionally, the periods of the four interdigital electrode groups 111 in the same interdigital transduction group 11 are: p, pa, p-2a and p-3a, respectively, where p is a positive number and 5%≤a / p≤10%.

[0042] Based on the above embodiment, referring to FIG2 and FIG3 , the interdigital transduction group 11 includes a first interdigital electrode group 111A, a second interdigital electrode group 111B, a third interdigital electrode group 111C and a fourth interdigital electrode group 111D that are adjacent to each other in the first direction X.

[0043] As a feasible implementation, the period of the first interdigital electrode group 111A is p, the period of the second interdigital electrode group 111B is p-2a, the period of the third interdigital electrode group 111C is pa, and the period of the fourth interdigital electrode group 111D is p-3a.

[0044] As another feasible embodiment, the period of the first interdigital electrode group 111A is p, the period of the second interdigital electrode group 111B is p-3a, the period of the third interdigital electrode group 111C is pa, and the period of the fourth interdigital electrode group 111D is p-2a.

[0045] The periods of the first interdigital electrode group 111A, the second interdigital electrode group 111B, the third interdigital electrode group 111C, and the fourth interdigital electrode group 111D may also be p, pa, p-2a, and p-3a, respectively. It should be noted that the embodiment of the present application does not limit the periodic arrangement of the first interdigital electrode group 111A, the second interdigital electrode group 111B, the third interdigital electrode group 111C, and the fourth interdigital electrode group 111D that are adjacent to each other along the first direction X in the same interdigital transduction group 11. They may be arranged in any of the following ways: p, pa, p-2a, and p-3a. Those skilled in the art may set them according to actual needs.

[0046] It is understood that the electrostatic capacitance of the notch resonator 100 is positively correlated with the product of the total number of pairs of interdigital electrode pairs 1111 in the notch resonator 100 and the aperture of the notch resonator 100 (resonant cavity area). It should be noted that the aperture of the notch resonator 100 is the aperture of the interdigital electrode group 111. Assuming that the total number of pairs of interdigital electrode pairs in the existing resonator and the notch resonator 100 described above is the same, the electrostatic capacitance of the notch resonator 100 using the above-mentioned periodic combinations (p, pa, p-2a, and p-3a) is smaller than that of the existing resonator having an interdigital electrode group with a period of p. Therefore, to ensure that the electrostatic capacitance of the notch resonator 100 is similar to that of the existing resonator, the aperture of the notch resonator 100 is proportionally amplified by a factor K, with a value of K ranging from 1.5 to 2.5. This means that the aperture of the notch resonator 100 is 1.5 to 2.5 times the aperture of the existing resonator.

[0047] FIG4 is a comparison of the admittance characteristic curves of resonators in three different configurations. Referring to FIG4 , S1 is the admittance characteristic curve of a resonator without any parallel resonator connection, S2 is the admittance characteristic curve of a resonator connected in parallel with an existing resonator without a reflective grating. The period of the interdigital electrode groups of the existing resonator is all p, and S3 is the admittance characteristic curve of a resonator connected in parallel with the trap resonator 100 provided in FIG1 . The trap resonator 100 provided in FIG1 includes an interdigital transducer 10, which includes M identical interdigital transducer groups 11. The periods of the four adjacent interdigital electrode groups 111 in the same interdigital transducer group 11 along the first direction X are all different. It can be seen that a resonator without any parallel resonator connection has only a resonant point and an antiresonant point. Connecting an existing resonator without a reflective grating in parallel with a resonator can bring the resonant point and antiresonant point closer together. However, the existing resonator without a reflective grating will form a larger resonance in the high-frequency region of the resonator, thereby affecting the out-of-band suppression effect of the resonator. Connecting the notch resonator 100 provided in FIG. 1 in parallel to the resonator not only brings the resonance point and antiresonance point of the resonator closer together, but also makes the amplitudes of the multiple resonance points formed by the notch resonator 100 in the high-frequency part of the resonator relatively small, which is beneficial to improving the out-of-band suppression effect of the resonator.

[0048] FIG5 is a schematic diagram of the structure of another notch resonator provided in an embodiment of the present application. Referring to FIG5 , the notch resonator 100 in the embodiment of the present application further includes a first reflective grating 20 and a second reflective grating 30. Along a first direction X, the first reflective grating 20 and the second reflective grating 30 are respectively disposed on opposite sides of the interdigital transducer 10.

[0049] In the embodiment of the present application, the first reflection grating 20 and the second reflection grating 30 are provided to reduce acoustic wave leakage, which is beneficial to improving the Q value of the trap resonator 100 .

[0050] FIG6 is a comparison diagram of the admittance characteristic curves of the notch resonator provided in FIG5 and other resonators. Referring to FIG6, S4 is the admittance characteristic curve of the existing resonator, which includes an interpolation transducer and a reflection grating, and the period of the interdigital electrode group of the existing resonator is p. S5 is the admittance characteristic curve of a notch resonator provided in FIG5, wherein the notch resonator 100 includes an interdigital transducer 10, a first reflection grating 20 and a second reflection grating 30, and the interdigital transducer 10 includes M identical interdigital transducer groups 11, and the period of four interdigital electrode groups 111 adjacent to each other in the first direction X in the same interdigital transducer group 11 is p. 5 , the notch resonator 100 comprises an IDT 10, a first reflection grating 20 and a second reflection grating 30, the IDT 10 comprises M identical IDT groups 11, and the periods of the four adjacent IDT electrode groups 111 in the same IDT group 11 along the first direction X are p, p-2a, pa and p-3a, respectively. It can be seen that the notch resonators corresponding to S5 and S6 can form multiple resonance points, and the notch resonator corresponding to S3 has more resonance points and a more balanced resonance amplitude.

[0051] Example 2

[0052] The present invention provides a filter. FIG7 is a schematic diagram of the structure of one filter according to the present invention, and FIG9 is a schematic diagram of the structure of another filter according to the present invention. Referring to FIG7 and FIG9 , the filter 200 according to the present invention includes the notch resonator 100 according to the above-described embodiment. Therefore, the filter includes the technical features of the notch resonator 100, and similarities can be found in the above description.

[0053] As a feasible embodiment, filter 200 includes an input terminal in, an output terminal out, at least one first resonator 201, at least one second resonator 202, and a notch resonator 100. First resonator 201 is arranged in series in a loop between input terminal in and output terminal out. One end of second resonator 202 is connected to first resonator 201, and the other end of second resonator 202 is grounded. Notch resonator 100 includes an interdigital transducer 10, and notch resonator 100 is connected in parallel with first resonator 201, or alternatively, notch resonator 100 is connected in parallel with second resonator 202.

[0054] Exemplarily, when the trap resonator 100 includes only the IDT 10 but no reflective grating, referring to FIG. 7 , the trap resonator 100 may be connected in parallel with the first resonator 201 . It should be noted that the trap resonator 100 may also be connected in parallel with the second resonator 202 .

[0055] FIG8 is a performance curve comparison diagram of the filter provided in FIG7 and other filters. Referring to FIG8 , S7 is the performance curve of the conventional filter, and S8 is the performance curve of the filter provided in FIG7 . It should be noted that the structure of the conventional filter is substantially the same as that of the filter provided in FIG7 , with the only difference being that the periods of the interdigital electrode groups of the resonators connected in parallel at both ends of the first resonator 201 in the conventional filter are the same. It can be seen that connecting the notch resonator 100 in the above embodiment in parallel with the first resonator 201 of the filter 200 not only forms multiple resonance points outside the band of the filter 200, but also reduces the amplitude of the resonance points formed outside the band of the filter 200, thereby improving the out-of-band suppression effect of the filter 200.

[0056] As a feasible embodiment, the filter 200 includes an input terminal in, an output terminal out, at least one first resonator 201, at least one second resonator 202, and a notch resonator 100. The first resonator 201 is arranged in series in a loop between the input terminal in and the output terminal out. One end of the second resonator 202 is connected to the first resonator 201, and the other end of the second resonator 202 is grounded. The notch resonator 100 includes an interdigital transducer 10, a first reflection grating 20, and a second reflection grating 30. Along a first direction X, the first reflection grating 20 and the second reflection grating 30 are respectively arranged on opposite sides of the interdigital transducer 10. One end of the notch resonator 100 is connected to the first resonator 101, and the other end of the notch resonator 100 is grounded.

[0057] Exemplarily, when the trap resonator 100 includes the IDT 10 , the first reflection grating 20 and the second reflection grating 30 , referring to FIG9 , one end of the trap resonator 100 is connected to the first resonator 101 , and the other end of the trap resonator 100 is grounded.

[0058] The embodiment of the present application applies the notch resonator 100 in the above embodiment to the filter 200 , which is beneficial to improving the out-of-band suppression effect of the filter 200 .

[0059] Example 3

[0060] An embodiment of the present application provides a duplexer. FIG10 is a schematic structural diagram of a duplexer provided in an embodiment of the present application. Referring to FIG10 , the duplexer 300 in the embodiment of the present application includes an antenna 301, a receive filter 302, and a transmit filter 303. At least one of the receive filter 302 and the transmit filter 303 includes the filter 200 described in any of the above embodiments. Therefore, the duplexer 300 includes the technical features of the filter 200, and similarities can be referred to above.

[0061] The duplexer 300 in the embodiment of the present application has a transmission frequency band range of 1850 MHz to 1910 MHz and a reception frequency band range of 1930 MHz to 1990 MHz.

[0062] Exemplarily, referring to Figure 10, the transmit filter 303 is connected between the antenna 301 and the transmit port Tx, and the receive filter 302 is connected between the antenna 301 and the receive port Rx. The transmit filter 303 includes a filter 200, and the filter 200 includes five first resonators 201, three second resonators 202 and a notch resonator 100. One end of the notch resonator 100 is connected to the first resonator 101, and the other end of the notch resonator 100 is grounded. The notch resonator 100 includes an interdigital transducer 10, a first reflection grating 20 and a second reflection grating 30, wherein the resonant frequency of the notch resonator 100 must be greater than the resonant frequency of any one of the first resonators 201 and the resonant frequency of any one of the second resonators 202, and must be within the receiving frequency band of the duplexer. In addition, the electrostatic capacitance of the notch resonator 100 is smaller than the electrostatic capacitance of any one of the first resonators 201 and the electrostatic capacitance of any one of the second resonators 202. Optionally, the electrostatic capacitance of the notch resonator 100 is at least lower than 50% of the electrostatic capacitance of any one of the first resonators 201 and the electrostatic capacitance of the second resonator 202.

[0063] FIG11 is a performance curve comparison of the duplexer shown in FIG10 and other duplexers. Referring to FIG11 , S9 is the performance curve of the conventional duplexer, and S10 is the performance curve of the duplexer shown in FIG10 . It should be noted that the structure of the conventional duplexer is essentially the same as that of the duplexer shown in FIG10 , with the difference being that the notch resonator in the conventional duplexer uses a conventional resonator with a smaller electrostatic capacitance. The interdigital electrode groups of the conventional resonator all have a period of p and only one resonance point. This shows that the duplexer including the notch resonator 100 can form multiple resonance points in the high-frequency band (2010 MHz to 2025 MHz, 2040 MHz to 2060 MHz) to the right of the duplexer 300 , which helps improve the out-of-band suppression and isolation of the duplexer 300 .

[0064] The technical solution of the embodiment of the present application provides a notch resonator, a filter and a duplexer, wherein the notch resonator includes an interdigital transducer, the interdigital transducer includes M interdigital transduction groups, wherein M is a positive integer, the interdigital transduction group includes four interdigital electrode groups, the interdigital electrode group includes N interdigital electrode pairs, wherein N is a positive integer, and in the same interdigital transduction group, there is a difference in the periods of any two interdigital electrode groups, and in the same interdigital transduction group, two interdigital electrode groups adjacent along the first direction include a first interdigital electrode group and a second interdigital electrode group, and the period of the interdigital electrode group is the distance in the first direction between the interdigital electrode pair in the first interdigital electrode group away from the second interdigital electrode group and the interdigital electrode pair in the second interdigital electrode group close to the first interdigital electrode group. The present application sets a difference in the period of any two interdigital electrode groups in the same interdigital transducer group, so that the notch resonator can form multiple resonance points in a specific frequency band. By applying the above-mentioned notch resonator to the filter, it is beneficial to improve the out-of-band suppression effect of the filter, and applying the above-mentioned filter to the duplexer is beneficial to improving the out-of-band suppression effect and isolation of the duplexer 300.

Claims

1. A notch resonator comprising an interdigital transducer; The interdigital transducer comprises M interdigital transducer groups, wherein: M is a positive integer; The interdigital transduction group includes four interdigital electrode groups; The interdigital electrode group includes N interdigital electrode pairs, wherein N is a positive integer; In the same interdigital transduction group, the periods of any two interdigital electrode groups are different; the period of the interdigital electrode group is the sum of the lengths of one interdigital electrode pair in the interdigital electrode group and the gap adjacent to the interdigital electrode pair in the first direction.

2. The trap resonator according to claim 1, wherein: In the same interdigital transducer group, any two interdigital electrode groups have the same aperture; the aperture is the overlapping length of the long finger electrodes connected to different bus bars along the second direction; the second direction intersects the first direction; In the same interdigital transduction group, the duty ratios of any two interdigital electrode groups are the same; the duty ratio is the ratio between the length of one interdigital electrode pair in the interdigital electrode group in the first direction and the period of the interdigital electrode group; In the same interdigital transduction group, the numbers of interdigital electrode pairs in any two interdigital electrode groups are the same.

3. The trap resonator according to claim 1, wherein: The periods of the four interdigital electrode groups in the same interdigital transduction group are: p, pa, p-2a and p-3a respectively; Wherein, p is a positive number, 5%≤a / p≤10%.

4. The trap resonator according to claim 3, wherein: The interdigital transduction group includes a first interdigital electrode group, a second interdigital electrode group, a third interdigital electrode group and a fourth interdigital electrode group that are adjacent to each other in sequence along the first direction; The period of the first interdigital electrode group is p; the period of the second interdigital electrode group is p-2a; the period of the third interdigital electrode group is pa; and the period of the fourth interdigital electrode group is p-3a; Alternatively, the period of the first interdigitated electrode group is p; The period of the second interdigitated electrode group is p-3a; The period of the third interdigital electrode group is pa; the period of the fourth interdigital electrode group is p-2a.

5. The trap resonator according to claim 1, wherein: M≥8； N=1 or 2.

6. The trap resonator according to any one of claims 1 to 5, wherein: The trap resonator further comprises a first reflection grating and a second reflection grating; Along the first direction, the first reflection grating and the second reflection grating are respectively arranged on two opposite sides of the interdigital transducer.

7. A filter comprising the notch resonator according to any one of claims 1 to 6.

8. The filter according to claim 7, comprising an input terminal, an output terminal, at least one first resonator, at least one second resonator and one said notch resonator; The first resonator is arranged in series in a loop between the input terminal and the output terminal; one end of the second resonator is connected to the first resonator, and the other end of the second resonator is grounded; The trap resonator comprises an interdigital transducer; the trap resonator is connected in parallel with the first resonator; Alternatively, the trap resonator is connected in parallel with the second resonator.

9. The filter according to claim 7, comprising an input terminal, an output terminal, at least one first resonator, at least one second resonator and one said notch resonator; The first resonator is arranged in series in a loop between the input terminal and the output terminal; one end of the second resonator is connected to the first resonator, and the other end of the second resonator is grounded; The trap resonator includes an interdigital transducer, a first reflection grating and a second reflection grating; along the first direction, the first reflection grating and the second reflection grating are respectively arranged on two opposite sides of the interdigital transducer; one end of the trap resonator is connected to the first resonator, and the other end of the trap resonator is grounded.

10. A duplexer comprising an antenna, a receiving filter and a transmitting filter; At least one of the receiving filter and the transmitting filter comprises the filter as claimed in any one of claims 7 to 9.

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