Elastic wave filter, elastic wave multiplexer and radio frequency front-end circuit

Abstract

An elastic wave filter, an elastic wave multiplexer and a radio frequency front-end circuit. In an elastic wave filter (100), a first-type resonator (30) is arranged in series in a loop between an input terminal (10) and an output terminal (20); a first end of a second-type resonator (40) is connected in the loop between the input terminal (10) and the output terminal (20), and a second end of the second-type resonator (40) is grounded; the resonant frequency of the first-type resonator (30) and the anti-resonant frequency of the second-type resonator (40) are located within the frequency band range of a passband of the elastic wave filter (100); and the resonant frequency and the anti-resonant frequency of a third-type resonator (50) are both located outside the frequency band range of the passband of the elastic wave filter (100), and are greater than the maximum frequency value of the passband of the elastic wave filter (100).

Description

Elastic wave filters, elastic wave multiplexers, and RF front-end circuits

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on November 22, 2023, with application number 202311567479.2, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of filter technology, for example, to an elastic wave filter, an elastic wave multiplexer, and a radio frequency front-end circuit. Background Art

[0003] As one of the most important components in the RF front-end field, elastic wave filter devices are widely used in the communications field. With the rapid development of RF communication technology, higher performance requirements are being placed on elastic wave filter devices.

[0004] At present, elastic wave filters and duplexers have requirements for characteristics such as extremely low insertion loss and high out-of-band attenuation. Therefore, in the design of elastic wave filters and duplexers, special means are generally required to improve the out-of-band attenuation characteristics of specific frequency bands; secondly, in Thin-Film Surface Acoustic Wave (TF-SAW) filters or duplexers, there are also parasitic noise on the out-of-band high-frequency side. The presence of these noises causes the out-of-band attenuation and isolation of the device to deteriorate sharply in the corresponding frequency band. At the same time, it also causes the transmission wave to mix with the out-of-band interference waves of the transmission band and the receiving band, resulting in intermodulation distortion in the receiving band, which reduces the communication quality (signal-to-noise ratio) of the communication equipment.

[0005] Therefore, in practical applications, there is an urgent need to find technical means to improve the out-of-band attenuation of elastic wave devices and suppress the above-mentioned parasitic waves without deteriorating the overall performance of the elastic wave devices. Summary of the Invention

[0006] The embodiments of the present application provide an elastic wave filter, an elastic wave duplexer, and a radio frequency front-end circuit to improve the out-of-band attenuation of the elastic wave filter.

[0007] In a first aspect, an elastic wave filter provided by an embodiment of the present application includes: an input terminal, an output terminal, a first type of resonator, a second type of resonator, and a third type of resonator; the first type of resonator includes at least one first resonator, and the second type of resonator includes at least one second resonator;

[0008] The third type resonator includes at least one interdigital transducer;

[0009] The first type resonator is arranged in series in a loop between the input terminal and the output terminal; a first end of the second type resonator is connected to the loop between the input terminal and the output terminal, and a second end of the second type resonator is grounded; a resonant frequency of the first type resonator and an anti-resonant frequency of the second type resonator are both within a frequency band of the passband of the elastic wave filter;

[0010] The resonant frequency and the anti-resonant frequency of the third type resonator are both outside the frequency band of the passband of the elastic wave filter and are greater than the maximum frequency value of the passband of the elastic wave filter.

[0011] In some embodiments, the resonant frequency of the first type of resonator is greater than the resonant frequency of the second type of resonator, and the anti-resonant frequency of the first type of resonator is greater than the anti-resonant frequency of the second type of resonator;

[0012] The resonant frequency and the anti-resonant frequency of the third type resonator are greater than the anti-resonant frequency of the first resonator.

[0013] In some embodiments, a first end of the third type resonator is connected in a loop between the input terminal and the output terminal, and a second end of the third type resonator is grounded.

[0014] In some embodiments, the third type of resonator includes at least two interdigital transducers;

[0015] At least two of the interdigital transducers are arranged in parallel.

[0016] In some embodiments, the at least two IDTs arranged in parallel include a first IDT and a second IDT, the first IDT and the second IDT are arranged along a first direction, and the first IDT and the second IDT share a first bus bar;

[0017] The first interdigital transducer includes a first long finger electrode and a second long finger electrode, the first long finger electrode and the second long finger electrode are arranged along the first direction and extend along the second direction; the second interdigital transducer includes a third long finger electrode and a fourth long finger electrode, the third long finger electrode and the fourth long finger electrode are arranged along the first direction and extend along the second direction; the first direction and the second direction intersect;

[0018] The period of the first IDT is different from the period of the second IDT; the period of the first IDT is at least one of the following intervals: the period of the first IDT is the interval between two adjacent first long finger electrodes in the first direction, or the period of the first IDT is the interval between two adjacent second long finger electrodes in the first direction; the period of the second IDT is at least one of the following intervals: the period of the second IDT is the interval between two adjacent third long finger electrodes in the first direction, or the period of the second IDT is the interval between two adjacent fourth long finger electrodes in the first direction;

[0019] The third type resonator further includes a first open-grid bar located between the first IDT and the second IDT along the first direction, the first open-grid bar extending along the second direction and having a gap between the first open-grid bar and the first bus bar in the second direction.

[0020] In some embodiments, the third type resonator further includes a second bus bar, and the first open grid bar is connected to the second bus bar;

[0021] Along the second direction, a gap exists between the second bus bar and the first bus bar.

[0022] In some embodiments, the third type resonator is arranged in series in a loop between the input terminal and the output terminal.

[0023] In some embodiments, the third type resonator includes at least two of the interdigital transducers;

[0024] At least two of the interdigital transducers are arranged in parallel.

[0025] In some embodiments, the at least two IDTs arranged in parallel include a third IDT and a fourth IDT, the third IDT and the fourth IDT are arranged along the second direction, and the third IDT and the fourth IDT share a third bus bar;

[0026] The third IDT includes a fifth long finger electrode and a sixth long finger electrode, the fifth long finger electrode and the sixth long finger electrode are arranged along the second direction and extend along the first direction; the fourth IDT includes a seventh long finger electrode and an eighth long finger electrode, the seventh long finger electrode and the eighth long finger electrode are arranged along the second direction and extend along the first direction; the first direction and the second direction intersect;

[0027] The period of the third IDT is different from the period of the fourth IDT; the period of the third IDT is at least one of the following spacings: the period of the third IDT is the spacing between two adjacent fifth long finger electrodes in the second direction, or the period of the third IDT is the spacing between two adjacent sixth long finger electrodes in the second direction; the period of the fourth IDT is at least one of the following spacings: the period of the fourth IDT is the spacing between two adjacent seventh long finger electrodes in the second direction, or the period of the fourth IDT is the spacing between two adjacent eighth long finger electrodes in the first direction;

[0028] The third type resonator further includes a second open-grid bar located between the third IDT and the fourth IDT along the second direction, wherein the second open-grid bar extends along the first direction and has a gap with the third bus bar in the first direction.

[0029] In some embodiments, the third type resonator further includes a fourth bus bar, and the second open grid bar is connected to the fourth bus bar;

[0030] Along the first direction, a gap exists between the fourth bus bar and the third bus bar.

[0031] In some embodiments, the elastic wave filter further comprises a longitudinally coupled resonator type filter;

[0032] The longitudinally coupled resonator filter is provided in series in a loop between the input terminal and the output terminal.

[0033] In some embodiments, the electrostatic capacitance of the third type resonator is smaller than the electrostatic capacitance of the first type resonator, and smaller than the electrostatic capacitance of the second type resonator.

[0034] In a second aspect, an embodiment of the present application further provides an elastic wave multiplexer, comprising an antenna terminal, at least one receiving unit, and at least one transmitting unit;

[0035] The antenna terminals are communicatively connected to the receiving unit and the transmitting unit respectively;

[0036] At least one of the receiving unit and the transmitting unit includes the elastic wave filter described in any one of the first aspects.

[0037] In a third aspect, an embodiment of the present application further provides a radio frequency front-end circuit, comprising a low-noise amplifier and the elastic wave multiplexer described in the second aspect, wherein the low-noise amplifier amplifies the radio frequency signal fed via the elastic wave multiplexer. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] FIG1 is a schematic diagram of a circuit structure of an elastic wave filter provided in an embodiment of the present application;

[0039] FIG2 is a schematic structural diagram of a third type of resonator provided in an embodiment of the present application;

[0040] FIG3 is a schematic diagram of the circuit structure of another elastic wave filter provided in an embodiment of the present application;

[0041] FIG4 is a schematic diagram of the circuit structure of another elastic wave filter provided in an embodiment of the present application;

[0042] FIG5 is a schematic structural diagram of another third type of resonator provided in an embodiment of the present application;

[0043] FIG6 is a passband characteristic and resonance characteristic curve of an elastic wave filter corresponding to FIG3;

[0044] FIG7 is an admittance curve of a third type of resonator in an elastic wave filter corresponding to FIG3 ;

[0045] FIG8 is a transmission curve of a third type of resonator in an elastic wave filter corresponding to FIG3 ;

[0046] FIG9 is a schematic structural diagram of another third type of resonator provided in an embodiment of the present application;

[0047] FIG10 is a schematic structural diagram of another third type of resonator provided in an embodiment of the present application;

[0048] FIG11 is a schematic diagram of the circuit structure of another elastic wave filter provided in an embodiment of the present application;

[0049] FIG12 is a schematic diagram of the circuit structure of another elastic wave filter provided in an embodiment of the present application;

[0050] FIG13 is a schematic structural diagram of another third type of resonator provided in an embodiment of the present application;

[0051] FIG14 is a schematic structural diagram of another third type of resonator provided in an embodiment of the present application;

[0052] FIG15 is a schematic diagram of the circuit structure of another elastic wave filter provided in an embodiment of the present application;

[0053] FIG16 is a schematic diagram of the circuit structure of another elastic wave filter provided in an embodiment of the present application;

[0054] FIG17 is a schematic structural diagram of a third type of resonator provided in FIG5 along the section line aa';

[0055] FIG18 is a schematic diagram of the circuit structure of an elastic wave multiplexer provided in an embodiment of the present application;

[0056] FIG19 is a schematic diagram of the circuit structure of another elastic wave multiplexer provided in an embodiment of the present application;

[0057] FIG20 is a schematic diagram of a transmission characteristic curve of an elastic wave duplexer provided in an embodiment of the present application;

[0058] Figure 21 is a structural diagram of a radio frequency front-end circuit provided in an embodiment of the present application. DETAILED DESCRIPTION

[0059] The present application is described below in conjunction with the accompanying drawings and embodiments. The embodiments described herein are used to explain the present application. For ease of description, only some structures related to the present application are shown in the accompanying drawings.

[0060] FIG1 is a schematic diagram of a circuit structure of an elastic wave filter provided in an embodiment of the present application, and FIG2 is a schematic diagram of a structure of a third type resonator provided in an embodiment of the present application. As shown in FIG1 and FIG2, the elastic wave filter includes: an input terminal 10, an output terminal 20, a first type resonator 30, a second type resonator 40, and a third type resonator 50; the first type resonator 30 includes at least one first resonator 301, the second type resonator 40 includes at least one second resonator 401; the third type resonator 50 includes at least one interdigital transducer (IDT) Transducer (IDT) 501; a first type resonator 30 is arranged in series in a loop between the input terminal 10 and the output terminal 20; a first end of a second type resonator 40 is connected to the loop between the input terminal 10 and the output terminal 20, and a second end of the second type resonator 40 is grounded; the resonant frequency of the first type resonator 30 and the anti-resonant frequency of the second type resonator 40 are both within the frequency band of the passband of the elastic wave filter 100; the resonant frequency and anti-resonant frequency of the third type resonator 50 are outside the frequency band of the passband of the elastic wave filter 100 and are greater than the maximum frequency value of the passband of the elastic wave filter 100.

[0061] The passband range of the elastic wave filter 100 can be understood as the frequency range on both sides of the 3 decibel (dB) bandwidth, ie, [fmin, fmax]. The maximum frequency value is the right side of the 3dB bandwidth, ie, fmax.

[0062] Exemplarily, the first type resonator 30 is arranged in series in the loop between the input terminal 10 and the output terminal 20, that is, the first type resonator 30 is a series arm resonator, and the series arm resonator may include a first resonator 301. In other embodiments, the number of first resonators 301 may also be multiple, and the number of first resonators 301 in the embodiment of the present application can be set according to actual needs. Exemplarily, the first type resonator 30 may include 2, 3 or even more first resonators 301. Exemplarily, the first type resonator in the elastic wave filter 100 shown in Figure 1 includes 4 first resonators 301. The embodiments of the present application are all described by taking 4 first resonators 301 as an example.

[0063] Exemplarily, the first end of the second type resonator 40 is connected to the loop between the input terminal 10 and the output terminal 20, and the second end of the second type resonator 40 is grounded, that is, the second type resonator 40 is a parallel arm resonator, and the parallel arm resonator may include a second resonator 401. In other embodiments, the number of second resonators 401 can also be multiple. Exemplarily, the second type resonator 40 may include 2, 3 or even more second resonators 401. Exemplarily, the second type resonator 40 in the elastic wave filter 100 shown in Figure 1 includes 3 second resonators 401. The embodiments of the present application are all described by taking 3 second resonators 401 as an example.

[0064] For example, the resonant frequency of the first-type resonator 30 is within the passband of the elastic wave filter 100, and the antiresonant frequency of the second-type resonator 40 is within the passband of the elastic wave filter 100. The resonant frequency and antiresonant frequency of the third-type resonator 50 are outside the passband of the elastic wave filter 100 and are greater than the maximum frequency of the passband of the elastic wave filter 100. In other words, the resonant frequency and antiresonant frequency of the third-type resonator 50 are located on the high-frequency side outside the passband of the elastic wave filter 100. This allows the third-type resonator 50 to form an attenuation pole, or zero, on the high-frequency side of the passband of the elastic wave filter 100. This allows the elastic wave filter 100 to form a notch at the resonant frequency or antiresonant frequency of the third-type resonator 50, thereby enhancing the out-of-band suppression of the elastic wave filter 100.

[0065] The third-type resonator 50 can be a series-arm resonator or a parallel-arm resonator. FIG1 illustrates a technical solution for the third-type resonator 50 as a parallel-arm resonator. The technical solution for the third-type resonator 50 as a series-arm resonator will be described in the following embodiments. Furthermore, the third-type resonator 50 can be located at any position in the loop between the input terminal 10 and the output terminal 20, i.e., it can be located near the input terminal 10, near the output terminal 20, or near the center between the input terminal 10 and the output terminal 20.

[0066] Referring to Figure 2 , an IDT 501 includes a first long finger electrode 51 and a second long finger electrode 52. The first and second long finger electrodes 51 are interdigitated electrodes, and together with the bus bar 502, they form an IDT. By adjusting the period of the interdigitated electrodes, the antiresonance frequency of the third-type resonator 50 can be adjusted to lie outside the passband of the elastic wave filter 100 and be greater than the maximum frequency of the passband. The third-type resonator 50 also includes a reflective grating 504, which reduces acoustic leakage and improves the quality factor (Q) of the third-type resonator 50.

[0067] In an elastic wave filter provided by an embodiment of the present application, a third-type resonator includes at least one interdigital transducer. The resonant frequency and antiresonant frequency of the third-type resonator are outside the passband of the elastic wave filter and are greater than the maximum frequency of the passband. In other words, the resonant frequency and antiresonant frequency of the third-type resonator are outside the passband of the elastic wave filter and are located on the high-frequency side of the passband. This allows the third-type resonator to form an attenuation pole, or zero, on the high-frequency side of the passband of the elastic wave filter. This allows the elastic wave filter to form a notch at the resonant frequency or antiresonant frequency of the third-type resonator, thereby increasing the out-of-band attenuation of the elastic wave filter.

[0068] In some embodiments, with continued reference to FIG1 , the resonant frequency of the first type resonator 30 is greater than the resonant frequency of the second type resonator 40 , and the anti-resonant frequency of the first type resonator 30 is greater than the anti-resonant frequency of the second type resonator 40 ; the anti-resonant frequency of the third type resonator 50 is greater than the anti-resonant frequency of the first type resonator 30 .

[0069] For example, the resonant frequency of the series arm resonator is greater than the resonant frequency of the parallel arm resonator, and the anti-resonant frequency of the series arm resonator is greater than the anti-resonant frequency of the parallel arm resonator. Since the resonant frequency and anti-resonant frequency of the first resonator 301 are both large, the resonant frequency and anti-resonant frequency of the third type resonator 50 are greater than the anti-resonant frequency of the first resonator 301, that is, an attenuation pole, that is, a zero point, can be formed on the high-frequency side of the passband of the elastic wave filter 100, thereby causing the elastic wave filter 100 to form a notch fallback at the resonant frequency or anti-resonant frequency of the third type resonator 50, thereby increasing the out-of-band suppression of the elastic wave filter 100.

[0070] As a feasible implementation, when the number of the interdigital transducers 501 is one, the resonant frequency and the anti-resonant frequency of the interdigital transducer 501 can both be located outside the frequency band range of the passband of the elastic wave filter 100, and both are greater than the maximum frequency value of the passband of the elastic wave filter 100, thereby improving the out-of-band suppression of the elastic wave filter 100.

[0071] As another feasible embodiment, when there are two or more IDTs 501, the maximum resonant frequency and the maximum antiresonant frequency of the multiple IDTs 501 can both be outside the frequency band of the passband of the elastic wave filter 100 and be greater than the maximum frequency value of the passband of the elastic wave filter 100. Alternatively, all resonant frequencies and all antiresonant frequencies of the multiple IDTs 501 can both be outside the frequency band of the passband of the elastic wave filter 100 and be greater than the maximum frequency value of the passband of the elastic wave filter 100. This can improve the out-of-band suppression of the elastic wave filter 100.

[0072] Optionally, continuing to refer to Figure 1, the first end of the third type resonator 50 is connected to the loop between the input terminal 10 and the output terminal 20, and the second end of the third type resonator 50 is grounded, that is, the third type resonator 50 is a parallel arm resonator.

[0073] Figure 3 is a schematic diagram of the circuit structure of another elastic wave filter provided in an embodiment of the present application, and Figure 4 is a schematic diagram of the circuit structure of yet another elastic wave filter provided in an embodiment of the present application. As shown in Figures 3 and 4, the third type of resonator 50 includes at least two interdigital transducers 501; at least two interdigital transducers 501 are arranged in parallel.

[0074] As a feasible implementation method, referring to FIG3 , FIG3 shows a technical solution in which the third type resonator 50 includes two interdigital transducers 501. In this way, the third type resonator 50 includes two resonant peaks and two anti-resonant peaks, that is, a notch fallback can be formed in the passband near the two resonant frequencies of the third type resonator 50, thereby increasing the out-of-band suppression of the filter.

[0075] As another feasible embodiment, referring to Figure 4, the third type resonator 50 shown in Figure 4 includes more than three IDTs 501, so that the third type resonator 50 includes N resonant peaks and N anti-resonant peaks, where N represents the number of IDTs 501, that is, multiple notch falls can be formed in the passband near the N resonant frequencies of the third type resonator 50, which is beneficial to increase the out-of-band suppression of the filter.

[0076] Optionally, Figure 5 is a structural schematic diagram of another third type of resonator provided in an embodiment of the present application. As shown in Figure 5, at least two IDTs 501 arranged in parallel include a first IDT 5011 and a second IDT 5012, the first IDT 5011 and the second IDT 5012 are arranged along a first direction (the X direction as shown in the figure), and the first IDT 5011 and the second IDT 5012 share a first bus bar 502; the first IDT 5011 includes a first long finger electrode 51 and a second long finger electrode 52, the first long finger electrode 51 and the second long finger electrode 52 are arranged along the first direction X and both extend along the second direction (the Y direction as shown in the figure); the second IDT 5012 includes a third long finger electrode 53 and a fourth long finger electrode 54, the third long finger electrode 53 and the fourth long finger electrode 54 are arranged along the first direction X and both extend along the second direction Y; the first direction X and the second direction Y intersect; the first IDT 5011 The period of the first IDT 5011 is different from the period of the second IDT 5012; the period of the first IDT 5011 is at least one of the following spacings: the period of the first IDT 5011 is the spacing between two adjacent first long finger electrodes 51 in the first direction X, or the period of the first IDT 5011 is the spacing between two adjacent second long finger electrodes 52 in the first direction X; the period of the second IDT 5012 is at least one of the following spacings: the period of the second IDT 5012 is the spacing between two adjacent third long finger electrodes 53 in the first direction X, or the period of the second IDT 5012 is the spacing between two adjacent fourth long finger electrodes 54 in the first direction X; the third type resonator 50 further includes a first open grid 5031 located between the first IDT 5011 and the second IDT 5012 along the first direction X, the first open grid 5031 extending along the second direction Y and having a gap between it and the first bus bar 502 in the second direction Y.

[0077] Exemplarily, the first IDT 5011 and the second IDT 5012 are arranged in parallel along a first direction X and share a first bus bar 502. This arrangement is simple. When an AC signal of a certain frequency is applied to the first bus bar 502, surface acoustic waves can be generated in the effective aperture region of the third type resonator 50. The effective aperture region, also known as the active region, can be understood as the region along the first direction X where the first long finger electrode 51 and the second long finger electrode 52 overlap, or where the third long finger electrode 53 and the fourth long finger electrode 54 overlap. Surface acoustic waves are primarily concentrated in the effective aperture region and propagate primarily along the first direction X. However, some surface acoustic waves may propagate and leak toward the first bus bar 502 along the second direction Y. Therefore, reflection gratings 504 are typically provided on both sides of the effective aperture region along the first direction X to reduce surface acoustic wave leakage, thereby reducing acoustic wave energy loss and improving the Q value of the third type resonator 50.

[0078] Exemplarily, the first IDT 5011 includes a first long finger electrode 51 and a second long finger electrode 52, and the second IDT 5012 includes a third long finger electrode 53 and a fourth long finger electrode 54. Exemplarily, the first long finger electrode 51, the second long finger electrode 52, the third long finger electrode 53, and the fourth long finger electrode 54 can be true finger electrodes. In the first IDT 5011, the first long finger electrode 51 and the second long finger electrode 52 are arranged along the first direction X and extend along the second direction Y, forming a comb-shaped interdigital electrode structure; in the second IDT 5012, the third long finger electrode 53 and the fourth long finger electrode 54 are arranged along the first direction X and extend along the second direction Y, forming a comb-shaped interdigital electrode structure.

[0079] Continuing to refer to Figure 5, the first interdigital transducer 5011 and the second interdigital transducer 5012 can also include pseudo-finger electrodes, that is, short-finger electrodes. The short-finger electrodes and the long-finger electrodes are arranged alternately in sequence along the first direction X, and both extend along the second direction Y. The extension length of the short-finger electrodes along the second direction Y is less than the extension length of the long-finger electrodes along the second direction Y.

[0080] The period of the first IDT 5011 is different from the period of the second IDT 5012. That is, the electrode period of the first IDT 5011 is different from the electrode period of the second IDT 5012. Exemplarily, the period of the first IDT 5011 is at least one of the following spacings: the period of the first IDT 5011 is the spacing λ1 between two adjacent first long finger electrodes 51 in the first direction X, or the period of the first IDT 5011 is the spacing λ2 between two adjacent second long finger electrodes 52 in the first direction X. λ1 can be the spacing between the centers of any two adjacent first long finger electrodes 51 along the first direction X; λ2 can be the spacing between the centers of any two adjacent second long finger electrodes 52 along the first direction X. Exemplarily, λ1 = λ2. The period of the second IDT 5012 is at least one of the following intervals: the period of the second IDT 5012 is the interval λ3 between two adjacent third long finger electrodes 53 in the first direction X, or the period of the second IDT 5012 is the interval λ4 between two adjacent fourth long finger electrodes 54 in the first direction X. Exemplarily, λ3=λ4.

[0081] Figure 5 shows a technical solution in which the period of the first interdigital transducer 5011 is smaller than the period of the second interdigital transducer 5012, that is, λ1<λ3. In some embodiments, the period of the first interdigital transducer 5011 can also be larger than the period of the second interdigital transducer 5012, that is, λ1>λ3. In the embodiment of the present application, the size relationship between the period of the first interdigital transducer 5011 and the period of the second interdigital transducer 5012 can be set according to actual needs. By ensuring that the periods of the first interdigital transducer 5011 and the second interdigital transducer 5012 are different, it is possible to form a notch fallback on the high-frequency side of the elastic wave filter 100, thereby improving the out-of-band attenuation of the elastic wave filter.

[0082] The number of interdigital electrodes in the first IDT 5011 can be equal to the number of interdigital electrodes in the second IDT 5012, or the number of interdigital electrodes in the two IDTs can be unequal. In the embodiment of the present application, the number of interdigital electrodes in the first IDT 5011 and the second IDT 5012 can be set according to actual needs, for example, can be flexibly adjusted according to the performance requirements of the third type resonator 50.

[0083] The first open grid bar 5031 is located between the first IDT 5011 and the second IDT 5012 along the first direction X. The first open grid bar 5031 extends along the second direction Y and there is a gap between the first open grid bar 5031 and the first bus bar 502 in the second direction Y. By providing the first open grid bar 5031, on the one hand, crosstalk between the first IDT 5011 and the second IDT 5012 can be prevented. On the other hand, there is a gap between the first open grid bar 5031 and the first bus bar 502 in the second direction Y, which can avoid a short circuit caused by the contact and connection between the first open grid bar 5031 and the first bus bar 502, thereby affecting the performance of the third type resonator 50.

[0084] Figure 6 shows the passband and resonance characteristics of an elastic wave filter corresponding to Figure 3 . As shown in Figure 6 , the antiresonant frequency of the first-type resonator 30 is fas, and the resonance frequency is frs; the antiresonant frequency of the second-type resonator 40 is fap, and the resonance frequency is frp. Compared to the related art scheme in which only the first-type resonator 30 and the second-type resonator 40 are provided, the resonant frequency frp of the second-type resonator 40 and the antiresonant frequency fas of the first-type resonator 30 in this embodiment respectively form the first and second zero points of the elastic wave filter 100. The dashed line in the figure shows the admittance characteristic curve of the third-type resonator 50. The resonant frequencies frA and frB and the antiresonant frequencies faA and faB of the third-type resonator 50 are higher than the upper edge frequency fmax of the passband range [fmin, fmax] (i.e., BW) of the elastic wave filter 100. Since the third type resonator 50 is connected in parallel to the elastic wave filter 100, the resonant frequency peak of the third type resonator 50 forms multiple attenuation poles (zero points) on the high-frequency side of the filter passband, so that the elastic wave filter 100 forms a notch fallback in the frequency band near the resonant frequency frA and the resonant frequency frB of the third type resonator 50, thereby increasing the out-of-band suppression of the filter.

[0085] FIG7 is an admittance curve of a third type of resonator in an elastic wave filter corresponding to FIG3 , and FIG8 is a transmission curve of a third type of resonator in an elastic wave filter corresponding to FIG3 . As shown in FIG7 and FIG8 , the third type of resonator 50 is connected in parallel to the circuit. It can be seen from the transmission curve that there are two zero points A and B. These zero points A and B cause the elastic wave filter 100 to form a notch fallback in the frequency band near the resonant frequencies frA and frB of the third type of resonator 50, thereby increasing the out-of-band suppression of the filter.

[0086] Optionally, Figure 9 is a schematic structural diagram of another third type resonator provided in an embodiment of the present application. As shown in Figure 9, the third type resonator 50 also includes a second bus bar 505, and the first open grid bar 5031 is connected to the second bus bar 505; along the second direction Y, there is a gap between the second bus bar 505 and the first bus bar 502.

[0087] Exemplarily, the first open grid bar 5031 is connected to the second bus bar 505 but not to the first bus bar 502. In this way, the first open grid bar 5031 is a short-circuit grid. On the one hand, it can prevent crosstalk between the signals of the first interdigital transducer 5011 and the second interdigital transducer 5012. On the other hand, the setting method of the first open grid bar 5031 is simple.

[0088] The first open grid bars 5031 can be integrated to simplify the process.

[0089] The number of the first open bars 5031 can be multiple, and the number of the open bars 503 in the embodiment of the present application can be set according to actual needs. Along the first direction X, the period between two adjacent first open bars 5031, that is, the spacing between two adjacent first open bars 5031 can also be set according to actual needs. The multiple first open bars 5031 between the first interdigital transducer 5011 and the second interdigital transducer 5012 can form an open bar group. When the third type resonator 50 includes M interdigital transducers 501 arranged in parallel, the number of open bar groups can be (M-1), that is, an open bar group is provided between any two adjacent interdigital transducers 501, so that it can be ensured that the signals between the multiple interdigital transducers 501 do not crosstalk, thereby improving the working performance of the third type resonator 50.

[0090] Figure 10 is a structural schematic diagram of another third type resonator provided in an embodiment of the present application. As shown in Figure 10, Figure 10 exemplarily shows that the third type resonator 50 includes four first interdigital transducers 5011, second interdigital transducers 5012, fourth interdigital transducers 5015 and fifth interdigital transducers 5016 arranged in parallel. When the third type resonator 50 includes four interdigital transducers 501 arranged in parallel, a group of open grid groups is also included between any two adjacent interdigital transducers 501, and the open grid group is composed of multiple first open grid bars 5031. In some embodiments, the number of first open bars 5031 between the second IDT 5012 and the fourth IDT 5015 can be greater than the number of first open bars 5031 between the first IDT 5011 and the second IDT 5012, and can also be greater than the number of first open bars 5031 between the fourth IDT 5015 and the fifth IDT 5016. In other words, the number of first open bars 5031 between two adjacent IDTs 501 located in the middle of the third type resonator 50 is greater than the number of first open bars 5031 located at the edge of the third type resonator 50. This helps prevent signal crosstalk between the IDTs 501 located in the middle and the IDTs 501 located at the edge. In some embodiments, the number of first open bars 5031 can increase from the edge of the third type resonator 50 to the center.

[0091] Optionally, Figure 11 is a schematic diagram of the circuit structure of another elastic wave filter provided in an embodiment of the present application. As shown in Figure 11, the third type resonator 50 is arranged in series in the loop between the input terminal 10 and the output terminal 20.

[0092] FIG12 is a schematic diagram of the circuit structure of another elastic wave filter provided in an embodiment of the present application. As shown in FIG12 , the third-type resonator 50 includes at least two IDTs 501 . These at least two IDTs 501 are connected in parallel. Specifically, the at least two IDTs 501 are connected in parallel and then in series in the loop between the input terminal 10 and the output terminal 20 .

[0093] As a feasible implementation, referring to Figure 12, Figure 12 shows a technical solution in which the third type resonator 50 includes two interdigital transducers 501. In this way, the third type resonator 50 includes two resonant peaks and two anti-resonant peaks, that is, a notch can be formed in the passband near the two anti-resonant frequencies of the third type resonator 50, thereby increasing the out-of-band suppression of the filter.

[0094] As another feasible implementation, the third type resonator 50 may also include three or more interdigital transducers 501, so that the third type resonator 50 includes N resonant peaks and N anti-resonant peaks, where N represents the number of interdigital transducers 501, that is, multiple notch falls can be formed in the passband near the N anti-resonant frequencies of the third type resonator 50, which is beneficial to increase the out-of-band suppression of the filter.

[0095] Optionally, FIG13 is a schematic structural diagram of another third type of resonator provided in an embodiment of the present application. As shown in FIG13 , at least two IDTs 501 arranged in parallel include a third IDT 5013 and a fourth IDT 5014. The third IDT 5013 and the fourth IDT 5014 are arranged along the second direction Y, and the third IDT 5013 and the fourth IDT 5014 share a third bus bar 506. 013 includes a fifth long finger electrode 55 and a sixth long finger electrode 56, which are arranged along the second direction Y and extend along the first direction X; the fourth interdigital transducer 5014 includes a seventh long finger electrode 57 and an eighth long finger electrode 58, which are arranged along the second direction Y and extend along the first direction X; the first direction X and the second direction Y intersect; the period of the third interdigital transducer 5013 is the same as that of the fourth interdigital transducer The period of the third IDT 5013 is at least one of the following spacings: the period of the third IDT 5013 is the spacing between two adjacent fifth long finger electrodes 55 in the second direction Y, or the period of the third IDT 5013 is the spacing between two adjacent sixth long finger electrodes 56 in the second direction Y; the period of the fourth IDT 5014 is at least one of the following spacings: the period of the fourth IDT 5014 is the spacing between two adjacent seventh long finger electrodes 57 in the second direction Y, or the period of the fourth IDT 5014 is the spacing between two adjacent eighth long finger electrodes 58 in the first direction X; the third type resonator 50 further includes a second open grid 5032 located between the third IDT 5013 and the fourth IDT 5014 along the second direction Y, the second open grid 5032 extending along the first direction X and having a gap between it and the third bus bar 506 in the first direction X.

[0096] Exemplarily, the third interdigital transducer 5013 and the fourth interdigital transducer 5014 are arranged in parallel along the second direction Y and share the third bus bar 506. This arrangement is simple. When an AC signal of a certain frequency is applied to the third bus bar 506, a surface acoustic wave can be generated in the effective aperture area of ​​the third type resonator 50.

[0097] Exemplarily, the third IDT 5013 includes a fifth long finger electrode 55 and a sixth long finger electrode 56, and the fourth IDT 5014 includes a seventh long finger electrode 57 and an eighth long finger electrode 58. Exemplarily, the fifth long finger electrode 55, the sixth long finger electrode 56, the seventh long finger electrode 57, and the eighth long finger electrode 58 can be true finger electrodes. In the third IDT 5013, the fifth long finger electrode 55 and the sixth long finger electrode 56 are arranged along the second direction Y and extend along the first direction X, forming a comb-shaped interdigital electrode structure; in the fourth IDT 5014, the seventh long finger electrode 57 and the eighth long finger electrode 58 are arranged along the second direction Y and extend along the first direction X, forming a comb-shaped interdigital electrode structure.

[0098] The third IDT 5013 and the fourth IDT 5014 may further include dummy electrodes, i.e., short finger electrodes. The short finger electrodes and the long finger electrodes are alternately arranged in sequence along the second direction Y and both extend along the first direction X. The extension length of the short finger electrodes along the first direction X is less than the extension length of the long finger electrodes along the first direction X.

[0099] The period of the third IDT 5013 is different from the period of the fourth IDT 5014. That is, the electrode period of the third IDT 5013 is different from the electrode period of the fourth IDT 5014. Exemplarily, the period of the third IDT 5013 is at least one of the following spacings: the period of the third IDT 5013 is the spacing λ5 between two adjacent fifth long finger electrodes 55 in the second direction Y, or the period of the third IDT 5013 is the spacing λ6 between two adjacent sixth long finger electrodes 56 in the second direction Y. λ5 can be the spacing between the centers of any two adjacent fifth long finger electrodes 55 along the second direction Y; λ6 can be the spacing between the centers of any two adjacent sixth long finger electrodes 56 along the second direction Y. Exemplarily, λ5 = λ6. The period of the fourth IDT 5014 is at least one of the following intervals: the period of the fourth IDT 5014 is the interval λ7 between two adjacent seventh long finger electrodes 57 in the second direction Y, or the period of the fourth IDT 5014 is the interval λ8 between two adjacent eighth long finger electrodes 58 in the second direction Y. For example, λ5=λ7.

[0100] Figure 13 shows a technical solution in which the period of the third interdigital transducer 5013 is smaller than the period of the fourth interdigital transducer 5014, that is, λ5<λ7. In some embodiments, the period of the third interdigital transducer 5013 can also be larger than the period of the fourth interdigital transducer 5014, that is, λ5>λ7. In the embodiment of the present application, the size relationship between the period of the third interdigital transducer 5013 and the period of the fourth interdigital transducer 5014 can be set according to actual needs. By ensuring that the periods of the third interdigital transducer 5013 and the fourth interdigital transducer 5014 are different, it is possible to form a notch fallback on the high-frequency side of the elastic wave filter 100, thereby improving the out-of-band attenuation of the elastic wave filter.

[0101] The second open grid bar 5032 is located between the third IDT 5013 and the fourth IDT 5014 along the second direction Y. The second open grid bar 5032 extends along the first direction X and has a gap between it and the third bus bar 506 in the first direction X. In this way, by providing the second open grid bar 5032, on the one hand, crosstalk between the third IDT 5013 and the fourth IDT 5014 can be prevented. On the other hand, the gap between the second open grid bar 5032 and the third bus bar 506 in the first direction X can avoid a short circuit caused by contact between the second open grid bar 5032 and the third bus bar 506, thereby avoiding affecting the performance of the third type resonator 50.

[0102] Optionally, Figure 14 is a structural schematic diagram of another third type resonator provided in an embodiment of the present application. As shown in Figure 14, the third type resonator 50 also includes a fourth bus bar 507, and the second open grid bar 5032 is connected to the fourth bus bar 507; along the first direction X, there is a gap between the fourth bus bar 507 and the third bus bar 506.

[0103] Exemplarily, the second open grid bar 5032 is connected to the fourth bus bar 507 but not to the third bus bar 506 . Thus, the second open grid bar 5032 is a short-circuit grid, which can prevent crosstalk between the third IDT 5013 and the fourth IDT 5014 .

[0104] The second open grid bars 5032 can be integrated to simplify the process.

[0105] The configuration and number of the second open bars 5032 are similar to those of the first open bars 5031 .

[0106] Optionally, Figure 15 and Figure 16 illustrate the circuit structure of yet another elastic wave filter according to an embodiment of the present application. As shown in Figures 15 and 16 , the elastic wave filter further includes a longitudinally coupled resonator filter 60, which is arranged in series in the loop between the input terminal 10 and the output terminal 20.

[0107] As a feasible implementation, referring to Figure 15, the elastic wave filter 100 also includes a longitudinally coupled resonator-type filter 60, and the third type of resonator 50 is connected in parallel in the elastic wave filter 100. In this way, on the one hand, a diversified design of the elastic wave filter 100 can be achieved, and on the other hand, the out-of-band attenuation of the elastic wave filter can be improved by setting the third type of resonator 50.

[0108] As another feasible embodiment, referring to Figure 16, the elastic wave filter 100 also includes a longitudinally coupled resonator-type filter 60, and the third type of resonator 50 is connected in series in the elastic wave filter 100. In this way, on the one hand, a diversified design of the elastic wave filter 100 can be achieved, and on the other hand, the out-of-band attenuation of the elastic wave filter can be improved by setting the third type of resonator 50.

[0109] Optionally, with continued reference to FIG. 5 , the electrostatic capacitance of the third type resonator 50 is smaller than the electrostatic capacitance of the first type resonator 30 , and smaller than the electrostatic capacitance of the second type resonator 40 .

[0110] For example, electrostatic capacitance can be understood as the capacitance between the comb-shaped interdigitated electrodes, which is roughly proportional to the product of the aperture length of the effective aperture region along the second direction Y and the logarithm of the number of long-finger electrodes (i.e., the resonant cavity area). The lower electrostatic capacitance of the third-type resonator 50 reduces its area, facilitating a miniaturized design for the elastic wave filter 100 while minimizing the impact on the filter's passband characteristics.

[0111] In summary, the elastic wave filter provided in the embodiments of the present application comprises a third-type resonator including at least one interdigital transducer, and the resonant frequency and antiresonant frequency of the third-type resonator are outside the frequency band of the elastic wave filter's passband and are greater than the maximum frequency value of the elastic wave filter's passband. In other words, the resonant frequency and antiresonant frequency of the third-type resonator are outside the frequency band of the elastic wave filter's passband and are located on the high-frequency side of the elastic wave filter's passband. Thus, the third-type resonator can form an attenuation pole, i.e., a zero point, on the high-frequency side of the elastic wave filter's passband, thereby causing the elastic wave filter to form a notch drop at the resonant frequency or antiresonant frequency of the third-type resonator, thereby increasing the out-of-band suppression of the elastic wave filter. Furthermore, the third-type resonator can be connected in parallel or in series in the elastic wave filter, thereby enabling a diversified configuration of the elastic wave filter.

[0112] FIG17 is a schematic structural diagram of a third type resonator provided in FIG5 along the section line a-a'. As shown in FIG17 , the first long finger electrode 51, the second long finger electrode 52, the reflective grating 504, and the intermediate open-circuit grating 503 of the third type filter 50 can be configured on different piezoelectric substrates. The piezoelectric substrate can be a composite multilayer substrate, including a piezoelectric layer 01, a low acoustic impedance layer 02, a high acoustic impedance layer 03, and a support layer 04. The material of the piezoelectric layer 01 can be lithium tantalate, lithium niobate, aluminum nitride, or quartz. The material of the low acoustic impedance layer 02 can be silicon dioxide, glass, silicon oxynitride, or tantalum oxide. The material of the high acoustic impedance layer 03 can be silicon, silicon nitride, silicon carbide, aluminum nitride, or aluminum oxide. The material of the support layer 04 can be single crystal silicon, silicon nitride, quartz, sapphire, or diamond. The piezoelectric layer 01 , the low acoustic impedance layer 02 and the high acoustic impedance layer 03 are stacked in sequence on one side of the support layer 04 , and the low acoustic impedance layer 02 and the high acoustic impedance layer 03 are located between the piezoelectric layer 01 and the support layer 04 .

[0113] For example, the piezoelectric substrate can be a single piezoelectric layer 01, and the piezoelectric material can be lithium tantalate, lithium niobate, aluminum nitride, or quartz. The lithium tantalate cut is a rotated Y-cut X-propagation direction with a rotation angle range of 0° to 64°, and the lithium niobate cut is a rotated Y-cut X-propagation direction with a rotation angle range of 0° to 64° or 120° to 175°. Interdigitated electrodes are provided on the piezoelectric layer 01. A first dielectric layer 05 and a second dielectric layer 06 can also be provided on the piezoelectric layer 01 and the interdigitated electrodes. The first dielectric layer 05 can be made of silicon dioxide or silicon oxynitride, while the second dielectric layer 06 can be made of silicon nitride, aluminum nitride, or aluminum nitride. The first dielectric layer 05 improves the device's frequency and temperature stability, while the second dielectric layer 06 enables adjustment of the device's operating frequency.

[0114] The embodiments of the present application also provide an elastic wave multiplexer. FIG18 is a schematic diagram of the circuit structure of an elastic wave multiplexer provided in the embodiments of the present application, and FIG19 is a schematic diagram of the circuit structure of another elastic wave multiplexer provided in the embodiments of the present application. As shown in FIG18 and FIG19 , the elastic wave multiplexer includes an antenna terminal (ANT), at least one receiving unit 101, and at least one transmitting unit 102; the antenna terminal ANT is communicatively connected to the receiving unit 101 and the transmitting unit 102, respectively; and at least one of the receiving unit 101 and the transmitting unit 102 includes the elastic wave filter 100 of the above-mentioned embodiment.

[0115] For example, taking the elastic wave multiplexer as the elastic wave duplexer 200 as an example, the receiving unit 101 is arranged between the antenna terminal ANT and the receiving terminal 701, and forms the first passband of the elastic wave duplexer 200, and the transmitting unit 102 is arranged between the antenna terminal ANT and the transmitting terminal 702, and forms the second passband of the elastic wave duplexer 200.

[0116] Exemplarily, the receiving unit 101 may include a ladder topology filter and may also include a longitudinally coupled resonator filter. The embodiments of the present application are all described using a ladder topology filter as an example. In addition, the third type resonator 50 can be connected in series or in parallel in the transmitting unit 102 or the receiving unit 101. FIG18 shows a technical solution for connecting the third type resonator 50 in parallel in the receiving unit 101. Referring to FIG19, the third type resonator 50 can also be set in parallel in the receiving unit 101 and in series in the transmitting unit 102. In addition, the third type resonator 50 can also be connected in the transmitting unit 102 or the receiving unit 101 in at least one of series and / or parallel connection.

[0117] Figure 20 is a schematic diagram of the transmission characteristic curve of an elastic wave duplexer provided in an embodiment of the present application. As shown in Figure 20, the black dotted line is the admittance curve of the third type resonator 50. It can be seen that the attenuation pole (zero point) formed by the third type resonator 50 in the filter circuit can improve the attenuation outside the passband of the elastic wave duplexer and the isolation of the elastic wave duplexer.

[0118] When the elastic wave multiplexer is a quadplexer, the quadplexer includes four terminals, an antenna terminal, and four elastic wave filters. A passband is formed between each terminal and the antenna terminal, and at least one of the four elastic wave filters includes the third type resonator in the above embodiment.

[0119] The elastic wave filter and multiplexer provided in the embodiments of the present application can be a surface acoustic wave filter (Surface Acoustic Wave, SAW), a temperature compensated surface acoustic wave filter (Temperature Compensated SAW, TC-SAW), a thin film surface acoustic wave filter (Thin-Film Surface Acoustic Wave, TF-SAW), a laterally-excited bulk acoustic wave filter (Laterally-excited Bulk-wave resonators, XBAR), a lamb wave resonator (LAMB), etc., which can be used to form a filtering element with low insertion loss, high suppression, high rectangularity and extremely low in-band ripple.

[0120] The embodiment of the present application also provides a radio frequency front-end circuit, which includes the elastic wave filter, elastic wave multiplexer, etc. in the above-mentioned embodiment. Figure 21 is a structural schematic diagram of a radio frequency front-end circuit provided by an embodiment of the present application. As shown in Figure 21, the radio frequency front-end circuit 300 includes a switch 70, a first elastic wave filter 21, a second elastic wave filter 22, a first duplexer (the first duplexer includes a first duplexer transmit filter 23 and a first duplexer receive filter 24), a second duplexer (the second duplexer includes a second duplexer transmit filter 25 and a second duplexer receive filter 26), a low noise amplifier 80, and a power amplifier 90.

[0121] Exemplarily, the RF front-end circuit 300 is connected to the RF signal processing circuit 31 and the baseband signal processing circuit 32 to form a RF communication device 400 .

[0122] The switch 70 is used to control the RF signal, connecting the antenna terminal ANT to at least one signal path corresponding to a given frequency band. The at least one signal path connected to the antenna terminal ANT can also be multiple signal paths (corresponding to multiple filters and duplexers). The RF front-end circuit 300 can support carrier aggregation technology; the low-noise amplifier 80 amplifies the RF signal fed via the antenna terminal ANT, the switch 70, and the first duplexer receive filter 24 and the second duplexer receive filter 26, and feeds the amplified signal to the RF signal processing circuit 31; the power amplifier 90 amplifies the RF signal provided by the RF signal processing circuit 31 and feeds the amplified signal to the antenna terminal ANT via the first duplexer transmit filter 23, the second duplexer transmit filter 25, and the switch 70 for transmission.

[0123] The RF signal processing circuit 31 in the RF communication device 400 performs signal processing on the RF receive signal provided from the antenna terminal ANT via the receive signal path, and feeds the receive signal generated by the signal processing; and the RF signal processing circuit 31 performs signal processing on the fed transmit signal, and feeds the RF transmit signal generated by the signal processing to the power amplifier 90.

[0124] The RF front-end circuit 300 further includes a first elastic wave filter 21 and a second elastic wave filter 22 . The first elastic wave filter 21 and the second elastic wave filter 22 are connected between the RF signal processing circuit 31 and the switch 70 without passing through the low noise amplifier 80 or the power amplifier 90 .

Claims

1. An elastic wave filter, comprising: An input terminal, an output terminal, a first type resonator, a second type resonator, and a third type resonator; the first type resonator includes at least one first resonator, and the second type resonator includes at least one second resonator; The third type resonator comprises at least one interdigital transducer; The first type resonator is arranged in series in a loop between the input terminal and the output terminal; a first end of the second type resonator is connected to the loop between the input terminal and the output terminal, and a second end of the second type resonator is grounded; a resonant frequency of the first type resonator and an anti-resonant frequency of the second type resonator are both within a frequency band of a passband of the elastic wave filter; The resonant frequency and the anti-resonant frequency of the third type resonator are both outside the frequency band range of the passband of the elastic wave filter and are greater than the maximum frequency value of the passband of the elastic wave filter.

2. The elastic wave filter according to claim 1, wherein: The resonant frequency of the first type of resonator is greater than the resonant frequency of the second type of resonator, and the anti-resonant frequency of the first type of resonator is greater than the anti-resonant frequency of the second type of resonator; The resonant frequency and the anti-resonant frequency of the third type resonator are greater than the anti-resonant frequency of the first resonator.

3. The elastic wave filter according to claim 1, wherein: A first end of the third type resonator is connected in a loop between the input terminal and the output terminal, and a second end of the third type resonator is grounded.

4. The elastic wave filter according to claim 3, wherein: The third type resonator comprises at least two interdigital transducers; At least two of the interdigital transducers are arranged in parallel.

5. The elastic wave filter according to claim 4, wherein: The at least two IDTs arranged in parallel include a first IDT and a second IDT, the first IDT and the second IDT are arranged along a first direction, and the first IDT and the second IDT share a first bus bar; The first interdigital transducer comprises a first long finger electrode and a second long finger electrode, the first long finger electrode and the second long finger electrode are arranged along the first direction and both extend along the second direction; the second interdigital transducer comprises a third long finger electrode and a fourth long finger electrode, the third long finger electrode and the fourth long finger electrode are arranged along the first direction and both extend along the second direction; the first direction and the second direction intersect; The period of the first IDT is different from the period of the second IDT; the period of the first IDT is at least one of the following intervals: the period of the first IDT is the interval between two adjacent first long finger electrodes in the first direction, or the period of the first IDT is the interval between two adjacent second long finger electrodes in the first direction; the period of the second IDT is at least one of the following intervals: the period of the second IDT is the interval between two adjacent third long finger electrodes in the first direction, or the period of the second IDT is the interval between two adjacent fourth long finger electrodes in the first direction; The third type resonator further includes a first open-circuit grid bar located between the first IDT and the second IDT along the first direction, the first open-circuit grid bar extending along the second direction and having a gap between the first open-circuit grid bar and the first bus bar in the second direction.

6. The elastic wave filter according to claim 5, wherein: The third type resonator further includes a second bus bar, and the first open grid bar is connected to the second bus bar; Along the second direction, there is a gap between the second bus bar and the first bus bar.

7. The elastic wave filter according to claim 1, wherein: The third type resonator is arranged in series in a loop between the input terminal and the output terminal.

8. The elastic wave filter according to claim 7, wherein: The third type resonator comprises at least two of the interdigital transducers; At least two of the interdigital transducers are arranged in parallel.

9. The elastic wave filter according to claim 8, wherein: The at least two IDTs arranged in parallel include a third IDT and a fourth IDT, the third IDT and the fourth IDT are arranged along the second direction, and the third IDT and the fourth IDT share a third bus bar; The third IDT includes a fifth long finger electrode and a sixth long finger electrode, the fifth long finger electrode and the sixth long finger electrode are arranged along the second direction and extend along the first direction; the fourth IDT includes a seventh long finger electrode and an eighth long finger electrode, the seventh long finger electrode and the eighth long finger electrode are arranged along the second direction and extend along the first direction; the first direction intersects with the second direction; The period of the third IDT is different from the period of the fourth IDT; the period of the third IDT is at least one of the following spacings: the period of the third IDT is the spacing between two adjacent fifth long finger electrodes in the second direction, or the period of the third IDT is the spacing between two adjacent sixth long finger electrodes in the second direction; the period of the fourth IDT is at least one of the following spacings: the period of the fourth IDT is the spacing between two adjacent seventh long finger electrodes in the second direction, or the period of the fourth IDT is the spacing between two adjacent eighth long finger electrodes in the first direction; The third type resonator further includes a second open-grid bar located between the third IDT and the fourth IDT along the second direction, wherein the second open-grid bar extends along the first direction and has a gap with the third bus bar in the first direction.

10. The elastic wave filter according to claim 9, wherein: The third type resonator further includes a fourth bus bar, and the second open grid bar is connected to the fourth bus bar; Along the first direction, there is a gap between the fourth bus bar and the third bus bar.

11. The elastic wave filter according to claim 1, further comprising a longitudinally coupled resonator type filter; The longitudinally coupled resonator-type filter is provided in series in a loop between the input terminal and the output terminal.

12. The elastic wave filter according to claim 1, wherein: The electrostatic capacitance of the third type resonator is smaller than the electrostatic capacitance of the first type resonator, and smaller than the electrostatic capacitance of the second type resonator.

13. An elastic wave multiplexer comprising an antenna terminal, at least one receiving unit and at least one transmitting unit; The antenna terminals are respectively connected to the receiving unit and the transmitting unit for communication; At least one of the receiving unit and the transmitting unit includes the elastic wave filter according to any one of claims 1 to 12.

14. A radio frequency front-end circuit, comprising a low noise amplifier and the elastic wave multiplexer as claimed in claim 13, wherein the low noise amplifier amplifies the radio frequency signal fed via the elastic wave multiplexer.

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