CN117394824A

CN117394824A - Elastic wave filter, elastic wave multiplexer and radio frequency front-end circuit

Info

Publication number: CN117394824A
Application number: CN202311567479.2A
Authority: CN
Inventors: 梁丹; 姜建利
Original assignee: Tiantong Ruihong Technology Co ltd
Current assignee: Tiantong Ruihong Technology Co ltd
Priority date: 2023-11-22
Filing date: 2023-11-22
Publication date: 2024-01-12

Abstract

The invention discloses an elastic wave filter, an elastic wave multiplexer and a radio frequency front-end circuit, wherein a first type resonator in the elastic wave filter is arranged in a loop between an input terminal and an output terminal in series; one end of the second type resonator is connected in a loop between the input terminal and the output terminal, and the other end of the second type resonator is grounded; the resonant frequency of the first type resonator and the antiresonant frequency of the second type resonator are located in the frequency band range of the passband of the elastic wave filter; the resonant frequency and the antiresonant frequency of the third type resonator are both outside the 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. By adopting the technical means, notch fallback can be formed at the resonance frequency or anti-resonance frequency of the third type resonator, and further the out-of-band attenuation degree and the multiplexer isolation degree of the elastic wave filter can be improved.

Description

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

Technical Field

The present invention relates to the field of filters, and in particular, to an elastic wave filter, an elastic wave multiplexer, and a radio frequency front-end circuit.

Background

Elastic wave filter devices are widely used in the communication field as one of important elements in the radio frequency front end field. With the rapid development of radio frequency communication technology, higher requirements are put on the performance of the elastic wave filter device.

At present, in the elastic wave filter and the duplexer, the characteristics such as extremely low insertion loss and high out-of-band attenuation degree are required, so that in the design of the elastic wave filter and the duplexer, special means are generally required to improve the out-of-band attenuation degree of a specific frequency band; in addition, in a Thin film surface acoustic wave filter (Thin-Film Surface Acoustic Wave, TF-SAW), a duplexer, or the like, spurious components exist on the high frequency side of the band, and the presence of these spurious components causes the out-of-band attenuation and isolation of the device to deteriorate sharply in the corresponding frequency band, and at the same time, causes mixing of a transmission wave with an interference wave outside the frequency band such as the transmission frequency band and the reception frequency band, and causes intermodulation distortion in the reception frequency band, which reduces the communication quality (signal-to-noise ratio) of the communication device.

Therefore, in practical applications, there is an urgent need to find a technical means to improve the out-of-band attenuation of the elastic wave device and suppress these parasitic waves, and not to deteriorate the overall performance of the elastic wave device.

Disclosure of Invention

The embodiment of the invention provides an elastic wave filter, an elastic wave duplexer and a radio frequency front-end circuit, which are used for improving the out-of-band attenuation degree of the elastic wave filter.

In a first aspect, an elastic wave filter provided in an embodiment of the present invention includes: an input terminal, an output terminal, a first type resonator, a second type resonator, and a third type resonator; the first type resonator comprises at least one first resonator and the second type resonator comprises 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; one end of the second type resonator is connected in a loop between the input terminal and the output terminal, and the other end of the second type resonator is grounded; the resonant frequency of the first type resonator and the antiresonant frequency of the second type resonator are all located in the frequency band range of the passband of the elastic wave filter;

the resonant frequency and the antiresonant frequency of the third type resonator are both located 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.

Optionally, the resonant frequency of the first type resonator is greater than the resonant frequency of the second type resonator, and the antiresonance frequency of the first type resonator is greater than the antiresonance frequency of the second type resonator;

the third type resonator has a resonant frequency and an anti-resonant frequency greater than the anti-resonant frequency of the first resonator.

Optionally, one end of the third type resonator is connected in a loop between the input terminal and the output terminal, and the other end of the third type resonator is grounded.

Optionally, the third type resonator comprises at least two interdigital transducers;

at least two interdigital transducers are arranged in parallel.

Optionally, the at least two interdigital transducers arranged in parallel include a first interdigital transducer and a second interdigital transducer, the first interdigital transducer and the second interdigital transducer are arranged along a first direction, and the first interdigital transducer and the second interdigital transducer share a first bus bar;

the first interdigital transducer comprises a first long-finger electrode and a second long-finger electrode, and 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 comprises a third long-finger electrode and a fourth long-finger electrode, wherein 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;

The period of the first interdigital transducer is different from the period of the second interdigital transducer; the period of the first interdigital transducer is the interval between two adjacent first long-finger electrodes in the first direction, and/or the period of the first interdigital transducer is the interval between two adjacent second long-finger electrodes in the first direction; the period of the second interdigital transducer is the interval between two adjacent third long-finger electrodes in the first direction, and/or the period of the second interdigital transducer is the interval between two adjacent fourth long-finger electrodes in the first direction;

the third type resonator further includes a first open-circuited grid located between the first interdigital transducer and the second interdigital transducer along the first direction, the first open-circuited grid extending along the second direction and having a gap between the first bus bar and the second direction.

Optionally, the third type resonator further comprises a second bus bar, and the first open-circuit grid bar is connected with the second bus bar;

in the second direction, a gap exists between the second bus bar and the first bus bar.

Optionally, the third type resonator is arranged in series in a loop between the input terminal and the output terminal.

Optionally, the third type resonator includes at least two of the interdigital transducers;

at least two interdigital transducers are arranged in parallel.

Optionally, the at least two interdigital transducers arranged in parallel include a third interdigital transducer and a fourth interdigital transducer, the third interdigital transducer and the fourth interdigital transducer are arranged along a second direction, and the third interdigital transducer and the fourth interdigital transducer share a third bus bar;

the third interdigital transducer comprises a fifth long interdigital electrode and a sixth long interdigital electrode, wherein the fifth long interdigital electrode and the sixth long interdigital electrode are arranged along the second direction and extend along the first direction; the fourth interdigital transducer comprises a seventh long-finger electrode and an eighth long-finger electrode, wherein 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;

the period of the third interdigital transducer is different from the period of the fourth interdigital transducer; the period of the third interdigital transducer is the interval between two adjacent fifth long interdigital electrodes in the second direction, and/or the period of the third interdigital transducer is the interval between two adjacent sixth long interdigital electrodes in the second direction; the period of the fourth interdigital transducer is the interval between two adjacent seventh long-finger electrodes in the second direction, and/or the period of the fourth interdigital transducer is the interval between two adjacent eighth long-finger electrodes in the first direction;

The third type resonator further includes a second open-circuited grid located between the third interdigital transducer and the fourth interdigital transducer along the second direction, the second open-circuited grid extending along the first direction and having a gap between the first direction and the third bus bar.

Optionally, the third type resonator further includes a fourth bus bar, and the second open-circuit grid bar is connected to the fourth bus bar;

in the first direction, a gap exists between the fourth bus bar and the third bus bar.

Optionally, the elastic wave filter further comprises a longitudinally coupled resonator type filter;

the longitudinally coupled resonator filter is disposed in series in a loop between the input terminal and the output terminal.

Optionally, 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.

In a second aspect, an embodiment of the present invention further provides an elastic wave multiplexer, including an antenna terminal, at least one receiving unit, and at least one transmitting unit;

the antenna terminal is respectively in communication connection with the receiving unit and the transmitting unit;

At least one of the receiving unit and the transmitting unit includes the elastic wave filter according to any one of the first aspect.

In a third aspect, an embodiment of the present invention further provides a radio frequency front-end circuit, including the elastic wave multiplexer according to the second aspect.

According to the technical scheme, the third type resonator comprises at least one interdigital transducer, and the resonant frequency and the antiresonant frequency of the third type resonator are both located outside the frequency band range of the passband of the elastic wave filter and are larger than the maximum frequency value of the passband of the elastic wave filter. That is, the resonance frequency and the antiresonance frequency of the third type resonator are located outside the band range of the passband of the elastic wave filter and are located at the high frequency side of the passband of the elastic wave filter, so that the third type resonator can form an attenuation pole, i.e., a zero point, at the high frequency side of the passband of the elastic wave filter, thereby causing the elastic wave filter to form a notch fall back at the resonance frequency or antiresonance frequency of the third type resonator, and increasing the out-of-band attenuation degree of the elastic wave filter.

Drawings

Fig. 1 is a schematic circuit schematic diagram of an elastic wave filter according to an embodiment of the present invention;

Fig. 2 is a schematic structural diagram of a third type resonator according to an embodiment of the present invention;

FIG. 3 is a schematic circuit schematic diagram of another elastic wave filter according to an embodiment of the present invention;

fig. 4 is a schematic circuit schematic structure diagram of another elastic wave filter according to an embodiment of the present invention;

fig. 5 is a schematic structural diagram of another third type resonator according to an embodiment of the present invention;

FIG. 6 is a graph showing the passband characteristics and resonance characteristics of an elastic wave filter according to FIG. 3;

FIG. 7 is an admittance curve of a third type of resonator in an elastic wave filter corresponding to FIG. 3;

FIG. 8 is a transmission curve of a third type of resonator in the elastic wave filter according to FIG. 3;

fig. 9 is a schematic structural diagram of another third type resonator according to an embodiment of the present invention;

fig. 10 is a schematic structural diagram of yet another third type resonator according to an embodiment of the present invention;

FIG. 11 is a schematic circuit schematic diagram of another elastic wave filter according to an embodiment of the present invention;

fig. 12 is a schematic circuit schematic diagram of another elastic wave filter according to an embodiment of the present invention;

FIG. 13 is a schematic diagram of a third type of resonator according to an embodiment of the present invention;

FIG. 14 is a schematic diagram of a third type of resonator according to an embodiment of the present invention;

fig. 15 is a schematic circuit schematic structure of another elastic wave filter according to an embodiment of the present invention;

FIG. 16 is a schematic circuit schematic diagram of another elastic wave filter according to an embodiment of the present invention;

FIG. 17 is a schematic view of the structure of a third type of resonator provided in FIG. 5 along section line a-a';

FIG. 18 is a schematic circuit diagram of an elastic wave multiplexer according to an embodiment of the present invention;

FIG. 19 is a schematic circuit diagram of another elastic wave multiplexer according to an embodiment of the present invention;

fig. 20 is a schematic diagram of a transmission characteristic curve of an elastic wave duplexer according to an embodiment of the present invention;

fig. 21 is a schematic structural diagram of a radio frequency front-end circuit according to an embodiment of the present invention.

Detailed Description

The invention is described in further detail below with reference to the drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting thereof. It should be further noted that, for convenience of description, only some, but not all of the structures related to the present invention are shown in the drawings.

Fig. 1 is a schematic circuit diagram of an elastic wave filter according to an embodiment of the present invention, and fig. 2 is a schematic circuit diagram of a third type resonator according to an embodiment of the present invention, where, as shown in fig. 1 and fig. 2, 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 comprises at least one first resonator 301 and the second type resonator 40 comprises at least one second resonator 401; the third type of resonator 50 comprises at least one interdigital transducer 501; the first type resonator 30 is disposed in series in a loop between the input terminal 10 and the output terminal 20; one end of the second type resonator 40 is connected in a loop between the input terminal 10 and the output terminal 20, and the other end of the second type resonator 40 is grounded; the resonant frequency of the first type resonator 30 and the antiresonant frequency of the second type resonator 40 are both within the band range of the passband of the elastic wave filter 100; the resonance frequency and the antiresonance frequency of the third type resonator 50 are located outside the band range of the passband of the elastic wave filter 100 and are larger than the maximum frequency value of the passband of the elastic wave filter 100.

It should be noted that the passband of the elastic wave filter 100 is understood to be a frequency range on both sides of the 3dB bandwidth, that is, [ fmin, fmax ], and the maximum frequency value is the right side of the 3dB bandwidth, that is, fmax.

Specifically, the first type resonator 30 is disposed 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 one first resonator 301, and in other embodiments, the number of first resonators 301 may be plural, and the number of first resonators 301 is not specifically limited in the embodiment of the present invention. Illustratively, the first type resonator 30 may include 2, 3, or even more first resonators 301. Illustratively, the first type resonator in the acoustic wave filter 100 shown in fig. 1 includes 4 first resonators 301, and the embodiments of the present invention are each illustrated by taking 4 first resonators 301 as an example.

Specifically, one end of the second type resonator 40 is connected in the loop between the input terminal 10 and the output terminal 20, and the other 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 one second resonator 401, and in other embodiments, the number of second resonators 401 may be plural. Illustratively, the second type resonator 40 may include 2, 3, or even more second resonators 401. Illustratively, the second type resonator 40 in the acoustic wave filter 100 shown in fig. 1 includes 3 second resonators 401, and the embodiment of the present invention is illustrated by taking 3 second resonators 401 as an example.

Specifically, the resonance frequency of the first type resonator 30 is located within the frequency band of the passband of the elastic wave filter 100, and the antiresonance frequency of the second type resonator 40 is located within the frequency band of the passband of the elastic wave filter 100; the resonance frequency and the antiresonance frequency of the third type resonator 50 are located outside the band range of the passband of the elastic wave filter 100 and are larger than the maximum frequency value of the passband of the elastic wave filter 100. In other words, the resonance frequency and the antiresonance frequency of the third type resonator 50 are located at the high frequency side outside the band range of the passband of the elastic wave filter 100, so that the third type resonator 50 can form an attenuation pole, i.e., a zero point, at 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 resonance frequency or antiresonance frequency of the third type resonator 50, increasing the out-of-band suppression degree of the elastic wave filter 100.

Note that, the third type resonator 50 may be a series-arm resonator or a parallel-arm resonator, and fig. 1 only shows a solution in which the third type resonator 50 is a parallel-arm resonator, and a solution in which the third type resonator 50 is a series-arm resonator will be described in the following embodiments. Further, the third type resonator 50 may be located at any position in the loop between the input terminal 10 and the output terminal 20, i.e., on the side close to the input terminal 10 or the side close to the output terminal 20, and may be located at a position close to the middle of the input terminal 10 and the output terminal 20.

Referring to fig. 2, the interdigital transducer 501 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 51 are interdigital electrodes, the interdigital electrodes and the bus bar 502 form an interdigital transducer, and the antiresonance frequency of the third type resonator 50 can be located outside the band range of the passband of the elastic wave filter 100 and is greater than the maximum frequency value of the passband of the elastic wave filter 100 by adjusting the period of the interdigital electrodes. The third type resonator 50 further includes a reflective grating 504, which can reduce acoustic wave leakage and increase the Q-value of the third type resonator 50.

According to the elastic wave filter provided by the embodiment of the invention, the third type resonator comprises at least one interdigital transducer, and the resonant frequency and the antiresonant frequency of the third type resonator are positioned outside the frequency band range of the passband of the elastic wave filter and are larger than the maximum frequency value of the passband of the elastic wave filter. That is, the resonance frequency and the antiresonance frequency of the third type resonator are located outside the band range of the passband of the elastic wave filter and are located at the high frequency side of the passband of the elastic wave filter, so that the third type resonator can form an attenuation pole, i.e., a zero point, at the high frequency side of the passband of the elastic wave filter, thereby causing the elastic wave filter to form a notch fall-back at the resonance frequency or antiresonance frequency of the third type resonator, increasing the out-of-band suppression degree of the elastic wave filter.

Optionally, with continued reference to fig. 1, the resonant frequency of the first type resonator 30 is greater than the resonant frequency of the second type resonator 40, and the antiresonant frequency of the first type resonator 30 is greater than the antiresonant frequency of the second type resonator 40; the antiresonant frequency of the third type resonator 50 is greater than the antiresonant frequency of the first type resonator 30.

Specifically, the resonance frequency of the series arm resonator is greater than the resonance frequency of the parallel arm resonator, and the anti-resonance frequency of the series arm resonator is greater than the anti-resonance frequency of the parallel arm, because the resonance frequency and the anti-resonance frequency of the first resonator 301 are both greater, the resonance frequency and the anti-resonance frequency of the third type resonator 50 are greater than the anti-resonance 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, so that the elastic wave filter 100 forms a notch fall at the resonance frequency or the anti-resonance frequency of the third type resonator 50, and the out-of-band suppression degree of the elastic wave filter 100 is increased.

As a possible implementation, when the number of interdigital transducers 501 is one, the resonant frequency and the antiresonant frequency of the interdigital transducer 501 may both be located outside the band range of the passband of the elastic wave filter 100, and both be larger than the maximum frequency value of the passband of the Yu Danxing wave filter 100, so that the out-of-band rejection of the elastic wave filter 100 can be further improved.

As another possible embodiment, when the number of interdigital transducers 501 is two or more, the maximum resonance frequency and the maximum antiresonance frequency in the plurality of interdigital transducers 501 may be both located outside the band range of the passband of the elastic wave filter 100, and both are larger than the maximum frequency value of the passband of the Yu Danxing wave filter 100. Alternatively, all resonant frequencies and all antiresonant frequencies in the interdigital transducers 501 may be located outside the band range of the passband of the elastic wave filter 100, and the maximum frequency value of the passband of the Yu Danxing wave filter 100 is all greater, so that the out-of-band rejection of the elastic wave filter 100 can be further improved.

Alternatively, with continued reference to fig. 1, one end of the third type resonator 50 is connected in a loop between the input terminal 10 and the output terminal 20, and the other end of the third type resonator 50 is grounded, i.e., the third type resonator 50 is a parallel resonator.

Further, fig. 3 is a schematic circuit diagram of another elastic wave filter according to an embodiment of the present invention, and fig. 4 is a schematic circuit diagram of another elastic wave filter according to an embodiment of the present invention, where, as shown in fig. 3 and fig. 4, a third type resonator 50 includes at least two interdigital transducers 501; at least two interdigital transducers 501 are arranged in parallel.

As a possible implementation, referring to fig. 3, fig. 3 shows a solution where the third type resonator 50 includes two interdigital transducers 501, so that the third type resonator 50 includes two resonance peaks and two antiresonance peaks, i.e. notch fallback can be formed in the passband near the two resonance frequencies of the third type resonator 50, increasing the out-of-band rejection degree of the filter.

As another possible embodiment, referring to fig. 4, the third type resonator 50 shown in fig. 4 includes three or more interdigital transducers 501, so that the third type resonator 50 includes N resonant peaks and N antiresonant peaks, where N represents the number of interdigital transducers 501, that is, a plurality of notch drops are formed in a passband around the N resonant frequencies of the third type resonator 50, which is advantageous for further increasing the out-of-band suppression degree of the filter.

Optionally, fig. 5 is a schematic structural diagram of another third type resonator according to an embodiment of the present invention, as shown in fig. 5, at least two interdigital transducers 501 disposed in parallel include a first interdigital transducer 5011 and a second interdigital transducer 5012, the first interdigital transducer 5011 and the second interdigital transducer 5012 are arranged along a first direction (X direction as shown in the drawing), and the first interdigital transducer 5011 and the second interdigital transducer 5012 share a first bus bar 502; the first interdigital transducer 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 being arranged in the first direction X and each extending in the second direction (Y direction as shown in the drawing); the second interdigital transducer 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 being arranged in the first direction X and each extending in the second direction Y; the first direction X and the second direction Y intersect; the period of the first interdigital transducer 5011 is different from the period of the second interdigital transducer 5012; the period of the first interdigital transducer 5011 is the pitch of two adjacent first long-finger electrodes 51 in the first direction X, and/or the period of the first interdigital transducer 5011 is the pitch of two adjacent second long-finger electrodes 52 in the first direction X; the period of the second interdigital transducer 5012 is the pitch of the adjacent two third long-finger electrodes 53 in the first direction X, and/or the period of the second interdigital transducer 5012 is the pitch of the adjacent two fourth long-finger electrodes 54 in the first direction X; the third type resonator 50 further includes a first open-circuit grid 5031 located between the first interdigital transducer 5011 and the second interdigital transducer 5012 along the first direction X, the first open-circuit grid 5031 extending along the second direction Y with a gap between the first bus bar 502 in the second direction Y.

Specifically, the first interdigital transducer 5011 and the second interdigital transducer 5012 are arranged in parallel along the first direction X and share the first bus bar 502, and thus the arrangement is simple, and when an ac signal of a certain frequency is applied to the first bus bar 502, a surface acoustic wave can be generated in the effective aperture area of the third type resonator 50. The effective aperture area, i.e., the active area, is understood to be the area where the first long finger electrode 51 and the second long finger electrode 52 overlap or the area where the third long finger electrode 53 and the fourth long finger electrode 54 overlap in the first direction X. The surface acoustic wave is mainly concentrated in the effective aperture area and mainly propagates along the first direction X, but there is also a part of the surface acoustic wave that propagates and leaks to the first bus bar 502 side along the second direction Y, so the reflective grating 504 is generally disposed at two sides of the effective aperture area along the first direction X to reduce the leakage of the surface acoustic wave, so that the loss of the acoustic wave energy can be reduced, and the Q value of the third type resonator 50 can be improved.

Specifically, the first interdigital transducer 5011 includes a first long-finger electrode 51 and a second long-finger electrode 52, and the second interdigital transducer 5012 includes a third long-finger electrode 53 and a fourth long-finger electrode 54. Illustratively, 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 may be real-finger electrodes. In the first interdigital transducer 5011, the first long-finger electrode 51 and the second long-finger electrode 52 are arranged along the first direction X and each extend along the second direction Y, forming a comb-shaped interdigital electrode structure; in the second interdigital transducer 5012, the third long-finger electrode 53 and the fourth long-finger electrode 54 are arranged in the first direction X and each extend in the second direction Y, forming a comb-shaped interdigital electrode structure.

It will be appreciated that with continued reference to fig. 5, the first interdigital transducer 5011 and the second interdigital transducer 5012 may further include dummy electrodes, i.e., short finger electrodes, which are alternately arranged in sequence along the first direction X and each extend along the second direction Y, and the extension length of the short finger electrodes along the second direction Y is smaller than the extension length of the long finger electrodes along the second direction Y.

Further, the period of the first interdigital transducer 5011 is different from the period of the second interdigital transducer 5012, that is, the electrode period of the first interdigital transducer 5011 is different from the electrode period of the second interdigital transducer 5012. Specifically, the period of the first interdigital transducer 5011 is the pitch λ1 of the adjacent two first long finger electrodes 51 in the first direction X, and/or the period of the first interdigital transducer 5011 is the pitch λ2 of the adjacent two second long finger electrodes 52 in the first direction X. It will be appreciated that λ1 may be the spacing between the centers of any two adjacent first long finger electrodes 51 along the first direction X, and similarly λ2 may be the spacing between the centers of any two adjacent second long finger electrodes 52 along the first direction X. Illustratively, λ1=λ2. The period of the second interdigital transducer 5012 is the pitch λ3 of the adjacent two third long-finger electrodes 53 in the first direction X, and/or the period of the second interdigital transducer 5012 is the pitch λ4 of the adjacent two fourth long-finger electrodes 54 in the first direction X. Illustratively, λ3=λ4.

It should be understood that fig. 5 only shows a 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, it should be noted that the period of the first interdigital transducer 5011 may also be larger than the period of the second interdigital transducer 5012, that is, λ1 > λ3. The embodiment of the invention does not specifically limit the size relation between the period of the first interdigital transducer 5011 and the period of the second interdigital transducer 5012, ensures that the periods are different, and can realize the formation of notch fall-back on the high frequency side of the elastic wave filter 100, thereby improving the out-of-band attenuation degree of the elastic wave filter.

It should be noted that the number of interdigital electrodes in the first interdigital transducer 5011 may be equal to the number of interdigital electrodes in the second interdigital transducer 5012, or the number of interdigital electrodes may be unequal. It is to be understood that the number of interdigital electrodes in the first interdigital transducer 5011 and the second interdigital transducer 5012 is not particularly limited, and can be flexibly adjusted according to the performance requirements of the third type resonator 50.

It should be noted that, the first open-circuit grid 5031 is located between the first interdigital transducer 5011 and the second interdigital transducer 5012 along the first direction X, the first open-circuit grid 5031 extends along the second direction Y, and a gap exists between the first open-circuit grid 5031 and the first bus bar 502 in the second direction Y, by providing the first open-circuit grid 5031, on the one hand, crosstalk of signals between the first interdigital transducer 5011 and the second interdigital transducer 5012 can be prevented, and on the other hand, a gap exists between the first open-circuit grid 5031 and the first bus bar 502 in the second direction Y, so that a short circuit caused by contact connection between the first open-circuit grid 5031 and the first bus bar 502 can be avoided, and further, performance of the third type resonator 50 is affected.

Fig. 6 is a passband characteristic and a resonance characteristic curve of an elastic wave filter corresponding to fig. 3, where, as shown in fig. 6, the antiresonance frequency of the first type resonator 30 is fas, and the resonance frequency is frs; the second type resonator 40 has an anti-resonance frequency fap and a resonance frequency frp. Compared with the scheme in the prior art that only the first type resonator 30 and the second type resonator 40 are provided, in the embodiment of the present invention, the resonant frequency frp of the second type resonator 40 and the antiresonant frequency fas of the first type resonator 30 form the 1 st zero point and the 2 nd zero point of the elastic wave filter 100 respectively, the dashed line in the figure is the admittance characteristic curve of the third type resonator 50, the resonant frequencies frA, frB and the antiresonant frequencies faA, 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 Yu Danxing wave filter 100, and since the resonant frequency peak of the third type resonator 50 is connected in parallel to the elastic wave filter 100, a plurality of attenuation poles (zero points) are formed on the high frequency side of the passband of the filter, so that the elastic wave filter 100 falls back in the frequency band around the resonant frequency frA of the third type resonator 50 and the resonant frequency frB of the third type resonator 50, and the rejection degree of the filter is increased.

Fig. 7 is an admittance curve of a third type resonator in an elastic wave filter corresponding to fig. 3, fig. 8 is a transmission curve of a third type resonator in an elastic wave filter corresponding to fig. 3, and as shown in fig. 7 and 8, the third type resonator 50 is connected in parallel to a circuit, and two zero points A, B are seen on the transmission curve, and the zero points A, B enable the elastic wave filter 100 to form notch fallback in a frequency band near the resonant frequencies frA and frB of the third type resonator 50, thereby increasing the out-of-band suppression degree of the filter.

Optionally, fig. 9 is a schematic structural diagram of another third type resonator according to an embodiment of the present invention, as shown in fig. 9, where the third type resonator 50 further includes a second bus bar 505, and the first open-circuit grid 5031 is connected to the second bus bar 505; in the second direction Y, a gap exists between the second bus bar 505 and the first bus bar 502.

Specifically, the first open-circuit grid 5031 is connected to the second bus bar 505, but is not connected to the first bus bar 502, so that the first open-circuit grid 5031 is a short-circuit grid, on the one hand, crosstalk of signals between the first interdigital transducer 5011 and the second interdigital transducer 5012 can be prevented, and on the other hand, the arrangement mode of the first open-circuit grid 5031 is simple.

It is understood that the first open bars 5031 may be integrally provided, which can simplify the process.

It should be noted that the number of the first open bars 5031 may be plural, and in the embodiment of the present invention, the number of the open bars 503 is not specifically limited, and the period between two adjacent first open bars 5031 along the first direction X, that is, the interval between two adjacent first open bars 5031 is not specifically limited. It can be appreciated that the plurality of first open grating bars 5031 between the first interdigital transducer 5011 and the second interdigital transducer 5012 may form an open grating group, and when the third type resonator 50 includes M interdigital transducers 501 disposed in parallel, the number of open grating groups may be (M-1), that is, open grating groups are disposed between any two adjacent interdigital transducers 501, so that signals between the plurality of interdigital transducers 501 are ensured not to generate crosstalk, and thus the working performance of the third type resonator 50 can be improved.

Fig. 10 is a schematic structural diagram of a third type resonator according to an embodiment of the present invention, as shown in fig. 10, where fig. 10 exemplarily shows that the third type resonator 50 includes 4 first interdigital transducers 5011, second interdigital transducers 5012, fourth interdigital transducers 5015 and fifth interdigital transducers 5016 arranged in parallel, and thus, when the third type resonator 50 includes 4 interdigital transducers 501 arranged in parallel, any two adjacent interdigital transducers 501 further include a set of open-circuit grating groups, and the open-circuit grating groups are formed by a plurality of first open-circuit grating strips 5031, it is required that the number of first open-circuit grating strips 5031 between the second interdigital transducers 5012 and the fourth interdigital transducers 5012 may be greater than the number of first open-circuit grating strips 5031 between the first interdigital transducers 5011 and the second interdigital transducers 5012, and may also be greater than the number of first open-circuit grating strips 5031 between the fourth interdigital transducers 5015 and the fifth interdigital transducers 5016, that is, the number of open-circuit grating strips 5031 between the two adjacent interdigital transducers 501 is located at the middle positions of the third type resonator is further than the number of open-circuit grating strips 5031 is located at the middle positions between the two adjacent interdigital transducers 501. It will be appreciated that the number of first open bars 5031 may be sequentially increased by the direction of the edges of the third type resonator 50 pointing in the center.

Alternatively, fig. 11 is a schematic circuit schematic structure of still another elastic wave filter according to an embodiment of the present invention, and as shown in fig. 11, a third type resonator 50 is disposed in series in a loop between the input terminal 10 and the output terminal 20.

Further, fig. 12 is a schematic circuit schematic diagram of still another elastic wave filter according to an embodiment of the present invention, and as shown in fig. 12, a third type resonator 50 includes at least two interdigital transducers 501; at least two interdigital transducers 501 are arranged in parallel. I.e. at least two interdigital transducers 501 are connected in parallel and then connected in series in a loop between the input terminal 10 and the output terminal 20.

As a possible implementation, with continued reference to fig. 12, fig. 12 shows a solution where the third type resonator 50 includes two interdigital transducers 501, so that the third type resonator 50 includes two resonance peaks and two antiresonance peaks, i.e. notch fallback can be formed in the passband around the two antiresonance frequencies of the third type resonator 50, increasing the out-of-band suppression degree of the filter.

As another possible embodiment, the third type resonator 50 may further include three or more interdigital transducers 501, such that the third type resonator 50 includes N resonant peaks and N antiresonant peaks, where N represents the number of interdigital transducers 501, i.e., a plurality of notch drops can be formed in the passband around the N antiresonant frequencies of the third type resonator 50, which is advantageous for further increasing the out-of-band suppression degree of the filter.

Optionally, fig. 13 is a schematic structural diagram of still another third type resonator according to an embodiment of the present invention, as shown in fig. 13, at least two interdigital transducers 501 disposed in parallel include a third interdigital transducer 5013 and a fourth interdigital transducer 5014, the third interdigital transducer 5013 and the fourth interdigital transducer 5014 are arranged along the second direction Y, and the third interdigital transducer 5013 and the fourth interdigital transducer 5014 share a third bus bar 506; the third interdigital transducer 5013 includes a fifth long-interdigital electrode 55 and a sixth long-interdigital electrode 56, the fifth long-interdigital electrode 55 and the sixth long-interdigital electrode 56 being arranged in the second direction Y and each extending in the first direction X; the fourth interdigital transducer 5014 includes a seventh long-finger electrode 57 and an eighth long-finger electrode 58, the seventh long-finger electrode 57 and the eighth long-finger electrode 58 being arranged in the second direction Y and each extending in the first direction X; the first direction X and the second direction Y intersect; the period of the third interdigital transducer 5013 is different from the period of the fourth interdigital transducer 5014; the period of the third interdigital transducer 5013 is the pitch of the adjacent two fifth long interdigital electrodes 55 in the second direction Y, and/or the period of the third interdigital transducer 5013 is the pitch of the adjacent two sixth long interdigital electrodes 56 in the second direction Y; the period of the fourth interdigital transducer 5014 is the pitch of the adjacent two seventh long-finger electrodes 57 in the second direction Y, and/or the period of the fourth interdigital transducer 5014 is the pitch of the adjacent two eighth long-finger electrodes 58 in the first direction X; the third type resonator 50 further includes a second open-circuited grid 5032 located between the third interdigital transducer 5013 and the fourth interdigital transducer 5014 in the second direction Y, the second open-circuited grid 5032 extending in the first direction X with a gap between the third bus bar 506 in the first direction X.

Specifically, 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, and this arrangement is simple, and 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.

Specifically, the third interdigital transducer 5013 includes a fifth long-finger electrode 55 and a sixth long-finger electrode 56, and the fourth interdigital transducer 5014 includes a seventh long-finger electrode 57 and an eighth long-finger electrode 58. Illustratively, 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 may be true finger electrodes. In the third resonator 5013, the fifth long finger electrode 55 and the sixth long finger electrode 56 are arranged along the second direction Y and each extend along the first direction X, forming a comb-shaped interdigital electrode structure; in the fourth interdigital transducer 5014, the seventh long finger electrode 57 and the eighth long finger electrode 58 are arranged in the second direction Y and each extend in the first direction X, forming a comb-like interdigital electrode structure.

It will be appreciated that the third interdigital transducer 5013 and the fourth interdigital transducer 5014 can further comprise dummy finger electrodes, i.e., short finger electrodes, which are alternately arranged in sequence with long finger electrodes along the second direction Y and each extend along the first direction X, and the extension length of the short finger electrodes along the first direction X is smaller than the extension length of the long finger electrodes along the first direction X.

Further, the period of the third interdigital transducer 5013 is different from the period of the fourth interdigital transducer 5014, that is, the electrode period of the third interdigital transducer 5013 is different from the electrode period of the fourth interdigital transducer 5014. Specifically, the period of the third interdigital transducer 5013 is the pitch λ5 of the adjacent two fifth long finger electrodes 55 in the second direction Y, and/or the period of the third interdigital transducer 5013 is the pitch λ6 of the adjacent two sixth long finger electrodes 56 in the second direction Y. It will be appreciated that λ5 may be the spacing between the centers of any two adjacent fifth long finger electrodes 55 in the second direction Y, and similarly λ6 may be the spacing between the centers of any two adjacent sixth long finger electrodes 56 in the second direction Y. Illustratively, λ5=λ6. The period of the fourth interdigital transducer 5014 is the pitch λ7 of the adjacent two seventh long finger electrodes 57 in the second direction Y, and/or the period of the fourth interdigital transducer 5014 is the pitch λ8 of the adjacent two eighth long finger electrodes 58 in the second direction Y. Illustratively, λ5=λ7.

It should be understood that fig. 13 only shows a 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, it should be noted that the period of the third interdigital transducer 5013 may also be larger than the period of the fourth interdigital transducer 5014, that is, λ5 > λ7. The embodiment of the invention does not specifically limit the size relation between the period of the third interdigital transducer 5013 and the period of the fourth interdigital transducer 5014, ensures that the periods are different, and can realize the formation of notch fall-back on the high frequency side of the elastic wave filter 100, thereby improving the out-of-band attenuation degree of the elastic wave filter.

It should be noted that, the second open-circuit grid 5032 is located between the third interdigital transducer 5013 and the fourth interdigital transducer 5014 along the second direction Y, the second open-circuit grid 5032 extends along the first direction X and has a gap between the third bus bar 506 and the first direction X, so by providing the second open-circuit grid 5032, on the one hand, crosstalk of signals between the third interdigital transducer 5013 and the fourth interdigital transducer 5014 can be prevented, and on the other hand, a gap exists between the second open-circuit grid 5032 and the third bus bar 506 in the first direction X, which can avoid a short circuit caused by contact connection between the second open-circuit grid 5032 and the third bus bar 506, and further affect performance of the third type resonator 50.

Optionally, fig. 14 is a schematic structural diagram of still another third type resonator according to an embodiment of the present invention, as shown in fig. 14, where the third type resonator 50 further includes a fourth bus bar 507, and the second open-circuit grid 5032 is connected to the fourth bus bar 507; in the first direction X, a gap exists between the fourth bus bar 507 and the third bus bar 506.

Specifically, the second open-circuit grid 5032 is connected to the fourth bus bar 507 but is not connected to the third bus bar 506, and thus the second open-circuit grid 5032 is a short-circuit grid, so that crosstalk between signals of the third interdigital transducer 5013 and the fourth interdigital transducer 5014 can be prevented.

It is understood that the second open bars 5032 may be integrally provided, which can simplify the process.

It should be noted that the second open grid 5032 is disposed in a similar manner to the first open grid 5031, and will not be described herein.

Optionally, fig. 15 is a schematic circuit schematic structure diagram of another elastic wave filter provided in an embodiment of the present invention, and fig. 16 is a schematic circuit schematic structure diagram of another elastic wave filter provided in an embodiment of the present invention, where, as shown in fig. 15 and 16, the elastic wave filter further includes a longitudinally coupled resonator type filter 60; the longitudinally coupled resonator filter 60 is disposed in series in a loop between the input terminal 10 and the output terminal 20.

As a possible implementation manner, referring to fig. 15, the elastic wave filter 100 further includes a longitudinally coupled resonator type filter 60, and the third type resonator 50 is connected in parallel in the elastic wave filter 100, so that on one hand, a diversified design of the elastic wave filter 100 can be achieved, and on the other hand, the out-of-band attenuation degree of the elastic wave filter can be improved by providing the third type resonator 50.

As another possible embodiment, referring to fig. 16, the elastic wave filter 100 further includes a longitudinally coupled resonator type filter 60, and the third type resonator 50 is connected in series in the elastic wave filter 100, so that on one hand, a diversified design of the elastic wave filter 100 can be achieved, and on the other hand, the out-of-band attenuation degree of the elastic wave filter can be improved by providing the third type resonator 50.

Alternatively, with continued reference to fig. 5, the electrostatic capacitance of the third type resonator 50 is less than the electrostatic capacitance of the first type resonator 30 and less than the electrostatic capacitance of the second type resonator 40.

Specifically, the electrostatic capacitance can be understood as the electrostatic capacitance value between the comb-like interdigital electrodes, which is approximately proportional to the product of the aperture length of the effective aperture region in the second direction Y and the logarithm of the long-finger electrodes (resonator area). The third type resonator 50 has a small electrostatic capacitance, which can reduce the area of the third type resonator 50, and is advantageous in realizing a miniaturized arrangement of the elastic wave filter 100 while also reducing the influence on the filter passband characteristics.

In summary, in the elastic wave filter provided by the embodiment of the present invention, the third type resonator includes at least one interdigital transducer, and the resonant frequency and the antiresonant frequency of the third type resonator are located 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. That is, the resonance frequency and the antiresonance frequency of the third type resonator are located outside the band range of the passband of the elastic wave filter and are located at the high frequency side of the passband of the elastic wave filter, so that the third type resonator can form an attenuation pole, i.e., a zero point, at the high frequency side of the passband of the elastic wave filter, thereby causing the elastic wave filter to form a notch fall-back at the resonance frequency or antiresonance frequency of the third type resonator, increasing the out-of-band suppression degree of the elastic wave filter. Furthermore, the third type resonator may be connected in parallel or in series in the elastic wave filter, so that diversified arrangement of the elastic wave filter can be realized.

Fig. 17 is a schematic structural diagram of a third type resonator along a section line a-a' shown in fig. 5. As shown in fig. 17, the first long finger electrode 51, the second long finger electrode 52, the reflective grating 504 and the middle open grating 503 of the third type filter 50 may be disposed on different piezoelectric substrates. The piezoelectric substrate may be a composite multilayer substrate including a piezoelectric layer 01, a low acoustic impedance layer 02, and a high acoustic impedance layer 03 supporting layer 04. The material of the piezoelectric layer 01 may be lithium tantalate, lithium niobate, aluminum nitride, quartz, or the like. The material of the low acoustic impedance layer 02 may be selected from silicon dioxide, glass, silicon oxynitride, tantalum oxide, and the like. The material of the high acoustic impedance layer 03 is selected from silicon, silicon nitride, silicon carbide, aluminum nitride, aluminum oxide, and the like. The material of the support layer 04 may be selected from monocrystalline silicon, silicon nitride, quartz, sapphire, diamond, etc. The piezoelectric layer 01, the low acoustic impedance layer 02 and the high acoustic impedance layer 03 are laminated in this order 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.

Specifically, the piezoelectric substrate may be a single piezoelectric layer 01, and the piezoelectric material may be lithium tantalate, lithium niobate, aluminum nitride, quartz, or the like, and the cut lithium tantalate, lithium niobate may be 20 ° -64 ° YX-LT, 0 ° -64 ° YX-LN, 120 ° -175 ° YX-LN, or the like. The piezoelectric layer 01 is provided with an interdigital electrode, the piezoelectric layer 01 and the interdigital electrode can be further provided with a first dielectric layer 05 and a second dielectric layer 06, the material of the first dielectric layer 05 can be silicon dioxide or silicon oxynitride, and the material of the second dielectric layer 06 can be silicon nitride, aluminum nitride, and the like. The first dielectric layer 05 can improve the temperature stability of the frequency of the device, and the second dielectric layer 06 can realize the adjustment of the working frequency of the device.

Based on the same inventive concept, an embodiment of the present invention further provides an elastic wave multiplexer, fig. 18 is a schematic circuit diagram of an elastic wave multiplexer provided by the embodiment of the present invention, and fig. 19 is a schematic circuit diagram of another elastic wave multiplexer provided by the embodiment of the present invention, where, as shown in fig. 18 and 19, the elastic wave multiplexer includes an antenna terminal ANT, at least one receiving unit 101 and at least one transmitting unit 102; the antenna terminals ANT are respectively connected with the receiving unit 101 and the transmitting unit 102 in a communication manner; at least one of the receiving unit 101 and the transmitting unit 102 includes the elastic wave filter 100 in the above-described embodiment.

Specifically, taking the acoustic wave multiplexer as the acoustic wave duplexer 200 as an example, the receiving unit 101 is disposed between the antenna terminal ANT and the receiving terminal 701, and forms a first passband of the acoustic wave duplexer 200, and the transmitting unit 102 is disposed between the antenna terminal ANT and the transmitting terminal 702, and forms a second passband of the acoustic wave duplexer 200.

Illustratively, the receiving unit 101 may include a ladder topology type filter, and may further include a longitudinally coupled resonator type filter, and the embodiments of the present invention are described by taking the ladder topology type filter as an example. Furthermore, the third type resonator 50 may be connected in series or in parallel in the transmitting unit 102 or the receiving unit 101, fig. 18 only shows a solution in which the third type resonator 50 is connected in parallel in the receiving unit 101, it being understood that the third type resonator 50 may also be arranged in parallel in the receiving unit 101 and in series in the transmitting unit 102 with reference to fig. 19. Furthermore, the third type resonator 50 may also be connected in series and/or in parallel in the transmitting unit 102 or the receiving unit 101.

Fig. 20 is a schematic diagram of a transmission characteristic curve of an elastic wave duplexer according to an embodiment of the present invention, where, as shown in fig. 20, a black dotted line is an admittance curve of a third type resonator 50, so that it can be seen that an attenuation pole (zero point) formed in a filter circuit by the third type resonator 50 can improve the attenuation degree outside the passband of the elastic wave duplexer and the isolation degree of the elastic wave duplexer.

It will be appreciated that when the acoustic wave multiplexer is a quad-multiplexer, the quad-multiplexer comprises four terminals, one antenna terminal and four acoustic wave filters, each terminal and antenna terminal forming a passband therebetween, at least one of the four acoustic wave filters comprising the third type resonator of the above-described embodiments.

In summary, the elastic wave filter and the multiplexer provided by the embodiment of the invention 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 transverse-excited Bulk-wave filter (XBAR), a LAMB wave filter (LAMB wave resonator, LAMB), and the like, and can be applied to filter elements forming low insertion loss, high rejection, high rectangle degree, and extremely low in-band ripple.

Based on the same inventive concept, the embodiment of the invention also provides a radio frequency front-end circuit, which comprises the elastic wave filter, the elastic wave multiplexer and the like in the embodiment. Fig. 21 is a schematic structural diagram of a radio frequency front-end circuit according to an embodiment of the present invention, and as shown in fig. 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 transmitting filter 23 and a first duplexer receiving filter 24), a second duplexer (the second duplexer includes a second duplexer transmitting filter 25 and a second duplexer receiving filter 26), a low noise amplifier 80, and a power amplifier 90.

Specifically, the rf front-end circuit 300 is connected to the rf signal processing circuit 31 and the baseband signal processing circuit 32 to form the rf communication device 400.

Further, the switch 70 is used to control the radio frequency signal, and connects the antenna terminal ANT with at least one signal path corresponding to a given frequency band, and the at least one signal path connected to the antenna terminal ANT may be a plurality of signal paths (corresponding to a plurality of filters and diplexers). The radio frequency front-end circuit 300 may support carrier aggregation techniques; the low noise amplifier 80 amplifies the radio frequency signal fed through the antenna terminal ANT, the switch 70, the first and second duplexer reception filters 24, 26 and feeds the amplified signal to the radio frequency signal processing circuit 31; the power amplifiers 90 amplify the radio frequency signals supplied from the radio frequency signal processing circuit 31 and feed the amplified signals to the antenna terminal ANT for transmission via the first duplexer transmission filter 23, the second duplexer transmission filter 25, and the switch 70, respectively.

The radio frequency signal processing circuit 31 in the radio frequency communication apparatus 400 performs signal processing on a radio frequency reception signal supplied from the antenna terminal ANT via a reception signal path, and feeds a reception signal generated by the signal processing; and the radio frequency signal processing circuit 31 performs signal processing on the fed transmission signal, and feeds the radio frequency transmission signal generated by the signal processing to the power amplifier 90.

The rf front-end circuit 300 further includes a first elastic wave filter 21 and a second elastic wave filter 22, and the first elastic wave filter 21 and the second elastic wave filter 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.

Note that the above is only a preferred embodiment of the present invention and the technical principle applied. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, and that various obvious changes, rearrangements, combinations, and substitutions can be made by those skilled in the art without departing from the scope of the invention. Therefore, while the invention has been described in connection with the above embodiments, the invention is not limited to the embodiments, but may be embodied in many other equivalent forms without departing from the spirit or scope of the invention, which is set forth in the following claims.

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 comprises at least one first resonator and the second type resonator comprises 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; one end of the second type resonator is connected in a loop between the input terminal and the output terminal, and the other end of the second type resonator is grounded; the resonant frequency of the first type resonator and the antiresonant frequency of the second type resonator are all positioned in the frequency band range of the passband of the elastic wave filter;

2. The acoustic wave filter according to claim 1, wherein the resonant frequency of the first type resonator is greater than the resonant frequency of the second type resonator, and the antiresonant frequency of the first type resonator is greater than the antiresonant frequency of the second type resonator;

3. The acoustic wave filter according to claim 1, wherein one end of the third type resonator is connected in a loop between the input terminal and the output terminal, and the other end of the third type resonator is grounded.

4. An acoustic wave filter according to claim 3, wherein the third type of resonator comprises at least two interdigital transducers;

at least two interdigital transducers are arranged in parallel.

5. The acoustic wave filter according to claim 4, wherein at least two of the interdigital transducers arranged in parallel include a first interdigital transducer (IDT) and a second interdigital transducer, the first interdigital transducer and the second interdigital transducer being arranged in a first direction, and the first interdigital transducer and the second interdigital transducer sharing a first bus bar;

6. The acoustic wave filter according to claim 5, wherein the third type resonator further comprises a second bus bar, the first open-circuit grid bar being connected to the second bus bar;

7. The acoustic 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 acoustic wave filter according to claim 7, wherein the third type resonator comprises at least two of the interdigital transducers;

at least two interdigital transducers are arranged in parallel.

9. The acoustic wave filter according to claim 8, wherein at least two of the interdigital transducers arranged in parallel include a third interdigital transducer and a fourth interdigital transducer, the third interdigital transducer and the fourth interdigital transducer being arranged in a second direction, and the third interdigital transducer and the fourth interdigital transducer sharing a third bus bar;

10. The acoustic wave filter according to claim 9, wherein the third type resonator further comprises a fourth bus bar, the second open-circuit grid bar being connected to the fourth bus bar;

11. The acoustic wave filter of claim 1, further comprising a longitudinally coupled resonator type filter;

12. The acoustic 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 is characterized by comprising an antenna terminal, at least one receiving unit and at least one transmitting unit;

at least one of the receiving unit and the transmitting unit comprising an elastic wave filter according to any of claims 1-12.

14. A radio frequency front-end circuit comprising the elastic wave multiplexer of claim 13.