WO2023216465A1

WO2023216465A1 - Surface acoustic wave filter and multiplexer

Info

Publication number: WO2023216465A1
Application number: PCT/CN2022/115229
Authority: WO
Inventors: 石麒麟; 左成杰; 何军
Original assignee: 安徽安努奇科技有限公司
Priority date: 2022-05-12
Filing date: 2022-08-26
Publication date: 2023-11-16
Also published as: CN114938217A

Abstract

A surface acoustic wave filter, comprising: a surface acoustic wave element (10), the surface acoustic wave element (10) being connected between an input terminal (30) and an output terminal (40) of the surface acoustic wave filter; and a surface acoustic wave resonant unit (20), the surface acoustic wave resonant unit (20) being connected between the input terminal (30) and the output terminal (40). A multiplexer, comprising the surface acoustic wave filter (50).

Description

Surface acoustic wave filters and multiplexers

This application claims priority to the Chinese patent application with application number 202210516804.1, which was submitted to the China Patent Office on May 12, 2022. The entire content of the above application is incorporated into this application by reference.

Technical field

Embodiments of the present application relate to the field of filtering technology, for example, to a surface acoustic wave filter and a multiplexer.

Background technique

In the communication industry, filters play an important role. For example, active filters can improve the stability of communication systems and power distribution systems, and extend the service life of communication equipment and power equipment. In the complex communication circuits of 5G (5th Generation Mobile Communication Technology), saving circuit space and cost is a major problem in circuit design. In related technologies, smaller surface acoustic wave filters are used to save circuit space. However, when a surface acoustic wave filter is used in the filter circuit, the suppression effect at the near end outside the passband is poor, thus affecting the quality of the communication signal.

Contents of the invention

This application provides a surface acoustic wave filter and a multiplexer.

According to one aspect of the present application, a surface acoustic wave filter is provided, which includes:

A surface acoustic wave element, which is connected between the input terminal and the output terminal of the surface acoustic wave filter;

A surface acoustic wave resonance unit is connected between the input terminal and the output terminal.

According to another aspect of the present application, a multiplexer is provided. The multiplexer includes the surface acoustic wave filter provided by any embodiment of the present application.

It should be understood that the content described in this section is not intended to identify key or important features of the embodiments of the application, nor is it intended to limit the scope of the application. Other features of the present application will become readily understood from the following description.

Description of the drawings

In order to explain the embodiments of the present application more clearly, the drawings needed to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application. For ordinary people in the art, For technical personnel, other drawings can also be obtained based on these drawings without exerting creative work.

Figure 1 is a schematic structural diagram of a surface acoustic wave filter provided according to an embodiment of the present application;

Figure 2 is a schematic structural diagram of another surface acoustic wave filter provided according to an embodiment of the present application;

Figure 3 is an insertion loss characteristic curve diagram of a surface acoustic wave filter provided according to an embodiment of the present application;

Figure 4 is an admittance characteristic curve diagram of a surface acoustic wave filter provided according to an embodiment of the present application;

Figure 5 is a schematic structural diagram of another surface acoustic wave filter provided according to an embodiment of the present application;

Figure 6 is an insertion loss characteristic curve of yet another surface acoustic wave filter provided according to an embodiment of the present application;

Figure 7 is an admittance characteristic curve of yet another surface acoustic wave filter provided according to an embodiment of the present application;

Figure 8 is a schematic structural diagram of another surface acoustic wave filter provided according to an embodiment of the present application;

Figure 9 is a schematic structural diagram of another surface acoustic wave filter provided according to an embodiment of the present application;

Figure 10 is a schematic structural diagram of another surface acoustic wave filter provided according to an embodiment of the present application;

Figure 11 is a schematic structural diagram of a multiplexer provided according to an embodiment of the present application;

Figure 12 is a partial structural schematic diagram of yet another surface acoustic wave filter provided according to an embodiment of the present application.

Detailed ways

In order to enable those skilled in the art to better understand the embodiments of the present application, the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. The described embodiments are only a part of the present application. Examples, not all examples. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts should fall within the scope of protection of this application.

It should be noted that the terms "first", "second", etc. in the description and claims of this application and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It is to be understood that the data so used are interchangeable under appropriate circumstances so that the embodiments of the application described herein can be practiced in sequences other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, e.g., a process, method, system, product, or apparatus that encompasses a series of steps or units and need not be limited to those explicitly listed. Those steps or elements may instead include other steps or elements not expressly listed or inherent to the process, method, product or apparatus.

An embodiment of the present application provides a surface acoustic wave filter. Figure 1 is a schematic structural diagram of a surface acoustic wave filter provided by an embodiment of the present application. As shown in FIG. 1 , the surface acoustic wave filter includes: a surface acoustic wave element 10 and a surface acoustic wave resonant unit 20 . The surface acoustic wave element 10 is connected between the input terminal 30 and the output terminal 40 of the surface acoustic wave filter; the surface acoustic wave resonance unit 20 is connected between the input terminal 30 and the output terminal 40 .

For example, the surface acoustic wave element 10 utilizes the characteristics of an acoustic-electric transducer to achieve acoustic-to-electrical conversion, so that electrical signals can be converted into surface acoustic waves for transmission, thereby realizing the propagation of electrical signals. One end of the surface acoustic wave element 10 is electrically connected to the input terminal 30 , and the other end is electrically connected to the output terminal 40 . When the electrical signal is input to the surface acoustic wave element 10 through the input terminal 30, the surface of the base material of the surface acoustic wave element 10 will generate mechanical vibration, and at the same time, a surface acoustic wave with the same frequency as the external electrical signal will be excited. The surface acoustic wave can travel along the surface of the base material. propagates and is output by the output terminal 40, thereby realizing the propagation of electrical signals. In addition, the volume of the surface acoustic wave element 10 is smaller than that of other electromagnetic wave devices and has a higher quality factor. When the electrical signal propagates in the surface acoustic wave element 10 , the rate of energy loss is slow. Therefore, in complex communication circuits, the use of surface acoustic wave components 10 can save circuit space and ensure the quality of communication signals.

At the same time, a surface acoustic wave resonance unit 20 is added to the surface acoustic wave filter. One end of the surface acoustic wave resonance unit 20 is electrically connected to the input terminal 30 , and the other end is electrically connected to the output terminal 40 . That is, the surface acoustic wave element 10 is integrally connected to the input terminal 30 . The surface acoustic wave resonance unit 20 is connected in parallel and connected between the input terminal 30 and the output terminal 40 . The surface acoustic wave resonant unit 20 has frequency selection capability, which can retain electrical signals of specific frequencies and filter electrical signals other than specific frequencies. For example, the surface acoustic wave resonant unit 20 can filter the out-of-band near-end signal corresponding to the frequency on the high-frequency side of the passband to achieve a good suppression effect of the out-of-band near-end electrical signals, so that the distance between the passband and the stopband can be reduced. The roll-off slope of the transition phase increases. This improves the out-of-band suppression capability of the surface acoustic wave filter, has a good filtering effect, and improves the quality of the electrical signals transmitted by the surface acoustic wave filter.

To sum up, in the surface acoustic wave filter provided in this embodiment, by adding a surface acoustic wave resonance unit between the input terminal and the output terminal, the surface acoustic wave resonance unit can adjust the passband edge position of the surface acoustic wave filter. The corresponding frequency signal is suppressed, so that the steep drop in the transition area between the passband and the stopband of signal transmission increases, and the roll-off slope increases. Therefore, adding a surface acoustic wave resonance unit between the input terminal and the output terminal of the surface acoustic wave filter can improve the signal suppression effect of the surface acoustic wave filter at the near end outside the passband, and can increase the corresponding frequency at the edge of the passband. The transmission quality of electrical signals.

In one embodiment, the surface acoustic wave element 10 may be a surface acoustic wave resonator.

In one embodiment, FIG. 2 is a schematic structural diagram of another surface acoustic wave filter provided by an embodiment of the present application. Based on the above embodiments, as shown in FIG. 2 , the surface acoustic wave resonant unit 20 includes: a surface acoustic wave resonator 21 .

The first end of the surface acoustic wave resonator 21 is connected to the input terminal 30 , and the second end of the surface acoustic wave resonator 21 is connected to the output terminal 40 .

For example, the surface acoustic wave resonator 21 mainly utilizes the piezoelectric properties of the piezoelectric material to perform an electrical-acoustic-electrical signal conversion process on the input electrical signal. The surface acoustic wave resonator 21 is connected between the input terminal 30 and the output terminal 40 of the surface acoustic wave filter. When the electrical signal is input from the input terminal 30, it is converted into surface acoustic waves by the input transducer in the surface acoustic wave resonator 21, and mechanical vibration occurs. Among them, the mechanical vibration with the same frequency as the resonant frequency of the surface acoustic wave resonator 21 propagates along the surface of the piezoelectric material to one end of the output terminal 40, and at the output end, the transmitted mechanical vibration of a specific frequency is converted into electrical energy through the output transducer. The signal is output from the output terminal 40; and the mechanical vibration with a frequency different from the resonant frequency of the surface acoustic wave resonator 21 cannot propagate along the surface of the piezoelectric material. Therefore, the surface acoustic wave resonator 21 can realize the electrical signal of a specific frequency. Transmit and filter electrical signals at unwanted frequencies. Therefore, adding the surface acoustic wave resonator 21 between the input terminal 30 and the output terminal 40 of the surface acoustic wave filter can increase the steep drop at the out-of-band near-end position of the passband, increase the roll-off slope, and improve the acoustic performance. The out-of-band suppression capability of the surface wave filter prevents the transmission signal from being interfered by signals of other frequencies and improves the quality of the transmission signal.

In one embodiment, based on the above embodiment, the resonant frequency of the surface acoustic wave resonant unit 20 is located in the adjacent band frequency range of the surface acoustic wave filter close to the maximum value of the passband.

For example, when the surface acoustic wave resonator unit 20 is a surface acoustic wave resonator 21 , the resonant frequency of the surface acoustic wave resonator 21 is the resonant frequency of the surface acoustic wave resonator unit 20 . The resonant frequency of the surface acoustic wave resonator 21 can be set to any frequency value according to the needs of actual applications. Adjacent band frequencies are the channel frequency ranges immediately adjacent to both sides of the main channel passband range. For example, setting the resonant frequency of the surface acoustic wave resonator 21 in the adjacent band frequency range of the surface acoustic wave filter close to the maximum value of the passband can increase and weaken the steep drop of the high frequency side of the passband in the adjacent band frequency range. The adjacent channel signal interferes with the signal transmitted by the main channel; and the surface acoustic wave resonator 21 forms additional transmission zero points in the adjacent band frequency range on the high frequency side of the passband, adding a new resonance peak, thereby broadening the acoustic Passband bandwidth of surface wave filter.

Exemplarily, FIG. 3 is an insertion loss characteristic curve diagram of the surface acoustic wave filter provided by the embodiment of the present application. For example, the resonant frequency of the surface acoustic wave resonator may be set to 1.03 GHz. As shown in Figure 3, the dotted line 100 is the insertion loss characteristic curve of the transmission signal tested for the traditional filter circuit; the solid line 200 is the insertion loss characteristic curve of the transmission signal tested for the surface acoustic wave filter provided in this embodiment.

As can be seen from Figure 3, the insertion loss of the signal of the traditional filter circuit represented by the dotted line 100 drops sharply on the low-frequency side of the passband, that is, in the range of 0.99-0.98GHz. This indicates that the out-of-band suppression effect of the traditional filter circuit is worse on the low-frequency side. Good; on the high-frequency side of the passband, that is, at the frequency of 1.02GHz, the transmitted signal strength begins to slowly attenuate, and the attenuation process of the signal strength continues from 1.02GHz to a frequency slightly greater than 1.04GHz. In the frequency range of 1.02-1.04GHz, the signal strength of the in-band transmission signal weakens and is easily affected by other signals of the same frequency, causing the signal quality to decrease. In the surface acoustic wave filter provided by this embodiment represented by the solid line 200, the out-of-band suppression effect on the low-frequency side of the passband is still good, and on the high-frequency side of the passband, due to the resonant frequency of 1.03GHz, the out-of-band suppression effect is still good. The effect of the surface wave resonator causes the signal insertion loss to increase sharply in the frequency range of 1.028-1.03GHz at the edge of the passband, that is, the roll-off slope increases. Therefore, connecting a surface acoustic wave resonator between the input terminal and the output terminal can improve the signal quality at the edge of the passband, and at the same time expand the bandwidth of the passband, that is, widen the bandwidth from the frequency range of 0.988-1.02GHz to Frequency range 0.988-1.028GHz.

Figure 4 is an admittance characteristic curve diagram of a surface acoustic wave filter provided by an embodiment of the present application. It should be noted that electrical admittance is used to describe the difficulty of AC current passing through a circuit. Electrical admittance consists of conductance and susceptance. Electrical admittance is a vector, including real and imaginary parts. Among them, the real part of the electrical admittance represents the electrical conductance. The higher the electrical conductance value, the easier it is for the charge to pass through. As shown in Figure 4, the dotted line 101 is the admittance characteristic curve of the traditional filter circuit, and the solid line 201 is the admittance characteristic curve of the surface acoustic wave filter provided in this embodiment. The solid line 201 has a new resonant peak at a frequency of approximately 1.028 GHz and has a higher conductance value, indicating that the surface acoustic wave filter can receive electrical signals with a frequency of 1.028 GHz. Therefore, it can be shown that connecting a surface acoustic wave resonator between the input terminal and the output terminal increases the bandwidth of the surface acoustic wave filter.

In one embodiment, FIG. 5 is a schematic structural diagram of another surface acoustic wave filter provided by an embodiment of the present application. Based on the above embodiments, as shown in FIG. 5 , the surface acoustic wave resonant unit 20 includes at least two surface acoustic wave resonators 21 , and the at least two surface acoustic wave resonators 21 are connected in series.

The first end of the surface acoustic wave resonator 21 located at the head end is connected to the input terminal 30 , and the second end of the surface acoustic wave resonator 21 located at the end is connected to the output terminal 40 .

For example, there may be one or more surface acoustic wave resonators 21 connected between the input terminal 30 and the output terminal 40. When multiple surface acoustic wave resonators 21 are connected, there may be It is a series connection relationship or a parallel connection relationship. Illustratively, in this embodiment, FIG. 5 shows a structure of a surface acoustic wave filter in which two surface acoustic wave resonators 21 are connected in series. Two surface acoustic wave resonators 21 are connected in series, the first end of the surface acoustic wave resonator 21 at the head end is connected to the input terminal 30, and the second end of the surface acoustic wave resonator 21 at the head end is connected to the end acoustic wave resonator 21. The first end of the surface wave resonator 21 and the second end of the surface acoustic wave resonator 21 located at the end are connected to the output terminal 40 .

Figure 6 is an insertion loss characteristic curve of yet another surface acoustic wave filter provided by an embodiment of the present application. As shown in Figure 6, the dotted line 102 is the signal insertion loss characteristic curve of the traditional filter circuit, and the solid line 202 is the signal insertion loss characteristic curve of the surface acoustic wave filter provided in this embodiment. It can be seen that connecting two surface acoustic wave resonators 21 with different resonant frequencies in series can also increase the roll-off slope of the signal insertion loss in the passband edge transition zone, thereby improving the bandwidth of the surface acoustic wave filter on the high-frequency side. The near-end signal suppression effect improves the quality of the transmitted signal. However, when two surface acoustic wave resonators 21 are connected in series, there will be large ripples on the high-frequency side during in-band signal transmission, making the signal transmission unstable. Therefore, by connecting a surface acoustic wave resonator 21 between the input terminal and the output terminal, the in-band signal transmission is more stable and the signal quality is better.

Since the effect of connecting two surface acoustic wave resonators 21 with the same resonant frequency in series is the same as that of connecting one surface acoustic wave resonator 21 with the same resonant frequency, when the surface acoustic wave resonant unit 20 is a plurality of surface acoustic wave resonators, At 21 o'clock, the resonant frequencies of each surface acoustic wave resonator 21 are set in the adjacent band frequency range of the surface acoustic wave filter close to the maximum value of the passband, and there are slight differences between them, then the resonant frequency of the surface acoustic wave resonant unit 20 It is equal to the maximum resonant frequency among the plurality of surface acoustic wave resonators 21 . For example, the resonant frequencies of the two surface acoustic wave resonators 21 can be set to two different values near 1.03 GHz. For example, the resonant frequencies of the two surface acoustic wave resonators 21 can be set to 1.028 GHz and 1.03 respectively. GHz. Figure 7 is an admittance characteristic curve of yet another surface acoustic wave filter provided by an embodiment of the present application. As shown in Figure 7, the dotted line 103 is the admittance characteristic curve of the traditional filter circuit, and the solid line 203 is the admittance characteristic curve of the surface acoustic wave filter provided in this embodiment. It can be seen that connecting two surface acoustic wave resonators 21 in series can also widen the bandwidth of the surface acoustic wave filter. And compared with connecting one surface acoustic wave resonator 21, connecting two surface acoustic wave resonators 21 with slightly different resonant frequencies in series can further widen the bandwidth from 1.028GHz to 1.03GHz, increasing the bandwidth range of the surface acoustic wave filter. , broaden the effective signal range that can be received.

In one embodiment, based on the above embodiment, the surface acoustic wave resonator unit 20 further includes: a bulk acoustic wave resonator.

The first end of the BAW resonator is connected to the input terminal 30 , and the second end of the BAW resonator is connected to the output terminal 40 .

For example, the bulk acoustic wave resonator is connected between the input terminal 30 and the output terminal 40, and also has the function of allowing signals of a specific resonant frequency to pass through and filtering out all signals other than the specific frequency, thereby improving the performance of the surface acoustic wave filter on the high-frequency side. The out-of-band near-end signal suppression effect. When the surface acoustic wave resonant unit 20 is a bulk acoustic wave resonator, the resonant frequency of the bulk acoustic wave resonator is the resonant frequency of the surface acoustic wave resonant unit 20 . Illustratively, the bulk acoustic wave resonator may include a thin film bulk acoustic wave resonator. Different from the surface acoustic wave resonator 21, the bulk acoustic wave resonator is made of silicon substrate using micro-electromechanical technology and thin film technology. Therefore, the preparation process of bulk acoustic wave resonators is relatively complex, and production and preparation are difficult.

In one embodiment, based on the above embodiment, the surface acoustic wave resonant unit 20 further includes: a resonant circuit, the first end of the resonant circuit is connected to the input terminal 30, and the second end of the resonant circuit is connected to the output terminal 40. For example, the resonant circuit is resistive and has the ability to select frequencies. It can retain electrical signals at specific frequencies and filter out electrical signals outside specific frequencies, thereby improving the quality of electrical signals and reducing noise or interference caused by other signals.

The resonant circuit may include a series resonant circuit 221 and a parallel resonant circuit 222 . Exemplarily, FIG. 8 is a schematic structural diagram of yet another surface acoustic wave filter provided by an embodiment of the present application. As shown in Figure 8, the resonant circuit includes an inductor 2202, a capacitor 2203 and a resistor 2201. The first end of the resistor 2201 serves as the first end of the resonant circuit. The second end of the resistor 2201 is electrically connected to the first end of the inductor 2202. The second end of the inductor 2202 is electrically connected to the first end of the capacitor 2203, and the second end of the capacitor 2203 serves as the second end of the resonant circuit, forming a series resonant circuit 221. When the surface acoustic wave resonant unit 20 is a series resonant circuit 221, the resonant frequency of the series resonant circuit 221 is the resonant frequency of the surface acoustic wave resonant unit 20.

FIG. 9 is a schematic structural diagram of another surface acoustic wave filter provided by an embodiment of the present application. As shown in Figure 9, the first end of the resistor 2201, the first end of the inductor 2202 and the first end of the capacitor 2203 are all used as the first end of the resonant circuit. The second end of the resistor 2201 and the second end of the inductor 2202 The second end of the capacitor 2203 and the second end of the capacitor 2203 serve as the second end of the resonant circuit, forming a parallel resonant circuit 222. When the surface acoustic wave resonant unit 20 is a parallel resonant circuit 222, the resonant frequency of the parallel resonant circuit 222 is the resonant frequency of the surface acoustic wave resonant unit 20.

The parameters of the inductor 2202 and the capacitor 2203 are adjusted so that the resonant frequency of the series resonant circuit 221 or the resonant frequency of the parallel resonant circuit 222 is within the adjacent band frequency range on the high-frequency side of the passband, thereby making the passband on the high-frequency side of the passband The roll-off slope increases in the transition region between the band and the stop band. Therefore, the signal suppression effect of the surface acoustic wave filter at the out-of-band near-end on the high-frequency side of the passband is improved. However, it should be noted that compared with surface acoustic wave resonators, the resonant circuit has a smaller quality factor, a larger signal energy loss, and the resonant circuit is larger in size, which is not conducive to the effect of saving circuit space.

In one embodiment, FIG. 10 is a schematic structural diagram of yet another surface acoustic wave filter provided by an embodiment of the present application. Based on the above embodiment, as shown in Figure 10, the surface acoustic wave filter also includes a piezoelectric substrate 13, and the surface acoustic wave element 10 includes: at least three odd-numbered interdigital transducers 11 and reflectors. 12.

At least three interdigital transducers 11 are arranged along the first direction, and the interdigital transducer 11 includes a plurality of electrode fingers; the plurality of electrode fingers extend along the second direction and are arranged along the first direction, wherein the first direction is the propagation direction of the surface acoustic wave signal on the piezoelectric substrate 13, and the second direction is orthogonal to the first direction;

The reflector 12 is disposed on both sides of the plurality of interdigital transducers 11 in the first direction. The reflector 12 includes a plurality of electrode fingers. The plurality of electrode fingers are arranged along the first direction and extend along the second direction.

For example, the surface acoustic wave filter includes an odd number of interdigital transducers (IDTs) 11, and the number is at least 3. An odd number of IDTs 11 are arranged in a row along the first direction, and are connected in a centrally symmetrical manner. Illustratively, one end of the centrally located interdigital transducer 11 is electrically connected to the input terminal 30 and the other end is grounded; the interdigital transducers 11 arranged on both sides adjacent to the centrally located interdigital transducer 11 One end is electrically connected to the output terminal 40, and the other end is grounded. The odd number of interdigital transducers 11 arranged in a centrally symmetrical connection manner can avoid the occurrence of small local fluctuations and improve the insertion loss in the passband of the surface acoustic wave filter.

The odd number of interdigital transducers 11 include transmitting transducers and receiving transducers. Each interdigital transducer 11 includes multiple electrode fingers, and the number of electrode fingers is not specifically limited. The direction in which the electrode fingers extend is the second direction, and the direction in which the electrode fingers extend is orthogonal to the direction of signal propagation.

Surface acoustic wave filters propagate electrical signals based on the piezoelectric effect produced by a piezoelectric substrate. When an electrical signal is input to the transmitting transducer, a potential difference is generated between adjacent electrode fingers in the transmitting transducer, thereby forming an electric field between the input electrode fingers, causing the piezoelectric substrate to mechanically vibrate and vibrate along the surface in the form of surface acoustic waves. First direction propagation. When surface acoustic waves are transmitted to the receiving transducer, charges are generated between the electrode fingers of the receiving transducer due to the piezoelectric effect, thereby outputting an alternating electrical signal to achieve signal screening and transmission.

The surface acoustic wave element 10 also includes reflectors 12, which are arranged on both sides of the odd-numbered interdigital transducers 11 arranged along the first direction, which can further suppress the occurrence of small fluctuations in the signal in the passband and improve the signal transmission in the band. of stability.

In one embodiment, the arrangement of the piezoelectric substrate 13 may refer to FIG. 12 .

An embodiment of the present application also provides a multiplexer. Figure 11 is a schematic structural diagram of a multiplexer provided by an embodiment of the present application. As shown in FIG. 11 , the multiplexer includes the surface acoustic wave filter 50 provided by any embodiment of the present application.

The multiplexer contains at least two surface acoustic wave filters 50 and has one input port and at least two output ports. For example, referring to Figure 11, the multiplexer includes an input port IN and n output ports, respectively OUT1, OUT2...OUTn. Each surface acoustic wave filter 50 is connected in series between the input port IN and any output port. For example, the surface acoustic wave filter 50 is connected in series between the input port IN and the output port OUT1, or the surface acoustic wave filter 50 is connected in series between Between input port IN and output port OUT2. The multiplexer includes the surface acoustic wave filter 50 provided in any embodiment of the present application. Therefore, the multiplexer has the beneficial effects of the surface acoustic wave filter 50 , that is, the multiplexer increases the high-frequency side of the passband and the resistance. The roll-off slope of the transition area between the bands improves the signal suppression capability of the out-of-band near-end, effectively prevents interference from other signals, and increases the operating bandwidth of the surface acoustic wave filter 50 .

It will be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions are possible depending on design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principles of this application shall be included in the protection scope of this application.

Claims

A surface acoustic wave filter including:

Surface acoustic wave element (10), the surface acoustic wave element (10) is connected between the input terminal (30) and the output terminal (40) of the surface acoustic wave filter;

Surface acoustic wave resonance unit (20), the surface acoustic wave resonance unit (20) is connected between the input terminal (30) and the output terminal (40).
The surface acoustic wave filter according to claim 1, wherein the surface acoustic wave resonance unit (20) includes: a surface acoustic wave resonator (21);

The first end of the surface acoustic wave resonator (21) is connected to the input terminal (30), and the second end of the surface acoustic wave resonator (21) is connected to the output terminal (40).
The surface acoustic wave filter according to claim 1, wherein the resonant frequency of the surface acoustic wave resonance unit (20) is located in an adjacent band frequency range of the surface acoustic wave filter close to the maximum value of the passband.
The surface acoustic wave filter according to claim 2 or 3, wherein the surface acoustic wave resonance unit (20) includes at least two surface acoustic wave resonators (21), and at least two surface acoustic wave resonators (21). The resonators (21) are connected in series;

The first end of the surface acoustic wave resonator (21) located at the head end is connected to the input terminal (30); the second end of the surface acoustic wave resonator (21) located at the end is connected to the output terminal (40).
The surface acoustic wave filter according to claim 1, wherein the surface acoustic wave resonance unit (20) further includes: a bulk acoustic wave resonator;

The first end of the bulk acoustic wave resonator is connected to the input terminal (30), and the second end of the bulk acoustic wave resonator is connected to the output terminal (40).
The surface acoustic wave filter according to claim 1, wherein the surface acoustic wave resonance unit (20) further includes: a resonance circuit;

The first end of the resonant circuit is connected to the input terminal (30), and the second end of the resonant circuit is connected to the output terminal (40).
The surface acoustic wave filter according to claim 6, wherein the resonant circuit includes an inductor (2202), a capacitor (2203) and a resistor (2201), and a first end of the resistor (2201) serves as the resonant circuit. The first end of the circuit, the second end of the resistor (2201) is electrically connected to the first end of the inductor (2202), and the second end of the inductor (2202) is electrically connected to the capacitor (2203). The first end is electrically connected, and the second end of the capacitor (2203) serves as the second end of the resonant circuit.
The surface acoustic wave filter according to claim 6, wherein the resonant circuit includes an inductor (2202), a capacitor (2203) and a resistor (2201), a first end of the resistor (2201), the inductor The first end of the resistor (2202) and the first end of the capacitor (2203) are respectively used as the first end of the resonant circuit. The second end of the resistor (2201) and the third end of the inductor (2202) The two terminals and the second terminal of the capacitor (2203) serve as the second terminal of the resonant circuit respectively.
The surface acoustic wave filter according to claim 1, further comprising a piezoelectric substrate (13), and the surface acoustic wave element (10) includes:

At least three odd-numbered interdigital transducers (11), at least three of the interdigital transducers (11) are arranged along the first direction, and each interdigital transducer (11) includes a plurality of electrodes means; a plurality of the electrode fingers extend along the second direction and are arranged along the first direction, wherein the first direction is the propagation direction of the surface acoustic wave signal on the piezoelectric substrate, and the second The direction is orthogonal to the first direction;

Reflector (12), the reflector (12) is disposed on both sides of the at least three interdigital transducers (11) along the first direction, the reflector (12) includes a plurality of electrodes Fingers, a plurality of electrode fingers are arranged along the first direction and extend along the second direction.
A multiplexer, including the surface acoustic wave filter according to any one of claims 1-9.
The multiplexer of claim 10, wherein the number of surface acoustic wave filters is at least two.
The multiplexer according to claim 11, said multiplexer further comprising an input port and a plurality of output ports;

The at least two surface acoustic wave filters are respectively connected to the one input port, and each surface acoustic wave filter in the at least two surface acoustic wave filters corresponds to one of the plurality of output ports. Output port connection.