CN114938217A - A surface acoustic wave filter and multiplexer - Google Patents

Abstract

The invention discloses a surface acoustic wave filter and a multiplexer. The surface acoustic wave filter includes: a surface acoustic wave element and a surface acoustic wave resonance unit. The surface acoustic wave element is connected between the input terminal and the output terminal; the surface acoustic wave resonance unit is connected in series between the input terminal and the output terminal. The surface acoustic wave filter provided by the technical solution of the embodiment of the present invention can increase the roll-off slope of the transition region between the passband and the stopband, improve the signal suppression capability of the out-of-band near-end on the high-frequency side of the passband, and ensure that the The transmitted signal within the passband is of higher quality.

Description

A surface acoustic wave filter and multiplexer

technical field

Embodiments of the present invention relate to the technical field of filtering, and in particular, 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 prolong the service life of communication equipment and power equipment. In the current 5G complex communication circuit, saving circuit space and cost is a major problem in circuit design. In the prior art, a smaller volume surface acoustic wave filter is used, which can save circuit space. However, using the surface acoustic wave filter in the filter circuit has the problem of poor suppression effect at the near end outside the passband, thus affecting the quality of the communication signal.

SUMMARY OF THE INVENTION

The invention provides a surface acoustic wave filter and a multiplexer, so as to improve the out-of-band signal suppression effect at the near-end of the high-frequency side of the passband and improve the quality of the communication signal.

According to an aspect of the present invention, there is provided a surface acoustic wave filter, the surface acoustic wave filter comprising:

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

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

Optionally, the surface acoustic wave resonance unit includes: a surface acoustic wave resonator;

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

Optionally, the resonant frequency of the surface acoustic wave resonator unit is located in the adjacent band frequency range of the surface acoustic filter close to the maximum value of the pass band.

Optionally, the surface acoustic wave resonance unit includes at least two of the surface acoustic wave resonators, and at least two of the surface acoustic wave resonators are connected in series;

The first end of the surface acoustic wave resonator located at the head end is connected to the input terminal; the second end of the surface acoustic wave resonator located at the end is connected to the output terminal.

Optionally, the surface acoustic wave resonance unit further includes: a bulk acoustic wave resonator;

The first end of the bulk acoustic wave resonator is connected to the input terminal, and the second end of the bulk acoustic wave resonator is connected to the output terminal.

Optionally, the surface acoustic wave resonance unit further includes: a resonance circuit,

The first end of the resonance circuit is connected to the input terminal, and the second end of the resonance circuit is connected to the output terminal.

Optionally, the resonant circuit includes an inductor, a capacitor and a resistor, a first end of the resistor serves as a first end of the resonant circuit, and a second end of the resistor is electrically connected to the first end of the inductor. connected, the second end of the inductor is electrically connected to the first end of the capacitor, and the second end of the capacitor serves as the second end of the resonant circuit.

Optionally, the resonant circuit includes an inductor, a capacitor and a resistor, and the first end of the resistor, the first end of the inductor and the first end of the capacitor are all used as the first end of the resonant circuit , the second end of the resistor, the second end of the inductor and the second end of the capacitor are all used as the second end of the resonant circuit.

Optionally, the surface acoustic wave filter further includes a piezoelectric substrate, and the surface acoustic wave element includes:

At least three odd-numbered interdigital transducers, at least three of the interdigital transducers are arranged along the first direction, and the interdigital transducer includes a plurality of electrode fingers; the plurality of electrode fingers are arranged along the first direction. extending in two directions and 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 direction is orthogonal to the first direction;

a reflector, the reflectors are arranged on both sides of the plurality of interdigital transducers along the first direction, the reflector includes a plurality of electrode fingers, and the plurality of electrode fingers are arranged along the first direction arranged in a direction extending along the second direction.

According to another aspect of the present invention, a multiplexer is provided, and the multiplexer includes the surface acoustic wave filter provided in any embodiment of the present invention.

In the surface acoustic wave filter provided by the embodiment of the present invention, by adding a surface acoustic wave resonance unit between the input terminal and the output terminal, the surface acoustic wave resonance unit can perform the corresponding frequency signal on the passband edge position of the surface acoustic wave filter. Suppression, so that the steep drop at the transition region between the passband and the stopband of the 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 improve the frequency corresponding to the edge of the passband the transmission quality of electrical signals.

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

Description of drawings

In order to illustrate the technical solutions in the embodiments of the present invention more clearly, the following briefly introduces the accompanying drawings used in the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained from these drawings without creative effort.

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

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

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

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

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

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

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

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

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

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

FIG. 11 is a schematic structural diagram of a multiplexer according to an embodiment of the present invention.

Detailed ways

In order to make those skilled in the art better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only Embodiments are part of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

It should be noted that the terms "first", "second" and the like in the description and claims of the present invention and the above drawings are used to distinguish similar objects, and are not necessarily used to describe a specific sequence or sequence. It is to be understood that the data so used may be interchanged under appropriate circumstances such that the embodiments of the invention described herein can be practiced in sequences other than those illustrated or described herein. Furthermore, the terms "comprising" and "having" and any variations thereof, are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those expressly listed Rather, those steps or units may include other steps or units not expressly listed or inherent to these processes, methods, products or devices.

Embodiments of the present invention provide a surface acoustic wave filter. FIG. 1 is a schematic structural diagram of a surface acoustic wave filter according to an embodiment of the present invention. As shown in FIG. 1 , the surface acoustic wave filter includes a surface acoustic wave element 10 and a surface acoustic wave resonance 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 .

Specifically, the surface acoustic wave element 10 utilizes the characteristics of the acoustic-electric transducer to realize acousto-electric conversion, so that the electrical signal can be converted into a surface acoustic wave for transmission, so as to realize the propagation of the electrical signal. 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 an electrical signal is input to the surface acoustic wave element 10 from the input terminal 30, the surface of the substrate of the surface acoustic wave element 10 generates mechanical vibration, and simultaneously excites a surface acoustic wave with the same frequency as the applied electrical signal, and the surface acoustic wave can propagate along the surface of the substrate. Propagation, and output by the output terminal 40, so as to realize the propagation of the electrical signal. 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, using the surface acoustic wave element 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 whole of the surface acoustic wave element 10 is electrically connected to the input terminal 30. The surface acoustic wave resonance unit 20 is connected in parallel, and is connected between the input terminal 30 and the output terminal 40 . The surface acoustic wave resonance unit 20 has the capability of frequency selection, which can retain electrical signals of a specific frequency and filter out electrical signals other than a specific frequency. Exemplarily, the surface acoustic wave resonator unit 20 can filter out the signal of the frequency corresponding to the out-of-band near-end on the high-frequency side of the passband, so as to achieve a good suppression effect of the out-of-band near-end electrical signal, so that the gap between the passband and the stopband is reduced. The roll-off slope of the transition phase increases. Therefore, the out-of-band suppression capability of the surface acoustic wave filter is improved, the filtering effect is good, and the quality of the electrical signal transmitted by the surface acoustic wave filter is improved.

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 affect the passband edge position of the surface acoustic wave filter. The corresponding frequency signal is suppressed, so that the steep drop at the transition region between the passband and the stopband of the 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 improve the frequency corresponding to the edge of the passband the transmission quality of electrical signals.

Optionally, FIG. 2 is a schematic structural diagram of still another surface acoustic wave filter provided by an embodiment of the present invention. On the basis of the above embodiment, as shown in FIG. 2 , the surface acoustic wave resonator 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 .

Specifically, the surface acoustic wave resonator 21 mainly uses the piezoelectric properties of the piezoelectric material to perform an electro-acoustic-electric 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 a surface acoustic wave by the input transducer in the surface acoustic wave resonator 21, and mechanical vibration occurs. Among them, the mechanical vibration of 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 the output transducer converts the transmitted mechanical vibration of a specific frequency into electrical energy. The signal is output by the output terminal 40; and the mechanical vibration whose frequency is different from the resonant frequency of the surface acoustic wave resonator 21 cannot propagate along the surface of the piezoelectric material, so the surface acoustic wave resonator 21 can realize the electrical signal of a specific frequency. Transmission and filtering of unwanted frequency electrical signals. 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 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.

Optionally, on the basis of the above embodiment, the resonance frequency of the surface acoustic wave resonator unit 20 is located in the adjacent band frequency range of the surface acoustic filter close to the maximum value of the passband.

Specifically, when the surface acoustic wave resonance unit 20 is the surface acoustic wave resonator 21 , the resonance frequency of the surface acoustic wave resonator 21 is the resonance frequency of the surface acoustic wave resonance unit 20 . The resonant frequency of the surface acoustic wave resonator 21 can be set to any frequency value according to actual application requirements. Adjacent band frequencies are the range of channel frequencies immediately adjacent to both sides of the passband range of the main channel. Preferably, the resonant frequency of the surface acoustic wave resonator 21 is set in the adjacent band frequency range of the surface acoustic wave filter close to the maximum value of the pass band, so that the steep drop of the high frequency side of the pass band in the adjacent band frequency range can be increased, Attenuate the interference of the adjacent channel signal to the signal transmitted by the main channel; and, the surface acoustic wave resonator 21 forms an additional transmission zero point in the adjacent band frequency range on the high frequency side of the passband, adding a new resonance peak, thereby widening the The passband bandwidth of the SAW filter.

Exemplarily, FIG. 3 is a graph showing an insertion loss characteristic of a surface acoustic wave filter provided by an embodiment of the present invention. Illustratively, the resonance frequency of the surface acoustic wave resonator may be set to 1.03 GHz. As shown in FIG. 3 , the dotted line 100 is the insertion loss characteristic curve of the transmission signal obtained by the traditional filter circuit test; the solid line 200 is the insertion loss characteristic curve of the transmission signal obtained by the surface acoustic wave filter test provided in this embodiment.

It can be seen from Figure 3 that the traditional filter circuit represented by the dotted line 100 has a steep drop in the insertion loss of the signal on the low-frequency side of the passband, that is, in the range of 0.99-0.98GHz, indicating that on the low-frequency side, the out-of-band suppression effect of the traditional filter circuit is better. Good; on the high-frequency side of the passband, that is, at the frequency of 1.02GHz, the transmitted signal strength begins to decay slowly, and the decay 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 is weakened, and it is easily affected by other signals of the same frequency, and the signal quality is degraded. However, in the surface acoustic wave filter provided by the embodiment indicated 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 acoustic resonance frequency of 1.03 GHz The effect of the surface wave resonator makes the insertion loss of the signal increase steeply in the frequency range of 1.028-1.03GHz at the edge of the passband, that is, the roll-off slope increases. Therefore, connecting the SAW resonator between the input terminal and the output terminal can improve the signal quality of the edge part of the passband, and at the same time, the bandwidth of the passband can be expanded, that is, the bandwidth can be expanded from the frequency range of 0.988-1.02GHz to 0.988-1.028GHz frequency range.

FIG. 4 is an admittance characteristic curve diagram of a surface acoustic wave filter provided by an embodiment of the present invention. It should be noted that the conductance is used to describe the difficulty of the alternating current passing through the circuit. The conductance is composed of conductance and susceptance. Among them, the real part of the conductance represents the conductance, and the higher the conductance value, the easier it is for the electric charge to pass through. As shown in FIG. 4 , the dotted line 101 is the admittance characteristic curve of the conventional 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 adds a new resonance peak at a frequency of about 1.028 GHz, and the conductance value is high, indicating that the SAW filter can receive electrical signals with a frequency of 1.028 GHz. Therefore, it can be shown that connecting the surface acoustic wave resonator between the input terminal and the output terminal can increase the bandwidth of the surface acoustic wave filter.

Optionally, FIG. 5 is a schematic structural diagram of still another surface acoustic wave filter provided by an embodiment of the present invention. On the basis of the above embodiment, as shown in FIG. 5 , the surface acoustic wave resonator 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 at the head end is connected to the input terminal 30 , and the second end of the surface acoustic wave resonator 21 at the end is connected to the output terminal 40 .

Specifically, 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, the number of surface acoustic wave resonators 21 is It can be connected in series or in parallel. Exemplarily, 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 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 of the acoustic wave resonator 21. The first end of the surface wave resonator 21 and the second end of the surface acoustic wave resonator 21 at the end are connected to the output terminal 40 .

FIG. 6 is an insertion loss characteristic curve of another surface acoustic wave filter provided by an embodiment of the present invention. As shown in FIG. 6 , the dotted line 102 is the signal insertion loss characteristic curve of the conventional 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 the series connection of two SAW resonators 21 with different resonant frequencies can also increase the roll-off slope of the signal insertion loss in the transition region of the passband edge, thereby improving the band of the SAW filter on the high frequency side. The signal suppression effect of the outer and near ends improves the quality of the transmitted signal. However, when two SAW resonators 21 are connected in series, there is a large ripple on the high frequency side during in-band signal transmission, and the signal transmission is unstable. Therefore, by connecting a surface acoustic wave resonator 21 between the input terminal and the output terminal, the in-band signal transmission has higher stability and better signal quality.

Since the effect of connecting two SAW resonators 21 with the same resonant frequency in series is the same as that of connecting one SAW resonator 21 with the same resonant frequency, when the SAW resonator unit 20 is a plurality of SAW resonators 21, the resonant frequency of each surface acoustic wave resonator 21 is set in the adjacent band frequency range of the surface acoustic wave filter close to the maximum value of the passband, and there is a slight difference between them, then the resonant frequency of the surface acoustic wave resonator unit 20 It is equal to the maximum resonance frequency among the plurality of surface acoustic wave resonators 21 . Exemplarily, the resonant frequencies of the two surface acoustic wave resonators 21 can be set to two different values around 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 GHz, respectively. GHz. FIG. 7 is an admittance characteristic curve of another surface acoustic wave filter provided by an embodiment of the present invention. As shown in FIG. 7 , the dotted line 103 is the admittance characteristic curve of the conventional 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 the bandwidth of the surface acoustic wave filter can also be widened by connecting two surface acoustic wave resonators 21 in series. And compared with connecting one SAW resonator 21, connecting two SAW resonators 21 with slightly different resonance frequencies in series can further widen the bandwidth from 1.028GHz to 1.03GHz, increasing the bandwidth range of the SAW filter. , widen the effective signal range that can be received.

Optionally, on the basis of the foregoing embodiment, the surface acoustic wave resonance 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 .

Specifically, the BAW 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 all signals other than the specific frequency, so as to improve the performance of the surface acoustic wave filter at high frequencies. out-of-band near-end signal suppression effect. When the surface acoustic wave resonance unit 20 is a bulk acoustic wave resonator, the resonance frequency of the bulk acoustic wave resonator is the resonance frequency of the surface acoustic wave resonance unit 20 . Illustratively, the bulk acoustic wave resonator may comprise a thin film bulk acoustic wave resonator. Different from the surface acoustic wave resonator 21 , the bulk acoustic wave resonator is fabricated by using a silicon substrate with the help of microelectromechanical technology and thin film technology. Therefore, the preparation process of the bulk acoustic wave resonator is relatively complicated, and the production and preparation are difficult.

Optionally, based on the above embodiment, the surface acoustic wave resonance unit 20 further includes: a resonance circuit, the first end of the resonance circuit is connected to the input terminal 30 , and the second end of the resonance circuit is connected to the output terminal 40 . Specifically, the resonant circuit is resistive and has frequency selection ability, which can retain electrical signals of a specific frequency and filter out electrical signals other than a specific frequency, thereby improving the quality of electrical signals and reducing noise or interference generated by other signals. .

The resonance circuit may include a series resonance circuit 221 and a parallel resonance circuit 222 . Exemplarily, FIG. 8 is a schematic structural diagram of still another surface acoustic wave filter provided by an embodiment of the present invention. As shown in FIG. 8 , the resonant circuit includes an inductor 2202, a capacitor 2203 and a resistor 2201. The first end of the resistor 2201 is used as the first end of the resonant circuit, and 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 to form a series resonant circuit 221 . When the surface acoustic wave resonance unit 20 is the series resonance circuit 221 , the resonance frequency of the series resonance circuit 221 is the resonance frequency of the surface acoustic wave resonance unit 20 .

FIG. 9 is a schematic structural diagram of another surface acoustic wave filter provided by an embodiment of the present invention. As shown in FIG. 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 capacitor 2203 are both used as the second end of the resonant circuit to form a parallel resonant circuit 222 . When the surface acoustic wave resonance unit 20 is a parallel resonance circuit 222 , the resonance frequency of the parallel resonance circuit 222 is the resonance frequency of the surface acoustic wave resonance 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 located in the adjacent band frequency range on the high-frequency side of the passband, so that the passband on the high-frequency side of the passband can be adjusted. The roll-off slope of the transition region between the band and stop band increases. 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 the surface acoustic wave resonator, the resonant circuit has a smaller quality factor, a larger signal energy loss, and a larger volume of the resonant circuit, which is not conducive to achieving the effect of saving circuit space.

Optionally, FIG. 10 is a schematic structural diagram of still another surface acoustic wave filter provided by an embodiment of the present invention. On the basis of the above embodiment, as shown in FIG. 10 , the SAW filter further includes a piezoelectric substrate, and the SAW 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, and the second direction is orthogonal to the first direction;

The reflectors 12 are disposed on both sides of the plurality of interdigital transducers 11 along the first direction. The reflectors 12 include a plurality of electrode fingers, which are arranged along the first direction and extend along the second direction.

Specifically, the surface acoustic wave filter includes an odd number of interdigital transducers (IDTs) 11, and the minimum number is three. The odd-numbered interdigital transducers 11 are arranged in a row along the first direction, and the connection mode is in the form of center symmetry. Exemplarily, one end of the interdigital transducer 11 at the central position 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 interdigital transducer 11 at the central position One end is electrically connected to the output terminal 40, and the other end is grounded. The odd-numbered interdigital transducers 11 arranged in a center-symmetric connection manner can avoid the problem of small fluctuations locally, and improve the insertion loss in the passband of the surface acoustic wave filter.

The odd-numbered interdigital transducers 11 include a transmitting transducer and a receiving transducer. Each interdigital transducer 11 includes a plurality of electrode fingers, and the number of the electrode fingers is not specifically limited. The extending direction of the electrode fingers is the second direction, and the extending direction of the electrode fingers is orthogonal to the signal propagation direction.

The surface acoustic wave filter propagates electrical signals according to the piezoelectric effect generated by the piezoelectric substrate. When the electrical signal is input into the transmitting transducer, a potential difference is generated between the adjacent electrode fingers in the transmitting transducer, thereby forming an electric field between the input electrode fingers, causing the piezoelectric substrate to vibrate mechanically, and along the surface acoustic waves in the form of surface acoustic waves. Propagation in the first direction. When the surface acoustic wave is transmitted to the receiving transducer, electric charges will be generated between the electrode fingers of the receiving transducer due to the piezoelectric effect, thereby outputting an alternating electrical signal to realize the screening and transmission of the signal.

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 generation of small fluctuations of signals in the passband and improve the transmission of signals in the band. stability.

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

The multiplexer includes at least two surface acoustic wave filters 50, and has one input port and at least two output ports. Illustratively, referring to FIG. 11 , the multiplexer includes an input port IN and n output ports, namely OUT1 , OUT2 . . . OUTn. Each SAW filter 50 is connected in series between the input port IN and any output port, for example, the SAW filter 50 is connected in series between the input port IN and the output port OUT1, or the SAW filter 50 is connected in series with Between the input port IN and the output port OUT2. The multiplexer includes the surface acoustic wave filter 50 provided in any embodiment of the present invention. Therefore, the multiplexer has the beneficial effect 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 region between the bands improves the signal rejection capability of the out-of-band near-end, effectively prevents the interference of other signals, and increases the working bandwidth of the surface acoustic wave filter 50 .

The above-mentioned specific embodiments do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions may occur depending on design requirements and other factors. Any modifications, equivalent replacements and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. a surface acoustic wave filter, is characterized in that, comprises: a surface acoustic wave element, the surface acoustic wave element is connected between the input terminal and the output terminal of the surface acoustic wave filter; A surface acoustic wave resonance unit, the surface acoustic wave resonance unit is connected between the input terminal and the output terminal. 2. The surface acoustic wave filter according to claim 1, wherein the surface acoustic wave resonance unit comprises: a surface acoustic wave resonator; The first end of the surface acoustic wave resonator is connected to the input terminal, and the second end of the surface acoustic wave resonator is connected to the output terminal. 3 . The surface acoustic wave filter according to claim 1 , wherein the resonance frequency of the surface acoustic wave resonating unit is located in the adjacent band frequency range of the surface acoustic wave filter close to the maximum value of the passband. 4 . 4. The surface acoustic wave filter according to claim 2 or 3, wherein the surface acoustic wave resonance unit comprises at least two of the surface acoustic wave resonators, and at least two of the surface acoustic wave resonators connected in series; The first end of the surface acoustic wave resonator located at the head end is connected to the input terminal; the second end of the surface acoustic wave resonator located at the end is connected to the output terminal. 5. The surface acoustic wave filter according to claim 1, wherein the surface acoustic wave resonance unit further comprises: a bulk acoustic wave resonator; The first end of the bulk acoustic wave resonator is connected to the input terminal, and the second end of the bulk acoustic wave resonator is connected to the output terminal. 6. The surface acoustic wave filter according to claim 1, wherein the surface acoustic wave resonance unit further comprises: a resonance circuit, The first end of the resonance circuit is connected to the input terminal, and the second end of the resonance circuit is connected to the output terminal. 7 . The surface acoustic wave filter according to claim 6 , wherein the resonant circuit comprises an inductor, a capacitor and a resistor, and the first end of the resistor serves as the first end of the resonant circuit, and the The second end of the resistor is electrically connected to the first end of the inductor, the second end of the inductor is electrically connected to the first end of the capacitor, and the second end of the capacitor serves as the first end of the resonant circuit. two ends. 8. The surface acoustic wave filter according to claim 6, wherein the resonant circuit comprises an inductor, a capacitor and a resistor, the first end of the resistor, the first end of the inductor and the The first end of the capacitor is used as the first end of the resonant circuit, the second end of the resistor, the second end of the inductor and the second end of the capacitor are all used as the second end of the resonant circuit . 9. The surface acoustic wave filter of claim 1, further comprising a piezoelectric substrate, the surface acoustic wave element comprising: At least three odd-numbered interdigital transducers, at least three of the interdigital transducers are arranged along the first direction, and the interdigital transducer includes a plurality of electrode fingers; the plurality of the electrode fingers are arranged along the first direction. extending in two directions and 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 direction is orthogonal to the first direction; a reflector, the reflectors are arranged on both sides of the plurality of interdigital transducers along the first direction, the reflector includes a plurality of electrode fingers, and the plurality of electrode fingers are arranged along the first direction arranged in a direction extending along the second direction. 10. A multiplexer, comprising the surface acoustic wave filter according to any one of claims 1-9.

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