Filter, high-frequency device, and electronic device

Abstract

The present invention provides a filter, a high-frequency device, and an electronic device. The filter includes a series branch circuit, N parallel branch circuits, and a bridge branch circuit. The series branch circuit includes M series resonators installed in series. Each parallel branch circuit includes a parallel resonator. The bridge branch circuit includes a bridge resonator and a first inductor. Each parallel branch circuit includes an opposing first end and a second end. The first end of each parallel branch circuit is grounded, and the second end of each parallel branch circuit is connected to the series branch circuit. The bridge branch circuit includes a third end and a fourth end. The third end is located on the side away from the first inductor of the bridge resonator, and the fourth end is located on the side away from the bridge resonator of the first inductor. The third end is connected to the first end of the i-th parallel branch circuit, and the fourth end is connected to the second end of the (i + k)-th parallel branch circuit. Both M and N are positive integers of 3 or more. i is a positive integer of 1 or more and N - 2 or less, and k is a positive integer of 2 or more. Thereby, the filter can simultaneously reduce the insertion loss and improve the out-of-band rejection performance.

Description

Technical Field

[0001] Embodiments of the present disclosure relate to filters, high-frequency devices, and electronic devices.

Background Art

[0002] With the rapid development of mobile communication technology, the application of high-frequency devices has been greatly expanded. As an important component in high-frequency devices, the usage of filters has increased significantly, thereby causing the filter market to grow explosively. Currently, the filters applied to personal mobile terminals (e.g., mobile phones) are piezoelectric acoustic wave filters, which are mainly composed of resonators. These resonators may include thin-film bulk acoustic wave resonators (FBARs), solidly mounted resonators (SMRs), and surface acoustic wave resonators (SAWs). The thin-film bulk acoustic wave resonators (FBARs) and solidly mounted resonators (SMRs) may be collectively referred to as BAW (bulk acoustic wave resonators).

[0003] The operating principle of a surface acoustic wave resonator is to convert an electrical signal into an acoustic wave propagating on the surface of a piezoelectric layer by an interdigital transducer, and its resonance frequency may be determined by the distance between strip electrodes in the interdigital transducer. The operating principle of a bulk acoustic wave resonator is to convert an electrical signal into a bulk acoustic wave propagating along the thickness direction of a piezoelectric layer, and the resonance frequency is determined by the thickness of the piezoelectric layer. The difference between a thin-film bulk acoustic wave resonator and a solidly mounted resonator is that the thin-film bulk acoustic wave resonator utilizes the fact that the acoustic impedance of air is almost zero to achieve total reflection of acoustic waves at the interface, while the solidly mounted resonator realizes total reflection based on a Bragg reflection layer composed of alternately arranged high-acoustic-impedance layers and low-acoustic-impedance layers.

Summary of the Invention

Problems to be Solved by the Invention

[0004] Embodiments of the present disclosure provide a filter, a high-frequency device, and an electronic device. After the bridge resonator is connected in series to the first inductor and bridged between the first end of the i-th parallel branch circuit and the second end of the (i + 2)-th parallel branch circuit, two zero points can be added within the passband by introducing the bridge resonator. By moving these two zero points to appropriate positions outside the passband according to the value of the first inductor, the out-of-band suppression can be increased, and the impedance matching of the input and output ports can be optimized, thereby reducing the insertion loss. As a result, the filter can simultaneously reduce the insertion loss and improve the out-of-band suppression performance.

Means for Solving the Problems

[0005] At least one embodiment of the present disclosure provides a filter, which includes a series branch circuit including M series resonators installed in series, N parallel branch circuits each including a parallel resonator, and a bridge branch circuit including a bridge resonator and a first inductor. Each of the parallel branch circuits includes opposite first and second ends. The first end of each of the parallel branch circuits is grounded, the second end of each of the parallel branch circuits is connected to the series branch circuit. The bridge branch circuit includes a third end and a fourth end. The third end is located on the side away from the first inductor of the bridge resonator, the fourth end is located on the side away from the bridge resonator of the first inductor. The third end is connected to the first end of the i-th parallel branch circuit, the fourth end is connected to the second end of the (i + k)-th parallel branch circuit, where M and N are both positive integers greater than or equal to 3, i is a positive integer greater than or equal to 1 and less than or equal to N - k, and k is a positive integer greater than or equal to 2.

[0006] For example, in the filter according to an embodiment of the present disclosure, the value of k is 2.

[0007] For example, in the filter according to an embodiment of the present disclosure, the second end of the first parallel branch circuit is located between the first series resonator and the second series resonator, the second end of the j-th parallel branch circuit is located between the j-th series resonator and the (j + 1)-th series resonator, the second end of the N-th parallel branch circuit is located between the N-th series resonator and the (N - 1)-th series resonator, and j is a positive integer greater than 1 and less than N.

[0008] For example, in the filter according to an embodiment of the present disclosure, the value of i is 1, and the values of M and N are equal.

[0009] For example, in the filter according to an embodiment of the present disclosure, the series branch circuit includes an input end and an output end installed opposite to each other, the M series resonators are installed between the input end and the output end, and the filter further includes a second inductor installed in parallel with the first series resonator.

[0010] For example, in the filter according to an embodiment of the present disclosure, the value range of the inductance of the second inductor is 5 nH to 9 nH.

[0011] For example, the filter according to an embodiment of the present disclosure further includes a third inductor having one end grounded and the other end connected to the output end.

[0012] For example, in the filter according to an embodiment of the present disclosure, the value range of the inductance of the third inductor is 10 nH to 17 nH.

[0013] For example, in the filter according to an embodiment of the present disclosure, the value range of the inductance of the first inductor is 10 nH to 17 nH.

[0014] For example, in the filter according to an embodiment of the present disclosure, the series branch circuit includes an input end and an output end installed opposite to each other, the M series resonators are installed between the input end and the output end, and the filter further includes a fourth inductor installed in series between the first series resonator and the second end of the first parallel branch circuit.

[0015] For example, in the filter according to an embodiment of the present disclosure, the value range of the inductance of the first inductor is 11 nH to 18 nH, and the value range of the inductance of the fourth inductor is 0.3 nH to 0.7 nH.

[0016] For example, in the filter according to an embodiment of the present disclosure, the filter further includes a fifth inductor installed in series between the first end of the Nth parallel branch circuit and the parallel resonator.

[0017] For example, in the filter according to an embodiment of the present disclosure, the value range of the inductance of the first inductor is 10 nH to 17 nH, and the value range of the inductance of the fifth inductor is 4.5 nH to 6.5 nH.

[0018] For example, in the filter according to an embodiment of the present disclosure, at least one of the M series resonators and the parallel resonators in the N parallel branch circuits is a bulk acoustic wave resonator.

[0019] For example, in the filter according to an embodiment of the present disclosure, the bulk acoustic wave resonator includes a substrate, a piezoelectric thin film, a first driving electrode, and a second driving electrode.

[0020] For example, in a filter according to an embodiment of the present disclosure, the M series resonators include a first bulk acoustic wave resonator and a second bulk acoustic wave resonator. The first bulk acoustic wave resonator and the second bulk acoustic wave resonator adopt the structure of the bulk acoustic wave resonator. The filter further includes an insulating layer, and a first connection electrode, a second connection electrode, a third connection electrode, and a fourth connection electrode located on a side of the insulating layer away from the substrate. The first connection electrode is electrically connected to the first drive electrode of the first bulk acoustic wave resonator by vias located in the insulating layer and the piezoelectric thin film. The second connection electrode is electrically connected to the second drive electrode of the first bulk acoustic wave resonator by vias located in the insulating layer. The third connection electrode is electrically connected to the first drive electrode of the second bulk acoustic wave resonator by vias located in the insulating layer and the piezoelectric thin film. The fourth connection electrode is connected to the second drive electrode of the second bulk acoustic wave resonator by vias located in the insulating layer. The third connection electrode is connected to the second connection electrode so as to connect the first bulk acoustic wave resonator and the second bulk acoustic wave resonator in series.

[0021] For example, in a filter according to an embodiment of the present disclosure, the i-th parallel branch circuit includes a first bulk acoustic wave resonator, and the bridge resonator includes a second bulk acoustic wave resonator. The first bulk acoustic wave resonator and the second bulk acoustic wave resonator adopt the structure of the bulk acoustic wave resonator. The filter further includes an insulating layer, and a first connection electrode, a second connection electrode, a third connection electrode, and a fourth connection electrode located on a side of the insulating layer away from the substrate. The first connection electrode is electrically connected to the first drive electrode of the first bulk acoustic wave resonator by vias located in the insulating layer and the piezoelectric thin film. The second connection electrode is electrically connected to the second drive electrode of the first bulk acoustic wave resonator by vias located in the insulating layer. The third connection electrode is electrically connected to the first drive electrode of the second bulk acoustic wave resonator by vias located in the insulating layer and the piezoelectric thin film. The fourth connection electrode is connected to the second drive electrode of the second bulk acoustic wave resonator by vias located in the insulating layer. The third connection electrode is connected to the second connection electrode so as to connect the first bulk acoustic wave resonator and the second bulk acoustic wave resonator in series.

[0022] For example, in a filter according to an embodiment of the present disclosure, the bulk acoustic wave filter further includes an air gap located inside the substrate, the first drive electrode is located on the side of the piezoelectric thin film close to the substrate, the second drive electrode is located on the side of the piezoelectric thin film away from the substrate, the air gap is located on the side of the substrate close to the first drive electrode, or the air gap is located on the side of the substrate away from the first drive electrode.

[0023] For example, in a filter according to an embodiment of the present disclosure, the M series resonators include a third bulk acoustic wave resonator and a fourth bulk acoustic wave resonator, the third bulk acoustic wave resonator and the fourth bulk acoustic wave resonator adopt the structure of the bulk acoustic wave resonator, the first drive electrode of the third bulk acoustic wave resonator is located on the side of the piezoelectric thin film away from the substrate, the second drive electrode of the third bulk acoustic wave resonator is located on the side of the piezoelectric thin film close to the substrate, the first drive electrode of the fourth bulk acoustic wave resonator is located on the side of the piezoelectric thin film close to the substrate, the second drive electrode of the fourth bulk acoustic wave resonator is located on the side of the piezoelectric thin film away from the substrate, and the second drive electrode of the third bulk acoustic wave resonator and the first drive electrode of the fourth bulk acoustic wave resonator are installed in the same layer and electrically connected so that the third bulk acoustic wave resonator and the fourth bulk acoustic wave resonator are connected in series.

[0024] For example, in a filter according to an embodiment of the present disclosure, the i-th parallel branch circuit includes a third bulk acoustic wave resonator, the bridge resonator includes a fourth bulk acoustic wave resonator, the third bulk acoustic wave resonator and the fourth bulk acoustic wave resonator adopt the structure of the bulk acoustic wave resonator, the first drive electrode of the third bulk acoustic wave resonator is located on the side away from the substrate of the piezoelectric thin film, the second drive electrode of the third bulk acoustic wave resonator is located on the side close to the substrate of the piezoelectric thin film, the first drive electrode of the fourth bulk acoustic wave resonator is located on the side close to the substrate of the piezoelectric thin film, the second drive electrode of the fourth bulk acoustic wave resonator is located on the side away from the substrate of the piezoelectric thin film, and the second drive electrode of the third bulk acoustic wave resonator and the first drive electrode of the fourth bulk acoustic wave resonator are installed in the same layer and electrically connected so that the third bulk acoustic wave resonator and the fourth bulk acoustic wave resonator are connected in series.

[0025] For example, in a filter according to an embodiment of the present disclosure, the bulk acoustic wave filter further includes a high acoustic impedance layer and a low acoustic impedance layer which are alternately installed, and the high acoustic impedance layer and the low acoustic impedance layer are located on the side close to the substrate of the piezoelectric thin film.

[0026] For example, in the filter according to an embodiment of the present disclosure, the bridge resonator includes a fifth bulk acoustic wave resonator, the (i + k)-th series resonator includes a sixth bulk acoustic wave resonator, the fifth bulk acoustic wave resonator and the sixth bulk acoustic wave resonator adopt the structure of the bulk acoustic wave resonator, the filter further includes an insulating layer, and a fifth connection electrode, a sixth connection electrode, a seventh connection electrode, and an eighth connection electrode located on a side of the insulating layer away from the substrate. The fifth connection electrode is electrically connected to the first drive electrode of the fifth bulk acoustic wave resonator through vias located in the insulating layer and the piezoelectric thin film. The sixth connection electrode is electrically connected to the second drive electrode of the fifth bulk acoustic wave resonator through vias located in the insulating layer. The seventh connection electrode is electrically connected to the first drive electrode of the sixth bulk acoustic wave resonator through vias located in the insulating layer and the piezoelectric thin film. The eighth connection electrode is connected to the second drive electrode of the sixth bulk acoustic wave resonator through vias located in the insulating layer. The first inductor is located on a side of the insulating layer away from the substrate and is connected to the sixth connection electrode and the eighth connection electrode, respectively.

[0027] For example, in the filter according to an embodiment of the present disclosure, the first inductor is a single-layer inductor or a three-dimensional inductor.

[0028] At least one embodiment of the present disclosure further provides a high-frequency device including the filter according to any one of the above items.

[0029] At least one embodiment of the present disclosure further provides an electronic device including the above filter.

[0030] To more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings of the embodiments will be briefly described below. Obviously, the drawings described below relate to a part of the embodiments of the present disclosure and do not limit the present disclosure.

Brief Description of the Drawings

[0031]

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DETAILED DESCRIPTION OF THE INVENTION

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present disclosure clearer, the following will clearly and completely describe the technical solutions of the embodiments of the present disclosure with reference to the drawings of the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of them. Based on the described embodiments of the present disclosure, any other embodiments obtained by those skilled in the art without creative labor all fall within the protection scope of the present disclosure.

[0033] Unless otherwise defined, technical terms or scientific terms used in the present disclosure should have the ordinary meanings understood by those skilled in the art within the field to which the present disclosure belongs. The "first", "second", and similar terms used in the present disclosure do not indicate any order, number, or importance, but are only used to distinguish different components. Similar terms such as "comprise" or "include" refer to covering the elements or members described before the term and the elements or members enumerated after the term and their equivalents, and do not exclude other elements or members. Similar terms such as "connect" or "couple" are not limited to physical or mechanical connections, and may include electrical connections, whether direct or indirect.

[0034] Unless otherwise defined, features such as "parallel", "perpendicular", and "same" used in the embodiments of the present disclosure include both situations of "parallel", "perpendicular", "same", etc. in a strict sense and situations including a certain error such as "substantially parallel", "substantially perpendicular", "substantially same", etc. For example, the above "substantially" may indicate that the difference between the objects being compared is within 10% or 5% of the average value of the objects being compared. If the number of a member or element is not specifically indicated in the following description of the embodiments of the present disclosure, it means that the member or element may be one or more, or may be understood as at least one. "At least one" refers to one or more, and "a plurality" refers to at least two.

[0035] Regarding the filter applied to a high-frequency device, its important performance indicators include insertion loss, out-of-band rejection, and roll-off coefficient, etc. The insertion loss is always indicated by the parameter IL (Insert Loss). Since the signal cannot reach the output end completely, energy loss will inevitably occur when passing through the filter. The insertion loss defines this energy loss and may be expressed as the ratio of the input power Pin to the output power PL, that is, IL(dB)=10*lg(Pin / PL)=-S21. Here, S21 is the transmission coefficient from the input end to the output end and may be tested by a vector network analyzer. The out-of-band rejection is the attenuation amount outside the passband range of the filter and indicates the suppression ability for unnecessary frequency signals. The roll-off coefficient, also known as the rectangularity coefficient, represents the steepness of the transition band of the filter. The steeper it is, the better the frequency selection performance of the filter. The roll-off coefficient may generally be indicated by the ratio of the 60dB bandwidth to the 3dB bandwidth.

[0036] Figure 1 is a schematic diagram of a bulk acoustic wave filter. As shown in Figure 1, the bulk acoustic wave filter 10 includes an input end 11, an output end 12, a series branch circuit 13 connected between the input end 11 and the output end 12, and three parallel branch circuits 14. The series branch circuit 13 includes three series resonators S1, S2, and S3 installed in series. The three parallel branch circuits 14 include a first parallel branch circuit, a second parallel branch circuit, and a third parallel branch circuit. The first parallel branch circuit includes a parallel resonator P1. One end of the parallel resonator P1 is connected in series between the series resonator S1 and the series resonator S2, and the other end is grounded. The second parallel branch circuit includes a parallel resonator P2. One end of the parallel resonator P2 is connected in series between the series resonator S2 and the series resonator S3, and the other end is grounded. The third parallel branch circuit includes a parallel resonator P3. One end of the parallel resonator P3 is connected in series between the series resonator S3 and the output end 12, and the other end is grounded.

[0037] FIG. 2 is a diagram showing the transmission coefficient curve of the filter shown in FIG. 1 within a wideband range, and FIG. 3 is a diagram showing the transmission coefficient curve of the filter shown in FIG. 1 at the center frequency. As shown in FIGS. 2 and 3, the minimum value of the insertion loss of the filter is 1.18 dB, and the out-of-band rejection is less than 40 dB. This is because, for the filter with the three-stage topology structure, since the number of resonant units through which the signal should pass is relatively large, the insertion loss increases. However, for the out-of-band rejection parameter, since the order of the filter with the three-stage topology structure is relatively small, more optimal out-of-band rejection cannot be achieved.

[0038] Therefore, in order to simultaneously improve the insertion loss and the out-of-band rejection performance, embodiments of the present disclosure provide a filter, a high-frequency device, and an electronic device. The filter includes a series branch circuit, N parallel branch circuits, and a bridge branch circuit. The series branch circuit includes M series resonators installed in series. Each of the parallel branch circuits includes a parallel resonator. The bridge branch circuit includes a bridge resonator and a first inductor. Each of the parallel branch circuits includes an opposing first end and a second end. The first end of each of the parallel branch circuits is grounded, and the second end of each of the parallel branch circuits is connected to the series branch circuit. The bridge branch circuit includes a third end and a fourth end. The third end is located on the side away from the first inductor of the bridge resonator, and the fourth end is located on the side away from the bridge resonator of the first inductor. The third end is connected to the first end of the i-th parallel branch circuit, and the fourth end is connected to the second end of the (i + 2)-th parallel branch circuit. Both M and N are positive integers greater than or equal to 3, and i is a positive integer greater than or equal to 1 and less than or equal to N - 2.

[0039] In the filter according to an embodiment of the present disclosure, after the bridge resonator is connected in series to the first inductor, it is bridged between the first end of the i-th parallel branch circuit and the second end of the (i + 2)-th parallel branch circuit. By introducing the bridge resonator, two zero points can be added within the passband. However, by moving these two zero points to appropriate positions outside the passband according to the value of the first inductor, the out-of-band suppression can be increased, and at the same time, it can play a role in optimizing the impedance matching of the input and output ports, thereby reducing the insertion loss. As a result, the filter can simultaneously reduce the insertion loss and improve the out-of-band suppression performance.

[0040] Hereinafter, with reference to the drawings, a filter, a high-frequency device, and an electronic device according to an embodiment of the present disclosure will be described in detail.

[0041] At least one embodiment of the present disclosure provides a filter. FIG. 4 is a schematic diagram of a filter according to an embodiment of the present disclosure. As shown in FIG. 4, the filter 100 includes a series branch circuit 110, N parallel branch circuits 120, and a bridge branch circuit 130. The series branch circuit 110 includes M series resonators 210 installed in series. Each parallel branch circuit 120 includes a parallel resonator 220. The bridge branch circuit 130 includes a bridge resonator 230 and a first inductor 241. Each parallel branch circuit 120 includes opposite first ends 120A and second ends 120B. The first end 120A of each parallel branch circuit 120 is grounded, and the second end 120B of each parallel branch circuit 120 is connected to the series branch circuit 110. The bridge branch circuit 130 includes a third end 130A and a fourth end 130B. The third end 130A is located on the side away from the first inductor 241 of the bridge resonator 230, and the fourth end 130B is located on the side away from the bridge resonator 230 of the first inductor 241, that is, the bridge resonator 230 and the first inductor 241 are installed in series between the third end 130A and the fourth end 130B.

[0042] As shown in FIG. 4, the third terminal 130A is connected to the first terminal 120A of the i-th parallel branch circuit 120, and the fourth terminal 130B is connected to the second terminal 120B of the (i + k)-th parallel branch circuit 120. That is, the third terminal 130A is connected to the side away from the series branch circuit 110 of the parallel resonator 220 in the i-th parallel branch circuit 120, and the fourth terminal 130B is connected to the connection point between the (i + k)-th parallel branch circuit 120 and the series branch circuit 110. Both M and N are positive integers of 3 or more, i is a positive integer of 1 or more and N - k or less, and k is a positive integer of 2 or more. It should be noted that the above "connection" is an electrical connection.

[0043] In the filter according to the embodiment of the present disclosure, after the bridge resonator is connected in series to the first inductor, it is bridged between the first terminal of the i-th parallel branch circuit and the second terminal of the (i + k)-th parallel branch circuit. By introducing the bridge resonator, two zero points can be added within the passband. However, by moving these two zero points to appropriate positions outside the passband according to the value of the first inductor, the out-of-band suppression can be increased, and at the same time, the impedance matching of the input and output ports can be optimized, thereby reducing the insertion loss. As a result, the filter can simultaneously reduce the insertion loss and improve the out-of-band suppression performance.

[0044] In some examples, at least one of the series resonators 210 of M and the parallel resonators 220 in the N parallel branch circuits 120 is a bulk acoustic wave resonator. Thereby, the filter can have advantages such as lower insertion loss, higher Q value, steeper roll-off characteristics, and larger power capacitance.

[0045] In some examples, all of the series resonators 210 of M and the parallel resonators 220 in the N parallel branch circuits 120 may adopt bulk acoustic wave resonators.

[0046] For example, the above bulk acoustic wave resonator may be at least one of a thin film bulk acoustic wave resonator (FBAR) and a solidly mounted resonator (SMR).

[0047] FIG. 5A is a schematic structural diagram of a bulk acoustic wave resonator according to an embodiment of the present disclosure, FIG. 5B is a schematic structural diagram of another bulk acoustic wave resonator according to an embodiment of the present disclosure, and FIG. 5C is a schematic structural diagram of another bulk acoustic wave resonator according to an embodiment of the present disclosure.

[0048] As shown in FIG. 5A, the bulk acoustic wave resonator 260 includes a substrate 261, an air gap 262 located inside the substrate 261, a piezoelectric thin film 263, and a first drive electrode 264 and a second drive electrode 265 located on both sides of the piezoelectric thin film 263. The first drive electrode 264 is located on the side of the piezoelectric thin film 263 close to the substrate 261, and the second drive electrode 265 is located on the side of the piezoelectric thin film 263 away from the substrate 261. The air gap 262 is located on the side of the substrate 161 close to the first drive electrode 264, and may be etched from the side of the substrate 161 close to the first drive electrode 264. Thereby, the bulk acoustic wave resonator 260 can convert an electrical signal into a bulk acoustic wave propagating along the thickness direction of the piezoelectric thin film, and utilize the air gap to realize total reflection of the acoustic wave at the interface.

[0049] As shown in FIG. 5B, the bulk acoustic wave resonator 260 includes a substrate 261, an air gap 262 located inside the substrate 261, a piezoelectric thin film 263, and a first drive electrode 264 and a second drive electrode 265 located on both sides of the piezoelectric thin film 263. The first drive electrode 264 is located on the side of the piezoelectric thin film 263 close to the substrate 261, and the second drive electrode 265 is located on the side of the piezoelectric thin film 263 away from the substrate 261. The air gap 262 is located on the side of the substrate 161 away from the first drive electrode 264, and may be etched from the side of the substrate 161 away from the first drive electrode 264. Thereby, the bulk acoustic wave resonator 260 can convert an electrical signal into a bulk acoustic wave propagating along the thickness direction of the piezoelectric thin film, and utilize the air gap to realize total reflection of the acoustic wave at the interface. As shown in FIG. 5C, the bulk acoustic wave resonator 270 includes a substrate 271, a plurality of high acoustic impedance layers 272 and low acoustic impedance layers 273 alternately arranged on the substrate 271, a piezoelectric thin film 274, and a first drive electrode 275 and a second drive electrode 276 located on both sides of the piezoelectric thin film 274. The first drive electrode 275 is located on the side of the piezoelectric thin film 274 close to the substrate 271, and the second drive electrode 276 is located on the side of the piezoelectric thin film 274 away from the substrate 271. Thereby, the bulk acoustic wave resonator 270 can convert an electrical signal into a bulk acoustic wave propagating along the thickness direction of the piezoelectric thin film, and utilize a Bragg reflection layer formed by alternately arranging high acoustic impedance layers and low acoustic impedance layers to realize total reflection.

[0050] In some examples, at least one of the parallel resonators 220 in the M series resonators 210 and the N parallel branch circuits 120 may employ the resonator shown in FIG. 5A, the resonator shown in FIG. 5B, or the resonator shown in FIG. 5C. Of course, the embodiments of the present disclosure include the above, but are not limited thereto. At least one of the parallel resonators in the M series resonators and the N parallel branch circuits may employ other types of resonators.

[0051] FIG. 5D is a schematic structural diagram when the bulk acoustic wave resonators according to an embodiment of the present disclosure are connected in series. As shown in FIG. 5D, the structure includes a first bulk acoustic wave resonator 260A and a second bulk acoustic wave resonator 260B. The first bulk acoustic wave resonator 260A includes a substrate 261, an air gap 262A located inside the substrate 261, a piezoelectric thin film 263, and a first drive electrode 264A and a second drive electrode 265A located on both sides of the piezoelectric thin film 263. The second bulk acoustic wave resonator 260B includes a substrate 261, an air gap 262B located inside the substrate 261, a piezoelectric thin film 263, and a first drive electrode 264B and a second drive electrode 265B located on both sides of the piezoelectric thin film 263. The first bulk acoustic wave resonator 260A and the second bulk acoustic wave resonator 260B may share the substrate 261 and the piezoelectric thin film 263.

[0052] As shown in FIG. 5D, the structure may further include an insulating layer 280, a first connection electrode 291A, a second connection electrode 292A, a third connection electrode 291B, and a fourth connection electrode 292B located on the side of the insulating layer 280 away from the substrate 261. The first connection electrode 291A is electrically connected to the first drive electrode 264A in the first bulk acoustic wave resonator 260A through a via passing through the insulating layer 280 and the piezoelectric thin film 263. The second connection electrode 292A is electrically connected to the second drive electrode 265A in the first bulk acoustic wave resonator 260A through a via passing through the insulating layer 280. The third connection electrode 291B is electrically connected to the first drive electrode 264B in the second bulk acoustic wave resonator 260B through a via passing through the insulating layer 280 and the piezoelectric thin film 263. The fourth connection electrode 292B is electrically connected to the second drive electrode 265B in the second bulk acoustic wave resonator 260B through a via passing through the insulating layer 280. At this time, by connecting the third connection electrode 291B and the second connection electrode 292A, it is possible to realize the series connection of the first bulk acoustic wave resonator 260A and the second bulk acoustic wave resonator 260B. Thereby, any two adjacent series resonators in the series branch circuit of the filter according to the embodiment of the present disclosure may be serially connected in the above manner. The parallel resonators in any one parallel branch circuit of the filter may be connected after the series resonators in the series branch circuit in the above manner. Also, the bridge-type resonators in the bridge branch circuit may be connected after the parallel resonators in the parallel branch circuit in the above manner. For example, by integrally connecting the second drive electrode of the first series resonator 211 in the series branch circuit 110 in FIG. 4, the first drive electrode of the second series resonator 212 in the series branch circuit 110, and the first drive electrode of the first parallel resonator 221 in the first parallel branch circuit 121 with the above connection electrodes, the connection relationship in FIG. 4 can be realized.

[0053] FIG. 5E is a schematic structural diagram when another bulk acoustic wave resonator according to an embodiment of the present disclosure is connected in series. As shown in FIG. 5E, the structure includes a third bulk acoustic wave resonator 270A and a fourth bulk acoustic wave resonator 270B. The third bulk acoustic wave resonator 270A includes a substrate 271, a plurality of high acoustic impedance layers 272 and low acoustic impedance layers 273 alternately disposed on the substrate 271, a piezoelectric thin film 274, and a first drive electrode 275A and a second drive electrode 276A located on both sides of the piezoelectric thin film 274. The fourth bulk acoustic wave resonator 270B includes a substrate 271, a plurality of high acoustic impedance layers 272 and low acoustic impedance layers 273 alternately disposed on the substrate 271, a piezoelectric thin film 274, and a first drive electrode 275B and a second drive electrode 276B located on both sides of the piezoelectric thin film 274. As can be seen from the above, the third bulk acoustic wave resonator 270A and the fourth bulk acoustic wave resonator 270B can share the substrate 271, a plurality of high acoustic impedance layers 272 and low acoustic impedance layers 273 alternately disposed, and the piezoelectric thin film 274.

[0054] As shown in FIG. 5E, the first drive electrode 275A of the third bulk acoustic wave resonator 270A is located on the side away from the substrate 271 of the piezoelectric thin film 274, and the second drive electrode 276A of the third bulk acoustic wave resonator 270A is located on the side close to the substrate 271 of the piezoelectric thin film 274. However, the first drive electrode 275B of the fourth bulk acoustic wave resonator 270B is located on the side close to the substrate 271 of the piezoelectric thin film 274, and the second drive electrode 276B of the fourth bulk acoustic wave resonator 270B is located on the side away from the substrate 271 of the piezoelectric thin film 274. Thereby, the second drive electrode 276A of the third bulk acoustic wave resonator 270A and the first drive electrode 275B of the fourth bulk acoustic wave resonator 270B can be installed in the same layer and electrically connected, thereby realizing the series connection of the third bulk acoustic wave resonator 270A and the fourth bulk acoustic wave resonator 270B. Thereby, any two adjacent series resonators in the series branch circuit of the filter according to the embodiment of the present disclosure may be serially connected in the above manner, the parallel resonators in any one parallel branch circuit of the filter may be connected after the series resonators in the series branch circuit in the above manner, and the bridge type resonators in the bridge branch circuit may also be connected after the parallel resonators in the parallel branch circuit in the above manner. For example, by installing the second drive electrode of the first series resonator 211 in the series branch circuit 110 in FIG. 4, the first drive electrode of the second series resonator 212 in the series branch circuit 110, and the first drive electrode of the first parallel resonator 221 in the first parallel branch circuit 121 in the same layer and electrically connecting them, the connection relationship in FIG. 4 can be realized.

[0055] For example, as shown in FIG. 5E, the second drive electrode 276A of the third bulk acoustic wave resonator 270A and the first drive electrode 275B of the fourth bulk acoustic wave resonator 270B may be integrally formed.

[0056] FIG. 5F is a structural schematic diagram of a connection method between a bulk acoustic wave resonator and an inductor according to an embodiment of the present disclosure. As shown in FIG. 5F, the structure includes a fifth bulk acoustic wave resonator 260C, a sixth bulk acoustic wave resonator 260D, and an inductor 240. The fifth bulk acoustic wave resonator 260C includes a substrate 261, an air gap 262C located inside the substrate 261, a piezoelectric thin film 263, and a first drive electrode 264C and a second drive electrode 265C located on both sides of the piezoelectric thin film 263. The sixth bulk acoustic wave resonator 260D includes a substrate 261, an air gap 262D located inside the substrate 261, a piezoelectric thin film 263, and a first drive electrode 264D and a second drive electrode 265D located on both sides of the piezoelectric thin film 263. The fifth bulk acoustic wave resonator 260C and the sixth bulk acoustic wave resonator 260D may share the substrate 261 and the piezoelectric thin film 263.

[0057] As shown in FIG. 5F, the structure may further include an insulating layer 280, a fifth connection electrode 291C, a sixth connection electrode 292C, a seventh connection electrode 291D, and an eighth connection electrode 292D located on a side of the insulating layer 280 away from the substrate 261. The fifth connection electrode 291C is electrically connected to the first drive electrode 264C in the fifth bulk acoustic wave resonator 260C through a via passing through the insulating layer 280 and the piezoelectric thin film 263. The sixth connection electrode 292C is electrically connected to the second drive electrode 265C in the fifth bulk acoustic wave resonator 260C through a via passing through the insulating layer 280. The seventh connection electrode 291D is electrically connected to the first drive electrode 264D in the sixth bulk acoustic wave resonator 260D through a via passing through the insulating layer 280 and the piezoelectric thin film 263. The eighth connection electrode 292D is electrically connected to the second drive electrode 265D in the sixth bulk acoustic wave resonator 260D through a via passing through the insulating layer 280. At this time, the inductor 240 may be a single-layer inductor, located on a side of the insulating layer 281 away from the substrate 261, and connected to the sixth connection electrode 292C and the eighth connection electrode 292D respectively. The insulating layer 281 is installed between each connection electrode and the inductor 240. Thus, the resonator and the inductor in the filter according to the embodiment of the present disclosure may be connected in the above manner. For example, the bridge resonator of the bridge-branching circuit and the first inductor may be connected to the series resonator in the series-branching circuit in the above manner.

[0058] FIG. 5G is a structural schematic diagram of another connection method between a bulk acoustic wave resonator and an inductor according to an embodiment of the present disclosure. As shown in FIG. 5G, the difference from the connection method shown in FIG. 5F is that the inductor 240 may be a three-dimensional inductor and may include sub-conductive parts 240A and 240B located in a plurality of film layers. The sub-conductive part 240A is located on the side away from the substrate 261 of the insulating layer 281, and the sub-conductive part 240B is located on the side away from the sub-conductive part 240A of the insulating layer 282.

[0059] In some examples, the piezoelectric thin film may include a piezoelectric crystal or a piezoelectric ceramic. Of course, the embodiments of the present disclosure include the above, but are not limited thereto, and the piezoelectric material layer may be other types of piezoelectric materials.

[0060] In some examples, the material of the piezoelectric thin film may be one or more of aluminum nitride (AlN), doped aluminum nitride (doped ALN), zinc oxide (ZnO), lead zirconate titanate (PZT), lithium niobate (LiNbO3), quartz, potassium niobate (KNbO3), and lithium tantalate (LiTaO3). Of course, the embodiments of the present disclosure include the above, but are not limited thereto, and the piezoelectric material layer may further be a piezoelectric thin film composite structure, such as a composite structure of a lithium tantalate piezoelectric thin film / silicon dioxide / silicon substrate.

[0061] In some examples, as shown in FIG. 4, the second end 120B of the first parallel branch circuit 120 is located between the first series resonator 210 and the second series resonator 210, the second end 120B of the jth parallel branch circuit 120 is located between the jth series resonator 210 and the (j + 1)th series resonator 210, and the second end 120B of the Nth parallel branch circuit 120 is located between the Nth series resonator 210 and the (N - 1)th series resonator 210, where j is a positive integer greater than 1 and less than N. It should be noted that the order of the above parallel branch circuits may be sorted along the direction from the input end to the output end of the filter.

[0062] In some examples, as shown in FIG. 4, the value of i is 1, and the values of M and N are equal. Thereby, the filter has higher filtering performance.

[0063] In some examples, as shown in FIG. 4, the filter 100 includes a series branch circuit 110, three parallel branch circuits 120, and one bridge branch circuit 130. The filter 100 includes an input terminal 100A and an output terminal 100B, and the series branch circuit 110 is installed between the input terminal 100A and the output terminal 100B. At this time, the input terminal 100A and the output terminal 100B may be regarded as both ends of the series branch circuit 110. The series branch circuit 110 includes three series resonators 210 installed in series, including a first series resonator 211, a second series resonator 212, and a third series resonator 213.

[0064] As shown in FIG. 4, each of the three parallel branch circuits 120 includes a first parallel branch circuit 121, a second parallel branch circuit 122, and a third parallel branch circuit 123. Each parallel branch circuit 120 includes a parallel resonator 220. At this time, the first parallel branch circuit 121 includes a first parallel resonator 221, the second parallel branch circuit 122 includes a second parallel resonator 222, and the third parallel branch circuit 123 includes a third parallel resonator 223. Each parallel branch circuit 120 includes opposite first end 120A and second end 120B. The first end 120A of the first parallel branch circuit 121 is grounded, the second end 120B of the first parallel branch circuit 121 is connected between the first series resonator 211 and the second series resonator 212, the first end 120A of the second parallel branch circuit 122 is grounded, the second end 120B of the second parallel branch circuit 122 is connected between the second series resonator 212 and the third series resonator 213, the first end 120A of the third parallel branch circuit 123 is grounded, and the second end 120B of the third parallel branch circuit 123 is connected between the third series resonator 213 and the output terminal 100B.

[0065] As shown in FIG. 4, the bridge branch circuit 130 includes a bridge resonator 230 and a first inductor 241. The bridge branch circuit 130 includes a third end 130A and a fourth end 130B. The third end 130A is connected to the first end 120A of the first parallel branch circuit 121, and the fourth end 130B is connected to the second end 120B of the third parallel branch circuit 123.

[0066] In some examples, the inductance value range of the first inductor 241 is 10 nH to 17 nH.

[0067] In some examples, as shown in FIG. 4, the series branch circuit 110 includes an input terminal 100A and an output terminal 100B which are oppositely arranged, M serial resonators 210 are arranged between the input terminal 100A and the output terminal 100B, and the filter 100 further includes a second inductor 242 which is arranged in parallel with the first serial resonator 210. Thereby, the electrostatic capacitors of the second inductor and the first serial resonator arranged in parallel can form a new LC resonance peak, and by adding additional zero points outside the passband of the filter, the out-of-band suppression can be further improved.

[0068] In some examples, the inductance value range of the second inductor 242 is 5 nH to 9 nH. Of course, the embodiments of the present disclosure include the above, but are not limited thereto.

[0069] In some examples, when the inductance value range of the second inductor 242 is 5 nH to 9 nH, the inductance value range of the first inductor 241 may be 10 nH to 17 nH. Of course, the embodiments of the present disclosure include the above, but are not limited thereto.

[0070] FIG. 5H is a schematic structural diagram when a resonator and an inductor according to an embodiment of the present disclosure are connected in parallel. As shown in FIG. 5H, the structure includes a seventh bulk acoustic wave resonator 260E and an inductor 240. The seventh bulk acoustic wave resonator 260E includes a substrate 261, an air gap 262C located inside the substrate 261, a piezoelectric thin film 263, and a first drive electrode 264E and a second drive electrode 265E located on both sides of the piezoelectric thin film 263. The inductor 240 may be a three-dimensional inductor and may include sub-conductive parts located in a plurality of film layers (specific descriptions may refer to the related descriptions in FIG. 5G). The structure may further include a ninth connection electrode 291E and a tenth connection electrode 292E. The ninth connection electrode 291E is connected to the first drive electrode 264E, and the tenth connection electrode 292E is connected to the second drive electrode 265E. One end of the inductor 240 is connected to the ninth connection electrode 191D, and the other end is connected to the tenth connection electrode 292D, thereby realizing the parallel connection of the inductor 240 and the seventh bulk acoustic wave resonator 260E.

[0071] For example, the second inductor 242 and the first series resonator 210 in the filter shown in FIG. 4 may be installed in parallel in the above manner.

[0072] In some examples, as shown in FIG. 4, in the filter, the value of i is 1 and the value of k is 2.

[0073] FIG. 6 is a comparison diagram of transmission coefficient curves of a filter according to an embodiment of the present disclosure and a conventional bulk acoustic wave filter within a broadband range, and FIG. 7 is a comparison diagram of transmission coefficient curves of a filter according to an embodiment of the present disclosure and a conventional bulk acoustic wave filter within a center frequency range. As shown in FIGS. 6 and 7, the insertion loss of the filter is about 0.83 dB lower than that of the conventional bulk acoustic wave filter, and is between 1.9 GHz and 1.98 GHz and between 1.98 GHz and 2.5 GHz. The out-of-band rejection of the filter is significantly improved.

[0074] Of course, the embodiments of the present disclosure include the above, but are not limited thereto. The second inductor may not be installed in the filter.

[0075] FIG. 8 is a schematic diagram of another filter according to an embodiment of the present disclosure. As shown in FIG. 8, the filter 100 includes the series branch circuit 110, the parallel branch circuit 120, and the bridge branch circuit 130.

[0076] As shown in FIG. 8, the series branch circuit 110 includes three series resonators 210 installed in series, including a first series resonator 211, a second series resonator 212, and a third series resonator 213. Each of the three parallel branch circuits 120 includes a first parallel branch circuit 121, a second parallel branch circuit 122, and a third parallel branch circuit 123. Each parallel branch circuit 120 includes a parallel resonator 220. At this time, the first parallel branch circuit 121 includes a first parallel resonator 221, the second parallel branch circuit 122 includes a second parallel resonator 222, and the third parallel branch circuit 123 includes a third parallel resonator 223. Each parallel branch circuit 120 includes opposite first end 120A and second end 120B. The first end 120A of the first parallel branch circuit 121 is grounded, the second end 120B of the first parallel branch circuit 121 is connected between the first series resonator 211 and the second series resonator 212, the first end 120A of the second parallel branch circuit 122 is grounded, the second end 120B of the second parallel branch circuit 122 is connected between the second series resonator 212 and the third series resonator 213, the first end 120A of the third parallel branch circuit 123 is grounded, and the second end 120B of the third parallel branch circuit 123 is connected between the third series resonator 213 and the output end 100B.

[0077] As shown in FIG. 8, the third end 130A of the bridge branch circuit 130 is connected to the first end 120A of the first parallel branch circuit 121, and the fourth end 130B of the bridge branch circuit 130 is connected to the second end 120B of the third parallel branch circuit 123.

[0078] FIG. 9 is a diagram showing the transmission coefficient curve of another filter according to an embodiment of the present disclosure within a wideband range, and FIG. 10 is a diagram showing the transmission coefficient curve of another filter according to an embodiment of the present disclosure within a center frequency range. As shown in FIGS. 9 and 10, since the bridge resonator is connected in series to the first inductor and then bridged between the first end of the first parallel branch circuit and the second end of the third parallel branch circuit, two zero points can be added within the passband due to the introduction of the bridge resonator. However, by moving these two zero points to appropriate positions outside the passband according to the value of the first inductor, the out-of-band rejection can be increased, and at the same time, it can play a role in optimizing the impedance matching of the input and output ports, thereby reducing the insertion loss. Thereby, the filter can simultaneously reduce the insertion loss and improve the out-of-band rejection performance.

[0079] FIG. 11 is a schematic diagram of another filter according to an embodiment of the present disclosure. As shown in FIG. 11, the filter 100 includes the above-mentioned series branch circuit 110, parallel branch circuit 120, bridge branch circuit 130, and second inductor 242. The series branch circuit 110 includes three series resonators 210 installed in series, including a first series resonator 211, a second series resonator 212, and a third series resonator 213. Each of the three parallel branch circuits 120 includes a first parallel branch circuit 121, a second parallel branch circuit 122, and a third parallel branch circuit 123. Each parallel branch circuit 120 includes a parallel resonator 220. At this time, the first parallel branch circuit 121 includes a first parallel resonator 221, the second parallel branch circuit 122 includes a second parallel resonator 222, and the third parallel branch circuit 123 includes a third parallel resonator 223. Each parallel branch circuit 120 includes opposite first end 120A and second end 120B. The first end 120A of the first parallel branch circuit 121 is grounded, the second end 120B of the first parallel branch circuit 121 is connected between the first series resonator 211 and the second series resonator 212, the first end 120A of the second parallel branch circuit 122 is grounded, the second end 120B of the second parallel branch circuit 122 is connected between the second series resonator 212 and the third series resonator 213, the first end 120A of the third parallel branch circuit 123 is grounded, and the second end 120B of the third parallel branch circuit 123 is connected between the third series resonator 213 and the output end 100B.

[0080] As shown in FIG. 11, the third terminal 130A of the bridge-branching circuit 130 is connected to the first terminal 120A of the first parallel-branching circuit 121, the fourth terminal 130B of the bridge-branching circuit 130 is connected to the second terminal 120B of the third parallel-branching circuit 123, and the second inductor 242 is installed in parallel with the first series resonator 211. Further, the filter 100 further includes a third inductor 243, one end of the third inductor 243 is grounded, and the other end of the third inductor 243 is connected to the output terminal 100B. Thereby, the impedance matching within the passband can be improved by introducing the grounded third inductor 243.

[0081] FIG. 12 is a curve diagram of the transmission coefficient of another filter according to an embodiment of the present disclosure within a wideband range, and FIG. 13 is a curve diagram of the transmission coefficient of another filter according to an embodiment of the present disclosure within a center frequency range. As shown in FIGS. 12 and 13, the out-of-band rejection between 1.64 GHz and 1.81 GHz and between 2.06 GHz and 2.2 GHz of the filter can reach 60 dB.

[0082] In some examples, the value range of the inductance of the third inductor is 10 nH to 17 nH. Of course, the embodiments of the present disclosure include, but are not limited to, the above.

[0083] FIG. 14 is a schematic diagram of another filter according to an embodiment of the present disclosure. As shown in FIG. 14, the filter 100 includes the series branch circuit 110, the parallel branch circuit 120, and the bridge branch circuit 130. The series branch circuit 110 includes three series resonators 210 installed in series, including the first series resonator 211, the second series resonator 212, and the third series resonator 213. Each of the three parallel branch circuits 120 includes the first parallel branch circuit 121, the second parallel branch circuit 122, and the third parallel branch circuit 123. Each parallel branch circuit 120 includes a parallel resonator 220. At this time, the first parallel branch circuit 121 includes the first parallel resonator 221, the second parallel branch circuit 122 includes the second parallel resonator 222, and the third parallel branch circuit 123 includes the third parallel resonator 223. Each parallel branch circuit 120 includes opposite first end 120A and second end 120B. The first end 120A of the first parallel branch circuit 121 is grounded, the second end 120B of the first parallel branch circuit 121 is connected between the first series resonator 211 and the second series resonator 212, the first end 120A of the second parallel branch circuit 122 is grounded, and the second end 120B of the second parallel branch circuit 122 is connected between the second series resonator 212 and the third series resonator 213. The first end 120A of the third parallel branch circuit 123 is grounded, and the second end 120B of the third parallel branch circuit 123 is connected between the third series resonator 213 and the output end 100B.

[0084] As shown in FIG. 14, the third end 130A of the bridge branch circuit 130 is connected to the first end 120A of the first parallel branch circuit 121, and the fourth end 130B of the bridge branch circuit 130 is connected to the second end 120B of the third parallel branch circuit 123. Further, the filter 100 further includes a fourth inductor 244, and the fourth inductor 244 is installed in series between the first series resonator 211 and the second end 120B of the first parallel branch circuit 121. Thereby, by connecting the fourth inductor 244 in series between the first series resonator 211 and the second end 120B of the first parallel branch circuit 121, impedance matching within the passband can be improved, thereby making the in-band variation of the filter gentler.

[0085] FIG. 15 is a graph of the transmission coefficient of another filter according to an embodiment of the present disclosure within a wideband range, and FIG. 16 is a graph of the transmission coefficient of another filter according to an embodiment of the present disclosure within a center frequency range. As shown in FIGS. 15 and 16, the in-band variation of the filter becomes smoother.

[0086] In some examples, the inductance value range of the fourth inductor is 0.3 nH to 0.7 nH. Of course, the embodiments of the present disclosure include the above, but are not limited thereto.

[0087] In some examples, when the inductance value range of the fourth inductor is 0.3 nH to 0.7 nH, the inductance value range of the first inductor may be between 11 nH and 18 nH. Of course, the embodiments of the present disclosure include the above, but are not limited thereto.

[0088] FIG. 17 is a schematic diagram of another filter according to an embodiment of the present disclosure. As shown in FIG. 17, the filter 100 includes the above-described series branch circuit 110, parallel branch circuit 120, and bridge branch circuit 130. The series branch circuit 110 includes three series resonators 210 installed in series, including a first series resonator 211, a second series resonator 212, and a third series resonator 213. Each of the three parallel branch circuits 120 includes a first parallel branch circuit 121, a second parallel branch circuit 122, and a third parallel branch circuit 123, and each parallel branch circuit 120 includes a parallel resonator 220. At this time, the first parallel branch circuit 121 includes a first parallel resonator 221, the second parallel branch circuit 122 includes a second parallel resonator 222, and the third parallel branch circuit 123 includes a third parallel resonator 223. Each parallel branch circuit 120 includes opposite first end 120A and second end 120B. The first end 120A of the first parallel branch circuit 121 is grounded, the second end 120B of the first parallel branch circuit 121 is connected between the first series resonator 211 and the second series resonator 212, the first end 120A of the second parallel branch circuit 122 is grounded, the second end 120B of the second parallel branch circuit 122 is connected between the second series resonator 212 and the third series resonator 213, the first end 120A of the third parallel branch circuit 123 is grounded, and the second end 120B of the third parallel branch circuit 123 is connected between the third series resonator 213 and the output end 100B.

[0089] As shown in FIG. 17, the third terminal 130A of the bridge-branching circuit 130 is connected to the first terminal 120A of the first parallel-branching circuit 121, and the fourth terminal 130B of the bridge-branching circuit 130 is connected to the second terminal 120B of the third parallel-branching circuit 123. Further, the filter 100 further includes a fifth inductor 245, and the fifth inductor 245 is installed in series between the first terminal 120A of the third parallel-branching circuit 123 and the third parallel resonator 223. Thus, based on the idea of reducing the circuit complexity, compared with the filter shown in FIG. 13, the filter removes the inductor connected in series beside the first series resonator, and introduces a fifth inductor connected in series between the first terminal of the third parallel-branching circuit and the third parallel resonator. Since the parallel-arm resonator exhibits capacitive characteristics outside the passband frequency of the filter, a new LC resonance can be formed with the fifth inductor, and a new zero point can be formed outside the band. By adjusting the inductance of the fifth inductor, the new zero point can be made to almost overlap with the zero point introduced into the bridge resonator. At this time, the out-of-band suppression effect is optimal, and an out-of-band suppression level of 40 dB can be achieved.

[0090] FIG. 18 is a diagram of the transmission coefficient curve of another filter according to an embodiment of the present disclosure within a wideband range, and FIG. 19 is a diagram of the transmission coefficient curve of another filter according to an embodiment of the present disclosure within a center frequency range. As shown in FIGS. 18 and 19, the filter can make the new zero point almost overlap with the zero point introduced into the bridge resonator. At this time, the out-of-band suppression effect is optimal, and an out-of-band suppression level of 40 dB can be achieved.

[0091] In some examples, the value range of the inductance of the fifth inductor is 4.5 nH to 6.5 nH. Of course, the embodiments of the present disclosure include the above, but are not limited thereto.

[0092] In some examples, when the value range of the inductance of the fifth inductor is 4.5 nH to 6.5 nH, the value range of the inductance of the first inductor may be between 10 nH and 17 nH. Of course, the embodiments of the present disclosure include the above, but are not limited thereto.

[0093] FIG. 20 is a schematic diagram of another filter according to an embodiment of the present disclosure. As shown in FIG. 20, the filter 100 includes a series branch circuit 110, four parallel branch circuits 120, a bridge branch circuit 130, and a second inductor 242.

[0094] The series branch circuit 110 includes four series resonators 210 installed in series, including a first series resonator 211, a second series resonator 212, a third series resonator 213, and a fourth series resonator 214. Each of the four parallel branch circuits 120 includes a first parallel branch circuit 121, a second parallel branch circuit 122, a third parallel branch circuit 123, and a fourth parallel branch circuit 124. Each parallel branch circuit 120 includes a parallel resonator 220. At this time, the first parallel branch circuit 121 includes a first parallel resonator 221, the second parallel branch circuit 122 includes a second parallel resonator 222, the third parallel branch circuit 123 includes a third parallel resonator 223, and the fourth parallel branch circuit 124 includes a fourth parallel resonator 224. Each parallel branch circuit 120 includes opposite first ends 120A and second ends 120B. The first end 120A of the first parallel branch circuit 121 is grounded, and the second end 120B of the first parallel branch circuit 121 is connected between the first series resonator 211 and the second series resonator 212. The first end 120A of the second parallel branch circuit 122 is grounded, and the second end 120B of the second parallel branch circuit 122 is connected between the second series resonator 212 and the third series resonator 213. The first end 120A of the third parallel branch circuit 123 is grounded, and the second end 120B of the third parallel branch circuit 123 is connected between the third series resonator 213 and the fourth series resonator 214. The second end 120B of the fourth parallel branch circuit 124 is connected between the fourth series resonator 214 and the output end 100B.

[0095] As shown in FIG. 20, the third terminal 130A of the bridge-branching circuit 130 is connected to the first terminal 120A of the first parallel-branching circuit 121, and the fourth terminal 130B of the bridge-branching circuit 130 is connected to the second terminal 120B of the third parallel-branching circuit 123. The second inductor 242 is installed in parallel with the first series resonator 211. Thereby, the electrostatic capacitors of the second inductor and the first series resonator installed in parallel can form a new LC resonance peak, and the out-of-band suppression can be improved by adding additional zeros outside the passband of the filter. Also, compared with the filter shown in FIG. 4, the filter has a four-stage topology structure and can achieve more optimal out-of-band suppression.

[0096] It should be noted that the filter according to the embodiments of the present disclosure includes, but is not limited to, the above three-stage topology structure and four-stage topology structure, and may include a higher-stage topology structure. The added series resonator and parallel-branching circuit may refer to the installation of the fourth series resonator and the fourth parallel-branching circuit.

[0097] FIG. 21 is a schematic diagram of another filter according to an embodiment of the present disclosure. As shown in FIG. 21, the filter 100 includes a series branch circuit 110, four parallel branch circuits 120, a bridge branch circuit 130, and a second inductor 242. The difference from the filter shown in FIG. 20 is that the filter further includes a sixth inductor 246 and a seventh inductor 247. The sixth inductor 246 is serially installed between the first end 120A of the third parallel branch circuit 123 and the third parallel resonator 223, and the seventh inductor 257 is serially installed between the first end 120A of the fourth parallel branch circuit 124 and the fourth parallel resonator 224. Since the parallel arm resonator exhibits capacitive characteristics outside the passband frequency of the filter, the third parallel resonator can form a new LC resonance with the sixth inductor, and the fourth parallel resonator can form a new LC resonance with the seventh inductor, thereby forming a new zero point outside the band, and by adjusting the inductances of the sixth inductor and the seventh inductor, the new zero point can be made to substantially overlap with the zero point introduced into the bridge resonator. At this time, the out-of-band suppression effect is optimal, and an out-of-band suppression level of 40 dB can be achieved.

[0098] FIG. 22 is a schematic diagram of another filter according to an embodiment of the present disclosure. As shown in FIG. 22, the filter 100 includes a series branch circuit 110, four parallel branch circuits 120, a bridge branch circuit 130, and a second inductor 242. The difference from the filter shown in FIG. 20 is that the third end 130A of the bridge branch circuit 130 is connected to the first end 120A of the first parallel branch circuit 121, and the fourth end 130B of the bridge branch circuit 130 is connected to the second end 120B of the fourth parallel branch circuit 124, that is, the third end 130A of the bridge branch circuit 130 is connected to the side away from the series branch circuit 110 of the parallel resonator 220 in the first parallel branch circuit 121, and the fourth end 130B of the bridge branch circuit 130 is connected to the connection point between the fourth parallel branch circuit 124 and the series branch circuit 110. Thereby, the bridge branch circuit can bridge three parallel branch circuits. Of course, the embodiments of the present disclosure include the above, but are not limited thereto, and the bridge branch circuit can also bridge more parallel branch circuits.

[0099] In the filter according to this example, after the bridge resonator is connected in series to the first inductor, it is bridged between the first end of the first parallel branch circuit and the second end of the fourth parallel branch circuit. By introducing the bridge resonator, two zeros can be added within the passband. However, by moving these two zeros to appropriate positions outside the passband according to the value of the first inductor, the out-of-band suppression can be increased, and at the same time, it can play a role in optimizing the impedance matching of the input and output ports, thereby reducing the insertion loss. As a result, the filter can simultaneously reduce the insertion loss and improve the out-of-band suppression performance.

[0100] At least one embodiment of the present disclosure further provides a high-frequency device. FIG. 23 is a schematic diagram of a high-frequency device according to an embodiment of the present disclosure. As shown in FIG. 23, the high-frequency device 300 includes the above filter. Since the filter can simultaneously reduce the insertion loss and improve the out-of-band suppression performance, the high-frequency device including the filter has higher performance.

[0101] In some examples, the above high-frequency device includes, but is not limited to, a high-frequency front-end module.

[0102] At least one embodiment of the present disclosure further provides an electronic device. FIG. 24 is a schematic diagram of an electronic device according to an embodiment of the present disclosure. As shown in FIG. 24, the electronic device 500 includes the above high-frequency device 300. The electronic device also has higher performance and lower cost.

[0103] In some examples, the above electronic device may be a terminal product such as a smartphone, WIFI, or drone.

[0104] The points to be explained are as follows.

[0105] First, the drawings of the embodiments of the present disclosure only relate to the structures according to the embodiments of the present disclosure, and other structures may refer to normal designs.

[0106] Second, unless they conflict, the features in the same and different embodiments of the present disclosure may be combined with each other.

[0107] The above are merely specific embodiments of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present disclosure shall be included within the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should conform to the protection scope of the claims.

Explanation of Reference Numerals

[0108] 100 Filter 100A Input Terminal 100B Output Terminal 110 Series Branch Circuit 120 Parallel Branch Circuit 120A First Terminal 120B Second Terminal 121 First Parallel Branch Circuit 122 Second Parallel Branch Circuit 123 Third Parallel Branch Circuit 124 Fourth Parallel Branch Circuit 130 Bridge Branch Circuit 130A Third Terminal 130B Fourth Terminal 161 Substrate 191D Ninth Connection Electrode 210 Series Resonator 211 First Series Resonator 212 Second Series Resonator 213 Third Series Resonator 214 Fourth Series Resonator 220 Parallel Resonator 221 First Parallel Resonator 222 Second Parallel Resonator 223 Third Parallel Resonator 224 Fourth Parallel Resonator 230 Bridge-Type Resonator 240 Inductor 240A Sub-Conductive Portion 240B Sub-Conductive Portion 241 First Inductor 242 Second Inductor 243 Third Inductor 244 Fourth Inductor 245 Fifth Inductor 246 Sixth Inductor 247 Seventh Inductor 257 Seventh Inductor 260 Bulk Acoustic Wave Resonator 260A First Bulk Acoustic Wave Resonator 260B Second Bulk Acoustic Wave Resonator 260C Fifth Bulk Acoustic Wave Resonator 260D Sixth Bulk Acoustic Wave Resonator 260E Seventh Bulk Acoustic Wave Resonator 261 Substrate 263 Piezoelectric Thin Film 264 First Driving Electrode 264A First Driving Electrode 264B First Driving Electrode 264C First Driving Electrode 264D First Driving Electrode 264E First Driving Electrode 265 Second Driving Electrode 265A Second Driving Electrode 265B Second Driving Electrode 265C Second Driving Electrode 265D Second Driving Electrode 265E Second Driving Electrode 270 Bulk Acoustic Wave Resonator 270A Third Bulk Acoustic Wave Resonator 270B Fourth Bulk Acoustic Wave Resonator 271 Substrate 272 High-Acoustic Impedance Layer 273 Low-Acoustic Impedance Layer 274 Piezoelectric Thin Film 275 First Driving Electrode 275A First Driving Electrode 275B First Driving Electrode 276 Second Driving Electrode 276A Second Driving Electrode 276B Second Driving Electrode 280 Insulating Layer 281 Insulating layer 282 Insulating layer 291A First connection electrode 291B Third connection electrode 291C Fifth connection electrode 291D Seventh connection electrode 291E Ninth connection electrode 292A Second connection electrode 292B Fourth connection electrode 292C Sixth connection electrode 292D Eighth connection electrode 292D Tenth connection electrode 292E Tenth connection electrode 300 High-frequency device 500 Electronic device IL parameter N Series-branching circuit N Series resonator P1 Parallel resonator P2 Parallel resonator P3 Parallel resonator Pin Input power PL Output power S1 Series resonator S2 Series resonator S3 Series resonator

Claims

1. A filter, a series branch circuit including M series resonators arranged in series; N parallel branch circuits each including a parallel resonator; a bridge branch circuit including a bridge-type resonator and a first inductor, each of the parallel branch circuits includes opposing first and second ends, the first end of each of the parallel branch circuits is grounded, and the second end of each of the parallel branch circuits is connected to the series branch circuit; the bridge branch circuit includes a third end and a fourth end, the third end being located on a side of the bridge resonator that is away from the first inductor, the fourth end being located on a side of the first inductor that is away from the bridge resonator, the third end being connected to the first end of the i-th parallel branch circuit, and the fourth end being connected to the second end of the (i+k)-th parallel branch circuit, wherein M and N are both positive integers greater than or equal to 3, i is a positive integer greater than or equal to 1 and less than or equal to N-k, and k is a positive integer greater than or equal to 2.

2. 2. The filter of claim 1, wherein the value of k is two.

3. 2. The filter of claim 1, wherein the second end of the first parallel branch circuit is located between the first series resonator and the second series resonator, the second end of the jth parallel branch circuit is located between the jth series resonator and the (j+1)th series resonator, and the second end of the Nth parallel branch circuit is located between the Nth series resonator and the (N-1)th series resonator, and j is a positive integer greater than 1 and less than N.

4. 2. The filter of claim 1, wherein the value of i is 1 and the values of M and N are equal.

5. The series branch circuit includes an input terminal and an output terminal disposed opposite to each other, and M series resonators are disposed between the input terminal and the output terminal, and the filter comprises:

5. The filter according to claim 1, further comprising a second inductor arranged in parallel with the first series resonator.

6. 6. The filter according to claim 5, wherein the inductance of the second inductor ranges from 5 nH to 9 nH.

7. 6. The filter according to claim 5, further comprising a third inductor having one end grounded and the other end connected to the output terminal.

8. 8. The filter according to claim 7, wherein the inductance of the third inductor ranges from 10 nH to 17 nH.

9. 6. The filter according to claim 5, wherein the inductance of the first inductor ranges from 10 nH to 17 nH.

10. The series branch circuit includes an input terminal and an output terminal disposed opposite to each other, and M series resonators are disposed between the input terminal and the output terminal, and the filter comprises:

5. The filter according to claim 1, further comprising a fourth inductor disposed in series between a first series resonator and the second end of the first parallel branch circuit.

11. 11. The filter according to claim 10, wherein the inductance of the first inductor ranges from 11 nH to 18 nH, and the inductance of the fourth inductor ranges from 0.3 nH to 0.7 nH.

12. The filter is 5. The filter according to claim 1, further comprising a fifth inductor disposed in series between the first end of the Nth parallel branch circuit and the parallel resonator.

13. 13. The filter according to claim 12, wherein the inductance of the first inductor ranges from 10 nH to 17 nH, and the inductance of the fifth inductor ranges from 4.5 nH to 6.5 nH.

14. 5. The filter according to claim 1, wherein at least one of the M series resonators and the parallel resonators in the N parallel branch circuits is a bulk acoustic wave resonator.

15. The bulk acoustic wave resonator comprises: A substrate; a piezoelectric thin film; a first drive electrode; a second drive electrode.

16. The M series resonators include a first bulk acoustic wave resonator and a second bulk acoustic wave resonator, and the first bulk acoustic wave resonator and the second bulk acoustic wave resonator adopt the structure of the bulk acoustic wave resonator; the filter further comprises an insulating layer, and a first connection electrode, a second connection electrode, a third connection electrode, and a fourth connection electrode located on a side of the insulating layer away from the substrate, the first connection electrode being electrically connected to the first drive electrode of the first bulk acoustic wave resonator by a via located in the insulating layer and the piezoelectric thin film, the second connection electrode being electrically connected to the second drive electrode of the first bulk acoustic wave resonator by a via located in the insulating layer, the third connection electrode being electrically connected to the first drive electrode of the second bulk acoustic wave resonator by a via located in the insulating layer and the piezoelectric thin film, and the fourth connection electrode being connected to the second drive electrode of the second bulk acoustic wave resonator by a via located in the insulating layer; 16. The filter according to claim 15, wherein the third connecting electrode is connected to the second connecting electrode so as to connect the first bulk acoustic wave resonator and the second bulk acoustic wave resonator in series.

17. the i-th parallel branch circuit includes a first bulk acoustic wave resonator, the bridge-type resonator includes a second bulk acoustic wave resonator, and the first bulk acoustic wave resonator and the second bulk acoustic wave resonator adopt the structure of the bulk acoustic wave resonator; the filter further comprises an insulating layer, and a first connection electrode, a second connection electrode, a third connection electrode, and a fourth connection electrode located on a side of the insulating layer away from the substrate, the first connection electrode being electrically connected to the first drive electrode of the first bulk acoustic wave resonator by a via located in the insulating layer and the piezoelectric thin film, the second connection electrode being electrically connected to the second drive electrode of the first bulk acoustic wave resonator by a via located in the insulating layer, the third connection electrode being electrically connected to the first drive electrode of the second bulk acoustic wave resonator by a via located in the insulating layer and the piezoelectric thin film, and the fourth connection electrode being connected to the second drive electrode of the second bulk acoustic wave resonator by a via located in the insulating layer; 16. The filter according to claim 15, wherein the third connecting electrode is connected to the second connecting electrode so as to connect the first bulk acoustic wave resonator and the second bulk acoustic wave resonator in series.

18. The first bulk acoustic wave resonator and the second bulk acoustic wave resonator include: an air gap located within the substrate; 17. The filter of claim 16, wherein the first drive electrode is located on a side of the piezoelectric thin film that is closer to the substrate, the second drive electrode is located on a side of the piezoelectric thin film that is farther from the substrate, and the air gap is located on a side of the substrate that is closer to the first drive electrode, or the air gap is located on a side of the substrate that is farther from the first drive electrode.

19. The M series resonators include a third bulk acoustic wave resonator and a fourth bulk acoustic wave resonator, and the third bulk acoustic wave resonator and the fourth bulk acoustic wave resonator adopt the structure of the bulk acoustic wave resonator; the first drive electrode of the third bulk acoustic wave resonator is located on a side of the piezoelectric thin film that is farther from the substrate, the second drive electrode of the third bulk acoustic wave resonator is located on a side of the piezoelectric thin film that is closer to the substrate, the first drive electrode of the fourth bulk acoustic wave resonator is located on a side of the piezoelectric thin film that is closer to the substrate, and the second drive electrode of the fourth bulk acoustic wave resonator is located on a side of the piezoelectric thin film that is farther from the substrate, 16. The filter of claim 15, wherein the second drive electrode of the third bulk acoustic wave resonator and the first drive electrode of the fourth bulk acoustic wave resonator are disposed on the same layer and electrically connected together so as to connect the third bulk acoustic wave resonator and the fourth bulk acoustic wave resonator in series.

20. the i-th parallel branch circuit includes a third bulk acoustic wave resonator, the bridge-type resonator includes a fourth bulk acoustic wave resonator, and the third bulk acoustic wave resonator and the fourth bulk acoustic wave resonator adopt the structure of the bulk acoustic wave resonator; the first drive electrode of the third bulk acoustic wave resonator is located on a side of the piezoelectric thin film that is farther from the substrate, the second drive electrode of the third bulk acoustic wave resonator is located on a side of the piezoelectric thin film that is closer to the substrate, the first drive electrode of the fourth bulk acoustic wave resonator is located on a side of the piezoelectric thin film that is closer to the substrate, and the second drive electrode of the fourth bulk acoustic wave resonator is located on a side of the piezoelectric thin film that is farther from the substrate, 16. The filter of claim 15, wherein the second drive electrode of the third bulk acoustic wave resonator and the first drive electrode of the fourth bulk acoustic wave resonator are disposed on the same layer and electrically connected together so as to connect the third bulk acoustic wave resonator and the fourth bulk acoustic wave resonator in series.

21. The third bulk acoustic wave resonator and the fourth bulk acoustic wave resonator are The acoustic transducer further comprises alternating high and low acoustic impedance layers, 20. The filter of claim 19, wherein the high acoustic impedance layer and the low acoustic impedance layer are located on a side of the piezoelectric thin film adjacent to the substrate.

22. the bridge-type resonator includes a fifth bulk acoustic wave resonator, the (i+k)th series resonator includes a sixth bulk acoustic wave resonator, and the fifth bulk acoustic wave resonator and the sixth bulk acoustic wave resonator adopt the structure of the bulk acoustic wave resonator; the filter further comprises an insulating layer, and fifth, sixth, seventh and eighth connection electrodes located on a side of the insulating layer away from the substrate, the fifth connection electrode being electrically connected to the first drive electrode of the fifth bulk acoustic wave resonator by a via located in the insulating layer and the piezoelectric thin film, the sixth connection electrode being electrically connected to the second drive electrode of the fifth bulk acoustic wave resonator by a via located in the insulating layer, the seventh connection electrode being electrically connected to the first drive electrode of the sixth bulk acoustic wave resonator by a via located in the insulating layer and the piezoelectric thin film, and the eighth connection electrode being connected to the second drive electrode of the sixth bulk acoustic wave resonator by a via located in the insulating layer; 16. The filter according to claim 15, wherein the first inductor is located on a side of the insulating layer away from the substrate and is connected to the sixth connecting electrode and the eighth connecting electrode, respectively.

23. 23. The filter of claim 22, wherein the first inductor is a single layer inductor or a three-dimensional inductor.

24. A high-frequency device comprising the filter according to any one of claims 1 to 4.

25. An electronic device comprising the high-frequency device according to claim 24.

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