Cascade resonator, elastic wave filter, and multiplexer
By designing a cascaded resonator structure, optimizing the edge shape with a second bus region and a pseudo-finger region, and suppressing lateral modes, the problem of performance degradation of traditional filters at high frequencies is solved, achieving miniaturization and stable performance of the device.
Patent Information
- Application Number
- CN202510970902.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-15
- Publication Date
- 2025-10-31
AI Technical Summary
Traditional resonators and filters have limitations in frequency selectivity and suppression characteristics when operating in high-frequency or multi-frequency environments. In particular, the generation of transverse modes in miniaturized designs leads to performance degradation, making it difficult to maintain high passband flatness under extreme space constraints.
By adopting a cascaded resonator structure, and by setting a second bus region and optimizing its edge shape to be the same as or a mirror image of the interdigital region edge, combined with the pseudo-finger region and the reflection region, the lateral mode is suppressed, thereby achieving device miniaturization.
Effective suppression of transverse modes was achieved in miniaturized designs, ensuring the performance stability and frequency selectivity of elastic wave filters and multiplexers.
Smart Images
Figure CN120880375A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor technology, and in particular to a cascaded resonator, elastic wave filter, and multiplexer. Background Technology
[0002] With the rapid development of wireless communication technology, the demand for high-frequency signal processing is constantly increasing. In wireless communication systems, filters and multiplexers are key components used to select signals of specific frequencies and suppress unwanted frequency components. Traditional resonator and filter designs have certain limitations in terms of frequency selectivity and suppression characteristics, especially in high-frequency or multi-frequency operating environments.
[0003] Elastic wave filters, as a rapidly developing filtering technology, utilize the propagation characteristics of elastic waves in piezoelectric materials, offering advantages such as small size, low insertion loss, and high temperature stability. However, in achieving ultra-compact filter designs, miniaturization of the resonator structure may induce transverse mode generation, potentially impacting passband flatness. Specifically, this manifests as fluctuations in admittance and conductance between the resonant and anti-resonant frequencies, leading to a degraded performance of the elastic wave filter. Maintaining high passband flatness under extreme space constraints has become a core technological bottleneck in the miniaturization evolution of elastic wave filters. Summary of the Invention
[0004] Based on the above problems, the purpose of this invention is to provide a cascaded resonator, elastic wave filter and multiplexer to suppress the transverse mode of the elastic wave resonator and promote the miniaturization of the device.
[0005] To achieve the above objectives, in a first aspect, the present invention adopts the following technical solution:
[0006] A cascaded resonator includes a piezoelectric substrate and a conductive thin film pattern disposed on the piezoelectric substrate. The conductive thin film pattern includes a first bus region, a second bus region, an interdigitated region, and a pseudo-finger region, wherein:
[0007] The two first bus regions extend along the direction of elastic wave propagation and are arranged at intervals, serving as the input and output of the resonator signal;
[0008] Several second bus zones are set between two first bus zones to divide the area between the two first bus zones into several interdigitated zones and to enable signal transmission between adjacent interdigitated zones;
[0009] The interdigitated region is used for the conversion of electroacoustic signals. The length of the electrode fingers in the interdigitated region gradually changes with the direction of elastic wave propagation, making the edge of the interdigitated region zigzag or curved. The edge shape of the second bus region is the same as or a mirror image of the edge shape of the interdigitated region.
[0010] The pseudo-finger area is located between the first busbar area and the interdigitated finger area adjacent to the first busbar area to prevent elastic wave leakage.
[0011] As an alternative, the interdigitated region includes first and second electrode fingers that are staggered and parallel to each other in the direction of elastic wave propagation. The first end of the first electrode finger is connected to the first or second busbar region on the first side, and the second end of the first electrode finger is disconnected from the second or first busbar region on the second side. The first end of the second electrode finger is disconnected from the first or second busbar region on the first side, and the second end of the second electrode finger is connected to the second or first busbar region on the second side.
[0012] As an alternative, the spur finger area includes a first spur finger and a second spur finger. The first spur finger is disposed on the first busbar area on the first side and is arranged at intervals opposite to the first end of each second electrode finger. The second spur finger is disposed on the first busbar area on the second side and is arranged at intervals opposite to the second end of each first electrode finger.
[0013] As an alternative, the length dimensions of each first and second electrode finger in the interdigitated region along the direction of elastic wave propagation are gradually varied by setting weighting coefficients.
[0014] As an alternative, each second busbar area is also provided with a pseudo-finger area between the interdigitated areas of the adjacent second busbar area, and the number of pseudo-finger areas is twice the number of interdigitated areas.
[0015] As an alternative, the conductive thin film pattern also includes reflective regions located on both sides of the interdigitated region along the direction of elastic wave propagation, which are used to reflect elastic waves.
[0016] As an alternative, the two sides of the single interdigitated region are mirror-symmetrical, and the two sides of the second confluence region are mirror-symmetrical.
[0017] As an alternative, the edge lines of the interdigitated area are periodic.
[0018] Secondly, the present invention adopts the following technical solution:
[0019] An elastic wave filter includes a series arm resonator and a parallel arm resonator, wherein the series arm resonator and / or the parallel arm resonator includes the cascaded resonator described above.
[0020] Thirdly, the present invention adopts the following technical solution:
[0021] A multiplexer includes an antenna terminal connected to an antenna and a plurality of filter devices connected to the antenna terminal, wherein at least one filter device is the aforementioned elastic wave filter.
[0022] The beneficial effects of this invention are:
[0023] This cascaded resonator can split an elastic wave resonator into two or even more resonators by setting a second bus region. By optimizing the edge shape of the second bus region to be the same as or a mirror image of the edge shape of the interdigitated region, it exhibits good transverse mode suppression function, thereby ensuring the performance of elastic wave filters and multiplexers based on this cascaded resonator, while promoting the miniaturization of the device. Attached Figure Description
[0024] Figure 1 This is a top view of the elastic wave resonator provided in Comparative Example 1;
[0025] Figure 2 This is a region division diagram of the conductive thin film pattern in the elastic wave resonator provided in Comparative Example 1;
[0026] Figure 3 This is a measured admittance / conductance-frequency curve of the elastic wave resonator provided in Comparative Example 1;
[0027] Figure 4 This is a top view of the elastic wave resonator provided in Comparative Example 2;
[0028] Figure 5 This is the measured admittance / conductance-frequency curve of the elastic wave resonator provided in Comparative Example 2;
[0029] Figure 6 This is a top view of the cascaded resonator provided in Comparative Example 3;
[0030] Figure 7 This is a top view of the cascaded resonator provided in Embodiment 1 of the present invention;
[0031] Figure 8 This is a measured admittance / conductance-frequency curve of the cascaded resonator provided in Embodiment 1 of the present invention;
[0032] Figure 9 This is a top view of the cascaded resonator provided in Embodiment 2 of the present invention;
[0033] Figure 10 This is a top view of the cascaded resonator provided in Embodiment 3 of the present invention;
[0034] Figure 11 This is a top view of the cascaded resonator provided in Embodiment 4 of the present invention;
[0035] Figure 12 This is a top view of the cascaded resonator provided in Embodiment 5 of the present invention.
[0036] In the attached image:
[0037] 1. Piezoelectric substrate; 2. Conductive thin film pattern; 21. First busbar region; 22. Second busbar region; 23. Interdigitated region; 231. First electrode finger; 232. Second electrode finger; 24. Pseudo-finger region; 241. First pseudo-finger; 242. Second pseudo-finger; 25. Reflective region. Detailed Implementation
[0038] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.
[0039] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.
[0040] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.
[0041] In the description of this embodiment, terms such as "upper," "lower," "left," and "right" are based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of description and simplification of operation, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.
[0042] Furthermore, the terms "first" and "second" are merely used to distinguish between different terms in description and do not have any special meaning.
[0043] Comparative Example 1:
[0044] In recent years, elastic wave devices based on piezoelectric substrates have attracted widespread attention due to their high Q value (quality factor), large electromechanical coupling coefficient, and good heat dissipation, and have been applied in many fields such as radar, communication, and navigation.
[0045] Figure 1 A schematic diagram of a typical elastic wave resonator based on a piezoelectric substrate is shown. This resonator consists of a conductive thin film pattern 2 formed on a piezoelectric substrate 1. The conductive thin film pattern 2 includes interdigitated transducer (IDT) electrodes, reflector electrodes, interdigitated transducer busbars, and reflector busbars. The IDT electrodes include multiple first electrode fingers 231 and multiple second electrode fingers 232 interleaved with each other, as well as first and second busbars facing each other in the extension direction of the first electrode fingers 231 and second electrode fingers 232. The distance between adjacent first electrode fingers 231 (or second electrode fingers 232) is generally referred to as the "wavelength" of the IDT. The overlapping distance between the first electrode fingers 231 and second electrode fingers 232 is generally referred to as the "aperture" or finger length of the IDT.
[0046] Specifically, dummy fingers exist in the region between the multiple first electrode fingers 231 and the second busbar, and in the region between the multiple second electrode fingers 232 and the first busbar. The dummy fingers include first dummy fingers 241 and second dummy fingers 242. The multiple first dummy fingers 241 and the multiple first electrode fingers 231 are connected to the first busbar, and the multiple second dummy fingers 242 and the multiple second electrode fingers 232 are connected to the second busbar.
[0047] To more clearly define the functions of each region of the elastic wave resonator, Figure 2 The diagram shows the regional division of the conductive thin film pattern 2 in the elastic wave resonator. The first bus region 21 is mainly used for the input and output of the resonator signal; the interdigitated region 23 is mainly used for the conversion of electroacoustic signals; the pseudo-finger region 24 mainly prevents the leakage of elastic waves; and the reflection region 25 is located on both sides of the interdigitated region 23 along the direction of elastic wave propagation, mainly for reflecting elastic waves.
[0048] Figure 3 The measured admittance / conductance-frequency curves of the elastic wave resonator in this comparative example are shown. As can be seen from the curves, the elastic wave resonator exhibits a transverse mode, specifically characterized by fluctuations in admittance and conductance between the resonant and anti-resonant frequencies. This "transverse mode" is typically caused by diffraction of the elastic wave during propagation.
[0049] Comparative Example 2:
[0050] Figure 4A schematic diagram of the elastic wave resonator provided in this comparative example is shown. The elastic wave resonator consists of a piezoelectric substrate 1 and a conductive thin film pattern 2 formed on the piezoelectric substrate 1. The conductive thin film pattern 2 is composed of four regions: a first bus region 21, a reflection region 25, a pseudo-finger region 24, and an interdigitated finger region 23. The first bus region 21 is mainly used for the input and output of the resonator signal; the reflection region 25 is disposed on both sides of the interdigitated finger region 23 along the direction of elastic wave propagation and is mainly used for reflecting elastic waves; the pseudo-finger region 24 mainly prevents the leakage of elastic waves; the interdigitated finger region 23 is mainly used for the conversion of electroacoustic signals, and the interdigitated finger region 23 includes multiple first electrode fingers 231 and second electrode fingers 232 arranged in a staggered manner.
[0051] The difference between the elastic wave resonator of this comparative example and the elastic wave resonator of Comparative Example 1 is that the lengths of the first electrode finger 231 and the second electrode finger 232 in the interdigitated region 23 of the elastic wave resonator of this comparative example gradually change with the direction of elastic wave propagation, so that the shape formed by the upper and lower edges of the interdigitated region 23 is different from that of the elastic wave resonator of Comparative Example 1. In this way, the transverse mode of the elastic wave resonator can be suppressed.
[0052] Figure 5 The measured admittance / conductance-frequency curves of the elastic wave resonator in this comparative example are shown. As can be seen from the curves, the admittance and conductance of this elastic wave resonator show virtually no fluctuations between the resonant and anti-resonant frequencies, and there is essentially no transverse mode.
[0053] However, in actual filter design, a single elastic wave resonator often suffers from poor filter performance and low layout utilization due to its small aperture. Therefore, multiple elastic wave resonators are usually cascaded into a cascaded resonator for design.
[0054] Comparative Example 3:
[0055] Figure 6 A schematic diagram of the cascaded resonator provided in this comparative example is shown. The cascaded resonator consists of a piezoelectric substrate 1 and a conductive thin film pattern 2 formed on the piezoelectric substrate 1. The conductive thin film pattern 2 comprises five regions: a first bus region 21, a second bus region 22, a reflection region 25, a pseudo-finger region 24, and an interdigitated finger region 23. The first bus region 21 is mainly used for the input and output of resonator signals; the second bus region 22 is mainly used for signal transmission between resonators; the reflection region 25 is located on both sides of the interdigitated finger region 23 along the direction of elastic wave propagation and is mainly used for reflecting elastic waves; the pseudo-finger region 24 mainly prevents elastic wave leakage; and the interdigitated finger region 23 is mainly used for the conversion of electroacoustic signals. The interdigitated finger region 23 includes multiple first electrode fingers 231 and second electrode fingers 232 arranged in a staggered manner. The lengths of the first electrode fingers 231 and second electrode fingers 232 in the interdigitated finger region 23 gradually change with the direction of elastic wave propagation.
[0056] The cascaded resonator in this comparative example is equivalent to the elastic wave resonator in Comparative Example 2; that is, the elastic wave resonator in Comparative Example 2 is split into two cascaded resonators. Therefore, this cascaded resonator also has the function of transverse mode suppression.
[0057] However, the cascaded resonator in this comparative example significantly increases the area of the resonator layout compared to the elastic wave resonator in Comparative Example 2, which is not conducive to the miniaturization of the device.
[0058] Example 1:
[0059] Figure 7 A schematic diagram of the cascaded resonator provided in this embodiment is shown. The cascaded resonator includes a piezoelectric substrate 1 and a conductive thin film pattern 2 disposed on the piezoelectric substrate 1. The conductive thin film pattern 2 includes a first bus region 21, a second bus region 22, an interdigitated region 23, and a pseudo-finger region 24, wherein:
[0060] The two first bus regions 21 extend along the direction of elastic wave propagation and are arranged at intervals, and are used for the input and output of the resonator signal;
[0061] Several second bus regions 22 are disposed between two first bus regions 21 to divide the area between the two first bus regions 21 into several interdigitated regions 23 and to realize signal transmission between adjacent interdigitated regions 23.
[0062] The interdigitated region 23 is used for the conversion of electroacoustic signals. The length of the electrode fingers in the interdigitated region 23 gradually changes with the direction of elastic wave propagation, making the edge of the interdigitated region 23 zigzag or curved. The edge shape of the second bus region 22 is the same as or a mirror image of the edge shape of the interdigitated region 23.
[0063] The pseudo-finger area 24 is located between the first busbar area 21 and the interdigitated finger area 23 adjacent to the first busbar area 21 to prevent elastic wave leakage.
[0064] Specifically, the interdigitated region 23 includes a first electrode finger 231 and a second electrode finger 232 that are interleaved and parallel to each other in the direction of elastic wave propagation. The first end of the first electrode finger 231 is connected to the first busbar region 21 or the second busbar region 22 on the first side, and the second end of the first electrode finger 231 is disconnected from the second busbar region 22 or the first busbar region 21 on the second side. The first end of the second electrode finger 232 is disconnected from the first busbar region 21 or the second busbar region 22 on the first side, and the second end of the second electrode finger 232 is connected to the second busbar region 22 or the first busbar region 21 on the second side.
[0065] In this embodiment, each second busbar 22 is also provided with a pseudo finger area 24 between it and the interdigitated finger area 23 adjacent to the second busbar 22, and the number of pseudo finger areas 24 is twice the number of interdigitated finger areas 23.
[0066] Each pseudo-finger area 24 includes a first pseudo-finger 241 and a second pseudo-finger 242. The first pseudo-finger 241 is disposed on the first busbar area 21 (or the second busbar area 22) on the first side and is arranged at intervals opposite to the first end of each second electrode finger 232. The second pseudo-finger 242 is disposed on the first busbar area 21 (or the second busbar area 22) on the second side and is arranged at intervals opposite to the second end of each first electrode finger 231.
[0067] Specifically, the length dimensions of each first electrode finger 231 and second electrode finger 232 in the interdigitated region 23 in the direction of elastic wave propagation gradually change with a set weighting coefficient, so that the edge of the interdigitated region 23 presents a special shape, which is exemplified by a broken line shape in this embodiment.
[0068] Furthermore, the two side edges of the single interdigitated region 23 are mirror-symmetrical, and the two side edges of the second confluence region 22 are also mirror-symmetrical.
[0069] In addition, the conductive thin film pattern 2 also includes a reflective region 25, which is located on both sides of the interdigitated region 23 along the direction of elastic wave propagation. The reflective region 25 is used to reflect elastic waves.
[0070] The cascaded resonator in this embodiment is equivalent to the cascaded resonator in Comparative Example 3. The difference lies in that the edge shape of the second bus region 22 of the cascaded resonator in this embodiment is the same as or a mirror image of the edge shape of the interdigitated region 23, and the edge shape of the pseudo-finger region 24 adjacent to the second bus region 22 is the same as or a mirror image of the shape formed by connecting the upper and lower edges of the plurality of interdigitated regions 23. In this way, the size of the cascaded resonator can be reduced while achieving the transverse mode suppression function of the device.
[0071] Figure 8 The measured admittance / conductance-frequency curves of the cascaded resonator in this embodiment are shown. As can be seen from the curves, the admittance and conductance of this cascaded resonator show virtually no fluctuations between the resonant and anti-resonant frequencies, and there is essentially no transverse mode.
[0072] Example 2:
[0073] Figure 9A schematic diagram of the cascaded resonator provided in this embodiment is shown. The cascaded resonator includes a piezoelectric substrate 1 and a conductive thin film pattern 2 disposed on the piezoelectric substrate 1. The conductive thin film pattern 2 includes a first bus region 21, a second bus region 22, interdigitated regions 23, pseudo-finger regions 24, and a reflection region 25. The first bus region 21 is used for the input and output of the resonator signal. The second bus region 22 is used to divide the area between the two first bus regions 21 into several interdigitated regions 23 and realize signal transmission between adjacent interdigitated regions 23. The interdigitated regions 23 are used for the conversion of electroacoustic signals. The length of the electrode fingers of the interdigitated regions 23 gradually changes with the direction of elastic wave propagation, so that the edge of the interdigitated regions 23 is zigzag-shaped. The edge shape of the second bus region 22 is the same as or a mirror image of the edge shape of the interdigitated regions 23. The pseudo-finger region 24 is disposed between the first bus region 21 and the interdigitated regions 23 adjacent to the first bus region 21 to prevent elastic wave leakage.
[0074] The difference between the cascaded resonator in this embodiment and the cascaded resonator in Embodiment 1 is that the interdigitated region 23 and the second bus region 22 of the cascaded resonator in this embodiment are not connected through the pseudo-finger region 24, that is, the number of pseudo-finger regions 24 is fixed at two; the pseudo-finger region 24 connected to the first bus region 21 includes a first pseudo-finger 241 and a second pseudo-finger 242. The first pseudo-finger 241 is disposed on the first bus region 21 on the first side and is arranged at intervals opposite to the first end of each second electrode finger 232, and the second pseudo-finger 242 is disposed on the first bus region 21 on the second side and is arranged at intervals opposite to the second end of each first electrode finger 231. In this way, the size of the cascaded resonator can be further reduced.
[0075] Example 3:
[0076] Figure 10 A schematic diagram of the cascaded resonator provided in this embodiment is shown. The cascaded resonator includes a piezoelectric substrate 1 and a conductive thin film pattern 2 disposed on the piezoelectric substrate 1. The conductive thin film pattern 2 includes a first bus region 21, a second bus region 22, interdigitated regions 23, pseudo-finger regions 24, and a reflection region 25. The first bus region 21 is used for the input and output of the resonator signal. The second bus region 22 is used to divide the area between two first bus regions 21 into several interdigitated regions 23 and realize signal transmission between adjacent interdigitated regions 23. The interdigitated regions 23 are used for the conversion of electroacoustic signals. The length of the electrode fingers of the interdigitated regions 23 gradually changes with the direction of elastic wave propagation, so that the edge of the interdigitated regions 23 is zigzag-shaped. The edge shape of the second bus region 22 is the same as or a mirror image of the edge shape of the interdigitated regions 23. The pseudo-finger region 24 is used to prevent elastic wave leakage.
[0077] The difference between the cascaded resonator in this embodiment and the cascaded resonator in Embodiment 2 is that the number of cascaded resonators is different. Based on the cascaded resonator in Embodiment 2, the number of the second bus region 22 and the interdigitated region 23 can be further expanded.
[0078] For the same reasons as in Embodiments 1 and 2, the structure of this embodiment can not only exhibit good transverse mode suppression function, but also greatly reduce the size of the cascaded resonator.
[0079] Example 4:
[0080] Figure 11 A schematic diagram of the cascaded resonator provided in this embodiment is shown. The cascaded resonator includes a piezoelectric substrate 1 and a conductive thin film pattern 2 disposed on the piezoelectric substrate 1. The conductive thin film pattern 2 includes a first bus region 21, a second bus region 22, interdigitated regions 23, pseudo-finger regions 24, and a reflection region 25. The first bus region 21 is used for the input and output of the resonator signal. The second bus region 22 is used to divide the area between two first bus regions 21 into several interdigitated regions 23 and realize signal transmission between adjacent interdigitated regions 23. The interdigitated regions 23 are used for the conversion of electroacoustic signals. The length of the electrode fingers of the interdigitated regions 23 gradually changes with the direction of elastic wave propagation, so that the edge of the interdigitated regions 23 is curved. The edge shape of the second bus region 22 is the same as or a mirror image of the edge shape of the interdigitated regions 23. The pseudo-finger region 24 is used to prevent elastic wave leakage.
[0081] The difference between the cascaded resonator in this embodiment and the cascaded resonator in Embodiment 2 is that the edge shapes of the interdigitated region 23 and the second bus region 22 of the cascaded resonators are different. In this embodiment, the edge shapes of the interdigitated region 23 and the second bus region 22 are both periodic curves along the direction of elastic wave propagation.
[0082] For the same reasons as in Embodiments 1, 2 and 3, the structure of this embodiment can not only exhibit good transverse mode suppression, but also greatly reduce the size of the cascaded resonator.
[0083] Example 5:
[0084] Figure 12A schematic diagram of the cascaded resonator provided in this embodiment is shown. The cascaded resonator includes a piezoelectric substrate 1 and a conductive thin film pattern 2 disposed on the piezoelectric substrate 1. The conductive thin film pattern 2 includes a first bus region 21, a second bus region 22, interdigitated regions 23, pseudo-finger regions 24, and a reflection region 25. The first bus region 21 is used for the input and output of the resonator signal. The second bus region 22 is used to divide the area between two first bus regions 21 into several interdigitated regions 23 and realize signal transmission between adjacent interdigitated regions 23. The interdigitated regions 23 are used for the conversion of electroacoustic signals. The length of the electrode fingers of the interdigitated regions 23 gradually changes with the direction of elastic wave propagation, so that the edge of the interdigitated regions 23 is curved. The edge shape of the second bus region 22 is the same as or a mirror image of the edge shape of the interdigitated regions 23. The pseudo-finger region 24 is used to prevent elastic wave leakage.
[0085] The difference between the cascaded resonator in this embodiment and the cascaded resonator in Embodiment 4 is that the edge shapes of the interdigitated region 23 and the second bus region 22 of the two cascaded resonators are different. The edge shapes of the interdigitated region 23 and the second bus region 22 in this embodiment are non-periodic curves.
[0086] For the same reasons as in Embodiments 1, 2, 3 and 4, the structure of this embodiment can not only exhibit good transverse mode suppression, but also greatly reduce the size of the cascaded resonator.
[0087] Example 6:
[0088] Based on Embodiments 1 to 5, this embodiment provides an elastic wave filter, including a series arm resonator and a parallel arm resonator, wherein at least one of the series arm resonator and the parallel arm resonator includes the cascaded resonator described above, thereby ensuring the stable performance of the filter.
[0089] Example 7:
[0090] Based on Embodiment Six, this embodiment provides a multiplexer, including an antenna terminal connected to an antenna and a plurality of filter devices connected to the antenna terminal, wherein at least one filter device is the aforementioned elastic wave filter, thereby ensuring the stable performance of the multiplexer.
[0091] In summary, the cascaded resonators in the above embodiments can split an elastic wave resonator into two or more cascaded resonators by setting a second bus region 22. By optimizing the edge shape of the second bus region 22 to make it the same as or a mirror image of the edge shape of the interdigitated region 23, it exhibits good transverse mode suppression function, thereby ensuring the performance of elastic wave filters and multiplexers based on the cascaded resonators.
[0092] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art will be able to make various obvious changes, readjustments, and substitutions without departing from the scope of protection of the present invention. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.
Claims
1. A cascaded resonator, comprising a piezoelectric substrate (1) and a conductive thin film pattern (2) disposed on the piezoelectric substrate (1), characterized in that, The conductive thin film pattern (2) includes a first busbar region (21), a second busbar region (22), an interdigitated region (23), and a pseudo-finger region (24), wherein: The two first bus regions (21) extend along the direction of elastic wave propagation and are arranged at intervals, for the input and output of resonator signals; A plurality of second bus regions (22) are disposed between two first bus regions (21) to divide the area between the two first bus regions (21) into a plurality of interdigitated regions (23) and to realize signal transmission between adjacent interdigitated regions (23); The interdigitated area (23) is used for the conversion of electroacoustic signals. The length of the electrode fingers of the interdigitated area (23) gradually changes with the direction of elastic wave propagation, so that the edge of the interdigitated area (23) is in the shape of a broken line or a curve. The edge shape of the second busbar (22) is the same as or a mirror image of the edge shape of the interdigitated area (23). The pseudo-finger area (24) is disposed between the first confluence area (21) and the interdigitated finger area (23) adjacent to the first confluence area (21) to prevent elastic wave leakage.
2. The cascaded resonator according to claim 1, characterized in that, The interdigitated region (23) includes a first electrode finger (231) and a second electrode finger (232) that are interleaved and parallel to each other in the direction of elastic wave propagation. The first end of the first electrode finger (231) is connected to the first busbar region (21) or the second busbar region (22) on the first side. The second end of the first electrode finger (231) is disconnected from the second busbar region (22) or the first busbar region (21) on the second side. The first end of the second electrode finger (232) is disconnected from the first busbar region (21) or the second busbar region (22) on the first side. The second end of the second electrode finger (232) is connected to the second busbar region (22) or the first busbar region (21) on the second side.
3. The cascaded resonator according to claim 2, characterized in that, The pseudofinger area (24) includes a first pseudofinger (241) and a second pseudofinger (242). The first pseudofinger (241) is disposed on the first busbar area (21) on the first side and is arranged at intervals opposite to the first end of each second electrode finger (232). The second pseudofinger (242) is disposed on the first busbar area (21) on the second side and is arranged at intervals opposite to the second end of each first electrode finger (231).
4. The cascaded resonator according to claim 2, characterized in that, The length dimensions of each of the first electrode fingers (231) and the second electrode fingers (232) in the interdigitated region (23) along the direction of elastic wave propagation gradually change with a weighting coefficient.
5. The cascaded resonator according to claim 1, characterized in that, Each of the second busbars (22) is also provided with a pseudo-finger area (24) between it and the interdigitated area (23) adjacent to the second busbar (22), and the number of pseudo-finger areas (24) is twice the number of interdigitated areas (23).
6. The cascaded resonator according to claim 1, characterized in that, The conductive thin film pattern (2) further includes a reflective region (25), which is located on both sides of the interdigitated region (23) along the direction of elastic wave propagation. The reflective region (25) is used to reflect elastic waves.
7. The cascaded resonator according to claim 1, characterized in that, The two sides of the single interdigitated region (23) are mirror-symmetrical, and the two sides of the second confluence region (22) are mirror-symmetrical.
8. The cascaded resonator according to claim 1, characterized in that, The edge lines of the interdigitated area (23) are periodic.
9. An elastic wave filter, characterized in that, It includes series arm resonators and parallel arm resonators, wherein the series arm resonators and / or the parallel arm resonators include the cascaded resonators according to any one of claims 1-8.
10. A multiplexer, characterized in that, It includes an antenna terminal connected to an antenna and a plurality of filter devices connected to the antenna terminal, wherein at least one of the filter devices is the elastic wave filter as described in claim 9.