Electroacoustic resonator and RF filter

Abstract

Electroacoustic resonator, comprehensive an acoustic track with a first busbar and a second busbar, a medium excitation range between the first and second busbars, an electrode structure with a first electrical connection, a second electrical connection and a plurality of electrode fingers, which are electrically connected to either the first or the second electrical connection, a first gap region between the middle excitation area and the first busbar and a second gap region between the middle excitation area and the second busbar, a velocity compensation structure designed and configured to create a homogeneous transverse velocity profile, wherein the velocity compensation structure includes dielectric material in the first and / or second gap region and wherein the dielectric material chosen for the velocity compensation structure has a smaller specific acoustic impedance than the material of the electrode structure.

Description

[0001] The present invention relates to electroacoustic resonators that can be combined to form RF filters that can be used in wireless communication devices.

[0002] Electroacoustic resonators can be electrically combined, for example in a ladder-type or lattice-type circuit topology, to form RF filters such as bandpass or bandstop filters. Such filters can be used in wireless communication devices. The trend toward miniaturization necessitates smaller dimensions. The trend toward a greater number of wireless features leads to stricter specifications that must be met. Therefore, a common challenge is providing resonators for filters with good electrical and acoustic performance that comply with these specifications.

[0003] Conventional electroacoustic resonators can include an acoustic track in which acoustic waves can propagate. An electrode structure is arranged on a piezoelectric material and converts—via the piezoelectric effect—between electromagnetic RF signals and acoustic RF signals propagating in the acoustic track. Typically, it is desirable to have a single acoustic wave mode. However, in real transducers, interfering modes can be excited, which degrade the acoustic and electrical performance of the resonator and, consequently, also of the RF filter.

[0004] From US 2013 / 0051588 A1, electroacoustic transducers and corresponding resonators with reduced losses and reduced transverse emission of acoustic energy and improved performance as well as improved suppression of transverse modes are known.

[0005] However, it was found that the technical measures disclosed therein may have reduced effects in a new type of electroacoustic resonator that uses the piezoelectric material provided as a thin film.

[0006] DE 10 2014 118897 A1 describes a resonator in which a dielectric is used that has an acoustic impedance as close as possible to that of the electrode material used. However, even here only a reduced improvement in electrical and acoustic performance occurs.

[0007] Therefore, it is desirable to have an improved electroacoustic resonator that provides RF filters with good electrical and acoustic performance and is compatible with a piezoelectric thin-film material.

[0008] Furthermore, a suitable transducer should have suppressed or eliminated interference modes, reduced acoustic losses, improved dielectric strength to prevent electrostatic discharge, and improved power stability.

[0009] For this purpose, an electroacoustic resonator is provided according to the independent claim. Dependent claims provide preferred embodiments and preferred filters.

[0010] The electroacoustic resonator comprises an acoustic track with a first busbar and a second busbar. The resonator also features a central excitation region between the first and second busbars. Furthermore, the resonator has an electrode structure with a first electrical terminal, a second electrical terminal, and a plurality of electrode fingers. Each of the plurality of electrode fingers is electrically connected to either the first or the second electrical terminal. The resonator also features a first gap region between the central excitation region and the first busbar, and a second gap region between the central excitation region and the second busbar.

[0011] Furthermore, the resonator has a velocity compensation structure. The velocity compensation structure is designed and configured to form a homogeneous transverse velocity profile, wherein the velocity compensation structure comprises dielectric material in the first and / or second gap region, and wherein the dielectric material chosen for the velocity compensation structure has a lower specific acoustic impedance than the material of the electrode structure.

[0012] Thus, the present electroacoustic resonator differs drastically from the technical measures provided in US 2013 / 0051588 A1 or DE 10 2014 118897 A1.

[0013] In the present resonator, the acoustic track is the region of the piezoelectric material designated for the propagation of acoustic waves. The direction of propagation of the acoustic waves is defined by the longitudinal direction of the acoustic track and the resonator. The first and second transverse sides of the acoustic track flank it and extend longitudinally parallel to a central excitation region of the acoustic track. The first and second electrical terminals can (currently) comprise the busbars that supply the electrode fingers with an electromagnetic RF signal obtained from an external circuit. The busbars can be located on the first and second transverse sides, respectively. The electrode fingers extend along the transverse direction.The transverse direction is essentially orthogonal to the longitudinal direction in the plane, which is essentially defined by the surface of the piezoelectric material. The velocity compensation structure can include a material positioned at specific locations in the acoustic track to improve the homogeneity of the transverse velocity profile. The transverse velocity profile is defined as the velocity of the acoustic waves propagating in the acoustic track, which is considered to extend along a path in the transverse direction from one corresponding transverse side to the other of the first and second transverse sides.

[0014] Thus, the transverse velocity profile determines the wave velocity as a function of the transverse position.

[0015] It should be noted that "x" denotes a position along the longitudinal direction. "y" denotes a position along the transverse direction, and "z" denotes a position along the vertical direction orthogonal to both the longitudinal and transverse directions.

[0016] Thus, the transverse velocity profile determines the relationship between the transverse position y and the velocity of the acoustic waves.

[0017] It has been found that the propagation of acoustic waves in thin-film-based electroacoustic resonators differs from the propagation of waves in conventional electroacoustic resonators with an electrode structure mounted on a piezoelectric mass material. Wave propagation determines acoustic losses, which can be caused by wave emission in a transverse direction or by transverse modes. Unfortunately, measures to achieve a piston mode, as defined in the aforementioned publication, become less effective when a piezoelectric thin-film material is used.

[0018] The presented resonator is based on a counterintuitive two-stage approach: The resonator is compatible with piezoelectric thin films and can still reduce acoustic losses. However, to obtain such a resonator, a departure from conventional methods was deemed necessary.

[0019] The gap region forms an electrical gap between the two busbars. When the resonator is operating, the two busbars are connected with opposite polarities. Without an electrical gap between the busbars, the resonator would be short-circuited and inoperative. To achieve electrical isolation between the busbars, a corresponding gap is provided between the conductive material of one electrode and the conductive material of the corresponding electrode. This can be achieved by maintaining a distance between the fingertips of one electrode and the conductive material of the corresponding electrode. However, the situation with electroacoustic resonators is complex, and each segment of the conductive material in the electrode structure also affects the acoustics of the resonator.A gap between the conductive material of the two electrodes thus affects the propagation of acoustic waves. In general, a reduction in the mass load of material arranged on the piezoelectric material, caused, for example, by a gap in the electrode structure, leads to a local increase in acoustic velocity. This local increase in acoustic velocity results in heterogeneity of the transverse velocity profile, which follows the recommendation of US 2013 / 0051588 A1. Other parameters that can change the velocity include the stiffness values ​​of a material.

[0020] However, in order to achieve the counterintuitive homogeneous transverse velocity profile, the velocity compensation structure can create a local mass loading, especially in the gaps, which creates a homogeneous environment for the acoustic waves but prevents a short circuit of the opposing electrodes.

[0021] Accordingly, it is possible that the compensation structure comprises such a material and a pattern of components that a homogeneous acoustic impedance is created for the acoustic waves by the mass loading on the piezoelectric material. Thus, the acoustic waves experience a homogeneous acoustic environment between the busbars.

[0022] It is possible that the material of the velocity compensation structure is provided as a plurality of dielectric strips (patches) arranged in the first and / or second gap region.

[0023] In particular, the patches can be placed on the fingertips that point towards the opposite electrode.

[0024] It is possible that the material of the velocity compensation structure is located in a vertical position below, above, and / or next to the material of the electrode fingers.

[0025] If the material of the compensation structure is provided as patches arranged at the fingertips, the material can be designed so that there is no overlap between the material of the electrode fingers and the material of the compensation structure. However, it is possible that the material of the electrode fingers or the electrode structure overlaps with the material of the compensation structure, or vice versa, for example, if additional material of the compensation structure is provided alongside the electrode fingers.

[0026] It is possible that the velocity compensation structure material is provided as patches with an extension along the longitudinal direction that is smaller, equal to, or larger than the width of the electrode fingers.

[0027] The electrode fingers extend along the transverse direction. The width of the electrode fingers is defined as their thickness in the longitudinal direction. The patches can have a longitudinal extent that is equal to or differs from the finger width.

[0028] If the acoustic impedance of the compensation structure material is essentially equal to the acoustic impedance of the electrode finger material, then the longitudinal extent of the patches can be equal to the finger thickness. In particular, the height of the patches in the vertical direction can be equal to the height of the electrode fingers in the vertical direction.

[0029] According to the invention, the material selected for the compensation structure is chosen to have a lower (specific) acoustic impedance than the material of the electrode structure, so that the reduced impedance is achieved through increased mass loading and / or increased volume. This allows for an excess of height, width, or length in the patches to be created in order to achieve an overall homogeneous acoustic impedance in the acoustic track.

[0030] Different longitudinal, transverse, or vertical extents can be advantageous when further effects on the propagation of acoustic waves are desired. For example, a longitudinal extent allows for adjusting the velocity for different resonators. Thus, series and parallel resonators with different longitudinal extents can be used to compensate for varying spacing and / or metallization ratios. In this context, a series resonator can be an electroacoustic resonator connected in series in the signal path of an RF filter. A parallel resonator forms a resonator in a shunt path, electrically connecting the filter's signal path to ground.

[0031] Although it is possible for the height of the compensation structure material to vary locally, it is preferred that the compensation structure material be applied to the surface of the converter in just a few production steps. Therefore, it is preferred that the compensation structure material has a homogeneous height across the entire chip.

[0032] A special extension of the compensation structure material in the transverse direction enables the compensation of contact angles at the finger ends, which can occur in real transducers due to production-related limitations. This allows for fine-tuning of the continuous velocity profile.

[0033] Furthermore, the specific shape of the patches in the compensation structure can be modified for further optimization.

[0034] It is possible that the electroacoustic resonator includes stubby fingers. The material of the velocity compensation structure is arranged in a transverse direction between the stubby fingers and the electrode fingers of the respective opposite electrical connection.

[0035] Stub fingers (an alternative name is dummy fingers) can be used to tune wave propagation. In conventional resonators, the transverse gaps between the structures of the opposing electrodes are tightly structured. However, tight gaps correspond to small distances between the electrodes.

[0036] The provision of the compensation structure allows for larger distances between opposing electrodes, thus increasing the dielectric strength, e.g. against ESD pulses (ESD = Electrostatic Discharge), and the power stability.

[0037] It is possible that the dielectric material used for the compensation structure has a lower relative electrical permittivity than the dielectric material located near the compensation structure. The dielectric material near the compensation structure could be the piezoelectric material beneath the electrode structure, a temperature compensation layer, or a trimming layer above or below the electrode structure. A reduced relative permittivity of the compensation structure material allows for a reduction of the electric field in the transverse gaps, thus further improving dielectric strength and power stability. Additionally, potentially degrading excitation or conversion of acoustic waves in the gap region can be reduced.

[0038] Thus, the provision of the compensation structure ensures good compatibility with stubby fingers.

[0039] It is possible that the electroacoustic resonator is selected from a SAW resonator (SAW = Surface Acoustic Wave), a TC-SAW resonator (TC = Temperature Compensation), a GBAW resonator (GBAW = Guided Bulk Acoustic Wave) and a TF-SAW resonator (TF = Thin Film).

[0040] A TC-SAW resonator incorporates a temperature compensation material above or below the electrode structure. The stiffness parameters of the temperature compensation material are selected to reduce or eliminate temperature-induced drift in the resonator's characteristic frequencies. This temperature compensation structure may comprise an oxide, such as silicon oxide (SiO₂).

[0041] A GBAW resonator comprises a sagittal waveguide structure arranged above and / or below the electrode structure, so that the propagating waves spread along the interface between the piezoelectric material and a corresponding waveguide layer.

[0042] A TF-SAW resonator utilizes a piezoelectric material provided as a thin film. The thin film can be produced using thin-film processing techniques, such as wafer bonding followed by mechanical polishing or smart cut, and with conventional deposition techniques, such as CVD (chemical vapor deposition), PVD (physical vapor deposition), sputtering, MBE (molecular beam epitaxy), and the like.

[0043] It is possible that the piezoelectric thin-film material is arranged on a support substrate and functional layers, e.g. for temperature compensation, are added to the stack.

[0044] The electrode structure can be selected from an unweighted transducer, an apodized transducer, a tilted transducer, a kinked tilted transducer, and a zigzag tilted transducer. In an unweighted transducer, each pair of electrode fingers contributes essentially the same amount to the conversion between electromagnetic RF signals and acoustic RF signals. For this purpose, the overlap along the transverse direction of adjacent electrode fingers of opposite polarity along the longitudinal direction of the acoustic track can be equal.

[0045] In contrast, a weighted transducer makes different contributions to the overall excitation of acoustic waves for different pairs of adjacent electrode fingers of opposite polarity. For this purpose, the transverse overlap of the adjacent fingers can differ along the longitudinal direction. Such a weighted transducer can be an apodized transducer. An apodized transducer can be a sine-weighted transducer or a cosine-weighted transducer.

[0046] An inclined transducer has an angle between the propagation direction of the acoustic waves and the extent of the busbars or gaps, such that each electrode finger is shifted in the transverse direction relative to its neighboring electrode fingers. Typically, the electrode fingers are oriented orthogonally to the piezoelectric axis of the piezoelectric material. The electrode fingers are also typically oriented orthogonally to the propagation direction of the acoustic waves of the desired acoustic principal mode. Thus, the extent of the busbars and gaps in an inclined transducer is not parallel to the propagation direction of acoustic waves, i.e., the longitudinal direction.

[0047] It has been found that inclined or apodizing resonators in a TF-SAW resonator can even effectively reduce unwanted transverse modes.

[0048] Furthermore, it was found that diffraction effects in the gap region of an apodized or tilted resonator have a greater impact on the resonator's performance than in unweighted resonators, because the interaction between acoustic waves and the gap region is amplified in such geometries. Thus, the counterintuitive approach of providing a homogeneous transverse velocity profile, which can correspond to a homogeneous acoustic impedance even in the gap region, minimizes undesirable acoustic effects in the gap region.

[0049] Thus, improved electroacoustic resonators compatible with piezoelectric thin-film materials can be achieved using the measures described above.

[0050] A kinked inclined transducer has segments along its acoustic path with different angles of inclination. Therefore, a kinked inclined transducer has at least two segments. It is possible that the angle of inclination in one segment is 0°. Such a segment corresponds to a segment of a conventional, non-inclined resonator.

[0051] A zigzag inclined converter comprises iteratively repeated inclined segments with angles of inclination with alternating signs.

[0052] It is possible that the electroacoustic resonator is selected from a single-port resonator, a two-port resonator, and a DMS resonator (DMS = Dual Mode SAW).

[0053] A single-port resonator has only one port for connecting to an external circuit environment. A dual-port resonator has two ports for connecting to an external circuit environment. One of the two ports can be an input port for receiving electromagnetic RF signals. The other port can be an output port for providing electromagnetic RF signals to an external circuit environment.

[0054] A strain gauge resonator can be configured as a single-port or a dual-port resonator. More than one fundamental acoustic mode can propagate within a strain gauge resonator. A strain gauge resonator can include a first interdigital converter (IDC) and a second IDC, or more than two IDCs.

[0055] The resonator can have a single transducer or multiple transducers. The single or multiple transducers of the resonator can be arranged between elements of an acoustic reflector, e.g., elements of Bragg reflectors.

[0056] One or more transducers can be weighted, apodized, inclined, kinked inclined, or zigzagged inclined. However, it is also possible for multiple transducers to be inclined in such a way that a plurality of transducers in the acoustic track form a kinked inclined or zigzagged inclined excitation structure.

[0057] The IDTs of resonators can be arranged between the reflector structures of the resonator.

[0058] It is possible to use the described resonator in an RF filter.

[0059] Accordingly, it is possible that an RF filter includes an electroacoustic resonator as described above.

[0060] The RF filter can be a bandpass filter or a bandstop filter and can be used in the front-end circuitry of a wireless communication device. It is possible for the RF filter to have a conductor-type or grid-type filter topology.

[0061] In a ladder-type filter topology, one or more series resonators are electrically connected in series in a signal path between an input port and an output port. One or more parallel resonators can be arranged in one or more shunt paths that electrically connect the signal path to ground.

[0062] A grid-type filter topology can have an input port and an output port. The input port can include a first input terminal and a second input terminal. The output port can include a first output terminal and a second output terminal. A grid-type filter topology is achieved when a resonator electrically connects the first input terminal to the second output terminal. Signal crossing of signals propagating through a first resonator and a second resonator is achieved.

[0063] It is possible that such a filter is a filter of a multiplexer. The multiplexer can be a duplexer, a quadplexer, or a multiplexer of a higher order than two. One, several, or all of the multiplexer's filters can be configured as described above.

[0064] The resonator described above reduces or smooths discontinuities in the transverse velocity profile via the compensation structure, resulting in a resonator with good electrical and acoustic properties that is compatible with piezoelectric thin-film materials.

[0065] Key aspects of the provided resonator and details of the preferred embodiments are illustrated and explained in the accompanying schematic drawings. Fig. Figure 1 shows a preferred acoustic impedance environment experienced by the acoustic waves; Fig. 2 shows the corresponding electrode structure; Fig. Figure 3 shows possible patch geometries in a top view; Fig. Figure 4 shows the corresponding cross-sections of the patches; Fig. Figure 5 shows an inclined IDT structure of a resonator; The Fig. 6 and Fig. Figure 7 shows embodiments of kinked inclined IDT structures; Fig. 8 and Fig. Figure 9 shows IDT structures inclined in a zigzag pattern; Fig. Figure 10 shows the electrode structure of a cosine-weighted transducer from a purely electrical point of view; Fig. Figure 11 shows a preferred acoustic impedance that is based on the acoustic waves of the in Fig. 10 of the converters shown is applied; and Fig. Figure 12 shows a possible application of the described resonators in a multiplexer.

[0066] Fig. Figure 1 shows a preferred acoustic impedance structure in a top-down view. The longitudinal direction extends along the x-direction. The transverse direction extends along the y-direction. In the upper part of Fig. Figure 1 shows the acoustic transverse velocity profile. Two busbars BB are provided at the flanks of the acoustic track, connecting the electrode fingers EF to an external circuit environment. The electrode fingers EF are not short-circuited, since Fig. 1 shows the acoustic properties of the transducer. Electrical properties can be derived from Fig. 2 can be taken from the data. The acoustic velocity between the two busbars BB is essentially homogeneous and constant and corresponds to that which is v. track The acoustic velocity is defined as v. The busbars have a higher mass load. Accordingly, the acoustic velocity in the area of ​​the busbars BB is lower and is defined as v. met This is referred to as... Typically, the busbars contain metals, and the metallization of the busbars reduces the acoustic velocity locally.

[0067] Fig. Figure 1 shows the desired structure when only the acoustics of the resonator are considered. However, discontinuities in the electrical structure are necessary to prevent a short circuit and ensure the excitation of acoustic waves.

[0068] Accordingly, it shows Fig. 2. A possible technical solution for providing an electrode structure without a short circuit, which is in Fig. The acoustic structure shown in Figure 1 can provide this. Electrode fingers EF and stub fingers SF can be arranged between the two busbars. The ends of the electrode fingers EF and the ends of the correspondingly opposing stub fingers SF are separated by a gap G. The gap G creates electrical insulation between the two electrodes. Material of the velocity compensation structure VCS is provided in the area of ​​the gap G, e.g., in the form of patches P. The patches P create homogeneity of acoustic velocity between the two busbars BB, as shown in the upper part of Figure 1. Fig. Figure 2 shows that without the presence of the velocity compensation structure VCS, the acoustic velocity in the gaps would be v tgap By providing the compensation structure VCS, the velocity in the gaps G can be reduced to the overall velocity in the middle excitation area v. trackThis reduces the acoustic velocity profile, as in Fig. 1 shown and achieved as desired, without short-circuiting the busbars BB.

[0069] Fig. Figure 3 shows two possible arrangements of the patches P relative to the electrode finger EF and the stub finger SF in a top view. In the left part of Fig. 3. Where electrode finger EF or stub finger SF material is present, patch P material is arranged on top of the corresponding finger material. In an area where no finger material is present, patch P material can be placed directly on the piezoelectric material. Thus, patch P can overlap the electrode fingers EF and the stub fingers SF, as shown in the left part of Figure 3. Fig. 3 shown.

[0070] In contrast, the right part of Fig. 3. An arrangement in which the material of patch P is located beneath the material of the fingers. Thus, the material of patch P is always located directly on the piezoelectric material. When patch P material is present, the material of the fingers is located on top of the corresponding patch material.

[0071] The two in Fig. The 3 arrangements shown are in Fig. 4 shown in a cross-section parallel to the yz-plane. The upper left part and the upper right part of Fig. 4 correspond to those in Fig. 3 idealized arrangements shown. The lower left part and the lower right part of Fig. Figure 4 shows a realistic distribution of the material with rounded edges, as it was actually produced. In the left part of Fig. 4. The material of patch P is arranged between fingers EF and SF where no finger material is present. Where finger material EF and SF is present, the material of patch P is arranged on the fingers.

[0072] In contrast, the right part of Fig. 4 the reverse arrangement in which the material of patch P is arranged on the piezoelectric material (not shown), while the material of fingers EF, SF is arranged accordingly on the material of patch P.

[0073] Fig. Figure 5 shows an important embodiment of the resonator in which the transducer, comprising the busbars, electrode fingers, stub fingers, and patches, is inclined. Thus, the extent of the busbars BB and the gap G deviates from an extent parallel to the longitudinal direction x, while the electrode fingers maintain their extent essentially along the transverse direction y. The inclination angle α can be between 2° and 20°, e.g., in the range of 10°.

[0074] Tilting a resonator is an effective means of reducing transverse modes, even or especially when using a piezoelectric thin-film material. Together with the velocity structure, this achieves good performance of a TF-SAW resonator.

[0075] Fig. Figure 6 shows the base area of ​​a bent, inclined transducer. The transducer comprises a first segment S1 and a second segment S2. The first segment S1 is inclined. The second segment S2 has a conventional orientation. In the inclined segment S1, the busbars are rotated relative to the busbars of the conventionally oriented segment S2. The direction of extension of the electrode fingers is the same for all segments.

[0076] Fig. Figure 7 shows a possible layout of a kinked inclined converter with two inclined segments. A first segment, S1, is inclined. The second segment, S2, is also inclined. The rotation can be the same in absolute value but opposite in sign for both inclined segments, S1 and S2.

[0077] Fig. Figure 8 shows the layout of a zigzag-tilted converter with four segments. Segments S1 and S3 have the same orientation. Segments S2 and S4 have the same orientation. Thus, the combination of segments S1 and S2 is repeated as segments S3 and S4. Furthermore, it shows Fig. 8 a zigzag inclined resonator in which each segment is inclined.

[0078] In contrast, it shows Fig. Figure 9 shows a converter inclined in a zigzag pattern, where segments S1 and S3 are inclined, while segments S2 and S4 are conventionally oriented. Additionally, the entire structure is rotated in the xy-plane.

[0079] Fig. Figure 10 shows a possible electrode layout for a cosine-weighted transducer. The busbars BB are connected to electrodes, and the length of the local overlap region varies along the longitudinal direction such that a maximum value is reached in the longitudinal central region of the transducer, while a reduced overlap length is achieved in the outer regions. Accordingly, the dotted curve COS follows the gaps and indicates the cosine weighting of the excitation.

[0080] It should be noted that Fig. Figure 10 shows the configuration exclusively with regard to the electrically important structures, without considering acoustically relevant parts, such as stubby fingers. Thus, the transducer can also have stubby fingers for the "upper" electrode.

[0081] In contrast, it shows Fig. 11. The acoustic configuration, which – due to stub fingers and / or the compensation structure – is homogeneous along the transverse direction between the busbars BB. The cosine weighting is only present for the electrical excitation. The acoustic properties are homogeneous – with respect to a λ periodicity along the longitudinal direction.

[0082] Fig. Figure 12 shows the possible applications of the resonator described above. Fig.Figure 12 shows a duplexer as an embodiment of a multiplexer MUL, to which the concept is generally applicable. The duplexer comprises a transmit filter TXF and a first receive filter RXF1 and a second receive filter RXF2. The transmit filter TXF, the first receive filter RXF1, and the second receive filter RXF2 form bandpass filters BPF. The transmit filter TXF and the first receive filter RXF1 are implemented in a ladder-type filter topology with series resonators SR electrically connected in the signal path. Parallel resonators PR are electrically connected in shunt paths that connect the signal path to ground. The resonators in the ladder-type circuit topologies can be single-port or dual-port resonators. The second receive filter RXF2 is implemented as a strain gauge filter with an input port comprising three input terminals and an output port comprising two output terminals. Each input terminal is connected to an input converter.Each output terminal is connected to an output transducer. Thus, five transducers are arranged between reflectors in the acoustic path of the strain gauge filter. An antenna AN can be connected to an antenna terminal AC. The antenna terminal AC is coupled to an output port of the transmit filter TXF and an input port of the first receive filter RXF1. An impedance matching circuit IMC can be provided between the AC and the input port of the first receive filter RXF1 to match the antenna impedance, or the output impedance of the transmit filter TXF, to the input impedance of the receive filter RXF1.

[0083] The resonator and filter are not limited to the technical features described above or the embodiments shown in the figures. Resonators may include further acoustically or electrically active elements, such as reflector elements or impedance matching elements, for example, for impedance conversion. Filters may include further resonators and acoustically active or inactive transducer structures and impedance elements. Reference symbol list AC antenna connection ON antenna BB busbar BPF bandpass filter COS Cosine weighting DMS DMS filter EF electrode finger G gap IMC impedance matching circuit MUL multiplexer, duplexer P Patch PR Parallel Resonator RXF1 ​​first receive filter RXF2 second receive filter S1,..,S4 converter segments SF Stummelfinger SR series resonator TXF transmit filter v speed VCS velocity compensation structure vmet acoustic velocity in the busbar vtgap acoustic velocity in the gap vtrack speed in the middle excitation range x Longitudinal direction y transverse direction z vertical direction α Inclination / shear angle of the busbar

Claims

[1] Electroacoustic resonator comprising an acoustic track with a first busbar and a second busbar, a medium excitation range between the first and second busbars, an electrode structure with a first electrical connection, a second electrical connection and a plurality of electrode fingers, which are electrically connected to either the first or the second electrical connection, a first gap region between the middle excitation area and the first busbar and a second gap region between the middle excitation area and the second busbar, a velocity compensation structure designed and configured to create a homogeneous transverse velocity profile, wherein the velocity compensation structure includes dielectric material in the first and / or second gap region and wherein the dielectric material chosen for the velocity compensation structure has a smaller specific acoustic impedance than the material of the electrode structure. [2] Electroacoustic resonator according to the preceding claim, wherein the material of the velocity compensation structure creates a homogeneous acoustic impedance. [3] Electroacoustic resonator according to one of the preceding claims, wherein the material of the velocity compensation structure is provided as a plurality of dielectric patches arranged in the first and / or second gap region. [4] Electroacoustic resonator according to one of the preceding claims, wherein the material of the velocity compensation structure is arranged vertically below the material of the electrode fingers, above the material of the electrode fingers and / or next to the material of the electrode fingers. [5] Electroacoustic resonator according to one of the preceding claims, wherein the material of the velocity compensation structure is provided as patches with an extent along the longitudinal direction that is less than, equal to or greater than a width of the electrode fingers. [6] Electroacoustic resonator according to one of the preceding claims, comprising stub fingers, wherein material of the velocity compensation structure is arranged in a transverse direction between the stub fingers and the electrode fingers of the correspondingly opposite electrical connection. [7] Electroacoustic resonator according to any of the preceding claims, selected from a SAW resonator, a TC-SAW resonator, a GBAW resonator, a TF-SAW resonator. [8] Electroacoustic resonator according to one of the preceding claims, wherein the electrode structure is selected from an unweighted transducer, an apodized transducer, an inclined transducer, a kinked inclined transducer, a zigzag inclined transducer. [9] Electroacoustic resonator according to one of the preceding claims, selected from a single-port resonator, a two-port resonator, a strain gauge resonator. [10] RF filter comprising an electroacoustic resonator according to any one of the preceding claims. [11] RF filter according to the preceding claim, having a conductor-type topology or a grid-type topology. [12] Multiplexer comprising an RF filter according to one of the two preceding claims.

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