Interdigital transduction structure, resonator and filter

Abstract

The invention provides an interdigital transduction structure, a resonator and a filter, and the structure comprises a first busbar and a second busbar which are arranged in parallel, a plurality of first interdigital electrodes connected to the first busbar, and a plurality of second interdigital electrodes connected to the second busbar. The first interdigital electrodes and the second interdigital electrodes are alternately arranged in an electrode area between the first busbar and the second busbar; the electrode area comprises a central area, and in the central area, the width of the first interdigital electrode is not equal to that of the second interdigital electrode. The widths of the first interdigital electrode and the second interdigital electrode in the central area are not equal, so that the first interdigital electrode and the second interdigital electrode form an asymmetric structure, the speed of the resonator in the area is controlled, transverse mode suppression is carried out, and the performance of the resonator and the performance of the filter are improved.

Description

Technical Field

[0001] The present invention relates to the field of communication technology, and in particular to an interdigital transducer structure, a resonator and a filter. Background Art

[0002] In modern communication systems, filters are often used to filter out unnecessary signals outside the target communication frequency band, and surface acoustic wave (SAW) resonators have been widely used in RF filter design due to their advantages such as high Q value, small size, high reliability, and easy mass production. Piezoelectric SAW resonators include a PE substrate and an IDT (Inter Digital Transducer) formed by conductive electrodes. Due to the PE effect, SAW is generated and propagated within the electrode grating, allowing the structure to have different resonance characteristics.

[0003] The increase in the number of frequency bands and the broadening of the RF spectrum require the development of a new SAW device with extremely high performance, high power durability and low spurious. However, in SAW resonators, transverse modes are generated and propagated in the transverse direction simultaneously with the main mode. These transverse modes easily distort the frequency response of the resonator in the critical passband region, resulting in a decrease in the overall performance of the resonator and the filter. Summary of the invention

[0004] The object of the present invention is to provide an interdigital transducer structure, a resonator and a filter, which can suppress the transverse mode and improve the performance of the resonator and the filter.

[0005] To solve the above technical problems, the first aspect of the present invention provides an interdigital transducer structure, comprising: a first bus and a second bus arranged in parallel, both connected to a plurality of first interdigital electrodes of the first bus, both connected to a plurality of second interdigital electrodes of the second bus, the first interdigital electrodes and the second interdigital electrodes being alternately arranged in an electrode area between the first bus and the second bus; the electrode area comprises a central area, in which the width of the first interdigital electrodes is not equal to the width of the second interdigital electrodes.

[0006] Optionally, the electrode area also includes edge areas located on both sides of the central area, in which the widths of the first interdigitated electrode and the second interdigitated electrode are equal, and the duty ratios of the first interdigitated electrode and the second interdigitated electrode are both DF, where 0.1≤DF≤0.9.

[0007] Optionally, the duty cycle DF=0.5.

[0008] Optionally, in the extension direction of the first interdigitated electrode, the length of the edge region is 0.2 times the wavelength to 2 times the wavelength.

[0009] Optionally, in the central area, the duty cycle DF1 of the first interdigital electrode is equal to DF-DF_d, and the duty cycle DF2 of the second interdigital electrode is equal to DF+DF_d, wherein DF_d is an absolute asymmetry parameter, 0.1≤DF_d≤0.9, and DF_d<DF.

[0010] Optional, 0.2≤DF_d≤0.3.

[0011] Optionally, in the central area, the duty cycle DF1 of the first interdigital electrodes is equal to DF, and the duty cycle DF2 of the second interdigital electrodes is greater than DF.

[0012] Optionally, the edge region includes a first edge region between the first bus bar and the central region and a second edge region between the second bus bar and the central region; the electrode region also includes a first gap region between the first edge region and the first bus bar and a second gap region between the second edge region and the second bus bar;

[0013] A first dummy bus and a first dummy electrode connected to the first dummy bus are arranged in the first gap region, the first dummy bus is arranged in parallel with the first bus, and the first dummy electrode is isolated from the second interdigital electrode and overlaps with the second interdigital electrode in an extension direction;

[0014] A second pseudo bus and a second pseudo electrode connected to the second pseudo bus are arranged in the second gap area, the second pseudo bus is arranged parallel to the second bus, and the second pseudo electrode is isolated from the first interdigitated electrode and overlaps with the first interdigitated electrode in the extension direction.

[0015] Optionally, the electrode region also includes an extended region located between the edge region and the central region, and a duty ratio of the first interdigitated electrode in the extended region is greater than a duty ratio of the first interdigitated electrode in the edge region and in the central region, and a duty ratio of the second interdigitated electrode in the extended region is less than a duty ratio of the second interdigitated electrode in the edge region and in the central region.

[0016] Optionally, in the central region and the edge region, the first interdigital electrodes and the second interdigital electrodes are both patterned interdigital electrodes.

[0017] To solve the above technical problem, according to a second aspect of the present invention, a resonator is provided, comprising: a substrate, an IDT structure as described above disposed on the substrate, and a passivation layer disposed on the IDT structure.

[0018] In order to solve the above technical problem, according to a third aspect of the present invention, a filter is provided, comprising the resonator as described above.

[0019] Compared with the prior art, in the interdigital transducer structure, resonator and filter provided by the present invention, the widths of the first interdigital electrode connected to the first bus and the second interdigital electrode connected to the second bus in the central area are not equal, so that the first interdigital electrode and the second interdigital electrode form an asymmetric structure in the central area, thereby controlling the speed of the resonator in this area and suppressing the lateral mode, and effectively suppressing the lateral mode without using the engineering hammer head or mass loading structure in the prior art, thereby improving the performance of the resonator and the filter.

[0020] In addition, the interdigital transducer structure provided by the present invention can be applied to a wide range of SAW resonator structures such as SAW, TC-SAW, POI, X- or Y-BAR, and can also be used together with other lateral suppression and resonator performance improvement methods, and has a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Those skilled in the art will appreciate that the accompanying drawings are provided for a better understanding of the present invention and do not constitute any limitation on the scope of the present invention.

[0022] Figure 1 It is a schematic structural diagram of an interdigital transducer structure provided by an embodiment of the present invention.

[0023] Figure 2 It is a schematic structural diagram of an interdigital transducer structure provided by another embodiment of the present invention.

[0024] Figure 3 It is a schematic structural diagram of an interdigital transducer structure provided by another embodiment of the present invention.

[0025] Figure 4 It is a schematic structural diagram of an interdigital transducer structure provided by another embodiment of the present invention.

[0026] Figure 5 It is a schematic structural diagram of an interdigital transducer structure provided by another embodiment of the present invention.

[0027] Figure 6 It is a schematic diagram of the structure of a resonator provided in one embodiment of the present invention.

[0028] Figure 7It is a partial structural schematic diagram of an interdigital transducer structure in a resonator provided by an embodiment of the present invention and a corresponding schematic diagram of the lateral velocity distribution of the resonator.

[0029] Figure 8a Schematic diagram of resonator admittance under different absolute asymmetry parameters provided by an embodiment of the present invention.

[0030] Figure 8b It is a schematic diagram of the admittance of resonators in different electrode edge regions when the absolute asymmetry parameters are fixed provided by an embodiment of the present invention.

[0031] Fig. 9 It is a schematic diagram of the relationship between the velocity and piezoelectric coupling coefficient of the resonator provided by an embodiment of the present invention and the absolute asymmetry parameter.

[0032] In the attached figure:

[0033] 10-substrate; 20-interdigital transducer structure; 30-passivation layer; 20a-central region; 20b-first edge region; 20b′-second edge region; 20c-first gap region; 20c′-second gap region; 20d-first extension region; 20d′-second extension region; 210-first bus; 211-first interdigital electrode; 220-second bus; 221-second interdigital electrode; 231-third pseudo electrode; 232-fourth pseudo electrode; 240-first pseudo bus; 241-first pseudo electrode; 250-second pseudo bus; 251-second pseudo electrode. DETAILED DESCRIPTION

[0034] In order to make the purpose, advantages and features of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and are not drawn to scale, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. In addition, the structure shown in the drawings is often a part of the actual structure. In particular, the emphasis of each drawing is different, and sometimes different scales are used.

[0035] As used in the present invention, the singular forms "one", "an", and "the" include plural objects, unless the content clearly indicates otherwise. As used in the present invention, the term "or" is generally used in a sense that includes "and / or", unless the content clearly indicates otherwise. As used in the present invention, the term "several" is generally used in a sense that includes "at least one", unless the content clearly indicates otherwise. As used in the present invention, the term "at least two" is generally used in a sense that includes "two or more", unless the content clearly indicates otherwise. In addition, the terms "first", "second", and "third" are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first", "second", and "third" may explicitly or implicitly include one or at least two of the features.

[0036] Figure 1 FIG. 1 is a schematic diagram of the structure of an interdigital transducer structure provided by an embodiment of the present invention. Figure 1 As shown, the interdigital transducer structure provided by the embodiment of the present invention includes: a first bus 210 and a second bus 220 arranged in parallel, a plurality of first interdigital electrodes 211 connected to the first bus 210, a plurality of second interdigital electrodes 221 connected to the second bus 220, the first interdigital electrodes 211 and the second interdigital electrodes 221 are alternately arranged in the electrode region between the first bus 210 and the second bus 220; the electrode region includes a central region 20a, in which the width of the first interdigital electrode 211 is not equal to the width of the second interdigital electrode 221. Wherein, width refers to Figure 1 The width in the vertical direction, that is, the width in the direction perpendicular to the extending direction of the interdigital electrodes.

[0037] For example, in this embodiment, the extension direction of the first interdigital electrode 211 is perpendicular to the extension direction of the first bus 210, and the extension direction of the second interdigital electrode 221 is perpendicular to the extension direction of the second bus 220. In actual implementation, the first interdigital electrode 211 and the second interdigital electrode 221 may not be perpendicular to the corresponding bus, and this embodiment does not limit this. In addition, it should be noted that Figure 1 And subsequent Figures 2 to 5 Only one first interdigitated electrode 211 and one second interdigitated electrode 221 are shown. Another first interdigitated electrode 211 connected to the first bus 210 may be arranged below the second interdigitated electrode 221. The first interdigitated electrodes 211 and the second interdigitated electrodes 221 are alternately arranged in the electrode area between the first bus 210 and the second bus 220.

[0038] In the interdigital transducer structure provided by the present invention, in the central area 20a, the width of the first interdigital electrode 211 is not equal to the width of the second interdigital electrode 221, so that the first interdigital electrode 211 and the second interdigital electrode 221 form an asymmetric structure, thereby controlling the speed of the resonator in this area and suppressing the lateral mode, and effectively suppressing the lateral mode without using the engineered hammer or mass loading structures in the prior art, thereby improving the performance of the resonator and the filter.

[0039] Please continue to refer to Figure 1 As shown, the electrode area also includes edge areas located on both sides of the central area 20a, and the edge areas include a first edge area 20b located between the first bus 210 and the central area 20a and a second edge area 20b′ located between the second bus and the central area 20a. In the edge areas, the widths of the first interdigitated electrodes 211 and the second interdigitated electrodes 221 are equal, and the duty ratios of the first interdigitated electrodes 211 and the second interdigitated electrodes 221 are both DF, wherein 0.1≤DF≤0.9, and preferably, the duty ratio DF=0.5.

[0040] The duty cycle of an electrode refers to the electrode width divided by the sum of the electrode width and the electrode spacing, that is, duty cycle = electrode width / (electrode width + electrode spacing). For example: please refer to Figure 1As shown, in the first edge region 20b, the width of the first interdigital electrode 211 is d, and the spacing between the first interdigital electrode 211 and the second interdigital electrode 221 is s. Then the duty cycle DF of the first interdigital electrode 211 is d / (d + s). The width of the second interdigital electrode 221 is also d, and the duty cycle DF of the second interdigital electrode 221 is also d / (d + s). In the central region 20a, the duty cycle DF1 of the first interdigital electrode 211 is the width of the first interdigital electrode 211 in the central region 20a divided by the sum of the electrode width and the electrode spacing of the first interdigital electrode 211 in the central region 20a. For example, if the width of the first interdigital electrode 211 in the central region 20a is d1, and the spacing between the first interdigital electrode 211 and the second interdigital electrode 221 is s1, then the duty cycle DF1 of the first interdigital electrode 211 = d1 / (d1 + s1). Similarly, if the width of the second interdigital electrode 211 in the central region 20a is d2, and the spacing between the second interdigital electrode 221 and the first interdigital electrode 211 is S2 (not shown in the figure, which is the spacing between the second interdigital electrode 221 and the next first interdigital electrode), then the duty cycle DF2 of the second interdigital electrode 221 = d2 / (d2 + s2). Among them, d1 + s1 = d2 + s2 = d + s = half of the wavelength. If the width of the interdigital electrode becomes narrower, the spacing becomes wider, and for a fixed wavelength, the total width (d + s) is constant..

[0041] In an embodiment of the present invention, DF1 < DF < DF2. For example: the duty cycle DF1 of the first interdigital electrode 211 = DF - DF_d, the duty cycle DF2 of the second interdigital electrode 221 = DF + DF_d, where DF_d is the absolute asymmetry parameter, 0.1 ≤ DF_d ≤ 0.9, and DF_d < DF. The interdigital transducer structure can be optimized through the absolute asymmetry parameter DF_d for effective lateral suppression. In the central region 20a, the speed in this region is controlled by the absolute asymmetry parameter DF_d for lateral mode suppression.

[0042] In another embodiment of the present invention, DF1 = DF < DF2. That is, the duty cycle DF1 of the first interdigital electrode 211 = DF, and the duty cycle DF2 of the second interdigital electrode 221 > DF.

[0043] Please continue to refer to Figure 1 As shown, the electrode region further includes a first gap region 20c located between the first edge region 20b and the first bus bar 210, and a second gap region 20c' located between the second edge region 20b' and the second bus bar 220.

[0044] Figure 1In the illustrated embodiment, only the first interdigital electrode 211 is disposed in the first gap region 20c, that is, the second interdigital electrode 221 does not extend to the first gap region 20c. Similarly, only the second interdigital electrode 221 is disposed in the second gap region 20c′, and the first interdigital electrode 211 does not extend to the second gap region 20c′.

[0045] like Figure 1 As shown, the first interdigital electrode 211 is located in the first gap region 20c, the first edge region 20b, the central region 20a and the second edge region 20b′, the duty ratio of the first interdigital electrode 211 in the central region 20a is DF1, and the duty ratio in the first edge region 20b and the second edge region 20b′ is DF. The second interdigital electrode 221 is located in the second gap region 20c′, the second edge region 20b′, the central region 20a and the first edge region 20b, the duty ratio of the second interdigital electrode 221 in the central region 20a is DF2, and the duty ratio in the first edge region 20b and the second edge region 20b′ is DF. Wherein DF1 is not equal to DF2.

[0046] Exemplarily, in the extension direction of the first interdigitated electrode 211, when the aperture of the resonator is in the range of 10 times the wavelength to 100 times the wavelength, the length of the central region 20a is between 20 times the wavelength and 60 times the wavelength. The length of the gap region is between 1 times the wavelength and 10 times the wavelength, preferably between 2 times the wavelength and 5 times the wavelength. The length of the edge region is between 0.2 times the wavelength and 2 times the wavelength, preferably 1 times the wavelength. Of course, for some resonators, the length of the edge region may also exceed 2 times the wavelength. The present invention is not limited to this. In order to avoid a reduction in the lateral suppression effect, the length of the central region 20a should be as small as possible. In addition, the length of the edge region can be determined according to actual process conditions.

[0047] Figure 2 is a schematic diagram of the structure of an interdigital transducer structure provided by another embodiment of the present invention. Figure 2 As shown, Figure 1The difference of the embodiment shown is that a third dummy electrode 231 is provided in the first gap region 20c, the third dummy electrode 231 is connected to the first bus 210, the third dummy electrode 231 is isolated from the second interdigital electrode 221, and overlaps with the second interdigital electrode 221 in the extension direction. Similarly, a fourth dummy electrode 232 is provided in the second gap region 20c′, the fourth dummy electrode 232 is connected to the second bus 220, the fourth dummy electrode 232 is isolated from the first interdigital electrode 211, and overlaps with the first interdigital electrode 211 in the extension direction. In this embodiment, the duty cycle of the third dummy electrode 231 can be the same as the duty cycle of the second interdigital electrode 221 in the first edge region 20b, and the duty cycle of the fourth dummy electrode 232 can be the same as the duty cycle of the first interdigital electrode 211 in the second edge region 20b′, but is not limited thereto. The dummy electrode is provided to reduce the scattering loss in the resonator.

[0048] Figure 3 is a schematic diagram of the structure of an interdigital transducer structure provided by another embodiment of the present invention. Figure 3 As shown, Figure 1 The embodiment shown is different in that a first dummy bus 240 and a first dummy electrode 241 connected to the first dummy bus 240 are provided in the first gap region 20c, the first dummy bus 240 is provided in parallel with the first bus 210, and the first dummy electrode 241 is isolated from the second interdigital electrode 221, and overlaps with the second interdigital electrode 221 in the extension direction. Similarly, a second dummy bus 250 and a second dummy electrode 251 connected to the second dummy bus 250 are provided in the second gap region 20c′, the second dummy bus 250 is provided in parallel with the second bus 220, and the second dummy electrode 251 is isolated from the first interdigital electrode 211, and overlaps with the first interdigital electrode 211 in the extension direction.

[0049] Figure 4 is a schematic diagram of the structure of an interdigital transducer structure provided by another embodiment of the present invention. Figure 4 As shown, Figure 1The embodiment shown is different in that the electrode region also includes an extension region between the edge region and the central region 20a (for example, a first extension region 20d between the central region 20a and the first edge region 20b, and a second extension region 20d′ between the central region 20a and the second edge region 20b′), the duty cycle of the first interdigitated electrode 211 in the extension region is greater than the duty cycle of the first interdigitated electrode 211 in the edge region and in the central region 20a, and the duty cycle of the second interdigitated electrode 221 in the extension region is less than the duty cycle of the second interdigitated electrode 221 in the edge region and in the central region 20a. The extension region is provided between the central region 20a and the edge region to improve the steepness of the SAW velocity distribution and the lateral suppression effect. The length of the extension region can be 0.5 times the wavelength to 3 times the wavelength, or 1 times the wavelength to 10 times the wavelength, and the extension region can also be used to improve SAW energy limitation, scattering loss and lateral suppression.

[0050] Figure 5 is a schematic diagram of the structure of an interdigital transducer structure provided by another embodiment of the present invention. Figure 5 As shown, Figure 1 The embodiment shown is different in that, in the central region 20a and the edge region, the first interdigital electrode 211 and the second interdigital electrode 221 are both patterned interdigital electrodes, that is, patterned interdigital electrodes can be formed by selective etching. In the edge region, the size of the area without pattern in the patterned interdigital electrode is smaller than the size of the edge region, for example: in the extension direction of the first interdigital electrode 211, if the length of the edge region is 2 times the wavelength, the length of the area without pattern can be between 0.1 times the wavelength and 2 times the wavelength. Similarly, in the central region 20a, the size of the area without pattern in the patterned interdigital electrode is smaller than the central region 20a. For example: in the extension direction of the first interdigital electrode 211, if the length of the central region 20a is between 10 times the wavelength and 50 times the wavelength, the length of the area without pattern can be between 1 times the wavelength and 10 times the wavelength. Of course, the pattern sizes in different interdigital electrodes can be different.

[0051] Of course, the interdigital transducer structure provided in the present application only needs to satisfy the following conditions: in the central area 20a, the width of the first interdigital electrode 211 is not equal to the width of the second interdigital electrode 221. The interdigital transducer structure is not limited to the above-mentioned embodiments, and may also be other structures known to those skilled in the art.

[0052] In addition, the interdigital transducer structure provided by the present invention can be applied to a wide range of SAW resonator structures such as SAW, TC-SAW (Thermal compensated SAW), POI (Piezoelectric On Insulator), X- or Y-BAR (Bulk Acoustic Resonator), etc. At the same time, it can also be used together with other lateral suppression and resonator performance improvement methods, such as phase shifting, apodization, velocity control, passivation, energy confinement, and scuttering improvement structures. The scuttering improvement structures include, for example, dummy IDT, mini busbar, engineered busbar, etc., and its application range is wide.

[0053] Correspondingly, the present invention also provides a resonator, including: a substrate, the interdigital transducer structure as described above disposed on the substrate, and a passivation layer disposed on the interdigital transducer structure.

[0054] In this embodiment, it is described by taking the resonator including Figure 1 the shown interdigital transducer structure, and DF1 < DF < DF2 in the interdigital transducer structure as an example.

[0055] Figure 6 is a schematic structural diagram of a resonator provided by an embodiment of the present invention. Please refer to Figure 6 As shown, the resonator includes a substrate 10, an interdigital transducer structure 20 disposed on the substrate 10, and a passivation layer 30 disposed on the interdigital transducer structure 20. Exemplarily, the material of the interdigital transducer structure 20 includes copper, the thickness is 300 nm, the wavelength is 4 μm, and the material of the passivation layer 30 includes silicon oxide, and the thickness is 1 μm.

[0056] Figure 7 is a partial structural diagram of the interdigital transducer structure in a resonator provided by an embodiment of the present invention and a schematic diagram of the lateral velocity distribution of the corresponding resonator. In Figure 7 the velocity distributions in the lateral direction of a normal resonator in the prior art and the resonator with an asymmetric structure in the present application are compared. Compared with the prior art, the reduction in velocity at the edge region in the present application has a piston effect, and this piston effect allows the suppression of the lateral mode due to the reduction of the excitation coefficient of the spurious mode propagating in the lateral direction.

[0057] In order to confirm the effectiveness of lateral stray suppression, a periodic three-dimensional model of TC-SAW resonator with different design parameters was solved. Figure 6 As shown in the figure, in this model, the edge region of the interdigital electrode has a fixed duty cycle DF = 0.5, and the duty cycle of the interdigital electrode in the central region is controlled by the absolute asymmetry parameter DF_d. Figure 8a and Figure 8b As shown, Figure 8a is a schematic diagram of resonator admittance under different absolute asymmetry parameters provided by an embodiment of the present invention, Figure 8b Schematic diagram of the admittance of resonators in different edge regions when the absolute asymmetry parameters are fixed according to an embodiment of the present invention. Figure 8a As shown, the horizontal axis is frequency, the vertical axis is admittance, and curves 1 to 9 respectively represent the admittance curves when DF_d=1, DF_d=0.1, DF d=0.2, DF d=0.25, DF d=0.28, DF d=0.3, DF d=0.32, DF d=0.35 and DF_d=0.4. Figure 8a It can be seen that when DF_d=0, strong lateral stray occurs, which corresponds to the duty cycle of the interdigital electrodes in the central area being 0.5. When DF_d increases, the lateral stray decreases, but when DF_d increases, the piezoelectric coupling coefficient k2 decreases, resulting in a decrease in the performance of the resonator. Therefore, the optimal range of DF_d is between 0.2 and 0.3, that is, 0.2≤DF_d≤0.3.

[0058] Please refer to Figure 8b As shown, the abscissa is frequency, the ordinate is admittance, and DF_d=0.2. Curve 1 to curve 8 respectively represent the admittance curves when pl=0.1, pl=0.5, pl=0.8, pl=1, pl=1.2, pl=1.4, pl=1.6 and pl=2, where pl represents the length of the edge area, that is, Figure 1 The length of the edge area in the horizontal direction. Figure 8b It can be seen that when the edge area is very narrow, the lateral suppression function is relatively poor due to the small effect on the SAW speed in the lateral direction. When the edge area is relatively wide, due to the generation of other coupling modes, the use of a relatively wide edge area at the resonant frequency causes lead distortion and the overall lateral suppression effect is reduced. Therefore, for SAW, TC-SAW or POI structures, the length of the edge area is between 0.2 times the wavelength and 2 times the wavelength, and the optimal range is around 1 times the wavelength. For some special designs, such as XBAR or YBAR UHB resonators, the length of the edge area can exceed 2 wavelengths. Of course, the optimal design parameters depend on the resonator stack, structure, and materials used.

[0059] The performance of the resonator mainly depends on the absolute asymmetry parameter DF_d. A relatively low absolute asymmetry parameter DF_d cannot effectively suppress the lateral mode, but a higher absolute asymmetry parameter DF_d will significantly reduce the piezoelectric coupling coefficient k2. Fig. 9 Schematic diagram of the relationship between the velocity and piezoelectric coupling coefficient of the resonator and the absolute asymmetry parameter provided by an embodiment of the present invention. Fig. 9 As shown, the abscissa is the absolute asymmetry parameter DF_d, and the ordinate is the speed of the resonator and the piezoelectric coupling coefficient k2. As the absolute asymmetry parameter DF_d increases, the speed of the resonator increases, but the piezoelectric coupling coefficient k2 decreases. Considering the high k2 of the resonator, the absolute asymmetry parameter DF_d is optimally in the range of 0.2 to 0.3. In some embodiments, depending on the structure of the resonator, the absolute asymmetry parameter DF_d can be in the range of 0.1 to 0.9.

[0060] Correspondingly, the present invention also provides a filter, comprising the resonator as described above.

[0061] To summarize, in the interdigital transducer structure, resonator and filter provided by the present invention, the widths of the first interdigital electrode connected to the first bus and the second interdigital electrode connected to the second bus in the central area are not equal, so that the first interdigital electrode and the second interdigital electrode form an asymmetric structure in the central area, thereby controlling the speed of the resonator in this area and suppressing the lateral mode, and effectively suppressing the lateral mode can be achieved without using an engineering hammer or mass loading structure in the prior art, thereby improving the performance of the resonator and the filter.

[0062] In addition, the interdigital transducer structure provided by the present invention can be applied to a wide range of SAW resonator structures such as SAW, TC-SAW, POI, X- or Y-BAR, and can also be used together with other lateral suppression and resonator performance improvement methods, and has a wide range of applications.

[0063] The above description is only a description of the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention. Any changes or modifications made by a person skilled in the art in the field of the present invention based on the above disclosure shall fall within the scope of protection of the claims.

Claims

1. An interdigital transducer structure, comprising: A first bus and a second bus arranged in parallel are both connected to a plurality of first interdigitated electrodes of the first bus, and are both connected to a plurality of second interdigitated electrodes of the second bus, and are characterized in that the first interdigitated electrodes and the second interdigitated electrodes are alternately arranged in an electrode area between the first bus and the second bus; the electrode area includes a central area, in which the width of the first interdigitated electrodes is not equal to the width of the second interdigitated electrodes.

2. The interdigital transducer structure according to claim 1, characterized in that: The electrode region also includes edge regions located on both sides of the central region, in which the widths of the first interdigitated electrodes and the second interdigitated electrodes are equal, and the duty ratios of the first interdigitated electrodes and the second interdigitated electrodes are both DF, wherein 0.1≤DF≤0.

9.

3. The interdigital transducer structure according to claim 2, characterized in that: The duty cycle DF=0.

5.

4. The interdigital transducer structure according to claim 2, characterized in that: In the extension direction of the first interdigitated electrode, the length of the edge region is 0.2 times the wavelength to 2 times the wavelength.

5. The interdigital transducer structure according to claim 2, characterized in that: In the central area, the duty cycle DF1 of the first interdigital electrode is DF-DF_d, and the duty cycle DF2 of the second interdigital electrode is DF+DF_d, wherein DF_d is an absolute asymmetry parameter, 0.1≤DF_d≤0.9, and DF_d<DF.

6. The interdigital transducer structure according to claim 5, characterized in that: 0.2≤DF_d≤0.

3.

7. The interdigital transducer structure according to claim 2, characterized in that: In the central area, the duty ratio DF1 of the first interdigital electrodes is equal to DF, and the duty ratio DF2 of the second interdigital electrodes is greater than DF.

8. The interdigital transducer structure according to claim 2, characterized in that: The edge region includes a first edge region between the first busbar and the central region and a second edge region between the second busbar and the central region; the electrode region also includes a first gap region between the first edge region and the first busbar and a second gap region between the second edge region and the second busbar; A first dummy bus and a first dummy electrode connected to the first dummy bus are arranged in the first gap region, the first dummy bus is arranged in parallel with the first bus, and the first dummy electrode is isolated from the second interdigital electrode and overlaps with the second interdigital electrode in an extension direction; A second pseudo bus and a second pseudo electrode connected to the second pseudo bus are arranged in the second gap area, the second pseudo bus is arranged parallel to the second bus, and the second pseudo electrode is isolated from the first interdigitated electrode and overlaps with the first interdigitated electrode in the extension direction.

9. The interdigital transducer structure according to claim 2, characterized in that: The electrode region also includes an extended region between the edge region and the central region, wherein a duty ratio of the first interdigitated electrode in the extended region is greater than a duty ratio of the first interdigitated electrode in the edge region and in the central region, and a duty ratio of the second interdigitated electrode in the extended region is less than a duty ratio of the second interdigitated electrode in the edge region and in the central region.

10. The interdigital transducer structure according to claim 2, characterized in that: In the central region and the edge region, the first interdigital electrodes and the second interdigital electrodes are both patterned interdigital electrodes.

11. A resonator, characterized in that: include: A substrate, an interdigital transducing structure according to any one of claims 1 to 10 disposed on the substrate, and a passivation layer disposed on the interdigital transducing structure.

12. A filter, characterized in that: Comprising the resonator of claim 11.

Images