Elastic wave resonator and elastic wave filter device

Abstract

The invention discloses an elastic wave resonator and an elastic wave filter device. The elastic wave resonator comprises at least two sub-resonators arranged in series; each of the sub-resonators comprises an interdigital transducer and a reflection grating; the interdigital transducer comprises a plurality of interdigital electrodes, namely, a plurality of first interdigital electrodes and a plurality of second interdigital electrodes; the reflection grating comprises a plurality of third finger-shaped electrodes; at least two structural parameters are different between two adjacent sub-resonators; the structural parameters comprise the period of the interdigital electrodes, the number of the interdigital electrodes, the number of the third finger-shaped electrodes, the aperture of the sub-resonator, the width of the interdigital electrodes, the length of the first interdigital electrodes, the gap between the interdigital electrodes, the thickness of the interdigital electrodes, the duty cycle of the interdigital electrodes, the boundary profile of the first interdigital electrodes, the connection mode of the interdigital electrodes and the material ratio of the interdigital electrodes, so that the superposition of clutter responses in the cascade resonator can be improved, the clutter parasitics in the forbidden band of the elastic wave resonator can be weakened, and the resonator performance can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of radio frequency filters, and in particular to an elastic wave resonator and an elastic wave filter device. Background Art

[0002] In a surface acoustic wave device, an electrical signal is applied to the interdigital transducer (IDT) electrode to excite the main acoustic wave mode. The excited acoustic wave signal propagates to both sides of the IDT electrode. The reflection gratings set on both sides of the IDT can suppress acoustic wave leakage, thereby preventing the desired acoustic wave mode from being attenuated, thereby forming a resonator. Multiple resonators of this type are connected to each other to form a surface acoustic wave filter.

[0003] In recent years, with the development of 5G communication technology, requirements such as miniaturization, high frequency and high power have been put forward for surface acoustic wave devices. On the one hand, miniaturization and high frequency require that the resonator area of ​​the device be small, the packaging be complex, the period of the IDT be smaller, and the distance between the metal electrodes of the IDT will also be smaller. On the other hand, in order to achieve high power, a larger heat dissipation path and greater power tolerance are required. However, miniaturization, high frequency and high power are relatively contradictory requirements. In order to achieve miniaturization and high power, high power distribution will be caused on each resonator, resulting in high electric field stress and mechanical stress on the IDT, which makes the metal electrode of the IDT more susceptible to damage and reduces its life. At this stage, a feasible and widely used solution is to replace a smaller resonator with multiple sub-resonators connected in series (i.e. cascade) to improve its power life.

[0004] However, in addition to exciting the main acoustic wave mode, the IDT also excites the resonant parasitics of some other acoustic wave modes, such as lateral scattering, Rayleigh scattering, body wave scattering, body wave reflection, and high-order modes. When the resonators are cascaded, since each sub-resonator constituting the cascade is the same, the clutter mode of each sub-resonator is also the same. Therefore, these clutter modes will be superimposed and enhanced on each other during cascading, making the cascaded resonator have a more serious clutter response, resulting in the deterioration of the passband and near-band attenuation characteristics of the filter, reducing the performance of the filter. Summary of the invention

[0005] The embodiments of the present invention provide an elastic wave resonator and an elastic wave filter device to improve the superposition of clutter responses in cascade resonators, weaken clutter parasitics in the bandgap of the elastic wave resonator, and improve the performance of the elastic wave resonator.

[0006] In a first aspect, an embodiment of the present invention provides an elastic wave resonator, comprising: at least two sub-resonators arranged in series; two adjacent sub-resonators are electrically connected through the same common bus bar, and the sub-resonators each include an interdigital transducer and a reflection grating located on both sides of the interdigital transducer along a first direction; the interdigital transducer includes a plurality of interdigital electrodes, the plurality of interdigital electrodes include a plurality of first interdigital electrodes and a plurality of second interdigital electrodes, the first interdigital electrodes and the second interdigital electrodes are alternately arranged in sequence along the first direction and both extend along the second direction; along the second direction, the extension length of the first interdigital electrode is less than the extension length of the second interdigital electrode; the first direction intersects with the second direction; the reflective grating includes a plurality of third finger electrodes, and the plurality of third finger electrodes are arranged along the first direction and extend along the second direction; there are at least two different structural parameters in two adjacent sub-resonators; wherein the structural parameters include the period of the interdigitated electrodes, the number of the interdigitated electrodes, the number of the third finger electrodes, the aperture of the sub-resonator, the width of the interdigitated electrodes, the length of the first interdigitated electrodes, the gap between the interdigitated electrodes, the thickness of the interdigitated electrodes, the duty cycle of the interdigitated electrodes, the boundary contour of the first interdigitated electrodes, the connection method of the interdigitated electrodes and the material ratio of the interdigitated electrodes.

[0007] Optionally, the structural parameters include modal parameters and frequency response parameters; in two adjacent sub-resonators, there is one different modal parameter and at least one different frequency response parameter; wherein the modal parameters include: the period of the interdigitated electrodes, the aperture of the sub-resonator, the width of the interdigitated electrodes, the thickness of the interdigitated electrodes, the duty cycle of the interdigitated electrodes, the boundary profile of the first interdigitated electrodes, the connection method of the interdigitated electrodes and the material ratio of the interdigitated electrodes; the frequency response parameters include: the number of the interdigitated electrodes, the number of the third finger electrodes, the length of the first interdigitated electrodes and the gap between the interdigitated electrodes.

[0008] Optionally, in two adjacent sub-resonators, the difference between the periods of the interdigitated electrodes is p1, the difference between the widths of the interdigitated electrodes is p2, the difference between the duty cycles of the interdigitated electrodes is p3, and the difference between the thicknesses of the interdigitated electrodes is p4; wherein, p1≤30%, p2≤30%, p3≤30%, p4≤30%; in two adjacent sub-resonators, the difference between the apertures of the sub-resonators is p5, the difference between the lengths of the first interdigitated electrodes is p6, and the difference between the gaps of the interdigitated electrodes is p7, wherein, 5%≤p5≤50%, 10%≤p6≤50%, 10%≤p7≤50%; in two adjacent sub-resonators, the difference between the material ratios of the interdigitated electrodes is p8, wherein, 10%≤p8≤40%.

[0009] Optionally, at least two sub-resonators cascaded in series include a first sub-resonator and a second sub-resonator arranged along the second direction; the first sub-resonator includes a first interdigital transducer and a first reflection grating located on both sides of the first interdigital transducer along the first direction; the second sub-resonator includes a second interdigital transducer and a second reflection grating located on both sides of the second interdigital transducer along the first direction; the first interdigital transducer and the second interdigital transducer are electrically connected through the same common bus bar.

[0010] Optionally, a period of the interdigital electrodes in the first sub-resonator is different from a period of the interdigital electrodes in the second sub-resonator, and a duty cycle of the interdigital electrodes in the first sub-resonator is different from a duty cycle of the interdigital electrodes in the second sub-resonator.

[0011] Optionally, the first IDT further includes a first bus bar; the second IDT further includes a second bus bar; along the second direction, the first bus bar and the second bus bar are respectively located on both sides of the common bus bar, and are both electrically connected to the interdigital electrodes.

[0012] Optionally, along the second direction, the first reflection grating and the second reflection grating located on the same side of the IDT are electrically connected.

[0013] Optionally, the elastic wave resonator further includes: a piezoelectric substrate; and the sub-resonator is located on one side of the piezoelectric substrate.

[0014] Optionally, the piezoelectric substrate includes a single piezoelectric layer, or the piezoelectric substrate includes multiple piezoelectric layers.

[0015] In a second aspect, an embodiment of the present invention further provides an elastic wave filter device, comprising the elastic wave resonator described in any one of the first aspects.

[0016] The technical solution of the embodiment of the present invention is to set at least two sub-resonators in series, and at least two structural parameters are different in two adjacent sub-resonators, so as to avoid the problem of superposition of clutter responses caused by the prior art of using two identical sub-resonators in series. The embodiment of the present invention can improve the problem of superposition of clutter responses in the cascade resonator by setting at least two structural parameters different in two adjacent sub-resonators, weaken the clutter parasitics in the bandgap of the elastic wave resonator, and thus improve the performance of the elastic wave resonator; secondly, it can improve the ripple characteristics in the passband of the elastic wave filter formed by the above elastic wave resonator. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1A schematic structural diagram of a first elastic wave resonator provided in an embodiment of the present invention.

[0018] Figure 2 for Figure 1 The corresponding simulated admittance characteristic curve of the first elastic wave resonator.

[0019] Figure 3 A schematic diagram comparing measured admittance characteristic curves of an elastic wave resonator provided in an embodiment of the present invention and an elastic wave resonator in the prior art.

[0020] Figure 4 A schematic diagram comparing measured admittance characteristic curves of the elastic wave resonator provided in an embodiment of the present invention and the elastic wave resonator in a comparative example.

[0021] Figure 5 A schematic structural diagram of a second elastic wave resonator provided in an embodiment of the present invention.

[0022] Figure 6 for Figure 1 A schematic cross-sectional view of the corresponding elastic wave resonator along the section line AA′.

[0023] Figure 7 A schematic structural diagram of a third elastic wave resonator provided in an embodiment of the present invention.

[0024] Figure 8 for Figure 7 The corresponding simulated admittance characteristic curve of the elastic wave resonator.

[0025] Fig. 9 A schematic structural diagram of a fourth elastic wave resonator provided in an embodiment of the present invention.

[0026] Fig.10 for Fig. 9 A schematic cross-sectional structure diagram of the corresponding elastic wave resonator along the section line BB'.

[0027] Fig.11 for Fig. 9 The corresponding simulated admittance characteristic curve of the elastic wave resonator.

[0028] Fig.12 for Figure 1 The corresponding simulated admittance characteristic curve of the second elastic wave resonator.

[0029] Fig.13 A schematic structural diagram of a fifth elastic wave resonator provided in an embodiment of the present invention.

[0030] Fig.14 A schematic structural diagram of a sixth elastic wave resonator provided in an embodiment of the present invention.

[0031] Fig.15 A schematic structural diagram of a seventh elastic wave resonator provided in an embodiment of the present invention.

[0032] Fig.16 A schematic structural diagram of an elastic wave filter device provided by an embodiment of the present invention.

[0033] Figure numerals: 100, elastic wave resonator; 10, sub-resonator; 11, first sub-resonator; 12, second sub-resonator; 20, common bus bar; 30, first bus bar; 40, second bus bar; 101, interdigital transducer; 101-1, first interdigital transducer; 101-2, second interdigital transducer; 1011, interdigital electrode; 1011-1, first interdigital electrode; 1011-2, second interdigital electrode; 1021, third finger electrode; 102, reflection grating; 102-1, first reflection grating; 102-2, second reflection grating; 50, piezoelectric substrate; a1, period of interdigital electrodes; a2, aperture of sub-resonator; a3, gap of interdigital electrodes; b, boundary contour of first interdigital electrode; X, first direction; Y, second direction; 1000, elastic wave filter device. DETAILED DESCRIPTION

[0034] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0035] Figure 1 A schematic diagram of the structure of a first elastic wave resonator provided by an embodiment of the present invention is shown in FIG. Figure 1 As shown, the elastic wave resonator 100 includes: at least two sub-resonators 10 arranged in series; two adjacent sub-resonators 10 are electrically connected through the same common bus bar 20, and each sub-resonator 10 includes an interdigital transducer 101 and a first direction (such as Figure 1 The reflective gratings 102 are located on both sides of the IDT 101 (the X direction shown in FIG); the IDT 101 includes a plurality of interdigital electrodes 1011, the plurality of interdigital electrodes 1011 include a plurality of first interdigital electrodes 1011-1 and a plurality of second interdigital electrodes 1011-2, the first interdigital electrodes 1011-1 and the second interdigital electrodes 1011-2 are alternately arranged in sequence along the first direction X and are arranged along the second direction (as shown in FIG). Figure 1The first finger electrode 1011-1 extends in the second direction Y (in the Y direction shown in FIG); along the second direction Y, the extension length of the first finger electrode 1011-1 is less than the extension length of the second finger electrode 1011-2; the first direction X intersects with the second direction Y; the reflective grating 102 includes a plurality of third finger electrodes 1021, and the plurality of third finger electrodes 1021 are arranged along the first direction X and extend along the second direction Y; there are at least two different structural parameters in two adjacent sub-resonators 10; wherein the structural parameters include the period of the finger electrode 1011, the number of the finger electrodes 1011, the number of the third finger electrodes 1021, the aperture of the sub-resonator 10, the width of the finger electrode 1011, the length of the first finger electrode 1011-1, the gap of the finger electrode 1011, the thickness of the finger electrode 1011, the duty cycle of the finger electrode 1011, the boundary profile of the first finger electrode 1011-1, the connection mode of the finger electrode 1011 and the material ratio of the finger electrode 1011.

[0036] Specifically, at least two sub-resonators 10 are arranged in series, that is, multiple sub-resonators 10 are cascaded, which can improve the power of the resonator, reduce static capacitance and balance impedance. It should be noted that the number of sub-resonators 10 connected in series can be two or more. For ease of description, the embodiments of the present invention are described by taking two as an example.

[0037] Specifically, along the second direction Y, the extension length of the first interdigital electrode 1011-1 is smaller than the extension length of the second interdigital electrode 1011-2, that is, the first interdigital electrode 1011-1 is a fake finger electrode, that is, a short finger electrode, and the second interdigital electrode 1011-2 is a real finger electrode, that is, a long finger electrode.

[0038] As a comparative example, in the prior art, two sub-resonators with exactly the same structural parameters are connected in series, so that the clutter modes of the two sub-resonators are also the same, and then these clutter modes will be superimposed and enhanced when cascaded, so that the cascaded resonator has a more serious clutter response, resulting in the deterioration of the passband and near-band attenuation characteristics of the filter, and reducing the performance of the filter. However, in the embodiment of the present invention, by setting at least two structural parameters of two adjacent sub-resonators 10 to be different, their reflection of sound waves and electroacoustic conversion are also different. Although the main mode is basically the same, the frequency response of other modes changes, so that the clutter of adjacent sub-resonators has different frequency characteristics, so that the clutter of the cascaded resonator will not be superimposed on each other, or even weaken each other, thereby reducing the influence of the harmonic characteristics of the filter and increasing the attenuation of the high frequency domain outside the passband of the filter, thereby improving the performance of the resonator.

[0039] Specifically, the period a1 of the interdigital electrode 1011 can be understood as the width of the second interdigital electrode 1011-2 along the first direction X and the width of the gap between the first interdigital electrode 1011-1 and the second interdigital electrode 1011-2 arranged adjacent thereto along the first direction X. The number of interdigital electrodes 1011 can be understood as the sum of the number of first interdigital electrodes 1011-1 and the number of second interdigital electrodes 1011-2 in the interdigital transducer. The number of third finger electrodes 1021 can be understood as the total number of third finger electrodes 1021 in the reflective grating 102. The aperture a2 of the sub-resonator 10, i.e., the active area, is also called the effective aperture area. It can also be understood as the size of the overlapping area of ​​the second interdigital electrode 1011-2 in the second direction Y. The width of the interdigital electrode 1011, i.e., the size of the first interdigital electrode 1011-1 and the second interdigital electrode 1011-2 along the first direction X. The length of the first interdigital electrode 1011-1 is the extension dimension of the first interdigital electrode 1011-1 along the second direction Y. The gap a3 of the interdigital electrode 1011 can be understood as the distance between the end of the first interdigital electrode 1011-1 away from the bus bar and the end of the second interdigital electrode 1011-2 away from the bus bar along the second direction Y. The thickness of the interdigital electrode 1011 can be understood as the thickness of the first interdigital electrode 1011-1 and the second interdigital electrode 1011-2 along the thickness direction of the elastic wave resonator. Generally, in the same sub-resonator, the thickness of the interdigital electrodes is the same and the width is also the same. The duty cycle of the interdigital electrode 1011 can be understood as the ratio of the width of a single interdigital electrode to the period of the interdigital electrode, exemplarily, the ratio of the width of the first interdigital electrode 1011-1 to the period of the interdigital electrode, or the ratio of the width of the second interdigital electrode 1011-2 to the period of the interdigital electrode. The boundary contour of the first interdigitated electrode 1011-1 can be understood as a shape formed by connecting the boundary contours of the end of the first interdigitated electrode 1011-1 away from the bus bar. The connection mode of the interdigitated electrode 1011 represents the arrangement mode of the first interdigitated electrode 1011-1 and the second interdigitated electrode 1011-2. Exemplarily, the connection mode of the interdigitated electrodes in the first sub-resonator 11 and the second sub-resonator 12 can be mirrored or non-mirror-imaged. Since the interdigitated electrode 1011 is made of metal, the metal can be a single component, such as aluminum, copper or gold, or a layered structure or alloy of multiple components. Exemplarily, a single interdigital electrode 1011 may be composed of n different metal materials, that is, the mass M of each interdigital electrode 1011 is, M = (ρ1*v1+ρ2*v2+…+ρn*vn)* V, where ρ1, ρ2…ρn are the densities of different metals, v1, v2…vn are the volume ratios of different metals, and V is the volume of a single interdigital electrode. The material ratio of the interdigital electrode 1011 can be understood as the mass of the interdigital electrode.

[0040] As a feasible implementation method, continue to refer to Figure 1 In two adjacent sub-resonators 10, the period of the interdigital electrodes 1011 and the duty cycle of the interdigital electrodes 1011 are different, that is, the period of the interdigital electrodes in the first sub-resonator 11 is different from the period of the interdigital electrodes in the second sub-resonator 12, and the duty cycle of the interdigital electrodes in the first sub-resonator 11 is different from the duty cycle of the interdigital electrodes in the second sub-resonator 12. Exemplarily, the period of the interdigital electrodes of the first sub-resonator 11 is 0.8 μm, the duty cycle of the interdigital electrodes is 0.5, the period of the interdigital electrodes of the second sub-resonator 12 is 0.797 μm, the duty cycle of the interdigital electrodes is 0.55, the aperture of the first sub-resonator and the aperture of the second sub-resonator are both 50 μm, and the other structural parameters remain the same. Figure 2 for Figure 1 The simulated admittance characteristic curve of the corresponding elastic wave resonator is taken as an example in which the first sub-resonator 11 and the second sub-resonator 12 are connected in series on a multi-layer piezoelectric substrate. Figure 2 As shown, the solid lines represent the admittance mode curve and the real part curve of the first sub-resonator 11, and the dotted lines represent the admittance mode curve and the real part curve of the second sub-resonator 12. The difference between the two sub-resonators can be found by comparing the two real part curves of admittance. It can be seen that in the range of 2.4 GHz -2.5GHz, although the main modes of the two resonators are the same, the responses of the other multiple clutter modes are not consistent. Therefore, by adjusting the period of the forked electrode and the duty cycle of the forked electrode, the superposition of the clutter modes between the two sub-resonators can be avoided, thereby solving the problem of the superposition of clutter in the cascaded resonators.

[0041] It should be noted that Figure 2 The peak frequency of the admittance mode curve between 2.35GHz and 2.4GHz is the resonance point, and the trough frequency of the admittance mode curve between 2.45GHz and 2.5GHz is the anti-resonance point. The entire curve represents the admittance value of the resonator.

[0042] Figure 3 Schematic diagram comparing the measured admittance characteristic curves of the elastic wave resonator provided in the embodiment of the present invention and the elastic wave resonator in the prior art. As a comparative example, the structural parameters of the two sub-resonators in the prior art are the same, that is, the period of the interdigital electrodes is 0.8um, the duty cycle of the interdigital electrodes is 0.5, the aperture of the sub-resonator is 51um, and the remaining structural parameters are the same. Figure 1 The parameters of the embodiment of the present invention are the same as Figure 3As shown, the solid lines respectively represent the admittance mode curve and the real part curve of the admittance of the elastic wave resonator in the embodiment of the present invention, and the dotted lines respectively represent the admittance mode curve and the real part curve of the admittance of the elastic wave resonator in the prior art. By comparing the two real part curves of admittance, it can be found that in the range of 2.45 GHz -2.5 GHz, the clutter in the elastic wave resonator provided by the embodiment of the present invention is significantly reduced, especially the clutter near the antiresonance point basically disappears, which shows that the elastic wave resonator provided by the embodiment of the present invention can improve the clutter superposition problem caused by cascading.

[0043] As another comparative example, that is, only one structural parameter of the two sub-resonators is adjusted, and the apertures of two adjacent sub-resonators are different. Figure 4 Schematic diagram comparing the measured admittance characteristic curves of the elastic wave resonator provided in the embodiment of the present invention and the elastic wave resonator in the comparative example. For example, the period of the interdigital electrodes of the two sub-resonators in the comparative example is 0.8um, the duty cycle of the interdigital electrodes is 0.5, the apertures of the two sub-resonators are 48.7um and 53.55um respectively, and the remaining structural parameters are the same as Figure 1 The parameters of the embodiment of the present invention are the same, that is, the apertures of adjacent sub-resonators in the comparative example are different, such as Figure 4 As shown, the solid lines respectively represent the admittance mode curve and the real part curve of the admittance of the elastic wave resonator in the embodiment of the present invention, and the dotted lines respectively represent the admittance mode curve and the real part curve of the elastic wave resonator in the comparative example. By comparing the two real part curves of admittance, it can be found that in the range of 2.45GHz-2.5GHz, the elastic wave resonator provided by the embodiment of the present invention has obvious improvement in the clutter near the antiresonance point. This shows that the elastic wave resonator provided by the embodiment of the present invention can improve the clutter superposition problem caused by cascading by setting at least two structural parameters of the two sub-resonators to be different.

[0044] The elastic wave resonator provided by the embodiment of the present invention can avoid the problem of superposition of clutter caused by the series arrangement of two identical resonators in the prior art by arranging at least two sub-resonators in series, and at least two structural parameters are different in two adjacent sub-resonators. The embodiment of the present invention can improve the superposition problem of clutter response in the cascade resonator, weaken the clutter parasitics in the bandgap of the elastic wave resonator, and thus improve the performance of the elastic wave resonator by arranging at least two structural parameters in two adjacent sub-resonators differently.

[0045] Optionally, the structural parameters include modal parameters and frequency response parameters; in two adjacent sub-resonators, there is one different modal parameter and at least one different frequency response parameter; wherein the modal parameters include: the period of the interdigitated electrodes, the aperture of the sub-resonator, the width of the interdigitated electrodes, the thickness of the interdigitated electrodes, the duty cycle of the interdigitated electrodes, the boundary profile of the first interdigitated electrodes, the connection method of the interdigitated electrodes and the material ratio of the interdigitated electrodes; the frequency response parameters include: the number of interdigitated electrodes, the number of third finger electrodes, the length of the first interdigitated electrodes and the gap between the interdigitated electrodes.

[0046] Specifically, the modal parameters may be understood as structural parameters that have a significant impact on each mode of the resonator, and the frequency response parameters may be understood as structural parameters that affect the frequency response characteristics of the resonator.

[0047] Specifically, in two adjacent sub-resonators, by adjusting any one of the modal parameters, the superposition of clutter in the cascaded resonator can be improved. In addition, by adjusting at least one frequency response parameter, it is possible to ensure that the frequency response characteristics of the cascaded resonator and the uncascaded resonator remain basically consistent, that is, on the basis of ensuring that the main mode of the resonator before and after the cascade does not change much, the superposition of clutter responses in the cascaded resonator is improved, the clutter parasitics in the bandgap of the elastic wave resonator are weakened, and the performance of the elastic wave resonator is improved.

[0048] It should be noted that in the process of adjusting the frequency response parameters, it can be ensured that the resonance point, anti-resonance point and admittance value of the cascaded resonator and the non-cascaded resonator are approximately equal, that is, the deviation of the resonant frequency and anti-resonance frequency before and after adjustment is optimally controlled within 1000ppm, and the maximum difference cannot be 1%; the deviation of the admittance value is optimally controlled within 12000ppm, and the maximum difference cannot be 3%.

[0049] Optional, continue to refer to Figure 1 In two adjacent sub-resonators 10, the difference between the periods a1 of the interdigital electrodes 1011 is p1, the difference between the widths of the interdigital electrodes 1011 is p2, the difference between the duty cycles of the interdigital electrodes 1011 is p3, and the difference between the thicknesses of the interdigital electrodes 1011 is p4; wherein, p1≤30%, p2≤30%, p3≤30%, p4≤30%; in two adjacent sub-resonators 10, the difference between the apertures a2 of the sub-resonators 10 is p5, the difference between the lengths of the first interdigital electrodes 1011-1 is p6, and the difference between the gaps a3 of the interdigital electrodes 1011 is p7, wherein, 5%≤p5≤50%, 10%≤p6≤50%, 10%≤p7≤50%; in two adjacent sub-resonators 10, the difference between the material ratios of the interdigital electrodes 1011 is p8, wherein, 10%≤p8≤40%.

[0050] Specifically, the difference in the structural parameter changes of two adjacent sub-resonators 10 needs to be limited to a certain range, so as to ensure that the frequency response characteristics of the cascaded resonator and the non-cascaded resonator are basically consistent, and the non-cascaded resonator can be replaced by the cascaded resonator.

[0051] For example, taking the period a1 of the interdigitated electrode 1011 as an example, the difference between the periods a1 of the interdigitated electrodes 1011 in two adjacent sub-resonators 10 is p1, and p1≤30%. If p1>30%, the frequency response characteristics of the cascaded resonator and the non-cascaded resonator are quite different, and the main mode cannot be guaranteed to be basically consistent, that is, the cascaded resonator cannot replace the non-cascaded resonator.

[0052] Optional, continue to refer to Figure 1 At least two sub-resonators 10 cascaded in series include a first sub-resonator 11 and a second sub-resonator 12 arranged along a second direction Y; the first sub-resonator 11 includes a first IDT 101-1 and a first reflection grating 102-1 located on both sides of the first IDT 101-1 along the first direction X; the second sub-resonator 12 includes a second IDT 101-2 and a second reflection grating 102-2 located on both sides of the second IDT 101-2 along the first direction X; the first IDT 101-1 and the second IDT 101-2 are electrically connected through the same common bus bar 20.

[0053] Specifically, taking the first sub-resonator 11 as an example, the first sub-resonator 11 includes a first IDT 101-1 and a first reflection grating 102-1 located on both sides of the first IDT 101-1 along a first direction X. When an AC signal is applied to the bus bar of the first IDT 101-1, a surface acoustic wave can be excited in the first IDT. The surface acoustic wave mainly propagates in the aperture of the first sub-resonator 11 along the first direction X, but a small amount of surface acoustic waves will also propagate toward the edge position along the second direction Y. By arranging the first reflection grating 102-1 on both sides of the first IDT 101-1, the first reflection grating 102-1 can reflect the sound wave that is about to leak back to the aperture area, thereby reducing the sound wave leakage and improving the Q value of the resonator.

[0054] Specifically, the first IDT 101 - 1 and the second IDT 101 - 2 are electrically connected via the same common bus bar 20 , which simplifies the configuration and enables the first sub-resonator and the second sub-resonator to be connected in series.

[0055] Optional, continue to refer to Figure 1The first IDT 101 - 1 further includes a first bus bar 30 ; the second IDT 101 - 2 further includes a second bus bar 40 ; along the second direction Y, the first bus bar 30 and the second bus bar 40 are respectively located on both sides of the common bus bar 20 , and are both electrically connected to the interdigital electrodes 1011 .

[0056] Specifically, in the first IDT 101-1, the first interdigital electrode 1011-1 and the second interdigital electrode 1011-2 on the same side are both electrically connected to the first bus bar 30, and the first interdigital electrode 1011-1 and the second interdigital electrode 1011-2 on the other side are both electrically connected to the common bus bar 20. In the second IDT 101-2, the first interdigital electrode 1011-1 and the second interdigital electrode 1011-2 on the same side are both electrically connected to the second bus bar 40, and the first interdigital electrode 1011-1 and the second interdigital electrode 1011-2 on the other side are both electrically connected to the common bus bar 20.

[0057] Optional, Figure 5 A schematic diagram of the structure of a second elastic wave resonator provided in an embodiment of the present invention is shown in FIG. Figure 5 As shown, along the second direction Y, the first reflection grating 102 - 1 and the second reflection grating 102 - 2 located on the same side of the IDT 101 are electrically connected.

[0058] Specifically, along the second direction Y, the first reflection grating 102-1 and the second reflection grating 102-2 on the same side of the IDT 101 are electrically connected, indicating that the first reflection grating 102-1 and the second reflection grating 102-2 can be integrated, which can simplify the process and the setting method is simple.

[0059] It should be noted that in each sub-resonator 10 , the period of the third finger electrodes 1021 in the reflection grid is the same as the period of the interdigital electrodes in the IDT 101 , and the width of the third finger electrodes 1021 is the same as the width of the interdigital electrodes in the IDT 101 .

[0060] Optional, Figure 6 for Figure 1 The corresponding cross-sectional diagram of the elastic wave resonator along the section line A-A' is shown in FIG. Figure 6 As shown, the elastic wave resonator 100 further includes: a piezoelectric substrate 50 ; and a sub-resonator 10 located on one side of the piezoelectric substrate 50 .

[0061] For further information, please refer to Figure 6 The piezoelectric substrate 50 includes a single piezoelectric layer, or the piezoelectric substrate includes a plurality of piezoelectric layers.

[0062] Specifically, as a feasible implementation, the piezoelectric substrate may be a single-layer piezoelectric material, such as LiTaO3, LiNbO3, quartz or AlN, etc. As another feasible implementation, the piezoelectric substrate may be a multi-layer structure including piezoelectric materials.

[0063] For example, Figure 7 A schematic diagram of the structure of a third elastic wave resonator provided in an embodiment of the present invention is shown in FIG. Figure 7 As shown, a first sub-resonator 11 and a second sub-resonator 12 are arranged in series on a multi-layer piezoelectric substrate. The period of the interdigital electrodes, the duty cycle of the interdigital electrodes, the length of the first interdigital electrodes and the gap between the interdigital electrodes in the first sub-resonator 11 are all different from the period of the interdigital electrodes, the duty cycle of the interdigital electrodes, the length of the first interdigital electrodes and the gap between the interdigital electrodes in the first sub-resonator 12, that is, there are four different structural parameters between the first sub-resonator and the second sub-resonator. Among them, the period of the interdigital electrodes in the first sub-resonator 11 is 0.8μm, the duty cycle of the interdigital electrodes is 0.5, the length of the first interdigital electrodes is 1.6μm, and the gap between the interdigital electrodes is 0.3μm. The period of the interdigital electrodes in the second sub-resonator 12 is 0.797μm, the duty cycle of the interdigital electrodes is 0.55, the length of the first interdigital electrodes is 1.28μm, and the gap between the interdigital electrodes is 0.4μm, and the remaining structural parameters are the same.

[0064] Figure 8 for Figure 7 The corresponding simulated admittance characteristic curve of the elastic wave resonator is as follows: Figure 8 As shown in the figure, as a comparative example, the structural parameters of the two sub-resonators in the prior art are the same, that is, the period of the interdigital electrodes is 0.8um, the duty cycle of the interdigital electrodes is 0.5, the aperture of the sub-resonator is 51um, and the remaining structural parameters are the same as Figure 7 The parameters of the embodiment of the present invention are the same as Figure 8 As shown, the solid lines respectively represent the admittance mode curve and the real part curve of the admittance of the elastic wave resonator in the embodiment of the present invention, and the dotted lines respectively represent the admittance mode curve and the real part curve of the elastic wave resonator in the prior art. By comparing the two real part curves of admittance, it can be found that in the range of 2.45 GHz -2.5 GHz, the clutter in the elastic wave resonator provided by the embodiment of the present invention is significantly reduced, especially the clutter near the antiresonance point basically disappears, which shows that the elastic wave resonator provided by the embodiment of the present invention can improve the clutter superposition problem caused by cascading and improve the performance of the elastic wave resonator.

[0065] For example, Fig. 9 A schematic diagram of the structure of a fourth elastic wave resonator provided in an embodiment of the present invention, Fig.10 for Fig. 9The corresponding cross-sectional structure diagram of the elastic wave resonator along the section line BB' is as follows: Fig. 9 and Fig.10 As shown, a first sub-resonator 11 and a second sub-resonator 12 are arranged in series on a piezoelectric substrate of a multilayer structure. The duty cycle of the interdigital electrodes in the first sub-resonator 11 and the thickness of the interdigital electrodes are different from the duty cycle of the interdigital electrodes in the second sub-resonator 12 and the thickness of the interdigital electrodes. Among them, the period of the interdigital electrodes in the first sub-resonator 11 is 0.8μm, the duty cycle of the interdigital electrodes is 0.5, the aperture is 50μm, and the thickness of the interdigital electrodes is 130nm. The period of the interdigital electrodes in the second sub-resonator 12 is 0.8μm, the duty cycle of the interdigital electrodes is 0.53, the aperture is 50μm, and the thickness of the interdigital electrodes is 125nm, and the other structural parameters are the same.

[0066] As a comparative example, the structural parameters of the two sub-resonators in the prior art are the same. Fig.11 for Fig. 9 The corresponding simulated admittance characteristic curve of the elastic wave resonator is as follows: Fig.11 As shown, the solid lines respectively represent the admittance mode curve and the real part curve of the admittance of the elastic wave resonator in the embodiment of the present invention, and the dotted lines respectively represent the admittance mode curve and the real part curve of the admittance of the elastic wave resonator in the prior art. By comparing the two real part curves of admittance, it can be found that in the range of 2.45 GHz -2.5 GHz, the clutter in the elastic wave resonator provided by the embodiment of the present invention is significantly reduced, especially the clutter near the antiresonance point is significantly reduced or even disappears, which shows that the elastic wave resonator provided by the embodiment of the present invention can improve the clutter superposition problem caused by cascading and improve the performance of the elastic wave resonator.

[0067] Optional, continue to refer to Figure 1 , a first sub-resonator 11 and a second sub-resonator 12 may be arranged in series on a single-layer piezoelectric substrate. The period of the interdigital electrodes in the first sub-resonator 11 and the duty cycle of the interdigital electrodes are different from the period of the interdigital electrodes in the second sub-resonator 12 and the duty cycle of the interdigital electrodes. Among them, the period of the interdigital electrodes in the first sub-resonator 11 is 0.8 μm, the duty cycle of the interdigital electrodes is 0.55, and the aperture is 50 μm. The period of the interdigital electrodes in the second sub-resonator 12 is 0.798 μm, the duty cycle of the interdigital electrodes is 0.6, and the aperture is 50 μm.

[0068] As a comparative example, the structural parameters of the two sub-resonators in the prior art are the same, and the period of the interdigital electrodes in the two sub-resonators is 0.8 μm, the duty cycle of the interdigital electrodes is 0.55, the aperture is 52 μm, and the other structural parameters are the same. Fig.12 for Figure 1 The corresponding simulated admittance characteristic curve of the second elastic wave resonator is as follows: Fig.12As shown, the solid lines respectively represent the admittance mode curve and the real part curve of the admittance of the elastic wave resonator in the embodiment of the present invention, and the dotted lines respectively represent the admittance mode curve and the real part curve of the elastic wave resonator in the prior art. By comparing the two real part curves of admittance, it can be found that in the range of 2.5GHz-2.6GHz, the clutter in the elastic wave resonator provided by the embodiment of the present invention is significantly reduced, which means that the elastic wave resonator provided by the embodiment of the present invention can improve the clutter superposition problem caused by cascading and improve the performance of the elastic wave resonator.

[0069] Fig.13 A schematic diagram of the structure of a fifth elastic wave resonator provided in an embodiment of the present invention is shown in FIG. Fig.13 As shown, on the basis of ensuring that the interdigital electrode period and the duty cycle of the interdigital electrode in the first sub-resonator 11 and the second sub-resonator 12 are different, the connection mode of the interdigital electrodes in the first sub-resonator 11 and the second sub-resonator 12 is not a mirror relationship. That is, the first second interdigital electrode 1011-2 on the left side in the first sub-resonator 11 is electrically connected to the common bus bar 20, and the first second interdigital electrode 1011-2 on the left side in the second sub-resonator 12 is electrically connected to the second bus bar 40, that is, the two are not connected to the same bus bar, so that on the one hand, the elastic wave resonator can be diversified, and on the other hand, the problem of clutter superposition caused by cascading can be improved, thereby improving the performance of the elastic wave resonator.

[0070] Understandably, continue to refer to Figure 1 The connection mode of the interdigital electrodes in the first sub-resonator 11 and the second sub-resonator 12 is a mirror image relationship, that is, the first second interdigital electrode 1011-2 on the left side in the first sub-resonator 11 is electrically connected to the common bus bar 20, and the first second interdigital electrode 1011-2 on the left side in the second sub-resonator 12 is also electrically connected to the common bus bar 20.

[0071] Optionally, the thickness of the interdigital electrodes, the composition of the interdigital electrodes, the gap between the interdigital electrodes, and the length of the first interdigital electrodes in the first sub-resonator are all different from the thickness of the interdigital electrodes, the composition of the interdigital electrodes, the gap between the interdigital electrodes, and the length of the first interdigital electrodes in the second sub-resonator, that is, the four structural parameters are different, so that on the basis of replacing the non-cascaded resonator with the cascaded resonator, the superposition of multiple noises caused by the cascade is suppressed at the same time. This structure that requires adjustment of the thickness and composition of the interdigital electrodes is more advantageous for devices such as duplexers that require different frequency bands and powers, because no additional photolithography process is required, and devices with multiple metal electrode thicknesses are more advantageous.

[0072] Optional, Fig.14 A schematic diagram of the structure of a sixth elastic wave resonator provided in an embodiment of the present invention is shown in FIG. Fig.14As shown, the thickness of the interdigital electrodes, the composition of the interdigital electrodes, the aperture of the sub-resonator, the gap between the interdigital electrodes and the length of the first interdigital electrodes in the first sub-resonator 11 and the second sub-resonator 12 are all different, that is, there are five different structural parameters in adjacent sub-resonators, which can ensure that the performance of the resonators is basically consistent and at the same time suppress the superposition of various interferences caused by cascading.

[0073] Fig.15 A schematic diagram of the structure of a seventh elastic wave resonator provided in an embodiment of the present invention is shown in FIG. Fig.15 As shown, the period of the interdigital electrodes, the duty cycle of the interdigital electrodes, and the boundary profile of the first interdigital electrodes are all different from those of the first sub-resonator 11 and the second sub-resonator 12. The boundary profile b of the first interdigital electrodes can be understood as the profile formed by the end connection line of the first interdigital electrodes away from the bus bar. It can be seen that the shape of the boundary profile b of the first interdigital electrodes in the first sub-resonator 11 is wavy, and the shape of the boundary profile of the first interdigital electrodes in the second sub-resonator 12 is a straight line. This structure can suppress the superposition of multiple noises caused by cascading.

[0074] Exemplarily, the boundary contour of the first interdigital electrode may also be a pulse shape, a “V” shape, etc., which is not specifically limited in the embodiment of the present invention.

[0075] It should be noted that the shape of the first bus bar in the first sub-resonator may be different from the shape of the second bus bar in the second sub-resonator. For example, the bus bar may not be a regular rectangle, that is, the side of the bus bar away from the interdigital electrodes may be serrated or wavy.

[0076] It is understandable that the embodiments of the present invention only list technical solutions in which at least two structural parameters of two adjacent sub-resonators are different. It should be noted that the at least two different structural parameters may be a combination of the above-mentioned multiple structural parameters.

[0077] In summary, the elastic wave resonator provided in the embodiment of the present invention can avoid the problem of superposition of clutter caused by the prior art of using two identical resonators in series by setting at least two sub-resonators in series, and at least two structural parameters are different in two adjacent sub-resonators. The embodiment of the present invention can improve the problem of superposition of clutter responses in the cascade resonator, weaken the clutter parasitics in the bandgap of the elastic wave resonator, and thus improve the performance of the elastic wave resonator by setting at least two structural parameters in two adjacent sub-resonators to be different.

[0078] Based on the same inventive concept, an embodiment of the present invention further provides an elastic wave filter device, which includes the elastic wave resonator described in the above embodiment. Fig.16A schematic diagram of the structure of an elastic wave filter device provided by an embodiment of the present invention is shown in FIG. Fig.16 As shown, the elastic wave filter device 1000 includes at least one series arm resonator and at least one parallel arm resonator, wherein the series arm resonator and the parallel arm resonator can both include the elastic wave resonator described in the above embodiments. Therefore, the elastic wave filter device provided in the embodiment of the present invention also has the beneficial effects described in the above embodiments, which will not be repeated here.

[0079] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments, combinations and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. An elastic wave resonator, characterized in that: include: at least two sub-resonators arranged in series; Two adjacent sub-resonators are electrically connected via a common bus bar, and each of the sub-resonators comprises an IDT and a reflection grating located on both sides of the IDT along a first direction; The interdigital transducer comprises a plurality of interdigital electrodes, the plurality of interdigital electrodes comprises a plurality of first interdigital electrodes and a plurality of second interdigital electrodes, the first interdigital electrodes and the second interdigital electrodes are alternately arranged in sequence along the first direction and both extend along the second direction; along the second direction, the extension length of the first interdigital electrodes is less than the extension length of the second interdigital electrodes; the first direction intersects with the second direction; the reflector comprises a plurality of third finger electrodes, the plurality of third finger electrodes are arranged along the first direction and both extend along the second direction; There are at least two different structural parameters between two adjacent sub-resonators; The structural parameters include the period of the interdigital electrodes, the number of the interdigital electrodes, the number of the third finger electrodes, the aperture of the sub-resonator, the width of the interdigital electrodes, the length of the first interdigital electrodes, the gap between the interdigital electrodes, the thickness of the interdigital electrodes, the duty cycle of the interdigital electrodes, the boundary profile of the first interdigital electrodes, the connection method of the interdigital electrodes and the material ratio of the interdigital electrodes; The aperture of the sub-resonator is the size of the overlapping area of ​​the second interdigital electrodes in the second direction; the gap between the interdigital electrodes is the distance between the end of the first interdigital electrode away from the bus bar and the end of the second interdigital electrode away from the bus bar along the second direction; the material of the interdigital electrodes includes at least one of aluminum, copper and gold; Among them, in two adjacent sub-resonators, the difference between the periods of the interdigital electrodes is p1, the difference between the widths of the interdigital electrodes is p2, the difference between the duty cycles of the interdigital electrodes is p3, and the difference between the thicknesses of the interdigital electrodes is p4; wherein p1≤30%, p2≤30%, p3≤30%, p4≤30%; In two adjacent sub-resonators, the difference between the apertures of the sub-resonators is p5, the difference between the lengths of the first interdigital electrodes is p6, and the difference between the gaps between the interdigital electrodes is p7, wherein 5%≤p5≤50%, 10%≤p6≤50%, and 10%≤p7≤50%; In two adjacent sub-resonators, the difference between the material ratios of the interdigitated electrodes is p8, wherein 10%≤p8≤40%.

2. The elastic wave resonator according to claim 1, characterized in that: The structural parameters include modal parameters and frequency response parameters; Two adjacent sub-resonators have one different modal parameter and at least one different frequency response parameter; The modal parameters include: the period of the interdigital electrodes, the aperture of the sub-resonator, the width of the interdigital electrodes, the thickness of the interdigital electrodes, the duty cycle of the interdigital electrodes, the boundary profile of the first interdigital electrodes, the connection mode of the interdigital electrodes and the material ratio of the interdigital electrodes; The frequency response parameters include: the number of the interdigital electrodes, the number of the third finger electrodes, the length of the first interdigital electrodes, and the gap between the interdigital electrodes.

3. The elastic wave resonator according to claim 1, characterized in that: At least two sub-resonators cascaded in series include a first sub-resonator and a second sub-resonator arranged along the second direction; The first sub-resonator comprises a first interdigital transducer and a first reflection grating located at both sides of the first interdigital transducer along the first direction; the second sub-resonator comprises a second interdigital transducer and a second reflection grating located at both sides of the second interdigital transducer along the first direction; The first IDT and the second IDT are electrically connected via the same common bus bar.

4. The elastic wave resonator according to claim 3, characterized in that: The period of the interdigital electrodes in the first sub-resonator is different from the period of the interdigital electrodes in the second sub-resonator, and the duty ratio of the interdigital electrodes in the first sub-resonator is different from the duty ratio of the interdigital electrodes in the second sub-resonator.

5. The elastic wave resonator according to claim 3, characterized in that: The first interdigital transducer further comprises a first bus bar; the second interdigital transducer further comprises a second bus bar; Along the second direction, the first bus bar and the second bus bar are respectively located on two sides of the common bus bar, and are both electrically connected to the interdigital electrodes.

6. The elastic wave resonator according to claim 3, characterized in that: Along the second direction, the first reflection grating and the second reflection grating located on the same side of the IDT are electrically connected.

7. The elastic wave resonator according to claim 1, characterized in that: The elastic wave resonator further includes: a piezoelectric substrate; The sub-resonator is located on one side of the piezoelectric substrate.

8. The elastic wave resonator according to claim 7, characterized in that: The piezoelectric substrate includes a single piezoelectric layer, or the piezoelectric substrate includes a plurality of piezoelectric layers.

9. An elastic wave filter device, characterized in that: The elastic wave resonator comprises the elastic wave resonator as described in any one of claims 1 to 8.

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