Surface acoustic wave structure, surface acoustic wave filter and communication equipment

Abstract

The invention provides a surface acoustic wave structure, a surface acoustic wave filter and communication equipment, and is characterized in that the lengths of at least part of first interdigital electrodes are set to be sequentially increased in the surface acoustic wave propagation direction, the increasing amplitudes are sequentially reduced, and the lengths of second interdigital electrodes are set to be sequentially reduced in the surface acoustic wave propagation direction; and the reduction amplitude is sequentially reduced, so that the excitation intensity of the surface acoustic waves of the interdigital transducer in each region in the surface acoustic wave propagation direction is non-linearly changed, and the excitation intensity is weakened in the region where a part of first interdigital electrodes arranged at the rear part in the surface acoustic wave propagation direction are located. The weakening can improve the near-band suppression capability of the surface acoustic wave filter, so that the resonant frequency burr phenomenon caused by transverse sound waves can be reduced or suppressed, namely, the resonant frequency splitting phenomenon is not easily caused. In addition, the surface acoustic wave structure provided by the invention does not need to be additionally provided with a structure for inhibiting a transverse mode, and is simple in preparation process, low in preparation cost and small in occupied area.

Description

Technical Field

[0001] The embodiments in this application relate to the field of electronic device technology, specifically to surface acoustic wave (SAW) structures, SAW filters, and communication devices. Background Technology

[0002] With the rapid development of modern communication technologies, wireless communication devices are increasingly demanding higher precision and stability in signal processing. Against this backdrop, surface acoustic wave (SAW) filters, as important passive devices, play a crucial role in radio frequency (RF) front-end signal processing due to their superior performance and reliability. SAW filters not only effectively filter out noise and interference, improving signal quality, but also enable precise frequency selection and bandwidth allocation, meeting the diverse needs of complex communication systems. In recent years, the rise of emerging fields such as 5G communication, the Internet of Things (IoT), and smart manufacturing has placed even higher demands on the performance of SAW filters.

[0003] During operation, SAW filters may generate transverse acoustic waves, known as transverse acoustic waves. These transverse acoustic waves can interfere with the SAW filter's operating acoustic waves (longitudinal acoustic waves), thus affecting the filter's filtering performance and signal processing quality. They can also cause the SAW filter to emit interference signals that can affect other systems. Therefore, it is necessary to suppress transverse acoustic waves; this suppression is known as transverse mode suppression.

[0004] An existing surface acoustic wave structure that can achieve transverse mode suppression is as follows: Figure 1 As shown, this structure achieves transverse mode suppression by altering the sound velocity through a piston structure at the end of the interdigital transducer's interdigital fingers. However, this method requires the fabrication of an additional piston structure, which demands high dimensional accuracy, making its fabrication relatively complex and costly. Another existing surface acoustic wave structure capable of achieving transverse mode suppression is shown below. Figure 2 As shown, this structure sets the interdigital transducer's interdigital fingers into an inclined structure to achieve lateral mode suppression. However, the inclined interdigital fingers increase the area of ​​the SAW filter, which does not meet the development requirements of device miniaturization. Summary of the Invention

[0005] In view of this, this application provides a surface acoustic wave structure, surface acoustic wave filter, and communication device that are simple to manufacture, low in cost, can suppress transverse modes, and occupy a small area.

[0006] In a first aspect, embodiments of this application provide a surface acoustic wave structure, including an interdigital transducer; The interdigital transducer includes a first electrode unit and a second electrode unit disposed opposite to each other. The first electrode unit includes a first busbar and a plurality of first interdigital electrodes connected to the first busbar. The second electrode unit includes a second busbar and a plurality of second interdigital electrodes connected to the second busbar. The first interdigitated electrode and the second interdigitated electrode extend in a first direction to form an interdigitated structure, and are arranged alternately in a second direction; Along the second direction, the length increase of at least a portion of the first interdigital electrode decreases sequentially, while the length decrease of the second interdigital electrode decreases sequentially; the length is the extension dimension in the first direction.

[0007] In some embodiments, the plurality of first interdigitated electrodes include a first portion of interdigitated electrodes arranged forward in the second direction and a second portion of interdigitated electrodes arranged backward, wherein the number of the first portion of interdigitated electrodes is greater than the number of the second portion of interdigitated electrodes. Along the second direction, the length of the first part of the interdigitated electrode increases to a first target value in a manner that increases with decreasing increments, while the length of the second part of the interdigitated electrode remains unchanged and is the same as the first target value.

[0008] In some embodiments, one of the first electrode unit and the second electrode unit is a positive electrode unit and the other is a negative electrode unit. The extended ends of the first interdigital electrodes arranged along the second direction define a first trace, and the extended ends of each of the second interdigital electrodes define a second trace. The first trace and the second trace are respectively parabolic or parabolic in a set coordinate system. Wherein, the origin of the set coordinate system is the starting point of the extension of the first interdigitated electrode arranged along the second direction, the positive direction of the first coordinate axis of the set coordinate system is the extension direction of the interdigitated electrode in the positive electrode unit, and the positive direction of the second coordinate axis is the second direction.

[0009] In some embodiments, the surface acoustic wave structure further includes a first reflective grating unit; Along the second direction, the first reflective grating unit is located downstream of the interdigital transducer, and the first reflective grating unit includes a plurality of first reflective grating electrodes extending in the first direction and spaced apart in the second direction; The first end of each of the first reflective gate electrodes is flush with the first adjacent extension end in the first direction; wherein, the first adjacent extension end is the extension end of one of the first interdigital electrodes close to the first reflective gate unit. The second end of the first reflective grid electrode is located on the first extension line of the second trace; wherein the second trace is defined by the extension ends of each of the second interdigital electrodes, and the first extension line has the same trend as the second trace.

[0010] In some embodiments, the surface acoustic wave structure second reflective grating unit; Along the second direction, the second reflective grating unit is located upstream of the interdigital transducer, and the second reflective grating unit includes a plurality of second reflective grating electrodes extending in the first direction and spaced apart in the second direction; The first end of the second reflective grid electrode is located on the second extension line of the first trace; wherein the first trace is defined by the extension end of the second interdigitated electrode arranged in the first direction, and the second extension line has the same trend as the first trace. The second end of each of the second reflective gate electrodes is flush with the second adjacent extension end in the first direction; wherein the second adjacent extension end is the extension end of one of the second interdigital electrodes close to the second reflective gate unit.

[0011] In some embodiments, the number of interdigitated electrodes in the second portion is less than 10.

[0012] In some embodiments, the first trace is a translation of the second trace in the first direction.

[0013] In some embodiments, the equation representing the second trace in the set coordinate system is: y=k x^m; Wherein, y represents the distance between the projection of a point on the second trace onto the first coordinate axis and the origin, x represents the distance between the projection of a point on the second trace onto the second coordinate axis and the origin, k is a preset constant greater than 1, and m is a preset constant in the range of 0.3 to 0.7.

[0014] In some embodiments, the first electrode unit further includes a plurality of first dummy fingers connected to the first busbar, and the second electrode unit further includes a plurality of second dummy fingers connected to the second busbar. The dummy fingers and interdigitated fingers connected to the same busbar are arranged alternately in the second direction, and the dummy fingers connected to one busbar and the interdigitated fingers connected to another busbar are opposite to each other in the first direction. There is a first gap between the first pseudo-finger electrode and the second interdigital electrode, and there is a second gap between the second pseudo-finger electrode and the first interdigital electrode. The distance between the first gap and the first busbar is a first distance, and the distance between the second gap and the first busbar is a second distance. Along the second direction, the increase in the first distance of each of the first gaps decreases sequentially, and the increase in the second distance of at least some of the second gaps decreases sequentially.

[0015] Secondly, embodiments of this application provide a surface acoustic wave (SAW) filter, including a piezoelectric layer and a SAW structure as described in any of the preceding claims, wherein the SAW structure is disposed on the piezoelectric layer.

[0016] Thirdly, embodiments of this application provide a communication device including the surface acoustic wave filter provided in the second aspect.

[0017] In the surface acoustic wave (SAW) structures, SAW filters, and communication devices provided in the various embodiments of this application, by setting the length of at least a portion of the first interdigital electrodes to increase sequentially along the second direction with decreasing increments, and setting the length of the second interdigital electrodes to decrease sequentially along the second direction with decreasing increments, the SAW excitation intensity of the interdigital transducer in each region along the second direction changes nonlinearly, but weakens in the region where a portion of the first interdigital electrodes arranged towards the rear along the second direction are located. This weakening can improve the near-band suppression capability of the SAW filter, thereby reducing or suppressing the resonant frequency spike phenomenon caused by transverse acoustic waves, i.e., it is less likely to cause resonant frequency splitting. Furthermore, the SAW structure provided in this application does not require additional structures for suppressing transverse modes, has a simple fabrication process, low fabrication cost, and occupies a small area. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of an existing surface acoustic wave structure.

[0020] Figure 2 This is a schematic diagram of another existing surface acoustic wave structure.

[0021] Figure 3 This is a schematic diagram of a surface acoustic wave structure provided according to some embodiments of this application.

[0022] Figure 4 This is a schematic diagram of a surface acoustic wave structure provided according to some embodiments of this application.

[0023] Figure 5 This is a schematic diagram of the surface acoustic wave excitation intensity of a surface acoustic wave structure provided according to some embodiments of this application.

[0024] Figure 6 This embodiment provides a schematic diagram comparing the surface acoustic wave structure with the admittance curves of a comparative example.

[0025] Figure 7 This is a schematic diagram of a surface acoustic wave structure provided according to some embodiments of this application.

[0026] Figure 8 This is a schematic diagram of the surface acoustic wave excitation intensity of a surface acoustic wave structure provided according to some embodiments of this application.

[0027] Figure 9 This embodiment provides a schematic diagram comparing the passband of the surface acoustic wave (SAW) structure and the corresponding SAW filter in the comparative example.

[0028] Figure 10 This is a schematic diagram of the structure of a surface acoustic wave filter provided according to some embodiments of this application.

[0029] Figure 11 This is a schematic diagram comparing the admittance curves of the surface acoustic wave filter provided in this embodiment with those of the comparative example.

[0030] Figure 12 This is a schematic diagram comparing the real part admittance curves of the surface acoustic wave filter provided in this embodiment with those of the comparative example.

[0031] Explanation of reference numerals in the attached figures: Interdigital transducer 1, first busbar 11, second busbar 12, first interdigital electrode 13, second interdigital electrode 14, first pseudo-finger electrode 15, second pseudo-finger electrode 16, first gap 17, second gap 18, first trace 101, second trace 102, third trace 103; First reflective grid unit 2, first reflective grid electrode 23, third bus bar 21, fourth bus bar 22, first extension line 202, fourth trace 201; Second reflective grid unit 3, second reflective grid electrode 33, fifth bus bar 31, sixth bus bar 32, second extension line 301, fifth trace 302; Substrate layer 400, piezoelectric layer 500, surface acoustic wave structure 600, single crystal silicon layer 401, polycrystalline silicon layer 402, silicon dioxide layer 403. Detailed Implementation

[0032] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0033] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0034] exist Figure 1 In the existing surface acoustic wave structure shown, the ends of the interdigitated fingers on opposite sides are flush, that is, the two trajectory lines defined by the ends of the interdigitated fingers on opposite sides in the extension direction are respectively ( Figure 1 Assuming the thick black lines in the diagram represent parallel lines, and the piston structures at the ends of each interdigital finger are positioned identically in the first direction (the extension direction of the interdigital finger), the surface acoustic wave propagation depth in the piston structure region is reduced due to the thickness of the piston structure. This makes it easier to excite a resonant frequency lower than the center region of the interdigital finger in this region, resulting in a cluttered peak on one side of the resonant frequency. This phenomenon is called resonant frequency splitting. This resonant frequency splitting becomes more pronounced as the thickness or width of the piston structure increases. Therefore, as... Figure 1 The existing surface acoustic wave (SAW) structures shown are insufficient to meet the increasing demands for frequency selectivity and bandwidth control in SAW filters, making them unsuitable for high-speed transmission and complex communication requirements. Furthermore, with the trend towards miniaturization and integration of SAW filters, Figure 2 The surface acoustic wave (SAW) structure shown requires a large area, making it difficult for SAW filters to meet the space-compact requirements of portable and wearable devices.

[0035] Based on the problems existing in the surface acoustic wave (SAW) structures, this application provides a SAW structure that is simple to fabricate, has low fabrication cost, occupies a small area, is not prone to causing resonant frequency splitting, and can suppress transverse modes, as well as a SAW filter and communication device containing the structure.

[0036] Please see Figure 3The diagram shows a surface acoustic wave (SAW) structure according to some embodiments of this application. In some embodiments, the SAW structure provided in this application includes an interdigital transducer 1. The interdigital transducer 1 includes a first electrode unit and a second electrode unit. When the SAW structure is applied to a device or equipment, the voltage polarity of one of the first electrode unit and the second electrode unit is positive, and the voltage polarity of the other is negative. For example, the first electrode unit can be a positive electrode unit, and the second electrode unit can be a negative electrode unit. In this embodiment, the first electrode unit includes a first busbar 11 and multiple first interdigital electrodes 13 connected to the first busbar; the second electrode unit includes a second busbar 12 and multiple second interdigital electrodes 14 connected to the second busbar 12. In other embodiments, the positions of the first electrode unit and the second electrode unit can be interchanged.

[0037] The first interdigital electrode 13 and the second interdigital electrode 14 extend in a first direction to form an interdigital structure. Here, the interdigital structure refers to a structure formed by the first interdigital electrode 13 and the second interdigital electrode 14 intersecting each other in the first direction, and in the interdigital structure, the first interdigital electrode 13 and the second interdigital electrode 14 are arranged alternately in a second direction. The first direction refers to the extension direction of each interdigital electrode. In some embodiments, the second direction can be the target propagation direction of the surface acoustic wave, and the first direction and the second direction are perpendicular or intersecting directions. It should be noted that in the embodiments of this application, the length of the interdigital electrode refers to its extension dimension in the first direction, while the width refers to its extension dimension in the second direction.

[0038] Along the second direction, the lengths of at least a portion of the first interdigital electrodes 13 increase sequentially, with the rate of increase decreasing sequentially, while the lengths of the second interdigital electrodes 14 decrease sequentially, with the rate of decrease decreasing sequentially. In some embodiments, the lengths of all the first interdigital electrodes 13 arranged along the second direction may vary according to a trend of sequentially increasing length and sequentially decreasing rate of increase. In other embodiments, the lengths of at least a portion of the first interdigital electrodes arranged along the second direction may also vary in this manner.

[0039] In this embodiment, by varying the lengths of the first interdigital electrodes 13 and the second interdigital electrodes 14 as described above, when applied to a surface acoustic wave (SAW) filter, the SAW excitation intensity of the interdigital transducer 1 varies nonlinearly in each region along the second direction, but weakens in the region where a portion of the first interdigital electrodes 13 are located further back along the second direction. This weakening improves the near-band suppression capability of the SAW filter, thereby reducing or suppressing resonant frequency glitches caused by transverse acoustic waves, i.e., it is less likely to cause resonant frequency splitting. The near-band suppression capability of the SAW filter refers to its attenuation capability for interference signals near the operating frequency (typically within 1.1 times the center frequency). Furthermore, the SAW structure provided in this embodiment does not require additional structures such as Piston for suppressing transverse modes, has a simple fabrication process, low fabrication cost, and requires less area compared to SAW structures with tilted interdigital electrodes.

[0040] Please continue reading. Figure 3 As shown, the extended ends of each of the first interdigital electrodes 13 arranged along the second direction define a first trace 101, and the extended ends of each of the second interdigital electrodes 14 define a second trace 102. The first trace 101 and the second trace 102 are respectively parabolic quasi-parabolic curves or parabolic curves in a set coordinate system. A parabolic quasi-parabolic curve is a curve similar to a parabola. For example, in some embodiments, its corresponding equation in the set coordinate system can be: y = a + k x^m. If the origin of the coordinate system is set as the extension starting point of the first interdigital electrode 13 arranged in the second direction, the positive direction of the first coordinate axis is the extension direction of the first interdigital electrode 13, and the positive direction of the second coordinate axis is the second direction, then y is the distance between the projection of the corresponding point on the trace onto the first coordinate axis and the origin, and x is the distance between the projection of the corresponding coordinate point on the trace onto the second coordinate axis and the origin. The extension starting point of the first interdigital electrode 13 can be the midpoint of the connecting line between the first interdigital electrode 13 and the first busbar 11. a is a preset constant determined according to the aperture requirement of the interdigital transducer 1, k is a preset constant greater than 1, and m is a preset constant ranging from 0.3 to 0.7.

[0041] Where y represents the distance between the projection of a point on the corresponding trace onto the first coordinate axis and the origin, x represents the distance between the projection of a point on the second trace onto the second coordinate axis and the origin, k is a preset constant greater than 1, and m is a preset constant in the range of 0.3 to 0.7.

[0042] In this embodiment, the first trace 101 and the second trace 102 are set as parabolic or parabolic curves. When the surface acoustic wave structure provided in this embodiment is applied to the surface acoustic wave filter, the passband frequency of the surface acoustic wave filter can be made smoother, and the ripple at the passband edge can be reduced.

[0043] Please continue reading. Figure 3 As shown, in some embodiments, the first trace 101 is a translation of the second trace 102 in the first direction. For example, in some embodiments, the equation corresponding to the second trace 102 in the above-mentioned coordinate system can be: y=k Then, the equation for the first trace 101 in the above-mentioned coordinate system is y = W + k. x^m, that is, the value of a in the first trace 101 is equal to the required aperture value W. In this embodiment, since the first trace 101 is a translation line of the second trace 102, even if the first trace 101 and the second trace 102 are not similar Figure 1 and Figure 2 The two opposing trajectories are parallel, and the distance between the first trajectories 101 and the second trajectories 102 remains constant along the second direction. That is, the aperture length W of the interdigital transducer 1 remains constant in the second direction, thereby improving the Q value of the surface acoustic wave filter while achieving transverse mode suppression.

[0044] Please continue reading. Figure 3 As shown, in some embodiments, the first electrode unit further includes multiple first dummy fingers 15 connected to the first busbar 11, and the second electrode unit further includes multiple second dummy fingers 16 connected to the second busbar 12. Dummy fingers and interdigitated fingers connected to the same busbar are arranged alternately in the second direction, with one dummy finger connected to one busbar facing another interdigitated finger in the first direction. For example, the first dummy fingers 15 and the first interdigitated fingers 13 are arranged alternately in the second direction, and the second dummy fingers 16 and the second interdigitated fingers 14 are arranged alternately in the second direction. For each first dummy finger 15, there is a corresponding second interdigitated finger 14 facing it in the first direction; for each second dummy finger 16, there is a corresponding first interdigitated finger 13 facing it in the first direction. A first gap 17 exists between the opposing first dummy fingers 15 and the second interdigitated fingers 14, and a second gap 18 exists between the opposing second dummy fingers 16 and the first interdigitated fingers 13.

[0045] The dummy fingers and interdigitated electrodes connected to the same busbar extend in the same direction. In the first direction, the extension length of the interdigitated electrodes connected to the same busbar is greater than the extension length of the dummy fingers. This means that no interdigitated structure is formed between the dummy fingers and their counterparts, thus they do not participate in the acoustic-electric conversion. Therefore, the dummy fingers can also be called virtual fingers. The dummy fingers can provide additional exposure and development reference points during the photolithography process of the interdigital transducer 1 to compensate for edge effects, thereby ensuring the consistency requirements of the linewidth and pattern of the interdigital electrodes throughout the entire interdigital transducer 1.

[0046] The first gaps 17 are spaced apart in the second direction, and the positions of each first gap 17 in the first direction are different. The second gaps 18 are spaced apart in the second direction, and the positions of each second gap 18 in the first direction are different. The distance between each first gap 17 and the first busbar 11 in the first direction is defined as the first distance, and the distance between each second gap 18 and the first busbar 11 is defined as the second distance. Figure 3 As shown, along the second direction, the extension length of the first interdigital electrode 11 increases sequentially, but the magnitude of the increase decreases sequentially, while the extension length of the second interdigital electrode 12 decreases sequentially, and the magnitude of the decrease also decreases sequentially. Therefore, along the second direction, the magnitude of the increase in the first distance of each first gap 17 decreases sequentially, and the magnitude of the increase in the second distance of at least some of the second gaps 18 decreases sequentially. This arrangement of the first gaps 17 and the second gaps 18 reduces the likelihood of surface acoustic wave (SAW) reflection, scattering, and energy loss due to abrupt boundary conditions when it propagates to the edge of the acoustic device. This improves the end-effect of the SAW filter and enhances its out-of-band suppression. Out-of-band suppression refers to the attenuation capability of the SAW filter for signals outside the passband.

[0047] Please see Figure 4 As shown, in some embodiments, the plurality of first interdigital electrodes 13 include a first portion of interdigital electrodes and a second portion of interdigital electrodes. The first portion of interdigital electrodes is the portion of the plurality of first interdigital electrodes 13 arranged forward in the second direction, and the second portion of interdigital electrodes is the remaining portion of the plurality of first interdigital electrodes 13 excluding the first portion of interdigital electrodes. Along the second direction, the length of each interdigital electrode in the first portion of interdigital electrodes increases sequentially to a first target value, and the rate of increase decreases sequentially, while the length of each interdigital electrode in the second portion of interdigital electrodes remains unchanged, and is respectively the first target value. The first target value is the extension length of the last interdigital electrode among the plurality of first interdigital electrodes arranged along the second direction. The first target value can be determined based on the first trace and the required aperture W of the interdigital transducer 1.

[0048] In this embodiment, the extended ends of the interdigital electrodes in the first part of the interdigital electrodes determine the first trace 101, the extended ends of the second interdigital electrodes 14 determine the second trace 102, and the extended ends of the interdigital electrodes in the second part of the interdigital electrodes determine the third trace 103. The first trace 101 and the second trace 102 can be respectively a quasi-parabola or a parabola, and the first trace 101 can be a translation line of the second trace 102 in the first direction. The third trace 103 is a straight line parallel to the second direction. The number of the first part of the interdigital electrodes is greater than the number of the second part of the interdigital electrodes, that is, the first part of the interdigital electrodes is most of the multiple first interdigital electrodes 13. The number of the interdigital electrodes in the second part of the interdigital electrodes can be but is not limited to less than 10, for example, it can be 4 or 5, etc.

[0049] Please refer to Figure 5 shown in the figure, which is a schematic diagram of the acoustic surface wave excitation intensity of the acoustic surface wave structure provided by the embodiment of the present application. Among them, the X-axis represents the serial number of each first interdigital electrode 13 arranged along the second direction, and the Y-axis represents the acoustic surface wave excitation intensity. For example, in this embodiment, the total number of multiple first interdigital electrodes 13 is N, and the number of each electrode in the second part of the interdigital electrodes is f. Then, the serial number n of the first interdigital electrode represents the nth electrode arranged along the second direction, where 1≤n≤N, 0<f<10. When n is f, it represents the fth first interdigital electrode 13, and when n is N-f, it represents the fth first interdigital electrode 13 from the bottom. Based on the setting method of each interdigital electrode of the acoustic surface wave structure provided by the embodiment of the present application, along the second direction, the acoustic surface wave excitation intensity of the interdigital transducer 1 first increases and then can remain unchanged. When reaching the end area where the last f first interdigital electrodes 13 are located, the excitation intensity of the acoustic surface wave will significantly weaken. As Figure 6 shown, this significant weakening can further improve the near-band rejection effect of the acoustic surface wave filter, thereby improving the performance of the resonant frequency splitting. Among them, Figure 6 is a schematic diagram of the comparison of the real part of the admittance curve of this embodiment (red dotted line) and the acoustic surface wave structure shown in Figure 1 as a comparative example (blue solid line). It can be clearly seen from Figure 6 that by using the acoustic surface wave structure provided by this embodiment, the near-band rejection effect of the acoustic surface filter is significantly improved, and the resonant frequency spectrum splitting phenomenon is well improved.

[0050] Please continue to refer to Figure 3As shown, some embodiments of the surface acoustic wave (SAW) structure provided in this application further include a first reflective grating unit 2 and a second reflective grating unit 3. The first reflective grating unit 2 includes multiple first reflective grating electrodes 23 extending in a first direction and spaced apart along a second direction. The second reflective grating unit 3 includes multiple second reflective grating electrodes 33 extending in the first direction and spaced apart along the second direction. In the second direction, the first reflective grating unit 2 is located downstream of the interdigital transducer 1, and the second reflective grating unit 3 is located upstream of the interdigital transducer 1. The first reflective grating unit 2 also includes a third busbar 21 and a fourth busbar 22 located on both sides of the first reflective grating electrode 33 in the first direction, with each first reflective grating electrode 33 connected to the third busbar 21 and the fourth busbar 22 respectively. The second reflective grating unit 3 also includes a fifth busbar 31 and a sixth busbar 32 located on both sides of the second reflective grating electrode 33 in the first direction, with each second reflective grating electrode 33 connected to the fifth busbar 31 and the sixth busbar 32 respectively. By setting reflection grating units on both sides or at least one side of the interdigital transducer 1, selective reflection of surface acoustic waves of a specific frequency can be generated through the periodic structure of the reflection grating units, thereby working in conjunction with the interdigital transducer 1 to achieve the signal filtering function.

[0051] Please see Figure 7As shown, in some embodiments, the first end of each first reflective gate electrode 23 is flush with the first adjacent extension end in the first direction, that is, the fourth trace 201 defined by the first end of each first reflective gate electrode 23 is a straight line. The first adjacent extension end is the extension end of a first interdigital electrode 13 near the first reflective gate unit 2. In this embodiment, the extension ends of each interdigital electrode in the first portion of interdigital electrodes arranged forward in the second direction among the plurality of first interdigital electrodes 13 define the first trace 101, and the extension ends of each interdigital electrode in the second portion of interdigital electrodes arranged backward in the second direction among the plurality of first interdigital electrodes 13 define the third trace 103. Therefore, the first adjacent extension end is the last interdigital electrode in the second portion of interdigital electrodes along the second direction, and the fourth trace 201 is a straight line aligned with the third trace 103 in the second direction, that is, the fourth trace 201 is an extension of the third trace 103. In other embodiments, if there is no third trace 103 between the first trace 101 and the fourth trace 201, then the first adjacent extension end is the extension end of the last interdigitated electrode of the first trace 101 along the second direction. The second end of the first reflective gate electrode 23 is located on the first extension line 202 of the second trace 102, wherein the first extension line 202 and the second trace 102 have the same trend of change, that is, the first extension line 202 and the second trace 102 have the same expression equation in the set coordinate system. For example, the second trace 102 and the first extension line 202 are two adjacent curve segments on a parabola or a parabola-like curve, respectively. In the second direction, the second trace 102 is located at the front end of the first extension line 202.

[0052] In addition, please continue to refer to Figure 7 As shown, in some embodiments, the first end of the second reflective gate electrode 33 is located on the second extension line 301 of the first trace 101. The trend of the second extension line 301 is the same as that of the first trace 101, meaning that the equations corresponding to the second extension line 301 and the first trace 101 in a set coordinate system are the same. For example, the first trace 101 and the second extension line 301 are two adjacent curve segments on a parabola or a parabola-like curve. In the second direction, the first trace 101 is located at the rear end of the second extension line 301. The second end of each second reflective gate electrode 33 is flush with the second adjacent extension end in the first direction, meaning that the fifth trace 302 defined by the second end of each second reflective gate electrode 33 is a straight line. The second adjacent extension end is the extension end of a second interdigitated electrode 14 near the second reflective gate unit 3.

[0053] The surface acoustic wave structure provided in this application embodiment has the trajectory lines at both ends of the first reflective grating electrode 23 and / or the second reflective grating electrode 33 designed as above. Then, along the second direction, the length a1 of each first reflective grating electrode 23 decreases sequentially, and the magnitude of the decrease decreases sequentially, while the length a2 of each second reflective grating electrode 33 increases sequentially, and the magnitude of the increase decreases sequentially.

[0054] Please see Figure 8 The diagram shown illustrates the surface acoustic wave (SAW) excitation intensity of a SAW structure provided in some embodiments of this application. The X-axis represents the sequence number n of the reflective grating electrodes and first interdigital electrodes arranged along the second direction, where the number of reflective grating electrodes in each reflective grating unit is r. The Y-axis represents the SAW excitation intensity. When the sequence number n is r, it represents the r-th second reflective grating electrode 33 of the second reflective grating unit 3. When the sequence number n is N, it represents the N-th first interdigital electrode 13. Figure 8 It can be seen that, based on setting the first trace 101 and the second trace 102 in the manner described above, and then setting the traces corresponding to each reflective grating electrode in the manner described in this embodiment, the length of the reflective grating electrode changes in the manner described above. For example... Figure 9 As shown, it is an embodiment (blue implementation) and... Figure 1 The diagram shown illustrates the passband comparison of the surface acoustic wave (SAW) structure as a comparative example (red dashed line) to the corresponding SAW filter. From... Figure 9 As can be seen, this configuration of the reflective grating unit in this embodiment can improve the passband edge ripple caused by the Gibbs effect, making the passband of the surface acoustic wave filter smoother.

[0055] Please see Figure 10 As shown, it is a schematic diagram of the structure of a surface acoustic wave filter provided according to some embodiments of this application. The surface acoustic wave filter provided in the embodiments of this application includes a piezoelectric layer 500 and a surface acoustic wave structure 600 provided according to any embodiment of this application. The surface acoustic wave structure 600 is disposed on the piezoelectric layer 500.

[0056] The piezoelectric layer 500 is a piezoelectric substrate or piezoelectric film layer made of a piezoelectric material. The piezoelectric material can be a single-crystal piezoelectric material or a composite piezoelectric material. The single-crystal piezoelectric material can include, but is not limited to, quartz. Lithium niobate () ) and lithium tantalate ( Composite piezoelectric materials can include, but are not limited to, piezoelectric ceramic-polymer composites, type 0-3 and type 1-3 piezoelectric composites. The piezoelectric layer can also be zinc oxide ( Piezoelectric thin films or gallium oxide ( ) Piezoelectric thin film. In this embodiment, the material for forming the piezoelectric layer 500 is... This allows surface acoustic wave (SAW) filters to have high-frequency, low-loss characteristics.

[0057] In some embodiments, the surface acoustic wave (SAW) filter provided in this application further includes a substrate layer 401, a polysilicon layer 402, and an insulating layer 403 stacked sequentially, wherein a piezoelectric layer 500 is disposed on the insulating layer 403, and the SAW structure is disposed on the side of the piezoelectric layer 500 away from the insulating layer 403. The substrate layer 401, the polysilicon layer 402, the insulating layer 403, and the piezoelectric layer 500 constitute a POI (Piezoelectric on Insulator) substrate. Due to the excellent piezoelectric properties and ease of integration of the POI substrate, the SAW filter provided in this embodiment has a higher resonant frequency, a larger Q value, a wider bandwidth, better filtering performance, and higher stability.

[0058] In this embodiment, a polycrystalline silicon layer 402 is added between the insulating layer 403 and the substrate layer 401 in the POI substrate. The ample grain boundaries in the polycrystalline silicon film can provide interface traps to capture free carriers, thereby improving the effective resistivity of the support layer, reducing current leakage, and contributing to improved device electrical stability. However, in other embodiments, the POI substrate can also be constructed by stacking the substrate layer 401, the insulating layer 403, and the piezoelectric layer 500, which will not be described in detail here. The insulating layer 403 can be, but is not limited to, a silicon dioxide (SiO2) layer, and the substrate layer 401 can be, but is not limited to, a single-crystal silicon (Si) substrate. Of course, in other embodiments, the piezoelectric layer 500 can also be directly disposed on the substrate layer 401.

[0059] Figure 11 and Figure 12 These figures show a comparison of the admittance curves and the real part of the admittance curves between the surface acoustic wave filter provided in this embodiment (black solid line) and the comparative example (red solid line). The comparative example is an application... Figure 1 The surface acoustic wave (SAW) filter with the structure shown is an SAW filter. Figure 11 and Figure 12 As can be seen, the surface acoustic wave filter provided in this application embodiment can effectively suppress the generation of shear wave modes and improve passband performance, while also effectively suppressing resonant frequency glitches caused by shear wave modes.

[0060] The surface acoustic wave filter provided in this application embodiment can achieve essentially the same technical effect as the surface acoustic wave structure provided in any embodiment of this application, and will not be described again here.

[0061] In some embodiments, this application also provides a communication device that includes the surface acoustic wave filter provided in any embodiment of this application. The communication device provided in this application can be a radio frequency communication device, and the communication signal received by the communication device can be filtered or otherwise processed by the surface acoustic wave device provided in this application.

[0062] The communication device provided in this application embodiment can achieve essentially the same technical effect as the surface acoustic wave device provided in this application embodiment, and will not be described again here.

[0063] It is understood that the specific examples in this document are only intended to help those skilled in the art better understand the embodiments of this application, and are not intended to limit the scope of the invention.

[0064] It is understood that in the various embodiments of this application, the sequence number of each process does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0065] It is understood that the various embodiments described in this application can be implemented individually or in combination, and the embodiments of this application are not limited in this respect.

[0066] Unless otherwise stated, all technical and scientific terms used in the embodiments of this application have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. The term "and / or" as used in this application includes any and all combinations of one or more of the associated listed items. The singular forms "a," "the," and "the" as used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0067] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0068] The above are merely specific embodiments of this application, but the scope of protection of this invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this invention should be determined by the scope of the claims.

Claims

1. A surface acoustic wave structure, characterized in that, Including interdigital transducers; The interdigital transducer includes a first electrode unit and a second electrode unit disposed opposite to each other. The first electrode unit includes a first busbar and a plurality of first interdigital electrodes connected to the first busbar. The second electrode unit includes a second busbar and a plurality of second interdigital electrodes connected to the second busbar. The first interdigitated electrode and the second interdigitated electrode extend in a first direction to form an interdigitated structure, and are arranged alternately in a second direction; Along the second direction, the length increase of at least a portion of the first interdigital electrode decreases sequentially, while the length decrease of the second interdigital electrode decreases sequentially; the length is the extension dimension in the first direction.

2. The surface acoustic wave structure according to claim 1, characterized in that, The plurality of first interdigitated electrodes include a first portion of interdigitated electrodes arranged forward in the second direction and a second portion of interdigitated electrodes arranged backward, wherein the number of the first portion of interdigitated electrodes is greater than the number of the second portion of interdigitated electrodes. Along the second direction, the length of the first part of the interdigitated electrode increases to a first target value in a manner that increases with decreasing increments, while the length of the second part of the interdigitated electrode remains unchanged and is the same as the first target value.

3. The surface acoustic wave structure according to claim 1, characterized in that, One of the first electrode unit and the second electrode unit is a positive electrode unit, and the other is a negative electrode unit. The extended ends of the first interdigital electrodes arranged along the second direction define a first trace, and the extended ends of each of the second interdigital electrodes define a second trace. The first trace and the second trace are parabolic or parabolic quasi-parabolic curves in a set coordinate system, respectively. Wherein, the origin of the set coordinate system is the starting point of the extension of the first interdigitated electrode arranged along the second direction, the positive direction of the first coordinate axis of the set coordinate system is the extension direction of the interdigitated electrode in the positive electrode unit, and the positive direction of the second coordinate axis is the second direction.

4. The surface acoustic wave structure according to claim 1, characterized in that, It also includes a first reflective grating unit; Along the second direction, the first reflective grating unit is located downstream of the interdigital transducer, and the first reflective grating unit includes a plurality of first reflective grating electrodes extending in the first direction and spaced apart in the second direction; The first end of each of the first reflective gate electrodes is flush with the first adjacent extension end in the first direction; wherein, the first adjacent extension end is the extension end of one of the first interdigital electrodes close to the first reflective gate unit. The second end of the first reflective grid electrode is located on the first extension line of the second trace; wherein the second trace is defined by the extension ends of each of the second interdigital electrodes, and the first extension line and the second trace have the same trend of change.

5. The surface acoustic wave structure according to claim 1, characterized in that, It also includes a second reflective grating unit; Along the second direction, the second reflective grating unit is located upstream of the interdigital transducer, and the second reflective grating unit includes a plurality of second reflective grating electrodes extending in the first direction and spaced apart in the second direction; The first end of the second reflective grid electrode is located on the second extension line of the first trace; wherein the first trace is defined by the extension end of the second interdigitated electrode arranged in the first direction, and the second extension line has the same trend as the first trace. The second end of each of the second reflective gate electrodes is flush with the second adjacent extension end in the first direction; wherein the second adjacent extension end is the extension end of one of the second interdigital electrodes close to the second reflective gate unit.

6. The surface acoustic wave structure according to claim 2, characterized in that, The number of interdigitated electrodes in the second part is less than 10.

7. The surface acoustic wave structure according to claim 3, characterized in that, The first trace is a translation of the second trace in the first direction.

8. The surface acoustic wave structure according to claim 7, characterized in that, The equation representing the second trace in the set coordinate system is: y=k x^m; Wherein, y represents the distance between the projection of a point on the second trace onto the first coordinate axis and the origin, x represents the distance between the projection of a point on the second trace onto the second coordinate axis and the origin, k is a preset constant greater than 1, and m is a preset constant in the range of 0.3 to 0.

7.

9. The surface acoustic wave structure according to claim 7, characterized in that, The first electrode unit further includes multiple first dummy finger electrodes connected to the first busbar, and the second electrode unit further includes multiple second dummy finger electrodes connected to the second busbar. The dummy finger electrodes and interdigitated electrodes connected to the same busbar are arranged alternately in the second direction, and the dummy finger electrodes connected to one busbar and the interdigitated electrodes connected to another busbar are opposite to each other in the first direction. There is a first gap between the first pseudo-finger electrode and the second interdigital electrode, and there is a second gap between the second pseudo-finger electrode and the first interdigital electrode. The distance between the first gap and the first busbar is a first distance, and the distance between the second gap and the first busbar is a second distance. Along the second direction, the increase in the first distance of each of the first gaps decreases sequentially, and the increase in the second distance of at least some of the second gaps decreases sequentially.

10. A surface acoustic wave filter, characterized in that, It includes a piezoelectric layer and a surface acoustic wave (SAW) structure as described in any one of claims 1 to 9, wherein the SAW structure is disposed on the piezoelectric layer.

11. A communication device, characterized in that, Includes the surface acoustic wave filter as described in claim 10.

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