A surface acoustic wave resonator with busbars of different tilt angles

Abstract

This invention discloses a surface acoustic wave resonator with busbars of different tilt angles, belonging to the field of piezoelectric technology. It includes an interdigital transducer and two reflective grids, with the two reflective grids respectively disposed on both sides of the interdigital transducer. Each reflective grid includes two short-circuit bars and reflective grid fingers, with the reflective grid fingers disposed between the two short-circuit bars. The short-circuit bars short-circuit the reflective grid fingers, forming a short-circuit reflective grid. The upper and lower busbars of this invention have different tilt angles, resulting in multiple different deflection angles in the resonator. By changing the deflection angle of the resonator, the energy flow direction of the resonator is made closer to the arrangement direction of the resonator fingers, reducing the transverse component of the acoustic wave. Simultaneously, each part of the resonator has a different aperture, weakening the resonance of the transverse mode. This design disrupts the resonance conditions of the transverse mode, preventing the transverse mode excited by the interdigital electrodes from resonating, thus achieving the effect of suppressing the transverse mode and is worthy of widespread application.

Description

Technical Field

[0001] This invention relates to the field of piezoelectric technology, and more specifically to a surface acoustic wave resonator with busbars having different tilt angles. Background Technology

[0002] Resonators (interdigital transducers, IDTs) fabricated on 42°YX lithium tantalate substrates are widely used in mobile communications. Piezoelectric devices based on 42°YX lithium tantalate (with a substrate thickness much greater than the mechanical wave wavelength in the resonator) excite leakage waves. These leakage waves are characterized by continuously scattering bulk waves into the substrate during propagation. The energy of these scattered bulk waves leads to a certain decrease in the Q value of the interdigital transducer. Therefore, thinning the piezoelectric substrate to a certain extent and fabricating a high-velocity acoustic layer at the bottom of the piezoelectric substrate is used to reflect the scattered acoustic waves back to the interdigital transducer. This approach can improve the Q value of the interdigital transducer and reduce device losses. If the high-velocity acoustic layer has a temperature coefficient opposite to that of the piezoelectric substrate, this approach can also reduce the device's temperature drift coefficient. The practice of thinning the piezoelectric substrate and fabricating a high-velocity acoustic layer at the bottom (POI device) alters the boundary conditions of the acoustic waves, causing the interdigital transducer to excite other modes of acoustic waves. Among these, the transverse resonant mode has the most significant impact on device performance. Therefore, suppressing the transverse resonant mode is a key technical consideration in the design of POI devices. Therefore, a surface acoustic wave resonator with different tilt angle busbars is proposed. Summary of the Invention

[0003] The technical problem to be solved by this invention is: how to solve the transverse resonant mode problem in existing surface acoustic wave resonators. This invention provides a surface acoustic wave resonator with busbars of different tilt angles. In this surface acoustic wave resonator, the upper and lower busbars are in the shape of broken lines with different tilt angles. The different tilt angles of the busbars make each part of the interdigital electrode have different apertures and make the interdigital electrode have multiple energy flow angles, which destroys the resonance condition of the transverse mode. The transverse mode excited by the interdigital electrode cannot resonate, thus achieving the effect of suppressing the transverse mode.

[0004] The present invention solves the above-mentioned technical problems through the following technical solution: The present invention includes an interdigital transducer and two reflective grids, the two reflective grids being respectively disposed on both sides of the interdigital transducer; each reflective grid includes two short-circuit bars and reflective grid fingers, the reflective grid fingers being disposed between the two short-circuit bars, the short-circuit bars short-circuiting the reflective grid fingers to form a short-circuit reflective grid; the interdigital transducer includes two interdigital electrodes arranged side by side, each interdigital electrode including a zigzag busbar and electrode fingers, the electrode fingers being connected to the zigzag busbar, the electrode fingers being divided into true fingers and false fingers, the true fingers and false fingers on the same interdigital electrode being spaced apart, and the true fingers and false fingers on different interdigital electrodes being staggered.

[0005] Furthermore, the distance between the reflective grating finger strip in the closest reflective grating and the electrode finger strip in the interdigital electrode is half the cycle wavelength of the interdigital transducer.

[0006] Furthermore, the center-to-center distance between the real and spur fingers on the same interdigital electrode is half the cycle wavelength of the interdigital transducer.

[0007] Furthermore, the distance between the real and fake fingers at relative positions on different interdigital electrodes is Dg, and the value of Dg is less than 0.5 times the period wavelength of the interdigital transducer.

[0008] Furthermore, the zigzag busbar includes at least two connected segments, and the deflection angle values ​​of the two segments in the zigzag busbar are both within the range of the energy flow angle ±10° or the supplementary energy flow angle ±10°, wherein the energy flow angle is the angle between the energy flow and the perpendicular direction of the interdigital electrode, and the deflection angle is the angle between each segment in the zigzag busbar and the perpendicular direction of the interdigital electrode.

[0009] Furthermore, the zigzag busbar comprises four connected segments, wherein the first segment of the upper interdigital electrode's zigzag busbar has an angle of θ1 with the positive X-axis, the second segment has an angle of θ2 with the negative X-axis, the third segment has an angle of θ1 with the positive X-axis, and the fourth segment has an angle of 0° with the negative X-axis; wherein the first segment of the lower interdigital electrode's zigzag busbar has an angle of θ3 with the positive X-axis, the second segment has an angle of θ4 with the negative X-axis, the third segment has an angle of θ3 with the positive X-axis, and the fourth segment has an angle of 0° with the negative X-axis; wherein the range of θ1 to θ4 is 0° to 15°.

[0010] Furthermore, the X-axis is set along the vertical direction of the interdigitated electrode and is located in the plane where the interdigitated electrode is located, while the Y-axis is set along the direction of the interdigitated electrode, is located in the plane where the interdigitated electrode is located, and is perpendicular to the X-axis.

[0011] Furthermore, when two surface acoustic wave resonators with different tilt angle busbars are cascaded, the busbar of the cascaded part has an angle of 0° with the X-axis.

[0012] Furthermore, the zigzag busbar comprises two connected segments, wherein the first segment of the zigzag busbar of the upper and lower interdigital electrodes has an angle of 6° with the positive X-axis, the second segment has an angle of 6° with the negative X-axis, and the short-circuit bar has an angle of 0° with the X-axis.

[0013] Furthermore, the zigzag busbar comprises two connected segments, wherein the first segment of the zigzag busbar of the upper and lower interdigital electrodes makes an angle of 6° with the positive X-axis, the second segment makes an angle of 6° with the negative X-axis, the short-circuit bar near the first segment of the zigzag busbar makes an angle of 6° with the positive X-axis, and the short-circuit bar near the second segment of the zigzag busbar makes an angle of 6° with the negative X-axis.

[0014] Compared with the prior art, the present invention has the following advantages: the surface acoustic wave resonator with different tilt angle busbars has different tilt angles in the upper and lower busbars, so that the resonator has multiple different deflection angles. By changing the deflection angle of the resonator, the energy flow direction of the resonator is made closer to the arrangement direction of the resonator fingers, and the transverse component of the acoustic wave is reduced. At the same time, each part of the resonator has a different aperture, which weakens the resonance of the transverse mode. This design destroys the resonance condition of the transverse mode, and the transverse mode excited by the interdigitated electrodes cannot resonate, thus achieving the effect of suppressing the transverse mode. It is worth promoting and using. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the surface acoustic wave resonator in Embodiment 1 of the present invention;

[0016] Figure 2 This is a schematic diagram of the structure of the cascaded surface acoustic wave resonators in Embodiment 1 of the present invention;

[0017] Figure 3 This is a schematic diagram of the surface acoustic wave resonator in Embodiment 2 of the present invention;

[0018] Figure 4 This is a schematic diagram comparing the test data of the surface acoustic wave resonator designed in Embodiment 2 of the present invention with the test data of the resonator without tilt angle design;

[0019] Figure 5 This is a schematic diagram of the surface acoustic wave resonator in Embodiment 3 of the present invention. Detailed Implementation

[0020] The embodiments of the present invention are described in detail below. These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiments.

[0021] Example 1

[0022] This embodiment provides a technical solution: a surface acoustic wave resonator with busbars of different tilt angles, including an interdigital transducer and two reflective grids. The interdigital transducer adopts a zigzag busbar design, with the interdigital electrodes arranged in a staggered manner. Reflective grids are disposed on both sides of the interdigital transducer, reflecting acoustic wave signals leaking to both sides of the interdigital transducer back to the interdigital transducer. The reflective grid includes reflective grid fingers 12 and short-circuit bars 11. The short-circuit bars 11 short-circuit the reflective grid fingers 12, forming a short-circuit reflective grid. If there are no short-circuit bars 11, it forms an open-circuit reflective grid. The center-to-center distance between the reflective grids and the adjacent fingers (finger bars on the side edges) of the interdigital transducer is the pitch value, which can be changed as needed.

[0023] The interdigital transducer includes two interdigital electrodes arranged side-by-side, used for excitation and absorption of surface acoustic waves. The center-to-center spacing of the interdigital electrodes is denoted by Pitch, which is the half-cycle wavelength of the interdigital transducer. Pitch is used to select the resonant frequency of the resonator. The upper and lower interdigital electrodes are formed by true fingers 231 and false fingers 232 (both true fingers 231 and false fingers 232 are the interdigital electrodes in the interdigital transducer) facing each other. The spacing between true fingers 231 and false fingers 232 is denoted by Dg, which is usually less than 0.5 times the cycle wavelength of the interdigital transducer. Finally, both true fingers 231 and false fingers 232 are connected to the broken-line busbars 21 / 22. The interdigital transducer also includes two consecutive broken-line busbars 21 / 22. The zigzag busbars 21 and 22 have different bending angles. The angle between the zigzag busbars 21 / 22 and the X-axis is called the electrode deflection angle. For the lower electrode, the first segment of the busbar (zigzag busbar 22) has an angle of θ1 with the positive X-axis, the second segment has an angle of θ2 with the negative X-axis, the third segment has an angle of θ1 with the positive X-axis, and the fourth segment has an angle of 0° with the negative X-axis. For the upper electrode, the first segment of the busbar (zigzag busbar 21) has an angle of θ3 with the positive X-axis, the second segment has an angle of θ2 with the negative X-axis, the third segment has an angle of θ1 with the positive X-axis, and the fourth segment has an angle of 0° with the negative X-axis. The directional angle is θ4, the angle between the third segment and the positive X-axis is θ3, and the angle between the fourth segment and the negative X-axis is 0°. The broken-line busbar 21 / 22 makes multiple deflection angles exist in the interdigital transducer and makes the interdigital transducer have different apertures. When the deflection angle is close to the energy flow angle (the angle between the energy flow and the perpendicular direction of the interdigital electrode) θ or (180°-θ), the transverse mode of the sound wave in half-cycle L is suppressed. The different apertures of each part of the interdigital electrode can reduce the resonance of the transverse mode.

[0024] like Figure 2 The diagram shows a cascaded surface acoustic wave resonator with different tilt angles. To facilitate cascading, the busbars in the cascaded section can be designed with a 0° tilt angle (straight busbars).

[0025] Example 2

[0026] like Figure 3 The diagram shown is a schematic of the surface acoustic wave resonator in this embodiment. The upper and lower busbars of the interdigital transducer adopt a double-zigzag design with an inclination angle of 6°. Specifically, the first section of the busbars of the upper and lower electrodes makes an angle of 6° with the positive X-axis, and the second section makes an angle of 6° with the negative X-axis. The same inclination angle of the upper and lower busbars of the interdigital electrodes ensures that the interdigital transducer has the same aperture. Figure 4 for Figure 3 The test data of the surface acoustic wave resonator (SAW) is compared with that of the resonator without tilt design. The solid line represents the test data of the resonator without tilt design, and a sharp lateral mode can be seen in the figure. The dashed line represents... Figure 3 The test data for the designed structure in this embodiment Figure 4As can be seen, the admittance curve between the positive and negative resonance peaks is smooth, and the transverse mode has been well suppressed.

[0027] Example 3

[0028] like Figure 5 The diagram shown is a schematic of the surface acoustic wave resonator in this embodiment. The short-circuit bars of the short-circuit reflector also employ an angled design. The reflector and the busbar segment adjacent to the interdigital transducer have the same angle, and possess [missing information - likely related to angle design]. Figure 3 The same effect of suppressing the transverse modulus is also observed in the embodiments.

[0029] In summary, the surface acoustic wave resonators with different tilt angle busbars described in the above embodiments have different tilt angles in the upper and lower busbars, resulting in multiple different deflection angles in the resonator. By changing the deflection angle of the resonator, the energy flow direction of the resonator is made closer to the arrangement direction of the resonator fingers, thus reducing the transverse component of the acoustic wave. At the same time, the different apertures of each part of the resonator weaken the resonance of the transverse mode. This design disrupts the resonance condition of the transverse mode, preventing the transverse mode excited by the interdigitated electrodes from resonating, thereby achieving the effect of suppressing the transverse mode. This design is worthy of widespread application.

[0030] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A surface acoustic wave resonator having different-tilt-angle bus bars, characterized by, The application relates to a surface acoustic wave resonator, which comprises an interdigital transducer, two reflective gratings, two short-circuit strips, reflective grating strips and electrode strips. The reflective grating strips are arranged between the two short-circuit strips, the short-circuit strips short-circuit the reflective grating strips, and the short-circuit strips form short-circuit reflective gratings. The interdigital transducer comprises two interdigital electrodes arranged side by side, the interdigital electrodes comprise fold line bus bars and electrode strips, the electrode strips are connected with the fold line bus bars, the electrode strips are divided into true electrode strips and false electrode strips, the true electrode strips and the false electrode strips on the same interdigital electrode are arranged at intervals, and the true electrode strips and the false electrode strips on different interdigital electrodes are arranged in a staggered mode. The interval between the true electrode strips and the false electrode strips in the opposite positions on different interdigital electrodes is Dg, and the value of Dg is less than 0.5 times the period wavelength of the interdigital transducer. The fold line bus bar comprises at least two segments, the deflection angles of the two segments in the fold line bus bar are within the range of the energy flow angle plus or minus 10 degrees or the supplementary angle of the energy flow angle plus or minus 10 degrees, wherein the energy flow angle is the angle between the energy flow and the vertical direction of the interdigital electrode, and the deflection angle is the angle between each segment of the fold line bus bar and the vertical direction of the interdigital electrode. The fold line bus bar causes multiple deflection angles to exist in the interdigital transducer and causes the interdigital transducer to have different apertures.

2. The SAW resonator with different angle bus bars according to claim 1, characterized in that: The fold line bus bar comprises four segments, wherein the first segment of the fold line bus bar of the lower interdigital electrode and the positive direction of the X-axis form an angle of theta 1, the second segment and the negative direction of the X-axis form an angle of theta 2, the third segment and the positive direction of the X-axis form an angle of theta 1, and the fourth segment and the negative direction of the X-axis form an angle of 0 degree; wherein the first segment of the fold line bus bar of the upper interdigital electrode and the positive direction of the X-axis form an angle of theta 3, the second segment and the negative direction of the X-axis form an angle of theta 4, the third segment and the positive direction of the X-axis form an angle of theta 3, and the fourth segment and the negative direction of the X-axis form an angle of 0 degree; wherein the angle range of theta 1 to theta 4 is 0-15 degrees; theta 3 is greater than theta 1, and theta 4 is greater than theta 2; and the X-axis is perpendicular to the interdigital electrode.

3. The SAW resonator with different-angled busbars according to claim 2, characterized in that: The interval between the reflective grating strips in the reflective grating with the closest interval and the electrode strips in the interdigital electrode is half the period wavelength of the interdigital transducer.

4. The SAW resonator with different-tilt-angle bus bars according to claim 1, characterized in that: The center interval between the true electrode strips and the false electrode strips on the same interdigital electrode is half the period wavelength of the interdigital transducer.

5. The SAW resonator with different-angled busbars according to claim 4, characterized in that: The X-axis is arranged along the vertical direction of the interdigital electrode and is located in the plane of the interdigital electrode, and the Y-axis is arranged along the direction of the interdigital electrode and is located in the plane of the interdigital electrode and perpendicular to the X-axis.

6. The SAW resonator with different-angled busbars according to claim 5, characterized in that: When the two surface acoustic wave resonators with different inclination bus bars are cascaded, the bus bar of the cascaded part is 0 degrees with the X-axis. The fold line bus bar comprises two segments, wherein the first segment of the fold line bus bar of the upper and lower interdigital electrodes and the positive direction of the X-axis form an angle of 6 degrees, the second segment and the negative direction of the X-axis form an angle of 6 degrees, and the short-circuit strip and the X-axis form an angle of 0 degree.

7. The SAW resonator with different-angled busbars according to claim 6, characterized in that: The meander-shaped bus bar comprises two segments connected with each other, wherein the first segment of the meander-shaped bus bar of the upper and lower interdigital electrodes is 6° with the positive direction of the X-axis, the second segment is 6° with the negative direction of the X-axis, the short-circuit strip close to the first segment of the meander-shaped bus bar is 6° with the positive direction of the X-axis, and the short-circuit strip close to the second segment of the meander-shaped bus bar is 6° with the negative direction of the X-axis.

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