Surface acoustic wave filter, out-of-band rejection method thereof, electronic component, and electronic device

Abstract

This specification provides a surface acoustic wave (SAW) filter designed based on the principle that the thickness of the piezoelectric layer in a resonator affects higher-order resonant frequencies. In a SAW resonator, the shear wave excited by the interdigital transducer propagates along the surface of the piezoelectric layer to form the dominant mode, while the longitudinal acoustic wave excited by the interdigital transducer propagates along a complex path and reflects to form higher-order spurious modes. Based on these characteristics, by adjusting the piezoelectric layer thickness of at least some of the resonators in the filter, the higher-order spurious modes can be adjusted without significantly affecting the dominant mode. Further research based on this principle reveals that by making the piezoelectric layer thickness of the series resonators in the filter greater than that of the parallel resonators, the target higher-order resonant frequency of the series resonators is made lower than that of the parallel resonators. This suppresses the out-of-band passband formed by the target higher-order resonant frequency, thereby improving device performance.

Description

Technical Field

[0001] This specification relates to the field of semiconductor technology, specifically to acoustic wave device technology within the semiconductor technology field, and more specifically to a surface acoustic wave filter and its out-of-band suppression method, electronic components, and electronic equipment. Background Technology

[0002] Acoustic wave devices are a class of devices that utilize the properties of sound waves propagating in a medium to achieve various functions. Acoustic wave devices are widely used in fields such as communication, signal processing, and sensors.

[0003] Taking surface acoustic wave (SAW) filters as an example, the resonant frequencies, anti-resonant frequencies, and spurious modes of the series and parallel resonators in a SAW filter jointly determine the performance of the SAW resonator. Among these, the resonant and anti-resonant frequencies are crucial in determining the operating frequency range of the device, while spurious modes can degrade the device's characteristics both inside and outside the passband. Therefore, it is necessary to suppress the out-of-band passband of the SAW filter to improve its performance. Summary of the Invention

[0004] This specification provides a surface acoustic wave filter and its out-of-band suppression method, electronic components, and electronic devices to achieve the purpose of suppressing the out-of-band passband of the surface acoustic wave filter and improving device performance.

[0005] To achieve the above technical objectives, the embodiments described in this specification provide the following technical solutions:

[0006] In a first aspect, a surface acoustic wave (SAW) filter is provided, comprising: a plurality of resonators, wherein the resonators are series resonators or parallel resonators; wherein...

[0007] The thickness of the piezoelectric layer in the series resonator is greater than the thickness of the piezoelectric layer in the parallel resonator;

[0008] The target higher-order resonant frequency of the series resonator is lower than that of the parallel resonator.

[0009] In conjunction with the first aspect, in some embodiments of the first aspect, the target higher-order resonant frequency of the parallel resonator is less than the target higher-order anti-resonant frequency of the series resonator;

[0010] The target higher-order anti-resonance frequency of the series resonator is less than the target higher-order anti-resonance frequency of the parallel resonator.

[0011] In conjunction with the first aspect, in some embodiments of the first aspect, the thickness of the piezoelectric layer of the resonator ranges from 0.2 pitch to 1 pitch, where pitch represents the interdigital electrode period of the interdigital transducer in the resonator.

[0012] In conjunction with the first aspect, in some embodiments of the first aspect, the thickness of the piezoelectric layer of the series resonator ranges from 0.65pitch1, where pitch1 represents the interdigital electrode period of the interdigital transducer in the series resonator.

[0013] The thickness of the piezoelectric layer of the parallel resonator ranges from 0.25pitch2 to 0.6pitch2, where pitch2 represents the interdigital electrode period of the interdigital transducer in the parallel resonator.

[0014] In conjunction with the first aspect, in some embodiments of the first aspect, the bandwidth of the surface acoustic wave filter is in the range of 1%fc to 5%fc, where fc represents the center frequency of the surface acoustic wave filter.

[0015] In conjunction with the first aspect, in some embodiments of the first aspect, the resonator includes:

[0016] A substrate, a high-velocity acoustic layer, a temperature compensation layer, and a piezoelectric layer are stacked sequentially.

[0017] Interdigital transducers located on the side of the piezoelectric layer away from the substrate.

[0018] In conjunction with the first aspect, in some embodiments of the first aspect, the target higher-order resonant frequency includes: a first higher-order resonant frequency, and / or, a second higher-order resonant frequency; the second higher-order resonant frequency is greater than the first higher-order resonant frequency.

[0019] Secondly, a method for out-of-band suppression of a surface acoustic wave filter is provided, including:

[0020] An initial filter is provided, wherein the resonant frequency of the series resonator in the initial filter is higher than the resonant frequency of the parallel resonator;

[0021] The piezoelectric layer thickness of the parallel resonator in the initial filter is reduced, and / or the piezoelectric layer thickness of the series resonator in the initial filter is increased, so that the piezoelectric layer thickness of the series resonator is greater than that of the parallel resonator, and the target higher-order resonant frequency of the series resonator is less than that of the parallel resonator, thus obtaining the target filter.

[0022] In conjunction with the second aspect, in some embodiments of the second aspect, in the initial filter, the thickness of the piezoelectric layer of the series resonator is 0.65pitch1, and the thickness of the piezoelectric layer of the parallel resonator is 0.65pitch2, where pitch1 represents the interdigital electrode period of the interdigital transducer in the series resonator, and pitch2 represents the interdigital electrode period of the interdigital transducer in the parallel resonator.

[0023] The reduction of the piezoelectric layer thickness of the parallel resonator in the initial filter includes:

[0024] Within the target adjustment range, the piezoelectric layer thickness of the parallel resonator in the initial filter is reduced; the target adjustment range includes 0.05pitch2 to 0.4pitch2.

[0025] Thirdly, an electronic component is provided, comprising one or more surface acoustic wave filters as described in any of the preceding claims.

[0026] Fourthly, an electronic device is provided, comprising:

[0027] A transceiver for receiving or transmitting signals, the transceiver comprising electronic components as described in any of the preceding claims;

[0028] A processor for processing the signal, wherein the processor is coupled to the transceiver.

[0029] As can be seen from the above technical solutions, the surface acoustic wave (SAW) filter provided in this specification is designed based on the principle that the thickness of the piezoelectric layer in the resonator affects the higher-order resonant frequency. Research has shown that in a SAW resonator, the shear wave excited by the interdigital transducer propagates along the surface of the piezoelectric layer to form the dominant mode, while the longitudinal acoustic wave excited by the interdigital transducer propagates along a complex path and reflects to form higher-order spurious modes. Based on these characteristics, by adjusting the piezoelectric layer thickness of at least some resonators in the SAW filter, the higher-order spurious modes can be adjusted without significantly affecting the dominant mode. Further research based on this principle has revealed that by making the thickness of the piezoelectric layer in the series resonator greater than that in the parallel resonator, the target higher-order resonant frequency of the series resonator is lower than that of the parallel resonator, thereby suppressing the out-of-band passband formed by the target higher-order resonant frequency and improving device performance. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of this specification 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 this specification. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of the admittance response curve of a surface acoustic wave filter in related technologies;

[0032] Figure 2 This is a top view schematic diagram of a surface acoustic wave resonator.

[0033] Figure 3 For along Figure 2 Schematic diagram of the cross-sectional structure of line AA' in the middle;

[0034] Figure 4 A schematic diagram of the admittance response curve of a surface acoustic wave resonator;

[0035] Figure 5 Simulated admittance response curves for surface acoustic wave resonators (specifically, POI-SAW resonators) with different piezoelectric layer thicknesses;

[0036] Figure 6 A schematic diagram of the structure of a surface acoustic wave filter provided for one embodiment of this specification;

[0037] Figure 7 A cross-sectional structural diagram of a series resonator and a parallel resonator provided for one embodiment of this specification;

[0038] Figure 8 The diagram shows the admittance curves of series resonators and parallel resonators in surface acoustic wave filters with bandwidths of 1% and 5% of the center frequency.

[0039] Figure 9 The admittance response curve obtained after reducing the piezoelectric layer thickness of the parallel resonator in a surface acoustic wave filter with a bandwidth of 1% of the center frequency;

[0040] Figure 10 The admittance response curve obtained after reducing the piezoelectric layer thickness of the parallel resonator in a surface acoustic wave filter with a bandwidth of 5% of the center frequency;

[0041] Figure 11 A schematic diagram of the admittance response curve of a surface acoustic wave filter provided for one embodiment of this specification;

[0042] Figure 12 The admittance response curve of a surface acoustic wave filter in related technologies;

[0043] Figure 13 A schematic diagram of the admittance response curve of a surface acoustic wave filter in the related art, provided as one embodiment of this specification;

[0044] Figure 14 This is a flowchart illustrating an out-of-band suppression method for a surface acoustic wave filter, provided as one embodiment of this specification.

[0045] Explanation of reference numerals in the attached figures

[0046] 100 - Filter; 101 - Series resonator; 102 - Parallel resonator; 10 / 5 - Substrate; 20 / 4 - High-velocity acoustic layer; 30 / 3 - Temperature compensation layer; 40 / 2 - Piezoelectric layer; 50 / 1 - Interdigitated electrode; 11 - Main mode; 12 - First higher-order spurious mode; 13 - Second higher-order spurious mode. Detailed Implementation

[0047] Unless otherwise defined, the technical or scientific terms used in the embodiments of this specification shall have the ordinary meaning understood by one of ordinary skill in the art to which this specification pertains. The terms "first," "second," and similar terms used in the embodiments of this specification do not indicate any order, quantity, or importance, but are merely used to avoid confusion of constituent elements.

[0048] Unless the context otherwise requires, throughout this specification, "a plurality of" means "at least two," and "including" is interpreted as open-ended or encompassing, that is, "including, but not limited to." In the description of this specification, terms such as "one embodiment," "some embodiments," "exemplary embodiment," "example," "specific example," or "some examples" are intended to indicate that a particular feature, structure, material, or characteristic associated with that embodiment or example is included in at least one embodiment or example of this specification. The illustrative representations of the above terms do not necessarily refer to the same embodiment or example.

[0049] The technical solutions in the embodiments of this specification will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments in this specification, and not all of them. Based on the embodiments in this specification, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this specification.

[0050] Overview

[0051] For surface acoustic wave (SAW) filters, the dominant mode refers to the primary acoustic mode that is desired to be utilized during the design phase. The frequency and characteristics of the dominant mode are the main objectives of filter design, typically exhibiting a high electromechanical coupling coefficient and good frequency selectivity. Higher-order spurious modes refer to other acoustic modes besides the dominant mode. These modes may form unexpected passbands (called out-of-band passbands), which can interfere with the dominant mode signal, leading to a degraded filter performance, such as frequency drift and increased insertion loss.

[0052] refer to Figure 1 ,exist Figure 1 In the diagram, the horizontal axis represents frequency (freq) in GHz, and the vertical axis represents admittance in dB. When designing surface acoustic wave (SAW) filters, engineers typically design the resonant frequency fs1 of the series resonator to be higher than the resonant frequency fp1 of the parallel resonator, thus forming the passband of the main mode. However, research has shown that for filters such as POI-SAW (Piezoelectric On Insulator-Surface Acoustic Wave) filters, this design goal also results in the resonant frequencies of higher-order spurious modes in the series resonator being higher than those in the parallel resonator (e.g., fs2 > fp2, fs3 > fp3, etc.). While this still forms the passband of the main mode, higher-order spurious modes also create out-of-band passbands. These out-of-band channels can cause spurious signals to pass through the filter during application.

[0053] To address this problem, the inventors studied the formation principles of the dominant and spurious modes in surface acoustic wave (SAW) filters, referencing... Figure 2 and Figure 3 , Figure 2 A top view schematic diagram of a feasible surface acoustic wave resonator is shown. Figure 3 for Figure 2 A cross-sectional view along line AA' shows that the surface acoustic wave (SAW) resonator may include a substrate 5, a high-velocity acoustic layer 4, a temperature compensation layer 3, a piezoelectric layer 2, and an interdigital transducer 7 located on the surface of the piezoelectric layer 2, stacked sequentially. The interdigital transducer may include interdigital electrodes 1. Additionally, the SAW resonator may include a reflective grating 6 located on the surface of the piezoelectric layer. The dominant mode in the SAW filter is mainly formed by shear waves excited by the interdigital transducers propagating along the surface of the piezoelectric layer. Shear waves are waves in which the direction of particle vibration is perpendicular to the direction of wave propagation. When propagating in the piezoelectric layer of the resonator, they mainly propagate along the surface layer and play a decisive role in the performance of the resonator. Studies have shown that changes in the thickness of the piezoelectric layer have a relatively small impact on the propagation of shear waves along the surface of the piezoelectric layer; therefore, changes in the thickness of the piezoelectric layer do not significantly affect the dominant mode of the SAW resonator.

[0054] And reference Figure 3 Higher-order stray modes are usually formed due to reflections of longitudinal acoustic waves at the interfaces between layers of the resonator. Figure 3 In the diagram, the white arrow indicates the direction of longitudinal sound wave propagation. After being excited, the longitudinal sound wave propagates downwards to the contact boundaries of each layer, where it is reflected due to impedance discontinuities. Each interdigital electrode excites a certain amount of sound wave energy. When the sound wave energy excited by multiple interdigital electrodes couples together, it forms one or more strong stray modes, such as... Figure 4 As shown, Figure 4 The figure shows the admittance response curve of a surface acoustic wave resonator. The horizontal axis represents frequency in GHz, and the vertical axis represents admittance in dB. Figure 4 In the diagram, 11 represents the dominant mode, 12 represents the first higher-order spurious mode, and 13 represents the second higher-order spurious mode. Changes in the piezoelectric layer thickness significantly alter the propagation path and direction of longitudinal acoustic waves within the piezoelectric layer and other films. Therefore, variations in the piezoelectric layer thickness have a significant impact on the higher-order spurious modes of the surface acoustic wave resonator.

[0055] Furthermore, in order to investigate the effect of variations in piezoelectric layer thickness on higher-order stray modes, reference Figure 5 , Figure 5 The simulated admittance response curves for surface acoustic wave resonators (specifically, POI-SAW resonators) with different piezoelectric layer thicknesses are shown. Figure 5 The figure shows the admittance response curves of surface acoustic wave (SAW) filters with piezoelectric layer thicknesses (h_lt) of 600 nm, 650 nm, and 700 nm. These three SAW filters are identical in all structural parameters except for the piezoelectric layer thickness. Figure 5 The horizontal axis represents frequency (freq) in MHz, and the vertical axis represents admittance. (This is achieved through...) Figure 5 It can be observed that the resonant frequency of the main mode of the surface acoustic wave filter does not change significantly with the thickness of the piezoelectric layer. However, the resonant frequency of the higher-order spurious modes (such as the first and second higher-order spurious modes) changes significantly with the thickness of the piezoelectric layer. Specifically, as the thickness of the piezoelectric layer increases, the resonant frequency of the higher-order spurious modes decreases (as h_lt increases from 600nm to 700nm, the center frequency of the first higher-order spurious mode decreases from approximately 2700MHz to around 2500MHz, and the center frequency of the second higher-order spurious mode decreases from around 3750MHz to around 3500MHz).

[0056] After obtaining the relationship between the piezoelectric layer thickness and the resonant frequency corresponding to the higher-order spurious modes, the piezoelectric layer thickness of the series resonator in the surface acoustic wave filter can be increased, and / or decreased, to make the piezoelectric layer thickness of the series resonator greater than that of the parallel resonator. As a result, the target higher-order resonant frequency of the series resonator is lower than that of the parallel resonator, thereby suppressing the out-of-band passband formed by the target higher-order resonant frequency and improving the device performance.

[0057] Based on the above concept, this specification provides a surface acoustic wave filter. The surface acoustic wave filter provided in this specification will be described exemplarily below with reference to the accompanying drawings.

[0058] Exemplary devices

[0059] One embodiment of this specification provides a surface acoustic wave filter, such as... Figure 6 and Figure 7 As shown, it includes: multiple resonators, wherein the resonators are series resonators 101 or parallel resonators 102; wherein,

[0060] The thickness of the piezoelectric layer 40 of the series resonator 101 is greater than the thickness of the piezoelectric layer 40 of the parallel resonator 102.

[0061] The target higher-order resonant frequency of the series resonator 101 is lower than the target higher-order resonant frequency of the parallel resonator 102.

[0062] refer to Figure 6 In one embodiment, the surface acoustic wave filter 100 may include seven resonators named SNP1 to SNP7, which together form a seventh-order trapezoidal filter. It is understood that... Figure 6 This specification is only intended to illustrate a feasible layout and connection method of the resonators in the surface acoustic wave filter 100. In other embodiments, the surface acoustic wave filter 100 may include more or fewer resonators. This specification does not limit the number, layout, and connection method of the resonators included in the surface acoustic wave filter 100, but depends on the actual situation.

[0063] exist Figure 6 In the diagram, resonators named SNP1 to SNP4 are series resonators 101, and resonators named SNP5 to SNP7 are parallel resonators 102. The cross-sectional structures of series resonators 101 and parallel resonators 102 are shown in the reference diagram. Figure 7 ,from Figure 7As can be seen, the resonator in the surface acoustic wave filter 100 may include a substrate 10, a high-velocity acoustic layer 20, a temperature compensation layer 30, a piezoelectric layer 40, and interdigitated electrodes 50 located on the surface of the piezoelectric layer 40. The interdigitated electrodes 50 serve as interdigitated transducers. Figure 7 (Not all of which are shown) exists. From Figure 7 A comparison of the series resonator 101 and the parallel resonator 102 shows that by setting the thickness H1 of the piezoelectric layer 40 of the series resonator 101 to be greater than the thickness H2 of the piezoelectric layer 40 of the parallel resonator 102, based on the principle described above, the target high-order resonant frequency of the series resonator 101 can be made smaller than the target high-order resonant frequency of the parallel resonator 102. This allows for the suppression of the out-of-band passband of the surface acoustic wave filter 100 without significantly changing the resonant frequencies corresponding to the main modes of each resonator, while ensuring that the passband of the surface acoustic wave filter 100 remains basically unchanged, thus improving the device performance.

[0064] In one embodiment, in order to improve the out-of-band suppression effect of the surface acoustic wave filter 100, the target higher-order resonant frequency of the parallel resonator 102 is lower than the target higher-order anti-resonant frequency of the series resonator 101.

[0065] The target high-order anti-resonance frequency of the series resonator 101 is less than the target high-order anti-resonance frequency of the parallel resonator 102.

[0066] In this embodiment, simulations and experiments revealed that by adjusting the thickness of the piezoelectric layer 40 of the series resonator 101 and / or the thickness of the piezoelectric layer 40 of the parallel resonator 102, the target higher-order resonant frequency of the parallel resonator 102 is less than the target higher-order anti-resonant frequency of the series resonator 101, and the target higher-order resonant frequency of the series resonator 101 is less than the target higher-order resonant frequency of the parallel resonator 102, resulting in the best suppression effect on the target higher-order spurious modes of the surface acoustic wave filter 100. The target higher-order spurious modes may include a first higher-order spurious mode, a second higher-order spurious mode, etc., which will not be exhaustively listed here. The first higher-order spurious mode corresponds to the first higher-order resonant frequency, and the second higher-order spurious mode corresponds to the second higher-order resonant frequency.

[0067] To avoid the adverse effects on the performance of the parallel resonator 102 caused by an excessively small thickness of the piezoelectric layer 40, the inventors, through research on the bandwidth of the surface acoustic wave filter 100, discovered that when the bandwidth of the surface acoustic wave filter 100 is within the range of 1% to 5% of its center frequency (i.e., the bandwidth range is 1%fc to 5%fc, where fc represents the center frequency of the surface acoustic wave filter 100), it helps to avoid the situation where the frequency difference between the series resonator 101 and the parallel resonator 102 is too large due to an excessively large filter bandwidth. This would necessitate excessively reducing the thickness of the piezoelectric layer 40 in the parallel resonator 102 to meet the target requirement that "the target higher-order resonant frequency of the series resonator 101 is less than the target higher-order resonant frequency of the parallel resonator 102." This avoids the problem of adverse effects on device performance caused by an excessively small thickness of the piezoelectric layer 40 in the parallel resonator 102.

[0068] Similarly, to avoid the adverse effects on the performance of the resonator caused by abnormal thickness of the piezoelectric layer 40, in one embodiment, the thickness of the piezoelectric layer 40 of the resonator is in the range of 0.2pitch to 1pitch, where pitch represents the interdigital electrode period of the interdigital transducer in the resonator.

[0069] Simulations and experiments have shown that when the thickness of the piezoelectric layer 40 of the resonator is within the range mentioned above, it can meet the design requirements of various surface acoustic wave filters 100 while avoiding the device performance degradation caused by the excessively small thickness of the piezoelectric layer 40 of the resonator, thus improving the overall performance of the surface acoustic wave filter 100.

[0070] In one embodiment, a feasible range of values ​​for the thickness of the piezoelectric layer 40 of the parallel resonator 102 is given when the thickness of the piezoelectric layer 40 of the series resonator 101 includes 0.65pitch1. Specifically, the range of values ​​for the thickness of the piezoelectric layer 40 of the series resonator 101 includes 0.65pitch1, where pitch1 represents the interdigital electrode period of the interdigital transducer in the series resonator 101.

[0071] The thickness of the piezoelectric layer 40 of the parallel resonator 102 ranges from 0.25pitch2 to 0.6pitch2, where pitch2 represents the interdigital electrode period of the interdigital transducer in the parallel resonator 102.

[0072] In this embodiment, when the thickness of the piezoelectric layer 40 of the series resonator 101 is 0.65pitch1, simulations show that, for the design requirement that the bandwidth of the surface acoustic wave resonator is 1% to 5% of the center frequency, the thickness of the piezoelectric layer 40 of the parallel resonator 102, when within the above range, can meet the requirement of adjusting the target high-order resonant frequency of the series resonator 101 to be lower than the target high-order resonant frequency of the parallel resonator 102 under different design requirements, thereby achieving the suppression of the out-of-band passband of the surface acoustic wave filter 100 and improving device performance.

[0073] Specifically, refer to Figure 8 , Figure 8 The admittance curves of the series resonator 101 and the parallel resonator 102 in the surface acoustic wave filter 100 with bandwidths of 1% and 5% of the center frequency are shown. Figure 8 In the graph, the horizontal axis represents frequency (freq) in GHz, and the vertical axis represents admittance in dB. The pitch = 1 μm curve (in...) Figure 8 The curve shown in blue in the image corresponds to the admittance curve of the series resonator 101, with the curve at pitch = 1.011 μm (in...). Figure 8 The curve shown in green corresponds to the admittance curve of the parallel resonator 102 in the 1% bandwidth surface acoustic wave filter 100, with a pitch of 1.061 μm. Figure 8 The curve shown in red corresponds to the admittance curve of the parallel resonators 102 in the 5% bandwidth surface acoustic wave filter 100. The piezoelectric layer 40 of these resonators has a thickness of 0.65pitch.

[0074] By reducing the thickness of the piezoelectric layer 40 of the parallel resonator 102 in each of the above surface acoustic wave filters 100, the following can be obtained: Figure 9 and Figure 10 The admittance response curve shown is in Figure 9 and Figure 10 In the diagram, the horizontal axis represents frequency (freq) in GHz, and the vertical axis represents admittance in dB. Figure 9 In order to reduce the thickness of the piezoelectric layer 40 of the parallel resonator 102 in the 1% bandwidth surface acoustic wave filter 100 from 0.65 pitch2 to 0.6 pitch2, so that the target high-order resonant frequency of the series resonator 101 in the filter is lower than the target high-order resonant frequency of the parallel resonator 102. Figure 10To reduce the thickness of the piezoelectric layer 40 of the parallel resonator 102 in a 5% bandwidth surface acoustic wave (SAW) filter 100 from 0.65 pitch 2 to 0.25 pitch 2, so that the target higher-order resonant frequency of the series resonator 101 in the filter is lower than the target higher-order resonant frequency of the parallel resonator 102, the simulation process described above shows that when the thickness of the piezoelectric layer 40 of the series resonator 101 ranges from 0.65 pitch 1, and the thickness of the piezoelectric layer 40 of the parallel resonator 102 ranges from 0.25 pitch 2 to 0.6 pitch 2, the design requirements for a 1% to 5% bandwidth SAW resonator can be met.

[0075] In an alternative implementation, reference is still made to Figure 7 The resonator includes: a substrate 10, a high-velocity acoustic layer 20, a temperature compensation layer 30 and a piezoelectric layer 40 stacked sequentially;

[0076] Interdigital transducers located on the side of the piezoelectric layer 40 opposite to the substrate 10 Figure 7 Part of the interdigital electrode 50 is shown; the interdigital transducer is not fully shown.

[0077] In some embodiments, the substrate 10 may include a single-crystal silicon layer, the high-velocity acoustic layer 20 may include a polycrystalline silicon layer, the temperature compensation layer 30 may include a silicon dioxide layer, the piezoelectric layer 40 may include a lithium tantalate layer, a lithium niobate layer, or an aluminum nitride layer, and the interdigital transducer may be composed of aluminum metal electrodes or stacked metal electrodes (e.g., stacked aluminum and copper metal electrodes, or stacked aluminum, copper, and titanium metal electrodes, etc.). In this structure, the high-velocity acoustic layer 20 can enhance the propagation speed of sound waves and reduce sound wave loss in the substrate 10, thereby helping to improve the performance and efficiency of the device. The temperature elasticity of the temperature compensation layer 30 may be opposite to that of the piezoelectric layer 40, which can effectively compensate for the influence of temperature changes on the resonant frequency, thereby improving the operating stability of the device.

[0078] In order to specifically suppress one or more higher-order spurious modes, in one embodiment, the target higher-order resonant frequency includes: a first higher-order resonant frequency, and / or, a second higher-order resonant frequency; the second higher-order resonant frequency is greater than the first higher-order resonant frequency.

[0079] For example, in one embodiment, the target higher-order resonant frequency includes a first higher-order resonant frequency, thereby suppressing the first higher-order spurious mode; in another embodiment, the target higher-order resonant frequency includes a second higher-order resonant frequency, thereby suppressing the second higher-order spurious mode; and in yet another embodiment, the target higher-order resonant frequency includes both a first higher-order resonant frequency and a second higher-order resonant frequency, thereby suppressing both the first and second higher-order spurious modes.

[0080] It is understandable that the first higher-order resonant frequency can refer to a higher-order resonant frequency than the resonant frequency corresponding to the main mode, while the second higher-order resonant frequency can refer to a higher-order resonant frequency than the first higher-order resonant frequency.

[0081] In one specific implementation, as follows Figure 6 Taking the surface acoustic wave filter 100 shown as an example, the suppression effect of the surface acoustic wave filter 100 on the out-of-band passband provided in the embodiments of this specification is verified by comparative simulation experiments.

[0082] refer to Figure 7 In the surface acoustic wave filter 100 provided in this embodiment, the piezoelectric layer 40 thickness of the series resonator 101 can be 0.65pitch1, where pitch1 = 1 μm; the piezoelectric layer 40 thickness of the parallel resonator 102 can be 0.25pitch2, where pitch2 = 1.061 μm. Simulation results show... Figure 11 The admittance response curve shown is... Figure 11 In the diagram, Y(1,1) is the admittance response curve of the parallel resonator 102, and Y(3,3) is the admittance response curve of the series resonator 101. Figure 11 In the diagram, the horizontal axis represents frequency (freq) in GHz, and the vertical axis represents admittance in dB. S(6,5) represents the configuration as shown in the diagram. Figure 6 The passband response curve of the 7th-order trapezoidal filter shown is obtained by... Figure 11 It can be observed that by optimizing the thickness of the piezoelectric layer 40, the higher-order resonant frequencies corresponding to the first and second higher-order spurious modes of the parallel resonator 102 are adjusted to be higher than the higher-order resonant frequencies corresponding to the first and second higher-order spurious modes of the series resonator 101. Furthermore, when the higher-order resonant frequencies corresponding to the first and second higher-order spurious modes of the parallel resonator 102 are adjusted to be near the higher-order resonant frequencies corresponding to the first and second higher-order spurious modes of the series resonator 101, the higher-order spurious mode response of the surface acoustic wave filter 100 dips downwards. This indicates that the surface acoustic wave filter 100 effectively suppresses the higher-order spurious mode signals within this frequency range. This helps reduce the negative impact of higher-order modes on filter performance, such as in-band ripple and out-of-band leakage.

[0083] refer to Figure 12 , Figure 12 In related technologies, the admittance response curve of a surface acoustic wave filter is shown. Figure 12 In the diagram, the horizontal axis represents frequency (freq) in GHz, and the vertical axis represents admittance in dB. S(7,8) is the passband response curve of the filter in the relevant technique, and Y(3,3) is the admittance response curve of the series resonator in the relevant technique. The structure of this series resonator can be compared with... Figure 11 The structure of the series resonator 101 shown is the same. Y(9,9) is the admittance response curve of the parallel resonator in the related technology. The piezoelectric layer thickness of the parallel resonator in the related technology is 0.65pitch, pitch1 = 1.061um, and the other parameters are the same as those of the parallel resonator. Figure 11 The parallel resonator 102 shown is the same.

[0084] refer to Figure 13 ,exist Figure 13 In the figure, the horizontal axis represents frequency (freq) in GHz, and the vertical axis represents admittance in dB. By comparing the admittance response curves of surface acoustic wave filters in the aforementioned related technologies with the admittance response curve of the surface acoustic wave filter 100 provided in the embodiments of this specification, it can be found that the out-of-band bulge caused by the second higher-order spurious mode in the surface acoustic wave filters in the related technologies is well suppressed in the surface acoustic wave filter 100 provided in the embodiments of this specification.

[0085] Exemplary methods

[0086] In one embodiment of this specification, an out-of-band suppression method for a surface acoustic wave filter is also provided, such as... Figure 14 As shown, it includes:

[0087] S1401: Provide an initial filter in which the resonant frequency of the series resonator is higher than the resonant frequency of the parallel resonator;

[0088] An initial filter can refer to a surface acoustic wave (SAW) filter designed based on the objective that the resonant frequency of the series resonator is higher than that of the parallel resonator. In other words, the initial filter can be a filter model built by the designer in relevant design software based on the aforementioned objective; it is not a physical filter actually manufactured. This filter model can be used to describe various filter parameters and other information.

[0089] The fact that the resonant frequency of a series resonator is higher than that of a parallel resonator can mean that the resonant frequency corresponding to the main mode of the series resonator is higher than that corresponding to the main mode of the parallel resonator, thus forming the passband of the filter. However, as mentioned earlier, the higher-order resonant frequencies corresponding to the higher-order spurious modes of the series resonator will also be higher than those corresponding to the higher-order resonant frequencies of the higher-order spurious modes of the parallel resonator, which may form an out-of-band passband.

[0090] S1402: Reduce the piezoelectric layer thickness of the parallel resonator in the initial filter, and / or increase the piezoelectric layer thickness of the series resonator in the initial filter, so that the piezoelectric layer thickness of the series resonator is greater than the piezoelectric layer thickness of the parallel resonator, and the target higher-order resonant frequency of the series resonator is less than the target higher-order resonant frequency of the parallel resonator, to obtain the target filter.

[0091] Similarly, step S1402 is also implemented during the filter design phase. Reducing the piezoelectric layer thickness can refer to reducing the thickness parameter of the piezoelectric layer of the resonator described in the initial filter to meet specific design goals. Specifically, in this embodiment, by adjusting the piezoelectric layer thickness of the parallel resonator and / or series resonator, the thickness of the piezoelectric layer of the series resonator can be made greater than that of the parallel resonator, and the target higher-order resonant frequency of the series resonator can be less than that of the parallel resonator, thus obtaining the target filter and achieving out-of-band suppression in the target filter, improving device performance.

[0092] Optionally, in one embodiment, in the initial filter, the thickness of the piezoelectric layer of the series resonator is 0.65pitch1, and the thickness of the piezoelectric layer of the parallel resonator is 0.65pitch2, where pitch1 represents the interdigital electrode period of the interdigital transducer in the series resonator, and pitch2 represents the interdigital electrode period of the interdigital transducer in the parallel resonator.

[0093] The reduction of the piezoelectric layer thickness of the parallel resonator in the initial filter includes:

[0094] Within the target adjustment range, the piezoelectric layer thickness of the parallel resonator in the initial filter is reduced; the target adjustment range includes 0.05pitch2 to 0.4pitch2.

[0095] In this embodiment, after obtaining the relevant parameters of the initial filter, a reduction value for the piezoelectric layer thickness of the parallel resonator can be determined within the target adjustment range (e.g., 0.05pitch2, 0.1pitch2, 0.15pitch2, 0.2pitch2, 0.3pitch2, and 0.4pitch2, etc.). Then, the piezoelectric layer thickness of the parallel resonator is reduced from 0.65pitch2 by this reduction value (e.g., when the reduction value is 0.05pitch2, after this step, the piezoelectric layer thickness of the parallel resonator is reduced from 0.65pitch2 to 0.6pitch2) to achieve the adjustment of the target higher-order resonant frequency of the parallel resonator, satisfying the design objective that the target higher-order resonant frequency of the series resonator is less than the target higher-order resonant frequency of the parallel resonator.

[0096] The process for determining the target adjustment range can be found in [reference needed]. Figures 8-10 As well as the relevant descriptions above, this instruction manual will not repeat them here.

[0097] Exemplary device

[0098] In one embodiment of this specification, an electronic component is also provided, including a surface acoustic wave filter as described in any of the above embodiments.

[0099] The surface acoustic wave (SAW) filter is designed based on the principle that the thickness of the piezoelectric layer in the resonator affects the higher-order resonant frequencies. Research has shown that in a SAW resonator, the shear wave excited by the interdigital transducer propagates along the surface of the piezoelectric layer to form the dominant mode, while the longitudinal acoustic wave excited by the interdigital transducer propagates along a complex path and reflects to form higher-order spurious modes. Based on these characteristics, by adjusting the piezoelectric layer thickness of at least some resonators in the SAW filter, the higher-order spurious modes can be adjusted without significantly affecting the dominant mode. Further research based on this principle has revealed that by making the piezoelectric layer thickness of the series resonators in the SAW filter greater than that of the parallel resonators, the target higher-order resonant frequency of the series resonators is lower than that of the parallel resonators. This suppresses the out-of-band passband formed by the target higher-order resonant frequency, thereby improving device performance.

[0100] The electronic components may be, but are not limited to, filters, duplexers, delay lines, frequency discriminators, or modulators.

[0101] This specification provides an embodiment of an electronic device including a transceiver and a processor. Specifically, the transceiver is used to receive or transmit signals. The transceiver includes the electronic components provided in this application. The processor is used to perform signal processing on the signals. The processor is coupled to the transceiver.

[0102] Electronic devices can be terminal devices, also known as user equipment (UE), access terminals, user units, user stations, mobile stations, mobile stations, remote stations, remote terminals, mobile devices, user terminals, terminals, wireless communication equipment, user agents, or user devices. As an example and not a limitation, terminal devices can be mobile phones, tablets, computers with wireless transceiver capabilities, virtual reality (VR) terminal devices, augmented reality (AR) terminal devices, wireless terminals in industrial control, wireless terminals in self-driving, wireless terminals in remote medical care, wireless terminals in smart grids, wireless terminals in transportation safety, wireless terminals in smart cities, wireless terminals in smart homes, etc.

[0103] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0104] The embodiments described above are merely illustrative of several implementations of this specification, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the solutions provided in this specification. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this specification, and these all fall within the scope of protection of this specification. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A surface acoustic wave filter, characterized by, include: Multiple resonators, wherein the resonators are series resonators or parallel resonators; wherein, The thickness of the piezoelectric layer in the series resonator is greater than the thickness of the piezoelectric layer in the parallel resonator; The target higher-order resonant frequency of the series resonator is lower than that of the parallel resonator.

2. The surface acoustic wave filter according to claim 1, characterized by, The target higher-order resonant frequency of the parallel resonator is less than the target higher-order anti-resonant frequency of the series resonator. The target higher-order anti-resonance frequency of the series resonator is less than the target higher-order anti-resonance frequency of the parallel resonator.

3. The surface acoustic wave filter according to claim 1, characterized by, The thickness of the piezoelectric layer of the resonator ranges from 0.2pitch to 1pitch, where pitch represents the interdigital electrode period of the interdigital transducer in the resonator.

4. The surface acoustic wave filter according to claim 3, characterized by, The thickness of the piezoelectric layer of the series resonator ranges from 0.65pitch1, where pitch1 represents the interdigital electrode period of the interdigital transducer in the series resonator.

5. The surface acoustic wave filter according to claim 4, wherein The thickness of the piezoelectric layer of the parallel resonator ranges from 0.25pitch2 to 0.6pitch2, where pitch2 represents the interdigital electrode period of the interdigital transducer in the parallel resonator.

6. The surface acoustic wave filter according to claim 1, wherein The bandwidth of the surface acoustic wave filter ranges from 1%fc to 5%fc, where fc represents the center frequency of the surface acoustic wave filter.

7. The surface acoustic wave filter according to any one of claims 1 to 6, characterized by The resonator includes: A substrate, a high-velocity acoustic layer, a temperature compensation layer, and a piezoelectric layer are stacked sequentially. Interdigital transducers located on the side of the piezoelectric layer away from the substrate.

8. The surface acoustic wave filter according to any one of claims 1 to 6, characterized by The target higher-order resonant frequency includes: a first higher-order resonant frequency, and / or a second higher-order resonant frequency; the second higher-order resonant frequency is greater than the first higher-order resonant frequency.

9. A method of out-of-band rejection for a surface acoustic wave filter, characterized by, include: An initial filter is provided, wherein the resonant frequency of the series resonator in the initial filter is higher than the resonant frequency of the parallel resonator; The piezoelectric layer thickness of the parallel resonator in the initial filter is reduced, and / or the piezoelectric layer thickness of the series resonator in the initial filter is increased, so that the piezoelectric layer thickness of the series resonator is greater than that of the parallel resonator, and the target higher-order resonant frequency of the series resonator is less than that of the parallel resonator, thus obtaining the target filter.

10. The method of claim 9, wherein, In the initial filter, the thickness of the piezoelectric layer of the series resonator is 0.65pitch1, and the thickness of the piezoelectric layer of the parallel resonator is 0.65pitch2. Pitch1 represents the interdigital electrode period of the interdigital transducer in the series resonator, and pitch2 represents the interdigital electrode period of the interdigital transducer in the parallel resonator. The reduction of the piezoelectric layer thickness of the parallel resonator in the initial filter includes: Within the target adjustment range, the piezoelectric layer thickness of the parallel resonator in the initial filter is reduced; the target adjustment range includes 0.05pitch² to 0.4pitch².

11. An electronic component, characterized by Includes one or more surface acoustic wave filters as described in any one of claims 1 to 8.

12. An electronic device, comprising: include: A transceiver for receiving or transmitting signals, the transceiver comprising the electronic components as described in claim 11; A processor for processing the signal, wherein the processor is coupled to the transceiver.

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