A surface acoustic wave resonator, a surface acoustic wave filter, and a duplexer

Abstract

The utility model relates to the technical field of surface acoustic wave resonator provides a surface acoustic wave resonator, surface acoustic wave filter and duplexer, wherein the surface acoustic wave resonator includes: piezoelectric layer;Interdigital transducer sets up on piezoelectric layer, and the interdigital transducer includes multiple interdigital electrodes;First reflection grating and second reflection grating are all set up on piezoelectric layer, and the interdigital transducer is located between first reflection grating and second reflection grating;Dielectric layer includes first dielectric part and second dielectric part, and the first dielectric part covers at least one interdigital electrode of the interdigital transducer close to first reflection grating, and the second dielectric part covers at least one interdigital electrode of the interdigital transducer close to second reflection grating. By being provided with the structure of dielectric layer, to reduce electromechanical coupling coefficient, since electromechanical coupling coefficient reduces and will make the frequency interval between resonant frequency and anti-resonance frequency correspondingly reduce, can reach the effect of improving abruptness, improves the performance of surface acoustic wave resonator.

Description

Technical Field

[0001] This utility model relates to the field of surface acoustic wave resonator technology, and in particular to a surface acoustic wave resonator, a surface acoustic wave filter, and a duplexer. Background Technology

[0002] A surface acoustic wave (SAW) resonator is a frequency-controlled device that operates using mechanical vibration. Its principle lies in using a piezoelectric crystal material with interdigital transducers (comprising metal electrodes) and reflective gratings on its surface. When an electrical signal is applied to the interdigital transducer, electrical energy is converted into a SAW wave of a specific frequency through the inverse piezoelectric effect. This wave propagates along the crystal surface and is reflected and constrained by the reflective gratings at both ends, thus forming a stable standing wave resonance within the cavity. The impedance is minimum at the resonant frequency and maximum at the anti-resonant frequency. Based on this characteristic of the SAW resonator, a SAW filter can be formed through circuit topology.

[0003] In existing technologies, surface acoustic wave (SAW) filters have high requirements for steepness in communication systems in order to effectively suppress frequencies outside the passband, thereby suppressing adjacent channel interference and meeting spectrum specifications.

[0004] However, existing surface acoustic wave (SAW) resonator structures suffer from insufficient kurtosis, making it difficult for the resulting SAW filters to meet the requirements of high-selectivity filtering. Therefore, improving the kurtosis of SAW resonators is an urgent problem to be solved. Utility Model Content

[0005] This invention provides a surface acoustic wave resonator, a surface acoustic wave filter, and a duplexer to address the deficiency of insufficient steepness in existing surface acoustic wave resonators.

[0006] This utility model provides a surface acoustic wave resonator, comprising: piezoelectric layer; An interdigital transducer is disposed on the piezoelectric layer, and the interdigital transducer includes a plurality of interdigital electrodes; The first and second reflective gratings are both disposed on the piezoelectric layer, and the interdigital transducer is located between the first and second reflective gratings; The dielectric layer includes a first dielectric portion and a second dielectric portion, the first dielectric portion covering at least one interdigital electrode of the interdigital transducer near the first reflective grating, and the second dielectric portion covering at least one interdigital electrode of the interdigital transducer near the second reflective grating.

[0007] According to the present invention, a surface acoustic wave resonator is provided in which the first dielectric section and the second dielectric section are symmetrically arranged with the center line of the interdigital transducer as the axis of symmetry.

[0008] According to the present invention, in a surface acoustic wave resonator, the number of interdigitated electrodes covered by the first dielectric portion is equal to the number of interdigitated electrodes covered by the second dielectric portion.

[0009] According to the present invention, the surface acoustic wave resonator is a polyimide layer or a silicon nitride layer.

[0010] According to the present invention, the number of interdigitated electrodes covered by the first dielectric portion is greater than or equal to 4, and the number of interdigitated electrodes covered by the second dielectric portion is greater than or equal to 4.

[0011] According to the present invention, a surface acoustic wave resonator further includes a substrate, the substrate including a high-velocity support layer and a low-velocity layer, the low-velocity layer being disposed on the high-velocity support layer and the piezoelectric layer being disposed on the low-velocity layer.

[0012] According to the present invention, the substrate further includes a high-velocity acoustic layer, which is disposed between the low-velocity acoustic layer and the high-velocity acoustic support layer.

[0013] According to the present invention, a surface acoustic wave resonator is provided, wherein the substrate includes a high-velocity support layer, at least two low-velocity layers and at least one high-velocity layer, the low-velocity layers and the high-velocity layers are stacked alternately with the low-velocity layer on top to form a stack group, the stack group is disposed on the high-velocity support layer, and the piezoelectric layer is disposed on the stack group.

[0014] The surface acoustic wave filter provided by this utility model includes at least one of the above-mentioned surface acoustic wave resonators.

[0015] This utility model also provides a duplexer, including a transmitting filter component and a receiving filter component, wherein the transmitting filter component includes at least one of the above-mentioned surface acoustic wave resonators, and / or the receiving filter component includes at least one of the above-mentioned surface acoustic wave resonators.

[0016] This invention provides a surface acoustic wave (SAW) resonator, SAW filter, and duplexer, which at least have the following advantages: By covering the regions of the interdigital transducer near the first and second reflective gratings with a first dielectric portion and a second dielectric portion of a dielectric layer, respectively, the electric field generated by the interdigital transducer will partially leak into the dielectric layer in the regions of the first and second dielectric portions, thereby reducing the electromechanical coupling coefficient between the interdigital transducer and the piezoelectric layer. Thus, by providing a dielectric layer structure, forming the first and second dielectric portions covering the interdigital electrodes near the first and second reflective gratings of the interdigital transducer, the electromechanical coupling coefficient is reduced. Since the electromechanical coupling coefficient is reduced, the frequency interval between the resonant frequency and the anti-resonant frequency is correspondingly reduced, thereby improving the steepness of the surface acoustic wave resonator. This is beneficial for improving the performance of the SAW resonator and also helps to meet the high-selectivity filtering requirements when forming a surface acoustic wave filter. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in this utility model or related technologies, the drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of one embodiment of a surface acoustic wave resonator provided by this utility model.

[0019] Figure 2 This utility model provides a surface acoustic wave resonator in... Figure 1 A cross-sectional view of the position of line AA' in the embodiment.

[0020] Figure 3 This is a comparative schematic diagram of the frequency response of a surface acoustic wave resonator provided by this utility model.

[0021] Figure 4 This is a schematic diagram of the frequency response of a surface acoustic wave resonator provided by this utility model when the dielectric layer is a polyimide layer.

[0022] Figure 5 This is a schematic diagram of the frequency response of a surface acoustic wave resonator provided by this utility model when the dielectric layer is a silicon nitride layer.

[0023] Figure 6 This is a schematic diagram of the frequency response of a surface acoustic wave resonator provided by this utility model under different numbers of covered interdigitated electrodes.

[0024] Figure 7 yes Figure 6The corresponding numerical table.

[0025] Figure 8 This is one of the schematic diagrams of a substrate for a surface acoustic wave resonator provided by this utility model.

[0026] Figure 9 This is the second schematic diagram of the substrate of a surface acoustic wave resonator provided by this utility model.

[0027] Figure 10 This is the third schematic diagram of the substrate of a surface acoustic wave resonator provided by this utility model.

[0028] Figure 11 This is the fourth schematic diagram of the substrate of a surface acoustic wave resonator provided by this utility model.

[0029] Figure 12 This is a circuit diagram of one embodiment of the duplexer provided by this utility model.

[0030] Figure 13 This is a schematic diagram of an existing surface acoustic wave resonator.

[0031] Figure label: 100: Piezoelectric layer; 200: Interdigital transducer; 210: Interdigital electrode; 300: First reflective grating; 310: Second reflective grating; 400: Dielectric layer; 410: First dielectric section; 420: Second dielectric section; 500: Substrate; 501: Stacked assembly; 510: Hypersonic support layer; 520: Low-velocity layer; 530: Hypersonic layer; 600: Transmitting filter assembly; 700: Receiving filter assembly. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this utility model clearer, the technical solutions of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0033] like Figure 13 As shown, in a surface acoustic wave (SAW) resonator, the pitch (period) of the interdigital transducer is a key parameter affecting the resonant frequency. The pitch is determined by the width of the interdigital electrodes and the spacing between them. The pitch is typically equal to half the wavelength of the sound wave, while the resonant frequency is determined by the wavelength and velocity of the sound wave. The velocity of the sound wave is also related to the material properties of the interdigital electrode contacts. Therefore, based on the desired resonant frequency, the main interdigital transducer pitch parameters and piezoelectric layer material selection can be tailored to obtain a SAW resonator that meets performance requirements.

[0034] However, if the selection is based solely on the pitch parameters and the piezoelectric layer material, it is difficult to obtain the desired steepness while simultaneously achieving the desired resonant frequency.

[0035] For the above situation, refer to Figure 1 and Figure 2 This utility model provides a surface acoustic wave resonator, characterized in that it includes: Piezoelectric layer 100; An interdigital transducer 200 is disposed on the piezoelectric layer 100, and the interdigital transducer 200 includes a plurality of interdigital electrodes 210; The first reflective grating 300 and the second reflective grating 310 are both disposed on the piezoelectric layer 100, and the interdigital transducer 200 is located between the first reflective grating 300 and the second reflective grating 310; The dielectric layer 400 includes a first dielectric portion 410 and a second dielectric portion 420. The first dielectric portion 410 covers at least one interdigital electrode 210 of the interdigital transducer 200 near the first reflective grating 300, and the second dielectric portion 420 covers at least one interdigital electrode 210 of the interdigital transducer 200 near the second reflective grating 310.

[0036] By covering the first dielectric portion 410 and the second dielectric portion 420 of the dielectric layer 400 in the region of the interdigital transducer 200 near the first reflective grating 300 and the second reflective grating 310, respectively, the structure of the dielectric layer 400 is introduced, which causes the electric field generated by the interdigital transducer 200 to partially leak into the dielectric layer 400 in the region of the first dielectric portion 410 and the second dielectric portion 420, thereby reducing the electromechanical coupling coefficient between the interdigital transducer 200 and the piezoelectric layer 100.

[0037] Thus, by providing a dielectric layer 400, a first dielectric portion 410 and a second dielectric portion 420 are formed covering the interdigital electrodes 210 of the interdigital transducer 200 near the first reflective grating 300 and the second reflective grating 310, thereby reducing the electromechanical coupling coefficient. Since the reduction of the electromechanical coupling coefficient will reduce the frequency interval between the resonant frequency and the anti-resonant frequency, it can achieve the effect of improving the steepness, which is beneficial to improving the performance of the surface acoustic wave resonator. At the same time, it is beneficial to meet the high selective filtering requirements when forming a surface acoustic wave filter.

[0038] It is understandable that two or more surface acoustic wave (SAW) resonators connected by a circuit can form a SAW filter, such as... Figure 3 As shown, Figure 3 The left and middle figures show the frequency response curves of a surface acoustic wave (SAW) resonator. The dashed line corresponds to the SAW resonator provided by this invention. Through circuit connection, it can form... Figure 3 The filtering curve is shown in the right figure. Among them, Figure 3 The surface acoustic wave filter corresponding to the solid line in the middle right figure is formed by two surface acoustic wave resonators corresponding to the two solid lines in the left figure. Figure 3 The surface acoustic wave (SAW) filter, represented by the dashed line in the right-hand diagram, is formed by the SAW resonator represented by the solid line on the left side of the left diagram and the SAW resonator provided by this invention, represented by the dashed line in the left-hand diagram. It can be seen that the SAW resonator provided by this invention has a higher sloping angle, resulting in a steeper filter band edge for the formed SAW filter, which is beneficial for improving filtering performance.

[0039] As can be understood, the electromechanical coupling coefficient is a parameter that measures the efficiency of energy conversion between electrical and mechanical energy in piezoelectric materials. In other words, the electromechanical coupling coefficient reflects the strength of the ability to convert stored mechanical energy into electrical energy within the piezoelectric material. A larger electromechanical coupling coefficient indicates a higher efficiency in the conversion between electrical and acoustic energy, i.e., a higher efficiency in the conversion between electrical and mechanical energy. In a surface acoustic wave resonator, the electromechanical coupling coefficient can be determined based on the resonant frequency and anti-resonant frequency, as shown in the following expression: Where K² is the electromechanical coupling coefficient; The resonant frequency; It is the anti-resonant frequency.

[0040] Based on the electromechanical coupling coefficient, it can be known that the electromechanical coupling coefficient K² is proportional to the anti-resonant frequency. With resonant frequency The relative interval between them. Anti-resonant frequency. With resonant frequency The closer they are, the weaker the electromechanical coupling capability; anti-resonance frequency With resonant frequency The greater the distance, the stronger the electromechanical coupling capability. Therefore, by appropriately reducing the electromechanical coupling coefficient, the anti-resonant frequency can be reduced. With resonant frequency As they move closer together, the frequency intervals decrease, which in turn increases the steepness.

[0041] Understandably, reference Figure 3 The left figure shows the steepness of the curve between the resonant frequency and the anti-resonant frequency. With the admittances at the resonant and anti-resonant frequencies remaining constant, the closer the resonant and anti-resonant frequencies are, the steeper the curve. (Reference) Figure 3 As shown in the right figure, the greater the kurtosis of the surface acoustic wave (SAW) resonator, the steeper the bandpass edge of the resulting filter, meaning a better filtering effect on the signal. Therefore, increasing the kurtosis of the SAW resonator can improve the filtering effect of the resulting SAW filter.

[0042] It is important to emphasize that dividing the dielectric layer 400 into a first dielectric portion 410 covering the first reflector 300 and a second dielectric portion 420 covering the second reflector 310, thus avoiding covering the center of the interdigital transducer 200, is crucial because the central region of the interdigital transducer 200 is the most active and efficient area for acoustic energy conversion. Covering the central region of the interdigital transducer 200 with the dielectric layer 400 would significantly increase acoustic loss, i.e., significantly increase insertion loss. Furthermore, if the dielectric layer 400 covers the central region of the interdigital transducer 200, compared to a structure covering both sides, it would cause more severe disturbances to the acoustic propagation mode, making it easier to generate unnecessary frequency response peaks and valleys (in-band spurious signals) within the filter's passband, thus affecting performance. Therefore, dividing the dielectric layer 400 into the first dielectric portion 410 and the second dielectric portion 420 covering both sides of the interdigital transducer 200 can reduce the electromechanical coupling coefficient while minimizing the impact on insertion loss, thus contributing to optimal overall performance.

[0043] It should be noted that the aforementioned structure of adding the dielectric layer 400, which causes the electrical fork portion generated by the interdigital electrode 210 to leak into the dielectric layer 400, illustrates the principle of reducing the electromechanical coupling coefficient. The influence of the dielectric layer 400 on the sound velocity also demonstrates that the dielectric layer 400 can affect the electromechanical coupling coefficient. Specifically, by adding the dielectric layer 400, the acoustic wave propagation environment and effective mass load around the interdigital electrode 210 are altered in the area covered by the dielectric layer 400, causing a change in the sound velocity. This alters the resonant frequency and reflection phase, thus affecting the resonant and anti-resonant frequencies, and consequently reducing the electromechanical coupling coefficient.

[0044] By setting the thickness and coverage of the dielectric layer 400, the degree of influence on the electromechanical coupling coefficient can be flexibly adjusted. Based on the selection of the pitch parameters and the material of the piezoelectric layer 100, and combined with the structure of the dielectric layer 400 of this invention, the desired resonant frequency can be obtained while simultaneously achieving the desired steepness by adjusting the electromechanical coupling coefficient.

[0045] In some embodiments of this utility model, the piezoelectric layer 100 can be an implementation of common piezoelectric materials for surface acoustic waves, such as lithium tantalate layer and lithium niobate layer. In some embodiments, the piezoelectric layer 100 can also be an implementation of materials with piezoelectric effect, such as aluminum nitride and zinc oxide.

[0046] refer to Figure 1 and Figure 2 In some embodiments of the surface acoustic wave resonator of this utility model, the first dielectric part 410 and the second dielectric part 420 are symmetrically arranged with the center line of the interdigital transducer 200 as the axis of symmetry.

[0047] By interdigitating the first dielectric section 410 and the second dielectric section 420 with the center line of the interdigitator 200, i.e. Figure 1 The dotted line C in the diagram is symmetrically arranged along the axis of symmetry, which ensures a uniform influence on the propagation of sound waves and the distribution of the electric field on both sides. Since the interdigital transducer 200 converts the electrical energy of the signal into the mechanical energy of the sound wave, the sound wave will spread in all directions. By symmetrically arranging the first dielectric section 410 and the second dielectric section 420, it is beneficial to maintain the stability of the internal sound wave standing wave mode and suppress parasitic modes or in-band spurious signals that may be caused by asymmetry, thereby ensuring the stability and reliability of the surface acoustic wave resonator performance.

[0048] refer to Figure 1 and Figure 2 In some embodiments of the surface acoustic wave resonator of this utility model, the number of interdigital electrodes 210 covered by the first dielectric portion 410 is equal to the number of interdigital electrodes 210 covered by the second dielectric portion 420.

[0049] By making the number of interdigital electrodes 210 covered by the first dielectric section 410 and the second dielectric section 420 equal, the uniformity of the load on both sides of the interdigital transducer 200 is further enhanced. Combined with the symmetrical arrangement structure, the degree of reduction of the electromechanical coupling coefficient can be controlled more precisely, and the possible parasitic modes or in-band strays can be further suppressed, maintaining the stability of the acoustic standing wave mode, thereby ensuring the stability of the surface acoustic wave resonator.

[0050] By employing a symmetrical structure with dielectric layers 400, specifically by symmetrically arranging the first dielectric section 410 and the second dielectric section 420 about the centerline of the interdigital transducer 200, and ensuring that the number of interdigital electrodes 210 covered by the first dielectric section 410 and the second dielectric section 420 is equal, balanced disturbances to the acoustic wave propagation paths and electric field distribution on both sides of the interdigital transducer 200 are achieved. This ensures that the reduction in electromechanical coupling coefficients and the introduction of sound velocity changes on both sides are consistent and predictable. In this way, the symmetry of acoustic wave propagation within the resonator is maintained, avoiding distortion caused by structural asymmetry. Furthermore, the symmetrical arrangement of the first dielectric section 410 and the second dielectric section 420 helps suppress in-band stray emissions, improving the overall performance of the surface acoustic wave resonator.

[0051] In some embodiments of the surface acoustic wave resonator of this invention, the dielectric layer 400 is a polyimide layer or a silicon nitride layer.

[0052] Different dielectric materials, such as dielectric constant, sound velocity, and density, will have varying effects on the interdigital transducer 200, thus affecting the adjustment of the electromechanical coupling coefficient. Choosing a polyimide (PI) layer as the dielectric layer 400 offers advantages such as a lower dielectric constant, reducing the electromechanical coupling coefficient while minimizing the impact on insertion loss. Furthermore, the good flexibility of the polyimide layer improves process adaptability. Conversely, choosing a silicon nitride (SiN) layer as the dielectric layer 400 offers a higher dielectric constant, significantly reducing the electromechanical coupling coefficient. Additionally, the silicon nitride layer provides good mechanical strength, excellent chemical stability, and compatibility, contributing to a more stable and reliable structure. Both polyimide and silicon nitride layers, when used as the dielectric layer 400, can reduce the electromechanical coupling coefficient, i.e., reduce the interval between the resonant and anti-resonant frequencies, thereby increasing the steepness.

[0053] refer to Figure 4 , Figure 4 The data includes frequency response curves when the pitch is 1µm and there is no dielectric layer structure, and frequency response curves when, under the same pitch of 1µm, the dielectric layer 400 is a polyimide (PI) layer and the number N1 of the first dielectric portion 410 and the second dielectric portion 420 covering the interdigitated electrodes 210 is 10, i.e., N1=10. Figure 4 It can be seen that when a PI layer is set, both the resonant frequency and the anti-resonant frequency decrease, but the decrease in the anti-resonant frequency is greater than the decrease in the resonant frequency, which reduces the interval between the resonant frequency and the anti-resonant frequency, i.e., the electromechanical coupling coefficient decreases.

[0054] refer to Figure 5 , Figure 5 The data includes frequency response curves when the pitch is 1µm and there is no dielectric layer structure, and frequency response curves when, under the same pitch of 1µm, the dielectric layer 400 is a silicon nitride (SiN) layer and the number N1 of the interdigitated electrodes 210 covered by the first dielectric portion 410 and the second dielectric portion 420 is 10, i.e., N1=10. Figure 5 It can be seen that when a SiN layer is provided, both the resonant frequency and the anti-resonant frequency increase, but the increase in the resonant frequency is greater than the increase in the anti-resonant frequency, which reduces the interval between the resonant frequency and the anti-resonant frequency, i.e., the electromechanical coupling coefficient decreases.

[0055] based on Figure 4 and Figure 5 It can be seen that in this utility model, the dielectric layer 400 can be either a polyimide layer or a silicon nitride layer, which can achieve the effect of reducing the electromechanical coupling coefficient.

[0056] In some embodiments of this utility model, in addition to polyimide layer and silicon nitride layer, the dielectric layer 400 can also be made of silicon dioxide, aluminum oxide or other materials with suitable dielectric constant and acoustic properties.

[0057] refer to Figure 1 and Figure 2 In some embodiments of the surface acoustic wave resonator of this utility model, the number of interdigital electrodes 210 covered by the first dielectric portion 410 is greater than or equal to 4, and the number of interdigital electrodes 210 covered by the second dielectric portion 420 is greater than or equal to 4.

[0058] By ensuring that the number of interdigital electrodes 210 covered by the first dielectric section 410 and the second dielectric section 420 is greater than or equal to 4, sufficient working area is ensured between the dielectric layer 400 and the interdigital transducer 200 to provide a sufficiently significant reduction in the electromechanical coupling coefficient, thereby meeting the steepness requirements.

[0059] It should be noted that the more interdigital electrodes 210 the first dielectric section 410 and the second dielectric section 420 cover, the stronger the effect on reducing the electromechanical coupling coefficient. However, this also introduces in-band spurious signals, meaning unwanted frequency response components will appear between the resonant frequency and the anti-resonant frequency. If the number of interdigital electrodes 210 covered is too small, the effect on reducing the electromechanical coupling coefficient may be too weak, making it difficult to meet the steepness requirements. If the number of interdigital electrodes 210 covered is too large, it may introduce excessive in-band spurious signals, affecting performance.

[0060] refer to Figure 6 and Figure 7 Under the condition that the dielectric layer 400 is a silicon nitride layer and the number of interdigital electrodes 210 covered by the first dielectric portion 410 and the second dielectric portion 420 is equal, frequency response tests were performed for different numbers N1 of interdigital electrodes 210 covered by the first dielectric portion 410 and the second dielectric portion 420. The results are as follows: Figure 6 and Figure 7 As shown. Figure 6 The frequency response curves include those corresponding to the number N1 of the interdigitated electrodes 210 covering the first dielectric section 410 and the second dielectric section 420, which are 0, 4, 10, 20, and 30. Figure 7 This table presents the values ​​for resonant frequency, anti-resonant frequency, and electromechanical coupling coefficient under different numbers N1 of covered interdigitated electrodes 210. According to... Figure 6 and Figure 7 It can be seen that as the number N1 of the interdigitated electrodes 210 increases, the electromechanical coupling coefficient will gradually decrease, the steepness of the frequency response curve will increase, but the in-band spurious emissions will also increase. Figure 6 The curves with N1=0 and N1=4 almost overlap, meaning that the effect on steepness is not significant. Therefore, it is recommended that N1≥4.

[0061] Understandably, the optimal number N1 of interdigitated electrodes 210 needs to be determined through testing based on specific pitch parameters, piezoelectric materials, interdigitated electrode 210 dimensions, operating frequency, and target electromechanical coupling coefficient, in order to balance steepness and in-band straying and obtain the best overall performance.

[0062] refer to Figure 8 In some embodiments of the surface acoustic wave resonator of this utility model, a substrate 500 is further included. The substrate 500 includes a high-velocity support layer 510 and a low-velocity layer 520. The low-velocity layer 520 is disposed on the high-velocity support layer 510, and the piezoelectric layer 100 is disposed on the low-velocity layer 520.

[0063] Based on the structure of the substrate 500, which includes a high-velocity acoustic support layer 510 and a low-velocity acoustic layer 520, acoustic energy can be confined to the piezoelectric layer 100 or reflected back to the piezoelectric layer 100 based on acoustic impedance matching and mismatch effects. The high-velocity acoustic support layer 510 provides mechanical support, while the low-velocity acoustic layer 520 utilizes the acoustic impedance difference formed between itself and the piezoelectric layer 100 to acoustically guide or reflect surface acoustic waves. This structure reduces sound wave leakage to the substrate 500, thereby reducing insertion loss and improving overall performance.

[0064] refer to Figure 9 In some embodiments of the surface acoustic wave resonator of this utility model, the substrate 500 further includes a high-velocity layer 530, which is disposed between the low-velocity layer 520 and the high-velocity support layer 510.

[0065] Since the hypersonic support layer 510 needs to also provide mechanical support, the hypersonic layer 530 can be made of a material with a higher sound velocity. By setting the hypersonic layer 530 between the low-sonic layer 520 and the hypersonic support layer 510, the reflection of sound waves can be improved. At the same time, the hypersonic layer 530 is also conducive to constructing multi-level acoustic impedance mismatch, so that the sound waves can be more effectively confined within the piezoelectric layer 100, further reducing insertion loss.

[0066] refer to Figure 10 and Figure 11 In some embodiments of the surface acoustic wave resonator of this utility model, the substrate 500 includes a high-velocity support layer 510, at least two low-velocity layers 520 and at least one high-velocity layer 530. The low-velocity layers 520 and the high-velocity layers 530 are stacked alternately with the low-velocity layers 520 on top to form a stack group 501. The stack group 501 is disposed on the high-velocity support layer 510, and the piezoelectric layer 100 is disposed on the stack group 501.

[0067] The stacked group 501, formed by the periodic alternating layering of multiple low-velocity layers 520 and high-velocity layers 530, is equivalent to forming an acoustic Bragg reflector structure, constituting a high-bandwidth, high-efficiency acoustic mirror. Sound waves reflected from different interfaces will superimpose in phase, creating a stronger reflection effect. This helps confine acoustic energy to the piezoelectric layer 100 region and suppresses sound wave leakage to the substrate 500. Therefore, it helps to minimize insertion loss, provides strong suppression of bulk acoustic waves, and thus improves the overall performance of the surface acoustic wave resonator.

[0068] The following describes a surface acoustic wave filter provided by this utility model. The surface acoustic wave filter described below and the surface acoustic wave resonator described above can be referred to in correspondence.

[0069] A surface acoustic wave filter includes at least one of the above-described surface acoustic wave resonators.

[0070] A single surface acoustic wave (SAW) resonator has a specific resonant frequency and anti-resonant frequency. By connecting multiple SAW resonators in a circuit, a SAW filter with specific passband and stopband characteristics can be formed. The SAW filter includes at least one SAW resonator provided by this invention.

[0071] In the surface acoustic wave resonator of this invention, by covering the first dielectric portion 410 and the second dielectric portion 420 of the dielectric layer 400 in the region of the interdigital transducer 200 near the first reflective grating 300 and the second reflective grating 310 respectively, the structure of the dielectric layer 400 is introduced, which causes the electric field generated by the interdigital transducer 200 to partially leak into the dielectric layer 400 in the region of the first dielectric portion 410 and the second dielectric portion 420, thereby reducing the electromechanical coupling coefficient between the interdigital transducer 200 and the piezoelectric layer 100.

[0072] Thus, by providing a dielectric layer 400, a first dielectric portion 410 and a second dielectric portion 420 are formed covering the interdigital electrodes 210 of the interdigital transducer 200 near the first reflective grating 300 and the second reflective grating 310, thereby reducing the electromechanical coupling coefficient. Since the reduction of the electromechanical coupling coefficient will reduce the frequency interval between the resonant frequency and the anti-resonant frequency, it will be possible to improve the steepness, which is beneficial to improving the performance of the surface acoustic wave resonator.

[0073] The surface acoustic wave filter provided by this invention uses a surface acoustic wave resonator with reduced electromechanical coupling coefficient, which improves the steepness of the filtering band edge, thereby more effectively distinguishing the signal in the required frequency band from the interference signal in the adjacent frequency band and reducing adjacent channel interference.

[0074] It is understood that the surface acoustic wave resonator provided by this invention can be used in conjunction with conventional surface acoustic wave resonators. (Reference) Figure 12 ,exist Figure 12 In this invention, P1, P2, and P3 are surface acoustic wave resonators (SAWs) that form a parallel resonator. This reduces the electromechanical coupling coefficient of the parallel resonator, bringing the transmission zero closer to the passband edge, and thus making the filtered band edge steeper. Figure 3 As shown by the dashed line.

[0075] The following describes a duplexer provided by this utility model. The duplexer described below can be referred to in correspondence with the surface acoustic wave resonator described above.

[0076] A duplexer includes a transmit filter component 600 and a receive filter component 700, wherein the transmit filter component 600 includes at least one of the aforementioned surface acoustic wave resonators, and / or the receive filter component 700 includes at least one of the aforementioned surface acoustic wave resonators.

[0077] By employing the surface acoustic wave resonator provided by this invention in the transmitting filter assembly 600 and / or the receiving filter assembly 700, the surface acoustic wave resonator incorporates a structure in which the first dielectric portion 410 and the second dielectric portion 420 of the dielectric layer 400 are respectively covered in the region of the interdigital transducer 200 near the first reflective grating 300 and the second reflective grating 310. This structure causes the electric field generated by the interdigital transducer 200 to partially leak into the dielectric layer 400 in the region of the first dielectric portion 410 and the second dielectric portion 420, thereby reducing the electromechanical coupling coefficient between the interdigital transducer 200 and the piezoelectric layer 100.

[0078] Thus, by providing a dielectric layer 400, a first dielectric portion 410 and a second dielectric portion 420 are formed covering the interdigital electrodes 210 of the interdigital transducer 200 near the first reflective grating 300 and the second reflective grating 310, thereby reducing the electromechanical coupling coefficient. Since a reduced electromechanical coupling coefficient leads to a corresponding decrease in the frequency interval between the resonant frequency and the anti-resonant frequency, it can improve the steepness, which is beneficial for improving the performance of the surface acoustic wave resonator. Using a surface acoustic wave resonator for filtering in a duplexer can improve the out-of-band suppression effect of the filter, increase the isolation between adjacent frequency bands, effectively suppress adjacent-channel interference, reduce crosstalk from the transmitter to the receiver, ensure the purity of the communication link, and thus improve the overall performance of the duplexer.

[0079] refer to Figure 12This is one embodiment of the duplexer provided by the present invention. In this embodiment, P1, P2, P3 in the transmitting filter component 600 and P4 in the receiving filter component 700 are surface acoustic wave resonators provided by the present invention. By grounding through P1, P2, P3, and P4, a transmission zero point can be formed. Based on the improved steepness of the surface acoustic wave resonator itself, the out-of-band rejection capability of the transmitting filter component 600 and the receiving filter component 700 is significantly enhanced, thereby improving the transmission and reception isolation of the duplexer and effectively avoiding interference of the transmitted signal to the received signal.

[0080] In the description of this utility model, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this utility model, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0081] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and not to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model.

Claims

1. A surface acoustic wave resonator, characterized in that, include: Piezoelectric layer (100); An interdigital transducer (200) is disposed on the piezoelectric layer (100), and the interdigital transducer (200) includes a plurality of interdigital electrodes (210). The first reflective grating (300) and the second reflective grating (310) are both disposed on the piezoelectric layer (100), and the interdigital transducer (200) is located between the first reflective grating (300) and the second reflective grating (310); The dielectric layer (400) includes a first dielectric portion (410) and a second dielectric portion (420), the first dielectric portion (410) covering at least one interdigital electrode (210) of the interdigital transducer (200) near the first reflective grating (300), and the second dielectric portion (420) covering at least one interdigital electrode (210) of the interdigital transducer (200) near the second reflective grating (310).

2. A surface acoustic wave resonator according to claim 1, characterized in that, The first medium section (410) and the second medium section (420) are symmetrically arranged with the center line of the interdigital transducer (200) as the axis of symmetry.

3. A surface acoustic wave resonator according to claim 2, characterized in that, The number of interdigital electrodes (210) covered by the first dielectric portion (410) is equal to the number of interdigital electrodes (210) covered by the second dielectric portion (420).

4. A surface acoustic wave resonator according to any one of claims 1 to 3, characterized in that, The dielectric layer (400) is a polyimide layer or a silicon nitride layer.

5. A surface acoustic wave resonator according to claim 4, characterized in that, The first dielectric portion (410) covers 4 or more interdigital electrodes (210), and the second dielectric portion (420) covers 4 or more interdigital electrodes (210).

6. A surface acoustic wave resonator according to claim 1, characterized in that, It also includes a substrate (500), which includes a high-velocity support layer (510) and a low-velocity layer (520), the low-velocity layer (520) being disposed on the high-velocity support layer (510) and the piezoelectric layer (100) being disposed on the low-velocity layer (520).

7. A surface acoustic wave resonator according to claim 6, characterized in that, The substrate (500) further includes a high-velocity layer (530) disposed between the low-velocity layer (520) and the high-velocity support layer (510).

8. A surface acoustic wave resonator according to claim 1, characterized in that, It also includes a substrate (500), the substrate (500) including a high-velocity support layer (510), at least two low-velocity layers (520) and at least one high-velocity layer (530), the low-velocity layers (520) and the high-velocity layers (530) are stacked alternately with the low-velocity layer (520) on top to form a stack group (501), the stack group (501) is disposed on the high-velocity support layer (510), and the piezoelectric layer (100) is disposed on the stack group (501).

9. A surface acoustic wave filter, characterized in that, It includes at least one surface acoustic wave resonator as described in any one of claims 1 to 8.

10. A duplexer, characterized in that, It includes a transmit filter assembly (600) and a receive filter assembly (700), wherein the transmit filter assembly (600) includes at least one surface acoustic wave resonator as described in any one of claims 1 to 8, and / or the receive filter assembly (700) includes at least one surface acoustic wave resonator as described in any one of claims 1 to 8.

Images