Acoustic delay line and signal processing device

Abstract

This invention relates to the field of microelectronics technology, and particularly to an acoustic delay line and a signal processing device. The acoustic delay line includes at least: a first delay structure comprising a first piezoelectric layer and a first interdigital transducer; a transmission dielectric layer located on the first delay structure; and a second delay structure located on the transmission dielectric layer, the second delay structure comprising a second piezoelectric layer and a second interdigital transducer; the product of the passband low frequency of the acoustic delay line and the wavelength of the target mode of the acoustic delay line is greater than the slow shear wave velocity of the transmission dielectric layer, thereby allowing it to propagate within the transmission dielectric layer, and the target mode is excited by a transverse electric field, resulting in a simpler structure.

Description

Technical Field

[0001] This invention relates to the field of microelectronics technology, and in particular to an acoustic delay line and a signal processing device. Background Technology

[0002] Signal delay lines, as a fundamental functional component, are widely used in signal synchronization, filtering and shaping, and time measurement. Among them, acoustic delay lines exhibit significant advantages over electromagnetic delay lines due to their small size, low insertion loss, and weak crosstalk. With the rapid development of modern communication technologies such as 5G wireless communication systems, higher demands are placed on the performance indicators of radio frequency signal processing devices, such as operating frequency and bandwidth. This correspondingly creates an urgent need for performance optimization of acoustic delay lines.

[0003] Currently, the mainstream acoustic delay line technologies mainly include two approaches: surface acoustic wave (SAW) and bulk acoustic wave (BAW). SAW delay line technology is relatively mature, and its delay time can be precisely controlled through the design of interdigital transducers. However, the improvement of its operating frequency heavily relies on higher precision photolithography processes, and it is currently facing a technical bottleneck, making it difficult to further meet the needs of high-frequency applications.

[0004] For higher frequency applications, traditional BAW delay line technology offers a viable solution. A typical BAW delay line usually consists of a transmission medium, patterned bottom electrodes at both ends, an aluminum nitride (AlN) piezoelectric layer, and a top electrode. The conventional fabrication process involves depositing and photolithographically forming bottom electrode patterns on both ends of the transmission medium, followed by depositing and patterning the aluminum nitride piezoelectric layer on the bottom electrodes at both ends. While this structure can achieve higher operating frequencies, it also has significant drawbacks: First, this approach requires the fabrication of precisely patterned bottom electrodes at both ends of the transmission medium, resulting in a complex process that increases manufacturing costs and difficulty. Second, this structure primarily relies on a longitudinal electric field to excite the thickness-stretching vibration mode of the piezoelectric layer, but the longitudinal piezoelectric coefficient e33 of aluminum nitride is relatively limited, which fundamentally restricts the achievable electromechanical coupling coefficient and operating bandwidth of the device.

[0005] Therefore, how to further simplify the device structure, reduce the process complexity, and effectively broaden the operating bandwidth while ensuring high operating frequency has become an important technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] To address the aforementioned technical problems, this application discloses an acoustic delay line, which includes at least: The first delay structure includes a first piezoelectric layer and a first interdigital transducer; The transmission medium layer located on the first delay structure; A second delay structure located on the transmission medium layer, the second delay structure including a second piezoelectric layer and a second interdigital transducer; Wherein, the product of the passband low frequency of the acoustic delay line and the wavelength of the target mode of the acoustic delay line is greater than the slow shear wave velocity of the transmission medium layer.

[0007] Furthermore, the first piezoelectric layer includes at least two sub-piezoelectric layers; The second piezoelectric layer comprises at least two sub-piezoelectric layers; at least one piezoelectric coefficient of adjacent sub-piezoelectric layers has opposite signs.

[0008] Furthermore, the target mode is a hypersonic mode excited by a transverse electric field; The frequency and bandwidth of the acoustic delay line can be adjusted by regulating the electrode period of the first interdigital transducer and the second interdigital transducer; the bandwidth and loss can be adjusted by adjusting the number of sub-piezoelectric layers and the periodicity of the piezoelectric coefficient.

[0009] Furthermore, in the height direction of the acoustic delay line, the first interdigital transducer is partially or entirely embedded in the piezoelectric layer; the second interdigital transducer is partially or entirely embedded in the piezoelectric layer.

[0010] Furthermore, the first interdigital transducer includes at least a first electrode finger and a second electrode finger arranged alternately along a first direction; the second interdigital transducer includes at least a third electrode finger and a fourth electrode finger arranged alternately along the first direction; the distance between the center of an adjacent first electrode finger and the center of the second electrode finger is λ / 2; where λ is the wavelength of the target mode.

[0011] Furthermore, the material of the transmission medium layer is a semiconductor or an insulating material; The resistivity of the transmission medium layer is greater than 1000Ω×cm; The piezoelectric coefficients of the piezoelectric layer include e11, e13, e14, and e15, and the absolute value of at least one piezoelectric coefficient is greater than 1 C / m. 2 .

[0012] Furthermore, it also includes a first bonding layer and a second bonding layer; A first bonding layer is provided between the first piezoelectric layer and the transmission medium layer; A second bonding layer is provided between the second piezoelectric layer and the transmission medium layer.

[0013] Furthermore, the bonding layer material is at least one of silicon oxide, amorphous silicon, titanium, and gold.

[0014] Furthermore, the materials of the first piezoelectric layer and the second piezoelectric layer are one of lithium tantalate, lithium niobate, potassium niobate, scandium-doped aluminum nitride, lead zirconate titanate, or lead magnesium niobate-lead titanate.

[0015] On the other hand, a signal processing apparatus is provided, which includes the aforementioned acoustic delay line; The signal processing device includes at least one of a filter, an isolator, a circulator, a phase modulator, an amplifier, and an oscillator.

[0016] The acoustic delay line provided in this application includes at least: a first delay structure comprising a first piezoelectric layer and a first interdigital transducer; a transmission medium layer located on the first delay structure; and a second delay structure located on the transmission medium layer, the second delay structure comprising a second piezoelectric layer and a second interdigital transducer. Since the frequency of the delay line is mainly determined by the electrode period or the film thickness, the sound velocity can be increased to exceed the slow shear wave speed of the transmission medium layer by increasing the electrode period, thereby allowing it to propagate in the transmission medium. Furthermore, the target mode is excited by a transverse electric field, eliminating the need for an additional bottom electrode, resulting in a simpler structure. Attached Figure Description

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

[0018] Figure 1 A cross-sectional view of a first acoustic delay line is provided for embodiments of this application; Figure 2 for Figure 1 Top view of the first interdigital transducer; Figure 3 A cross-sectional view of a second acoustic delay line is provided for embodiments of this application; Figure 4 A cross-sectional view of a third acoustic delay line is provided for embodiments of this application; Figure 5 Insertion loss curves for a set of examples provided in this application; Figure 6 A cross-sectional view of a fourth acoustic delay line is provided for embodiments of this application; Figure 7 A cross-sectional view of a fifth acoustic delay line is provided for embodiments of this application; Figure 8 A cross-sectional view of a sixth acoustic delay line is provided for embodiments of this application; Figure 9A cross-sectional view of a seventh acoustic delay line is provided for embodiments of this application; Figure 10 for Figure 9 Top view of the first interdigital transducer; Figure 11 Insertion loss curve for Example 1 provided in this application embodiment; Figure 12 The group delay curve for Example 1 provided in this application embodiment; Figure 13 Insertion loss curves for another set of examples provided in the embodiments of this application; Figure 14 A cross-sectional view of an eighth acoustic delay line is provided for embodiments of this application; Figure 15 Insertion loss curves for Examples 4 and 5 provided in this application embodiment; Figure 16 This is a cross-sectional view of a signal processing device provided in an embodiment of this application.

[0019] The following is supplementary explanation of the attached figures: 1-First piezoelectric layer; 2-First interdigital transducer; 201-First busbar; 202-Second busbar; 203-First electrode finger; 204-Second electrode finger; 3-Transmission medium layer; 4-Second piezoelectric layer; 5-Second interdigital transducer; 501-Third electrode finger; 502-Fourth electrode finger; 6-Sub-piezoelectric layer. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0021] The term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of this application. In the description of this application, it should be understood that the terms "upper," "lower," "top," "bottom," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, 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. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Moreover, the terms "first," "second," etc., are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein.

[0022] Although the numerical ranges and parameters illustrating the broad scope of the invention are approximate, the values ​​listed in the specific examples are reported as precisely as possible. However, any numerical value inherently contains some error that is necessarily caused by the standard deviation found in their respective test measurements.

[0023] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are included. For example, a specified range from “1 to 10” should be considered to include any and all subranges between the minimum value 1 and the maximum value 10. Exemplary subranges of the range 1 to 10 include, but are not limited to, 1 to 6.1, 3.5 to 7.8, 5.5 to 10, etc.

[0024] Please see Figure 1 The diagram shows a cross-sectional view of a first acoustic delay line provided in an embodiment of this application. The acoustic delay line includes at least: a first delay structure comprising a first piezoelectric layer 1 and a first interdigital transducer 2; a transmission medium layer 3 located on the first delay structure; and a second delay structure located on the transmission medium layer 3, the second delay structure comprising a second piezoelectric layer 4 and a second interdigital transducer 5; wherein the product of the passband low frequency of the acoustic delay line and the wavelength of the target mode of the acoustic delay line is greater than the slow shear wave velocity of the transmission medium layer 3.

[0025] For example, the target mode is a hypersonic mode excited by a transverse electric field; the frequency and bandwidth of the acoustic delay line are adjusted by regulating the electrode periods of the first interdigital transducer 2 and the second interdigital transducer 5; the bandwidth and loss are adjusted by regulating the number of sub-piezoelectric layers 6 and the periodicity of the piezoelectric coefficient. Since hypersonic modes typically have strong dispersion characteristics, the operating frequency and bandwidth can be adjusted by changing the ratio of the electrode period to the piezoelectric layer and the number of piezoelectric layers. Therefore, this method not only has a simpler structure and a larger bandwidth, but also offers greater design flexibility.

[0026] In the embodiments of this application, please refer to Figure 2 The first interdigital transducer 2 includes a first busbar 201 and a second busbar 202 arranged at relatively intervals, and a plurality of first electrode fingers 203 and a plurality of second electrode fingers 204 arranged alternately along a first direction; the plurality of first electrode fingers 203 are connected to the first busbar 201, and the plurality of second electrode fingers 204 are connected to the second busbar 202; the distance between the centers of adjacent first electrode fingers 203 is λ. Similarly, the second interdigital transducer 5 includes a third busbar and a fourth busbar arranged at relatively intervals, and a plurality of third electrode fingers 501 and a plurality of fourth electrode fingers 502 arranged alternately along a first direction; the plurality of third electrode fingers 501 are connected to the third busbar, and the plurality of fourth electrode fingers 502 are connected to the fourth busbar. Optionally, the first interdigital transducer 2 and the second interdigital transducer 5 have the same structure to further improve the transmission delay effect. The first interdigital transducer 2 and the second interdigital transducer 5 can be collectively referred to as interdigital transducers. In the embodiments of this application, the multiple electrode fingers in the interdigital transducers can be evenly distributed, and the distance between the centers of adjacent electrode fingers is λ / 2.

[0027] For example, the first direction may specifically be the length extension direction of the first busbar 201 or the second busbar 202, or the direction perpendicular to the electrode pointer.

[0028] For example, please refer to Figure 3 The first piezoelectric layer 1 includes at least two sub-piezoelectric layers 6; the second piezoelectric layer 4 includes at least two sub-piezoelectric layers 6; the piezoelectric coefficients of adjacent sub-piezoelectric layers 6 have opposite signs. For example, the piezoelectric coefficients of the piezoelectric layers include e11, e13, e14, and e15, and the absolute value of at least one piezoelectric coefficient is greater than 1 C / m². Specifically, the absolute values ​​of corresponding piezoelectric coefficients in adjacent sub-piezoelectric layers 6 are equal, and their signs are opposite. For example, adjacent sub-piezoelectric layers 6 may have piezoelectric coefficients e11 of A and -A, respectively. Optionally, when the materials of adjacent sub-piezoelectric layers 6 are different, they still need to satisfy that the absolute values ​​of at least one piezoelectric coefficient are equal or almost identical (with very small differences), and their signs are opposite.

[0029] For example, the materials of the first piezoelectric layer 1 and the second piezoelectric layer 4 are one of lithium tantalate, lithium niobate, potassium niobate, scandium-doped aluminum nitride, lead zirconate titanate, or lead magnesium niobate-lead titanate.

[0030] In this embodiment, the acoustic delay line can be a mirror-symmetrical structure along the central axis, specifically, it can be along, for example... Figure 1 The dashed lines shown exhibit an axially symmetric structure. The first piezoelectric layer 1 and the second piezoelectric layer 4 are axially symmetric, as are the first interdigital transducer 2 and the second interdigital transducer 5. Therefore, the first piezoelectric layer 1 and the second piezoelectric layer 4 have the same number of layers and the same material for the corresponding layers to achieve optimal transmission delay. In other embodiments, the material of the first piezoelectric layer 1 may differ from that of the second piezoelectric layer 4; please refer to [reference needed]. Figure 4 When a piezoelectric layer contains multiple sub-piezoelectric layers 6, the materials of each sub-piezoelectric layer 6 can be the same, partially the same, or completely different, and there is no restriction here.

[0031] Provide a set of instances, the structure of which is as follows Figure 3 The structure shown has an interdigital transducer made of aluminum, an electrode period λ of 20 μm, and an electrode finger width of 1 μm. The piezoelectric layer is made of lithium niobate, and the Euler angle of the sub-piezoelectric layer 6 near the transport medium layer 3 is (0, -38°, 0), with a piezoelectric coefficient e15 of 4.47 C / m. 2 The Euler angle of the sub-piezoelectric layer 6, which is farthest from the transmission medium layer 3, is (180°, 142°, 0°), and the piezoelectric coefficient e15 is -4.47 C / m. 2 Each piezoelectric layer 6 has a thickness of 400 nm. The acoustic delay line has a mirror-image structure, with the transmission medium layer 3 made of silicon carbide and 500 μm thick. The vibration mode in each piezoelectric layer is the A1 mode (i.e., a first-order antisymmetric Lamb wave mode), and the number of piezoelectric layers on each side is N, where N is an integer greater than or equal to 1. By performing relevant calculations on acoustic delay lines with different numbers of piezoelectric layers, the insertion loss curves for this set of examples (e.g.) are obtained. Figure 5 (), conjugate matching has been performed, from Figure 5 As can be seen, the bandwidth gradually decreases with the increase of N. Due to the air boundaries at both ends, there is no energy leakage problem, and the insertion loss is low, with the minimum insertion loss being less than 5dB. It is evident that the bandwidth of the delay line can be adjusted by changing the number of sub-piezoelectric layers 6 contained in the piezoelectric layer.

[0032] For example, in the height direction of the acoustic delay line, the first interdigital transducer 2 is partially or entirely embedded in the piezoelectric layer; the second interdigital transducer 5 is partially or entirely embedded in the piezoelectric layer. Please continue reading. Figure 3 and Figure 4 The interdigital transducers are located on the piezoelectric layer; please refer to [link / reference]. Figure 6 and Figure 7 The interdigital transducers are all embedded in the piezoelectric layer. Optionally, the first interdigital transducer 2 is partially embedded in the piezoelectric layer, and the second interdigital transducer 5 is partially embedded in the piezoelectric layer, that is, the bottom of the first interdigital transducer 2 is located in the piezoelectric layer, and the bottom of the second interdigital transducer 5 is located in the piezoelectric layer.

[0033] For example, the first interdigital transducer 2 includes at least one first electrode finger 203 and one second electrode finger 204 arranged alternately along a first direction; the second interdigital transducer 5 includes at least one third electrode finger 501 and one fourth electrode finger 502 arranged alternately along the first direction; the distance between the center of an adjacent first electrode finger 203 and the center of the second electrode finger 204 is λ / 2; where λ is the wavelength of the target mode. For details, please refer to... Figure 8 The first interdigital transducer 2 includes a first electrode finger 203 and a second electrode finger 204 arranged alternately along a first direction; the second interdigital transducer 5 includes a third electrode finger 501 and a fourth electrode finger 502 arranged alternately along the first direction; the distance between the edge of an adjacent first electrode finger 203 and the edge of the second electrode finger 204 is λ / 2. In this way, sound waves can be transmitted in the transmission medium, achieving a transmission delay.

[0034] For example, please refer to Figure 9 and Figure 10 The first interdigital transducer 2 includes a first electrode finger 203, a second electrode finger 204, and another first electrode finger 203 arranged alternately along a first direction; the second interdigital transducer 5 includes a third electrode finger 501, a fourth electrode finger 502, and another third electrode finger 501 arranged alternately along the first direction; the distance between the edge of an adjacent first electrode finger 203 and the center of the second electrode finger 204 is λ / 2. Optionally, the width of the first electrode finger 203 is smaller than the width of the second electrode finger 204.

[0035] Provide another example, whose structure is as follows: Figure 9 The structure shown has an interdigital transducer made of aluminum, with an electrode period λ of 20 μm, an electrode finger width of 1 μm, and a thickness of 100 nm; the piezoelectric layer is made of lithium niobate, with an Euler angle of (0, -38°, 0) and a thickness of 400 nm; the acoustic delay line has a mirror-image structure, and the transmission medium layer 3 is made of silicon carbide with a thickness of 500 μm; the target mode is A1 mode. Through relevant calculations on the above acoustic delay line, the insertion loss curve of this example is obtained (e.g., ...). Figure 11 ) and group delay (e.g. Figure 12 (), conjugate matching has been performed, from Figure 11and Figure 12 As can be seen, the delay line has a minimum insertion loss of 4.5dB, an operating frequency of up to 3GHz, a 3dB bandwidth of at least 1GHz, and a group delay of around 20ns, which means it can achieve high-frequency, high-bandwidth, and low-loss transmission delay.

[0036] Provide another set of instances, whose structure is as follows: Figure 9 The structure shown has an interdigital transducer made of aluminum with a thickness of 100 nm; a piezoelectric layer made of lithium niobate with an Euler angle of (0, -38°, 0) and a thickness of 400 nm; and an acoustic delay line with a mirror-image structure, where the transmission medium layer 3 is made of silicon carbide with a thickness of 500 μm. The target mode is A1 mode. By performing relevant calculations on acoustic delay lines with different electrode periods, such as the electrode period λ of 4 μm and electrode width of 0.5 μm in Example 2, and the electrode period λ of 20 μm and electrode width of 1 μm in Example 3, the insertion loss curves for this group of examples (e.g.) were obtained. Figure 13 (), conjugate matching has been performed, from Figure 13 As can be seen, the operating frequency of the delay line can be adjusted by changing the electrode period λ, making the design more flexible compared to BAW delay lines.

[0037] For example, the material of the transmission medium layer 3 is a semiconductor or insulating material; the resistivity of the transmission medium layer 3 is greater than 1000 Ω × cm. Please refer to [link / reference]. Figure 14 The material of the transmission medium layer 3 is a piezoelectric material, that is, the same material as the piezoelectric layer.

[0038] Provide another set of instances, whose structure is as follows: Figure 1 The structure shown has an interdigital transducer made of aluminum, with an electrode period λ of 20 μm, an electrode finger width of 1 μm, and a thickness of 100 nm. The piezoelectric layer is made of lithium niobate, with Euler angles of (30°, 90°, -90°) and a thickness of 400 nm. The acoustic delay line has a mirror-image structure, and the transmission medium layer 3 has a thickness of 500 μm. The target mode is LL-SAW (SLAW longitudinal leakage surface acoustic wave). Calculations were performed on acoustic delay lines with transmission medium layers 3 made of different materials, such as lithium niobate in Example 4 (e.g.,...). Figure 14 The structure shown); the material of transmission medium layer 3 in Example 5 is silicon carbide; the insertion loss curves of this set of examples are obtained (e.g. Figure 15 (), conjugate matching has been performed, from Figure 15 As can be seen, due to the high velocity of sound in silicon carbide, the LL-SAW mode cannot leak into silicon carbide. Therefore, the fundamental premise of an acoustic delay line is that the product of the operating frequency and λ is greater than the slow shear wave velocity of the transmission medium.

[0039] For example, the acoustic delay line further includes a first bonding layer and a second bonding layer; a first bonding layer is provided between the first piezoelectric layer 1 and the transmission medium layer 3; and a second bonding layer is provided between the second piezoelectric layer 4 and the transmission medium layer 3.

[0040] For example, the bonding layer material is at least one of silicon oxide, amorphous silicon, titanium, and gold.

[0041] This scheme proposes an acoustic delay line, comprising at least a piezoelectric layer, interdigital transducers, and a transmission medium. The target mode is a hypersonic mode excited by a transverse electric field. Its speed of sound in the horizontal direction is determined by the frequency and the electrode period. By increasing the electrode period, the speed of sound of the target mode exceeds the speed of the slow shear wave in the transmission medium, thus allowing the target mode to propagate into the transmission medium.

[0042] Compared to existing solutions, this solution eliminates the need for a patterned bottom electrode structure, saving at least two processing steps on both surfaces of the transmission medium. The target mode is a hypersonic mode with a sound speed exceeding that of the transmission medium, allowing it to propagate within the medium. Due to the use of a target mode with a larger coupling coefficient, its operating bandwidth is also greater. The target mode exhibits dispersive characteristics, allowing for frequency and bandwidth adjustment by varying the electrode period, piezoelectric layer thickness, and number of layers. Therefore, this solution offers a simpler structure, greater design flexibility, and a wider bandwidth.

[0043] On the other hand, a signal processing apparatus is provided, which includes the acoustic delay line described above; the signal processing apparatus includes at least one of a filter, an isolator, a circulator, a phase modulator, an amplifier, and an oscillator.

[0044] For example, please refer to Figure 16 Its acoustic delay line is Figure 1 The structure shown is used to achieve functions such as amplification and phase modulation by setting DC bias sources at both ends of the transmission medium layer 3.

[0045] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An acoustic delay line, characterized in that, At least including: The first delay structure includes a first piezoelectric layer and a first interdigital transducer; The transmission medium layer located on the first delay structure; A second delay structure located on the transmission medium layer, the second delay structure including a second piezoelectric layer and a second interdigital transducer; Wherein, the product of the passband low frequency of the acoustic delay line and the wavelength of the target mode of the acoustic delay line is greater than the slow shear wave velocity of the transmission medium layer.

2. The acoustic delay line according to claim 1, characterized in that, The first piezoelectric layer includes at least two sub-piezoelectric layers; The second piezoelectric layer comprises at least two sub-piezoelectric layers; at least one piezoelectric coefficient of adjacent sub-piezoelectric layers has opposite signs.

3. The acoustic delay line according to claim 2, characterized in that, The target mode is a hypersonic mode excited by a transverse electric field. The frequency and bandwidth of the acoustic delay line can be adjusted by regulating the electrode period of the first interdigital transducer and the second interdigital transducer; the bandwidth and loss can be adjusted by adjusting the number of sub-piezoelectric layers and the periodicity of the piezoelectric coefficient.

4. The acoustic delay line according to claim 1, characterized in that, In the height direction of the acoustic delay line, the first interdigital transducer is partially or entirely embedded in the piezoelectric layer; the second interdigital transducer is partially or entirely embedded in the piezoelectric layer.

5. The acoustic delay line according to any one of claims 1-4, characterized in that, The first interdigital transducer includes at least one first electrode finger and one second electrode finger arranged alternately along a first direction; the second interdigital transducer includes at least one third electrode finger and one fourth electrode finger arranged alternately along the first direction; the distance between the center of an adjacent first electrode finger and the center of the second electrode finger is λ / 2; where λ is the wavelength of the target mode.

6. The acoustic delay line according to any one of claims 1-4, characterized in that, The material of the transmission medium layer is a semiconductor or an insulating material; The resistivity of the transmission medium layer is greater than 1000Ω×cm; The piezoelectric coefficients of the piezoelectric layer include e11, e13, e14, and e15, and the absolute value of at least one piezoelectric coefficient is greater than 1 C / m. 2 .

7. The acoustic delay line according to any one of claims 1-4, characterized in that, It also includes a first bonding layer and a second bonding layer; A first bonding layer is provided between the first piezoelectric layer and the transmission medium layer; A second bonding layer is provided between the second piezoelectric layer and the transmission medium layer.

8. The acoustic delay line according to claim 7, characterized in that, The bonding layer material is at least one of silicon oxide, amorphous silicon, titanium, and gold.

9. The acoustic delay line according to any one of claims 1-4, characterized in that, The materials of the first piezoelectric layer and the second piezoelectric layer are one of lithium tantalate, lithium niobate, potassium niobate, scandium-doped aluminum nitride, lead zirconate titanate, or lead magnesium niobate-lead titanate.

10. A signal processing apparatus, characterized in that, Includes the acoustic delay line as described in any one of claims 1-9; The signal processing device includes at least one of a filter, an isolator, a circulator, a phase modulator, an amplifier, and an oscillator.

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