Electroacoustic transducer, surface acoustic wave resonator and surface acoustic wave device

Abstract

The present application relates to an electroacoustic transducer, a surface acoustic wave resonator and a surface acoustic wave device, and relates to the field of radio frequency. The electroacoustic transducer provided in the present application includes: a transducer portion, which has a plurality of first electrode fingers and a plurality of second electrode fingers arranged relatively staggered, and a first bus bar and a second bus bar opposite to each other in the extension direction of the first electrode finger and the second electrode finger; a gate portion, which has a plurality of third electrode fingers arranged periodically and a third bus bar and a fourth bus bar opposite to each other in the extension direction of the third electrode finger; and a resistor portion, which has a fourth electrode finger, one end of the fourth electrode finger is connected to the first bus bar, and the other end is connected to the second bus bar; wherein, under the premise that the length of the first electrode finger and the second electrode finger is set to α and the length of the fourth electrode finger is set to β, β satisfies β≥3α. In this case, the problem of poor out-of-band suppression of the RF front-end device can be solved, and the performance of the device can be greatly improved.

Description

Technical Field

[0001] The present application relates to the field of radio frequency technology, and in particular to an electroacoustic transducer, a surface acoustic wave resonator, and a surface acoustic wave device. Background Art

[0002] RF front-end devices have the characteristics of low cost, small size and multiple functions, and have been widely used in radar, communication, navigation and other fields.

[0003] As is known in the art, surface acoustic wave devices use acoustic waves to convert radio frequency signals into mechanical vibrations and vice versa. To achieve this, the mechanical vibrations need to be excited by an electroacoustic transducer on a piezoelectric substrate. The electroacoustic transducer typically includes a plurality of first electrode fingers and a plurality of second electrode fingers arranged in an interlaced manner, and first and second bus bars that oppose each other in the direction in which the first and second electrode fingers extend. Furthermore, the electroacoustic transducer also has a reflective grating.

[0004] With the rapid commercialization of fifth-generation (5G) communication technology worldwide, market demand for surface acoustic wave (SAW) devices operating in the 5G frequency band has skyrocketed. In 5G communication applications, the market places higher demands on the out-of-band suppression of SAW devices. Good out-of-band suppression means the device effectively suppresses signals in the stopband, which is beneficial for device applications.

[0005] In the related art, patent CN114301422B provides a surface acoustic wave device, which can reduce the generation of parasitic capacitance and improve the out-of-band suppression level of the filter by providing a groove on the piezoelectric substrate and providing at least one pad and at least one trace on the groove.

[0006] However, the aforementioned SAW device's grooves in the piezoelectric substrate undoubtedly increase the difficulty of device fabrication, which is detrimental to device yield and ultimately mass production. Furthermore, this approach offers very limited improvement in the SAW device's out-of-band suppression. Summary of the Invention

[0007] The purpose of this application is to provide an electroacoustic transducer, a surface acoustic wave resonator and a surface acoustic wave device to solve the problems existing in the above-mentioned prior art.

[0008] To achieve the above objectives, the technical solutions adopted in this application are:

[0009] In a first aspect, the present application provides an electroacoustic transducer, comprising:

[0010] a transducer portion comprising a plurality of first electrode fingers and a plurality of second electrode fingers that are relatively staggered, and a first bus bar and a second bus bar that are opposite to each other in the extending direction of the first electrode fingers and the second electrode fingers, wherein the number of the transducer portion is one;

[0011] a gate portion having a plurality of periodically arranged third electrode fingers and a third bus bar and a fourth bus bar facing each other in an extending direction of the third electrode fingers; and

[0012] a resistor portion having a fourth electrode finger, wherein one end of the fourth electrode finger is connected to the first bus bar and the other end of the fourth electrode finger is connected to the second bus bar;

[0013] Wherein, under the premise that the lengths of the first electrode finger and the second electrode finger are set to α and the length of the fourth electrode finger is set to β, β satisfies β≥3α.

[0014] In a possible implementation, the resistor portion is disposed on both sides of the transducer portion in a sound wave propagation direction.

[0015] In a possible implementation, the first electrode finger, the second electrode finger, the third electrode finger, and the fourth electrode finger are made of one or more of aluminum, copper, platinum, tungsten, gold, silver, molybdenum, and tantalum.

[0016] In a second aspect, the present application provides a surface acoustic wave resonator, comprising:

[0017] a piezoelectric substrate; and

[0018] A conductive material film pattern, which is disposed on the working surface of the piezoelectric substrate;

[0019] Wherein, the conductive material film pattern forms at least one electroacoustic transducer, and the electroacoustic transducer is the electroacoustic transducer described above.

[0020] In a possible implementation, the piezoelectric substrate is a bulk material having piezoelectricity; or

[0021] The piezoelectric substrate is a piezoelectric multilayer material.

[0022] In a third aspect, the present application provides a surface acoustic wave device, which is a surface acoustic wave filter or a multiplexer, comprising a series arm resonator and a parallel arm resonator; wherein at least one resonator among the series arm resonator and the parallel arm resonator is the surface acoustic wave resonator as described above.

[0023] The beneficial effects of the technical solution provided by this application include at least:

[0024] The electroacoustic transducer provided in this application includes: a transducer portion having a plurality of first electrode fingers and a plurality of second electrode fingers arranged in a relatively staggered manner, and first and second bus bars opposing each other in the direction in which the first and second electrode fingers extend; a gate portion having a plurality of periodically arranged third electrode fingers and third and fourth bus bars opposing each other in the direction in which the third electrode fingers extend; and a resistor portion having a fourth electrode finger, one end of which is connected to the first bus bar and the other end to the second bus bar; wherein, assuming the lengths of the first and second electrode fingers are α and the length of the fourth electrode finger are β, β satisfies β ≥ 3α. In this case, the problem of poor out-of-band suppression of RF front-end devices can be solved, significantly improving device performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings are used to provide a further understanding of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the present application and do not constitute a limitation of the present application. In the accompanying drawings:

[0026] Figure 1 FIG. 2 shows a top view of a surface acoustic wave resonator 100 provided in Comparative Example 1;

[0027] Figure 2 FIG2 shows a schematic structural diagram of the electroacoustic transducer in the surface acoustic wave resonator 100 provided in Comparative Example 1;

[0028] Figure 3 FIG2 shows a top view of the surface acoustic wave resonator 200 provided in the first embodiment;

[0029] Figure 4 Schematic diagram of the structure of the electroacoustic transducer in the surface acoustic wave resonator 200 provided in the first embodiment is shown;

[0030] Figure 5 A comparison diagram of admittance-frequency curves of the surface acoustic wave resonator 200 provided in Example 1 and the surface acoustic wave resonator 100 provided in Comparative Example 1 is shown;

[0031] Figure 6 Shown Figure 5 Amplified diagram of the admittance at the anti-resonance point of R1~R6;

[0032] Figure 7 A comparison diagram of insertion loss-frequency curves of filters composed of the surface acoustic wave resonator 200 provided in Example 1 and the surface acoustic wave resonator 100 provided in Comparative Example 1 is shown;

[0033] Figure 8 FIG. 1 shows a top view of a surface acoustic wave resonator 300 provided in the first modification. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0035] Among them, the same parts are represented by the same figure marks. It should be noted that the words "front", "rear", "left", "right", "up" and "down" used in the following description refer to the directions in the drawings of the present application specification, and the words "bottom" and "top", "inside" and "outside" refer to directions toward or away from specific parts, respectively. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present application specification, the meaning of "multiple" is two or more.

[0036] Comparative Example 1:

[0037] Figure 1 1 shows a top view of a surface acoustic wave resonator 100 provided in Comparative Example 1. The height direction of the surface acoustic wave device 100 is not shown.

[0038] In detail, the surface acoustic wave resonator 100 includes a piezoelectric substrate 6 and an electroacoustic transducer arranged above the piezoelectric substrate 6. The electroacoustic transducer includes a first bus bar 2 and a second bus bar 3 opposite to each other, and a plurality of first electrode fingers 1a and a plurality of second electrode fingers 1b arranged at intervals and staggered along an extension direction parallel to the first bus bar 2 and the second bus bar 3.

[0039] In addition, the electroacoustic transducer has a reflection grid on both sides of the electroacoustic transducer in the direction of sound wave propagation. The reflection grid includes a third bus bar 4 and a fourth bus bar 7 that are opposed to each other, and a plurality of third electrode fingers 5 that are periodically arranged along a direction extending parallel to the third bus bar 4 and the fourth bus bar 7.

[0040] Optionally, the material of the piezoelectric substrate 6 is quartz, lithium niobate, lithium tantalate, aluminum nitride, zinc oxide, lead zirconate titanate, and a multilayer composite material including thin films of the above materials.

[0041] Optionally, the electrode material of the electroacoustic transducer includes at least one of aluminum, copper, platinum, tungsten, gold, silver, molybdenum, tantalum, or an alloy mainly composed of the above materials.

[0042] Figure 2The schematic diagram of the structure of the electroacoustic transducer in the surface acoustic wave resonator 100 provided in Comparative Example 1 is shown. The electroacoustic transducer can be divided into a transducer portion and a gate portion. The transducer is the region that performs the electroacoustic conversion function, and the gate portion is the region that performs the acoustic wave reflection function.

[0043] Example 1:

[0044] Figure 3 FIG2 shows a top view of the surface acoustic wave resonator 200 provided in Embodiment 1. The height direction of the surface acoustic wave device 200 is not shown.

[0045] In detail, the surface acoustic wave resonator 200 includes a piezoelectric substrate 6 and an electroacoustic transducer arranged above the piezoelectric substrate 6; the electroacoustic transducer includes a first bus bar 2 and a second bus bar 3 opposite to each other, and a plurality of first electrode fingers 1a and a plurality of second electrode fingers 1b arranged at intervals and staggered along an extension direction parallel to the first bus bar 2 and the second bus bar 3; wherein the electroacoustic transducer also includes a fourth electrode finger 8 located between the first bus bar 2 and the second bus bar 3, one end of the fourth electrode finger 8 is connected to the first bus bar 2, and the other end is connected to the second bus bar 3.

[0046] Specifically, fourth electrode finger 8 acts as the resistor in the electroacoustic transducer and needs to be longer than first electrode finger 1a and second electrode finger 1b. Assuming the length of first electrode finger 1a and second electrode finger 1b is α and the length of fourth electrode finger 8 is β, β must satisfy β ≥ 3α.

[0047] In addition, the electroacoustic transducer has a reflection grid on both sides of the electroacoustic transducer in the direction of sound wave propagation. The reflection grid includes a third bus bar 4 and a fourth bus bar 7 that are opposed to each other, and a plurality of third electrode fingers 5 that are periodically arranged along a direction extending parallel to the third bus bar 4 and the fourth bus bar 7.

[0048] Optionally, the material of the piezoelectric substrate 6 is quartz, lithium niobate, lithium tantalate, aluminum nitride, zinc oxide, lead zirconate titanate, and a multilayer composite material including thin films of the above materials.

[0049] Optionally, the electrode material of the electroacoustic transducer includes at least one of aluminum, copper, platinum, tungsten, gold, silver, molybdenum, tantalum, or an alloy mainly composed of the above materials.

[0050] Figure 4 The schematic diagram of the electroacoustic transducer structure in the surface acoustic wave resonator 200 provided in Example 1 is shown. The electroacoustic transducer can be divided into a transducer portion, a resistor portion, and a gate portion. The transducer is the region that performs the electroacoustic conversion function, the resistor portion is the region that performs the current limiting function, and the gate portion is the region that reflects the sound waves.

[0051] In order to better illustrate the difference between the surface acoustic wave resonator 200 provided in Example 1 and the surface acoustic wave resonator 100 provided in Comparative Example 1, Figure 5 A comparison of the admittance-frequency curves of the surface acoustic wave resonator 200 provided in Example 1 and the surface acoustic wave resonator 100 provided in Comparative Example 1 is shown. R6 represents the surface acoustic wave resonator 100, while R1 through R5 represent the surface acoustic wave resonator 200. For R1 through R5, the lengths of the fourth electrode fingers 8 of the resistor portion of the surface acoustic wave resonator 200 decrease, indicating a decreasing resistance.

[0052] Due to the difference in resistance value of the resistor, Figure 5 It can be seen that the admittance values ​​and Q values ​​of R1~R6 at the anti-resonance frequency are different. In order to show the difference more clearly, Figure 6 Shown Figure 5 Amplified diagram of the admittance at the anti-resonance point of R1~R6. Figure 6 , as the resistance of R1~R6 decreases, the Q value at the anti-resonance frequency of R1~R6 gradually increases.

[0053] Figure 7 A comparison of the insertion loss-frequency curves of filters composed of the SAW resonator 200 provided in Example 1 and the SAW resonator 100 provided in Comparative Example 1 is shown. Both SAW resonator 200 and SAW resonator 100 function as series-arm resonators. The curves show that the introduction of a resistor into the SAW resonator reduces the Q value at the resonator's antiresonant frequency, thereby enhancing the out-of-band rejection to the right of the SAW filter's passband by approximately 20 dB, significantly improving the SAW filter's performance.

[0054] Modification 1:

[0055] Figure 8 FIG. 3 shows a top view of a surface acoustic wave resonator 300 provided in Modification 1. The difference between Modification 1 and Embodiment 1 is that the shape of the fourth electrode finger 8 of the resistor portion is different.

[0056] Based on the same reasons as those of the first embodiment, the structure of this variation can enhance the out-of-band suppression on the right side of the filter passband.

[0057] In summary, the electroacoustic transducer provided in the present application includes: a transducer portion having a plurality of first electrode fingers and a plurality of second electrode fingers arranged in a relatively staggered manner, and a first bus bar and a second bus bar opposite each other in the direction in which the first and second electrode fingers extend; a gate portion having a plurality of periodically arranged third electrode fingers and a third bus bar and a fourth bus bar opposite each other in the direction in which the third electrode fingers extend; and a resistor portion having a fourth electrode finger, one end of the fourth electrode finger being connected to the first bus bar and the other end being connected to the second bus bar; wherein, under the premise that the lengths of the first and second electrode fingers are set to α and the length of the fourth electrode finger is set to β, β satisfies β ≥ 3α. In this case, the problem of poor out-of-band suppression of RF front-end devices can be solved, significantly improving the performance of the device.

[0058] In the embodiments disclosed herein, terms such as "installed," "connected," "connected," and "fixed" should be interpreted broadly. For example, "connected" may refer to a fixed connection, a detachable connection, or an integral connection; and "connected" may refer to a direct connection or an indirect connection via an intermediary. Those skilled in the art will understand the specific meanings of the above terms in the embodiments disclosed herein based on specific circumstances.

[0059] The above is only a preferred embodiment of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. An electroacoustic transducer, characterized in that: include: a transducer portion comprising a plurality of first electrode fingers and a plurality of second electrode fingers that are relatively staggered, and a first bus bar and a second bus bar that are opposite to each other in the extending direction of the first electrode fingers and the second electrode fingers, wherein the number of the transducer portion is one; a gate portion having a plurality of periodically arranged third electrode fingers and a third bus bar and a fourth bus bar facing each other in an extending direction of the third electrode fingers; as well as a resistor portion having a fourth electrode finger, wherein one end of the fourth electrode finger is connected to the first bus bar and the other end of the fourth electrode finger is connected to the second bus bar; Wherein, under the premise that the lengths of the first electrode finger and the second electrode finger are set to α and the length of the fourth electrode finger is set to β, β satisfies β≥3α.

2. The electroacoustic transducer according to claim 1, characterized in that: The resistor portion is arranged on both sides of the transducer portion in a sound wave propagation direction.

3. The electroacoustic transducer according to claim 1, characterized in that: The first electrode finger, the second electrode finger, the third electrode finger, and the fourth electrode finger are made of one or more of aluminum, copper, platinum, tungsten, gold, silver, molybdenum, and tantalum.

4. A surface acoustic wave resonator, characterized in that include: Piezoelectric substrate; as well as A conductive material film pattern, which is disposed on the working surface of the piezoelectric substrate; Wherein, the conductive material film pattern forms at least one electroacoustic transducer, and the electroacoustic transducer is the electroacoustic transducer according to any one of claims 1 to 3.

5. The surface acoustic wave resonator according to claim 4, characterized in that: The piezoelectric substrate is a bulk material having piezoelectricity; or The piezoelectric substrate is a piezoelectric multilayer material.

6. A surface acoustic wave device, characterized in that: It is a surface acoustic wave filter or a multiplexer, which includes a series arm resonator and a parallel arm resonator; wherein at least one resonator among the series arm resonator and the parallel arm resonator is the surface acoustic wave resonator according to claim 5.

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