5G Small Base Station RF Acoustic Wave Filter

Abstract

The present invention provides a 5G small base station radio frequency acoustic wave filter, comprising: a resonator substrate (1), a resonator piezoelectric layer (5), a resonator upper electrode and a reflective component; the resonator substrate (1) is arranged at the bottom of the 5G small base station radio frequency acoustic wave filter; the resistance of the resonator substrate (1) is greater than a set threshold; the resonator piezoelectric layer (5) adopts a piezoelectric film material; the resonator upper electrode is arranged at the upper part of the 5G small base station radio frequency acoustic wave filter; the reflective component is arranged in the middle part of the 5G small base station radio frequency acoustic wave filter; the resonator piezoelectric layer (5) is arranged at the upper part of the 5G small base station radio frequency acoustic wave filter. The present invention increases the electrode area of ​​a common resonator by proposing a splitting method, thereby increasing the resonator's loadable power while maintaining the electrical performance of the resonator unchanged.

Description

Technical Field

[0001] The present invention relates to the field of filter technology, and in particular, to a 5G small base station radio frequency acoustic wave filter, and in particular to a 5G small base station radio frequency acoustic wave filter that can carry high power. Background Art

[0002] With the rapid development of 5G communication technology, there are increasingly higher requirements for the transmission rate, latency, and signal coverage capabilities of communication systems. 5G small base stations, as a supplement to macro base stations, can cover areas that macro base stations cannot serve, or achieve better communication performance within a local area. As one of the most critical components of a base station system, the RF filter divides the communication frequency band (receiving signals within the target frequency band and filtering signals in non-target frequency bands) on the one hand, and affects the degree of signal energy attenuation on the other hand. Its performance is crucial to the base station system. Traditional macro base stations generally use metal cavity filters or cavity dielectric filters due to their high power requirements. However, due to the significant reduction in the size of 5G small base stations and the substantial increase in the number of deployments, traditional metal cavity or cavity dielectric filters are no longer applicable. The existing technology urgently needs a high-power RF acoustic resonator to solve the power and size problems of 5G small base station filters.

[0003] Patent document CN105244575B discloses a novel dielectric cavity filter. This dielectric cavity filter, through a waveguide-to-coaxial conversion feed structure at the waveguide entrance, achieves waveguide-to-coaxial conversion and filters out higher-order electromagnetic modes in waveguide transmission signals, thereby ensuring the proper functioning of the filter and subsequent microwave radio frequency devices. However, this patent does not effectively address the power and size issues of 5G small base station filters. Summary of the Invention

[0004] In view of the defects in the prior art, the purpose of the present invention is to provide a 5G small base station radio frequency acoustic wave filter.

[0005] According to the present invention, a 5G small base station radio frequency acoustic wave filter is provided, including: a resonator substrate 1, a resonator piezoelectric layer 5, a resonator upper electrode and a reflective component; the resonator substrate 1 is arranged at the bottom of the 5G small base station radio frequency acoustic wave filter; the resistance of the resonator substrate 1 is greater than a set threshold; the resonator substrate 1 supports the 5G small base station radio frequency acoustic wave filter; the thickness of the resonator substrate 1 is about tens to hundreds of microns; the resonator piezoelectric layer 5 is made of piezoelectric thin film material; the resonator upper electrode is arranged on the upper part of the 5G small base station radio frequency acoustic wave filter; the reflective component is arranged in the middle of the 5G small base station radio frequency acoustic wave filter; the resonator piezoelectric layer 5 is arranged on the upper part of the 5G small base station radio frequency acoustic wave filter.

[0006] Preferably, the device further comprises: a sacrificial layer 2, a protective layer 3, and a resonator plate bottom electrode 4; the reflective component adopts an air reflection cavity 7; the sacrificial layer 2 is formed on the resonator substrate 1; the sacrificial layer 2 is a material pre-filled to form the resonator air reflection cavity 7, and its thickness is equal to the depth of the air reflection cavity. The thickness of the sacrificial layer 2 is equal to the thickness of the air reflection cavity 7;

[0007] Preferably, the resonator substrate 1 can be made of any one of the following materials: - sapphire; - silicon carbide; - single crystal silicon; - high-resistance silicon. The sacrificial layer 2 is made of any one of the following materials: - a material that is removed by wet etching; - a material that is removed by dry etching; the protective layer 3 is formed in the sacrificial layer 2; the protective layer 3 is usually made of a material that does not react with wet etching and is easier to polish. The protective layer 3 is intended to prevent the final etching process from proceeding in the left and right directions, thereby forming an air reflection cavity with a specific shape. In summary, the sacrificial layer 2 and the protective layer 3 respectively determine the depth and shape of the air reflection cavity, and they are the decisive structures of the air reflection cavity.

[0008] Preferably, the resonator plate bottom electrode 4 adopts a flat plate structure; an excitation electric field is formed between the resonator plate bottom electrode 4 and the resonator plate upper electrode 6; the excitation electric field can excite acoustic waves in the resonator piezoelectric layer 5; the resonator plate bottom electrode 4 adopts any of the following connection methods: - grounding; - power connection

[0009] The resonator plate bottom electrode 4 is made of metal thin film material; the resonator plate bottom electrode 4 is made of any of the following materials: - molybdenum thin film material; - ruthenium thin film material; - platinum thin film material; the thickness of the resonator plate bottom electrode 4 is less than a set threshold; the resonator plate bottom electrode 4 can be realized by dry etching metal or metal stripping process, and the thickness is between tens of nanometers and hundreds of nanometers.

[0010] Preferably, the resonator piezoelectric layer 5 is made of any of the following materials: - lithium niobate; - lithium tantalate; - aluminum nitride; - doped aluminum nitride; - barium strontium titanate;

[0011] The resonator plate bottom electrode 4 is made by any of the following methods: - ion slicing; - plasma assisted molecular beam epitaxy; - metal organic compound chemical vapor deposition; - physical vapor deposition. The thickness of the piezoelectric material 5 mainly determines the frequency of the resonator. Usually the thickness and the resonant frequency are inversely proportional and can be determined according to actual needs. The resonator upper electrode adopts the resonator plate upper electrode 6; the resonator plate upper electrode 6 adopts a flat plate structure; the resonator plate upper electrode 6 adopts any of the following connection methods: - grounding; - power connection. The resonator plate upper electrode 6 usually needs to be cross-connected or grounded with the bottom electrode 4 to form an electric field. The resonator plate upper electrode 6 adopts a metal thin film material; the resonator plate upper electrode 6 adopts any of the following materials: - molybdenum material; - ruthenium material; - platinum material; - aluminum material; - gold material;

[0012] The resonator's top electrode 6 can be fabricated using dry metal etching or metal lift-off processes, with a thickness ranging from tens to hundreds of nanometers. The air reflection cavity 7 reflects sound waves in the thickness direction back into the bottom electrode 4 and piezoelectric material 5. When the sound waves reach the air interface of the top electrode 6, they are reflected back into the top electrode 6 and piezoelectric material 5. This back-and-forth reflection creates a resonant sound wave.

[0013] Preferably, the resonator upper electrode adopts: a resonator cross upper electrode 8; the resonator cross upper electrode 8 adopts any one of the following connection methods: - grounding; - power connection; - the cross electrode is alternately connected to power and ground;

[0014] The resonator employs a cross-top electrode structure, where the number of electrodes can be determined as needed. Each electrode is of uniform size and shape, and the distance between them is also equal. The top electrode 8 can be connected in a variety of ways: electrically connected (when the bottom electrode 4 is grounded), grounded (when the bottom electrode 4 is electrically connected), or alternately connected and grounded. More importantly, the width of the top electrode 8 also affects the resonator's frequency. The width of the top electrode 8 can be determined using photolithography, making it extremely easy to define the electrode width and thus freely adjust the resonator's frequency.

[0015] Preferably, it also includes: a resonator plate bottom electrode 4; the reflective component adopts a mirror reflector 11; the resonator upper electrode adopts a resonator plate upper electrode 6; the mirror reflector 11 includes: one or more low-impedance reflective layers 9; the mirror reflector 11 includes: one or more high-impedance reflective layers 10; the multiple low-impedance reflective layers 9 and the multiple high-impedance reflective layers 10 form a mirror reflector 11.

[0016] Preferably, the number of layers of the low-impedance reflective layer 9 is one or more; the number of low-impedance reflective layers 9 is generally multiple; the low-impedance reflective layer 9 is arranged below the bottom electrode 4 of the resonator plate; the low-impedance reflective layer 9 is made of low acoustic wave impedance material; the low-impedance reflective layer 9 is made of silicon dioxide; in addition to having lower acoustic wave impedance, silicon dioxide also has a positive frequency temperature coefficient characteristic, which can be used to compensate for the negative frequency temperature coefficient of the resonator, so that the final resonator has a frequency temperature coefficient close to 0. The thickness of the low-impedance reflective layer is generally one-quarter wavelength, which can be adjusted appropriately according to actual conditions. The number of high-impedance reflective layers 10 is also multiple, with the first layer located below the first layer of the low-impedance reflective layer 9, and the second layer located below the second layer of the bottom-impedance reflective layer 9. The high-impedance reflective layer usually selects a material with high acoustic wave impedance,

[0017] Preferably, the high-impedance reflective layer 10 is made of any of the following materials: - tungsten material; - platinum material; - silicon nitride material; - aluminum nitride material; the thickness of the high-impedance reflective layer is generally also a quarter of the wavelength, and can also be appropriately adjusted according to actual conditions. The mirror reflector 11 composed of all the low-impedance reflective layers and the high-impedance reflective layers has a function similar to Figure 1 and Figure 2 The air reflection cavity in the resonator reflects the sound waves at the lower surface of the resonator bottom electrode 4 and the interface between 9 and 10, thereby reducing the leakage of the sound wave energy.

[0018] Preferably, the resonator upper electrode adopts: a resonator cross upper electrode 8; the electrodes of the resonator cross upper electrode 8 are grounded and powered in turn; so as to form a transverse electric field between two adjacent electrodes, thereby exciting longitudinal acoustic waves (through the piezoelectric coefficient e31 or e51). The upper electrode is usually a metal thin film material, such as aluminum, molybdenum, ruthenium, platinum, aluminum, gold, etc., which can be realized by means of metal dry etching or metal stripping process. The thickness of the metal film is between tens of nanometers and hundreds of nanometers. The reflecting component includes: a mirror reflector 11; the mirror reflector 11 includes: one or more low-impedance reflection layers 9; the mirror reflector 11 includes: one or more high-impedance reflection layers 10; the multiple low-impedance reflection layers 9 and the multiple high-impedance reflection layers 10 form the mirror reflector 11.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. This invention proposes a splitting method to increase the electrode area of ​​a conventional resonator, thereby increasing the resonator's power capacity while maintaining the resonator's electrical performance. The resulting high-power resonator is the core structural unit of 5G small base station filters.

[0021] 2. This invention uses a matrix listing method to represent all possible splitting schemes and provides an effective splitting region. Splitting schemes within this region can achieve the goal of maintaining the electrical performance of the resonator while increasing the carrying power. The effective splitting region provided by this invention points the way to a variety of splitting schemes;

[0022] 3. The present invention uses a resonator replacement method to replace ordinary resonators with resonators that can carry high power, thereby constructing a 5G small base station high-power filter. In addition, one or more or even all ordinary resonators can be replaced according to actual needs. The replacement solution proposed by the present invention has the advantages of simplicity and flexibility;

[0023] 4. This invention analyzes the aspect ratio of the resonator electrode shape and provides an optimal electrode shape solution, thereby further increasing the power handling capacity of high-power resonators or filters. The aspect ratio analysis conclusions provided by this invention further lay the foundation for solving the power problem of 5G small base station filters. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0025] Figure 1 Schematic diagram of the structure of the first piezoelectric resonator capable of constructing a filter in an embodiment of the present invention.

[0026] Figure 2 Schematic diagram of the structure of a second piezoelectric resonator capable of constructing a filter in an embodiment of the present invention.

[0027] Figure 3 Schematic diagram of the structure of a third piezoelectric resonator capable of constructing a filter in an embodiment of the present invention.

[0028] Figure 4 Schematic diagram of the structure of a fourth piezoelectric resonator capable of constructing a filter in an embodiment of the present invention.

[0029] Figure 5 Schematic diagram of the first principle comparison in an embodiment of the present invention.

[0030] Figure 6 2 is a comparative schematic diagram of the second principle in an embodiment of the present invention.

[0031] Figure 7 Schematic diagram for comparison of the third principle in an embodiment of the present invention.

[0032] Figure 8 Schematic diagram for comparison of the fourth principle in an embodiment of the present invention.

[0033] Figure 9Schematic diagram for comparison of the fifth principle in an embodiment of the present invention.

[0034] In the picture:

[0035] 1-Resonator substrate 8-Resonator cross-upper electrode

[0036] 2-Sacrificial layer 9-Low impedance reflective layer

[0037] 3-Protective layer 10-High impedance reflective layer

[0038] 4- resonator plate bottom electrode 11- mirror reflector

[0039] 5-Resonator piezoelectric material 12-Common resonator

[0040] 6-Resonator plate upper electrode 13-High power resonator

[0041] 7-Air reflection cavity 14-Resonator split unit DETAILED DESCRIPTION

[0042] The present invention will be described in detail below with reference to specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several changes and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0043] Example 1

[0044] Figure 1This is the first common type of resonator we propose. This piezoelectric resonator structure comprises a resonator substrate 1, a sacrificial layer 2, a protective layer 3, a resonator plate bottom electrode 4, a resonator piezoelectric layer 5, a resonator plate top electrode 6, and an air reflector cavity 7. The resonator substrate 1 provides support for the resonator and is typically made of a high-resistance material to reduce acoustic energy leakage. Substrate 1 can typically be made of sapphire, silicon carbide, single-crystal silicon, or high-resistance silicon, with a thickness ranging from tens to hundreds of microns. The sacrificial layer 2, formed on the resonator substrate 1, is a pre-filled material to form the resonator air reflector cavity 7. Its thickness determines the depth of the air reflector cavity. The sacrificial layer 2 is typically made of a material that is easily removed by wet or dry etching. The protective layer 3, formed within the sacrificial layer 2, is typically made of a material that is resistant to wet etching and easily polished. This protective layer 3 prevents the final etching process from proceeding in the left or right direction, thereby forming an air reflector cavity with a specific shape. In summary, the sacrificial layer 2 and protective layer 3 determine the depth and shape of the air reflection cavity, respectively, and are the defining structures of the air reflection cavity. The resonator's bottom electrode 4 is a flat plate structure. An electric field is formed between it and the top electrode 6, thereby exciting acoustic waves in the piezoelectric material 5. There are two ways to connect the bottom electrode 4: grounding and powering. The bottom electrode 4 is typically made of a thin metal film, such as molybdenum, ruthenium, or platinum. This can be achieved through dry metal etching or metal lift-off processes, with a thickness ranging from tens to hundreds of nanometers. The piezoelectric material 5 is a piezoelectric thin film material, such as lithium niobate (LiNbO3), lithium tantalate (LiTaO3), aluminum nitride (AlN), doped aluminum nitride (AlScN, AlGaN), or barium strontium titanate (BaSrTiO3). The fabrication techniques for the piezoelectric material 4 include ion slicing, plasma-assisted molecular beam epitaxy (MBE), metal-organic chemical vapor deposition (MOCVD), and physical vapor deposition (PVD). The thickness of the piezoelectric material 5 mainly determines the frequency of the resonator. Usually, the thickness and the resonant frequency are inversely proportional and can be determined according to actual needs. The upper electrode 6 of the resonator is a flat plate structure. An electric field is formed between it and the bottom electrode 4, thereby exciting sound waves in the piezoelectric material 5. There are two ways to connect the upper electrode 6: grounding and power connection. Usually, it is necessary to cross-connect or ground with the bottom electrode 4 to form an electric field. The upper electrode 6 is usually a metal thin film material, such as molybdenum, ruthenium, platinum, aluminum, gold, etc., which can be achieved by dry etching of metal or metal stripping process, with a thickness of tens of nanometers to hundreds of nanometers. The air reflection cavity 7 reflects the sound waves in the thickness direction back to the bottom electrode 4 and the piezoelectric material 5. When the sound waves propagate to the air interface of the upper electrode 6, they are reflected back to the upper electrode 6 and the piezoelectric material 5 again. After such back and forth reflection, a resonant sound wave is formed.

[0045] Example 2

[0046] Figure 2This is the second common type of resonator proposed by us. The piezoelectric resonator structure includes a resonator substrate 1, a sacrificial layer 2, a protective layer 3, a resonator flat bottom electrode 4, a resonator piezoelectric layer 5, an air reflection cavity 7, and a resonator cross upper electrode 8. Figure 2 The middle resonator utilizes a cross-top electrode structure. The number of electrodes can be determined as needed. Each electrode is of uniform size and shape, and the distance between electrodes is also equal. The top electrode 8 can be connected in a variety of ways: electrically connected (when the bottom electrode 4 is grounded), grounded (when the bottom electrode 4 is electrically connected), and alternately connected and grounded. Furthermore, and more importantly, the width of the top electrode 8 also affects the resonator frequency. The width of the top electrode 8 can be determined by photolithography, making it extremely easy to define the electrode width and thus freely adjust the resonator frequency.

[0047] Example 3

[0048] Figure 3 This is the third common type of resonator we propose. This piezoelectric resonator structure includes a resonator substrate 1, a resonator plate bottom electrode 4, a resonator piezoelectric layer 5, a resonator plate top electrode 6, a low-impedance reflective layer 9, and a high-impedance reflective layer 10. The portion formed by alternating layers of low-impedance reflective layers 9 and high-impedance reflective layers 10 is called a specular reflector and is labeled 11. The number of low-impedance reflective layers 9 is generally multiple, with the first layer located below the resonator plate bottom electrode 4, and the second and subsequent layers successively placed below the high-impedance reflective layer 10. The low-impedance reflective layer is typically made of a material with low acoustic impedance, the most common being silicon dioxide (SiO2). In addition to its low acoustic impedance, silicon dioxide also has a positive frequency temperature coefficient, which can be used to compensate for the negative frequency temperature coefficient of the resonator, resulting in a resonator with a frequency temperature coefficient close to zero. The thickness of the low-impedance reflective layer is generally one-quarter wavelength and can be adjusted appropriately based on actual conditions. The number of high-impedance reflective layers 10 is also multiple layers, with the first layer located below the first layer of low-impedance reflective layer 9, and the second layer located below the second layer of low-impedance reflective layer 9. The high-impedance reflective layer is usually made of a material with high acoustic impedance, and common materials include tungsten (W), platinum (Pt), silicon nitride (Si3N4), aluminum nitride (AlN), etc. The thickness of the high-impedance reflective layer is generally also one-quarter wavelength, and can also be adjusted appropriately according to actual conditions. The mirror reflector 11 composed of all the low-impedance reflective layers and the high-impedance reflective layers has a function similar to that of the mirror reflector. Figure 1 and Figure 2 The air reflection cavity in the resonator reflects the sound waves at the lower surface of the resonator bottom electrode 4 and the interface between 9 and 10, thereby reducing the leakage of the sound wave energy.

[0049] Example 4

[0050] Figure 4 This is the fourth common type of resonator we proposed. The piezoelectric resonator structure includes a resonator substrate 1, a resonator piezoelectric layer 5, a resonator cross-upper electrode 6, a low-impedance reflective layer 9, and a high-impedance reflective layer 10. This fourth resonator structure will Figures 1 to 3 The bottom electrode 4 of the resonator plate is removed because for some special piezoelectric materials, such as lithium niobate (LiNbO3) and lithium tantalate (LiTaO3), they have large piezoelectric constants e31 and e51, and the excitation of acoustic waves does not depend on the presence of the bottom electrode. Therefore, removing the bottom electrode here can reduce the complexity of the device structure and the difficulty of the process. The upper electrode 6 of the resonator is a cross-electrode structure. The electrodes are grounded and powered in turn to form a transverse electric field between two adjacent electrodes, thereby exciting longitudinal acoustic waves (through the piezoelectric coefficient e31 or e51). The upper electrode is usually a metal thin film material, such as aluminum, molybdenum, ruthenium, platinum, aluminum, gold, etc., which can be achieved by means of metal dry etching or metal stripping process. The thickness of the metal film is between tens of nanometers and hundreds of nanometers.

[0051] Figures 1 to 4 These are the four types of piezoelectric resonators that can be used to construct filters proposed in this patent. These four resonators can be used to construct terminal (mobile phones, tablets, WiFi, etc.) filters. They can usually carry a power of about 1W, but cannot be directly applied to 5G small base stations (carrying power of 1 to 10W). Here we call them ordinary resonators. Later, we will propose high-power resonators based on these four ordinary resonators, and then construct high-power filters for 5G small base stations.

[0052] This fourth resonator structure will Figures 1 to 3 The bottom electrode 4 of the resonator plate in the figure is removed. The reason is that for some special piezoelectric materials, such as lithium niobate (LiNbO3) and lithium tantalate (LiTaO3), they have large e31 and e51 piezoelectric constants. The excitation of the sound wave does not depend on the existence of the bottom electrode. Therefore, removing the bottom electrode here can reduce the complexity of the device structure and the difficulty of the process. The upper electrode 6 of the resonator is a cross-electrode structure. The above are the four common types of resonators we proposed. These four resonators will serve as the basis for the subsequent construction of high-power resonators and high-power filters. For the convenience of marking, we use the resonator symbol to represent the common resonator, such as Figure 5 Assume Figure 5The static capacitance value of an ordinary resonator is C0. Here we use static capacitance to characterize the electrical performance of a single resonator. We will approximately assume that other performance parameters (such as resonant frequency, coupling coefficient, quality factor, etc.) will not change with the change of C0. Resonators with the same C0 will have the same electrical performance. Normally, the static capacitance of a resonator is related to the electrode area, electrode spacing and dielectric material of the resonator. Because the electrode spacing and dielectric material of the resonator described in this application are fixed in the same batch processing project, and the resonator electrode area can be freely adjusted by photolithography, we will use the resonator electrode area to represent the static capacitance, and the two are linearly related. Figure 5 (b) shows a terminal filter structure constructed with ordinary resonators, which we call a ladder filter structure. It has two sets of resonators, one in series and one in parallel. The series resonators have the same or similar frequencies, while the parallel resonators have a lower frequency than the series resonators. Typically, the anti-resonance frequency of the parallel resonator is approximately equal to the resonant frequency of the series resonator. Terminal filters are limited by the power capacity of ordinary resonators, generally with an input power of 1W or less. They can be used in terminal devices such as mobile phones, laptops, Bluetooth, and WiFi, but cannot be applied to 5G small base stations because the power they need to carry is between 1 and 10W.

[0053] To meet the high power requirements of 5G small base station filters, we need to increase the resonator's carrying power. To this end, we propose a resonator that can carry high power (we will introduce the design principle later), such as Figure 6 As shown, here we use different resonator symbols to represent it. Figure 5 The ordinary resonator has the same static capacitance C0 and other performance parameters (such as resonant frequency, coupling coefficient, quality factor, etc.), so its electrical performance parameters are the same as those of the ordinary resonator. Figure 6 The medium resonator can carry high power. Placing it in a ladder filter structure to replace part or all of the ordinary resonators can greatly increase the filter's carrying power. Figure 6 (d) in the figure introduces several typical replacement schemes, among which Figure 6 Replace a common resonator (assuming that the carrying power of this common resonator is the lowest). In this case, the carrying power of the filter can be appropriately increased. Figure 6 By replacing two common resonators (assuming that the power they can carry is the lowest), the filter's power carrying capacity can be further increased. Figure 6 All the ordinary resonators are replaced in the filter. In this case, the filter can carry the maximum power. Figure 6The filters in (d) are called 5G small base station high power filters. The carrying power of these filters is greater than the carrying power of the terminal filter and can be used in 5G small base stations. Figure 6 The three replacement schemes listed are only examples. The number of ordinary resonators replaced can range from one to all, and can be designed according to actual needs.

[0054] Next we will introduce how to Figure 5 Medium and ordinary resonator implementation Figure 6 As mentioned above, the high power carrying filter has the same static capacitance C0 as the ordinary resonator, so their electrical performance is the same, the difference lies in the power they can carry. Figures 1 to 4 For the four common types of resonators or most acoustic wave resonators, the power that the resonator can withstand depends on the electrode area of ​​the resonator. Generally speaking, the larger the resonator area, the greater the power it can carry. However, simply increasing the area will increase the static capacitance of the resonator, which will in turn change the electrical properties of the resonator. In order to increase the electrode area of ​​the resonator while ensuring that the static capacitance of the resonator remains unchanged, we proposed a "splitting method", such as Figure 7 shown. Figure 7 The resonator on the left is a high-power resonator, and the matrix on the right is the splitting scheme for achieving it (splitting a conventional filter). Each element in the matrix is ​​called a resonator split unit. For example, consider the example split unit labeled 14. This split unit contains three identical resonators, each with a static capacitance of 3C0 (achieved by increasing the electrode area by three times that of a conventional resonator). The overall static capacitance of the three series resonators is still C0. Therefore, the split unit has the same electrical performance as a conventional resonator, but the overall area is nine times that of a conventional resonator, and the power it can theoretically handle should also be nine times that of a conventional resonator. Thus, we have increased the resonator's power handling capacity while maintaining the same electrical performance. This scheme is our proposed "splitting method." In addition to the 1x3 splitting method in example split unit 14, there are many other methods. We present all possible splitting methods in the form of a matrix. The total static capacitance of each split unit in this matrix is ​​C0, with the difference being the static capacitance of the individual resonators in each split unit. When the static capacitance of a single resonator in a split unit is greater than or equal to C0, in other words, the electrode area of ​​a single resonator is greater than or equal to the electrode area of ​​an ordinary resonator, the power that the entire split unit can carry will be greater than or much greater than the power that an ordinary resonator can carry. We set the static capacitance of a single resonator in a split unit to be greater than or equal to C0 as the condition for judging effective splitting, and we can delineate the "effective splitting area", such as Figure 7As shown. The split units in the “effective split area” have the same static capacitance C0 as ordinary resonators, and can carry more power than ordinary resonators. Therefore, we believe that the split units in the “effective split area” are all resonators that can carry high power, that is, Figure 6 The resonator in .

[0055] The static capacitance of the individual resonators in the "effective split area" is greater than or equal to C0, or their electrode area is greater than or equal to the electrode area of ​​the ordinary resonator. As a demonstration, we will introduce the most intuitive method of expanding the electrode area. Figure 8 As shown, Figure 8 (a) in the figure is the symbol, electrode shape, and area of ​​a common resonator. The static capacitance of a common resonator is C0, and the corresponding electrode area is S0. The electrode shape can generally be a variety of shapes, such as square, pentagon, semi-ellipse, cross electrode, etc. If we need to double the electrode area to obtain double the static capacitance, we can change the electrode area to Figure 8 The uniform expansion of (b) is 2 times, or similarly, Figure 8 In (c), the static capacitance is increased by 4 times.

[0056] Figure 8 The expansion of the middle electrode area is a uniform expansion in all directions, which is the most intuitive and direct approach in the traditional sense. However, this method is not the best way to expand the carrying power. When the resonator or filter is working, the power loaded on the resonator will generate heat. For the electrodes that are uniformly expanded in all directions, the heat will diffuse evenly in all directions because the distances in all directions are equal. If the distance of heat transmission can be shortened and the heat can be dissipated at a faster rate, the power carried by the resonator will be further increased. To achieve this goal, we propose an electrode shape suitable for rapid heat dissipation, such as Figure 9 As shown. Let’s take the 4C0 resonator with a 4-fold increase in electrode area as an example. If the electrode shape of a common resonator (static capacitance is C0) is square or quasi-square, then Figure 9 (a) in the figure is a possible solution for electrode expansion. Here we define the aspect ratio AR of the electrode as the ratio of the longitudinal length to the transverse length of the electrode. Figure 9 The electrode expansion scheme in (a)-(i) is a uniform expansion scheme, the longitudinal length L of the electrode is equal to the transverse length of the electrode, and the aspect ratio AR of the electrode is 1. Next, we consider the cases where AR is 2 and 4, respectively. Figure 9 (a)-(ii) and Figure 9As shown in (a)-(iii) in the figure. Assuming that the heat source point is at the center of the resonator and the filter when they are working, the heat source point is at the center of the resonator. After the heat is generated at the center point, it will spread in all directions. When the heat spreads to the edge of the electrode, it will be absorbed by the metal of the connecting piece (usually a metal with a very thick thickness and good thermal conductivity). When AR = 1, the heat transfer distance is d (d = W / 2); when AR = 2, the heat transfer distance is 0.7d; when AR = 4, the heat transfer distance is 0.5d. It can be seen that the larger the AR, the shorter the heat transfer distance and the faster the dissipation, so the power that the resonator can withstand is also correspondingly higher. Therefore, when expanding the capacitance or designing the electrode shape of a conventional resonator, the optimal electrode design scheme is to choose an electrode shape with a larger AR as much as possible (of course, because the resonator is also subject to other performance parameters and size restrictions, AR cannot be designed to be infinitely large). Figure 9 (b) and Figure 9 (c) is the corresponding electrode expansion scheme when the electrode shape of the common resonator is a regular pentagon or a quasi-pentagon, a semi-ellipse or a quasi-semi-ellipse, which is the same as Figure 9 Similar to the case (a) in Figure 3, the larger electrode shape of AR can dissipate heat faster.

[0057] like Figure 1-9 As shown, the present invention increases the electrode area of ​​ordinary resonators by proposing a splitting method, thereby increasing the power carrying capacity of the resonator while maintaining the electrical performance of the resonator unchanged. The high-power resonator formed is the core structural unit of the 5G small base station filter; the present invention uses a matrix listing method to represent all possible splitting schemes and provides an effective splitting area. The splitting schemes in this area can achieve the purpose of maintaining the electrical performance of the resonator unchanged and increasing the power carrying capacity. The effective splitting area provided by the present invention points out the direction for a variety of splitting schemes; the present invention replaces ordinary resonators with high-power resonators through a resonator replacement method, thereby constructing a 5G small base station high-power filter. In addition, one or more or even all ordinary resonators can be replaced according to actual needs. The replacement scheme proposed by the present invention has the advantages of simplicity and flexibility; the present invention provides an optimal electrode shape scheme through the aspect ratio analysis of the resonator electrode shape, thereby further increasing the power carrying capacity of the high-power resonator or filter. The aspect ratio analysis conclusion given by the present invention further lays the foundation for solving the power problem of the 5G small base station filter.

[0058] In the description of this application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and 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, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application.

[0059] The above describes specific embodiments of the present invention. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. The embodiments of this application and the features in the embodiments may be combined with each other in any manner unless there is a conflict.

Claims

1. A 5G small base station radio frequency acoustic wave filter, characterized in that: The device comprises at least one high-power piezoelectric resonator, wherein the high-power piezoelectric resonator comprises a single row or multiple rows of ordinary resonators connected in parallel, and each row of ordinary resonators comprises a plurality of ordinary resonators connected in series in sequence; Assuming that the static capacitance of the high-power-carrying piezoelectric resonator is C0, the static capacitance of a single common resonator in the high-power-carrying piezoelectric resonator is greater than or equal to C0; The conventional resonator comprises a resonator substrate (1), a resonator piezoelectric layer (5), a resonator upper electrode, and a reflective member; The resonator substrate (1) is arranged at the bottom of a 5G small base station radio frequency acoustic wave filter; The resistance of the resonator substrate (1) is greater than a set threshold; The resonator piezoelectric layer (5) is made of piezoelectric thin film material; The resonator upper electrode is arranged on the upper part of the 5G small base station radio frequency acoustic wave filter; The reflective component is arranged in the middle of the 5G small base station radio frequency acoustic wave filter; The resonator piezoelectric layer (5) is arranged on the upper part of the 5G small base station radio frequency acoustic wave filter; It also includes: a sacrificial layer (2), a protective layer (3), and a resonator plate bottom electrode (4); The reflecting component adopts an air reflecting cavity (7); The sacrificial layer (2) is formed on the resonator substrate (1); the thickness of the sacrificial layer (2) is equal to the thickness of the air reflection cavity (7); The protective layer (3) is formed in the sacrificial layer (2) and is located between the air reflection cavity (7) and the sacrificial layer (2).

2. The 5G small base station radio frequency acoustic wave filter according to claim 1, characterized in that The resonator substrate (1) is any one of the following: - sapphire substrate; -Silicon carbide substrate; -Single crystal silicon substrate; -High-resistance silicon substrate; The sacrificial layer (2) is any one of the following: - Materials removed by wet etching; -Material removed by dry etching.

3. The 5G small base station radio frequency acoustic wave filter according to claim 1, characterized in that The resonator flat bottom electrode (4) adopts a flat plate structure; An excitation electric field is formed between the resonator plate bottom electrode (4) and the resonator plate top electrode (6); The excitation electric field can excite acoustic waves in the resonator piezoelectric layer (5); The resonator plate bottom electrode (4) is connected in any of the following ways: - grounding; -Connecting to electricity The resonator plate bottom electrode (4) is made of a metal film; The resonator plate bottom electrode (4) is any one of the following: - Molybdenum thin film; -Ruthenium film; -Platinum thin film; The thickness of the resonator plate bottom electrode (4) is less than a set threshold; The resonator piezoelectric layer (5) adopts any one of the following: - lithium niobate; - lithium tantalate; -aluminum nitride; - doped aluminum nitride; -Barium strontium titanate.

4. The 5G small base station radio frequency acoustic wave filter according to claim 3, characterized in that The resonator upper electrode adopts the resonator plate upper electrode (6).

5. The 5G small base station radio frequency acoustic wave filter according to claim 4, characterized in that: The resonator plate upper electrode (6) adopts a flat plate structure; The resonator plate upper electrode (6) adopts any one of the following connection methods: - grounding; -Connect to electricity; The resonator plate upper electrode (6) is usually required to be cross-connected or grounded with the bottom electrode 4 to form an electric field; The resonator plate upper electrode (6) is a metal thin film electrode; The resonator plate upper electrode (6) is any one of the following: - Molybdenum electrodes; - Ruthenium electrodes; -Platinum electrodes; -Aluminum electrodes; -Gold electrodes.

6. The 5G small base station radio frequency acoustic wave filter according to claim 3, characterized in that The resonator upper electrode adopts: a resonator cross upper electrode (8); The resonator cross upper electrode (8) adopts any one of the following connection methods: - grounding; -Connect to electricity; - The cross electrodes are alternately connected to power and ground.

7. The 5G small base station radio frequency acoustic wave filter according to claim 1, characterized in that Also includes: a resonator plate bottom electrode (4); The reflecting component adopts a mirror reflector (11); The resonator upper electrode adopts the resonator plate upper electrode (6); The mirror reflector (11) comprises: one or more low-impedance reflection layers (9); The mirror reflector (11) comprises: one or more high-impedance reflection layers (10); The plurality of low-impedance reflective layers (9) and the plurality of high-impedance reflective layers (10) form a specular reflector (11).

8. The 5G small base station radio frequency acoustic wave filter according to claim 7, characterized in that: The number of layers of the low-impedance reflective layer (9) is one or more layers; the number of the low-impedance reflective layer 9 is generally multiple layers; The low-impedance reflective layer (9) is arranged below the resonator plate bottom electrode (4); The low-impedance reflective layer (9) is a low-acoustic-wave-impedance reflective layer; The low-impedance reflective layer (9) is a silicon dioxide reflective layer.

9. The 5G small base station radio frequency acoustic wave filter according to claim 8, characterized in that: The high-impedance reflective layer (10) is any one of the following: - tungsten reflective layer; - Platinum reflective layer; -Silicon nitride reflective layer; - Aluminum nitride reflective layer.

10. The 5G small base station radio frequency acoustic wave filter according to claim 1, characterized in that: The resonator upper electrode adopts: a resonator cross upper electrode (8); The electrodes of the cross-top electrode (8) of the resonator are respectively connected to the ground and the power in turn; The reflecting component comprises: a mirror reflector (11); The specular reflector (11) comprises: one or more low-impedance reflective layers (9); The mirror reflector (11) comprises: one or more high-impedance reflection layers (10); The plurality of low-impedance reflective layers (9) and the plurality of high-impedance reflective layers (10) form a specular reflector (11).

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