Miniaturized dielectric filter and production process thereof

Abstract

The invention relates to a miniaturized dielectric filter and a production process thereof, the miniaturized dielectric filter comprises a ceramic filter body and a ceramic cover plate, a plurality of columnar through holes are formed in the ceramic filter body at intervals, columnar through hole conducting layers are arranged on the inner walls of the columnar through holes, and the columnar through hole conducting layers are electrically connected; the ceramic cover plate is assembled at one end of the ceramic filter body in a sealed mode, a plurality of bonding pad assemblies corresponding to the columnar through holes in a one-to-one mode are arranged between the ceramic filter body and the lower end face of the ceramic cover plate, and blind hole cavities communicated with the columnar through holes are formed in the bonding pad assemblies. And a blind hole conductive layer electrically connected with the columnar through hole conductive layer is arranged in the blind hole cavity. The ceramic cover plate is sealed in the ceramic filter body, so that an electromagnetic field is completely wrapped in the ceramic dielectric, a strong electric field area between the resonance disc and the external shielding cover and the discharge risk are eliminated, and meanwhile, an effective capacitance effect can be generated between the blind hole conducting layer and the frequency modulation hole, so that the resonance frequency is reduced, and the miniaturization of the filter is realized.

Description

Technical Field

[0001] This application relates to the field of filter technology, and in particular to a miniaturized dielectric filter and its manufacturing process. Background Technology

[0002] A dielectric filter is a microwave filter that uses a resonator made of a high dielectric constant material (such as ceramic) to achieve frequency selection. It is widely used in communication systems and has advantages such as small size, low loss, and good temperature stability.

[0003] The prior art involves a frequency modulation filter, including a cavity, a limiting plate, a resonant rod, and a driving device. The limiting plate is fastened to the top of the cavity, and the connection between the driving device and each frequency modulation gear can realize synchronous frequency modulation of each resonant cavity of the filter or frequency modulation of a single resonant cavity.

[0004] However, the aforementioned and existing filters, which use metal shields as shielding carriers, cannot generate effective capacitance when applied to high-frequency bands such as U-band and L-band. They are also bulky, and during high-power operation, the electric field strength between the metal shield and the resonant disk is high, making them prone to arcing. Summary of the Invention

[0005] This application provides a miniaturized dielectric filter and its manufacturing process, which can solve the problems of existing dielectric filters, which are prone to electric field concentration and arcing under high power due to the use of metal shielding, thus limiting the power capacity; at the same time, in order to achieve a specific resonant frequency, their physical size is relatively large, making it difficult to meet the miniaturization requirements.

[0006] The technical solution of this application is as follows: A miniaturized dielectric filter, comprising: A ceramic filter body, wherein multiple columnar through holes are spaced apart inside the ceramic filter body, and a columnar through hole conductive layer is provided on the inner wall of the columnar through hole, and the multiple columnar through hole conductive layers are electrically connected to each other. A ceramic cover plate is sealed and assembled at one end of the ceramic filter body. A plurality of pad assemblies corresponding to columnar through holes are provided between the ceramic filter body and the lower end face of the ceramic cover plate. The pad assembly has a blind hole cavity communicating with the columnar through holes. The blind hole cavity has a blind hole conductive layer electrically connected to the conductive layer of the columnar through holes. The blind hole conductive layer and the internal cavity of the columnar through hole conductive layer combine to form a resonant cavity to generate a resonant frequency. The upper surface of the ceramic cover plate is provided with a plurality of frequency tuning holes corresponding one-to-one with the pad assembly. The frequency tuning holes, blind holes and columnar through holes are located on the same axis. The frequency tuning holes are configured to combine with the blind hole conductive layer to form a frequency tuning capacitor to reduce the resonant frequency.

[0007] By adopting the above scheme, by removing the metal shielding cover in conventional filters and sealing the ceramic filter body with a ceramic cover plate, the electromagnetic field is completely enclosed inside the ceramic medium. This fundamentally eliminates the strong electric field region and discharge risk between the resonant disk and the external shielding cover, resulting in a significant increase in the power capacity of the filter. At the same time, the blind hole conductive layer under the ceramic cover plate itself generates an effective capacitance effect between it and the tuning hole. This added capacitance can reduce the resonant frequency, allowing the device to use a smaller ceramic body under the same frequency requirements, thereby achieving filter miniaturization.

[0008] In one embodiment of this application, the pad assembly includes: The first pad is embedded on the lower end face of the ceramic cover plate, and a blind hole section is formed on the lower end face of the first pad. The second pad is mounted on the upper surface of the ceramic filter body and corresponds to the position of the first pad. The second pad has a circular hole inside, which communicates with the blind hole section to form the blind hole cavity. The second pad and the first pad are soldered together with silver paste.

[0009] By adopting the above solution, the first pad and the second pad are soldered together with silver paste, so that the first pad can be sealed and connected to the second pad. At the same time, the electrical connection stability of the first pad and the second pad is guaranteed, so that the ceramic cover plate can form a seamless integrated component with the ceramic filter body.

[0010] In one embodiment of this application, the inner wall of the blind hole segment and the inner wall of the round hole are respectively provided with a blind hole silver layer and a round hole silver layer. The blind hole silver layer and the round hole silver layer are combined to form the blind hole conductive layer. The blind hole silver layer is electrically connected to the round hole silver layer through the contact of the first pad and the second pad. The columnar through-hole conductive layer is a cylindrical silver component. The upper end of the columnar through-hole conductive layer is electrically connected to the round hole silver layer, and the lower end is grounded. The multiple columnar through-hole conductive layers are electrically connected to each other.

[0011] By adopting the above scheme, a columnar through-hole conductive layer is set on the inner wall of the columnar through-hole. After the power supply is connected, the lower end of the columnar through-hole conductive layer is grounded, forming a short-circuit boundary, which will generate strong electromagnetic wave reflection. The current is conducted to the blind hole conductive layer, forming an approximately open-circuit boundary, which will also generate strong reflection. This causes the electromagnetic waves to reflect back and forth, forming a stable standing wave and generating resonance. At the same time, the positions between multiple columnar through-hole conductive layers can be adjusted to make them inductively coupled to each other. Energy exchange and interaction can be carried out through electric or magnetic fields, combining the characteristics of multiple resonant cavities to form a complete filter with a specific bandwidth and steep edges.

[0012] In one embodiment of this application, the frequency modulation hole is a blind hole structure, and a frequency modulation silver layer is provided on the inner wall of the bottom end of the frequency modulation hole. The frequency modulation capacitor is formed between the frequency modulation silver layer, the ceramic cover plate and the blind hole silver layer to reduce the resonant frequency.

[0013] By adopting the above scheme, since the blind via silver layer is mounted on the first pad and electrically connected to the second pad, the potential of the frequency-modulated silver layer is close to zero when current is applied. The blind via silver layer has a high potential relative to the frequency-modulated silver layer. The portion of the ceramic cover plate located between the blind via silver layer and the frequency-modulated silver layer acts as a capacitor dielectric, thereby forming a capacitor loaded on the resonant cavity, thus reducing the resonant frequency of the entire resonant cavity. This means that under the same frequency requirement, a smaller ceramic body can be used, thereby achieving miniaturization of the filter. At the same time, when it is necessary to change the frequency, the distance between the blind via silver layer and the frequency-modulated silver layer can also be changed by improving the depth of the entire frequency-modulated hole, thereby changing the capacitor loaded by the device.

[0014] In one embodiment of this application, the ceramic filter body has an input port and an output port at both ends on one side, and the input port and the output port are electrically connected to the middle of two of the columnar through-hole conductive layers through conductive elements.

[0015] By adopting the above scheme, when the device is in use, external electromagnetic wave signals can be input into the device through the input port using the input port and the output port, so that the signal can be resonated by the resonant cavity and then the electromagnetic wave signal of a specific band can be output to the outside of the device through the output port.

[0016] In one embodiment of this application, the ceramic filter body includes an outer metal layer and a ceramic package. The outer metal layer is disposed on the outer surface of the ceramic package. The columnar through-hole is formed inside the ceramic package and extends along the length direction of the ceramic package. The lower end of the conductive layer of the columnar through-hole is connected to the outer metal layer.

[0017] By adopting the above scheme, an outer metal layer is set outside the ceramic package, and the lower end of the columnar through-hole conductive layer can be connected to the outer metal layer. This allows the lower end of the columnar through-hole conductive layer to be grounded, and the upper end to be connected to the circuit. The high potential at the upper end can form a capacitor with the silver layer inside the tuning hole, and the grounding at the lower end can also form a resonant cavity coaxial with the capacitor between it and the blind hole conductive layer. This enables the device to form a coaxial resonant device with a loaded capacitor, which facilitates the miniaturization of the device and improves the power capacity.

[0018] In one embodiment of this application, a grounding silver layer is further included. The grounding silver layer is disposed on the upper surface of the ceramic filter body. The surface of the grounding silver layer has multiple cutouts. The pad assembly is located at the cutouts. The grounding silver layer is connected to the outer metal layer.

[0019] By adopting the above scheme, the grounding silver layer is connected to the outer metal layer to form an integrated Faraday cage, thereby achieving the same electrostatic shielding function. Combined with the sealing effect of the entire ceramic component, the interference of external electromagnetic fields on the electromagnetic fields inside the ceramic package is greatly reduced. In addition, the hollowed-out grounding silver layer will not connect to the solder pad assembly, thus avoiding short circuits.

[0020] The second objective of this invention is to provide a manufacturing process for miniaturized dielectric filters.

[0021] To achieve the above objectives, the technical solution of this application is as follows: A manufacturing process for a miniaturized dielectric filter, comprising the following steps: The ceramic powder is dry-pressed and then sintered to prepare the ceramic filter body and ceramic cover plate. After sintering, the ceramic filter body and ceramic cover plate are ultrasonically cleaned, and the inner walls of the tuning holes, blind holes, round holes and columnar through holes are silver-plated. The silver-plated ceramic cover plate and the ceramic filter body are sealed into an integrated structure by a high-temperature silver welding process. According to the preset resonant frequency index, the depth of the tuning hole and the area of ​​the tuning silver layer are pre-processed.

[0022] In the above technical solution, by removing the conventional metal shield and replacing it with a ceramic cover plate, and by metallizing the ceramic cover plate, the volume used to generate resonance is highly consistent with the actual volume of the device, thereby indirectly achieving miniaturization of the device. At the same time, the resonant frequency of the device can be changed by adjusting the area of ​​the frequency-modulating silver layer according to the production needs of the device, thereby changing the capacitance value loaded into the circuit.

[0023] In summary, this application includes at least one of the following beneficial technical effects: 1. By replacing the metal cover with a ceramic cover plate and completely enclosing the electromagnetic field inside the ceramic medium, the strong electric field region and discharge risk between the resonant disk and the external shielding cover are fundamentally eliminated, which greatly improves the power tolerance of the filter.

[0024] 2. By metallizing the ceramic cover plate itself, it forms an effective capacitance effect in conjunction with the pad assembly below. This added capacitance can lower the resonant frequency, which means that a smaller ceramic body can be used under the same frequency requirements, thereby achieving filter miniaturization.

[0025] 3. By designing frequency holes on the ceramic cover plate, the distance between the cover plate and the metal resonant disk below can be changed by adjusting the depth of these holes. At the same time, the area of ​​the frequency tuning silver layer can also be ground off. Both methods can fine-tune the capacitor size to accurately tune the resonant frequency. This design can effectively compensate for the frequency deviation caused by production tolerances and ensure the first-pass yield of the product.

[0026] 4. By setting a metallized blind cavity, it can form a resonant cavity with the conductive layer of the through hole, and can also form a capacitor loaded into the circuit with the silver layer inside the tuning hole. Its highly coaxial design allows the shielding structure and the resonant structure to be integrated into one design. A ceramic cover plate that combines shielding, capacitance generation and frequency tuning functions can be used to synergistically improve the power capacity of the filter, reduce the physical size and simplify the frequency tuning process in production.

[0027] 5. The upper and lower ceramic bodies are completely sealed and welded using silver paste, which protects the internal grounding silver layer and solder pad components from the effects of external environmental moisture, oxidation, etc., thereby improving the stability and reliability of the product. Attached Figure Description

[0028] Figure 1 This is a perspective view of a miniaturized dielectric filter provided in an embodiment of this application; Figure 2 This is a three-dimensional exploded view of a miniaturized dielectric filter provided in the embodiments of this application; Figure 3 This is a planar cross-sectional view of a miniaturized dielectric filter provided in an embodiment of this application; Figure 4 yes Figure 3 An enlarged schematic diagram of part A in the middle; Figure 5 This is a test chart of the performance of a miniaturized dielectric filter provided in the embodiments of this application.

[0029] Explanation of reference numerals in the attached drawings: 1. Ceramic filter body; 11. Columnar through-hole; 12. Columnar through-hole conductive layer; 13. Input port; 14. Output port; 15. Ceramic package; 16. Outer metal layer; 2. Ceramic cover plate; 21. Frequency modulation hole; 211. Frequency modulation silver layer; 3. Pad assembly; 31. First pad; 311. Blind via segment; 312. Blind via silver layer; 32. Second pad; 321. Circular hole; 322. Circular hole silver layer; 33. Blind via cavity; 34. Blind via conductive layer; 4. Grounding silver layer. Detailed Implementation

[0030] The following is in conjunction with the appendix Figures 1-5 This application provides a detailed description of a miniaturized dielectric filter and its manufacturing process.

[0031] This application provides a miniaturized dielectric filter, comprising: a ceramic filter body and a ceramic cover plate.

[0032] Please see Figure 1 and Figure 2 The ceramic filter body 1 has multiple columnar through holes 11 spaced apart inside. Each columnar through hole 11 has a columnar through hole conductive layer 12 on its inner wall. These columnar through hole conductive layers 12 are electrically connected. A ceramic cover plate 2 is sealed and assembled at one end of the ceramic filter body 1. Multiple pad assemblies 3, corresponding one-to-one with the columnar through holes 11, are arranged between the lower end faces of the ceramic filter body 1 and the ceramic cover plate 2. Each pad assembly 3 has a blind via cavity 33 communicating with the columnar through holes 11. The blind via cavity 33 has a blind via conductive layer 34 electrically connected to the columnar through hole conductive layer 12. The blind via conductive layer 34 and the internal cavity of the columnar through hole conductive layer 12 combine to form a resonant cavity to generate a resonant frequency. The upper surface of the ceramic cover plate 2 is provided with a plurality of frequency tuning holes 21 corresponding one-to-one with the pad assembly 3. The frequency tuning holes 21, blind holes 33 and columnar through holes 11 are located on the same axis. The frequency tuning holes 21 are configured to combine with the blind hole conductive layer 34 to form a frequency tuning capacitor to reduce the resonant frequency. By removing the metal shield in the conventional filter, the strong electric field region and discharge risk between the resonant disk and the external shield are fundamentally eliminated, which greatly increases the power capacity of the filter from 1-5W to 15-25W. At the same time, an effective capacitance effect is generated between the blind hole conductive layers 34 under the ceramic cover plate 2 itself, which allows the device to use a smaller ceramic body under the same frequency requirements, thereby realizing the miniaturization of the filter.

[0033] Please see Figure 3 and Figure 4The pad assembly 3 includes a first pad 31 and a second pad 32. The first pad 31 is embedded on the lower end face of the ceramic cover plate 2. A blind hole segment 311 is formed on the lower end face of the first pad 31. The second pad 32 is assembled on the upper end face of the ceramic filter body 1 and corresponds to the position of the first pad 31. A circular hole 321 is formed inside the second pad 32. The circular hole 321 communicates with the blind hole segment 311 to form the blind hole cavity 33. The second pad 32 and the first pad 31 are soldered together with silver paste. By soldering the first pad 31 and the second pad 32 together with silver paste, the electrical connection stability of the first pad 31 and the second pad 32 is ensured, so that the ceramic cover plate 2 can be soldered more tightly to the ceramic filter body 1.

[0034] Please continue reading. Figure 3 and Figure 4 The inner walls of the blind via segment 311 and the inner walls of the circular via 321 are respectively provided with a blind via silver layer 312 and a circular via silver layer 322. The blind via silver layer 312 and the circular via silver layer 322 are combined to form the blind via conductive layer 34. The blind via silver layer 312 is electrically connected to the circular via silver layer 322 through the contact of the first pad 31 and the second pad 32. The columnar via conductive layer 12 is a cylindrical silver component. The upper end of the columnar via conductive layer 12 is electrically connected to the circular via silver layer 322, and the lower end is grounded. Multiple columnar via conductive layers 12 are connected to each other. The components are electrically connected by forming a columnar through-hole conductive layer 12 on the inner wall of the columnar through-hole 11. After power is connected, the columnar through-hole conductive layer 12 is connected to the blind hole silver layer 312 and the round hole silver layer 322, thereby forming a resonant cavity that can generate resonance to meet the resonance requirements of the device. In addition, the positions of multiple columnar through-hole conductive layers 12 can be adjusted to make the multiple columnar through-hole conductive layers 12 mutually inductively coupled, combining the characteristics of multiple resonant cavities to form a complete filter with a specific bandwidth and steep edges.

[0035] Please see Figure 4 The frequency modulation hole 21 is a blind hole structure. A frequency modulation silver layer 211 is provided on the inner wall of the bottom end of the frequency modulation hole 21. The frequency modulation capacitor is formed between the frequency modulation silver layer 211, the ceramic cover plate 2 and the blind hole silver layer 312 to reduce the resonant frequency. By setting the frequency modulation capacitor on the frequency modulation hole 21, a component with a capacitive effect is formed between it and the blind hole silver layer 312, thereby reducing the resonant frequency of the device. At the same time, when it is necessary to change the frequency, the distance between the blind hole silver layer 312 and the frequency modulation silver layer 211 can also be changed by improving the depth of the entire frequency modulation hole 21 or the area of ​​the frequency modulation silver layer 211, thereby changing the capacitance loaded by the device.

[0036] Please see Figure 1The ceramic filter body 1 has an input port 13 and an output port 14 at both ends on one side. The input port 13 and the output port 14 are electrically connected to the middle of two of the columnar through-hole conductive layers 12 through conductive components. By setting the input port 13 and the output port 14 in the middle of the columnar through-hole conductive layer 12, it is easy to form a potential difference between the two ends of the columnar through-hole conductive layer 12, so that the device can form a resonant cavity and a loaded capacitor.

[0037] Please see Figure 3 The ceramic filter body 1 includes an outer metal layer 16 and a ceramic package 15. The outer metal layer 16 is disposed on the outer surface of the ceramic package 15. The columnar through hole 11 is opened inside the ceramic package 15 and extends along the length direction of the ceramic package 15. The lower end of the columnar through hole conductive layer 12 is connected to the outer metal layer 16. By disposing of the outer metal layer 16 outside the ceramic package 15, the columnar through hole conductive layer 12 can be grounded so that a resonant cavity can be formed inside the columnar through hole 11.

[0038] The second objective of this invention is to provide a manufacturing process for miniaturized dielectric filters.

[0039] The technical solution is as follows: A manufacturing process for a miniaturized dielectric filter, comprising the following steps: The ceramic powder is dry-pressed and then sintered to prepare the ceramic filter body 1 and the ceramic cover plate 2. After sintering, the ceramic filter body 1 and ceramic cover plate 2 are ultrasonically cleaned, and the inner walls of the tuning hole 21, blind hole section 311, round hole 321 and columnar through hole 11 are silver-plated. The silver-plated ceramic cover plate 2 and the ceramic filter body 1 are sealed into an integrated structure by a high-temperature silver welding process. According to the preset resonant frequency index, the depth of the tuning hole 21 and the area of ​​the tuning silver layer 211 are pre-processed.

[0040] The area of ​​the frequency-modulated silver layer can be changed by means of chemical corrosion or laser ablation. The specific operation steps are conventional techniques for those skilled in the art and will not be described in detail here.

[0041] For the test results, please refer to [link / reference]. Figure 5 By removing the conventional metal shield and using a ceramic cover plate 2 that is integrated with the ceramic filter body 1, the power capacity can be effectively increased. At the same time, the resonant frequency of the device can be improved more accurately, which facilitates the miniaturization of the device and enables the device to perform better in the high-frequency band.

[0042] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A miniaturized dielectric filter characterized by, The application relates to a ceramic filter body (1) internally provided with a plurality of columnar through holes (11), the inner wall of the columnar through holes (11) is provided with columnar through hole conductive layers (12), and the columnar through hole conductive layers (12) are electrically connected. A ceramic cover plate (2) is sealed and assembled at one end of the ceramic filter body (1), a plurality of pad assemblies (3) corresponding to the columnar through holes (11) are arranged between the ceramic filter body (1) and the lower end surface of the ceramic cover plate (2), the pad assembly (3) is internally provided with a blind hole cavity (33) communicated with the columnar through hole (11), the blind hole cavity (33) is internally provided with a blind hole conductive layer (34) electrically connected with the columnar through hole conductive layer (12), and the blind hole conductive layer (34) and the internal cavity of the columnar through hole conductive layer (12) are combined to form a resonance cavity to generate a resonance frequency. The upper end surface of the ceramic cover plate (2) is provided with a plurality of frequency modulation holes (21) corresponding to the pad assemblies (3), the frequency modulation holes (21), the blind hole cavity (33) and the columnar through hole (11) are located on the same axis, and the frequency modulation holes (21) are configured to combine the blind hole conductive layer (34) to form a frequency modulation capacitor to reduce the resonance frequency. The pad assembly (3) comprises:

2. The miniaturized dielectric filter according to claim 1, characterized in that: A first pad (31) embedded on the lower end surface of the ceramic cover plate (2), and a blind hole section (311) is formed on the lower end surface of the first pad (31); A second pad (32) assembled on the upper end surface of the ceramic filter body (1) and corresponding to the position of the first pad (31), a circular hole (321) is formed in the second pad (32), the circular hole (321) is communicated with the blind hole section (311) to form the blind hole cavity (33), and the second pad (32) is silver paste welded with the first pad (31). The inner wall of the blind hole section (311) and the inner wall of the circular hole (321) are respectively provided with a blind hole silver layer (312) and a circular hole silver layer (322), the blind hole silver layer (312) and the circular hole silver layer (322) are combined to form the blind hole conductive layer (34), the blind hole silver layer (312) is electrically connected with the circular hole silver layer (322) through the contact of the first pad (31) and the second pad (32), the columnar through hole conductive layer (12) is a cylindrical silver member, the upper end of the columnar through hole conductive layer (12) is electrically connected with the circular hole silver layer (322), the lower end is grounded, and the columnar through hole conductive layers (12) are electrically connected with each other.

3. The miniaturized dielectric filter according to claim 2, wherein: The frequency modulation hole (21) is a blind hole structure, a frequency modulation silver layer (211) is arranged on the inner wall of the bottom end of the frequency modulation hole (21), the frequency modulation silver layer (211), the ceramic cover plate (2) and the blind hole silver layer (312) form the frequency modulation capacitor to reduce the resonance frequency.

4. The miniaturized dielectric filter according to claim 3, wherein: ​ 5. The miniaturized dielectric filter according to claim 1, wherein: The ceramic filter body (1) is provided with an input port (13) and an output port (14) at both ends of one side, respectively, and the input port (13) and the output port (14) are electrically connected with the middle part of two columnar through hole conductive layers (12) through conductive parts, respectively.

6. The miniaturized dielectric filter according to claim 1, wherein: The ceramic filter body (1) comprises an outer metal layer (16) and a ceramic package (15), the outer metal layer (16) is arranged on the outer surface of the ceramic package (15), the columnar through hole (11) is arranged in the ceramic package (15) and extends along the length direction of the ceramic package (15), and the lower end of the columnar through hole conductive layer (12) is connected with the outer metal layer (16).

7. The miniaturized dielectric filter according to claim 6, wherein: Further comprising a ground silver layer (4), the ground silver layer (4) is arranged on the upper end surface of the ceramic filter body (1), the surface of the ground silver layer (4) is provided with multiple hollows, the pad assembly (3) is located in the hollow, and the ground silver layer (4) is connected with the outer metal layer (16).

8. A production process of a miniaturized dielectric filter for producing a miniaturized dielectric filter as claimed in any one of claims 1 to 7, characterized in that, The method comprises the following steps: The ceramic powder is dry-pressed and then sintered to prepare a ceramic filter body (1) and a ceramic cover plate (2); The sintered ceramic filter body (1) and the ceramic cover plate (2) are ultrasonically cleaned, and the frequency adjustment hole (21), the blind hole section (311), the round hole (321) and the inner wall of the columnar through hole (11) are silver-plated; The silver-plated ceramic cover plate (2) and the ceramic filter body (1) are sealed into an integrated structure through high-temperature silver welding process; According to the preset resonant frequency index, the depth of the frequency adjustment hole (21) and the area of the frequency adjustment silver layer (211) are preprocessed. According to the preset resonant frequency index, the depth of the frequency adjustment hole (21) and the area of the frequency adjustment silver layer (211) are preprocessed.

Images