A filter

Abstract

The present application provides a kind of filter, comprising: printed circuit board, the printed circuit board includes dielectric plate and the metal layer covering the two side surfaces of dielectric plate;And metal loading cavity, the metal loading cavity is enclosed by metal perimeter wall and metal bottom wall, to form the hollow cavity with opening in top, the metal loading cavity is fixed to the printed circuit board with its opening towards the direction of printed circuit board;The metal layer of the side surface of the printed circuit board towards the metal loading cavity has hollowing-out corresponding to the opening, the dielectric plate is from the hollowing-out and the hollow cavity is connected, to form resonant cavity in combination.

Description

Technical Field

[0001] This invention relates to a filter. Background Technology

[0002] Substrate integrated waveguide (SIW) is a new type of transmission line structure based on printed circuit board (PCB) material that has been developed in recent years. It is widely used in microwave integrated circuits (MMIC) in the millimeter wave (mmWave) band, covering frequencies from about 6 GHz to over 100 GHz.

[0003] SIW transmission line-based filter design applications have emerged as a result. SIW filters fabricate resonators on a PCB, and the cascaded, mutually coupled resonators form the filtering characteristics. They are characterized by miniaturization, simple manufacturing process, and integration with active control / active RF circuits. Such SIW filters are widely used in millimeter-wave RF front-end design.

[0004] The problem with traditional SIW filters is that their resonators have a very low unloaded Q value, Qu. Traditional SIW filters cannot be applied to the broader demands of mobile communication RF front-ends, especially commercial mobile communication RF front-ends (RRUs, Radio Remote Units) below 6 GHz. Mobile communication RRUs below 6 GHz require filters that demand low loss, and their resonator Qu requirements are often greater than 1000.

[0005] Therefore, most traditional filters below 6GHz use a metal coaxial resonator structure. The entire filter is fabricated from metal components, including a metal cavity, metal resonant pillars, a metal cover plate with frequency / coupling tuning screws, and input / output coupling structures. Its advantages are high Qu values ​​(often greater than 1000) and ease of fabrication. The disadvantage is the need for independently fabricated metal components, making integration with other circuits difficult. Consequently, it's difficult for RRUs below 6GHz to integrate their required filters with other active control and active RF circuits onto a single PCB board, making it impossible to create integrated modules similar to microwave integrated circuits (MMICs). Instead, the filters must be separated and installed as individual components in the RF front-end, connected using RF connectors or cables, resulting in large size (especially in height) and low integration.

[0006] In summary, traditional SIW filters are characterized by their small size and ability to be made into microwave integrated circuits, but their disadvantage is that their low Qu value cannot meet the low loss requirements. On the other hand, traditional metal coaxial cavity filters have the advantage of high Qu value and can be used in RRUs below 6GHz. However, their disadvantage is that they are large in size and are often metal-machined and assembled parts, making them difficult to integrate with other circuit components of the RRU. Summary of the Invention

[0007] To address the above technical problems, this invention provides a filter that combines a metal loading cavity with a printed circuit board, which not only improves the filter's unloaded Q value but also significantly reduces the filter's size and manufacturing cost.

[0008] One embodiment provides a filter, including:

[0009] A printed circuit board, the printed circuit board comprising a dielectric substrate and metal layers covering both surfaces of the dielectric substrate; and

[0010] A metal loading cavity, which is formed by a metal peripheral wall and a metal bottom wall to form a hollow cavity with an opening at the top, is fixed to the printed circuit board with its opening facing the printed circuit board.

[0011] The metal layer on the side surface of the printed circuit board facing the metal loading cavity has a cutout corresponding to the opening, and the dielectric plate is connected to the hollow cavity through the cutout to form a resonant cavity.

[0012] In one embodiment, a circuit board resonant cavity corresponding to the metal loading cavity is formed within the dielectric substrate, and the edge of the circuit board resonant cavity is formed by metallized vias that are connected to the metal layers on both sides, and the metallized vias are arranged in parallel at intervals.

[0013] In one embodiment, it includes:

[0014] Multiple metal loading cavities are spaced apart.

[0015] Multiple circuit board resonant cavities are connected to adjacent circuit board resonant cavities through coupling windows, the edges of which are formed by the metallized vias.

[0016] In one embodiment, the metal loading cavity further includes a metal coupling disk adjacent to the printed circuit board;

[0017] The printed circuit board further includes a coupling blind via recessed from a surface of the printed circuit board opposite to the metal loading cavity, the surface of which is covered with a metal layer.

[0018] The metal coupling disk and the coupling blind hole are coupled to form a first capacitor-loaded structure.

[0019] In one embodiment, the metal coupling disk is located at the center of the cross-section of the metal loading cavity, and the position of the coupling blind hole corresponds to the metal coupling disk;

[0020] The thickness of the metal layer and / or dielectric substrate corresponding to the location of the coupling blind aperture is related to the frequency of the filter.

[0021] In one embodiment, the metal loading cavity further includes a punch hole recessed inward from the center of the metal bottom wall.

[0022] In one embodiment, the metal loading cavity further includes a metal coupling disk, which is disposed at the top of the stamping hole;

[0023] The printed circuit board further includes a coupling blind via recessed from a surface of the printed circuit board opposite to the metal loading cavity, the surface of which is covered with a metal layer.

[0024] The metal coupling disk and the coupling blind hole are coupled to form a first capacitor-loaded structure.

[0025] In one embodiment, it further includes:

[0026] A capacitive cross-coupling structure, wherein the capacitive cross-coupling structure is a metal strip formed in the dielectric substrate and isolated from the metal layer, and the two ends of the capacitive cross-coupling structure are respectively located in two non-adjacent circuit board resonant cavities.

[0027] In one embodiment, it further includes:

[0028] An inductive cross-coupling structure is a metal strip formed within the dielectric substrate, with each end connected to the metal layer via a metallized via. The two ends of the inductive cross-coupling structure are located within two non-adjacent circuit board resonant cavities.

[0029] In one embodiment, the thickness of the metal layer and / or dielectric substrate corresponding to the location of the coupling window is associated with the coupling degree of the filter.

[0030] As can be seen from the above technical solutions, this embodiment combines a metal loading cavity with a SIW filter (printed circuit board), thus combining the advantages of two different filters. Specifically, one side of the dielectric substrate of the printed circuit board 1 in this embodiment is entirely covered with a metal layer, while the other side is demetalized by a cutout at the position corresponding to the metal loading cavity 2. This allows the dielectric layer of the printed circuit board to communicate with the metal loading cavity 2 through the cutout. Therefore, the electromagnetic field is not confined to the dielectric between the two metal layers as in existing SIW resonators, but propagates in the air layer between the dielectric layer and the metal loading cavity 2, thereby greatly improving the unloaded Q value of the resonator.

[0031] In addition, the propagation medium of the electromagnetic field in this embodiment consists of air and a dielectric plate. The dielectric constant of the propagation medium is increased compared with the existing propagation method of dielectric plates, thereby reducing the thickness of the metal loading cavity while achieving the same unloaded Q value, so as to reduce the overall thickness of the filter. Attached Figure Description

[0032] The following figures are for illustrative purposes only and do not limit the scope of the invention.

[0033] Figure 1 This is a schematic diagram of the structure of the first embodiment of the filter of the present invention.

[0034] Figure 2 This is a schematic diagram of the second embodiment of the filter of the present invention.

[0035] Figure 3 yes Figure 2 The characteristic curve of the filter.

[0036] Figure 4 This is a schematic diagram of the third embodiment of the filter of the present invention.

[0037] Figure 5 yes Figure 4 The characteristic curve of the filter.

[0038] Figure 6 This is a schematic diagram of the fourth embodiment of the filter of the present invention.

[0039] Figure 7 yes Figure 6 The characteristic curve of the filter.

[0040] Figure 8 This is a structural schematic diagram of the fifth embodiment of the filter of the present invention.

[0041] Figure 9 yes Figure 8 The characteristic curve of the filter.

[0042] Figure 10 This is a top view of a second embodiment of the filter of the present invention. Detailed Implementation

[0043] To provide a clearer understanding of the technical features, objectives, and effects of the invention, specific embodiments of the invention are now described with reference to the accompanying drawings, in which the same reference numerals denote the same parts.

[0044] In this document, “illustrative” means “serving as an example, illustration or description”, and any illustration or implementation described herein as “illustrative” should not be construed as a more preferred or advantageous technical solution.

[0045] To keep the drawings concise, only the parts relevant to the invention are shown in each figure, and do not represent the actual structure of the product. Furthermore, to facilitate understanding, in some figures, only one of the components with the same structure or function is shown schematically, or only one is labeled.

[0046] In this article, terms such as "up," "down," "front," "back," "left," and "right" are used only to indicate the relative positional relationship between related parts, rather than to define the absolute position of these related parts.

[0047] In this article, "first," "second," etc., are used only to distinguish one another, and not to indicate degree of importance, order, or prerequisite for each other.

[0048] In this document, terms such as "equal" and "same" are not strict mathematical and / or geometric limitations, but also include errors that are understandable to those skilled in the art and permissible in manufacturing or use. Unless otherwise stated, numerical ranges in this document include not only the entire range within its two endpoints, but also several subranges contained therein.

[0049] The exemplary embodiments will now be described more fully with reference to the accompanying drawings.

[0050] To address the problems in the prior art, the present invention provides...

[0051] Figure 1 This is a schematic diagram of the structure of the filter of the present invention in the first embodiment. Figure 1 As shown, one embodiment of the present invention provides a filter, comprising:

[0052] Printed circuit board 1, the printed circuit board 1 includes a dielectric substrate 11 and metal layers 12 covering both sides of the dielectric substrate; and

[0053] The metal loading cavity 2 is formed by a metal peripheral wall 21 and a metal bottom wall 22 to form a hollow cavity with an opening at the top. The metal loading cavity 2 is fixed to the printed circuit board 1 with its opening facing the printed circuit board 1.

[0054] The metal layer on the side surface of the printed circuit board 1 facing the metal loading cavity 2 has a cutout corresponding to the opening. The dielectric board 11 is connected to the hollow cavity through the cutout to form a resonant cavity.

[0055] This embodiment combines a metal loading cavity with a SIW filter (printed circuit board), thus combining the advantages of two different filters. In this embodiment, one surface of the dielectric substrate of the printed circuit board 1 is entirely covered with a metal layer, while the other surface is demetalized at the location corresponding to the metal loading cavity 2 through a cutout. This allows the dielectric layer of the printed circuit board to communicate with the metal loading cavity 2 through the cutout. Therefore, the electromagnetic field is not confined to the dielectric between the two metal layers as in existing SIW resonators, but propagates in the air layer between the dielectric layer and the metal loading cavity 2, thereby greatly improving the unloaded Q value of the resonator. In one specific embodiment, the Qu value of the resonator can reach over 1000, thus meeting the requirements of Sub-6GHz RRU applications.

[0056] Meanwhile, because the main body of this metal cavity loaded SIW filter is a PCB or LTCC, it can be easily integrated with other active control circuits and active RF circuits to form a microwave integrated circuit (MMIC), making microwave integrated circuits in the Sub-6GHz band possible and avoiding the difficulty of integration of traditional metal cavity filters.

[0057] Furthermore, in this embodiment, the electromagnetic field propagation medium consists of air and a dielectric substrate. The dielectric constant of the propagation medium is increased compared to existing dielectric substrate propagation methods. The metal loading cavity serves to couple a portion of the electromagnetic energy into the metal-enclosed space, which is primarily composed of air (air is generally considered negligible and does not affect the Q value). This reduces electromagnetic energy loss in the PCB dielectric, thereby increasing the Q value. Consequently, the thickness of the metal loading cavity can be reduced while achieving the same unloaded Q value, thus lowering the overall thickness of the filter.

[0058] Furthermore, a circuit board resonant cavity 13 corresponding to the metal loading cavity 2 is formed in the dielectric substrate 11. The edge of the circuit board resonant cavity 13 is formed by metallized vias 14 that are connected to the metal layers 12 on both sides. The metallized vias 14 are arranged in parallel at intervals.

[0059] The metal layer 12 on the surface of the printed circuit board 1 may include an upper metal layer and a lower metal layer, wherein the position of the lower metal layer corresponding to the metal loading cavity 2 is demetallized by a cutout. Metallized vias 14 are used to connect the upper and lower metal layers, thereby confining the electromagnetic field propagating in the dielectric substrate 11 within the circuit board resonant cavity 13 corresponding to the metal loading cavity 2, in accordance with the pre-designed size of the SIW resonator.

[0060] In a preferred embodiment, in order to further satisfy the adjustment of the initial frequency of the filter, the metal loading cavity 2 further includes a metal coupling disk 23, which is adjacent to the printed circuit board 1.

[0061] The printed circuit board 1 further includes a coupling blind via 18, which is recessed from the surface of the printed circuit board 1 on the side opposite to the metal loading cavity 2, and the surface of the coupling blind via 18 is covered with a metal layer.

[0062] The metal coupling disk 23 and the coupling blind hole 18 are coupled to form a first capacitor-loaded structure.

[0063] Furthermore, the metal coupling disk 23 is located at the center of the cross-section of the metal loading cavity 2, and the position of the coupling blind hole 18 corresponds to that of the metal coupling disk 23.

[0064] The diameter and height of the metal coupling disk 23 and the coupling blind aperture 18 have a corresponding effect on the frequency of the filter. The purpose is to increase the frequency-conditioning capacitance so that the filter can operate in the lower frequency band below -6 GHz (e.g., 1.9 GHz in this example). Typically, the thickness of the coupling blind aperture 18 is 0.5 mm.

[0065] In a preferred embodiment, the metal loading cavity 2 further includes a stamped hole 24 recessed inward from the center of the metal bottom wall 22. The metal coupling disk 23 can be formed on top of the stamped hole 24 by stamping or welding.

[0066] Figure 2 This is a schematic diagram of the structure of the filter of the present invention in a second embodiment. Figure 2 As shown, one embodiment of the present invention provides a filter, comprising:

[0067] Printed circuit board 1, the printed circuit board 1 includes a dielectric substrate 11 and metal layers 12 covering both sides of the dielectric substrate; and

[0068] Multiple metal loading cavities 2, each metal loading cavity 2 is surrounded by a metal peripheral wall 21 and a metal bottom wall 22 to form a hollow cavity with an opening at the top. The metal loading cavity 2 is fixed to the printed circuit board 1 with its opening facing the printed circuit board 1. The multiple metal loading cavities 2 are arranged at intervals.

[0069] The metal layer on the side surface of the printed circuit board 1 facing the metal loading cavity 2 has a cutout corresponding to the opening. The dielectric board 11 is connected to the hollow cavity from the cutout to form a resonant cavity.

[0070] A circuit board resonant cavity 13 corresponding to the metal loading cavity 2 is formed in the dielectric substrate 11. The edge of the circuit board resonant cavity 13 is formed by metallized vias 14 that are connected to the metal layers 12 on both sides. The metallized vias 14 are arranged in parallel and spaced apart. Adjacent circuit board resonant cavities 13 are connected by coupling windows 15. The edge of the coupling window 15 is formed by metallized vias 14.

[0071] The coupling window 15 is formed by removing a portion of the metallized via 14 between adjacent circuit board resonant cavities 13.

[0072] This embodiment provides a multi-order (3rd order shown in the figure) filter, wherein multiple metal loading cavities 2 have identical structures, and each metal loading cavity 2 is independent of each other by being spaced apart, without direct coupling. The coupling between the resonant cavities is achieved through the coupling between the circuit board resonant cavities 13 in the printed circuit board 1. The coupling between adjacent circuit board resonant cavities 13 is achieved through coupling windows 15, and the formation of coupling windows 15 only requires adjusting the formation position of the metallized vias 14.

[0073] The multiple metal loading cavities 2 in this embodiment have a simple structure and do not require coupling structures. Compared with existing metal resonators, the coupling between multi-order resonant cavities does not require the design of new molds, which can greatly reduce mold opening and manufacturing costs. The coupling structure is implemented in the printed circuit board 1. As is well known, structural adjustments in the printed circuit board 1, i.e., adding or removing metallized interconnects or metallized vias at any position, are very easy to implement. Therefore, the filter in this embodiment, by combining the printed circuit board with the metal loading cavities, not only improves the unloaded Q value of the filter, but also transfers the coupling structures that are difficult to attach to the metal loading cavities to the printed circuit board 1, which can greatly reduce the complexity of the structure and manufacturing costs.

[0074] Similarly, in a preferred embodiment, in order to further satisfy the adjustment of the initial frequency of the filter, in a preferred embodiment, the metal loading cavity 2 further includes a metal coupling disk 23, which is adjacent to the printed circuit board 1.

[0075] The printed circuit board 1 further includes a coupling blind via 18, which is recessed from the surface of the printed circuit board 1 on the side opposite to the metal loading cavity 2, and the surface of the coupling blind via 18 is covered with a metal layer.

[0076] The metal coupling disk 23 and the coupling blind hole 18 are coupled to form a first capacitor-loaded structure.

[0077] Furthermore, the metal coupling disk 23 is located at the center of the cross-section of the metal loading cavity 2, and the position of the coupling blind hole 18 corresponds to that of the metal coupling disk 23.

[0078] The diameter and height of the metal coupling disk 23 and the coupling blind aperture 18 have a corresponding effect on the frequency of the filter. The purpose is to increase the frequency-conditioning capacitance so that the filter can operate in the lower frequency band below -6 GHz (e.g., 1.9 GHz in this example). Typically, the thickness of the coupling blind aperture 18 is 0.5 mm.

[0079] In a preferred embodiment, the metal loading cavity 2 further includes a stamped hole 24 recessed inward from the center of the metal bottom wall 22. The metal coupling disk 23 can be formed on top of the stamped hole 24 by stamping or welding.

[0080] Depend on Figure 3 The characteristic curve of the third-order metal-loaded filter shows that, when fitted with the ideal filter function shown by the dashed line, its equivalent Qu value is about 1500, which is much larger than the Qu value of the traditional SIW filter.

[0081] Furthermore, in Figure 2 Based on the illustrated embodiment, in order to generate a finite number of transmission zeros outside the filter passband, such as Figure 4 As shown, embodiments of the present invention further include:

[0082] The capacitive cross-coupling structure 31 is a metal strip formed in the dielectric substrate 11 and isolated from the metal layer 12. The two ends of the capacitive cross-coupling structure 31 are located in two non-adjacent circuit board resonant cavities 13.

[0083] In this embodiment, the printed circuit board 1 cannot be a double-sided board; instead, it requires at least three layers, with an additional intermediate layer to form a capacitive cross-coupling structure 31. Specifically, the intermediate layer is located in the middle, approximately 0.5 mm away from the metal layers on the upper and lower surfaces. Most of the metallization of the intermediate layer is removed, leaving a metallized transmission line suspended between the first and third metal loading cavities, i.e., the capacitive cross-coupling structure 31. This structure is used to couple electric field energy between these two non-adjacent metal loading cavities to generate capacitive coupling, thereby creating a finite transmission zero on the left side of the passband.

[0084] Figure 5 The response curve of this capacitive cross-coupled structure and its fit to the response curve of an ideal capacitive cross-coupled filter (shown by the dashed line) are shown. A finite transmission zero can be seen generated on the left side of the passband.

[0085] Similarly, in Figure 2 Based on the illustrated embodiment, in order to generate a finite number of transmission zeros outside the filter passband, such as Figure 6 As shown, embodiments of the present invention further include: [further details to be added].

[0086] The inductive cross-coupling structure 32 is a metal strip formed in the dielectric substrate 11. Its ends are connected to the metal layer 12 through a metallized via 14. The two ends of the inductive cross-coupling structure 32 are located in two non-adjacent circuit board resonant cavities 13.

[0087] In this embodiment, the printed circuit board 1 cannot be a double-sided board; instead, it requires at least three layers, with an additional intermediate layer to form the inductive cross-coupling structure 32. Specifically, the intermediate layer is located in the middle, approximately 0.5 mm away from the metal layers on the upper and lower surfaces. Most of the metallization of the intermediate layer is removed, leaving a metallized transmission line suspended between the first and third metal loading cavities, i.e., the inductive cross-coupling structure 32. The two ends of the inductive cross-coupling structure 32 are connected to the upper metal layer 12 through a metallized via 14, which is used to couple magnetic field energy between the two non-adjacent metal loading cavities to generate inductive coupling, thereby creating a finite transmission zero on the right side of the passband.

[0088] Figure 7 The response curve of this inductive cross-coupled structure and its fit to the response curve of an ideal inductive cross-coupled filter (shown by the dashed line) are shown. A finite transmission zero can be observed on the right side of the passband.

[0089] like Figure 8 As shown, an embodiment of the present invention provides a fourth-order filter, which further includes:

[0090] The capacitive cross-coupling structure 31 is a metal strip formed in the dielectric substrate 11 and isolated from the metal layer 12. The two ends of the capacitive cross-coupling structure 31 are located in two non-adjacent circuit board resonant cavities 13, which are the first circuit board resonator and the fourth circuit board resonator.

[0091] The capacitive cross-coupling structure 31 couples electric field energy between the first and fourth circuit board resonators, generating capacitive coupling and thus creating a finite transmission zero on both the left and right sides of the passband. Figure 9 The response curve of this capacitive cross-coupled structure and its fit to the response curve of an ideal capacitive cross-coupled filter (shown by the dashed line) are shown. It can be seen that a finite transmission zero is generated on both the left and right sides of the passband.

[0092] Figure 10 This is a top view of a second embodiment of the filter of the present invention.

[0093] In practical applications, after the filter is manufactured, it needs to be fine-tuned in terms of frequency and coupling. In this embodiment, for example... Figure 10As shown, in the first region 16 corresponding to the position of coupling window 15, the thickness of the metal layer 12 located between two adjacent PCB resonant cavities 13 and / or the width of the area in the dielectric substrate 11 without metallized vias 14 are related to the coupling degree of the filter. In the second region 17 corresponding to the position of coupling blind via 18, the thickness of the metal layer 12 and / or the dielectric substrate 11 is related to the frequency of the filter. The wider the area without metallized vias 14, the higher the coupling degree.

[0094] That is, the first region 16 can be called the coupling-sensitive region, and the second region 17 can be called the frequency-sensitive region. By polishing the first region 16 and the second region 17 with a polishing tool to remove the corresponding metallization layer or dielectric layer, the electromagnetic field can be slightly disturbed, thereby adjusting the response curve. Compared with the traditional sub-6GHz metal filter method using a tuning screw, this method has the advantages of small size and simple structure.

[0095] As can be seen from the above technical solutions, this embodiment combines a metal loading cavity with a SIW filter (printed circuit board), thus combining the advantages of two different filters. Specifically, one side of the dielectric substrate of the printed circuit board 1 in this embodiment is entirely covered with a metal layer, while the other side is demetalized by a cutout at the position corresponding to the metal loading cavity 2. This allows the dielectric layer of the printed circuit board to communicate with the metal loading cavity 2 through the cutout. Therefore, the electromagnetic field is not confined to the dielectric between the two metal layers as in existing SIW resonators, but propagates in the air layer between the dielectric layer and the metal loading cavity 2, thereby greatly improving the unloaded Q value of the resonator.

[0096] In addition, the propagation medium of the electromagnetic field in this embodiment consists of air and a dielectric plate. The dielectric constant of the propagation medium is increased compared with the existing propagation method of dielectric plates, thereby reducing the thickness of the metal loading cavity while achieving the same unloaded Q value, so as to reduce the overall thickness of the filter.

[0097] The filter in this embodiment improves the unloaded Q value of the filter by combining the printed circuit board with the metal loading cavity. It also transfers the coupling structure that is difficult to attach to the metal loading cavity to the printed circuit board 1, which can greatly reduce the complexity of the structure and the manufacturing cost.

[0098] The detailed descriptions listed above are merely specific descriptions of feasible embodiments of the present invention and are not intended to limit the scope of protection of the present invention. All equivalent implementation schemes or modifications made without departing from the spirit of the present invention, such as combinations, divisions or repetitions of features, should be included within the scope of protection of the present invention.

Claims

1. A filter, characterized in that, include: Printed circuit board (1), the printed circuit board (1) includes a dielectric substrate (11) and a metal layer (12) covering both sides of the dielectric substrate. and The metal loading cavity (2) is formed by a metal peripheral wall (21) and a metal bottom wall (22) to form a hollow cavity with an opening at the top. The metal loading cavity (2) is fixed to the printed circuit board (1) with its opening facing the printed circuit board (1). The metal layer on the side surface of the printed circuit board (1) facing the metal loading cavity (2) has a cutout corresponding to the opening, and the dielectric plate (11) is connected to the hollow cavity from the cutout to form a resonant cavity. The circuit board resonant cavity (13) corresponding to the metal loading cavity (2) is formed in the dielectric plate (11). The edge of the circuit board resonant cavity (13) is formed by metallized vias (14) that are connected to the metal layers (12) on both sides. The metallized vias (14) are arranged in parallel and spaced apart. This includes: Multiple metal loading cavities (2) are spaced apart; Multiple circuit board resonant cavities (13) are connected to each other through coupling windows (15), and the edges of the coupling windows (15) are formed by the metallized vias (14).

2. The filter according to claim 1, characterized in that, The metal loading cavity (2) further includes a metal coupling disk (23), which is adjacent to the printed circuit board (1). The printed circuit board (1) further includes a coupling blind via (18), which is recessed from the surface of the printed circuit board (1) facing away from the metal loading cavity (2), and the surface of the coupling blind via (18) is covered with a metal layer. The metal coupling disk (23) and the coupling blind hole (18) are coupled to form a first capacitor-loaded structure.

3. The filter according to claim 2, characterized in that, The metal coupling disk (23) is located at the center of the cross section of the metal loading cavity (2), and the position of the coupling blind hole (18) corresponds to that of the metal coupling disk (23); The thickness of the metal layer (12) and / or dielectric substrate (11) corresponding to the location of the coupling blind hole (18) is related to the frequency of the filter.

4. The filter according to claim 1, characterized in that, The metal loading cavity (2) further includes a punch hole (24) recessed inward from the center of the metal bottom wall (22).

5. The filter according to claim 4, characterized in that, The metal loading cavity (2) further includes a metal coupling disk (23), which is disposed on the top of the stamping hole (24); The printed circuit board (1) further includes a coupling blind via (18), which is recessed from the surface of the printed circuit board (1) facing away from the metal loading cavity (2), and the surface of the coupling blind via (18) is covered with a metal layer. The metal coupling disk (23) and the coupling blind hole (18) are coupled to form a first capacitor-loaded structure.

6. The filter according to claim 1, characterized in that, Further includes: A capacitive cross-coupling structure (31) is a metal strip formed in the dielectric substrate (11) and isolated from the metal layer (12). The two ends of the capacitive cross-coupling structure (31) are located in two non-adjacent circuit board resonant cavities (13).

7. The filter according to claim 1, characterized in that, Further includes: Inductive cross-coupling structure (32) is a metal strip formed in the dielectric substrate (11), with its ends connected to the metal layer (12) through a metallized via (14). The two ends of the inductive cross-coupling structure (32) are located in two non-adjacent circuit board resonant cavities (13).

8. The filter according to claim 1, characterized in that, The width of the region of the dielectric substrate (11) between two adjacent PCB resonant cavities (13) corresponding to the position of the coupling window (15) without metallized vias is related to the coupling degree of the filter.

Images