WO2015018051A1

WO2015018051A1 - Filter tuning device and filter

Info

Publication number: WO2015018051A1
Application number: PCT/CN2013/081142
Authority: WO
Inventors: 邱莉霞; 邓晓毅; 董利芳
Original assignee: 华为技术有限公司
Priority date: 2013-08-09
Filing date: 2013-08-09
Publication date: 2015-02-12
Also published as: CN103650237A; CN103650237B

Abstract

Embodiments of the invention disclose a filter tuning device and a filter, relate to the technical field of communication equipment and are invented to well avoid lowering the Q value of the filter. The tuning device of the filter and the filter comprise a resonance cavity, a cover and a resonance bar, a through hole is formed in the bottom of the resonance cavity, the resonance bar penetrates through the through hole from the interior of the resonant cavity, the cover body covers the resonant cavity, and the resonance bar is movable along a direction vertical to the bottom of the resonant cavity via the through hole. The present invention is mostly suitable for adjusting the resonant frequency of the filter.

Description

Filter tuning device and filter

The present invention relates to the field of communications equipment, and in particular, to a tuning device and a filter for a filter. Background technique

A tunable filter is a filter that derives the desired value of the center frequency by controlling the change in parameters. Among them, the capacitance is an important parameter to determine the center frequency of the filter. The size of the capacitor can be adjusted by the tuning structure in the filter. For example, the screw tuning structure shown in Figure 1 includes the resonant cavity 2', the resonant rod y, and the tuning screw. 8', the cover body, the resonant rod y is fixed inside the resonant cavity 2', and the tuning screw 8' is screwed onto the cover body through the nut 9' and protrudes into the inside of the resonant rod y; the resonant rod 3' is also A relief groove 32' for moving the tuning screw 8' up and down is provided. The size of the resonance between the resonant rod y and the cover is adjusted by adjusting the length of the tuning screw 8' into the interior of the resonant rod y to achieve the purpose of filter debugging.

In order to ensure safe adjustment of the tuning screw into the resonant rod, a certain safety distance between the outer diameter of the tuning screw and the inner diameter of the resonant rod is required to ensure the assembly, commissioning and production reliability of the filter, but The diameter of the resonant rod is increased. Moreover, when the resonant rod is fixed in the resonant cavity by screws, a part of the space needs to be reserved in the resonant rod to install the fixing screw, which also increases the diameter of the resonant rod, and the diameter of the resonant rod increases. It will reduce the Q value of the filter cavity and increase the loss of the filter. Summary of the invention

Embodiments of the present invention provide a tuning device and filter for a filter that facilitates increasing the Q value of the filter cavity and reducing the loss of the filter.

In order to achieve the above object, embodiments of the present invention use the following technical solutions:

In a first aspect, an embodiment of the present invention provides a filter tuning apparatus, including a resonant cavity, a cover, a resonant rod, and a through hole. The bottom of the resonant cavity is provided with a through hole, and the resonant rod is a resonant cavity. Passing through the through hole in the body, the cover is covered on the resonant cavity, and the resonant rod passes through the through hole from the bottom of the resonant cavity along a bottom perpendicular to the resonant cavity The direction can be moved.

In a first possible implementation manner, the bottom of the resonant cavity is provided with a through hole having an internal thread, and the resonant rod is provided with a matching line with the internal thread. An external thread, the resonant rod is screwed into the through hole, and is movable in a direction perpendicular to a bottom of the resonant cavity by rotating the resonant rod.

In conjunction with the first possible implementation of the first aspect, in a second possible implementation, the bottom surface of the resonant cavity is provided with a boss facing the cover body, and the boss and the cavity are The bottom surface is vertical, the height is smaller than the length of the resonant rod, and the through hole is provided on the boss.

In conjunction with the first or second possible implementation of the first aspect, in a third possible implementation, the method further includes a locking portion for locking the resonant rod in the resonant cavity Physically.

In conjunction with the third possible implementation of the first aspect, in a fourth possible implementation, the locking portion includes at least one second external thread disposed on the resonant rod and opposite the internal thread And at least a third external thread, each of the second external threads of the locking portion is adjacent to each of the third external threads; the second external thread has a larger pitch than the first external thread The pitch of the third external thread is smaller than the pitch of the first external thread.

In conjunction with the third possible implementation of the first aspect, in a fifth possible implementation, the locking portion includes two or more open slots disposed on the resonant rod and opposite to the internal thread, The opening depth of the open groove is greater than the depth of the first external thread.

In conjunction with the fifth possible implementation of the first aspect, in a sixth possible implementation, the width between adjacent ones of the open slots is at least greater than the pitch of the first external threads.

In conjunction with the sixth possible implementation of the first aspect, in a seventh possible implementation, the openings of the two adjacent open slots are opposite in direction.

In conjunction with the seventh possible implementation of the first aspect, in an eighth possible implementation, the opening slot has a depth greater than a radius of the resonant rod and less than a diameter of the resonant rod.

In conjunction with the eighth possible implementation of the first aspect, in a ninth possible implementation, the two or more open slots are adjacent to a bottom end of the resonant rod. In conjunction with the third possible implementation of the first aspect, in a tenth possible implementation, the locking portion includes a nut matching the first external thread for using the resonant rod from the resonance The first external thread extending from the bottom of the cavity is partially locked.

With reference to the tenth possible implementation manner of the first aspect, in an eleventh possible implementation manner, a bottom of the cavity outside the cavity and a position opposite to the boss are provided with a groove, where the groove The height is greater than the height of the nut, and the height of the groove is less than the thickness of the bottom of the resonant cavity, the first externally threaded portion of the resonant rod extending, and the nut are located within the recess.

In conjunction with the eleventh possible implementation of the first aspect, in the twelfth possible implementation, the resonant cavity, the cover, and the resonant rod are both metal members after surface treatment.

With reference to the twelfth possible implementation manner of the first aspect, in the thirteenth possible implementation manner, the materials of the resonant cavity and the cover are respectively an aluminum alloy and a magnesium alloy, and the material of the resonant rod For iron or copper.

In a second aspect, the present invention provides a filter comprising a body, the body comprising a plurality of filter tuning devices in any of the above possible implementations.

A filter tuning device and a filter provided by an embodiment of the present invention include a resonant cavity, a cover, a resonant rod, and a through hole. The cover is disposed on the resonant cavity, and the bottom of the resonant cavity Providing a through hole, the resonant rod is passed through the through hole from the cavity, the cover is covered on the resonant cavity, and the resonant rod passes through the through hole from the bottom of the resonant cavity The bottom of the resonant cavity is vertically movable, and the capacitance between the resonant rod and the cover is changed by adjusting the length of the resonant rod, thereby achieving the purpose of filter debugging. Compared with the filter debugged with the tuning screw, the filter of the present invention saves the tuning screw, and the safety rod does not need to reserve a safe distance between the tuning screw and the resonant rod, and the resonant rod does not need to pass the screw. It is fixed in the cavity, so that the diameter of the resonance rod can be reduced, which is beneficial to increase the Q value of the filter cavity and reduce the loss of the filter. DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will be true. The drawings used in the examples or the description of the prior art are briefly introduced. It is obvious that the drawings in the following description are only some embodiments of the present invention, and are not creative to those skilled in the art. Other drawings can also be obtained from these drawings on the premise of labor.

1 is a schematic structural diagram of a filter tuning device with a tuning screw provided by the prior art; FIG. 2 is a schematic structural diagram of a filter tuning device according to Embodiment 1 of the present invention;

3 is an exploded perspective view of a filter tuning apparatus according to Embodiment 2 of the present invention;

Figure 4 is a schematic structural view of Figure 3 after assembly;

FIG. 5 is a schematic diagram of a first structure of a locking portion according to an embodiment of the present invention; FIG.

6 is a schematic view showing a second structure of a locking portion according to an embodiment of the present invention;

7 is a schematic view showing a third structure of a locking portion according to an embodiment of the present invention;

FIG. 8 is a schematic structural diagram of a filter according to Embodiment 3 of the present invention.

Reference mark:

1, V-lid body, 10-cover bottom surface, 2, 2'-resonant cavity, 20-resonant cavity bottom surface, 21-through hole, 22-protrusion, 23-internal thread, 24-groove, 3, V-resonant rod, 30-resonator top surface, 31-first external thread, 32-resonator bottom, 32' - avoidance groove, 4, 5, 6-locking, 40-second external thread, 41-Third external thread, 50-open groove, 60-nut, 7-body, 8'-tuning screw, 9'-nut embodiment

The technical solutions in the embodiments of the present invention are clearly and completely described in the following with reference to the accompanying drawings in the embodiments of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts are within the scope of the present invention.

Embodiment 1:

FIG. 2 is a schematic structural diagram of a filter tuning apparatus according to this embodiment. As shown in FIG. 2, the filter tuning device includes a resonant cavity 2, a cover 1, and a resonant rod 3. The bottom of the resonant cavity 2 is provided with a through hole 21 through which the resonant rod 3 passes. The through hole 21, the cover 1 is covered in resonance On the cavity 2, the resonant rod 3 is movable up and down in a direction perpendicular to the bottom of the resonant cavity 2 through the through hole 21.

In this way, the distance between the top surface 30 of the resonant rod 3 inside the resonant cavity 2 and the bottom surface 10 of the cover can be changed by adjusting the length of the resonant rod 3 inside the resonant cavity 2, thereby adjusting the resonant rod 3 and the cover 1 The size of the capacitor between the two, that is, when the length of the resonant rod 3 inside the resonant cavity 2 is long, the distance between the top surface 30 of the resonant rod and the bottom surface 10 of the cover is reduced, and the capacitance is increased. Large; on the contrary, the capacitance is reduced. The filter tuning device of the invention saves the tuning screw, and the safety distance between the tuning screw and the resonant rod does not need to be reserved in the resonant rod, and the resonant rod does not need to be fixed in the resonant cavity by the fixing screw, thereby being The diameter of the small resonant rod helps to increase the Q value of the filter cavity and reduce the loss of the filter.

Generally, the increase of the diameter of the resonant rod will increase the power capacity of the filter. However, for a filter that only receives signals, there is no special requirement for the power capacity. In this case, in order to increase the Q value of the filter cavity, the diameter of the cavity is not Under variable conditions, the diameter of the resonant rod is reduced as much as possible. When the tuning device of the filter uses, for example, the structure in the background art, the diameter of the resonant rod is reduced by the tuning screw because the insertion of the tuning screw is ensured. The limitation of the diameter, while using the structure of the present invention, is not limited by the tuning screw, so the resonant rod in the embodiment of the present invention can be made thinner to further increase the Q value of the resonant cavity and reduce The loss of the filter.

Of course, the resonant rod is not as fine as possible, and a thinner resonant rod is usually fabricated on the premise that it has sufficient strength. Moreover, the thickness of the resonant rod is relative to the resonant cavity, since different filters have Different sizes of resonant cavity, so the thickness of the resonant rod is set according to the actual situation, and the size is not specifically limited here.

Embodiment 2:

The filter tuning apparatus provided in this embodiment will be further described below with reference to FIGS. 3-7. As shown in FIG. 3 and FIG. 4, the filter tuning device includes a resonant cavity 2, a cover 1, and a resonant rod 3. The bottom of the resonant cavity 2 is provided with a through hole 21, and the resonant rod 3 is a resonant cavity 2 The cover body 1 can be connected to the resonant cavity 2 through a screw connection or a soldering connection, and the cover 1 is opposite to the bottom surface 20 of the resonant cavity, and the resonant rod 3 is along the resonant cavity 2 Bottom vertical The direction can be moved up and down. In the embodiment of the present invention, the movable structure of the resonant rod 3 may be a threaded connection. For example, an internal thread 23 is provided on the inner side surface of the through hole 21, and the resonant rod 3 is provided with the internal thread 23 The first external thread 31 is matched (ie, screwed tightly with the internal thread 23), so that the resonant rod 3 can be screwed into the through hole 21, and the resonant rod 3 can be rotated to be perpendicular to the bottom surface 20. By moving, the length of the resonant rod 3 in the resonant cavity can be adjusted, and the capacitance between the resonant rod 3 and the cover 1 is adjusted to achieve the purpose of filter debugging. Of course, the structure for realizing the movement of the resonant rod is not limited thereto, and may be, for example, a slider type structure, that is, the resonant rod is moved up and down in a direction perpendicular to the bottom of the resonant cavity by sliding, or may be other A configuration known to those skilled in the art to achieve a resonant rod moving up and down in a direction perpendicular to the bottom of the resonant cavity. After the tuning is completed, the length of the resonant rod inside the resonant cavity 2 can be fixed. The embodiments of the present invention are not limited thereto.

The bottom surface of the resonant cavity 2 may also be provided with a boss 22 as shown in FIG. 3 or FIG. 4, the height of the boss 22 is smaller than the length of the resonant rod 3, and the bottom surface 20 of the boss 22 in the resonant cavity faces the cover body, and the bottom surface 20 Vertically, the boss 22 is provided with a through hole 21 having an internal thread 23, and the resonant rod 3 is screwed into the through hole 21 in a direction perpendicular to the bottom of the resonant cavity 2, so that the cavity can be improved not only by providing the boss 22 The strength of the body 2 also serves to guide the movement of the resonant rod 3.

The center frequency of the filter can be varied by adjusting the magnitude of the capacitance (capacitance of the filter) between the resonant rod 3 and the cover 1 when the length of the resonant rod 3 in the resonant cavity 2 is determined (ie, the top surface of the resonant rod 3) After determining the distance from the bottom surface 10 of the cover body, the center frequency of the filter is also determined. At this time, the resonant rod 3 can be locked to prevent the resonance rod 3 from moving and affecting the frequency, so that it can be selected in the embodiment of the present invention. The ground may also include a locking portion for locking the resonant rod 3 to the resonant cavity 2.

The locking portions may be respectively the following three different structures: First structure: As shown in FIG. 5, the locking portion 4 includes at least one second external thread disposed on the resonant rod 3 and opposite to the internal thread 23. 40 and at least a third external thread 41, wherein the second external thread 40 and the third external thread 41 in the locking portion 4 are adjacent, or when the locking portion 4 has a plurality of second external threads 40 and a plurality of third portions At the time of the external thread 41, at least one of the second external threads 40 and the at least one third external thread 41 are adjacent. Second external thread 40 The pitch of the teeth is greater than the pitch of the first external thread 31 (distance between two adjacent teeth), the pitch of the third external thread 41 is smaller than the pitch of the first external thread 31, wherein the locking portion 4 and the first The external threads 31 are adjacent to each other and may also be located between the two first external threads 31 of the resonant rod 3. Specifically, after the resonant rod 3 is screwed into the through hole 21, the portion of the second external thread 40 and the portion of the internal thread 23 opposite thereto are likely to occur due to the mismatch between the second external thread 40 and the third external thread 41 and the internal thread 23. The deformation, the resulting deformation force causes the resonant rod 3 to be locked in the through hole 21, that is, the resonant rod 3 is locked on the resonant cavity 2. When the debugging is required, the resonance rod 3 can be externally applied by a tool such as a screwdriver. At this time, the bottom portion 32 of the resonance rod 3 can be provided with a receiving groove for a tool such as a screwdriver. When the external force is greater than the locking force between the resonant rod 3 and the through hole 21 (ie, the above-mentioned deformation force), the resonant rod 3 can move up and down along the axis of the through hole 21 to achieve the purpose of debugging the resonant rod 3. .

In order to ensure that the resonant rod 3 has sufficient locking force in the through hole 21, the second external thread 40 may include at least three screws, generally including three to five screws; also for the third external thread 41. It may include at least 3 threads, and may generally include 3 to 5 threads.

Further, the length and position of the locking portion 4 may be determined according to the length of the resonance rod 3. When the length of the resonance rod 3 is relatively long, a reasonable number of the above-described locking portions 4 may be provided between the resonance rods 3.

The second structure: as shown in FIG. 6 , the locking portion 5 may include two or more open slots 50 disposed on the resonant rod 3 and opposite to the internal thread 23 , wherein the opening depth of the opening slot 50 is greater than the first outer portion The depth of the thread 31, in order to facilitate production, the opening direction may be perpendicular to the axial direction of the resonant rod 3, and the width between the two adjacent opening slots 50 shall be at least greater than the pitch, and the spacing between the open slots may be adjusted according to the nominal diameter of the internal thread 23. Width, in general, the nominal diameter of the internal thread 23 is large, the width between the two adjacent open slots is also greater, and the width between adjacent open slots affects the locking force. Specifically, after the resonant rod 3 is screwed into the through hole 21, since the portion of the resonant rod 3 located between the two adjacent open slots 50 is easily deformed, the generated deformation force causes the resonant rod 3 to be locked in the through hole 21. That is, the resonant rod 3 is locked on the resonant cavity 2, and the locking force is larger as the width between the adjacent two open slots 50 is larger. When the debugging is required, the resonance rod 3 can be externally applied by a tool such as a screwdriver. At this time, the bottom portion 32 of the resonance rod 3 can be provided with a receiving groove for a screwing of a tool such as a screwdriver. When the external force acts greater than the locking force between the resonant rod 3 and the through hole 21, the resonant rod 3 can be perpendicular to the bottom of the resonant cavity 2 The direction is moved up and down to achieve the purpose of the resonance rod 3 debugging.

Based on the second structure, the embodiment of the present invention can make the opening directions of the two adjacent open slots 50 opposite, such that when the resonant rod 3 rotates in the through hole 21, the direction of the torsion generated by the portion of one of the open slots 50 is The portions of the adjacent opening grooves 50 are twisted in the same direction, so that the portion of the resonant rod 3 between the adjacent opening grooves 50 is relatively easily deformed to produce a relatively firm deformation force.

In order to further make the portion of the resonant rod 3 between the adjacent open slots 50 susceptible to deformation, the depth of the open slot 50 may be greater than the radius of the resonant rod 3 and smaller than the diameter of the resonant rod 3, for example, the depth of the opening is the diameter of the resonant rod 3. Two-thirds of the size. It should be emphasized that while the depth of the open slot is greater than the radius of the resonant rod, it is also necessary to ensure that the resonant rod itself has good strength. Therefore, the specific depth value of the open slot should be reasonably valued according to actual conditions.

As an alternative, the locking portion includes at least two open slots 50, and the at least two open slots 50 are disposed close to the bottom end of the resonant rod 3, so that not only the portion between the two open slots 50 is easily generated. The deformation creates a locking force and does not cause the locking force to be too large for normal commissioning.

However, an opening groove may be provided in the portion of the resonance rod 3 near the bottom end as permitted, so that the portion of the resonance rod at the lower end of the opening groove is easily deformed, thereby generating a locking force for locking the resonance rod 3.

Third Structure: As shown in FIG. 7, the locking portion 6 includes a nut 60 that matches the first external thread 31, such that the nut 60 projects the first external thread 31 of the resonant rod 3 at the bottom of the cavity outside the cavity. Partially locked to lock the resonant rod 3 to the resonant cavity 2. When the resonance debugging is required, the nut 60 is loosened, the resonant rod 3 is rotated to move the resonant rod 3 up and down in a direction perpendicular to the bottom of the resonant cavity 2, and the nut 60 is locked by a tool such as a wrench or a sleeve. The purpose of the resonance rod 3 debugging.

Referring again to FIG. 7, a groove 24 may be disposed at a position outside the cavity 2 and opposite to the through hole 21, and a portion of the first external thread 31 from which the resonance rod 3 protrudes is located in the groove 24, the groove The height of the 24 is greater than the height of the nut, and the height of the groove 24 is smaller than the thickness of the bottom of the resonant cavity 2. After the tuning is completed, the resonant rod 3 can be extended beyond the bottom of the resonant cavity 2 without exceeding the groove, thereby not increasing. The overall height of the resonant cavity 2 increases the space utilization of the filter tuning device. The resonant cavity 2, the cover 1 and the resonant rod 3 mentioned in the foregoing various embodiments are all metal parts, wherein the material of the resonant cavity 2 and the cover 1 can be made of aluminum alloy, magnesium alloy, etc., the resonant rod 3 The material can be iron or copper, which improves the tuning performance of the filter. In order to further improve the tuning performance of the filter, these metal parts are subjected to surface treatment such as conductive oxidation, electroplating copper, silver plating, and the like.

It should be further noted that during the process of moving back and forth, the resonant rod 3 not only causes a change in the capacitance of the filter due to a change in the distance between the top surface 30 of the resonant rod and the bottom surface 10 of the cover, but also due to the top of the resonant rod. The distance between the face 30 and the bottom surface 20 in the cavity changes to cause a change in the inductance of the filter (when the distance increases, the inductance decreases, and vice versa).

In addition, it is also clear from the foregoing and the drawings that there is no tuning screw in the embodiment of the present invention, which reduces the number of components of the filter, on the one hand, the cost of the filter can be reduced, and on the other hand, the assembly can be simplified. .

Embodiment 3:

The embodiment of the present invention further provides a filter. As shown in FIG. 8, the filter includes a main body 7. The main body 7 is provided with at least one filter tuning device, and each of the filter tuning devices includes a resonant cavity 2. , the cover body 1, the resonant rod 3, the bottom of the resonant cavity 2 is provided with a through hole, the resonant rod 3 is screwed into the through hole, wherein the cover 1 is covered on the resonant cavity 2, and the resonant rod 3 passes through the through hole and the resonance The bottom of the cavity 2 is vertically movable in the vertical direction.

In this way, the distance between the top surface of the resonant rod 3 extending into the cavity 2 and the bottom surface of the cover can be changed by adjusting the length of the resonant rod 3 in the resonant cavity 2, thereby adjusting the resonant rod 3 and the cover 1 The size of the capacitor between the capacitors, that is, when the length of the resonant rod 3 in the resonant cavity 2 is long, the distance between the top surface of the resonant rod and the bottom surface of the cover is reduced, and the capacitance is increased. ; Conversely, the capacitance is reduced. The filter of the invention saves the tuning screw without considering the safety distance between the tuning screw and the resonant rod, so that the resonant rod can be made thinner, which is beneficial to increase the Q value of the filter cavity and reduce the filter. loss.

Since the filter tuning device there can be any of the foregoing possible implementations, the filter tuning device will not be described here. As an alternative manner, the plurality of resonant cavities 2 may be formed by providing a plurality of partitions in the main body 7, wherein the partitions may be fixed in the main body 7 by means of plugging, so that The application can be used to set the number of partitions; or it can be integrally formed in the main body 7, so that the filter is easy to manufacture and the process is simplified.

It can be understood that the filter structure shown in the figure does not constitute a limitation of the filter, and includes an input circuit, an output circuit, a connector, etc., and the input circuit and the output circuit are connected to the main body 7, and the input circuit and The output circuit is connected to the connector, and the connector can be connected to the functional unit through a cable, such as a printed circuit board (PCB) and an antenna.

The above is only the specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily think of changes or substitutions within the technical scope of the present invention, and should cover It is within the scope of the invention. Therefore, the scope of protection of the invention should be determined by the scope of the claims.

Claims

claims

1. A filter tuning device, characterized in that it includes a resonant cavity, a cover, and a resonant rod. The bottom of the resonant cavity is provided with a through hole, and the resonant rod passes through the through hole from the resonant cavity. , the cover is covered on the resonant cavity, and the resonant rod is movable through the through hole in a direction perpendicular to the bottom of the resonant cavity.

2. The filter tuning device according to claim 1, wherein the through hole has an internal thread, the resonant rod is provided with a first external thread matching the internal thread, and the resonant rod Screw it into the through hole and rotate the resonant rod so that it can move in a direction perpendicular to the bottom of the resonant cavity.

3. The filter tuning device according to claim 2, wherein the bottom surface of the resonant cavity is provided with a boss facing toward the cover, and the boss is perpendicular to the bottom surface of the resonant cavity and has a height of 'J. The length of the resonance rod, and the through hole is provided on the boss.

4. The filter tuning device according to claim 2 or 3, further comprising a locking part, the locking part being used to lock the resonant rod on the resonant cavity.

5. The filter tuning device according to claim 4, wherein the locking portion includes at least a second external thread and a third external thread provided on the resonant rod and opposite to the internal thread. thread, the second external thread and the third external thread in the locking part are adjacent; the pitch of the second external thread is greater than the pitch of the first external thread, and the third external thread The pitch of the thread is smaller than the pitch of the first external thread.

6. The filter tuning device according to claim 4, wherein the locking portion includes more than two opening grooves provided on the resonant rod and opposite to the internal thread, and the opening grooves The depth of the opening is greater than the depth of the first external thread.

7. The filter tuning device according to claim 6, wherein the width between two adjacent opening grooves is at least greater than the pitch of the first external thread.

8. The filter tuning device according to claim 6 or 7, characterized in that the opening directions of two adjacent opening slots are opposite.

9. The filter tuning device according to claim 8, wherein the depth of the opening groove is The degree is greater than the radius of the resonant rod and smaller than the diameter of the resonant rod.

10. The filter tuning device according to claim 9, wherein the two or more open slots are close to the bottom end of the resonant rod.

11. The filter tuning device according to claim 4, wherein the locking part includes a nut that matches the first external thread and is used to remove the resonant rod from the bottom of the resonant cavity. The protruding first external thread portion is locked.

12. The filter tuning device according to claim 11, wherein a groove is provided at the bottom outside the resonant cavity and at a position opposite to the boss, and the height of the groove is greater than that of the nut. The height of the groove is less than the thickness of the bottom of the resonant cavity, and the first externally threaded portion of the resonant rod and the nut are located in the groove.

13. The filter tuning device according to claims 1-12, characterized in that the resonant cavity, the cover and the resonant rod are all metal parts that have been surface-treated.

14. The filter tuning device according to claim 13, wherein the resonant cavity and the cover are made of aluminum alloy and magnesium alloy respectively, and the resonant rod is made of iron or copper.

15. A filter, characterized in that it includes a main body, and the main body includes a plurality of filter tuning devices according to any one of claims 1-14.