Low-pass filter

Abstract

The invention belongs to the technical field of communication equipment, and particularly relates to a low-pass filter. Comprising a metal cavity and a cover plate, the cover plate is arranged on the metal cavity, a plurality of chambers are arranged in the metal cavity, and the chambers are distributed in a front-back surrounding mode; through holes are formed among the cavities; a passive filter is arranged in one cavity; a plurality of low-pass filters are arranged in the opposite chamber; and far-end suppression is superposed by matching through holes penetrating through the bottoms of the cavities in the cavity depth direction and relative positions of the through holes, the cover plate, a resonance tuning screw rod and a coupling tuning screw rod which are arranged at the bottom of the first cavity. The LC filter and the metal low pass are connected in series in the metal cavity, so that the far-end suppression index of the ultra-low frequency filter meets the requirement; in the aspect of structure, module volume is saved, surrounding distribution and a front and back universal mode are adopted, the volume is reduced to 50% of that of the original design, and a far-end suppression index is realized at the same time.

Description

Technical Field

[0001] The present invention relates to the technical field of communication equipment, and in particular to a low-pass filter. Background Art

[0002] A low-pass filter is an electronic filter that allows signals below the cutoff frequency to pass through, but suppresses or attenuates signals above the cutoff frequency. The main function of this filter is to filter and adjust the input signal so that the high-frequency components in the output signal are weakened or eliminated, thereby retaining the low-frequency components. In signal processing, low-pass filters are often used to smooth signals, remove noise, and suppress high-frequency interference.

[0003] With the continuous development and updating of the communication field, low-frequency bands such as 200MHz filters are needed in the civilian or military fields, and there is a requirement for far-end suppression. The filter usually generates far-end harmonics itself and cannot be effectively avoided. Therefore, a low-pass filter that can effectively suppress the far-end is needed.

[0004] The low-frequency filter in the prior art is a conventional metal cavity or a spiral structure. Due to the influence of the low-frequency cavity depth or the spiral structure, the volume is large, and the far-end harmonics usually appear at 2G, and the far-end suppression is extremely poor. Summary of the invention

[0005] The present invention aims to solve the problems that the low-frequency filter in the prior art is a conventional metal cavity or a spiral structure, and due to the influence of the low-frequency cavity depth or the spiral structure, the far-end harmonic usually appears at 2G, and the far-end suppression is very poor. A low-pass filter is provided, comprising a metal cavity and a cover plate closing the opening of the metal cavity, at least two chambers are arranged in the metal cavity, and the front and back sides of the chambers are surrounded; a passive filter and a circuit board are arranged in the first chamber; at least two independent partitions are arranged in the second chamber; the independent partitions are connected by a connecting groove; a tap is arranged in the connecting groove; Low-pass filter units are respectively arranged in the vertical partition grooves; the low-pass filter units are coupled to each other through the taps in the connecting grooves; there are through holes between the chambers; a coupling structure is arranged in the through holes; the passive filter and the low-pass filter unit are coupled in a surround manner through the coupling structure arranged in the through holes to form a low-pass filter module; the cover plate and the bottom of the first chamber are provided with threaded holes and a resonance tuning screw and a coupling tuning screw passing through the threaded holes; the second chamber is also provided with a through hole that passes through the bottom of the chamber along the depth direction of the cavity; the through hole is arranged between the independent partition grooves in the second chamber.

[0006] Preferably, the through hole provided on the second chamber is a rectangle with chamfered edges, and the aspect ratio of the rectangle is ≥2.

[0007] Preferably, the independent partitions arranged in the second chamber are in a rectangular shape, and the low-pass filter units are horizontally arranged in the independent partitions of the second chamber.

[0008] Preferably, each independent partition groove arranged in the second chamber is parallel to the through hole and is arranged on both sides of the through hole at the same distance from the through hole.

[0009] Preferably, the first chamber and the second chamber are distributed in two layers, the first chamber and the second chamber are open to the outside at opposite side walls and have complementary shapes; the through hole only passes through the bottom of the second chamber without interfering with the first chamber and the side wall of the first chamber.

[0010] Preferably, the first chamber is rectangular, and the second chamber opposite to it is L-shaped, and the openings of the first chamber and the second chamber are arranged opposite to each other; a through hole is arranged between the first chamber and the second chamber; the first chamber and the second chamber are respectively provided with a first cover plate and a second cover plate on the top; the first chamber and the first cover plate, and the second chamber and the second cover plate are fixed by bolts at equal intervals.

[0011] Preferably, the side walls of the first chamber, the second chamber, the through hole and the independent partition groove have the same thickness; and there is a gap between the inner sides of the side walls of the first chamber and the second chamber and the low-pass filter unit.

[0012] Preferably, the passive filter is an LC filter, which is disposed in the first chamber, and has gaps with the inner side of the side wall of the first chamber and the bottom of the first chamber.

[0013] Preferably, the low-pass filter unit is a coaxial filter, and the coaxial filters are independently arranged in each independent slot in the second chamber, and are connected in series in sequence through the taps in the connecting slots.

[0014] Preferably, one end of the LC filter is connected to the connecting component, and the other end is connected in series in a surrounding manner through a coupling structure arranged in the through hole to form a very high frequency low pass filter module.

[0015] The beneficial effects of the present invention are as follows: The present invention connects an LC filter and a low-pass filter unit in series in a metal cavity, and through a cavity structure with surround distribution on the front and back sides of the metal cavity, in conjunction with a through hole arranged through the bottom of the cavity along the cavity depth direction and its relative position with a cover plate, a resonant tuning screw and a coupling tuning screw arranged at the bottom of the first cavity, superimposes far-end suppression, and achieves that the far-end suppression index of the ultra-low frequency filter meets the requirements; in terms of structure, in order to save the module volume, a surround distribution and a common front and back method are adopted, and the volume is reduced to 50% of the original design, while achieving the far-end suppression index. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural schematic diagram of an embodiment of the present invention.

[0017] Figure 2 It is a structural schematic diagram of another side of an embodiment of the present invention.

[0018] Figure 3 An exploded view of parts of an embodiment of the present invention.

[0019] Figure 4 The low-pass filter channel of the first low-pass filter unit 3 is directly used.

[0020] Figure 5 It is a test curve of directly using the low-pass filter of the first low-pass filter unit 3.

[0021] Figure 6 A low-pass filter channel according to an embodiment of the present invention.

[0022] Figure 7 This is a test curve of a low-pass filter according to an embodiment of the present invention.

[0023] Figure 8 This is the test curve of the low-pass filter that directly uses the LC filter.

[0024] Fig. 9 It is a test curve of directly using the low-pass filter of the second low-pass filter unit 4.

[0025] In the figure: 1-circuit board; 2-metal cavity; 3-first low-pass filter unit; 4-second low-pass filter unit; 5-first cover plate; 6-second cover plate; 7-tap; 8-line card; 9-fixing medium; 10-connector; 11-through hole; 12-resonance tuning screw; 13-coupling tuning screw. DETAILED DESCRIPTION

[0026] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0027] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0028] In the description of this embodiment, the terms "upper", "lower", "left", "right" and other directions or positional relationships are based on the directions or positional relationships shown in the drawings, and are only for the convenience of description and simplification of operation, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operate in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used to distinguish in the description and have no special meaning.

[0029] As is well known, in communication systems and other systems, communication devices such as base stations and terminal devices all include filters, and currently, in order to meet the requirements of low cost and miniaturization, dielectric filters are usually selected. The dielectric filter includes at least two dielectric resonators, and the at least two dielectric resonators are coupled and arranged in sequence. In practice, due to the coupling between at least two dielectric resonators in the dielectric filter, the magnetic field in the dielectric filter will be distributed in the range including all dielectric resonators, which will cause the high-order harmonic frequency to decrease, making the remote suppression capability worse. Based on this, the embodiment of the present application designs a low-pass filter so that the passive filter is connected in series with the low-pass filter, and is respectively arranged in a chamber with a surround distribution on the front and back sides, so as to improve the remote suppression capability. Further, the base station and terminal device containing the designed low-pass filter can better meet user needs during the communication process and improve the user experience. In addition, the low-pass filter designed in the embodiment of the present application is easy to implement, simple in structure, and small in size, so it has strong practicality.

[0030] The embodiment of the present invention provides a filtering device, such as Figures 1 to 4 As shown, a low-pass filter, specifically, the metal cavity 2 is a layered structure, each layer is provided with a cavity, and through holes are provided between each cavity. Figure 1 The chamber of the metal cavity 2 shown is a two-layer structure arranged on both sides, including a first chamber and a second chamber.

[0031] At least one LC filter is arranged in the first chamber, and a through hole is arranged between the first chamber and the second chamber.

[0032] One end of the LC filter is connected to a connector 10; a first low-pass filter unit 3 and a second low-pass filter unit 4 are arranged in the second chamber; one end of the second low-pass filter unit 3 is connected to the fourth low-pass filter unit 4 through a through hole; the other end of the first low-pass filter unit 3 is connected to one end of the second low-pass filter unit 4; the other end of the second low-pass filter unit 4 is led out by a cable through a line card 8 arranged in a slot in the second chamber; a tap 7 is arranged between the first low-pass filter unit 3 and the second low-pass filter unit 4, the tap 7 passes through the through hole, and is fixed by a fixing medium 9 arranged in the through hole; A circuit board 1 connected to a first low-pass filter unit 3 is also disposed in the first chamber; The first cover plate 5 is arranged on the top of the first chamber; the second cover plate 6 is arranged on the top of the second chamber.

[0033] Specifically, the first cover plate 5 and the second cover plate 6 are provided with evenly arranged threaded holes, and threaded holes are also provided at corresponding positions on the top of the side walls of the chambers in which they are provided. The cover plates 5 and 6 are fixedly connected to their corresponding chambers by screws to form a closed space.

[0034] It should be noted that Figure 1 In the low-pass filter shown, only the case where a through hole is set between two chambers is shown; optionally, through holes may be set between other chambers of the metal cavity 2, and multiple through holes may be set between other chambers of the metal cavity 2. This application will not list them one by one here.

[0035] In an optional embodiment, the through hole may be, but is not limited to, a straight through hole, a curved through hole, or an irregular through hole, etc. In an optional embodiment, when there are multiple through holes between a pair of adjacent chambers mentioned above, some of the multiple through holes may be straight through holes, some may be curved through holes, some may be irregular through holes, etc., and all may be straight through holes, all may be curved through holes, or all may be irregular through holes, etc., and the present application does not limit this.

[0036] It should be noted that in the schematic diagram of the low-pass filter shown in the embodiment of the present application, the through holes are all exemplified as circular holes. It should be understood that this is only an example. Optionally, the through holes can be square holes, irregular holes, etc., and the present application does not limit this. Similarly, it should be noted that the low-pass filter units shown in the embodiment of the present application are all shown as cylinders. This is also only an example. The low-pass filter units are not limited to cylinders, but can also be any other shapes.

[0037] It should be noted that the above-mentioned metal cavities 2 are all regular polyhedrons. In practice, the metal cavity 2 can also be an irregular polyhedron, that is, the number of side surfaces on the first side and the side surfaces on the second side are not equal, or the concave and convex surfaces are not equal, etc. However, as long as the two openings of the through hole are respectively located in at least two adjacent chambers, the specific forms will not be listed one by one in this application.

[0038] by Figure 1 Take a through hole in as an example: It can be understood that Figure 1The arrangement direction of the low-pass filter units in the low-pass filter described in the figure can be the width direction of the first low-pass filter unit 3 and the second low-pass filter unit 4; the first low-pass filter unit 3 to the second low-pass filter unit 4 are arranged in the chamber where they are located according to their lengths, and the two sides of the arrangement direction are in the L-shaped chamber shown in the figure. Other low-pass filter units can be set on one side of the first low-pass filter unit 3 or one side of the second low-pass filter unit 4, and the specific application is not limited to this.

[0039] It should be noted that each layer of the metal cavity 2 is provided with an opening, the purpose of which is to facilitate the disassembly of the low-pass filter during the assembly process, without interfering with other objects, and superimposing the far-end suppression; In this embodiment, the metal cavity 2 is divided into an upper and lower chamber, and the openings of the upper and lower chambers are arranged relatively to each other; the metal cavity 2 may have multiple sides. In this case, one opening of the upper chamber can be located on any one of the multiple sides of the first side, and the other opening can be located on any one of the multiple sides of the second side. This application does not limit this.

[0040] A cover plate is disposed on the top of each chamber, and a connector 10 for connecting an external device is disposed in one of the chambers.

[0041] In this embodiment, two chambers are arranged in the metal cavity, and the front and back sides of the chambers are arranged in a surround manner; a passive filter and a circuit board 1 are arranged in the first chamber; two independent partitions are arranged in the second chamber; the independent partitions are connected by a connecting groove; a tap 7 is arranged in the connecting groove; low-pass filter units are respectively arranged in the independent partitions; the low-pass filter units are coupled to each other through the tap 7 in the connecting groove; there is a through hole between the chambers; a coupling structure is arranged in the through hole; the passive filter and the low-pass filter unit are coupled in a surround manner through the coupling structure arranged in the through hole to form a low-pass filter module; the cover plate and the bottom of the first chamber are provided with threaded holes and a resonant tuning screw 12 and a resonant tuning screw 13 passing through the threaded holes; the second chamber is also provided with a through hole 11 that passes through the bottom of the chamber along the cavity depth direction; the through hole 11 is arranged between the independent partitions in the second chamber.

[0042] In this embodiment, the through hole 11 provided on the second chamber is a rectangle with chamfered edges, and the aspect ratio of the rectangle is 2.

[0043] The shape of the independent partitions arranged in the second chamber is rectangular, and the low-pass filter units are horizontally arranged in the independent partitions of the second chamber. The independent partitions arranged in the second chamber are parallel to the through hole 11, and are arranged on the left and right sides of the through hole 11 at the same distance from the through hole 11. The first chamber and the second chamber are distributed in two layers, the first chamber and the second chamber are opened to the outside on the opposite side walls and have complementary shapes; the through hole 11 only passes through the bottom of the second chamber, and does not interfere with the first chamber and the side wall of the first chamber. The first chamber is rectangular, and the second chamber opposite to it is L-shaped, and the openings of the first chamber and the second chamber are arranged oppositely; a through hole is arranged between the first chamber and the second chamber; the first cover plate 5 and the second cover plate 6 are respectively arranged on the top of the first chamber and the second chamber; the first chamber and the first cover plate 5, and the second chamber and the second cover plate 6 are fixed by bolts at equal intervals.

[0044] In this embodiment: the side walls of the first chamber, the second chamber, the through hole 11 and the independent partition groove have the same thickness; there is a gap between the inner sides of the side walls of the first chamber, the second chamber and the low-pass filter unit.

[0045] In this embodiment, the passive filter is an LC filter, which is disposed in the first chamber, and has gaps with the inner side of the side wall of the first chamber and the bottom of the first chamber.

[0046] In this embodiment Figure 3 Only the first low-pass filter unit 3 and the second low-pass filter unit 4 are shown. The first low-pass filter unit 3 can be understood as the first low-pass module, and the second low-pass filter unit 4 can be understood as the second low-pass module. The first low-pass module is composed of at least one coaxial filter, each coaxial filter is arranged in sequence and coupled with the adjacent coaxial filter along the arrangement direction; at least one coaxial filter is coupled with the adjacent coaxial filter along the arrangement direction to generate a transmission zero at the high-frequency end of the passband of the first low-pass module; the second low-pass module is composed of at least one coaxial filter, each coaxial filter is arranged in sequence and coupled with the adjacent coaxial filter along the arrangement direction; the coaxial filter located at the tail of the first low-pass module is coupled with the coaxial filter located at the head of the second low-pass module; the coaxial filter located at the tail of the first low-pass module is coupled with the coaxial filter located at the head of the second low-pass module through a coupling ring. The coupling ring is a metal lock silver part. Each coaxial filter is coupled with the adjacent coaxial filter along the arrangement direction through a coupling window.

[0047] In this embodiment, the thickness of the side walls between the first chamber, the second chamber, the through hole 11 and the independent partition groove is adjusted to 1 / 8 of the width of the first chamber; the first chamber and the second chamber are rectangular in shape, and their length-to-width ratios are 4:3 and 20:9 respectively; the through hole 11 is rectangular in shape, and its length-to-width ratio is 8:1, and the through hole 11 is symmetrically arranged along the central axis of the length direction of the second chamber; the threaded hole arranged at the bottom of the first chamber and the positional relationship of the resonant tuning screw 12 and the resonant tuning screw 13 passing through the threaded hole are adjusted, and the height of the resonant tuning screw 12 and the resonant tuning screw 13 protruding from the mounting surface, and the low-pass filter channel connected in series with the LC filter and the first low-pass filter unit 3 and the second low-pass filter unit 4 arranged in the metal chamber 2, and the far-end suppression is superimposed.

[0048] In this embodiment, Figures 1 to 3 The resonance tuning screw 12 and the resonance tuning screw 13 are not drawn in the figure, only the positions of the threaded holes for installing the resonance tuning screw 12 and the resonance tuning screw 13 are schematically shown. The positions of the threaded holes for installing the resonance tuning screw 12 and the resonance tuning screw 13 on the cover plate and the bottom of the first chamber include but are not limited to the positions shown in the drawings. The number, length and diameter of the resonance tuning screw 12 and the resonance tuning screw 13 can be any reasonable arrangement and combination.

[0049] After directly using the LC filter to suppress the harmonics in the 2.5G~3G frequency band, the suppression index approaches zero; directly using the first low-pass filter unit 3 or directly using the far-end index of the second low-pass filter unit 4, if you don't care about it in the 2G~3G range, its suppression is less than 30dB.

[0050] The far-end index of directly using the first low-pass filtering unit 3 or directly using the second low-pass filtering unit 4 is not considered in the range of 2G to 3G: stop band suppression <30dB.

[0051] Directly using LC filter can achieve the following indicators: Passband: 223-235MHz echo 20dB; Stopband suppression: ≥75dBc@800MHz~2700MHz; The simulation curve is as attached Figure 8 shown.

[0052] Directly using the first low-pass filter unit 3, which is a metal high-low impedance line alternating type, can achieve the following indicators: Passband: 223-235MHz; Echo: 20dB; Stopband Rejection: ≥60dBc@2700MHz~3800MHz; ≥56dBc@2700MHz~5000MHz; ≥45dBc@5000MHz~6000MHz; See the attached simulation curve Figure 5 shown.

[0053] Directly adopt the second low-pass filter unit 4, which is a metal high-low impedance line alternating type, and can achieve the following indicators: Passband: 223-235MHz; Echo 20dB; Stopband suppression: ≥50dBc@6000MHz~12750MHz; See the attached simulation curve Fig. 9 shown.

[0054] The low-pass filter of the present invention uses an LC filter and a low-pass filter in series with the first low-pass filter unit 3 and the second low-pass filter unit 4. After the low-pass filter is connected in series, the suppression index is superimposed in the same frequency band; in the frequency range of 2G~14G, the suppression reaches about 50dB.

[0055] like Figure 4 As shown, the low-pass filter channel of the first low-pass filter unit 3 is directly used; Figure 5 The test curve of the low-pass filter channel of the first low-pass filter unit 3 is directly used, and the displayed curve suppresses the result; Figure 8 This is the test curve of the low-pass filter that directly uses the LC filter; Fig. 9 A test curve for directly using the low-pass filter of the second low-pass filter unit 4; Figure 6 A low-pass filter channel in which an LC filter is arranged in the metal chamber 2 and is connected in series with a first low-pass filter unit 3 and a second low-pass filter unit 4; Figure 7 The test curve of the low-pass filter in which the LC filter arranged in the metal chamber 2 is connected in series with the first low-pass filter unit 3 and the second low-pass filter unit 4, and the curve suppression result is displayed; it can be seen that the low-pass filter in which the LC filter arranged in the metal chamber 2 is connected in series with the first low-pass filter unit 3 and the second low-pass filter unit 4 provided in the embodiment of the present application has a significant improvement in the suppression result at 8-10GHz compared with the low-pass filter directly using the LC filter, or directly using the first low-pass filter unit 3, or directly using the second low-pass filter unit 4, and the new superimposed suppression is about 50dB. The low-pass filter in which the LC filter arranged in the chamber 2 is connected in series with the first low-pass filter unit 3 and the second low-pass filter unit 4 forms a 200MHz low-pass filter, which solves the far-end suppression of the 200MHz filter after 2GHz, and the farthest suppression requirement can reach about 14GHz.

[0056] The low-pass filter performance of the present invention is: Passband frequency: 223-235MHz; Stopband Rejection: ≥75dBc@800MHz~2700MHz; ≥60dBc@2700MHz~3800MHz; ≥56dBc@2700MHz~5000MHz; ≥45dBc@5000MHz~6000MHz; ≥20dBc@6000MHz~12750MHz; The low-pass filter of the present invention has a very strong stop-band suppression of 75 dB from 800 MHz to 2700 MHz, and the stop-band suppression is 20 dB up to 12750 MHz.

[0057] The installation method of this embodiment is as follows: an antenna port connector is assembled on the metal cavity 2; one end of the LC filter is welded to the antenna port connector, and the other end is connected to the first low-pass filter unit 3, and is fixed using a first cover plate 5 and screws; one end of the first low-pass filter unit 3 and the second low-pass filter unit 4 are welded in series in the cavity on the same side of the metal cavity 2, and are fixed using a second cover plate 6 and screws; the other end of the second low-pass filter unit 4 is led out as a cable; the positions of the resonant tuning screw 12 and the resonant tuning screw 13 and their positional relationship with the through hole 11 are adjusted.

[0058] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

[0059] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A low-pass filter, characterized in that: It comprises a metal cavity and a cover plate for sealing the opening of the metal cavity, wherein at least two chambers are arranged in the metal cavity, and the front and back sides of the chambers are arranged in a surrounding manner; a passive filter and a circuit board are arranged in the first chamber; at least two independent partitions are arranged in the second chamber; the independent partitions are connected by a connecting groove; taps are arranged in the connecting groove; low-pass filter units are respectively arranged in the independent partitions; the low-pass filter units are coupled to each other through the taps in the connecting groove; there are through holes between the chambers; a coupling structure is arranged in the through holes; the passive filter and the low-pass filter unit are coupled in a surrounding manner through the coupling structure arranged in the through holes to form a low-pass filter module; the cover plate and the bottom of the first chamber are provided with threaded holes and a resonant tuning screw and a coupling tuning screw passing through the threaded holes; the second chamber is also provided with a through hole that passes through the bottom of the chamber along the cavity depth direction; the through hole is arranged between the independent chambers in the second chamber.

2. The low-pass filter according to claim 1, characterized in that: The through hole arranged on the second chamber is a rectangle with chamfered corners on four sides, and the aspect ratio of the rectangle is ≥2.

3. The low-pass filter according to claim 2, characterized in that: The independent partitions arranged in the second chamber are in a rectangular shape, and the low-pass filter units are horizontally arranged in the independent partitions of the second chamber.

4. The low-pass filter according to claim 3, characterized in that: The independent partitions arranged in the second chamber are parallel to the through hole and are arranged on both sides of the through hole at the same distance from the through hole.

5. The low-pass filter according to claim 4, characterized in that: The first chamber and the second chamber are distributed in two layers, the first chamber and the second chamber are open to the outside at opposite side walls and have complementary shapes; the through hole only passes through the bottom of the second chamber without interfering with the first chamber and the side wall of the first chamber.

6. The low-pass filter according to claim 1 or 5, characterized in that: The first chamber is rectangular, and the second chamber opposite to it is L-shaped. The openings of the first chamber and the second chamber are arranged opposite to each other; a through hole is arranged between the first chamber and the second chamber; a first cover plate and a second cover plate are arranged on the top of the first chamber and the second chamber respectively; the first chamber and the first cover plate, and the second chamber and the second cover plate are fixed by bolts with equal spacing.

7. The low-pass filter according to claim 6, characterized in that: The side walls of the first chamber, the second chamber, the through hole and the independent partition groove have the same thickness; there is a gap between the inner sides of the side walls of the first chamber and the second chamber and the low-pass filter unit.

8. The low-pass filter according to claim 7, characterized in that: The passive filter is an LC filter, which is arranged in the first chamber, and has gaps with the inner side of the side wall of the first chamber and the bottom of the first chamber.

9. The low-pass filter according to claim 8, characterized in that: The low-pass filter unit is a coaxial filter, which is independently arranged in each independent slot in the second chamber and connected in series in sequence through the taps in the connecting slots.

10. The low-pass filter according to claim 9, characterized in that: One end of the LC filter is connected to the connecting component, and the other end is connected in series in a surrounding manner through a coupling structure arranged in the through hole to form a very high frequency low pass filter module.

Images