Small size cavity filter for suppressing adjacent channel interference in power base stations

Abstract

The present invention relates to the field of cavity filter technology, and specifically to a small-size cavity filter for suppressing adjacent channel interference in a power base station, including a plurality of cavities, wherein the plurality of cavities are divided into two groups, and the two groups are symmetrically arranged front to back, and the ends of the two cavities on the left are provided with radio frequency connectors, wherein each cavity is provided with a resonance rod one, a resonance rod two and a resonance rod three, wherein the resonance rod one is distributed in the cavity along the length direction of the cavity, and the two ends of the resonance rod one are respectively connected to the inner wall of the cavity. In summary, the cavity filter operates in the 1.8 GHz frequency band, has low insertion loss and good frequency selectivity, can significantly attenuate interference originating from adjacent frequency bands, thereby effectively improving the anti-interference performance of the system, and according to the user's requirements for size and cost, it can be used in a single cavity cascaded with the original system, or in a multi-cavity independent use mode, and has greater flexibility in configuration.

Description

Technical Field

[0001] The present invention relates to the technical field of cavity filters, and in particular to a small-size cavity filter for suppressing adjacent channel interference in a power base station. Background Art

[0002] Cavity filters mainly use metal resonant cavity structures. A single cavity can be equivalent to a resonant circuit of inductors and capacitors in parallel or series, thus becoming a resonant unit. Single cavities are coupled through slots or metal rods, which can be equivalent to devices such as inductors (transformers) or capacitors, forming inductive or capacitive coupling, and then further improving their frequency selectivity through cascading. Compared with other filters, cavity filters have the advantages of firm structure, stable and reliable performance, good heat dissipation, high quality factor (Q), low loss and large power capacity, making them widely used in various microwave systems such as radar and wireless communications.

[0003] At present, many power-specific network base stations using TDD communication mode have an operating frequency band of 1790-1800MHz, while mobile communication public network base stations have added operating frequency bands as the number of users they serve increases. They have expanded the uplink 890-915MHz and downlink 935-960MHz bands that were initially configured, and first added uplink 1710MHz-1785MHz and downlink 1805MHz-1880MHz bands. Therefore, the operating frequency bands of many power-specific network base stations are currently between the operating frequency bands of mobile communication public network base stations, and the spacing is only 5MHz, that is, the operating frequency bands of many power-specific network base stations are in the gap between the operating frequency bands of mobile communication public network base stations.

[0004] In the above context, with the surge in mobile communication users and the adjustment of mobile communication public network base station parameters, the isolation of the existing cavity filters of the power private network base stations to the mobile public network signals has become insufficient, and the out-of-band suppression effect is poor, causing the power private network base stations to be interfered to varying degrees, affecting the normal transmission and operation of the power private network. Summary of the invention

[0005] In view of this, the purpose of the present invention is to propose a small-size cavity filter for suppressing adjacent channel interference in a power base station, so as to solve the problem of insufficient isolation of the cavity filter of the existing power private network base station to the mobile public network signal, that is, to solve the problem that the power private network base station is interfered to varying degrees by signals from the mobile communication public network and other networks.

[0006] Based on the above purpose, the present invention provides a small-size cavity filter for suppressing adjacent channel interference in a power base station, comprising a plurality of cavities, wherein the plurality of cavities are divided into two groups, and the two groups are symmetrically arranged front to back, and the ends of the two cavities on the left are both provided with radio frequency connectors;

[0007] Among them, each cavity is provided with a resonant rod 1, a resonant rod 2 and a resonant rod 3 with variable positions. The resonant rod 1 is distributed in the cavity along the length direction of the cavity, and the two ends of the resonant rod 1 are respectively connected to the inner wall of the cavity, the resonant rod 2 is distributed in front of the resonant rod 1 along the height direction of the cavity, and the bottom end of the resonant rod 2 is connected to the bottom of the cavity, and the resonant rod 3 is distributed in front of the resonant rod 2 along the height direction of the cavity, and the top end of the resonant rod 3 is connected to the top of the cavity.

[0008] Preferably, the four cavities are respectively a first cavity, a second cavity, a third cavity and a fourth cavity, and the first cavity and the second cavity are horizontally arranged to form a group, and the third cavity and the fourth cavity are horizontally arranged to form another group, which are symmetrically arranged front to back.

[0009] Preferably, the first cavity and the second cavity are inductively connected by arranging a cavity channel at the bottom of the two cavities, the second cavity and the third cavity are inductively connected by arranging a cavity channel in the middle and upper parts of the two cavities, the third cavity and the fourth cavity are inductively connected by arranging a cavity channel in the middle and lower parts of the two cavities, and the fourth cavity and the first cavity are coupled by arranging a solid copper column with a radius of 4mm and a height of 2.5mm, and the center of the copper column is 9mm away from the bottom of the cavity and 11mm away from the top of the cavity.

[0010] Preferably, the radio frequency connector is arranged on the first cavity and the fourth cavity, and a transmission line is arranged inside the radio frequency connector.

[0011] Preferably, the resonance rod one, the resonance rod two and the resonance rod three are all rectangular resonance rods, the shape of the cavity is also rectangular, and the resonance rod two is located at the front center of the resonance rod one, and the resonance rod three is located at the front center of the resonance rod two.

[0012] Preferably, the length, width and height ratio of the cavity is controlled within the range of 3.7:2:5-4; 2:5, the length, width and height ratio of the resonance rod one is 15:1:2, the length, width and height ratio of the resonance rod two is controlled within the range of 7:1:14-7:1:15, and the length, width and height ratio of the resonance rod three is 2:1:18.

[0013] Preferably, there are gaps between the resonance rod one, the resonance rod two and the resonance rod three.

[0014] Preferably, the distance ratio between the resonance rod 2 and the resonance rod 1 and the resonance rod 3 is 1:3, the distance ratio between the resonance rod 1 and the front and back sides of the cavity and the bottom is 5:2:9, and the distance ratio between the resonance rod 3 and the front and back sides of the inner wall of the cavity is controlled within the range of 1.6:1-1.8:1.

[0015] Preferably, the cavity and the first, second and third resonance rods are all made of any one of alloy aluminum or beryllium bronze alloy.

[0016] Preferably, the smoothness grade of the inner wall of the cavity is greater than Ra6.3.

[0017] The beneficial effects of the present invention are as follows:

[0018] 1. Compared with existing products, the size is greatly reduced, which is convenient for system integration and can also meet the needs of application scenarios with strict size requirements. The size of a single cavity (including two RF connectors) is only 8mm*29mm*20mm. Figure 8 As shown in the figure, the size of the four-cavity filter (including two RF connectors) is only 18.5mm*38mm*20mm. Fig. 9 shown.

[0019] Second, the target stopband frequency can be adjusted more flexibly. The stopband frequency can be changed by adjusting the resonant cavity, the resonant rod, and the distance between the resonant rod and the cavity. For example, the stopband frequency can be changed to the left adjacent channel (for example, around 1540MHz, such as Figure 7 As shown), the stopband frequency can also be changed to the right adjacent channel (for example, around 1880MHz, such as Figure 6 shown).

[0020] 3. It can implement a large attenuation on the target stopband. By using three rectangular resonant rods to cooperate with each other, fine-tuning the distance between each resonant rod, the distance connection between each cavity, and connecting them in a cross-coupling manner, a zero point with a large attenuation degree can be obtained (it can be as small as -120dB or less, such as Figure 5 As shown); the following experience is summarized in a large number of simulations (mainly using HFSS software): the interval between the resonant rod one and the resonant rod two is about 0.1mm, the interval between the resonant rod two and the resonant rod three is about 0.3mm, and by using inductive coupling between the first cavity and the second cavity, inductive coupling between the second cavity and the third cavity, inductive coupling between the third cavity and the fourth cavity, and capacitive coupling between the fourth cavity and the first cavity, the center frequency of the narrowband filter can be moved to around 1800MHz, and the target stopband can be greatly attenuated.

[0021] 4. The cavity unit configuration is very flexible during use, and it can be used with multiple cavities or a single cavity. Since the user's application scenario often places restrictions on the volume and size of the cavity filter, and the user's economic ability or inconvenient budget plan often places restrictions on the cost of the cavity filter. If the user has strict restrictions on the size and requires a significant reduction, but has no strict restrictions on the cost, the method of using multiple cavities independently (dismantling the original system) is generally adopted. This is because the simulation results show that the size of the four-cavity filter (including two RF connectors) is very small, only 18.5mm*38mm*20mm, such as Fig. 9 As shown; if the user has strict restrictions on cost, and the volume restriction only requires a small increment based on the size of the original system, a single-cavity configuration is generally adopted, and the single cavity is cascaded with the user's original cavity filter (without dismantling the original system). This is because the size of the single cavity (including two RF connectors) is smaller, only 8mm*29mm*20mm, as shown Figure 8 As shown in the figure, the increment of the overall size after cascading with the original cavity filter in any dimension is extremely small and can be ignored, so it is easy to meet the user's size restrictions and can greatly save economic costs, that is, it is easy to meet the user's cost restrictions. In addition, when a single cavity is cascaded with the user's original cavity filter, the impact on the original system is minimal, because Figure 6 and Figure 7 The frequency characteristics of the single-cavity filter show that, under the premise of maintaining a sufficiently large attenuation increment for the target adjacent channel, its insertion loss in the 1.8 GHz operating frequency band is very small and the flatness is also high.

[0022] 5. When a single cavity is cascaded with the original system to suppress interference from the right adjacent channel, it can show an extremely narrow transition band, that is, the falling edge is very steep. This performance is conducive to suppressing interference from the right adjacent channel very close to the passband. The closer to the passband, the greater the technical difficulty. This is one of the advantages over the existing technology. In addition, it shows a stopband extreme, and the attenuation increment can be maintained at about 20dB from the 1.8GHz to 3.0GHz band. The wider this band, the greater the technical difficulty. This is the second advantage over the existing technology.

[0023] 6. In summary, the cavity filter has low power loss near the operating frequency of 1.8 GHz, and the cavity filter has good frequency selectivity, and can significantly attenuate unwanted interference within the 1.8 GHz frequency range, thereby effectively improving the anti-interference performance of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 It is a structural schematic diagram of an embodiment of the present invention;

[0026] Figure 2 For the embodiment of the present invention Figure 1 Schematic diagram of the internal structure;

[0027] Figure 3 For the embodiment of the present invention Figure 1 A top sectional view of

[0028] Figure 4 For the embodiment of the present invention Figure 1 Internal structure diagram of a single cavity in the;

[0029] Figure 5 This is a diagram of the simulation results of the frequency characteristics of the multi-cavity filter of the present invention;

[0030] Figure 6 This is a simulation result diagram of the single-cavity filter (unit of the multi-cavity filter) of the present invention implementing fixed-point suppression of interference from a certain frequency domain adjacent to the right;

[0031] Figure 7 This is a simulation result diagram of the single-cavity filter (unit of the multi-cavity filter) of the present invention implementing fixed-point suppression of interference from a certain frequency domain adjacent to the left;

[0032] Figure 8 The three-dimensional dimensions of the single-cavity filter (including connectors) shown in the simulation results;

[0033] Fig. 9 The three-dimensional dimensions of the four-cavity filter (including connectors) shown in the simulation results.

[0034] In the figure: 1, RF connector; 2, copper column; G1, resonant rod one; G2, resonant rod two; G3, resonant rod three; Q1, first cavity; Q2, second cavity; Q3, third cavity; Q4, fourth cavity. DETAILED DESCRIPTION

[0035] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0036] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the embodiments of the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The "first", "second" and similar words used in the present invention do not represent any order, quantity or importance, but are only used to distinguish different components. "Including" or "comprising" and similar words mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connecting" or "connected" and similar words are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0037] like Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 , Fig. 9 As shown, a small-size cavity filter for suppressing adjacent channel interference in a power base station includes a plurality of cavities, wherein the plurality of cavities are divided into two groups, and the two groups are symmetrically arranged front to back, and the ends of the two cavities on the left are both provided with radio frequency connectors 1;

[0038] Among them, each cavity is provided with a resonance rod G1, a resonance rod G2 and a resonance rod G3, and the positions of the resonance rod G1, the resonance rod G2 and the resonance rod G3 are all variable, the resonance rod G1 is distributed in the cavity along the length direction of the cavity, and the two ends of the resonance rod G1 are respectively connected to the inner wall of the cavity, the resonance rod G2 is distributed in front of the resonance rod G1 along the height direction of the cavity, and the bottom end of the resonance rod G2 is connected to the bottom of the cavity, the resonance rod G3 is distributed in front of the resonance rod G2 along the height direction of the cavity, and the top of the resonance rod G3 is connected to the top of the cavity.

[0039] The target stopband frequency can be adjusted flexibly. The stopband frequency can be changed by adjusting the resonant cavity, the resonant rod, and the distance between the resonant rod and the cavity. For example, the stopband frequency can be changed to the left adjacent channel (for example, around 1540MHz, such as Figure 7 As shown), the stopband frequency can also be changed to the right adjacent channel (for example, around 1880MHz, such as Figure 6 shown).

[0040] In a preferred embodiment of the present invention, the four cavities are respectively a first cavity Q1, a second cavity Q2, a third cavity Q3 and a fourth cavity Q4. The first cavity Q1 and the second cavity Q2 are horizontally arranged to form a group, and the third cavity Q3 and the fourth cavity Q4 are horizontally arranged to form another group, which are symmetrically arranged front to back.

[0041] In another preferred embodiment of the present invention, the first cavity Q1 and the second cavity Q2 are inductively coupled by arranging a cavity channel at the bottom of the two cavities, the second cavity Q2 and the third cavity Q3 are inductively coupled by arranging a cavity channel in the middle and upper parts of the two cavities, the third cavity Q3 and the fourth cavity Q4 are inductively coupled by arranging a cavity channel in the middle and lower parts of the two cavities, and a solid copper column 2 with a radius of 4 mm and a height of 2.5 mm is arranged between the fourth cavity Q4 and the first cavity Q1 to achieve capacitive coupling, and the center of the copper column 2 is 9 mm away from the cavity bottom and 11 mm away from the cavity top.

[0042] In another preferred embodiment of the present invention, the RF connector 1 is disposed on the first cavity Q1 and the fourth cavity Q4 , and a transmission line is disposed in the RF connector 1 .

[0043] It should be noted that the resonance rod 1 G1, the resonance rod 2 G2 and the resonance rod 3 G3 are all rectangular resonance rods, and the resonance rod 2 G2 is located at the front center of the resonance rod 1 G1, and the resonance rod 3 G3 is located at the front center of the resonance rod 2 G2.

[0044] The ratio of length, width and height of the cavity is controlled within the range of 3.7:2:5-4.2:5, the ratio of length, width and height of the resonance rod G1 is controlled within the range of about 15:1:2, the ratio of length, width and height of the resonance rod G2 is controlled within the range of 7:1:14-7:1:15, and the ratio of length, width and height of the resonance rod G3 is controlled within the range of about 2:1:18.

[0045] Specifically, the cavity is 15mm long, 8mm wide, and 20mm high; the resonance rod G1 is 15mm long, 1mm wide, and 2mm high; the resonance rod G2 is 7mm long, 1mm wide, and 14.5mm high; and the resonance rod G3 is 2mm long, 1mm wide, and 18mm high.

[0046] It should be noted that the distance ratio between the resonance rod 2 G2 and the resonance rod 1 G1 and the resonance rod 3 G3 is controlled at about 1:3, the distance ratio between the resonance rod 1 G1 and the front and back sides of the cavity and the bottom is controlled at about 5:2:9, and the distance ratio between the resonance rod 3 G3 and the front and back sides of the inner wall of the cavity is controlled in the range of 1.6:1-1.8:1.

[0047] Specifically, the interval between the resonance rod G1 and the resonance rod G2 is 0.1mm, the interval between the resonance rod G2 and the resonance rod G3 is 0.3mm, the distance between the resonance rod G1 and the front and back sides of the inner wall of the cavity are 5mm and 2mm respectively, and the distance between the resonance rod G1 and the bottom of the inner wall of the cavity is 9mm, and the distance between the resonance rod G3 and the front and back sides of the inner wall of the cavity are 4.4mm and 2.6mm respectively, and the above-mentioned dimensional data are reference dimensions, and a certain error is allowed during actual processing.

[0048] It should be noted that the cavity and the resonance rod G1, the resonance rod G2 and the resonance rod G3 are all made of any one of alloy aluminum or beryllium bronze alloy, and the alloy aluminum or beryllium bronze alloy has the characteristics of good elasticity, high strength and easy processing.

[0049] It should be noted that the smoothness grade of the inner wall of the cavity is greater than Ra6.3. Considering the skin effect of high-frequency signals, the smoothness grade of the inner wall of the filter cavity is required to be greater than Ra6.3 during processing. The dimensional data provided above are reference dimensions, and a certain error is allowed during actual processing.

[0050] The stopband frequency can be changed by adjusting the resonant cavity, the resonant rod, and the distance between the resonant rod and the cavity. By using three rectangular resonant rods to cooperate with each other, the distance position between each resonant rod and the distance connection method between each cavity are fine-tuned many times, and they are connected in a cross-coupling manner; experience is summarized in a large number of simulations. For example, in this application, the cavity is 15mm long, 8mm wide, and 20mm high. The resonant rod G1 is 15mm long, 1mm wide, and 2mm high. The resonant rod G2 is 7mm long, 1mm wide, and 14.5mm high. The resonant rod G3 is 2mm long, 1mm wide, and 18mm high. The distance between the resonant rod G1 and the resonant rod G2 is 15mm long, 1mm wide, and 20mm high. The interval is 0.1mm, the interval between the second resonance rod G2 and the third resonance rod G3 is 0.3mm, the distance between the first resonance rod G1 and the front and back sides of the inner wall of the cavity are 5mm and 2mm respectively, and the distance between the first resonance rod G1 and the bottom of the inner wall of the cavity is 9mm, the distance between the third resonance rod G3 and the front and back sides of the inner wall of the cavity are 4.4mm and 2.2mm respectively, and through the inductive coupling of the first cavity Q1 and the second cavity Q2, the inductive coupling of the second cavity Q2 and the third cavity Q3, the emotional connection of the third cavity Q3 and the fourth cavity Q4, and the capacitive coupling of the fourth cavity Q4 and the first cavity Q1, the center frequency of the narrowband filter is 1800MHz.

[0051] The comparison of the main performance indicators of the filter without improvement and the filter improved by the present invention is shown in Table 1.

[0052] Table 1 Comparison of main performance indicators of filters without improvement and improved by the present invention

[0053]

[0054]

[0055] refer to Figure 5 The attenuation of this narrowband filter in the uplink 1710MHz-1785MHz and downlink 1805MHz-1880MH frequency bands is increased by more than 30dB, while the insertion loss in the 1790-1800MHz frequency band is only deteriorated by 0.1dB, and the in-band fluctuation is only deteriorated by 0.1dB. Therefore, cascading it with the cavity filter originally configured in the base station can not only improve the system's isolation from interference signals from the mobile communication public network, but also ensure that the impact on its own working frequency band is extremely small and can be ignored.

[0056] By repeatedly fine-tuning the distance between each resonant rod and the distance connection between each cavity, the out-of-band suppression simulation result graph of the frequency can be obtained through HFSS software simulation.

[0057] By using three rectangular resonant rods to cooperate with each other, fine-tuning the distance between each resonant rod, the distance connection between each cavity, and connecting them in a cross-coupling manner, a zero point with a large attenuation degree can be obtained (as small as -120dB or less, such as Figure 5 As shown); the following experience is summarized in a large number of simulations (mainly using HFSS software): the interval between the resonant rod one and the resonant rod two is about 0.1mm, the interval between the resonant rod two and the resonant rod three is about 0.3mm, and by using inductive coupling between the first cavity and the second cavity, inductive coupling between the second cavity and the third cavity, inductive coupling between the third cavity and the fourth cavity, and capacitive coupling between the fourth cavity and the first cavity, the center frequency of the narrowband filter can be moved to around 1800MHz, and the target stopband can be greatly attenuated.

[0058] For example, when the stopband frequency needs to be changed to around 1550MHz, the position of the resonant rod G1 remains unchanged, and the resonant rod G2 is adjusted so that the distance between the resonant rod G1 and the resonant rod G2 increases by 0.1mm. The out-of-band suppression simulation result diagram of the frequency is obtained through HFSS software simulation (see Figure 6 ) By referring to the simulation result diagram, it can be seen that it is possible to significantly attenuate unwanted interference within the 1600MHz frequency range, while achieving the effect of filtering both broadband and narrowband.

[0059] Since the user's application scenario often places restrictions on the volume and size of the cavity filter, and the user's economic ability or inconvenient budget plan often places restrictions on the cost of the cavity filter. If the user has strict restrictions on the size and requires a significant reduction, but has no strict restrictions on the cost, the method of using multiple cavities independently (dismantling the original system) is generally adopted. This is because the simulation results show that the size of the four-cavity filter (including two RF connectors) is very small, only 18.5mm*38mm*20mm, such as Fig. 9 As shown; if the user has strict restrictions on cost, and the volume restriction only requires a small increment based on the size of the original system, a single-cavity configuration is generally adopted, and the single cavity is cascaded with the user's original cavity filter (without dismantling the original system). This is because the size of the single cavity (including two RF connectors) is smaller, only 8mm*29mm*20mm, as shown Figure 8 As shown in the figure (the standard size for comparison is shown below each figure); the increment of the overall size after cascading with the original cavity filter in any dimension is very small and can be ignored, so it is easy to meet the user's size restrictions and can greatly save economic costs, that is, it is easy to meet the user's cost restrictions. In addition, when a single cavity is cascaded with the user's original cavity filter, the impact on the original system is minimal, because Figure 6 and Figure 7 The frequency characteristics of the single-cavity filter show that, under the premise of maintaining a sufficiently large attenuation increment for the target adjacent channel, its insertion loss in the 1.8 GHz operating frequency band is very small and the flatness is also high.

[0060] When the single cavity is cascaded with the original system to suppress the interference from the right adjacent channel, it can show an extremely narrow transition band, that is, the falling edge is very steep. This performance is conducive to suppressing the interference of the right adjacent channel very close to the passband. The closer to the passband, the greater the technical difficulty. This is one of the advantages over the existing technology. In addition, it shows a stopband extreme, and the attenuation increment can be maintained at about 20dB from the 1.8GHz to 3.0GHz band. The wider the frequency band, the greater the technical difficulty. This is the second advantage over the existing technology.

[0061] In summary, the cavity filter has low power loss near the operating frequency of 1.8 GHz, and the cavity filter has good frequency selectivity and can significantly attenuate unwanted interference within the 1.8 GHz frequency range, thereby effectively improving the anti-interference performance of the system.

[0062] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention is limited to these examples. Under the concept of the present invention, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

[0063] The embodiments of the present invention are intended to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A small-size cavity filter for suppressing adjacent channel interference in a power base station, comprising multiple cavities, characterized in that: The plurality of cavities are divided into two groups, and the two groups are symmetrically arranged front to back, and the ends of the two cavities on the left are both provided with radio frequency connectors (1); The four cavities are respectively a first cavity (Q1), a second cavity (Q2), a third cavity (Q3) and a fourth cavity (Q4); the first cavity (Q1) and the second cavity (Q2) are horizontally arranged left and right to form a group, and the third cavity (Q3) and the fourth cavity (Q4) are horizontally arranged left and right to form another group; The first cavity (Q1) and the second cavity (Q2) are inductively coupled by arranging a cavity channel at the bottom of the two cavities, the second cavity (Q2) and the third cavity (Q3) are inductively coupled by arranging a cavity channel at the middle and upper parts of the two cavities, the third cavity (Q3) and the fourth cavity (Q4) are inductively coupled by arranging a cavity channel at the middle and lower parts of the two cavities, and the fourth cavity (Q4) and the first cavity (Q1) are capacitively coupled by arranging a solid copper column (2) between the two cavities; Among them, each cavity is provided with a resonant rod 1 (G1), a resonant rod 2 (G2) and a resonant rod 3 (G3) with variable positions, the resonant rod 1 (G1) is distributed in the cavity along the length direction of the cavity, and the two ends of the resonant rod 1 (G1) are respectively connected to the inner wall of the cavity, the resonant rod 2 (G2) is distributed in front of the resonant rod 1 (G1) along the height direction of the cavity, and the bottom end of the resonant rod 2 (G2) is connected to the bottom of the cavity, the resonant rod 3 (G3) is distributed in front of the resonant rod 2 (G2) along the height direction of the cavity, and the top end of the resonant rod 3 (G3) is connected to the top of the cavity.

2. The small-size cavity filter for suppressing adjacent channel interference in a power base station according to claim 1 is characterized in that: The radio frequency connector (1) is arranged on the first cavity (Q1) and the fourth cavity (Q4), and a transmission line is arranged inside the radio frequency connector (1).

3. The small-size cavity filter for suppressing adjacent channel interference in a power base station according to claim 1 is characterized in that: The resonance rod one (G1), the resonance rod two (G2) and the resonance rod three (G3) are all rectangular resonance rods, the shape of the cavity is also rectangular, and the resonance rod two (G2) is located at the front center of the resonance rod one (G1), and the resonance rod three (G3) is located at the front center of the resonance rod two (G2).

4. The small-size cavity filter for suppressing adjacent channel interference in a power base station according to claim 3 is characterized in that: The length, width and height ratio of the cavity is controlled within the range of 3.7:2:5-4:2:5, the length, width and height ratio of the resonance rod one (G1) is controlled within the range of 15:1:2, the length, width and height ratio of the resonance rod two (G2) is controlled within the range of 7:1:14-7:1:15, and the length, width and height ratio of the resonance rod three (G3) is controlled within the range of 2:1:

18.

5. The small-size cavity filter for suppressing adjacent channel interference in a power base station according to claim 4 is characterized in that: There are gaps between the resonance rod 1 (G1), the resonance rod 2 (G2) and the resonance rod 3 (G3).

6. The small-size cavity filter for suppressing adjacent channel interference in a power base station according to claim 5 is characterized in that: The distance ratio between the resonance rod 2 (G2) and the resonance rod 1 (G1) and the resonance rod 3 (G3) is 1:3, the distance ratio between the resonance rod 1 (G1) and the front and back sides of the cavity and the bottom is 5:2:9, and the distance ratio between the resonance rod 3 (G3) and the front and back sides of the inner wall of the cavity is controlled within the range of 1.6:1-1.8:

1.

7. The small-size cavity filter for suppressing adjacent channel interference in a power base station according to claim 1 is characterized in that: The cavity and the resonance rod 1 (G1), the resonance rod 2 (G2) and the resonance rod 3 (G3) are all made of any one of alloy aluminum or beryllium bronze alloy.

8. The small-size cavity filter for suppressing adjacent channel interference in a power base station according to claim 1 is characterized in that: The smoothness grade of the inner wall of the cavity is greater than Ra6.3.

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