Up-down nested resonator for coaxial cavity filter

Abstract

The utility model relates to an up and down nested resonator for coaxial cavity filter, including cavity, cover plate, tuning screw, upper resonance cylinder and lower resonance cylinder, the cover plate is buckled in the upper part of cavity to form the resonant cavity, the tuning screw vertically passes through the middle part of the cover plate, and the depth of the tuning screw entering the resonant cavity is adjustable. The upper resonance cylinder is fixed on the inner surface of the cover plate, the lower resonance cylinder is connected to the inner side of the cavity, the tuning screw, the upper resonance cylinder and the lower resonance cylinder are in a coaxial relationship, the inner end of the tuning screw is surrounded by the lower resonance cylinder, and the lower resonance cylinder is surrounded by the upper resonance cylinder. Compared with a single resonance rod structure, the height of the resonator is shortened by 30%, the problem of air breakdown sparking caused by local electric quantity concentration is not easy to occur, the power capacity is obviously improved, the resonator is easy to process, the cost is low, the mass is light, and the allowance of a far-end suppression index is larger.

Description

Technical Field

[0001] This utility model relates to the field of communication technology, and in particular to a nested resonator for coaxial cavity filters. Background Technology

[0002] In modern mobile communication systems, metallic coaxial cavity filters have become the mainstream solution for RF front-end system modules in communication base stations due to their high single-cavity Q value, low insertion loss, and high power handling capability. The working principle of a metallic coaxial cavity filter is that its internal resonator resonates within its own dimensions within the operating frequency band. Therefore, the lower the operating frequency, the larger the resonator itself becomes, resulting in a larger and heavier overall filter. With the development of mobile communication, smaller size, lighter weight, and lower cost have become the development trend for filters. To enable metallic coaxial cavity filters to be used in the 300MHz to 500MHz frequency range, it is necessary to find ways to reduce the length of the resonator.

[0003] Existing metal coaxial cavity filters are composed of a series of cascaded resonators. The length of the resonant rod in each resonator determines the resonant frequency, which is also the operating frequency of the filter. This presents the following problems:

[0004] 1. Since a longer resonant rod allows for a lower resonant frequency, the resonant rod needs to be significantly longer to operate in the 300MHz to 500MHz frequency range. To meet the requirement of small size, a traditional approach is to insert a tuning screw into the resonant rod for capacitor loading, which can reduce the height by approximately 30%. However, this method has a limitation: if the tuning screw is inserted too deeply, when high power is input to the filter, the air between the tuning screw and the resonant rod will be broken down by the resonant electric field, causing arcing and short-circuiting the signal, thus preventing the entire RF system from functioning properly. An example is a dielectric filter (CN201985225U).

[0005] 2. If the resonant rod is made into a flanged shape, the capacitive loading formed by the flange and the side wall of the resonator can be used to reduce the height of the resonator. However, the limitation of this approach is that the flange cannot be made too long, otherwise it will be difficult to manufacture. Therefore, the reduction in overall height is limited. At the same time, because the resonant rod has a flanged shape, the manufacturing difficulty is high, the required material is significantly increased, and the cost is also significantly increased.

[0006] 3. When the resonant rod flange is long, the capacitive coupling between adjacent resonators increases significantly. This cancels out a considerable portion of the normal inductive coupling, leading to an excessively long coupling tuning screw. Simultaneously, a high connecting rib is required at the bottom of the cavity to compensate for the canceled coupling, resulting in the appearance of resonance peaks and failing to meet customer suppression requirements. An example is the capacitive coupling structure between coaxial cavity resonators in the CN2609200Y.

[0007] Therefore, a new resonator needs to be designed to avoid the above problems. Utility Model Content

[0008] The main objective of this invention is to provide a nested resonator for coaxial cavity filters, which is low in height, less prone to air breakdown and arcing, has a large power capacity, is easy to manufacture, has low cost, is lightweight, and has a large margin in far-end suppression performance.

[0009] This utility model achieves the above-mentioned objective through the following technical solution: a nested resonator for a coaxial cavity filter, comprising a cavity, a cover plate, a tuning screw, an upper resonant cylinder, and a lower resonant cylinder. The cover plate is fastened to the upper part of the cavity to form a resonant cavity. The tuning screw passes vertically through the middle of the cover plate and the depth of its entry into the resonant cavity is adjustable. The upper resonant cylinder is fixed to the inner surface of the cover plate, and the lower resonant cylinder is connected to the inner side of the cavity. The tuning screw, the upper resonant cylinder, and the lower resonant cylinder are coaxial. The inner end of the tuning screw is surrounded by the lower resonant cylinder, and the lower resonant cylinder is surrounded by the upper resonant cylinder.

[0010] Specifically, the cover plate is provided with a fastening nut that abuts the tuning screw against the cover plate.

[0011] Specifically, the inner edge of the tuning screw is rounded.

[0012] Specifically, the lower resonant cylinder has a bottom structure, and a boss is provided at the center of the bottom of the cavity. The bottom of the lower resonant cylinder is fixed to the top surface of the boss.

[0013] The beneficial effects of this utility model's technical solution are:

[0014] 1. With the same effective area, this nested structure can reduce the distance that the tuning screw 3 needs to extend into the resonant cavity by about 30%, so the height of the entire resonator can also be shortened by 30% compared with the traditional single resonant rod structure.

[0015] 2. The effective area of ​​the capacitor will not be lower than the inner surface area of ​​the upper resonant cylinder, so the charge is dispersed. During the adjustment process, the tuning screw is less likely to experience localized charge concentration, which could lead to air breakdown and sparking, and the power capacity is significantly improved.

[0016] 3. The lower and upper resonant cylinders have simple structures, are easier to process than flanged and coupled structures, have low cost and light weight, and have a larger margin for far-end suppression performance. Attached Figure Description

[0017] Figure 1 This is a cross-sectional view of the nested resonator in the embodiment.

[0018] The numbers in the diagram represent:

[0019] 1-Cavity; 11-Boss; 2-Cover plate; 3-Tuning screw; 31-Rounded corner; 4-Upper resonator cylinder; 5-Lower resonator cylinder; 6-Fasting nut. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to specific embodiments.

[0021] Example:

[0022] like Figure 1 As shown, this utility model discloses a nested resonator for a coaxial cavity filter, comprising a cavity 1, a cover plate 2, a tuning screw 3, an upper resonant cylinder 4, and a lower resonant cylinder 5. The cover plate 2 is fastened to the upper part of the cavity 1 to form a resonant cavity. The tuning screw 3 passes vertically through the middle of the cover plate 2 and its depth into the resonant cavity is adjustable. The upper resonant cylinder 4 is fixed to the inner surface of the cover plate 2. The lower resonant cylinder 5 is connected to the inner side of the cavity 1. The tuning screw 3, the upper resonant cylinder 4, and the lower resonant cylinder 5 are coaxial. The inner end of the tuning screw 3 is surrounded by the lower resonant cylinder 5, and the lower resonant cylinder 5 is surrounded by the upper resonant cylinder 4.

[0023] Under high-frequency conditions, cavity 1 and lower resonant cylinder 5 constitute the first pole of the resonator, while cover plate 2, tuning screw 3, and upper resonant cylinder 4 constitute the second pole. Because the outer surface of tuning screw 3 faces the inner surface of lower resonant cylinder 5, and the outer surface of lower resonant cylinder 5 faces the inner surface of upper resonant cylinder 4, capacitive loading occurs at both poles. The effective area of ​​the second pole is the sum of the area of ​​the sidewall of tuning screw 3 within the resonant cavity and the area of ​​the inner surface of upper resonant cylinder 4. Therefore, with the same effective area, this nested structure reduces the distance tuning screw 3 needs to extend into the resonant cavity by approximately 30%, thus shortening the overall height of the resonator by 30% compared to the traditional single-resonant-rod structure. Since the effective capacitor area is not lower than the inner surface area of ​​upper resonant cylinder 4, the charge is dispersed, and tuning screw 3 is less prone to localized charge concentration during adjustment, which could lead to air breakdown and arcing, significantly improving power capacity. The lower resonator 5 and the upper resonator 4 have simple structures, are easier to process than flanged structures and coupling structures, have low cost and light weight, and have a larger margin for far-end suppression performance.

[0024] like Figure 1As shown, the cover plate 2 is provided with a fastening nut 6 that abuts the tuning screw 3 against the cover plate 2.

[0025] After the depth of the tuning screw 3 through the cover plate 2 is adjusted, the fastening nut 6 should be adjusted towards the cover plate 2. When the fastening nut 6 is in close contact with the upper surface of the cover plate 2, the tuning screw 3 will not easily move axially, and the working state of the resonator will be more stable.

[0026] like Figure 1 As shown, the inner edge of the tuning screw 3 is provided with a rounded corner 31.

[0027] The fillet 31 can prevent the end of the tuning screw 3 from protruding, thus preventing the coaxial cavity filter from experiencing tip discharge at high frequencies.

[0028] like Figure 1 As shown, the lower resonant cylinder 5 has a bottom structure, and a boss 11 is provided at the center of the bottom of the cavity 1. The bottom of the lower resonant cylinder 5 is fixed to the top surface of the boss 11.

[0029] The boss 11 is part of the cavity 1 structure, so the coaxiality of the two is easy to ensure during processing. The lower resonant cylinder 5 is assembled on the boss 11, which also ensures the coaxiality of the two. This makes it easier to ensure the coaxial relationship of the tuning screw 3, the upper resonant cylinder 4 and the lower resonant cylinder 5, and avoid signal interference.

[0030] The above descriptions are merely some embodiments of this utility model. For those skilled in the art, various modifications and improvements can be made without departing from the inventive concept of this utility model, and all such modifications and improvements fall within the protection scope of this utility model.

Claims

1. An upper-lower nested resonator for a coaxial cavity filter, characterized by: The resonant cavity includes a cavity, a cover plate, a tuning screw, an upper resonant cylinder and a lower resonant cylinder, the cover plate is buckled on the upper part of the cavity to enclose a resonant cavity, the tuning screw vertically penetrates the middle part of the cover plate and enters the resonant cavity with adjustable depth, the upper resonant cylinder is fixed on the inner surface of the cover plate, the lower resonant cylinder is connected to the inner side of the cavity, the tuning screw, the upper resonant cylinder and the lower resonant cylinder are in coaxial relationship, the inner end of the tuning screw is enclosed by the lower resonant cylinder, and the lower resonant cylinder is enclosed by the upper resonant cylinder.

2. The upper-lower nested resonator for a coaxial cavity filter according to claim 1, characterized in that: A fastening nut is arranged on the cover plate to abut the tuning screw against the cover plate.

3. The upper-lower nested resonator for a coaxial cavity filter according to claim 1, wherein: The inner end edge of the tuning screw is provided with a round corner.

4. The upper-lower nested resonator for a coaxial cavity filter according to claim 1, characterized in that: The lower resonant cylinder is a bottom structure, the bottom center of the cavity is provided with a boss, and the bottom of the lower resonant cylinder is fixed with the top surface of the boss.

Images