A high-frequency stable tunable resonant cavity filter

Abstract

This invention relates to the field of filter technology, and more particularly to a high-frequency stability adjustable resonant cavity filter. Unlike existing adjustable resonant cavity filters that use insulating pads to fix the resonant rod only from the top and bottom, which easily leads to positional shifts, this invention features two dielectric blocks respectively disposed within corresponding cavities and fixedly connected to the inner wall of the resonant cavity. Furthermore, the two dielectric blocks are fixedly connected to opposite sides of a metal block, thus forming a unified whole with the dielectric blocks, metal block, and resonant rod. The cavity effectively limits the position of the dielectric blocks, and through the cooperation of the dielectric blocks and metal block, the resonant rod is reinforced from four directions (top, bottom, left, and right), effectively ensuring that the resonant rod's position does not shift, thereby stabilizing the capacitor and ensuring the stability of the filter's operating frequency.

Description

Technical Field

[0001] This invention relates to the field of filter technology, and in particular to a high-frequency stable tunable resonant cavity filter. Background Technology

[0002] A filter's function is to allow signals of a specific frequency to pass through while attenuating signals outside that frequency. If the passband is selectively variable, it is called an tunable filter. Typically, tunable cavity filters are required to have the widest possible tuning range, with the bandwidth remaining as constant as possible throughout the tuning range. Furthermore, the filter should have optimal insertion loss at the center operating frequency and appropriate out-of-band attenuation.

[0003] A typical tunable resonant cavity filter uses a coaxial cavity as the resonant cavity. The resonant cavity 1 has an input coupling ring 11, an output coupling ring 12, an input interface 13, and an output interface 14 on the inner and outer sides of its left and right side walls, respectively. One end of the resonant rod 2 is electrically connected to the inner wall of the resonant cavity 1, and the other end has a set of conductive plates with the same spacing, whose positions are fixed and referred to as stationary plates 3. A rotating shaft 5, which can be driven by a motor to rotate, is installed at the top of the cavity. A set of circular conductive plates with the same size notches, referred to as moving plates 4, are mounted on it. The stationary plates 3 and moving plates 4 partially overlap in spatial projection, such as... Figure 1 As shown, the moving plate and the stationary plate form a distributed capacitance in the shape of parallel plates. As the moving plate rotates with the shaft, the overlapping area between it and the stationary plate changes, causing the value of the distributed capacitance to change accordingly, thereby adjusting the center operating frequency of the filter.

[0004] Because one end of the resonant rod is fixed while the other end is suspended, its position may change in the actual working environment, leading to a change in capacitance value and causing the filter's operating frequency to shift, thus degrading its performance. The traditional method involves drilling two cylindrical through-holes symmetrically at the connection between the stationary plate and the resonant rod. Four insulating pads are inserted into these through-holes from both the top and bottom of the cavity, with the other end of each pad contacting the top and bottom walls of the cavity to ensure the resonant rod remains stationary and thus stabilize the filter's operating frequency. The performance curve is shown below. Figure 2 As shown, this structure has the following drawbacks:

[0005] (1) The insulating pads only fix the resonant rod in the upper and lower dimensions, while the surrounding area is filled with air, which is prone to permanent and irreversible changes (such as loosening of the insulating pads). This makes the filter performance curve too sensitive to changes in environmental factors (temperature, vibration, etc.) and internal stress of the structure. The performance curves before and after the high and low temperature tests are too different, and it is necessary to disassemble and professionally debug and repair them again to restore them. Therefore, it has the disadvantage of poor environmental adaptability.

[0006] (2) The insulation pads have high dimensional accuracy requirements and are difficult to adjust. Manual operation is difficult and product consistency is poor. Therefore, they have the disadvantage of being difficult to produce and debug.

[0007] (3) In actual engineering, during the assembly and debugging process, the stationary plate and the resonant rod are prone to tilting as a whole, which will destroy the parallel relationship between the stationary plate and the moving plate, resulting in the deterioration of the filter performance. The insulating pad cannot provide force from all sides to restore the stationary plate and the resonant rod to their original positions.

[0008] (4) The moving plate and the stationary plate should be arranged in parallel plates to form a distributed capacitor. However, in actual engineering, it was found that the metal surfaces on both sides are not parallel enough due to the overall rotation and tilting of the stationary plate and the resonant rod, which may even worsen the power capacity and other indicators. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide a high-frequency stable tunable resonant cavity filter that can overcome the above-mentioned technical problems.

[0010] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0011] A high-frequency stable tunable resonant cavity filter includes a resonant cavity, a resonant rod and a stationary plate respectively disposed inside the resonant cavity, and a metal block and a dielectric block disposed inside the resonant cavity. The dielectric block is an insulating material. The resonant rod is fixed and electrically connected to the stationary plate through the metal block. The two opposite inner sidewalls of the resonant cavity are respectively provided with cavities capable of accommodating the dielectric blocks. The two dielectric blocks are respectively disposed in the corresponding cavities and fixedly connected to the inner sidewalls of the resonant cavity. The two dielectric blocks are respectively fixedly connected to the opposite sides of the metal block.

[0012] The beneficial effects of this invention are as follows:

[0013] This invention provides a high-frequency stability adjustable resonant cavity filter. Unlike existing adjustable resonant cavity filters that use insulating pads to fix the resonant rod only from the top and bottom, which easily leads to positional shifts, this invention uses two dielectric blocks respectively located within corresponding cavities and fixedly connected to the inner wall of the resonant cavity. Furthermore, the two dielectric blocks are fixedly connected to opposite sides of a metal block, thus forming a unified whole with the dielectric blocks, metal block, and resonant rod. The cavity effectively limits the position of the dielectric blocks, and through the cooperation of the dielectric and metal blocks, the resonant rod is reinforced from four directions (top, bottom, left, and right), effectively preventing positional shifts and ensuring the stability of the filter's operating frequency. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of a typical tunable resonant cavity filter structure in the background technology of this invention;

[0015] Figure 2 This is a schematic diagram of the performance curves of a typical tunable resonant cavity filter in the background technology of this invention.

[0016] Figure 3 This is a schematic diagram of the structure of a high-frequency stable tunable resonant cavity filter according to the present invention;

[0017] Figure 4 for Figure 3 Side view;

[0018] Figure 5 This is a schematic diagram of the dielectric block of a high-frequency stable tunable resonant cavity filter according to the present invention.

[0019] Figure 6 for Figure 5 A top view of

[0020] Figure 7 This is a schematic diagram of the performance curve of a high-frequency stable tunable resonant cavity filter according to the present invention.

[0021] Label Explanation:

[0022] 1. Resonant cavity; 11. Input coupling ring; 12. Output coupling ring; 13. Input interface; 14. Output interface; 2. Resonant rod; 3. Stationary plate; 4. Moving plate; 5. Rotating shaft; 6. Dielectric block; 61. Upper dielectric block; 62. Lower dielectric block; 7. Rectangular metal block. Detailed Implementation

[0023] To explain in detail the technical content, objectives, and effects of the present invention, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0024] Please refer to Figures 3 to 7 This invention provides a high-frequency stable adjustable resonant cavity filter, comprising a resonant cavity and a resonant rod and a stationary plate respectively disposed inside the resonant cavity, and further comprising a metal block and a dielectric block disposed inside the resonant cavity. The dielectric block is an insulating material. The resonant rod is fixed and electrically connected to the stationary plate through the metal block. The two opposite inner sidewalls of the resonant cavity are respectively provided with cavities capable of accommodating the dielectric blocks. The two dielectric blocks are respectively disposed in the corresponding cavities and fixedly connected to the inner sidewalls of the resonant cavity, and the two dielectric blocks are respectively fixedly connected to the opposite sides of the metal block.

[0025] As can be seen from the above description, the beneficial effects of the present invention are as follows:

[0026] This invention provides a high-frequency stability adjustable resonant cavity filter. Unlike existing adjustable resonant cavity filters that use insulating pads to fix the resonant rod only from the top and bottom, which easily leads to positional shifts, this invention uses two dielectric blocks respectively located within corresponding cavities and fixedly connected to the inner wall of the resonant cavity. Furthermore, the two dielectric blocks are fixedly connected to opposite sides of a metal block, thus forming a unified whole with the dielectric blocks, metal block, and resonant rod. The cavity effectively limits the position of the dielectric blocks, and through the cooperation of the dielectric and metal blocks, the resonant rod is reinforced from four directions (top, bottom, left, and right), effectively preventing positional shifts and ensuring the stability of the filter's operating frequency.

[0027] Furthermore, the medium block and the metal block are fixedly connected by pins.

[0028] Furthermore, the medium block has a rectangular notch, and the pin is located at the center of the rectangular notch.

[0029] As can be seen from the above description, the fixed connection between the dielectric block and the metal block is achieved through the above structural design.

[0030] Furthermore, the inner wall of the resonant cavity is provided with an external thread, and the dielectric block is provided with an internal thread that matches the external thread.

[0031] As can be seen from the above description, the fixed connection between the medium block and the cavity is achieved through the above structural design.

[0032] Furthermore, the medium block is provided with multiple circular through holes.

[0033] As can be seen from the above description, the above structural design can reduce the performance degradation of the filter caused by dielectric loss.

[0034] Furthermore, the metal block is rectangular, and two dielectric blocks are respectively disposed on two opposite sides of the metal block in the vertical direction of the rectangle. The resonant rod and the stationary plate are respectively fixed to two opposite sides of the metal block in the horizontal direction of the rectangle.

[0035] As can be seen from the above description, the arrangement of each component is reasonably set through the above structural design.

[0036] Furthermore, the end of the resonant rod furthest from the metal block is electrically connected to the side wall of the resonant cavity.

[0037] Furthermore, it also includes a moving plate and a rotating shaft. The moving plate is fixed on the rotating shaft and is arranged opposite to the stationary plate. The projections of the stationary plate and the moving plate on the axial direction of the rotating shaft partially overlap, and the overlapping area of ​​the stationary plate and the moving plate changes as the moving plate rotates with the rotating shaft.

[0038] As described above, the moving plate and the stationary plate form a distributed capacitance in the shape of parallel plates. As the moving plate rotates with the shaft, the overlapping area between it and the stationary plate changes, which in turn changes the value of the distributed capacitance, thereby adjusting the center operating frequency of the filter.

[0039] Furthermore, the stationary plate is composed of a group of metal plates with the same spacing, and the group of metal plates is fixedly connected to the metal block respectively; the moving plate is composed of a group of circular metal plates with the same spacing and the same size notch.

[0040] Furthermore, the inner and outer sides of the two cavity walls of the resonant cavity are respectively provided with an input coupling ring, an output coupling ring, an input interface, and an output interface.

[0041] Please refer to Figures 3 to 7 Embodiment 1 of the present invention is as follows:

[0042] The present invention provides a high-frequency stable adjustable resonant cavity filter, comprising a resonant cavity 1, a resonant rod 2, a stationary plate 3, a moving plate 4, a rotating shaft 5, a rectangular metal block 7, and a dielectric block 6.

[0043] The resonant cavity 1 has input / output coupling rings and input / output interfaces on the inner and outer sides of the left and right cavity walls, respectively. Specifically, an input coupling ring 11 is set on the inner side of one cavity wall and an input interface 13 is set on the outer side, and an output coupling ring 12 is set on the inner side of the other cavity wall and an output interface 14 is set on the outer side. One end of the resonant rod 2 is fixed to the side wall of the resonant cavity and electrically connected, and the other end is connected to the stationary plate 3 via a rectangular metal block 7.

[0044] The stationary plate 3 is composed of a set of metal plates with the same spacing and is connected to a rectangular metal block at the other end of the resonant rod; the moving plate 4 is composed of a set of circular metal plates with the same spacing and the same size notch and is fixed on the rotating shaft 5; the stationary plate 3 and the moving plate 4 partially overlap in spatial projection (i.e., projection on the axial direction of the rotating shaft), and the overlapping area changes when the moving plate 4 rotates with the rotating shaft 5.

[0045] The dielectric block 6 is an insulating material with a rectangular notch. A pin is provided in the middle of the rectangular notch, and two internally threaded holes are provided symmetrically at the top of the dielectric block. Two dielectric blocks 6 are placed above and below the rectangular metal block 7 connected to the resonant rod 2 and the stationary plate 3, and are divided into an upper dielectric block 61 and a lower dielectric block 62, which are fixedly connected to the rectangular metal block 7 by pins. The upper and lower walls of the resonant cavity are provided with external threads, which are screwed to the internally threaded holes of the dielectric blocks. The length of the rectangular notch of the dielectric block is equal to the length of the rectangular metal block. Considering the dimensional deviations generated during the production of the resonant cavity, a dielectric block with a suitable tightness and contact force can be selected from a variety of pre-processed dielectric blocks of various width values ​​(discrete at a certain step interval with L0 as the center). Then, the actual positions of the starting and ending surfaces of the width L1 of the dielectric block are adjusted by means of cutting or sanding to adapt to the deviation and achieve seamless fitting between the dielectric block and the cavity wall. Finally, multiple circular through holes can be drilled on the dielectric block to reduce the filter performance degradation caused by dielectric loss.

[0046] In this embodiment, the distance L0 between the inner walls of the left and right sides of the resonant cavity is 34.9mm-35.2mm; the length L1 of the dielectric block is 34.9mm-35.2mm; the width W1 is 24.3mm; the thickness H1 is 7mm; the length L2 of the rectangular notch is 20mm; the width W2 of the rectangular notch is 1mm; the length L3 of the pin is 2.5mm; the width W3 is 3mm; the distance L4 between the two threaded holes at the top is 20mm; the radius R2 of the threaded hole is 2.5mm; and its depth W4 is 3mm. Figure 5 and Figure 6 As shown, a dielectric block of appropriate specifications is selected according to the actual resonant cavity size L0, and the actual positions of the starting and ending surfaces of the dielectric block length L1 are adjusted by cutting or grinding to ensure seamless fit between the dielectric block and the inner wall of the resonant cavity.

[0047] The radius R1 of the circular through-hole on dielectric block 6 is 0 mm. Dielectric block 6 is made of copper-free polytetrafluoroethylene glass cloth material with a relative permittivity of 2.2. The resonant rod 2 is made of a high-conductivity metal or alloy, such as copper, aluminum, silver, or other high-conductivity metal materials; alloy materials such as copper-silver alloys ensure that the outer surface of the resonant rod is a metal material with high conductivity.

[0048] The dielectric block used in this invention fits seamlessly with the inner wall of the resonant cavity from four directions (up, down, left, and right), ensuring that the position of the resonant rod does not shift, thus making the filter performance more stable. It has at least the following advantages: (1) The dielectric block has a simple structure, is easy to process and implement; (2) The filter structure is more stable and its environmental adaptability is significantly enhanced; The product was subjected to special high and low temperature environment tests. The results showed that the filter with this method has stable performance in the range of -40℃ to +65℃, and the performance curves before and after the test are small, making it more widely applicable; (3) The actual positions of the left and right sides of the length L1 of the dielectric block can be adjusted by simple cutting or sanding, making the filter performance easier to debug. This effectively avoids the filter performance degradation caused by the overall tilt of the resonant rod and the stationary plate in the filter assembly and debugging process in actual engineering, which leads to changes in the parallel plate capacitor.

[0049] In summary, the present invention provides a high-frequency stability adjustable resonant cavity filter, which differs from existing adjustable resonant cavity filters that use insulating pads to fix the resonant rod only from the top and bottom directions, making the resonant rod position prone to change. In this invention, two dielectric blocks are respectively disposed in corresponding cavities and fixedly connected to the inner sidewall of the resonant cavity. Furthermore, the two dielectric blocks are respectively fixedly connected to the opposite sides of the metal block, thereby forming a whole from the dielectric blocks, the metal block, and the resonant rod. The cavity can limit the position of the dielectric blocks, and through the cooperation of the dielectric blocks and the metal block, the resonant rod is reinforced from the top, bottom, left, and right directions, effectively ensuring that the position of the resonant rod does not shift, and thus stabilizing the capacitor to ensure the stability of the filter's operating frequency.

[0050] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent modifications made based on the content of the present invention specification and drawings, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A high-frequency stable tunable resonant cavity filter, comprising a resonant cavity and a resonant rod and a stationary plate respectively disposed inside the resonant cavity, characterized in that, It also includes a metal block and a dielectric block disposed inside the resonant cavity. The dielectric block is an insulating material. The resonant rod is fixed and electrically connected to the stationary plate through the metal block. The two opposite inner walls of the resonant cavity are respectively provided with cavities that can accommodate the dielectric blocks. The two dielectric blocks are respectively disposed in the corresponding cavities and fixedly connected to the inner walls of the resonant cavity. The two dielectric blocks are respectively fixedly connected to the opposite sides of the metal block. The medium block and the metal block are fixedly connected by pins; The medium block has a rectangular notch, and the pin is located at the center of the rectangular notch; The inner wall of the resonant cavity is provided with an external thread, and the dielectric block is provided with an internal thread that matches the external thread. The medium block is provided with multiple circular through holes; The metal block is rectangular, and two dielectric blocks are respectively located on two opposite sides of the metal block in the vertical direction of the rectangle. The resonant rod and the stationary plate are respectively fixed to two opposite sides of the metal block in the horizontal direction of the rectangle.

2. The high-frequency stability tunable resonant cavity filter according to claim 1, characterized in that, The end of the resonant rod furthest from the metal block is electrically connected to the side wall of the resonant cavity.

3. The high-frequency stability tunable resonant cavity filter according to claim 1, characterized in that, It also includes a moving plate and a rotating shaft. The moving plate is fixed on the rotating shaft and is arranged opposite to the stationary plate. The projections of the stationary plate and the moving plate on the axial direction of the rotating shaft partially overlap, and the overlapping area of ​​the stationary plate and the moving plate changes as the moving plate rotates with the rotating shaft.

4. The high-frequency stability tunable resonant cavity filter according to claim 3, characterized in that, The stationary plate consists of a set of metal plates with the same spacing, and each set of metal plates is fixedly connected to a metal block; the moving plate consists of a set of circular metal plates with the same spacing and the same size notch.

5. The high-frequency stability tunable resonant cavity filter according to claim 1, characterized in that, The inner and outer sides of the two cavity walls of the resonant cavity are respectively equipped with an input coupling ring, an output coupling ring, an input interface, and an output interface.

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