A cavity filter with temperature compensation function and a design method thereof

Abstract

The application discloses a cavity filter with a temperature compensation function and a design method thereof, and relates to the technical field of microwave communication. The temperature compensation filter comprises a shell and N bimetallic temperature compensation sheets, N resonant cavities are arranged in the shell, and N is an integer greater than or equal to 1; the temperature compensation sheets are arranged in the resonant cavities, the temperature compensation sheets are in a sheet structure, and the temperature compensation sheet material is a thermal bimetallic material; the thickness direction of the temperature compensation sheet is arranged along the axial direction of the corresponding resonant cavity, and the temperature compensation sheet does not contact the inner wall of the resonant cavity; the sizes of the resonant cavities are the same or different; and the structures and sizes of the temperature compensation sheets are the same or different. The temperature compensation of the cavity filter is realized by arranging the bimetallic temperature compensation tuning device in the cavity, the temperature frequency deviation of the filter under high and low temperatures can be effectively reduced, and the electrical performance of the filter under high and low temperature environments is improved.

Description

Technical Field

[0001] This invention relates to cavity filters, and more specifically to a cavity filter with temperature compensation function and its design method. Background Technology

[0002] Filters typically function to filter out noise and select useful signals, and their performance directly affects the communication quality of the transponder channel. In practical applications, filters are affected by external temperature; the structural dimensions of cavity filters deform accordingly with temperature changes, causing temperature drift in their frequency response and affecting the stability of their electrical performance.

[0003] Taking a single aluminum waveguide resonant cavity as an example: the coefficient of thermal expansion (CTE, representing the amount of expansion per unit of material when the temperature rises by one degree Celsius) of aluminum alloy is 23*10. -6 Therefore, it can be calculated that a waveguide cavity with a resonant frequency of 20 GHz will have a frequency deviation of -22.07 MHz at -25 ℃. When the application bandwidth of the filter is very narrow and the performance requirements are high, this temperature drift phenomenon will degrade its electrical performance to the point that it cannot work properly. Summary of the Invention

[0004] In view of the defects or deficiencies of the prior art, the present invention provides a cavity filter with temperature compensation function.

[0005] Therefore, the cavity filter with temperature compensation function provided by the present invention includes a housing, which contains N resonant cavities, where N is an integer greater than or equal to 1; each resonant cavity is equipped with a tuning screw; when there are multiple resonant cavities, a coupling window is provided between adjacent resonant cavities; one axial end of each resonant cavity is a signal input end and the other axial end is a signal output end; it also includes N bimetallic temperature compensation plates;

[0006] Each resonant cavity is equipped with a temperature-controlled patch, which is a sheet structure made of a thermoplastic bimetallic material. The thickness direction of the temperature-controlled patch is arranged along the axial direction of the corresponding resonant cavity, and the temperature-controlled patch does not contact the inner wall of the resonant cavity. The dimensions of each resonant cavity may be the same or different. The structure and dimensions of each temperature-controlled patch may be the same or different.

[0007] Alternatively, the thermal bimetallic material may be selected from 5J20110, 5J15120, or 5J1416 materials.

[0008] Alternatively, the temperature-compensating sheet can be a circular sheet, an annular sheet, or a square sheet.

[0009] An optional solution is that the thickness of the temperature patch is 0.2mm to 1.6mm.

[0010] An alternative approach is to provide a safe distance between the temperature compensation plate and the inner wall of the resonant cavity in both the radial and axial directions, wherein the safe distance is greater than or equal to 0.2 mm.

[0011] An optional solution is that the safety distance is 0.2mm to 2mm.

[0012] Alternatively, the temperature compensation piece is installed on the axial bottom or top of the resonant cavity by a fixing member, and the temperature compensation piece is installed on the fixing member by threading, welding or riveting.

[0013] Alternatively, the resonant cavity can be a square resonant cavity with chamfered corners or a circular resonant cavity.

[0014] An alternative approach is to arrange multiple resonant cavities in a horizontal, vertical, or oblique direction on the same plane.

[0015] An alternative is that the cavity filter operates at a frequency of 1 GHz to 50 GHz and at a temperature of -35 ℃ to 100 ℃.

[0016] An alternative approach is to use an N-order generalized Chebyshev cavity filter or a cavity filter with several transmission zeros, where N is an integer greater than or equal to 1.

[0017] This invention also provides a design method for the aforementioned cavity filter, which is based on known performance requirements of the cavity filter to be designed, and includes:

[0018] Generate the coupling matrix and topology of the filter based on the performance requirements of the cavity filter to be designed;

[0019] Based on the insertion loss of the cavity filter to be designed, the initial structure and dimensions of a single resonant cavity, the initial structure and dimensions of a single temperature patch, and the initial safe distance between the temperature patch and the inner wall of the resonant cavity, a single-cavity electromagnetic simulation is performed. Based on the electromagnetic simulation results, the dimensions of the single resonant cavity and the structure and dimensions of the single temperature patch are adjusted and optimized so that the single resonant cavity resonates at the required frequency and has a Q value and single-mode operating bandwidth that meet the functional performance requirements. The optimized single resonant cavity parameters are obtained, including the structure and dimensions of the resonant cavity, the structure and dimensions of the temperature patch, and the safe distance between the temperature patch and the inner wall of the resonant cavity.

[0020] Based on the single resonant cavity parameters and the initial material of the temperature-compensating plate, a multi-physics co-simulation of the single cavity is performed to obtain the temperature compensation effect of the single cavity. The temperature compensation effect is the single cavity frequency offset at the highest and lowest operating temperatures. According to the temperature compensation effect, the single cavity parameters, temperature-compensating plate material, structure, and size are adjusted and optimized so that the single cavity frequency offset at the highest and lowest operating temperatures is equal to 0 or approaches 0 MHz, thus obtaining new single resonant cavity parameters and temperature-compensating plate material. The highest and lowest operating temperatures are respectively taken as the upper and lower limits of the operating temperature of the cavity filter to be designed.

[0021] Electromagnetic simulation of the filter was performed based on the new single resonant cavity parameters, temperature patch material, and the coupling matrix and topology of the filter. The dimensions of each resonant cavity were optimized and adjusted according to the electromagnetic simulation results so that the overall electromagnetic characteristics of the filter met the requirements. The dimensions of each resonant cavity, the dimensions of the tuning screws in each resonant cavity, and the dimensions of the coupling window between adjacent resonant cavities were obtained.

[0022] This invention uses a thermoplastic bimetallic material as the temperature compensation mechanism, fully utilizing the temperature-dependent deformation characteristics of the bimetallic material. Compared to the temperature compensation scheme using Invar steel with an aluminum cavity, this technical solution does not involve complex mechanical transmission, internal metal stress, or potential metal fatigue issues. Compared to external bimetallic temperature compensation schemes, this technical solution does not involve electromagnetic leakage problems. Furthermore, the bimetallic temperature compensation mechanism within the cavity has a simple structure, is relatively easy to design, process, and install, and does not require high machining precision, effectively reducing machining cycle time and costs.

[0023] In the specific design, through a reasonable resonant cavity layout and a built-in bimetallic temperature compensation mechanism, the Q value of the resonant cavity will not be affected, thus ensuring the low insertion loss characteristics of the filter itself. Attached Figure Description

[0024] Figure 1 This is an exploded view of the cavity filter with temperature compensation function in an embodiment of the present invention.

[0025] Figure 2 for Figure 1 A side cross-sectional view of the assembled filter.

[0026] Figure 3 for Figure 1 Diagram of the bimetallic temperature patch structure built into the filter cavity.

[0027] Figure 4 This is a schematic diagram of the bimetallic temperature compensation plate fixing component inside the cavity.

[0028] Figure 5 for Figure 1The diagram shows the simulation results of the temperature compensation effect of the cavity filter, where the horizontal axis represents the frequency and the vertical axis represents the amplitude of the reflection characteristic curve (S11) or the transmission characteristic curve (S21). Detailed Implementation

[0029] Unless otherwise specified, the scientific and technical terms used in this article are intended for understanding by those skilled in the art.

[0030] The cavity filter of this invention, based on the existing cavity filter structure, installs temperature-compensating plates of reasonable structure and size in each resonant cavity, and designs the installation position of the temperature-compensating plates in the resonant cavity to overcome the temperature drift phenomenon while ensuring the filter's operating performance. The related design method is based on existing cavity filter design schemes, and a reasonable optimization approach is adopted. In relevant steps, reasonable indicators are used to optimize the relevant parameters (structure and materials) of the temperature-compensating plates, comprehensively considering the filter's operating performance requirements and eliminating the temperature drift phenomenon.

[0031] It should be noted that, in the specific design scheme, the initial parameters involved in each step can be selected and given based on the characteristics of existing cavity filters and the relevant parameters disclosed in this invention. The simulations involved in the method steps can be implemented in relevant software. For example, electromagnetic simulation can be performed using the HFSS module in the electromagnetic simulation software ANSYS Electronics; multiphysics co-simulation can be performed using the HFSS module in the electromagnetic simulation software ANSYS Electronics and the Workbench module in the mechanical and thermal simulation software ANSYS.

[0032] The cavity filter of this invention can be an Nth-order generalized Chebyshev filter or a filter with several transmission zeros, where N is an integer greater than or equal to 1. The filter in the following embodiment is specifically a 6th-order filter with one transmission zero.

[0033] Example:

[0034] The filter in this embodiment operates at a frequency of 19 GHz and has a bandwidth of 500 MHz. This embodiment utilizes the design method of the present invention to optimize the filter's performance.

[0035] Step 1: Obtain the coupling matrix and topology of the filter, which is in 6-1 form;

[0036] Step 2: The initial size and shape of the filter's single resonant cavity are selected as a circular cavity with a diameter of 11.0 mm and a height of 7.5 mm; the initial shape of the temperature patch is an annular shape. Figure 3 As shown, it has a thickness of 0.6mm, an outer diameter of 10.5mm, and an inner diameter of 3mm, and is fixed to the bottom of the cavity with screws, with a distance of 0.5mm from the bottom of the resonant cavity;

[0037] After optimization in step 2, the single resonant cavity size and shape of the filter are selected as a circular cavity with a diameter of 11.4 mm and a height of 7.9 mm; the temperature patch is annular in shape. Figure 3 As shown, it has a thickness of 0.5mm, an outer diameter of 10.5mm, and an inner diameter of 2mm, and is fixed to the bottom of the cavity with screws, with a distance of 0.5mm from the bottom of the resonant cavity;

[0038] Step 3: The initial material for the temperature patch is 5J20110 (a material synthesized from Mn75Ni15Cu10 and Ni36). Based on the optimized single resonant cavity size and shape of the filter in Step 3, a circular cavity with a diameter of 11.5 mm and a height of 7.8 mm is selected; the temperature patch material is 5J20110, and its shape is annular (…). Figure 3 As shown, it has a thickness of 0.5mm, an outer diameter of 10mm, and an inner diameter of 2mm, and is fixed to the bottom of the cavity with screws, with a distance of 0.5mm from the bottom of the resonant cavity;

[0039] Step 4: Based on the relevant parameters designed in Step 3, the final cavity filter structure diagram of this embodiment is obtained. Figure 1-2 As shown, there are 6 resonant cavities 2 with diameters between 11.4 mm and 11.8 mm, and the width of the inter-cavity coupling window is between 3.4 mm and 7 mm. Tuning screws 5 are installed at the top of each resonant cavity, and temperature compensation plates 3 are installed at the bottom through bolt fasteners 4. Considering the convenience of processing, the housing 1 is assembled from an upper housing 11 and a lower housing 12.

[0040] Furthermore, multiphysics simulation was employed to verify the overall temperature compensation effect of the filter in this embodiment. The multiphysics simulation results are as follows: Figure 5 As shown, Figure 5 The performance curves of the medium filter at room temperature (23℃) and at high temperature (100℃) are basically the same, proving that the filter has almost no frequency deviation at high temperature (100℃), indicating that the temperature compensation effect of the bimetallic temperature compensation mechanism meets the usage requirements.

Claims

1. A design method for a cavity filter with temperature compensation function, the method being carried out based on known performance requirements of the cavity filter to be designed, characterized in that, The cavity filter with temperature compensation function includes a housing (1), which contains N resonant cavities (2), where N is an integer greater than or equal to 1; each resonant cavity is equipped with a tuning screw (5); when there are multiple resonant cavities, a coupling window is provided between adjacent resonant cavities; one axial end of each resonant cavity is a signal input end and the other axial end is a signal output end; characterized in that it also includes N temperature compensation plates (3). Each resonant cavity is equipped with a temperature-compensating plate, which is a sheet structure made of a thermoplastic bimetallic material; the thickness direction of the temperature-compensating plate is arranged along the axial direction of the corresponding resonant cavity, and the temperature-compensating plate does not contact the inner wall of the resonant cavity; The dimensions of each resonant cavity may be the same or different; the structure and dimensions of each temperature patch may be the same or different. The temperature compensation sheet is a circular sheet, a ring-shaped sheet, or a square sheet; the thickness of the temperature compensation sheet is 0.2mm~1.6mm; The temperature compensation plate and the inner wall of the resonant cavity are provided with a safe distance in both the radial and axial directions, and the safe distance is 0.2mm~2mm; The temperature compensation piece is installed on the bottom or top of the resonant cavity through a fixing piece (4), and the temperature compensation piece is installed on the fixing piece by thread, welding or riveting; The design method includes: Generate the coupling matrix and topology of the filter based on the performance requirements of the cavity filter to be designed; Based on the insertion loss of the cavity filter to be designed, the initial structure and dimensions of a single resonant cavity, the initial structure and dimensions of a single temperature patch, and the initial safe distance between the temperature patch and the inner wall of the resonant cavity, a single-cavity electromagnetic simulation is performed. Based on the electromagnetic simulation results, the dimensions of the single resonant cavity and the structure and dimensions of the single temperature patch are adjusted and optimized so that the single resonant cavity resonates at the required frequency and has a Q value and single-mode operating bandwidth that meet the functional performance requirements. The optimized single resonant cavity parameters are obtained, including the structure and dimensions of the resonant cavity, the structure and dimensions of the temperature patch, and the safe distance between the temperature patch and the inner wall of the resonant cavity. Based on the single resonant cavity parameters and the initial material of the temperature-compensating plate, a multi-physics co-simulation of the single cavity is performed to obtain the temperature compensation effect of the single cavity. The temperature compensation effect is the single cavity frequency offset at the highest and lowest operating temperatures. According to the temperature compensation effect, the single cavity parameters, temperature-compensating plate material, structure, and size are adjusted and optimized so that the single cavity frequency offset at the highest and lowest operating temperatures is equal to 0 or approaches 0 MHz, thus obtaining new single resonant cavity parameters and temperature-compensating plate material. The highest and lowest operating temperatures are respectively taken as the upper and lower limits of the operating temperature of the cavity filter to be designed. Electromagnetic simulation of the filter was performed based on the new single resonant cavity parameters, temperature patch material, and the coupling matrix and topology of the filter. The dimensions of each resonant cavity were optimized and adjusted according to the electromagnetic simulation results so that the overall electromagnetic characteristics of the filter met the requirements. The dimensions of each resonant cavity, the dimensions of the tuning screws in each resonant cavity, and the dimensions of the coupling window between adjacent resonant cavities were obtained.

2. The design method according to claim 1, characterized in that, The thermal bimetallic material is selected from 5J20110, 5J15120 or 5J1416.

3. The design method according to claim 1, characterized in that, The resonant cavity is a square resonant cavity with chamfered corners or a circular resonant cavity.

4. The design method according to claim 1, characterized in that, In the case of multiple resonant cavities, the multiple resonant cavities are arranged in a horizontal, vertical or oblique direction on the same plane.

5. The design method according to claim 1, characterized in that, The cavity filter operates at a frequency of 1 GHz to 50 GHz and at a temperature of -35 ℃ to 100 ℃.

6. The design method according to claim 1, characterized in that, The cavity filter is an N-order generalized Chebyshev cavity filter or a cavity filter with several transmission zeros, where N is an integer greater than or equal to 1.

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