Cavity filter with temperature compensation function and design method thereof

Abstract

The invention 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; each resonant cavity is internally provided with a temperature compensation sheet, and the temperature compensation sheet is of a sheet structure and is made of a thermal bimetal material; the thickness direction of the temperature patch is arranged along the axial direction of the corresponding resonant cavity, and the temperature patch is not in contact with the inner wall of the resonant cavity; the sizes of the resonant cavities are the same or different; and the structures and the sizes of the temperature patching sheets are the same or different. The temperature compensation of the cavity filter is realized by arranging the double-metal temperature compensation tuning device in the cavity, the temperature frequency offset of the filter at high and low temperatures can be effectively reduced, and the electrical performance of the filter in high and low temperature environments is improved.

Description

Technical Field

[0001] The invention relates to a cavity filter, and in particular to a cavity filter with a temperature compensation function and a design method thereof. Background Art

[0002] The filter usually plays the role of filtering out clutter and selecting useful signals, and its performance directly affects the communication quality of the repeater channel. In practical applications, the filter is affected by the external temperature, and the structure and size of the cavity filter will change accordingly with the change of temperature, causing its frequency response to produce temperature drift, affecting the stability of electrical performance.

[0003] Take a single aluminum waveguide resonator as an example: the thermal expansion coefficient (CTE, which indicates the expansion of a unit material when the temperature rises by one degree Celsius) of aluminum alloy is 23*10 -6 , it can be calculated that a waveguide cavity with a resonant frequency of 20GHz will have a frequency deviation of -22.07MHz in a -25℃ environment. When the filter application frequency band is very narrow and the index requirements are high, this temperature drift phenomenon will deteriorate its electrical performance to the point where it cannot work normally. Summary of the invention

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

[0005] To this end, the cavity filter with temperature compensation function provided by the present invention comprises a housing, wherein N resonant cavities are arranged in the housing, where N is an integer greater than or equal to 1; a tuning screw is installed in each resonant cavity; when there are multiple resonant cavities, a coupling window is arranged 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; and N bimetallic temperature compensation plates are also included;

[0006] A temperature patch is installed in each resonant cavity. The temperature patch is a sheet structure, and the temperature patch material is a thermal bimetallic material. The thickness direction of the temperature patch is arranged along the axial direction of the corresponding resonant cavity, and the temperature patch does not contact the inner wall of the resonant cavity. The sizes of each resonant cavity are the same or different; the structures and sizes of each temperature patch are the same or different.

[0007] An optional solution is that the thermal bimetal material is selected from 5J20110 material, 5J15120 material or 5J1416 material.

[0008] An optional solution is that the warm patch is a circular sheet, an annular sheet or a square sheet.

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

[0010] An optional solution is that a safety distance is left between the temperature patch and the inner wall of the resonance cavity in both radial and axial directions, and the safety distance is greater than or equal to 0.2 mm.

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

[0012] An optional solution is that the temperature patch is installed at the axial bottom or top of the resonance cavity through a fixing piece, and the temperature patch is installed on the fixing piece by threading, welding or riveting.

[0013] An optional solution is that the resonant cavity is a square resonant cavity or a circular resonant cavity with chamfers.

[0014] An optional solution is that, when there are multiple resonant cavities, the multiple resonant cavities are arranged and distributed in a horizontal, vertical or oblique direction on the same plane.

[0015] An optional solution is that the cavity filter has an operating frequency of 1 GHz to 50 GHz and an operating temperature of -35°C to 100°C.

[0016] An optional solution is that the cavity filter is an N-th order generalized Chebyshev cavity filter or a cavity filter with a number of transmission zeros, where N is an integer greater than or equal to 1.

[0017] The present invention also provides a design method for the cavity filter. The method is performed based on the known working performance requirements of the cavity filter to be designed. The method includes:

[0018] Generate a coupling matrix and a topological structure of the filter according to the working performance requirements of the cavity filter to be designed;

[0019] Perform electromagnetic simulation of a single cavity according to the insertion loss of the cavity filter to be designed, the initial structure and size of a single resonant cavity, the initial structure and initial size of a single temperature patch, and the initial safe distance between the temperature patch and the inner wall of the resonant cavity; adjust and optimize the size of the single resonant cavity and the structure and size of a single temperature patch according to the electromagnetic simulation results, so that the single resonant cavity resonates at the required frequency and has a Q value and a single-mode working bandwidth that meet the functional performance requirements, and obtain optimized parameters of the single resonant cavity, which include the structure and size of the resonant cavity, the structure and size 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 patch, a single cavity multi-physical field collaborative simulation is performed to obtain the temperature compensation effect of the single cavity, wherein the temperature compensation effect is the frequency offset of the single cavity at the highest working temperature and the lowest working temperature; according to the temperature compensation effect, the single cavity parameters and the material, structure and size of the temperature patch are adjusted and optimized so that the frequency offset of the single cavity at the highest working temperature and the lowest working temperature is equal to 0 or approaches 0MHz, and new single resonant cavity parameters and temperature patch materials are obtained; the highest working temperature and the lowest working temperature are respectively the upper limit and the lower limit of the working temperature of the cavity filter to be designed;

[0021] Electromagnetic simulation of the filter is carried out based on the new single resonant cavity parameters, temperature patch materials, coupling matrix and topological structure of the filter. The size of each resonant cavity is optimized and adjusted according to the electromagnetic simulation results so that the overall electromagnetic characteristics of the filter meet the index requirements. The size of each resonant cavity, the size of the tuning screw in each resonant cavity and the size of the coupling window between adjacent resonant cavities are obtained.

[0022] The present invention uses a thermal bimetallic material as a temperature compensation mechanism, making full use of the bimetallic material's own deformation characteristics with temperature. Compared with the temperature compensation scheme of the Invar steel and aluminum cavity, this technical scheme does not involve complex mechanical conduction, metal internal stress and possible metal fatigue problems. Compared with the external bimetallic temperature compensation scheme, this technical scheme does not involve electromagnetic leakage and other problems. In addition, the bimetallic temperature compensation mechanism in the cavity has a simple structure, is relatively easy to design, process and install, does not require high machining accuracy, and can effectively reduce the machining cycle and cost.

[0023] In the specific solution, through reasonable resonant cavity layout and 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is an exploded structural diagram of a cavity filter with temperature compensation function in an embodiment of the present invention.

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

[0026] Figure 3 for Figure 1 Structural diagram of the built-in bimetallic temperature patch in the filter cavity.

[0027] Figure 4 Schematic diagram of the bimetallic temperature patch fixing piece built into the cavity.

[0028] Figure 5 for Figure 1The figure shows a schematic diagram of the simulation results of the temperature compensation effect of the cavity filter, where the horizontal axis is the frequency; the vertical axis is the amplitude of the reflection characteristic curve (S11) or the amplitude of the transmission characteristic curve (S21). DETAILED DESCRIPTION

[0029] Unless otherwise specified, the scientific and technical terms used herein are understood according to the knowledge of ordinary technicians in the relevant fields.

[0030] The cavity filter of the present invention installs a temperature patch of reasonable structure and size in each resonant cavity based on the existing cavity filter structure, and designs the installation position of the temperature patch in the resonant cavity to ensure the working performance of the filter while overcoming the temperature drift phenomenon. The related design method is based on the existing cavity filter design scheme, designs a reasonable optimization idea, and optimizes the relevant parameters (structure and material) of the temperature patch by using reasonable indicators in the related steps, comprehensively considers the working performance requirements of the filter and eliminates 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 according to the characteristics of the existing cavity filter and the relevant parameters disclosed in the present invention. The simulation involved in the method steps can be implemented in relevant software, such as electromagnetic simulation can be performed using the HFSS module in the electromagnetic simulation software ANSYS Electronics; multi-physics field collaborative simulation can be performed in 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 the present invention may be an N-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 6-order filter with one transmission zero.

[0033] Example:

[0034] The filter of this embodiment has an operating frequency of 19 GHz and an operating bandwidth of 500 MHz. This embodiment uses the design method of the present invention to optimize the filter's operating performance:

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

[0036] Step 2: The initial size and shape of the filter single resonant cavity is 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 a circular ring ( Figure 3 As shown, the thickness is 0.6mm, the outer diameter is 10.5mm, and the inner hole diameter is 3mm), and it is fixed to the bottom of the cavity by screws, and it is 0.5mm away from the bottom of the resonant cavity;

[0037] The size and shape of the single resonant cavity of the filter optimized in step 2 are selected as a circular cavity with a diameter of 11.4 mm and a height of 7.9 mm; the shape of the temperature patch is a circular ring ( Figure 3 As shown, the thickness is 0.5mm, the outer diameter is 10.5mm, and the inner hole diameter is 2mm), and it is fixed to the bottom of the cavity by screws, and it is 0.5mm away from the bottom of the resonant cavity;

[0038] Step 3: The initial material of the temperature patch is 5J20110 material (the material is synthesized from Mn75Ni15Cu10 and Ni36). Based on the size and shape of the single resonant cavity of the filter optimized in step 3, a circular cavity with a diameter of 11.5 mm and a height of 7.8 mm is selected; the material of the temperature patch is 5J20110 material, and the shape is a circular ring ( Figure 3 As shown, the thickness is 0.5mm, the outer diameter is 10mm, and the inner hole diameter is 2mm), and it is fixed to the bottom of the cavity by screws, and it is 0.5mm away 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 specifically 6 resonant cavities 2 with diameters ranging from 11.4 mm to 11.8 mm, and the width of the inter-cavity coupling window ranging from 3.4 mm to 7 mm. A tuning screw 5 is installed on the top of each resonant cavity, and a temperature patch 3 is installed on the bottom through a bolt fixing 4. Considering the convenience of processing, the shell 1 is assembled from an upper shell 11 and a lower shell 12.

[0040] The multi-physics field simulation method is further used to verify the overall temperature compensation effect of the filter in this embodiment. The multi-physics field simulation effect is as follows: Figure 5 As shown, Figure 5 The performance curve of the medium filter at room temperature of 23°C basically coincides with the performance curve at high temperature of 100°C, proving that the filter has basically no frequency deviation at the high temperature of 100°C, indicating that the temperature compensation effect of the bimetallic temperature compensation mechanism meets the use requirements.

Claims

1. A cavity filter with a temperature compensation function, comprising a housing (1), wherein N resonant cavities (2) are arranged in the housing, where N is an integer greater than or equal to 1; a tuning screw (5) is installed in each resonant cavity; when there are multiple resonant cavities, a coupling window is arranged 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; and the characteristics are as follows: Also includes N temperature patch sheets (3); A temperature patch is installed in each resonant cavity. The temperature patch is a sheet structure, and the material of the temperature patch is a thermal bimetallic material. The thickness direction of the temperature patch is arranged along the axial direction of the corresponding resonant cavity, and the temperature patch does not contact the inner wall of the resonant cavity. The sizes of the resonant cavities are the same or different; the structures and sizes of the temperature patch plates are the same or different.

2. The cavity filter with temperature compensation function according to claim 1, characterized in that: The thermal bimetal material is selected from 5J20110 material, 5J15120 material or 5J1416 material.

3. The cavity filter with temperature compensation function according to claim 1, characterized in that: The warm patch is a circular sheet, an annular sheet or a square sheet.

4. The cavity filter with temperature compensation function according to claim 1, characterized in that: The thickness of the warm patch is 0.2 mm to 1.6 mm.

5. The cavity filter with temperature compensation function according to claim 1, characterized in that: A safety distance is left between the temperature patch and the inner wall of the resonance cavity in both radial and axial directions, and the safety distance is greater than or equal to 0.2 mm.

6. The cavity filter with temperature compensation function according to claim 5, characterized in that: The safety distance is 0.2 mm to 2 mm.

7. The cavity filter with temperature compensation function according to claim 1, characterized in that: The temperature patch is installed on the axial bottom or top of the resonance cavity through a fixing piece (4), and the temperature patch is installed on the fixing piece through threading, welding or riveting.

8. The cavity filter with temperature compensation function according to claim 1, characterized in that: The resonant cavity is a square resonant cavity or a circular resonant cavity with chamfered corners.

9. The cavity filter with temperature compensation function according to claim 1, characterized in that: When there are multiple resonant cavities, the multiple resonant cavities are arranged and distributed in a horizontal, vertical or oblique direction on the same plane.

10. The cavity filter with temperature compensation function according to claim 1, characterized in that: The cavity filter has an operating frequency of 1 GHz to 50 GHz and an operating temperature of -35°C to 100°C.

11. The cavity filter with temperature compensation function according to claim 1, characterized in that: The cavity filter is an N-order generalized Chebyshev cavity filter or a cavity filter with a plurality of transmission zeros, where N is an integer greater than or equal to 1.

12. The method for designing a cavity filter according to claim 1 is performed on the basis of the known working performance requirements of the cavity filter to be designed, characterized in that: Methods include: Generate a coupling matrix and a topological structure of the filter according to the working performance requirements of the cavity filter to be designed; Perform electromagnetic simulation of a single cavity according to the insertion loss of the cavity filter to be designed, the initial structure and size of a single resonant cavity, the initial structure and initial size of a single temperature patch, and the initial safe distance between the temperature patch and the inner wall of the resonant cavity; adjust and optimize the size of the single resonant cavity and the structure and size of a single temperature patch according to the electromagnetic simulation results, so that the single resonant cavity resonates at the required frequency and has a Q value and a single-mode working bandwidth that meet the functional performance requirements, and obtain optimized parameters of the single resonant cavity, which include the structure and size of the resonant cavity, the structure and size 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 patch, a single cavity multi-physical field collaborative simulation is performed to obtain the temperature compensation effect of the single cavity, wherein the temperature compensation effect is the frequency offset of the single cavity at the highest working temperature and the lowest working temperature; according to the temperature compensation effect, the single cavity parameters and the material, structure and size of the temperature patch are adjusted and optimized so that the frequency offset of the single cavity at the highest working temperature and the lowest working temperature is equal to 0 or approaches 0MHz, and new single resonant cavity parameters and temperature patch materials are obtained; the highest working temperature and the lowest working temperature are respectively the upper limit and the lower limit of the working temperature of the cavity filter to be designed; Electromagnetic simulation of the filter is carried out based on the new single resonant cavity parameters, temperature patch materials, coupling matrix and topological structure of the filter. The size of each resonant cavity is optimized and adjusted according to the electromagnetic simulation results so that the overall electromagnetic characteristics of the filter meet the index requirements. The size of each resonant cavity, the size of the tuning screw in each resonant cavity and the size of the coupling window between adjacent resonant cavities are obtained.

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