Elliptical waveguide polarization rotating filter

Abstract

This invention provides an elliptical waveguide polarization rotating filter, comprising a metal housing containing multiple elliptical waveguide resonant cavities and two rectangular waveguides. The axes of symmetry of the two rectangular waveguides and their cross-sections parallel to the long side, as well as the major axis of the elliptical cross-section of each elliptical waveguide resonant cavity, serve as rotation reference axes. The direction of each subsequent rotation reference axis is formed by rotating the direction of the preceding rotation reference axis by a predetermined angle about the length direction of the metal housing. This allows for flexible design of the polarization direction of the filter's input and output ports at any angle between 0° and 90°, achieving excellent bandpass filtering response. Utilizing the electromagnetic coupling between the elliptical waveguide resonant cavities and the cylindrical cavity, and the rotational symmetry of the cylindrical cavity structure, the polarization rotation angle of the filter ports can be flexibly achieved without sacrificing cavity distortion, thus avoiding deformation or processing errors induced by cavity distortion during filter manufacturing.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic field and microwave technology, and more specifically, relates to an elliptical waveguide polarized rotating filter. Background Technology

[0002] Waveguide filters and torsional waveguides are crucial passive components in millimeter-wave communication systems. Filters provide frequency selection and interference suppression capabilities for the communication link, while torsional waveguides connect waveguide ports with different orientations and electromagnetic polarization directions. In traditional technologies, waveguide filters and torsional waveguides are often designed and manufactured independently. To enable polarization rotation in waveguide filters, discrete waveguide filters can be cascaded with torsional waveguides, which increases circuit size and introduces additional RF losses. A better approach is to integrate the torsional waveguide structure into the waveguide filter design, achieving both filtering and polarization rotation functions in a single device, thus improving integration. Traditionally, there are two implementation schemes for such polarization-rotating waveguide filters: first, torsion of the regular filter cavity structure after the waveguide filter design is complete; second, graded rotation of the regular resonant cavity and coupling structure during the waveguide filter design process.

[0003] Traditional technical solutions mainly have the following problems: (1) The torsion process causes distortion of the filter cavity structure, which complicates the mode analysis of the irregular resonant cavity and its coupling structure after distortion, and increases the difficulty of optimizing the filter response; (2) The filter structure after distortion is complex, and the processing and assembly are more difficult; (3) Although 3D printing technology can realize the integrated additive manufacturing of polarized rotating waveguide filters and simplify processing and assembly, the structural design scheme of traditional polarized rotating waveguide filters is not fully compatible with 3D printing technology. This compatibility defect between structure and process is specifically reflected in: (1) The cavity wall of the rectangular waveguide resonant cavity and its coupling structure is flat, and there are concave or convex corners at the intersection of the cavity walls. After torsion, distortion will occur, and the forming quality of 3D printing is poor; (2) The rectangular waveguide resonant cavity and its coupling structure are not rotationally symmetric structures, which will make the cavity structure more complex during polarization rotation, further posing a challenge to 3D printing; (3) 3D printing support material is easy to remain in the rectangular waveguide resonant cavity and its coupling structure, and the post-processing of the inner surface of the cavity after distortion is difficult. Therefore, improving the structural flexibility of polarized rotating waveguide filters and enhancing the compatibility of filter structures with 3D printing processes have become important technical approaches to effectively improve the manufacturing quality of such filters. Summary of the Invention

[0004] The purpose of this invention is to provide an elliptical waveguide polarization rotation filter, which aims to utilize the structural symmetry, surface profile, and similarity of resonant modes of elliptical and circular waveguides to realize a waveguide bandpass filter with polarization rotation characteristics, thereby enhancing the design flexibility of such filter structures and their compatibility with 3D printing technology.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: an elliptical waveguide polarization rotating filter is provided, comprising a metal housing, wherein the interior of the metal housing has multiple elliptical waveguide resonant cavities and two rectangular waveguides, wherein one rectangular waveguide, the multiple elliptical waveguide resonant cavities, and the other rectangular waveguide are connected in sequence, and the axes of symmetry of the two rectangular waveguides parallel to the long side of their cross-sections and the major axis of the elliptical cross-section of each elliptical waveguide resonant cavity are both rotation reference axes, wherein the direction of the latter rotation reference axis is formed by rotating the direction of the former rotation reference axis by a predetermined angle with the length direction of the metal housing as the rotation axis, and the two adjacent elliptical waveguide resonant cavities and the adjacent elliptical waveguide resonant cavities and the rectangular waveguides are all coupled together through cylindrical cavities.

[0006] Optionally, the central axis of the elliptical waveguide resonant cavity, the central axis of the rectangular waveguide, and the central axis of the cylindrical cavity are arranged collinearly.

[0007] Optionally, the major axis lengths and minor axis lengths of each of the elliptical waveguide resonant cavities are equal.

[0008] Optionally, the number of elliptical waveguide resonators is odd, with the two elliptical waveguide resonators symmetrically arranged around the middle elliptical waveguide resonator having equal axial lengths; or, the number of elliptical waveguide resonators is even, with the two elliptical waveguide resonators symmetrically arranged around the connection point of the two middle elliptical waveguide resonators having equal axial lengths.

[0009] Optionally, the axial lengths of each of the cylindrical cavities are equal.

[0010] Optionally, the number of cylindrical cavities is odd, with the innermost cylindrical cavity as the center, and the cross-sectional radii of the two cylindrical cavities arranged symmetrically are equal; or, the number of cylindrical cavities is even, with the cross-sectional radii of the two cylindrical cavities arranged symmetrically as the center of the line connecting the centers of the two innermost cylindrical cavities are equal.

[0011] Optionally, a transition waveguide is further provided between the rectangular waveguide and the adjacent elliptical waveguide resonant cavity, and the rectangular waveguide, the transition waveguide, the cylindrical cavity and the elliptical waveguide resonant cavity are connected in sequence.

[0012] Optionally, the included angle between two adjacent rotational reference axes is α, where 0 < α < 45°.

[0013] Optionally, the included angle between any two adjacent rotational reference axes is equal.

[0014] Optionally, if the number of rotational reference axes is x, then α(x–1) = (90±5)°.

[0015] The beneficial effects of the elliptical waveguide polarization rotating filter provided by this invention are as follows: each elliptical waveguide resonator is cascaded sequentially through a cylindrical cavity. Both the elliptical waveguide resonator and the cylindrical cavity have a rotation reference axis. Each subsequent elliptical waveguide resonator can be considered as being formed by rotating the preceding elliptical waveguide resonator. The direction of the subsequent rotation reference axis is formed by rotating the direction of the preceding rotation reference axis by a predetermined angle around the length direction of the metal shell. Therefore, the polarization direction of the filter's input and output ports can be flexibly designed at any angle between 0° and 90°, while simultaneously obtaining a good bandpass filtering response. The polarization rotation angle of the elliptical waveguide polarization rotating filter port provided by this invention is not limited by the structure, and the rotatable angle of each stage of the elliptical waveguide resonator is not limited by the structure. Its designed rotation angle depends on the actual required total polarization rotation angle and the order of the filter. By utilizing the electromagnetic coupling between the elliptical waveguide resonant cavity and the cylindrical cavity, as well as the rotational symmetry of the cylindrical cavity structure, the polarization rotation function of the filter can be flexibly realized. All structures of the filter do not produce distortion during the polarization rotation process, and maintain good compatibility with 3D printing technology, which helps the filter to be manufactured in a high-quality integrated manner using 3D printing technology. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 A three-dimensional structural diagram of an air cavity simulation model of an elliptical waveguide polarized rotating filter provided in an embodiment of the present invention;

[0018] Figure 2 A three-dimensional structural diagram of an elliptical waveguide polarization rotating filter provided in an embodiment of the present invention;

[0019] Figure 3 for Figure 2 A three-dimensional half-sectional view of the filter;

[0020] Figure 4 for Figure 1 and Figure 2 Passband S of medium-voltage filter simulation and measurement 11 and S 21 Parametric curves;

[0021] Figure 5 for Figure 1 and Figure 2 Wideband S-band filter simulation and measurement 11 and S 21 Parametric curves;

[0022] Figure 6 for Figure 1 and Figure 2 Loss of the medium filter in simulation and measurement (1-|S 11 | 2 -|S 21 | 2 ) Parameter curve.

[0023] The following are the labeling elements in the figure:

[0024] 1-Metal housing; 11-Waveguide flange; 111-Mounting through hole; 101-Elliptical waveguide resonant cavity; 102-Rectangular waveguide; 103-Cylindrical cavity; 104-Transition waveguide. Detailed Implementation

[0025] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0026] It should be noted that when a component is referred to as being "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0027] It should be understood that the terms "length", "upper", "lower", "front", "rear", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0028] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0029] The elliptical waveguide polarization rotating filter provided in the embodiments of the present invention will now be described.

[0030] Please see Figures 1 to 3 , Figure 1 This is a three-dimensional structural diagram of an air cavity simulation model of an elliptical waveguide polarized rotating filter provided in an embodiment of the present invention. Figure 2 This is a three-dimensional structural diagram of an elliptical waveguide polarization rotating filter provided in an embodiment of the present invention. Figure 3 for Figure 2 A three-dimensional half-sectional view of the filter. The elliptical waveguide polarized rotating filter includes a metal housing 1. Inside the metal housing 1 are multiple elliptical waveguide resonant cavities 101, multiple cylindrical cavities 103, and two rectangular waveguides 102. The cross-sections of the elliptical waveguide resonant cavities 101 are elliptical, the cross-sections of the cylindrical cavities 103 are circular, and the cross-sections of the rectangular waveguides 102 are rectangular. The multiple elliptical waveguide resonant cavities 101 are arranged sequentially along the length of the metal housing 1. Adjacent elliptical waveguide resonant cavities 101 are connected sequentially through cylindrical cavities 103. The two rectangular waveguides 102 are located at opposite ends of the metal housing 1, i.e., at opposite ends of the multiple elliptical waveguide resonant cavities 101. The rectangular waveguides 102 and their adjacent elliptical waveguide resonant cavities 101 are also coupled together through cylindrical cavities 103. From another perspective, the inner wall of the metal housing 1 has multiple annular partitions, and the aforementioned cylindrical cavities 103 are formed at the inner rings of the annular partitions. The axes of symmetry of the two rectangular waveguides 102 and their cross-sections parallel to the long side, and the major axis of the elliptical cross-section of each elliptical waveguide resonator 101, are all set as rotational reference axes, with the length direction of the metal housing 1 as the rotation axis. The direction of each subsequent rotational reference axis is obtained by rotating the direction of the previous rotational reference axis by a predetermined angle. The angle between any two rotational reference axes can be called the polarization rotation angle. It should be noted that the major axis, minor axis, axial length, and other dimensions of the ellipse of two adjacent elliptical waveguide resonators 101 are not necessarily the same.

[0031] The elliptical waveguide polarization rotating filter in this embodiment of the invention utilizes the resonant cavities 101 of each elliptical waveguide. e TE 111 The mode is used as the dominant mode. The TE signal transmitted in rectangular waveguide 102... 10The mode is input from the waveguide port of the first rectangular waveguide 102 in the first polarization direction, coupled into the first elliptical waveguide resonant cavity 101 through the first cylindrical cavity 103, and excited therein. e TE 111 mold. e TE 111 Each time the mode passes through an elliptical waveguide resonator 101, it rotates by a preset angle and is coupled to the next elliptical waveguide resonator 101 through the cylindrical cavity 103, until it is output through the waveguide port of the rectangular waveguide 102 at the tail end in the second polarization direction.

[0032] In the elliptical waveguide polarization rotating filter of the above embodiment, each elliptical waveguide resonator 101 is cascaded sequentially through a cylindrical cavity 103. Both the elliptical waveguide resonator 101 and the cylindrical cavity 103 have a rotation reference axis. Each subsequent elliptical waveguide resonator 101 can be considered as being formed by rotating the previous elliptical waveguide resonator 101. The direction of the subsequent rotation reference axis is formed by rotating the direction of the previous rotation reference axis by a predetermined angle with the length direction of the metal shell 1 as the rotation axis. Therefore, the polarization direction of the filter's input and output ports can be flexibly designed at any angle between 0° and 90°, while simultaneously obtaining a good bandpass filtering response. The polarization rotation angle of the elliptical waveguide polarization rotating filter provided by this invention is not limited by the structure, and the rotatable angle of each stage of the elliptical waveguide resonator 101 is not limited by the structure. Its designed rotation angle depends on the actual required total polarization rotation angle and the order of the filter. By utilizing the electromagnetic coupling between the elliptical waveguide resonant cavity 101 and the cylindrical cavity 103, as well as the rotational symmetry of the cylindrical cavity 103 structure, the polarization rotation function of the filter can be flexibly realized. No distortion occurs in any part of the filter structure during the polarization rotation process, and good compatibility with 3D printing technology is maintained. This helps the filter to be manufactured in a high-quality integrated manner using 3D printing technology.

[0033] In one embodiment of the present invention, the central axis of the elliptical waveguide resonant cavity 101, the central axis of the rectangular waveguide 102, and the central axis of the cylindrical cavity 103 are collinear. This collinear structure allows for a more intuitive change in the polarization rotation angle of the resonant cavity, effectively avoiding the problem of other topologies requiring internal support for the cavity during 3D printing, thus increasing post-processing difficulties.

[0034] In one embodiment of the present invention, the major axis length and minor axis length of each elliptical waveguide resonator 101 are equal, meaning that the cross-sectional dimensions of each elliptical waveguide resonator 101 are the same. This arrangement facilitates the RF design of the elliptical waveguide polarization rotating filter. In other embodiments, the major axis length and minor axis length of each elliptical waveguide resonator 101 may also be unequal.

[0035] In one embodiment of the present invention, the number of elliptical waveguide resonators 101 is odd, and the axial lengths of two elliptical waveguide resonators 101 symmetrically arranged with the central elliptical waveguide resonator 101 as the center are equal. For example, the number of elliptical waveguide resonators 101 is five, with the axial lengths of the first and fifth elliptical waveguide resonators 101 being equal, and the axial lengths of the second and fourth elliptical waveguide resonators 101 being equal. In another embodiment of the present invention, the number of elliptical waveguide resonators 101 is even, and the axial lengths of two elliptical waveguide resonators 101 symmetrically arranged with the connection point of the two central elliptical waveguide resonators 101 as the center are equal. For example, there are four elliptical waveguide resonators 101. The axial lengths of the first and fourth elliptical waveguide resonators 101 are equal, and the axial lengths of the second and third elliptical waveguide resonators 101 are equal. In other embodiments of the invention, the axial lengths of the individual elliptical waveguide resonators 101 may be equal or unequal. The axial length of each elliptical waveguide resonator 101 is only one of the dimensions controlling the resonant frequency of the resonator. During the design process, the resonant frequency of the elliptical waveguide resonator 101 can be controlled by combining the resonator loading technology. This indicates that the change in resonant frequency caused by the difference in the axial length of the elliptical waveguide resonators 101 can be compensated for by other techniques. Specifically, when the axial lengths are equal, different degrees of loading can be applied to each elliptical waveguide resonator 101 to achieve the required bandpass filter response; when the axial lengths are unequal, the loading may not be necessary or may be adjusted accordingly to achieve the required bandpass filter response.

[0036] By optimizing the dimensions of the elliptical cross-sections of each elliptical waveguide resonator 101, the unloaded Q-value (Q0) can be obtained. u Optimal cavity dimensions also help to keep higher-order modes away from the fundamental mode. Given a fixed elliptical cross-sectional dimension of the elliptical waveguide resonant cavity 101, the mode resonant frequencies of the elliptical waveguide resonant cavity 101 are determined by its axial length. For example, when the major axis of the ellipse of the elliptical waveguide resonant cavity 101 is 22.86 mm, the minor axis is 13.06 mm, and the axial length is 24 mm, the intrinsic resonant frequency of the fundamental mode of the elliptical waveguide resonant cavity 101 is 10 GHz, and the intrinsic resonant frequency of the first higher-order mode is 14.248 GHz.

[0037] In one embodiment of the present invention, to simplify filter modeling, the axial lengths of each cylindrical cavity 103 are set to be equal, thus reducing the dimensional variables that need to be adjusted. In other embodiments, the axial lengths of each cylindrical cavity 103 may also be unequal. The axial length of each cylindrical cavity 103 is only one of the dimensions controlling the interstage coupling coefficient of the resonant cavity. During the design process, the cross-sectional radius of each cylindrical cavity 103 can be adjusted simultaneously to control the interstage coupling coefficient of the resonant cavity. This indicates that the change in the interstage coupling coefficient caused by the difference in the axial length of the cylindrical cavity 103 can be compensated for by adjusting the cross-sectional radius of the cylindrical cavity 103.

[0038] In one embodiment of the present invention, the number of cylindrical cavities 103 is odd, and the cross-sectional radii of two symmetrically arranged cylindrical cavities 103 are equal, with the central cylindrical cavity 103 as the center. For example, the number of cylindrical cavities 103 is five, with the first and fifth cylindrical cavities 103 having equal cross-sectional radii, and the second and fourth cylindrical cavities 103 having equal cross-sectional radii. In other embodiments of the present invention, the number of cylindrical cavities 103 is even, and the axial lengths of two symmetrically arranged cylindrical cavities 103 are equal, with the center of the line connecting the centers of the two central cylindrical cavities 103 as the center. For example, the number of cylindrical cavities 103 is four, with the first and fourth cylindrical cavities 103 having equal axial lengths, and the second and third cylindrical cavities 103 having equal axial lengths.

[0039] The interstage coupling coefficient of the filter can be controlled by adjusting the radius of the cross-sectional circle of the cylindrical cavity 103 between two adjacent elliptical waveguide resonant cavities 101. The external coupling coefficient of the filter can be controlled by adjusting the radius of the cross-sectional circle of the cylindrical cavity 103 connected to the rectangular waveguide 102. For example, the radii of the cross-sectional circles of the cylindrical cavities 103 used to adjust the interstage coupling coefficient are 5.075 mm and 4.76 mm, respectively, with an axial length of 2 mm for both; the radii of the cross-sectional circles of the cylindrical cavities 103 used to adjust the external coupling coefficient are both 6.425 mm, with an axial length of 0.8 mm for both.

[0040] In one embodiment of the present invention, please refer to Figure 1 and Figure 3 A transition waveguide 104 is also provided between the rectangular waveguide 102 and the adjacent elliptical waveguide resonant cavity 101. The transition waveguide 104 is used to smoothly connect the rectangular waveguide 102 and the cylindrical cavity 103, so that the inner wall of the metal shell 1 is smooth. The rectangular waveguide 102, the transition waveguide 104, the cylindrical cavity 103 and the elliptical waveguide resonant cavity 101 are connected in sequence.

[0041] In one embodiment of the present invention, the inner wall of the metal housing 1 is smoothly disposed, which helps to improve the quality of the integrated additive manufacturing of the filter and can improve the Q of the elliptical waveguide resonant cavity 101. u This reduces the RF loss of the filter. All contours of the elliptical waveguide resonant cavity 101 and the cylindrical cavity 103 are rounded, making the entire inner contour of the filter a plane or a smooth curved surface.

[0042] In one embodiment of the present invention, the included angle between two adjacent rotating reference axes is α. That is, in the sequentially connected rectangular waveguide 102 and elliptical waveguide resonant cavity 101, or two elliptical waveguide resonant cavities 101, the rotation angle of the latter structure relative to the former structure is α, where α is the polarization rotation angle. By adjusting the polarization rotation angle α between two adjacent elliptical waveguide resonant cavities 101, the interstage coupling coefficient of the filter can be controlled; by adjusting the polarization rotation angle α between the sequentially connected rectangular waveguide 102 and elliptical waveguide resonant cavity 101, the external coupling coefficient of the filter can be controlled. α can take any value between 0° and 45°.

[0043] Optionally, the included angle between any two adjacent rotation reference axes is equal, that is, the polarization rotation angle α is the same for all polarizations.

[0044] The polarization directions of the waveguide ports of the two rectangular waveguides 102 are determined by TE. 10 The direction of the electric field of the mode determines the angle between the polarization directions, which can be flexibly set to any angle between 0° and 90°. That is, the angle between the long or short sides of the two rectangular waveguides 102 can be any angle between 0° and 90°. The number of rotation reference axes is x, and α(x-1) can be any angle between 0° and 90°. When it is 0°, there is no polarization rotation between the input and output ports of the filter; when it is 90°, the maximum polarization rotation is achieved between the input and output ports of the filter, rotating from horizontal polarization to vertical polarization, or from vertical polarization to horizontal polarization.

[0045] This invention provides an elliptical waveguide polarization rotation filter with a designed center frequency of 10 GHz, a relative bandwidth of 3%, and a corresponding passband frequency range of 9.85–10.15 GHz. The designed passband reflection coefficient is less than -20 dB. Four elliptical waveguide resonant cavities 101 are used, each with a polarization rotation angle of 18°. The angle between the polarization directions of the first and last rectangular waveguides 102 is 90°. For such a filter, combined with… Figure 1A preferred set of dimensions is as follows: the major axis of the elliptical cross-section of the elliptical waveguide resonator 101 is 22.86 mm, the minor axis is 13.06 mm, and the axial lengths of each elliptical waveguide resonator 101 are 19.64 mm, 21.49 mm, 21.49 mm, and 19.64 mm, respectively; the cross-sectional radii of each cylindrical cavity 103 are 6.425 mm, 5.075 mm, 4.76 mm, 5.075 mm, and 6.425 mm, respectively, and the thicknesses of the annular partitions are 0.80 mm, 2 mm, 2 mm, 2 mm, and 0.80 mm, respectively; the length of each transition waveguide 104 is 2.5 mm; the waveguide flange 11 is the standard flange size in the international code BJ100, and the waveguide flange 11 has mounting through holes 111. The long side and short side lengths of the waveguide port of the rectangular waveguide 102 are 22.86 mm and 10.16 mm, respectively. In order to balance the mechanical strength of the filter metal housing 1 and the amount of redundant structural material, the thickness of the filter metal housing 1 is set between 4.5 mm and 5.5 mm.

[0046] Please see Figures 4 to 6 , Figure 4 for Figure 1 and Figure 2 Passband S of medium-voltage filter simulation and measurement 11 and S 21 Parameter curves Figure 5 for Figure 1 and Figure 2 Wideband S-band filter simulation and measurement 11 and S 21 Parameter curves Figure 6 for Figure 1 and Figure 2 Loss of the medium filter in simulation and measurement (1-|S 11 | 2 -|S 21 | 2 Parameter curves. To experimentally verify the RF performance of the elliptical waveguide polarized rotating filter provided in this embodiment of the invention, a high-precision multi-head inkjet 3D printing process was used to integrally manufacture the elliptical waveguide polarized rotating filter with photosensitive resin. Chemical copper plating was then performed on the surface of the 3D-printed resin structure to complete the metallization of the entire housing surface. During the integral 3D printing process, the metal housing 1 of the filter does not require any internal support material. Figure 4 and Figure 5 As can be seen, the simulation and measurement results of the filter agree well. The measured return loss within the passband is mostly better than 15dB, the insertion loss is less than 2.1dB, the measured center frequency offset is less than 15MHz (0.15%), and the first parasitic passband appears around 14GHz. Figure 6 It can be seen that the loss measured within the passband (1-|S11 | 2 -|S 21 | 2 The average loss is approximately 2 dB, primarily due to conductor losses in the filter cavity. The main reason this loss exceeds the simulated value is insufficient metal plating thickness. Increasing the thickness of the copper plating can significantly reduce this loss.

[0047] In the embodiments provided by this invention, it should be understood that: First, how to utilize the mode distribution patterns of the elliptical waveguide resonant cavity 101 and the cylindrical cavity 103, as well as the rotational symmetry of the two cavity structures, to achieve a polarization-rotated bandpass filter response while avoiding distortion of the filter cavity structure is the core technical problem solved by this invention; Second, the order of the filter and the polarization rotation angle are merely illustrative and not unique, but only represent a relatively optimal and achievable structure. Specifically, the order of the filter can be arbitrary, and the polarization rotation angle of the filter can be any angle between 0° and 90°; Third, the elliptical waveguide resonant cavity 101 and the cylindrical cavity 103 are more compatible with 3D printing technology than traditional rectangular cavities. The inner contour of the filter is rounded, making it a plane or a smooth curved surface, suitable for various non-metallic / metallic 3D printing processes and printing materials, and the structural design method has strong universality.

[0048] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An elliptical waveguide polarized rotating filter, characterized in that: The device includes a metal housing, inside which are multiple elliptical waveguide resonators and two rectangular waveguides. One rectangular waveguide, the multiple elliptical waveguide resonators, and the other rectangular waveguide are sequentially connected. The axes of symmetry of the two rectangular waveguides, which are parallel to the long side of their cross-sections, and the major axis of the elliptical cross-section of each elliptical waveguide resonator are both rotation reference axes. The rotation reference axis of the rectangular waveguide is the axis of symmetry of the rectangular waveguide. The axis of symmetry of the rectangular waveguide is parallel to the length direction of the cross-section of the rectangular waveguide and passes through the center of the cross-section of the rectangular waveguide. The cross-section of the rectangular waveguide is perpendicular to the transmission direction of the rectangular waveguide. The direction of the subsequent rotation reference axis is obtained by rotating the direction of the previous rotation reference axis by a predetermined angle with the length direction of the metal housing as the rotation axis. Two adjacent elliptical waveguide resonators and adjacent elliptical waveguide resonators and rectangular waveguides are coupled together through cylindrical cavities.

2. The elliptical waveguide polarization rotating filter as described in claim 1, characterized in that: The central axis of the elliptical waveguide resonant cavity, the central axis of the rectangular waveguide, and the central axis of the cylindrical cavity are arranged collinearly.

3. The elliptical waveguide polarization rotating filter as described in claim 1, characterized in that: The major axis length and minor axis length of each of the elliptical waveguide resonant cavities are equal.

4. The elliptical waveguide polarization rotating filter as described in claim 1, characterized in that: The number of elliptical waveguide resonators is odd, with the two elliptical waveguide resonators symmetrically arranged around the middle elliptical waveguide resonator having equal axial lengths; or the number of elliptical waveguide resonators is even, with the two elliptical waveguide resonators symmetrically arranged around the connection point of the two middle elliptical waveguide resonators having equal axial lengths.

5. The elliptical waveguide polarization rotating filter as described in claim 1, characterized in that: The axial lengths of each of the cylindrical cavities are equal.

6. The elliptical waveguide polarization rotating filter as described in claim 1, characterized in that: The number of cylindrical cavities is odd, with the innermost cylindrical cavity as the center, and the cross-sectional radii of the two cylindrical cavities arranged symmetrically are equal; or, the number of cylindrical cavities is even, with the cross-sectional radii of the two cylindrical cavities arranged symmetrically as the center of the line connecting the centers of the two innermost cylindrical cavities are equal.

7. The elliptical waveguide polarization rotating filter as described in any one of claims 1-6, characterized in that: A transition waveguide is also provided between the rectangular waveguide and the adjacent elliptical waveguide resonant cavity, and the rectangular waveguide, the transition waveguide, the cylindrical cavity and the elliptical waveguide resonant cavity are connected in sequence.

8. The elliptical waveguide polarization rotating filter according to any one of claims 1-6, characterized in that: The included angle between two adjacent rotational reference axes is α, where 0 < α < 45°.

9. The elliptical waveguide polarization rotating filter as described in claim 8, characterized in that: The included angle between any two adjacent rotational reference axes is equal.

10. The elliptical waveguide polarization rotating filter as described in claim 9, characterized in that: If the number of rotational reference axes is x, then α(x–1)=(90±5)°.

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