Shaped resonator polarizing rotating filter

Abstract

The application provides a shaped resonant cavity polarization rotating filter, comprising a metal shell, an air cavity in the metal shell, the air cavity comprising two rectangular waveguides, two hemispherical coupling cavities, n shaped resonant cavities and n-1 inter-stage coupling cavities, wherein one of the rectangular waveguides, one of the hemispherical coupling cavities, the n shaped resonant cavities, the other hemispherical coupling cavity and the other rectangular waveguide are sequentially connected, two adjacent shaped resonant cavities are connected through the inter-stage coupling cavities, two adjacent polarization center axes are arranged at an included angle, and two adjacent bending center axes are arranged at an included angle. The shaped resonant cavity polarization rotating filter provided by the application utilizes the rotational symmetry of the shaped resonant cavity and the inter-stage coupling cavity and the electromagnetic coupling of the two, flexibly realizes the polarization rotating and bending rotating functions of the filter, all the inner cavity structures of the filter do not produce distortion in the polarization rotating and bending rotating processes, and the filter is helpful for high-quality integrated manufacturing by using 3-D printing technology.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic field and microwave technology, and more specifically, relates to a shaped resonant cavity polarization rotating filter. Background Technology

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

[0003] Traditional technical solutions have the following main problems: (1) The polarization rotation and bending rotation process leads to the 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, which increases the difficulty of processing and assembly; (3) Although 3D printing technology can realize the integrated additive manufacturing of polarization rotation and bending rotation waveguide filters, simplifying processing and assembly, the traditional structural design scheme of polarization rotation and bending rotation waveguide filters is not compatible with 3D printing process. The specific incompatibility defects between this structure and process are as follows: (1) The cavity walls of the rectangular waveguide resonator and its coupling structure are planar, and there are concave or convex corners at the intersection of the cavity walls. After twisting, distortion will occur, resulting in poor 3D printed structure forming quality; (2) The rectangular waveguide resonator and its coupling structure are not rotationally symmetric structures, which will make the cavity structure more complex during polarization rotation, further posing challenges to 3D printing; (3) 3D printed support material is easily left in the rectangular waveguide resonator and its coupling structure, and the post-processing of the inner surface of the distorted cavity is difficult. All of the above defects will increase the risk of deterioration of the radio frequency performance of the waveguide filter. Therefore, improving the structural flexibility of polarization rotation and bending rotation waveguide filters and enhancing the compatibility of the filter structure with the 3D printing process 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 a shaped resonant cavity polarization rotation filter, which aims to utilize the structural symmetry of the shaped resonant cavity and the interstage coupling cavity, as well as the similarity of their resonant modes, to realize a waveguide bandpass filter with bending and polarization rotation characteristics, thereby enhancing the design flexibility of this type of filter structure and its compatibility with 3D printing technology.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A shaped resonant cavity polarization rotating filter is provided, comprising a metal housing, an air cavity within the metal housing, the air cavity comprising two rectangular waveguides, two hemispherical coupling cavities, n shaped resonant cavities, and n-1 interstage coupling cavities. One of the rectangular waveguides, one of the hemispherical coupling cavities, n shaped resonant cavities, another hemispherical coupling cavity, and another rectangular waveguide are sequentially connected, where n is an integer greater than or equal to 2. Adjacent shaped resonant cavities are connected through the interstage coupling cavities. The central axis of the rectangular waveguide parallel to its polarization direction and the central axis of the shaped resonant cavity parallel to its polarization direction are both polarization central axes, and adjacent polarization central axes are set at an angle. The central axis of the rectangular waveguide parallel to its axial direction, the central axis of the hemispherical coupling cavity parallel to its axial direction, the central axis of the shaped resonant cavity parallel to its axial direction, and the central axis of the interstage coupling cavity parallel to its axial direction are all bending central axes, and adjacent bending central axes are set at an angle.

[0006] Optionally, each of the bending center axes is arranged coplanarly.

[0007] Optionally, the cross-section of the shaped resonant cavity is elliptical, and the major axis length of the ellipse of the cross-section of each shaped resonant cavity is equal, and the minor axis length of the ellipse of the cross-section of each shaped resonant cavity is equal.

[0008] Optionally, in the arrangement direction of the plurality of shaped resonant cavities, the axial lengths of two symmetrically arranged shaped resonant cavities are equal.

[0009] Optionally, the interstage coupling cavity is spherical, and in the arrangement direction of the plurality of interstage coupling cavities, two interstage coupling cavities that are symmetrically arranged have equal radii.

[0010] Optionally, the included angle between two adjacent polarization center axes is α, where 0 < α ≤ 45°.

[0011] Optionally, the included angle between any two adjacent polarization center axes is equal.

[0012] Optionally, the included angle between two adjacent bending center axes is β, where 0 < β < 45°.

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

[0014] Optionally, the shaped resonant cavity polarization rotating filter is integrally manufactured using 3D printing technology, and the inner wall of the metal shell is smoothly formed.

[0015] The beneficial effects of the shaped resonant cavity polarization rotation filter provided by this invention are as follows: Compared with the prior art, in the shaped resonant cavity polarization rotation filter of this invention, each shaped resonant cavity is cascaded sequentially through interstage coupling cavities. Both the shaped resonant cavity and the interstage coupling cavity have a polarization rotation reference axis, and each subsequent shaped resonant cavity can be considered as a polarization rotation of the preceding shaped resonant cavity. The shaped resonant cavity, interstage coupling cavity, and hemispherical coupling cavity all have a bending central axis, and each subsequent shaped resonant cavity can be considered as a rotation of the preceding shaped resonant cavity around a defined center and radius of curvature. Therefore, the polarization direction of the filter's input and output ports can be flexibly designed at any angle between 0° and 90°, and the bending direction can be flexibly designed at any angle between 0° and 180°, while simultaneously obtaining a good bandpass filtering response. The polarization rotation angle of the waveguide port of the shaped resonant cavity polarization rotation filter provided by this invention is not structurally limited. The polarization rotation angle of each stage of the shaped resonant cavity is also unrestricted by the structure, depending on the total polarization rotation angle actually required by the filter and the filter order. Similarly, the bending rotation angle of the waveguide port of the shaped resonant cavity polarization rotation filter provided by this invention is also unrestricted by the structure. The bending rotation angle of each stage cavity is also unrestricted by the structure, depending on the total bending rotation angle actually required by the filter and the filter order. Utilizing the electromagnetic coupling between the shaped resonant cavity and the interstage coupling cavity, as well as the rotational symmetry of their structures, the polarization rotation and bending rotation functions of the filter can be flexibly realized. Theoretically, this filter can achieve a bending structure and port polarization rotation function at any spatial angle. All structures of the filter do not produce distortion during polarization rotation and bending rotation, and maintain good compatibility with 3D printing technology, which helps to manufacture the filter 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 one embodiment 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 the air cavity simulation model of the shaped resonant cavity polarization rotating filter provided in an embodiment of the present invention;

[0018] Figure 2 A three-dimensional structural diagram of the fabrication model of the shaped resonant cavity 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 Parameter curve.

[0022] The following are the labeling elements in the figure:

[0023] 1-Metal housing; 11-Waveguide flange; 111-Mounting through hole; 101-Shaped resonant cavity; 102-Interstage coupling cavity; 103-Hemispherical coupling cavity; 104-Transition waveguide; 105-Rectangular waveguide. Detailed Implementation

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] The shaped resonant cavity polarization rotating filter provided in the embodiments of the present invention will now be described.

[0029] Please see Figures 1 to 3 , Figure 1 This is a three-dimensional structural diagram of the air cavity simulation model of the shaped resonant cavity polarization rotating filter provided in an embodiment of the present invention. Figure 2 This is a three-dimensional structural diagram of the fabrication model of the shaped resonant cavity 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 shaped resonant cavity polarization rotating filter includes a metal housing 1, and an air cavity is located inside the metal housing 1. The air cavity includes two rectangular waveguides 105, two hemispherical coupling cavities 103, n shaped resonant cavities 101, and n-1 interstage coupling cavities 102. n is an integer greater than or equal to 2. For example, if n is 4, there are four shaped resonant cavities 101 and three interstage coupling cavities 102; if n is 5, there are five shaped resonant cavities 101 and four interstage coupling cavities 102. The connection order of the cavities in the air cavity is as follows: one rectangular waveguide 105, one hemispherical coupling cavity 103, n shaped resonant cavities 101, another hemispherical coupling cavity 103, and another rectangular waveguide 105 are connected in sequence, and every two adjacent shaped resonant cavities 101 are connected through an interstage coupling cavity 102.

[0030] The shaped resonant cavity 101 has an elliptical cross-section, the interstage coupling cavity 102 has a circular cross-section, and the rectangular waveguide 105 has a rectangular cross-section. The direction parallel to the length of the minor axis of the elliptical cross-section of the shaped resonant cavity 101 is the polarization direction of the shaped resonant cavity 101, and the central axis of the shaped resonant cavity 101 parallel to its polarization direction is the polarization central axis. The direction perpendicular to the elliptical cross-section of the shaped resonant cavity 101 is the axial direction of the shaped resonant cavity 101. The direction perpendicular to the cross-section of the rectangular waveguide 105 is the axial direction of the rectangular waveguide 105, i.e., the extension direction of the rectangular waveguide 105. The direction perpendicular to the cross-section of the interstage coupling cavity 102 is the axial direction of the interstage coupling cavity, i.e., the extension direction of the interstage coupling cavity 102. The central axes parallel to the axial directions of the rectangular waveguide 105, the hemispherical coupling cavity 103, the shaped resonant cavity 101, and the interstage coupling cavity 102 are all curved central axes.

[0031] Two adjacent polarization center axes are set at an angle. In the extension direction of the air cavity, the direction of the latter polarization center axis can be considered as the direction of the former polarization center axis rotated by a predetermined angle. The angle between any two polarization center axes can be called the polarization rotation angle. The polarization rotation angle of the filter is the sum of the angles between any two adjacent polarization center axes, that is, the polarization rotation angle (the angle between polarization directions) between the two rectangular waveguides 105. Two adjacent bending center axes are set at an angle. In the extension direction of the air cavity, the latter bending center axis can be considered as the direction of the former bending center axis rotated by a predetermined angle. The angle between any two bending center axes can be called the bending rotation angle. The bending rotation angle of the filter is the sum of the angles between any two adjacent bending center axes, that is, the angle between the axial directions of the two rectangular waveguides 105.

[0032] The shaped resonant cavity polarization rotating filter in this embodiment of the invention employs quasi-shaped resonant cavities 101. e TE 111 The mode is used as the dominant mode. The TE signal transmitted in the rectangular waveguide 105... 10 The mode is input from the waveguide port of the rectangular waveguide 105 at the first end in the first polarization direction, coupled into the first shaped resonant cavity 101 through the first hemispherical coupling cavity 103, and excited within it a quasi-resonant. e TE 111 Model. Standard e TE 111Each time the filter passes through an interstage coupling cavity 102 and reaches the next shaped resonant cavity 101, it undergoes a polarization rotation of a preset angle α. The filter cavity structure bends by a preset angle β after passing through a hemispherical coupling cavity 103 at either the beginning or end. After passing through an interstage coupling cavity 102, its adjacent two shaped resonant cavities 101 bend by a preset angle 2β. That is, at each coupling structure between a shaped resonant cavity 101 and an interstage coupling cavity 102, the filter structure bends by the same preset angle β. After polarization rotation and bending, the quasi-polarization rotation... e TE 111 The mode is coupled to the rectangular waveguide 105 through the second hemispherical coupling cavity 103 at the tail end, and outputs at the waveguide port of the rectangular waveguide 105 via TE. 10 The mode outputs in the second polarization direction.

[0033] In the shaped resonant cavity polarization rotation filter of the above embodiment, each shaped resonant cavity 101 is cascaded sequentially through interstage coupling cavities 102. Both the shaped resonant cavity 101 and the interstage coupling cavity 102 have polarization rotation reference axes. The subsequent shaped resonant cavity 101 can be regarded as the polarization rotation of the previous shaped resonant cavity 101. The shaped resonant cavity 101, the interstage coupling cavity 102 and the hemispherical coupling cavity 103 all have bending central axes. The subsequent shaped resonant cavity 101 can be regarded as the previous shaped resonant cavity 101 rotating around a defined center and radius of curvature. Therefore, each shaped resonant cavity 101 undergoes both polarization rotation and bending rotation in the cascaded direction. The interstage coupling cavity 102 and the hemispherical coupling cavity 103 act as joints for the polarization and bending rotation of the shaped resonant cavity 101. Ultimately, the polarization direction of the filter's input and output ports can be flexibly designed at any angle between 0° and 90°, and the bending direction can be flexibly designed at any angle between 0° and 180°, while simultaneously obtaining a good bandpass filtering response. The polarization rotation angle of the waveguide port of the shaped resonant cavity polarization rotation filter provided by this invention is not structurally limited, and the polarization rotation angle of each stage of the shaped resonant cavity 101 is not structurally limited; its polarization rotation angle depends on the total polarization rotation angle actually required by the filter and the order of the filter. The bending rotation angle of the waveguide port of the shaped resonant cavity polarization rotation filter provided by this invention is also not structurally limited, and the bending rotation angle of each stage of the cavity is not structurally limited; its bending rotation angle depends on the total bending rotation angle actually required by the filter and the order of the filter. By utilizing the electromagnetic coupling between the shaped resonant cavity 101 and the interstage coupling cavity 102, as well as the rotational symmetry of their structures, the polarization rotation and bending rotation functions of the filter can be flexibly realized. Theoretically, this filter can achieve a bending structure and port polarization rotation function at any angle in space. All structures of the filter do not produce distortion during polarization rotation and bending rotation, and maintain good compatibility with 3D printing technology, which facilitates the high-quality, integrated manufacturing of the filter using 3D printing technology.

[0034] In one embodiment of the present invention, please refer to Figures 1 to 3 All bending center axes are set coplanarly. Combined Figure 1 In other words, all bending center axes are located on the xoz plane. The coplanar structure allows for direct modification of the polarization rotation angle and bending rotation angle of the shaped resonant cavity 101. In other embodiments of the invention, the bending center axes may not be coplanar, thus flexibly realizing bending structures and port polarization rotation functions at arbitrary spatial angles.

[0035] In one embodiment of the present invention, the major axis length and minor axis length of the ellipse of the cross-section of each shaped resonant cavity 101 are equal, that is, the cross-sectional dimensions of each shaped resonant cavity 101 are the same. This configuration simplifies the RF design of the shaped resonant cavity polarization rotating filter. In other embodiments, the major axis length and minor axis length of the ellipse of the cross-section of each shaped resonant cavity 101 may also be unequal.

[0036] In one embodiment of the present invention, in the arrangement direction of the plurality of shaped resonant cavities 101, the axial lengths of two symmetrically arranged shaped resonant cavities 101 are equal.

[0037] Optionally, the number of shaped resonant cavities 101 is even, with the connection point of the two middle shaped resonant cavities 101 as the midpoint, and the axial lengths of the two shaped resonant cavities 101 located at opposite ends of the midpoint and in symmetrical positions are equal. For example, the number of shaped resonant cavities 101 is four, with the first and fourth shaped resonant cavities 101 having equal axial lengths, and the second and third shaped resonant cavities 101 having equal axial lengths.

[0038] Optionally, the number of shaped resonant cavities 101 is odd, with the geometric center of the middle shaped resonant cavity 101 as the midpoint, and the axial lengths of two shaped resonant cavities 101 located symmetrically at opposite ends of the midpoint being equal. For example, if there are five shaped resonant cavities 101, the axial lengths of the first and fifth shaped resonant cavities 101 are equal, and the axial lengths of the second and fourth shaped resonant cavities 101 are equal.

[0039] In other embodiments, the axial lengths of each shaped resonant cavity 101 can be equal or unequal. The axial length of each shaped resonant cavity 101 is merely one dimension controlling the resonant frequency of that cavity. During the design process, loading techniques can be combined to achieve flexible control of the resonant frequency of the shaped resonant cavity 101. This indicates that the variation in resonant frequency caused by differences in the axial lengths of the shaped resonant cavities 101 can be compensated for using other techniques. Specifically, when the axial lengths are equal, different degrees of loading can be applied to each shaped resonant cavity 101 to achieve the desired bandpass filter response; when the axial lengths are unequal, the loading may be unnecessary or adjusted accordingly to achieve the desired bandpass filter response.

[0040] By optimizing the dimensions of the elliptical cross-sections of each shaped resonant cavity 101, the unloaded Q-value (Q0) can be obtained. u Optimal cavity dimensions help to keep higher-order modes away from the fundamental mode. Given a fixed elliptical cross-section, the mode resonant frequencies of the shaped resonant cavity 101 are determined by its axial length. For example, when the major axis of the elliptical cross-section of the shaped resonant cavity 101 is 7.112 mm, the minor axis is 4.071 mm, and the axial length is 11.112 mm, the intrinsic resonant frequency of the fundamental mode of the shaped resonant cavity 101 is 30 GHz, and the intrinsic resonant frequency of the first higher-order mode is 40.496 GHz.

[0041] In one embodiment of the present invention, to simplify the modeling of the filter's physical structure, the embedding depths of each interstage coupling cavity 102 and each shaped resonant cavity 101 are equal, and the embedding depths of each hemispherical coupling cavity 103 and each shaped resonant cavity 101 are also equal, thus reducing the size variables that need to be adjusted. In other embodiments, the embedding depths of each interstage coupling cavity 102 and each shaped resonant cavity 101 may not be equal, and the embedding depths of each hemispherical coupling cavity 103 and each shaped resonant cavity 101 may also not be equal. The embedding depths of each interstage coupling cavity 102 and each shaped resonant cavity 101 are merely one of the dimensions controlling the interstage coupling coefficient of the resonant cavity, and the embedding depths of each hemispherical coupling cavity 103 and each shaped resonant cavity 101 are merely one of the dimensions controlling the external coupling coefficient. During the design process, the radius of each interstage coupling cavity 102 can be adjusted simultaneously to control the interstage coupling coefficient of the resonant cavity, and the radius of each hemispherical coupling cavity 103 can be adjusted simultaneously to control the external coupling coefficient. This indicates that the change in the interstage coupling coefficient caused by the difference in the embedding depth of the interstage coupling cavity 102 can be compensated by adjusting the radius of the interstage coupling cavity 102, and the change in the external coupling coefficient caused by the difference in the embedding depth of the hemispherical coupling cavity 103 can be compensated by adjusting the radius of the hemispherical coupling cavity 103.

[0042] In one embodiment of the present invention, the interstage coupling cavity 102 is spherical, and in the arrangement direction of the plurality of interstage coupling cavities 102, two interstage coupling cavities 102 symmetrically arranged have equal radii.

[0043] Optionally, the number of interstage coupling cavities 102 is even, with the connection point between the geometric centers of the two middle interstage coupling cavities 102 as the midpoint. The two interstage coupling cavities 102 located at opposite ends of the midpoint and in symmetrical positions have equal radii. For example, if there are four interstage coupling cavities 102, the first and fourth interstage coupling cavities 102 have equal radii, and the second and third interstage coupling cavities 102 have equal radii.

[0044] Optionally, the number of interstage coupling cavities 102 is odd, with the geometric center of the middle interstage coupling cavity 102 as the midpoint, and the radii of two interstage coupling cavities 102 located at opposite ends of the midpoint and symmetrically positioned are equal. For example, the number of interstage coupling cavities 102 is three, and the radii of the first and third interstage coupling cavities 102 are equal.

[0045] The interstage coupling coefficient of the filter can be controlled by adjusting the radius of the interstage coupling cavity 102. The external coupling coefficient of the filter can be controlled by adjusting the radius of the hemispherical coupling cavity 103 connected to the rectangular waveguide 105. For example, there are three interstage coupling cavities 102, with the first and third interstage coupling cavities having a radius of 2.564 mm, and the second interstage coupling cavity having a radius of 2.348 mm; the radius of the hemispherical coupling cavity 103 used to adjust the external coupling coefficient is 3.153 mm.

[0046] In one embodiment of the present invention, the angle between two adjacent polarization center axes is α, which can take any value between 0° and 45°, such as 25°, 35°, 38°, etc. The sum of all α values ​​is the polarization rotation angle of the filter, which is the angle between the polarization directions of the two rectangular waveguides 105. The polarization directions of the waveguide ports of the two rectangular waveguides 105 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 sides of the rectangular waveguide 105 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 between the input and output ports of the filter is achieved, rotating from horizontal polarization to vertical polarization, or from vertical polarization to horizontal polarization.

[0047] Optionally, the included angle between any two adjacent polarization center axes is equal, that is, the polarization rotation angle α is the same for all polarizations. In other embodiments, the polarization rotation angle α may also be unequal.

[0048] In one embodiment of the present invention, the included angle between two adjacent bending center axes is β. That is, in the sequentially connected rectangular waveguide 105 and hemispherical coupling cavity 103, hemispherical coupling cavity 103 and shaped resonant cavity 101, or shaped resonant cavity 101 and interstage coupling cavity 102, the bending rotation angle of the latter structure relative to the former structure is β. β can control the interstage coupling coefficient and external coupling coefficient of the filter. β can take any value between 0° and 45°.

[0049] Optionally, the included angle between any two adjacent bending center axes is equal, that is, all bending rotation angles β are the same. In other embodiments, the bending rotation angles β may also be unequal.

[0050] The included angle of the bending direction can be flexibly set, taking any angle between 0° and 180°, that is, the axial direction of the two rectangular waveguides 105 can be any angle between 0° and 180°. When it is 0°, there is no bending rotation between the input and output ports of the filter; when it is 180°, the maximum bending rotation (in reverse) is achieved between the input and output ports of the filter.

[0051] In one embodiment of the present invention, the shaped resonant cavity polarization rotating filter is integrally manufactured using 3D printing technology. The inner wall of the metal shell 1 is smoothly designed, which helps to improve the quality of the integral additive manufacturing of the filter and helps to reduce the radio frequency loss of the filter. All overlapping edges between the shaped resonant cavity 101 and the interstage coupling cavity 102, and between the shaped resonant cavity 101 and the hemispherical coupling cavity 103, are rounded, making the entire inner contour of the filter a smooth curved surface.

[0052] 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 105 and the adjacent hemispherical coupling cavity 103. The transition waveguide 104 is used to smoothly connect the rectangular waveguide 105 and the hemispherical coupling cavity 103, making the inner wall of the metal housing 1 smooth. At one end of the filter, the rectangular waveguide 105, the transition waveguide 104, the hemispherical coupling cavity 103 and the shaped resonant cavity 101 are connected in sequence.

[0053] In one embodiment of the present invention, please refer to Figure 2 and Figure 3 The filter also includes two waveguide flanges 11, which are located at both ends of the filter. Mounting through holes 111 are provided on the waveguide flanges 11.

[0054] This invention provides a shaped resonant cavity polarization rotation filter with a designed center frequency of 30 GHz, a relative bandwidth of 3%, a corresponding passband frequency range of 29.55–30.45 GHz, a designed passband reflection coefficient of less than -20 dB, a fourth-order filter, and a Chebyshev bandpass response in its transfer function. Four shaped resonant cavities 101 are used, each with a polarization rotation angle of 18°. The angle between the polarization directions of the rectangular waveguide 105 at the beginning and end of the filter is 90°. Three interstage coupling cavities 102 and two hemispherical coupling cavities 103 are used, each with a bending rotation angle of 9°. The angle between the axial direction of the rectangular waveguide 105 at the beginning and end of the filter is 90°. For such a filter, combined with… Figure 1 A preferred set of dimensions is as follows: the major axis of the elliptical cross-section of the shaped resonant cavity 101 is 7.112 mm, the minor axis is 4.071 mm, and the axial lengths of each shaped resonant cavity 101 are 8.723 mm, 9.460 mm, 9.460 mm, and 8.723 mm, respectively; the radii of each interstage coupling cavity 102 are 2.564 mm, 2.348 mm, and 2.564 mm, respectively; the radii of the two hemispherical coupling cavities are both 3.153 mm; the length of each transition waveguide 104 is 2 mm; the waveguide flange 11 is a standard flange size according to the international code BJ320, wherein the wide side length and narrow side length of the rectangular waveguide 105 are 7.112 mm and 3.556 mm, respectively; in order to compromise 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 2.5 mm and 3.5 mm.

[0055] Please see Figures 4 to 5 , 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. To experimentally verify the RF performance of the shaped resonant cavity polarization rotating filter provided in this embodiment of the invention, a high-precision multi-head inkjet 3D printing process was used to integrally manufacture the 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 structure. Figure 4 and Figure 5It is evident that the simulation and measurement results of the filter exhibit some deviation within the passband, but show good agreement outside the passband. The RF performance deviation within the passband is due to processing errors during the surface metallization process of the filter housing, primarily manifested in passband center frequency shift and deterioration of passband return loss. The measured return loss within the passband is better than 10.5 dB (simulated return loss is better than 20 dB), the measured insertion loss is less than 0.5 dB, and the measured center frequency shift is less than 172 MHz (0.57%). The filter's first parasitic passband appears around 37 GHz.

[0056] In the embodiments provided by this invention, it should be understood that: First, how to utilize the mode distribution patterns of the shaped resonant cavity 101, the interstage coupling cavity 102, and the hemispherical coupling cavity 103, as well as the rotational symmetry of the above three cavity structures, to realize a distortion-free polarization rotation and bending rotation filter structure is the core technical problem solved by this invention; Second, the order, polarization rotation angle, and bending rotation angle of the filter are merely illustrative and not unique, but only represent a relatively optimal and achievable structure. Specifically, the order of the filter can be arbitrary, the polarization rotation angle of the filter can be any angle between 0° and 90°, and the bending rotation angle of the filter can be any angle between 0° and 180°; Third, the shaped resonant cavity 101 and the interstage coupling cavity 102 are more compatible with 3D printing technology than traditional rectangular cavities. The inner contour of the filter air cavity is rounded to form a smooth curved surface, which is suitable for various non-metallic / metallic 3D printing processes and printing materials, and the structural design method has strong universality.

[0057] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A shaped resonant cavity polarization rotating filter, characterized in that: The system includes a metal housing containing an air cavity, the air cavity comprising two rectangular waveguides, two hemispherical coupling cavities, n shaped resonant cavities, and n... One interstage coupling cavity is provided, in which one rectangular waveguide, one hemispherical coupling cavity, n shaped resonant cavities, another hemispherical coupling cavity, and another rectangular waveguide are sequentially connected, where n is an integer greater than or equal to 2. Adjacent shaped resonant cavities are connected through the interstage coupling cavity. The central axis of the rectangular waveguide parallel to its polarization direction and the central axis of the shaped resonant cavity parallel to its polarization direction are both polarization central axes, and adjacent two polarization central axes are set at an angle. The central axis of the rectangular waveguide parallel to its axial direction, the central axis of the hemispherical coupling cavity parallel to its axial direction, the central axis of the shaped resonant cavity parallel to its axial direction, and the central axis of the interstage coupling cavity parallel to its axial direction are all bending central axes, and adjacent two bending central axes are set at an angle. The shaped resonant cavity polarization rotation filter is integrally manufactured using 3D printing technology, and the inner wall of the metal shell is smoothly formed.

2. The shaped resonant cavity polarization rotating filter as described in claim 1, characterized in that: The central axes of each of the aforementioned bends are arranged in a coplanar manner.

3. The shaped resonant cavity polarization rotating filter as described in claim 1, characterized in that: The cross-section of the shaped resonant cavity is elliptical, and the major axis of the ellipse of the cross-section of each shaped resonant cavity is equal in length, and the minor axis of the ellipse of the cross-section of each shaped resonant cavity is equal in length.

4. The shaped resonant cavity polarization rotating filter as described in claim 1, characterized in that: In the arrangement direction of the plurality of shaped resonant cavities, the axial lengths of two symmetrically arranged shaped resonant cavities are equal.

5. The shaped resonant cavity polarization rotating filter as described in claim 1, characterized in that: The interstage coupling cavity is spherical, and in the arrangement direction of the plurality of interstage coupling cavities, two interstage coupling cavities that are symmetrically arranged have equal radii.

6. The shaped resonant cavity polarization rotating filter according to any one of claims 1-5, characterized in that: The included angle between two adjacent polarization center axes is α 0 < α ≤ 45°.

7. The shaped resonant cavity polarization rotating filter as described in claim 6, characterized in that: The included angle between any two adjacent polarization center axes is equal.

8. The shaped resonant cavity polarization rotating filter according to any one of claims 1-5, characterized in that: The included angle between two adjacent bending center axes is β 0 < β < 45°.

9. The shaped resonant cavity polarization rotating filter as described in claim 8, characterized in that: The included angle between any two adjacent bending center axes is equal.

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