Coupled spherical cavity waveguide antenna

Abstract

The application provides a coupled spherical cavity waveguide antenna, which comprises a rectangular waveguide, a metal shell coupled with the rectangular waveguide, a resonant cavity formed in the metal shell, the resonant cavity comprising a spherical main resonant cavity and two parasitic resonant cavity structures, the two parasitic resonant cavity structures being coupled with the spherical main resonant cavity, and a radiation hole being formed on a side of the metal shell away from the rectangular waveguide, and the parasitic resonant cavity structure comprising at least one spherical parasitic resonant cavity. The coupled spherical cavity waveguide antenna provided by the application realizes the wideband high-gain radiation performance through the spherical cavity coupling and only a single radiation hole, and ensures that the radiation structure of the waveguide antenna has a high enough mechanical strength; the coupled spherical cavity waveguide antenna is shaped through the spherical cavity coupling, and the structural height of the coupled spherical cavity waveguide antenna is compatible with the 3-D printing process, which helps to improve the forming quality of the integrated additive manufacturing of the waveguide antenna.

Description

Technical Field

[0001] This invention belongs to the field of antenna technology, and more specifically, relates to a coupled spherical cavity waveguide antenna. Background Technology

[0002] Waveguide slot antennas possess advantages such as low profile, high aperture efficiency, large power capacity, and high directivity, leading to their widespread application in millimeter-wave communication systems such as satellites and radars. Traditional waveguide slot antennas are mostly slot arrays based on rectangular waveguide architectures, which can be divided into resonant slot arrays and non-resonant slot arrays. Resonant slot arrays cannot maintain in-phase excitation of all slots when the operating frequency changes, causing a rapid deterioration in the antenna's impedance matching, resulting in a narrow operating bandwidth, typically only a few percent. In non-resonant slot arrays, the transmitted electromagnetic field approximates a traveling wave, thus maintaining good impedance matching over a wider frequency band. However, the traveling wave excitation of the slots introduces a linear phase difference, causing the maximum beam direction to deviate from the array surface normal and vary with frequency. Furthermore, a significant portion of the power fed into the antenna by the feed source is absorbed by the matching load, leading to a reduction in the antenna's overall efficiency.

[0003] Currently, there are two main methods to extend the operating bandwidth of rectangular waveguide slot antennas: one is to use a ridge waveguide structure, and the other is to use a multi-stage coupled feed structure. However, these two methods complicate the structure of the waveguide slot antenna, increasing the difficulty of machining using computer numerical control (CNC) milling, resulting in high machining and assembly costs and long processing times. Although 3D printing technology can be used to achieve rapid integrated additive manufacturing of these complex antenna structures, the closed structure of the waveguide slot antenna makes it difficult to guarantee the quality of 3D printing and post-processing of its internal structure.

[0004] In recent years, with the advancement of 3D printing technology, the fabrication difficulty of spherical resonators has been greatly reduced, and they have been applied in waveguide antennas and waveguide filters. For example, utilizing the high quality factor and multimode characteristics of spherical resonators, low-loss bandpass filters can be realized; by slotting the sidewalls of the spherical resonator to radiate higher-order modes, the formation of parasitic passbands by these higher-order modes can be suppressed, significantly improving the stopband performance of the bandpass filter. Given the multimode characteristics of spherical resonators, it is foreseeable that slotting can simultaneously radiate multiple resonant modes, forming stable radiation performance with a certain bandwidth. This lays the foundation for realizing broadband high-gain spherical resonator antennas. In existing technologies, a scheme can be adopted to create multiple parallel rectangular circumferential slots on the metal shell of the spherical resonator along the surface current direction perpendicular to the radiated mode to achieve a linearly polarized waveguide antenna with dual-frequency / broadband high-gain radiation performance. Increasing the number and size of the slots helps to improve the operating bandwidth of the waveguide antenna. However, the drawbacks of this approach are: (1) the mechanical strength of the slotted radiating structure is significantly reduced, and it is not fully compatible with 3D printing technology. During the 3D printing and use of the antenna, it is prone to deformation and breakage, which seriously deteriorates the RF performance and reliability of the antenna, making the antenna easily scrapped; (2) in the millimeter-wave high-frequency band, the physical size of the antenna is small, and the mechanical strength of the slotted structure is further weakened, resulting in even worse reliability. This limits the frequency bands in which the antenna can be used. Therefore, how to obtain broadband high-gain linearly polarized antenna radiation performance in the millimeter-wave band with a slotted structure that has the fewest possible slots, sufficient mechanical strength, and strong applicability has become an urgent technical problem to be solved. Summary of the Invention

[0005] The purpose of this invention is to provide a coupled spherical cavity waveguide antenna, which aims to achieve broadband high-gain antenna radiation performance in the millimeter-wave band based on a spherical resonant cavity and a slotted structure that is as simple as possible, and to obtain a 3-D printing compatible and highly reliable antenna radiation structure, thereby enhancing the universality of spherical resonant cavities in microwave and millimeter-wave antennas.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a coupled spherical cavity waveguide antenna is provided, comprising a rectangular waveguide and a metal housing coupled to the rectangular waveguide, wherein a resonant cavity is formed inside the metal housing, the resonant cavity comprising a spherical main resonant cavity and two parasitic resonant cavity structures, both of which are coupled to the spherical main resonant cavity, and a radiation aperture is provided on the side of the metal housing away from the rectangular waveguide, wherein the parasitic resonant cavity structure comprises at least one spherical parasitic resonant cavity.

[0007] Optionally, the plane containing the center lines of the two wide sides of the rectangular waveguide is a symmetrical plane, and the two parasitic resonant cavity structures are symmetrically arranged about the symmetrical plane.

[0008] Optionally, the spherical main resonant cavity and the spherical parasitic resonant cavity have the same radius. In the same parasitic resonant cavity structure, the center-to-center distance between adjacent spherical main resonant cavities and spherical parasitic resonant cavities, as well as the center-to-center distance between two adjacent spherical parasitic resonant cavities, are all the same.

[0009] Optionally, the parasitic resonant cavity structure includes multiple spherical parasitic resonant cavities, and within the same parasitic resonant cavity structure, the centers of each spherical parasitic resonant cavity and the center of the spherical main resonant cavity are arranged collinearly.

[0010] Optionally, within the same parasitic resonant cavity structure, the center of each spherical parasitic resonant cavity and the center of the spherical main resonant cavity are located on the extension line, and the angle between the extension line and the central axis of the rectangular waveguide is (45±5)°.

[0011] Optionally, the radiation aperture is formed by removing the cuboid structure that runs through the metal housing, wherein the length direction of the cuboid structure is parallel to the width direction of the rectangular waveguide.

[0012] Optionally, the ratio of the width of the radiation aperture to the radius of the spherical parasitic resonant cavity is (0.8 ± 0.1).

[0013] Optionally, the radiation aperture is formed by removing the conical structure that runs through the metal housing. The apex of the conical structure coincides with the center of the spherical main resonant cavity, and the central axis of the conical structure is coaxial with the central axis of the rectangular waveguide.

[0014] Optionally, the apex angle of the conical structure is (82±8)°.

[0015] Optionally, the radiation aperture is formed by removing the elliptical cone structure that runs through the metal shell. The apex of the elliptical cone coincides with the center of the spherical main resonant cavity. The central axis of the elliptical cone structure is coaxial with the central axis of the rectangular waveguide. The major axis of the elliptical base ellipse of the elliptical cone structure is perpendicular to the plane of symmetry of the two parasitic resonant cavity structures.

[0016] The beneficial effects of the coupled spherical cavity waveguide antenna provided by this invention are as follows: Compared with the prior art, the coupled spherical cavity waveguide antenna provided by this invention achieves broadband high-gain radiation performance through spherical cavity coupling and only a single radiation aperture, while ensuring that the radiation structure of the waveguide antenna has sufficiently high mechanical strength; after spherical cavity coupling and shaping, the structure of the coupled spherical cavity waveguide antenna is highly compatible with 3D printing technology, avoiding the degradation of the waveguide antenna's RF performance caused by deformation due to residual stress during the traditional slotted radiation structure 3D printing, and helping to improve the molding quality of the integrated additive manufacturing of the waveguide antenna. This invention provides a universally feasible technical solution for the application of spherical resonant cavities in millimeter-wave high-frequency antennas. Attached Figure Description

[0017] 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.

[0018] Figure 1 A three-dimensional structural diagram of a waveguide slot antenna consisting of a single spherical cavity, as shown in the three-dimensional electromagnetic simulation model.

[0019] Figure 2 A three-dimensional structural diagram of the three-dimensional electromagnetic simulation model of the coupled spherical cavity waveguide antenna provided in the first embodiment of the present invention;

[0020] Figure 3 for Figure 2 A half-section view;

[0021] Figure 4 for Figure 1 and Figure 2 Port reflection coefficient curves from antenna simulation and measurement;

[0022] Figure 5 for Figure 1 and Figure 2 Gain curves from antenna simulation and measurement;

[0023] Figure 6 A three-dimensional structural diagram of the three-dimensional electromagnetic simulation model of the coupled spherical cavity waveguide antenna provided in the second embodiment of the present invention;

[0024] Figure 7 for Figure 6 A half-section view;

[0025] Figure 8 for Figure 6 Port reflection coefficient curves from antenna simulation and measurement;

[0026] Figure 9 for Figure 6 Gain curves from antenna simulation and measurement;

[0027] Figures 10(a) to 10(f) for Figure 6 Normalized radiation patterns from antenna simulation and measurement are shown in Figure 10(a), which is the E-plane radiation pattern at 30 GHz; Figure 10(b), which is the H-plane radiation pattern at 30 GHz; Figure 10(c), which is the E-plane radiation pattern at 34 GHz; Figure 10(d), which is the H-plane radiation pattern at 34 GHz; Figure 10(e), which is the E-plane radiation pattern at 38 GHz; and Figure 10(f), which is the H-plane radiation pattern at 38 GHz.

[0028] Figure 11 A three-dimensional structural diagram of the three-dimensional electromagnetic simulation model of the coupled spherical cavity waveguide antenna provided in the third embodiment of the present invention;

[0029] Figure 12 for Figure 11 A half-section view;

[0030] Figure 13 for Figure 11 Port reflection coefficient curves from antenna simulation and measurement;

[0031] Figure 14 for Figure 11 Gain curves from antenna simulation and measurement;

[0032] Figures 15(a) to 15(f) for Figure 11 Normalized radiation patterns from antenna simulation and measurement are shown in Figure 15(a), which is the E-plane radiation pattern at 30 GHz; Figure 15(b), which is the H-plane radiation pattern at 30 GHz; Figure 15(c), which is the E-plane radiation pattern at 34 GHz; Figure 15(d), which is the H-plane radiation pattern at 34 GHz; Figure 15(e), which is the E-plane radiation pattern at 38 GHz; and Figure 15(f), which is the H-plane radiation pattern at 38 GHz.

[0033] Figure 16 for Figure 2 , Figure 6 and Figure 11 The overall efficiency curve of the antenna simulation.

[0034] The following are the labeling elements in the figure:

[0035] 901 - Spherical resonant cavity; 902 - Rectangular waveguide; 903 - Rectangular radiating slot;

[0036] 1-Metal shell; 11-Spherical main resonant cavity; 12-Parasitic resonant cavity structure; 121-Spherical parasitic resonant cavity; 13-Radiation aperture; 2-Rectangular waveguide; 21-Rectangular waveguide port; 22-Rectangular coupling window; 3-Waveguide flange; 30-Connection hole. Detailed Implementation

[0037] 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.

[0038] It should be noted that when a component is referred to as being "connected to" another component, it can be directly connected to the other component or indirectly connected to that other component.

[0039] It should be understood that the terms "length", "width", "upper", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and 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, and therefore should not be construed as a limitation of the present invention.

[0040] 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.

[0041] Please see Figure 1 , Figure 1 This is a three-dimensional electromagnetic simulation model of a waveguide slot antenna consisting of a single spherical cavity. The antenna includes a spherical resonant cavity 901 and a rectangular waveguide 902 connected to it. A rectangular radiating slot 903 is formed at the end of the spherical resonant cavity 901 away from the rectangular waveguide 902. The rectangular radiating slot 903 is a circular slot with a rectangular cross-section, and is axisymmetric and centrosymmetric about the central axis of the rectangular waveguide 903. Radio frequency power is fed into the rectangular waveguide 903 from the port of the rectangular waveguide and coupled to the spherical resonant cavity 901 through a rectangular coupling window. Figure 1The waveguide slot antenna shown, constructed from a single spherical cavity, has very limited bandwidth and gain, failing to meet practical application requirements. While increasing the number of rectangular radiating slots 903 can increase the antenna's operating bandwidth, an excessive number of slots leads to a significant decrease in the mechanical strength of the antenna housing near the slots. These areas are prone to deformation or breakage due to residual stress during manufacturing. Especially in the millimeter-wave high-frequency band, the antenna size decreases accordingly, further reducing the mechanical strength of the spherical cavity slotted structure. This makes traditional spherical cavity waveguide slot antenna designs unsuitable for application in the millimeter-wave high-frequency band.

[0042] The coupled spherical cavity waveguide antenna provided in the embodiments of the present invention will now be described.

[0043] Please see Figure 2 and Figure 3 , Figure 2 This is a three-dimensional structural diagram of the three-dimensional electromagnetic simulation model of the coupled spherical cavity waveguide antenna provided in the first embodiment of the present invention. Figure 3 for Figure 2 A half-sectional view is shown. The coupled spherical cavity waveguide antenna includes a rectangular waveguide 2 and a metal housing 1 connected thereto, with a resonant cavity formed inside the metal housing 1. The resonant cavity includes a spherical main resonant cavity 11 and two parasitic resonant cavity structures 12, both of which are coupled to the spherical main resonant cavity 11. One end of the rectangular waveguide 2 connected to the spherical main resonant cavity 11 has a rectangular coupling window 22, and the other end of the rectangular waveguide 2 has a rectangular waveguide port 21. Each parasitic resonant cavity structure 12 includes at least one spherical parasitic resonant cavity 121. A radiation aperture 13 is provided on the side of the metal housing 1 away from the rectangular waveguide 2, allowing both the spherical main resonant cavity 11 and the spherical parasitic resonant cavity 121 to radiate through the radiation aperture 13.

[0044] When the spherical main resonant cavity 11 is fed through the rectangular waveguide 2, the fundamental mode TM excited in the spherical main resonant cavity 11 101 and the first higher order TM 211 The two modes are directly radiated out of the spherical main resonant cavity 11 and simultaneously coupled into the parasitic resonant cavity structure 12, radiating through the radiation aperture 13 on the metal shell 1. It can be equivalently considered that, under this feeding method, the resonant cavity within the metal shell 1 reassembles the resonant modes in the original spherical main resonant cavity 11. The surface current distribution of the reassembled resonant modes indicates that the setting of the radiation aperture 13 can achieve synchronous radiation of multiple resonant modes in the coupled resonant cavity, thereby extending the antenna bandwidth.

[0045] In one embodiment of the present invention, please refer to Figure 2 and Figure 3The coupled spherical cavity waveguide antenna also includes a waveguide flange 3, on which a connection hole 30 for connecting to an external circuit is provided.

[0046] In one embodiment of the present invention, please refer to Figure 2 and Figure 3 The rectangular waveguide 2 has a rectangular cross-section. The length direction of this rectangle is the width direction of the rectangular waveguide 2, and the width direction is the narrow side direction of the rectangular waveguide 2. The central axis perpendicular to the cross-section of the rectangular waveguide 2 is the central axis of the rectangular waveguide 2. One of the central planes of the rectangular waveguide 2 is parallel to its narrow side direction, and the central axis lies on this central plane. This central plane is designated as a symmetry plane, and the two parasitic resonant cavity structures 12 are symmetrically arranged about this symmetry plane. The symmetrical arrangement ensures that the mode distribution in the two parasitic resonant cavity structures 12 is the same, which facilitates obtaining broadband, stable, and pattern-symmetric radiation performance under a single symmetrical radiation aperture 13 structure. The center of the spherical main resonant cavity 11 is located on the central axis of the rectangular waveguide 2, and the spherical main resonant cavity 11 is also symmetrically arranged about the aforementioned symmetry plane.

[0047] In one embodiment of the present invention, preferably, the spherical main resonant cavity 11 and the spherical parasitic resonant cavity 121 have the same radius. When the parasitic resonant cavity structure 12 includes multiple spherical parasitic resonant cavities 121, preferably, the multiple spherical parasitic resonant cavities 121 have the same radius. In the same parasitic resonant cavity structure 12, preferably, the center-to-center distance between two adjacent spherical parasitic resonant cavities 121 is the same, and the center-to-center distance between adjacent spherical main resonant cavities 11 and spherical parasitic resonant cavities 121 is the same. In this way, modeling can be simplified, and broadband and stable radiation performance can be obtained.

[0048] In one embodiment of the present invention, please refer to Figure 2 and Figure 3 Each parasitic resonant cavity structure 12 includes a spherical parasitic resonant cavity 121. The coupled spherical cavity waveguide antenna includes two parasitic resonant cavity structures 12, and the angle between the line connecting the center of the two spherical parasitic resonant cavities 121 and the center of the spherical main resonant cavity 11 is (90±10)°.

[0049] In one embodiment of the present invention, please refer to Figure 2 After removing the cuboid structure that runs through it, the metal casing 1 forms a radiation hole 13, which is a circular hole with a rectangular cross-section. The length direction of the cuboid structure is parallel to the width direction of the rectangular waveguide 2, and correspondingly, the width direction of the cuboid structure is parallel to the narrow side direction of the rectangular waveguide 2.

[0050] Optionally, the ratio of the width of the radiation aperture 13 to the radius of the spherical parasitic resonant cavity 121 is (0.8 ± 0.1).

[0051] To ensure the antenna structure is compatible with 3D printing technology, both the inner and outer surfaces of the metal housing 1 are smoothed.

[0052] To verify Figure 2 The radio frequency performance of the coupled spherical cavity waveguide antenna in the embodiment is designed in the millimeter-wave Ka band. Figure 1 and Figure 2 The antenna in the image was achieved using a high-precision photosensitive resin multi-nozzle inkjet 3D printing process. Figure 2 The antenna model was integrally additively manufactured, and its surface was metallized using a chemical copper plating process. The geometrically shaped antenna shell required no support material during the 3D printing process. Figure 1 In the structure, the rectangular coupling window has a length of 6 mm and a width of 3.556 mm, the rectangular waveguide 902 has a length of 10 mm, the rectangular waveguide port has a length of 7.112 mm and a width of 3.556 mm, and the spherical resonant cavity 901 has a radius of 5 mm. Figure 2 and Figure 3 In the structure, the rectangular coupling window 22 has a length of 6 mm and a width of 3.556 mm, the rectangular waveguide 2 has a length of 10 mm, the rectangular waveguide port has a length of 7.112 mm and a width of 3.556 mm, the radii of the spherical main resonant cavity 11 and the spherical parasitic resonant cavity 121 are both 5 mm, the distance between adjacent spherical cavities is 7 mm, the waveguide flange 3 is the standard flange size in the national standard code BJ320, and the radiation aperture 13 has a width of 4 mm, a length of 24 mm, and a height of 8.6 mm. To balance the mechanical strength of the antenna metal housing 1 and the amount of redundant structural material, the thickness of the metal housing 1 is set between 2 mm and 3 mm. Please refer to [link / reference]. Figure 4 and Figure 5 , Figure 4 for Figure 1 and Figure 2 Port reflection coefficient curves from antenna simulation and measurement. Figure 5 for Figure 1 and Figure 2 Gain curves from antenna simulation and measurement are shown in the figure. As can be seen from the figure, using... Figure 2 The structural scheme shown uses only one radiating aperture 13, yet the antenna can achieve broadband, high-gain directional radiation performance, and is compatible with... Figure 1 Compared to the antennas in the previous model, the bandwidth and gain are significantly improved. Specifically, Figure 2 The antenna measured in the study operates in the frequency range of 26.5–40 GHz, covering the entire Ka band, with a corresponding relative bandwidth exceeding 40%. The measured in-band gain reached 7.2–12.2 dBi. Figure 1 Compared to the antennas in the previous model, the bandwidth has increased by more than 2 times, and the gain has been improved by 2.1–5 dBi.

[0053] In one embodiment of the present invention, please refer to Figure 6 and Figure 7 , Figure 6 This is a three-dimensional structural diagram of the three-dimensional electromagnetic simulation model of the coupled spherical cavity waveguide antenna provided in the second embodiment of the present invention. Figure 7 for Figure 6 A half-sectional view. In this embodiment, the metal housing 1 is formed by removing the conical structure that runs through it to form a radiation hole 13. The apex of the conical structure coincides with the center of the spherical main resonant cavity 11, and the central axis of the conical structure is coaxial with the central axis of the rectangular waveguide 2.

[0054] Optionally, the cone apex angle of the cone structure is (82±8)°, such as 80°, 85°, 90°, etc.

[0055] In other embodiments, the metal housing 1 may also have its elliptical cone structure removed to form a radiation hole 13. The apex of the elliptical cone coincides with the center of the spherical main resonant cavity 11. The central axis of the elliptical cone structure is coaxial with the central axis of the rectangular waveguide 2. The major axis of the elliptical cone structure is perpendicular to the plane of symmetry of the two parasitic resonant cavity structures 12.

[0056] Designed in the millimeter-wave Ka band Figure 6 The antenna in the middle is processed into a single unit using the same additive manufacturing process. Figure 6 The base radius of the conical structure removed from the metal housing 1 of the central antenna is 13 mm, and the height is 15 mm. The angle between the lines connecting the centers of the two spherical parasitic cavities 121 and the center of the spherical main resonant cavity 11 is 90°. Other parameters are the same as those of the conical structure. Figure 2 The antennas are the same. Please refer to [link / reference]. Figures 8 to 10(f) , Figure 8 for Figure 6 Port reflection coefficient curves from antenna simulation and measurement. Figure 9 for Figure 6 Gain curves from antenna simulation and measurement. Figures 10(a) to 10(f) for Figure 6 Normalized radiation patterns from antenna simulation and measurement are shown in Figure 10(a), which is the E-plane radiation pattern at 30 GHz; Figure 10(b), the H-plane radiation pattern at 30 GHz; Figure 10(c), the E-plane radiation pattern at 34 GHz; Figure 10(d), the H-plane radiation pattern at 34 GHz; Figure 10(e), the E-plane radiation pattern at 38 GHz; and Figure 10(f), the H-plane radiation pattern at 38 GHz. Figure 2 Compared to the antenna measurement results in the middle, Figure 6The measured operating frequency range of the antenna still covers the entire Ka band, and the measured gain is improved by 1.7–4.7 dBi, with a measured gain of 12–14 dBi across the entire Ka band. As shown in the figure, the measured and simulated results of the antenna agree well, maintaining stable directional radiation performance within the band. The measured cross-polarization ratio of the antenna is better than 20 dB.

[0057] In one embodiment of the present invention, please refer to Figure 11 and Figure 12 , Figure 11 This is a three-dimensional structural diagram of the three-dimensional electromagnetic simulation model of the coupled spherical cavity waveguide antenna provided in the third embodiment of the present invention. Figure 12 for Figure 11 A half-sectional view. Each parasitic resonant cavity structure 12 includes multiple spherical parasitic resonant cavities 121. The centers of the multiple spherical parasitic resonant cavities 121 are arranged in a coplanar manner. Within the same parasitic resonant cavity structure 12, the center of the spherical main resonant cavity 11 and the centers of each spherical parasitic resonant cavity 121 are arranged collinearly, which makes the spherical cavities within the metal housing 1 arranged in a V-shape.

[0058] Within the same parasitic resonant cavity structure 12, the line where the center of each spherical parasitic resonant cavity 121 is located is an extension line. The angle between the two extension lines corresponding to the two parasitic resonant cavity structures 12 is (90±10)°, such as 85°, 90°, 95°, etc. The angle between each extension line and the central axis of the rectangular waveguide 2 is (45±5)°, such as 40°, 45°, 50°, etc.

[0059] Designed in the millimeter-wave Ka band Figure 11 The antenna in the middle is processed into a single unit using the same additive manufacturing process. Figure 11 The parasitic resonant cavity structure 12 of the antenna includes two spherical parasitic resonant cavities 121. The resonant cavity body is composed of a total of five spherical cavities coupled together, forming an overall V-shape. A conical structure is removed from the metal housing 1 to form a radiation aperture 13. The base radius of the conical structure is 16.5 mm, and its height is 22 mm. Other parameters are the same as... Figure 6 The parameters are the same. Please refer to [link / reference]. Figures 13 to 15(f) , Figure 13 for Figure 11 Port reflection coefficient curves from antenna simulation and measurement. Figure 14 for Figure 11 Gain curves from antenna simulation and measurement. Figures 15(a) to 15(f) for Figure 11Normalized radiation patterns from antenna simulation and measurement are shown in Figure 15(a), which is the E-plane radiation pattern at 30 GHz; Figure 15(b), the H-plane radiation pattern at 30 GHz; Figure 15(c), the E-plane radiation pattern at 34 GHz; Figure 15(d), the H-plane radiation pattern at 34 GHz; Figure 15(e), the E-plane radiation pattern at 38 GHz; and Figure 15(f), the H-plane radiation pattern at 38 GHz. Figure 6 Compared to the antenna measurement results in the middle, Figure 11 The measured operating frequency range of the antenna still covers the entire Ka band, and the measured gain has been further improved, reaching 12.4–14.6 dBi across the Ka band. As shown in the figure, the measured and simulated results of the antenna agree well, maintaining stable directional radiation performance within the band. The measured antenna cross-polarization ratio is better than 20 dB. The results indicate that increasing the number of coupled spherical parasitic resonators 121 can further improve the antenna gain while maintaining its broadband radiation performance, but at the expense of the antenna's compactness. Therefore, this type of antenna requires a trade-off between gain and size. Figure 2 , Figure 6 and Figure 11 The antenna bandwidth and gain of this antenna are significantly better than those of existing spherical cavity waveguide slot antennas. Furthermore, the antenna has a simple radiation structure, high mechanical strength, and will not deform or break due to residual stress.

[0060] Please see Figure 16 , Figure 16 for Figure 2 , Figure 6 and Figure 11 The overall efficiency curve of the antenna simulation is shown in the figure. As can be seen from the figure, with the root mean square surface roughness of the metal shell 1 being 2 micrometers, the overall efficiency of the antenna simulation is better than 95% across the entire Ka band.

[0061] In the coupled spherical cavity waveguide antenna of the above embodiment, the radius of both the spherical main resonant cavity 11 and the spherical parasitic resonant cavity 121 is r0. The resonant frequency of the mode radiated by the antenna is uniquely determined by r0. By changing r0, coupled spherical cavity waveguide antennas operating in different frequency bands can be designed. For example, when the center frequency of this antenna operating in the Ka band is designed to be 33 GHz, the corresponding spherical cavity radius r0 is 5 mm. The range of the radius r0 is not limited. The center-to-center distance between adjacent coupled spherical cavities is 1.2r0 to 1.6r0; the width of the rectangular coupling window 22 is 1.2r0 to 1.4r0, and the width of the narrow side is 0.5r0 to 0.7r0. The length of the rectangular waveguide 2 is not limited. The thickness of the metal shell 1 is not limited.

[0062] The coupled spherical cavity waveguide antenna in the above embodiments achieves broadband high-gain radiation performance through spherical cavity coupling and only a single radiation aperture 13, while ensuring that the radiation structure of the waveguide antenna has sufficiently high mechanical strength. Through spherical cavity coupling and shaping, the structure of the coupled spherical cavity waveguide antenna is highly compatible with 3D printing technology, avoiding the degradation of the waveguide antenna's RF performance caused by deformation due to residual stress during the traditional 3D printing of slotted radiation structures. This helps improve the molding quality of the integrated additive manufacturing of the waveguide antenna. This invention provides a universally feasible technical solution for the application of spherical resonant cavities in millimeter-wave high-frequency antennas.

[0063] In the embodiments provided by this invention, it should be understood that: First, how to shape the metal shell 1 and radiating structure of a traditional waveguide antenna according to the design concept of geometric shaping, and how to utilize the multi-mode nature of the spherical resonator to achieve stable radiation performance with broadband high gain under the simplest possible slotted structure, are the core technical problems solved by this invention; Second, the slotted structure and its dimensions used for radiation are merely illustrative and not unique, but only a relatively optimal and achievable structure, and other equivalent radiating slots can be realized according to the design principle; Third, the number and coupling positions of the spherical cavities are merely illustrative and not unique, but only a relatively optimal and achievable structure, and other various coupled spherical cavity antenna structures can be realized according to the design principle; Fourth, the shaped antenna structure is suitable for various non-metallic / metallic 3-D printing processes and printing materials, the structural design method has strong universality, and compared with traditional slotted spherical cavity antennas, it has a wider applicable frequency range and can be applied in the millimeter-wave high-frequency band.

[0064] The above is a description of a coupled spherical cavity waveguide antenna provided by the present invention. For those skilled in the art, based on the ideas of the embodiments of the present invention, there will be changes in specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A coupled spherical cavity waveguide antenna, characterized in that: The device includes a rectangular waveguide and a metal housing coupled to the rectangular waveguide. A resonant cavity is formed inside the metal housing. The resonant cavity includes a spherical main resonant cavity and two parasitic resonant cavity structures. Both parasitic resonant cavity structures are coupled to the spherical main resonant cavity. A radiation aperture is provided on the side of the metal housing away from the rectangular waveguide. The parasitic resonant cavity structure includes at least one spherical parasitic resonant cavity. The rectangular waveguide has a rectangular cross-section, with its length direction being the width direction and its width direction being the narrow side direction. The central axis perpendicular to the cross-section of the rectangular waveguide is its central axis. The center of the spherical main resonant cavity is located on the central axis of the rectangular waveguide. One of the central planes of the rectangular waveguide is parallel to its narrow side direction, and the central axis is located on this central plane, which is a plane of symmetry. The spherical main resonant cavity and the two parasitic resonant cavities are symmetrically arranged about this plane of symmetry. The radii of the spherical main resonant cavity and each of the spherical parasitic resonant cavities are the same. In the same parasitic resonant cavity structure, the center-to-center distance between two adjacent spherical parasitic resonant cavities is the same, and the center-to-center distance between adjacent spherical main resonant cavities and spherical parasitic resonant cavities is also the same.

2. The coupled spherical cavity waveguide antenna as described in claim 1, characterized in that: The parasitic resonant cavity structure includes multiple spherical parasitic resonant cavities. Within the same parasitic resonant cavity structure, the centers of each spherical parasitic resonant cavity and the center of the spherical main resonant cavity are arranged collinearly.

3. The coupled spherical cavity waveguide antenna as described in claim 2, characterized in that: Within the same parasitic resonant cavity structure, the center of each spherical parasitic resonant cavity and the center of the spherical main resonant cavity are located on the extension line, and the angle between the extension line and the central axis of the rectangular waveguide is (45 ± 5)°.

4. The coupled spherical cavity waveguide antenna as described in any one of claims 1-3, characterized in that: The radiation aperture is formed by removing the cuboid structure that runs through the metal shell, and the length direction of the cuboid structure is parallel to the width direction of the rectangular waveguide.

5. The coupled spherical cavity waveguide antenna as described in claim 4, characterized in that: The ratio of the width of the radiation aperture to the radius of the spherical parasitic resonant cavity is (0.8 ± 0.1).

6. The coupled spherical cavity waveguide antenna as described in any one of claims 1-3, characterized in that: The radiation aperture is formed by removing the conical structure that runs through the metal shell. The apex of the conical structure coincides with the center of the spherical main resonant cavity, and the central axis of the conical structure is coaxial with the central axis of the rectangular waveguide.

7. The coupled spherical cavity waveguide antenna as described in claim 6, characterized in that: The apex angle of the cone structure is (82 ± 8)°.

8. The coupled spherical cavity waveguide antenna as described in any one of claims 1-3, characterized in that: The radiation aperture is formed by removing the elliptical cone structure that runs through the metal shell. The apex of the elliptical cone coincides with the center of the spherical main resonant cavity. The central axis of the elliptical cone structure is coaxial with the central axis of the rectangular waveguide. The major axis of the elliptical base of the elliptical cone structure is perpendicular to the plane of symmetry of the two parasitic resonant cavity structures.

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