Cavity-backed slot antenna for low-orbit satellite communication and low-orbit satellite

Abstract

The invention discloses a cavity-backed slot antenna for low earth orbit satellite communication and a low earth orbit satellite, and belongs to the technical field of antennae, the cavity-backed slot antenna comprises a coaxial feed structure, an impedance matching section, a circular feed source and a rectangular back cavity, the coaxial feed structure comprises a rectangular coaxial inner conductor and a rectangular outer conductor, the rectangular back cavity is provided with a gradual change type gap which is symmetrical about the center line of the rectangular back cavity. The rectangular outer conductor is connected with the rectangular back cavity, the rectangular coaxial inner conductor is connected with the circular feed source through the impedance matching section, and the circular feed source is arranged in the rectangular back cavity in a suspended mode and located under the gradual change type gap. According to the cavity-backed slot antenna, the loss of the antenna working in the Q wave band is reduced through the air-filled rectangular coaxial structure, and the working bandwidth and the half-power beam width of the rectangular cavity-backed slot radiation antenna for low-orbit satellite communication are broadened through the gradual change slot and the circular feed source; and meanwhile, the relatively high antenna gain from 4.02 dBi to 5.72 dBi and the radiation efficiency greater than 92% are realized.

Description

Technical Field

[0001] The present invention relates to the field of antenna technology, and in particular to a cavity-backed slot antenna for low-orbit satellite communications and a low-orbit satellite. Background Art

[0002] In recent years, the explosive growth in global satellite communications demand, particularly with the advancement of low-orbit satellite constellations (such as Starlink and OneWeb), high-throughput satellites (HTS), and deep space exploration missions, has placed higher demands on high-frequency, high-capacity, and low-latency satellite communication technologies. The Q-band (33 to 50 GHz), a key component of the millimeter-wave spectrum, is considered a core frequency band for next-generation satellite communications due to its large continuous bandwidth resources (up to tens of GHz) and strong anti-interference capabilities. Electromagnetic waves in this band have the characteristics of short wavelength, excellent ionospheric penetration, and relatively controllable atmospheric propagation losses, making them particularly suitable for Earth-Moon communications and high-capacity data transmission.

[0003] However, traditional antenna technology faces significant challenges in the Q-band. Microstrip antennas are widely used at low frequencies and have a simple structure, but conductor loss and dielectric loss increase dramatically in the Q-band, resulting in a decrease in radiation efficiency. Furthermore, their inherent bandwidth is narrow, making it difficult to meet the needs of broadband communications. Although substrate integrated waveguide (SIW) antennas have low transmission loss characteristics, they require extremely high processing precision. Minor deviations can cause resonant frequency drift and performance deterioration. Furthermore, the multi-layer stacked structure increases manufacturing costs, making it difficult to meet the needs of lightweight satellite payloads.

[0004] Micro-coaxial antennas employ a design similar to coaxial cables, with air or a low-loss dielectric supporting the inner and outer conductors. In the Q-band, micro-coaxial structures effectively reduce conductor and dielectric losses, improving antenna radiation efficiency. Furthermore, their flexible structural design supports broadband operation, making them suitable for high-frequency, broadband applications. Furthermore, micro-coaxial structures facilitate high integration and are compatible with existing planar circuit processes, helping to reduce manufacturing costs.

[0005] Therefore, there is an urgent need to propose a Q-band cavity-backed slot antenna with simple structure, wide bandwidth, low loss and high radiation efficiency for low-orbit satellite communications. Summary of the Invention

[0006] The purpose of the present invention is to provide a cavity-backed slot antenna and a low-orbit satellite for low-orbit satellite communications to solve one or more of the above-mentioned technical problems. The present invention provides a cavity-backed slot antenna for low-orbit satellite communications, which has the characteristics of large bandwidth, high gain, and wide half-power beamwidth. It can be widely used in various microwave systems, especially in radar and satellite communications.

[0007] To achieve the above-mentioned objectives, on the one hand, the present invention provides a cavity-backed slot antenna for low-orbit satellite communications, comprising a coaxial feeding structure, an impedance matching section, a circular feed source, and a rectangular cavity-backed cavity. The coaxial feeding structure comprises a rectangular coaxial inner conductor and a rectangular outer conductor. A gradient slot is provided on the rectangular cavity-backed cavity, and the gradient slot is symmetrical about the center line of the rectangular cavity-backed cavity. The rectangular outer conductor is connected to the rectangular cavity-backed cavity, and the rectangular coaxial inner conductor is connected to the circular feed source through the impedance matching section. The circular feed source is suspended in the rectangular cavity-backed cavity, and the circular feed source is located directly below the gradient slot.

[0008] Furthermore, two trapezoids symmetrical about the central axis are etched on the top surface of the rectangular back cavity to form a gradient gap, and the upper base of the trapezoid is located at the center line of the top surface of the rectangular back cavity.

[0009] Furthermore, the thickness of the circular feed source is greater than the thickness of the rectangular coaxial inner conductor.

[0010] Furthermore, the width of the impedance matching section is greater than the width of the rectangular coaxial inner conductor.

[0011] Furthermore, the rectangular coaxial inner conductor is suspended on the inner side of the rectangular outer conductor along the coaxial feeding structure through the support structure.

[0012] Furthermore, the length and width of the rectangular back cavity are one quarter of the wavelength corresponding to the center frequency of the Q band.

[0013] Furthermore, the cavity-backed slot antenna is formed based on a micro-metal additive manufacturing process and has a nine-layer structure, each layer has the same thickness, and the coaxial feeding structure, impedance matching section, circular feed source and rectangular cavity-backed slot antenna are all made of copper.

[0014] Furthermore, release holes are evenly spaced apart on the rectangular outer conductor, and the release holes are symmetrical about the axis of the rectangular outer conductor.

[0015] Furthermore, the corners around the gradient gap are smoothly transitioned through rounded corners.

[0016] The present invention can also provide a low-orbit satellite, comprising the above-mentioned cavity-backed slot antenna for low-orbit satellite communication.

[0017] Compared with the prior art, the present invention has the following beneficial effects: the cavity-backed slot antenna provided by the present invention is used for Q-band low-orbit satellite communications. The air-filled rectangular coaxial structure reduces the antenna loss working in the Q band, and the tapered slot and circular feed widen the working bandwidth and half-power beamwidth of the cavity-backed slot antenna used for low-orbit satellite communications. The symmetrical design of the tapered slot can also suppress high-order modes and improve radiation efficiency; the circular feed is suspended under the slot to form coupled feeding, reducing conductor loss. Its impedance bandwidth is approximately 29.30%, S11≤-10dB, the frequency range is 35.60GHz to 47.82GHz, and the gain range can be 4.02dBi to 5.72dBi. The front-to-back ratio reaches 16dB, the half-power beamwidth is better than 100°, and the radiation efficiency is greater than 92%.

[0018] Furthermore, the double trapezoidal slots are arranged symmetrically through the center of the upper and bottom edges to form a continuous gradient opening. The gradient slot increases the half-power beamwidth of the cavity-backed slot antenna, while having good achievable gain, can better cover the Q band, achieve impedance matching through gradient transition, and reduce return loss.

[0019] Furthermore, the width of the impedance matching section is increased to form a stepped impedance transformation structure, thereby improving the impedance matching performance, alleviating the impedance mutation from the coaxial line to the circular feed, and increasing the bandwidth of the cavity-backed slot antenna.

[0020] Furthermore, the nine-layer micro-coaxial cavity-backed slot antenna processed by the Micro-Machined Additive Manufacturing (M-MAM) process has a simpler structure, lower loss, and wider bandwidth than common microstrip antennas and substrate integrated waveguide antennas. The cavity-backed slot antenna of the present invention is formed based on the M-MAM process. The release holes on the rectangular outer conductor are used to remove sacrificial materials. The arrangement of the release holes symmetrically to the axis of the rectangular outer conductor promotes the removal of polymer residues, helps to reduce processing alignment deviation, and ensures the dimensional consistency of the hole structure. The release holes with a rectangular symmetrical layout can effectively share the heat load, and can also relieve processing thermal stress and packaging pressure through the symmetrical distribution of the stress field, inhibit crack initiation, and maintain the electromagnetic shielding integrity of the rectangular outer conductor. In addition, the geometrically symmetrical design is conducive to the coordinated optimization of multiple physical fields, improving device performance from the perspectives of process compatibility and structural reliability.

[0021] Furthermore, the thicknesses of the rectangular coaxial inner conductor and the circular feed are 0.3 mm and 0.4 mm, respectively. The thickness of the feed is greater than that of the rectangular coaxial inner conductor, which enhances the uniformity of current distribution in the feed area and improves radiation efficiency. The gap inductance is compensated by increasing the feed equivalent capacitance, thereby improving matching.

[0022] Furthermore, an all-copper integrated structure design is adopted, and the rectangular coaxial inner conductor, rectangular outer conductor, circular feed and rectangular back cavity are all made of copper. The rectangular outer conductor and rectangular back cavity are designed as thin-walled structures, which take into account the processing technology while ensuring structural strength. The copper material significantly reduces the ohmic loss, especially under high-frequency working conditions, effectively suppressing the signal attenuation caused by the skin effect. The good thermal conductivity also ensures the antenna's rapid heat dissipation capability under high-power conditions. In terms of structural design, the thickness of the circular feed not only helps to maintain the morphological stability of the radiating surface, but also helps to suppress the disturbance of the circular feed radiation pattern caused by external interference through the rectangular back cavity, while also matching the size limitations of the micromachining process. The all-copper material not only eliminates the potential difference problem caused by the contact of heterogeneous materials, but also provides a stable grounding environment through the closed back cavity design, greatly improving the electromagnetic compatibility performance of the system, and is relatively outstanding in terms of electrical performance, thermal management and mechanical reliability, and is suitable for high-frequency and high-power microsystem scenarios.

[0023] Furthermore, a support structure made of SU-8 photoresist is used to suspend the rectangular coaxial inner conductor, ensuring mechanical stability while avoiding additional losses introduced by additional metal.

[0024] Furthermore, the length and width of the rectangular back cavity are one quarter of the wavelength corresponding to the center frequency of the Q band. The cavity resonance is used to enhance the radiation directivity and suppress the backward radiation. The height dimension of the back cavity achieves a low profile.

[0025] Furthermore, the smooth transition of rounded corners can provide a gradual and smooth current path, reduce the discontinuity effect, help make the actual input impedance of the antenna closer to the ideal value, and thus achieve better impedance matching within a wider frequency band; and suppress small-scale local current disturbances that will produce cross-polarization components. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art; obviously, the drawings described below are some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 The following schematically illustrates the structure of a cavity-backed slot antenna for low-orbit satellite communications according to an embodiment of the present invention; Figure 2 A top view of a cavity-backed slot antenna for low-orbit satellite communications according to an embodiment of the present invention is schematically shown; Figure 3 A side view of a cavity-backed slot antenna for low-orbit satellite communications according to an embodiment of the present invention is schematically shown; Figure 4The figure schematically shows the M-MAM coaxial feeding structure of the cavity-backed slot antenna for low-orbit satellite communications according to an embodiment of the present invention; Figure 5 A graph schematically illustrates how the return loss of a cavity-backed slot antenna for low-orbit satellite communications varies with frequency according to an embodiment of the present invention; Figure 6 A graph schematically illustrates how the achievable gain of a cavity-backed slot antenna for low-orbit satellite communications varies with frequency according to an embodiment of the present invention; Figure 7 The figure schematically shows the YOZ radiation pattern of the cavity-backed slot antenna for low-orbit satellite communications at 36 GHz according to an embodiment of the present invention; Figure 8 The XOZ plane radiation pattern of the cavity-backed slot antenna for low-orbit satellite communications at 36 GHz according to an embodiment of the present invention is schematically shown; Figure 9 The figure schematically shows the YOZ radiation pattern of the cavity-backed slot antenna for low-orbit satellite communications at 41 GHz according to an embodiment of the present invention; Figure 10 The XOZ plane radiation pattern of the cavity-backed slot antenna for low-orbit satellite communications at 41 GHz according to an embodiment of the present invention is schematically shown; Figure 11 The figure schematically illustrates the YOZ radiation pattern of the cavity-backed slot antenna for low-orbit satellite communications at 47 GHz according to an embodiment of the present invention. Figure 12 The XOZ plane radiation pattern of the cavity-backed slot antenna for low-orbit satellite communications at 47 GHz according to an embodiment of the present invention is schematically shown; In the accompanying drawings, 1. coaxial feeding structure; 2. impedance matching section; 3. circular feed source; 4. rectangular back cavity; 5. supporting structure; 6. release hole; 7. gradient gap. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0029] It should be noted that the terms "including" and "having" and any variations thereof in the description and claims of the present invention are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other units not explicitly listed or inherent to these processes, products or apparatuses.

[0030] In the description of the present invention, it should be understood that the terms "center", "up", "down", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0031] The present invention is described in further detail below with reference to the accompanying drawings: An embodiment of the present invention discloses a cavity-backed slot antenna for low-orbit satellite communications, comprising a coaxial feeding structure 1, an impedance matching section 2, a circular feed 3, a rectangular cavity-backed cavity 4, a support structure 5, a release hole 6, and a tapered slot 7 provided on the rectangular cavity-backed cavity 4. Specifically, two trapezoids symmetrical about a central axis are etched on the top surface of the rectangular cavity-backed cavity 4 to form the tapered slot 7. The coaxial feeding structure 1 comprises an air-filled rectangular coaxial inner conductor and a rectangular outer conductor. The rectangular coaxial inner conductor is suspended on the inner side of the rectangular outer conductor along the coaxial feeding structure 1 through the support structure 5. The rectangular outer conductor is connected to the rectangular cavity-backed cavity 4. The rectangular outer conductor is provided with release holes 6 symmetrically distributed about the axis of the rectangular outer conductor. The circular feed 3 is located directly below the tapered slot 7. The circular feed 3 is suspended in the rectangular cavity-backed cavity 4. The circular feed 3 is connected to the rectangular coaxial inner conductor of the coaxial feeding structure 1 through the impedance matching section 2.

[0032] Specifically, the thickness of the support structure 5 is h 2=0.04mm, the support structure 5 is made of SU-8 material. The SU-8 photoresist used in this application is a submicron photoresist with a relative dielectric constant of 3 and a loss tangent of 0.045. Its function is to support the rectangular coaxial inner conductor and has little effect on the simulation and performance of the cavity-backed slot antenna; the release hole 6 is used to clean the sputtered glue in Micro-Machined Additive Manufacturing (M-MAM). The release hole 6 is 0.20mm long, 0.23mm wide, and 0.30mm high. The spacing between adjacent release holes 6 is 0.2mm; the gradient gap 7 is formed by two bottom sides of length s 2=2.696mm, the length of the upper base is s 4=0.582mm, height is w2=1.573mm trapezoidal butt joint is formed, and the upper base of the trapezoid is located at the center line of the top surface of the rectangular back cavity 4; the corners of the gradient slot 7 are smoothly transitioned by rounded corners; the rounded corners provide a gradual and smooth current path transition, reduce the discontinuity effect, and help make the actual input impedance of the antenna closer to the ideal value, thereby achieving better impedance matching in a wider frequency band; suppress small-scale, local current disturbances that will produce cross-polarization components; the smooth rounded corners can significantly reduce the electric field concentration effect, homogenize the electric field distribution, and thus improve the power capacity of the antenna.

[0033] In a specific embodiment of the present invention, in a cavity-backed slot antenna, an excitation signal is input by a coaxial feeding structure 1, transmitted via the coaxial line to the impedance matching section 2 and the circular feed 3, and radiated outward through the gradient slot 7 in the rectangular cavity-backed slot 4. The length and width of the rectangular cavity-backed slot 4 are one-quarter of the wavelength corresponding to the center frequency of the Q band, and are used to achieve broadband matching and high gain. The cavity resonance of the rectangular cavity-backed slot 4 is used to enhance the radiation directivity and suppress backward radiation. The height dimension of the rectangular cavity-backed slot 4 is used to achieve a low profile. The impedance matching section 2 is used to achieve broadband impedance matching within the Q band, and the width of the impedance matching section 2 is greater than the width of the inner conductor of the rectangular coaxial cable. The thickness of the circular feed 3 is increased by 0.1 mm compared to the thickness of the inner conductor of the rectangular coaxial cable, thereby increasing the bandwidth of the cavity-backed slot antenna. The gradient slot 7 increases the half-power beamwidth of the cavity-backed slot antenna while having good achievable gain. The system utilizes a 0.1mm thin-walled rectangular outer conductor and a rectangular back cavity 4, integrated into a copper structure. Copper's low resistivity significantly reduces conductor ohmic losses, effectively mitigating signal attenuation caused by the skin effect at high frequencies. Furthermore, its high thermal conductivity ensures rapid heat dissipation during high-power operation. The structural design utilizes a composite configuration of a circular feed 3 and a rectangular back cavity 4, effectively isolating external interference through the electromagnetic shielding provided by the rectangular back cavity 4. The overall dimensions strictly meet micromachining process requirements. The all-copper integrated construction eliminates contact potential differences between dissimilar materials, significantly improving the system's electromagnetic compatibility. This design achieves an optimal balance between RF performance, thermal management efficiency, and mechanical reliability.

[0034] In the embodiment, in order to verify the effectiveness of the above-mentioned cavity-backed slot antenna for low-orbit satellite communication based on the micro-coaxial processing technology, the following structural dimensions are used as an example for description: See also Figure 1 、 Figure 2 and Figure 3 , Figure 1The structural diagram of the cavity-backed slot antenna for low-orbit satellite communication according to an embodiment of the present invention is schematically shown; the cavity-backed slot antenna for low-orbit satellite communication disclosed in an embodiment of the present invention includes a coaxial feeding structure 1, an impedance matching section 2, a circular feed source 3, a rectangular cavity 4, a supporting structure 5, a release hole 6 and a gradient slot 7 opened above the cavity. Figure 2 and Figure 3 The top view and side view of the micro-coaxial broadband cavity-backed slot antenna for Q band according to an embodiment of the present invention are schematically shown. The impedance matching section 2 is located in the rectangular cavity 4. The length of the impedance matching section 2 in the figure is s 3=1.775mm, width is w 3=0.5mm, thickness is h 3=0.3mm, the radius of the circular feed 3 is r =0.4mm, thickness is h 4=0.4mm, the length of the rectangular back cavity 4 is s 1=3.75mm, width is w 1=3.75mm.

[0035] Figure 4 The schematic diagram of the M-MAM coaxial feeding structure 1 of the cavity-backed slot antenna for low-orbit satellite communication according to an embodiment of the present invention is shown schematically. Figure 4 (a) is a cross-sectional schematic diagram of the coaxial feeding structure 1. Figure 4 (b) is a schematic diagram of a partial three-dimensional structure. The cavity-backed slot antenna of the present invention is formed based on a micro-metal additive manufacturing process and is designed with a nine-layer structure. L 1 to L 9. Thickness of each layer h 1=0.1mm, the rectangular coaxial inner conductor is made by three-layer molding process, the width of the rectangular coaxial inner conductor is w i =0.291mm, the distance between the rectangular coaxial inner conductor and the rectangular outer conductor w g =0.254mm. Among them, multiple support structures 5 are located in the fifth layer of the nine-layer structure, and the thickness of the support structure 5 is h 2=0.04mm, and a plurality of release holes 6 are located on the outer wall of the rectangular outer conductor.

[0036] Figure 5 The frequency band in which the cavity-backed slot antenna for low-orbit satellite communications according to an embodiment of the present invention operates is schematically shown. The return loss of the cavity-backed slot antenna is better than 10 dB between 35.60 GHz and 47.82 GHz.

[0037] Figure 6The achievable gain of the cavity-backed slot antenna for low-orbit satellite communications according to an embodiment of the present invention is schematically shown. In the frequency range of 35.60 GHz to 47.82 GHz, the achievable gain ranges from 4.02 dBi to 5.72 dBi, and the maximum achievable gain of 5.72 dBi is at 47 GHz.

[0038] A right-handed rectangular coordinate system (Cartesian coordinate system) is used, with the geometric center of the rectangular back cavity as the origin. The X-axis is along the length of the rectangular back cavity, the Y-axis is along the width of the rectangular back cavity, and the Z-axis is perpendicular to the top surface of the back cavity, that is, the plane where the gradient gap is located is upward. Figure 7 The figure schematically shows the YOZ radiation pattern of the cavity-backed slot antenna for low-orbit satellite communications at 36 GHz according to an embodiment of the present invention; Figure 8 The XOZ plane radiation pattern of the cavity-backed slot antenna for low-orbit satellite communications at 36 GHz according to an embodiment of the present invention is schematically shown; Figure 9 The figure schematically shows the YOZ radiation pattern of the cavity-backed slot antenna for low-orbit satellite communications at 41 GHz according to an embodiment of the present invention; Figure 10 The XOZ plane radiation pattern of the cavity-backed slot antenna for low-orbit satellite communications at 41 GHz according to an embodiment of the present invention is schematically shown; Figure 11 The figure schematically illustrates the YOZ radiation pattern of the cavity-backed slot antenna for low-orbit satellite communications at 47 GHz according to an embodiment of the present invention. Figure 12 The schematic diagram shows the XOZ radiation pattern of the cavity-backed slot antenna for low-orbit satellite communications at 47 GHz according to an embodiment of the present invention. Figures 7 to 12 According to the radiation pattern results, the low-orbit satellite communication cavity-backed slot antenna designed in this embodiment shows excellent radiation characteristics at 36 GHz, 41 GHz and 47 GHz frequencies, with good cross-polarization suppression (better than 10 dB to 22 dB), a stable wide half-power beamwidth (78° to 84°) and an acceptable front-to-back ratio (8 dB to 17 dB) in the YOZ plane. In the XOZ plane, the antenna exhibits extremely strong cross-polarization suppression capability (better than 45 dB), and the half-power beamwidth covers a wide range of 107° to 141°. Overall, the antenna design successfully achieves high polarization purity, ultra-wide beam coverage and good directivity, which can meet the core requirements of low-orbit satellite communications for wide-angle scanning capability and anti-interference.

[0039] The present invention can also provide a low-orbit satellite, wherein the antenna used by the low-orbit satellite includes the above-mentioned cavity-backed slot antenna based on micro-coaxial processing technology, which meets the communication requirements in the Q band.

[0040] In summary, an embodiment of the present invention discloses a cavity-backed slot antenna for low-orbit satellite communications, comprising a coaxial feeding structure 1 and a cavity-backed slot antenna portion; specifically, a tapered slot 7 is formed by etching two trapezoids symmetrically about the central axis on the upper surface of a rectangular cavity-backed cavity 4; the coaxial feeding structure 1 comprises an air-filled rectangular coaxial inner conductor and a rectangular outer conductor, the rectangular coaxial inner conductor being suspended at the center of the rectangular outer conductor by a supporting structure 5, the rectangular outer conductor being connected to the rectangular cavity-backed cavity 4 and having symmetrically distributed release holes 6; the circular feed 3 is located directly below the tapered slot 7, the circular feed 3 being suspended in the rectangular cavity-backed cavity 4 and connected to the rectangular coaxial inner conductor of the coaxial feeding structure 1 through an impedance matching section 2. The present invention reduces the loss of the antenna through the coaxial structure, enabling the antenna to operate at high frequencies, and increases the bandwidth and half-power beamwidth of the cavity-backed slot antenna through the tapered slot 7 and the circular feed 3, while maintaining a good gain.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A cavity-backed slot antenna for low-orbit satellite communications, characterized in that: The invention comprises a coaxial feeding structure (1), an impedance matching section (2), a circular feed source (3) and a rectangular back cavity (4). The coaxial feeding structure (1) comprises a rectangular coaxial inner conductor and a rectangular outer conductor. A gradient slot (7) is provided on the rectangular back cavity (4), and the gradient slot (7) is symmetrical about the center line of the rectangular back cavity (4). The rectangular outer conductor is connected to the rectangular back cavity (4), and the rectangular coaxial inner conductor is connected to the circular feed source (3) through the impedance matching section (2). The circular feed source (3) is suspended in the rectangular back cavity (4), and the circular feed source (3) is located directly below the gradient slot (7).

2. The cavity-backed slot antenna for low-orbit satellite communications according to claim 1, wherein: Two trapezoids symmetrical about the central axis are etched on the top surface of the rectangular back cavity (4) to form a gradient gap (7), wherein the upper base of the trapezoids is located at the center line of the top surface of the rectangular back cavity (4).

3. The cavity-backed slot antenna for low-orbit satellite communications according to claim 1, wherein: The thickness of the circular feed (3) is greater than the thickness of the rectangular coaxial inner conductor.

4. The cavity-backed slot antenna for low-orbit satellite communications according to claim 1, wherein: The width of the impedance matching section (2) is greater than the width of the rectangular coaxial inner conductor.

5. The cavity-backed slot antenna for low-orbit satellite communications according to claim 1, wherein: The rectangular coaxial inner conductor is suspended on the inner side of the rectangular outer conductor along the coaxial feeding structure (1) through a support structure (5).

6. The cavity-backed slot antenna for low-orbit satellite communications according to claim 1, wherein: The length and width of the rectangular back cavity (4) are one quarter of the wavelength corresponding to the center frequency of the Q band.

7. The cavity-backed slot antenna for low-orbit satellite communications according to claim 1, wherein: The cavity-backed slot antenna is formed based on a micro-metal additive manufacturing process and has a nine-layer structure, each layer having the same thickness. The coaxial feeding structure (1), the impedance matching section (2), the circular feed source (3) and the rectangular cavity-backed slot antenna (4) are all made of copper.

8. The cavity-backed slot antenna for low-orbit satellite communications according to claim 1, wherein: Release holes (6) are evenly spaced apart on the rectangular outer conductor, and the release holes (6) are symmetrical about the axis of the rectangular outer conductor.

9. The cavity-backed slot antenna for low-orbit satellite communications according to claim 1, wherein: The corners of the gradient gap (7) are all smoothly transitioned through rounded corners.

10. A low-orbit satellite, characterized in that: A cavity-backed slot antenna for low-orbit satellite communications comprising any one of claims 1-9.

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