Hemispherical array antenna and low-altitude coverage base station

Abstract

The invention provides a hemispherical array antenna and a low-altitude coverage base station, and relates to the technical field of communication. The hemispherical array antenna comprises a hemispherical base body which is used for providing a curved surface structure for supporting an antenna array; the antenna array is distributed along the outer side face of the hemispherical base body and comprises a top dot matrix and multiple layers of circular ring arrays, the elevation angle of the top dot matrix and each layer of circular ring array is theta, the elevation angle is an included angle between a first axis and a second axis, the first axis is a connecting line between the vertex of the hemispherical base body and the sphere center, and the second axis is a connecting line between the vertex and the sphere center; the second shaft is a connecting line between the center point of any antenna unit of the top dot matrix or each layer of circular ring array and the sphere center of the hemispherical base body, and the circle center of each layer of circular ring array is located on the first shaft; and the feed network is at least used for controlling the radiation phase of the antenna array and comprises the step of applying phase differences which are gradually increased from top to bottom to the top dot matrix and the multiple layers of circular ring arrays according to respective theta. According to the invention, the hemispherical array antenna for compressing the vertical plane wave beam is realized.

Description

Technical Field

[0001] The present application relates at least to the field of communication technology, and in particular to a hemispherical array antenna and a low-altitude coverage base station. Background Art

[0002] Existing spherical array antenna designs, due to their specific application scenarios, lack designs that incorporate spherical conformal phase compensation and do not effectively compress vertical beams, which to some extent limits their application scenarios. Summary of the Invention

[0003] In response to the above-mentioned deficiencies, the present application provides a hemispherical array antenna and a low-altitude coverage base station to solve the following technical problem: how to design a new spherical array antenna.

[0004] In a first aspect, the present application provides a hemispherical array antenna, comprising:

[0005] a hemispherical substrate for providing a curved surface structure supporting the antenna array;

[0006] An antenna array distributed along the outer surface of a hemispherical substrate includes a top dot matrix and multiple layers of circular arrays. The top dot matrix and each layer of circular array each have an elevation angle of θ, which is the angle between a first axis and a second axis. The first axis is a line connecting the vertex of the hemispherical substrate and the center of the sphere. The second axis is a line connecting the center point of any antenna unit of the top dot matrix or each layer of circular array and the center of the hemispherical substrate. The center of each layer of circular array is located on the first axis.

[0007] The feeding network is at least used for controlling the phase of the antenna array radiation, including applying a top-down increasing phase difference to the top dot array and the multi-layer circular array according to their respective θ.

[0008] Further, wherein:

[0009] The phase difference formula between the top dot array and the multi-layer ring array is: Where λ is the wavelength of the main radiation of the antenna array, R is the radius of the hemispherical substrate, The unit is radian rad;

[0010] The feed network is also used to control the amplitude of the antenna array radiation. The amplitude of the top dot array and the multi-layer circular array decreases from top to bottom.

[0011] Further, wherein:

[0012] The number of antenna units in each layer of the multi-layer circular array increases gradually from top to bottom. The size of each antenna unit is determined by the material of the hemispherical substrate and the frequency / wavelength of the main radiation. The antenna units in each layer are evenly distributed, and the arc length distance d between the centers of any two adjacent antenna units is ≤0.5λ.

[0013] Further, wherein:

[0014] The top dot matrix includes an antenna unit distributed at the vertex of the outer side surface of the hemispherical base at an elevation angle θ = 0°;

[0015] The multi-layer ring array includes:

[0016] The first circular array includes 8 antenna units evenly distributed on a first circular ring on the outer side of a hemispherical base with an elevation angle of θ=30°.

[0017] The second circular array includes 12 antenna units evenly distributed on a second circular ring on the outer side of a hemispherical base with an elevation angle of θ=45°.

[0018] The third circular array includes 16 antenna units evenly distributed on a third circular ring on the outer side of a hemispherical base with an elevation angle θ=60°;

[0019] The amplitude weights of the top dot array and the multi-layer circular array are 1→0.8→0.6→0.4 from top to bottom.

[0020] Further, wherein:

[0021] Each antenna unit is a microstrip patch antenna unit, each antenna unit is vertically polarized, and provides wireless communication frequency Sub-6GHz below 6GHz.

[0022] Further, wherein:

[0023] Each microstrip patch antenna unit is a rectangular microstrip patch antenna unit, which realizes a wide bandwidth with the main radiation frequency f = 3.5 ~ 3.6 GHz as the center frequency through slot loading. λ = c / f, c is the speed of light. The length and width of each rectangular microstrip patch antenna unit are calculated based on the material of the hemispherical substrate and the frequency / wavelength of the main radiation. The spherical curvature error of the hemispherical substrate is ≤ ±0.1mm, and the position deviation of each microstrip patch antenna unit is ≤ ±0.5mm.

[0024] Further, wherein:

[0025] The radius of the hemispherical substrate R = A*λ, where A is designed according to the size and number of the antenna array and the arc length spacing d;

[0026] The hemispherical substrate is 3D printed, and the antenna array and feed network are laser engraved on the outer and inner sides of the hemispherical substrate respectively;

[0027] Each antenna unit is connected to a feeding point of the feeding network through a via hole. The impedance of each antenna unit and the feeding point is matched to Z0=50Ω. Each feeding point is 0.1λ away from the edge of the corresponding antenna unit.

[0028] Further, wherein:

[0029] The material of the hemispherical substrate is FR4, a composite material based on epoxy resin and glass fiber cloth, or Rogers RO4350B, a ceramic / hydrocarbon laminate reinforced with glass cloth. The dielectric constant of FR4 is ε r =4.4, thickness h = 1.6mm, the dielectric constant ε of Rogers RO4350B r =3.48, thickness h = 0.508mm;

[0030] The vertical coverage height of the antenna array is not less than 500m, the horizontal plane has 360° omnidirectional coverage, the omnidirectional error is ≤±1.5dB, the vertical plane beam points to a 45° elevation angle, the 3dB beam width covers 30°~60°, the gain is 8~10dBi, and the standing wave ratio is ≤1.5.

[0031] Furthermore, it also includes:

[0032] The hemispherical base is supported by a honeycomb hollow aluminum alloy hemispherical shell with a thickness of 1.2 to 2.0 mm and a hollowing rate of 60 to 70%.

[0033] The hemispherical substrate is covered with polytetrafluoroethylene (PTFE) film to ensure that the hemispherical array antenna reaches the required protection level.

[0034] It has an interface for connecting to the radio remote unit RRU, and is connected to the RRU through a radio frequency cable. The RRU output signal is distributed to each antenna unit through the feed network.

[0035] In a second aspect, the present application provides a low-altitude coverage base station, comprising:

[0036] The existing base station consists of multiple active antenna units (AAUs), which provide mobile network service signals covering 120° in front of the base station.

[0037] The hemispherical array antenna as described above is set in the middle position between multiple AAU antennas of the existing base station to provide blind spot filling signals for the signal coverage blind spots upward between the multiple AAU antennas.

[0038] Furthermore, it also includes:

[0039] The remote radio unit (RRU) is connected to the hemispherical array antenna and is used to convert and amplify baseband signals into radio frequency signals, drive the hemispherical array antenna to radiate, and process received signals.

[0040] Further, wherein:

[0041] The AAU antenna is the fifth-generation mobile communication technology 5GAAU antenna, the RRU is 5GRRU, the spherical array antenna provides 5GSub-6GHz frequency band radiation, and the low-altitude coverage base station provides communication services for drone flight control and air traffic management.

[0042] The present application provides a hemispherical array antenna and a low-altitude coverage base station. By distributing an antenna array including a top dot array and multiple layers of circular arrays on a hemispherical substrate, the radiation phase is controlled to maintain a certain phase difference according to the elevation angle of the antenna units distributed on the hemispherical substrate. The phase difference is used to compensate for the wave path difference caused by the spherical curvature, so that the radiation fields of each layer are superimposed in phase at the target elevation angle, thereby compressing the vertical beam width, thereby realizing a hemispherical array antenna with compressed vertical plane beam. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 is a side view schematic diagram of a hemispherical array antenna according to an embodiment of the present application;

[0044] Figure 2 is a schematic top view of a hemispherical array antenna according to an embodiment of the present application;

[0045] Figure 3 This is a schematic diagram of a blind spot of an existing base station in an embodiment of the present application;

[0046] Figure 4 It is a structural diagram of a low-altitude coverage base station in an embodiment of the present application. DETAILED DESCRIPTION

[0047] In order to enable those skilled in the art to better understand the technical solution of the present application, the implementation methods of the present application will be further described in detail below with reference to the accompanying drawings.

[0048] It should be understood that the specific embodiments and drawings described herein are only used to explain the present application, rather than to limit the present application.

[0049] It can be understood that, in the absence of conflict, the various embodiments and features in the embodiments of the present application can be combined with each other.

[0050] It will be understood that, for the sake of ease of description, the drawings of this application only show the parts related to this application, while the parts not related to this application are not shown in the drawings.

[0051] It should be noted that, in the description of this application, the indications of orientation or positional relationship such as “upper” are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience and simplification of the description. They do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as a limitation on this application.

[0052] It should be noted that, in the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance.

[0053] It should be noted that, in the description of this application, unless otherwise clearly specified and limited, the terms "connect", "set", "install", "fix", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be a connection between the internal parts of two elements.

[0054] For those skilled in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0055] Example 1:

[0056] like Figure 1 and 2 As shown, the present application provides a hemispherical array antenna 01, comprising:

[0057] A hemispherical substrate 1, used to provide a curved structure supporting the antenna array;

[0058] An antenna array distributed along the outer side of a hemispherical substrate 1 includes a top lattice 21 and multiple layers of circular arrays (e.g., 221, 222, and 223). The top lattice 21 and each layer of circular arrays (e.g., 221, 222, or 223) each have an elevation angle θ, which is the angle between a first axis 41 and a second axis 42. The first axis 41 is a line connecting the vertex of the hemispherical substrate 1 and the center of the sphere. The second axis 42 is a line connecting the center point of any antenna unit of the top lattice 21 or each layer of circular arrays (e.g., 221, 222, or 223) and the center of the hemispherical substrate 1. The center of each layer of circular arrays (e.g., 221, 222, 223) is located on the first axis 41.

[0059] The feeding network (including 31 mainly located on the inner side of the hemispherical substrate 1) is at least used to control the phase of the antenna array radiation, including applying a top-down increasing phase difference to the top dot matrix 21 and the multi-layer circular array (such as 221, 222 and 223) according to their respective θ.

[0060] In this embodiment, the hemispherical array antenna 01 distributes an antenna array including a top dot matrix 21 and multiple layers of circular arrays (such as 221, 222 and 223) on a hemispherical substrate 1. According to the elevation angle of the antenna unit on the hemispherical substrate 1, the radiation phase is controlled to maintain a certain phase difference. The phase difference is used to compensate for the path difference caused by the spherical curvature, so that the radiation fields of each layer are superimposed in phase at the target elevation angle, thereby compressing the vertical plane beam width, thereby realizing a hemispherical array antenna 01 with compressed vertical plane beam. The hemispherical array antenna 01 is particularly suitable for low-altitude economic base station blind spot filling, but other application scenarios are not excluded.

[0061] More specifically, this embodiment provides a 5G (fifth generation mobile communication technology) spherical array antenna (i.e., hemispherical array antenna 01) and system for low-altitude coverage, and provides antenna design methods and parameters. A specific application scenario is that with the development of the low-altitude economy, the problem of blind spots in the top coverage of existing base stations needs to be solved. The use of AAU (active antenna unit) in the mid-to-low frequency band (Sub-6GHz, wireless communication technology with a frequency below 6GHz) to fill the blind spots has the problems of high cost and unsatisfactory effect. In view of this, it is necessary to design an antenna with low cost and good blind spot filling effect. Spherical array antennas are a feasible option. The existing spherical array antenna design, due to the different application scenarios it considers, lacks a design that combines spherical conformal phase compensation and does not effectively compress the vertical plane beam. As a result, it fails to meet the requirements in providing communication services for drone flight control and air traffic management to supplement the blind spots of existing base station coverage. Therefore, further improvement is necessary.

[0062] Currently, the low-altitude economy is a new economic growth point with an increasingly rapid development speed. As a supporting means for drone flight control and air traffic management in the low-altitude economy, network technology can provide low-altitude perception, obstacle avoidance, video streaming and real-time feedback of flight control data. It is widely used. In low-altitude economic applications, it is necessary to obtain the support of mobile network signals in the low-altitude airspace of 300 to 1000 meters. However, the current mobile cellular network does not have full coverage at low altitudes of 100 to 300 meters, and the coverage at high altitudes of 300 to 1000 meters is even weaker. The blind spots and weak coverage in the air do not meet the needs of the new economy.

[0063] Before low-altitude access was introduced, mobile network optimization primarily targeted ground users. Due to factors such as antenna downtilt, coverage at altitudes above 100 meters was significantly interrupted, and data rates decreased with altitude. Actual measurements show that LTE (Long Term Evolution) data rates drop by 30% at an altitude of 120 meters. If a drone flies within 150 to 300 meters of a base station, the main lobe will not be covered, resulting in a signal strength below -110dBm (decibels per milliwatt, relative to a milliwatt power level), making it impossible to establish a stable network connection.

[0064] The low-altitude coverage of current base station signals (i.e., the vertical coverage height of the signal) is related to the antenna height, vertical beam width, and downtilt angle. Antenna height is typically 30 to 50 meters (in urban areas) to 100 meters (in rural areas). Lower antenna heights increase the blind spot above the tower. The vertical beam width is typically 5° to 15°. Within the three antenna sectors, the tower's airspace forms an inner blind zone of 112 to 500 meters. Downtilt angles are typically set between 3° and 15°, with larger angles increasing the blind spot.

[0065] Current base station signal frequency bands and attenuation factors: Low-frequency bands (such as 700MHz) have strong penetration and cover longer airspaces, while high-frequency bands (such as 3.5GHz) have a smaller coverage area. Within a cellular coverage area composed of multiple base stations, each tower-centered area will form a significant blind spot.

[0066] Deploying dedicated aerial antennas for 5G and 5G-A (5G-Advanced, 5G evolution) not only involves network replanning but also requires significant investment. 3D (Three Dimensions) beamforming antennas, especially those integrated into AAUs, can dynamically adjust horizontal and vertical coverage through 3D beams. However, their cost is significantly affected by hardware complexity, frequency band, and antenna size (such as the number of MIMO (Multiple-Input, Multiple-Output) channels). Real-time beamforming algorithms require dedicated DSP (Digital Signal Processing) or FPGA (Field Programmable Gate Array) processors. The software licensing fee is high, and the price of a single AAU in the low and medium frequency bands is expensive depending on the number of channels and power. In particular, the 3D beam antenna has an upward elevation angle (e.g., 30° to 60°). The maximum elevation angle of 60° will also form a blind spot in the airspace outside it. If it is in the millimeter wave band, the price may double due to the increased complexity of high-frequency hardware (but the coverage range is smaller). The traffic demand of low-altitude application customers is not large, and the investment recovery ratio is not high.

[0067] This embodiment aims to design an array coverage antenna to solve the airspace blind spot problem with small investment and without changing the existing network. The design analyzes the current low-altitude signal coverage situation and proposes a targeted compensatory coverage solution, which can quickly solve the basic guarantee needs of drones for network connection signals in the low-altitude economy.

[0068] This embodiment provides a design scheme for a curved array antenna, which mainly realizes vertical beam compression through an asymmetric spherical array layout and phase control method of layered concentric rings + top dot matrix 21, and a progressive phase difference formula based on spherical curvature. The antenna includes: a hemispherical substrate 1, a top dot matrix 21, a multi-layer circular array (such as 221, 222 and 223) and a feeding network. The top dot matrix 21 and the multi-layer circular array (such as 221, 222 and 223) are radiation units responsible for electromagnetic wave radiation to achieve low-altitude blind signal coverage. The top dot matrix 21 is responsible for high-gain coverage in the vertical direction, and the multi-layer circular array (such as 221, 222 and 223) is responsible for expanding the horizontal omnidirectional coverage range. Among them, the multi-layer circular array (such as 221, 222 and 223) is a ring-shaped patch array distributed at a specific elevation angle (such as 30°, 45°, 60°), and the feeding network applies an incremental phase difference to each layer of the circular array unit. It is understandable that the hemispherical surface described in the present application is not absolutely half of a complete sphere, but can be a partial sphere. As long as the top dot matrix 21 and the multi-layer circular array (such as 221, 222 and 223) can be distributed, it meets the requirements.

[0069] In one embodiment, wherein:

[0070] The phase difference formula between the top dot matrix 21 and the multi-layer ring array (such as 221, 222 and 223) is: Where λ is the wavelength of the main radiation of the antenna array, R is the radius of the hemispherical substrate, The unit is radian rad;

[0071] The feeding network is also used to control the amplitude of the antenna array radiation. The amplitudes of the top dot matrix 21 and the multi-layer circular arrays (such as 221, 222 and 223) decrease from top to bottom.

[0072] In this embodiment, the phase difference formula is: Among them, θ is the design elevation angle, by adjusting The principle of compressing the vertical beam is to apply an increasing phase difference to each layer of the ring array. This innovative design allows the radiation fields of each layer to be superimposed in phase at the target elevation angle (e.g., 45°), compressing the beamwidth and combining it with spherical conformal phase compensation. The technical principle primarily involves the use of a vertical beam compression mechanism, which compensates for the path difference caused by spherical curvature through phase differences, allowing the radiation fields of each ring unit to be superimposed in phase at the target elevation angle. For example, the vertical beamwidth is compressed to 30° to 60°. At the same time, sidelobes are suppressed through amplitude weighting. For example, the amplitude ratio of the top and three rings is 1.0:0.8:0.6:0.4, reducing the sidelobe level by >5dB and focusing the energy more closely on the target low-altitude area. The spherical array beamforming effect, for example, at θ = 45°, the 3dB beamwidth is only 40° (covering 30° to 60°), improving energy efficiency by over 50%.

[0073] The hemispherical array antenna (the present spherical array) provided in this embodiment has differentiated advantages compared to other technologies as shown in Table 1 below:

[0074] Table 1 Differentiation comparison of several antennas

[0075] Technical Solution Vertical beam steering Applicability of low-altitude blind spot filling Interference suppression Traditional omnidirectional antenna No 120° wide beam Difference (energy dispersion) weak Mechanical downtilt antenna Fixed downtilt angle (cannot be adjusted dynamically middle Planar Phased Array Electronic scanning ±30° Good (but high profile) excellent This spherical array 40° fixed compression excellent powerful

[0076] In one embodiment, wherein:

[0077] The number of antenna units in each layer of the multi-layer circular array increases gradually from top to bottom. The size of each antenna unit is determined by the material of the hemispherical substrate and the frequency / wavelength of the main radiation. The antenna units in each layer are evenly distributed, and the arc length distance d between the centers of any two adjacent antenna units is ≤0.5λ.

[0078] In this embodiment, the selection of antenna type and structure includes: designing a wide-beam microstrip patch curved array antenna, designing a feeding network including phase control and amplitude weighting, and designing the antenna unit spacing so that the arc length between adjacent rings is ≤0.5λ to avoid grating lobes. When the array unit spacing exceeds half a wavelength (0.5λ), grating lobes (unwanted beams) will be generated due to insufficient spatial sampling. This design suppresses grating lobes by controlling the spacing arc length ≤0.5λ (e.g., d ≤ 42.85mm at the main radiation frequency of 3.5GHz). Since the size of the antenna unit is determined by the material of the hemispherical substrate and the frequency / wavelength of the main radiation, the antenna units on each layer are distributed as evenly as possible. The antenna units on each layer of the multi-layer circular ring array are calculated based on the ring circumference, antenna unit size, and spacing requirements. For example, assuming the spherical array consists of K concentric ring layers, the core formula for designing the number of elements in each layer is: n(θ) = floor(B·C(θ) / λ). Parameter description: n(θ) is the number of elements in the ring with an elevation angle of θ, B is the spatial compression factor (ranging from 0.8 to 1.2 to avoid grating lobes and overlap), and C(θ) = 2πR sinθ, R is the radius of the sphere, θ is the target elevation angle (with the horizontal plane as 0°), λ is the operating wavelength, floor() is a function related to the projected area of the antenna unit, and the formula is constrained by d≤0.5λ. B is related to the installation method, and normal installation is preferred (the patch plane is perpendicular to the spherical normal, that is, pointing to the center of the sphere): take B = 0.8-1.0 (large projection size), or you can choose inclined installation, which will reduce 0.3-0.5db (the patch plane is tilted at a specific angle toward the zenith, take B = 1.0-1.2 (small projection size), and the projection size refers to the projected area of the patch on the sphere. The design steps may include: A [determine the spherical radius R] --> B [select the target elevation angle θ] --> C [calculate the ring circumference C = 2πR sinθ]-->D[Select installation method]-->|Normal installation|E[Take B=0.8-1.0]-->|Inclined installation|F[Take B=1.0-1.2]-->G[Calculate n=floor(B·C / λ)]-->H[Verify that unit spacing > patch projection size]-->|Satisfied|I[Determine the number of units in this layer]-->|Not satisfied|J[Increase θ or decrease B].

[0079] In one embodiment, wherein:

[0080] The top dot matrix 21 includes an antenna unit distributed at the vertex of the outer side surface of the hemispherical substrate 1 at an elevation angle θ=0°;

[0081] The multi-layer ring array includes:

[0082] The first circular array 221 includes 8 antenna units evenly distributed on a first circular ring on the outer side of a hemispherical substrate 1 with an elevation angle θ=30°.

[0083] The second circular array 222 includes 12 antenna units evenly distributed on a second circular ring on the outer side of the hemispherical substrate 1 with an elevation angle θ=45°.

[0084] The third circular array 223 includes 16 antenna units evenly distributed on a third circular ring on the outer side of the hemispherical substrate 1 with an elevation angle θ=60°;

[0085] The amplitude weights of the top dot matrix 21 and the multi-layer circular arrays (221, 222 and 223) are 1→0.8→0.6→0.4 from top to bottom.

[0086] In this embodiment, the layered structure of the antenna array includes: a top dot matrix 21 located at the top of the sphere at θ = 0°, including one square patch unit; a multi-layer circular array includes: a first circular array 221 with an elevation angle of θ = 30° and 8 evenly distributed patch units; a second circular array 222 with an elevation angle of θ = 45° and 12 evenly distributed patch units; a third circular array 223 with an elevation angle of θ = 60° and 16 evenly distributed patch units. The amplitude weighting of the feed network is: the top dot matrix feeding amplitude is the largest (weight coefficient is 1), and the amplitude of each ring decreases downward (weight coefficient 0.8 → 0.6 → 0.4), suppressing side lobes. The feeding method of the feed network adopts spherical conformal stripline feeding, with the hemispherical substrate 1 as the intermediate dielectric layer, the inner layer as the ground layer, the outer layer as the radiation layer, and the via connecting the feed point 31.

[0087] In one embodiment, wherein:

[0088] Each antenna unit is a microstrip patch antenna unit, each antenna unit is vertically polarized, and provides wireless communication frequency Sub-6GHz below 6GHz.

[0089] In this embodiment, microstrip patches are used to make antenna units, which are easy to process. Each antenna unit is vertically polarized, which can suppress co-channel interference and provide Sub-6GHz wireless communication frequency to meet the communication needs of drones and other equipment.

[0090] In one embodiment, wherein:

[0091] Each microstrip patch antenna unit is a rectangular microstrip patch antenna unit, which realizes a wide bandwidth with the main radiation frequency f = 3.5 ~ 3.6 GHz as the center frequency through slot loading, λ = c / f, c is the speed of light, the length and width of each rectangular microstrip patch antenna unit are calculated based on the material of the hemispherical substrate 1 and the frequency / wavelength of the main radiation, the spherical curvature error of the hemispherical substrate 1 is ≤ ± 0.1 mm, and the position deviation of each microstrip patch antenna unit is ≤ ± 0.5 mm.

[0092] In this embodiment, the antenna element patches are designed as rectangular microstrip patches, which are low-cost and easy to process. The patch dimensions are calculated based on theoretical calculations. Manufacturing tolerance requirements for the hemispherical array antenna 01 include: spherical curvature error ≤ ±0.1mm (requires 3D printing accuracy) to ensure accurate spherical phase distribution and avoid beam distortion; patch position deviation ≤ ±0.5mm to avoid pattern distortion and prevent inter-element phase error accumulation, which affects pattern omnidirectionality and beam pointing. This design ensures 30° to 60° vertical beam coverage and horizontal omnidirectionality through precise spherical geometry and phase control.

[0093] In one embodiment, wherein:

[0094] The radius of the hemispherical substrate 1 is R=A*λ, where A is designed according to the size and number of the antenna array and the arc length spacing d;

[0095] The hemispherical substrate 1 is 3D printed, and the antenna array and feed network are laser engraved on the outer and inner sides of the hemispherical substrate 1 respectively;

[0096] Each antenna unit is connected to a feeding point 31 of the feeding network through a via hole. The impedance between each antenna unit and the feeding point 31 is matched to Z0=50Ω. Each feeding point 31 is 0.1λ away from the edge of the corresponding antenna unit.

[0097] In this embodiment, the design radius of the hemispherical substrate 1 is: R = A * λ, λ is the working wavelength, assuming that the 5G frequency band is 3.5 GHz, λ ≈ 85.7 mm, 3.5 GHz is the main frequency band of the current 5G network, and the wavelength λ is determined here as c / f ≈ 85.7 mm, which is used to calculate the patch size (such as ), R is determined based on the sufficient number of antenna patch elements per layer and the spacing requirements. A high-precision 3D-printed substrate and laser-engraved patches ensure consistent geometric and electrical performance. Feed point 31 is located 0.1λ = 8.57mm from the edge of the patch element, with impedance matching to 50Ω.

[0098] In one embodiment, wherein:

[0099] The material of the hemispherical substrate 1 is a composite material FR4 with epoxy resin and glass fiber cloth as the main body or a ceramic / hydrocarbon laminate reinforced with glass cloth, Rogers RO4350B. The dielectric constant of FR4 is ε r =4.4, thickness h = 1.6mm, the dielectric constant ε of Rogers RO4350B r =3.48, thickness h = 0.508mm;

[0100] The vertical coverage height of the antenna array is not less than 500m, the horizontal plane has 360° omnidirectional coverage, the omnidirectional error is ≤±1.5dB, the vertical plane beam points to a 45° elevation angle, the 3dB beam width covers 30°~60°, the gain is 8~10dBi, and the standing wave ratio is ≤1.5.

[0101] In this embodiment, 3D-printed ceramic substrates and flexible circuit integration technology are used to address the challenges of high-precision spherical array fabrication. The substrate material is FR4 (a composite material based on epoxy resin and glass fiber cloth, widely used in PCB manufacturing and electronic insulation), with a dielectric constant of 4.4 and a thickness of 1.6 mm, or Rogers RO4350B (a glass-reinforced ceramic / hydrocarbon laminate, widely used in RF / microwave frequency circuits or high-speed signal applications with high requirements for dielectric constant stability), offering high performance and minimal loss. Microstrip patch elements are fabricated on the surface of the ceramic or composite material, forming the radiating layer. While a high-precision spherical mold can theoretically be used to fabricate the hemispherical substrate 1, these molds are expensive and unsuitable for multi-band customized designs. Conventional processes cannot guarantee the geometric accuracy of the spherical substrate. Therefore, 3D printing is recommended for the hemispherical substrate. The antenna array and feed network can be laser engraved on the outer and inner surfaces of the hemispherical substrate, respectively, reducing assembly steps and achieving lightweight and optimized heat dissipation.

[0102] The core design goals include: frequency band 3.4~3.6GHz (center frequency 3.5GHz); coverage angle: omnidirectional 360° coverage on the horizontal plane, and upward coverage of 30°~60° on the vertical plane (radiating upward based on the horizontal plane, with a beam width of 30°~60°); gain 8~10dBi; the structure is a hemispherical curved array, and the application scenarios support the three-dimensional coverage requirements of low-altitude drones, smart cities and other scenarios, as well as aerial network blind spots, with a coverage height of 50~500 meters.

[0103] In one embodiment, it further includes:

[0104] A honeycomb hollow aluminum alloy hemispherical shell is used to support the hemispherical substrate 1, with a thickness of 1.2 to 2.0 mm and a hollowing rate of 60 to 70%. It needs to meet the preset support strength requirements, such as a thickness of 1.5 mm.

[0105] The hemispherical substrate 1 is covered with a polytetrafluoroethylene (PTFE) film so that the hemispherical array antenna reaches the required protection level, such as IP67;

[0106] It has an interface for connecting to the remote radio unit RRU03 and is connected to the RRU03 via a radio frequency cable. The output signal of the RRU03 is distributed to each antenna unit through the feed network.

[0107] In this embodiment, the mechanical structure of the hemispherical array antenna 01 includes: a support frame constructed from a honeycomb-shaped, hollowed-out metal hemispherical shell (made of aluminum alloy), balancing lightweighting and heat dissipation. The hollowing design reduces weight, while the honeycomb structure enhances rigidity. Aluminum alloy offers excellent heat dissipation. Thickness can range from 1.2 to 2.0 mm. A thickness of 1.2 mm or greater ensures compressive strength greater than 50 MPa and resistance to level 6 wind loads. Too thick a thickness can result in excessive weight or compromised heat dissipation. The hollowing ratio should be 60-70%. A waterproof design is achieved by coating the exterior with a polytetrafluoroethylene (PTFE) film to achieve an IP67 protection rating. Industry standards require that base station antennas meet IP65 (water spray and dust resistance) or higher in 3GPP TS38.141-2, and that outdoor communication equipment in Class 3.2 environments (such as drone base stations) must meet IP67 protection according to ETSI EN 300 019. The assembly relationship is such that the honeycomb shell serves as an independent support frame, separate from the hemispherical base (ceramic) and covered with a waterproof film. The antenna is equipped with a set of 5G RRU (5G Remote Radio Unit) 03 to form a combination, which is specially used to solve the blind spots and signal connection in low-altitude airspace, providing a blind spot filling and coverage method.

[0108] More specifically, if Figure 3 As shown, first analyze the low-altitude coverage blind area:

[0109] The current 5G frequency band is the Sub-6GHz band (such as 3.5GHz and 4.9GHz). Its theoretical coverage range can reach 1-2 kilometers in an accessible environment. According to the base station density planning, the station distance in rural areas is 1.5-2.5 kilometers, and the coverage radius of a single base station is >1 kilometer.

[0110] In a typical scenario, the 5G vertical beam width is 5° to 15°, the antenna downtilt angle is 3° to 15°, and the signal beam covers the sky 200 to 700 meters away from the base station along the upper edge of the coverage width, creating a blind spot in the airspace above it. The blind spot diameter at different altitudes ranges from 200 to 720 meters. Therefore, the hemispherical array antenna 01 provided in this embodiment has a coverage height of 50 to 500 meters, with the goal of eliminating low-altitude blind spots, and has omnidirectional horizontal coverage of 360°.

[0111] Estimation model: Assuming base station height H, vertical beamwidth β, downtilt angle α, and mainlobe peak height H_{max}, coverage height increases nonlinearly with distance (d). Theoretically, coverage height can reach 300 meters for a 1 km process, but is limited by signal attenuation (e.g., free space loss). In actual coverage, the effective coverage height in urban environments is typically 100-300 meters (due to building obstruction and interference). In rural and suburban environments, it can extend to 500 meters, but signal strength decays rapidly with height.

[0112] Coverage blind spots caused by downtilt: If the downtilt angle is too large, a "black spot on the tower" will form at high altitudes near the base station. The range of the blind spot increases with the downtilt angle α, and the height of the near-end blind spot decreases. For example, when α = 10°, the highest point of the main lobe increases with increasing distance, but the area directly above the base station is not covered by the beam, forming a "black spot on the tower" blind spot. A weak signal area may appear 100 meters directly above the base station, and higher areas may have no coverage.

[0113] Multi-base station coordination issues: Cellular network design is mainly based on ground switching, and high-altitude areas may be disconnected due to switching failures.

[0114] Topographic impact: Mountainous areas or dense urban areas will exacerbate the fragmented distribution of blind spots.

[0115] An example of calculating the airspace blind area above the base station tower is shown in Table 2 below:

[0116] Table 2 Examples of blind spot measurement results at different heights above base station towers

[0117] high Downward tilt angle 3~15° Beam width 5~15° Blind spot radius: m Blind zone diameter: m 300 10° 10° 109 218 500 10° 10° 182 384 1000 10° 10° 364 728

[0118] This example application is 3.5GHz frequency band (Sub-6GHz), horizontal plane omnidirectional coverage antenna and air blind spot optimization, blind spot filling method is as follows Figure 4 As shown, the existing 5G AAU antenna 02 provides normal mobile network service signal coverage. Due to the elevation angle, coverage is weak at the top and rear of the antenna, primarily covering the area within a 120-degree field of view in front of the antenna. The hemispherical array antenna 01 designed in this embodiment complements the existing 5G AAU antenna 02 to address low-altitude coverage blind spots. The 5GRRU 03 added to hemispherical array antenna 01 converts and amplifies baseband signals to RF signals, drives hemispherical array antenna 01 to radiate, and processes received signals. The designed hemispherical array antenna 01 covers a 30-60° horizontal area, with a vertical coverage of at least 500 meters. Its horizontal diameter increases with altitude, ranging from 200 to 720 meters, achieving omnidirectional 360° horizontal coverage and vertical coverage with an elevation angle of 30° to 60°. Filling the gaps in low-altitude coverage is a task that must be improved in the early stages of the current low-altitude economic development. If the airspace coverage is replanned and large-scale investment is made, it is bound to face the two opposing problems of large project investment and small number of users. Therefore, the hemispherical array antenna 01+5GRRU03 method is undoubtedly an effective solution that uses small investment and technical transformation. It is a relatively fast and advantageous action plan and can be quickly implemented without changing the existing network optimization. It adapts to the needs of perception and networking in the low-altitude economy.

[0119] Among them, this embodiment mainly designs a hemispherical array antenna 01, which is a spherical wide beam array coverage antenna system, using a wide beam microstrip patch curved array antenna design, such as Figures 1-2 As shown, it mainly consists of a hemispherical substrate 1, a top lattice 21, a concentric ring array, a radiating element, a feed network, a support frame, and a waterproof structural shell. The design work is mainly divided into five steps: patch element position and size design (designing the position and size of the top lattice 21 and the concentric ring array), hemispherical substrate 1 design, patch element radiation design (designing the radiation of the top lattice 21 and the concentric ring array), feed network design, and mechanical structure design. The assembly relationship of each part is as follows: the hemispherical substrate 1 serves as the core carrier, the radiating element and feed network are attached, the top lattice 21 is located at the top of the sphere, the concentric ring array is arranged on the substrate in layers according to the elevation angle, the support frame wraps the substrate, and the waterproof shell covers the outermost layer. The functions of each part include: a hemispherical substrate 1, which supports the curved structure of the entire antenna array and ensures that the radiating units are distributed according to the spherical geometry to achieve wide beam coverage; the top dot matrix 21 is a single patch unit located at the top of the sphere, which serves as the main radiation source and is responsible for high-gain coverage in the vertical direction; the concentric ring array (i.e., multi-layer ring arrays 221, 222, 223) is a ring-shaped patch array distributed at specific elevation angles (30°, 45°, 60°), which is responsible for expanding the horizontal omnidirectional coverage range; the radiating unit, which uses a rectangular microstrip patch, is responsible for electromagnetic wave radiation and expands the bandwidth through a slotted design; the feeding network controls the phase and amplitude of each radiating unit to achieve beamforming (such as compressing the vertical beam, suppressing side lobes, etc.); the supporting frame uses a honeycomb aluminum alloy shell to provide structural stability, mechanical support and heat dissipation, while reducing weight; the waterproof structural shell is covered with PTFE film to ensure an IP67 protection level. Its working state is to install this antenna on the existing tower (tower-shaped base station, referring to the physical support structure for installing the antenna) and equip it with a group of 5G RRU03 to form a combination. It is a blind spot filling and coverage method specifically used to solve low-altitude airspace blind spots and signal connection. This antenna (hemispherical array antenna 01) is connected to the 5G RRU03 through an RF cable. The RRU03 output signal is distributed to each radiation unit through the feed network. The 5G RRU completes the conversion and amplification of the baseband signal to the RF signal, drives the antenna to radiate, and processes the received signal.

[0120] The main design objectives of the hemispherical array antenna 01 are as follows: frequency band 3.4-3.6 GHz (center frequency 3.5 GHz); coverage angle: 360-degree omnidirectional coverage on the horizontal plane, and 30-60-degree upward coverage at an elevation angle of 30-60 degrees (radiating upward based on the horizontal plane, with a beam width of 30-60 degrees); gain: 8-10 dBi; structure: hemispherical curved array; application scenarios: supporting the three-dimensional coverage requirements of low-altitude drones, smart cities, and other scenarios, as well as filling in aerial network blind spots, with a coverage altitude of 50-500 meters.

[0121] The design of the hemispherical array antenna 01 is a wide-beam microstrip patch curved array antenna, including: patch unit design, hemispherical substrate 1 design, radiation unit design, feed network design, and mechanical structure design. The details are as follows:

[0122] Patch unit size design:

[0123] The patch is in the shape of a rectangular microstrip patch (low cost, easy to process) and is set on a substrate; the substrate material is FR4 (dielectric constant 4.4, thickness 1.6mm) or Rogers RO4350B (high performance, lower loss).

[0124] Theoretical calculation of patch unit size (taking Rogers RO4350B as an example):

[0125]

[0126] Where W is the patch width; c is the speed of light; f is the operating frequency (3.5 GHz); ε r : substrate dielectric constant; L: patch effective length; ε eff : effective dielectric constant; ΔL: edge extension correction.

[0127] Hemispherical substrate design:

[0128] Radius: R = 0.9λ (λ is the operating wavelength, assuming the 5G frequency band is 3.5GHz, λ≈85.7mm, then R≈77.13mm). Using Rogers RO4350B substrate (ε r =3.48, thickness 0.508mm), 3D printed hemispherical ceramic substrate, spherical curvature error ≤±0.1mm (3D printing accuracy must be guaranteed).

[0129] Hierarchical structure design:

[0130] Top dot matrix 21: located at the top of the sphere (θ = 0°, with the center of the sphere as the origin, and θ = 0° vertically upward), 1 square patch unit.

[0131] Concentric ring array:

[0132] First circular array 221: elevation angle θ = 30°, 8 patch elements evenly distributed;

[0133] Second circular array 222: elevation angle θ = 45°, 12 patch elements evenly distributed;

[0134] The third circular array 223 has an elevation angle θ = 60° and 16 patch elements are evenly distributed.

[0135] Unit spacing: The arc length between adjacent rings is ≤ 0.5λ (42.85mm) to avoid grating lobes.

[0136] The above design results are verified as shown in Table 3 below:

[0137] Table 3 Example of patch spacing verification on each layer

[0138] Hierarchy Elevation angle θ Ring radius r = R*sinθ Number of units Unit spacing (arc length) 2πr / n vertex 0° 0mm (single point on the top of the ball) 1 First Ring 30° 77.13*sin30°≈38.57mm 8 2π38.57 / 8=30.27mm Second Ring 45° 77.13*sin45°≈54.54mm 12 2π54.54 / 12≈28.5mm The third ring 60° 77.13*sin60°≈66.8mm 16 2π66.8 / 16≈26.2mm

[0139] Radiating unit design:

[0140] This dual-band microstrip patch (compatible with the 5G Sub-6GHz band) achieves a wide bandwidth (3.4-3.8GHz) through slot loading. This single-bandwidth patch uses slot loading to create a perturbation current path, extending the microstrip patch's bandwidth to 3.4-3.8GHz, covering the 5G Sub-6GHz band. Vertical polarization makes it suitable for low-altitude mobile terminals. The radiating element measures 24.5mm, with a central rectangular slot measuring 8mm by 2mm.

[0141] Feed network design:

[0142] Phase difference formula of each ring array unit: (θ=30°, 45°, 60°), for example, the third ring θ=60°, The phase difference between adjacent units increases by this value to achieve beamforming.

[0143] The top matrix feeding amplitude is the largest, and the amplitude of each ring decreases downward (weight coefficient 0.8→0.6→0.4), suppressing the side lobes.

[0144] Feeding method: Spherical conformal stripline feeding is used, the inner layer is the ground layer, the outer layer is the radiation layer, and the via is connected to the feeding point 31. The feeding point 31 is located 0.1λ=8.57mm away from the edge of the patch, and the impedance is matched to 50Ω.

[0145] Feed line width: The stripline width is 1.2 mm. Based on the Rogers RO4350B substrate (dielectric constant 3.48, thickness 0.508 mm), the line width is calculated to be 1.2 mm according to the microstrip line characteristic impedance formula to achieve a 50Ω match.

[0146] The laser engraved radiation patch and feed line are made on the ceramic substrate using a multi-layer PCB (Printed Circuit Board) process. The inner layer is the ground layer, the outer layer is the radiation patch, and the middle layer is the dielectric layer (Rogers RO4350B).

[0147] Mechanical structure design:

[0148] The supporting frame adopts a honeycomb hollow metal hemispherical shell (material: aluminum alloy) with a thickness of 1.5mm, an inner diameter of 128.6mm, and an outer diameter of 134.6mm.

[0149] The waterproof design uses an external PTFE film covering, IP67 protection level, 0.2mm thickness, covering the entire spherical surface.

[0150] Performance simulation verification:

[0151] Performance simulation verification has yielded the following directivity characteristics: horizontal omnidirectional error ≤±1.5dB, vertical beam pointing at a 45° elevation angle, 3dB beamwidth 40° (covering 30° to 60°); gain: 9.2dB (center frequency 3.6GHz); standing wave ratio (the ratio of the maximum to minimum standing wave amplitude on a transmission line, reflecting the degree of impedance matching) ≤1.5 (3.4 to 3.8GHz).

[0152] This design achieves efficient coverage of low-altitude 5G signals through innovative spherical array arrangement and phase control methods, combining high gain and precise beamforming capabilities; covers different elevation angles through spherical array layout and concentric ring array; adjusts horizontal omnidirectionality through progressive phase difference based on the progressive phase difference of spherical curvature; adopts 3D printing ceramic substrate + flexible circuit composite process, and adopts 3D printing of arc surface integrated structure to achieve high-precision spherical array manufacturing, solving the problem of spherical conformal circuit processing.

[0153] The comparison of the main indicators achieved by the hemispherical array antenna of this design with the traditional omnidirectional antenna is shown in Table 4 below:

[0154] Table 4 Comparison of the performance indicators of hemispherical array antenna and traditional omnidirectional antenna

[0155] parameter Traditional omnidirectional antenna This design hemispherical array Vertical beamwidth 120°+ 40°(30°-60° directional) Horizontal coverage 360° 360° omnidirectional Low-altitude drone signal strength -90dBm (edge weak area) -75dBm (stable coverage)

[0156] Advantages include:

[0157] The interference suppression capability is stronger. In terms of spatial filtering, the narrow beam avoids ground multipath reflection interference (the reflected signal attenuation with delay > 5μs is > 15dB); in terms of polarization isolation, the vertical polarization design suppresses co-channel interference (cross-polarization ratio > 25dB).

[0158] Energy efficiency and cost are optimized. In terms of radiation efficiency, the spherical conformal structure reduces surface wave loss and the efficiency reaches 85% (traditional planar array is about 70%). In terms of power consumption, under the same coverage range, the power consumption is reduced by 40% (due to energy focusing).

[0159] Based on the above advantages, the hemispherical array antenna provided in this embodiment can be expanded to other application scenarios, such as: high-altitude platform blind spot filling, when mounted on a balloon, it can provide continuous coverage (beam natural downward tilt) for low-altitude drone swarms 500m to 1km above the ground; smart city perception, 30° to 60° elevation angle beam matching signal reflection paths between buildings, enhancing AR navigation positioning accuracy; emergency communication, rapid deployment as a temporary base station, narrow beam to avoid co-frequency interference with surrounding base stations.

[0160] Example 2:

[0161] like Figure 4 As shown, the present application provides a low-altitude coverage base station, including:

[0162] The existing network base station consists of multiple active antenna units (AAUs) antenna 02, which provide mobile network service signals covering 120° in front of the base station.

[0163] The hemispherical array antenna 01 as described in Example 1 is arranged in the middle position between multiple AAU antennas 02 of the existing base station, and is used to provide blind spot compensation signals for the signal coverage blind spots upward between the multiple AAU antennas 02.

[0164] In one embodiment, it further includes:

[0165] The remote radio unit RRU03 is connected to the hemispherical array antenna 01 and is used to convert and amplify baseband signals into radio frequency signals, drive the hemispherical array antenna 01 to radiate, and process received signals.

[0166] In one embodiment, wherein:

[0167] AAU antenna 02 is a 5G AAU antenna using the fifth-generation mobile communication technology, RRU03 is a 5G RRU, and hemispherical array antenna 01 provides 5G Sub-6GHz frequency band radiation. The low-altitude coverage base station provides communication services for drone flight control and air traffic management.

[0168] Embodiments 1-2 of the present application provide a hemispherical array antenna 01 and a low-altitude coverage base station, by distributing an antenna array including a top dot matrix 21 and a multi-layer circular array on a hemispherical substrate 1. According to the elevation angle of the antenna units distributed on the hemispherical substrate 1, the radiation phase is controlled to maintain a certain phase difference. The phase difference is used to compensate for the path difference caused by the spherical curvature, so that the radiation fields of each layer are superimposed in phase at the target elevation angle, thereby compressing the vertical beam width, and realizing a hemispherical array antenna 01 with a compressed vertical plane beam. The hemispherical array antenna 01 is particularly suitable for low-altitude economic base station blind spot filling, but other application scenarios are not ruled out.

[0169] It is understood that the above embodiments are merely exemplary embodiments for illustrating the principles of the present application, and the present application is not limited thereto. Those skilled in the art may make various modifications and improvements without departing from the spirit and substance of the present application, and such modifications and improvements are also considered to be within the scope of protection of the present application.

Claims

1. A hemispherical array antenna, characterized in that: include: a hemispherical substrate for providing a curved surface structure supporting the antenna array; An antenna array distributed along the outer surface of a hemispherical substrate includes a top dot matrix and multiple layers of circular arrays. The top dot matrix and each layer of circular array each have an elevation angle of θ, which is the angle between a first axis and a second axis. The first axis is a line connecting the vertex of the hemispherical substrate and the center of the sphere. The second axis is a line connecting the center point of any antenna unit of the top dot matrix or each layer of circular array and the center of the hemispherical substrate. The center of each layer of circular array is located on the first axis. The feeding network is at least used for controlling the phase of the antenna array radiation, including applying a top-down increasing phase difference to the top dot array and the multi-layer circular array according to their respective θ.

2. The hemispherical array antenna according to claim 1, wherein: in: The phase difference formula between the top dot array and the multi-layer ring array is: Where λ is the wavelength of the main radiation of the antenna array, R is the radius of the hemispherical substrate, The unit is radian rad; The feed network is also used to control the amplitude of the antenna array radiation. The amplitude of the top dot array and the multi-layer circular array decreases from top to bottom.

3. The hemispherical array antenna according to claim 2, wherein: in: The number of antenna units in each layer of the multi-layer circular array increases gradually from top to bottom. The size of each antenna unit is determined by the material of the hemispherical substrate and the frequency / wavelength of the main radiation. The antenna units in each layer are evenly distributed, and the arc length distance d between the centers of any two adjacent antenna units is ≤0.5λ.

4. The hemispherical array antenna according to claim 3, characterized in that: in: The top dot matrix includes an antenna unit distributed at the vertex of the outer side surface of the hemispherical base at an elevation angle θ = 0°; The multi-layer ring array includes: The first circular array includes 8 antenna units evenly distributed on a first circular ring on the outer side of a hemispherical base with an elevation angle of θ=30°. The second circular array includes 12 antenna units evenly distributed on a second circular ring on the outer side of a hemispherical base with an elevation angle of θ=45°. The third circular array includes 16 antenna units evenly distributed on a third circular ring on the outer side of a hemispherical base with an elevation angle θ=60°; The amplitude weights of the top dot array and the multi-layer circular array are 1→0.8→0.6→0.4 from top to bottom.

5. The hemispherical array antenna according to any one of claims 1 to 4, characterized in that: in: Each antenna unit is a microstrip patch antenna unit, each antenna unit is vertically polarized, and provides wireless communication frequency Sub-6GHz below 6GHz.

6. The hemispherical array antenna according to claim 5, characterized in that: in: Each microstrip patch antenna unit is a rectangular microstrip patch antenna unit, which realizes a wide bandwidth with the main radiation frequency f = 3.5 ~ 3.6 GHz as the center frequency through slot loading. λ = c / f, c is the speed of light. The length and width of each rectangular microstrip patch antenna unit are calculated based on the material of the hemispherical substrate and the frequency / wavelength of the main radiation. The spherical curvature error of the hemispherical substrate is ≤ ±0.1mm, and the position deviation of each microstrip patch antenna unit is ≤ ±0.5mm.

7. The hemispherical array antenna according to claim 5, characterized in that: in: The radius of the hemispherical substrate R = A*λ, where A is designed according to the size and number of the antenna array and the arc length spacing d; The hemispherical substrate is 3D printed, and the antenna array and feed network are laser engraved on the outer and inner sides of the hemispherical substrate respectively; Each antenna unit is connected to a feeding point of the feeding network through a via hole. The impedance of each antenna unit and the feeding point is matched to Z0=50Ω. Each feeding point is 0.1λ away from the edge of the corresponding antenna unit.

8. The hemispherical array antenna according to claim 5, characterized in that: in: The material of the hemispherical substrate is FR4, a composite material based on epoxy resin and glass fiber cloth, or Rogers RO4350B, a ceramic / hydrocarbon laminate reinforced with glass cloth. The dielectric constant of FR4 is ε r =4.4, thickness h = 1.6mm, the dielectric constant ε of RogersRO4350B r =3.48, thickness h = 0.508mm; The vertical coverage height of the antenna array is not less than 500m, the horizontal plane has 360° omnidirectional coverage, the omnidirectional error is ≤±1.5dB, the vertical plane beam points to a 45° elevation angle, the 3dB beam width covers 30°~60°, the gain is 8~10dBi, and the standing wave ratio is ≤1.

5.

9. The hemispherical array antenna according to claim 8, characterized in that: Also includes: The hemispherical base is supported by a honeycomb hollow aluminum alloy hemispherical shell with a thickness of 1.2 to 2.0 mm and a hollowing rate of 60 to 70%. The hemispherical substrate is covered with polytetrafluoroethylene (PTFE) film to ensure that the hemispherical array antenna reaches the required protection level. It has an interface for connecting to the radio remote unit RRU, and is connected to the RRU through a radio frequency cable. The RRU output signal is distributed to each antenna unit through the feed network.

10. A low-altitude coverage base station, characterized in that: include: The existing base station consists of multiple active antenna units (AAUs), which provide mobile network service signals covering 120° in front of the base station. The hemispherical array antenna according to any one of claims 1 to 9 is arranged in the middle position between multiple AAU antennas of an existing base station, and is used to provide a blind spot compensation signal for the signal coverage blind spots upward between the multiple AAU antennas.

11. The low-altitude coverage base station according to claim 10, characterized in that: Also includes: The remote radio unit (RRU) is connected to the hemispherical array antenna and is used to convert and amplify baseband signals into radio frequency signals, drive the hemispherical array antenna to radiate, and process received signals.

12. The low-altitude coverage base station according to claim 10 or 11, characterized in that: in: The AAU antenna is the fifth-generation mobile communication technology 5GAAU antenna, the RRU is 5GRRU, the hemispherical array antenna provides 5G Sub-6GHz frequency band radiation, and the low-altitude coverage base station provides communication services for drone flight control and air traffic management.

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