Miniaturized Beidou anti-interference array antenna with low mutual coupling

Abstract

The antenna comprises an antenna dielectric plate, a radiator array, a metal ground, a decoupling structure, a low-noise amplification module, an anti-interference integrated module and a complete machine protection structure, the decoupling structure is composed of an antenna ground decoupling structure and a ferrite wave absorber, and the space of the antenna ground decoupling structure and the space of the ferrite wave absorber are precisely overlapped. And a'blocking + absorbing 'dual decoupling mechanism is formed. The antenna ground decoupling structure is etched on the metal ground to block ground current so as to suppress electric coupling; the ferrite wave-absorbing body is embedded into a strong coupling area of the antenna dielectric plate to absorb near-field magnetic energy so as to suppress magnetic coupling. Under the compact layout that the array element spacing is smaller than or equal to 0.35 lambda, the actually measured isolation between the array elements is smaller than or equal to-25 dB, the radiation efficiency is larger than or equal to 65%, the axial ratio is smaller than or equal to 3 dB, the ideal null-null value of the array is increased by 10 dB or above, the overall section height is smaller than or equal to 10 mm, and the problem that low mutual coupling, miniaturization and high radiation performance are difficult to consider is effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of antenna technology for BeiDou satellite navigation systems, specifically relating to a miniaturized BeiDou anti-interference array antenna with low mutual coupling. Background Technology

[0002] With the comprehensive deployment and widespread application of my country's BeiDou Navigation Satellite System (BDS), the importance of high-precision, high-reliability navigation and positioning services in military, transportation, surveying and mapping, emergency communications, and unmanned aerial vehicle (UAV) fields is becoming increasingly prominent. However, in complex electromagnetic environments, navigation receivers are highly susceptible to intentional or unintentional radio frequency interference (such as suppression interference and deceptive interference), leading to positioning failure or even system paralysis. To improve system reliability, anti-interference array antenna technology based on adaptive beamforming has become a key development direction for BeiDou terminals.

[0003] Anti-jamming array antennas typically consist of multiple antenna elements arranged in a specific geometric configuration. Digital signal processing is used to adjust the weights of each channel in real time, creating spatial nulls to suppress interference signals. The effectiveness of this technology highly depends on the good low mutual coupling characteristics between the array elements. Strong mutual coupling between array elements will lead to: (1) Crosstalk between channels disrupts the amplitude and phase consistency of the received signal; (2) The performance of the adaptive algorithm is severely degraded, and it cannot accurately form interference nulls; (3) The direction finding accuracy decreases, affecting the stability of positioning.

[0004] Meanwhile, modern mobile platforms (such as small drones, handheld terminals, and vehicle-mounted devices) impose stringent constraints on the size, weight, and profile height of antenna systems, necessitating miniaturized designs. However, traditional methods for reducing mutual coupling (such as increasing element spacing, introducing electromagnetic bandgap structures, metamaterial coatings, and loading decoupling networks) often sacrifice compactness, conflicting with the miniaturization goal.

[0005] Therefore, it is urgent to propose a new type of BeiDou anti-interference array antenna structure that can significantly suppress electromagnetic mutual coupling between array elements and improve channel isolation while ensuring overall miniaturization, thereby providing a reliable hardware foundation for the stable and high-precision operation of BeiDou terminals in strong interference environments.

[0006] Currently, to suppress mutual coupling between array elements, existing technologies mainly employ the following methods: (1) Increasing the spacing between array elements can effectively reduce coupling, but it goes against the trend of miniaturization; (2) Adding metal isolation walls is an intuitive and commonly used physical decoupling method, but its suppression of magnetic coupling is limited, it introduces additional weight and volume, which goes against the trend of miniaturization / lightweighting, and may excite parasitic resonances and degrade radiation performance. Additional simulation optimization is required, and the design cycle is long. (3) Introducing electromagnetic bandgap (EBG) or artificial magnetic conductor (AMC) structures can suppress surface waves, but they are usually complex in structure, have limited bandwidth and high processing cost; (4) Loading an active decoupling network or matching circuit can improve mutual coupling at specific frequency points, but introducing additional active devices will increase noise, power consumption and system complexity, and it is difficult to cover multiple frequency bands of Beidou (such as B1 / B3 / B2a).

[0007] (5) Parasitic decoupling unit. Although it can reduce coupling, the parasitic unit itself occupies extra space, which is not conducive to miniaturization. The decoupling effect is highly dependent on the size, position and frequency of the parasitic unit. The bandwidth is narrow and it is difficult to cover multiple frequency bands at the same time. It may affect the radiation pattern and impedance matching of the main antenna. It needs to be repeatedly optimized and has high design complexity.

[0008] (6) Metamaterial coating can reduce coupling to a certain extent. However, the metamaterial structure is thick and heavy, which will destroy miniaturization and low profile. The bandwidth is extremely narrow. Most of them are resonant designs, which are difficult to process, expensive, and difficult to mass-produce.

[0009] Although the aforementioned decoupling methods have achieved certain results in specific scenarios, existing technologies still generally suffer from the limitations of "single mechanism and local optimization," and in particular, they lack a systematic design that integrates multiple physical decoupling methods for spatial coordination and functional complementarity.

[0010] This "single-point breakthrough, isolated implementation" approach makes it difficult to balance multiple objectives such as miniaturization constraints, multi-band coverage, low mutual coupling, and maintaining radiation performance. Especially in applications like BeiDou anti-jamming array antennas, which have extremely high requirements for channel consistency and phase stability, relying solely on a single decoupling mechanism often results in compromises and fails to achieve a broadband, robust, and mass-producible engineering solution.

[0011] Therefore, there is an urgent need for a collaborative decoupling architecture that integrates structural control and material dissipation, and to construct a low-coupling array antenna system that is truly suitable for compact BeiDou terminals by jointly suppressing multi-physics coupling paths. Summary of the Invention

[0012] In view of the above-mentioned technical problems in the prior art, the purpose of this invention is to provide a miniaturized BeiDou anti-interference array antenna with low mutual coupling, which solves the problem of strong mutual coupling between array elements caused by the small spacing between array elements in the compact layout of existing miniaturized BeiDou anti-interference array antennas. At the same time, it takes into account the antenna's radiation performance, multi-band coverage capability and engineering mass production feasibility, ensures the effectiveness of the adaptive anti-interference algorithm, and improves the positioning stability and anti-interference capability of BeiDou terminals in complex electromagnetic environments.

[0013] To address the aforementioned technical problems, embodiments of the present invention provide the following technical solution: a miniaturized BeiDou anti-interference array antenna with low mutual coupling, comprising an antenna dielectric substrate, a radiator array, a metal ground, and a decoupling structure; the radiator array is disposed on the front side of the antenna dielectric substrate, and is a four-element circularly polarized radiator arranged in a centrally symmetrical, right-rotating array. Each radiator is single-fed and uses a chamfered structure to excite two orthogonal degenerate modes and introduce a 90° phase difference to achieve circularly polarized radiation; the metal ground is entirely copper-clad and disposed on the back side of the antenna dielectric substrate; the decoupling structure includes antenna ground decoupling. The structure and ferrite absorber are spatially coordinated and functionally complementary, forming a joint suppression mechanism for electrical and magnetic coupling. The antenna ground decoupling structure is a slotted geometric pattern etched on the metal ground and located between adjacent radiators, used to block the path of ground current and suppress surface wave propagation. The ferrite absorber is a ferrite absorber embedded on the radiating surface of the antenna dielectric substrate and located in the strong coupling region between adjacent radiators, used to absorb near-field magnetic energy and suppress magnetic coupling, and the projection of the ferrite absorber on the horizontal plane completely covers the area of ​​the slotted geometric pattern.

[0014] Furthermore, the antenna dielectric substrate is a TP antenna dielectric substrate with dimensions of 110mm×110mm×5mm and a dielectric constant of 10.2; the element spacing of the radiator array is ≤0.35λ, where λ is the center wavelength of the BeiDou operating frequency band, achieving a compact antenna layout and meeting the installation requirements of small mobile platforms.

[0015] Furthermore, the ferrite absorber is made of a high-dielectric-constant ferrite absorbing material with a sawtooth design. The ferrite absorbing material is a rigid epoxy composite material of nickel-zinc ferrite or manganese-zinc ferrite series. It has an electromagnetic wave attenuation efficiency of 12.6dB / cm in the 1GHz band and has a high magnetic loss tangent and moderate relative permeability in the BeiDou 1.1–1.6GHz operating frequency band. This ensures efficient absorption of near-field magnetic energy while avoiding excessively high permeability that could cause antenna resonant frequency shift or excessively high Q value, thus preventing deterioration of radiation performance.

[0016] Furthermore, an absorber embedding groove is formed on the antenna dielectric board corresponding to the strong coupling region of the adjacent radiator. The depth of the absorber embedding groove is 2mm. The ferrite absorber adopts a structure in which it is embedded 2mm inside the absorber embedding groove and exposed 2mm outside. This thickness design ensures sufficient magnetic loss while minimizing the obstruction of the radiation field. The ferrite absorber is fixed in the absorber embedding groove by applying adhesive and is locked in place with mounting screws and nuts to ensure the stability and reliability of the structure and to adapt to vibration scenarios such as drones.

[0017] Furthermore, the geometric parameters of the slotted geometric pattern are optimized for the entire BeiDou frequency band, including slot length, slot width, and arm length, so that the metal ground forms a high impedance characteristic in the BeiDou B1 / B3 / B2a frequency band, achieving high isolation across the entire frequency band and meeting the anti-interference application requirements of the entire BeiDou system. The slotted geometric pattern is directly etched onto the metal ground using PCB etching technology, without additional vertical structures or shielding walls, eliminating the need to increase the size and weight of the antenna and ensuring miniaturized design.

[0018] Furthermore, the antenna also includes a low-noise amplifier module, which comprises a low-noise amplifier PCBA and a shield. The low-noise amplifier PCBA is soldered and fixed to the back of the metal ground via reserved pads and is set close to the antenna dielectric board. This design reduces the use of RF transmission lines, effectively reduces insertion loss and noise introduction, and improves the system integration. The shield covers the low-noise amplifier PCBA to shield external electromagnetic interference and prevent the circuit's own interference from radiating outward, ensuring the operational stability of the low-noise amplifier circuit.

[0019] Furthermore, the antenna also includes an integrated anti-interference module and an RF transmission component. The RF transmission component includes RF cables, SMA connectors, and J30J-15P connectors. The four elements of the radiator array are electrically connected to the integrated anti-interference module via RF cables. The integrated anti-interference module integrates up-conversion circuits and digital anti-interference baseband processing circuits, and is packaged in a small metal cavity. The highly integrated architecture significantly improves the system's compactness and electromagnetic compatibility (EMC), effectively enhancing the robustness and anti-interference capability of the entire device in complex electromagnetic environments. The integrated anti-interference module outputs one RF signal and one RS422 serial port signal through SMA connectors and J30J-15P connectors, respectively, facilitating connection with external BeiDou receivers or terminal equipment.

[0020] Furthermore, the antenna also includes a complete protective structure, which comprises an antenna radome, antenna cavity, sealing ring, waterproof and breathable valve, and connector assembly. The antenna cavity is made of aluminum alloy, precision CNC machined, and anodized to form a dense oxide film, providing electromagnetic shielding, structural support, and heat dissipation. It also effectively improves corrosion resistance and insulation performance, maintaining good conductivity to ensure RF grounding integrity. The radome is made of ABS material, covering the opening of the antenna cavity, and is lightweight with good protective performance. The sealing ring is made of closed-cell silicone and is located at the joint surface between the radome and the antenna cavity to achieve a seal. The screw mounting holes in the antenna cavity are blind holes filled with sealant to prevent through holes from becoming water seepage channels, enabling the entire antenna to achieve an IP67 protection rating.

[0021] Furthermore, the overall protective structure also includes a wire baffle and mounting screws. The wire baffle is located inside the antenna cavity and is used to organize the radio frequency cables. The mounting screws are evenly distributed on the mating surface between the antenna cover and the antenna cavity to tighten the sealing ring and achieve a reliable seal. The mounting screws, together with the nuts on the back, fix the ferrite absorber to the antenna dielectric substrate.

[0022] Furthermore, the antenna features a purely passive planar design, eliminating the need for active decoupling circuits and additional power supply modules. This prevents the introduction of additional noise, power consumption, or nonlinear distortion, effectively ensuring receiver sensitivity. The overall antenna profile height is ≤10mm, the measured isolation between array elements is ≤-25dB, the radiation efficiency is ≥65%, the axial ratio is ≤3dB, and the ideal null value of the array is improved by more than 10dB compared to structures without decoupling. This achieves a good balance between miniaturization, low mutual coupling, and high radiation performance.

[0023] The beneficial effects of the above-described technical solution of the present invention are as follows: 1. This invention adopts a spatially coordinated layout of antenna-ground decoupling structure and ferrite absorber to form a dual decoupling mechanism of "blocking + absorption". It achieves joint suppression of mutual coupling between array elements from both electrical and magnetic coupling dimensions. Under a compact layout with an array element spacing of ≤0.35λ, the measured isolation between array elements can reach below -25dB, which effectively solves the problem of strong mutual coupling under miniaturized layout, ensures the effectiveness of adaptive anti-interference algorithm, and improves the ideal null value of the array by more than 10dB compared with the structure without decoupling, significantly improving the anti-interference capability of Beidou terminal.

[0024] 2. This invention uses high magnetic loss ferrite absorbing materials from the nickel-zinc / manganese-zinc ferrite series to fabricate ferrite absorbers, replacing traditional carbon-based or polymer microwave absorbing materials. This material still possesses high permeability and an electromagnetic wave attenuation efficiency of 12.6 dB / cm in the BeiDou 1.1–1.6 GHz low-frequency band, and can efficiently absorb near-field magnetic energy. It effectively solves the technical pain point of difficult magnetic coupling suppression in the BeiDou low-frequency band in the prior art, and achieves low mutual coupling coverage of the entire BeiDou B1 / B3 / B2a frequency band, meeting the anti-interference application requirements of the entire BeiDou system.

[0025] 3. This invention employs a multi-dimensional, refined design of the ferrite absorber, placing it only in the strong coupling region between adjacent array elements, avoiding the main radiation region and high field strength regions near the feed. The thickness is controlled to a structure of 2mm embedded in the absorber groove and 2mm exposed. The material is ferrite with moderate relative permeability, and the shape adopts a sawtooth design that matches the outline of the slotted geometric pattern, achieving "precise dissipation of the coupling path." While ensuring low mutual coupling, the antenna's radiation efficiency is maintained above 65%, and the axial ratio is better than 3dB. This effectively solves the technical problem of balancing decoupling effect and radiation performance, ensuring the receiving sensitivity and positioning accuracy of BeiDou satellite signals.

[0026] 4. The antenna ground decoupling structure of this invention is directly etched onto the metal ground using PCB etching technology, without any additional vertical structure or shielding wall; the ferrite absorber is fixed in the absorber embedding slot by embedding and mounting, and the antenna as a whole is a pure passive planar design, without active decoupling circuits and additional power supply modules, and will not introduce additional noise, power consumption or nonlinear distortion; the overall antenna profile height is ≤10mm, the structure is compact and the weight is light, which fully meets the requirements of small mobile platforms such as drones, handheld terminals, and vehicle-mounted equipment for antenna size, weight and profile height.

[0027] 5. This invention solders the low-noise amplifier PCBA tightly to the back of the antenna dielectric board, reducing the use of RF cables, effectively reducing insertion loss and noise introduction, and improving system integration. The anti-interference integrated module integrates the up-conversion circuit and the digital anti-interference baseband processing circuit in a small metal cavity, improving the electromagnetic compatibility of the system. At the same time, the antenna is designed with a complete IP67 protection structure. The aluminum alloy antenna cavity has electromagnetic shielding, structural support and heat dissipation functions. Multiple protection measures such as closed-hole silicone sealing ring, waterproof connector, and blind hole sealing ensure that the antenna can operate stably for a long time in harsh environments such as humidity, dust and vibration.

[0028] 6. The overall design of this invention does not require complex processing technology and expensive materials. The metal ground decoupling structure adopts mature PCB etching technology, and the ferrite absorber can be CNC machined. The whole machine is assembled with common components such as mounting screws and sealing rings. The process is simple, the cost is low, and it has the characteristics of high reliability and easy deployment. Attached Figure Description

[0029] Figure 1 This is a block diagram illustrating the working principle of the four-element anti-interference array antenna of the present invention. Figure 2 This is a schematic diagram of the front and back structures of the array antenna of the present invention without a decoupling structure; Figure 3 This is a test curve of the coupling value of the array antenna elements in this invention without a decoupling structure; Figure 4 This is a surface current distribution diagram of the antenna in this invention without a decoupling structure; Figure 5 This is a schematic diagram of the slotted geometric pattern of the antenna ground decoupling structure of the present invention; Figure 6 This is a schematic diagram of the antenna surface current distribution after adding an antenna ground decoupling structure according to the present invention; Figure 7 A schematic diagram of the structure of the array antenna of the present invention with the addition of a ferrite absorber; Figure 8 The array element coupling value test curves are shown for the two decoupling structures added to this invention. Figure 9 To provide a comparison test diagram of the array element gain before and after the decoupling structure in this invention; Figure 10 The array zero-trap value test diagram after adding the decoupling structure to the present invention; Figure 11 This is a three-dimensional exploded view of the overall structure of the anti-interference antenna of the present invention; Figure 12 This is a two-dimensional schematic diagram of the overall structure of the anti-interference antenna of the present invention.

[0030] In the diagram: 1-Radiator cover, 2-Sealing ring, 3-Ferrite absorber, 4-Antenna dielectric board, 5-Antenna ground decoupling structure, 6-Low noise amplifier PCBA, 7-RF cable, 8-Wire baffle, 9-Antenna cavity, 10-J30J-15P connector, 11-SMA connector, 12-Radiator array, 13-Absorber embedding slot, 14-Anti-interference integrated module, 15-Waterproof and breathable valve, 16-Mounting screw. Detailed Implementation

[0031] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0032] This invention provides a miniaturized BeiDou anti-interference array antenna with low mutual coupling, aiming to solve the problem of strong mutual coupling caused by the small spacing between array elements in the compact layout of existing miniaturized array antennas, ensuring the effectiveness of the adaptive anti-interference algorithm, while taking into account antenna radiation performance, miniaturization requirements and engineering mass production feasibility, and providing hardware support for high-precision and high-reliability navigation and positioning of BeiDou terminals in complex electromagnetic environments.

[0033] The core of this invention lies in the synergistic innovative design of the antenna's metallic ground and ferrite absorbing material. These two elements precisely overlap spatially and complement each other functionally, forming a dual decoupling mechanism of "blocking + absorption." The special slotted design of the metallic ground primarily suppresses electrical coupling between array elements by physically blocking the path of ground current. The ferrite absorbing material primarily suppresses magnetic coupling between array elements by absorbing and dissipating near-field magnetic field energy through the material's magnetic loss characteristics. Together, they significantly reduce the total mutual coupling between array elements within the BeiDou operating frequency band, achieving a measured isolation of below -25dB (array element spacing ≤ 0.35λ), far superior to the -10 to -15dB of traditional miniaturized array antennas. Furthermore, while achieving low mutual coupling, it effectively maintains the antenna's high radiation efficiency and good circular polarization characteristics.

[0034] The following is a detailed description of the technical solution: This invention designs a four-element anti-jamming array antenna specifically for small unmanned aerial vehicle (UAV) navigation systems. Its main operating frequency band is the BeiDou B1 / L1 band, while also being compatible with the full BeiDou B3 / B2a band. Its overall working principle is as follows: Figure 1 As shown, this antenna system receives circularly polarized radio frequency (RF) signals from BeiDou navigation satellites via a 4-element B1L1 antenna array. The received satellite signals are first amplified by a low-noise amplifier (LNA) to effectively reduce noise introduction during signal transmission. The amplified signal is then converted to an intermediate frequency (IF) signal by a down-conversion circuit and subsequently sent to a digital anti-interference baseband processing module. This module, based on an adaptive beamforming algorithm, collects the signal amplitude and phase information of each array element channel in real time. By dynamically adjusting the weights of each channel, it creates spatial nulls in the direction of interference signal incidence, accurately identifying and suppressing RF interference signals from one or more directions. The clean satellite signal, after spatial adaptive filtering, is then converted back to an RF signal by an up-conversion circuit. This signal can be directly used for testing and calibration or transmitted back to the UAV flight control system. Finally, the BeiDou receiver performs navigation calculations and outputs high-precision position, velocity, time, and other navigation information. The entire signal processing process achieves precise anti-interference in the spatial domain, significantly improving the positioning reliability and flight safety of the UAV in complex electromagnetic environments.

[0035] Since this antenna is directly applied to a small unmanned aerial vehicle (UAV) system, the UAV's fuselage size, payload, and installation space are subject to stringent limitations. This places extreme demands on the miniaturization and lightweighting of the antenna system's size, weight, and profile height. Therefore, this invention strictly controls the antenna element spacing to ≤0.35λ (λ is the center wavelength of the BeiDou B1 band), achieving an ultra-compact antenna array layout. However, under this compact layout, the electromagnetic coupling between elements is drastically enhanced, directly leading to a severe degradation in the performance of the anti-interference adaptive algorithm, making it impossible to accurately form interference nulls. The element coupling characteristics of the antenna become the core bottleneck restricting the overall anti-interference system from achieving high performance. To address this key technical problem, this invention, through multiple rounds of simulation optimization and physical testing verification, designed a step-by-step decoupling structure optimization process to gradually achieve efficient suppression of electrical and magnetic coupling. The specific optimization process is as follows: I. Basic Array Antenna Structure Design (without decoupling structure) First, a four-element anti-interference array antenna without any decoupling structure was designed as the basic verification model. Its front and back structures are as follows: Figure 2 As shown. This basic array antenna uses a single integrated TP antenna dielectric substrate. The substrate's dimensions (length × width × height) are precisely designed to be 110mm × 110mm × 5mm, with a dielectric constant of 10.2. This dielectric constant parameter has been selected through multiple rounds of simulations to ensure both the antenna's radiation performance and the impedance matching requirements under miniaturized layout. The antenna radiator adopts a single-feed method, abandoning the complex dual-feed or multi-feed structures. This simplifies the antenna manufacturing process while reducing signal loss caused by the feed network. By designing a chamfered structure at the edge of the radiator, two orthogonal degenerate modes (such as TM) are excited through perturbation. 10 and TM 01By precisely optimizing the chamfer dimensions, a 90° phase difference is naturally introduced between the two degenerate modes, achieving stable circular polarization radiation and ensuring efficient reception of BeiDou satellite circular polarization signals. The four antenna radiators are arranged in a centrally symmetrical, right-rotating array, with the array center coinciding with the center of the antenna substrate. The rotation angle has been optimized through simulation to ensure the radiation direction of each element. Figure 1 For consistency, the back of the antenna is a full-surface copper-clad metal ground, which provides good RF grounding for the antenna, while effectively suppressing back radiation and improving the forward radiation gain of the antenna.

[0036] Electromagnetic simulation and physical testing were performed on the undecoupled basic array antenna. The test results are as follows: Figure 3 As shown, within the operating bandwidth of BeiDou B1 / B3 / B2a, the maximum overall coupling between array elements is 12.5dB, indicating severe electromagnetic coupling between elements, which fails to meet the channel isolation requirements of anti-interference algorithms; for example... Figure 4 As shown, the antenna surface current distribution test reveals that there is no obstruction to the ground current flow path between adjacent array elements, and the surface wave propagates freely along the dielectric-ground interface, resulting in significant electrical coupling between array elements and severe crosstalk in each channel signal, which directly affects the weight adjustment accuracy of the adaptive beamforming algorithm.

[0037] 2. Add a metal ground decoupling structure to suppress electrical coupling. Based on the basic array antenna, this invention first adds a metallic ground decoupling structure to suppress electrical coupling between array elements. Its structural design is as follows: Figure 5 As shown, specifically, a specially simulated and optimized slotted structure and geometric pattern are added to the common metal ground on the back of the antenna using PCB etching technology. This slotted geometric pattern is precisely etched into the ground plane area between adjacent array elements. Its geometric parameters, such as slot length, slot width, arm length, and bending angle, are all customized and optimized for the entire BeiDou B1 / B3 / B2a frequency band. This enables the metal ground to form a high impedance characteristic within the entire BeiDou operating frequency band, directly blocking the flow path of ground current from a physical structure perspective. This effectively suppresses surface waves propagating along the dielectric-ground interface and reduces long-distance coupling between array elements. At the same time, the design of the slotted geometric pattern can change the local electric field distribution of the metal ground, reduce the electric field overlap between adjacent array elements, and further suppress electromagnetic coupling between array elements through the ground plane.

[0038] The surface current distribution of the array antenna after the addition of a metallic ground decoupling structure was tested, and the results are as follows: Figure 6 As shown, after adding the metal ground decoupling structure, the surface current of the antenna metal ground is significantly blocked by the slotted structure. The ground current that originally flowed freely between adjacent array elements is restricted to the ground area corresponding to a single array element. The coupling energy between adjacent array elements is greatly reduced, and the electrical coupling is significantly suppressed.

[0039] 3. Add ferrite absorbers to suppress magnetic coupling. Building upon the effective reduction of surface current coupling effects by the metallic decoupling structure, this invention further incorporates a ferrite absorber to specifically suppress magnetic coupling between array elements. Its structural design is as follows: Figure 7 The black section shows the process. Specifically, a 2mm deep absorber embedding groove is made on the front side of the dielectric substrate between antenna elements, along the gap between adjacent elements. A specially designed high-dielectric-constant ferrite absorber is embedded in the groove. This ferrite absorber adopts a sawtooth shape design. Compared with traditional rectangular absorbers, the sawtooth design can effectively increase the absorption surface of electromagnetic waves, extend the propagation path of electromagnetic waves inside the absorber, and significantly improve the magnetic energy absorption efficiency.

[0040] The ferrite absorbing material selected in this invention is a rigid epoxy composite material of nickel-zinc / manganese-zinc ferrite series. This material is a special composite material that is lossy, magnetic, and machinable, and has extremely high electromagnetic wave absorption efficiency. In the 1GHz frequency band, its electromagnetic wave attenuation efficiency can reach 12.6dB / cm, which is much higher than that of ordinary carbon-based or polymer absorbing materials. At the same time, this material still has high magnetic loss tangent characteristics in the BeiDou 1.1–1.6GHz low frequency band, which can efficiently absorb the near-field magnetic energy leaked between array elements, thereby significantly suppressing the magnetic coupling between array elements.

[0041] It is worth noting that while ferrite absorbing materials possess excellent low-frequency magnetic loss characteristics, their high permeability and dielectric loss can also adversely affect the radiation performance of the antenna itself. Specifically, if the ferrite material coverage area is too large, the thickness is too high, or the permeability parameter is improperly selected, excessive absorption of electromagnetic energy in the main radiation direction will occur, leading to problems such as decreased antenna gain, reduced radiation efficiency, and deteriorated axial ratio, thereby severely affecting the receiving sensitivity and positioning accuracy of BeiDou satellite signals. To address this technical contradiction, this invention achieves a perfect balance between magnetic coupling suppression and antenna radiation performance through multi-dimensional and refined design optimization. The specific optimization measures are as follows: 1) Spatial positioning optimization: Ferrite material is precisely placed only in the strong coupling area between adjacent array elements, that is, the area directly above the metal ground slot structure, strictly avoiding the main radiation area of ​​the antenna and the high field strength area near the feed, so as to avoid the influence of ferrite material on satellite signal reception in space. 2) Thickness optimization: After simulation iteration and physical testing, the ferrite absorber was finally designed as a composite structure with 2mm embedded in the dielectric layer and 2mm exposed, with a total thickness of 4mm. This thickness design ensures sufficient magnetic loss to suppress magnetic coupling while minimizing the obstruction of the antenna radiation field and avoiding excessive loss of radiated energy. 3) Material parameter optimization: Ferrite system materials with high magnetic loss tangent but moderate relative permeability are selected in the Beidou B1 / B3 / B2a frequency band (1.1–1.6GHz) to avoid antenna resonant frequency shift or Q value too high due to excessive permeability, and to ensure the impedance matching and radiation stability of the antenna in the whole frequency band. 4) Shape matching optimization: The sawtooth contour of the ferrite absorber is basically consistent with the regional contour of the slotted structure of the metal ground below, realizing "precise dissipation of coupling path", absorbing only the coupling magnetic energy between the elements, without affecting the normal radiation of the antenna.

[0042] Through the above-mentioned multi-dimensional and refined design, after simultaneously adding a metal ground slot and a ferrite absorber to the array antenna, a comprehensive electromagnetic performance test was conducted, and the results are as follows: Figure 8 , Figure 9 , Figure 10 As shown, the isolation level between array elements is significantly improved, and the maximum coupling value is reduced to 25.5dB, which is 12dB lower than that of the basic array antenna without any decoupling structure. At the same time, the overall radiation efficiency of the antenna is stably maintained above 65%, and the axial ratio is better than 3dB, which fully meets the requirements of Beidou high-precision navigation for the circular polarization characteristics of the antenna. The ideal null value of the array is improved by more than 10dB compared with the basic model, and the effectiveness of the anti-interference algorithm is fully guaranteed. All performance indicators meet the engineering application requirements of Beidou anti-interference terminals.

[0043] IV. Overall Structure Integration and Design of Anti-interference Antenna Based on the optimization of the core radiation structure and decoupling structure of the array antenna, this invention further completes the integrated design of the anti-interference antenna structure, achieving a high degree of integration of antenna radiation, signal amplification, anti-interference processing, and overall protection. The three-dimensional exploded view and two-dimensional schematic diagram of the overall structure are shown below. Figure 11 , Figure 12 As shown.

[0044] (1) Integrated design of core structure This invention integrates the antenna array with the decoupling structure. The four antenna radiators are directly fabricated on a single dielectric substrate and arranged in a symmetrical, clockwise array to form a four-element antenna array. The back of the antenna is a copper-clad metal ground, on which the decoupling geometric pattern is directly etched using an etching process, eliminating the need for additional splicing structures and effectively ensuring the integrity and processing precision of the antenna structure. High-strength thermally and electrically conductive adhesive is coated into the groove embedded in the antenna radiating surface to bond and fix the ferrite absorbing material within the groove. Four mounting screws, along with nuts on the back, are used for mechanical locking. This dual fixing method of bonding and mechanical fixation ensures both the fit between the ferrite absorbing material and the antenna dielectric substrate and effectively resists vibrations and impacts during UAV flight, ensuring the stability of the decoupling structure and adapting to the harsh working environment of UAVs.

[0045] The metal ground decoupling structure is directly etched onto the antenna ground plane using a mature PCB etching process, without the need for any additional vertical structures or metal shielding walls, and without increasing the overall thickness and volume of the antenna. The ferrite absorber is precision machined using CNC and fixed to the antenna dielectric board by surface mounting, without the need for complex assembly processes. The overall cross-sectional height of the antenna array can be strictly controlled to ≤10mm, resulting in a compact size and light weight, making it perfectly suitable for mobile platforms that are highly sensitive to size and weight, such as drones, handheld terminals, and vehicle-mounted equipment.

[0046] (2) Integrated design of low-noise amplifier module On the back of the antenna's metal ground plane, this invention integrates a first-stage low-noise amplifier circuit closely attached to the antenna. The low-noise amplifier PCBA is directly soldered and fixed to the metal ground plane on the back of the antenna via pre-reserved pads, achieving close-range integration of the low-noise amplifier and the antenna radiator. This design significantly shortens the RF signal transmission path, reduces the use of RF transmission lines, effectively reduces signal insertion loss and noise introduction, and significantly improves the antenna's receiving sensitivity. Simultaneously, a metal shield fully encloses and shields the low-noise amplifier PCBA. This shield is well grounded to the metal ground, preventing interference from complex external electromagnetic environments and ensuring circuit stability. It also prevents electromagnetic interference generated by the circuit itself from radiating outwards and affecting the normal operation of the antenna radiator, further improving the system's electromagnetic compatibility.

[0047] (3) Integrated module design of anti-interference circuit This invention integrates the antenna's up-conversion circuit and digital anti-interference baseband processing circuit into a single module, forming an integrated anti-interference module within a small metal cavity. This highly integrated architecture not only significantly reduces the circuit size and improves the system's compactness, but the shielding effect of the metal cavity also effectively isolates external electromagnetic interference, improving the circuit's electromagnetic compatibility (EMC). This, in turn, effectively enhances the overall robustness and anti-interference capability of the device in complex electromagnetic environments.

[0048] The RF signals output from the four antenna elements are electrically connected to the integrated anti-interference module via low-loss RF cables. After processing by the anti-interference module, the entire antenna outputs only one RF signal and one RS422 serial port signal. Simultaneously, the core radiation and decoupling structure of the entire antenna array is a purely passive design, requiring no active decoupling circuitry or additional power supply. This avoids introducing additional noise, power consumption, and nonlinear distortion, effectively ensuring receiver sensitivity, further simplifying the antenna structure, and reducing the overall failure rate.

[0049] (4) Overall protective structure design To adapt to various harsh working environments such as drones, vehicle-mounted devices, and field base stations, this invention features a high-protection-level structural design for the antenna assembly. The antenna assembly adopts a split upper and lower cavity structure, with the lower cavity made of high-strength aluminum alloy and the radome made of engineering-grade ABS material. The entire assembly incorporates comprehensive waterproof, dustproof, and vibration-resistant design, with specific protective measures as follows: 1) Cavity Material and Processing: The antenna cavity is made of high-strength aluminum alloy through precision CNC machining. This material has excellent electromagnetic shielding, structural support and heat dissipation functions. It can effectively shield external electromagnetic interference, provide reliable mechanical support for internal components, and dissipate the heat generated by the low-noise amplifier PCBA and anti-interference integrated module in a timely manner to ensure the stability of circuit operation. The surface of the aluminum alloy cavity is anodized to form a dense oxide film, which effectively improves the corrosion resistance and insulation performance of the cavity, while maintaining good conductivity continuity and ensuring the integrity of RF grounding.

[0050] 2) Sealing Structure Design: A closed-cell silicone sealing ring is installed at the joint surface between the aluminum alloy lower cavity and the ABS radome. This sealing ring has excellent elasticity and aging resistance. It is pressed and sealed by evenly distributed mounting screws to form a reliable waterproof and dustproof barrier. All external interfaces, including the RF output port and power / communication interface, use waterproof connectors. The joint between the connector and the cavity is sealed with potting compound to completely block the infiltration path of moisture and dust. All screw mounting holes are designed as blind holes with sealant filling structure to avoid through holes becoming water seepage channels and structurally eliminate the risk of water leakage.

[0051] Combining the above content and Figure 12 The working principle of this invention is as follows: The working principle of this BeiDou anti-interference array antenna is based on a dual decoupling mechanism of "blocking + absorption" and adaptive beamforming technology, achieving high-performance anti-interference under a miniaturized layout. The antenna dielectric substrate 4 is a TP substrate, with a radiator array 12 on the front. It adopts a four-element circularly polarized structure with a centrally symmetrical, right-rotating array. Each radiator excites orthogonal degenerate modes through single feeding and corner cutting, introducing a 90° phase difference to achieve stable circularly polarized radiation for receiving BeiDou satellite signals. The back of the antenna is a copper-clad metal ground, providing RF ground and suppressing back radiation.

[0052] In a compact layout with an element spacing ≤0.35λ, to suppress strong electromagnetic coupling, the decoupling structure consists of an antenna-to-ground decoupling structure 5 and a ferrite absorber 3. The antenna-to-ground decoupling structure 5 is a slotted geometric pattern etched onto a metal ground plane, located between adjacent radiators. It blocks the path of ground current flow and suppresses surface wave propagation, thereby reducing electrical coupling. The ferrite absorber 3 is embedded in the absorber embedding slot 13 on the front side of the antenna dielectric substrate 4, located in the strong coupling region between adjacent radiators. It uses high magnetic loss materials such as nickel-zinc / manganese-zinc ferrite to absorb near-field magnetic energy and suppress magnetic coupling. The two structures spatially overlap and functionally complement each other, achieving low mutual coupling.

[0053] The received RF signal is amplified by the low-noise amplifier PCBA6, which is shielded to isolate interference. The amplified signal is transmitted to the anti-interference integrated module 14 via RF cable 7. This module integrates up-conversion and digital anti-interference baseband processing circuits, and uses an adaptive beamforming algorithm to create spatial nulls in the interference direction to suppress suppression or deceptive interference. After processing, one RF signal is output via SMA connector 11, and one RS422 serial port signal is output via J30J-15P connector 10 for use by external receivers.

[0054] The entire unit adopts a protective structure: the antenna cavity 9 is made of aluminum alloy, the antenna cover 1 is made of ABS material, and a sealing ring 2 is provided at the joint surface to achieve waterproof and dustproof protection; a waterproof and breathable valve 15 balances the internal and external air pressure; a cable baffle 8 organizes the RF cables 7; and mounting screws 16 are evenly distributed, pressing the sealing ring and fixing the ferrite absorber 3 and the antenna dielectric board 4. The overall antenna profile height is ≤10mm, the measured isolation is ≤-25dB, the radiation efficiency is ≥65%, and the axial ratio is ≤3dB, meeting the miniaturization and high reliability requirements of Beidou anti-interference terminals.

[0055] In summary, this invention constructs a BeiDou anti-interference array antenna that combines low coupling, miniaturization, multi-frequency compatibility, and high radiation efficiency through the spatially coordinated layout and functionally complementary design of the antenna's metallic ground decoupling structure and ferrite absorber. This effectively solves the technical challenge of simultaneously achieving low mutual coupling, miniaturization, and high radiation performance in existing miniaturized BeiDou array antennas. This antenna not only achieves a balance between low mutual coupling and high radiation performance across the entire BeiDou frequency band in terms of electromagnetic performance, but also achieves high integration, miniaturization, and high protection levels in its structural design. It features low cost, high reliability, and easy deployment, and can be widely used in various BeiDou terminals such as UAVs, handheld terminals, vehicle-mounted equipment, and emergency communication base stations. This has significant industrial implications for promoting the deep application of the BeiDou navigation system in key areas such as intelligent driving, unmanned systems, emergency communication, and surveying and mapping.

[0056] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A miniaturized BeiDou anti-interference array antenna with low mutual coupling, characterized in that, The antenna includes an antenna dielectric substrate (4), a radiator array (12), a metal ground, and a decoupling structure. The radiator array (12) is located on the front side of the antenna dielectric substrate (4) and is a four-element circularly polarized radiator arranged in a center-symmetric, right-rotating array. Each radiator is fed by a single feed and excites two orthogonal degenerate modes through a chamfered structure, and introduces a 90° phase difference to achieve circularly polarized radiation. The metal ground is entirely copper-clad and located on the back side of the antenna dielectric substrate (4). The decoupling structure includes an antenna ground decoupling structure (5) and a ferrite absorber (3). The antenna ground decoupling structure (5) is a slotted geometric pattern etched on the metal ground and located between adjacent radiators to block the path of ground current flow and suppress surface wave propagation. The ferrite absorber (3) is a ferrite absorber embedded on the radiating surface of the antenna dielectric substrate (4) and located in the strong coupling region between adjacent radiators to absorb near-field magnetic energy and suppress magnetic coupling. The projection of the ferrite absorber (3) on the horizontal plane completely covers the area of ​​the slotted geometric pattern.

2. The miniaturized BeiDou anti-interference array antenna with low mutual coupling according to claim 1, characterized in that, The antenna dielectric substrate (4) is a TP antenna dielectric substrate with dimensions of 110mm×110mm×5mm and a dielectric constant of 10.

2.

3. The miniaturized BeiDou anti-interference array antenna with low mutual coupling according to claim 1, characterized in that, The ferrite absorber (3) is made of a high dielectric constant ferrite absorbing material with a sawtooth design. The ferrite absorbing material is a rigid epoxy composite material of nickel-zinc ferrite or manganese-zinc ferrite series.

4. A miniaturized BeiDou anti-interference array antenna with low mutual coupling according to claim 1, characterized in that, The antenna dielectric substrate (4) has a wave absorber embedding groove (13) in the strong coupling area corresponding to the adjacent radiator. The depth of the wave absorber embedding groove (13) is 2mm. The ferrite wave absorber (3) adopts a structure in which it is embedded in the wave absorber embedding groove (13) for 2mm and exposed for 2mm. The ferrite wave absorber (3) is fixed in the wave absorber embedding groove (13) by applying adhesive and is locked in place by mounting screws (16) and nuts.

5. A miniaturized BeiDou anti-interference array antenna with low mutual coupling according to claim 1, characterized in that, The geometric parameters of the slotted geometric pattern are optimized by the BeiDou full-band design, including slot length, slot width, and arm length. The slotted geometric pattern is directly etched onto the metal ground using PCB etching process.

6. A miniaturized BeiDou anti-interference array antenna with low mutual coupling according to claim 1, characterized in that, It also includes a low-noise amplifier module, which includes a low-noise amplifier PCBA (6) and a shield. The low-noise amplifier PCBA (6) is fixed to the back of the metal ground by pre-reserved solder pads and is set close to the antenna dielectric board (4). The shield covers the low-noise amplifier PCBA (6) to shield external electromagnetic interference and prevent the circuit's own interference from radiating outward.

7. A miniaturized BeiDou anti-interference array antenna with low mutual coupling according to claim 1, characterized in that, It also includes an integrated anti-interference module (14) and a radio frequency transmission component. The radio frequency transmission component includes a radio frequency cable (7), an SMA connector (11), and a J30J-15P connector (10). The four array elements of the radiator array (12) are electrically connected to the integrated anti-interference module (14) through the radio frequency cable (7). The integrated anti-interference module (14) integrates up and down conversion circuits and digital anti-interference baseband processing circuits and is packaged in a small metal cavity. The integrated anti-interference module (14) outputs one radio frequency signal and one RS422 serial port signal to the outside through the SMA connector (11) and the J30J-15P connector (10), respectively.

8. A miniaturized BeiDou anti-interference array antenna with low mutual coupling according to claim 1, characterized in that, It also includes a whole-machine protective structure, which includes an antenna cover (1), an antenna bottom cavity (9), a sealing ring (2), and a waterproof and breathable valve (15). The antenna bottom cavity (9) is made of aluminum alloy, CNC machined and anodized. The antenna cover (1) is made of ABS material and covers the opening of the antenna bottom cavity (9). The sealing ring (2) is made of closed-cell silicone material and is located on the mating surface of the antenna cover (1) and the antenna bottom cavity (9). The waterproof and breathable valve (15) is located on the antenna bottom cavity (9). The screw mounting holes of the antenna bottom cavity (9) are blind holes and filled with sealant.

9. A miniaturized BeiDou anti-interference array antenna with low mutual coupling according to claim 8, characterized in that, The overall protective structure also includes a wire baffle (8) and mounting screws (16). The wire baffle (8) is located inside the antenna cavity (9) and is used to organize the radio frequency cable (7). The mounting screws (16) are evenly distributed on the mating surface of the antenna cover (1) and the antenna cavity (9) to press the sealing ring (2) to achieve sealing. The mounting screws (16) cooperate with the nuts on the back to fix the ferrite absorber (3) to the antenna dielectric plate (4).

10. A miniaturized BeiDou anti-interference array antenna with low mutual coupling according to any one of claims 1-9, characterized in that, The antenna is a purely passive planar design with no active decoupling circuit or additional power supply module. The overall profile height is ≤10mm, the measured isolation between array elements is ≤-25dB, the radiation efficiency is ≥65%, and the axial ratio is ≤3dB.

Images