Low coupling multi-modal OAM array antenna and decoupling method

Abstract

The application relates to a low-coupling multi-modal OAM array antenna and a decoupling method, and belongs to the technical field of antennas. In view of the problems of serious mutual coupling between radiation units, high sidelobe level, difficulty in multi-modal generation and high system complexity of an existing OAM array antenna, a novel antenna structure is provided. The antenna adopts a double-layer metal floor structure composed of circular metal plates with adjustable spacing between the upper and lower layers, and guides the current by adjusting and controlling the layer distance and surface slot line distribution to suppress the mutual coupling between units; the annular radiation array is composed of a plurality of coaxial circular ring sub-arrays arranged at non-equal intervals, and each sub-array comprises a plurality of radiation units arranged at non-equal intervals; each radiation unit is provided with an excitation signal with a specific phase gradient through a one-to-one corresponding feeding probe to realize the generation of a multi-modal OAM beam. The scheme effectively reduces the coupling, suppresses the sidelobe and supports high-purity multi-modal OAM beam output without relying on a complex active system.

Description

Technical Field

[0001] This application relates to the field of radar detection, and in particular to a low-coupled multimode OAM array antenna and a decoupling method. Background Technology

[0002] In modern wireless communication and radar systems, orbital angular momentum (OAM) electromagnetic waves possess unique spatial mode orthogonality due to their spiral phase leader characteristics, providing a new technical path for improving spectrum utilization and achieving multiplexing. Currently, the main methods for generating OAM beams include array geometry-based design and digital beamforming techniques. The former constructs a vortex wavefront by symmetrically arranging multiple radiating elements in a ring or spiral shape and applying specific phase gradient excitation, offering advantages such as simple structure and physical intuitiveness. The latter utilizes independent transmit and receive channels to precisely control the amplitude and phase of each element, achieving flexible multimodal synthesis and demodulation in the digital domain, and is widely used in high-degree-of-freedom beamforming scenarios. These technologies have shown promising application prospects in millimeter-wave communication, high-resolution imaging, and target recognition.

[0003] However, traditional OAM arrays based on geometric structures suffer from severe mutual coupling between radiating elements, causing the excitation distribution to deviate from the ideal state, affecting OAM beam purity and orthogonality, and making it difficult to effectively suppress sidelobe levels. Furthermore, achieving multimode switching typically requires complex feeding networks or reconfiguration mechanisms, increasing system losses and design complexity. While digital beamforming methods offer high flexibility, they rely on numerous active devices and high-speed signal processing units, resulting in high hardware costs, high power consumption, and high system complexity, limiting their widespread application on low-cost, miniaturized platforms. Therefore, how to effectively suppress mutual coupling, improve pattern performance, and support multimode OAM beam generation while reducing system complexity has become a key challenge facing the development of current OAM antenna technology. Summary of the Invention

[0004] The purpose of this application is to provide a low-coupling multimode OAM array antenna. This invention can effectively suppress the mutual coupling effect between radiating elements while reducing system complexity and cost, and support the generation and sidelobe suppression of multimode OAM beams.

[0005] To achieve the above objectives, this application adopts the following technical solution: In a first aspect, this application provides a low-coupling multimode OAM array antenna, comprising: a double-layer metal ground plane structure serving as a support and electromagnetic boundary structure, a ring-shaped radiating array disposed thereon, and an integrated structure for coupling suppression and feeding for excitation signal input; The double-layer metal floor structure includes two parallel circular metal plates, the distance between the two metal plates is adjustable, which is used to regulate the current distribution on the antenna surface, and the two metal plates are connected through the outer surface of the radiating unit. The annular radiation array is located on the upper surface of the lower panel of the double-layer metal floor structure and passes through the upper panel of the double-layer metal floor structure; the annular radiation array includes multiple annular sub-arrays that are coaxial with the double-layer metal floor structure and are not equally spaced, and each annular sub-array is composed of several radiation units with the same structure and not equally spaced. The integrated coupling suppression and feeding structure includes several feeding probes, each corresponding to a radiating element in the annular radiating array. These probes are used to provide the radiating element with the required amplitude and a specific phase gradient to generate a multimode OAM beam.

[0006] As a further improvement of this application, the annular radiation array also includes a separate central radiation element located at the center of the array, which can suppress the coupling effect of other elements on the central element.

[0007] As a further improvement of this application, the radiation structure of the radiation unit is horn-shaped, placed perpendicular to the plane of the double-layer metal floor structure and closely connected to the double-layer metal floor structure.

[0008] As a further improvement of this application, the horn-shaped radiating unit includes a rectangular horn metal structure and a multi-level graded metal stepped structure disposed therein; the feeding probe passes through the lower panel of the double-layer metal floor structure and is connected to the multi-level graded metal stepped structure.

[0009] As a further improvement of this application, the annular radiation array includes seven layers of annular subarrays extending outward from the center, and each subarray contains multiple radiation elements. The double-layer metal floor structure and the annular radiation array are made of metal; the feed probe is made of polytetrafluoroethylene wrapped around a metal column.

[0010] As a further improvement of this application, the annular radiation array includes seven layers of annular subarrays extending outward from the center. The number of radiation units in each subarray is 6, 12, 18, 26, 32, 26 and 26, respectively, and they are distributed in a non-equal manner to adapt to the phase modulation requirements under different radii.

[0011] As a further improvement of this application, the surface of the upper metal plate of the double-layer metal floor structure is loaded with a groove structure. The groove is arranged radially or circumferentially to guide the surface current path and further weaken the mutual coupling effect between the radiating units.

[0012] This application provides a decoupling method for a low-coupling multimode OAM array antenna based on the aforementioned double-layer ground plane multidirectional current modulation. The method achieves the modulation of the antenna surface current by adjusting the spacing between the upper and lower metal plates and the loading slot line in the double-layer metal ground plane structure. A specific phase gradient excitation is applied to each radiating element in the ring radiating array through the coupling suppression and feeding integrated structure. The modulated surface current distribution cancels the mutual coupling current between radiating elements, reduces the mutual coupling effect between elements, improves the radiation pattern, suppresses sidelobes, and supports the generation of high-purity multimode OAM beams.

[0013] As a further improvement of this application, the spacing of the double-layer metal floor structure is adjustable, and the surface current distribution is adjusted by loading the groove lines. The height of each level and the transition curve of the multi-level graded metal stepped structure are determined according to the required radiation characteristics.

[0014] As a further improvement of this application, the multimode OAM beam includes no less than 7 different modes of OAM beam, and the sidelobe level suppression is lower than -12dB through feed amplitude and phase optimization.

[0015] Compared with the prior art, this application has the following technical effects: This application effectively controls the current distribution path on the antenna surface by introducing an adjustable-spacing double-layer metal ground plane structure, thereby physically weakening the electromagnetic mutual coupling effect between radiating elements and improving antenna efficiency and radiation stability. By employing a non-equidistant concentric ring subarray layout combined with a one-to-one corresponding feed probe structure, precise control of the excitation amplitude and phase of each radiating element is achieved without the need for a complex digital beamforming system. This supports the flexible generation of multiple OAM modes while maintaining good orthogonality. The integrated design of coupling suppression and feeding functions simplifies the overall structure and reduces manufacturing difficulty and system losses. The horn-shaped radiating element integrates a multi-level graded metal ladder structure, enhancing impedance matching capability and energy transmission efficiency, significantly improving far-field radiation pattern characteristics, and effectively suppressing sidelobe levels. The overall solution significantly reduces system complexity and hardware costs while ensuring high performance, making it suitable for applications with high requirements for multi-dimensional information carrying capacity, such as radar detection and high-capacity wireless communication. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall structure of the low-coupling multimode OAM array antenna in the embodiments listed in this application; Figure 2 This is a schematic diagram of the antenna radiating element structure of the embodiments listed in this application; Figure 3 The far-field radiation patterns of the OAM array under different modes were obtained through simulation in the embodiments listed in this application. Detailed Implementation

[0017] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of this application.

[0018] The first objective of this application is to provide a low-coupled multimode OAM (Orbital Angular Momentum) array antenna based on a double-layer ground plane with multidirectional current modulation, comprising: a double-layer metal ground plane structure L1, a ring radiating array L2, and an integrated coupling suppression and feeding structure L3; The double-layer metal floor structure L1 includes two parallel circular metal plates, with an adjustable spacing between them to regulate the surface current distribution of the antenna. The two metal plates are connected through the outer surface of the radiating element. Grooves are loaded on the surface of the metal plates to achieve surface current distribution adjustment. Among them, the annular radiation array L2 is located on the upper surface of the lower panel of the double-layer metal floor structure L1 and passes through the upper panel of the double-layer metal floor structure L1; the annular radiation array L2 includes multiple annular subarrays that are coaxial with the double-layer metal floor structure L1 and are not equally spaced. Each annular subarray consists of several radiation units with the same structure and not equally spaced. The number of radiation units contained in each subarray is designed according to the radiation requirements. The coupling suppression and feeding integrated structure L3 includes several feeding probes A3, which correspond one-to-one with the radiating elements in the ring radiating array L2. These probes are used to provide the radiating elements with the required amplitude and a specific phase gradient to generate multimode OAM beams.

[0019] Specifically, the ring-shaped radiating array L2 also includes a separate central radiating element located at the center of the array. Its radiation performance differs from the other elements, and its radiating structure design suppresses the coupling effects of other elements on the central element. The radiating element has a horn-shaped radiating structure, placed perpendicular to the plane of the double-layer metal floor structure L1 and tightly connected to it. This horn-shaped radiating structure, perpendicular to the plane of the double-layer metal floor and electrically connected to it, enhances directivity and improves grounding performance.

[0020] More specifically, the horn-shaped radiating unit includes a rectangular horn-shaped metal structure A1 and a multi-level graded metal stepped structure A2 disposed inside it; the feed probe A3 passes through the lower panel of the double-layer metal floor structure L1 and is connected to the multi-level graded metal stepped structure A2. The multi-level graded metal stepped structure is disposed inside the rectangular horn-shaped metal structure, and the height and transition curve of each level can be optimized according to the required radiation characteristics; Specifically, the multi-level graded metal stepped structure consists of three metal steps, with the height and transition curve of each step designed according to impedance matching and radiation pattern optimization objectives. The ring-shaped radiation array L2 comprises seven ring-shaped sub-arrays extending outward from the center. The number of radiating elements in each sub-array is designed according to radiation requirements. The ring-shaped radiation array comprises seven ring-shaped sub-arrays extending outward from the center, with each sub-array containing 6, 12, 18, 26, 32, 26, and 26 radiating elements, respectively, exhibiting a non-uniform distribution to accommodate phase modulation requirements at different radii.

[0021] As a specific design, the double-layer metal ground plane structure L1 and the annular radiation array L2 are made of metal; the feed probe A3 is made of polytetrafluoroethylene (PTFE) wrapped around a metal pillar to ensure good electromagnetic performance. The outer insulating medium provides good high-frequency insulation and mechanical support, preventing electromagnetic crosstalk between adjacent probes.

[0022] Specifically, the spacing between the upper and lower metal plates in the double-layer metal floor structure can be adjusted from 10mm to 30mm to adapt to the surface current distribution optimization requirements under different operating frequency bands or coupling states. The upper metal plate of the double-layer metal floor structure has a grooved structure loaded on its surface, with the grooves arranged radially or circumferentially to guide the surface current path and further weaken the mutual coupling effect between radiating units. The feed probe passes through the lower metal plate of the double-layer metal floor structure and is directly connected to the multi-level graded metal stepped structure inside the corresponding radiating unit, achieving efficient energy transmission and stable electrical contact.

[0023] Furthermore, by controlling the amplitude and phase gradient of the excitation signal of each radiating element, at least seven different OAM beams can be generated simultaneously, with good orthogonality and spatial separation characteristics among the modes. When generating multimode OAM beams, by optimizing the excitation amplitude and phase distribution, the sidelobe level suppression (besides the main lobe) is reduced to below -12dB, thereby improving the antenna's anti-interference capability and detection accuracy.

[0024] The antenna of this application includes a metal ground plane as a support and electromagnetic boundary structure, a ring-shaped radiating array disposed thereon, and a feeding structure for excitation signal input. The metal ground plane is a double-layer metal ground plane structure consisting of two parallel circular metal plates with an adjustable spacing between them. The two layers are physically connected to the outer surface of the radiating elements to regulate the current distribution on the antenna surface. The ring-shaped radiating array is located on the upper surface of the lower metal plate and extends outward through the upper metal plate. It includes multiple ring-shaped sub-arrays that are coaxial with the double-layer metal ground plane and arranged at non-equidistant intervals. Each sub-array consists of several radiating elements with the same structure and arranged at non-equidistant intervals. The antenna also includes an integrated coupling suppression and feeding structure containing several feeding probes that are connected to each radiating element one by one to provide an excitation signal with a specific phase gradient and amplitude distribution to generate a multimode OAM beam. By using a double-layer metal ground plane structure and slotted loading to regulate surface current, compared to traditional OAM arrays, it can effectively reduce the mutual coupling effect between radiating elements, thereby improving antenna efficiency and radiation performance; it can flexibly generate no fewer than seven OAM modes, with good orthogonality among the modes, making it suitable for radar detection and other scenarios; it does not require a complex beamforming system, has a relatively simple structure, and does not require a complex feed network or expensive active devices, resulting in lower cost and ease of fabrication; it effectively suppresses sidelobe levels, which helps improve radar anti-interference capability and detection accuracy.

[0025] The spacing of the double-layer metal floor structure L1 is adjustable, and the surface current distribution is regulated through slot loading. The multi-mode OAM beam includes no fewer than seven different modes of OAM beams, and sidelobe level suppression is below -12dB through feed amplitude and phase optimization. The height and transition curve of each stage of the multi-level graded metal stepped structure A2 are optimized according to the required radiation characteristics.

[0026] The second objective of this application is to provide a decoupling method for a low-coupling multimode OAM array antenna, comprising: adjusting the current distribution on the antenna surface by adjusting the spacing between the upper and lower metal plates in the double-layer metal ground plane structure L1; applying a specific phase gradient excitation to each radiating element in the ring radiating array L2 through the coupling suppression and feeding integrated structure L3; and canceling the mutual coupling current between the radiating elements by adjusting the surface current distribution, thereby reducing the mutual coupling effect, improving the antenna radiation pattern, suppressing sidelobes, and generating a high-purity multimode OAM beam.

[0027] By controlling the amplitude and phase gradient of the excitation signal of each radiating element, it is possible to generate at least 7 different modes of OAM beams simultaneously, with good orthogonality and spatial separation characteristics among the modes.

[0028] Therefore, the aforementioned device includes a double-layer metal ground plane structure, a ring-shaped radiating array, and an integrated coupling suppression and feeding structure. The double-layer metal ground plane structure consists of two parallel circular metal plates with adjustable spacing between the upper and lower layers, used to regulate the surface current distribution. The ring-shaped radiating array consists of multiple concentric ring subarrays and a single central radiating element. The integrated coupling suppression and feeding structure provides the radiating elements with the required amplitude and a specific phase gradient excitation through a feeding probe. This application, by adjusting the spacing between the double-layer ground planes and the slot line loading, and applying a specific phase excitation, regulates the antenna surface current distribution to counteract the mutual coupling effect between radiating elements, effectively suppressing sidelobes, improving the antenna's radiation performance, and generating high-purity multimode OAM beams. This application solves the problems of severe mutual coupling, high sidelobes, difficulty in multimode generation, or excessive system complexity in existing OAM arrays, and has the advantages of low cost, high performance, and ease of fabrication.

[0029] The specific structure of this application will be described below with reference to specific embodiments.

[0030] This application provides a low-coupling multimode OAM array antenna, such as... Figure 1 As shown, it includes: a double-layer metal floor structure L1, a ring-shaped radiating array L2, and an integrated coupling suppression and feeding structure L3. The surface of the upper panel of the double-layer metal floor structure L1 is loaded with grooves, and the ring-shaped radiating array L2 is located on the upper surface of the lower panel of the double-layer metal floor structure L1 and passes through the upper panel of the double-layer metal floor structure L1.

[0031] The annular radiating array L2 comprises seven annular subarrays coaxial with the double-layer metal plate and arranged at non-equidistant intervals, and a single central radiating element. The annular subarrays expand outwards from the center, and each annular subarray consists of several structurally identical radiating elements arranged at non-equidistant intervals. There are seven layers from the center to the edge of the double-layer metal plate, with each layer containing 6, 12, 18, 26, 32, 26, and 26 radiating elements, respectively. The radiating structure of the radiating element is horn-shaped, placed perpendicular to the plane of the double-layer metal floor structure L1, and closely connected to the double-layer metal floor structure L1.

[0032] Among them, such as Figure 2 As shown, the radiating unit includes a rectangular horn-shaped metal structure A1, a multi-level graded metal stepped structure A2, and a feed probe A3. The multi-level graded metal stepped structure A2 and the feed probe A3 pass through the lower panel of the double-layer metal floor structure L1 and are connected to the multi-level graded metal stepped structure A2.

[0033] This application provides a decoupling method for a low-coupled multimode OAM array antenna based on multidirectional current modulation of a double-layer ground plane. This method involves adjusting the spacing between the upper and lower metal plates in the double-layer metal ground plane structure L1 and the loading groove lines. The embodiments of this application can obtain OAM beams with seven modes, such as... Figure 3As shown, simulations can obtain the far-field radiation patterns of the OAM array in the E and H planes under seven modes, achieving sidelobe level suppression of less than -12dB.

[0034] In this embodiment, the double-layer metal floor structure L1 has a radius of 270mm and a thickness of 2mm, with a spacing of 20mm between the upper and lower metal plates; the multi-level gradient metal step structure A2 has 3 levels, with heights of 6mm, 6mm, and 1.59mm from top to bottom, and a width of 4.7mm.

[0035] This application discloses a novel integrated antenna architecture. Specifically, the antenna is mounted on a circular mounting base with a diameter of 540mm. The double-layer metal ground plane structure L1 consists of two circular copper plates, each 540mm in diameter and 2mm thick, made of T2 copper, which has high conductivity and is easy to process. The upper and lower plates are aligned at the center with a spacing of 20mm, adjustable within the range of 10–30mm via a precision screw mechanism. The two metal plates are electrically connected through the outer metal structure of the annular radiating array, forming a closed electromagnetic environment. The annular radiating array L2 is located on the upper surface of the lower ground plane and comprises seven concentric circular subarrays with radii of 30mm, 60mm, 90mm, 120mm, 150mm, 180mm, and 210mm from the center, respectively. The number of radiating elements in each layer is 6, 12, 18, 26, 32, 26, and 26, respectively, exhibiting a non-equidistant and non-uniform distribution to break periodic symmetry and reduce mode crosstalk. All radiating units are vertically mounted rectangular horn structures, 25mm high, with an opening size of 15mm × 15mm, and connected at the bottom to a multi-level stepped metal structure. The feed probe (A3) is a 2mm diameter silver-plated copper pillar, encased in a PTFE insulating layer (5mm outer diameter), passing through holes in the bottom floor and precisely docking to the stepped feed point of each unit. The signal source is input via an SMA interface, directly exciting the radiating units through the probe, applying a phase gradient step of 0° to 315° (e.g., ...). =+1 mode corresponds to an increment of 45° per unit), realizing multi-mode OAM beamforming.

[0036] This antenna reduces electromagnetic coupling between elements by controlling the surface current path through a double-layer ground plane; the non-equidistant ring array increases spatial freedom and supports flexible phase configuration; and the integrated feeding structure ensures excitation accuracy and avoids complex network losses. This implementation significantly reduces mutual coupling between radiating elements (measured S21 < -25dB), improves OAM beam purity and orthogonality, and can stably generate multimode vortex beams without the need for a digital beamforming system. It has the advantages of compact structure, low cost, and excellent performance.

[0037] To adapt to different frequency bands and performance indicators, this embodiment features a customized design for a multi-level stepped metal structure. A three-dimensional electromagnetic model was established using Ansys HFSS, with three steps. Variable parameters included the heights h1, h2, and h3 of each step, and the type of sidewall transition curve (right angle, circular arc, exponential). Parameter scanning and optimization algorithms (such as DFMO) were used to find the combination that minimizes S11 and maximizes bandwidth. The optimal solution was determined to be: h1=6mm, h2=6mm, h3=1.59mm, with a 3mm circular arc transition curve. This structure exhibits a return loss better than -15dB in the 33–35GHz band, approximately 4dB better than a straight-wall structure. In practical applications, the design can be adjusted to 2 or 4 steps depending on specific requirements; this embodiment does not limit this. This optimized design enables the stepped structure to achieve the best impedance gradient effect over a wide frequency range, improving energy transmission efficiency and radiation consistency. This embodiment enhances the design freedom of the radiating element, allowing for precise tuning of antenna performance for specific application scenarios.

[0038] To meet the requirements of high-capacity communication and multi-target detection, this implementation supports the generation of... = ±1, ±2, ..., ±7, a total of 14 OAM modes. Each mode is controlled by a host computer via a multi-channel phase shifter and attenuator, independently setting the excitation amplitude and phase of each radiating element. The phase is set according to... distribute( The amplitude is weighted using a Taylor distribution to optimize the radiation pattern performance (where azimuth is the k-th unit). The excitation parameters are optimized through MATLAB simulation, aiming to minimize the maximum sidelobe level outside the main lobe. Experimental results show that at 34 GHz, the average sidelobe voltage of all modes is below -12 dB, the main lobe width is stable at approximately 18°, and the inter-mode correlation is less than -15 dB, exhibiting good orthogonality. This multi-mode excitation strategy, combined with amplitude and phase joint optimization, effectively suppresses stray radiation while ensuring mode separation. This implementation achieves high-purity, low-interference multi-mode OAM beam output, providing reliable physical layer support for multiplexing systems.

[0039] The low-coupling multimode OAM array antenna proposed in this application has the following advantages: 1) By adjusting the spacing of the double-layer metal ground plane and the slot line loading to regulate the distribution of the antenna surface current, this device can effectively suppress and reduce the mutual coupling effect between radiating elements, thereby improving the antenna's radiation characteristics. 2) It helps to make the actual excitation of the array closer to the ideal distribution, thereby suppressing sidelobe levels and improving the antenna's anti-interference capability. 3) Without the need for complex digital beamforming systems and high-cost hardware, it can reliably generate multimode high-purity OAM beams by providing the required amplitude and excitation with a specific phase gradient through a simple feeding structure, reducing system complexity and cost. 4) This device has a simple structure, high reliability, is easy to manufacture, and is easy to implement.

[0040] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A low-coupling multimode OAM array antenna, characterized in that, include: The structure consists of a double-layer metal floor (L1) serving as a support and electromagnetic boundary structure, a ring-shaped radiation array (L2) mounted thereon, and an integrated structure for coupling suppression and power feeding for excitation signal input (L3). The double-layer metal floor structure (L1) includes two parallel circular metal plates, the distance between the two metal plates is adjustable, and it is used to regulate the current distribution on the antenna surface. The two metal plates are connected through the outer surface of the radiating unit. The annular radiation array (L2) is located on the upper surface of the lower panel of the double-layer metal floor structure (L1) and passes through the upper panel of the double-layer metal floor structure (L1); the annular radiation array (L2) includes multiple annular subarrays that are coaxial with the double-layer metal floor structure (L1) and are not equally spaced, and each annular subarray is composed of several radiation units with the same structure and not equally spaced; The integrated coupling suppression and feeding structure (L3) includes several feeding probes (A3), each of which corresponds to a radiating element in the annular radiating array (L2). The feeding probes (A3) are used to provide the radiating element with the required amplitude and phase gradient excitation. Each mode can independently set the excitation amplitude and phase of each radiating element to generate a multimode OAM beam.

2. The low-coupling multimode OAM array antenna according to claim 1, characterized in that, The ring-shaped radiation array (L2) also includes a separate central radiation element located at the center of the array. This separate central radiation element can suppress the coupling effect of other elements on the central element.

3. The low-coupling multimode OAM array antenna according to claim 1, characterized in that, The radiation unit has a horn-shaped radiation structure, is placed perpendicular to the plane of the double-layer metal floor structure (L1), and is closely connected to the double-layer metal floor structure (L1).

4. A low-coupling multimode OAM array antenna according to claim 3, characterized in that, The horn-shaped radiating unit includes a rectangular horn metal structure (A1) and a multi-level graded metal stepped structure (A2) disposed inside it; the feed probe (A3) passes through the lower panel of the double-layer metal floor structure (L1) and is connected to the multi-level graded metal stepped structure (A2).

5. A low-coupling multimode OAM array antenna according to claim 1, characterized in that, The annular radiating array (L2) comprises seven layers of annular subarrays extending outward from the center, and each subarray contains multiple radiating elements; The double-layer metal floor structure (L1) and the annular radiation array (L2) are made of metal; the feed probe (A3) is made of polytetrafluoroethylene wrapped around a metal column.

6. A low-coupling multimode OAM array antenna according to claim 1, characterized in that, The annular radiation array comprises seven layers of annular subarrays extending outward from the center. The number of radiation units in each subarray is 6, 12, 18, 26, 32, 26 and 26, respectively, and they are distributed in a non-uniform manner to adapt to the phase modulation requirements under different radii.

7. A low-coupling multimode OAM array antenna according to claim 1, characterized in that, The upper metal plate of the double-layer metal floor structure is loaded with a grooved structure, which is arranged radially or circumferentially to guide the surface current path.

8. A decoupling method for a low-coupling multimode OAM array antenna, based on a low-coupling multimode OAM array antenna according to any one of claims 1-7, characterized in that, include: The current distribution on the antenna surface can be controlled by adjusting the spacing between the upper and lower metal plates in the double-layer metal ground plane structure (L1). Phase gradient excitation is applied to each radiating element in the ring radiating array (L2) through the integrated coupling suppression and feeding structure (L3); By adjusting the surface current distribution, the mutual coupling current between radiating elements is canceled out, thereby reducing the mutual coupling effect, improving the antenna radiation pattern, suppressing sidelobes, and generating a high-purity multimode OAM beam.

9. The decoupling method for a low-coupling multimode OAM array antenna according to claim 8, characterized in that, The spacing of the double-layer metal floor structure (L1) is adjustable, and the surface current distribution is adjusted by loading the groove lines. The height of each level and the transition curve of the multi-level graded metal stepped structure (A2) are determined according to the required radiation characteristics.

10. The decoupling method for a low-coupling multimode OAM array antenna according to claim 8, characterized in that, The multi-mode OAM beam includes no fewer than 7 different modes of OAM beam, and sidelobe level suppression is reduced to less than -12dB through feed amplitude and phase optimization.

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