A flexible ultra-wideband MIMO antenna based on composite decoupling structure

Abstract

The application relates to a flexible ultra-wideband MIMO antenna based on a composite decoupling structure and belongs to the technical field of antennas. The antenna comprises a flexible dielectric substrate, antenna units, a ground plate, a parasitic isolation unit and parasitic elements arranged on one side of the flexible dielectric substrate; the antenna units are arranged in a rotationally symmetrical manner around the center on the front surface of the flexible dielectric substrate; the ground plate and the parasitic isolation unit are arranged in the area surrounded by the multiple antenna units; the ground plate is arranged in one-to-one correspondence with the antenna units, and the ground plate is connected with the antenna units; the parasitic elements are arranged in multiple and are respectively located between two adjacent antenna units; the ground plate and the parasitic isolation unit are formed based on the same metal patch and in a symmetrical division manner. The scheme has the advantages of compact structure, high isolation, good radiation characteristics and stable bending performance, and is fully suitable for various conformal wireless communication devices.

Description

Technical Field

[0001] This invention relates to the field of antenna technology, and in particular to a flexible ultra-wideband MIMO antenna based on a composite decoupling structure. Background Technology

[0002] In today's era of rapid technological advancement, modern wireless communication devices are constantly evolving towards high integration and conformal architecture. This trend makes the need for antennas capable of operating on complex curved surfaces increasingly urgent. Ultra-wideband multiple-input multiple-output (UWB-MIMO) antennas, due to their enormous potential in improving channel capacity and transmission reliability, have attracted the attention of many researchers and become a current research hotspot.

[0003] Ultra-wideband multiple-input multiple-output (UWB-MIMO) technology, as a key technology in modern wireless communication, possesses unique advantages. UWB technology, with its extremely wide spectral bandwidth, enables high-speed data rates, high-precision ranging and positioning, and extremely low power spectral density, exhibiting excellent performance in dense multipath environments. MIMO technology, on the other hand, cleverly utilizes the multipath effect by simultaneously deploying multiple antenna elements at both ends of the communication link for signal transmission and reception, significantly improving channel capacity, data transmission rate, and link reliability without increasing bandwidth or transmission power. Theoretically, combining UWB and MIMO technologies could theoretically create a UWB-MIMO antenna system that simultaneously possesses superior performance characteristics such as high resolution, strong anti-interference capability, and high channel capacity, thus becoming a research focus for many scholars.

[0004] However, in practical applications, UWB-MIMO antennas face numerous severe challenges. Especially in conformal applications, the antenna must not only achieve low coupling between multiple elements within a limited space to ensure each element operates independently and effectively, but also achieve ultra-wideband operation to meet the communication requirements of different frequency bands. More importantly, its performance must remain stable when the antenna is subjected to physical deformations such as bending or twisting, placing extremely stringent requirements on the antenna's structural design and decoupling methods. Specifically, when integrating multiple UWB antenna elements into devices with limited physical dimensions, severe inter-element coupling problems arise. These coupling problems lead to deteriorated port isolation, increased interference between antenna ports, reduced antenna radiation efficiency (failing to effectively radiate signals), and decreased system diversity performance, reducing the reliability of the communication system in complex environments. These problems are the main obstacles to improving the performance of UWB-MIMO antennas.

[0005] To adapt to the trend of modern electronic devices moving towards wearable, implantable, and conformal designs, flexible antenna technology has emerged. Flexible antennas use flexible materials such as polyimide, liquid crystal polymers, or elastomers as dielectric substrates, giving the antenna the ability to bend, twist, and even stretch. This allows them to be attached to non-planar structures such as clothing, curved robot shells, or drone skins, enabling conformal applications and bringing greater flexibility and adaptability to the design of wireless communication devices.

[0006] However, while flexible antenna design brings new application prospects, it also presents a series of challenges that traditional rigid antennas have never faced. When a flexible antenna bends or deforms, the change in its physical structure directly affects key performance parameters such as the antenna's resonant frequency, impedance matching, radiation pattern, and gain, potentially leading to performance degradation. For example, in wearable devices, human movement causes the antenna to bend and deform continuously. This requires the antenna to not only have good radiation performance in a straight state, but more importantly, to maintain stability and reliability under various bending conditions. This undoubtedly places extremely high demands on material selection and antenna structural design.

[0007] In summary, the current flexible UWB-MIMO antenna technology has the following main shortcomings: Performance stability issues: Most existing antennas are still based on rigid substrates, which makes them unable to effectively maintain performance stability when faced with bending. Once the carrier on which the antenna is located bends, its performance will be significantly affected, failing to meet the stability requirements of practical applications.

[0008] Bandwidth and isolation issues: On the one hand, bandwidth coverage is not complete enough to fully meet the ultra-wideband requirements of modern wireless communication; on the other hand, achieving high isolation within a wide frequency band is difficult. This leads to interference between different frequency bands during actual communication, affecting communication quality.

[0009] Port isolation issue: Current port isolation is generally below 20 dB, which severely impacts the capacity and diversity performance of MIMO systems. Insufficient port isolation causes signal interference between antenna ports, reducing the overall system performance.

[0010] Structural design issues: Decoupling structures are either too complex, increasing the difficulty of design and manufacturing, or they occupy a large space, which contradicts the trend of miniaturization and integration in modern wireless communication equipment and is not conducive to the integrated application of antennas in limited space.

[0011] Therefore, there is an urgent need to propose a new MIMO antenna to fully solve the above problems. Summary of the Invention

[0012] The technical problem to be solved by the present invention is to provide a flexible ultra-wideband MIMO antenna based on a composite decoupling structure.

[0013] To achieve the above-mentioned objectives, the present invention provides a flexible ultra-wideband MIMO antenna based on a composite decoupling structure, comprising: a flexible dielectric substrate, an antenna element, a ground plane, a parasitic isolation unit, and a parasitic element disposed on one side of the flexible dielectric substrate; The antenna elements are arranged in a rotationally symmetrical manner around the center on the front side of the flexible dielectric substrate. The ground plane and the parasitic isolation unit are arranged in the area surrounded by the plurality of antenna units; The ground plane and the antenna unit are configured to correspond one-to-one, and the ground plane and the antenna unit are connected; Multiple parasitic elements are provided, and each is located between two adjacent antenna elements; The grounding plate and the parasitic isolation unit are formed based on the same metal patch and are divided symmetrically.

[0014] According to one aspect of the invention, the antenna element is a circular metal radiating patch with double rectangular cutouts.

[0015] According to one aspect of the invention, the two rectangular cutouts on the antenna element are axially symmetrically distributed; The antenna element is etched with an open resonant slot to change the surface current distribution path and suppress high-frequency coupling.

[0016] According to one aspect of the invention, the radius of the circular metal radiating patch used in the antenna element is 9 mm; The length of the long side of the rectangular cut is 8mm, and the vertical distance between the long side and the center of the circular metal radiating patch is 7.5mm. The included angle formed by the long sides of the two rectangular cuts is 80°; The wire diameter of the open resonant groove is 0.5 mm, and the opening width is 2 mm.

[0017] According to one aspect of the invention, four antenna elements are provided and are arranged in a rotationally symmetrical orthogonal manner around the center of the flexible dielectric substrate.

[0018] According to one aspect of the present invention, the ground plane is a rectangular metal patch, and the ground plane is arranged in a rotationally symmetrical orthogonal manner around the center of the flexible dielectric substrate on the flexible dielectric substrate; The orthogonal arrangement direction of the ground plane is consistent with the orthogonal arrangement direction of the antenna element, and the long side of the ground plane is opposite to the antenna element; The length of the grounding plate is 7mm and the width is 6mm.

[0019] According to one aspect of the invention, the parasitic isolation unit comprises: a central parasitic isolation zone and an edge parasitic isolation zone surrounding the central parasitic isolation zone; The central parasitic isolation strip is arranged at the center of the flexible dielectric substrate, and the central parasitic isolation strip and the edge parasitic isolation strip are arranged at intervals. The edge parasitic isolation strip and the grounding plate are arranged in an alternating pattern with intervals.

[0020] According to one aspect of the invention, the central parasitic isolation strip comprises: a first rectangular patch portion and a plurality of second rectangular patch portions; Multiple second rectangular patch portions are arranged at equal intervals around the first rectangular patch portion; The area of ​​the first rectangular patch portion is greater than the area of ​​the second rectangular patch portion; The edge parasitic isolation strip includes: multiple edge patch portions; Multiple edge patch portions are arranged at equal intervals around the center of the flexible dielectric substrate, and the edge patch portions are located between adjacent ground planes; The edge patch portion has an axisymmetric structure and is provided with a first side, a second side, a third side and a fourth side connected in sequence; wherein the first side and the third side are arranged opposite to each other; Both the second and fourth sides are straight edges, and the second and fourth sides are arranged perpendicular to each other; The first side is a 1 / 4 circular arc edge; The third side is provided with two tangent arc portions and two straight edge portions. The third side is connected to the second side and the fourth side respectively based on the two straight edge portions, and the two straight edge portions are arranged perpendicularly to each other. The first side and the radius of the arc portion are the same.

[0021] According to one aspect of the invention, the parasitic element is an open resonant ring, and the opening direction of the parasitic element is toward the center of the flexible dielectric substrate; The ratio of the wire diameter of the parasitic element to the wire diameter of the open resonant slot of the antenna element is 4:1.

[0022] According to one aspect of the present invention, the flexible dielectric substrate is a polyimide flexible material plate with a thickness of 0.13 mm and a side length of 70 mm × 70 mm; Multiple antenna elements are fed by 50-ohm coplanar waveguides.

[0023] According to one aspect of the present invention, a flexible ultra-wideband MIMO antenna with a compact structure, high isolation, good radiation characteristics, and stable bending performance is provided, making it suitable for various conformal wireless communication devices.

[0024] According to one aspect of the present invention, the present invention introduces a split ground technique to form a ground plane and a parasitic isolation unit, and a composite decoupling mechanism with an open resonant slot and parasitic elements, thereby achieving a high port isolation of better than 20dB in the operating frequency band (5.0-18.9 GHz). This significantly reduces mutual coupling interference between antenna elements, allowing them to work independently without interference, and effectively improves the channel capacity and transmission reliability of multi-antenna systems.

[0025] According to one aspect of the present invention, the decoupling structure is ingeniously designed, achieving coordinated suppression of coupling paths across the entire operating frequency band without increasing antenna profile thickness or structural complexity, thus demonstrating excellent wideband decoupling capability.

[0026] According to one aspect of the present invention, the flexible ultra-wideband MIMO antenna employs an ultra-thin flexible substrate with an overall thickness of only 0.13 mm, exhibiting excellent flexibility. Verification through multi-radius curvature bending tests shows that the antenna maintains stable radiation characteristics and impedance matching even under bending conditions, making it suitable for various conformal curved surface applications.

[0027] According to one aspect of the present invention, four high-performance antenna elements can be integrated within a compact size of 70×70 mm². Good diversity characteristics are achieved through orthogonal layout of radiating patches and ground rotation. The measured envelope correlation coefficient is less than 0.004. Miniaturization and high integration of high-performance MIMO antennas are achieved in a limited space.

[0028] According to one aspect of the present invention, the antenna structure is simple, adopts a single-layer flexible board process, has low processing cost, good consistency, and good directional radiation characteristics and operating bandwidth, and has broad application prospects in complex electromagnetic environments such as drones, robots, and wearable devices.

[0029] According to one aspect of the present invention, the traditional shared ground plane design is divided into a ground plane and a parasitic isolation unit, which gives the present invention an excellent mid-frequency decoupling effect. At the same time, by setting two different open resonant ring structures, namely the open resonant slot and the parasitic element, the problem of poor isolation in the low-frequency and high-frequency regions of the ultra-wideband MIMO antenna is solved.

[0030] According to one aspect of the present invention, the antenna element is designed with double rectangular cutouts to optimize the impedance matching of the antenna element. Together with the ground plane structure, this expands the operating bandwidth, enabling the present invention to achieve extremely high port isolation and stable radiation performance under different radii of curvature in an ultra-wide bandwidth of 5-18.9 GHz.

[0031] According to one aspect of the present invention, by physically partitioning the traditional shared floor design, the integration of grounding and central and edge parasitic units is achieved, realizing effective decoupling of the mid-frequency band within the operating frequency band. Specifically, the slot structure formed by the physical partitioning physically cuts off the most direct strong coupling current path between antenna elements, confining surface current within their respective edge blocks and fundamentally suppressing energy transfer through the floor. Furthermore, the central and edge parasitic isolation bands can neutralize energy; after being excited by the near-field of adjacent elements, they generate an anti-phase electromagnetic field, effectively canceling or "neutralizing" the remaining coupled energy. This method of physically partitioning the traditional shared floor naturally optimizes the radiation pattern of each antenna element, giving it good pattern diversity characteristics and further reducing channel correlation from a spatial perspective.

[0032] According to one aspect of the present invention, the resonant frequency of the parasitic elements between antenna elements is designed at 5 GHz, which effectively absorbs the low-frequency coupling energy between antenna elements; the resonant frequency of the open resonant slot etched on the antenna element is set at 18 GHz, which suppresses the high-frequency coupling between antennas.

[0033] According to one aspect of the present invention, the present invention makes full use of the layout space of traditional shared floors, and achieves excellent decoupling effect in the ultra-wide bandwidth by using a composite decoupling method without increasing additional volume and complexity.

[0034] According to one aspect of the present invention, the invention is prepared using flexible materials and has passed rigorous bending tests, demonstrating its mechanical robustness and electrical stability in complex curved surface applications such as smart skin.

[0035] According to one aspect of the present invention, the present invention can be widely applied to next-generation high-speed wireless communication systems, especially in fields such as aircraft, drones, and wearable devices where there are stringent requirements for antenna conformality and high performance. Attached Figure Description

[0036] Figure 1 This is a structural diagram of the flexible ultra-wideband MIMO antenna based on a composite decoupling structure according to the present invention; Figure 2 The present invention relates to a flexible ultra-wideband MIMO antenna based on a composite decoupling structure. 11 Line graph; Figure 3The present invention relates to a flexible ultra-wideband MIMO antenna based on a composite decoupling structure. 21 Line graph; Figure 4 The present invention relates to a flexible ultra-wideband MIMO antenna based on a composite decoupling structure. 31 Line graph; Figure 5 The present invention provides a flexible ultra-wideband MIMO antenna based on a composite decoupling structure under different radii of curvature r. 11 Line graph; Figure 6 This is a gain curve of the flexible ultra-wideband MIMO antenna based on a composite decoupling structure according to the present invention. Figure 7 The envelope correlation coefficient (ECC) of the flexible ultra-wideband MIMO antenna based on a composite decoupling structure of this invention is given. 12 Line graph; Figure 8 The envelope correlation coefficient (ECC) of the flexible ultra-wideband MIMO antenna based on a composite decoupling structure of this invention is given. 13 Line graph; Figure 9 The diagram shows the E-plane and H-plane radiation patterns of the flexible ultra-wideband MIMO antenna based on a composite decoupling structure at a frequency of 5 GHz, as described in this invention. Figure 9 (a) shows the radiation pattern of the E-plane. Figure 9 (b) shows the radiation pattern of the H-plane; Figure 10 The figures show the E-plane and H-plane radiation patterns of the flexible ultra-wideband MIMO antenna based on a composite decoupling structure at 11 GHz, as described in this invention. Figure 10 (a) shows the radiation pattern of the E-plane. Figure 10 (b) shows the radiation pattern of the H-plane; Figure 11 The figures show the E-plane and H-plane radiation patterns of the flexible ultra-wideband MIMO antenna based on a composite decoupling structure at 18 GHz, as described in this invention. Figure 11 (a) shows the radiation pattern of the E-plane. Figure 11 (b) shows the radiation pattern of the H-plane. Detailed Implementation

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are merely some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0038] In describing embodiments of the present invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer" express orientations or positional relationships based on the orientations or positional relationships shown in the relevant drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limitations on the present invention.

[0039] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The embodiments cannot be described in detail here, but the embodiments of the present invention are not limited to the following embodiments.

[0040] like Figure 1 As shown, according to one embodiment of the present invention, a flexible ultra-wideband MIMO antenna based on a composite decoupling structure includes: a flexible dielectric substrate 1, antenna elements 2, a ground plane 3, a parasitic isolation unit 4, and parasitic elements 5 disposed on one side of the flexible dielectric substrate 1; in this embodiment, multiple antenna elements 2 are arranged in a rotationally symmetrical manner around a center on the front surface of the flexible dielectric substrate 1; the ground plane 3 and the parasitic isolation unit 4 are arranged in the area surrounded by the multiple antenna elements 2. Further, the ground plane 3 is arranged in a one-to-one correspondence with the antenna elements 2, and the ground plane 3 is connected to the antenna elements 2; further, multiple parasitic elements 5 are disposed, and are respectively located between two adjacent antenna elements 2. In this embodiment, the ground plane 3 and the parasitic isolation unit 4 are formed based on the same metal patch and using a symmetrically divided manner.

[0041] Through the above configuration, the ground plane 3 and the parasitic isolation unit 4 in this scheme are symmetrically segmented using the same metal patch. This allows the combined structure formed by the ground plane 3 and the parasitic isolation unit 4 to block the coupling current path, effectively confining the current to the local ground block to which the excitation port belongs and around the central parasitic structure, preventing it from propagating to other units. This fundamentally suppresses the coupling of current through the ground. Specifically, this scheme transforms the traditional continuous, shared ground layer into four isolated independent ground blocks. This segmentation physically cuts off the metal path for surface current to flow between units. Therefore, the strong current generated at the excitation port is effectively confined within its corresponding ground block and cannot flow to other unit ports as it would in a shared ground structure, thus fundamentally suppressing conductive coupling through the ground path.

[0042] Furthermore, the parasitic isolation structure generated by the symmetrical segmentation produces an electromagnetic field that is out of phase with the original coupling field. This out-of-phase field effectively cancels out the energy directly coupled from the excitation unit to the non-excitation unit, which is more beneficial to ensuring the working performance of this scheme.

[0043] like Figure 1 As shown, according to one embodiment of the present invention, the antenna element 2 is a circular metal radiating patch with double rectangular cutouts; in this embodiment, the antenna element 2 has an axisymmetric structure, and the two rectangular cutouts on the antenna element 2 are also distributed in an axisymmetric manner; specifically, the long side of the rectangular cutout is inclined relative to the axis of symmetry of the antenna element 2, and the opening direction of the rectangular cutout is towards the side away from the axis of symmetry of the antenna element 2. Thus, the long sides of the two rectangular cutouts have a certain angle, thereby making the antenna element 2 present as an irregularly shaped structural component with different arc lengths at opposite ends.

[0044] In this embodiment, the antenna element 2 is arranged in a ring shape, with its small end formed by two rectangular cuts facing the center of the flexible dielectric substrate 1.

[0045] By setting up the above configuration, the double rectangular opening on antenna element 2 can be used to extend the surface current path and effectively introduce multi-resonance characteristics, thus providing a basis for achieving ultra-wideband impedance matching.

[0046] like Figure 1 As shown, according to one embodiment of the present invention, an open resonant groove 21 for changing the surface current distribution path and suppressing high-frequency coupling is etched on the antenna element 2. In this embodiment, the open resonant groove 21 can be configured as a rectangular open groove, which is located near the large end of the antenna element 2, and the opening of the open resonant groove 21 faces the small end of the antenna element 2. In this embodiment, the opening of the open resonant groove 21 is located at the middle of its long side to ensure the symmetry of the open resonant groove 21.

[0047] With the above settings, the current distribution path on the surface of the antenna element 2 can be effectively changed based on the set open resonant slot 21, which can effectively block the coupling path at around 18GHz, significantly improve the isolation of the high-frequency band, and fully achieve the effect of suppressing high-frequency coupling.

[0048] like Figure 1As shown, according to one embodiment of the present invention, the radius of the circular metal radiating patch used in the antenna element 2 is 9 mm, and the distance between its center and the center of the flexible dielectric substrate 1 is 24.5 mm. In this embodiment, the length of the long side of the rectangular cut is 8 mm, and the vertical distance between the long side and the center of the circular metal radiating patch is 7.5 mm; in addition, the included angle formed by the long sides of the two rectangular cuts is 80°; therefore, when the two rectangular cuts are symmetrically distributed about the axis of symmetry of the antenna element 2, the included angle between the long side of the rectangular cut and the axis of symmetry is 40°.

[0049] In this embodiment, when the open resonant groove 21 is set as a rectangular open groove, its length is 12mm, its width is 6.5mm, its wire diameter is 0.5mm, and its opening width is 2mm.

[0050] In this embodiment, the inner edge of the side with the opening of the open resonant groove 21 is aligned with the center of the circular metal radiating patch, that is, the side with the opening of the open resonant groove 21 extends beyond the center of the circular metal radiating patch by one line diameter in the direction of the smaller end.

[0051] In this embodiment, the open resonant groove 21 is disposed through the opposite sides of the circular metal radiating patch.

[0052] like Figure 1 As shown, according to one embodiment of the present invention, four antenna elements 2 are provided and arranged orthogonally with rotational symmetry around the center of the flexible dielectric substrate 1. In this embodiment, the four antenna elements 2 are arranged at equal angular intervals along the circumference of the flexible dielectric substrate 1, thereby achieving a rotationally symmetric orthogonal arrangement, i.e., the lines connecting any two antenna elements 2 are orthogonally intersecting in a cross shape. In this embodiment, the antenna elements 2 are directly opposite the edge of the flexible dielectric substrate 1. Furthermore, in the four orthogonally distributed antenna elements 2, each antenna element 2 can be directly opposite the center of the edge of the flexible dielectric substrate 1, thus more fully ensuring the rotational symmetry of this solution.

[0053] By setting up four antenna elements 2 in a rotationally symmetrical orthogonal arrangement, this scheme makes more effective use of spatial diversity characteristics. On this basis, combined with the optimized design of the antenna element 2 structure itself (such as setting up double rectangular openings), it plays a more favorable role in improving the ultra-wideband impedance matching capability of this scheme.

[0054] like Figure 1As shown, according to one embodiment of the present invention, the ground plane 3 is a rectangular metal patch, and the ground plane 3 is arranged orthogonally with rotational symmetry around the center of the flexible dielectric substrate 1. Since the ground plane 3 corresponds one-to-one with the antenna element 2, four ground planes 3 can also be provided. In this embodiment, to ensure structural symmetry, the ground plane 3 also adopts an orthogonal arrangement with rotational symmetry around the center of the flexible dielectric substrate 1, and the orthogonal arrangement direction of the ground plane 3 is consistent with the orthogonal arrangement direction of the antenna element 2. Furthermore, the ground plane 3 is exactly aligned with the small end of the antenna element 2, achieving the coincidence of the axis of symmetry, thus fully ensuring the structural symmetry.

[0055] In this embodiment, the ground plane 3 and the antenna element 2 are spaced apart and connected to each other by a conductor to form a feed point for the antenna element 2 at the connection point; wherein, the long side of the ground plane 3 is opposite to the antenna element 2. In this embodiment, the ground plane 3 has a length of 7mm and a width of 6mm.

[0056] like Figure 1 As shown, according to one embodiment of the present invention, the parasitic isolation unit 4 includes: a central parasitic isolation strip 41, and an edge parasitic isolation strip 42 surrounding the central parasitic isolation strip 41; in this embodiment, the central parasitic isolation strip 41 is arranged at the center of the flexible dielectric substrate 1, and the central parasitic isolation strip 41 and the edge parasitic isolation strip 42 are arranged at intervals; the edge parasitic isolation strip 42 and the ground plane 3 are arranged in an alternating pattern at intervals.

[0057] like Figure 1 As shown, according to one embodiment of the present invention, the central parasitic isolation strip 41 includes: a first rectangular patch portion 411 and a plurality of second rectangular patch portions 412; wherein, the plurality of second rectangular patch portions 412 are arranged at equal intervals around the first rectangular patch portion 411; in this embodiment, one first rectangular patch portion 411 is provided and is located in the middle position, while four second rectangular patch portions 412 are provided for surrounding the first rectangular patch portion 411; specifically, the four second rectangular patch portions 412 are arranged diagonally, corresponding one-to-one with the four corners of the first rectangular patch portion 411, wherein the diagonals of the second rectangular patch portions 412 are collinear with the diagonals of the first rectangular patch portion 411. In this embodiment, the diagonals of the first rectangular patch portion 411 are collinear with the diagonals of the flexible dielectric substrate 1.

[0058] In this embodiment, the area of ​​the first rectangular patch portion 411 is larger than the area of ​​the second rectangular patch portion 412. Specifically, the first rectangular patch portion 411 is a square patch with a side length of 4mm; the second rectangular patch portion 412 is a square patch with a side length of 3.5mm. In this embodiment, the first rectangular patch portion 411 and the second rectangular patch portion 412 are arranged diagonally with a 0.5mm offset in both the horizontal and vertical directions.

[0059] The above-mentioned configuration effectively ensures the isolation performance of the central parasitic isolation strip 41, and its high structural symmetry gives it better working performance. In addition, the different sizes of the first rectangular patch portion 411 and the second rectangular patch portion 412 in the middle further enhance the working performance of the central parasitic isolation strip 41.

[0060] like Figure 1 As shown, according to one embodiment of the present invention, the edge parasitic isolation strip 42 includes: a plurality of edge patch portions 421; wherein the plurality of edge patch portions 421 are arranged at equal intervals around the center of the flexible dielectric substrate 1, and the edge patch portions 421 are located between adjacent ground planes 3. In this embodiment, the edge patch portions 421 have an axisymmetric structure and are provided with a first side, a second side, a third side and a fourth side connected in sequence; wherein the first side and the third side are arranged opposite to each other; the second side and the fourth side are both straight edges, and the second side and the fourth side are arranged perpendicular to each other; in this embodiment, the first side is a 1 / 4 arc edge; the third side is provided with two tangent arc portions and two straight edge portions, wherein the third side is connected to the second side and the fourth side respectively based on the two straight edge portions, and the two straight edge portions are arranged perpendicular to each other; in this embodiment, the radii of the first side and the arc portions are the same.

[0061] The edge patch portion 421, based on the above configuration, has excellent isolation effect due to its symmetrical design. Furthermore, the irregular design of its edge makes the change in current path more obvious, resulting in even better isolation effect.

[0062] In this embodiment, the edge patch portion 421 can be formed by removing a square metal patch. Specifically, a right-angle portion is removed from the corner of a square metal patch with a fixed radius as the center to form a first side. Further, a third side is formed by removing the two right-angled sides opposite to the first side. The corresponding area on the square metal patch is removed from the two right-angled sides opposite to the first side with a fixed radius, thereby forming two arc portions. The two arc portions are tangent to the diagonal of the square metal patch, thus completing the forming of the entire edge patch portion 421.

[0063] In this embodiment, the square metal patch used in the edge patch portion 421 has a side length of 8.5mm, a radius of 3mm for the first side, and a radius of 3mm for the two tangent arc portions on the third side.

[0064] In this embodiment, the symmetry axis of the edge patch portion 421 coincides with the diagonal of the flexible dielectric substrate 1 to effectively ensure the coordinated configuration of the edge patch portion 421 arrangement position and the various structures.

[0065] Therefore, the edge patch portion 421 based on the above settings can fully achieve the corresponding isolation effect, and the symmetrical setting also makes its performance even better.

[0066] like Figure 1 As shown, according to one embodiment of the present invention, the parasitic element 5 is an open resonant ring, and the opening of the parasitic element 5 faces the center of the flexible dielectric substrate 1. In this embodiment, the parasitic element 5 is a rectangular open ring, wherein the opening is located on the long side of the rectangle and at the center of the long side, so that the structure of the parasitic element 5 remains symmetrical. In this embodiment, the resonant frequency of the parasitic element 5 is designed to be 5 GHz. Thus, based on the parasitic element 5, the low-frequency coupling energy between the antenna elements 2 can be effectively shunted and absorbed, significantly improving the port isolation in the low-frequency band.

[0067] In this embodiment, the ratio of the wire diameter of the parasitic element 5 to the wire diameter of the open resonant slot 21 of the antenna unit 2 is 4:1. Based on this ratio, the performance of the two open resonant structures is effectively coordinated and matched, which is more beneficial to ensuring the working performance of this solution.

[0068] In this embodiment, when the parasitic element 5 is a rectangular open ring, its length is 14 mm, its width is 8 mm, its wire diameter is 2 mm, and its opening width is 3 mm. In this embodiment, the axis of symmetry of the parasitic element 5 coincides with the diagonal of the flexible dielectric substrate 1.

[0069] Of course, the parasitic element 5 can also be a circular open ring, a double circular open ring, etc., and can be adjusted accordingly according to actual needs.

[0070] Furthermore, this scheme uses the segmented ground plane 3 and parasitic isolation unit 4, combined with two different integrated open resonant structures (i.e., open resonant slot 21 and parasitic element 5) to form a composite decoupling structure, which effectively and fully suppresses the electromagnetic coupling between antenna elements 2, and effectively ensures the intermediate frequency decoupling effect of this scheme.

[0071] like Figure 1 As shown, according to one embodiment of the present invention, the flexible dielectric substrate 1 is a polyimide flexible material plate with a thickness of 0.13 mm and a side length of 70 mm × 70 mm; wherein, the dielectric constant of the flexible dielectric substrate 1 is 3.5 and the loss tangent is 0.01. The flexible dielectric substrate 1 configured as described above possesses ultra-thin and flexible characteristics, achieving excellent UWB-MIMO performance while maintaining flexibility. This makes the solution applicable to conformal applications on various curved surfaces, effectively ensuring the application flexibility of the solution.

[0072] like Figure 1 As shown, according to one embodiment of the present invention, multiple antenna elements 2 are fed by 50-ohm coplanar waveguides to match the SMA interface and achieve convenient connection.

[0073] To further illustrate this scheme, the flexible ultra-wideband MIMO antenna of this scheme was simulated, analyzed and optimized using the electromagnetic full-wave simulation software CST. Its structural parameters, S-parameters, radiation characteristics, diversity performance and bending performance were verified in depth.

[0074] like Figure 2 As shown, the return loss S of the flexible ultra-wideband MIMO antenna 11 The impedance difference is less than -10dB in the 5.0-18.9GHz frequency range, proving that the proposed solution has good ultra-wideband impedance matching characteristics. Figure 3 and Figure 4 S shown 21 and S 31 The curves show that the isolation of this scheme is better than 20dB throughout the entire operating frequency band.

[0075] like Figure 5 As shown, the S-axis of the flexible ultra-wideband MIMO antenna under different curvature radii of curvature is... 11 In the curve, under various bending conditions such as r=20mm, 40mm, and 60mm, this solution can still maintain good impedance matching, proving that it has excellent flexibility and conformal application reliability.

[0076] like Figure 6As shown, the gain curve of the flexible ultra-wideband MIMO antenna is displayed. The antenna gain is stable within the operating frequency band, and the peak gain reaches 5.2 dBi, indicating that the antenna has good radiation efficiency. Figure 7 and Figure 8 The envelope correlation coefficient (ECC) is given. 12 and ECC 13 The curves are all below 0.004, which meets the requirement of ECC<0.5 and is close to the ideal value of 0, proving that the scheme has excellent diversity performance and can effectively combat multipath fading.

[0077] Figure 9 , Figure 10 and Figure 11 The E-plane and H-plane radiation patterns of the flexible ultra-wideband MIMO antenna at 5 GHz, 11 GHz, and 18 GHz are presented. The patterns show that the proposed scheme exhibits a figure-eight pattern in the E-plane and a circular pattern in the H-plane, achieving good omnidirectional radiation. This demonstrates the good consistency of the radiation patterns across different frequencies, proving its radiation stability within the operating bandwidth.

[0078] In summary, based on the special design of its structure (such as the composite decoupling design of ground plane 3, parasitic isolation unit 4, open resonant groove 21 and parasitic element 5), this solution achieves high isolation in the ultra-wideband range, has stable radiation characteristics and excellent diversity performance, and can maintain good performance even under bending conditions. It can be widely used in wireless communication systems in complex curved environments such as drones, robots, and wearable devices.

[0079] The above description is merely an example of a specific solution of the present invention. For any devices and structures not described in detail herein, it should be understood that they are implemented using common devices and methods already available in the art.

[0080] The above description is merely one embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A flexible ultra-wideband MIMO antenna based on a composite decoupling structure, characterized in that, include: A flexible dielectric substrate (1), an antenna unit (2), a ground plane (3), a parasitic isolation unit (4) and a parasitic element (5) disposed on one side of the flexible dielectric substrate (1); The antenna unit (2) is arranged in multiple ways around the center on the front side of the flexible dielectric substrate (1); The ground plane (3) and the parasitic isolation unit (4) are arranged in the area surrounded by the plurality of antenna units (2); The ground plane (3) is configured to correspond one-to-one with the antenna unit (2), and the ground plane (3) is connected to the antenna unit (2); Multiple parasitic elements (5) are provided, and they are located between two adjacent antenna elements (2); The grounding plate (3) and the parasitic isolation unit (4) are formed based on the same metal patch and in a symmetrically divided manner; The antenna unit (2) is etched with an open resonant groove (21) for changing the surface current distribution path and suppressing high-frequency coupling. The inner edge of the opening side of the resonant slot (21) is aligned with the center of the circular metal radiating patch used in the antenna unit (2); The parasitic isolation unit (4) includes: a central parasitic isolation zone (41) and an edge parasitic isolation zone (42) surrounding the central parasitic isolation zone (41); The central parasitic isolation strip (41) is arranged at the center of the flexible dielectric substrate (1), and the central parasitic isolation strip (41) and the edge parasitic isolation strip (42) are arranged at intervals. The edge parasitic isolation strip (42) and the grounding plate (3) are arranged in an alternating pattern with intervals; The central parasitic isolation zone (41) includes: a first rectangular patch portion (411) and a plurality of second rectangular patch portions (412). Multiple second rectangular patch portions (412) are arranged at equal intervals around the first rectangular patch portion (411); The area of ​​the first rectangular patch portion (411) is larger than the area of ​​the second rectangular patch portion (412); The edge parasitic isolation strip (42) includes: multiple edge patch portions (421); Multiple edge patch portions (421) are arranged at equal intervals around the center of the flexible dielectric substrate (1), and the edge patch portions (421) are located between adjacent ground planes (3); The edge patch portion (421) has an axisymmetric structure and is provided with a first side, a second side, a third side and a fourth side connected in sequence; wherein the first side and the third side are arranged opposite to each other; Both the second and fourth sides are straight edges, and the second and fourth sides are arranged perpendicular to each other; The first side is a 1 / 4 circular arc edge; The third side is provided with two tangent arc portions and two straight edge portions. The third side is connected to the second side and the fourth side respectively based on the two straight edge portions, and the two straight edge portions are arranged perpendicularly to each other. The radii of the first side and the arc portion are the same; The parasitic element (5) is an open resonant ring, and the opening direction of the parasitic element (5) is toward the center of the flexible dielectric substrate (1). The ratio of the wire diameter of the parasitic element (5) to the wire diameter of the open resonant slot (21) of the antenna unit (2) is 4:

1.

2. The flexible ultra-wideband MIMO antenna based on a composite decoupling structure according to claim 1, characterized in that, The antenna element (2) is a circular metal radiating patch with double rectangular cutouts.

3. The flexible ultra-wideband MIMO antenna based on a composite decoupling structure according to claim 2, characterized in that, The two rectangular cuts on the antenna unit (2) are axially symmetrically distributed.

4. The flexible ultra-wideband MIMO antenna based on a composite decoupling structure according to claim 3, characterized in that, The radius of the circular metal radiating patch used in the antenna unit (2) is 9mm; The length of the long side of the rectangular cut is 8mm, and the vertical distance between the long side and the center of the circular metal radiating patch is 7.5mm. The included angle formed by the long sides of the two rectangular cuts is 80°; The wire diameter of the open resonant groove (21) is 0.5 mm and the opening width is 2 mm.

5. The flexible ultra-wideband MIMO antenna based on a composite decoupling structure according to any one of claims 1 to 4, characterized in that, The antenna unit (2) is provided in four parts, and is arranged in a rotationally symmetrical orthogonal manner around the center of the flexible dielectric substrate (1) on the flexible dielectric substrate (1).

6. The flexible ultra-wideband MIMO antenna based on a composite decoupling structure according to claim 5, characterized in that, The ground plane (3) is a rectangular metal patch, and the ground plane (3) is arranged orthogonally around the center of the flexible dielectric substrate (1) on the flexible dielectric substrate (1) with rotational symmetry. The orthogonal arrangement direction of the ground plane (3) is consistent with the orthogonal arrangement direction of the antenna element (2), and the long side of the ground plane (3) is opposite to the antenna element (2); The length of the grounding plate (3) is 7mm and the width is 6mm.

7. The flexible ultra-wideband MIMO antenna based on a composite decoupling structure according to any one of claims 1 to 4, characterized in that, The flexible dielectric substrate (1) is a polyimide flexible material board with a thickness of 0.13 mm and a side length of 70 mm × 70 mm. Multiple antenna elements (2) are fed by 50-ohm coplanar waveguides.

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