Metasurface-loaded wide-angle broadband Van Atta array antenna and its design method based on characteristic mode analysis

Abstract

The application discloses a kind of super surface based on feature mode analysis of wide-angle wide-frequency Van Atta array antenna and design method thereof, it is related to radio frequency antenna technical field.The array antenna is sequentially arranged super surface patch radiation structure, upper layer dielectric substrate, parasitic patch structure, middle layer dielectric substrate, lower layer metal ground, lower layer dielectric substrate and bottom microstrip line group from top to bottom;Super surface patch radiation structure is formed by multiple basic units, each basic unit is composed of first rectangular patch of inner four quadrant arrangement, second rectangular patch of peripheral encirclement and center circular coupling patch;Bottom microstrip line group is connected by phase compensation conjugate mechanism with the port of center-symmetrical basic unit two by two.The application realizes stable backward RCS enhancement in 4.5~5.1GHz frequency band, relative bandwidth reaches 10-12%, and-10dB angle coverage is stably above 144°-148°, with wide frequency band, wide angle domain, high flatness, low profile and simple structure and the like advantages.

Description

Technical Field

[0001] This invention relates to the field of radio frequency antenna technology, and in particular to a metasurface-loaded wide-angle broadband Van Atta array antenna based on characteristic mode analysis and its design method. Background Technology

[0002] Precise control of radar cross section (RCS) is one of the key technologies in radar countermeasures and target identification. RCS enhancement technology is mainly used in scenarios such as target simulation, radar test calibration, passive communication relay, and electronic warfare decoy systems. By increasing the target's RCS, radar can detect targets at long distances or simulate larger real targets in test environments, while ensuring that the target has predictable and stable echo characteristics.

[0003] Traditional RCS enhancement techniques mainly include corner reflectors, helical reflectors, and microstrip patch reflectors. While corner reflectors can achieve high RCS gain, their large physical size makes them difficult to integrate on space-constrained platforms. Helical reflectors have a low profile but limited angular coverage, and their RCS performance degrades sharply at large incident angles. In recent years, the Van Atta array, as a passive reflective array, achieves back-focusing of incident waves based on the phase conjugation principle through an equivalent phase-reversal feed network between centrally symmetrical antenna element pairs. With its outstanding advantages such as requiring no active components, light weight, low profile, and ease of conformal application, it has shown great application potential in the field of RCS enhancement.

[0004] Early research on Van Atta arrays primarily focused on improving gain performance, while recent studies have emphasized planarization, multi-polarization, wide-angle, and wide-bandwidth approaches. For example, Chinese invention patent CN 115411512 B discloses a planarized passive two-dimensional wide-angle Van Atta inverted array antenna, which achieves a planarized design of an 8×8 inverted array phase conjugate network through a double-layer microstrip line and a cross-layer structure. However, in such existing technologies, the antenna elements constituting the array are mostly conventional patch elements, operating only in a single fundamental mode. Their inherent narrowband characteristics and frequency-dependent pattern distortion mean that Van Atta arrays still face technical bottlenecks in practical engineering applications, including limited operating bandwidth, excessively high angle sensitivity, poor frequency response flatness, and RCS enhancement effects that are highly dependent on frequency accuracy.

[0005] To address the aforementioned issues, there is an urgent need to design a novel low-profile, wide-bandwidth, wide-angle domain RCS-enhanced Van Atta array. Optimizing Van Atta array elements using eigenmode analysis (CMA) can improve bandwidth and pattern stability. Furthermore, multi-mode excitation extends the RCS-enhanced angular domain, providing an effective design path for low-profile, wide-bandwidth, wide-angle Van Atta arrays. Summary of the Invention

[0006] To address the shortcomings and improvement needs of existing technologies, the present invention aims to provide a metasurface-loaded wide-angle broadband Van Atta array antenna based on characteristic mode analysis and its design method. The metasurface-loaded wide-angle broadband Van Atta array antenna based on characteristic mode analysis includes multiple sets of patches with different sizes. By designing the spacing between the patches, the bandwidth and radiation pattern stability of the Van Atta array antenna are improved. Simultaneously, multi-mode excitation is achieved through parasitic patch coupling feeding and center feeding. These two excitation methods complement each other, enhancing the angular RCS of the Van Atta array and solving the problems of existing Van Atta arrays where RCS enhancement is highly dependent on frequency accuracy and insufficient angular coverage.

[0007] This invention discloses a metasurface-loaded wide-angle broadband Van Atta array antenna based on characteristic mode analysis, comprising, from top to bottom, a metasurface patch radiating structure 1, an upper dielectric substrate 2, a parasitic patch structure 3, a middle dielectric substrate 4, a lower metallic ground layer 5, a lower dielectric substrate 6, and a bottom microstrip line group 7, and a feeding structure 8; wherein: The metasurface patch radiating structure 1 is attached to the upper surface of the upper dielectric substrate 2 and consists of an even array of basic units. The metasurface patch radiating structure 1 is designed based on characteristic mode analysis to achieve a wideband electromagnetic response of the antenna. Each basic unit is arranged along the array direction and is symmetrically arranged in pairs about the center of the array. Each basic unit includes multiple first rectangular patches and multiple second rectangular patches. The multiple first rectangular patches are arranged in a square array to form a first rectangular patch combination. Second rectangular patches are evenly arranged around the perimeter of the first rectangular patch combination. Adjacent basic units share a column of second rectangular patches located on the right side of the first rectangular patch combination. This column of second rectangular patches is arranged longitudinally to form a shared side. A circular patch a117 is set at the geometric center of each group of basic units. Multiple first rectangular patches are arranged around the circular patch a117. Multiple second rectangular patches are arranged around the periphery of the multiple first rectangular patches to form a metasurface loading form. Parasitic patch structure 3 is laid flat on the upper surface of the middle layer dielectric substrate 4 in a one-to-one correspondence with the basic unit. It includes multiple parasitic patches. When the multiple parasitic patches on the parasitic patch structure 3 are fed by the side-fed metal pillar a61, the metasurface patch radiating structure 1 operates in the first operating mode. When the center-fed metal pillar a62 on the parasitic patch structure 3 is fed, the metasurface patch radiating structure 1 operates in the second operating mode. In the first operating mode, the radiation pattern of the metasurface patch radiating structure 1 is a first shape, and the metasurface patch radiating structure 1 is sensitive to normally incident electromagnetic waves. In the second operating mode, the radiation pattern of the radiating structure 1 is a second shape, and the metasurface patch radiating structure 1 is sensitive to obliquely incident electromagnetic waves. The first operating mode and the second operating mode do not interfere with each other and operate simultaneously to achieve the wide-angle electromagnetic response of the antenna. Each power supply structure 8 corresponds one-to-one with a basic unit. Each power supply structure includes a central power supply metal pillar a62 and a side power supply metal pillar a61. The central power supply metal pillar a62 vertically penetrates the upper dielectric substrate 2, the middle dielectric substrate 4, and the lower dielectric substrate 6, connecting the metasurface patch radiation structure 1 and the bottom microstrip line group 7. The side power supply metal pillar a61 penetrates the middle dielectric substrate 4 and the lower dielectric substrate 6, connecting the parasitic patch structure 3 and the bottom microstrip line group 7. Each parasitic patch has a circular hole in its center, allowing the central power supply metal pillar a62 to pass through without contact. The lower metal ground 5 is disposed between the middle dielectric substrate 4 and the lower dielectric substrate 6, and has holes on it for the power supply structure 8 to pass through without contact. The bottom microstrip line group 7 is attached to the lower surface of the lower dielectric substrate 6 and consists of multiple microstrip lines. It connects the central feed metal pillar and the side feed metal pillar in the feed structure to the corresponding microstrip line ports. The connected microstrip line ports are on the same axis as the feed metal pillars. The bottom microstrip line group 7 connects the same type of feed ports in the centrally symmetrical basic unit in pairs. That is, the two ends of the same microstrip line are respectively connected to the same type of feed metal pillar of a pair of centrally symmetrical basic units to achieve phase conjugation and enhance RCS.

[0008] In summary, the above-described technical solutions conceived in this invention can achieve the following beneficial effects: (1) The Van Atta array antenna designed in this invention solves the problems of narrow bandwidth and high frequency sensitivity of traditional Van Atta array antennas by designing appropriate basic units, namely appropriate patch size, combination and spacing. When designing the unit of the array antenna, characteristic mode analysis is used to optimize the unit of the array antenna, so that the array antenna has high radiation pattern stability and high flatness of RCS enhancement response in the working frequency band.

[0009] (2) This invention improves the RCS enhancement effect of the Van Atta array in the wide-angle domain by regulating and simultaneously exciting the array antenna to make it work in two modes, namely, the center feed and the parasitic patch combined feed.

[0010] (3) By constructing a microstrip line structure through a fed metal pillar, the electromagnetic response phase conjugation of the antenna is realized, forming a VanAtta array antenna and enhancing the RCS. Attached Figure Description

[0011] Figure 1 A front view of a metasurface-loaded wide-angle Van Atta array antenna provided according to an embodiment of the present invention.

[0012] Figure 2 The schematic diagram of the structure of the metasurface loaded wide-angle Van Atta array antenna provided in the embodiment of the present invention shows the stacking relationship of the metasurface patch radiating structure 1, the upper dielectric substrate 2, the parasitic patch structure 3, the middle dielectric substrate 4, the lower metal ground 5, the lower dielectric substrate 6, the bottom microstrip line group 7, and the feed structure 8.

[0013] Figure 3 A front view of a unit cell of a metasurface-loaded wide-angle Van Atta array antenna according to an embodiment of the present invention.

[0014] Figure 4 The schematic diagram of the unit layer of the metasurface-loaded wide-angle Van Atta array antenna provided according to an embodiment of the present invention shows the unit-level radiating patch a1, upper dielectric substrate a2, parasitic patch a3, middle dielectric substrate a4, metal ground a5, and side-feed metal pillar a61 and center-feed metal pillar a62.

[0015] Figure 5 The top view of the metasurface-loaded wide-angle Van Atta array antenna provided according to an embodiment of the present invention shows the arrangement of four first rectangular patches a113 to a116, twelve second rectangular patches a11 to a112, and a central circular patch a117.

[0016] Figure 6 The top view of the metasurface-loaded wide-angle Van Atta array antenna provided according to an embodiment of the present invention shows a structural reuse form in which four basic units share a second rectangular patch.

[0017] Figure 7 This is a top view of the upper dielectric substrate 2 in a metasurface-loaded wide-angle Van Atta array antenna provided according to an embodiment of the present invention.

[0018] Figure 8This is a top view of the parasitic patch structure 3 in a metasurface-loaded wide-angle Van Atta array antenna according to an embodiment of the present invention.

[0019] Figure 9 A top view of the middle dielectric substrate 4 in a metasurface-loaded wide-angle Van Atta array antenna provided according to an embodiment of the present invention.

[0020] Figure 10 A top view of the lower metal ground 5 in a metasurface-loaded wide-angle Van Atta array antenna provided according to an embodiment of the present invention shows eight circular holes.

[0021] Figure 11 This is a top view of the lower dielectric substrate 6 in a metasurface-loaded wide-angle Van Atta array antenna provided according to an embodiment of the present invention.

[0022] Figure 12 The top view of the bottom microstrip line group 7 in the metasurface-loaded wide-angle Van Atta array antenna provided according to an embodiment of the present invention is shown, with the first microstrip line 91, the second microstrip line 92, the third microstrip line 93 and the fourth microstrip line 94 labeled.

[0023] Figure 13 A side view of a metasurface-loaded wide-angle Van Atta array antenna provided according to an embodiment of the present invention.

[0024] Figures 14-20 The figures show the monostation RCS simulation results of the metasurface-loaded wide-angle Van Atta array at 4.5 GHz, 4.6 GHz, 4.7 GHz, 4.8 GHz, 4.9 GHz, 5.0 GHz, and 5.1 GHz, respectively, in dB. The dashed lines in each figure represent the normalized RCS results of the present invention, and the solid lines represent the normalized RCS results of the same-sized metal plate (PEC). The -10 dB coverage angles of the present invention at each frequency are approximately 143.94°, 156.48°, 161.63°, 170.73°, 173.04°, 174.65°, and 175.23°, respectively.

[0025] Figure 21 This is an enlarged schematic diagram of the phase-shifted microstrip line and the feeding structure provided according to an embodiment of the present invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0027] In this invention, the terms "first," "second," etc. (if present) in the invention and the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0028] This invention discloses a metasurface-loaded wide-angle broadband Van Atta array antenna based on characteristic mode analysis, comprising, from top to bottom, a metasurface patch radiating structure, an upper dielectric substrate, a parasitic patch structure, a middle dielectric substrate, a lower metal ground layer, a lower dielectric substrate, and a bottom microstrip line group, as well as a feeding structure; wherein: The metasurface patch radiating structure is attached to the upper surface of the upper dielectric substrate and consists of an even array of basic units. The metasurface patch radiating structure is designed based on characteristic mode analysis to achieve a wideband electromagnetic response of the antenna. Each basic unit is arranged along the array direction and is symmetrically paired about the array center. Each basic unit includes multiple first rectangular patches and multiple second rectangular patches. The multiple first rectangular patches are arranged in a square array to form a first rectangular patch combination. Second rectangular patches are evenly arranged around the perimeter of the first rectangular patch combination. Adjacent basic units share a column of second rectangular patches located on the right side of the first rectangular patch combination. This column of second rectangular patches is arranged longitudinally to form a shared side. A circular patch is set at the geometric center of each group of basic units. Multiple first rectangular patches are arranged around the circular patch. Multiple second rectangular patches are arranged around the perimeter of the multiple first rectangular patches to form a metasurface loading form. Parasitic patch structures are laid out on the upper surface of the middle layer dielectric substrate in a one-to-one correspondence with the basic units. These structures include multiple parasitic patches. When the multiple parasitic patches on the parasitic patch structure are fed by side-fed metal pillars, the metasurface patch radiating structure operates in the first operating mode. When the center-fed metal pillar on the parasitic patch structure is fed, the metasurface patch radiating structure operates in the second operating mode. In the first operating mode, the radiation pattern of the metasurface patch radiating structure has a first shape, such as an inverted C-shape, and the metasurface patch radiating structure is sensitive to normally incident electromagnetic waves. In the second operating mode, the radiation pattern of the radiating structure has a second shape, such as a donut-like shape, and the metasurface patch radiating structure is sensitive to obliquely incident electromagnetic waves. The first and second operating modes operate simultaneously without interference, achieving a wide-angle electromagnetic response for the antenna. Each power supply structure corresponds one-to-one with a basic unit. Each power supply structure includes a central power supply metal pillar and side power supply metal pillars. The central power supply metal pillar vertically penetrates the upper, middle, and lower dielectric substrates, connecting the metasurface patch radiation structure with the bottom microstrip line group. The side power supply metal pillars penetrate the middle and lower dielectric substrates, connecting the parasitic patch structure with the bottom microstrip line group. Each parasitic patch has a circular hole in its center, allowing the central power supply metal pillar to pass through without contact. The lower metal ground layer is disposed between the middle dielectric substrate and the lower dielectric substrate, and has holes on it for the power supply structure to pass through without contact. The bottom microstrip line group is attached to the lower surface of the lower dielectric substrate and consists of multiple microstrip lines. It connects the center feed metal pillar and the side feed metal pillar in the feed structure to the corresponding microstrip line ports. The connected microstrip line ports are on the same axis as the feed metal pillars. The bottom microstrip line group 7 connects the feed ports of the same type in the centrally symmetrical basic unit in pairs. That is, the two ends of the same microstrip line are respectively connected to the same type of feed metal pillar of a pair of centrally symmetrical basic units to achieve phase conjugation, form a Van Atta array antenna, and enhance RCS. The parasitic patch is connected in a centrally symmetrical manner, and the specific number will be used as an example to explain.

[0029] Preferably, the metasurface patch radiation structure consists of 4 sets of basic units to form a 1×4 array patch, with each pair of adjacent basic units sharing a second rectangular side; the center-to-center distance between adjacent basic units is 25~35 mm.

[0030] Preferably, each basic unit group includes 16 rectangular radiating patches and 1 circular patch: including 4 first rectangular patches arranged in four quadrants around the inner perimeter to form a first rectangular patch combination, 12 second rectangular patches arranged clockwise around the outer perimeter of the first rectangular patch combination, and the circular patch located at the geometric center between the 4 first rectangular patches, serving as a coupling feed port connected to the central feed metal pillar, and two adjacent basic units sharing the second rectangular patch.

[0031] Preferably, the side length of the first rectangular patch is 8-12mm, the side length of the second rectangular patch is 4-8mm, the gap width between adjacent second rectangular patches is 0.5-1.5mm, the distance between the second rectangular patch and the first rectangular patch is 0.3-1.6mm, and the distance between the second rectangular patches is 2-4mm; the radius of the circular patch is 0.6-1.7mm, and the distance between the center of the circular patch and the four first rectangular patches is 0.25-0.75mm.

[0032] Preferably, the parasitic patch structure includes a number of parasitic patches equal to the number of basic units. The size of the parasitic patches in the parasitic patch structure is designed according to the impedance of the array antenna. By adjusting the length, width, and aperture radius of the parasitic patches, the return loss S11 of the array antenna is made less than a preset loss, such as -10 dB, but not limited to this.

[0033] Preferably, the upper dielectric substrate, the middle dielectric substrate, and the lower dielectric substrate are made of microwave dielectric material with a dielectric constant εr = 3.05-4.05, and the three have equal planar dimensions and decreasing thickness in sequence.

[0034] Preferably, the planar dimensions of the lower metal ground layer are the same as those of the upper dielectric substrate, the middle dielectric substrate, and the lower dielectric substrate, and a total of 8 circular holes are opened on it, the positions of which are located by the feeding metal pillars in the feeding structure.

[0035] Preferably, when the metasurface patch radiating structure is composed of 4 basic units, the bottom microstrip line group includes a first microstrip line, a second microstrip line, a third microstrip line, and a fourth microstrip line; the x-axis lengths of the first microstrip line, the second microstrip line, the third microstrip line, and the fourth microstrip line are designed based on the dielectric constant of the dielectric substrate and the operating frequency of the array antenna, and the y-axis lengths of the first microstrip line, the second microstrip line, the third microstrip line, and the fourth microstrip line are related to the positions of the center feed metal pillar and the side feed metal pillar in the feed structure.

[0036] In embodiments of the present invention, the array antenna operates in a frequency band of 4.5 to 5.1 GHz, with a relative bandwidth of not less than 10% to 14%, and the -10 dB angle coverage range of a single station RCS within the operating frequency band is not less than 140°, preferably between 140° and 180°.

[0037] To better understand the structure of the metasurface-loaded wide-angle broadband Van Atta array antenna based on characteristic mode analysis in this invention, the following will combine... Figures 1-13 This paper describes a specific example of a metasurface-loaded wide-angle broadband Van Atta array antenna, particularly an array antenna with specific patch size, number of patches, and other parameters. The following is only one specific implementation method and is not a limitation of the present invention.

[0038] Example 1: This embodiment uses a 1×4 array as an example to illustrate the specific implementation of the present invention. Figure 1 , Figure 2 As shown, the array antenna has a stacked structure. From bottom to top, the layers are: bottom microstrip line group 7, bottom dielectric substrate 6, bottom metal ground 5, middle dielectric substrate 4, parasitic patch structure 3, top dielectric substrate 2, and metasurface patch radiation structure 1.

[0039] Metasurface patch radiating structure 1 adopts a four-group basic unit reuse structure, such as Figure 5 , Figure 6 As shown. To achieve stable broadband radiation, each basic unit adopts a configuration of "four first rectangular patches (10.5 mm side length) arranged in four quadrants, twelve second rectangular patches (6 mm side length) surrounding the perimeter, and a central circular patch (1.5 mm radius) for coupling and feeding", with a unit spacing of 30 mm. This size combination was optimized through characteristic mode analysis to ensure that the mode current distribution within the target frequency band is not distorted.

[0040] At the parasitic coupling level, the parasitic patch structure 3 is a rectangular patch, 15.2 mm long and 9.8 mm wide, laid flat on the upper surface of the middle layer dielectric substrate 4. A circular hole with a radius of 0.8 mm is formed within it, allowing the central feed metal pillar a62 to pass through without contact. The lower layer metal ground 5 has eight circular holes with a radius of 0.8 mm at the corresponding feed positions to prevent short circuits with the feed structure. This hole design, combined with the layered through-type connection of the central / side dual feed pillars (with a horizontal spacing of 5.3 mm), enables simultaneous excitation of both central feed and parasitic coupling feed modes without mutual interference.

[0041] The bottom microstrip line group 7 consists of four microstrip lines with the following in-plane dimensions: first microstrip line: (13-14.4 mm) × (89.5-92.7 mm); second microstrip line: (8.55-9.15 mm) × (28.1-34.1 mm); third microstrip line: (11.3-17.3 mm) × (98.7-104.7 mm); fourth microstrip line: (6.85-10.85 mm) × (28.7-44.7 mm). The linewidth is 0.9-1.2 mm. Based on the dielectric constant of the substrate (e.g., εr=3.55) and the operating frequency band, the feed ports of the same type in the four basic units that are in a centrally symmetrical position are connected in pairs to form a phase conjugate network.

[0042] The array antenna with the above-described dimensions and structural configuration achieved stable backward RCS enhancement in the 4.5–5.1 GHz frequency band, with a -10 dB coverage angle at each frequency as shown below. Figures 14-20 As shown, the angles are all no less than 143.94°, verifying the effectiveness of this embodiment.

[0043] Specifically, such as Figure 12 As shown, the bottom microstrip line group 7 consists of a first microstrip line 91, a second microstrip line 92, a third microstrip line 93, and a fourth microstrip line 94, connecting the ports of the same type of two basic units located in a centrally symmetrical position. Specifically, in conjunction with... Figure 8 , Figure 10 , Figure 11As shown, the central feed metal pillar in the leftmost feed structure is connected to the left port of the first microstrip line 91, and the side feed metal pillar is connected to the left port of the third microstrip line 93. Following this pattern, the remaining six sets of feed metal pillars are connected to their corresponding microstrip line ports. Finally, the y-axis length of microstrip line 91 is the distance between the central feed metal pillar in the leftmost feed structure and the side feed metal pillar in the rightmost feed structure. The y-axis length of microstrip line 93 is the distance between the side feed metal pillar in the leftmost feed structure and the central feed metal pillar in the rightmost feed structure. Microstrip lines 92 and 94 are the distances between the feed metal pillars in the two middle feed structures after being connected symmetrically at the center.

[0044] In Example 1, the metasurface patch radiating structure 1 is made of metal and consists of four sets of basic units reusing the second patch edge. (Reference) Figure 5 In the middle, a113, a114, a115, and a116, there are 12 second rectangular patches a11 to a112 arranged around the perimeter. Adjacent basic units share 4 second rectangular patches, among which the second rectangular patches a11 to a112 are the optimization results of the mode term coefficient analysis.

[0045] In one embodiment of the present invention, the first rectangular patch has a side length of 10.5 mm, the second rectangular patch has a side length of 6 mm, the gap width between the first rectangular patches is 1 mm, the distance between the first and second rectangular patches is 1 mm, and the distance between the second rectangular patches is 3.5 mm. A circular patch is provided at the geometric center of the entire patch assembly. Figure 5 In the middle, a117 serves as the coupling feed port. This circular patch has a radius of 1.5 mm, and its spacing with the four first rectangular patches is 0.5 mm. In the four sets of basic units of the metasurface patch radiation structure 1, every two adjacent basic units share a row of second rectangular patches, and the center-to-center spacing between any two basic units is 30 mm. (Refer to...) Figure 6 As shown, the entire metasurface patch radiating structure 1 is covered on the top layer of the upper dielectric substrate 2. The size of the patch and the spacing between the patches are only one specific embodiment and are not limitations of the present invention.

[0046] In one embodiment, the upper dielectric substrate 2 is made of Rogers RO4003 material with a dielectric constant εr = 3.55, a thickness H1 = 3.016 mm, a long side of 140 mm, and a short side of 50 mm. Figure 7 As shown, the substrate has pre-drilled holes for placing the central power supply metal pillar a62.

[0047] Parasitic patch structures 3 are disposed between the upper dielectric substrate 2 and the middle dielectric substrate 4, and are laid flat on the upper surface of the middle dielectric substrate 4, totaling 4 groups. Each parasitic patch is rectangular in shape, with a long side of 15.2 mm and a short side of 9.8 mm. A circular hole with a radius of 0.8 mm is formed in the center of each patch to prevent contact between the parasitic patch and the central feed metal pillar a62. The position of the hole is determined by the central feed metal pillar. Figure 8 As shown. The parasitic patch structure 3 is bonded to the upper dielectric substrate 2 and the middle dielectric substrate 4 by lamination. Its thickness is related to the lamination process. Under ideal conditions, the total thickness is the three dielectric substrates plus the metal layer.

[0048] Optionally, the middle dielectric substrate 4 is made of Rogers RO4003 material with a dielectric constant εr = 3.55, a thickness H2 = 1.508 mm, a long side of 140 mm, and a short side of 50 mm. Figure 9 As shown, the substrate has pre-drilled holes for placing the central power supply metal pillar a62 and the side power supply metal pillar a61.

[0049] Optionally, a lower metal ground layer 5 is disposed between the middle dielectric substrate 4 and the lower dielectric substrate 6, with a long side of 140 mm and a short side of 50 mm, and has eight circular holes formed thereon. Figure 10 As shown, the hole radius is 0.8 mm, and its position is determined by the power supply structure to prevent the metal ground 5 from contacting the power supply structure 8.

[0050] Optionally, the lower dielectric substrate 6 is made of Rogers RO4003 material with a dielectric constant εr = 3.55, a thickness H3 = 0.508 mm, a long side of 140 mm, and a short side of 50 mm. (See reference.) Figure 11 As shown, the substrate has pre-drilled holes for placing the central power supply metal pillar a62 and the side power supply metal pillar a61.

[0051] In one embodiment, the short-distance difference between the contact point between the microstrip line and the feed metal pillar in the x-axis direction is 0.55 mm, that is, the distance from the edge of the microstrip line to the center of the feed metal pillar in the x-axis direction is 0.55 mm. Figure 21 The diagram shown is an enlarged schematic showing the specific details of the phase-shifted microstrip line and its feeding structure.

[0052] The phase shift line length is calculated by CST and fine-tuned by HFSS to ensure consistent electrical length, ensuring that the two pairs of microstrip lines provide the same phase shift to achieve incoming wave backtracking.

[0053] Optionally, the power supply structure 8 is made of metal, see reference. Figure 2The feed structure 8 consists of four groups, arranged symmetrically in a mirror image along the central axis. Each feed structure includes a central feed metal pillar a62 and a side feed metal pillar a61, with a horizontal distance of 5.3 mm between them. The central feed metal pillar a62 vertically penetrates the entire array surface, connecting the metasurface patch radiating structure 1 to the bottom microstrip line group 7; the side feed metal pillar a61 only penetrates the middle dielectric substrate 4 and the lower dielectric substrate 6, connecting the parasitic patch structure 3 to the bottom microstrip line group 7, as shown below. Figure 13 As shown. The feed structure has an 8-column radius of 0.3mm, and the central feed metal column is directly electrically connected to the circular patch a117. The microstrip line has a characteristic impedance of 50 ohms. The above dimensions are only one implementation method and are not limited thereto.

[0054] Figures 14-20 The figures show the monostation RCS simulation results of the metasurface-loaded wide-angle Van Atta array in this invention at 4.5 GHz, 4.6 GHz, 4.7 GHz, 4.8 GHz, 4.9 GHz, 5.0 GHz, and 5.1 GHz, respectively, in dB. The dashed lines in each figure represent the normalized RCS results of this invention, while the solid lines represent the normalized RCS results of a PEC metal plate of the same size. The -10 dB coverage angles of this invention at each frequency are approximately 143.94°, 156.48°, 161.63°, 170.73°, 173.04°, 174.65°, and 175.23°, respectively. Figures 14-20 As can be seen, compared with metal plates of the same size, the present invention achieves significant RCS enhancement over a wide range of angles deviating from the normal, and remains stable with frequency changes.

[0055] Example 2: To achieve the wideband characteristics of a Van Atta array antenna, the elements comprising the Van Atta array are designed using a metasurface configuration. This invention discloses a design method for a metasurface-loaded wide-angle wideband Van Atta array antenna based on eigenmode analysis, including: S1: Establish the prototype of the basic unit in the metasurface patch radiation structure, including multiple first rectangular patches, multiple second rectangular patches and one circular patch, arranged according to the structural form of the basic unit in claim 1, perform characteristic mode analysis on the array antenna, obtain the current distribution, radiation pattern and importance MS parameters of multiple modes under characteristic mode analysis, and screen the operating modes that can be excited and meet the bandwidth and radiation pattern requirements from multiple modes, including the first operating mode and the second operating mode; S2: For the current distribution diagrams corresponding to the two working modes, by adjusting the size and spacing of the first rectangular patch and the size and spacing of the second rectangular patch in the first rectangular patch assembly, the current distribution diagram remains stable and undistorted under the target bandwidth. The target bandwidth is determined according to the design specifications. The spacing of the first rectangular patch and the spacing of the second rectangular patch include the distance between the first rectangular patches, the distance from the center of the circular patch, the distance from the second rectangular patch, and the distance between adjacent second rectangular patches. S3: Design the size, holes, and position of the side feed metal pillars of the parasitic patch. Adjust the length and width of the parasitic patch, the radius of the holes, and the position of the side feed metal pillars on the prototype of the parasitic patch so that the return loss S11 of the array antenna is less than the target loss, such as -10 dB. S4: In the metasurface patch radiation structure, multiple even-numbered basic units are extended, and a corresponding number of parasitic patches are extended. S5: Determine the structure of multiple sets of microstrip lines based on the positions of the side-feed metal pillars and the center-feed metal pillars on the parasitic patch, including the lengths of the microstrip lines along the x and y axes.

[0056] The above is one implementation method of the array antenna design in Example 1. For specific structure, please refer to [reference needed]. Figure 1-13 The structure will not be described in detail to avoid redundancy.

[0057] To verify the technical effect of the metasurface-loaded wide-angle broadband Van Atta array antenna based on characteristic mode analysis in this invention, a single-station RCS simulation was performed on the Van Atta array antenna of this embodiment, with a metal plate (PEC) of the same size as the comparison benchmark. Figures 14-20 Normalized monocentric RCS simulation results are presented for various frequency points within the 4.5–5.1 GHz range. The -10 dB coverage angles at each frequency point are approximately 143.94°, 156.48°, 161.63°, 170.73°, 173.04°, 174.65°, and 175.23°, respectively. The results demonstrate that this invention achieves stable RCS enhancement within the 4.5 GHz to 5.1 GHz frequency band, with a relative bandwidth of 12%. The -10 dB angle coverage remains stable above 144° across a wide bandwidth. The bandwidth criterion here is a frequency band with a -10 dB fluctuation coverage angle ≥ 144°. Within this bandwidth, the Vanatta array can guarantee stable RCS enhancement without drastic fluctuations. Extending the frequency range further out results in a deterioration due to pattern distortion, reflecting the superior frequency response flatness, frequency stability, and wide-angle domain characteristics of this invention.

[0058] In summary, a metasurface-loaded wide-angle broadband Van Atta array antenna based on eigenmode analysis and its design method were presented. This approach broadened the operating bandwidth and achieved higher frequency stability. Furthermore, structural reuse during array configuration further reduced the overall array size. Simultaneously, parasitic patch coupling feeding and center feeding were employed to excite two modes, achieving complementary excitation.

[0059] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A metasurface-loaded wide-angle broadband Van Atta array antenna based on eigenmode analysis, characterized in that, The structure includes, from top to bottom, a metasurface patch radiating structure (1), an upper dielectric substrate (2), a parasitic patch structure (3), a middle dielectric substrate (4), a lower metal ground layer (5), a lower dielectric substrate (6), and a bottom microstrip line group (7), as well as a feeding structure (8); wherein: The metasurface patch radiating structure (1) is attached to the upper surface of the upper dielectric substrate (2) and consists of an even number of basic units. The metasurface patch radiating structure (1) is designed based on characteristic mode analysis to achieve the wideband electromagnetic response of the antenna. Each basic unit is arranged along the array direction and is symmetrically arranged in pairs about the center of the array. Each basic unit includes multiple first rectangular patches and multiple second rectangular patches. Multiple first rectangular patches are arranged in a square array to form a first rectangular patch combination. Second rectangular patches are evenly arranged around the first rectangular patch combination. Adjacent basic units share a column of second rectangular patches located on the right side of the first rectangular patch combination. This column of second rectangular patches is arranged longitudinally to form a shared side. A circular patch (a117) is set at the geometric center of each group of basic units. Multiple first rectangular patches are arranged around the circular patch (a117). Multiple second rectangular patches are arranged around the periphery of multiple first rectangular patches to form a metasurface loading form. Parasitic patch structure (3) is laid flat on the upper surface of the middle layer dielectric substrate (4) in a one-to-one correspondence with the basic unit. It includes multiple parasitic patches. When multiple parasitic patches on the parasitic patch structure (3) are fed by the side-feed metal pillar (a61), the metasurface patch radiating structure (1) operates in the first working mode. When the center-feed metal pillar (a62) on the parasitic patch structure (3) is fed, the metasurface patch radiating structure (1) operates in the second working mode. In the first working mode, the radiation pattern of the metasurface patch radiating structure (1) is a first shape, and the metasurface patch radiating structure (1) is sensitive to electromagnetic waves that are incident normally. In the second working mode, the radiation pattern of the radiating structure (1) is a second shape, and the metasurface patch radiating structure (1) is sensitive to electromagnetic waves that are incident obliquely. The first working mode and the second working mode do not interfere with each other and work simultaneously to realize the wide-angle electromagnetic response of the antenna. Each power supply structure (8) corresponds to a basic unit. Each power supply structure includes a central power supply metal pillar (a62) and a side power supply metal pillar (a61). The central power supply metal pillar (a62) vertically penetrates the upper dielectric substrate (2), the middle dielectric substrate (4), and the lower dielectric substrate (6), connecting the metasurface patch radiation structure (1) and the bottom microstrip line group (7). The side power supply metal pillar (a61) penetrates the middle dielectric substrate (4) and the lower dielectric substrate (6), connecting the parasitic patch structure (3) and the bottom microstrip line group (7). Each parasitic patch has a circular hole in the center, allowing the central power supply metal pillar (a62) to pass through without contact. The lower metal ground (5) is disposed between the middle dielectric substrate (4) and the lower dielectric substrate (6), and a hole is provided on it for the power supply structure (8) to pass through without contact. The bottom microstrip line group (7) is attached to the lower surface of the lower dielectric substrate (6) and consists of multiple microstrip lines. The center feed metal pillar and the side feed metal pillar in the feed structure are connected to the corresponding microstrip line ports. The connected microstrip line ports are on the same axis as the feed metal pillars. The bottom microstrip line group (7) connects the feed ports of the same type in the basic unit in the central symmetric position to each other. That is, the two ends of the same microstrip line are respectively connected to the same type of feed metal pillars of a pair of central symmetric basic units to achieve phase conjugation, form a Van Atta array antenna, and enhance RCS.

2. The Van Atta array antenna according to claim 1, characterized in that, The metasurface patch radiation structure (1) consists of 4 sets of basic units to form a 1×4 array patch. Each pair of adjacent basic units shares a second rectangular side; the center-to-center distance between adjacent basic units is 25~35 mm.

3. The Van Atta array antenna according to claim 2, characterized in that, Each basic unit group includes 16 rectangular radiating patches and 1 circular patch (a117): four first rectangular patches (a113, a114, a115, a116) are arranged in four quadrants around the inner perimeter to form a first rectangular patch combination; 12 second rectangular patches (a11, a12, a13, a14, a15, a16, a17, a18, a19, a110, a111, and a112) are arranged clockwise around the outer perimeter of the first rectangular patch combination; the circular patch (a117) is located at the geometric center between the four first rectangular patches and serves as a coupling feed port connected to the central feed metal pillar (a62); two adjacent basic units share the second rectangular patches a14, a15, a16, and a17.

4. The Van Atta array antenna according to claim 3, characterized in that, The first rectangular patch has a side length of 8-12mm, the second rectangular patch has a side length of 4-8mm, the gap width between adjacent second rectangular patches is 0.5-1.5mm, the distance between the second rectangular patch and the first rectangular patch is 0.3-1.6mm, and the distance between the second rectangular patches is 2-4mm; the radius of the circular patch (a117) is 0.6-1.7mm, and the distance between the center of the circular patch (a117) and the four first rectangular patches is 0.25~0.75mm.

5. The Van Atta array antenna according to claim 1, characterized in that, The parasitic patch structure (3) includes a number of parasitic patches equal to the number of basic units. The size of the parasitic patch in the parasitic patch structure (3) is designed according to the impedance of the array antenna. By adjusting the length, width and aperture radius of the parasitic patch, the return loss S11 of the array antenna is made less than the preset loss.

6. The Van Atta array antenna according to claim 1, characterized in that, The upper dielectric substrate (2), the middle dielectric substrate (4) and the lower dielectric substrate (6) are made of microwave dielectric material with dielectric constant εr=3.05-4.

05. The three have the same planar dimensions and their thickness decreases sequentially.

7. The Van Atta array antenna according to claim 1, characterized in that, The planar dimensions of the lower metal ground (5) are the same as those of the upper dielectric substrate (2), the middle dielectric substrate (4) and the lower dielectric substrate (6). A total of 8 circular holes are opened on it, and their positions are located by the feeding metal pillars in the feeding structure (8).

8. The Van Atta array antenna according to claim 2, characterized in that, When the metasurface patch radiating structure (1) is composed of 4 basic units, the bottom microstrip line group (7) includes a first microstrip line (91), a second microstrip line (92), a third microstrip line (93), and a fourth microstrip line (94). The x-axis lengths of the first microstrip line (91), the second microstrip line (92), the third microstrip line (93), and the fourth microstrip line (94) are designed according to the dielectric constant of the dielectric substrate and the operating frequency of the array antenna. The y-axis lengths of the first microstrip line (91), the second microstrip line (92), the third microstrip line (93), and the fourth microstrip line (94) are related to the positions of the center feed metal pillar and the side feed metal pillar in the feed structure.

9. The Van Atta array antenna according to any one of claims 1 to 8, characterized in that, The array antenna operates in the frequency band of 4.5 to 5.1 GHz, with a relative bandwidth of not less than 10% to 14%, and the -10 dB angle coverage of a single station RCS within the operating frequency band is not less than 140°.

10. A design method for a Van Atta array antenna according to any one of claims 1 to 9, characterized in that, Includes the following steps: S1: Establish the prototype of the basic unit in the metasurface patch radiation structure, including multiple first rectangular patches, multiple second rectangular patches and one circular patch. The multiple first rectangular patches are arranged in a square array to form a first rectangular patch combination. Second rectangular patches are evenly arranged around the perimeter of the first rectangular patch combination. A circular patch is set at the geometric center of each basic unit group. Perform characteristic mode analysis on the array antenna to obtain the current distribution, radiation pattern and importance MS parameters of multiple modes under characteristic mode analysis. Select the operating modes that can be excited and meet the bandwidth and radiation pattern requirements from multiple modes, including the first operating mode and the second operating mode. S2: For the current distribution diagrams corresponding to the two working modes, by adjusting the size and spacing of the first rectangular patch and the size and spacing of the second rectangular patch in the first rectangular patch assembly, the current distribution diagram remains stable and undistorted under the target bandwidth. The target bandwidth is determined according to the design specifications. The spacing of the first rectangular patch and the spacing of the second rectangular patch include the distance between the first rectangular patches, the distance from the center of the circular patch, the distance from the second rectangular patch, and the distance between adjacent second rectangular patches. S3: Design the size, holes, and position of the side feed metal pillars of the parasitic patch. Adjust the length and width of the parasitic patch, the radius of the holes, and the position of the side feed metal pillars on the prototype of the parasitic patch so that the return loss S11 of the array antenna is less than the target loss. S4: In the metasurface patch radiation structure, multiple even-numbered basic units are extended, and a corresponding number of parasitic patches are extended. S5: Determine the structure of multiple sets of microstrip lines based on the positions of the side-feed metal pillars and the center-feed metal pillars on the parasitic patch, including the lengths of the microstrip lines along the x and y axes.

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