Reconfigurable metasurface integrated low-rsc wideband tight-coupling antenna element and array

Abstract

The application discloses a reconfigurable metasurface integrated low-RCS wideband tightly coupled antenna unit and array, and mainly solves the problem of narrow frequency band in the integration design of the existing antenna and reconfigurable metasurface. The antenna unit is formed by a first dielectric layer, an air layer, a metal patch layer, a second dielectric layer, a matching layer, a third dielectric layer, a metal back plate layer, a fan-shaped patch layer and a fourth dielectric layer from top to bottom, and a flat tightly coupled structure is formed. The metal patch layer is distributed with a 'ladder type' dipole patch, a coupling patch and a reconfigurable metasurface patch. The 'ladder type' dipole patch and the reconfigurable metasurface patch are cross-distributed to realize the independent work of the antenna and the reconfigurable metasurface. A plurality of antenna units are arranged periodically to form a wideband tightly coupled antenna array. The application can not only realize flexible regulation and control of the scattering electric field on the cross polarization, but also realize a wide antenna working bandwidth on the main polarization. The application has good effect in the single-station RCS reduction of the dual polarization and can be used for radar detection stealth.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of radar detection, and particularly relates to a low radar cross section (RCS) wideband tightly coupled antenna and antenna array, which can be used for radar detection of stealth. BACKGROUND

[0002] With the development of radar detection systems, stealth technology plays an important role in breaking through radar detection. In aircraft onboard equipment, antennas play an indispensable role in RCS reduction, and how to further reduce the RCS of antennas has become a research hotspot. Electromagnetic super surface is often applied in RCS reduction due to its great potential. Electromagnetic super surface realizes the regulation of scattered electromagnetic waves through special phase arrangement, and finally realizes RCS reduction.

[0003] Ying Liu et al. proposed a low radar cross section antenna array with reconfigurable scattering pattern based on digital antenna unit. The digital antenna unit has two scattering states controlled by PIN diode. Under y polarization incidence, the two scattering phases of the unit have a 180° phase difference at 4.2 GHz and 5 GHz, and the maximum RCS reduction is 15 dB. On the x polarization, the unit can be used as an antenna for wave absorption. Within 4.4-6 GHz, the maximum RCS reduction of the antenna is 7 dB. However, in this design, the working frequency band of the antenna is relatively narrow, and the wideband RCS reduction effect cannot be achieved.

[0004] The patent document with publication number CN110611165A discloses a low RCS antenna based on phase gradient super surface with polarization conversion function, which is composed of a polarization conversion super surface and an antenna. The super surface is composed of 8 unit structures arranged in two-dimensional phase gradient, and can realize polarization conversion of electromagnetic waves within 8-14 GHz frequency band. The antenna and the super surface work on the same polarization, and have good stealth effect for single-polarized radar. However, this polarization conversion method of electromagnetic wave can only realize single-polarized RCS reduction, and does not have the ability of dual-polarized RCS reduction.

[0005] The patent document with publication number CN109638456B discloses a phased array RCS reduction method based on reconfigurable scattering phase, which designs a phased array with reconfigurable scattering phase. The antenna unit is loaded with PIN diode, and the scattering phase is modulated by the on-off of the diode. When the phased array works, the diodes are all turned off, and the phased array works normally. When the phased array does not work, the scattering phase is controlled by adjusting the on-off of the diodes. The array is distributed in a chessboard pattern, and the RCS reduction is realized by phase cancellation. However, in this method, the antenna and the super surface cannot work independently at the same time, and the flexibility is poor. SUMMARY

[0006] The purpose of this invention is to address the shortcomings of the prior art by proposing a reconfigurable metasurface integrated low RCS broadband tightly coupled antenna element and antenna array, so as to improve the antenna operating bandwidth in the dual-polarized RCS reduction scheme formed by combining the reconfigurable metasurface and the antenna.

[0007] The approach to achieving the objective of this invention is as follows: By combining a flat, tightly coupled antenna with a reconfigurable metasurface, a wide operating bandwidth of the antenna can be achieved while flexibly controlling the cross-polarized scattering electric field. RCS reduction on the main polarization is achieved by using the antenna as an absorbing device to absorb electromagnetic waves. Through the integrated design of the metasurface and antenna—that is, the metasurface and antenna are cross-distributed and operate on different polarizations—and by loading PIN diodes onto the metasurface to control the scattering phase, the flexibility of the metasurface in controlling the scattering electric field is enhanced. By using a checkerboard distribution of the metasurface scattering phase, RCS reduction on the cross-polarization is achieved using the phase cancellation principle.

[0008] Based on the above ideas, the technical solution of the present invention includes the following:

[0009] 1. A low RCS broadband tightly coupled antenna based on reconfigurable metasurface integration, comprising a multilayer structure and feed copper pillars and ground copper pillars for connecting the layers, characterized in that:

[0010] From top to bottom, the layers are: first dielectric layer, air layer, metal patch layer, second dielectric layer, matching layer, third dielectric layer, metal backplate layer, fan-shaped patch layer, and fourth dielectric layer, forming a flat, tightly coupled structure.

[0011] The metal patch layer has "stepped" dipole patches, coupling patches and reconfigurable metasurface patches distributed on it, forming an integrated structure of a flat tightly coupled antenna and a reconfigurable metasurface, so as to achieve flexible control of the scattered electric field in cross polarization and simultaneously achieve a wide antenna operating bandwidth in the main polarization.

[0012] The stepped dipole patch and the reconfigurable metasurface patch are cross-distributed to ensure the independent operation of the flat tightly coupled antenna and the reconfigurable metasurface.

[0013] Furthermore, the matching layer has two rectangular metal patches that are close to each other, which are connected to the power supply copper pillar to form a "rib" structure. The length L8 of each rectangular metal patch is 1.3mm to 1.5mm, the width w8 is 0.5mm to 0.7mm, and the distance between them is 0.05mm to 0.1mm.

[0014] The fan-shaped patch layer has three fan-shaped branches and their connected metal wires;

[0015] The fourth dielectric layer has a circular slot for inserting an external coaxial interface.

[0016] Furthermore, the metal backplate has a first set of power supply copper and two sets of grounding copper pillars connected between it and the metal patch layer; the fan-shaped patch layer has a second set of power supply copper pillars connected between it and the metal patch layer; and a bias grounding copper is connected between it and the metal backplate layer.

[0017] Furthermore, all four dielectric layers are made of F4B board with a dielectric constant of 2.2 and a loss tangent of 0.0015. Their heights are different, namely, the thickness h1 of the first dielectric layer is 4mm to 4.2mm, the thickness h2 of the second dielectric layer is 0.3mm to 0.5mm, the thickness h3 of the third dielectric layer is 2.5mm to 2.7mm, and the thickness h4 of the fourth dielectric layer is 0.8mm to 1mm. The second, third, and fourth dielectric layers are connected by an adhesive layer with a dielectric constant of 2.8.

[0018] Furthermore, according to claim 1, the antenna is characterized in that the distance between the first dielectric layer and the metal patch layer, i.e. the thickness of the air, is 1mm to 1.2mm.

[0019] Furthermore, the "stepped" dipole patch consists of two symmetrical three-segment rectangular patches, each with different length and width parameters, and is fed through a first set of feeding copper pillars and connected to the metal backplate through a first set of grounding copper pillars; the coupling patch, with a width w0 of 0.3mm to 0.5mm, is distributed around the periphery of the "stepped" dipole patch and is connected to the metal backplate through a second set of grounding copper pillars to improve the impedance matching of the antenna; the reconfigurable metasurface patch consists of four rectangular metal segments, divided into positive and negative parts by PIN diodes, and is DC fed through a second set of feeding copper pillars, with each rectangular patch having different length and width parameters.

[0020] Furthermore, each of the three rectangular segments in the "stepped" dipole patch has different parameters: the first rectangular segment has a length L1 of 1mm to 1.15mm and a width w1 of 0.3mm to 0.5mm; the second rectangular segment has a length L2 of 1.1mm to 1.25mm and a width w2 of 1mm to 1.2mm; and the third rectangular segment has a length L3 of 1mm to 1.15mm and a width w3 of 2.8mm to 3.0mm. In the reconfigurable metasurface patch... The four rectangular patches are as follows: the length L4 of the first rectangular patch is 0.3mm to 0.5mm and the width w4 is 0.9mm to 1.1mm; the length L5 of the second rectangular patch is 3.5mm to 3.7mm and the width w5 is 1mm to 1.2mm; the length L6 of the third rectangular patch is 1.8mm to 2mm and the width w6 is 1.3mm to 1.5mm; and the length L7 of the fourth rectangular patch is 2.3mm to 2.5mm and the width w7 is 1mm to 1.2mm.

[0021] Furthermore, the metal backplate is a copper layer with circular holes. The first copper feeder in the second group of copper feeders passes through the first circular hole and connects to the fan-shaped patch layer; the second copper feeder in the second group of copper feeders passes through the second circular hole and connects to the fan-shaped patch; and the second copper feeder in the first group of copper feeders passes through the third circular hole and connects to the fourth dielectric layer.

[0022] Furthermore, the three fan-shaped segments of the fan-shaped patch have the following characteristics: the radius d1 of the first fan-shaped segment is 4mm to 4.1mm, and it is connected to the second feed copper column and the bias ground copper column in the second group of feed copper columns respectively through metal wires; the radius of the second fan-shaped segment is the same as that of the first fan-shaped segment, and it is connected to the first feed copper column in the second group of feed copper columns through metal wires; the radius d2 of the third fan-shaped segment is 3.4mm to 3.5mm, and it is connected to the second fan-shaped segment through metal wires.

[0023] Furthermore, the circular slots opened on the fourth medium are positioned corresponding to the second feed copper pillar in the first group of feed copper pillars, and the diameter R of the slots is 3.4mm to 3.45mm.

[0024] 2. A low RCS broadband tightly coupled antenna array based on reconfigurable metasurface integration, comprising multiple antenna elements arranged periodically, characterized in that: the metal patch layers between each antenna element are connected, the coupling plates between adjacent elements are connected to form a tightly coupled structure, the reconfigurable metasurface patches between adjacent elements are connected to form a whole, the reflection phase of the reconfigurable metasurface is controlled by controlling the switching state of the PIN diodes in each element, and the reflection phase is distributed in a checkerboard pattern in the array; the metal backplate layers between each antenna element are connected to form a complete metal backplate, forming antenna arrays of different sizes.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] First, the present invention employs a flat, tightly coupled structure consisting of a first dielectric layer, an air layer, a metal patch layer, a second dielectric layer, a matching layer, a third dielectric layer, a metal backplate layer, a fan-shaped patch layer, and a fourth dielectric layer from top to bottom, which enables the antenna to have a wider operating bandwidth.

[0027] Secondly, due to the integrated design of the flat tightly coupled antenna and the reconfigurable metasurface, the present invention can not only flexibly control the scattering electric field on the cross polarization, but also achieve a wide antenna operating bandwidth on the main polarization, thus achieving good results in dual-polarization RCS reduction.

[0028] Third, the present invention employs a method of cross-distribution of reconfigurable metasurface patches and "stepped" dipole patches, which allows the two to work independently without affecting each other. Attached Figure Description

[0029] Figure 1 This is an overall structural diagram of the present invention;

[0030] Figure 2 This is a diagram of the single-layer structure in this invention.

[0031] Figure 3 A diagram showing a 7x8 antenna array constructed using the antenna elements of this invention;

[0032] Figure 4 Simulation diagram of reflection coefficient and reflection phase of reconfigurable metasurface;

[0033] Figure 5 Simulation diagrams of the standing wave ratio (SWR) of the antenna E-plane and H-plane under two states of the reconfigurable metasurface;

[0034] Figure 6 To test the radiation patterns of the E-plane and H-plane of a 5x5 antenna array;

[0035] Figure 7 This diagram illustrates the RCS reduction effect of a 7x8 antenna array for testing purposes. Detailed Implementation

[0036] The technology, solution, and effects of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0037] Reference Figure 1 and Figure 2 The antenna element of the present invention is provided in the following three embodiments.

[0038] Example 1:

[0039] This embodiment includes an air layer, a metal patch layer, a matching layer, a metal backplate, a fan-shaped patch layer, and four dielectric layers, wherein:

[0040] The first dielectric layer 1, which is located on the top layer, is made of F4B material with a dielectric constant of 2.2 and a loss tangent of 0.0015, and a thickness h1 of 4 mm. The function of this layer is to improve the impedance matching of the antenna and widen the scanning angle of the antenna.

[0041] The air layer 2 is the air between the first dielectric layer 1 and the metal patch layer 3, and has a thickness of 1 mm.

[0042] The metal patch layer 3, located below the air layer 2, has "stepped" dipole patches 31, coupling patches 32, and reconfigurable metasurface patches 33 distributed on it, forming an integrated structure of a flat, tightly coupled antenna and a reconfigurable metasurface. This allows for flexible control of the scattered electric field in cross-polarization and simultaneously achieves a wide antenna operating bandwidth in the main polarization. A first set of feed copper pillars 10 and 11, and two sets of ground copper pillars 12, 13, and 14, 15 connect the metal patch layer 3 to the metal backplate layer 7. A second set of feed copper pillars 16 and 17 connect the metal patch layer 3 to the fan-shaped patch layer 8. Figure 2 As shown in (a).

[0043] The "stepped" dipole patch 31 consists of two symmetrical three-segment rectangular patches, each fed through a first set of feeding copper pillars 10 and 11, and connected to the metal backplane layer 7 through a first set of grounding copper pillars 12 and 13 to eliminate common-mode resonance. The first rectangular patch of each three-segment patch has a length L1 of 1.15 mm and a width w1 of 0.5 mm; the second rectangular patch has a length L2 of 1.25 mm and a width w2 of 1.2 mm; and the third rectangular patch has a length L3 of 1.15 mm and a width w3 of 3 mm.

[0044] The coupling patch 32 is distributed around the periphery of the "stepped" dipole patch 31, with a width w0 of 0.5 mm, and is connected to the metal backplate layer 7 through the second set of ground copper pillars 14 and 15 to improve the impedance matching of the antenna.

[0045] The reconfigurable metasurface patch 33 is interspersed with the "stepped" dipole patch 31 to ensure independent operation of the flat, tightly coupled antenna and the reconfigurable metasurface. The reconfigurable metasurface patch consists of four rectangular metal segments, divided into positive (331) and negative (332) parts by PIN diodes. These two parts are DC-fed through a second set of feed copper pillars 16 and 17. Each rectangular patch segment has different length and width parameters: the first segment has a length L4 of 0.5 mm and a width w4 of 1.1 mm; the second segment has a length L5 of 3.7 mm and a width w5 of 1.2 mm; the third segment has a length L6 of 2 mm and a width w6 of 1.5 mm; and the fourth segment has a length L7 of 2.5 mm and a width w7 of 1.2 mm.

[0046] The second dielectric layer 4 is located below the metal patch layer 3. It is made of F4B material with a dielectric constant of 2.2 and a loss tangent of 0.0015, and a thickness h2 of 0.3 mm.

[0047] The matching layer 5 is located below the second dielectric layer 4, and has two closely spaced rectangular metal patches on it. These two rectangular metal patches are connected to the first set of power-feeding copper pillars 10 and 11 to form a "rib" structure. Each rectangular metal patch has a length L8 of 1.5 mm and a width w8 of 0.7 mm, and the distance between them is 0.1 mm. Figure 2 As shown in (b).

[0048] The third dielectric layer 6 is located below the matching layer 5. It is made of F4B material with a dielectric constant of 2.2 and a loss tangent of 0.0015, and its thickness h3 is 2.5 mm.

[0049] The metal backplate layer 7, located below the third dielectric layer 6, is a copper layer. It is connected to the fan-shaped patch layer 8 via a bias grounding post 18 and has three circular holes 71, 72, and 73 to facilitate the connection of the feed copper posts through these holes, enabling the metal patch layer 3 to connect with the fan-shaped patch layer 8 and the fourth dielectric layer 9. Specifically, the connections are as follows: the first feed copper post 16 in the second group of feed copper posts connects to the fan-shaped patch layer 8 through the first circular hole 71; the second feed copper post 17 in the second group of feed copper posts connects to the fan-shaped patch layer 8 through the second circular hole 72; and the second feed copper post 11 in the first group of feed copper posts connects to the fourth dielectric layer 9 through the third circular hole 73. Figure 2 As shown in (c).

[0050] The fan-shaped patch layer 8 is located below the metal backplate layer 7, and has three fan-shaped branches 81, 82, and 83 and their connected metal wires. The first fan-shaped branch 81 has a radius d1 of 4.1 mm, and is connected to the second feed copper pillar 17 and the bias ground copper pillar 18 in the second group of feed copper pillars via metal wires; the second fan-shaped branch 82 has the same radius as the first fan-shaped branch, and is connected to the first feed copper pillar 16 in the second group of feed copper pillars via metal wires; the third fan-shaped branch 83 has a radius d2 of 3.5 mm, and is connected to the second fan-shaped branch 82 via metal wires. The function of the three fan-shaped branches 81, 82, and 83 is to eliminate the influence of the feed copper pillars on the reconfigurable metasurface 33, such as... Figure 2 As shown in (d).

[0051] The fourth dielectric layer 9 is located below the fan-shaped patch layer 8. It is made of F4B material with a dielectric constant of 2.2 and a loss tangent of 0.0015. Its thickness h4 is 0.8mm. A circular slot 91 is provided on it for the insertion of an external coaxial interface. The position of the slot corresponds to the second feed copper pillar 11 in the first group of feed copper pillars. The diameter R of the slot is 3.4mm.

[0052] The second dielectric layer 3, the third dielectric layer 6, and the fourth dielectric layer 9 are connected by an adhesive layer 19 with a dielectric constant of 2.8 and a thickness of 0.2 mm, ultimately forming a multi-layered antenna unit structure stacked from top to bottom. The antenna unit has a width dx of 7.5 mm, a length dy of 10 mm, and a height of 9 mm.

[0053] Example 2

[0054] The structure of this example is the same as that of Example 1, but the parameters are changed as follows:

[0055] The first dielectric layer 1 has a thickness h1 of 4.1 mm.

[0056] The air layer 2 has a thickness of 1.1 mm.

[0057] The metal patch layer 3 has a stepped dipole patch 31 with the following characteristics: the first rectangular patch segment has a length L1 of 1 mm and a width w1 of 0.3 mm; the second rectangular patch segment has a length L2 of 1.1 mm and a width w2 of 1 mm; the third rectangular patch segment has a length L3 of 1 mm and a width w3 of 2.8 mm; the coupling patch 32 has a width w0 of 0.3 mm; the reconfigurable metasurface patch 33 has a first rectangular patch segment with a length L4 of 0.3 mm and a width w4 of 0.9 mm; the second rectangular patch segment has a length L5 of 3.5 mm and a width w5 of 1 mm; the third rectangular patch segment has a length L6 of 1.8 mm and a width w6 of 1.3 mm; and the fourth rectangular patch segment has a length L7 of 2.3 mm and a width w7 of 1 mm.

[0058] The second dielectric layer 4 has a thickness of 0.4 mm.

[0059] The matching layer 5 has rectangular metal patches with a length L8 of 1.3 mm and a width w8 of 0.5 mm, and the spacing between them is 0.05 mm.

[0060] The third dielectric layer 6 has a thickness h3 of 2.6 mm.

[0061] The fan-shaped patch layer 8 has a first fan-shaped branch 81 with a radius d1 of 4 mm, a second fan-shaped branch 82 with the same radius as the first fan-shaped branch, and a third fan-shaped branch 83 with a radius d2 of 3.4 mm.

[0062] The fourth dielectric layer 9 has a thickness h4 of 0.9 mm and a diameter R of 3.3 mm for the circular slot 91.

[0063] Example 3

[0064] The structure of this example is the same as that of Example 1, but the parameters are changed as follows:

[0065] The first dielectric layer 1 has a thickness h1 of 4.2 mm.

[0066] The air layer 2 has a thickness of 1.2 mm.

[0067] The metal patch layer 3 has a stepped dipole patch 31 with the following dimensions: the first rectangular patch segment has a length L1 of 1.1 mm and a width w1 of 0.4 mm; the second rectangular patch segment has a length L2 of 1.2 mm and a width w2 of 1.1 mm; the third rectangular patch segment has a length L3 of 1.1 mm and a width w3 of 2.9 mm; the coupling patch 32 has a width w0 of 0.4 mm; the reconfigurable metasurface patch 33 has a first rectangular patch segment with a length L4 of 0.4 mm and a width w4 of 1 mm; the second rectangular patch segment has a length L5 of 3.6 mm and a width w5 of 1.1 mm; the third rectangular patch segment has a length L6 of 1.9 mm and a width w6 of 1.4 mm; and the fourth rectangular patch segment has a length L7 of 2.4 mm and a width w7 of 1.1 mm.

[0068] The second dielectric layer 4 has a thickness of 0.5 mm.

[0069] The matching layer 5 has a length L8 of 1.4 mm and a width w8 of 0.6 mm for each rectangular metal patch, and the spacing between them is 0.08 mm.

[0070] The third dielectric layer 6 has a thickness h3 of 2.7 mm.

[0071] The fan-shaped patch layer 8 has a first fan-shaped branch 81 with a radius d1 of 4.05 mm, a second fan-shaped branch 82 with the same radius as the first fan-shaped branch, and a third fan-shaped branch 83 with a radius d2 of 3.45 mm.

[0072] The fourth dielectric layer 9 has a thickness h4 of 1 mm and a diameter R of 3.35 mm for the circular slot 91.

[0073] Multiple antenna elements are arranged periodically, with metal patch layers 3 connecting each element. Couplers 32 between adjacent elements are connected to form a tightly coupled structure, and reconfigurable metasurface patches 33 between adjacent elements are connected to form a whole. The reflection phase of the reconfigurable metasurface 33 is controlled by controlling the switching state of the PIN diodes in each element, and the reflection phase is distributed in a checkerboard pattern in the array to achieve RCS reduction. The metal backplate layers 7 between the antenna elements are connected to form a complete metal backplate, which can be used to assemble antenna arrays of different sizes.

[0074] The present invention uses a 7*8 antenna array composed of antenna elements from Embodiment 1, such as... Figure 3 As shown.

[0075] The reflection phases are distributed in a checkerboard pattern in the array, achieving a significant reduction in RCS. The principle is as follows:

[0076] When an electromagnetic wave is incident perpendicularly, the magnitude of the monostatic RCS can be expressed as follows:

[0077]

[0078] in and A1 and A2 are the two reflection phases of the unit, respectively, and the reflection amplitudes of the unit under the two reflection phases.

[0079] From the above formula, we can see that when A1 and A2 are close to 1, and When the angle approaches 180°, the single-station RCS will be significantly reduced. At this point, the scattered electromagnetic waves will cancel each other out, dispersing the vertically incident electromagnetic waves to all directions, thereby reducing the electromagnetic waves scattered in the vertical direction.

[0080] The effects of this invention can be further illustrated through simulation experiments.

[0081] I. Simulation Conditions

[0082] The simulation was conducted using HFSS electromagnetic simulation software. The antenna element was simulated using its periodic boundary, floquet port, and lumped port. The antenna array was simulated using FI-BI boundary, lumped port, and incident wave excitation.

[0083] Multiple antenna elements from Embodiment 1 are arranged periodically to form a 7*8 antenna array, and the reconfigurable metasurface reflection phases in the antenna elements are distributed in a checkerboard pattern.

[0084] The units in Embodiment 1 of the present invention are arranged periodically to form a 5*5 antenna array.

[0085] II. Simulation Content

[0086] Simulation 1. The reflection coefficient and reflection phase of the reconfigurable metasurface of the antenna element in Embodiment 1 of this invention were tested under two states of PIN diode switching by using the periodic boundary and floquet terminals. The results are as follows: Figure 4 ,in Figure 4 (a) represents the reflection coefficient of the reconfigurable metasurface. Figure 4 (b) is the reconfigurable metasurface reflection phase.

[0087] from Figure 4 As can be seen, the reconfigurable metasurface of the present invention exhibits a reflection amplitude greater than -2dB in both PIN diode switching states within the 9GHz to 12GHz frequency band, with a phase difference of 180°±37°. This indicates that the reconfigurable metasurface can achieve a good reflection effect on electromagnetic waves, and the near 180° reflection phase difference enables the reconfigurable metasurface to achieve a good RCS reduction effect.

[0088] Simulation 2. The antenna VSWR of the reconfigurable metasurface of the antenna element in Embodiment 1 of this invention was tested under two states of PIN diode switching by using periodic boundaries and lumped ports. The results are as follows: Figure 5 ,in Figure 5 (a) is the E-plane VSWR of the antenna in the diode off state. Figure 5 (b) is the H-plane VSWR of the antenna in the diode off state. Figure 5 (c) represents the E-plane VSWR of the antenna in the diode-on state. Figure 5 (d) represents the H-plane VSWR of the antenna in diode on state.

[0089] from Figure 5 As can be seen, the VSWR of the antenna in the 5.1GHz to 12.4GHz frequency band is less than 3, and the scanning angle in both the E-plane and H-plane can reach ±50°. This shows that the antenna element in this invention can effectively radiate electromagnetic waves and achieve a wide scanning angle.

[0090] Simulation 3: The radiation pattern and gain of the 5*5 antenna array in Embodiment 1 of this invention were tested at the 12GHz test frequency using FI-BI boundaries and lumped ports. The results are as follows: Figure 6 ,in Figure 6 (a) is the E-plane beam scanning pattern. Figure 6 (b) is the H-plane beam scanning pattern.

[0091] from Figure 6 As can be seen, the array's radiation pattern can achieve precise pointing and a gain of 14 dBi.

[0092] Simulation 4. The RCS reduction effect of the 7*8 antenna array in Embodiment 1 of this invention was tested by using FI-BI boundary and incident wave excitation. The results are as follows: Figure 7 ,in Figure 7 (a) is the radar cross section of a flat, tightly coupled antenna. Figure 7 (b) is the radar cross section of the reconfigurable metasurface.

[0093] from Figure 7 As can be seen, the antenna achieves a maximum RCS reduction of 14.7 dB in the 5.1 GHz to 12.4 GHz band, with an average RCS reduction of 10 dB. The reconfigurable metasurface achieves a maximum RCS reduction of 17.8 dB in the 9 GHz to 12 GHz band, with an average RCS reduction of 13 dB, indicating that the array can achieve good dual-polarization RCS reduction.

[0094] The above description is merely a few specific embodiments of the present invention and does not constitute any limitation on the present invention. Obviously, those skilled in the art, after understanding the content and principles of the present invention, may make various modifications and changes in form and details without departing from the principles and structure of the present invention. However, these modifications and changes based on the ideas of the present invention are still within the scope of protection of the claims of the present invention.

Claims

1. A low RCS broadband tightly coupled antenna element based on reconfigurable metasurface integration, comprising: Multi-layer structure The power supply copper pillars and grounding copper pillars used to connect the various layers are characterized in that: From top to bottom, the layers are: first dielectric layer (1), air layer (2), metal patch layer (3), second dielectric layer (4), matching layer (5), third dielectric layer (6), metal backplate layer (7), fan-shaped patch layer (8), and fourth dielectric layer (9), forming a flat, tightly coupled structure. The metal patch layer (3) has a "stepped" dipole patch (31), a coupling patch (32) and a reconfigurable metasurface patch (33) distributed on it, forming an integrated structure of a flat tightly coupled antenna and a reconfigurable metasurface, so as to achieve flexible control of the scattering electric field in cross polarization and simultaneously achieve a wide antenna operating bandwidth in the main polarization. The "stepped" dipole patch (31) and the reconfigurable metasurface patch (33) are cross-distributed to ensure the independent operation of the flat tightly coupled antenna and the reconfigurable metasurface.

2. The antenna element according to claim 1, characterized in that: The matching layer (5) has two rectangular metal patches that are close to each other. They are connected to the power supply copper pillars to form a "rib" structure. The length L8 of each rectangular metal patch is 1.3 mm to 1.5 mm, the width w8 is 0.5 mm to 0.7 mm, and the distance between them is 0.05 mm to 0.1 mm. The fan-shaped patch layer (8) has three fan-shaped branches (81, 82, 83) and their connected metal wires.

3. The antenna element according to claim 1, characterized in that: The metal backplate layer (7) is connected to the metal patch layer (3) by a first set of power supply copper pillars (10, 11) and two sets of grounding copper pillars (12, 13) and (14, 15). The fan-shaped patch layer (8) is connected to the metal patch layer (3) by a second set of power supply copper pillars (16, 17); and it is connected to the metal backplate layer (7) by a bias grounding copper pillar (18).

4. The antenna element according to claim 1, characterized in that: The four dielectric layers are all made of F4B board with a dielectric constant of 2.2 and a loss tangent of 0.0015. Their heights are different, that is, the thickness h1 of the first dielectric layer (1) is 4 mm to 4.2 mm, the thickness h2 of the second dielectric layer (4) is 0.3 mm to 0.5 mm, the thickness h3 of the third dielectric layer (6) is 2.5 mm to 2.7 mm, and the thickness h4 of the fourth dielectric layer (9) is 0.8 mm to 1 mm. The second dielectric layer (4), the third dielectric layer (6), and the fourth dielectric layer (9) are connected by an adhesive layer (19) with a dielectric constant of 2.

8.

5. The antenna element according to claim 1, characterized in that: The distance between the first dielectric layer (1) and the metal patch layer (3), i.e. the thickness of the air layer (2), is 1mm~1.2mm; The fourth dielectric layer (9) has a circular slot (91) for inserting an external coaxial interface. Its position corresponds to the second power supply copper column (11) in the first group of power supply copper columns. The diameter R of the slot is 3.3 mm to 3.4 mm.

6. The antenna element according to claim 1, characterized in that: The "stepped" dipole patch (31) consists of two symmetrical three-segment rectangular patches. Each segment of the rectangular patch has different length and width parameters and is fed through the first set of feeding copper pillars (10, 11). It is connected to the metal backplate layer (7) through the first set of grounding copper pillars (12, 13). The coupling patch (32), with a width w0 of 0.3mm to 0.5mm, is distributed around the periphery of the "stepped" dipole patch (31) and is connected to the metal backplate layer (7) through a second set of grounding copper pillars (14, 15) to improve the impedance matching of the antenna. The reconfigurable metasurface patch (33) consists of three rectangular metal pieces, which are divided into positive (331) and negative (332) parts by PIN diodes. Both parts are DC fed through the second set of feeding copper pillars (16, 17). The length and width parameters of each rectangular patch are different.

7. The antenna element according to claim 6, characterized in that: Each of the three rectangular patches in the "stepped" dipole patch (31) has different parameters: the first rectangular patch has a length L1 of 1 mm to 1.15 mm and a width w1 of 0.3 mm to 0.5 mm; the second rectangular patch has a length L2 of 1.1 mm to 1.25 mm and a width w2 of 1 mm to 1.2 mm; and the third rectangular patch has a length L3 of 1 mm to 1.15 mm and a width w3 of 2.8 mm to 3 mm. The reconfigurable metasurface patch (33) has four rectangular patches, the first rectangular patch has a length L4 of 0.3 mm to 0.5 mm and a width w4 of 0.9 mm to 1.1 mm; the second rectangular patch has a length L5 of 3.5 mm to 3.7 mm and a width w5 of 1 mm to 1.2 mm; the third rectangular patch has a length L6 of 1.8 mm to 2 mm and a width w6 of 1.3 mm to 1.5 mm; and the fourth rectangular patch has a length L7 of 2.3 mm to 2.5 mm and a width w7 of 1 mm to 1.2 mm.

8. The antenna element according to claim 1, characterized in that: The metal backplate layer (7) is a copper layer with circular holes (71, 72, 73) on it. The first copper pillar (16) in the second group of power supply copper pillars passes through the first circular hole (71) and is connected to the fan-shaped patch layer (8). The second copper pillar (17) in the second group of power supply copper pillars passes through the second circular hole (72) and is connected to the fan-shaped patch layer (8). The second copper pillar (11) in the first group of power supply copper pillars passes through the third circular hole (73) and is connected to the fourth dielectric layer (9).

9. The antenna element according to claim 2, characterized in that: The fan-shaped patch layer (8) has three fan-shaped branches (81, 82, 83). The radius d1 of the first fan-shaped branch (81) is 4 mm to 4.1 mm, and it is connected to the second feed copper column (17) and the bias ground copper column (18) in the second group of feed copper columns through metal wires respectively. The radius of the second fan-shaped branch (82) is the same as that of the first fan-shaped branch, and it is connected to the first feed copper column (16) in the second group of feed copper columns through metal wires. The radius d2 of the third fan-shaped branch (83) is 3.4 mm to 3.5 mm, and it is connected to the second fan-shaped branch (82) through metal wires.

10. The low RCS broadband tightly coupled antenna array composed of any one of the antenna elements according to claims 1-9 is characterized in that: multiple antenna elements are arranged periodically. The metal patch layers (3) between each antenna element are connected, the coupling plates (32) between adjacent elements are connected to form a tightly coupled structure, and the reconfigurable metasurface patches (33) between adjacent elements are connected to form a whole. The reflection phase of the reconfigurable metasurface patch (33) is controlled by controlling the switching state of the PIN diodes in each element, and the reflection phase is distributed in a checkerboard pattern in the array. The metal backplate layers (7) between each antenna element are connected to form a complete metal backplate, forming antenna arrays of different sizes.

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