A Low RCS Circularly Polarized Slot Array Antenna with Encoded Metasurface

Abstract

This invention discloses a low RCS circularly polarized slot array antenna with an coded metasurface, comprising an upper dielectric substrate and a lower dielectric substrate. The upper surface of the upper dielectric substrate is printed with a 2-bit coded metasurface, the upper surface of the lower dielectric substrate has a printed metal ground plane, and the lower surface of the lower dielectric substrate has a printed feed structure. The 2-bit coded metasurface is constructed by arranging four phase gradient elements with a 90° phase difference using a genetic algorithm, with each element coded in 2-bit. The slot array antenna consists of four strip slots, with adjacent slot antennas rotated clockwise around the center. This invention uses strip patches and ring patches to construct the phase gradient elements and performs 2-bit coding, then loads the coded metasurface as a cladding layer onto the circularly polarized slot array antenna to achieve RCS reduction.

Description

Technical Field

[0001] This invention relates to the field of antenna technology, and in particular to a low RCS circularly polarized slot array antenna with a coded metasurface. Background Technology

[0002] Electromagnetic metasurfaces are subwavelength structures that manipulate electromagnetic waves in a controllable manner to obtain electromagnetic properties unattainable in natural materials, such as left-handed materials, perfect absorbing metamaterials (PAMs), polarization conversion metasurfaces (PCMs), and phase-gradient metasurfaces (PGMs). Compared to 3D metamaterials, they are easier to fabricate, have lower complexity, and smaller thickness, making them suitable for a wider range of applications. While periodicity is not a necessary condition for metasurfaces, many inventions are based on the arbitrary control of wave propagation, scattering, and polarization using repeating unit cells. Metamaterials have been used in numerous applications, including electromagnetic cloaking, negative refraction, and subwavelength focusing.

[0003] In recent years, C. Giovampaola et al. proposed a new concept of digital bit-controlled metasurface cell electromagnetic response, different from the traditional metamaterial effective medium theory. TJ Cui et al. enhanced this concept of digital metamaterials by introducing coding and programmable metasurfaces. The coded bits consist of 0° and 180° phase responses, considered as the "0" and "1" of the coded metasurface. By spatially arranging the "0" and "1" cells into an array and changing the coding sequence of the metasurface, a digital metasurface with a certain degree of modulation function for electromagnetic waves is formed. When the specified code sequence is periodically arranged as "0101…", a vertically incident electromagnetic wave will be split into two beams with the same elevation angle, which can be applied to target RCS reduction.

[0004] In order to control the transmission and acquisition of information on the battlefield in modern warfare and to carry out precision strikes against the enemy, it is an urgent issue to comprehensively study target stealth technology and reduce RCS (radar cross-section). Summary of the Invention

[0005] To address the aforementioned issues, this invention provides a low RCS circularly polarized slot array antenna with a coded metasurface. By optimizing the size of the elements, a 90° phase difference is achieved between their respective digital codes, resulting in a 2-bit phase response. A genetic algorithm is applied to the array factor to obtain the optimal coding sequence matrix, causing diffuse reflection of the incident electromagnetic wave. The 2-bit coded metasurface is then loaded as a cladding layer onto the circularly polarized slot array antenna. By sequentially rotating the feed network, the antenna's radiation performance is ensured while achieving a wideband RCS reduction of over 8 dB.

[0006] This invention provides a low RCS circularly polarized slot array antenna with an coded metasurface, the specific technical solution of which is as follows:

[0007] It includes an upper dielectric substrate and a lower dielectric substrate. The upper surface of the upper dielectric substrate is printed with a 2-bit encoded metasurface, and the upper surface of the lower dielectric substrate is printed with a metal ground plane, and the lower surface is printed with a power supply structure.

[0008] The 2-bit encoded metasurface is composed of phase gradient units arranged in a genetic algorithm using 2-bit encoding of four types of units with sequentially 90° phase differences in reflection.

[0009] Four slot array antennas are etched on the metal floor. The slot array antennas are arranged in a checkerboard pattern on the metal floor, and the adjacent slot antennas are distributed in a clockwise rotation around the center.

[0010] Furthermore, the slot array antenna consists of four strip slots.

[0011] Furthermore, the four strip-shaped slits have the same length and width.

[0012] Furthermore, in the antenna feeding structure using a rectangular microstrip line, the rectangular microstrip line is perpendicular to the strip slot.

[0013] Furthermore, the upper dielectric plate is composed of a rectangular plate with a dielectric constant of 4.4, and the upper dielectric plate has a gap of 19.3mm × 3.2mm × 2mm.

[0014] Furthermore, the lower dielectric substrate is composed of a substrate with a dielectric constant of 2.65.

[0015] Furthermore, the phase gradient unit includes four annular chamfered patches, four strip patches, and an annular patch located in the middle;

[0016] The annular patch is connected to the annular chamfered patch via the four strip-type patches. Adjacent strip-type patches are perpendicular to each other, and the strip-type patches are perpendicular to the annular patch and the annular chamfered patch.

[0017] Furthermore, the ring width of the circular bevel patch is 0.2mm, the width of the strip patch is 0.62mm, and the bevel length of the circular bevel patch is 0.4mm.

[0018] Furthermore, the radii of the annular patch are 2.72 mm, 3.24 mm, 4.14 mm, and 4.76 mm.

[0019] The beneficial effects of this invention are as follows:

[0020] The phase gradient unit in this invention adopts a strip patch and a ring patch structure to achieve the effect of expanding the phase bandwidth of the unit reflection. The phase gradient unit is arranged by 2-bit encoding through a genetic algorithm, and then the resulting 2-bit encoded metasurface is used as the cladding of the array antenna to cause diffuse reflection of the incident electromagnetic wave, thereby better reducing the antenna RCS. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall antenna structure of the present invention;

[0022] Figure 2 This is a schematic diagram of the phase gradient unit structure;

[0023] Figure 3 This is a schematic diagram of the phase gradient unit design process;

[0024] Figure 4 This is a schematic diagram of the simulation results of the reflection amplitude of the phase gradient unit;

[0025] Figure 5 This is a schematic diagram of the simulation results of the phase difference of the phase gradient unit reflection.

[0026] Figure 6 This is a schematic diagram comparing the reflection coefficients of the antenna and the reference antenna of the present invention;

[0027] Figure 7 This is a schematic diagram comparing the axial ratios of the antenna and the reference antenna of the present invention;

[0028] Figure 8 This is a schematic diagram comparing the radiation directions of the antenna xoz plane of the present invention and the reference antenna at 11 GHz;

[0029] Figure 9 This is a schematic diagram comparing the radiation directions of the antenna yoz plane of the present invention and the reference antenna at 11 GHz;

[0030] Figure 10 This is a schematic diagram comparing the radar cross section (RCS) of the antenna of this invention and the reference antenna under x-polarized incident waves;

[0031] Figure 11 This is a schematic diagram comparing the radar cross section (RCS) of the antenna of the present invention and the reference antenna under y-polarized incident waves.

[0032] Explanation of reference numerals in the attached diagram: 1. Upper dielectric substrate, 2. 2-bit encoded metasurface, 3. Metal ground plane, 4. Lower dielectric substrate, 5. Power supply network, 21. Circular bevel patch, 22. Strip patch, 23. Circular patch. Detailed Implementation

[0033] The technical solutions in the embodiments of the present invention are clearly and completely described in the following description. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0034] In the description of the embodiments of the present invention, it should be noted that the indicated orientation or positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the invention is conventionally placed during use, or the orientation or positional relationship in which those skilled in the art conventionally understand it during use. This is only for the convenience of describing the present invention and simplifying the description, and is not intended to 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, it should not be construed as a limitation of the present invention. Furthermore, the terms "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0035] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the present invention based on the specific circumstances.

[0036] Example 1

[0037] Embodiment 1 of the present invention discloses a low RCS circularly polarized slot array antenna with a coded metasurface, such as Figure 1 As shown, the details are as follows:

[0038] It includes an upper dielectric substrate 1 and a lower dielectric substrate 4. The upper surface of the upper dielectric substrate 1 is printed with a 2-bit coded metasurface 2, the upper surface of the lower dielectric substrate 4 is printed with a metal ground plane 3, and the lower surface of the lower dielectric substrate 4 is printed with a feeding structure, forming an antenna assembly of 96mm×96mm×2.5mm.

[0039] The 2-bit encoded metasurface 2 is composed of phase gradient units arranged in a genetic algorithm using 2-bit encoding of four types of units with sequentially 90° phase differences in reflection.

[0040] Four slot array antennas are etched on the metal floor 3. The slot array antennas are arranged in a checkerboard pattern on the metal floor 3, and the adjacent slot antennas are distributed in a clockwise rotation around the center.

[0041] The chessboard-like arrangement is the arrangement structure obtained by rotating 90° clockwise around the center.

[0042] In this embodiment, the slot array antenna is composed of four strip slots;

[0043] The four strip-shaped gaps have the same length and width.

[0044] In this embodiment, a rectangular microstrip line is used as the antenna feeding structure, and the rectangular microstrip line is perpendicular to the strip slot.

[0045] It can effectively couple the energy fed in through the coaxial line located below the microstrip line into the slot array antenna, thereby achieving effective antenna radiation.

[0046] The coaxial cable is the excitation source when feeding the antenna, that is, the end of the feeding structure.

[0047] In this embodiment, the upper dielectric plate 1 is composed of a rectangular plate with a dielectric constant of 4.4, and the upper dielectric plate 1 has a gap of 19.3mm × 3.2mm × 2mm.

[0048] The lower dielectric substrate 4 is made of a substrate with a dielectric constant of 2.65.

[0049] like Figure 2 As shown, in this embodiment, the 2-bit encoded metasurface 2 is composed of phase gradient units arranged according to the principle of finding the minimum axial scattering energy of the incident electromagnetic wave using a genetic algorithm.

[0050] Each phase gradient unit includes four annular chamfered patches 21, four strip patches 22, and an annular patch 23 located in the middle;

[0051] The annular patch 23 is connected to the annular chamfered patch 21 through the four strip patches 22. The adjacent strip patches 22 are perpendicular to each other, and the strip patches 22 are perpendicular to the annular patch 23 and the annular chamfered patch 21.

[0052] Specifically, in this embodiment, the ring width of the annular chamfer patch 21 is 0.2mm, the width of the strip patch 22 is 0.62mm, and the chamfer length of the annular patch 23 is 0.4mm;

[0053] The radii of the annular patch 23 are 2.72 mm, 3.24 mm, 4.14 mm, and 4.76 mm;

[0054] Combination Figure 3 As shown, the design flow of the phase gradient unit is as follows:

[0055] In this embodiment, Matlab-CST co-simulation is used to optimize the design of the coding unit. The relationship between the reflection phase and the radius 'a' is modeled using a nonlinear formula. In this embodiment, the range of the annular radius 'a' is set to 2-5.5 mm with a step size of 0.1 mm. The phase gradient unit radius in the CST unit structure is replaced with the 'a' that meets the conditions. Then, simulations are performed one by one, and the data after each set of simulations is saved to a Matlab matrix.

[0056] Next, any two sets of reflection phases corresponding to all ring radii 'a' are compared. Each set of data represents the reflection phases corresponding to several frequency points. The absolute value of the difference between the two sets of reflection phases is the phase difference. The absolute value of the phase difference and 90° is obtained, and it is determined whether the difference is less than 20°. If it is less, the number of frequency points with a phase difference between 70-110° is counted, and the size of the number of frequency points in the two sets is compared. The ring radius result corresponding to the larger number of frequency points is output. If it is greater than 20°, the next two sets are compared. After comparing all the reflection phases pairwise, the more frequency points within this phase difference range, the wider the bandwidth of the phase gradient unit. Finally, the radii 'a' of each phase gradient unit can be obtained, which are 2.72mm, 3.24mm, 4.14mm, and 4.76mm, respectively.

[0057] Based on the above antenna structure, the simulation results are as follows;

[0058] like Figure 4 and Figure 5 As shown, the simulation results of the phase gradient unit under the condition of perpendicular incident electromagnetic wave are shown. It can be seen that in this embodiment, the reflection amplitude of the phase gradient unit at 14-23GHz is greater than 0.8, and the reflection phase difference is 90°, which meets the design requirements of 2-bit encoded metasurface 2.

[0059] Based on the above antenna structure, the simulation results are as follows;

[0060] The antenna of the present invention, namely the antenna shown in the figure, is a slot array antenna loaded with a 2-bit coded metasurface 2; the reference antenna is a slot array antenna without a 2-bit coded metasurface 2, and will not be described again below.

[0061] like Figure 6 and Figure 7 The figure shows the simulation results of the reflection coefficient and axial ratio of the antenna and reference antenna of the present invention under radiation conditions. From... Figure 6 It can be seen that the reference antenna's -10dB impedance bandwidth is 10.64-12.11GHz, with a relative bandwidth of 12.9%. The invented antenna's impedance bandwidth (10.48-13.46GHz, 24.9%) is 12% higher than the reference antenna's bandwidth. Figure 7 It can be seen that the axial ratio of the reference antenna remains below 3dB from 10.7GHz to 11.43GHz, while the relative bandwidth of the axial ratio of the invented antenna with a 2-bit coded surface is 4.8% from 10.60 to 11.13GHz.

[0062] like Figure 8 and Figure 9 The figure shows the simulation results of the radiation patterns of the invented antenna and the reference antenna at 11 GHz. It can be seen that the invented antenna and the reference antenna have good radiation patterns in the xoz and yoz planes, and can achieve circular polarization in the X-band.

[0063] like Figure 10 and Figure 11 The figure shows the simulation results of the single-station radar cross section of the invented antenna and the reference antenna under incident wave illumination of two polarizations. It can be seen that the antenna in this embodiment achieves a larger RCS reduction compared to the reference antenna. For different polarizations, the maximum single-station RCS reduction is 33.1dB at 20.6GHz. In addition, the average RCS reduction value is 8dB in the wide frequency band from 13.5GHz to 23.5GHz, achieving out-of-band RCS reduction of the antenna.

[0064] This invention is not limited to the specific embodiments described above. The invention extends to any new feature or combination disclosed in this specification, as well as any new method or process step or combination disclosed herein.

Claims

1. A low RCS circularly polarized slot array antenna with a coded metasurface, characterized in that, It includes an upper dielectric substrate and a lower dielectric substrate. The upper surface of the upper dielectric substrate is printed with a 2-bit encoded metasurface, the upper surface of the lower dielectric substrate is printed with a metal ground plane, and the lower surface of the lower dielectric substrate is printed with a power supply structure. The 2-bit encoded metasurface is composed of phase gradient units arranged in a genetic algorithm using 2-bit encoding of four types of units with sequentially 90° phase differences in reflection. The phase gradient unit includes four annular chamfered patches, four strip patches, and a central annular patch. The annular patch is connected to the annular chamfered patch through the four strip-type patches. Adjacent strip-type patches are perpendicular to each other, and the strip-type patches are perpendicular to the annular patch and the annular chamfered patch. Four slot array antennas are etched on the metal floor. The slot array antennas are arranged in a checkerboard pattern on the metal floor, and the adjacent slot antennas are arranged in a clockwise rotation around the center. The slot array antenna consists of four strip slots; the four strip slots have the same length and width. The feeding structure uses a rectangular microstrip line as the antenna, wherein the rectangular microstrip line is perpendicular to the strip slot.

2. The low RCS circularly polarized slot array antenna with coded metasurface according to claim 1, characterized in that, The upper dielectric substrate is made of a rectangular plate with a dielectric constant of 4.4, and the upper dielectric substrate has a gap of 19.3mm × 3.2mm × 2mm.

3. The low RCS circularly polarized slot array antenna with coded metasurface according to claim 1, characterized in that, The lower dielectric substrate is made of a material with a dielectric constant of 2.

65.

4. The low RCS circularly polarized slot array antenna with coded metasurface according to claim 1, characterized in that, The circular bevel patch has a ring width of 0.2 mm, the strip patch has a width of 0.62 mm, and the bevel length of the circular bevel patch is 0.4 mm.

5. The low RCS circularly polarized slot array antenna with coded metasurface according to claim 1, characterized in that, The radii of the annular patches are 2.72 mm, 3.24 mm, 4.14 mm, and 4.76 mm.

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