Low RCS broadband electromagnetic metasurface array of regional link structure based on liquid crystal

Abstract

The invention discloses a liquid crystal-based low RCS broadband electromagnetic metasurface array of a regional link structure, each unit of the metasurface array is of a combined structure of three layers of dielectric substrates and a bottom metal ground, the upper layer and the lower layer are dielectric substrates, the middle layer is a liquid crystal layer, a metal patch with a design pattern is arranged between the bottom of the upper dielectric substrate and the liquid crystal layer, and the metal patch is arranged between the bottom of the lower dielectric substrate and the bottom metal ground. According to the invention, cross grooving is carried out on a metal patch structure, a link strip is added to enhance area resonance and expand bandwidth, an array plane adopts an N * N layout, a chessboard type coding method is used, the dielectric constant of a liquid crystal material is adjusted to serve as an array element to carry out '0-1' cross coding, the RCS reduction frequency band range of more than 10dB is 20.5-21.9 GHz, and good RCS reduction performance is achieved.

Description

Technical Field

[0001] This invention relates to the field of antenna and microwave technology, and in particular to a low RCS broadband electromagnetic metasurface array based on a liquid crystal region-linked structure. Background Technology

[0002] With the rapid development of high-resolution radar and active phased array systems, weapons and equipment have put forward comprehensive requirements for radio frequency stealth performance, namely "wide bandwidth, large angle, low profile, and reconfigurability".

[0003] While traditional radar absorbing materials can provide RCS reduction in some frequency bands, they have drawbacks such as large thickness, high weight, narrow bandwidth, and inability to be adjusted in real time, making it difficult to meet the requirements of next-generation platforms for lightweight and multifunctional conformal skins.

[0004] Electromagnetic metasurfaces, through subwavelength artificial structures, can manipulate the phase, amplitude, and polarization of electromagnetic waves in a two-dimensional plane, providing a new approach for low-detectability technologies. Existing research has shown that using a checkerboard-like 180°±37° anti-phase reflection phase arrangement can create scattered field cancellation within the target frequency band, achieving a significant reduction in monostatic RCS. Currently, most RCS reduction studies still focus on the 0dB bandwidth, while 10dB RCS reduction has a narrow bandwidth or only occurs at certain frequency points. Summary of the Invention

[0005] To address the problems existing in the above-mentioned background technology, this invention proposes a low RCS broadband electromagnetic metasurface array based on a liquid crystal region-linked structure: in the frequency range of 20.5-21.9 GHz, the reflection coefficient of the electromagnetic metasurface array remains below -10 dB, achieving an effective improvement in RCS reduction bandwidth.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The low RCS broadband electromagnetic metasurface array based on the region link structure of liquid crystal is composed of N×N units and uses a checkerboard coding. The upper layer of the metasurface unit is a dielectric substrate, and a metal patch for extending the frequency band is loaded between it and the central slotted liquid crystal layer. The lower layer is another dielectric substrate with a grounding metal plate loaded at the bottom. Furthermore, each metasurface unit enhances regional resonance and expands bandwidth by slotting the metal patch structure and adding connecting strips.

[0007] The beneficial effects of the above-mentioned technical solution adopted by the present invention are as follows: This patent employs a checkerboard layout of a liquid crystal metasurface to reduce the target RCS (Rapid Cross Section). Within the checkerboard array structure, by adjusting the dielectric constant of the liquid crystal and controlling the phase shift of the control unit, a 180° phase difference is achieved between the encoding units. Based on the principle of phase cancellation, RCS reduction is realized. The low-RCS broadband electromagnetic metasurface array designed in this patent focuses on liquid crystal encoding and increases the RCS reduction bandwidth by 10dB. Specifically: a) In the frequency range of 20.5-21.9 GHz, the reflection coefficient of the array remains below -10 dB.

[0008] b) With a total thickness of only 0.762mm and a surface density of ≤0.7kg / m², it can be directly conformally fitted to metal skins with a curvature radius of ≥200mm without taking up additional cabin space or damaging the platform's aerodynamic shape.

[0009] c) Liquid crystal voltage regulation eliminates the need for PIN / varactor diodes, thus eliminating parasitic losses introduced by solder joints and DC power supply networks. Insertion loss is <0.3dB, resulting in high reliability. Attached Figure Description

[0010] Figure 1 A front view of a low RCS broadband electromagnetic metasurface structure based on a liquid crystal region-linked structure. Figure 2 A side view of a low RCS broadband electromagnetic metasurface structure based on a liquid crystal region-linked structure; Figure 3 A three-dimensional view of a low RCS broadband electromagnetic metasurface structure based on a liquid crystal region-linked structure. Figure 4 A front view of a low RCS broadband electromagnetic metasurface unit structure based on a liquid crystal region-linked structure. Figure 5 A side view of a low RCS broadband electromagnetic metasurface unit structure based on a liquid crystal region-linked structure; Figure 6 A three-dimensional view of a low RCS broadband electromagnetic metasurface unit structure based on a liquid crystal region-linked structure. Figure 7 Simulation plot of reflection phase characteristic curves of liquid crystal metasurface unit S11 under different liquid crystal dielectric constants; Figure 8 Simulation graph of the S11 characteristic curve of an 8x8 metasurface array; The diagram is marked as follows: 1- Upper Rogers4350 dielectric substrate; 2- Metal pattern layer; 3- Liquid crystal layer; 4- Lower Rogers4350 dielectric substrate; 5- Metal ground; 6- Nematic liquid crystal. Detailed Implementation

[0011] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0012] Low RCS broadband electromagnetic metasurface arrays based on liquid crystal region-linked structures, such as Figure 1 , Figure 2 and Figure 3 As shown, it consists of 8×8 units, divided into four regions with 4×4 units as a whole, and performs cross-0-1 encoding and dynamic RCS reduction. The structure of each metasurface unit is as follows. Figure 4 , Figure 5 and Figure 6 As shown, the overall dimensions are 4×4×0.762mm³, where the unit side length x0=4mm and the encapsulated liquid crystal side length x1=3mm. The structure consists of three dielectric layers, a metal patch, and a metal ground layer, arranged from top to bottom as follows: Upper Rogers4350 dielectric substrate 1 (thickness h1=0.254mm); a metal pattern layer 2 with grooves and connecting strips, thickness ht=0.035mm, which is bonded to the upper Rogers4350 dielectric substrate 1 with adhesive; a liquid crystal layer 3 with a thickness h2=0.254mm, filled with adjustable nematic liquid crystal 6; a lower Rogers4350 dielectric substrate 4 with a thickness h3=0.254mm, connected to the bottom metal ground layer 5 with a height hg=0.035mm; and an epoxy dam around the liquid crystal layer 3 to seal the liquid crystal cavity. The metasurface unit encoding uses liquid crystal dielectric constants of 2.4 and 3.0, with a difference of 180°±37°. By arranging the two types of units in a checkerboard pattern to form a metasurface array, the RCS is effectively reduced by utilizing the principle of phase cancellation.

[0013] This application enhances regional resonance and expands bandwidth by creating a cross-shaped groove in the metal patch structure and adding connecting strips. The array adopts an N×N layout and uses a checkerboard coding method. The dielectric constant of the liquid crystal material is adjusted as the array element for "0-1" cross coding, achieving an RCS reduction of more than 10dB in the frequency range of 20.5-21.9GHz, with good RCS reduction performance.

[0014] like Figure 7 The reflection phase characteristic curves of the S11 liquid crystal metasurface unit under different liquid crystal dielectric constants are presented. Simulation results show that a phase difference of 180°±37° is satisfied in the 20.2-21.2 GHz frequency band. Figure 8The RCS reduction frequency band is slightly off, achieving a 10dB RCS reduction in the 20.5-21.9GHz range, which is slightly different from the theoretical value. This is due to the frequency band shift caused by the bandwidth expansion through resonance, but the overall curve trend is consistent.

[0015] In summary, this low RCS broadband electromagnetic metasurface array based on a liquid crystal region-linked structure increases the bandwidth of the 10dBRCS reduction while maintaining a small thickness, thus achieving effective RCS reduction.

Claims

1. A low-RCS broadband electromagnetic metasurface array based on liquid-crystal area-linked structures, characterized in that, The super surface array adopts a chessboard type coding of N*N unit structure, each unit has a dielectric substrate on the upper layer, a metal patch loaded between the middle slotted liquid crystal layer and the dielectric substrate on the lower layer, and a ground metal plate loaded at the bottom.

2. The liquid-crystal-based, low-RCS, wideband, electromagnetic metasurface array of area-linked structures of claim 1, wherein, By adjusting the dielectric constant of the liquid crystal material in the liquid crystal layer, the array area is divided into four quadrants, and each quadrant is coded and arrayed as a whole by regulating (N / 2) * (N / 2) interconnected units.

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