Reconfigurable electromagnetic metasurface antenna and hidden state communication method thereof

Abstract

The invention discloses a reconfigurable electromagnetic metasurface antenna and a hidden state communication method thereof, solves the problem of how to realize high concealment of the antenna, and belongs to the field of artificial electromagnetic metamaterials. The metasurface array comprises a metasurface unit array, the middle layer of each metasurface unit is a dielectric layer, the lower layer of each metasurface unit is a metal layer, the upper layer of each metasurface unit is engraved with two strip-shaped hollowed-out parts and four square hollowed-out parts, the two strip-shaped hollowed-out parts are perpendicular to each other and intersect at the midpoints, and the intersection point of the two strip-shaped hollowed-out parts is arranged in the center of the metal layer. The four square hollowed-out parts are symmetrically distributed in four corners separated by the two strip-shaped hollowed-out parts, and photosensitive silicon is filled in one strip-shaped hollowed-out part; codes corresponding to each metasurface unit are '0', '1', '2' and '3', and the phase responses of the four kinds of coding metasurface units at the working frequency differ by 90 degrees in sequence. Regulation and control of the reflected electromagnetic wave phase are realized by changing the length b. According to the invention, reverse design is carried out on the antenna to obtain an RCS reduction array code, so that the antenna can realize broadband RCS reduction, and electromagnetic stealth is realized.

Description

Technical Field

[0001] The invention relates to a reconfigurable electromagnetic metasurface antenna and a hidden communication method thereof, and belongs to the field of artificial electromagnetic metamaterials and wireless communications. Background Art

[0002] The rapid progress of wireless technology has greatly accelerated the informatization process of modern warfare and led electronic confrontation into a new stage. With the continuous breakthroughs and innovations in radar technology, the battlefield survivability of key weapons and equipment such as missiles and aircraft is facing unprecedented severe challenges. In this context, the research and development and application of electromagnetic stealth technology has become an effective way to improve the survivability of weapons and a key direction for the development of national defense science and technology. However, it is worth noting that traditional electromagnetic stealth technology is often restricted by various conditions in practical applications and it is difficult to fully meet the high standards of stealth combat capabilities in modern warfare. 6G technology heralds the arrival of a highly digitalized society with inclusive intelligence and intelligent interconnection of all things. To realize this vision, future wireless networks need to have two core capabilities: one is to support the connection of massive communication and perception terminals, and the other is to process huge amounts of data in real time to meet the needs of 6G potential application scenarios such as holographic communication, sensory interconnection, digital twins and full coverage. However, the immersive, intelligent and global development of 6G has exposed a large number of sensitive communication and perception devices to an open wireless environment, facing severe security challenges. In particular, the physical characteristics of these devices, such as spatial position, movement direction and speed, are easily detected by unauthorized radars, which may lead to the leakage of sensitive information such as commercial secrets or personal privacy, posing a huge risk to the information security of the next generation of wireless networks. In the commercial scenario of 6G, this security issue is particularly prominent. In the military field, communication and perception security are also of great concern. With the rapid development of military technology, detection and tracking technology has become increasingly sophisticated, posing a serious threat to the survivability of weapons such as missiles and fighter jets, and also placing higher requirements on the concealment of military equipment. Therefore, how to effectively ensure the security of sensitive communication perception equipment and military equipment has become an important issue in maintaining national security. "Stealth" technology aims to make the target difficult to detect or identify, while "communication" emphasizes the seamless integration of communication functions with other systems or equipment. The combination of the two not only improves the concealment of the target, but also enhances the flexibility and security of information transmission. In the military field, this combination is crucial, which can not only protect key assets from reconnaissance, but also ensure unimpeded command and control. With the advancement of materials science and information technology, the integration of stealth and communications is developing towards higher integration and stronger concealment, which will have a profound impact on future battlefield situation awareness and combat command.

[0003] Traditional metasurfaces are limited by the equivalent medium theory, making it difficult to achieve flexible control of electromagnetic fields and electromagnetic waves. However, the introduction of the concept of "digitally coded metasurfaces" has successfully built a bridge between the physical world and the digital world, greatly simplifying the design and optimization process of metasurfaces. This digital coding method has prompted researchers to explore and design metasurfaces from a new perspective of information science, thus creating a new research framework. In recent years, the rapid development of programmable electromagnetic metasurface technology has been regarded as a revolutionary innovation for the next generation of wireless networks. Programmable electromagnetic metasurfaces can construct a wireless environment that is both intelligent and reconfigurable in an economical and efficient way. Its essence is that it consists of a large number of independently controllable units forming a two-dimensional plane. These units can adjust the parameters of the incident electromagnetic wave, including amplitude and phase, in real time in a programmable manner, thereby reshaping the propagation path of the electromagnetic wave on demand. By precisely controlling these units, the programmable electromagnetic metasurface not only achieves active enhancement of signal transmission, but also has powerful functions such as beam steering and interference elimination. This feature makes it a powerful supplement to traditional electromagnetic stealth technology, indicating that future electromagnetic stealth technology will move towards a new stage of both high performance and multifunctionality. The application prospects of programmable electromagnetic metasurfaces are broad, and are expected to bring new vitality and possibilities to diversified scenarios such as smart oceans, smart borders, and smart cities. Summary of the invention

[0004] In order to solve the problem of how to achieve high concealment of antennas, the present invention provides a reconfigurable electromagnetic metasurface antenna and a stealth communication method thereof.

[0005] A reconfigurable electromagnetic metasurface antenna of the present invention comprises a metasurface unit array, each metasurface unit is a 2-bit unit, comprising an upper layer, a dielectric layer, and a lower layer, wherein the dielectric layer is located between the upper layer and the lower layer;

[0006] The upper layer includes a photosensitive silicon layer and a metal layer. Two strip-shaped hollows and four square hollows that are perpendicular to each other and intersect at the midpoint are engraved on the metal layer. The intersection of the two strip-shaped hollows is set at the center of the metal layer. The four square hollows are symmetrically distributed in the four corners separated by the two strip-shaped hollows. One strip-shaped hollow is filled with photosensitive silicon to form a photosensitive silicon layer.

[0007] The lower layer is a metal layer;

[0008] The corresponding codes of each metasurface unit are "0", "1", "2", and "3", and the phase responses of the four coded metasurface units at the operating frequency differ by 90° respectively.

[0009] Preferably, the width of the photosensitive silicon layer is w=10 μm, and the length is b, where b is a variable, and the phase of the reflected electromagnetic wave is regulated by changing the size of b.

[0010] Preferably, the thickness of the upper layer is 0.2 μm; the dielectric layer is silicon dioxide with a thickness of h=10 μm; and the thickness of the lower layer is 0.5 μm.

[0011] Preferably, both the upper and lower metal layers are made of copper.

[0012] Preferably, the period p of the metasurface unit array is 40 μm.

[0013] Preferably, when the length b of the photosensitive silicon layer is 19.8um, 32.7um, 35um and 38um, its phase is -5.7°, -94.9°, -185°, and -275.6°, respectively. The phase difference is 90°, and the corresponding coding states are "0", "1", "2" and "3".

[0014] This embodiment also provides a stealth communication method for a reconfigurable electromagnetic metasurface antenna, comprising: reverse engineering the above-mentioned reconfigurable electromagnetic metasurface antenna to obtain the RCS reduction array coding of the metasurface unit array, so that the reconfigurable electromagnetic metasurface antenna can achieve broadband RCS reduction and realize electromagnetic stealth.

[0015] Preferably, the method for obtaining the RCS reduction array encoding comprises:

[0016] S1, initializing the period of the metasurface unit array and the metasurface unit parameters;

[0017] S2, randomly generate an initial population, where the individuals in the initial population are random coding sequences of the super surface unit array;

[0018] S3, calculate the objective function value of each individual in the current population under the corresponding coding sequence, and determine whether the termination condition is met. If so, output the optimal coding sequence and end; otherwise, go to S4;

[0019] The objective function is set as 360° and 90° are the azimuth angle θ and the elevation angle range, represents the far-field scattering of the coding sequence under normal incidence;

[0020] S4: Perform selection, crossover and mutation operations on the population and transfer to S3.

[0021] Preferably, the covert communication method of the present application further includes:

[0022] By dynamically modulating the quantized code distribution on the metasurface unit array, a multi-mode OAM vortex electromagnetic beam is constructed.

[0023] The beneficial effects of the present invention are that the present invention is integrated and multifunctional, realizes the integration of multiple functions such as communication and stealth, and improves the overall performance of the system; it also has a high degree of concealment: in the reflection mode, the electromagnetic metasurface is adjusted accordingly based on the optimization algorithm, thereby minimizing the radar scattering cross-sectional area of ​​the target, achieving the optimal electromagnetic stealth effect, and reducing the risk of being detected by the enemy. Low cost and scalability: The reconfigurable electromagnetic metasurface has the advantages of being lightweight and conformable, with lower deployment costs and better scalability. In addition, the system does not require additional RF links, which significantly reduces power consumption and hardware costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the structure of a reconfigurable electromagnetic metasurface unit cell of the present invention;

[0025] Figure 2 The coding states and specific phase responses of the 2-bit reconfigurable electromagnetic metasurface units of four different structural sizes are shown;

[0026] Figure 3 It is a schematic diagram of the beam dynamic control function of the reconfigurable electromagnetic metasurface;

[0027] Figure 4 Schematic diagram of the stealth communication principle of the reconfigurable electromagnetic metasurface antenna of the present invention, (a) is a schematic diagram of high-precision beam control integrating metasurface multi-antennas, (b) is a schematic diagram of reverse design of metasurface electromagnetic stealth communication based on optimization algorithm;

[0028] Figure 5 is the effect diagram of the reverse design, where (a) is the coding diagram of the reconfigurable metasurface unit array obtained by reverse design, (b) is the modeling diagram of the metasurface unit array coding, (c) is the three-dimensional far-field scattering diagram of the metasurface unit array coding, and (d) is the simulated RCS curve diagram of the reconfigurable metasurface compared with the metal plate of the same size;

[0029] Figure 6 Far-field scattering results and phase results of l=+1 in OAM mode, where (a) is the quantized coding distribution of OAM mode, (b) is the array modeling diagram of OAM mode, (c) is the far-field direction diagram of the vortex electromagnetic wave generated by the reconfigurable electromagnetic metasurface unit, and (d) is the phase distribution of OAMl=+1 mode;

[0030] Figure 7 The far-field scattering results and phase results of l = -1 in the OAM mode, (a) is the quantized coding distribution of the OAM mode, (b) is the array modeling diagram of the OAM mode, (c) is the far-field pattern of the vortex electromagnetic wave generated by the reconfigurable electromagnetic metasurface, and (d) is the phase distribution of the OAMl = -1 mode. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0033] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0034] For a 1-bit reconfigurable electromagnetic metasurface, the corresponding codes are "0" and "1", and the phase responses of the two coding units differ by 180° at the operating frequency. The reconfigurable electromagnetic metasurface antenna of this embodiment includes a metasurface unit array, each metasurface unit is a 2-bit unit, including an upper layer, a dielectric layer, and a lower layer, and the dielectric layer is located between the upper layer and the lower layer;

[0035] The upper layer includes a photosensitive silicon layer and a metal layer. Two strip-shaped hollows and four square hollows that are perpendicular to each other and intersect at the midpoint are engraved on the metal layer. The intersection of the two strip-shaped hollows is set at the center of the metal layer. The four square hollows are symmetrically distributed in the four corners separated by the two strip-shaped hollows. One strip-shaped hollow is filled with photosensitive silicon to form a photosensitive silicon layer.

[0036] The lower layer is a metal layer;

[0037] The corresponding codes of each metasurface unit are "0", "1", "2", and "3", and the phase responses of the four coded metasurface units at the operating frequency differ by 90° respectively.

[0038] The metasurface unit proposed in this embodiment is as follows: Figure 1 As shown in the figure, the unit is composed of three layers of materials, of which the upper layer is composed of 0.2μm thick photosensitive silicon and metal copper, the middle layer is a dielectric layer, the dielectric layer is silicon dioxide, its dielectric constant is 3.9, the thickness is h = 10μm, the lower layer is 0.5μm thick metal copper, and the unit period p = 40μm. The photosensitive silicon embedded in the metal structure has a dielectric constant of 11.5, a width of w = 10μm, and a length b as a variable. The phase of the reflected electromagnetic wave is controlled by changing the structural parameter b. The conductivity of the adjustable material photosensitive silicon changes with the energy of the pump light. The relationship between the conductivity σ of the photosensitive silicon and the pump light power I is σ = 4.863×10 -4 ×I 2+0.1856×I+1.569. When there is no pump excitation, the conductivity of photosensitive silicon is 0 and it is in a dielectric state; when the pump light power is 790μJ / cm 2 When the conductivity is 5.0×10 5 S / m, in metallic state.

[0039] Figure 2 These are the coding states and specific phase responses corresponding to four 2-bit reconfigurable electromagnetic metasurface units of different structural sizes. When the length b of the active material photosensitive silicon in the reconfigurable electromagnetic metasurface unit is designed to be 19.8um, 32.7um, 35um, and 38um, its phase is -5.7°, -94.9°, -185°, and -275.6°, respectively, with a phase difference of 90°, and the corresponding coding states are "0", "1", "2", and "3".

[0040] Figure 3 The figure is a schematic diagram of the dynamic beam control function of the reconfigurable electromagnetic metasurface unit. The deflection angle of the beam can be calculated according to θ=arcsin(λ / Γ), where λ is the free space wavelength and Γ represents the period length of the coding sequence. When the electromagnetic wave is incident vertically, the coding metasurface with a coding sequence of 01230123… along the X direction can control the angle of the reflected beam.

[0041] The reconfigurable electromagnetic metasurface antenna and stealth communication method proposed in this embodiment are as follows: Figure 4 shown. Figure 4 (a) shows the application of reconfigurable metasurface multi-antennas in the field of communications. By adjusting the structure of the metasurface, these antennas can flexibly change the transmission direction of electromagnetic waves. When multiple such antennas work together, they can achieve precise control of the electromagnetic beam to point it in a specific direction. This high-precision beam steering technology greatly enhances the directionality of electromagnetic waves, ensuring that signals can be transmitted to the target location more accurately while reducing unnecessary interference. In practical applications, this means that legally authorized users can use this technology to achieve more efficient and secure communications, ensuring the accuracy and confidentiality of information during transmission. Figure 4 (b) reveals the application of reverse-engineered metasurfaces based on optimization algorithms in electromagnetic stealth. By reverse-engineering the metasurface through optimization algorithms, it is possible to achieve specific manipulation of electromagnetic waves, thereby achieving the effect of stealth. This technology makes objects equipped with such metasurface antennas "invisible" in front of radar waves, greatly reducing the risk of being detected by enemy radars. In the military field, this electromagnetic stealth technology has extremely high strategic value because it can help our equipment remain concealed under the surveillance of enemy radars, thereby gaining greater flexibility and safety when performing tasks.

[0042] In this embodiment, the stealth communication method of the reconfigurable electromagnetic metasurface antenna is reverse-engineered to obtain the RCS reduction array coding of the metasurface unit array, so that the reconfigurable electromagnetic metasurface antenna can achieve broadband RCS reduction and electromagnetic stealth. In this embodiment, the reconfigurable electromagnetic metasurface can realize different electromagnetic functions by designing a specific coding sequence. In terms of the electromagnetic stealth function, based on the reconfigurable metasurface, the array coding is reversely designed using a genetic algorithm to achieve the RCS reduction function. First, the coding array obtained by the reverse design is modeled and simulated in CST to obtain the far-field scattering amplitude. Then, the far-field scattering amplitude of a metal plate of the same size as the coding metasurface is calculated using the same method. Finally, the RCS values ​​of the two are compared to obtain the RCS reduction value.

[0043] like Figure 5 As shown in Figure 2, the metasurface optimized by genetic algorithm achieves a terahertz broadband RCS reduction of more than 10 dB in the range of 6-6.3 THz. The reverse design process of the metasurface array encoding based on genetic algorithm includes:

[0044] Step 1, initializing parameters such as the period of the metasurface unit array and the size of the metasurface array;

[0045] Step 2: Randomly generate an initial population, including 50 individuals. The individuals in the initial population are random coding sequences of the metasurface unit array, and each individual is a 32×32 random coding sequence;

[0046] Step 3: Calculate the objective function value of each individual in the current population under the corresponding coding sequence, and determine whether the termination condition is met, such as reaching the maximum number of iterations of 1500. If so, output the optimal coding sequence and end; otherwise, proceed to step 4;

[0047] The objective function of RCS reduction is set as 360° and 90° are the azimuth angle θ and the elevation angle range, represents the far-field scattering of the coding sequence under normal incidence;

[0048] Step 4: Perform selection, crossover and mutation operations on the population and proceed to step 3.

[0049] This cycle is repeated until the set number of iterations is reached, and the optimal array coding sequence is finally output. First, the coding array obtained by reverse design is modeled and simulated in CST to obtain the far-field scattering amplitude. Then the far-field scattering amplitude of the metal plate of the same size as the coding metasurface is calculated in the same way. Finally, the RCS values ​​of the two are compared to obtain the RCS reduction value. The reconfigurable metasurface array coding is designed using genetic algorithms to achieve the RCS reduction function.

[0050] In terms of beam control, based on the far-field scattering principle of the coding metasurface, beam control functions such as beam scanning and vortex electromagnetic waves are realized through different coding sequences. The present invention further uses the designed reconfigurable metasurface to generate electromagnetic waves carrying orbital angular momentum (OAM). By dynamically modulating the quantized code distribution on the metasurface, a reconfigurable multi-mode OAM vortex electromagnetic beam can be constructed. The results of single vortex beam generation with different topological charge numbers at the working frequency of the coding metasurface are as follows: Figure 2 and Figure 3 shown.

[0051] Figure 6 The far-field scattering results and phase results for l = +1. By observing the phase results, it can be found that when the topological charge number is l = +1, the phase has one cycle from 0° to 360° in the counterclockwise direction, which is consistent with the characteristics of the vortex beam.

[0052] Figure 7 The far-field scattering results and phase results for l = -1. By observing the phase results, it can be found that when the topological charge number is l = -1, the phase has one cycle from 0° to 360° in the clockwise direction, which is consistent with the characteristics of the vortex beam.

[0053] The present embodiment is not limited to a certain waveband, and it can be extended to millimeter wave, microwave, terahertz and optical wavebands.

[0054] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should therefore be understood that many modifications may be made to the exemplary embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in a manner different from that described in the original claims. It should also be understood that features described in conjunction with individual embodiments may be used in other described embodiments.

Claims

1. A reconfigurable electromagnetic metasurface antenna, characterized in that: It includes a metasurface unit array, each metasurface unit is a 2-bit unit, including an upper layer, a dielectric layer, and a lower layer, and the dielectric layer is located between the upper layer and the lower layer; The upper layer includes a photosensitive silicon layer and a metal layer. Two strip-shaped hollows and four square hollows that are perpendicular to each other and intersect at the midpoint are engraved on the metal layer. The intersection of the two strip-shaped hollows is set at the center of the metal layer. The four square hollows are symmetrically distributed in the four corners separated by the two strip-shaped hollows. One strip-shaped hollow is filled with photosensitive silicon to form a photosensitive silicon layer. The lower layer is a metal layer; The code corresponding to each metasurface unit is "0", "1", "2", and "3", and the phase responses of the four coded metasurface units at the operating frequency differ by 90° respectively.

2. The reconfigurable electromagnetic metasurface antenna according to claim 1, characterized in that: The width of the photosensitive silicon layer is w=10 μm, and the length is b, where b is a variable. The phase of the reflected electromagnetic wave can be controlled by changing the size of b.

3. The reconfigurable electromagnetic metasurface antenna according to claim 2, characterized in that: The thickness of the upper layer is 0.2 μm; the dielectric layer is silicon dioxide with a thickness of h=10 μm; and the thickness of the lower layer is 0.5 μm.

4. The reconfigurable electromagnetic metasurface antenna according to claim 3, characterized in that: The upper and lower metal layers are both made of copper.

5. The reconfigurable electromagnetic metasurface antenna according to claim 4, characterized in that: The period of the metasurface unit array is p = 40 μm.

6. The 5-bit reconfigurable electromagnetic metasurface antenna according to claim 3, characterized in that: When the length b of the photosensitive silicon layer is 19.8um, 32.7um, 35um and 38um, its phase is -5.7°, -94.9°, -185°, and -275.6°, respectively. The phase difference is 90°, and the corresponding coding states are "0", "1", "2" and "3".

7. The stealth communication method of the reconfigurable electromagnetic metasurface antenna according to claim 2, characterized in that: include: The reconfigurable electromagnetic metasurface antenna described in claim 2 is reverse-engineered to obtain the RCS reduction array coding of the metasurface unit array, so that the reconfigurable electromagnetic metasurface antenna can achieve broadband RCS reduction and electromagnetic stealth.

8. The covert communication method according to claim 7, characterized in that: Methods for obtaining RCS reduced array encoding include: S1, initializing the period of the metasurface unit array and the metasurface unit parameters; S2, randomly generate an initial population, where the individuals in the initial population are random coding sequences of the super surface unit array; S3, calculate the objective function value of each individual in the current population under the corresponding coding sequence, and determine whether the termination condition is met. If so, output the optimal coding sequence and end; otherwise, go to S4; The objective function is set as 360° and 90° are the azimuth angle θ and the elevation angle range, represents the far-field scattering of the coding sequence under normal incidence; S4: Perform selection, crossover and mutation operations on the population and transfer to S3.

9. The covert communication method according to claim 7, characterized in that: The hidden communication method further includes: By dynamically modulating the quantized code distribution on the metasurface unit array, a multi-mode OAM vortex electromagnetic beam is constructed.

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