Coding metasurface array for microwave transmitting end of microwave wireless energy transmission system

Abstract

The invention discloses a coding metasurface array for a microwave transmitting end of a microwave wireless energy transmission system. The coding metasurface array comprises n * n supercells which are arranged in an array form, the supercell comprises m * m coding units which are arranged in an array form; the coding unit comprises an upper surface layer for receiving electromagnetic waves, a dielectric layer and a lower surface layer; the upper surface layer is located at the top and the lower surface layer is located at the bottom; the dielectric layer is positioned between the upper surface layer and the lower surface layer; the upper surface layer comprises two metal patches which are arranged in parallel; a diode is embedded in a gap between the two metal patches which are arranged in parallel, and power supply to the diode is realized through feeder lines on two sides of the two metal patches; the phase gradient of the coding metasurface is changed and different reflection beam angles are obtained by controlling the conduction and cutoff of the diodes, and the reflection characteristics of the metasurface are controlled by adjusting the form of the coding sequence, so that the dual-beam coding metasurface can reflect dual beams at different angles.

Description

Technical Field

[0001] The present invention belongs to the field of fully automated products and relates to a coded metasurface array for a microwave transmitting end of a microwave wireless energy transmission system. Background Art

[0002] Electromagnetic metamaterials (EM) are a new type of artificially synthesized composite material. Since physicist Veselago first proposed the concept of metamaterials in 1967, its application frequency band has gradually developed to the terahertz and light wave bands through continuous development.

[0003] Due to the limitations of early experimental conditions, it was not until 30 years later that Professor Pendry of Imperial College London confirmed that EM has the characteristics of negative dielectric constant and negative relative permeability by periodically arranging metal wires and open resonant rings (SRR). Professor Smith of Duke University in the United States used the above method to combine SRR with metal wires and proved for the first time that EM has the characteristics of negative refractive index. Professor Eleftheriades further proposed a metamaterial lens structure based on left-handed transmission lines, with a resolution of 0.21 equivalent wavelengths, breaking the limit of previous diffraction conditions. After the publication of the above representative papers, they attracted the attention of researchers around the world and laid a solid foundation for the future research and application of EM.

[0004] By manipulating the polarization, phase, and amplitude properties of electromagnetic waves, researchers have successfully achieved supernatural physical phenomena such as metamaterial lenses, negative refraction, high anisotropy, and illusion devices. EM has shown broad application potential in many fields such as wireless communications, artificial intelligence, and radar.

[0005] In the study of metamaterial properties, their properties are generally described at a macroscopic level, so this type of metamaterial is widely referred to as "analog metamaterial". With the development of the information age, the representation of information is inseparable from binary coding, so Professor Cui Tiejun proposed the concept of digital coding metamaterials with phase changes. [1] , which is a breakthrough in the field of metamaterials. Coded metamaterials simulate various digital units by binary encoding units with different phase characteristics, thus realizing the transformation from "analog metamaterials" to "digital metamaterials".

[0006] In recent years, digital coding and coding metamaterials have gradually developed from the microwave band to the terahertz frequency band, and expanded from reflection coding to transmission coding, amplitude coding, fractal coding, polarization coding and amplitude-phase combined coding. These studies have proved that digital coding and coding metasurfaces have powerful functions and broad application prospects in electromagnetic wave control. Summary of the invention

[0007] In order to solve the above problems, the technical solution adopted by the present invention is: a coded metasurface array for the microwave transmitting end of a microwave wireless energy transmission system, comprising n×n supercells arranged in an array form;

[0008] The supercell includes m×m encoding units arranged in an array;

[0009] The encoding unit includes an upper surface layer for receiving electromagnetic waves, for reflecting the electromagnetic waves, and performing sequence encoding;

[0010] Intermediate dielectric layer;

[0011] Lower surface layer: used for grounding;

[0012] The upper surface layer is located at the top, the lower surface layer is located at the bottom; the medium layer is located between the upper surface layer and the lower surface layer

[0013] The upper surface layer includes two metal patches arranged in parallel;

[0014] A diode is embedded in the gap between the two parallel metal patches, and the diode is powered by feed lines on both sides of the two metal patches;

[0015] By controlling the conduction and cutoff of the diode, the phase gradient of the coded metasurface can be changed to obtain different reflected beam angles. By adjusting the on-off state of the diode, the form of the programmable coding unit sequence can be changed to control the reflection characteristics of the metasurface.

[0016] Furthermore: the diode is a PIN diode.

[0017] Furthermore: the coded metasurface array operates at a frequency of 5.8 GHz.

[0018] Furthermore, the two parallel metal patches have the same structure; the metal patches are rectangular,

[0019] The thickness of the metal patch is 0.035 mm;

[0020] The width of the metal patch W1=5.7 mm, the length of the metal patch L1=9.8 mm, the length of the feeder line l2=1.6 mm; the length of the feeder line d1=0.3 mm.

[0021] Furthermore: the optimal value of m is 4.

[0022] Furthermore: the lower surface layer is a metal reflector with a thickness of 0.035 mm, and the dielectric layer is made of F4B material with a relative dielectric constant of 2.65 and a thickness of 3 mm.

[0023] Furthermore: the coded metasurface array is capable of reflecting dual beams of -30° and 45° simultaneously.

[0024] The present invention provides a coded metasurface array for the microwave transmitting end of a microwave wireless energy transmission system. In order to flexibly control the reflected beam of the coded metasurface, the present application uses the designed reflective coding unit to optimize the coding sequence of the 2-bit coded metasurface, thereby obtaining a coded metasurface that can achieve different functions. In addition, the present application sets specific design goals for different design requirements, solves the far-field function characteristics of the coded metasurface, and iteratively optimizes it to adjust the coding sequence of the coded metasurface so that the design goals can achieve the optimal effect.

[0025] It has the following advantages:

[0026] A coding unit structure that can work at a frequency of 5.8GHz and a coding sequence optimization design method based on a genetic algorithm are proposed, which realizes the free control function of the reflected beam angle of the coding metasurface. Based on the designed coding unit structure, this application designs a 1-bit coding metasurface that can reflect multiple beams. Secondly, a coding metasurface composed of different array forms is constructed through the coding unit to design a coding metasurface that can reflect a single beam at 45° and 0° at a frequency of 5.8GHz, and a dual-beam coding metasurface that can reflect -30° and 45° at the same time. Finally, the designed coding metasurface is sampled and tested to verify the feasibility of the design.

[0027] This application studies the reflection beam angle control of 2-bit coding metasurfaces, including the research on single-beam and dual-beam reflection angle control, and designs coding metasurfaces composed of different array forms. On this basis, the genetic algorithm is used to optimize the coding sequence of the coding metasurface, and a single-beam coding metasurface that can reflect a specific angle and a dual-beam coding metasurface that can reflect different angles are obtained. Finally, the designed coding metasurface is sampled and tested to verify the feasibility of the design. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0029] Figure 1 is a schematic diagram of a reflective encoding unit, wherein (a) is a side view and (b) is a front view;

[0030] Figure 2 is the internal equivalent circuit of the PIN diode, where (a) is when the diode is in the on state, and (b) is when the diode is in the off state;

[0031] Figure 3 is a schematic diagram of a coding unit, wherein (a) is a reflection amplitude curve, and (b) is a reflection phase curve;

[0032] Figure 4 The magnetic field distribution on the unit surface of the diode in different states, where (a) is the diode on, and (b) is the diode off;

[0033] Figure 5 The three-dimensional far-field simulation results. (a) is the coding metasurface "00010001", (b) is the coding metasurface "00100100", (c) is the coding metasurface "01010101", and (d) is the coding metasurface "00110011".

[0034] Figure 6 The test results of two reflective coding metasurfaces, where (a) is coding metasurface V2 and (b) is coding metasurface W1.

[0035] Figure 7 To test samples for the coded metasurface;

[0036] Figure 8 Shown are the test results of measuring the reflection pattern of the coded metasurface with the coding sequence of "01010101". DETAILED DESCRIPTION

[0037] 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. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0038] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings 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. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. 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.

[0039] Generally, there are two methods to control phase coding. One is to control the phase change of the unit at a specific frequency by changing the size and resonant frequency of the coding unit, which is a common method in passive unit design; the other is to control the phase change by changing the state of the active device in the unit structure. In order to more flexibly control the "0" and "1" units of the 1-bit coding metasurface, this application designs a coding unit structure. Its structural schematic diagram is shown in the figure. Figure 1 As shown, wherein (a) is a side view, and (b) is a front view;

[0040] A coded metasurface array for a microwave transmitting end of a microwave wireless energy transmission system: comprising n×n supercells arranged in an array form;

[0041] The supercell includes m×m encoding units arranged in an array;

[0042] The coding unit includes an upper surface layer for receiving electromagnetic waves, and a layer for reflecting electromagnetic waves as a coding sequence layer.

[0043] Dielectric layer: located in the middle,

[0044] The lower surface layer is used for grounding;

[0045] The upper surface layer is located at the top, and the lower surface layer is located at the bottom; the medium layer is located between the upper surface layer and the lower surface layer;

[0046] The upper surface layer includes two metal patches arranged in parallel;

[0047] A diode is embedded in the gap between the two parallel metal patches, and the diode is powered by feed lines on both sides of the two metal patches;

[0048] By controlling the conduction and cutoff of the diode, the phase gradient of the coding metasurface is changed to obtain different reflection beam angles, and the form of the programmable coding unit sequence is changed by adjusting the diode on and off to control the reflection characteristics of the metasurface. n, m are positive integers; the optimal value of m is 4;

[0049] The upper surface layer is composed of two parallel metal patches with a thickness of 0.035mm, and a PIN diode is embedded in the gap between the patches and powered by feeders on both sides. The lower surface layer is a metal reflector with a thickness of 0.035mm, and the middle dielectric layer is made of F4B material with a relative dielectric constant of 2.65 and a thickness of 3mm.

[0050] The coding unit is structurally optimized and designed, and boundary conditions are set in the electromagnetic simulation software CST. Since the designed unit structure is symmetrical, symmetrical electromagnetic wall boundary conditions are used to simulate the infinite periodic array structure, where the two sides of the x-axis are set as symmetrical magnetic walls, the two sides of the y-axis are set as symmetrical electric walls, and wave port excitation is set at one electrical wavelength from the upper and lower surfaces of the unit on both sides of the z-axis for time domain simulation. The internal equivalent circuit of the PIN diode used in the unit is as follows: Figure 2 As shown, (a) is when the diode is in the on state, and (b) is when the diode is in the off state;

[0051] When the diode is in the on state, it is equivalent to an RL series circuit (R = 0.5Ω, L = 0.75nH), and when the diode is in the off state, it is equivalent to an LC series circuit (L = 0.5nH, C = 0.24pF). After multiple optimizations, the structural parameters of the unit are finally set to: l1 = 13mm, W1 = 5.7mm, L1 = 9.8mm, d1 = 0.3mm, d2 = 0.6mm, l2 = 1.6mm.

[0052] Simulate the y-polarized incident wave irradiating the upper surface of the unit and obtain the following Figure 3 The simulation results of the coding unit shown, where (a) is the reflection amplitude curve, (b) is the reflection phase curve;

[0053] From the reflection amplitude curve and reflection phase curve, it can be found that the reflection amplitude of the unit at 5.8GHz frequency is close to 1, and the phase difference is about 180°. Figure 4 The figure shows the magnetic field distribution on the surface of the unit in different states of the diode, where (a) is the diode conducting and (b) is the diode cutting off;

[0054] It can be seen that when the diode is turned on, its surface magnetic field is significantly enhanced, meeting the design requirements. Therefore, the unit structure in which the diode is in the on and off states is used as the "0" unit and the "1" unit.

[0055] In order to further realize the electromagnetic control method, a 1-bit coding unit structure containing a PIN diode is designed. Different bias voltages are provided by FPGA to control the array form of the coding metasurface, thereby achieving different electromagnetic reflection characteristics. Finally, the function of flexibly controlling the angle of the reflected beam of the coding metasurface is realized.

[0056] By switching the diode on and off and changing the phase gradient of the coding metasurface, different reflected beam angles can be obtained, and by adjusting the form of the coding sequence, the scattering characteristics of the coding metasurface can be controlled. We will design coding metasurfaces with different functions, and study the reflected beams of the coding metasurfaces, especially the angles and number of reflected beams, and make and measure samples.

[0057] After the coding unit design is completed, these units are combined into a coding metasurface to achieve dynamic control of the reflected beam. In order to simplify the design of the coding metasurface control circuit, this paper adopts a column-based control method, which not only reduces the number of control channels but also reduces the capacity. Although ideally, independent control of each supercell can provide a wider range of functions, in reality, multiple independent control channels will increase the volume of the metasurface and may cause crosstalk between microwave signals and DC signals, thereby affecting the performance of the metasurface and being unfavorable for actual testing.

[0058] Since it is impossible to simulate the application of different voltages to change the state of the coding unit in a simulation environment, the change of the coding unit state can be simulated by directly adjusting the equivalent parameter value of the PIN diode. In actual applications, different bias voltages can be output by FPGA to control the array form of the coding metasurface, thereby achieving different functions. To verify the feasibility of the design, several coding metasurfaces were constructed in the electromagnetic simulation software and far-field simulation was performed on them, as shown below: Figure 5 The three-dimensional far-field simulation results are shown in Figure 2. (a) is the coding metasurface "00010001", (b) is the coding metasurface "00100100", (c) is the coding metasurface "01010101", and (d) is the coding metasurface "00110011". The simulation results show that by adjusting the array form of the coding metasurface, a variety of reflection modes can be achieved. In particular, the designed coding metasurface consists of 8×8 supercells, each of which consists of 4×4 coding units, and the coding states of all units in each supercell are the same.

[0059] In summary, the coded metasurface composed of different forms of coding units can not only achieve complex multi-beam reflection effects, but also complete powerful functions such as beam scanning and RCS reduction under specific coding sequences, reflecting the powerful control function of the coded metasurface over electromagnetic waves.

[0060] In summary, by setting the target angle and combining the genetic algorithm to optimize the design of the coding sequence of the coding metasurface, the reflected beam energy of the coding metasurface at this angle is much larger than other side lobes, and the side lobe values ​​at other angles are minimized. It is considered that the optimization target conditions are achieved, and the optimization program can optimize the design of the coding metasurface that reflects multiple beams at different angles, thereby completing the free control function of the reflected beam of the coding metasurface.

[0061] The designed coding metasurface is sampled and tested to verify whether the reflected beam of the coding metasurface will produce the expected effect. The purpose is to evaluate the operating ability of the designed coding metasurface in a practical environment.

[0062] like Figure 6 The figure shows the test results of two reflective coding metasurfaces, where (a) is the coding metasurface V2 and (b) is the coding metasurface W1. From the reflection pattern obtained from the test, it can be found that the strong reflections of the two coding metasurfaces are concentrated at 20° and 38°, while the reflectivity at other angles is relatively low, which is close to the simulation results, further verifying the feasibility of the design.

[0063] In addition, the designed coding metasurface was sampled and the PIN diode was welded on the metasurface to obtain the following Figure 7 The coding metasurface test sample shown in the figure, in which the change of the coding metasurface array form is realized by FPGA programming. Figure 8 Shown are the test results of measuring the reflection pattern of a coded metasurface with a coding sequence of "01010101". The metasurface is also composed of 8×8 supercells, and each supercell contains 4×4 coding units. The overall size is 440mm×416mm.

[0064] From the reflection directional diagram obtained from the test, it can be found that the coded metasurface has strong reflection in the directions of -28° and 28°, which is similar to the simulation results, verifying the feasibility of the design. However, since the metasurface requires the welding of a large number of PIN diodes and there are certain errors in the experimental process, its reflectivity in the 0° direction is higher than the simulation results.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

[0066] [1]Cui,T.,Qi,M.,Wan,X.et al.Coding metamaterials,digitalmetamaterials and programmable metamaterials.Light Sci Appl 3,e218(2014).https: / / doi.org / 10.1038 / lsa.2014.99。

Claims

1. A coded metasurface array for a microwave transmitting end of a microwave wireless energy transmission system, characterized in that: It includes super cells arranged in an n×n array; The supercell includes m×m encoding units arranged in an array; The encoding unit includes an upper surface layer for receiving electromagnetic waves, for reflecting the electromagnetic waves, and performing sequence encoding; Intermediate dielectric layer; Lower surface layer: used for grounding; The upper surface layer is located at the top, the lower surface layer is located at the bottom; the medium layer is located between the upper surface layer and the lower surface layer The upper surface layer includes two metal patches arranged in parallel; A diode is embedded in the gap between the two parallel metal patches, and the diode is powered by feed lines on both sides of the two metal patches; By controlling the conduction and cutoff of the diode, the phase gradient of the coded metasurface can be changed to obtain different reflected beam angles. By adjusting the on-off state of the diode, the form of the programmable coding unit sequence can be changed to control the reflection characteristics of the metasurface.

2. According to claim 1, a coded metasurface array for a microwave transmitting end of a microwave wireless energy transmission system is characterized in that: The diode is a PIN diode.

3. The coded metasurface array for the microwave transmitting end of the microwave wireless energy transmission system according to claim 1, characterized in that: The coded metasurface array operates at a frequency of 5.8 GHz.

4. The coded metasurface array for the microwave transmitting end of the microwave wireless energy transmission system according to claim 1, characterized in that: The two parallel metal patches have the same structure; the metal patches are rectangular. The thickness of the metal patch is 0.035 mm; The width of the metal patch W1=5.7 mm, the length of the metal patch L1=9.8 mm, the length of the feeder line l2=1.6 mm; the length of the feeder line d1=0.3 mm.

5. The coded metasurface array for the microwave transmitting end of the microwave wireless energy transmission system according to claim 1, characterized in that: The optimal value of m is 4.

6. The coded metasurface array for the microwave transmitting end of the microwave wireless energy transmission system according to claim 1, characterized in that: The lower surface layer is a metal reflector with a thickness of 0.035 mm, and the dielectric layer is made of F4B material with a relative dielectric constant of 2.65 and a thickness of 3 mm.

7. The coded metasurface array for the microwave transmitting end of the microwave wireless energy transmission system according to claim 1, characterized in that: The coded metasurface array is able to reflect dual beams of -30° and 45° simultaneously.

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