A multi-dimensional controllable digitally coded metasurface

Abstract

The present invention discloses a multi-dimensional controllable digital coding metasurface, including M×M metasurface units, wherein the metasurface units include an upper dielectric substrate, a metal floor, a middle dielectric substrate, an upper reflective baffle, a lower dielectric substrate and a lower reflective baffle, a metal patch with parasitic branches is etched on the upper dielectric substrate, a PIN diode is arranged on the metal patch, an upper reflective baffle and a lower reflective baffle are arranged on the upper and lower surfaces of the lower dielectric substrate respectively, and a DC feed network is arranged on the lower surface of the middle dielectric substrate and the lower dielectric substrate; each group of metasurface units is connected by a DC feeder and connected to a single-chip control system, and the mutual conversion of electromagnetic wave polarization is realized by switching the bias voltage on the PIN diode. The metasurface has a strong control function for electromagnetic waves incident perpendicular to the surface, and the state arrangement of the metasurface array units is controlled in real time by an external circuit, so as to realize the functions of abnormal reflection, radar cross section reduction and polarization rotation.

Description

Technical Field

[0001] The present invention belongs to the technical field of artificial electromagnetic surfaces, and specifically relates to a multi-dimensionally controllable digitally coded metasurface that can be used for radar cross-section reduction and electronically controllable, and can be used to simultaneously achieve control of co-polarization and cross-polarization in the 8GHz-12GHz frequency band. Background Art

[0002] As a new technology, electromagnetic metamaterials have attracted widespread attention since their birth due to their unique electromagnetic properties, and have rapidly developed into a cutting-edge interdisciplinary subject involving physics, chemistry, materials, information, etc. Compared with the early electromagnetic metasurfaces that could only achieve a single function, multifunctional metasurfaces can achieve multi-dimensional regulation of electromagnetic waves, and their application scenarios are also more extensive. Various countries and institutions are constantly promoting the industrial application of multi-dimensional metamaterials.

[0003] Polarization is one of the properties of electromagnetic waves. Polarization rotation metasurfaces use the anisotropy of metasurfaces to change the polarization direction of incident electromagnetic waves to another direction. Generally speaking, metasurfaces can be divided into two types: transmission type and reflection type. Traditional metasurfaces can usually only work in reflection state or transmission state and have only a single function. In recent years, people have proposed some multifunctional metasurfaces in the microwave band, which can regulate the incoming waves to different degrees. However, once the design is completed, the functions of these metasurfaces will not change. In view of the defects of traditional metasurfaces, metasurface reconfigurable technology has been further proposed.

[0004] The technologies for achieving metasurface reconfiguration can be divided into two categories: mechanical methods and electrical control methods. Mechanical reconstruction is slow, space is limited, control is complex, and accuracy is easily affected by mechanical errors; electrical control methods have outstanding advantages such as fast response speed, high integration, and flexible design, but the structure is relatively complex. Recently, by using digital states to represent electromagnetic parameters, the concept of coded metasurfaces has been proposed, directly linking digital technology at the information level with metasurface technology at the physical level. By encoding and arranging metasurface units in different states with predetermined functions, the predetermined control of electromagnetic waves can be achieved. This encoding method of metamaterial units greatly reduces the complexity of the design, makes the design of metasurfaces more flexible, and can ensure good control effects on electromagnetic waves.

[0005] With the development of coded metasurface technology, multifunctional metasurfaces have developed rapidly in the past decade. Specific applications include polarization conversion, RCS reduction, circular polarization of antennas and other fields. However, existing multifunctional metasurfaces generally have a narrow working bandwidth and can only regulate the cross-polarization of electromagnetic waves. There is little research on co-polarization regulation, or, for example, due to the structure of the metasurface itself, the reconfigurable function is not realized. For example, Chun sheng Guan proposed a method of simultaneously manipulating cross-polarization and co-polarization in his published paper "Dual-polarized multiplexed meta-holograms utilizing coding metasurface" (NANOPHOTONICS, 2020), but because the system structure is complex, reconfigurable design cannot be performed. Therefore, the existing metasurface application scenarios are subject to certain limitations. Summary of the invention

[0006] In order to solve the above defects in the prior art, the purpose of the present invention is to provide a multi-dimensional controllable digital coding metasurface, including a reflective reconfigurable metasurface and a single-chip control system connected thereto, to solve the problem of insufficient control of co-polarization. The metasurface has the function of changing the beam direction and polarization of electromagnetic waves incident perpendicular to the surface, and the function switching is flexible.

[0007] The present invention is achieved through the following technical solutions.

[0008] The present invention provides a multi-dimensionally controllable digital coding metasurface, comprising M×M metasurface units, wherein the metasurface units comprise an upper dielectric substrate, a metal floor, a middle dielectric substrate, an upper reflective baffle, a lower dielectric substrate and a lower reflective baffle which are sequentially distributed from top to bottom, a metal patch with parasitic branches is etched on the upper dielectric substrate, a PIN diode is arranged on the metal patch, an upper reflective baffle and a lower reflective baffle are arranged on the upper and lower surfaces of the lower dielectric substrate respectively, and a DC feeding network is arranged on the lower surfaces of the middle dielectric substrate and the lower dielectric substrate;

[0009] The metal patch passes through the metallized via holes of the upper dielectric substrate, the metal floor, the middle dielectric substrate, the upper reflective baffle and the lower dielectric substrate to be connected to the DC feeding network;

[0010] Each group of metasurface units is connected through a DC feeder and connected to a single-chip microcomputer control system. By switching the bias voltage on the PIN diode, the mutual conversion of electromagnetic wave polarization is achieved.

[0011] Preferably, the metal patches of the parasitic branches include a central patch, a cross-shaped patch and a diamond-shaped peripheral patch. The cross-shaped patch and the central patch are intermittently slotted and connected via a PIN diode. The diamond-shaped peripheral patches are distributed around the central patch.

[0012] Preferably, the PIN diode is arranged at an angle of 45° to the x-axis, and the polarization and phase of the electromagnetic wave are controlled by the unit by changing the bias voltage at both ends of the switching diode.

[0013] Preferably, the central patch is a square metal patch with a missing corner, the missing corner is a square, and is connected to the metal floor through a metallized via.

[0014] Preferably, the cross-shaped patches have the same width and different lengths, and are connected to the DC feed networks of the middle dielectric substrate and the lower dielectric substrate respectively through metallized vias with different radii on the outside of the patches.

[0015] Preferably, the diamond-shaped peripheral patch is a square structure with a triangle cut out, and the inner angle of the square of the peripheral patch corresponds to the missing angle of the central patch.

[0016] Preferably, two symmetrically placed circular metal patches with a radius of R1 are distributed on both the upper reflection baffle and the lower reflection baffle.

[0017] Preferably, the DC feed network includes circular metal patches connected by metal wires, arranged in the same period and with the same radius, several circular metal patches connected by metal wires form an angle of 45 degrees with the x-axis, and one circular metal patch connected by metal wires forms an angle of 135 degrees with the x-axis.

[0018] Preferably, the upper dielectric substrate, the middle dielectric substrate and the lower dielectric substrate are all made of F4B with a dielectric constant of 4.5 and a loss tangent of 0.0035; the metal patch, the metal floor and the metal reflective baffle are all made of copper.

[0019] The present invention adopts the above technical solution, which has the following beneficial effects:

[0020] (1) Since the patch structure in the metasurface unit of the present invention adopts diamond-shaped parasitic branches, the working bandwidth of the metasurface is greatly expanded, as well as the conversion between left-hand circular polarization and right-hand circular polarization. By controlling phase coding, the beam deflection and the reduction of radar scattering cross section can be achieved.

[0021] (2) The present invention can switch the voltage loaded on the switch diode in real time by controlling the external circuit through a computer, thereby switching the working state of the metasurface in real time. Since the present invention can switch functions at any time according to the actual scene, it has great application value.

[0022] (3) The present invention has the characteristics of wide frequency band coverage, flexible control, diverse functions, strong practicality, etc. The metasurface can achieve a 10dB radar cross-section reduction in the 8-12GHz frequency range. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The drawings described herein are used to provide a further understanding of the present invention, constitute a part of the present application, and do not constitute an improper limitation of the present invention. In the drawings:

[0024] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0025] Figures 2(a)-(e) are schematic diagrams of the unit structure of the present invention; Figure 2(a) is a schematic diagram of the overall structure of the unit, Figure 2(b) is a top view, Figure 2(c) is a metal floor, and Figures 2(d) and 2(e) are two layers of metal reflective baffles, respectively;

[0026] Figure 3 It is a schematic diagram of the structure of a 4x4 unit X-type DC feeder network of the present invention;

[0027] FIG4(a)-(c) are simulation results of the cross-polarization reflection amplitude and phase of vertically incident electromagnetic waves according to the present invention as the switching diode bias voltage changes, wherein FIG4(a) is the reflection amplitude, FIG4(b) is the reflection phase, and FIG4(c) is the polarization conversion efficiency;

[0028] FIG5(a)-(b) are simulation results of the present invention showing the change of the co-polarized reflection amplitude and phase of a vertically incident electromagnetic wave with the bias voltage of a switching diode, wherein FIG5(a) is the reflection amplitude and FIG5(b) is the reflection phase;

[0029] Figures 6(a)-(c) are schematic diagrams of the three unit state distributions designed in the present invention and the simulation results of the corresponding functions, where Figure 6(a) is for controlling the reflected wave beam pointing, Figure 6(b) is for achieving RCS reduction in the X-band, and Figure 6(c) is for controllable reflected wave polarization. DETAILED DESCRIPTION

[0030] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. The exemplary embodiments and descriptions of the present invention are used to explain the present invention but are not intended to limit the present invention.

[0031] like Figure 1 As shown, a multi-dimensional controllable digital coding metasurface for freely manipulating co-polarized waves and cross-polarized waves provided by an embodiment of the present invention is formed by periodically extending identical reflective metasurface units in an xy two-dimensional plane, and its electromagnetic characteristics are controlled in real time by an external control circuit. In this embodiment, the total number of metasurface units is 16×16, which are evenly divided into 4 groups along the x direction. The number of metasurface units contained in the metasurface array is N, and N=256. Each group of metasurface units is connected through a DC feeder and connected to an I / O port of a single-chip microcomputer control system, and the state of each unit is controlled by computer input.

[0032] As shown in Figure 2(a), the upper dielectric substrate 3, the metal floor 4, the middle dielectric substrate 5, the upper reflective baffle 6, the lower dielectric substrate 7 and the lower reflective baffle 8 are arranged in sequence from top to bottom. A metal patch 1 is etched on the upper dielectric substrate 3, a PIN diode 2 is provided on the metal patch 1, an upper reflective baffle 6 and a lower reflective baffle 8 are provided on the upper and lower surfaces of the lower dielectric substrate 7 respectively, metallized vias 9 are provided on the metal patch 1, the metal floor 4, the middle dielectric substrate 5, the upper reflective baffle 6 and the lower dielectric substrate 7, and the metal patch 1 and the metal floor 4 are connected through the metallized vias 9.

[0033] In one embodiment, the thickness of the upper dielectric substrate is H1, the thickness of the middle dielectric substrate is H2, and the thickness of the lower dielectric substrate is H3. The side lengths of the three dielectric substrates are all P, where H1=2mm, H2=0.25mm, H3=0.25mm, P=12mm, where L1=2.8mm, and W1=0.375mm.

[0034] In one embodiment, the materials of the upper dielectric substrate 3, the middle dielectric substrate 5 and the lower dielectric substrate 7 are all F4B with a dielectric constant of 4.5 and a loss tangent of 0.0035. Two adjacent layers of the dielectric substrate are spaced apart by insulating resin gaskets. The metallized vias 9 connect the metal patch 1 and the metal floor 4 and provide a grounding cathode for the PIN diode. The metallized vias around the metal patch 1 and the reflective baffle 8 and provide a control anode for the PIN diode. The use of metallized vias with different radii can affect the working bandwidth of the metasurface.

[0035] As shown in FIG2(b), the metal patch 1 includes a central patch 2-1, a cross-shaped patch 2-2, and a diamond-shaped peripheral patch 2-3 surrounding the central patch. The peripheral patch 2-3 is divided into four, each of which is the same and is evenly arranged around the central patch 2-1; the central patch 2-1 is a square metal patch with a missing corner, and the missing corner is a square. The peripheral patch 2-3 is a square with a triangular structure cut off. The corners of the peripheral patch 2-3 corresponding to the cut corner correspond to the missing corner of the central patch 2-1; the cross-shaped patch 2-2 is four rectangular structures symmetrical with the central patch 2-1 as the center. The widths of the cross-shaped patches are the same but the lengths are different. Two pairs of vias of different sizes are distributed on the cross-shaped patch 2-2; the cross-shaped patch 2-2 is slotted and discontinuous with the central patch 2-1, and each is connected with a PIN diode 2. The positive pole of each switching diode faces the cross patch and the negative pole faces the central patch. One end of the PIN diode 2 is connected to the cross-shaped patch 2-2, and the other end is connected to the central patch 2-1, and is connected to the lower layer DC feeding network through the metallized via 9 on the cross-shaped patch 2-2.

[0036] In the predefined orthogonal x-axis and y-axis coordinate system, the cross patch is placed at a 45° angle to the x-axis, and the lower end of the diamond patch is parallel to the x-axis or y-axis. The polarization and phase of the electromagnetic wave of the unit can be regulated by changing the bias voltage at both ends of the switching diode.

[0037] As shown in FIG. 2( c ), two pairs of vias with different diameters are symmetrically distributed on the metal floor 4 , corresponding to the positions of the metallized vias 9 on the cross-shaped patch 2 - 2 , respectively, for isolating the DC circuit.

[0038] As shown in FIG. 2( d ) and FIG. 2( e ), two symmetrically placed first circular metal patches 6 - 1 and second circular metal patches 8 - 1 with a radius R1 are distributed on both the upper reflective baffle 6 and the lower reflective baffle 8 .

[0039] The metal reflective baffle is used to connect the DC circuit and reflect the leaked electromagnetic waves. The bias voltage at both ends of the PIN tube on the metasurface unit is controlled by the single-chip control system, thereby controlling the state of the metasurface unit, and realizing different functions by real-time control of the state arrangement of different metasurface units.

[0040] In one embodiment, the metal patch, the metal floor and the metal reflective baffle are all made of copper, and the thickness is 0.018 mm or 0.035 mm. Each 4x4 unit circular reflective baffle is connected through an X-type cross feed network and connected to an external feed source loading voltage.

[0041] The length of the center square patch is L1, and the length of the missing corner is L2, where L1 = 2.8mm, W1 = 0.375mm. The length of the cross-shaped patch is L3, the width is W1, the length of the other side is L4, the width is W2, where L3 = 4.7mm, W1 = 1.6mm, L4 = 4.85mm, W2 = 1.6mm. The length of the diamond-shaped patch is L5, the length of the long hypotenuse is L6, and the length of the short hypotenuse is L7, where L5 = 3.53mm, L6 = 3.8mm, L7 = 1.3mm.

[0042] The circular reflective baffle has a radius of R1, R1 = 2.3 mm. The radius of the central metallized via hole is R2, and the radii of the surrounding metallized via holes are R3 and R4, where R2 = 0.15 mm, R3 = 0.34 mm, and R4 = 0.22 mm.

[0043] The radii of the via holes dug out of the metal floor are R5 and R6, R5=1mm, R6=0.8mm respectively.

[0044] Reference Figure 3 , the DC feeding network of the present invention is further described.

[0045] Figure 3In the figure, the DC feed network is located on the lower surface of the middle dielectric substrate 5 and the lower dielectric substrate 7. It includes circular metal patches connected by metal wires, arranged in the same period and with the same radius. The radius of the circular metal patches is 2.3 mm. Several circular metal patches connected by metal wires with a width of 0.2 mm are at an angle of 45 degrees to the x-axis, and a circular metal patch connected by a metal wire with a width of 0.5 mm is at an angle of 135 degrees to the x-axis. The width of the metal wire will affect the AC resistance. The smaller the width, the better the DC resistance effect.

[0046] Referring to Figure 4(a)-(c), in order to verify the feasibility of the multi-dimensionally controllable digitally coded metasurface, we processed the metasurface using PCB technology and soldered the switching diode to the metasurface patch using wave soldering technology.

[0047] Referring to Figure 5(a) and (b), in order to verify the feasibility of the single-chip microcomputer control system, we used PCB technology to process the single-chip microcomputer control system, and used the connected LED lights to judge the working status of the corresponding diode on the metasurface.

[0048] The effects of the present invention are further described below in conjunction with simulation experiments.

[0049] The specific electromagnetic characteristics of the multi-dimensionally controllable digitally coded metasurface unit are analyzed as follows.

[0050] In order to illustrate the electromagnetic characteristics of the multi-dimensionally controllable digitally coded metasurface unit, the commercial simulation software ANSYS HFSS was used to model and simulate the unit structure of reference Figure 2(a).

[0051] Referring to Figure 4(a), when the x-polarized electromagnetic wave is incident vertically, the bias voltage of the switching diode is changed to make the metasurface operate in state "1" and state "0". The co-polarization reflection coefficient of the metasurface unit is lower than -10dB within the 8-12GHz bandwidth. As shown in Figure 4(b), the cross-polarization reflection phase difference between the two states is 180°. As shown in Figure 4(c), the unit polarization conversion efficiency is greater than 90%.

[0052] Reference Figure 5(a) , 5(b) This is a simulation curve diagram of the present invention for co-polarization regulation within the 8-12 GHz bandwidth. As shown in Figure 4 (a), within the 8-12 GHz range, the bias voltage of the switching diode is changed to make the metasurface work in state "3" and state "4", showing a total reflection effect for co-polarization. As shown in Figure 4 (b), the co-polarization reflection phase difference between the two states is 180°±30°.

[0053] 6( a ) is a schematic diagram of the unit state distribution corresponding to the three functions designed in the present invention and a simulation result diagram of the corresponding functions.

[0054] 6(a) shows the function of controlling beam deflection, where the beam deflection is excited by an x-polarized horn feed, and the distance between the horn feed and the metasurface antenna is greater than 2L. 2 / λ, at this time, the electromagnetic wave radiated by the horn can be approximated as a plane wave when it reaches the metasurface. The metasurface is linearly distributed along the x direction, and the phase difference between the units is 180°. Through the 00...11 arrangement, the calculated theoretical deflection angles are 45° and 135°, respectively. As shown in the figure, the left side of Figure 6(a) is a schematic diagram of the state distribution of the metasurface unit, and the right side of Figure 6(a) is a simulation result diagram of the corresponding function. The simulation results show that the two beam angles are 45° and 135°, respectively, which is consistent with the theoretical calculation value, proving the correctness of the design.

[0055] Refer to Figure 6(b) for the RCS reduction function in the X-band. The radar cross section reduction is also excited by the horn feed, and its excitation method is similar to the control beam deflection function. The distance between the horn feed and the metasurface antenna is greater than 2*L 2 / λ, satisfying the far-field condition. The left side of Figure 6(b) shows a schematic diagram of the unit state distribution under random coding of the metasurface, and the right side of Figure 6(b) shows the simulation result of the corresponding function. The simulation results show that by randomly coding the metasurface units, the metasurface achieves a 10dB radar cross-section reduction in the 8-12GHz frequency range compared to the metal reflector of the same size, proving the correctness of the design.

[0056] Refer to Figure 6(c) for the function of the controllable polarization rotator, which is also excited by the X-polarized horn feed. Its excitation method is similar to the control beam deflection function. The distance between the horn feed and the metasurface antenna is greater than 2*L 2 / λ, satisfying the far-field condition. The left side of Figure 6(c) shows a schematic diagram of the distribution of the metasurface unit states. When the metasurface units are all working in state "1" or state "0", the metasurface functions as a polarization rotator; when the metasurface units are all working in state "3" or state "4", the metasurface functions as a metal reflector. The right side of Figure 6(c) shows the simulation results of the corresponding functions. The simulation results are consistent with the theory, proving the correctness of the design.

[0057] The present invention is not limited to the above-mentioned embodiments. On the basis of the technical solution disclosed in the present invention, technicians in this field can make some substitutions and deformations to some technical features therein according to the disclosed technical content without creative labor, and these substitutions and deformations are all within the protection scope of the present invention.

Claims

1. A multi-dimensional controllable digital coding metasurface, characterized in that: The invention comprises M×M metasurface units, where M is a positive integer, and the metasurface units comprise an upper dielectric substrate, a metal floor, a middle dielectric substrate, an upper reflective baffle, a lower dielectric substrate and a lower reflective baffle, which are sequentially distributed from top to bottom; a metal patch with parasitic branches is etched on the upper dielectric substrate, a PIN diode is arranged on the metal patch, and a DC feeding network is arranged on the lower surfaces of the middle dielectric substrate and the lower dielectric substrate; The metal patch includes a central patch, a cross-shaped patch and a diamond-shaped peripheral patch. The cross-shaped patch and the central patch are intermittently slotted and connected via a PIN diode. The diamond-shaped peripheral patches are distributed around the central patch. The central patch is a square metal patch with a missing corner, and the missing corner is a square, and is connected to the metal floor through a first metallized via; The cross-shaped patches have the same width and different lengths, and two pairs of second metallized vias with different radii are provided on the outside of the patches, one pair of vias is connected to the DC feed network of the middle dielectric substrate, and the other pair of vias is connected to the DC feed network of the lower dielectric substrate; Each group of metasurface units is connected through a DC feeder and connected to a single-chip microcomputer control system. By switching the bias voltage on the PIN diode, the mutual conversion of electromagnetic wave polarization is achieved.

2. The multi-dimensional controllable digitally coded metasurface according to claim 1, characterized in that: The PIN diode is arranged at an angle of 45° to the x-axis, and the polarization and phase of the electromagnetic wave are regulated by the unit by changing the bias voltage at both ends of the switching diode.

3. The multi-dimensional controllable digitally coded metasurface according to claim 1, characterized in that: The diamond-shaped peripheral patch is a square structure with a triangle cut off, and the inner angle of the square of the peripheral patch corresponds to the missing angle of the central patch.

4. The multi-dimensional controllable digitally coded metasurface according to claim 1, characterized in that: Two symmetrically placed first circular metal patches are distributed on both the upper reflection baffle and the lower reflection baffle.

5. The multi-dimensional controllable digitally coded metasurface according to claim 4, characterized in that: The DC feeding network includes second circular metal patches connected by metal wires, arranged in the same period and with the same radius, a plurality of second circular metal patches connected by metal wires form an angle of 45 degrees with the x-axis, and a second circular metal patch connected by metal wires forms an angle of 135 degrees with the x-axis.

6. The multi-dimensionally controllable digitally coded metasurface according to claim 5, characterized in that: The materials of the upper dielectric substrate, the middle dielectric substrate and the lower dielectric substrate are all F4B with a dielectric constant of 4.5 and a loss tangent of 0.0035; the materials of the metal patch, the metal floor and the first circular metal patch are all copper.

7. The multi-dimensional controllable digital coding metasurface according to any one of claims 1 to 6, characterized in that: The metasurface achieves a 10dB radar cross-section reduction in the 8-12GHz frequency range.

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