Dual-polarization 3-bit phase-independently adjustable reconfigurable smart metasurface unit

Abstract

The invention discloses a dual-polarization 3-bit phase-independently adjustable reconfigurable intelligent metasurface unit, the unit has a four-layer structure, the second and third layers are feed layers, and the fourth layer is a metal ground; the first layer includes four isosceles right-angled triangle metal patches and four cross-shaped metal patches, each isosceles right-angled triangle is connected to its corresponding cross-shaped metal patch through a varactor; the four isosceles right-angled triangle metal patches are respectively connected to a metal via, the metal via in the x-axis direction is connected to the second-layer feed layer, and the metal via in the y-axis direction is connected to the third-layer feed layer. By adjusting the voltages at both ends of the varactor in two orthogonal polarization directions, the unit can independently realize 3-bit phase modulation within the oblique incidence range of 0 to 45° in the two orthogonal polarization directions, and then decouple in the two polarization directions, respectively realize beam scanning functions, and is insensitive to the incident angle of electromagnetic waves.

Description

Technical Field

[0001] The invention relates to a reconfigurable intelligent super surface unit. Background Art

[0002] With the continuous development of wireless communication technology, the information transmission speed of the network has reached a new peak, but problems have also followed. For example, compared with 4G, 5G signals have weaker penetration and greater energy loss. At present, the more common practice is to establish an ultra-dense network (UDN) to solve the problem, by deploying more dense base stations (BS) or access points (AP) to increase the system throughput, but this is accompanied by higher costs and power consumption, and dense base stations will also aggravate network interference and other problems. Therefore, it is imperative to find an efficient, reliable, and low-cost signal transmission solution.

[0003] In this context, reconfigurable smart surface (RIS) is regarded as a promising technology. Generally speaking, the propagation process of signals from transmitter to receiver is uncontrollable and random, but the emergence of RIS technology has changed this situation. Since RIS can adjust the state of each unit to control the reflected electromagnetic waves, an intelligent electromagnetic environment is formed. This reduces the complex reflection and diffraction caused by obstacles during signal propagation, making the propagation of signals controllable to a certain extent. Compared with traditional wireless relays, RIS can achieve full-duplex transmission mode without introducing self-interference, and has the characteristics of low cost, light weight, and low energy consumption. Based on this feature, RIS has been widely used in wireless communications, such as reducing the multipath effect of wireless channels, improving wireless communication security and channel estimation, etc.

[0004] The main hardware part of RIS is based on the concept of "metasurface". Specifically, metasurface is an artificial electromagnetic material whose surface is composed of a large number of low-cost sub-wavelength metal and dielectric units. Active metasurface further arranges active units on each unit, such as pin diodes, varactors, MEMS switches, etc. By adjusting the state of these active units, the electromagnetic waves reflected by the RIS can be made to change in amplitude or phase according to actual needs. By adjusting the reflection coefficients of these units according to a certain rule, the purpose of beamforming can be achieved, ultimately making the originally static communication environment dynamic and controllable.

[0005] In order to increase the coverage range, most mobile communication base stations use dual-polarized transmitting antennas to improve performance, which requires RIS to be dual-polarized. Otherwise, when the polarization direction of RIS is inconsistent with the polarization direction of the incoming wave, polarization loss will occur, that is, only one polarization signal can be received. In addition, the polarization of RIS will also affect the reception of the reflected wave by the user's receiving antenna. If RIS and the user's receiving antenna are single-polarized, the signal can only be received to the greatest extent when the polarization direction of the receiving antenna and RIS is consistent. Otherwise, the received signal energy will be greatly reduced or even cannot be received when the two are orthogonal. Secondly, the oblique incidence stability of RIS is also crucial. When the incident wave is not vertically incident, due to the spatial dispersion inside the RIS unit, its phase response is extremely sensitive to the incident angle of the incoming wave. If this problem is not solved, the encoding of RIS under normal incidence will not be able to correctly control the reflected beam under oblique incidence. In addition, the number of bits that can be adjusted in phase determines the performance of RIS. The higher the number of bits, the more precise the control of RIS on electromagnetic waves. At present, there is no RIS unit design that can meet the above points at the same time, which undoubtedly restricts the further application of RIS in communication systems. Summary of the invention

[0006] Purpose of the invention: In view of the above-mentioned prior art, a dual-polarization 3-bit phase-independently adjustable reconfigurable intelligent metasurface unit is proposed which is insensitive to the incident angle.

[0007] Technical solution: A dual-polarization 3-bit phase-independently adjustable reconfigurable intelligent metasurface unit, the unit includes a four-layer functional structure, wherein the second and third layers are feed layers, and the fourth layer is a metal ground; the upper surface of the unit is the first layer, and the lower surface of the unit is the fourth layer, the upper surface and the lower surface of the unit are both squares, and the side lengths are equal, that is, the unit side length; the first layer includes four isosceles right-angled triangle metal patches and four cross-shaped metal patches, each isosceles right-angled triangle is connected to a corresponding cross-shaped metal patch through a varactor; the four isosceles right-angled triangle metal patches are respectively connected to a metal via, the two metal vias in the x-axis direction are connected to the second-layer feed layer, and the two metal vias in the y-axis direction are connected to the third-layer feed layer; by adjusting the voltages at both ends of the varactor in two orthogonal polarization directions, the unit independently realizes 3-bit phase modulation within the oblique incidence range of 0 to 45° in the two orthogonal polarization directions, and then decouples in the two polarization directions to realize beam scanning functions respectively, and is insensitive to the incident angle of electromagnetic waves.

[0008] Furthermore, the first layer includes a square metal patch and a square ring metal patch, the square metal patch is located at the center of the first layer and inside the square ring metal patch, and the diagonals of the square metal patch and the square ring metal patch coincide with each other; the first layer also includes four rectangular metal patches, each side of the square ring metal patch vertically crosses with a rectangular metal patch to form a cross structure; along the diagonal, the square metal patch and the square ring metal patch are separated by gaps, the square metal patch is divided along the diagonal to form the four isosceles right triangle metal patches, and the square metal patch is divided along the diagonal to form the four cross metal patches; each isosceles right triangle metal patch is connected to the nearest cross metal patch by a varactor.

[0009] Furthermore, a square ring-shaped metal strip as a grounding wire is attached to the periphery of the first layer, and the side length of the square ring-shaped metal strip is the unit side length; each side of the square ring-shaped metal strip is directly connected to one side of the rectangular metal patch in the cross-shaped metal patch.

[0010] Furthermore, taking the first layer as a reference, a rectangular coordinate system is set, one side of the square metal patch is taken as the x-axis direction, and the other side of the square metal patch perpendicular to the x-axis is taken as the y-axis direction; the second layer is the first square metal feeding layer, the side of the first square metal feeding layer is parallel to the corresponding side of the square ring-shaped metal strip, and the side length is less than the side length of the square ring-shaped metal strip; at the edge of the first square metal feeding layer, a first metal strip and a second metal strip are respectively arranged in the positive and negative directions of the y-axis for connecting the square ring-shaped metal strip; the third layer is the second square metal feeding layer, the side of the second square metal feeding layer is parallel to the corresponding side of the square ring-shaped metal strip, and the side length is less than the side length of the square ring-shaped metal strip; the side length of the second square metal feeding layer is equal to that of the first square metal feeding layer; at the edge of the second square metal feeding layer, a third metal strip and a fourth metal strip are respectively arranged in the positive and negative directions of the x-axis for connecting the square ring-shaped metal strip.

[0011] Furthermore, the fourth layer is a square metal ground, the sides of which are parallel to the corresponding sides of the square ring-shaped metal strip, and the side length is equal to the unit side length, that is, each side of the square metal ground is directly connected to the square ring-shaped metal strip.

[0012] Furthermore, in the x-axis direction and y-axis direction of the first layer, four isosceles right-angled triangle metal patches are respectively connected to a metal via, the metal via is perpendicular to the plane of the first layer, and passes through the second layer, the third layer and the fourth layer; wherein, two metal vias in the x-axis direction are connected to the first square metal feed layer of the second layer, and the two metal vias in the x-axis direction are not connected to the second square metal feed layer of the third layer; two metal vias in the y-axis direction are connected to the second square metal feed layer of the third layer, and the two metal vias in the y-axis direction are not connected to the first square metal feed layer of the second layer; and the four metal vias are not connected to the square metal ground of the fourth layer.

[0013] Furthermore, the relative dielectric constant of the first dielectric layer between the first layer and the second layer is ε r =2.65, using polytetrafluoroethylene F4B with loss tangent tanδ=0.001; the relative dielectric constant of the second dielectric layer between the second and third layers is ε r =3.7, using Rogers RO4450 prepreg with loss tangent tanδ=0.004; the relative dielectric constant of the third dielectric layer between the third and fourth layers is ε r =2.65, and polytetrafluoroethylene F4B with loss tangent tanδ=0.001 is used.

[0014] Furthermore, the varactor model is SMV1405; when a voltage of 11V is applied to both sides of the varactor, its equivalent RLC model is a series connection of a 0.36Ω resistor, a 0.7nH inductor, and a 0.76pF capacitor.

[0015] Beneficial effects: (1) Each unit of the present invention integrates a pair of varactors in the x and y directions, and the two pairs of varactors can be controlled by DC feeding to achieve independent 3-bit phase modulation in the x and y directions. (2) The present invention optimizes the unit structure and introduces low-loss varactors to maintain high energy efficiency while maintaining a continuous phase change range of more than 315°. (3) The present invention reduces the mutual coupling between units by reducing the unit electrical size and introducing a mushroom-type EBG feeding structure, and can still maintain a stable phase response and a large reflected wave amplitude under oblique incidence of TE and TM polarized electromagnetic waves. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic diagram of the structure of a reconfigurable intelligent metasurface unit of the present invention;

[0017] Figure 2 Schematic diagram of the interlayer dimensions of the reconfigurable intelligent metasurface unit of the present invention;

[0018] Figure 3 Schematic diagram of the first-layer structure of the reconfigurable intelligent metasurface unit of the present invention;

[0019] Figure 4 Schematic diagram of the second-layer structure of the reconfigurable intelligent metasurface unit of the present invention;

[0020] Figure 5 This is a schematic diagram of the third layer structure of the reconfigurable intelligent super surface unit of the present invention;

[0021] Figure 6 Schematic diagram of the fourth-layer structure of the reconfigurable intelligent metasurface unit of the present invention;

[0022] Figure 7 It is a surface current diagram of the reconfigurable intelligent metasurface unit of the present invention along the polarization direction of the x-axis;

[0023] Figure 8 It is the surface current diagram of the reconfigurable intelligent metasurface unit of the present invention along the y-axis polarization direction;

[0024] Fig. 9 It is the cross-polarization amplitude diagram of the reconfigurable intelligent metasurface unit of the present invention;

[0025] Fig.10 It is the reflected wave amplitude diagram of 8 coding states of the reconfigurable intelligent metasurface unit of the present invention under x-axis and y-axis polarization respectively;

[0026] Fig.11 It is the reflected wave phase diagram of 8 coding states of the reconfigurable intelligent metasurface unit of the present invention under x-axis and y-axis polarization respectively;

[0027] Fig.12 is a reflection wave amplitude diagram of state 4 under oblique incidence of the reconfigurable intelligent metasurface unit of the present invention;

[0028] Fig.13 is a reflection wave phase diagram of state 4 under oblique incidence of the reconfigurable intelligent metasurface unit of the present invention;

[0029] Fig.14 It is the beam scanning result in the x-axis direction after the reconfigurable intelligent metasurface units of the present invention are arrayed;

[0030] Fig.15 It is the beam scanning result in the y-axis direction after the reconfigurable intelligent metasurface units of the present invention are arrayed;

[0031] Fig.16 It is the directional diagram of 0° emission when the reconfigurable intelligent metasurface units of the present invention are arrayed at 40° oblique incidence in the x-axis direction. DETAILED DESCRIPTION

[0032] The present invention will be further explained below in conjunction with the accompanying drawings.

[0033] A dual-polarization 3-bit phase-independently adjustable reconfigurable smart metasurface unit that is insensitive to the incident angle is used to achieve independent control of electromagnetic waves under orthogonal polarization incident waves. Figure 1 and Figure 2 The unit resonant structure shown in FIG. The unit includes four layers of functional structures, namely the first layer, the second layer, the third layer and the fourth layer, and dielectric layers are provided between each layer. The upper surface of the unit is the first layer, and the lower surface of the unit is the fourth layer. The upper surface and the lower surface of the unit are both square, and the side lengths are equal, which is the unit side length p.

[0034] like Figure 3 As shown, the first layer includes a square metal patch with a side length of l1 and a square ring metal patch with an outer side length of l2 and a width of w2. The square metal patch is located in the center of the first layer and inside the square ring metal patch. The square metal patch coincides with the diagonal of the square ring metal patch. The first layer also includes four rectangular metal patches with a width of w1. Each side of the square ring metal patch vertically crosses with a rectangular metal patch to form a cross structure. Along the diagonal, a gap with a width of g2 is used to separate the square metal patch and the square ring metal patch. The square metal patch is divided into four isosceles right triangle metal patches along the diagonal, and the square metal patch is divided into four cross metal patches along the diagonal. The distance between each isosceles right triangle metal patch and the nearest cross metal patch is g1, and they are connected by a varactor. A total of four varactor tubes are required.

[0035] like Figure 1 , Figure 2 As shown, a square ring-shaped metal strip is attached to the periphery of the first layer as a grounding wire, and the outer side length of the square ring-shaped metal strip is p and the width is t; each side of the square ring-shaped metal strip is directly connected to one side of the rectangular metal patch in the cross-shaped metal patch.

[0036] Taking the first layer as a reference, a rectangular coordinate system is set, with one side of the square metal patch as the x-axis direction, and the other side of the square metal patch perpendicular to the x-axis as the y-axis direction.

[0037] like Figure 4 As shown, the second layer is a first square metal feed layer, the side of the first square metal feed layer is parallel to the corresponding side of the square ring metal strip, and the side length is l3. At the edge of the first square metal feed layer, a first metal strip with a length of l4 and a width of w3 is respectively arranged in the positive and negative directions of the y-axis, for connecting the square metal feed layer. In the middle of the first square metal feed layer, there are two circular holes with a radius of r1 on the positive and negative semi-axes of the y-axis.

[0038] like Figure 5As shown, the third layer is the second square metal feed layer, the side of the second square metal feed layer is parallel to the corresponding side of the square ring metal strip, and the side length is l3; the side length of the second square metal feed layer is equal to that of the first square metal feed layer. At the edge of the second square metal feed layer, a third metal strip with a length of l4 and a width of w3 and a fourth metal strip are respectively arranged in the positive and negative directions of the x-axis to connect the square metal feed layer. In the middle of the first square metal feed layer, there are two circular holes with a radius of r1 on the positive and negative semi-axes of the x-axis.

[0039] like Figure 6 As shown, the fourth layer is a square metal ground, the side of which is parallel to the corresponding side of the square ring metal strip, and the side length is p. There are four circular holes with a radius of r1 in the middle of the square metal ground on the positive and negative semi-axes of the x and y axes respectively.

[0040] The first dielectric layer between the first layer and the second layer has a thickness of h1 and a relative dielectric constant of ε r =2.65, loss tangent tanδ = 0.001 polytetrafluoroethylene F4B. The second dielectric layer between the second and third layers is made of a thickness of h2 and a relative dielectric constant of ε r =3.7, loss tangent tanδ = 0.004 Rogers RO4450 prepreg. The third dielectric layer between the third and fourth layers has a thickness of h3 and a relative dielectric constant of ε r =2.65, loss tangent tanδ=0.001 polytetrafluoroethylene F4B.

[0041] In the x-axis and y-axis directions of the first layer, four isosceles right-angled triangle metal patches are respectively connected to a metal via with a radius of r2. The metal via is perpendicular to the plane of the first layer and passes through the second, third and fourth layers. Among them, two metal vias in the x-axis direction are connected to the first square metal feed layer of the second layer, and two metal vias in the x-axis direction pass through the two circular holes of the second square metal feed layer of the third layer and are not connected thereto; two metal vias in the y-axis direction are connected to the second square metal feed layer of the third layer, and two metal vias in the y-axis direction pass through the two circular holes of the first square metal feed layer of the second layer and are not connected thereto; four metal vias pass through the four circular holes of the square metal ground of the fourth layer and are not connected thereto.

[0042] In the above unit structure, the feeding voltage of the varactor in the x-axis and y-axis directions is adjusted respectively by the first and second metal strips and the third and fourth metal strips, so that the capacitance of the varactor changes continuously and the resonant frequency in the x-axis and y-axis directions is independently regulated.

[0043] In this embodiment, the varactor model is SMV1405; when a voltage of 11V is applied to both sides of the varactor, its equivalent RLC model is a series connection of a 0.36Ω resistor, a 0.7nH inductor, and a 0.76pF capacitor, and the dual-polarization independent adjustable unit realizes decoupling between polarizations, and the unit independently performs phase regulation in two polarization directions. When the capacitance of the varactor changes continuously, the dual-polarization unit has 8 phase encoding states with a phase interval of about 45°, thereby realizing 3-bit encoding.

[0044] The double-layer feeding structure of the second and third layers is respectively used for varactor feeding in the polarization directions of the x-axis and y-axis; wherein, the first square metal feeding layer of the second layer is connected in the y-axis direction by the first metal strip and the second metal strip, the metal strip is equivalent to an inductor, and the alternating current is separated and the direct current is passed. Since the first square metal feeding layer is also connected to two metal vias in the x-axis direction, the RIS unit is controlled in the y-axis direction to form a phase gradient in the x-axis direction to achieve beam scanning in the x-axis direction; the second square metal feeding layer of the third layer is connected in the x-axis direction by the third metal strip and the fourth metal strip, the metal strip is equivalent to an inductor, and the alternating current is separated and the direct current is passed. Since the second square metal feeding layer is also connected to two metal vias in the y-axis direction, the RIS unit is controlled in the x-axis direction to form a phase gradient in the y-axis direction to achieve beam scanning in the y-axis direction. The amplitude of the RIS unit only changes in size when the incident wave is oblique, and no frequency deviation is generated. Therefore, the phase difference is also small, which improves the angular stability of the RIS unit under oblique incidence of TE and TM polarizations.

[0045] Figures 1 to 6 In the present invention, the structural parameters of a dual-polarization 3-bit phase-independently adjustable reconfigurable intelligent metasurface unit that is insensitive to the incident angle are determined by Table 1.

[0046] Table 1

[0047]

[0048] By adjusting the feeding voltage of the varactor in the x-axis and y-axis directions, the capacitance of the varactor changes continuously, and the resonant frequency of the equivalent resonant cavity in the x-axis and y-axis directions is independently regulated. The equivalent reactance of the reconfigurable intelligent metasurface unit of the present invention, which is insensitive to the incident angle and has a dual-polarization 3-bit phase independently adjustable, is determined by the characteristics of the varactor, which requires the selection of a suitable varactor to meet the design requirements. After selection, the varactor SMV1405 produced by Skyworks was decided to be used because it has the advantages of high Q value, low series resistance, and low phase noise. When a reverse bias of 0 to 30V is applied to both ends of it, its parasitic inductance and resistance are stabilized at 0.7nH and 0.36Ω, and the capacitance value changes from 1.74pF to 0.58pF.

[0049] The main technical difficulty of the dual-polarization 3-bit phase-independent adjustable RIS unit is the decoupling between polarizations, that is, when the first and second varactors in the x-polarization direction change their states, the reflected wave amplitude phase in the y-polarization direction is not affected, and vice versa. To further illustrate this point, a full-wave simulation of its single-polarization operating mode is performed in the electromagnetic simulation software CST. When a voltage of 11v is applied to both sides of the varactor, its equivalent RLC model is a series connection of a 0.36Ω resistor, a 0.7nH inductor, and a 0.76pF capacitor. By analyzing the surface current diagram, as shown in FIG. Figure 7 , 8 It can be seen that when the electric field is polarized along the x-axis, the surface current is mainly distributed on the copper sheets on both sides of the varactor in the x-axis direction, while there is almost no surface current on both sides of the varactor in the y-axis direction. Similar conclusions can be drawn when the electric field is polarized along the y-axis. This shows that the varactor is decoupled in the two polarization directions, and the electromagnetic wave on one polarization has no effect on the varactor on the other polarization, which is reflected in the cross polarization, such as Fig. 9 This is a cross-polarization amplitude diagram of a reconfigurable intelligent metasurface unit with dual-polarization 3-bit phase that is independently adjustable and insensitive to the incident angle of the present invention. It can be seen from the figure that the cross-polarization is less than -30dB, which enables the unit to independently perform phase control on two polarizations.

[0050] In order to study the specific performance of a dual-polarization 3-bit phase-independently adjustable reconfigurable intelligent metasurface unit structure that is insensitive to the incident angle of the present invention, the full-wave simulation software CST is used to simulate it. Fig.10 It is a reflection wave amplitude diagram of 8 coding states of a dual-polarization 3-bit phase-independently adjustable reconfigurable intelligent metasurface unit in the present invention that is insensitive to the incident angle under x-axis and y-axis polarization. Fig.11 It is a reflection wave phase diagram of 8 coding states of a dual-polarization 3-bit phase-independently adjustable reconfigurable intelligent metasurface unit under x-axis and y-axis polarization respectively. Fig.10 , Fig.11 It can be seen that at 2.55GHz, the reflected wave amplitudes and phases under the two polarizations are consistent, the amplitudes of each state are greater than -3dB, and the maximum adjustable phase range also meets the 315° required for 3-bit phase encoding. In addition, since the capacitance of the varactor changes continuously, it is easy to find 8 phase encoding states with a phase interval of about 45°. The equivalent capacitance parameters of the varactor are shown in Table 2.

[0051] Table 2

[0052] state Equivalent Capacitance x-polarization reflection phase y-polarization reflection phase 0 1.740pF -184° -184° 1 0.850pF -139° -139° 2 0.798pF -95° -96° 3 0.774pF -49° -52° 4 0.756pF -2° -7° 5 0.737pF 44° 40° 6 0.716pF 87° 84° 7 0.636pF 132° 131°

[0053] Take state 4 as an example. Fig.12This is a reflection wave amplitude diagram of state 4 of a dual-polarization 3-bit phase-independently adjustable reconfigurable intelligent metasurface unit under oblique incidence of the present invention. Fig.13 It is a reflection wave phase diagram of state 4 of a reconfigurable intelligent metasurface unit under oblique incidence and with a dual-polarization 3-bit phase that is insensitive to the incident angle. Fig.12 , Fig.13 The reflection amplitude and phase are shown when the TE and TM waves are incident at an angle of 45°. Furthermore, in order to verify the insensitivity to the incident angle and the particularity of the varactor capacitance, a more detailed simulation of the reflected wave amplitude and phase of the unit at 2.55GHz in 8 phase coding states with TE and TM oblique incidence was performed at intervals of 22.5°. The results are shown in Table 2. It can be seen that at 2.55GHz, the amplitude of the reflected wave under 45° oblique incidence in each coding state is greater than -3dB, and the phase deviation compared with the normal incidence is basically within the maximum quantization error, i.e., 22.5°, which meets the error range required by 3-bit phase modulation.

[0054] Table 3

[0055]

[0056]

[0057] The unit of the present invention is used to design a 3-bit dual-beam RIS composed of 30*30 units that can independently perform beam scanning on two orthogonal polarizations. At 2.55GHz, its side length is 399mm, about 3.4λ0, where λ0 is the wavelength of the electromagnetic wave in free space at 2.55GHz. The phase encoding at reflection angles of 0°, 10°, 20°, 30°, and 40° under normal incidence is calculated and simulated. Fig.14 It is the beam scanning result in the x-axis direction of a reconfigurable intelligent metasurface unit array that is insensitive to the incident angle and has dual-polarization 3-bit phase independently adjustable. Fig.15 It is the beam scanning result in the y-axis direction of a reconfigurable intelligent metasurface unit array that is insensitive to the incident angle and has a dual-polarization 3-bit phase that is independently adjustable. Fig.14 , Fig.15 The operating frequency is 2.55GHz. The deviation between the beam pointing and the theoretical value is basically within 1.5°. In order to verify the angular stability of RIS under oblique incidence, the incident wave is irradiated on RIS at an incident angle of 40°, and its phase encoding is still the phase encoding of 0° incidence and 40° emission. Fig.16 This is a dual-polarization 3-bit phase-independently adjustable reconfigurable intelligent metasurface unit array that is insensitive to the incident angle and emits at 0° when the incident angle is 40° in the x-axis direction. Fig.16It can be seen that the reflected wave is vertically emitted, which proves that the RIS still maintains the same phase gradient at oblique incidence as at normal incidence, that is, RIS is insensitive to the incident angle.

[0058] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. Dual-polarization 3-bit phase-independently adjustable reconfigurable smart metasurface unit, characterized by: The unit includes a four-layer functional structure, wherein the second and third layers are feed layers, and the fourth layer is a metal ground; the upper surface of the unit is the first layer, and the lower surface of the unit is the fourth layer, the upper surface and the lower surface of the unit are both squares, and the side lengths are equal, that is, the unit side length; the first layer includes four isosceles right-angled triangle metal patches and four cross-shaped metal patches, and each isosceles right-angled triangle is connected to a corresponding cross-shaped metal patch through a varactor; the four isosceles right-angled triangle metal patches are respectively connected to a metal via, the two metal vias in the x-axis direction are connected to the second-layer feed layer, and the two metal vias in the y-axis direction are connected to the third-layer feed layer; by adjusting the voltages at both ends of the varactor in two orthogonal polarization directions, the unit independently realizes 3-bit phase modulation within the oblique incidence range of 0 to 45° in the two orthogonal polarization directions; The first layer includes a square metal patch and a square ring metal patch, the square metal patch is located at the center of the first layer and inside the square ring metal patch, and the diagonal of the square metal patch coincides with the diagonal of the square ring metal patch; the first layer also includes four rectangular metal patches, each side of the square ring metal patch vertically crosses with a rectangular metal patch to form a cross structure; along the diagonal, the square metal patch and the square ring metal patch are separated by a gap, the square metal patch is divided along the diagonal to form the four isosceles right triangle metal patches, and the square metal patch is divided along the diagonal to form the four cross metal patches; each isosceles right triangle metal patch is connected to the nearest cross metal patch by a varactor; A square ring-shaped metal strip is attached to the periphery of the first layer as a grounding wire, and the side length of the square ring-shaped metal strip is the side length of the unit; each side of the square ring-shaped metal strip is directly connected to one side of the rectangular metal patch in the cross-shaped metal patch; Taking the first layer as a reference, a rectangular coordinate system is set, one side of the square metal patch is taken as the x-axis direction, and the other side of the square metal patch perpendicular to the x-axis is taken as the y-axis direction; the second layer is the first square metal feeding layer, the side of the first square metal feeding layer is parallel to the corresponding side of the square ring-shaped metal strip, and the side length is less than the side length of the square ring-shaped metal strip; at the edge of the first square metal feeding layer, a first metal strip and a second metal strip are respectively arranged in the positive and negative directions of the y-axis for connecting the square ring-shaped metal strip; the third layer is the second square metal feeding layer, the side of the second square metal feeding layer is parallel to the corresponding side of the square ring-shaped metal strip, and the side length is less than the side length of the square ring-shaped metal strip; the side lengths of the second square metal feeding layer and the first square metal feeding layer are equal; at the edge of the second square metal feeding layer, a third metal strip and a fourth metal strip are respectively arranged in the positive and negative directions of the x-axis for connecting the square ring-shaped metal strip; The fourth layer is a square metal ground, the sides of which are parallel to the corresponding sides of the square ring-shaped metal strip, and the side length is equal to the unit side length, that is, each side of the square metal ground is directly connected to the square ring-shaped metal strip; In the x-axis and y-axis directions of the first layer, four isosceles right-angled triangle metal patches are respectively connected to a metal via, the metal vias are perpendicular to the plane of the first layer, and pass through the second, third and fourth layers; among them, two metal vias in the x-axis direction are connected to the first square metal feed layer of the second layer, and the two metal vias in the x-axis direction are not connected to the second square metal feed layer of the third layer; two metal vias in the y-axis direction are connected to the second square metal feed layer of the third layer, and the two metal vias in the y-axis direction are not connected to the first square metal feed layer of the second layer; the four metal vias are not connected to the square metal ground of the fourth layer.

2. The dual-polarization 3-bit phase-independently adjustable reconfigurable smart metasurface unit according to claim 1 is characterized in that: The relative dielectric constant of the first dielectric layer between the first layer and the second layer is ε r =2.65, using polytetrafluoroethylene F4B with loss tangent tanδ=0.001; the relative dielectric constant of the second dielectric layer between the second and third layers is ε r =3.7, using Rogers RO4450 prepreg with loss tangent tanδ=0.004; the relative dielectric constant of the third dielectric layer between the third and fourth layers is ε r =2.65, and polytetrafluoroethylene F4B with loss tangent tanδ=0.001 is used.

3. The dual-polarization 3-bit phase-independently adjustable reconfigurable smart metasurface unit according to claim 2 is characterized in that: The varactor model is SMV1405; when a voltage of 11V is applied to both sides of the varactor, its equivalent RLC model is a series connection of a 0.36Ω resistor, a 0.7nH inductor, and a 0.76pF capacitor.

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