Low-loss transmissive metasurface based on varactor modulation

Abstract

This invention discloses a low-loss transmissive smart metasurface based on varactor diode modulation, relating to the field of wireless communication networks, and particularly to devices and access point devices specifically designed for wireless communication networks. The invention includes: designing a low-loss transmissive smart metasurface unit based on varactor diode modulation using the Huygens surface as a design principle; achieving low-loss phase modulation in the x-axis polarization direction by controlling the voltage values ​​across the varactor diode; optimizing its geometric parameters using electromagnetic simulation software and outputting the transmissive electromagnetic response of the design model; and designing the overall smart metasurface panel based on the designed unit model, including a main panel composed of multiple low-loss transmissive smart metasurface units based on varactor diode modulation, and a control panel connecting external power supply equipment and the main panel.

Description

Technical Field

[0001] This invention relates to the field of wireless communication networks, and particularly to a prototype design of a novel low-loss transmissive smart metasurface based on varactor diode modulation, specifically designed for wireless communication networks and access point devices. Background Technology

[0002] With the explosive growth of emerging applications such as holographic video and the metaverse, 6G is expected to achieve 10 times the spectral efficiency of 5G. Key performance indicators, including data rate, reliability, latency, spectral / energy efficiency, and connection density, will outperform 5G. For example, 6G's energy efficiency and spectral efficiency are projected to be 10-100 times and 5 times that of 5G, respectively. However, existing 5G physical layer technologies, including massive MIMO, millimeter-wave (mmWave) communication, and ultra-dense heterogeneous networks, cannot fully achieve these metrics. In particular, massive MIMO requires a large number of antennas and active RF chains to achieve high spectral efficiency, leading to high energy consumption and high hardware costs. Furthermore, moving to the millimeter-wave band makes electromagnetic waves more susceptible to obstruction by obstacles such as furniture and walls in indoor environments.

[0003] Therefore, significant performance improvements are expected when new technologies are adopted to optimize for uncontrolled reflections, refractions, and accidental interference in the wireless environment as an additional variable. Reconfigurable Smart Surfaces (RIS) have become an essential candidate technology. RIS can reconfigure the wireless propagation environment into a transmission medium with more desirable characteristics. To achieve this, dynamic beamforming is realized by adjusting the phase and amplitude response of the incident electromagnetic waves, thereby improving spectral efficiency and overcoming congestion.

[0004] However, existing research primarily considers the use of reflective RIS, which can lead to coverage blind spots within the communication cell. Specifically, for reflective RIS, the base station and the user need to be located on the same side of the RIS, which imposes additional geographical constraints on the physical topology. For example, reflective RIS struggles to facilitate communication between an external transmitter and an internal receiver in a vehicle. To address this issue, transmissive RIS, hereinafter referred to as Transmissive Smart Metasurface (ITS), has recently been proposed, where signals can be transmitted through the RIS to form directional beams. Thus, ITS has the potential to fill the coverage gaps of reflective RIS.

[0005] Phase reconfigurability is the most fundamental performance characteristic of ITS (Integrated Switching Components). Therefore, solid-state electronic devices such as PIN diodes and varactor diodes are typically integrated into each ITS element to dynamically control its phase response. However, ITS based on the traditional frequency-selective surface mount principle suffers from very high insertion loss, thus significantly reducing the aperture efficiency of the ITS. Furthermore, most existing designs focus on ITS with 1-bit phase reconfigurability based on PIN diodes, where the design and manufacturing difficulties are manageable. Therefore, the design and fabrication of multi-bit phase reconfigurable ITS based on varactor diodes urgently requires further research.

[0006] To address the inherently high insertion loss, Huygens' principle is applied to the design of transmissive metasurfaces. The number of layers in the transmissive metasurface is reduced by simultaneously designing and juxtaposing currents and magnetic currents on the surface. Huygens' metasurfaces are characterized by near-perfect transmission characteristics; therefore, non-reconfigurable Huygens metasurfaces can achieve beam bending and splitting, Airy beam generation, broadband wave manipulation, parametric wave control, and more. Thus, the concept of Huygens' metasurfaces can be incorporated into the design of ITS hardware. Summary of the Invention

[0007] The purpose of this invention is to provide a low-loss transmissive smart metasurface based on varactor diode modulation, which can achieve low-loss phase modulation function in the x-axis polarization direction by controlling the voltage values ​​on both sides of the varactor diode.

[0008] To achieve the above objectives, the present invention provides the following solution:

[0009] A low-loss transmissive smart metasurface based on varactor diode modulation includes a main panel composed of multiple low-loss transmissive smart metasurface units based on varactor diode modulation, and a control panel connecting an external power supply device and the main panel.

[0010] The low-loss transmissive smart metasurface unit based on varactor diode modulation has a five-layer structure.

[0011] The first layer of the intelligent metasurface unit in this invention is a metal layer. The metal patch portion includes two M-shaped copper metal patches with opposite directions. The two patches are connected by a varactor diode. Taking the center of the first layer as the origin, the connection direction of the varactor diode is set as the x-axis of the rectangular coordinate system, and the connection direction perpendicular to the y-axis is taken as the y-axis. The following description follows this principle.

[0012] The fifth layer of the intelligent metasurface unit in this invention is a metal layer, which has the same structural parameters as the first metal layer and is axially symmetric with it along the y-axis.

[0013] In this invention, the varactor diode of the intelligent metasurface unit is located between two M-shaped copper metal patches facing opposite directions on the first and fifth metal layers. The capacitance value of the varactor diode is changed by external DC power supply, thereby controlling the degree of electrical and magnetic resonance coupling excited by the transmission metasurface unit and thus controlling the change in the phase of the electromagnetic wave.

[0014] In this invention, the second and fourth layers of the intelligent metasurface unit are dielectric substrate layers with the same thickness and material. The four metal vias in the middle are used to connect the varactor diodes in the first and fifth metal layers to the DC feed line of the third metal layer.

[0015] Optionally, the four metal vias are located on the Cartesian coordinate system and are evenly distributed on the x-axis;

[0016] In this invention, the third layer of the intelligent metasurface unit is a metal layer, which includes a DC feed line for connecting the top-layer diode and the bottom-layer diode. It is designed as a feed line network connecting the varactor diodes loaded in the first metal layer and the fifth metal layer, wherein the side with applied voltage is connected and the other ground terminal is connected, thereby realizing the function of a set of voltage linkage modulation of the capacitance value of the varactor diodes loaded in the first metal layer and the fifth metal layer.

[0017] The transmissive smart metasurface of this invention includes a transmissive metasurface main panel and a power feeding control panel;

[0018] The main panel of the transmissive metasurface consists of 8×8 periodically arranged transmissive metasurface units, with 8 rows of transmissive metasurface units arranged along the x-axis and 8 columns of transmissive metasurface units arranged along the y-axis.

[0019] Among them, the metal patches of the third metal layer of adjacent smart metasurface units on the x-axis are connected by the same DC bias line. The varactor diodes loaded in the entire row of smart metasurface units are fed by a DC voltage source to save on the cost of plate making and reduce the complexity of the control end.

[0020] The power supply control panel consists of 9 DC bias lines and 9 ports, including 8 power supply ports that supply different voltages and 1 grounding port.

[0021] Among them, 8 rows of intelligent metasurface units are connected to 8 DC bias lines, corresponding to 8 power supply ports. 1 DC bias line and 1 DC power supply port are connected to ground. The phase response of the intelligent metasurface units on the main panel can be controlled by DC voltage feeding through an external control system.

[0022] The nine DC power supply ports in this invention consist of nine through metal holes arranged along the y-axis. The design diameter of each through hole and the distance between the through holes are based on the model of the external control terminal connection cable.

[0023] Beneficial effects

[0024] According to specific embodiments provided by the present invention, the present invention achieves the following technical effects:

[0025] This invention provides a low-loss transmissive smart metasurface based on varactor diode modulation, comprising multiple low-loss transmissive smart metasurface units based on varactor diode modulation. Each low-loss transmissive smart metasurface unit based on varactor diode modulation integrates a pair of varactor diodes along the x-axis polarization direction. The transmission phase can be controlled by adjusting the voltage values ​​on both sides of the varactor diodes.

[0026] The low-loss transmission-type intelligent metasurface unit of the present invention can achieve 2-bit control of the transmission phase in the x-axis polarization direction.

[0027] The low-loss transmission-type intelligent metasurface unit of the present invention has a minimum insertion loss of 2.58 dB and an average insertion loss of 0.8 dB within the range of transmission phase modulation in the x-axis polarization direction.

[0028] The low-loss transmissive intelligent metasurface unit of this invention has a center frequency of 11 GHz, a bandwidth of 10.25 GHz to 11.25 GHz, and a total bandwidth of 500 MHz. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the Huygens principle involved in the low-loss transmission intelligent metasurface unit designed in this invention.

[0031] Figure 2 This is a topological schematic diagram of the low-loss transmission-type intelligent metasurface unit designed in this invention;

[0032] Figure 3 This is a schematic diagram of the first metal layer of the low-loss transmission intelligent metasurface unit designed in this invention;

[0033] Figure 4 This is a schematic diagram of the third metal layer of the low-loss transmission intelligent metasurface unit designed in this invention;

[0034] Figure 5 This is a schematic diagram of the fifth metal layer of the low-loss transmission intelligent metasurface unit designed in this invention;

[0035] Figure 6 This is a schematic diagram of the side view of the low-loss transmission intelligent metasurface unit designed in this invention.

[0036] Figure 7 This is a current distribution diagram of the first metal layer of the low-loss transmission intelligent metasurface unit designed in this invention;

[0037] Figure 8 This is a current distribution diagram of the fifth metal layer of the low-loss transmission intelligent metasurface unit designed in this invention;

[0038] Figure 9 This is a trend diagram of the phase variation of the reflection coefficient of the low-loss transmissive smart metasurface designed in this invention as a function of frequency.

[0039] Figure 10 This is a trend graph showing the insertion loss of the low-loss transmissive smart metasurface designed in this invention as a function of frequency.

[0040] Figure 11 This is a schematic diagram of the low-loss transmissive intelligent metasurface panel designed in this invention;

[0041] Figure 12 This is a schematic diagram of a low-loss transmissive smart metasurface illuminated by a feed antenna under x-polarized electromagnetic wave excitation, as designed in this invention.

[0042] Figure 13 Two-dimensional far-field simulation beammap of a low-loss transmissive smart metasurface with different coding sequences under x-polarized electromagnetic wave excitation, designed for this invention. Detailed Implementation

[0043] The technical solutions of the embodiments of the present invention will be clearly and comprehensively described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] The system architecture or scenario in which this invention is applied

[0045] Reconfigurable smart surfaces are considered one of the key technologies for next-generation mobile communication systems. Transmitting RIS (ITS) can achieve dynamic beamforming while transmitting radio frequency signals within its transmission band, and has broad prospects in various practical communication application scenarios, such as vehicle communication and solving the problem of cell blind spots.

[0046] Detailed description of the principle of the transmission-intelligent metasurface of the present invention

[0047] This invention belongs to the field of electromagnetic materials. Electromagnetic metamaterials can control electromagnetic waves at deep subwavelength scales. However, unlike the phase control of traditional devices, the control mechanism of phase-discontinuous artificial electromagnetic surfaces is not the cumulative phase generated during electromagnetic wave propagation, but rather the phase abrupt change introduced by a scatterer on a controllable electromagnetic surface to control the scattered electromagnetic waves. Therefore, the generalized Snell's law is needed to explain the phase abrupt change.

[0048] When a phase abrupt change related to the interface location is introduced into the electromagnetic wave propagation path, the total phase change of the propagation path is:

[0049]

[0050] Where k is the wave number. The propagation path must also satisfy Fermat's principle; therefore, the generalized Snell's law can be derived based on Fermat's principle.

[0051] According to the generalized Snell's law, space electromagnetic waves can be manipulated by designing changes in the phase gradient of the propagation coefficient. This law is stated as follows:

[0052]

[0053] Where θ t and θ i n represents the angles of incidence and reflection, respectively. t and n i These represent the refractive indices of the two media separated by the electromagnetic metasurface. When there is no abrupt phase change, the normal refraction law applies, and the angle of incidence and angle of refraction can only have the same sign, with their magnitudes related to the refractive indices of the media on both sides of the interface. When there is no abrupt phase change, the angle of incidence and angle of refraction can have the same or opposite signs, and the magnitudes of the refractive indices of the media on both sides of the interface do not need to be considered. Only a suitable phase gradient (which can be positive, negative, or zero) is needed to obtain any desired angle of refraction, which is the underlying principle of transmission metasurfaces.

[0054] Furthermore, by introducing Huygens' principle, the design method of Huygens metasurfaces involves controlling the interaction between the virtual current and virtual magnetic current of the metasurface and the incident field, thereby influencing the transmission and reflection fields.

[0055] According to the appendix Figure 1 The electromagnetic space is divided into two regions, region I and region II, with independent field distributions defined. Since the field distribution on a metasurface is typically discontinuous, the boundary conditions of Maxwell's equations must be satisfied:

[0056]

[0057]

[0058] Electromagnetic waves projected near a metasurface can induce currents and magnetic currents on the metasurface; therefore, the electromagnetic characteristics of a Huygens surface can be expressed by its surface admittance. and surface magnetic impedance To describe. and They respectively satisfy:

[0059]

[0060]

[0061] J s and M s This represents the surface-induced current and surface-induced magnetic current obtained from tangential electric and magnetic fields on the surface. The subscript 's' indicates that it is a surface distribution, the subscript 'e' indicates that this term is related to the surface current of the Huygens surface, the subscript 'm' indicates that this term is related to the surface magnetic current of the Huygens surface, and I and II represent two regions; the subscript 't' indicates transmission, the subscript 'r' indicates reflection, and the subscript 'av' indicates that it is the average value. E t,av | S and H t,av | S These represent the average tangential electric field and magnetic field on the surface, respectively.

[0062] Generally, and It is a tensor. When the polarization direction of the electromagnetic wave is aligned with the principal axis of the tensor, the tensor can be simplified to a scalar Y. es and Z ms .

[0063] According to the boundary conditions of Maxwell's equations, Y es and Z ms It can be determined by the coefficients of reflection (R) and transmission (T), that is, using S-parameters to describe surface impedance and surface admittance as follows:

[0064]

[0065]

[0066] wave impedance μ0 and ε0 are the permittivity and permeability in free space. T represents the transmission coefficient and R represents the reflection coefficient, both of which are complex numbers containing amplitude and phase information.

[0067] To illustrate the S-parameter information of reflection and transmission, the above two equations are rewritten as follows:

[0068]

[0069]

[0070] in and

[0071] From the above analysis, it can be seen that if and If they are equal and are purely imaginary numbers, then let... The transmission coefficient T can then be simplified to:

[0072]

[0073] Therefore, when the modulus of the transmission coefficient T is 1, the phase component is -2arctan(α) eff Therefore, for a fully transparent metasurface unit...

[0074] Detailed description of the transmission-intelligent metasurface unit of the present invention

[0075] The topology diagram of the transmission-inspired intelligent metasurface unit designed in this invention is attached. Figure 2 As shown, the top metal layer design drawing, the third metal layer design drawing, the bottom metal layer design drawing, and the side view are attached. Figure 3 , 4 As shown in Figures 5 and 6, the Huygens element consists of antisymmetric M-type modified dipole pairs etched on both sides of an F4B substrate, distributed along the x-axis. For a pair of antisymmetric metal plots, a surface current with a time delay is excited on the surface of the metal layer. Due to the time delay, the upper and lower dipoles sometimes exhibit the same surface current direction and sometimes opposite surface current directions. These correspond to even-mode coupling and odd-mode coupling between the surface currents, exciting electric resonance and magnetic resonance, respectively. Under appropriate conditions, when the impedance matching of the design satisfies electromagnetic resonance, Huygens resonance can be excited.

[0076] To achieve electromagnetic response phase adjustment, this invention modulates the impedance change of dipole pairs by loading varactor diodes, thereby altering the electromagnetic coupling between orthogonal units. This ensures high transmittance while achieving controllable modulation of the transmission phase. A third metal layer feed network is designed, bridging the varactor diodes of the upper and lower metal layers through metal bias lines and vias. A single control voltage can simultaneously control the varactor diodes on both the upper and lower surfaces.

[0077] This invention determines a set of optimal geometric parameter values ​​by adjusting the geometric parameters of the metasurface cell period, the geometric parameters of the M-shaped copper metal patches in the first and fifth metal layers, the geometric parameters of the DC feed line in the third metal layer, and the geometric parameters of the thickness of the two dielectric substrates. This results in the maximum range of phase variation and the minimum insertion loss of the intelligent metasurface cell controlled by the varactor diode.

[0078] The periodic unit cell of the transmission-sensitive smart metasurface designed in this invention has a size of p = 14.5 mm, and the parameters of the two F4B dielectric substrates are a thickness of h = 2.6 mm and a dielectric constant ε. r =2.2, loss coefficient tanδ=0.001. In order to minimize the electromagnetic coupling between orthogonal elements, the parameters w and d should be as small as possible, and the overlap between the electromagnetic fields contributed by the orthogonal elements should be as weak as possible.

[0079] The specific dimensions of the transmission-modulated smart metasurface unit designed in this invention are shown in the table below:

[0080]

[0081] The varactor diode selected in this invention is model MAVR-000020-1411. This diode exhibits a continuous change in equivalent capacitance from 0V to 0.15pF as the voltage varies from 0V to 15V, with equivalent inductance and equivalent resistance of 0.02nH and 0.88Ω, respectively. This continuous capacitance variation characteristic of the varactor diode is the foundation for multi-bit phase modulation achieved by intelligent metasurfaces.

[0082] The odd-mode couplings of the transmission metasurface currents designed in this invention are shown in the appendix. Figure 7 and attached Figure 8 As shown, it can be observed that the top and bottom layers excite strong current distributions in opposite directions, i.e., magnetic resonance is excited, thus it can be regarded as a Huygens element operating in the 11 GHz band.

[0083] This invention utilizes the commercial software Ansys HFSS to perform full-wave simulation of the electromagnetic response of the metasurface unit of this invention. The simulation results of the transmission response are shown in the appendix. Figure 9 and attached Figure 10 As shown. Since the capacitance value of a varactor diode can continuously change with the external voltage, several specific voltage values ​​corresponding to capacitance values ​​can be selected to achieve multi-bit phase encoding.

[0084] The metasurface unit designed in this invention adopts a 2-bit encoded modulation method, which combines the accuracy of beam design with the simplicity of encoding. (See attached diagram) Figure 9As shown, at a center frequency of 11 GHz, selecting capacitance values ​​of 0.15 pF, 0.24 pF, 0.29 pF, and 0.55 pF, the difference between each phase state is approximately 90 degrees, enabling accurate 2-bit phase encoding. Within the frequency range of 10.75 GHz to 11.25 GHz, the phase response of the transmissive metasurface unit of this invention varies with the varactor diode from 0.15 pF to 0.95 pF, with a phase difference greater than 270 degrees, thus enabling 2-bit phase modulation.

[0085] Furthermore, as shown in the appendix Figure 10 As shown, within the phase modulation frequency range of 10.75GHz-11.25GHz, the minimum insertion loss of the transmissive metasurface unit of the present invention is 2.58dB, and the average insertion loss is 0.8dB, which is lower than the loss of the currently designed ITS structure.

[0086] Detailed description of the transmission-sensitive smart metasurface of the present invention

[0087] This invention, after designing the structure of a single transmissive smart metasurface unit and confirming its phase and transmission loss characteristics through full-wave simulation, designs a transmissive smart metasurface panel that can be practically fabricated using printed circuit board technology. The prototype transmissive smart metasurface panel designed in this invention includes a main panel composed of multiple repeating transmissive smart metasurface units and a control panel responsible for connecting the main panel to an external power supply.

[0088] The main panel of the transmissive smart metasurface designed in this invention consists of 8*8=64 metasurface units, of which 8 rows of transmissive metasurface units are arranged along the x-axis and 8 columns of transmissive metasurface units are arranged along the y-axis; the metal patches of the third metal layer of adjacent smart metasurface units on the x-axis are connected by the same DC bias line, and the varactor diodes loaded in the entire row of smart metasurface units are fed by a DC voltage source to save on the cost of board making and reduce the complexity of the control terminal;

[0089] The transmission-controlled intelligent metasurface power supply control panel of this invention consists of 9 DC bias lines and 9 ports. The 9 DC power supply ports include 8 power supply ports with different voltages and 1 grounded port. The 8 rows of intelligent metasurface units are connected to the 8 DC bias lines corresponding to the 8 power supply ports. The 1 DC bias line and the 1 DC power supply port are connected to ground. The phase response of the intelligent metasurface units on the main panel can be controlled by DC voltage supply through an external control system.

[0090] The nine DC power supply ports in this invention consist of nine through-holes arranged along the y-axis. The distance between each through-hole is based on the model of the external control terminal connection cable. The design parameters are a through-hole diameter of 0.64 mm and a distance between through-holes of 2.54 mm, which meets the size requirements of DuPont wires and pins on the market.

[0091] This invention simulates the beam manipulation performance of a designed transmissive smart metasurface panel by setting up simulation conditions where a rectangular aperture horn antenna illuminates a transmissive metasurface panel in a real-world scenario. (See attached diagram) Figure 11 As shown, a feed antenna with a center frequency of 11 GHz is generated using the ADK toolbox in HFSS, and the feed distance is set to 0.1 m perpendicular to the center of the metasurface. The compensation values ​​for the phase of different elements of the transmitting metasurface during beam deflection are calculated according to the generalized Snell's law, and then normalized to 2-bit encoding, corresponding inversely to the capacitance value of the varactor diode. During simulation, a FEBI solver (finite element-integral equation hybrid algorithm solver) needs to be set on both the feed and metasurface sides. Further, the above operations are repeated to simulate beam deflection angles of 15 degrees, 30 degrees, and 45 degrees, as shown in the attached diagram. Figure 12 As shown. The transmissive smart metasurface of the present invention can achieve significant beam deflection.

[0092] Future Prospects of the Invention

[0093] This invention uses specific examples to illustrate its principles and implementation methods. It provides pioneering ideas for future researchers in the prototype design of transmission-enabled smart metasurfaces. The descriptions of the above embodiments are merely to aid in understanding the method and core ideas of this invention; obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A low-loss transmissive smart metasurface based on varactor diode modulation, characterized in that, It includes a main panel for a transmissive metasurface and a power supply control panel for connecting an external DC power supply to the main panel for the transmissive metasurface; The main panel of the transmissive metasurface includes multiple periodically arranged transmissive smart metasurface units; Each of the aforementioned transmissive smart metasurface units is a five-layer structure stacked together, the five-layer structure consisting of a first metal layer, a second dielectric substrate layer, a third metal layer, a fourth dielectric substrate layer, and a fifth metal layer; The first metal layer includes two M-shaped copper metal patches facing opposite directions, and a varactor diode is connected between the two M-shaped copper metal patches facing opposite directions. With the center of the first metal layer as the origin, the connection direction of the varactor diode in the first metal layer is set as the x-axis, and the direction perpendicular to the x-axis is set as the y-axis. The fifth metal layer has the same structural parameters as the first metal layer and is symmetrically distributed along the y-axis with the first metal layer. A varactor diode is also connected between the two M-shaped copper metal patches in opposite directions in the fifth metal layer. The second dielectric substrate layer and the fourth dielectric substrate layer have the same thickness and material. Metal vias are provided in the second dielectric substrate layer and the fourth dielectric substrate layer. The metal vias are used to connect the varactor diodes in the first metal layer and the fifth metal layer to the third metal layer. The third metal layer includes a DC feed network that connects the applied voltage side of the varactor diodes in the first metal layer and the fifth metal layer, and connects the ground side of the varactor diodes in the first metal layer and the fifth metal layer, so that a set of DC control voltages can modulate the capacitance value of the varactor diodes in the first metal layer and the fifth metal layer in a coordinated manner. By changing the capacitance of the varactor diode, the degree of electro-resonance and magnetic-resonance coupling of the transmissive smart metasurface unit is adjusted, thereby performing transmission phase modulation on the incident electromagnetic wave.

2. The low-loss transmissive smart metasurface based on varactor diode modulation according to claim 1, characterized in that, There are four metal through holes, which are located on a rectangular coordinate system and are evenly distributed in the x-axis direction.

3. The low-loss transmissive smart metasurface based on varactor diode modulation according to claim 1, characterized in that, The varactor diodes in the first metal layer and the fifth metal layer are both MAVR-000020-1411 type varactor diodes. When the applied DC voltage changes from 0V to 15V, the equivalent capacitance of the varactor diode changes continuously from 0.95pF to 0.15pF.

4. The low-loss transmissive smart metasurface based on varactor diode modulation according to claim 3, characterized in that, At the center frequency of 11 GHz, when the capacitance value of the varactor diode is selected as 0.15 pF, 0.24 pF, 0.29 pF and 0.55 pF, the transmissive smart metasurface unit forms four transmissive phase states, and the phase difference between adjacent transmissive phase states is approximately 90°, thereby realizing 2-bit transmissive phase encoding.

5. The low-loss transmissive smart metasurface based on varactor diode modulation according to claim 1, characterized in that, The periodic dimension of the transmissive smart metasurface unit is p=14.5mm; both the second dielectric substrate layer and the fourth dielectric substrate layer use F4B dielectric substrates with a dielectric constant of 2.2 and a loss tangent of 0.

001.

6. The low-loss transmissive smart metasurface based on varactor diode modulation according to claim 1, characterized in that, The main panel of the transmissive metasurface is composed of 8×8 periodically arranged transmissive smart metasurface units, of which 8 rows of transmissive smart metasurface units are arranged along the x-axis and 8 columns of transmissive smart metasurface units are arranged along the y-axis; the third metal layer of adjacent transmissive smart metasurface units on the x-axis is connected by the same DC bias line so as to provide linked power to the varactor diodes in the same row of transmissive smart metasurface units through the same DC control voltage.

7. The low-loss transmissive smart metasurface based on varactor diode modulation according to claim 6, characterized in that, The power supply control panel includes 9 DC bias lines and 9 ports. The 9 ports include 8 power supply ports for applying different control voltages and 1 grounding port. The 8 rows of transmissive intelligent metasurface units are connected to the 8 DC bias lines and correspond to the 8 power supply ports, respectively. The other DC bias line is connected to the grounding port.

8. The low-loss transmissive smart metasurface based on varactor diode modulation according to claim 7, characterized in that, The nine ports consist of nine through-holes arranged along the y-axis. The diameter of each through-hole is 0.64 mm, and the distance between adjacent through-holes is 2.54 mm.

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