3-bit multifunctional reconfigurable metasurface

Abstract

The present invention belongs to the field of communication technology, specifically a 3-bit phase reconfigurable metasurface. The metasurface of the present invention includes a two-dimensional array composed of metasurface units and a DC bias network composed of bias lines of each metasurface unit; the unit is composed of three metal layers and two dielectric layers, the top layer is used to receive and radiate electromagnetic waves, the middle layer serves as a ground layer, and the bottom layer serves as a phase shifter to realize the 3-bit reconfigurable function; the phase shifter is divided into three parts, which respectively realize 45°, 90°, and 180° phase shift functions, and 8 phase states are realized by combining the three parts; the three parts are respectively controlled by a DC bias line, and the DC bias line of each unit constitutes a bias network, and the independent regulation of each unit is realized by loading the DC control voltage from an external field FPGA to the phase shifter. By changing the phase array coding of the metasurface, the invisible cloak and RCS reduction functions can be realized. This metasurface has the characteristics of high precision, low loss and multi-function.

Description

Technical Field

[0001] The present invention belongs to the field of communication technology, and in particular relates to a 3-bit phase reconfigurable metasurface. Background Art

[0002] Reconfigurable reflective metasurfaces are ultra-thin surfaces composed of a large number of adjustable elements, and have attracted widespread attention due to their ability to dynamically manipulate electromagnetic waves. Compared with traditional metasurfaces with simple designs but fixed functions, reconfigurable reflective metasurfaces can achieve different functions through real-time dynamic control. Continuous phase response reconfigurable metasurfaces are usually complex in design and difficult to provide precise phase accuracy. Therefore, current research focuses on discrete phase response reconfigurable metasurfaces, which only utilize a limited number of phase states while maintaining performance requirements. Specifically, n-bit phase quantization represents 2 n Available quantization phases. Among them, 1-bit reconfigurable metasurfaces have the most research results due to their low design complexity and high quantization accuracy. However, 1-bit reconfigurable metasurfaces often suffer from large quantization errors, making them difficult to adjust with high flexibility. 2-bit reconfigurable metasurfaces have attracted attention due to their neutral balance between design complexity and quantization error.

[0003] Currently, research on 3-bit coded metasurfaces is relatively scarce. This is because the design complexity and processing cost of 3-bit coded metasurfaces are significantly higher than those of 1-bit and 2-bit coded metasurfaces. However, 3-bit metasurfaces have smaller phase quantization errors and more precise control of electromagnetic waves, which are advantages that 1-bit and 2-bit coded metasurfaces do not have. Summary of the Invention

[0004] The purpose of the present invention is to provide a phase-reconfigurable metasurface with a 3-bit working frequency band, high control accuracy, low energy loss, and diverse functions, so as to meet the needs of more application scenarios.

[0005] The present invention provides a 3-bit phase reconfigurable metasurface, comprising a two-dimensional array (preferably an 8×8 two-dimensional array) composed of 3-bit reconfigurable metasurface units, and a DC bias network composed of bias lines of each metasurface unit, the structure of which is as follows: Figure 1 As shown. The metasurface unit is composed of three metal layers and two dielectric layers; the top metal layer (metal patch) is used to receive and radiate electromagnetic waves, the middle metal layer is used as the intermediate layer, and the bottom metal layer is used as a phase shifter to achieve 3-bit reconfigurable function; the two dielectric layers are respectively between the top metal layer and the middle metal layer, and between the middle metal layer and the bottom metal layer. Figure 2As shown, the phase shifter is divided into three parts, achieving 45°, 90°, and 180° phase shifts, respectively. Both the 45° and 90° phase shifters are designed based on a loaded-line phase shifter. The phase shifter consists of a transmission line with two vertical stubs and a horizontal branch with two rectangular patches at each end. Two PIN diodes connect the vertical stubs and the horizontal branch. The 180° phase shifter's design mechanism ensures a 180° phase difference when the transmission line is short-circuited or open-circuited. A fan-shaped capacitor simulates the short-circuit condition, and a PIN diode connects the fan-shaped patch to the transmission line. The operating state of the phase shifter is controlled by the PIN diode. When the diode is conducting, the phase shifter operates; when the diode is off, the phase shifter does not operate. The three parts work together to achieve eight phase states. Each of the three parts is controlled by a DC bias line. The DC bias lines of each metasurface unit together form a bias network. Independent control of each metasurface unit is achieved by applying a DC control voltage from an external FPGA to the phase shifter's PIN diode.

[0006] An RLC filter is added to each bias circuit to block radio frequency (RF) signals and allow direct current (DC) signals to pass.

[0007] In the present invention, the phase shifting function of the metasurface unit is controlled by two loaded linear phase shifters and a fan-shaped capacitor; the two loaded linear phase shifters respectively implement 45° and 90° phase shifting functions, and the fan-shaped capacitor implements a 180° phase shifting function. Specifically, a forward bias voltage is simultaneously applied to the two PIN diodes on the 45° phase shifter via a DC bias line, causing the diodes to simultaneously conduct, and the 45° phase shifter to operate. At this time, the phase of the reflected wave is delayed by 45°. A reverse voltage is simultaneously applied to the two PIN diodes, causing the diodes to simultaneously cut off, and the 45° phase shifter to not operate. At this time, the reflected wave has no phase delay. Similarly, a forward bias voltage is simultaneously applied to the two PIN diodes on the 90° phase shifter, causing the diodes to simultaneously conduct, and the 90° phase shifter to operate. At this time, the phase of the reflected wave is delayed by 90°. A reverse voltage is simultaneously applied to the two diodes, causing the diodes to simultaneously cut off, and the 90° phase shifter to not operate. At this time, the reflected wave has no phase delay. When a forward bias voltage is applied to the PIN diode on the 180° phase shifter, the diode is turned on, and the transmission line is equivalent to a short circuit. When a reverse voltage is applied, the diode is cut off, and the transmission line is disconnected. The phase difference between the short-circuit and disconnected states of the transmission line is 180°.

[0008] In the present invention, the side length of the metasurface unit is 14.5 mm-16 mm, the thickness of the upper dielectric layer is 2.5 mm-3 mm, and the thickness of the lower dielectric layer is 0.5 mm-1 mm; the side length of the top metal patch is 8 mm-9 mm; the length of the intermediate transmission line of the bottom phase shifter is 8.4 mm-9 mm, and the width is 1 mm-1.5 mm; the two vertical branches of the 45° phase shifter are 1 mm-1.5 mm long and 0.1 mm-0.3 mm wide; the length of the horizontal branch is 8 mm-9 mm and the width is 0.2 mm-0.5 mm; the side length of the two square patches is 3.2 mm-4 mm; the two vertical branches of the 90° phase shifter are 2 mm-3 mm long and 0.1 mm-0.3 mm wide; the length of the horizontal branch is 8 mm-9 mm and the width is 0.2 mm-0.5 mm; the side length of the two square patches is 2 mm-2.5 mm; the radius of the fan-shaped patch of the 180° phase shifter is 2.2 mm-2.8 mm; the radius of the metal through-hole connecting the top metal patch and the bottom phase shifter is 0.4 mm-0.5 mm, and the height is 3 mm-4 mm; a circular hole with a radius of 0.6 mm-0.7 mm is opened at the through-hole position on the middle layer to avoid short circuit; the radius of the through-hole connecting the top metal patch and the middle layer is 0.15 mm-0.2 mm, and the height is 3 mm-4 mm; the radius of the through-hole connecting the bias line and the middle layer is 0.15 mm-0.2 mm, and the height is 0.5 mm-1 mm.

[0009] The 3-bit phase reconfigurable metasurface designed by the present invention can y Polarized incident waves can freely switch between eight phase states, with a phase difference of 45° between adjacent phase states. By encoding the metasurface array and assigning corresponding DC control voltages to the metasurface according to the encoding matrix, the incident electromagnetic wave can be regulated and reflected. The metasurface has the characteristics of high precision, low loss, and multifunctionality. The control functions that can be realized include stealth cloaking and radar cross section (RCS) reduction.

[0010] Specifically, if the metasurface coding matrix is ​​not given, the metasurface is similar to a strong reflective surface. When a plane wave is irradiated perpendicular to the horizontal plane, if the angle between the strong reflective surface and the horizontal plane is θ When, according to Snell's law, the angle between the reflected wave and the incident wave is 2 θ.This is mainly caused by the phase change caused by the optical path difference of the wave. The metasurface can introduce a phase gradient for adjacent units to compensate for the phase difference by designing a coding matrix, so that the reflected wave is reflected perpendicular to the horizontal plane. The present invention can introduce 45°, 90°, 135°, 180°, 225°, 270°, and 315° phase gradients for adjacent units to achieve the invisible cloak function with an inclination angle of 10°, 15°, 25°, 30°, 35°, and 50°. In addition, by designing a random coding matrix for the metasurface, electromagnetic waves can be diffusely reflected on the metasurface, thereby greatly reducing the reflected RCS.

[0011] Literature search results show that there has not yet been any metasurface using this 3-bit phase-shifting structure between 9 GHz and 10.5 GHz, and no results have been achieved using this metasurface to achieve invisible cloaking or RCS reduction functions. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a top view of the overall structure of the 3-bit multifunctional reconfigurable metasurface working in the X-band of the present invention.

[0013] Figure 2 This is an exploded schematic diagram of the 3-bit multifunctional reconfigurable metasurface unit of the present invention and a 3-bit phase-shifting structure diagram.

[0014] Figure 3 These are the amplitude simulation diagram and phase simulation diagram of the 3-bit multifunctional reconfigurable metasurface unit of the present invention.

[0015] Figure 4 This is a functional simulation diagram of the 3-bit multifunctional reconfigurable metasurface stealth cloak of the present invention.

[0016] Figure 5 This is a simulation diagram of the RCS reduction function of the 3-bit multifunctional reconfigurable metasurface of the present invention.

[0017] The numbers in the figure are: 1 is a two-dimensional array composed of 3-bit reconfigurable metasurface units, 2 is a phase-shifting array at the bottom of the metasurface, 3 is a DC bias network composed of bias lines, 4 is a port connected to the FPGA, 5 is the top metal patch of the metasurface unit, 7 is the middle metal layer, 9 is a metal through-hole for transmitting signals, 6 and 8 are dielectric layers, 10 is a grounding through-hole, 11 is a circular hole to avoid short circuit, 12 is a through-hole connecting the bias line and the middle ground layer, 13 is a diagram of the phase shifter structure, 14 is a transmission line with two vertical branches, 15 is a horizontal branch, 16 is a rectangular patch; 17 is two PIN diodes between the vertical branches and the horizontal branch, 18 is a fan-shaped capacitor, 19 is a PIN diode between the fan-shaped patch and the transmission line, and 20 is an RLC filter on each bias circuit. DETAILED DESCRIPTION

[0018] The present invention will be further described below with reference to the accompanying drawings and examples. This example provides a detailed implementation method and a specific operating process, but the protection scope of the present invention is not limited to the following examples.

[0019] like Figure 1 As shown, the present invention provides a 3-bit multifunctional reconfigurable metasurface working in the X-band, with an operating frequency band of 9 GHz to 10.5 GHz and an overall size of 150×124×3.7 mm. 3 (length × width × height), this embodiment includes: an 8×8 two-dimensional array composed of 3-bit reconfigurable metasurface units and a 3-bit reconfigurable metasurface composed of a DC bias network composed of bias lines of each metasurface unit.

[0020] like Figure 2 As shown, the metasurface unit described in this embodiment consists of three metal layers and two dielectric layers. The top metal patch 5 is used to receive and radiate electromagnetic waves, the middle metal layer 7 serves as the intermediate layer, and the bottom metal layer serves as a phase shifter 13, achieving 3-bit reconfigurable functionality. The phase shifter is divided into three parts, respectively implementing 45°, 90°, and 180° phase shifting functions. The 45° and 90° phase shifters are both designed based on loaded line phase shifters. The phase shifter consists of a transmission line 14 with two vertical stubs and a horizontal branch 15 with two rectangular patches 16 at each end. Two PIN diodes 17 connect the vertical stubs and the horizontal branch. The 180° phase shifter is designed to achieve a 180° phase difference when the transmission line is short-circuited and open-circuited. A fan-shaped capacitor 18 simulates a short-circuit state, and a PIN diode 19 connects the fan-shaped patch to the transmission line. The operating state of the phase shifter is controlled by the PIN diode. When the diode is on, the phase shifter operates; when the diode is off, the phase shifter does not operate. Eight phase states are achieved through the combined operation of three components. Each component is controlled by a DC bias line. Together, the DC bias lines of each unit form a bias network. Independent control of each unit is achieved by applying a DC control voltage from an external FPGA to the phase shifter's PIN diode.

[0021] In this embodiment:

[0022] The side length of the metasurface unit is 15 mm, the thickness of the upper medium 6 is 3 mm, and the thickness of the lower medium 8 is 0.5 mm.

[0023] The side length of the top metal patch 5 is 8.5 mm. The middle transmission line of the bottom phase shifter 13 is 8.7 mm long and 1.2 mm wide.

[0024] The two vertical branches 14 of the 45° phase shifter are 1 mm long and 0.1 mm wide; the horizontal branch 15 is 8 mm long and 0.2 mm wide; and the two square patches 16 have a side length of 3.6 mm.

[0025] The two vertical branches 14 of the 90° phase shifter are 2 mm long and 0.1 mm wide; the horizontal branch 15 is 8 mm long and 0.2 mm wide; and the side length 16 of the two square patches is 2.4 mm.

[0026] The radius of the sector-shaped patch 18 of the 180° phase shifter is 2.4 mm.

[0027] A metal connection through hole 9 is opened between the top metal patch 5 and the bottom phase shifter 13, with a radius of 0.45 mm and a height of 3.5 mm;

[0028] A circular hole 11 is opened at the through hole position on the middle stratum to prevent short circuit, and the radius of the circular hole 11 is 0.65 mm;

[0029] A connecting through hole 10 is opened between the top metal patch and the middle ground layer, with a radius of 0.2 mm and a height of 3.5 mm.

[0030] The through hole 12 connecting the bias line and the middle layer has a radius of 0.2 mm and a height of 0.5 mm.

[0031] The top metal patch, middle layer, and bottom phase shifter are made of copper foil with a thickness of 0.02 mm.

[0032] The dielectric material is F4B material with a dielectric constant of 2.55 and a loss tangent of 0.001.

[0033] The resistor, inductor, and capacitor used in the bias line RLC filter 20 are all in 0201 package, with a resistor value of 47 Ω, an inductor value of 100 nH, and a capacitor value of 100 pF.

[0034] like Figure 3 As shown in the figure, by simulating the metasurface unit, it is found that in the frequency band from 9 GHz to 10.5 GHz, the metasurface unit can realize the envisioned 3-bit phase shift function, the phase difference between adjacent phase states is about 45°, and the reflection loss of the eight phase states is controlled within 1 dB.

[0035] like Figure 4As shown in the figure, when the metasurface placed on the horizontal plane is illuminated by a plane wave perpendicular to the horizontal plane, the angles between the metasurface and the horizontal plane are 0°, 10°, 15°, 25°, 30°, 35°, and 50°, respectively. A coding matrix with corresponding phase gradients is designed for the metasurface. From the electric field diagram obtained by simulation, it can be seen that the reflected electric field distribution of the metasurface is parallel to the horizontal plane, which can simulate the electric field distribution on the horizontal plane, thereby playing the role of an invisible cloak.

[0036] like Figure 5 As shown in the figure, according to the simulation results, in the frequency band from 8 GHz to 10.5 GHz, the reflection RCS reduction value of the randomly encoded reconfigurable metasurface is more than 10 dB.

[0037] The technical solutions of the present invention are not limited to the above-mentioned specific embodiments. For example, the present invention is a 3-bit multifunctional reconfigurable metasurface operating at 9 GHz to 10.5 GHz. By designing different coding matrices, electromagnetic waves can be freely controlled to achieve other functions, such as beam steering and DOA estimation. All technical variations based on the technical solutions of the present invention fall within the scope of protection of the present invention.

Claims

1. A 3-bit phase reconfigurable metasurface, characterized in that: The invention comprises a two-dimensional array composed of 3-bit reconfigurable metasurface units and a DC bias network composed of bias lines of each metasurface unit; wherein: The metasurface unit consists of three metal layers and two dielectric layers. The top metal layer is used to receive and radiate electromagnetic waves, the middle metal layer serves as an intermediate layer, and the bottom metal layer serves as a phase shifter to achieve 3-bit reconfigurable function. The two dielectric layers are respectively between the top metal layer and the middle metal layer, and between the middle metal layer and the bottom metal layer. The phase shifter is divided into three parts, which respectively realize the phase shift functions of 45°, 90° and 180°; wherein: Both the 45° and 90° phase shifters are designed based on a loaded line phase shifter. The phase shifter consists of a transmission line with two vertical branches and a horizontal branch with two rectangular patches at each end. The vertical branches and the horizontal branch are connected by two PIN diodes. The 180° phase shifter is designed to achieve a 180° phase difference when the transmission line is short-circuited or open-circuited. A fan-shaped capacitor is used to simulate the short-circuit state, and a PIN diode is used to connect the fan-shaped patch to the transmission line. The working state of the phase shifter is controlled by a PIN diode. When the diode is turned on, the phase shifter works, and when the diode is cut off, the phase shifter does not work. Eight phase states can be achieved by combining the three parts. Each of the three parts of the phase shifter is controlled by a DC bias line. The DC bias lines of each metasurface unit together form a bias network. By loading the DC control voltage from an external FPGA into the PIN diode of the phase shifter, each metasurface unit can be independently controlled. An RLC filter is added to each bias circuit to block RF signals and allow DC signals to pass.

2. The 3-bit phase reconfigurable metasurface according to claim 1, characterized in that: The phase shifting function of the metasurface unit is controlled by two loaded linear phase shifters and a fan-shaped capacitor. The two loaded linear phase shifters realize 45° and 90° phase shifting functions respectively, and the fan-shaped capacitor realizes 180° phase shifting function. The two PIN diodes on the 45° phase shifter are simultaneously loaded with forward bias voltage through the DC bias line. The diodes are turned on at the same time, and the 45° phase shifter works. At this time, the phase of the reflected wave is delayed by 45°. The two diodes are simultaneously loaded with reverse voltage. The diodes are cut off at the same time, and the 45° phase shifter does not work. At this time, there is no phase delay in the reflected wave. Similarly, , the two PIN diodes on the 90° phase shifter are loaded with forward bias voltage at the same time, the diodes are turned on at the same time, the 90° phase shifter works, and the phase of the reflected wave is delayed by 90°; the two diodes are loaded with reverse voltage at the same time, the diodes are cut off at the same time, the 90° phase shifter does not work, and the reflected wave has no phase delay; the PIN diodes on the 180° phase shifter are loaded with forward bias voltage, the diodes are turned on, and the transmission line is equivalent to a short circuit. When reverse voltage is loaded, the diodes are cut off, and the transmission line is broken. The phase difference between the short-circuit and broken states of the transmission line is 180°.

3. The 3-bit phase reconfigurable metasurface according to claim 1, characterized in that : The side length of the metasurface unit is 14.5 mm-16 mm, the thickness of the upper dielectric layer is 2.5 mm-3 mm, and the thickness of the lower dielectric layer is 0.5 mm-1 mm; The side length of the top metal patch of the top metal layer is 8 mm-9 mm; The two vertical branches of the 45° phase shifter are 1 mm to 1.5 mm long and 0.1 mm to 0.3 mm wide; the horizontal branches are 8 mm to 9 mm long and 0.2 mm to 0.5 mm wide; the two rectangular patches are square patches with side lengths of 3.2 mm to 4 mm; The two vertical branches of the 90° phase shifter are 2 mm to 3 mm long and 0.1 mm to 0.3 mm wide; the horizontal branches are 8 mm to 9 mm long and 0.2 mm to 0.5 mm wide; the two rectangular patches are square patches with side lengths of 2 mm to 2.5 mm; The radius of the sector patch of the 180° phase shifter is 2.2 mm-2.8 mm; The metal vias connecting the top metal patch and the bottom phase shifter have a radius of 0.4 mm to 0.5 mm and a height of 3 mm to 4 mm. A circular hole with a radius of 0.6 mm-0.7 mm is opened at the through hole position on the middle layer to avoid short circuit; The radius of the through hole connecting the top metal patch and the middle layer is 0.15 mm-0.2 mm and the height is 3 mm-4 mm; The radius of the through hole connecting the bias line and the middle layer is 0.15 mm-0.2 mm, and the height is 0.5 mm-1 mm.

4. The 3-bit phase reconfigurable metasurface according to claim 3, wherein: The side length of the metasurface unit is 15 mm, the thickness of the upper dielectric layer is 3 mm, and the thickness of the lower dielectric layer is 0.5 mm; The side length of the top metal patch is 8.5 mm; The two vertical branches of the 45° phase shifter are 1 mm long and 0.1 mm wide; the horizontal branch is 8 mm long and 0.2 mm wide; the two square patches have a side length of 3.6 mm; The two vertical branches of the 90° phase shifter are 2 mm long and 0.1 mm wide; the horizontal branch is 8 mm long and 0.2 mm wide; the two square patches have a side length of 2.4 mm; The radius of the sector-shaped patch of the 180° phase shifter is 2.4 mm.

5. The 3-bit phase reconfigurable metasurface according to claim 3, wherein: The metal vias connecting the top metal patch and the bottom phase shifter have a radius of 0.45 mm and a height of 3.5 mm; A circular hole with a radius of 0.65 mm is opened at the through hole position on the middle layer to avoid short circuit; The through hole connecting the top metal patch and the middle ground layer has a radius of 0.2 mm and a height of 3.5 mm; The through hole connecting the bias line to the middle layer has a radius of 0.2 mm and a height of 0.5 mm.

6. The 3-bit phase reconfigurable metasurface according to claim 3, wherein: The top metal patch, the middle metal layer, and the bottom phase shifter are made of copper foil with a thickness of 0.02 mm; The dielectric material is F4B with a dielectric constant of 2.55 and a loss tangent of 0.001; The resistor, inductor, and capacitor used in the bias line RLC filter are all in 0201 package, with a resistor value of 47 Ω, an inductor value of 100 nH, and a capacitor value of 100 pF.

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