3-bit multifunctional reconfigurable metasurface

Abstract

The invention belongs to the technical field of communication, and particularly relates to a 3-bit phase reconfigurable metasurface. The metasurface comprises a two-dimensional array formed by metasurface units and a direct-current bias network formed by bias lines of the metasurface units. Each unit is composed of three metal layers and two dielectric layers, the top layer is used for receiving and radiating electromagnetic waves, the middle layer serves as a ground layer, and the bottom layer serves as a phase shifter to achieve a 3-bit reconfigurable function. The phase shifter is divided into three parts which respectively realize 45-degree, 90-degree and 180-degree phase shifting functions, and eight phase states are realized through combined work of the three parts; the three parts are respectively controlled by a direct-current bias line, the direct-current bias lines of the units form a bias network, and independent regulation and control of the units are realized by loading direct-current control voltage from an external field FPGA (field programmable gate array) for the phase shifter. By changing the phase array coding of the metasurface, the functions of invisible cloak and RCS reduction can be realized. The metasurface has the characteristics of high precision, low loss and multiple functions.

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 ultrathin surfaces composed of a large number of adjustable elements. They 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 There are many 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, the quantization error of 1-bit reconfigurable metasurfaces is often large, making it difficult to achieve high flexibility adjustment. 2-bit reconfigurable metasurfaces have attracted attention due to their neutrality between design complexity and quantization error.

[0003] At present, research on 3-bit coded metasurfaces is relatively scarce, because compared with 1-bit and 2-bit coded metasurfaces, the design complexity and processing cost of 3-bit coded metasurfaces are significantly increased. However, the phase quantization error of 3-bit metasurfaces is smaller, and the control of electromagnetic waves is more precise and accurate, which is an advantage 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, wherein the structure 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 ground 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, which respectively realize the phase shifting functions of 45°, 90°, and 180°. The 45° phase shifter and the 90° phase shifter are designed based on the 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 both ends. The vertical branches and the horizontal branches are connected by two PIN diodes. The design mechanism of the 180° phase shifter is that the phase difference is 180° when the transmission line is short-circuited and disconnected. The short-circuit state is simulated by a fan-shaped capacitor, and the fan-shaped patch is connected to the transmission line by a PIN diode. The working state of the phase shifter is controlled by the 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 are realized by the combined operation of the three parts. The three parts are respectively controlled by a DC bias line. The DC bias lines of each metasurface unit together constitute a bias network. The independent regulation of each metasurface unit is realized by loading the DC control voltage from the external FPGA to the PIN diode of the phase shifter.

[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 realize 45° and 90° phase shifting functions respectively, and the fan-shaped capacitor realizes 180° phase shifting function; specifically, the two PIN diodes on the 45° phase shifter are simultaneously loaded with forward bias voltage through the DC bias line, the diodes are simultaneously turned on, the 45° phase shifter works, and at this time the reflected wave phase is delayed by 45°; the two PIN diodes are simultaneously loaded with reverse voltage, the diodes are simultaneously cut off, the 45° phase shifter does not work, and at this time the reflected wave has no phase delay. Similarly, the two PIN diodes on the 90° phase shifter are simultaneously loaded with forward bias voltage, the diodes are simultaneously turned on, the 90° phase shifter works, and at this time the reflected wave phase is delayed by 90°; the two diodes are simultaneously loaded with reverse voltage, the diodes are simultaneously cut off, the 90° phase shifter does not work, and 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 disconnection states of the transmission line is 180°.

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

[0009] The 3-bit phase reconfigurable metasurface designed by the present invention can realize free switching of 8 phase states for y-polarized incident waves, and the phase difference between adjacent phase states is 45°. By encoding the metasurface array and assigning the corresponding DC control voltage 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 multi-function. The control functions that can be realized include invisibility cloak and radar cross section (RCS) reduction function;

[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, according to Snell's law, the angle between the generated reflected wave and the incident wave is 2θ. 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] The results of literature search show that there has not been any metasurface using this 3-bit phase-shifting structure in the range of 9GHz to 10.5GHz, and there has not been any result of using this metasurface to achieve the functions of invisibility cloaking and RCS reduction. 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 It 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] Numbers in the figure: 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 sheet 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 bottom 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 branch 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 is further described below in conjunction with the accompanying drawings and embodiments; this embodiment provides a detailed implementation method and a specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[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 range 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 2As shown, the metasurface unit described in this embodiment is composed 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 is used as the ground layer, and the bottom metal is used as the phase shifter 13 to realize the 3-bit reconfigurable function. The phase shifter is divided into three parts to realize the 45°, 90°, and 180° phase shifting functions respectively. Among them, the 45° phase shifter and the 90° phase shifter are designed based on the loaded line phase shifter. The phase shifter consists of a transmission line 14 with two vertical branches and a horizontal branch 15 with two rectangular patches 16 at both ends. The vertical branches and the horizontal branches are connected by two PIN diodes 17. The design mechanism of the 180° phase shifter is that the phase difference is 180° when the transmission line is short-circuited and disconnected. The fan-shaped capacitor 18 simulates the short-circuit state, and the fan-shaped patch is connected to the transmission line by a PIN diode 19. The working state of the phase shifter is controlled by the 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 are achieved by combining the three parts. Each of the three parts is controlled by a DC bias line. The DC bias lines of each unit together form a bias network. The independent regulation of each unit is achieved by loading the DC control voltage from the external FPGA to the PIN diode of the phase shifter.

[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 side length of the two square patches 16 is 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 provided 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 avoid short circuit, and the radius of the circular hole 11 is 0.65 mm;

[0029] A connecting through hole 10 is provided between the top metal patch and the middle ground layer, and has 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 bottom layer has a radius of 0.2 mm and a height of 0.5 mm.

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

[0032] The material of the medium 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 resistance value of 47Ω, an inductance value of 100nH and a capacitance value of 100pF.

[0034] like Figure 3 As shown, by simulating the metasurface unit, in the frequency band range of 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 losses of the eight phase states are all controlled within the range of 1 dB.

[0035] like Figure 4 As shown, when the metasurface placed on the horizontal plane is irradiated with a plane wave perpendicular to the horizontal plane, when 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, according to the simulation results, in the frequency band range of 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 solution of the present invention is 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, which can realize other functions such as beam deflection, DOA estimation, etc. by designing different coding matrices to realize free control of electromagnetic waves. Any technical variations made according to the technical solution of the present invention fall within the protection scope of the present invention.

Claims

1. A 3-bit phase reconfigurable metasurface, characterized in that: It includes 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 is composed of three metal layers and two dielectric layers; the top metal layer is used to receive and radiate electromagnetic waves, the middle metal layer is used as a ground layer, and the bottom metal layer is used as a phase shifter to achieve a 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° phase shifter and the 90° phase shifter are designed based on the 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 both ends. The vertical branches are connected to the horizontal branch by two PIN diodes. The 180° phase shifter is designed so that the phase difference is 180° when the transmission line is short-circuited or open-circuited. The short-circuit state is simulated by a fan-shaped capacitor, and the fan-shaped patch is connected to the transmission line by a PIN diode. The working state of the phase shifter is controlled by the 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. The three parts of the phase shifter are controlled by a DC bias line respectively. The DC bias lines of each metasurface unit together form a bias network. The independent regulation of each metasurface unit is achieved by loading the DC control voltage from the external FPGA to the PIN diode of the phase shifter. 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 one 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; specifically, a forward bias voltage is simultaneously loaded on two PIN diodes on the 45° phase shifter through a DC bias line, the diodes are simultaneously turned on, the 45° phase shifter works, and the reflected wave phase is delayed by 45°; a reverse voltage is simultaneously loaded on the two diodes, the diodes are simultaneously cut off, the 45° phase shifter does not work, and the reflected wave has no phase delay; Similarly, when a forward bias voltage is applied to the two PIN diodes on the 90° phase shifter at the same time, the diodes are turned on at the same time, and the 90° phase shifter works. At this time, the reflected wave has a phase delay of 90°; when a reverse voltage is applied to the two diodes at the same time, the diodes are cut off at the same time, and the 90° phase shifter does not work. At this time, the reflected wave has no phase delay; when a forward bias voltage is applied to the PIN diodes on the 180° phase shifter, the diodes are turned on. At this time, the transmission line is equivalent to a short circuit. When a reverse voltage is applied, the diodes are cut off. At this time, the transmission line is open. The phase difference between the short circuit and open circuit states is 180°.

3. The 3-bit phase reconfigurable metasurface according to claim 1, characterized in that : The side length of the metasurface unit is 14.5mm-16mm, the thickness of the upper dielectric layer is 2.5mm-3mm, and the thickness of the lower dielectric layer is 0.5mm-1mm; The side length of the top metal patch is 8mm-9mm; The middle transmission line of the bottom phase shifter has a length of 8.4mm-9mm and a width of 1mm-1.5mm; The length of the two vertical branches of the 45° phase shifter is 1mm-1.5mm, and the width is 0.1mm-0.3mm; the length of the horizontal branch is 8mm-9mm, and the width is 0.2mm-0.5mm; the side length of the two square patches is 3.2mm-4mm; The length of the two vertical branches of the 90° phase shifter is 2mm-3mm, and the width is 0.1mm-0.3mm; the length of the horizontal branch is 8mm-9mm, and the width is 0.2mm-0.5mm; the side length of the two square patches is 2mm-2.5mm; The radius of the sector patch of the 180° phase shifter is 2.2mm-2.8mm; The radius of the metal via connecting the top metal patch and the bottom phase shifter is 0.4mm-0.5mm and the height is 3mm-4mm; A circular hole with a radius of 0.6mm-0.7mm is opened at the through hole position on the middle stratum to avoid short circuit; The radius of the through hole connecting the top metal patch and the middle bottom layer is 0.15mm-0.2mm and the height is 3mm-4mm; The through hole connecting the bias line and the middle bottom layer has a radius of 0.15mm-0.2mm and a height of 0.5mm-1mm.

4. The 3-bit phase reconfigurable metasurface according to claim 3, characterized in that: 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 8.5mm; The middle transmission line of the bottom phase shifter is 8.7 mm long and 1.2 mm wide; The two vertical branches of the 45° phase shifter are 1mm long and 0.1mm wide; the horizontal branch is 8mm long and 0.2mm wide; the side length of the two square patches is 3.6mm; The two vertical branches of the 90° phase shifter are 2mm long and 0.1mm wide; the horizontal branch is 8mm long and 0.2mm wide; the side length of the two square patches is 2.4mm; The radius of the sector patch of the 180° phase shifter is 2.4 mm.

5. The 3-bit phase reconfigurable metasurface according to claim 3, characterized in that: The radius of the metal via connecting the top metal patch and the bottom phase shifter is 0.45mm and the height is 3.5mm; 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 radius of the through hole connecting the top metal patch and the middle bottom layer is 0.2mm and the height is 3.5mm; The vias connecting the bias line to the middle bottom layer have a radius of 0.2 mm and a height of 0.5 mm.

6. The 3-bit phase reconfigurable metasurface according to claim 3, characterized in that: The top metal patch, the middle layer, and the bottom phase shifter are made of copper foil with a thickness of 0.02mm; The material of the medium is F4B material 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 resistance of 47Ω, an inductance of 100nH and a capacitance of 100pF.

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