Phase regulation curved surface conformal active metasurface

Abstract

The invention discloses a phase regulation curved surface conformal active metasurface, and relates to the technical field of metasurface design, a metasurface unit is composed of a metal layer and a dielectric layer, the metal layer comprises a metal structure layer and a metal backboard layer, and the dielectric layer comprises an F4B dielectric substrate and an ABS dielectric layer. The metasurface unit is sequentially provided with a metal structure layer, an F4B dielectric substrate, an ABS dielectric layer and a metal backboard layer from top to bottom, and the metal structure layer is externally connected with a feed structure by adopting a circular through hole technology and is used for adjusting the voltage at the two ends of the variable capacitance diode. According to the phase regulation curved surface conformal active metasurface, the 3D printed curved surface substrate is combined with the voltage programmable 2-bit phase code, so that the metasurface has high adaptability to the curved surface structure, and electromagnetic wave dynamic regulation and control and vortex wave generation can be carried out within the frequency band of 9.3 GHz to 10.5 GHz and within the angle range of 0 degree to 50 degrees.

Description

Technical Field

[0001] This invention relates to the field of metasurface design technology, specifically to a phase-tunable curved conformal active metasurface. Background Technology

[0002] Metasurfaces, as two-dimensional superatomic arrays at the subwavelength scale, have become a powerful platform for precisely controlling the amplitude, phase, and polarization of electromagnetic waves. Due to their small size, low loss, simple fabrication, and unique electromagnetic properties, metasurfaces have attracted widespread attention and demonstrated extensive applications in the microwave to visible light frequency band, such as achromatic lenses, vortex beam generators, surface wave couplers, and super holograms. Notably, to meet the demands of highly integrated applications, many multifunctional metasurfaces with strong multiplexing capabilities have been developed. However, most metasurfaces are passive, and their electromagnetic properties are fixed once fabricated, which essentially limits their flexibility in practical applications. Fortunately, the emergence of active metasurfaces has effectively overcome the above problems and achieved a series of significant successes. Active metasurfaces integrate metasurfaces with active components controlled by electrical bias, optical switches, mechanical drives, etc. Active metasurfaces can dynamically control the characteristics of electromagnetic waves. Due to their advantages of speed and simplicity, metasurfaces loaded with PIN diodes or varactor diodes are widely used at microwave frequencies.

[0003] However, most existing metasurface designs are limited by planar geometry and static functionality, which leads to impedance mismatch and performance degradation when integrated into curved platforms, severely limiting their applicability to curved platforms such as aircraft, missiles, and unmanned aerial vehicles (UAVs). Furthermore, although recent advances in programmable metasurfaces have enabled dynamic wavefront control, most designs are limited to single-function operation and cannot meet the growing demand for multifunctional, broadband, and wide-angle dynamic electromagnetic manipulation. Summary of the Invention

[0004] This invention provides a phase-tunable curved conformal active metasurface, which solves the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a phase-tunable curved conformal active metasurface, wherein the metasurface unit is composed of a metal layer and a dielectric layer, the metal layer includes a metal structure layer and a metal backplate layer, and the dielectric layer includes an F4B dielectric substrate and an ABS dielectric layer. The metasurface unit is arranged from top to bottom as a metal structure layer, an F4B dielectric substrate, an ABS dielectric layer, and a metal backplate layer. The metal structure layer is externally connected to a power supply structure using circular through-hole technology to adjust the voltage across the varactor diode.

[0006] Optionally, the unit structure period of the metasurface unit is p = 10 mm.

[0007] Optionally, the metal structure layer is composed of two rectangular structures forming an H-shaped metal patch, with the center of the H-shaped metal patch being the location for loading an active device, and a PIN diode integrated between the two rectangular structures.

[0008] Optionally, the thickness of the F4B flexible dielectric substrate is set to 0.1 mm, the relative permittivity of the F4B flexible dielectric substrate is set to 2.67, and the loss tangent of the F4B flexible dielectric substrate is set to 0.001.

[0009] Optionally, the thickness of the ABS dielectric layer is set to 3 mm, the relative permittivity of the ABS dielectric layer is set to 2.65, and the loss tangent of the ABS dielectric layer is set to 0.005.

[0010] Optionally, the metal layers are all made of copper and have a thickness of 0.018 mm.

[0011] Optionally, the width of the two rectangular structures on the left and right sides of the metal structure layer is set to a = 12 mm, the length is set to b = 10 mm, and through holes with a diameter of s = 4.67 mm are opened at the top and bottom ends of the two rectangular structures. The gap between the top and bottom ends of the two rectangular structures is set to f = 8 mm, and the gap between the middle parts of the two rectangular structures is set to f = 5 mm.

[0012] Optionally, the PIN diode is configured as SMV1430-040LF.

[0013] A conformal active metasurface with continuously dynamic tunable RCS in both wide frequency and wide angle domains includes the following operational steps:

[0014] S1, Analysis of Metasurface Units

[0015] The equivalent circuit parameters of the varactor diodes under different DC biases were calculated by establishing a Spice model in the commercial software ADS. This was used to obtain the equivalent parameters of the RLC. The extracted equivalent parameters were then used as simulation data. The reflection phase of the metasurface unit under the condition of perpendicular incident x-polarized wave was simulated in the commercial software CST Microwave Studio. The results were obtained. In the simulation, the center operating frequency was selected as 10 GHz. Different effective circuit parameters were used to adapt to different feed voltages. By adjusting the voltage, the phase response between different units was changed for flexible beam control.

[0016] S2, Beam Control

[0017] By arranging coding units with specific phase differences in a two-dimensional plane, a metasurface can carry binary sequences to express coded information, thus constructing a programmable metasurface. Different coding sequences provide different electromagnetic wave manipulation capabilities. The realization of the reflective metasurface follows the generalized law of reflection.

[0018]

[0019] In the formula, θ r and θ i Here, θ represents the angle of reflection and the angle of incidence, respectively, and λ0 is the wavelength of the electromagnetic wave in free space. Let be the phase gradient of the metasurface along the x-direction.

[0020] According to formula (1), the phase distribution of the metasurface must satisfy a linear relationship to achieve beam deflection:

[0021]

[0022] According to formulas (1) and (2), a specific phase gradient is selected. Reflection angle θ r It is constant, and at the same time, it changes with the incident angle θ. i Changes in reflection angle θ r Then it will change;

[0023] S3, OAM generation

[0024] Due to its unique phase structure, a vortex beam carrying orbital angular momentum can simultaneously transmit signals of several different OAM modes at the same frequency. Because of its phase singularity, the vortex beam exhibits an extremely low radar cross-section. The vortex phase distribution, based on orbital angular momentum theory, is used to achieve OAM generation. The phase distribution of the metasurface must satisfy a helical relationship. For discrete metasurface units, the phase distribution can be discretized as follows:

[0025]

[0026] In the formula, (x i y i (x0, y0) represents the position of the element in the metasurface, (x0, y0) represents the center coordinates of the metasurface, and l represents the number of topological charges carried.

[0027] S4, Curvature Compensation Phase Correction Algorithm

[0028] When electromagnetic waves strike an irregularly curved metal surface, they are reflected in various directions, exhibiting a different wavefront than that of planar metal. This allows for effective control of the reflection direction of reflected waves from curved targets. Conformal active metasurfaces with specific phase distributions can be applied to the curved target to achieve flexible control of the incident electromagnetic waves.

[0029] Based on formula (2), the incident angle of the planar active metasurface can be calculated to be θ. i The incident wave is reflected at a reflection angle of θ. r Required phase distribution in direction Based on the perpendicular distance h between the conformal active metasurface and the planar active metasurface, the phase distribution that the conformal active metasurface needs to compensate for can be obtained. for:

[0030]

[0031] Phase distribution of conformal active metasurfaces This is the phase of a planar active metasurface. With compensation phase The sum of

[0032] First, calculate the required spiral phase distribution for realizing the planar active metasurface according to formula (3). Then, calculate the phase distribution required for compensation between the conformal active metasurface and the planar active metasurface according to formula (4). The spiral phase distribution required for the generation of a conformal active metasurface is then the phase distribution of a planar active metasurface. With compensation phase The sum of By designing the geometric parameters of the unit structure and the bias voltage of the varactor diode, the desired spiral phase distribution can be achieved on the metasurface to generate OAM beams.

[0033] S5, PCM-CAM Design Simulation

[0034] Based on the beam deflection control of electromagnetic waves by CAM in the X direction, the multi-dimensional control of electromagnetic waves by CAM is further analyzed. Furthermore, the control of the encoded gradient metasurface in the Y direction and the two-dimensional metasurface is analyzed, leading to the conclusion that the phase distribution of the metasurface must satisfy a linear relationship to achieve beam deflection in three-dimensional space.

[0035]

[0036] According to formula (5), on the two-dimensional metasurface, based on the incident angle of the electromagnetic wave and the angle to be reflected, the phase gradient required along the x and y directions is designed by designing the bias voltage of the varactor diode in the unit structure. Used to control the propagation direction of electromagnetic waves in three-dimensional space;

[0037] S6, PCM-CAM Sample Fabrication and Experimental Verification

[0038] A detailed prototype identical to the simulation model was fabricated using low-cost printed circuit board technology, and the required varactor diodes were soldered in the corresponding locations to verify the practicality of the CAM.

[0039] The prototype and the transmitting horn antenna connected to VNA port 1 are fixed on a turntable support, while the receiving horn antenna connected to VNA port 2 is placed at a sufficiently far distance so that it can rotate around the prototype for measurement, thus presenting the measurement sample at different incident angles θ. i and deflection angle θ r The far-field scattering pattern is shown below, with different incident angles θ in the experiment. i and deflection angle θ r The encoding sequence is the same as that designed in the simulation and is dynamically controlled by the connected FPGA. In each sub-graph, a curve is used to represent the far-field scattering pattern at a specific deflection angle, and the vertical line indicates the theoretically predicted scattering direction. When the deflection angle of the scattered beam is close to the theoretical value at different incident angles, and the deflection angle error is 1°, this is used to verify the effectiveness of CAM.

[0040] The present invention has the following beneficial effects:

[0041] 1. This phase-tunable curved conformal active metasurface combines a 3D-printed curved substrate with a voltage-programmable 2-bit phase code, enabling the metasurface to have strong adaptability to curved structures and to dynamically control electromagnetic waves and generate vortex waves in the frequency band of 9.3GHz to 10.5GHz and the angle range of 0° to 50°.

[0042] 2. This phase-tuned conformal active metasurface, through a combination of simulation and experimental results, demonstrates that in beam control mode, the CAM can deflect incident waves with incident angles ranging from θ = 0° to 50° to a preset reflection direction with a pointing accuracy better than ±2°. In the original incident direction, the CAM can reduce the radar cross-section by more than 10dB. At the preset reflection angle, the CAM can enhance the RCS by up to +8.9dB in the preset deflection direction, thus effectively achieving radar phantom stealth. In orbital angular momentum mode, the CAM generates an OAM beam, which can effectively improve the spectral efficiency of wireless communication systems. This work has transformative potential in phantom stealth, camouflage, and communication. Attached Figure Description

[0043] Figure 1 This is a diagram of the conformal active metasurface (CAM) of the present invention;

[0044] Figure 2 This is a schematic diagram of the PCM-CAM structural unit of the present invention;

[0045] Figure 3This is a functional demonstration diagram of the PCM-CAM of the present invention in beam control mode and OAM mode;

[0046] Figure 4 This is a functional demonstration diagram of the PCM-CAM of the present invention in beam control mode;

[0047] Figure 5 This is a functional demonstration diagram of the PCM-CAM of the present invention in beam control mode;

[0048] Figure 6 This is a functional demonstration diagram of the PCM-CAM of the present invention in beam control mode;

[0049] Figure 7 This is a functional demonstration diagram of the PCM-CAM of the present invention at a frequency of 10GHz;

[0050] Figure 8 This is a diagram illustrating the experimental setup for the PCM-CAM of the present invention and its far-field scattering directions at different incident angles.

[0051] Figure 9 The equivalent circuit parameter diagram of the varactor diode SMV1430-040LF of this invention is shown. Detailed Implementation

[0052] The technical solutions of the embodiments of the present invention will be clearly and completely 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.

[0053] Please see Figures 1 to 9 This invention provides a technical solution: a phase-tunable curved conformal active metasurface, wherein the metasurface unit is composed of a metal layer and a dielectric layer. The metal layer includes a metal structure layer and a metal backplate layer, and the dielectric layer includes an F4B dielectric substrate and an ABS dielectric layer. The metasurface unit is arranged from top to bottom as a metal structure layer, an F4B dielectric substrate, an ABS dielectric layer, and a metal backplate layer. The metal structure layer is externally connected to a power supply structure using circular via technology, which supplies power to a varactor diode through the via to adjust the voltage across the varactor diode.

[0054] The unit cell structure period of the metasurface unit is p = 10 mm.

[0055] The metal structure layer consists of two rectangular structures forming an H-shaped metal patch, with the center of the H-shaped metal patch designated as the loading position for active devices. A PIN diode is integrated between the two rectangular structures.

[0056] The thickness of the F4B flexible dielectric substrate is set to 0.1 mm, the relative permittivity of the F4B flexible dielectric substrate is set to 2.67, and the loss tangent of the F4B flexible dielectric substrate is set to 0.001.

[0057] The thickness of the ABS dielectric layer is set to 3mm, the relative permittivity of the ABS dielectric layer is set to 2.65, and the loss tangent of the ABS dielectric layer is set to 0.005.

[0058] The metal layers are all made of copper, and the thickness is set to 0.018mm.

[0059] The width of the two rectangular structures on the left and right sides of the metal structure layer is set to a = 12 mm, and the length is set to b = 10 mm. Both ends of the two rectangular structures have through holes with a diameter of s = 4.67 mm. The gap between the upper and lower ends of the two rectangular structures is set to f = 8 mm, and the gap between the middle parts of the two rectangular structures is set to f = 5 mm.

[0060] The PIN diode is set to SMV1430-040LF.

[0061] A conformal active metasurface with continuously dynamic tunable RCS in both wide frequency and wide angle domains includes the following operational steps:

[0062] S1, Analysis of Metasurface Units

[0063] Figure 2 The diagram shows the PCM-CAM structural unit, where (a) is a schematic diagram of the designed meta-atom, where p = 10 mm, a = 1.2 mm, b = 9 mm, aa = 0.2 mm, bb = 0.8 mm, s = 1 mm, (b) is the equivalent circuit model of the designed meta-atom, (c) is the definition of the incident angle θ and the deformation angle δ, (d)-(f) are the simulated reflection phases of the meta-atom at incident angles θ = 0°, θ = 30° and θ = 50°, and (g)-(i) are the simulated reflection phases of the meta-atom in the range of deformation angle δ from 1° to 5°.

[0064] according to Figure 2 (a) and (b) show the Spice model of the varactor diode and its effective RLC series resonant circuit, respectively. The equivalent circuit parameters of the varactor diode under different DC biases were calculated using a Spice model established in the commercial software ADS, which were then used to obtain the equivalent parameters of the RLC circuit. Figure 9 As shown, the extracted equivalent parameters were then used as simulation data. The reflection phase of the metasurface element under perpendicular incident x-polarized wave conditions was simulated in the commercial software CST Microwave Studio, and the results were obtained as follows. Figure 2As shown in (c), in the simulation, the center operating frequency was selected as 10GHz, and different effective circuit parameters were used to adapt to different feed voltages. According to the simulation results, at the 10GHz frequency, the phase difference is 75° between -23V and -15V, 95° between -15V and -8V, and 105° between -8V and -0.5V, basically covering four discrete states (0°, 90°, 180°, 270°). The phase modulation error is ≤37°, which can realize 2-bit phase modulation. By adjusting the voltage, the phase response between different units can be changed for flexible beam control.

[0065] Meanwhile, the phase change of the conformal active metasurface in this design also exhibits a certain robustness to incident angle and deformation, as shown in the figure. Figure 2 (c)-(e) show the variation of the reflection phase of the metasurface structure unit with the incident angle θ. It can be seen that as the incident angle of the electromagnetic wave increases, θ... i Within the incident angle range of 0°-50°, the reflection phase of the metasurface structural unit remains essentially unchanged, and the phase difference between them still basically covers the four discrete states (0°, 90°, 180°, 270°). The phase modulation error is ≤37°, and 2-bit phase modulation can be achieved. Figure 2 (f)-(h) show the simulation results of the reflection phase changing with the curvature of the structural unit. It can be seen that the designed structural unit reflection phase has good adaptability to changes within a certain curvature. When the central angle δ corresponding to the surface is less than 7°, the phase difference between the reflection phases of the structural units still basically covers the four discrete states (0°, 90°, 180°, 270°), which can realize 2-bit phase modulation. At the same time, the metasurface achieves 2-bit phase while exhibiting high reflection amplitude, ensuring that most of the incident energy is effectively utilized instead of being lost through absorption or scattering. This enables complex wavefront shaping and beam control functions, making this metasurface design very attractive and suitable for various practical applications.

[0066] S2, Beam Control

[0067] To improve the performance of wireless communication systems and multiple-input multiple-output (MIMO) communication, reconfigurable metasurfaces possess strong tunability for electromagnetic wave patterns. By arranging coding units with specific phase differences in a two-dimensional plane, the metasurface carries binary sequences to express coded information, thus constructing a programmable metasurface. Different coding sequences offer different electromagnetic wave manipulation capabilities. For metasurface-based reflectors, the incident angle is relatively narrow. The realization of reflective metasurfaces follows the generalized law of reflection.

[0068]

[0069] In the formula, θr and θ i Here, θ represents the angle of reflection and the angle of incidence, respectively, and λ0 is the wavelength of the electromagnetic wave in free space. Let be the phase gradient of the metasurface along the x-direction.

[0070] According to formula (1), the phase distribution of the metasurface must satisfy a linear relationship to achieve beam deflection:

[0071]

[0072] According to formulas (1) and (2), a specific phase gradient is selected. Reflection angle θ r It is constant, and at the same time, it changes with the incident angle θ. i Changes in reflection angle θ r Then it will change;

[0073] Therefore, by rationally designing the phase distribution of the planar active metasurface, flexible control over the reflection directions of different incident electromagnetic waves can be achieved. Thus, based on the incident angle of the electromagnetic wave and the required reflection angle, the desired phase gradient can be achieved on the metasurface by designing the bias voltage of the varactor diode in the unit structure. This deflects the incident wave to a predetermined direction;

[0074] S3, OAM generation

[0075] Vortex beams carrying orbital angular momentum, due to their unique phase structure, can simultaneously transmit signals of several different OAM modes at the same frequency, breaking the diffraction limit of traditional optical systems and improving the capacity and imaging resolution of wireless communication systems. They have attracted widespread attention in wireless communication and radar detection. Due to phase singularity, vortex beams exhibit extremely low radar cross-sections. The vortex phase distribution, based on orbital angular momentum theory, is used to achieve OAM generation. The phase distribution of the metasurface must satisfy a helical relationship. For discrete metasurface units, the phase distribution can be discretized as follows:

[0076]

[0077] In the formula, (x i y i (x0, y0) represents the position of the element in the metasurface, (x0, y0) represents the center coordinates of the metasurface, and l represents the number of topological charges carried.

[0078] S4, Curvature Compensation Phase Correction Algorithm

[0079] When electromagnetic waves strike an irregularly curved metal surface, they are reflected in various directions, exhibiting a different wavefront than that of planar metal. This allows for effective control of the reflection direction of reflected waves from curved targets. Conformal active metasurfaces with specific phase distributions can be applied to the curved target to achieve flexible control of the incident electromagnetic waves.

[0080] Based on formula (2), the incident angle of the planar active metasurface can be calculated to be θ. i The incident wave is reflected at a reflection angle of θ. r Required phase distribution in direction Based on the perpendicular distance h between the conformal active metasurface and the planar active metasurface, the phase distribution that the conformal active metasurface needs to compensate for can be obtained. for:

[0081]

[0082] Phase distribution of conformal active metasurfaces This is the phase of a planar active metasurface. With compensation phase The sum of Therefore, the metasurface is designed and verified by simulation. Different supercell reflection phases can be obtained by arranging the varactor diodes with different voltages. When the encoding is set to 2-bit, the corresponding cell phase responses are "0, π / 2, π, 3π / 2" respectively by voltage regulation. The CAM metasurface is calculated at different incident angles (θ) according to formulas (2) and (3). i ), expected reflection angle (θ) r The calculation of the compensation phase under both polarization states (OAM and normal incidence) can enable modulation with various functions.

[0083] To generate an OAM beam on a curved conformal active metasurface, the spiral phase distribution required for achieving the planar active metasurface is first calculated according to formula (3). Then, calculate the phase distribution required for compensation between the conformal active metasurface and the planar active metasurface according to formula (4). The spiral phase distribution required for the generation of a conformal active metasurface is then the phase distribution of a planar active metasurface. With compensation phase The sum of By designing the geometric parameters of the unit structure and the bias voltage of the varactor diode, the desired spiral phase distribution can be achieved on the metasurface to generate OAM beams.

[0084] S5, PCM-CAM Design Simulation

[0085] A phase-controlled conformal active metasurface was developed, and its function was simulated. The results are as follows: Figure 3 As shown, the PCM-CAM is demonstrated in beam control mode and OAM mode at a frequency of 10 GHz and an incident angle of θi = 0°. (a) and (f) are the phase distribution of the CAM, (b) and (g) are the 3D phase distribution after phase compensation, (c) and (d) are the far-field 3D distributions of the same bent copper plate and CAM in the coded state, (h) and (i) are the phase distribution and far-field distribution of the generated OAM, and (e) and (j) are the incident angle θi. i and reflection angle θ r The definition of CAM and the RCS distribution of CAM in the encoded state, and the effect of electromagnetic wave incident angle θ on CAM metasurface. i The electromagnetic response at 0° was analyzed, and the phase and gain of the electromagnetic wave were controlled by changing the geometric parameters of the metasurface. Figure 3 (a)-(d) show the incident angle θ under normal incident conditions. i =0°, reflection angle θ r Figure (a) shows the phase distribution of the CAM metasurface at 0°. It can be seen that the phase changes with the row and column, exhibiting a periodic distribution. Figure (b) shows the three-dimensional phase distribution after phase compensation, demonstrating the spatial distribution characteristics of the phase. Figure (c) shows the three-dimensional scattering distribution of a uniformly sized curved copper plate. Figure (d) shows the CAM metasurface after adjustment at a reflection angle θ. r The far-field 3D distribution at θ = 0°, as shown in Figures (c) and (d), demonstrates that phase-controlled CAM achieves the desired effect on electromagnetic waves at a reflection angle θ. r The effect of increased RCS at θ = 0° is illustrated in Figure (e), which shows the incident angle θ described in the text. i Based on the definition of the reflection angle θr and the RCS of the CAM metasurface in the reflection and control states at the incident angle θ = 0°, it can be seen that the CAM metasurface has a similar distribution to a curved copper plate of the same size in the reflection state, at the reflection angle θr... r At 0°, the RCS of the CAM metasurface in the controlled state is significantly higher than that in the reflection state, with a maximum increase of 8.9 dB, indicating that the CAM metasurface has a significant effect on electromagnetic wave manipulation.

[0086] The vortex wave generation result is as follows Figure 3As shown: Figure (f) shows the planar phase distribution of the CAM metasurface in the OAM state. It can be seen that the phase distribution of the electromagnetic wave in the OAM state is different from that in the normal incident state, exhibiting more complex distribution characteristics. Figure (g) is a three-dimensional diagram after phase compensation, which further intuitively shows the spatial distribution characteristics of the phase. Figure (h) shows the phase distribution of the generated OAM wave. Figure (i) shows the far-field distribution of the generated OAM wave. Figure (j) shows the RCS distribution of the generated OAM wave. It can be seen that through 2-bit phase modulation, the CAM metasurface achieves effective generation of OAM with l=1. The designed curved conformal active metasurface can generate different far-field scattering patterns through different coding sequences, and has a strong tuning capability for the radiation pattern.

[0087] like Figure 4 Demonstration of PCM-CAM functionality in beam control mode: (a)-(d) Frequency 10GHz, incident angle θ i =0°, preset reflection angles are θ r =30°, -30°, 50° and -50°, (e) incident angle is θ i When the angle is 0°, the preset reflection angle θ r =0° and θ r = 30° RCS distribution, (f) incident angle is θ i When the angle is 0°, the preset reflection angle θ r =0° and θ r The RCS distribution is -50°. To further verify the effect of the designed CAM on electromagnetic wave beam control, the incident angle θ was calculated according to formulas (1)-(4). i The phase encoding and simulation results at 0° are as follows: Figure 4 As shown, Figure 4 (a)–(d) respectively show the incident angle θ of the electromagnetic wave. i =0°, expected reflection angle θ r The phase distribution, 3D far-field plot, and RCS distribution of the CAM at the expected reflection angles of 30°, -30°, 50°, and -50° show that, unlike the planar metasurface where the phase gradient between columns is a constant, the phase gradient generated by electromagnetic waves is no longer a fixed value when electromagnetic waves irradiate the curved metal surface due to the curvature. The phase distribution on the CAM changes significantly with different expected reflection angles. To effectively control the reflection direction of the reflected wave from the curved target, more complex phase compensation is needed for different metasurfaces. The designed CAM can control the electromagnetic wave incident angle θ. i =0° deflection to the preset reflection direction θ r=30°, -30°, 50°, -50° (pointing accuracy better than ±2°), and compared with a curved copper plate of the same size, the CAM's RCS in the controlled state increased by 8.1dB, 8.2dB, 6dB, and 7.6dB respectively in the preset reflection direction, realizing dynamic control of the target RCS. Figure 4 (e)-(f) respectively show the changes in RCS of CAM under different control states and the same size curved copper plate. Figure 4 (e) demonstrates the situation when the incident angle of the electromagnetic wave is θ. i When θ = 0°, when CAM reflects electromagnetic waves to θ r =0° and θ r When the angle of incidence is -30°, at the incident angle θ i The RCS control range at 0° reaches 26dB. Figure 4 (f) shows the electromagnetic wave incident at an angle of θ. i When θ = 0°, when CAM reflects electromagnetic waves to θ r =0° and θ r When the angle of incidence is 50°, at the incident angle θ i The RCS control range at 0° reaches 19.7dB. It can be seen that the designed CAM can achieve a wider range of RCS control in the incident angle direction through different control state transitions, so as to realize the illusion of curved targets to the detection radar and achieve the purpose of deceiving the detector.

[0088] like Figure 5 This is a demonstration of PCM-CAM functionality in beam control mode, at a frequency of 10 GHz and an incident angle of θ. i =30°, preset reflection angle is θ r =-30°: (a) Phase distribution of CAM, (b) 3D phase distribution after phase compensation, (c), (d) Far-field 3D distribution of the same curved copper plate and CAM in the encoding state, (e) Incident angle θ i and reflection angle θ r The definition of CAM and its RCS distribution in the coded state, (f), (g) CAM in beam control mode, with an incident angle of θ. i =30°, preset reflection angles are θ r =0°, θ r In the case of θ = 30°, to achieve electromagnetic wave beam manipulation over a wide incident angle domain, the effect of CAM on electromagnetic wave incident angle θ was further analyzed. i =30° beam deflection, Figure 5 (a)–(d) respectively show the incident angle θ of the electromagnetic wave. i =30°, expected reflection angle θ rAt -30°, the phase distribution of the CAM, the three-dimensional phase distribution after phase compensation, the same-size curved copper plate, and the far-field 3D scattering diagram of the CAM show that the phase distribution on the CAM changes significantly with different incident angles. To effectively control the reflection direction of the reflected wave from the curved target, phase compensation becomes more complex. The far-field 3D scattering diagram shows that, compared to the same-size curved copper plate, the designed CAM can reduce the electromagnetic wave incident angle θ. i = 30° deflection to the preset reflection direction θ r = -30°, achieving RCS enhancement in the incident angle direction. Figure 5 (e) defines the angle of incidence and the angle of reflection, and shows the electromagnetic wave incident angle θ. i The RCS enhancement effect at 30° shows that CAM not only achieves effective deflection of the electromagnetic wave beam (pointing accuracy better than ±2°), but also increases the RCS by approximately 8.6 dB in the incident direction. Figure 5 (f)-(g) respectively show the incident angle θ of the electromagnetic wave i =30°, expected reflection angle θ r = -0° and θ r At -30°, the phase distribution of the CAM, the far-field 3D scattering pattern of the CAM, and the expected reflection angle θ. r = -0° and θ r The RCS enhancement effect of CAM in the -30° direction relative to the same large curved copper plate can be seen from the fact that when the incident angle of the electromagnetic wave is θ i At θ = 30°, CAM can efficiently deflect the electromagnetic wave beam to θ. r = -0° and θ r = -30° direction (pointing accuracy better than ±2°), and relative to the RCS of the same large curved copper plate, the RCS of the CAM in the controlled state is at the preset reflection direction θ r = -0° and θ r =30° increased by 8.1dB and 5.1dB respectively, realizing dynamic control of the target RCS;

[0089] like Figure 6 This is a demonstration of PCM-CAM functionality in beam control mode, at a frequency of 10 GHz and an incident angle of θ. i =50°, preset reflection angle is θ r = -30°: (a) Phase distribution of CAM, (b) 3D phase distribution after phase compensation, (c), (d) Far-field 3D distribution of the same curved copper plate and CAM in the encoding state; (e) Incident angle θ i and reflection angle θ r The definition of CAM and its RCS distribution in the coded state, (f), (g) CAM in beam control mode, with an incident angle of θ. i=50°, preset reflection angles are θ r =0°, θ r The situation is similar when the angle is 30°. Figure 6 (a)–(d) respectively show the incident angle θ of the electromagnetic wave. i =50°, expected reflection angle θ r At -50°, the phase distribution of the CAM, the three-dimensional phase distribution map after phase compensation, the far-field 3D scattering map of the same-size curved copper plate and the CAM, Figure 6 (f)-(g) respectively show the incident angle θ of the electromagnetic wave i =50°, expected reflection angle θ r =0° and θ r At an angle θ = 30°, the phase distribution corresponding to the CAM, the far-field 3D scattering pattern of the CAM, and the RCS enhancement effect of the CAM relative to the large curved copper plate show that when the electromagnetic wave incident angle θ = 30°, the phase distribution of the CAM, the far-field 3D scattering pattern of the CAM, and the RCS enhancement effect of the CAM relative to the large curved copper plate show that the electromagnetic wave incident angle θ = 30° is 30°. i At θ = 50°, CAM can efficiently deflect the electromagnetic wave beam to θ. r =-50°, θ r =0°, θ r =30° direction (pointing accuracy better than ±2°), and at the same time, compared with the RCS of the same large curved copper plate, the RCS of CAM in the control state is 9.7dB, 6.9dB, and 6.4dB in the preset reflection direction, realizing dynamic control of the target RCS;

[0090] Based on the beam deflection control of electromagnetic waves by CAM in the X direction, the multi-dimensional control of electromagnetic waves by CAM is further analyzed. Furthermore, the control of the encoded gradient metasurface in the Y direction and the two-dimensional metasurface is analyzed, leading to the conclusion that the phase distribution of the metasurface must satisfy a linear relationship to achieve beam deflection in three-dimensional space.

[0091]

[0092] According to formula (5), on the two-dimensional metasurface, based on the incident angle of the electromagnetic wave and the angle to be reflected, the phase gradient required along the x and y directions is designed by designing the bias voltage of the varactor diode in the unit structure. Used to control the propagation direction of electromagnetic waves in three-dimensional space;

[0093] like Figure 7 To demonstrate the functionality of PCM-CAM at a frequency of 10GHz, a preset reflection angle θ is used. r =30°, the angle of incidence is θ i =0°, by applying phase gradients along the X, Y, and XY directions and Achieve, (a)-(c) the phase distribution of CAM, (d)-(i) the corresponding far-field 3D scattering distribution for beam control, such as Figure 7 As shown, this illustrates the propagation direction control characteristics of the designed two-dimensional metasurface in three-dimensional space. Figure 7 (a)-(b) represent the incident angle θ i When the angle is 0°, design phase gradients along the x and y directions and the XY direction respectively. The resulting expected reflection angle θ r The phase distribution corresponding to CAM at 30°. Figure 7 (d)-(f), Figure 7 (g)-(i) represent the far-field 3D scattering diagrams corresponding to the beam modulation achieved, which can realize flexible control of the propagation direction of electromagnetic waves in three-dimensional space. It can be seen that if different phase gradients are set in the two-dimensional direction, the propagation direction of electromagnetic waves in three-dimensional space can be flexibly controlled.

[0094] S6, PCM-CAM Sample Fabrication and Experimental Verification

[0095] like Figure 8 The experimental setup of PCM-CAM and its far-field scattering directions at different incident angles are shown. The figure includes a photograph of the prototype, a schematic diagram of the experimental setup, and scattering direction diagrams measured at different angles.

[0096] A detailed prototype identical to the simulation model was fabricated using low-cost printed circuit board technology, and the required varactor diodes were soldered in the corresponding locations to verify the practicality of the CAM. Figure 8 As shown in (a), the far-field experiment of the prototype was conducted in a microwave anechoic chamber. The experimental setup included a vector network analyzer (VNA), a linearly polarized (LP) horn antenna, an FPGA, and a turntable support. These components together constituted a complete test environment for measuring the electromagnetic response of the prototype under different incident conditions, such as... Figure 8 As shown in (b) Figure 8 (c)-(k) show the different incident angles θ i and reflection angle θ r The far-field scattering pattern below,

[0097] The prototype and the transmitting horn antenna connected to VNA port 1 are fixed on a turntable support, while the receiving horn antenna connected to VNA port 2 is placed at a sufficiently far distance so that it can rotate around the prototype for measurement, thus presenting the measurement sample at different incident angles θ. i and deflection angle θ r The far-field scattering pattern is shown below, with different incident angles θ in the experiment. i and deflection angle θ rThe coding sequence is the same as that designed in the simulation, and is dynamically controlled by the connected FPGA. In each sub-graph, a curve is used to represent the far-field scattering pattern at a specific deflection angle, and the vertical line indicates the theoretically predicted scattering direction. When the deflection angle of the scattered beam is close to the theoretical value at different incident angles, and the deflection angle error is 1°, this is used to verify the effectiveness of CAM. However, there is a certain deviation between the experimental results and the theoretical value. This may be due to the inaccurate placement of the experimental device, the inaccuracy of the varactor diode performance, and the unavoidable manufacturing errors in PCB processing and soldering. But overall, the experimental results are consistent with the theoretical prediction, which strongly proves the feasibility of the proposed CAM.

[0098] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. The terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, unless otherwise explicitly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Moreover, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0099] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A phase-tuned conformal active metasurface, characterized in that: The metasurface unit is composed of a metal layer and a dielectric layer. The metal layer includes a metal structure layer and a metal backplate layer. The dielectric layer includes an F4B dielectric substrate and an ABS dielectric layer. The metasurface unit is arranged from top to bottom as a metal structure layer, an F4B dielectric substrate, an ABS dielectric layer, and a metal backplate layer. The metal structure layer is externally connected to a power supply structure using circular through-hole technology to adjust the voltage across the varactor diode.

2. The phase-tuned conformal active metasurface according to claim 1, characterized in that: The unit structure period of the metasurface unit is p = 10 mm.

3. The phase-tuned conformal active metasurface according to claim 1, characterized in that: The metal structure layer consists of two rectangular structures forming an H-shaped metal patch, with the center of the H-shaped metal patch designated as the loading position for an active device. A PIN diode is integrated between the two rectangular structures.

4. The phase-tuned conformal active metasurface according to claim 1, characterized in that: The thickness of the F4B flexible dielectric substrate is set to 0.1 mm, the relative permittivity of the F4B flexible dielectric substrate is set to 2.67, and the loss tangent of the F4B flexible dielectric substrate is set to 0.

001.

5. The phase-tuned conformal active metasurface according to claim 1, characterized in that: The thickness of the ABS dielectric layer is set to 3 mm, the relative permittivity of the ABS dielectric layer is set to 2.65, and the loss tangent of the ABS dielectric layer is set to 0.

005.

6. The phase-tuned conformal active metasurface according to claim 1, characterized in that: The metal layers are all made of copper, and the thickness is set to 0.018 mm.

7. The phase-tuned conformal active metasurface according to claim 3, characterized in that: The width of the two rectangular structures on the left and right sides of the metal structure layer is set to a = 12 mm, and the length is set to b = 10 mm. The upper and lower ends of the two rectangular structures are provided with through holes with a diameter of s = 4.67 mm. The gap between the upper and lower ends of the two rectangular structures is set to f = 8 mm, and the gap between the middle parts of the two rectangular structures is set to f = 5 mm.

8. The phase-tuned conformal active metasurface according to claim 1, characterized in that: The PIN diode is configured as SMV1430-040LF.

9. The wideband and wide-angle RCS continuously dynamically adjustable conformal active metasurface according to any one of claims 1-8, characterized in that, The following steps are included: S1, Analysis of Metasurface Units The equivalent circuit parameters of the varactor diodes under different DC biases were calculated by establishing a Spice model in the commercial software ADS. This was used to obtain the equivalent parameters of the RLC. The extracted equivalent parameters were then used as simulation data. The reflection phase of the metasurface unit under the condition of perpendicular incident x-polarized wave was simulated in the commercial software CST Microwave Studio. The results were obtained. In the simulation, the center operating frequency was selected as 10 GHz. Different effective circuit parameters were used to adapt to different feed voltages. By adjusting the voltage, the phase response between different units was changed for flexible beam control. S2, Beam Control By arranging coding units with specific phase differences in a two-dimensional plane, a metasurface can carry binary sequences to express coded information, thus constructing a programmable metasurface. Different coding sequences provide different electromagnetic wave manipulation capabilities. The realization of the reflective metasurface follows the generalized law of reflection. In the formula, θ r and θ i Here, θ represents the angle of reflection and the angle of incidence, respectively, and λ0 is the wavelength of the electromagnetic wave in free space. Let be the phase gradient of the metasurface along the x-direction. According to formula (1), the phase distribution of the metasurface must satisfy a linear relationship to achieve beam deflection: According to formulas (1) and (2), a specific phase gradient is selected. Reflection angle θ r It is constant, and at the same time, it changes with the incident angle θ. i Changes in reflection angle θ r Then it will change; S3, OAM generation Due to its unique phase structure, a vortex beam carrying orbital angular momentum can simultaneously transmit signals of several different OAM modes at the same frequency. Because of its phase singularity, the vortex beam exhibits an extremely low radar cross-section. The vortex phase distribution, based on orbital angular momentum theory, is used to achieve OAM generation. The phase distribution of the metasurface must satisfy a helical relationship. For discrete metasurface units, the phase distribution can be discretized as follows: In the formula, (x i y i (x0, y0) represents the position of the element in the metasurface, (x0, y0) represents the center coordinates of the metasurface, and l represents the number of topological charges carried. S4, Curvature Compensation Phase Correction Algorithm When electromagnetic waves strike an irregularly curved metal surface, they are reflected in various directions, exhibiting a different wavefront than that of planar metal. This allows for effective control of the reflection direction of reflected waves from curved targets. Conformal active metasurfaces with specific phase distributions can be applied to the curved target to achieve flexible control of the incident electromagnetic waves. Based on formula (2), the incident angle of the planar active metasurface can be calculated to be θ. i The incident wave is reflected at a reflection angle of θ. r Required phase distribution in direction Based on the perpendicular distance h between the conformal active metasurface and the planar active metasurface, the phase distribution that the conformal active metasurface needs to compensate for can be obtained. for: Phase distribution of conformal active metasurfaces This is the phase of a planar active metasurface. With compensation phase The sum of First, calculate the required spiral phase distribution for realizing the planar active metasurface according to formula (3). Then, calculate the phase distribution required for compensation between the conformal active metasurface and the planar active metasurface according to formula (4). The spiral phase distribution required for the generation of a conformal active metasurface is then the phase distribution of a planar active metasurface. With compensation phase The sum of By designing the geometric parameters of the unit structure and the bias voltage of the varactor diode, the desired spiral phase distribution can be achieved on the metasurface to generate OAM beams. S5, PCM-CAM Design Simulation Based on the beam deflection control of electromagnetic waves by CAM in the X direction, the multi-dimensional control of electromagnetic waves by CAM is further analyzed. Furthermore, the control of the encoded gradient metasurface in the Y direction and the two-dimensional metasurface is analyzed, leading to the conclusion that the phase distribution of the metasurface must satisfy a linear relationship to achieve beam deflection in three-dimensional space. According to formula (5), on the two-dimensional metasurface, based on the incident angle of the electromagnetic wave and the angle to be reflected, the phase gradient required along the x and y directions is designed by designing the bias voltage of the varactor diode in the unit structure. Used to control the propagation direction of electromagnetic waves in three-dimensional space; S6, PCM-CAM Sample Fabrication and Experimental Verification A detailed prototype identical to the simulation model was fabricated using low-cost printed circuit board technology, and the required varactor diodes were soldered in the corresponding locations to verify the practicality of the CAM. The prototype and the transmitting horn antenna connected to VNA port 1 are fixed on a turntable support, while the receiving horn antenna connected to VNA port 2 is placed at a sufficiently far distance so that it can rotate around the prototype for measurement, thus presenting the measurement sample at different incident angles θ. i and deflection angle θ r The far-field scattering pattern is shown below, with different incident angles θ in the experiment. i and deflection angle θ r The encoding sequence is the same as that designed in the simulation and is dynamically controlled by the connected FPGA. In each sub-graph, a curve is used to represent the far-field scattering pattern at a specific deflection angle, and the vertical line indicates the theoretically predicted scattering direction. When the deflection angle of the scattered beam is close to the theoretical value at different incident angles, and the deflection angle error is ±2°, this is used to verify the effectiveness of CAM.

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