Low-loss broadband 1-bit transmission type intelligent metasurface and dynamic beam regulation and control method

Abstract

The invention discloses a low-loss broadband 1-bit transmission type intelligent metasurface and a dynamic beam regulation and control method, and belongs to the technical field of wireless communication. The intelligent metasurface is composed of transmission type metasurface units arranged periodically, each unit comprises a receiving patch layer, a feeder line layer and a transmitting patch layer, and 1-bit phase modulation is achieved by loading a PIN diode. The transmission coefficient of the unit in the frequency band of 6.00-7.23 GHz is greater than-3dB, the transmission loss at the frequency band of 6.6 GHz is as low as-0.58 dB, and the reflection coefficient is-20.74 dB. By adjusting the phase compensation of the metasurface unit, beam focusing and beam scanning within the range of 0-30 degrees can be realized, and the gain of the feed source antenna and the efficiency of a communication system are remarkably improved. The transmission-type intelligent metasurface solves the problems that an existing transmission-type intelligent metasurface is high in loss and narrow in bandwidth, and is suitable for intelligent wireless environment regulation and control in a sixth-generation mobile communication system.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication technology, and in particular to a low-loss 1-bit transmission-type smart metasurface based on phase modulation and its application in beamforming and channel control. Background Art

[0002] Smart metasurfaces (RIS), a core technology for sixth-generation mobile communications (6G), enable intelligent reconfiguration of wireless channels by dynamically manipulating electromagnetic wave properties, offering a new paradigm for improving communication system capacity, coverage, and energy efficiency. Transmissive RIS, deployed in direct links between base stations and users, have become a key approach to enhancing signal transmission. However, their practical application faces significant challenges. Existing transmissive units generally employ a multilayer metal-dielectric stack structure. Impedance mismatch and multiple reflections result in transmission coefficients below -3dB, resulting in over 50% loss of incident energy. Furthermore, while designs relying on resonant mechanisms can achieve phase control, they are limited by their narrowband characteristics (typical bandwidth <1GHz), making them difficult to adapt to the broadband requirements of 6G communications. Furthermore, parasitic effects of traditional feed networks and active devices (such as PIN diodes) further exacerbate high-frequency signal attenuation, leading to a sharp deterioration in transmission performance at high frequencies. These challenges limit the performance of existing transmissive RIS in low-power scenarios and make them incapable of meeting the demanding requirements of high-power communications such as millimeter-waves.

[0003] On the other hand, the dynamic beam steering capabilities of transmissive RISs (RISs) urgently need improvement. Existing technologies often design phase compensation algorithms based on plane wave approximations. However, in real-world scenarios, the spherical wavefront radiated by the feed antenna introduces significant phase errors, resulting in beam pointing deviations exceeding 10°. Furthermore, limited by the number of elements (typically ≤8×8) and the number of independent control channels, existing systems only support fixed beams or static scanning within a limited angle (±15°), lacking the dynamic adaptive capability to respond to channel changes in real time. On the hardware side, the multi-layer stacked structure results in large element sizes (typically >0.3λ), limiting array integration and response speed. The switching delay (1-10μs) of traditional varactor diodes or mechanical adjustment schemes further restricts their application in high-speed mobile scenarios. These shortcomings make it difficult for transmissive RISs to achieve high-precision beamforming, severely hindering their practical application in dynamic environments such as the Internet of Vehicles and the Industrial Internet of Things. Therefore, a transmissive smart metasurface with low loss, broadband response, and dynamic wavefront compensation is urgently needed to overcome existing technological bottlenecks and promote the practical deployment of 6G communication systems. Summary of the Invention

[0004] Technical issues:

[0005] The present invention aims to solve the problems of high loss, narrow bandwidth and insufficient beam control capability of existing transmission-type intelligent metasurfaces.

[0006] Technical solution:

[0007] To address these technical issues, the present invention proposes a low-loss, broadband, 1-bit transmissive smart metasurface. The core structure of this invention is a metasurface composed of multiple subwavelength-scale units arranged in a specific pattern, forming a two-dimensional, ultra-thin artificial surface. Each unit receives a dedicated control signal.

[0008] The low-loss 1-bit transmission-type smart metasurface specifically includes: an array composed of M×N periodic transmission units; each transmission unit includes five metal layers and five dielectric layers, which are, from top to bottom, a receiving patch layer, a first metal ground layer, a feeder layer, a second metal ground layer, and a transmitting patch layer; the receiving patch layer is loaded with two PIN diodes (PIN1 and PIN2), and the two coding states of "0" and "1" are realized by controlling the on and off states of the diodes, and the transmission phase difference between the two states is 180°±10°; the transmission coefficient of the unit is greater than -3dB and the reflection coefficient is less than -10dB in the 6.00-7.23GHz frequency band.

[0009] Preferably, the receiving patch layer is a hollow H-shaped patch, and the transmitting patch layer is a hollow U-shaped patch, and the receiving patch and the transmitting patch are connected through a central feeding copper column.

[0010] Preferably, the feeder layer is composed of two 60° sector-shaped copper sheets and feeders, and is used to isolate AC signals and conduct DC control signals.

[0011] Preferably, the dielectric material of the receiving patch layer and the transmitting patch layer is F4B (dielectric constant 2.65, loss tangent 0.0015), and the metal formation medium is Rogers RO4450F (dielectric constant 3.7, loss tangent 0.004).

[0012] Preferably, the array controls the on-off state of each unit PIN diode through a field programmable gate array (FPGA) to achieve a dynamic beamforming function.

[0013] Preferably, the array can perform phase compensation on the spherical wavefront of the feed antenna to achieve beam focusing and beam scanning within a range of ±30°.

[0014] Preferably, the unit size is 13.17 mm×11.64 mm, the transmission loss at 6.6 GHz is as low as -0.58 dB, and the reflection coefficient is -20.74 dB.

[0015] Preferably, the array supports microsecond-level (<10 μs) unit state switching, which is suitable for dynamic channel reconstruction in vehicle networking and drone communication scenarios.

[0016] Preferably, the PIN diode is model MADP-000907-14020.

[0017] The present invention also provides a dynamic beam steering method, which is applied to the smart metasurface, comprising the following steps:

[0018] Calculate the required compensation phase of each unit based on the spherical wave phase compensation formula;

[0019] The state of each unit is controlled by FPGA to generate precoding phase distribution;

[0020] Achieve beam focusing and dynamic beam scanning within the range of 0° to 30°.

[0021] Preferably, the phase compensation formula is:

[0022]

[0023] The position of unit N on the transmissive smart metasurface is expressed as N(x n ,y n ,z n ), R is the distance between the transmission type intelligent metasurface unit and the feed antenna, k0 is the spatial wave vector, θ n and are the azimuth and elevation angles of the incident wave, respectively.

[0024] Beneficial effects:

[0025] 1. Ultra-low transmission loss: At the 6.6GHz operating frequency, the transmission coefficient reaches -0.58dB and the reflection coefficient is as low as -20.74dB, which is more than 1.2dB higher than the energy efficiency of existing transmission metasurfaces, and the energy utilization rate exceeds 90%;

[0026] 2. Broadband and efficient response: 3dB bandwidth extends to 1.23GHz (6.00-7.23GHz), with a relative bandwidth of 18.6%, covering the 6G communication core frequency band and supporting multi-band collaborative operation;

[0027] 3. High-precision beam steering: Based on the spherical wave phase compensation algorithm, it achieves beam scanning in the range of 0° to 30°, with a main lobe gain ≥16.7dBi, a 3dB beam width ≤13.7°, and a pointing accuracy error ≤1.5°;

[0028] 4. Polarization compatibility optimization: The 45° tilted polarization design suppresses cross-polarization interference in multipath environments and improves polarization matching with existing base station antennas by 40%;

[0029] 5. Dynamic real-time response: FPGA controls 100 independent channels, supports microsecond-level (<10μs) unit state switching, realizes dynamic beam tracking and adaptive channel reconstruction, and meets the needs of high-speed scenarios such as Internet of Vehicles and UAV communications. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the phase compensation of the transmission-type intelligent metasurface in the present invention, showing the geometric relationship between the feed antenna and the metasurface array, and explaining the principle of phase compensation;

[0031] Figure 2 This is a diagram of the working mechanism of the transmissive intelligent metasurface in the present invention, showing the electromagnetic wave transmission path of the unit in the "0" and "1" states, and demonstrating the flow direction of the PIN diode on-off control signal and the phase modulation principle;

[0032] Figure 3 Exploded diagram of the unit structure and layer design of the designed metasurface: (a) Exploded diagram of the five-layer metal-dielectric stack structure; (b) Layout of the receiving patch layer and diode loading position; (c) Fan-shaped copper patch design of the feeder layer; (d) U-shaped radiation structure of the transmitting patch layer;

[0033] Figure 4 Simulation diagram of the S parameters and phase response of the designed metasurface unit: (a) frequency response curves of the transmission coefficient (S21) and reflection coefficient (S11); (b) phase difference between the two states (180°±5°);

[0034] Figure 5 Current distribution diagram of the upper patch of the designed metasurface at 6.6 GHz: (a) In State "0", the current flows from the outer patch to the inner patch; (b) In State "1", the current flows in the opposite direction, forming a symmetric topology;

[0035] Figure 6 This is a simulation model of the metasurface beam focusing system in the present invention, showing the spatial layout and beam steering model of the 10×10 metasurface array and feed horn antenna;

[0036] Figure 7 This is the binary phase coding distribution diagram corresponding to different emission angles (θ = 0°, 10°, 20°, 30°) in the present invention;

[0037] Figure 8 The far-field beam simulation pattern of the metasurface in the present invention shows the gain distribution and main lobe directivity at different beam angles;

[0038] Figure 9 The experimental samples and test environment in this invention: (a) the actual image of the processed metasurface; (b) the test system and instrument configuration in the darkroom;

[0039] Figure 10 Comparison of measured and simulated performance in the present invention: (a) measured results of transmission / reflection coefficients; (b) phase difference verification of the two states;

[0040] Figure 11 This is a schematic diagram of the beam focusing test system in the present invention, showing the far-field test layout of the transmitting end (metasurface + feed) and the receiving end (standard horn antenna);

[0041] Figure 12 The radiation beam gain and measured far-field pattern of the metasurface system at different coding angles in the present invention. DETAILED DESCRIPTION

[0042] This invention provides a low-loss, 1-bit, transmissive intelligent metasurface design based on phase modulation. Its core is to achieve dynamic control of electromagnetic beams through a programmable unit structure. The following describes the specific implementation of this invention in detail, with reference to the accompanying figures. It begins with the principle of phase compensation for the metasurface and then gradually explains the entire process from unit structure design, simulation verification, to actual testing.

[0043] First, refer to Figure 1 As shown in the phase compensation diagram, the present invention needs to establish a phase matching model between the feed antenna and the metasurface array. When the spherical wave emitted by the feed antenna propagates to the metasurface, each unit needs to compensate for the phase difference between the incident wave and the target plane wave. Specifically, suppose the metasurface array consists of i×j units, and the phase compensation amount of unit N is It can be calculated by the formula:

[0044]

[0045] Where R is the distance between the transmission-type smart metasurface unit and the feed antenna, k0 is the spatial wave vector, θ n and are the azimuth and elevation angles of the incident wave, respectively. This model can be used to predetermine the phase distribution of each unit, providing a theoretical basis for subsequent unit design.

[0046] Next, in order to achieve the above phase compensation, a 1-bit transmission unit structure needs to be designed. Figure 2 As shown, the unit consists of four layers: a receiving patch, a metal ground, a feeder layer, and a transmitting patch. PIN diodes switch the electromagnetic wave transmission path. When PIN1 is on and PIN2 is off ("0" state), the electromagnetic wave is transmitted from the receiving patch via the feed copper pillar to the transmitting patch. When PIN2 is on and PIN1 is off ("1" state), the transmission path is reversed, resulting in a 180° phase difference between the two states. The key to this design is the symmetrical structure that achieves phase reversal while minimizing insertion loss.

[0047] Further, Figure 3 The layered structure and material parameters of the unit are shown in detail. The receiving patch layer and the transmitting patch layer are connected by copper pillars with a diameter of 0.75mm, and the dielectric layer is made of F4B material (ε r =2.65, tanδ=0.0015), thickness is 2.50mm. r =3.7) and RO4350B(ε r =3.66) materials, with thicknesses of 0.16mm and 0.17mm respectively. This laminate design effectively suppresses surface wave losses by optimizing the dielectric constant distribution, ensuring stable performance at high frequencies.

[0048] After completing the unit design, its electromagnetic characteristics need to be verified through simulation. Figure 4 The S-parameter simulation results show that in the 6.00-7.23GHz frequency band, the transmission coefficient is greater than -3dB, reaching -0.58dB at 6.6GHz, and the reflection coefficient is as low as -20.74dB, meeting the low loss requirement. At the same time, the phase difference between the "0" and "1" states is within the range of 180°±10°, meeting the 1-bit phase control accuracy requirement. In order to further analyze the mechanism, Figure 5 The current distribution at 6.6 GHz is demonstrated: in the "0" state, the current flows from the outer patch to the inner patch; in the "1" state, the opposite is true, forming a symmetrical current, verifying the physical mechanism of phase reversal.

[0049] The present invention is based on unit performance verification, which requires building a large-scale array and testing the beam steering capability. Figure 6 As shown in Figure 1, a metasurface array model of the unit was built and placed 247.95 mm in front of the feed horn antenna (5-8 GHz, gain 15.8 dB). The phase encoding table was set using CST simulation software, as shown in Figure 1. Figure 7 , the beam is scanned from 0° to 30° in the phi=0° plane. The simulation results are as follows Figure 8 It shows that at 6.6GHz, the mainlobe gain reaches more than 16.7dBi, the 3dB beamwidth is less than 13.7°, which is 1.2dBi higher than the original antenna gain, and the sidelobe level is lower than -10dB, proving that the array has excellent beam focusing capability.

[0050] Subsequently, the feasibility of the design of the present invention needs to be verified through experiments. Figure 9 As shown in the figure, when processing the unit sample, the PIN diode was soldered using surface mount technology and connected to the customized control board. The test was carried out in a microwave darkroom, and the S parameters and far-field radiation pattern were measured using a vector network analyzer. The measured results are shown in the figure. Figure 10It shows that the reflection coefficient in the 6.06-7.17 GHz frequency band is less than -10 dB, and the transmission coefficient is about 2 dB lower than the simulation, but the phase difference is still stable at 180°±10°, indicating that the actual processing error is within the controllable range.

[0051] Finally, through Figure 11 The test system measures the far-field pattern of the sample. The transmitting end is composed of a metasurface sample and a feed antenna, and the receiving end uses a broadband horn antenna and a rotating stage to achieve omnidirectional scanning. The test results are as follows: Figure 12 It shows that at coding angles of 0°, 10°, 20°, and 30°, the deviation between the main lobe pointing of the beam and the preset angle is less than 2°, the side lobe level is maintained below -12dB, and the measured gain reaches 15.3dBi, which is more than 90% consistent with the simulation results, fully verifying the engineering practicality of the present invention.

[0052] The core concepts, main features and advantages of the present invention have been fully explained in the foregoing. Based on the above technical solutions, the present invention has significant innovation and practicality in solving some key problems in the prior art. In order to ensure the wide applicability and technical coverage of the present invention, all reasonable modifications, improvements and innovations should be regarded as part of the present invention and included in its scope of protection without departing from the essence and technical scope of the present invention. Therefore, the specific scope of protection should be clearly defined by the attached claims and their equivalents to ensure that the legitimate rights and interests of the present invention are fully protected.

Claims

1. A low-loss 1-bit transmissive smart metasurface, characterized in that: include: An array consisting of M×N periodic transmission units; each transmission unit includes five metal layers and five dielectric layers, namely, from top to bottom, a receiving patch layer, a first metal ground layer, a feeder layer, a second metal ground layer, and a transmitting patch layer. The receiving patch layer is loaded with two PIN diodes (PIN1 and PIN2), which are controlled to achieve two coding states of "0" and "1" by controlling the on and off states of the diodes. The transmission phase difference between the two states is 180°±10°. The unit has a transmission coefficient greater than -3dB and a reflection coefficient less than -10dB in the 6.00-7.23GHz frequency band.

2. The smart metasurface according to claim 1, wherein: The receiving patch layer is a hollow H-shaped patch, and the transmitting patch layer is a hollow U-shaped patch. The receiving patch and the transmitting patch are connected through a central feeding copper column.

3. The smart metasurface according to claim 1, wherein: The feeder layer consists of two 60° sector-shaped copper sheets and feeders, and is used to isolate AC signals and conduct DC control signals.

4. The smart metasurface according to claim 1, wherein: The dielectric material of the receiving patch layer and the transmitting patch layer is F4B (dielectric constant 2.65, loss tangent 0.0015), and the metal layer medium is Rogers RO4450F (dielectric constant 3.7, loss tangent 0.004).

5. The smart metasurface according to claim 1, wherein: The array controls the on-off state of each unit PIN diode through a field programmable gate array (FPGA) to achieve a dynamic beamforming function.

6. The smart metasurface according to claim 1, wherein: The array can perform phase compensation on the spherical wavefront of the feed antenna to achieve beam focusing and beam scanning within a range of ±30°.

7. The smart metasurface according to claim 1, wherein: The unit size is 13.17mm×11.64mm, the transmission loss at 6.6GHz is as low as -0.58dB, and the reflection coefficient is -20.74dB.

8. The smart metasurface according to claim 1, wherein: The array supports microsecond-level (<10μs) unit state switching and is suitable for dynamic channel reconstruction in vehicle networking and drone communication scenarios.

9. A dynamic beam steering method, applied to the smart metasurface according to any one of claims 1 to 8, characterized in that: The following steps are involved: Calculate the required compensation phase of each unit based on the spherical wave phase compensation formula; The state of each unit is controlled by FPGA to generate precoding phase distribution; Achieve beam focusing and dynamic beam scanning within the range of 0° to 30°.

10. The method according to claim 9, characterized in that The phase compensation formula is: The position of unit N on the transmissive smart metasurface is expressed as N(x n ,y n ,z n ), R is the distance between the transmission type intelligent metasurface unit and the feed antenna, k0 is the spatial wave vector, θ n and are the azimuth and elevation angles of the incident wave, respectively.

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