An ultra-surface based on dual-frequency independent regulation

Abstract

The application discloses a kind of based on dual-frequency independent regulation's metasurface, including nested unit topology metasurface array board, nested unit topology metasurface array board is composed of metasurface unit, metasurface unit is divided into independent low frequency band and high frequency band;Low frequency band and high frequency band are respectively controlled by FPGA control system using different array regulation strategy, control low frequency band execution unit independent control, meet the real-time positioning and tracking demand of mobile target by high-precision beam scanning;While controlling high frequency band execution column level control, realize wideband double beam scanning.The application realizes low-frequency high-precision beam scanning positioning and high-frequency wideband low-loss double beam scanning by nested unit topology, parasitic metal decoupling structure and different array control, can meet the integrated application of mobile target tracking and multidirectional beam coverage.

Description

Technical Field

[0001] This invention belongs to the field of wireless communication system technology, and specifically relates to a metasurface based on dual-frequency independent control. Background Technology

[0002] Traditional wireless communication systems face significant challenges in terms of spectrum resource utilization, communication reliability, dynamic environmental adaptability, and energy supply. Particularly in complex electromagnetic environments and high-density terminal access scenarios, achieving integrated coordination of wireless communication, spatial sensing, and energy regulation has become a crucial research direction for next-generation communication systems.

[0003] In recent years, Reconfigurable Intelligent Surfaces (RIS) have gradually become one of the key candidate technologies for 6G due to their flexible electromagnetic wave manipulation capabilities. RIS is essentially a two-dimensional artificial structure composed of a large number of subwavelength artificial electromagnetic units. By dynamically controlling the reflection amplitude, phase, polarization, and frequency response of these units, it can actively reconstruct the propagation path of electromagnetic waves in space. Unlike traditional communication systems that rely on active transmission via radio frequency links, RIS does not require complex active transmission structures. It can achieve beamforming, beam scanning, spatial focusing, and interference suppression simply by controlling the reflection, scattering, or transmission of incident electromagnetic waves. Therefore, it has advantages such as low power consumption, low cost, and easy integration.

[0004] However, most traditional RIS research focuses on single-band control, where metasurfaces achieve phase or amplitude control only around a fixed frequency. While these single-band metasurfaces have relatively simple structural designs, their functions are limited and cannot meet the needs of future multi-task collaborative communication systems. Existing dual-band metasurface designs also face numerous technical bottlenecks. On one hand, because electromagnetic structures of different frequency bands typically share the same physical space, strong electromagnetic coupling easily occurs between high- and low-frequency units, leading to severe inter-band interference and affecting control accuracy and operational stability. Most dual-band structures can only achieve frequency reuse, making it difficult to truly achieve independent dynamic control of the two frequency bands. On the other hand, metasurfaces have limited functionality in complex mobile scenarios, rarely achieving differentiated division of labor between the two frequency bands within the same aperture.

[0005] In N. Zhang et al., "A Dual-Polarized Reconfigurable Reflect array Antenna Based on Dual-Channel Programmable Metasurface," in IEEE Transactions on Antennas and Propagation, vol. 70, no. 9, pp. 7403-7412, Sept. 2022, the metasurface unit extends the current path of the unit through slotting and gradation, thereby improving the dual-frequency phase response at 6.6 GHz and 12.3 GHz. Furthermore, the unit incorporates two PIN diodes, enabling a 2-bit phase adjustment resolution and improving the precision of electromagnetic wave control. The limitation of this unit is that it only achieves column control of the array and cannot achieve independent control of all units.

[0006] No one has yet studied how to achieve independent control and differentiated function of the two frequency bands in the design of dual-band independently tunable metasurfaces. Summary of the Invention

[0007] In order to overcome the shortcomings of the existing technology, the present invention aims to provide a metasurface based on dual-frequency independent control. Through nested unit topology, parasitic metal decoupling structure and differentiated array control, it can realize low-frequency high-precision beam scanning positioning and high-frequency broadband low-loss dual-beam scanning, which can meet the integrated application of moving target tracking and multi-directional beam coverage.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A metasurface based on independent dual-frequency control includes a nested unit topology metasurface array plate, which is composed of metasurface units, and the metasurface units are divided into independent low-frequency bands and high-frequency bands; The low-frequency band and high-frequency band adopt differentiated array control strategies through the FPGA control system. The low-frequency band execution unit is controlled independently, and the real-time positioning and tracking requirements of moving targets are met through high-precision beam scanning. Simultaneously, the high-frequency band is controlled to perform column-level control, achieving broadband dual-beam scanning.

[0009] By independently controlling the phase state of each low-frequency band, a fine spatial phase gradient is constructed on the surface of the nested unit topology metasurface array, enabling precise in-phase superposition of spatial electromagnetic waves in the target direction, thus achieving high-precision beam deflection and energy convergence.

[0010] The metasurface unit includes a dielectric plate T1, a PP adhesive layer and a dielectric plate T2 arranged sequentially from top to bottom along the Z-axis. The upper surface of the dielectric plate T1 is coplanarly nested with a low-frequency structure and a high-frequency structure. The low-frequency structure and the high-frequency structure can each be independently controlled by 1-bit phase dynamic adjustment.

[0011] The low-frequency structure includes an open-ended resonant ring located on the periphery, with a gap provided on the side of the open-ended resonant ring opposite to the opening, and a low-frequency diode D1 matched at the gap.

[0012] Leads extend from both ends of the open resonant ring near the opening, and the ends of the leads are connected to metal through holes for connection to the ground plane or DC bias.

[0013] The low-frequency diode D1 is installed in the gap of the outer open-circuit resonator, with its two ends connected to the metal parts on the left and right sides of the open-circuit resonator respectively, and connected to the low-frequency control terminal of the FPGA through an independent bias line. When the low-frequency diode D1 is turned on, the current path of the open-circuit resonator is closed, and when it is turned off, the current of the open-circuit resonator is cut off at the opening, thereby changing the low-frequency resonance state and realizing 1-bit reflection phase modulation in the approximately 11.3–12.5 GHz frequency band.

[0014] The high-frequency structure is located inside the open-loop resonant ring and includes a central metal rectangular patch. Two symmetrical cut slits are made on the metal rectangular patch to form three rectangular patches. The common central axis of the three rectangular patches is the line connecting the opening of the open-loop resonant ring and the midpoint of the slit. The slit is bridged by two identical PIN diodes, and the two identical PIN diodes are arranged to the left and right along the central rectangular patch. The PIN diodes are the upper high-frequency diode D2 and the lower high-frequency diode D3, respectively. The upper high-frequency diode D2 is connected across the upper horizontal slot of the central rectangular patch, with its two ends connected to the upper patch and the middle patch respectively. When the upper high-frequency diode D2 is turned on, the upper patch and the middle patch form a continuous current path. When it is turned off, the current needs to travel along the edge of the slot, thereby changing the equivalent electrical length and high-frequency phase response of the upper half of the central patch. The lower high-frequency diode D3 is connected across the lower horizontal gap of the central rectangular patch, with its two ends connected to the middle patch and the lower patch respectively. The switching of the lower high-frequency diode D3 mainly changes the current path of the lower half of the central patch, and together with the upper high-frequency diode D2, it completes the phase switching of the high-frequency band.

[0015] Parasitic metal decoupling structures are set on both sides of the metal rectangular patch and inside the open resonant ring. The parasitic metal decoupling structures are symmetrical about the unified central axis and isolated from each rectangular patch. They are used to change the current distribution pattern and electromagnetic coupling path on the surface of the metasurface unit. The parasitic metal decoupling structures are two parasitic metal strips.

[0016] A bias line network is provided on the lower surface of the dielectric substrate T2, including a slender feed line bar arranged in the lower layer of the dielectric substrate T2. The slender feed line bar is used as the X-axis reference line, with the center as the zero point. A longitudinal line is set along the negative Y-axis direction of the center. The end of the longitudinal line is connected to a metal through hole. The metal through hole passes through the dielectric substrate T1, the PP adhesive layer and the dielectric substrate T2, and is connected to the control terminals of the upper high-frequency diode D2 and the lower high-frequency diode D3 (two high-frequency PIN diodes connected on the central rectangular patch).

[0017] A bias trace is also provided on the lower surface of dielectric substrate T2. The bias is set along the negative Y-axis and located on the edge of dielectric substrate T2 in the negative X-axis direction. A fan-shaped structure is provided on the bias trace, and the fan-shaped structure serves as a bypass capacitor structure.

[0018] The low-frequency ring structure is used to achieve 1-bit high-precision beam scanning and positioning in the 11.3-12.5GHz frequency band. The impedance of the resonant circuit is adjusted by controlling the on and off of the low-frequency diode D1 (the low-frequency PIN diode on the outer open resonant ring) at the opening, thereby generating a phase difference of 180°±30°.

[0019] The high-frequency structure is used to achieve broadband low-loss dual-beam scanning in the 18.5-21.7GHz band. By switching the diodes bridged between the gaps, the surface current path is forced to change symmetrically, and the difference in current distribution is directly converted into a phase jump in the high-frequency band.

[0020] The low-frequency diode D1, the upper high-frequency diode D2, and the lower high-frequency diode D3 (all three PIN diodes) are connected to the control unit FPGA, which is used to independently switch the operating states of the high-frequency and low-frequency diodes in real time.

[0021] The beneficial effects of this invention are: This invention proposes a metasurface design based on independent dual-frequency control. By introducing a parasitic metal strip decoupling module through an innovative unit topology, a dual-frequency independently controllable multiplexed channel is constructed for the wireless system. This channel is completely separated in terms of spectrum allocation and electromagnetic response mechanism, thus avoiding signal crosstalk and spectrum conflict at the physical level.

[0022] By specifically designing a dual-band structure, this invention effectively overcomes the shortcomings of traditional single-band metasurfaces, such as limited functionality and adaptability. Simultaneously, it achieves differentiated division of labor between the two bands: the low-frequency band utilizes high-precision phase modulation to achieve low-loss beam scanning, meeting the real-time positioning and tracking requirements of moving targets; the high-frequency band enables broadband dual-beam scanning, significantly improving electromagnetic coverage and anti-interference capabilities, providing wireless systems with stronger signal enhancement and multi-scenario adaptability, thus possessing significant theoretical innovation value and promising engineering application prospects. Attached Figure Description

[0023] Figure 1 A schematic diagram of a metasurface with independent dual-frequency control.

[0024] Figure 2 (a) Perspective view (b) Top view (c) Bottom view of the designed metasurface unit geometry.

[0025] Figure 3 The high-frequency phase response before and after adding the metal strip.

[0026] Figure 4 This is a comparison diagram of high-frequency phases with and without low-frequency unit structures.

[0027] Figure 5 The high-frequency current response of the unit is shown in (a) without parasitic metal strips and (b) with parasitic metal strips.

[0028] Figure 6 The reflection coefficient and phase of the unit in (a) the low-frequency band and (b) the high-frequency band.

[0029] Figure 7 The design is for a 15×15 metasurface array.

[0030] Figure 8 (a) Low-frequency unit-controlled beam deflection (b) High-frequency train-controlled dual-beam deflection. Detailed Implementation

[0031] The present invention will now be described in further detail with reference to the accompanying drawings.

[0032] A metasurface based on dual-frequency independent control focuses on the needs of millimeter-wave communication and Internet of Things collaborative systems. Through nested unit topology, parasitic metal decoupling structure and differentiated array control, it realizes low-frequency high-precision beam scanning positioning and high-frequency broadband low-loss dual-beam scanning, which can meet the integrated application of mobile target tracking and multi-directional beam coverage. According to the appendix Figure 1As shown, the system relies on a central nested unit topology metasurface array board to achieve efficient integration of high and low frequency signal processing functions under the same physical aperture. To ensure stable parallel operation of dual tasks, a parasitic metal decoupling structure introduced in the design completely severs the electromagnetic coupling between the high and low frequency bands at the physical level, avoiding signal crosstalk and spectral conflicts, and ensuring the absolute independence of the dual-frequency channels. In terms of overall scheduling, the FPGA control system on the left adopts a differentiated array control strategy, directing the low-frequency band execution units to control independently, meeting the real-time positioning and tracking requirements of moving targets through high-precision beam scanning; at the same time, it arranges the high-frequency band execution units for column-level control to achieve broadband dual-beam scanning, thereby significantly improving the electromagnetic space coverage and system anti-interference capability. Ultimately, this design perfectly balances control accuracy and engineering feasibility while reducing hardware complexity, achieving compatibility and collaborative operation of communication and positioning functions under the same aperture. The principle of low-frequency high-precision beam scanning is based on independent unit control. By independently controlling the phase state of each low-frequency unit, a fine spatial phase gradient is constructed on the array surface, enabling precise in-phase superposition of spatial electromagnetic waves in the target direction, thereby achieving high-precision beam deflection and energy convergence.

[0033] The principle of high-frequency broadband low-loss dual-beam scanning is based on parasitic metal strip optimization and column-level control. On the one hand, the parasitic metal strip optimizes impedance matching by guiding high-density current concentration, controlling transmission loss to within 2dB and widening the bandwidth to over 3GHz. On the other hand, the high-frequency column-level control mode, under vertical plane wave illumination, due to the inherent symmetry of the 1-bit phase distribution, will inevitably generate two symmetrical beams in the far field after spatial Fourier transform, thus forming dual-beam coverage, which can meet the integrated application of moving target tracking and multi-directional beam coverage.

[0034] The differentiated array consists of 15×15 metasurface units, which is reflected in the use of two completely different control modes for the high and low frequency bands on the same physical array board: "independent unit control" for the low frequency band and "column-level control" for the high frequency band. A schematic diagram is shown below. Figure 1 As shown.

[0035] Nested unit topology: The spatial layout of metasurface units in terms of physical form. Its core is a nested integrated system composed of an outer low-frequency ring structure (open resonant ring) and an inner high-frequency strip structure (metal central rectangular patch). 1. Achieving physical isolation and independent control, the system cleverly places the response structures of two different frequency bands under the same aperture, thus achieving complete isolation of high and low frequency electromagnetic responses.

[0036] 2. Solving the frequency band coupling problem: It ensures that both frequency bands can be independently dynamically controlled with 1-bit phase, successfully overcoming the technical problem that high and low frequency bands in traditional multi-frequency metasurfaces are prone to mutual coupling and functional interference.

[0037] Parasitic metal decoupling structure: changes the current distribution pattern and electromagnetic coupling path on the unit surface; 1. Complete frequency band decoupling: The parasitic metal strip can effectively suppress the interference of the low-frequency structure on / off state on the high-frequency signal transmission path, reduce the electromagnetic coupling between the two frequency bands, and achieve true independent operation.

[0038] 2. Significantly widened bandwidth: After adding this metal strip, the effective 1-bit phase bandwidth of the high-frequency band is significantly widened, while the phase curve of the edge frequency band is made smoother, greatly improving the flexibility of the unit in wideband scenarios.

[0039] 3. Optimize current and reduce losses: When the high-frequency diode is turned on, the metal strip guides the current to concentrate at the chip gap, reducing transmission loss; when it is turned off, it can suppress current concentration, thereby significantly expanding the phase control range and differentiation.

[0040] Differentiated array control: Due to the small size of metasurface units, it is difficult to arrange complete dual-band bias circuits in each unit at the same time. Therefore, a differentiated arrangement method of independent control of low-frequency units and column-level control of high-frequency units is adopted. 1. Enables dual-band collaborative operation: It allows two frequency bands to perform their respective functions under the same aperture. The low-frequency band uses independent control, which can achieve high-precision, low-loss beam scanning, perfectly meeting the real-time positioning and tracking needs of moving targets.

[0041] 2. Enhanced coverage and anti-interference capabilities: The high-frequency band employs a train control mode, which, combined with vertical plane wave illumination, produces a symmetrical dual-beam phenomenon. This dual-beam scanning not only expands the signal coverage and reduces blind spots without increasing hardware costs, but also significantly improves adaptability to various scenarios.

[0042] By using a nested integrated design of a low-frequency open-loop resonator and a high-frequency rectangular patch, complete isolation and independent 1-bit phase modulation of high and low frequency electromagnetic responses are achieved, solving the problem of frequency band coupling in traditional multi-frequency metasurfaces. By employing a differentiated array control strategy that combines independent control of low-frequency units with column-level control of high-frequency units, dual-function collaborative operation of low-frequency high-precision beam scanning positioning and high-frequency broadband dual-beam scanning is achieved under the same aperture, balancing control accuracy and engineering feasibility.

[0043] Explanation of the technical solution for complete isolation and independent 1-bit phase modulation of high and low frequency electromagnetic responses: Technical solutions for complete isolation of electromagnetic response: By nesting and integrating a low-frequency open-circuit resonant ring with a high-frequency rectangular patch, the high- and low-frequency response structures are physically separated. In traditional designs, the switching on and off of the low-frequency diode can severely affect the high-frequency signal path through electromagnetic coupling. This solution introduces a parasitic metal strip as a decoupling module, effectively suppressing the interference of the low-frequency control circuit state on the high-frequency signal transmission path and phase.

[0044] Independent 1-bit phase modulation technology solution: The high-frequency rectangular chip employs a symmetrical slot design to ensure maximum symmetrical change in the current path when the diode is switched on and off. Combined with the electromagnetic induction effect of the parasitic metal strip, when the high-frequency diode is ON, the metal strip guides a high-density current concentration at the chip slot; when OFF, the metal strip suppresses current concentration, dispersing it across the chip edges. This significant difference in current distribution directly translates into a substantial phase transition at high frequencies, enabling independent 1-bit high-frequency control.

[0045] The low-frequency unit changes the impedance state of the low-frequency resonant circuit by controlling the on / off state of a single PIN diode on the open ring. Within the target frequency band, the phase difference between its ON and OFF states can reach 180°±30°, meeting the phase requirements of 1-bit beamforming.

[0046] As the core control unit, the FPGA outputs high and low level signals through independent bias networks. Because the RF signals and control signals are effectively isolated by the ground plane and vias, the FPGA can independently switch the operating states of the high-frequency and low-frequency diodes in real time, ensuring that the two frequency bands do not interfere with each other from the physical mechanism and control loop.

[0047] Appendix Figure 2 The spatial configuration and structural details of this metasurface unit are shown, including perspective view (a), top view (b), and bottom view (c). Figure 2 As shown in (a), the metasurface unit consists of two layers of Rogers RO4350 dielectric (ε) with thicknesses of T1 and T2 respectively. r The array is constructed with 3.66 Ω·cm and tanδ=0.004 Ω·cm, tightly bonded together with PP adhesive. The overall unit size is designed to be half-wavelength for the high-frequency band, which can effectively control the spacing between adjacent units and suppress the generation of extra grating lobes when building the array later.

[0048] like Figure 2As shown in (b), the low-frequency structure is located on the outer open-loop resonant ring, with a gap of a specific width reserved on the other side of the open-loop ring to precisely match a PIN diode. The high-frequency structure is located on a central metal rectangular patch, with two symmetrically cut slots on the patch, bridged by two identical PIN diodes. The decoupling structure adds two parasitic metal strips in the transition region between the low-frequency ring structure and the high-frequency strip structure. Figure 2 As shown in (a) and (c), to achieve precise active control, the unit has two sets of vias on both sides of the diode mounting slot. One set of vias is directly connected to the ground plane, providing a stable reference level for the diode and avoiding phase modulation errors caused by level drift. The other set of vias is connected to the bias line of the underlying microstrip line structure. The bias line adopts a low-loss design and is electromagnetically isolated from the metal radiating structure, reducing crosstalk between control signals and radio frequency signals.

[0049] The core functionality of the metasurface unit consists of a low-frequency ring structure, a high-frequency strip structure, and a parasitic metal strip between them, forming a nested, integrated, and optimized structural system. The metasurface unit as a whole comprises a dielectric plate T1, a PP adhesive layer, and a dielectric plate T2 arranged sequentially from top to bottom along the Z-axis. The dielectric plate T1 has a thickness of 1.254 mm, and the dielectric plate T2 has a thickness of 0.254 mm, both using Rogers RO4350 dielectric material.

[0050] The upper surface of the dielectric substrate T1 is coplanarly nested with a low-frequency ring structure and a high-frequency strip structure.

[0051] The low-frequency ring structure is used to achieve 1-bit high-precision beam scanning and positioning in the 11.3-12.5GHz band. The impedance of the resonant circuit is adjusted by controlling the on / off state of the PIN diode at the opening, generating a phase difference of 180°±30°.

[0052] The high-frequency strip structure is used to achieve broadband low-loss dual-beam scanning in the 18.5-21.7GHz frequency band. By switching the diodes bridged between the gaps, the surface current path is forced to change symmetrically, and the difference in current distribution is directly converted into a phase jump in the high-frequency band.

[0053] The parasitic metal strip is located in the transition region between the low-frequency ring structure and the high-frequency strip structure, arranged symmetrically on both sides. It serves the dual function of high-frequency bandwidth extension and frequency band isolation. When conducting, it guides the high-frequency current to concentrate in the gap to reduce losses, thus extending the high-frequency bandwidth to over 3GHz, while simultaneously suppressing crosstalk from the low-frequency structure to the high-frequency electromagnetic response. (See attached...) Figure 2 In the top view shown in b, the entire unit is square, and the outer periodic dimension P is 8.6 mm.

[0054] The low-frequency ring structure is located at the outermost edge of the unit, with a radius R1 of 3.6 mm and a linewidth W3 of 0.5 mm. This ring is not closed; it has a physical opening at the top and a pre-drilled gap below the opening. The gap size matches the MACOMMADP-000907 PIN diode package, and the two ends are connected via a single PIN diode. Leads with a length L3 of 0.9 mm and a width W2 of 0.2 mm extend from the upper left and upper right corners of the ring, connecting to metal vias for grounding or DC bias.

[0055] A high-frequency rectangular metal patch is nested in the center of a circular ring, with a width W1 of 2.5 mm and a length L2 of 3.2 mm. This square structure is divided by slots, with two identical PIN diodes connected in the middle via bridging to ensure symmetrical current path changes when the diodes are switched on and off. Parasitic metal strips on both sides have a length L1 of 3 mm and a width W4 of 0.5 mm. (See attached...) Figure 2 In the bottom view shown in c, a bias line network is set on the lower surface of dielectric substrate T2. A slender feed line crossbar with a width W5 of 0.2 mm is arranged at the top, with a vertically extending longitudinal line L4 of 2.4 mm below it. The end of this line connects to a metal via with a radius of 0.1 mm, which penetrates the dielectric layer upwards and connects to the control terminal of the top-layer PIN diode. A fan-shaped structure with a radius R2 of 2 mm is located on the bias trace on the left side of the unit. This fan-shaped structure serves as a bypass capacitor, providing electromagnetic isolation between the RF signal and the DC control signal, reducing crosstalk, and ensuring RF signal integrity and phase modulation accuracy.

[0056] The low-frequency ring structure of the unit is an open-loop resonant ring. A gap of a specific width is reserved on the other side of the open-loop ring. The gap size is precisely matched with the package size of the MACOMMADP-000907 PIN diode to ensure reliable installation and stable electrical connection of the diode.

[0057] In conjunction with the low-frequency ring structure, the high-frequency strip structure adopts a metal central rectangular patch design.

[0058] To achieve 1-bit phase modulation, two symmetrical slits are cut on the chip, distributed along the central axis of the chip, and bridged by diodes of the same type. This symmetrical slit design ensures that the current path changes symmetrically when the diode is switched on and off. The main dimensions of the cell are shown in Table 1 below.

[0059] Table 1. Dimensional parameters (unit: mm) parameter Value (mm) parameter Value (mm) W1 2.5 L1 3 W2 0.2 L2 3.2 W3 0.5 L3 0.9 W4 0.5 L4 2.4 W5 0.2 T1 1.254 R1 3.6 T2 0.254 R2 2 Via 0.1 P 8.6 To verify the feasibility and performance of the unit design, full-wave simulation analysis was performed using Ansys Electronics Desktop 2023b electromagnetic simulation software. When the PIN diode is in the ON state, its RLC equivalent circuit is a series structure, with parameters set to resistor R = 7.8Ω and inductor L = 25nH to match the low impedance characteristics during conduction. When the diode is in the OFF state, the equivalent circuit still adopts a series form, with parameters adjusted to inductor L = 25nH and capacitance C = 30pF to accurately reflect the high impedance capacitive characteristics during turn-off.

[0060] The parasitic metal strip is a key design element for achieving wideband performance and frequency isolation in the driver unit, and its role has been fully verified through two sets of comparative experiments. In the verification of high-frequency bandwidth extension, the experiment used the presence or absence of the parasitic metal strip as a variable, and quantitatively evaluated the bandwidth optimization effect of the parasitic metal strip by comparing the amplitude and phase responses of the driver unit under two operating conditions. Figure 3 As shown, the results indicate that without the parasitic metal strip, the 1-bit phase bandwidth in the high-frequency band is only 1.1 GHz; after adding the parasitic metal strip, the effective high-frequency bandwidth is significantly widened to 3 GHz. This optimization effect allows the unit to adapt to a wider range of high-frequency application scenarios, greatly improving the practicality and flexibility of the unit design. To verify the isolation and bandwidth expansion effect of the parasitic metal strip, a control experiment was set up as follows: Figure 4 The high-frequency phase response of the two schemes is shown: "complete high- and low-frequency structure with parasitic metal strip" and "low-frequency structure removed, no parasitic metal strip". The results show that in the 19–22 GHz band, the ON / OFF phase difference of the complete structure with parasitic metal strip is reduced by 10°, and the low-frequency interference to the high-frequency is effectively suppressed; in the 18–19 GHz band, the phase curve of the structure with parasitic metal strip is flatter, avoiding edge phase abrupt changes, confirming its dual role of decoupling and bandwidth expansion.

[0061] Figure 5 The high-frequency current distribution of metasurface cells with and without parasitic metal strips was compared. In the original structure without metal strips, due to electromagnetic coupling between high- and low-frequency circuits and the lack of current directional constraints, the current distribution of the high-frequency PIN diodes is similar in both ON and OFF states, resulting in weak switching control. After introducing the parasitic metal strips, the current distribution changes significantly: In the ON state, the metal strips guide the current to concentrate at a high density in the high-frequency patch gaps, reducing transmission losses; in the OFF state, the metal strips suppress current concentration, dispersing it at the patch edges, significantly reducing the current density. This significant difference in current distribution between ON and OFF states caused by the parasitic metal strips directly translates into a significant jump in the cell phase response, effectively expanding the phase control range and improving phase differentiation.

[0062] Figure 6The reflection characteristics of this unit in low and high frequency bands were demonstrated. In the low frequency band (11.3-12.5GHz), the insertion loss is less than 2.5dB, and the phase difference reaches 180°±30°, meeting the 1-bit beamforming requirements. In the high frequency band (18.5-21.7GHz), by optimizing impedance matching through electromagnetic coupling between the parasitic metal strip and the patch, the insertion loss is controlled within 2dB, effectively reducing the transmission loss of millimeter waves; its absolute bandwidth exceeds 3GHz, ensuring good channel capacity. This unit can achieve independent 1-bit control in both frequency bands, laying the foundation for subsequent dual-frequency communication and positioning functions.

[0063] Based on the designed unit, this application designed a 15×15 metasurface array for simulation, such as... Figure 7 As shown.

[0064] Considering the small size of the cell itself, it is difficult to arrange bias circuits for two frequency bands. Therefore, the low-frequency design is chosen to be cell-independent control, while the high-frequency design uses column control. Simulation results are as follows. Figure 8 As shown, in Figure 8 In (a), the low-frequency array achieves precise deflection from 0° to 50°, with a peak gain of 16.6 dBi at 0°. Due to the small physical aperture of the array (only about 5 wavelengths), and the further reduction in equivalent aperture during large-angle scanning, the main beam broadens. Nevertheless, the array gain remains stable above 15 dBi throughout the entire scanning range, with sidelobe levels below 10 dB, demonstrating excellent beam scanning and energy focusing performance. Figure 8 (b) Due to space constraints within the cell, the high-frequency beam is controlled using a column-level control mode with plane wave feeding. At 19.5 GHz, the array achieves a wide-angle, precise scan of 10° to 50°. It should be noted that perpendicular plane wave illumination of the 1-bit metasurface produces a symmetrical dual-beam phenomenon. In practical communication, the secondary beam not only does not interfere with the main channel but also expands the signal coverage without increasing cost, effectively reducing coverage blind spots.

[0065] This invention breaks the mutual restrictions and interference between two different frequency bands and functions, and with its unique electromagnetic control characteristics, it constructs a completely new independent transmission channel for communication systems.

[0066] This invention addresses the problems of electromagnetic response coupling and functional interference in multi-band metasurfaces. In traditional multi-band metasurface designs, the on / off state of the low-frequency control circuit severely affects the transmission path of high-frequency signals through electromagnetic coupling, preventing truly independent control between frequency bands. This invention achieves complete decoupling of high and low frequency structures by introducing a parasitic metal strip structure. By coplanarly integrating a low-frequency open-loop resonant ring and a high-frequency rectangular patch on the same dielectric substrate, a physical spatial isolation foundation is constructed. Based on this, parasitic metal strips are symmetrically placed in the transition region, achieving complete decoupling of the high and low frequency structures. The parasitic metal strips alter the current distribution and electromagnetic coupling path on the unit surface, effectively blocking electromagnetic interference from the low-frequency control circuit to the high-frequency signal transmission. When the diode is on, the current is directionally guided to focus on the gap to reduce losses; when off, the current distribution is constrained to maintain the phase differentiation of the switching control.

[0067] This invention addresses the issue of single-function metasurfaces in complex mobile scenarios. It achieves differentiated division of labor between two frequency bands within the same aperture. The low-frequency band employs an array unit-level independent control architecture, utilizing an FPGA to perform real-time phase modulation on each low-frequency ring unit, enabling high-precision beam scanning from 0° to 50° for accurate target locking and tracking. The high-frequency band employs a column-level array control optimization architecture. By sharing control commands among high-frequency strip structures in the same column, symmetrical dual beams are formed under plane wave illumination. This significantly expands the spatial coverage of the signal while avoiding physical bottlenecks in wiring, enhancing the communication capacity and anti-interference capabilities of the millimeter-wave band. Thus, while maximizing aperture utilization, it achieves adaptive synergy between metasurface sensing and communication functions. Independent low-frequency control enables low-loss beam scanning, meeting the real-time tracking requirements of moving targets, while the high-frequency column controls dual-beam scanning, achieving perfect compatibility and synergy of multiple functions.

Claims

1. A metasurface based on independent dual-frequency control, characterized in that, This includes nested unit topology metasurface arrays, which are composed of metasurface units, each of which is divided into independent low-frequency and high-frequency bands. The low-frequency band and high-frequency band adopt differentiated array control strategies through the FPGA control system. The low-frequency band execution unit is controlled independently, and the real-time positioning and tracking requirements of moving targets are met through high-precision beam scanning. Simultaneously, the high-frequency band is controlled to perform column-level control, achieving broadband dual-beam scanning.

2. The metasurface based on dual-frequency independent control according to claim 1, characterized in that, The metasurface unit includes a dielectric plate T1, a PP adhesive layer and a dielectric plate T2 arranged sequentially from top to bottom along the Z-axis. The upper surface of the dielectric plate T1 is coplanarly nested with a low-frequency structure and a high-frequency structure. The low-frequency structure and the high-frequency structure are each subject to independent 1-bit phase dynamic control.

3. The metasurface based on dual-frequency independent control according to claim 2, characterized in that, The low-frequency structure includes an open resonant ring located on the periphery, and a gap is provided on the side of the open resonant ring opposite to the opening, and a low-frequency diode D1 is matched at the gap; Leads extend from both ends of the open resonant ring near the opening, and the ends of the leads are connected to metal through holes for connection to the ground plane or DC bias. The low-frequency diode D1 is installed in the gap of the outer open resonant ring, with its two ends connected to the metal parts on the left and right sides of the open resonant ring respectively, and connected to the low-frequency control terminal of the FPGA through an independent bias line; When the low-frequency diode D1 is turned on, the current path of the open-ring resonator is closed. When it is turned off, the current of the open-ring resonator is cut off at the opening, thereby changing the low-frequency resonance state.

4. The metasurface based on dual-frequency independent control according to claim 3, characterized in that, The high-frequency structure is located inside the open-loop resonant ring and includes a central rectangular metal patch. Two symmetrical cuts are made on the rectangular metal patch to form three rectangular patches. The common central axis of the three rectangular patches is the line connecting the opening of the open-loop resonant ring and the midpoint of the cut. The two cuts are bridged by two identical PIN diodes, which are arranged to the left and right along the central rectangular patch. The PIN diodes are the upper high-frequency diode D2 and the lower high-frequency diode D3. The high-frequency diode D2 is connected across the upper horizontal gap of the central rectangular patch, with its two ends connected to the upper patch and the middle patch respectively; The high-frequency diode D3 is connected across the lower horizontal gap of the central rectangular patch, with its two ends connected to the middle patch and the lower patch, respectively.

5. A metasurface based on dual-frequency independent control according to claim 4, characterized in that, Parasitic metal decoupling structures are set on both sides of the metal rectangular patch and inside the open resonant ring. The parasitic metal decoupling structures are symmetrical about the unified central axis and isolated from each rectangular patch. They are used to change the current distribution pattern and electromagnetic coupling path on the surface of the metasurface unit. The parasitic metal decoupling structures are two parasitic metal strips.

6. The metasurface based on dual-frequency independent control according to claim 4, characterized in that, The lower surface of the dielectric substrate T2 is provided with a bias line network, including a slender feed line crossbar arranged in the lower layer of the dielectric substrate T2. The slender feed line crossbar is used as the X-axis reference line, with the center as the zero point. A longitudinal line is set along the negative Y-axis direction of the center. The end of the longitudinal line is connected to a metal through hole. The metal through hole passes through the dielectric substrate T1, the PP adhesive layer and the dielectric substrate T2, and is connected to the control terminal of the upper high-frequency diode D2 and the lower high-frequency diode D3.

7. A metasurface based on dual-frequency independent control according to claim 6, characterized in that, A bias trace is also provided on the lower surface of dielectric substrate T2. The bias is set along the negative Y-axis and located on the edge of dielectric substrate T2 in the negative X-axis direction. A fan-shaped structure is provided on the bias trace, and the fan-shaped structure serves as a bypass capacitor structure.

8. A metasurface based on dual-frequency independent control according to claim 4, characterized in that, The low-frequency structure is used to achieve 1-bit high-precision beam scanning and positioning in the 11.3-12.5GHz band. The impedance of the resonant circuit is adjusted by controlling the on / off state of the low-frequency diode D1 at the opening, generating a phase difference of 180°±30°.

9. A metasurface based on dual-frequency independent control according to claim 4, characterized in that, The high-frequency structure is used to achieve broadband low-loss dual-beam scanning in the 18.5-21.7GHz band. By switching the diodes bridged between the gaps, the surface current path is forced to change symmetrically, and the difference in current distribution is directly converted into a phase jump in the high-frequency band.

10. A metasurface based on dual-frequency independent control according to claim 4, characterized in that, The low-frequency diode D1, the upper high-frequency diode D2, and the lower high-frequency diode D3 are connected to the control unit FPGA. The control unit FPGA is used to switch the operating states of the high-frequency and low-frequency diodes independently in real time.

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