Design method of dual-frequency programmable metasurface unit based on lorentz dispersion

Abstract

This invention discloses a design method for a dual-frequency programmable metasurface unit based on Lorentz dispersion, comprising a top-layer metal resonant structure, a first dielectric layer, a metal ground plane, a second dielectric layer, and a bottom-layer feed line, stacked sequentially. The first dielectric layer is a metamaterial layer with Lorentz-type permeability dispersion characteristics, embedding two pairs of open resonant rings with a resonant frequency higher than the target low-frequency band. Without the Lorentz-dispersion metamaterial layer, the top-layer metal resonant structure only has phase modulation functionality at a single frequency point. By optimizing geometric parameters, the dual-frequency programmable metasurface unit based on Lorentz dispersion achieves 1-bit phase modulation in two target frequency bands. The dual-frequency programmable metasurface unit has grounding metal posts penetrating the dielectric layer and connected to the metal ground plane at opposite ends. This invention achieves dual-frequency phase modulation with a single-layer compact structure, which is simple in structure, low in cost, has wide-angle oblique incidence stability, and is compatible with a single FPGA control system, avoiding hardware resource redundancy.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic metamaterials technology, and in particular to a design method for dual-frequency programmable metasurface units based on Lorentz dispersion. Background Technology

[0002] Programmable metasurfaces, with their high flexibility and reconfigurability, are suitable for low-power, low-cost electromagnetic control systems. In recent years, this technology has been widely researched and applied in several cutting-edge fields, including dynamic beamforming, electromagnetic stealth camouflage, computational imaging, and intelligent sensing. Achieving simple dynamic beam deflection and switching is a fundamental and important application of programmable metasurfaces in next-generation wireless communication. In this scenario, typically only macroscopic control of the electromagnetic wave propagation direction is needed, without the need to generate complex, customized wavefronts.

[0003] However, with the increasing complexity of environments and the growing demand for diverse functions, single-frequency programmable metasurfaces have fixed operating frequency bands and limited degrees of control. This inherent physical characteristic creates a fundamental mismatch between the needs of multi-functionality and the system's performance, leading to severe performance limitations in multi-tasking scenarios. To overcome the single-frequency limitation, a unit cell for dual-frequency, dual-polarization programmable metasurfaces has been proposed. This design utilizes two PIN diodes integrated into the unit cell structure. By controlling the switching states of the diodes, the electromagnetic response is independently reconstructed in two discrete frequency bands. The polarization state of the reflected wave is controlled by the reflection phase difference generated by different state combinations, thus achieving digital beam control and polarization switching simultaneously in both frequency bands. Another method for realizing dual-frequency programmable coded metasurfaces employs a two-layer shared aperture unit cell structure. PIN diodes are integrated into the top and bottom layers, which are physically separated, and electromagnetic isolation is achieved using an intermediate ground layer. The geometric parameters of the two layers are independently optimized, and voltages are applied to the diodes in each layer through independent DC bias networks, thereby generating reflection phases independently in both frequency bands and achieving real-time beam control. Another study proposed a method for realizing a dual-band multi-bit programmable reflective metasurface. It utilizes a three-metal-layer and two-dielectric-layer structure, integrates two PIN diodes on the top radiating patch, and carefully designs the patch geometry to make it resonate simultaneously in the C-band and Ku-band. Then, it uses the four switching states of the diodes to achieve two-bit phase encoding in both frequency bands, thereby completing real-time electromagnetic wave control with high precision.

[0004] While the aforementioned solutions achieve dual-frequency control to some extent, they still have significant shortcomings. First, to achieve independent dual-frequency control, these designs often require multi-layer stacked structures, each layer needing its own resonant structure, dielectric substrate, and bias network. This significantly increases the design complexity of the unit, manufacturing costs, and the overall system thickness, hindering its application in thinner and lighter devices. Second, because two frequency bands need to be controlled independently, the control complexity and wiring density of hardware systems such as FPGAs increase significantly. Furthermore, at any given time, when the metasurface is operating in one frequency band, the hardware resources corresponding to the other frequency band are idle, failing to contribute to the current function, resulting in a waste of physical space and control resources. In addition, most existing programmable metasurface technologies only operate under normal electromagnetic wave incidence conditions, lacking effective control over obliquely incident electromagnetic wave signals. This limits the range of users that programmable metasurfaces can serve, imposes high precision requirements on installation location, and imposes certain limitations in practical applications. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the problems of complex dual-frequency programmable metasurface structure, redundant hardware resources, and poor oblique incidence performance in the prior art.

[0006] To address the aforementioned technical problems, this invention provides a method for designing dual-frequency programmable metasurface units based on Lorentz dispersion, comprising: The structure consists of a top-layer metal resonant structure, a first dielectric layer, a metal ground plane, a second dielectric layer, and a bottom-layer feed line, which are stacked sequentially. The method for designing the first dielectric layer is as follows: the first dielectric layer is a metamaterial layer with Lorentz-type permeability dispersion characteristics. The metamaterial layer includes an upper dielectric plate, a lower dielectric plate, and an intermediate layer disposed between the upper dielectric plate and the lower dielectric plate. The intermediate layer has two pairs of open-ended resonant rings embedded in it, each pair of open-ended resonant rings consisting of two open-ended rings with opposite opening directions. The resonant frequency of the metamaterial layer is higher than the low-frequency band of the target dual-frequency operating band. By adjusting the geometric parameters of the top metal resonant structure and the geometric parameters of the open resonant ring in the metamaterial layer, a dual-frequency programmable metasurface unit based on Lorentz dispersion that simultaneously achieves 1-bit phase modulation in the first and second target frequency bands is obtained. Multiple grounding metal posts are provided at each of the opposite two ends of the dual-frequency programmable metasurface unit. The grounding metal posts penetrate the first dielectric layer and are connected to the metal grounding plate.

[0007] In one embodiment of the present invention, a PIN diode is loaded in the top metal resonant structure.

[0008] In one embodiment of the present invention, the positive side of the PIN diode is connected to the underlying feed line through a metal via that vertically penetrates the first dielectric layer, the metal ground plane, and the second dielectric layer. An insulating isolation ring is provided between the metal via and the metal ground plane. The negative side of the PIN diode is connected to the metal ground plane through a metal via that vertically penetrates the first dielectric layer.

[0009] In one embodiment of the present invention, after adjusting the geometric parameters of the top metal resonant structure and the geometric parameters of the open resonant ring in the metamaterial layer, the reflection amplitude of the dual-frequency programmable metasurface unit based on Lorentz dispersion in the first target frequency band is not less than 0.98 in both the on-state and off-state of the PIN diode loaded in the top metal resonant structure, and not less than 0.75 in both the on-state and off-state of the PIN diode in the second target frequency band.

[0010] In one embodiment of the present invention, the bottom layer feed line includes a DC bias line corresponding to each of the PIN diodes. The DC bias line is electrically connected to the top layer metal resonant structure through a metal via. An insulating isolation ring is provided between the metallized via and the metal ground plane.

[0011] In one embodiment of the present invention, the grounded metal pillars are arranged at equal intervals on opposite sides of the dual-frequency programmable metasurface unit.

[0012] In one embodiment of the present invention, the opening directions of the two pairs of open resonant rings embedded in the intermediate layer are both perpendicular to the extension direction of the resonant arm of the top metal resonant structure, and the two pairs of open resonant rings are symmetrically distributed about the center of the dual-frequency programmable metasurface unit.

[0013] Based on the same inventive concept, this invention also provides a dual-frequency programmable metasurface unit based on Lorentz dispersion, comprising: The structure consists of a top-layer metal resonant structure, a first dielectric layer, a metal ground plane, a second dielectric layer, and a bottom-layer feed line, stacked sequentially. The first dielectric layer is a metamaterial layer with Lorentz-type permeability dispersion characteristics. The metamaterial layer includes an upper dielectric plate, a lower dielectric plate, and an intermediate layer disposed between the upper dielectric plate and the lower dielectric plate. The intermediate layer has two pairs of open-ended resonant rings embedded in it. Each pair of open-ended resonant rings consists of two open-ended rings with opposite opening directions. Multiple grounding metal posts are disposed at opposite ends of the dual-frequency programmable metasurface unit based on Lorentz dispersion, the grounding metal posts penetrating the first dielectric layer and connected to the metal ground plane.

[0014] The present invention also provides a dual-frequency programmable metasurface based on Lorentz dispersion, comprising a plurality of dual-frequency programmable metasurface units based on Lorentz dispersion, wherein the dual-frequency programmable metasurface units are arranged in a two-dimensional array.

[0015] In one embodiment of the present invention, an FPGA control system is further included, which is connected to the underlying feed lines of a plurality of dual-frequency programmable metasurface units.

[0016] The technical solution of the present invention has the following advantages compared with the prior art: This invention introduces a metamaterial layer with Lorentz-type permeability dispersion characteristics as the first dielectric layer, and embeds two pairs of open resonant rings within this dielectric layer. This allows the metasurface unit to achieve 1-bit phase modulation simultaneously in the first and second target frequency bands within a single compact structure, eliminating the need for traditional multi-layer stacked structures. This reduces the design complexity, manufacturing cost, and overall thickness of the unit. Furthermore, multiple grounded metal pillars are regularly arranged at opposite ends of the metasurface unit, forming equivalent metal walls between adjacent units. This ensures that the metasurface maintains good 1-bit phase modulation capability within a ±40° electromagnetic wave oblique incidence range, effectively overcoming the limitation of existing technologies that are only applicable to normal incidence. This provides a novel design scheme for dual-frequency programmable metasurfaces that is structurally simple, highly efficient in control, angularly stable, and low in loss. Attached Figure Description

[0017] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0018] Figure 1 This is a flowchart illustrating the design method for dual-frequency programmable metasurface units based on Lorentz dispersion provided in this embodiment of the invention. Figure 2 This is a schematic diagram of a dual-frequency programmable metasurface structure based on a Lorentz permeability dispersive metamaterial in an embodiment of the present invention; Figure 3 yes Figure 2 Side view along direction A; Figure 4 This is a schematic diagram of the amplitude and phase response of a dual-frequency programmable metasurface unit based on a Lorentz permeability dispersive metamaterial in a preferred embodiment of the present invention, including two working states: diode on and off. Figure 5 This is a schematic diagram of the amplitude and phase response of a programmable metasurface unit under normal and oblique incidence conditions in a preferred embodiment of the present invention. The incidence angles are 0°, 15° and 30°, and each incidence angle includes two working states: diode conduction and cutoff. Figure 6In a preferred embodiment of the present invention, a dual-frequency programmable metasurface achieves a far-field pattern with 20° beam deflection when electromagnetic waves are incident normally at a frequency of 3.83 GHz. Figure 7 In a preferred embodiment of the present invention, a dual-frequency programmable metasurface achieves a far-field pattern with 20° beam deflection when electromagnetic waves are incident normally at a frequency of 4.43 GHz. Figure 8 In a preferred embodiment of the present invention, a dual-frequency programmable metasurface achieves a far-field pattern with 40° beam deflection when electromagnetic waves are incident normally at a frequency of 3.83 GHz. Figure 9 In a preferred embodiment of the present invention, a dual-frequency programmable metasurface achieves a far-field pattern with 40° beam deflection when electromagnetic waves are incident normally at a frequency of 4.43 GHz. Figure 10 In a preferred embodiment of the present invention, a dual-frequency programmable metasurface achieves a far-field pattern of 40° beam deflection when electromagnetic waves are incident obliquely at 20° and at a frequency of 3.83GHz. Figure 11 In a preferred embodiment of the present invention, a dual-frequency programmable metasurface achieves a far-field pattern of 40° beam deflection when electromagnetic waves are incident obliquely at 20° and at a frequency of 4.43 GHz.

[0019] Explanation of reference numerals in the instruction manual's attached diagrams: 1. PIN diode; 2. Grounding metal post; 3. Metal ground plane; 4. Top H-type metal patch; 5. SRR dispersion metal ring; 6. First dielectric substrate; 7. Second dielectric substrate; 8. Third dielectric substrate; 9. Fourth dielectric substrate. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0021] Example 1: like Figure 1 As shown, this invention provides a method for designing dual-frequency programmable metasurface units based on Lorentz dispersion, comprising: The structure consists of a top-layer metal resonant structure, a first dielectric layer, a metal ground plane, a second dielectric layer, and a bottom-layer feed line, which are stacked sequentially. The method for designing the first dielectric layer is as follows: the first dielectric layer is a metamaterial layer with Lorentz-type permeability dispersion characteristics. The metamaterial layer includes an upper dielectric plate, a lower dielectric plate, and an intermediate layer disposed between the upper dielectric plate and the lower dielectric plate. The intermediate layer has two pairs of open-ended resonant rings embedded in it, each pair of open-ended resonant rings consisting of two open-ended rings with opposite opening directions. The resonant frequency of the metamaterial layer is higher than the low-frequency band of the target dual-frequency operating band. By adjusting the geometric parameters of the top metal resonant structure and the geometric parameters of the open resonant ring in the metamaterial layer, a dual-frequency programmable metasurface unit based on Lorentz dispersion that simultaneously achieves 1-bit phase modulation in the first and second target frequency bands is obtained. Multiple grounding metal posts are provided at each of the opposite two ends of the dual-frequency programmable metasurface unit. The grounding metal posts penetrate the first dielectric layer and are connected to the metal grounding plate.

[0022] This invention comprises a top-layer metal resonant structure, a first dielectric layer, a metal ground plane, a second dielectric layer, and a bottom-layer feed line, stacked sequentially. The first dielectric layer is designed as a metamaterial layer with Lorentz-type permeability dispersion characteristics. This metamaterial layer includes an upper dielectric plate, a lower dielectric plate, and an intermediate layer between them. The intermediate layer embeds two pairs of open-ended resonant rings, each pair consisting of two open-ended rings with opposite opening directions. The resonant frequency of the metamaterial layer is higher than the lower frequency band of the target dual-frequency operating frequency band. Then, the geometric parameters of the top-layer metal resonant structure and the geometric parameters of the open-ended resonant rings in the metamaterial layer are adjusted to obtain a dual-frequency programmable metasurface unit that simultaneously achieves 1-bit phase modulation in both the first and second target frequency bands. Finally, multiple grounding metal pillars are set at each of the opposite ends of the unit. These grounding metal pillars penetrate the first dielectric layer and are connected to the metal ground plane. This design introduces a Lorentz dispersive metamaterial layer, enabling a single compact structure to achieve independent 1-bit phase modulation in both frequency bands without the need for multi-layer stacking, significantly reducing structural complexity and manufacturing costs. Simultaneously, the two frequency bands share the same set of PIN diodes and power supply control network, avoiding hardware resource redundancy and achieving precise synchronization of the phase response between the two frequencies. Furthermore, the grounded metal pillars on both sides of the unit form an equivalent metal wall between adjacent units, allowing the metasurface to maintain good phase modulation capability over a wide oblique incidence range. This overcomes the limitation of traditional solutions that are only applicable to normal incidence, ultimately achieving high reflection amplitude and stable 0° / 180° reflection phase difference in both target frequency bands. This provides a simple, efficient, angle-stable, and low-loss solution for dual-frequency programmable metasurfaces.

[0023] like Figure 2 and Figure 3As shown, specifically, a top-layer metal resonant structure, a first dielectric layer, a metal ground plane 3, a second dielectric layer, and a bottom-layer feed line are stacked sequentially. The top-layer metal resonant structure uses an H-shaped metal patch 4. The two parallel arms and the connecting portion in the middle of this shape together constitute a resonant unit, which can form a symmetrical surface current distribution under the excitation of incident electromagnetic waves, thereby generating a stable resonant mode. A PIN diode 1 is loaded at a key location on the H-shaped metal patch 4, typically the gap with the highest current density. The conduction and cutoff states of the PIN diode 1 change the equivalent current path on the patch surface: when conducting, the current flows continuously; when cut off, the current is blocked. The reflection phases in the two states differ by approximately 180 degrees, thus achieving 1-bit phase modulation. The positive side of the PIN diode 1 is connected to the bottom-layer feed line through a metal via that vertically penetrates the first dielectric layer, the metal ground plane 3, and the second dielectric layer. An insulating isolation ring is provided between the metal via and the metal ground plane. The negative side of the PIN diode 1 is directly connected to the metal ground plane 3 through a metal via that vertically penetrates the first dielectric layer. The bottom-layer feed line includes DC bias lines corresponding one-to-one with the PIN diodes 1. These DC bias lines provide bias voltage to the PIN diodes 1 through the metal vias. To prevent short circuits between the metal vias and the metal ground plane 3, an insulating isolation ring is provided between the metal vias and the metal ground plane 3. This isolation ring is typically an annular gap surrounding the via or a structure filled with an insulating dielectric. The metal ground plane 3 not only acts as a reflective surface to reflect incident electromagnetic waves back but also provides electromagnetic isolation, preventing unnecessary coupling between the top-layer resonant structure and the bottom-layer feed line, thus ensuring stable operation of the metasurface.

[0024] The first dielectric layer is designed as a metamaterial layer with Lorentz-type permeability dispersion characteristics. This metamaterial layer includes an upper dielectric substrate, a lower dielectric substrate, and an intermediate layer disposed between them. The upper and lower dielectric substrates primarily serve as support and encapsulation, while also providing a certain dielectric constant environment. In this embodiment, the upper dielectric substrate is the first dielectric substrate 6, and the lower dielectric substrate is the third dielectric substrate 8. The intermediate layer consists of a second dielectric substrate 7 and two pairs of split-ring resonators embedded between the dielectrics. The split-ring resonators are SRR dispersive metal rings 5. Each pair of split-ring resonators consists of two open rings with opposite opening directions. This opposing placement structure generates complementary currents: when the current in one ring reaches its maximum value, it precisely compensates for the minimum current in the other ring at its opening gap, thereby enhancing the overall magnetic resonance intensity. The opening directions of both pairs of split-ring resonators are perpendicular to the resonant arm extension direction of the top H-shaped metal patch 4, and the two pairs of split-ring resonators are symmetrically distributed about the unit center. The symmetrical distribution ensures the unit cell's insensitivity to the polarization of incident electromagnetic waves, while the perpendicular design of the opening direction allows the resonant rings to effectively respond to an external magnetic field perpendicular to the ring plane. By rationally designing the size, opening width, and dielectric thickness of the open resonant rings, the resonant frequency of this metamaterial layer is made higher than the low-frequency band of the target dual-frequency operating band. When the external magnetic field is perpendicular to the plane of the open resonant rings, an induced current is generated in each open ring, forming a capacitance effect at the opening, and the whole constitutes an LC resonant circuit, thereby exciting resonance. Under these conditions, the equivalent permeability of the metamaterial layer exhibits Lorentz dispersion characteristics, specifically a higher refractive index in the low-frequency band near the resonant frequency and a lower refractive index in the high-frequency band. This dispersion characteristic allows the same unit cell structure to exhibit drastically different equivalent electromagnetic parameters for electromagnetic waves of different frequencies, providing a physical basis for dual-frequency control.

[0025] Furthermore, the geometric parameters of the top-layer H-shaped metal patch 4, including arm length, arm width, and slot spacing, were adjusted. Simultaneously, the geometric parameters of the open resonant ring 5 in the metamaterial layer were also adjusted, including ring side length, linewidth, and opening width. Through electromagnetic simulation optimization, the first target frequency band was positioned in the high refractive index region of the Lorentz dispersion curve, while the second target frequency band was positioned in the low refractive index region. The resulting metasurface unit can achieve 1-bit phase modulation simultaneously in both the first and second target frequency bands.

[0026] like Figure 4As shown, in a preferred embodiment, after parameter optimization, the target operating frequency bands of the dual-frequency programmable metasurface unit are the N78 band (3.74 GHz to 3.78 GHz) and the N79 band (4.47 GHz to 4.48 GHz). Within the first target frequency band N78, the reflection amplitude of PIN diode 1 in both on and off states is not less than 0.98; within the second target frequency band N79, the reflection amplitude is not less than 0.75. High reflection amplitude means that almost all the energy of the incident electromagnetic wave is reflected and effectively controlled, resulting in extremely low loss. Stable 0-degree and 180-degree reflection phase differences can be obtained in both frequency bands, ensuring the basic performance of the digitally coded metasurface.

[0027] Existing single-frequency units exhibit a reflection amplitude close to 0.98 and a 1-bit phase modulation capability within the 4.2 GHz to 4.28 GHz frequency band. In this invention, a Lorentz dispersive metamaterial is designed, consisting of a multilayer dielectric substrate and two pairs of embedded open resonant rings. Equivalent permeability is extracted through electromagnetic simulation, revealing a significant resonance peak near 4.8 GHz. The peak exhibits typical Lorentz dispersion characteristics: higher equivalent permeability at low frequencies and lower equivalent permeability at high frequencies. By replacing the dielectric layer of the single-frequency unit with this metamaterial layer and adjusting the geometric parameters, the unit can operate simultaneously in both the N78 and N79 frequency bands. The permeability of the Lorentz dispersive metamaterial varies drastically with frequency, resulting in the same physical structure having the same electrical dimensions at two different frequencies. By designing the single-frequency phase modulation unit to operate in the rising frequency band before the resonance peak, after replacing the dielectric, the dispersion effect automatically derives a second operating frequency band of the same mode in the frequency band after the resonance peak, thus achieving dual-frequency modulation.

[0028] To enhance the cell's ability to control obliquely incident electromagnetic waves, multiple grounded metal pillars 2 are provided at each of the opposite ends of the cell. These grounded metal pillars 2 penetrate the first dielectric layer and are directly electrically connected to the metal ground plate 3. Preferably, the grounded metal pillars 2 are evenly spaced at both ends of the cell. When multiple cells are arranged in a two-dimensional array, the grounded metal pillars 2 of adjacent cells together form an equivalent metal wall at the cell boundary. This equivalent metal wall can effectively suppress the lateral propagation of surface waves because obliquely incident electromagnetic waves often excite surface waves propagating horizontally in the dielectric layer. If these surface waves propagate to adjacent cells, they will cause mutual coupling and phase distortion. The equivalent wall formed by the grounded metal pillars 2 approximately isolates each cell, forcing surface waves to be reflected or attenuated at the cell boundary, thereby significantly reducing the electromagnetic coupling between cells during oblique incidence.

[0029] Electromagnetic simulations have verified that the dual-frequency programmable metasurface unit in this embodiment of the invention exhibits stable oblique incidence performance. For example... Figure 5As shown, the reflection amplitude and phase response of the unit were simulated for electromagnetic wave incident angles of 0°, 15°, and 30°. The results show that when the electromagnetic wave incident angle is within ±30°, the reflection amplitude of the unit remains almost constant, and the reflection phase change between the PIN diode's on and off states remains within 15° within the operating frequency band. When the incident angle continues to increase to ±40°, although the reflection amplitude decreases and the phase difference shifts slightly, it still meets the basic requirements of 1-bit phase modulation (the reflection phase difference remains within 180°±37°). Therefore, the unit designed in this invention can maintain good electromagnetic wave modulation capability within a relatively wide oblique incident angle range of ±40°, effectively overcoming the limitation of existing technologies that are only applicable to normal incidence.

[0030] Through the above design, in this embodiment of the invention, 1-bit phase modulation of dual-band frequencies can be achieved simultaneously in a single compact structure. This eliminates the need for traditional multi-layer stacked structures, meaning that separate resonant layers, dielectric substrates, and bias networks are not required for each frequency band, significantly reducing design complexity, manufacturing costs, and overall thickness. Furthermore, the phase response of both frequency bands is controlled by the same set of PIN diodes 1 and the same underlying feed line, sharing the same FPGA control system, thus avoiding hardware resource redundancy. Traditional solutions require independent diodes and bias networks for each frequency band, and only one frequency band operates at any given time, resulting in resource idleness. This invention achieves precise synchronization of the dual-frequency phase response and efficient utilization of hardware resources. In addition, the equivalent metal walls formed by the grounded metal pillars 2 on both sides of the unit enable the metasurface to maintain good phase modulation capability over a wide oblique incidence range, overcoming the limitation of existing technologies that are only suitable for normal incidence. This embodiment provides a novel design scheme for dual-frequency programmable metasurfaces that is structurally simple, highly efficient in control, angularly stable, and low-loss.

[0031] Example 2: like Figure 2 and Figure 3As shown, based on the same inventive concept as Embodiment 1, this embodiment provides a dual-frequency programmable metasurface unit based on Lorentz dispersion, including a top-layer metal resonant structure, a first dielectric layer, a metal ground plane 3, a second dielectric layer, and a bottom-layer feed line stacked sequentially. The top-layer metal resonant structure uses an H-shaped metal patch 4, with a PIN diode 1 loaded in the gap of the H-shaped metal patch 4 for 1-bit phase modulation. The positive terminal of the PIN diode 1 is connected to the bottom-layer feed line through a metal via perpendicularly penetrating the first dielectric layer, the metal ground plane 3, and the second dielectric layer. An insulating isolation ring is provided between the metal via and the metal ground plane. The negative terminal of the PIN diode 1 is connected to the metal ground plane 3 through a metal via perpendicularly penetrating the first dielectric layer. The bottom-layer feed line includes a DC bias line corresponding to the PIN diode 1, which provides a bias voltage to the PIN diode 1 through the metal via. An insulating isolation ring is provided between the metal via and the metal ground plane 3 to prevent short circuits. The metal ground plane 3 simultaneously acts as a reflective surface and an electromagnetic isolation layer, ensuring that incident electromagnetic waves are effectively reflected and blocking coupling between the top and bottom layers.

[0032] The first dielectric layer is a metamaterial layer with Lorentz-type permeability dispersion characteristics. This metamaterial layer includes an upper dielectric plate, a lower dielectric plate, and an intermediate layer disposed between them. Specifically, the upper dielectric plate is the first dielectric plate 6, the lower dielectric plate is the third dielectric plate 8, and the intermediate layer consists of a second dielectric plate 7 and two pairs of split-ring resonators embedded between the dielectric layers. The split-ring resonators are SRR dispersive metal rings 5. Each pair of split-ring resonators consists of two split rings with opposite opening directions. The opening directions of both pairs of split-ring resonators are perpendicular to the extension direction of the resonant arm of the top H-shaped metal patch 4, and the two pairs of split-ring resonators are symmetrically distributed about the unit center. The resonant frequency of this metamaterial layer is designed to be higher than the low-frequency band of the target dual-frequency operating band, thereby exciting resonance when the applied magnetic field is perpendicular to the plane of the split-ring resonators, causing the equivalent permeability to exhibit Lorentz dispersion characteristics, i.e., a higher refractive index in the low-frequency band near the resonant frequency and a lower refractive index in the high-frequency band.

[0033] In this embodiment of the invention, the dual-frequency programmable metasurface unit based on Lorentz dispersion further includes multiple grounded metal pillars 2. These grounded metal pillars 2 are disposed at opposite ends of the dual-frequency programmable metasurface unit, penetrate the first dielectric layer, and are directly electrically connected to the metal ground plane 3. The grounded metal pillars 2 are uniformly arranged at equal intervals at both ends of the unit. When multiple dual-frequency programmable metasurface units are arranged in an array, the grounded metal pillars 2 of adjacent units together form an equivalent metal wall to suppress the lateral propagation of surface waves, reduce the mutual coupling between units during oblique incidence, and thus improve the oblique incidence stability of the unit. With the above structure, the unit of this embodiment can simultaneously achieve 1-bit phase modulation of dual frequency bands in a single compact structure and has a wide range of applicable oblique incidence angles.

[0034] Example 3: This embodiment provides a dual-frequency programmable metasurface based on Lorentz dispersion, comprising multiple dual-frequency programmable metasurface units based on Lorentz dispersion as described in Embodiment 2. These dual-frequency programmable metasurface units are arranged in a two-dimensional array to form a complete large-aperture metasurface array. Figure 2 and Figure 3 As shown, each dual-frequency programmable metasurface unit has a top-layer metal resonant structure, a first dielectric layer, a metal ground plane, a second dielectric layer, and a bottom-layer feed line stacked sequentially. The top-layer metal resonant structure uses an H-type metal patch with PIN diodes loaded on it. The first dielectric layer is a metamaterial layer with Lorentz-type permeability dispersion characteristics. This metamaterial layer includes, from top to bottom, a first dielectric plate 6, a second dielectric plate 7, and a third dielectric plate 8. The second dielectric plate 7 has two pairs of open-circuit resonant rings (SRR dispersive metal rings 5) embedded in it. The metal ground plane 3 is located between the third dielectric plate 8 and the fourth dielectric plate 9, and the bottom-layer feed line is located below the fourth dielectric plate 9. Multiple grounding metal posts are equally spaced on opposite sides of the unit. These grounding metal posts only penetrate the first dielectric layer (i.e., sequentially pass through the first dielectric plate 6, the second dielectric plate 7, and the third dielectric plate 8) and are directly electrically connected to the metal ground plane 3. When multiple units are arranged in a two-dimensional array, the grounded metal pillars of adjacent units together form an equivalent metal wall at the unit boundary, which effectively suppresses the lateral propagation of surface waves and significantly improves the electromagnetic control stability of the entire metasurface under oblique incidence conditions.

[0035] Furthermore, the dual-frequency programmable metasurface also includes a field-programmable gate array (FPGA) control system. The FPGA control system is electrically connected to the bottom-layer feed lines of multiple dual-frequency programmable metasurface units. Each dual-frequency programmable metasurface unit's bottom-layer feed line contains a DC bias line corresponding to a PIN diode. These DC bias lines are electrically connected to the positive side of the PIN diode on the top-layer H-shaped metal patch through metal vias perpendicularly penetrating the fourth dielectric substrate 9, the metal ground plane 3, and the first dielectric layer; the negative side of the PIN diode is directly connected to the metal ground plane 3 through metal vias perpendicularly penetrating the first dielectric layer. Since the negative terminal of the PIN diode is directly grounded, the bias line only needs to be connected to the positive terminal. The FPGA control system applies a controllable bias voltage to the DC bias lines of each unit through independent output ports, thereby independently controlling the conduction or cutoff state of the PIN diode in each unit. Since the PIN diode of each unit simultaneously determines the reflection phase of that unit in the first and second target frequency bands, the FPGA control system can synchronously program the reflection phase distribution of the entire metasurface array in the two target frequency bands. Through a pre-designed coding sequence, this dual-frequency programmable metasurface can collaboratively achieve various electromagnetic control functions such as beam deflection, beam focusing, and beam shaping in two frequency bands.

[0036] Unlike traditional dual-frequency programmable metasurfaces that require two independent control systems to drive the phase modulation structure of different frequency bands, in this embodiment of the invention, the dual-frequency programmable metasurface only needs one field-programmable gate array control system to simultaneously complete the phase modulation of two frequency bands, which significantly reduces the complexity and hardware cost of the control system, avoids the idle waste of control resources, and achieves efficient dual-frequency collaborative control.

[0037] To verify the actual beam control capability of this dual-frequency programmable metasurface, beam deflection simulations were performed on a two-dimensional array composed of the aforementioned units. Figure 6 The image shows the far-field radiation pattern of a 20° beam deflection achieved when an electromagnetic wave is incident normally at a frequency of 3.83 GHz (N78 band); as shown... Figure 7 The image shows the results of a 20° beam deflection at a frequency of 4.43 GHz (N79 band) under the same incident conditions. Further increasing the deflection angle, such as... Figure 8 The image shown is a simulation diagram of a 40° beam deflection at 3.83 GHz, as follows. Figure 9 The image shown is a simulation of a 40° beam deflection at 4.43 GHz. Changing the incident angle of the electromagnetic wave, such as... Figure 10 The image shows the far-field radiation pattern of a 20° beam deflection achieved when an electromagnetic wave is incident at an angle of 20° and a frequency of 3.83 GHz (N78 band); as shown... Figure 11The image shows the results of 20° beam deflection at a frequency of 4.43 GHz (N79 band) under the same incident conditions.

[0038] The above results demonstrate that the dual-frequency programmable metasurface designed in this invention can achieve large-angle beam deflection in both target frequency bands, with accurate beam pointing and low sidelobe levels, thus verifying the effectiveness of the dual-frequency phase modulation scheme based on Lorentz dispersion.

[0039] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A design method for dual-frequency programmable metasurface units based on Lorentz dispersion, characterized in that, include: The structure consists of a top-layer metal resonant structure, a first dielectric layer, a metal ground plane, a second dielectric layer, and a bottom-layer feed line, which are stacked sequentially. The method for designing the first dielectric layer is as follows: the first dielectric layer is a metamaterial layer with Lorentz-type permeability dispersion characteristics. The metamaterial layer includes an upper dielectric plate, a lower dielectric plate, and an intermediate layer disposed between the upper dielectric plate and the lower dielectric plate. The intermediate layer has two pairs of open-ended resonant rings embedded in it, each pair of open-ended resonant rings consisting of two open-ended rings with opposite opening directions. The resonant frequency of the metamaterial layer is higher than the low-frequency band of the target dual-frequency operating band. By adjusting the geometric parameters of the top metal resonant structure and the geometric parameters of the open resonant ring in the metamaterial layer, a dual-frequency programmable metasurface unit based on Lorentz dispersion that simultaneously achieves 1-bit phase modulation in the first and second target frequency bands is obtained. Multiple grounding metal posts are provided at each of the opposite two ends of the dual-frequency programmable metasurface unit. The grounding metal posts penetrate the first dielectric layer and are connected to the metal grounding plate.

2. The design method for dual-frequency programmable metasurface units based on Lorentz dispersion according to claim 1, characterized in that: A PIN diode is loaded in the top-layer metal resonant structure.

3. The design method for dual-frequency programmable metasurface units based on Lorentz dispersion according to claim 2, characterized in that: The positive side of the PIN diode is connected to the underlying feed line through a metal via that vertically penetrates the first dielectric layer, the metal ground plane, and the second dielectric layer. An insulating isolation ring is provided between the metal via and the metal ground plane. The negative side of the PIN diode is connected to the metal ground plane through a metal via that vertically penetrates the first dielectric layer.

4. The design method for dual-frequency programmable metasurface units based on Lorentz dispersion according to claim 2, characterized in that: After adjusting the geometric parameters of the top metal resonant structure and the geometric parameters of the open resonant ring in the metamaterial layer, the reflection amplitude of the dual-frequency programmable metasurface unit based on Lorentz dispersion is not less than 0.98 in both the on and off states of the PIN diode loaded in the top metal resonant structure within the first target frequency band, and not less than 0.75 in both the on and off states of the PIN diode within the second target frequency band.

5. The design method for dual-frequency programmable metasurface units based on Lorentz dispersion according to claim 2, characterized in that: The bottom-layer feed line includes a DC bias line corresponding to each of the PIN diodes. The DC bias line is electrically connected to the top-layer metal resonant structure through a metal via. An insulating isolation ring is provided between the metallized via and the metal ground plane.

6. The design method for dual-frequency programmable metasurface units based on Lorentz dispersion according to claim 1, characterized in that: The grounding metal pillars are arranged at equal intervals on opposite sides of the dual-frequency programmable metasurface unit.

7. The design method for dual-frequency programmable metasurface units based on Lorentz dispersion according to claim 1, characterized in that: The opening directions of the two pairs of open resonant rings embedded in the intermediate layer are perpendicular to the extension direction of the resonant arm of the top metal resonant structure, and the two pairs of open resonant rings are symmetrically distributed about the center of the dual-frequency programmable metasurface unit.

8. A dual-frequency programmable metasurface unit based on Lorentz dispersion, characterized in that, include: The structure consists of a top-layer metal resonant structure, a first dielectric layer, a metal ground plane, a second dielectric layer, and a bottom-layer feed line, stacked sequentially. The first dielectric layer is a metamaterial layer with Lorentz-type permeability dispersion characteristics. The metamaterial layer includes an upper dielectric plate, a lower dielectric plate, and an intermediate layer disposed between the upper dielectric plate and the lower dielectric plate. The intermediate layer has two pairs of open-ended resonant rings embedded in it. Each pair of open-ended resonant rings consists of two open-ended rings with opposite opening directions. Multiple grounding metal posts are disposed at opposite ends of the dual-frequency programmable metasurface unit based on Lorentz dispersion, the grounding metal posts penetrating the first dielectric layer and connected to the metal ground plane.

9. A dual-frequency programmable metasurface based on Lorentz dispersion, characterized in that, It includes multiple dual-frequency programmable metasurface units based on Lorentz dispersion as described in claim 8, wherein the dual-frequency programmable metasurface units are arranged in a two-dimensional array.

10. The dual-frequency programmable metasurface based on Lorentz dispersion according to claim 9, characterized in that, It also includes an FPGA control system, which is connected to the underlying feed lines of multiple dual-frequency programmable metasurface units.

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