Composite super-structure surface unit with microwave window and infrared focusing and design method

Abstract

The invention belongs to the technical field of microwave frequency selective surface and infrared reflection focusing composite metasurface structures and design. A unit of a microwave band adopts a layered structure of metal pattern-ceramic dielectric-air gap-silicon substrate. The metal pattern is a miniaturized design of a three-order nested square patch, and the unit period is only 0.164 times of the working wavelength. According to the invention, a passive factor of a silicon substrate of an infrared band and an air gap generated by actual processing are creatively converted into an active design degree of freedom, and through collaborative optimization, a transmission coefficient higher than 0.99 at a center frequency of 15GHz, a-1dB bandwidth greater than 30%, and excellent angle stability under oblique incidence of 0-45 degrees are realized. The unit reflectivity of the infrared band is higher than 99% and close to 1, phase modulation can be achieved, and the infrared metasurface has a convergence function. The device is simple in structure and easy to integrate, and a new scheme is provided for realizing a function integrated device of microwave and infrared bands.

Description

Technical Field

[0001] This invention belongs to the field of microwave frequency selective surface and infrared reflection focusing composite metasurface structure and design technology, specifically involving a composite metasurface unit and design method that combines microwave window and infrared focusing. Background Technology

[0002] Frequency selective surfaces (FSTs), as a type of spatial filter, have wide applications in radar, communication, and stealth technologies. Traditional FSTs typically employ multi-layer structures to achieve broadband and high angular stability, which leads to complex design, difficult fabrication, high cost, and low integration.

[0003] With the development of metasurface technology, there is a growing demand for integrating different wavelength band functions into a single device. For example, in applications such as multi-functional aperture and composite seeker technology, it is necessary to achieve filtering in the microwave band while simultaneously achieving imaging or stealth functions in the infrared band. However, existing technologies mostly involve simple stacking or discrete design of metasurfaces in different wavelength bands, with little research on the interactions between microwave and infrared metasurfaces. In particular, when using silicon with a high dielectric constant as the substrate for infrared metasurfaces, it significantly affects the performance of adjacent microwave metasurfaces, including transmission efficiency, resonant frequency, bandwidth, and angular stability. Currently, there is a lack of an effective design method that can consider the influence of the dielectric substrate when designing microwave-infrared composite metasurfaces. Therefore, this invention provides a composite metasurface unit and design method that combines microwave windowing and infrared focusing. Summary of the Invention

[0004] The purpose of this invention is to provide a composite metasurface unit and design method that combines microwave windowing and infrared focusing. The invention aims to consider the silicon substrate supporting the infrared metasurface and the air gaps generated during processing, and through synergistic optimization, transform silicon from low transmission efficiency to high transmission efficiency through design. The infrared metasurface unit supported by the silicon substrate has a reflectivity close to 1, enabling phase modulation. The designed microwave metasurface unit adopts a single-layer structure, featuring miniaturization and low cost. In terms of performance, it achieves high-efficiency transmission approaching 100% in the microwave band with a center frequency of 15 GHz and maintains excellent transmission performance stability within the oblique incidence angle range of 0° to 45°, with a bandwidth exceeding 30%. The infrared metasurface unit is coated with multiple reflective films to ensure high reflectivity, and phase modulation enables reflection focusing.

[0005] The specific technical solution adopted by this invention is as follows: A composite metasurface unit combining microwave windowing and infrared focusing, and its design method, comprising a sequentially stacked arrangement: A metal patch layer whose pattern is configured to generate resonance in the microwave band to achieve frequency selectivity; a first dielectric layer; A metal gap layer; an air gap layer; a second dielectric layer. The second dielectric layer is made of silicon and is configured to carry metasurface functions in the infrared band; The parameters of the metal patch layer, the first dielectric layer, the metal gap layer, the air gap layer, and the second dielectric layer are synergistically optimized to jointly achieve the predetermined microwave transmission performance.

[0006] Preferably, the first dielectric layer is a single-layer structure with a unit period less than one-fifth of the microwave operating wavelength, which has the characteristics of miniaturization.

[0007] Preferably, the metal patch layer comprises a multi-level nested square patch structure.

[0008] Preferably, when electromagnetic waves are incident perpendicularly, the transmission coefficient at the 15GHz center frequency is higher than 0.99, the -1dB absolute bandwidth is not less than 5GHz, the relative bandwidth is greater than 30%, and it has a good transmission effect on electromagnetic waves incident from 0° to 45°.

[0009] The design method for composite metasurface units includes the following steps: A composite model was established, comprising a metal microstructure layer, a first dielectric layer, an air gap layer, and a silicon substrate. With the target transmission performance in the microwave band as the optimization objective, the geometric parameters of the metal microstructure layer, the parameters of the first dielectric layer, and the thickness of the air gap layer are co-simulated and optimized.

[0010] The technical effects achieved by this invention are as follows: The unit cell of this invention in the micro-band adopts a layered structure of "metal pattern - ceramic dielectric - air gap - silicon substrate". The metal pattern is a miniaturized design of three-order nested square patches, with a unit cell period of only 0.164 times the operating wavelength. This invention innovatively transforms the silicon functional substrate and the air gap generated during actual processing in the infrared band from passive factors into active design freedom. Through collaborative optimization, it achieves a transmission coefficient higher than 0.99 at a 15GHz center frequency, a -1dB bandwidth greater than 30%, and excellent angular stability under 0-45° oblique incidence. The unit cell reflectivity in the infrared band is higher than 99%, close to 1, enabling phase modulation. The infrared metasurface in this invention has a focusing function. This invention has a simple structure and is easy to integrate, providing a new solution for realizing integrated microwave and infrared band functional devices. Attached Figure Description

[0011] Figure 1a This is a schematic diagram of the microwave infrared composite metasurface structure of the present invention; Figure 1b This is a side view of the microwave infrared composite metasurface structure of the present invention; Figure 1c This is a schematic diagram of the structure of the frequency selective surface unit of the present invention; Figure 1d This is a plan view of the frequency selective surface unit patch layer of the present invention; Figure 1e This is a plan view of the frequency selective surface unit gap layer of the present invention; Figure 1f This invention relates to an infrared metasurface unit structure; Figure 2a This is the amplitude of the reflection coefficient of the infrared unit of this invention; Figure 2b This refers to the phase of the reflection coefficient of the infrared unit of this invention; Figure 3a This is the phase distribution diagram of the infrared metasurface array of the present invention; Figure 3b This is a schematic diagram of the infrared metasurface array of the present invention; Figure 4a This invention relates to the electric field intensity distribution of the xoz plane on the infrared metasurface. Figure 4b This invention relates to the electric field intensity distribution of the focal plane of the infrared metasurface. Figure 5 It is the transmission coefficient of the infrared unit silicon substrate of this invention in the microwave band; Figure 6a This is the transverse electromagnetic wave transmission coefficient of the microwave-infrared composite structure of the present invention; Figure 6b It is the transverse magnetic wave transmission coefficient of the microwave-infrared composite structure of this invention. Detailed Implementation

[0012] To make the objectives and advantages of this invention clearer, the invention will be specifically described below with reference to embodiments. It should be understood that the following text is merely used to describe one or more specific embodiments of the invention and does not strictly limit the scope of protection specifically claimed by the invention.

[0013] As shown in Figure 1, this invention relates to a microwave frequency selective surface and infrared reflective focusing composite metasurface structure and design method. The structure includes an infrared reflective focusing metasurface and a microwave frequency selective metasurface. The infrared metasurface has high reflectivity and is supported by a silicon substrate. The microwave metasurface is formed by the silicon substrate and the frequency selective surface, exhibiting wide viewing angles and high transmittance, enabling synergistic functionality in the microwave-infrared composite frequency band. Specific details to be disclosed: such as Figures 1a-1f As shown, a composite metasurface unit combining microwave windowing and infrared focusing comprises a sequentially stacked arrangement: A metal patch layer whose pattern is configured to generate resonance in the microwave band to achieve frequency selectivity; a first dielectric layer; A metal gap layer; an air gap layer; a second dielectric layer. The second dielectric layer is made of silicon and is configured to carry metasurface functions in the infrared band; The parameters of the metal patch layer, the first dielectric layer, the metal gap layer, the air gap layer, and the second dielectric layer are synergistically optimized to jointly achieve the predetermined microwave transmission performance.

[0014] Preferably, the first dielectric layer is a single-layer structure with a unit period less than one-fifth of the microwave operating wavelength, which has the characteristics of miniaturization.

[0015] Preferably, the metal patch layer comprises a multi-level nested square patch structure.

[0016] Preferably, when electromagnetic waves are incident perpendicularly, the transmission coefficient at the 15GHz center frequency is higher than 0.99, the -1dB absolute bandwidth is not less than 5GHz, the relative bandwidth is greater than 30%, and it has a good transmission effect on electromagnetic waves incident from 0° to 45°.

[0017] The design method of microwave infrared composite metasurface unit includes the following steps: A composite model was established, comprising a metal microstructure layer, a first dielectric layer, an air gap layer, and a silicon substrate. With the target transmission performance in the microwave band as the optimization objective, the geometric parameters of the metal microstructure layer, the parameters of the first dielectric layer, and the thickness of the air gap layer are co-simulated and optimized.

[0018] The working principle of this invention is as follows: In the infrared band, the metasurface unit structure type is cylindrical, such as... Figure 1f As shown, the unit height h1 = 2 μm, the period is 2 μm, the infrared metasurface unit is supported by a silicon substrate, and a multilayer reflective film is deposited below the dielectric silicon substrate. The film system consists of alternating germanium and aluminum oxide films with relative permittivity of 15.8 and 2.7, respectively, and a thickness h. ge =0.25607um, h al =0.7103um, making its reflectance at the operating wavelength as high as 99% or more, such as Figure 2a and Figure 2b As shown, the influence of the microwave structure on the infrared unit can therefore be ignored. The required phase is calculated using the phase distribution formula: ; Where λ is the target wavelength and f is the target focal length, which is 100 μm and 3900 nm respectively. The phase distribution is calculated as follows: Figure 3a andFigure 3b As shown.

[0019] Based on the designed infrared metasurface elements, infrared metasurface elements with corresponding phases were extracted from the element library according to the convergence phase distribution and assembled into an array. Simulation results in CST simulation software show that the designed metasurface has the function of reflection and focusing, with a focal length of approximately 87 μm and a focal shift rate of approximately 13%. Figure 4a and Figure 4b As shown.

[0020] In the microwave band, this design focuses on addressing the adverse effects of high-dielectric-constant silicon substrates on microwave transmission. A standalone silicon substrate exhibits low transmittance at a center frequency of 15 GHz, such as... Figure 5 As shown, the infrared dielectric silicon substrate and the air gap between it and the ceramic layer are used as design parameters, rather than passively accepting processing errors. By combining it with a metal patch layer-ceramic-metal gap layer, the transmission coefficient and angular stability in the microwave band are significantly improved while extending the bandwidth. This structure adds silicon and air to the outermost layer of the traditional MEFSS structure; it is not a simple superposition but a synergistically optimized whole. The microwave metasurface uses miniaturized resonant units based on a third-order square patch, with a unit period d that is only 0.164 times the operating wavelength of 20 mm, i.e., 3.28 mm, demonstrating miniaturization.

[0021] Through the synergistic design of the above structures and methods, composite metasurface structures can simultaneously achieve high-performance microwave transmission under both TE and TM polarizations, such as... Figure 6a and 6b As shown, the influence of the infrared metasurface substrate was also considered. Specific performance characteristics are: a transmission efficiency exceeding 99% at a center frequency of 15 GHz, a -1 dB bandwidth covering 12.5 GHz to 17.5 GHz, a relative bandwidth greater than 30%, and minimal performance variation within an incident angle of 0–45°.

[0022] The specific parameters are as follows: the dielectric constant of the ceramic dielectric is 3.2, the dielectric constant of the single crystal silicon is 11.9, the thickness of the single crystal silicon is hs=0.8mm, the metal thickness is 0.04mm, p=0.4mm, q=0.24mm, ls=3.6mm, ls2=1.44mm, ls3=0.84, ls4=0.4032mm, w=0.246mm, the air thickness is hair=0.5mm, and the ceramic thickness is h=1.23mm.

[0023] The above description is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described or explained in this invention are implemented according to conventional methods in the art unless otherwise specified or limited.

Claims

1. A composite metasurface unit with microwave window and infrared focusing, characterized in that: Comprise the arrangement of the following layers stacked in sequence: A metal patch layer, the pattern of which is configured to resonate at the microwave band to achieve frequency selection function; a first dielectric layer; A metal slot layer; an air gap layer; A second dielectric layer, The second dielectric layer is composed of silicon material and is configured to carry the super surface function of the infrared band; Wherein, the parameters of the metal patch layer, the first dielectric layer, the metal slot layer, the air gap layer and the second dielectric layer are optimized to achieve the predetermined microwave transmission performance.

2. The composite metasurface unit with microwave window and infrared focusing and design method according to claim 1, characterized in that: The first dielectric layer is a single layer structure, and the unit period is less than one fifth of the microwave working wavelength.

3. The composite metasurface unit with microwave window and infrared focusing and design method according to claim 1, characterized in that: The metal patch layer contains multi-order nested square patch structure.

4. The composite metasurface unit with microwave window and infrared focusing and design method according to claim 1, characterized in that: When the electromagnetic wave is vertically incident, the transmission coefficient at the center frequency of 15GHz is higher than 0.99, the absolute bandwidth is not less than 5GHz, and the relative bandwidth is greater than 30%.

5. The design method of the composite metasurface unit and design method according to any one of claims 1-4, characterized in that, Comprise the following steps: Establish a composite model containing a metal microstructure layer, a first dielectric layer, an air gap layer and a silicon substrate; With the target transmission performance of the microwave band as the optimization target, the geometric parameters of the metal microstructure layer, the parameters of the first dielectric layer and the thickness of the air gap layer are simulated and optimized.

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