Reconfigurable intelligent surface based on achromatic theory and construction method thereof

Abstract

The invention discloses a reconfigurable intelligent surface based on an achromatic theory and a construction method thereof, the reconfigurable intelligent surface comprises a metasurface unit, the metasurface unit comprises a substrate and a metal patch arranged on the substrate, the substrate has a certain thickness, and two paths of paths are connected between two opposite angles of the upper surface and the lower surface of the substrate. And the tunable integrated component is arranged on the metal patch of the metasurface unit to form a broadband achromatic metasurface unit. A plurality of broadband achromatic metasurface units are arranged and combined to form the reconfigurable intelligent surface. The capacitance value of the component is changed by changing the external voltage, so that the reflection phase of the metasurface unit is changed, the reflection phase of the metasurface unit is dynamically adjustable along with the external voltage, the dispersion curve of the metasurface unit meets the achromatic requirement, and the dynamic achromatic function is achieved.

Description

Technical Field

[0001] The present invention relates to the field of electromagnetic functional materials, and in particular to a reconfigurable intelligent surface based on achromatic theory and a construction method thereof. Background Art

[0002] Metasurfaces have excellent performance in manipulating electromagnetic waves, but the dependence of electromagnetic response on wavelength will cause chromatic aberration, which seriously affects the performance and application of beam deflectors. In recent years, the introduction of broadband achromatic components has attracted widespread attention in the field of full-color detection and imaging. Its advantage of successfully eliminating chromatic aberration in the continuous wavelength region has promoted the development of metasurfaces.

[0003] In the visible light, infrared, terahertz and even microwave bands, people have proposed various methods to achieve dispersion-free characteristics, such as dispersion compensation, non-resonant effects and multimode systems. Among them, dispersion compensation, as a traditional method of achromatic aberration, can modulate the group delay of the unit by changing the geometric phase and resonant phase. However, the geometric phase is affected by the circular polarization state of the incident electromagnetic wave, causing the surface to be sensitive to polarization. When designing a metasurface with broadband performance and independent of polarization, it is usually required that the unit has a low circuit quality factor (Q) at the resonant frequency, which often limits the adjustment of the group delay and deteriorates the achromatic performance. Therefore, previous research on achromatic aberration is often related to polarization, or is limited by the control range of phase dispersion, or the unit structure is very complex and difficult to implement. Moreover, these achromatic metasurfaces do not have dynamic adjustability, which has become one of the problems hindering their development and application.

[0004] The dependence of electromagnetic response on wavelength will cause chromatic aberration, which seriously affects the performance and application of beam deflectors. In order to achieve dispersion-free characteristics in the microwave band, the traditional dispersion compensation method that modulates the group delay of the unit by changing the geometric phase and the resonant phase is sensitive to polarization, and the reflection phase dispersion cannot be dynamically changed, and the dispersion compensation bandwidth is poor. It is necessary to solve the technical problem of dynamic adjustment of broadband reflection phase. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a reconfigurable smart surface based on achromatic theory and a construction method thereof, wherein tunable integrated components are added to the metasurface unit, and the capacitance value of the components is changed by changing the external voltage, thereby changing the reflection phase of the metasurface unit, so that the reflection phase of the metasurface unit can be dynamically adjusted with the external voltage, so that the dispersion curve of the metasurface unit meets the achromatic requirements, thereby realizing the dynamic achromatic function.

[0006] The object of the present invention is achieved through the following technical solution, a reconfigurable smart surface based on achromatic theory, comprising:

[0007] The metasurface unit comprises a substrate and a metal patch arranged on the substrate, wherein the substrate has a certain thickness and two paths are connected between two diagonals of the upper surface and the lower surface of the substrate.

[0008] Tunable integrated components are arranged on the metal patch of the metasurface unit to form a broadband achromatic metasurface unit.

[0009] Multiple broadband achromatic metasurface units are arranged and combined to form a reconfigurable smart surface.

[0010] Preferably, the material used for the substrate includes at least F4B high-frequency plate material.

[0011] Preferably, the tunable component includes at least a varactor diode.

[0012] Preferably, the capacitance value of the varactor diode ranges from 0.025 pF to 0.19 pF, and the corresponding voltage ranges from 0 V to 15 V.

[0013] In addition to providing a reconfigurable smart surface based on achromatic theory, the present invention further provides a method for constructing the reconfigurable smart surface, which specifically includes the following steps:

[0014] Step 1, determining the relationship between the phase difference of adjacent metasurface units and the normalized frequency of the electromagnetic wave, and constructing a phase dispersion curve of the metasurface unit within a wide frequency band;

[0015] Step 2: construct the first broadband achromatic metasurface unit through simulation, change the capacitance value of the tunable component to adjust the resonant frequency so that it satisfies the phase dispersion curve obtained in step 1, obtain the corresponding relationship between the phase and the capacitance value, and screen out suitable tunable components;

[0016] Step 3: According to the correspondence between the phase and the capacitance value obtained in step 2, a suitable capacitance value can be selected to construct broadband achromatic metasurface units at different positions. All constructed broadband achromatic metasurface units are arranged and combined to obtain a metasurface unit array, and the smart surface can be reconstructed.

[0017] Preferably, in step 1, the phase gradient of the broadband achromatic metasurface unit The following relationship must be satisfied:

[0018]

[0019] In the formula, is the phase difference between adjacent broadband achromatic metasurface units, P is the length of the broadband achromatic metasurface unit, and f=1 / λ is the normalized frequency of the electromagnetic wave.

[0020] Preferably, in step 2, HFSS three-dimensional structural electromagnetic field simulation software is used to construct the metasurface unit.

[0021] Preferably, in step 3, the beam deflection formula is derived from the generalized reflection law as follows:

[0022]

[0023] where n r =n i =1, λ0 is the wavelength of the incident electromagnetic wave, θ i is the incident angle, θ r is the reflection angle; the phase gradient is calculated from the above formula According to the corresponding relationship between the phase and the capacitance value obtained in step 2, a suitable capacitance value can be selected, and units at different positions can be designed to obtain the final desired array.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] The present invention provides a reconfigurable smart surface based on achromatic theory and a construction method thereof. A tunable integrated component is added to a metasurface unit. The capacitance value of the component is changed by changing an external voltage, thereby changing the reflection phase of the metasurface unit. The reflection phase of the metasurface unit is dynamically adjustable with the external voltage, so that the dispersion curve of the metasurface unit meets the achromatic requirement and realizes the dynamic achromatic function. A metasurface array with a phase gradient change of the reflected wave is designed based on the phase-adjustable metasurface unit, and the direction of beam deflection is dynamically adjusted in combination with the generalized reflection law.

[0026] The present invention applies achromatic theory to realize reflection: the structure of each array element in the array remains unchanged, and electromagnetic waves of different wavelengths within a continuous bandwidth are used to impinge on the metasurface, and the deflection direction of the reflected beam can remain basically unchanged, so that the surface can maintain stable deflection performance under broadband conditions.

[0027] The present invention uses a reconfigurable smart surface to achieve achromatic aberration without changing the structure or scaling of the unit. The resonant frequency of the unit can be adjusted by changing the loading capacitance of the tunable component using an external voltage, providing a phase dispersion curve with adjustable slope, and achieving the function of achromatic aberration. At the same time, since the phase of each unit is independently controllable, the deflection direction of the beam can be flexibly controlled by an external voltage under broadband conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the structure of a broadband achromatic metasurface unit in an embodiment of the present invention;

[0029] Figure 2 for Figure 1 A top view of

[0030] Figure 3 for Figure 1 Side view of;

[0031] Figure 4 This is an overall design flow chart of a method for constructing a broadband achromatic metasurface unit in an embodiment of the present invention;

[0032] Figure 5 This is a graph showing the transformation of the reflection amplitude of a broadband achromatic metasurface unit with the capacitance value in an embodiment of the present invention;

[0033] Figure 6 This is a diagram showing the transformation of the reflection phase of a broadband achromatic metasurface unit with the capacitance value in an embodiment of the present invention;

[0034] Figure 7 This is a diagram of an adjustable achromatic reflective array in an embodiment of the present invention;

[0035] Figure 8 The 12° deflection antenna pattern in the embodiment of the present invention;

[0036] Fig. 9 The 20° deflection antenna pattern in the embodiment of the present invention;

[0037] Fig.10 The 25° deflection antenna pattern in the embodiment of the present invention;

[0038] Fig.11 This is the 25° deflection antenna pattern in the embodiment of the present invention.

[0039] In the figure, 1 is a substrate; 2 is a metal patch; 3 is a via; and 4 is a tunable component. DETAILED DESCRIPTION

[0040] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0041] like Figures 1 to 3 As shown, the technical solution of the present invention provides a reconfigurable smart surface based on achromatic theory, characterized in that the reconfigurable smart surface includes:

[0042] The metasurface unit comprises a substrate 1 and a metal patch 2 arranged on the substrate, wherein the substrate 1 has a certain thickness, and two passages 3 are connected between two diagonals of the upper surface and the lower surface of the substrate 1.

[0043] The tunable integrated component 4 is arranged on the metal patch 2 of the metasurface unit to form a broadband achromatic metasurface unit.

[0044] Multiple broadband achromatic metasurface units are arranged and combined to form a reconfigurable smart surface. The reconfigurable smart surface (adjustable achromatic reflective array) is shown in Figure 7 shown.

[0045] In one embodiment of the present invention, the material used for the substrate 1 at least includes F4B high-frequency board material.

[0046] In one embodiment of the present invention, the tunable component 4 at least includes a varactor diode. The capacitance value of the varactor diode ranges from 0.025 pF to 0.19 pF, and the corresponding voltage is 0V to 15V.

[0047] like Figure 4 As shown, in addition to providing a reconfigurable smart surface based on achromatic theory, the present invention further provides a method for constructing the above-mentioned reconfigurable smart surface, which specifically includes the following steps:

[0048] Step 1, determining the relationship between the phase difference of adjacent metasurface units and the normalized frequency of the electromagnetic wave, and constructing a phase dispersion curve of the metasurface unit within a wide frequency band;

[0049] Step 2: construct the first broadband achromatic metasurface unit through simulation, change the capacitance value of the tunable component to adjust the resonant frequency so that it satisfies the phase dispersion curve obtained in step 1, obtain the corresponding relationship between the phase and the capacitance value, and screen out suitable tunable components;

[0050] Step 3: According to the correspondence between the phase and the capacitance value obtained in step 2, a suitable capacitance value can be selected to construct broadband achromatic metasurface units at different positions. All constructed broadband achromatic metasurface units are arranged and combined to obtain a metasurface unit array, and the smart surface can be reconstructed.

[0051] The present invention adds tunable integrated components to the metasurface unit. According to the relationship between the unit phase curve and the capacitance of the tunable component, the units at different positions can be designed in combination with the generalized reflection law to obtain a tunable phase distribution that realizes the achromatic function. During operation, the capacitance of the component is changed by changing the applied voltage, and the direction of beam deflection is dynamically adjusted. It has the advantages of small array, dynamic control of beam deflection direction, and the ability to work in a wide frequency band, which is of great significance for expanding the application of metasurfaces.

[0052] In one embodiment of the present invention, based on ANSYS Electronics simulation software, step 1 specifically includes the following steps:

[0053] Step 1: According to the following formula:

[0054]

[0055] Where θ is the deflection angle, is the phase difference between adjacent units, P is the length of the unit, and f = 1 / λ is the normalized frequency of the electromagnetic wave. From this formula, we can see that if we want to design a broadband achromatic unit, its phase gradient The following formula must be satisfied: It can be further obtained from this formula that when P remains unchanged, the phase difference between adjacent units needs to satisfy a linear relationship with f as much as possible. That is, the unit can provide a relatively stable phase dispersion curve with different slopes within a wide bandwidth.

[0056] In one embodiment of the present invention, step 1 specifically includes the following steps:

[0057] By using HFSS to design a Figures 1 to 3 The metasurface unit shown in Table 1 has detailed parameters, the operating frequency is 8 GHz, the material used for the substrate in this embodiment is F4B, the dielectric constant is 2.65, and the loss tangent is 0.001; the adjustment unit adjusts the resonant frequency by changing the capacitance value of the tunable component so that it can meet the phase dispersion curve requirements in step 1, thereby selecting a suitable tunable component. The tunable component selected in this embodiment is a varactor diode, model MAVR-011020-1411, with a capacitance range of 0.025 pF-0.19 pF, and a corresponding voltage of 0 V-15 V, and finally obtains the corresponding relationship between different phases and capacitance values, such as Figures 5 and 6 As shown. The advantages of this embodiment are: 1. The phase curve can be changed by changing the capacitance value of the tunable component without changing the unit structure. Compared with the array that controls the different deflection directions of the beam by changing the unit structure or ratio, it is beneficial to the overall construction of the array; 2. The unit period length p is only 0.16λ0 (where λ0 is the wavelength corresponding to the operating frequency), which effectively reduces the scale of the entire array when the number of array elements remains unchanged.

[0058] Table 1 Unit structure dimensions

[0059]

[0060] In one embodiment of the present invention, step 3 specifically includes the following steps: deriving the beam deflection formula according to the generalized reflection law is as follows:

[0061]

[0062] where n r =n i =1, λ0 is the wavelength of the incident electromagnetic wave, θ i is the incident angle, θ r is the reflection angle. The phase gradient can be calculated from this formula According to the corresponding relationship between phase and capacitance obtained in step 2, the appropriate capacitance value can be selected, and the units at different positions can be designed to obtain the final desired array. r , and then control the deflection direction of the beam. The design incident angle is 10°, and the deflection angle is 12°, 20°, ±25°, such as Figures 8 to 11 As shown in the figure, in the range of 7.3GHz-8.4GHz, the beam deflection direction remains basically unchanged. Since changing the capacitance value by applying an external voltage will cause a strong resonance in the unit, the achromatic performance will deteriorate, resulting in an error within 2°. This result proves the feasibility of using reconfigurable surfaces to achieve achromaticity.

[0063] The results show that:

[0064] 1) From Figure 5 and Figure 6 It can be seen that when the capacitance value changes in the range of [0.025V, 0.19V], the reflection amplitude is above -4.05dB, all reflection phase curves have good linear characteristics, and the slope of the phase dispersion curve changes with the change of the capacitance value of the tunable component, satisfying the phase dispersion curve conditions required for adjustable achromatism.

[0065] 2) If Figure 8 As shown in , in the frequency range of [7.3GHz, 8.4GHz], the beam deflection is always within [10°, 12°]; Fig. 9 As shown in , when the electromagnetic wave is incident at an angle of 10°, in the frequency range of [7.3GHz, 8.4GHz], the beam deflection is always within [18°, 20°]; Figure 10 to Figure 11 As shown in the figure, in the frequency range of [7.3GHz, 8.4GHz], the beam deflection is stable at 24° and -24° respectively. In summary, in the frequency range of [7.3GHz, 8.4GHz], the tunable components can control the beam to deflect in any direction between [-25°, 25°], and the error in the beam deflection direction does not exceed 2°, which proves that the tunable components can achieve the function of achromatic aberration.

[0066] In the embodiment of the present invention, tunable components are added to the metasurface to realize the switching between different functions, such as dynamically adjusting the deflection angle of the deflector, the focusing position of the metalens, etc., and the reconfigurable smart surface can realize this function. Reconfigurable smart surfaces (RISs) are a promising tunable metasurface that can replace traditional phased arrays. They are composed of a large number of ultra-low power passive units, each of which can electronically control the phase of the incident electromagnetic wave. RISs have properties such as negative refraction, complete absorption and anomalous reflection, and their spatial feeding mechanism reduces the power loss caused by the excessively large phased array feeding network. However, in previous work, most RISs work in a narrow band. Combining the achromatic theory with RISs can realize dynamic switching functions under wide-band conditions, which may promote the progress of RISs in application fields such as wireless power transmission and information processing.

[0067] The above are preferred embodiments of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A reconfigurable smart surface based on achromatic theory, characterized by: The reconfigurable smart surface comprises: A metasurface unit comprises a substrate (1) and a metal patch (2) arranged on the substrate, wherein the substrate (1) has a certain thickness, and two paths (3) are connected between two diagonal corners of the upper surface and the lower surface of the substrate (1); A tunable integrated component (4) is arranged on the metal patch (2) of the metasurface unit to form a broadband achromatic metasurface unit; A plurality of the broadband achromatic metasurface units are arranged and combined to form a reconfigurable smart surface.

2. The reconfigurable smart surface based on achromatic theory as claimed in claim 1, characterized in that: The material used for the substrate (1) at least includes F4B high-frequency plate material.

3. The reconfigurable smart surface based on achromatic theory as claimed in claim 2, characterized in that: The tunable component (4) at least comprises a varactor diode.

4. The reconfigurable smart surface based on achromatic theory as claimed in claim 3, characterized in that: The capacitance value of the varactor diode ranges from 0.025pF to 0.19pF, and the corresponding voltage ranges from 0V to 15V.

5. A method for constructing a reconfigurable smart surface based on achromatic theory, characterized in that: The method is used to construct the reconfigurable smart surface according to any one of claims 1 to 4, and specifically comprises the following steps: Step 1, determining the relationship between the phase difference of adjacent metasurface units and the normalized frequency of the electromagnetic wave, and constructing a phase dispersion curve of the metasurface unit within a wide frequency band; Step 2: constructing a first broadband achromatic metasurface unit through simulation, changing the capacitance value of the tunable component (4) to adjust the resonant frequency so that it satisfies the phase dispersion curve obtained in step 1, obtaining the corresponding relationship between the phase and the capacitance value, and screening out suitable tunable components; Step 3: According to the correspondence between the phase and the capacitance value obtained in step 2, a suitable capacitance value can be selected to construct broadband achromatic metasurface units at different positions. All constructed broadband achromatic metasurface units are arranged and combined to obtain a metasurface unit array, and the smart surface can be reconstructed.

6. The method for constructing a reconfigurable smart surface based on achromatic theory as claimed in claim 5, characterized in that: In step 1, the phase gradient of the broadband achromatic metasurface unit The following relationship must be satisfied: In the formula, is the phase difference between adjacent broadband achromatic metasurface units, P is the length of the broadband achromatic metasurface unit, and f=1 / λ is the normalized frequency of the electromagnetic wave.

7. The method for constructing a reconfigurable smart surface based on achromatic theory as claimed in claim 6, characterized in that: In the step 2, HFSS three-dimensional structure electromagnetic field simulation software is used to construct the super surface unit.

8. The method for constructing a reconfigurable smart surface based on achromatic theory as claimed in claim 7, characterized in that: In step 3, the beam deflection formula is derived from the generalized reflection law as follows: Where n r =n i =1, λ0 is the wavelength of the incident electromagnetic wave, θ i is the incident angle, θ r is the reflection angle; the phase gradient is calculated from the above formula According to the corresponding relationship between the phase and the capacitance value obtained in step 2, a suitable capacitance value can be selected, and units at different positions can be designed to obtain the final desired array.

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