Reflection type phase gradient metasurface based on geometric phase principle

Abstract

The invention relates to the field of electromagnetic metamaterial design, in particular to a reflective phase gradient metasurface based on a geometric phase principle, which is formed by linearly arranging reflective phase gradient metasurface units, and each reflective phase gradient metasurface unit comprises a metal pattern layer, a dielectric layer and a grounding metal layer, the dielectric layer is arranged between the metal pattern layer and the grounding plate metal layer; rCS reduction of more than 10 dB is achieved within the range of 8.00 GHz-18.00 GHz, the maximum reduction amount can reach 36.78 dB, and the antenna has the advantages of being high in RCS reduction efficiency, low in profile, small in size, easy to machine and the like.

Description

Technical Field

[0001] The present invention relates to the field of electromagnetic metamaterial design, and in particular to a reflective phase gradient metasurface based on a geometric phase principle. Background Art

[0002] Electronic jamming is the regulation of electromagnetic waves emitted by the target. It weakens the detectability of one's own signal through various anti-reconnaissance means, which can reduce the probability of one's own equipment being detected, tracked, or even attacked, thereby achieving the protection of one's own equipment. Radar Cross Section (RCS) is a physical quantity that describes the scattering characteristics of a target through numerical quantification, indicating the magnitude of the scattering power reflected in a certain direction after the target is irradiated by the incident electromagnetic wave.

[0003] Metasurface is a two-dimensional form of electromagnetic metamaterial, a periodic structure composed of planar sub-wavelength artificial material structures, which can realize flexible control of the amplitude, phase and polarization of electromagnetic waves. When electromagnetic waves propagate to the metasurface, different phase changes can be introduced at various local positions on its surface through artificial design according to the generalized Snell reflection law, thereby changing the wave surface and wavefront of electromagnetic wave transmission and realizing the control of beam pointing. Therefore, after loading the metasurface, the original scattering characteristics of the target can be changed; the abnormal reflection angle can be controlled, thereby changing the deflection direction; thereby achieving RCS reduction.

[0004] Prior art CN114759366A discloses a phase gradient-based coded metasurface antenna array structure and design method. Based on the idea of ​​coded metasurface and metasurface antenna, the radiation characteristics of the antenna and the RCS reduction characteristics are studied respectively, while ensuring that the antenna radiation performance is basically unaffected, the effect of dynamically regulating the antenna scattering performance is presented. This technical solution adopts a complex multi-layer structure and needs to load active devices, which is complex in process.

[0005] There is an urgent need to design a phase gradient metasurface that can effectively reduce RCS and has a simple structure. Summary of the invention

[0006] In view of this, the present invention discloses a reflective phase gradient metasurface based on the geometric phase principle to solve the above problems; the reflective phase gradient metasurface based on the geometric phase principle is composed of different reflective phase gradient metasurface units arranged linearly, and the reflective phase gradient metasurface unit includes: a metal pattern layer, a dielectric layer, and a grounded metal layer, and the dielectric layer is arranged between the metal pattern layer and the grounded metal layer.

[0007] Furthermore, the metal pattern layer includes: a horizontal metal strip, a vertical metal strip and two arc metal strips, wherein the horizontal metal strip and the vertical metal strip cross to form a "cross", and the two arc metal strips are evenly arranged at both ends of the vertical metal strip, and the arc direction is in the direction connected to the vertical metal strip.

[0008] The reflective phase gradient metasurface designed by the present invention based on the geometric phase principle has the performance of high polarization conversion rate and RCS reduction, and can achieve an RCS reduction of more than 10dB in the frequency band of 8.00GHz to 18.00GHz, and can achieve a maximum RCS reduction of 36.73dB at 11.52GHz. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is a front view of the super surface unit structure in the present invention;

[0010] Figure 2 It is a side view of the super surface unit structure in the present invention;

[0011] Figure 3 Schematic diagrams of different metasurface units of the present invention;

[0012] Figure 4 Schematic diagram of a reflective phase gradient metasurface in an embodiment of the present invention;

[0013] Figure 5 is a curve diagram of the reflection amplitude of the metasurface unit in an embodiment of the present invention;

[0014] Figure 6 is a reflection phase curve diagram of a metasurface unit in an embodiment of the present invention;

[0015] Figure 7 Graph showing polarization conversion efficiency of a metasurface unit in an embodiment of the present invention;

[0016] Figure 8 A comparison diagram of RCS reduction curves of an embodiment of the present invention and a comparative structure;

[0017] Fig. 9 The three-dimensional scattering diagrams of the embodiment of the present invention and the comparative structure under circular polarization incidence;

[0018] Fig.10 The yoz plane directivity diagrams of the embodiment of the present invention and the comparative structure when circularly polarized incident;

[0019] Fig.11 The three-dimensional scattering diagrams of the embodiment of the present invention and the comparative structure under linear polarization incidence;

[0020] Fig.12 The yoz plane directivity diagrams of the embodiment of the present invention and the comparative structure when linear polarization is incident;

[0021] In the figure, the numbers 1 are metal pattern layer, 2 are dielectric layer, 3 are ground metal layer, (a) is a comparative structure, and (b) is a structure of the present invention. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution, characteristics and advantages of the present invention more clearly understood, the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0023] The reflective phase gradient metasurface based on the geometric phase principle described in this embodiment is composed of different reflective phase gradient metasurface units arranged linearly. Figure 1 As shown, it includes: a metal pattern layer, a dielectric layer, and a grounding metal layer, wherein the dielectric layer is arranged between the metal pattern layer and the grounding metal layer. Figure 2 As shown, 1 is a metal pattern layer, 2 is a dielectric layer, and 3 is a grounding metal layer.

[0024] Furthermore, the metal pattern layer includes: a horizontal metal strip, a vertical metal strip and two arc metal strips, wherein the horizontal metal strip and the vertical metal strip cross to form a "cross", and the two arc metal strips are evenly arranged at both ends of the vertical metal strip, and the arc direction is in the direction connected to the vertical metal strip.

[0025] Furthermore, if Figure 1 As shown, the length 2r of the metal strip is 4 mm, the width w1 is 0.3 mm, and the thickness is 0.035 mm. The opening of the arc metal strip is 120°, the width w2 is 0.4 mm, and the thickness is 0.035 mm. Figure 2 As shown, the dielectric layer and the grounding metal layer are squares of the same size, with a side length of 6 mm, a dielectric layer thickness h of 3 mm, a grounding metal layer thickness of 0.035 mm, the metal pattern layer and the grounding metal layer are made of copper, and the dielectric layer is made of F4B; the conductivity of the metal pattern layer and the grounding metal layer is σ=5.8×107S / m, the material of the dielectric layer is a polytetrafluoroethylene-based high-frequency sheet (F4B), the relative dielectric constant is 3.0, and the loss tangent value is 0.002.

[0026] Furthermore, different units are obtained by rotating the image of the reflective phase gradient metasurface unit.

[0027] When arranged linearly, the rotation angles of the reflective phase gradient metasurface units in each row from left to right are 0°, 30°, 60°, 90°, 120°, and 150° in a cycle.

[0028] Specifically, data analysis was performed by simulating each unit in the frequency domain using the CST simulation software, with a frequency range of 8.00 GHz to 20.00 GHz. The boundary conditions were set to unit cell periodic boundary conditions in the x and y directions, and to open and space in the z direction. The electromagnetic incident wave was incident vertically along the -z direction. The rotation angle α of the metal pattern layer was adjusted to perform parameter scanning to obtain the reflection amplitude, reflection phase, and polarization conversion efficiency corresponding to different α.

[0029] Furthermore, if Figure 6 As shown, at a frequency of 12.23 GHz, when α = 0°, the reflection phase is 179.11°; when α = 30°, the reflection phase is -124.01°, approximately -120°; when α = 60°, the reflection phase is -61.91°, approximately -60°; when α = 90°, the reflection phase is 0.69°; when α = 120°, the reflection phase is 55.66, approximately 60°; when α = 150°, the reflection phase is 117.98°, approximately 120°; according to the theory of geometric phase, the reflection phase difference Δφ and the angle difference Δα basically satisfy the relationship of 2 times (Δφ = 2Δα); as shown in FIG. Figure 5 The reflection amplitude values ​​of the metasurface units at the six angles shown in the figure are all greater than 0.95 in the frequency range of 8.00 GHz to 18.00 GHz; Figure 7 As shown in the figure, the polarization conversion efficiency of the six metasurface units is higher than 95%. It can be seen that the phase gradient metasurface has high polarization conversion rate and abnormal angle reflection.

[0030] Specifically, the generalized Snell reflection law states that directly reducing or increasing a sudden phase at a certain point or place will change the propagation path of the electromagnetic wave, and the wave can be manipulated by artificially creating discontinuity of the surface phase; the geometric phase is achieved by spatially rotating the metasurface unit to achieve a phase shift within the full 360° range. Since the physical size of the metasurface unit has not changed, its phase value is determined by the geometric path parameters of the metasurface unit in space; the phase gradient metasurface can be obtained by arranging units with different phases according to the phase difference. At an interval of 30°, the reflection phase changes significantly and has a phase difference of 60°. If the interval is greater than this, the control of the electromagnetic wave will not be obvious, and if it is less than this, the number of metasurface units will increase significantly.

[0031] Furthermore, if Figure 3 As shown, the six types of units are arranged into phase gradient subarrays according to the linear phase gradient rule, the phase gradient subarrays are arranged in one direction, and the units are arranged in a continuous replication manner at the same position in another direction; Figure 4 , the phase gradient subarray is replicated 6 times along the y direction to form a phase gradient metasurface; and the phase gradient metasurface of this embodiment is formed by replicating it in the x and y directions respectively.

[0032] Specifically, the metasurface of this embodiment is compared with an ideal electric conductor (PEC) of the same size. The simulation results under circular polarization vertical incidence are as follows: Fig. 9 As shown in Figure 9, PEC has a constant reflection phase. From Figure 9(a), we can see that the contrast structure has a strong reflection property. From Figure 9(b), we can see that due to the phase difference between the metasurfaces of the present invention, the incident electromagnetic wave is abnormally reflected, causing the reflected wave to deflect in an abnormal direction. As a result, the energy from the main lobe of the surface is moved to the non-normal direction, thereby effectively reducing the radar scattering cross section. The scattering amplitude of the reflected wave of the designed metasurface is significantly reduced in the normal direction. Fig.11 As shown in FIG. 11(a), under the condition of vertical incidence of linear polarization, it can be seen that the comparison structure has a strong reflection property, and it can be seen from FIG. 11(b) that under the condition of linear polarization incidence, the reflected wave of the present invention is separated into two beams. The more beams there are, the smaller the energy of the beams in each direction. It can be seen that within 8.00 GHz to 18.00 GHz, the present invention has good RCS reduction; Figure 8 As shown, compared with the comparative structure, the RCS reduction value of the present invention in the 8.0 GHz to 18.00 GHz frequency band is more than 10 dB, and at 11.53 GHz, the RCS reduction value reaches a maximum of 36.73 dB.

[0033] Furthermore, if Fig. 9 As shown, Fig. 9 (a) is a three-dimensional scattering diagram of the comparative structure at circular polarization vertical incidence of 12.23 GHz, and 9(b) is a three-dimensional scattering diagram of the present invention at circular polarization vertical incidence of 12.23 GHz; Fig.11 (a) is a three-dimensional scattering diagram of the comparative structure at a linear polarization vertical incidence of 12.23 GHz, and 11(b) is a three-dimensional scattering diagram of the present invention at a linear polarization vertical incidence of 12.23 GHz. Fig.10 As shown, Fig.10 (a) is the directional diagram of the YOZ surface of the contrast structure with circular polarization incident at 12.23 GHz. In the two-dimensional direction, the contrast structure has a main lobe with relatively concentrated energy in the normal direction; 10(b) is the directional diagram of the YOZ surface of the present invention with circular polarization incident at 12.23 GHz. The energy in the normal direction is significantly reduced, achieving abnormal beam deflection. Fig.12 As shown, Fig.12 (a) is the yoz surface radiation pattern of the linear polarization incident contrast structure at 12.23 GHz. The two-dimensional directional contrast structure has a main lobe with relatively concentrated energy in the normal direction. (b) is the yoz surface radiation pattern of the linear polarization incident present invention at 12.23 GHz. The metasurface of the present invention clearly has two side lobes and the energy in the normal direction is significantly reduced. Fig.12In the two-dimensional contrast structure, the energy is concentrated in the normal direction, while the metasurface reflects the beam into multiple beams.

[0034] In summary, when a circularly polarized wave is incident, the present invention has the ability to deflect the reflected wave in an abnormal direction; and when the incident wave is linearly polarized, the reflected wave will be separated into two beams. The present invention can have abnormal reflection phenomena and high polarization conversion rates in the range of 8.00GHz to 18.00GHz, and the received reflected energy is significantly reduced. And an RCS reduction of more than 10dB is achieved, and the maximum reduction can reach 36.78dB. And the metasurface designed by the present invention has the advantages of low profile, small size, and easy processing.

[0035] Finally, it should be noted that the above only describes some embodiments of the present invention. For those skilled in the art, it is conceivable that various changes, modifications, substitutions and deformations may be made to these embodiments without departing from the principles and spirit of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents, and the above-mentioned actions should be covered within the scope of protection of the present invention.

Claims

1. A reflective phase gradient metasurface based on the geometric phase principle, which is composed of different reflective phase gradient metasurface units arranged linearly, characterized in that: The reflective phase gradient metasurface unit comprises: a metal pattern layer, a dielectric layer, and a grounding metal layer, wherein the dielectric layer is arranged between the metal pattern layer and the grounding metal layer.

2. The reflective phase gradient metasurface based on the geometric phase principle according to claim 1, characterized in that: The metal pattern layer includes: a horizontal metal strip, a vertical metal strip and two arc metal strips, wherein the horizontal metal strip and the vertical metal strip cross to form a "cross", and the two arc metal strips are evenly arranged at both ends of the vertical metal strip, and the arc direction is in the direction connected to the vertical metal strip.

3. The reflective phase gradient metasurface based on the geometric phase principle according to claim 2, characterized in that: The horizontal metal strip has the same size as the vertical metal strip, the two arc-shaped metal strips have the same size, and the metal pattern layer is symmetrical based on the vertical metal strip.

4. The reflective phase gradient metasurface based on the geometric phase principle according to claim 3, characterized in that: The transverse metal strip has a length of 4 mm, a width of 0.3 mm and a thickness of 0.035 mm.

5. The reflective phase gradient metasurface based on the geometric phase principle according to claim 3, characterized in that: The opening of the arc metal strip is 120°, the width is 0.4 mm, and the thickness is 0.035 mm.

6. The reflective phase gradient metasurface based on the geometric phase principle according to claim 1, characterized in that: The rotating reflective phase gradient metasurface unit obtains different units by rotating the metal pattern layer. When arranged linearly, the rotation angle of the metal pattern layer in each row of reflective phase gradient metasurface units from left to right is 0°, 30°, 60°, 90°, 120°, and 150° in a cycle.

7. The reflective phase gradient metasurface based on the geometric phase principle according to claim 1, characterized in that: The dielectric layer and the grounding metal layer are squares of the same size, with a side length of 6 mm, a dielectric layer thickness of 3 mm, and a grounding metal layer thickness of 0.035 mm.

8. The reflective phase gradient metasurface based on the geometric phase principle according to claim 1, characterized in that: The material of the metal pattern layer and the grounding metal layer is copper, and the material of the dielectric layer is a polytetrafluoroethylene-based high-frequency plate.

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