A full-space directional multiplexing multifunctional electromagnetic metasurface and a design method thereof

Abstract

The application relates to a full-space-direction multiplexing multifunctional electromagnetic super surface and a design method thereof. The electromagnetic super surface is mainly extended by two basic functional units according to an interlaced arrangement structure period; the two basic functional units are both stacked in a back-to-back mode by left-handed circular polarization microstrip antennas and right-handed circular polarization microstrip antennas; the phase response of the transmission and reflection functions of the basic functional units can be independently and randomly designed by rotating the left-handed circular polarization microstrip antennas and the right-handed circular polarization microstrip antennas of the basic functional units; when the same electromagnetic wave is irradiated to the super surface in a forward direction or a backward direction, the super surface can realize different transmission and reflection full-space function combinations according to four groups of phase arrangements which are designed in advance. The multifunctional electromagnetic super surface disclosed by the application further improves channel capacity, is beneficial to the integration and miniaturization of electromagnetic equipment in a modern wireless communication system, and has a wide application prospect in beam control and holographic imaging and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of artificial electromagnetic metamaterials, and particularly relates to a full-space-direction multiplexing multifunctional electromagnetic metasurface and a design method thereof. BACKGROUND

[0002] Electromagnetic metamaterial is an artificial electromagnetic material composed of subwavelength units arranged in a certain period. In recent years, due to its special electromagnetic properties that do not exist in nature, electromagnetic metamaterials have attracted widespread attention from researchers. With the rapid development of this field, in 2011, Capasso's team at Harvard University first proposed the concept of electromagnetic metasurface with two-dimensional planar structure. By introducing field discontinuity on the interface, the electromagnetic metasurface can arbitrarily adjust the basic characteristics of the electromagnetic wave front such as amplitude, phase and polarization.

[0003] The vigorous development of modern wireless communication systems makes it difficult for electromagnetic devices with single function to meet the increasingly complex electromagnetic environment. Based on this, multifunctional electromagnetic metasurfaces that can handle multiple tasks at the same time can effectively improve the integration of electromagnetic functions, thus being suitable for compact modern wireless communication systems. In terms of the implementation of multifunctional electromagnetic metasurfaces, the commonly used means at present include polarization multifunction, frequency multifunction and direction multifunction. Janus metasurface, also known as directional metasurface, can realize asymmetric different electromagnetic scattering functions when the same electromagnetic wave is incident on the metasurface along different propagation directions, thereby realizing directional multifunctional electromagnetic metasurfaces. At present, most of the work only focuses on realizing bidirectional asymmetric transmission function, ignoring the function design on the reflection channel, thus only having two functional transmission channels.

[0004] In summary, in order to further improve the number of functions of the directional metasurface, so that the multiple functions of the metasurface can cover both the transmission and reflection channels, it is necessary to explore a multifunctional electromagnetic metasurface that can realize full-space asymmetric transmission and reflection functions for the same incident electromagnetic wave. When the electromagnetic wave is incident on the metasurface along the forward direction, a specific set of transmission and reflection functions can be realized, while when the electromagnetic wave is incident on the metasurface along the backward direction, another set of transmission and reflection functions completely different from the first set can be realized, thus realizing a multifunctional electromagnetic device with four transmission channels. SUMMARY

[0005] The main purpose of the present application is to overcome the above-mentioned problems, and to provide a full-space-direction multiplexing multifunctional electromagnetic metasurface and a design method thereof. By combining the functional units of the transmission and reflection full-space metasurface with the design method of the directional multifunctional metasurface, when the same electromagnetic wave is incident on the metasurface from different directions, different asymmetric transmission and reflection function combinations can be realized, thus making the designed multifunctional metasurface have a total of four different functional transmission channels in the full space.

[0006] Technical solution: In order to achieve the above-mentioned purpose, the technical scheme adopted by the application is as follows:

[0007] A full-space direction multiplexing multifunctional electromagnetic super surface is periodically extended in a two-dimensional plane according to an interlaced arrangement mode by two basic functional units; the two basic functional units are both stacked in a back-to-back mode by a left-handed circularly polarized microstrip antenna and a right-handed circularly polarized microstrip antenna; the additional phase of the reflection function and the transmission function when the right-handed / left-handed circularly polarized wave is incident is adjusted by rotating the left-handed / right-handed circularly polarized microstrip antenna around the center of the basic functional unit; the additional phase of the transmission function when the right-handed / left-handed circularly polarized wave is incident is adjusted by rotating the right-handed / left-handed circularly polarized microstrip antenna around the center of the basic functional unit; when the same electromagnetic wave is irradiated to the super surface in the forward direction or the backward direction, the super surface can realize different transmission-reflection full-space function combinations according to four groups of pre-designed phase arrangements.

[0008] The basic functional unit in the super surface can realize the transmission / reflection function for the forward incident right-handed / left-handed circularly polarized wave and realize the reflection / transmission function for the backward incident right-handed / left-handed circularly polarized wave; and the other basic functional unit has opposite transmission characteristics and can realize the reflection / transmission function for the forward incident right-handed / left-handed circularly polarized wave and realize the transmission / reflection function for the backward incident right-handed / left-handed circularly polarized wave; the two basic functional units can both have two phase adjustment degrees of freedom through independent rotation of the upper and lower metal layers; through the functional multiplexing mode of interlaced arrangement of the two basic functional units, the phase distribution required for four different functions calculated is assigned to the four phase adjustment degrees of freedom that the two basic functional units have in total, so that the full-space direction multiplexing multifunctional electromagnetic super surface is realized.

[0009] As a preferred, the basic functional unit includes three metal layers and two dielectric layers from top to bottom, which are an upper metal layer, an upper dielectric layer, a middle metal layer, a lower dielectric layer, and a lower metal layer; the upper metal layer and the lower metal layer are connected through a vertically placed metallized via; the middle metal layer is provided with a circular hole in the center so that the vertically placed metallized via can pass through.

[0010] As a preferred, the geometric sizes of the two basic functional units are the same, and the two basic functional units are in a 180° upside-down relationship with each other, that is, the upper and lower circularly polarized microstrip antenna structures of one of the basic functional units are transposed to obtain the other basic functional unit.

[0011] As preferred, by rotating the upper and lower metal layers of the basic functional unit around the respective connection point positions of the metallized via, the phase response of the transmission and reflection functions of the basic functional unit can be independently and arbitrarily designed, and the phase response can completely cover a phase range of 360°.

[0012] As preferred, the circular polarization operating characteristics of the left-handed circular polarization microstrip antenna and the right-handed circular polarization microstrip antenna of the basic functional unit are derived from the combined effects of the rectangular slot in the center of the circular metal and the offset distance of the center of the circular metal from the connection point along the diagonal direction of the basic functional unit. The metal disc of the upper and lower metal layers is translated by a certain distance along the diagonal direction of the basic functional unit, and a rectangular slot of a certain size is opened in the center to ensure that the left-handed circular polarization microstrip antenna and the right-handed circular polarization microstrip antenna constituting the basic functional unit have high polarization purity.

[0013] In the embodiments, the upper layer of the basic functional unit "A" is a right-handed circular polarization microstrip antenna, and the lower layer is a left-handed circular polarization microstrip antenna; the upper layer of the basic functional unit "B" is a left-handed circular polarization microstrip antenna, and the lower layer is a right-handed circular polarization microstrip antenna.

[0014] In the embodiments, by adjusting the distribution of the rotation angles of the upper and lower metal layers of the basic functional unit "A", the transmission function under backward incidence of right-handed circularly polarized waves and the reflection function under forward incidence can be designed and implemented; by adjusting the distribution of the rotation angles of the upper and lower metal layers of the basic functional unit "B", the transmission function under forward incidence of right-handed circularly polarized waves and the reflection function under backward incidence can be designed and implemented. The function design of the two basic functional units can also be applied to left-handed circularly polarized incident waves, and the transmission or reflection characteristics achieved by the two basic functional units under left-handed circularly polarized incident waves are just the opposite of those under right-handed circularly polarized incident waves, i.e., the basic functional unit "A" can achieve the reflection function under backward incidence of left-handed circularly polarized waves and the transmission function under forward incidence; the basic functional unit "B" can achieve the reflection function under forward incidence of left-handed circularly polarized waves and the transmission function under backward incidence.

[0015] The design method of the full-space-direction multiplexing multifunctional electromagnetic metasurface comprises the following steps:

[0016] The desired composite functions in the transmission and reflection four function channels of the metasurface under forward and backward incidence are determined respectively; each composite function is realized by compounding multiple single functions, and the phase distribution required by the multiple single functions is added in phase to calculate the phase distribution of the metasurface required by the composite function;

[0017] The staggered arrangement mode of the two basic functional units is determined, so as to correspond the calculated four groups of composite function phases to the transmission and reflection phases of the two basic functional units;

[0018] The rotation angles of the left-handed circularly polarized microstrip antenna and the right-handed circularly polarized microstrip antenna of the basic functional unit are determined according to the transmission and reflection phases required to be realized by each basic functional unit.

[0019] As preferred, the relationship between the transmission and reflection phases of the designed metasurface basic functional unit and the rotation angles of the left-handed and right-handed circularly polarized microstrip antennas satisfies: when the incident wave is a right-handed / left-handed circularly polarized wave, changing the rotation angle of the right-handed / left-handed circularly polarized microstrip antenna does not affect the phase response of the co-polarized reflection coefficient, the phase response of the co-polarized reflection coefficient decreases with the increase of the rotation angle of the left-handed / right-handed circularly polarized microstrip antenna, and the size of the phase response change value is about twice the size of the rotation angle change value; the phase response of the cross-polarized transmission coefficient decreases with the increase of the rotation angle of the right-handed / left-handed circularly polarized microstrip antenna and the rotation angle of the left-handed / right-handed circularly polarized microstrip antenna, and the size of the phase response change value is equal to the size of the rotation angle change value.

[0020] Beneficial effects: The electromagnetic metasurface provided by the present application is mainly composed of two kinds of transmission and reflection full-space basic functional units, combined with the function multiplexing design method of directional metasurfaces, when the specific right-handed circularly polarized electromagnetic wave in the embodiment is irradiated on the metasurface along the forward and backward two different directions, different transmission and reflection full-space function combinations can be realized, so that a total of four function channels covering the full-space range are possessed. Compared with the prior art, the present application has the following advantages:

[0021] 1. The present application expands the function coverage range of the multi-functional directional metasurface in the traditional design from the transmission space to the transmission and reflection full space. Correspondingly, the number of functions of the multi-functional directional metasurface in the traditional design is expanded from two to four.

[0022] 2. The basic functional unit proposed in the present application has the advantages of high efficiency and high polarization purity, so that the transmission and reflection full-space four-channel scattering functions finally realized all have high efficiency, and the cross talk between different channels is low.

[0023] 3. The metasurface proposed in the present application has the advantages of compact structure, thin thickness, easy processing, etc., and has a wide prospect in practical engineering applications such as modern wireless communication systems.

[0024] 4. The design scheme proposed in the present application has good expandability, in addition to the microwave band application shown in the embodiment, it can also be extended to higher frequency bands such as terahertz and optical bands. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is the function schematic diagram of the electromagnetic metasurface of the embodiment of the present application when the right-handed circularly polarized electromagnetic wave is incident along +z forward (Fig. a) and along -z backward (Fig. b).

[0026] Figure 2 are schematic diagrams of two basic functional units of the electromagnetic metasurface of the embodiment of the present application (Fig. a), a top view (Fig. b) and a bottom view (Fig. c) of the actual processing sample of the electromagnetic metasurface.

[0027] Figure 3 is a three-dimensional structural view of the basic functional unit "A" in the embodiment of the present application.

[0028] Figure 4 are scattering amplitude characteristic diagrams of the basic functional unit "A" in the embodiment of the present application when the right-handed circularly polarized wave is incident along +z forward (Fig. a) and -z backward (Fig. b).

[0029] Figure 5 are the phase response diagrams of the co-polarized reflection coefficient of the basic functional unit "A" in the embodiment of the present application when the right-handed circularly polarized wave is incident along +z forward (Fig. a) and -z backward (Fig. b). are the phase response diagrams of the cross-polarized transmission coefficient of the basic functional unit "A" in the embodiment of the present application when the right-handed circularly polarized wave is incident along +z forward (Fig. a) and -z backward (Fig. b). are the phase response diagrams of the upper metal layer rotation angle (Fig. c) and the lower metal layer rotation angle (Fig. d).

[0030] Figure 6 are the measured energy distribution diagrams of the transmission three-focal focusing function realized by the metasurface sample in the embodiment of the present application under the irradiation of the right-handed circularly polarized wave incident along +z in the x-z plane (Fig. a) and the y-z plane (Fig. b).

[0031] Figure 7 are the three-dimensional simulation directivity diagrams in the uv coordinate system (Fig. a) and the two-dimensional simulation and test directivity diagrams in the x-z plane (Fig. b) of the reflection double-OAM beam function realized by the metasurface sample in the embodiment of the present application under the irradiation of the right-handed circularly polarized wave incident along +z.

[0032] Figure 8 are the measured energy distribution diagrams of the transmission double-focal focusing function realized by the metasurface sample in the embodiment of the present application under the irradiation of the right-handed circularly polarized wave incident along -z in the double-focal point in the x-z plane (Fig. a), the left focal point in the x-z plane (Fig. b) and the right focal point in the x-z plane (Fig. c).

[0033] Figure 9 are the three-dimensional simulation directivity diagrams in the uv coordinate system (Fig. a), the two-dimensional simulation and test directivity diagrams in the x-z plane (Fig. b) and the two-dimensional simulation and test directivity diagrams in the y-z plane (Fig. c) of the reflection three-beam function realized by the metasurface sample in the embodiment of the present application under the irradiation of the right-handed circularly polarized wave incident along -z. DETAILED DESCRIPTION

[0034] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0035] This invention discloses a multifunctional electromagnetic metasurface that reuses all directions in space. The design method for a multifunctional electromagnetic metasurface using two basic functional units is employed, which are arranged in an alternating pattern and then periodically extended to form the electromagnetic metasurface. The two basic functional units constituting the metasurface are arranged in an alternating pattern in a checkerboard pattern, with an equal number of units. The adjacent positions (top, bottom, left, right) of one basic functional unit are occupied by the other basic functional unit. When the same electromagnetic wave illuminates the metasurface along different propagation directions, the designed metasurface can achieve different combinations of transmissive and reflective functions in all space according to four pre-designed phase arrangements. That is, when the electromagnetic wave is incident in the forward direction, it can achieve two specific electromagnetic functions covering the entire transmissive and reflective space; while when the electromagnetic wave is incident in the backward direction, it can achieve two completely different characteristic electromagnetic functions covering the entire space.

[0036] The following is based on Figure 1 The structure and design of metasurfaces are described in detail using the functions shown as examples. (Refer to...) Figure 1 The present invention discloses an electromagnetic metasurface that achieves different electromagnetic scattering functions in four channels across the entire transmission and reflection space. Specifically, as shown in the embodiments of the present invention... Figure 1 As shown in (a), the metasurface can achieve a transmission trifocal focusing function 101 and a reflection dual OAM beam function 102 under +z forward incident right-hand circularly polarized wave illumination. Figure 1 As shown in (b), the metasurface can achieve a transmission bifocal focusing function 103 and a reflection tri-beam function 104 under illumination by a right-hand circularly polarized wave incident in the -z direction. In the transmission trifocal focusing function 101, the three focal points are designed to have the same focal length; while in the transmission bifocal focusing function 103, the two focal points are designed to have different focal lengths, with the focal length of the left focal point being shorter than that of the right focal point when viewed along the propagation direction.

[0037] To achieve the above functions, refer to Figure 2 In this embodiment, the electromagnetic metasurface is composed of two basic functional units, "A" and "B," with full-space transmission and reflection properties, arranged periodically in an alternating manner. Figure 2The basic functional unit "A" is a right-handed circularly polarized microstrip antenna, and the basic functional unit "B" is a left-handed circularly polarized microstrip antenna. According to the principle of antenna propagation, the left-handed circularly polarized antenna can only receive the left-handed circularly polarized wave and reflect the right-handed circularly polarized wave, and the right-handed circularly polarized antenna is just the opposite, which can only receive the right-handed circularly polarized wave and reflect the left-handed circularly polarized wave. Based on this principle and the proposed super surface structure, when the right-handed circularly polarized wave propagates forward along +z and irradiates on the super surface, the basic functional unit "A" will be used to realize the co-polarized reflection function, and the basic functional unit "B" will be used to realize the conversion polarization transmission function; when the right-handed circularly polarized wave propagates backward along -z and irradiates on the super surface, the basic functional unit "A" will be used to realize the conversion polarization transmission function, and the basic functional unit "B" will be used to realize the co-polarized reflection function. Finally, the electromagnetic super surface described in the application realizes the full-space four-channel scattering function of transmission and reflection, and the phase function in the four functional channels can be designed arbitrarily and independently. The top view and bottom view of the actual processing of the electromagnetic super surface in the embodiment of the application are respectively as shown in Figure 2 As shown in (b) and (c) of the figure, the electromagnetic super surface embodiment is composed of 24x24 basic functional units with a period of 9.5mm in a two-dimensional plane.

[0038] Referring to Figure 3Since the basic functional units "A" and "B" have the same geometric size and are 180° rotated along the y-axis with respect to each other, only the basic functional unit "A" is taken as an example to illustrate the structure and scattering characteristics of the unit. The basic functional unit is a multilayer laminated structure, which is composed of three metal layers and two dielectric layers. The material of the metal layer is copper foil with a thickness of 0.018 mm. The two dielectric layers are separated by the middle metal layer, and the thickness of each dielectric layer is 1.5 mm. The material of the dielectric is F4B type board, with a dielectric constant of 2.2 and a loss tangent of 0.001. The upper metal layer 301 and the lower metal layer 302 are located above and below the upper and lower dielectric layers, respectively, and are composed of metal discs with a radius of 3.1 mm. The center of the metal disc in the upper and lower metal layers is cut with the same rectangular slot, and the slot length and width are 5.2 mm and 0.6 mm, respectively. The center of the metal disc in the upper and lower metal layers is located at a position offset 1.6 mm to the lower left from the center of the basic functional unit along the diagonal direction. Finally, the upper and lower metal layers are connected by a vertical metalized via hole 304 at the center of the basic functional unit, and the radius of the metalized via hole 304 is 0.3 mm. In order to make the metalized via hole 304 pass through, a region with a radius of 0.5 mm needs to be cut out at the center of the middle metal layer 303. It should be noted that the "A" and "B" units of the present application can also adopt different structures, as long as the two basic functional units of the microstrip antenna have the same circularly polarized radiation characteristics; and the circularly polarized microstrip antenna constituting the "A" and "B" units can also be extended to other circularly polarized microstrip antenna structures, such as two-end slotted metal discs and center / two-end slotted square patches, which can all achieve similar circularly polarized receiving / radiating mechanisms.

[0039] In order to realize the specific phase function design, the upper and lower metal layers of each basic functional unit in the metasurface need to be rotated by different angles around the connection point (i.e. the center of the basic functional unit). Specifically, the rotation angle of the upper metal layer 301 of the basic functional unit "A" is denoted as α A , and the rotation angle of the lower metal layer 302 is denoted as β A .

[0040] Based on the above unit design, the designed basic functional unit is simulated and calculated by using the commercial simulation and calculation software CST Microwave Studio. First, referring to Figure 4 , the scattering amplitude responses of the basic functional unit "A" under the illumination of the +z forward incident right circularly polarized wave and the -z backward incident right circularly polarized wave are shown in Figure 4 (a) and (b), respectively. It can be seen that when the +z forward propagating right circularly polarized wave illuminates the basic functional unit "A", most of the energy is converted into the co-polarized reflection component When the right-handed circularly polarized wave propagating in the +z direction is incident on the basic functional unit A, the phase response of the co-polarized reflection coefficient The simulation results show that the basic functional unit A can realize the reflection function when the right-handed circularly polarized wave propagating in the +z direction is incident on the basic functional unit A, and can realize the transmission function when the right-handed circularly polarized wave propagating in the -z direction is incident on the basic functional unit A. Since the basic functional unit B is obtained by rotating the basic functional unit A by 180° along the y axis, the basic functional unit B can realize the transmission function when the right-handed circularly polarized wave propagating in the +z direction is incident on the basic functional unit B, and can realize the reflection function when the right-handed circularly polarized wave propagating in the -z direction is incident on the basic functional unit B.

[0041] With reference to Figure 5 , the basic functional unit in the embodiment of the present application can control the additional phase of the transmission function and the reflection function by independently and arbitrarily rotating the upper and lower metal layers. As shown in Figure 5 (a) and (b), when the right-handed circularly polarized wave propagating in the +z direction is incident on the basic functional unit A, the rotation angle a A of the upper metal layer is changed, which will not affect the phase response of the co-polarized reflection coefficient , while the phase response of the co-polarized reflection coefficient will decrease with the increase of the rotation angle b A of the lower metal layer, and the change value of the phase response is about twice the change value of the rotation angle. As shown in Figure 5 (c) and (d), when the right-handed circularly polarized wave propagating in the -z direction is incident on the basic functional unit A, the phase response of the co-polarized reflection coefficient will decrease with the increase of the rotation angle a A of the upper metal layer and the rotation angle b A of the lower metal layer, and the change value of the phase response is equal to the change value of the rotation angle. The phase modulation law realized by the above unit can be summarized as follows:

[0042]

[0043]

[0044] The two formulas can obtain the corresponding relationship between the rotation angle of the circularly polarized microstrip antenna on the super surface unit and the required phase response by transformation:

[0045]

[0046]

[0047] Therefore, the rotation angle of the upper and lower metal layers in each basic functional unit "A" in the metasurface embodiment can be determined after the transmission and reflection phase responses required to be achieved by each basic functional unit "A" are determined. Similarly, the above rule can also be applied to each basic functional unit "B" in the metasurface embodiment.

[0048] For the characteristic electromagnetic function achieved in the embodiment of the application, the phase distribution of each composite function can be calculated by performing phase complex addition or direct addition on the single basic function, for example, referring to Figure 6 , the phase distribution required to achieve the composite function of transmission three-focus focusing can be calculated by performing phase complex addition on the phase distributions required to achieve each single-focus focusing, and the calculation formula of phase complex addition is as follows:

[0049]

[0050] wherein, represents the phase response required by the basic functional unit at the mth row and the nth column position in the metasurface to achieve the i th function, I represents the number of single basic functions contained in a composite function; taking the composite function of transmission three-focus focusing as an example, i represents different focus serial numbers, i.e., i = 1, 2, 3 represent the 1st, 2nd and 3rd focus respectively, and this composite function is composed of 3 single basic functions, so I = 3. represents the actual phase response required by the basic functional unit at the mth row and the nth column position in the metasurface to achieve the designed function.

[0051] Referring to Figure 6 , when the metasurface is irradiated by a right-handed circularly polarized wave incident in the +z direction, the transmission function of the metasurface is designed to be a three-focus focusing function, and the focal lengths of the three focuses are all designed to be 110 mm. The phase distribution required to achieve the single-focus focusing function can be calculated by the following formula:

[0052]

[0053] wherein, x mn and y mn represent the x coordinate and y coordinate values of the basic functional unit at the mth row and the nth column position in the metasurface, x i , y i and F i represent the x coordinate, y coordinate and focal length of the i th focus respectively; λ0 is the central working wavelength corresponding to the central working frequency of 15 GHz. The final test result shows obvious three-focus focusing characteristics, and the measured focus positions are consistent with the theoretically designed focal length values.

[0054] Referring to Figure 7When the metasurface is illuminated by the right-handed circularly polarized wave from +z direction, the reflection function of the metasurface is designed as two OAM beams, and the deflection angles of the two OAM beams are designed as -21° and 32°, respectively. The phase distribution required for realizing the specific beam deflection can be calculated by the following formula:

[0055]

[0056] where θ r is the preset deflection angle value of the OAM beam, that is, the two angles of -21° and 32° described above, and Γ is the physical period length covering the 2π phase range in the phase gradient metasurface, so that for different deflection angles θ r , the different physical period lengths covering the 2π phase range Γ required can be calculated. The OAM beam function to be realized can be calculated by the following formula:

[0057]

[0058] where l represents the mode number of the generated OAM beam, and the mode number of the two OAM beams generated in the embodiment is designed as +1. Finally, by performing phase complex addition on the phase distributions required for realizing the beam deflection of the two different angles, and directly adding the phase distribution required for generating the OAM beam with the mode number l = +1, the phase distribution required for generating the double OAM beam can be obtained. Figure 7 In the three-dimensional simulation results shown in (a) in Figure 7 , two obvious OAM beams can be observed. As can be seen from (b) in , the two-dimensional directional diagram obtained by simulation calculation is in good agreement with the actual test, and the deflection angles of the two beams are consistent with the theoretical design angles.

[0059] Figure 8 When the metasurface is illuminated by the right-handed circularly polarized wave from -z direction, the transmission function of the metasurface is designed as double-focus focusing, and the left focus is designed as -110 mm, while the right focus is designed as -184 mm. Similarly, the phase distribution required for realizing the function can be calculated by the method and formula for realizing the three-focus focusing function described above. The final test results show two obvious foci, and the focal lengths of the two foci are consistent with the theoretical design.

[0060] Refer to Figure 9When the metasurface is illuminated by right-handed circularly polarized wave at -z incidence, the reflection function of the metasurface is designed as three-beam radiation, two beams in the x-z plane are designed as -32° and 21° respectively, and the deflection angle of one beam in the y-z plane is designed as 15°. Similarly, the phase distribution required to achieve this function can be obtained by the above-mentioned method of realizing double OAM beam function and public calculation. The final test results show obvious three-beam radiation function, the simulation results are in good agreement with the test results, and the deflection angle of each beam is consistent with the theoretical design.

[0061] The metasurface described in the embodiments of the present application exhibits the directional multiplexing multifunctional electromagnetic control characteristics possessed by the right-handed circularly polarized wave when it is incident from the front and back. The functional design of the metasurface can also be applied to left-handed circularly polarized incident waves. Under left-handed circularly polarized wave illumination, the two basic functional units can also achieve transmission or reflection phase modulation characteristics, so under left-handed circularly polarized wave illumination, only the rotation angle distribution of the upper and lower circularly polarized microstrip antennas of the two basic functional units needs to be redesigned to achieve similar directional multiplexing multifunctional electromagnetic control characteristics.

[0062] The above is only the preferred embodiment of the present application, and the same structure can be obtained by scaling the size of the full-space directional multiplexing multifunctional electromagnetic metasurface by the same proportion, flexibly designing the working frequency band of the multifunctional electromagnetic metasurface, and even extending to millimeter wave band, infrared, terahertz and visible light band. In addition, by changing the actual designed phase distribution, other multi-task different function combinations such as holographic imaging can also be achieved. The scope of the present application cannot be limited by this, that is, any simple equivalent changes and modifications made according to the claims and the content of the present application should still belong to the scope covered by the present application.

Claims

1. A full spatial direction multiplexing multifunctional electromagnetic metasurface, characterized in that, The two basic functional units are staggered and arranged in a chessboard pattern in a two-dimensional plane, and then are periodically extended, wherein the upper and lower and left and right adjacent positions of one basic functional unit are occupied by the other basic functional unit; both the two basic functional units are stacked in a back-to-back manner by a left-handed circularly polarized microstrip antenna and a right-handed circularly polarized microstrip antenna; the additional phase of the reflection function and the transmission function when the left-handed / right-handed circularly polarized wave is incident is adjusted by rotating the left-handed / right-handed circularly polarized microstrip antenna around the center of the basic functional unit; the additional phase of the transmission function when the right-handed / left-handed circularly polarized wave is incident is adjusted by rotating the right-handed / left-handed circularly polarized microstrip antenna around the center of the basic functional unit; when the same electromagnetic wave is irradiated to the metasurface in the forward or backward direction, the metasurface can realize different transmission-reflection full-space four-channel function combinations according to the pre-designed four groups of phase arrangements; The upper layer of one basic functional unit is a right-handed circularly polarized microstrip antenna, and the lower layer is a left-handed circularly polarized microstrip antenna, which is used to realize the transmission / reflection function when the right-handed / left-handed circularly polarized wave is incident in the backward direction and the reflection / transmission function when the right-handed / left-handed circularly polarized wave is incident in the forward direction; the upper layer of the other basic functional unit is a left-handed circularly polarized microstrip antenna, and the lower layer is a right-handed circularly polarized microstrip antenna, which is used to realize the transmission / reflection function when the right-handed / left-handed circularly polarized wave is incident in the forward direction and the reflection / transmission function when the right-handed / left-handed circularly polarized wave is incident in the backward direction; the relationship between the transmission-reflection phase of the basic functional unit and the rotation angle of the left-handed and right-handed circularly polarized microstrip antenna satisfies: when the incident wave is a right-handed / left-handed circularly polarized wave, changing the rotation angle of the right-handed / left-handed circularly polarized microstrip antenna will not affect the phase response of the co-polarization reflection coefficient, the phase response of the co-polarization reflection coefficient will decrease with the increase of the rotation angle of the left-handed / right-handed circularly polarized microstrip antenna, and the size of the phase response change value is about twice the size of the rotation angle change value; the phase response of the cross-polarization transmission coefficient will decrease with the increase of the rotation angle of the right-handed / left-handed circularly polarized microstrip antenna and the rotation angle of the left-handed / right-handed circularly polarized microstrip antenna, and the size of the phase response change value is equal to the size of the rotation angle change value.

2. The full spatial direction multiplexing multifunctional electromagnetic metasurface according to claim 1, characterized in that, The two basic functional units each include three metal layers and two dielectric layers, from top to bottom, the upper metal layer, the upper dielectric layer, the middle metal layer, the lower dielectric layer, and the lower metal layer; the upper metal layer and the lower metal layer are connected through a vertical metallized via hole placed at the center of the basic functional unit; the middle metal layer has a circular hole at the center to allow the vertically placed metallized via hole to pass through.

3. The full spatial direction multiplexing multifunctional electromagnetic metasurface according to claim 1, characterized in that, The two basic functional units have the same geometric size and are in a 180° upside-down relationship with each other, that is, the upper and lower circularly polarized microstrip antenna structures of one basic functional unit can be obtained by reversing the other basic functional unit.

4. The full spatial direction multiplexing multifunctional electromagnetic metasurface according to claim 1, characterized in that, By rotating the left-handed circularly polarized microstrip antenna and the right-handed circularly polarized microstrip antenna of the basic functional unit, the phase response of the transmission and reflection functions of the basic functional unit can be independently and arbitrarily designed, and the phase response can completely cover a 360° phase range.

5. The full spatial direction multiplexing multifunctional electromagnetic metasurface according to claim 1, characterized in that, The circular polarization working characteristics of the left-handed circular polarization microstrip antenna and the right-handed circular polarization microstrip antenna come from the fact that the circular metal center has a rectangular slot and the circular metal center is located at a distance from the connecting point along the diagonal direction of the basic functional unit.

6. The design method of a full-space directional multiplexing multifunctional electromagnetic metasurface according to any one of claims 1-5, characterized in that, The method comprises the following steps: Respectively determine the desired composite functions in the transmission and reflection four functional channels of the metasurface before and after the incidence; each composite function is realized by a plurality of single functions through compounding, and the phase distribution required by the plurality of single functions is added by phase compounding, and the phase distribution required by the composite function is calculated to obtain the phase distribution required by the metasurface; Determine the staggered arrangement mode of the two basic functional units, so as to correspond the four groups of composite function phases calculated to the transmission and reflection phases of the two basic functional units; According to the transmission and reflection phases required to be realized by each basic functional unit, the rotation angles of the left-handed circular polarization microstrip antenna and the right-handed circular polarization microstrip antenna of the basic functional unit are determined.

Images