An active reconfigurable electromagnetic metasurface supporting full-space multi-user asymmetric wireless communication

Abstract

The application discloses an active reconfigurable electromagnetic super surface supporting full-space multi-user asymmetric wireless communication, expands the super surface wireless communication technology to the full space, and can simultaneously perform independent information transmission on four users in the full space in a two-by-two group; by partitioning the chiral super surface and independently controlling the switch state of the switch diode in the row feeding unit of each channel, the amplitude of the electromagnetic wave in the transmission and reflection channel of the electromagnetic wave incident in the opposite direction can be independently controlled, so that the independent wireless information transmission of four users involved in the bidirectional transmission and reflection channel can be simultaneously realized; according to the difference of the propagation direction of the incident electromagnetic wave, two groups of independent transmission and reflection channels can be constructed in the same working frequency by means of the active super surface, and the application has the advantages of simple structure, easy control and low cost.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of artificial electromagnetic metamaterials, and particularly relates to an active reconfigurable electromagnetic metamaterial surface supporting full-space multi-user asymmetric wireless communication. BACKGROUND

[0002] Chiral metamaterials simulate chiral structures in nature in a highly efficient and thin manner, and significantly improve the chiral response thereof, and have singular electromagnetic properties such as circular dichroism and optical activity, and can be used to realize polarization conversion, asymmetric transmission, negative refraction and other functions. Compared with passive chiral metamaterials and metasurfaces, active chiral metamaterials loaded with adjustable materials or elements and reconfigurable metasurfaces utilizing chiral characteristics can realize flexible regulation of dynamic response and asymmetric transmission characteristics of electromagnetic waves, and help to fully develop the spatial resources on both sides of the chiral metasurface by utilizing the regulation freedom of electromagnetic waves in the propagation direction, so as to be applicable to more complex application scenarios.

[0003] The rapid development of new generation wireless communication technology and increasingly complex application scenarios have put forward higher requirements for wireless communication systems, and efficient new wireless communication systems have become a research hotspot in the communication field. In recent years, wireless communication technology based on programmable metasurfaces has attracted widespread attention from researchers. This technology can directly modulate the amplitude, phase, frequency and other characteristics of scattered electromagnetic waves with the information to be transmitted, simplifying the requirements of microwave components at the communication transmitting end, and thus having the advantages of low cost and high reliability. Currently, most of the related works published are based on reflective metasurfaces to realize wireless communication in the reflection space, but few have verified the wireless communication scheme of synchronously extending the reflection channel to the transmission space, which limits the application scenarios of metasurfaces.

[0004] Therefore, in order to meet the needs of practical applications and fully utilize spatial resources, it is urgent to explore a design scheme of a multi-user asymmetric wireless communication system supporting full-space transmission-reflection channel synchronization. Metasurfaces with chiral characteristics have asymmetric transmission characteristics and regulation freedom in the direction of electromagnetic wave propagation, which helps to construct channels independent of the direction of electromagnetic wave incidence, increases the channel capacity of metasurfaces, reduces the crosstalk between channels, and only needs to regulate the working state of active devices integrated in the reconfigurable chiral metasurface unit to realize independent information transmission in the channels contained in the two opposite incidence directions. SUMMARY

[0005] The application aims to provide an active reconfigurable electromagnetic metasurface supporting full-space multi-user asymmetric wireless communication, which can transmit two different information in forward and backward incident channels of the same incident polarization, and the information transmitted in the two channels of the same polarization and the two channels of the opposite polarization in each incident channel is the same, so that the reconfigurable metasurface can realize four-user asymmetric wireless communication under bidirectional incident electromagnetic waves. By switching the working state of the chiral metamaterial in real time, the amplitude response of the forward and backward incident x-polarized electromagnetic waves in the two independent transmission (reflection) channels can be dynamically controlled, and different time coding sequences can be loaded on the corresponding reconfigurable metasurface area, so that asymmetric wireless communication can be realized in the two opposite incident channels.

[0006] To achieve the above-mentioned application purposes, the application provides the following technical scheme: an active reconfigurable electromagnetic metasurface supporting full-space multi-user asymmetric wireless communication, the metasurface is periodically extended by basic units in a two-dimensional plane, and the electromagnetic response thereof is real-time controlled by an external control circuit; the basic unit comprises, from front to back, a first metal patch layer, a first dielectric layer, an air layer, a second metal patch layer and a second dielectric layer; the metal structures in the first metal patch layer and the second metal patch layer are completely identical, and each comprises a square double-open metal resonant ring with two orthogonal slits and two metal narrow-band lines above and below; the two metal structures in the square double-open resonant ring, which are divided by a group of orthogonal slits, are connected by a pair of switch diodes, and the positive and negative poles of the two diodes loaded on each layer are connected in a head-to-tail manner; the square double-open metal resonant ring is connected with the metal narrow-band lines transversely penetrating the basic unit, and after the basic unit is periodically extended into a metasurface array in a two-dimensional plane, the basic unit is connected with the adjacent unit by the transverse metal narrow-band line, thereby facilitating the unified control of the basic unit as a row of feeding units; the working states of the two groups of switch diodes loaded on the two metal patch layers are controlled respectively, so as to jointly control the working state and electromagnetic response of the basic unit.

[0007] Further, the two metal patch structures and the two groups of switch diodes loaded thereon constituting the basic unit can be independently controlled and cooperatively work; by controlling different combinations of the switch states of the diodes in the basic unit, the unit can be switched among the forward chiral state, the backward chiral state and the achiral state, and has different scattering responses to bidirectional incident x-polarized electromagnetic waves.

[0008] Further, when the x-polarized electromagnetic wave is forward and backward incident to the basic unit of the reconfigurable metasurface, the first diode is cut off and the second diode is turned on in the x direction of the first metal patch layer, and the third diode is turned on and the fourth diode is cut off in the y direction of the second metal patch layer, the unit works in a forward chiral state, realizing forward polarization conversion transmission of the x-polarized electromagnetic wave; when the first diode is turned on and the second diode is cut off, and the third diode is cut off and the fourth diode is turned on, the unit works in a backward chiral state, realizing backward polarization conversion transmission of the x-polarized electromagnetic wave; when the first diode is turned on and the second diode is cut off, and the third diode is turned on and the fourth diode is cut off, the unit works in an achiral state, and the polarization conversion transmission channel is closed.

[0009] Further, the basic unit constituting the metasurface array is divided into two parts as a feed unit, and the two regions of the metasurface are defined as a forward incident channel control region and a backward incident channel control region, so as to independently control the amplitudes of the electromagnetic waves in the transmission and reflection channels contained in the forward and backward incident waves respectively; by independently controlling the working states of the row feed units in the two regions, two groups of channels independent of the incident direction of electromagnetic waves are built, the electromagnetic responses in the polarization conversion transmission channel and the same polarization reflection channel contained in each group of incident channels change synchronously, the same information is transmitted to the users in the respective channels, and the electromagnetic control in the two groups of incident channels is independent, so that new information can be transmitted to the users in the other group of transmission and reflection channels, thereby realizing multi-user independent communication.

[0010] Further, the active reconfigurable electromagnetic metasurface contains 18 row feed units in the y direction, which are divided into a forward incident control region from the top to the bottom 1-4 rows and 10-14 rows, and a backward incident control region from the top to the bottom 5-9 rows and 15-18 rows.

[0011] Further, the working states of the row feed units in the forward incident channel control region are switched between the forward chiral state and the achiral state, realizing synchronous binary amplitude control of the polarization conversion transmission electromagnetic wave and the same polarization reflection electromagnetic wave in the forward incident channel; the working states of the row feed units in the backward incident channel control region are changed between the backward chiral state and the achiral state, constituting a binary amplitude keying of the polarization conversion transmission electromagnetic wave and the same polarization reflection electromagnetic wave in the backward incident channel.

[0012] Further, the control of the working states of the row feed units in the two incident channels of the metasurface is independent of each other, so the amplitude control in the transmission and reflection channels contained in each incident channel is also independent of each other.

[0013] Further, the FPGA is used as a control device, and the high and low levels of the binary encoding of the required transmission information correspond to the polarization conversion transmission and the high and low levels of the same polarization reflection amplitude, the working state of the row feed unit in the front and backward incident channel area of the active reconfigurable metasurface is modulated with time, so that the information transmitted by each channel can be received and recovered at the receiving end of the corresponding transmission and reflection channel.

[0014] Further, the square double-open metal resonant ring in the first metal patch layer and the second metal patch layer is located at the center of the unit structure, and the gap positions of the square double-open metal resonant ring in each layer are orthogonal.

[0015] Further, the two parts of the metal structure divided by a set of orthogonal slits in the square double-open resonant ring are connected with the metal narrow band lines on the upper and lower parts of the basic unit.

[0016] The application combines a switch diode to form an active reconfigurable metasurface with asymmetric transmission direction reversibility and opposite incident channel independent regulation of polarization conversion transmission (same polarization reflection) amplitude, under the forward and backward incidence of x polarization electromagnetic waves, different time encoding sequences are loaded into the working state of the switch diode in the unit of the metasurface corresponding to the incident channel by FPGA, so that independent wireless communication function can be realized in the bidirectional transmission (reflection) channel. Compared with the prior art, the application has the following advantages:

[0017] (1) The active reconfigurable metasurface with asymmetric transmission direction reversibility proposed in the application can construct two kinds of chiral states about the opposite incident direction at the same working frequency (4.26 GHz) by regulating the working state of the switch diode loaded in the unit, thereby realizing the dynamic flipping of asymmetric transmission in the whole space, developing the space resource, and constructing two groups of polarization conversion transmission (same polarization reflection) channels under the incident channel.

[0018] (2) The application can build two groups of polarization conversion transmission (same polarization reflection) channels with opposite incident directions by regulating the working state of the row feed unit of the metasurface, and can independently regulate the amplitude of the electromagnetic wave in the bidirectional transmission (reflection) channel.

[0019] (3) The active reconfigurable metasurface expands the metasurface wireless communication technology to the transmission and reflection whole space, and realizes the independent transmission (reflection) information transmission of the bidirectional incident channel, fully utilizes the space resource, provides a new way for expanding the channel capacity, and widens the application scene of the metasurface wireless communication technology.

[0020] (4) The asymmetric wireless communication function described in the embodiment can be moved from the microwave band to other target frequency bands by scaling proportionally and assisting with other variable materials and regulation methods, etc., and has good frequency band flexibility and application prospects. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a structural schematic diagram of an active reconfigurable metasurface in an embodiment of the present application.

[0022] Figure 2 is a three-dimensional structural schematic diagram of a basic unit in an embodiment of the present application.

[0023] Figure 3 is an equivalent circuit diagram when the switch diode is turned on (Fig. a) and turned off (Fig. b) in an embodiment of the present application.

[0024] Figure 4 is the transmission amplitude of x-polarized electromagnetic waves bidirectional incidence when the basic unit in the embodiment of the present application works in the forward chiral state (Fig. a), the transmission amplitude of x-polarized electromagnetic waves bidirectional incidence when the basic unit works in the backward chiral state (Fig. b), and the scattering amplitude of x-polarized electromagnetic waves forward incidence when the basic unit works in the achiral state (Fig. c).

[0025] Figure 5 is a test diagram of the active reconfigurable metasurface sample in the embodiment of the present application for simultaneous independent regulation of the amplitude of the conversion polarization transmission (Fig. a) and the amplitude of the co-polarization reflection (Fig. b) when x-polarized electromagnetic waves are forward incident.

[0026] Figure 6 is a test diagram of the active reconfigurable metasurface sample in the embodiment of the present application for simultaneous independent regulation of the amplitude of the conversion polarization transmission (Fig. a) and the amplitude of the co-polarization reflection (Fig. b) when x-polarized electromagnetic waves are backward incident.

[0027] Figure 7 is a schematic diagram of the active reconfigurable metasurface sample in the embodiment of the present application for assisting in realizing bidirectional incidence channel independent wireless image transmission. DETAILED DESCRIPTION

[0028] The present application will be further described below in conjunction with the drawings and specific embodiments. It should be understood that the present application can be implemented in various forms, and some exemplary and non-limiting embodiments shown in the drawings and described below are not intended to limit the present application to the specific embodiments described.

[0029] As Figure 1 , 2As shown, the active reconfigurable electromagnetic metasurface supporting full-space multi-user asymmetric wireless communication of the embodiment includes adjustable chiral basic units uniformly distributed in the xy two-dimensional plane, and the basic unit structure includes, from front to back, a first metal patch layer, a first dielectric layer, an air layer, a second metal patch layer, and a second dielectric layer. The first metal patch layer and the second metal patch layer are completely consistent in structure, and both contain a square double-open metal resonant ring in the middle of the unit. The two parts of the metal structure in the square double-open resonant ring, which are divided by a group of slits located in the middle of each side and orthogonal in position, are connected by a pair of switch diodes, and the positive and negative poles of the two diodes loaded on each layer are connected end to end. The first metal patch layer and the second metal patch layer are provided with a metal narrow band line transversely penetrating through the entire unit on the upper and lower parts of the square double-open metal resonant ring, which connects the transversely adjacent units together, facilitating the uniform regulation of the working state of the row of feed units, and the adjacent units in the same column are not connected by metal structures. Under the same kind of polarized electromagnetic wave along the forward and backward incidence, by adjusting the switch diodes loaded in the row of feed units, the row of feed units can be controlled to work in the forward chiral state, the backward chiral state or the achiral state, and the working states of the rows of feed units are completely independent.

[0030] The reconfigurable metasurface is planned to be divided into two independent working areas, and two different regulations are applied to the switch diodes in the two areas, so that the transmittance of the basic units in each area to the forward and backward incident x-polarized electromagnetic waves is different, that is, it has asymmetric transmission characteristics, and the asymmetric transmission characteristics between the two areas are opposite to the direction of electromagnetic wave incidence.

[0031] Because the basic units in the two working areas of the metasurface have opposite electromagnetic responses to the forward and backward incident x-polarized electromagnetic waves, the two areas can construct two groups of transmission (reflection) channels suitable for forward and backward incidence for x-polarized electromagnetic waves. By independently regulating the on-off state of each incident channel through an external circuit, the amplitude response of the corresponding channel can be controlled, binary amplitude keying is constructed, and the regulation is loaded into the two areas of the reconfigurable metasurface with two different time coding sequences, so that asymmetric wireless communication based on the independent and real-time amplitude changes in the two groups of transmission (reflection) channels is realized.

[0032] In this embodiment, a chiral metamaterial with 18x18 units extended in a two-dimensional plane with a period of 16 mm is taken as an example for experimental illustration. The structure of the first metal patch layer and the second metal patch layer is specifically composed of a square double-open metal resonant ring containing orthogonal slits connected with upper and lower metal narrow band lines and a group of switch diodes (Infineon, BAR65-02V). The metal structures in the two metal patch layers are completely consistent. The outer edge length of the square ring is 14 mm, the inner edge length is 4 mm, and the slit width is 1 mm. The thickness of the air layer between the first dielectric layer and the second metal patch layer is 2 mm. In this embodiment, the dielectric layer is made of F4B material with a dielectric constant of 2.2 and a loss tangent of 0.001, and the single-layer dielectric thickness is 1 mm; the metal patch is a copper sheet.

[0033] As shown in Figure 3 , when the diode BAR65-02V is turned on, the diode can be equivalent to a series circuit of an 80Ω resistor and a 0.25nH inductor; when the diode BAR65-02V is cut off, it can be equivalent to a series circuit of a 0.26pF capacitor and a 0.25nH inductor.

[0034] When the x-polarized electromagnetic wave is forward and backward incident to the reconfigurable metasurface unit, the first diode 11 loaded in the x direction in the first layer is cut off, the second diode 12 loaded in the y direction is turned on, the third diode 21 loaded in the x direction in the second layer is turned on, and the fourth diode 22 loaded in the y direction is cut off, the unit works in the forward chiral state, and the x-polarized electromagnetic wave can be realized. Forward polarization transmission, the simulation result is shown in Figure 4 (a); when the first diode 11 in the metasurface unit is turned on and the second diode 12 is cut off, and the third diode 21 is cut off and the fourth diode 22 is turned on, the unit works in the backward chiral state, and the x-polarized electromagnetic wave can be realized. Backward polarization transmission, the simulation result is shown in Figure 4 (b); when the first diode 11 in the metasurface unit is turned on and the second diode 12 is cut off, and the third diode 21 is turned on and the fourth diode 22 is cut off, the unit works in the achiral state, and the polarization transmission channel is closed, the simulation result is shown in Figure 4 (c).

[0035] Figure 1The active reconfigurable metasurface structure is shown in the schematic diagram, and in this embodiment, 18x18 units are periodically extended in a two-dimensional plane to form a sample and are used for experimental verification. The row feed units in the regions containing rows 1-4 and rows 10-14 in the active reconfigurable metasurface sample along the y direction from top to bottom are selected for the x-polarized electromagnetic forward incidence channel, and the switch state of the diode in the region is adjusted, so that the working state of the row feed unit can be flexibly switched between the forward chirality state and the achirality state, thereby the binary amplitude modulation of the electromagnetic wave in the forward incidence channel can be realized, and the test results are shown in (a) of FIG. 8. Figure 5 The amplitude change can also be reflected in the co-polarized reflection channel under forward incidence, and the test results are shown in (b) of FIG. 8. Figure 5 In addition, the row feed units in the regions containing rows 5-9 and rows 15-18 in the active reconfigurable metasurface sample along the y direction from top to bottom are selected for the x-polarized electromagnetic backward incidence channel, and the working state of the row feed unit in the backward region is adjusted to change between the backward chirality state and the achirality state, which also constitutes the binary amplitude keying of the electromagnetic wave in the backward incidence channel, and the test results are shown in (a) and (b) of FIG. 9. Figure 6 The working states of the row feed units corresponding to the two incidence channels and the amplitude modulation of the transmitted and reflected electromagnetic waves can be independently performed, thereby constructing two groups of transmitted and reflected information transmission channels about the opposite directions of incidence, and by means of the FPGA, the active reconfigurable metasurface can be modulated to change with time, different information can be independently transmitted in the two groups of channels contained in the forward and backward incidence channels, Figure 7 For example, the image transmission shows that the active reconfigurable electromagnetic metasurface can realize independent wireless communication of full-space multi-users under bidirectional incidence. The reconfigurable metasurface supporting asymmetric wireless communication in the embodiment has the advantages of simple structure, low preparation cost, easy to control and the like.

[0036] The above only describes the preferred embodiments of the present application. Since the design idea of the present application is clear, the application prospect is wide, the same structure can be scaled to the millimeter wave band, infrared, terahertz and visible light band, and the implementation range of the present application cannot be limited by this, that is, any simple equivalent change and modification made according to the claims and the description of the present application should still belong to the scope covered by the present application.

Claims

1. An active reconfigurable electromagnetic metasurface supporting full-space multi-user asymmetric wireless communication, characterized in that, The super-structured surface is periodically extended by basic units in a two-dimensional plane, and the electromagnetic response thereof is real-time regulated by an external control circuit; the basic unit comprises, from front to back, a first metal patch layer, a first dielectric layer, an air layer, a second metal patch layer and a second dielectric layer; the metal structures in the first metal patch layer and the second metal patch layer are completely identical, and each metal structure comprises a square double-opened metal resonant ring with two orthogonal slits and upper and lower metal narrow band lines; the two metal structures in the square double-opened resonant ring, which are divided by a group of orthogonal slits, are connected by a pair of switch diodes, and the anode and cathode of the two diodes loaded on each layer are connected end to end; the upper and lower parts of the square double-opened metal resonant ring are connected with the metal narrow band lines transversely penetrating through the basic unit, and after the basic unit is periodically extended into a super-structured surface array in the two-dimensional plane, the basic unit is connected with the adjacent unit by the transverse metal narrow band lines, thereby facilitating the unified regulation and control of the basic unit as a row of feed units; the working states of the two groups of switch diodes loaded on the two metal patch layers are regulated respectively, and the working state and electromagnetic response of the basic unit can be collectively regulated; the basic unit constituting the super-structured surface array is equally divided into two partial areas as feed units, and the two areas of the super-structured surface are defined as a forward incidence channel regulation area and a backward incidence channel regulation area, thereby independently regulating the amplitudes of the electromagnetic waves in the transmission and reflection channels contained in the forward and backward incident waves respectively; By independently regulating the working states of the row feed units in the two areas, two groups of channels independent of the electromagnetic wave incidence direction are built, the electromagnetic responses in the polarization conversion transmission channel and the same polarization reflection channel contained in each group of incidence channels change synchronously, the same information is transmitted to the users in the respective channels, and the electromagnetic regulation in the two groups of incidence channels is independent, so that new information can be transmitted to the users in the other group of transmission and reflection channels, thereby realizing multi-user independent communication.

2. The active reconfigurable electromagnetic metasurface supporting full-space multi-user asymmetric wireless communications of claim 1, wherein, The two metal patch structures and the two groups of switch diodes loaded thereon constituting the basic unit can be independently regulated or cooperatively work; by regulating different combinations of the switch states of the diodes in the basic unit, the unit can be switched between the forward chirality state, the backward chirality state and the non-chirality state, and has different scattering responses to bidirectional incident x-polarized electromagnetic waves.

3. The active reconfigurable electromagnetic metasurface supporting full-space multi-user asymmetric wireless communications of claim 2, wherein, When x-polarized electromagnetic waves are incident forward and backward to the reconfigurable super-structured surface basic unit, the first diode loaded in the x direction in the first metal patch layer is turned off, the second diode loaded in the y direction is turned on, the third diode loaded in the x direction in the second metal patch layer is turned on, and the fourth diode loaded in the y direction is turned off, the unit works in the forward chirality state, and realizes forward polarization conversion transmission of x-polarized electromagnetic waves; when the first diode is turned on and the second diode is turned off, and the third diode is turned off and the fourth diode is turned on, the unit works in the backward chirality state, and realizes backward polarization conversion transmission of x-polarized electromagnetic waves; when the first diode is turned on and the second diode is turned off, and the third diode is turned on and the fourth diode is turned off, the unit works in the non-chirality state, and the polarization conversion transmission channel is closed.

4. The active reconfigurable electromagnetic metasurface supporting full-space multi-user asymmetric wireless communications of claim 1, wherein, The active reconfigurable electromagnetic metasurface comprises 18 row feed units in the y direction, which are divided into forward incidence regulation areas by 1-4 rows and 10-14 rows from top to bottom in the y direction, and divided into backward incidence regulation areas by 5-9 rows and 15-18 rows.

5. The active reconfigurable electromagnetic metasurface supporting full-space multi-user asymmetric wireless communications of claim 1, wherein, The working states of the row feed units in the forward incidence channel regulation area are switched between the forward chiral state and the achiral state, realizing binary amplitude regulation of the synchronous trans-polarization transmission electromagnetic wave and the same-polarization reflection electromagnetic wave in the forward incidence channel; the working states of the row feed units in the backward incidence channel regulation area are changed between the backward chiral state and the achiral state, forming binary amplitude keying of the synchronous trans-polarization transmission electromagnetic wave and the same-polarization reflection electromagnetic wave in the backward incidence channel.

6. The active reconfigurable electromagnetic metasurface supporting full-space multi-user asymmetric wireless communications of claim 5, wherein, The working state regulation of the row feed units in the two incidence channels of the metasurface is independent of each other, so the amplitude regulation in the transmission and reflection channels of each incidence channel is also independent of each other.

7. The active reconfigurable electromagnetic metasurface supporting full-space multi-user asymmetric wireless communications of claim 6, wherein, FPGA is used as a control device, and the binary encoding of the required transmission information is used to correspond to the high and low levels of the trans-polarization transmission and same-polarization reflection amplitudes, and the working states of the row feed units in the forward and backward incidence channel areas of the active reconfigurable metasurface are modulated with time, so that the information transmitted by each channel can be received and recovered at the receiving end of the corresponding transmission and reflection channel.

8. The active reconfigurable electromagnetic metasurface supporting full-space multi-user asymmetric wireless communications of any of claims 1-7, wherein, The square double-open resonant ring in the first metal patch layer and the second metal patch layer is located at the center of the unit structure.

9. The active reconfigurable electromagnetic metasurface supporting full-space multi-user asymmetric wireless communications of any of claims 1-7, wherein, The two parts of the square double-open resonant ring, which are divided by a set of orthogonal slits, are connected to the upper and lower metal narrow-band lines of the basic unit, respectively.

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