Design method of metasurface control architecture

Abstract

The invention discloses a metasurface control architecture design method. According to the method, high and low voltages of each row unit and each column unit of the metasurface array are coded, phase codes of the metasurface array are obtained through a matrix multiplication method, and the control architecture method is called a basic cross control method or a one-area cross control method. Furthermore, according to the method, the metasurface array is divided into a plurality of areas of the basic cross control architecture, so that a multi-area cross control architecture is formed; according to the multi-zone cross control, the number and the zone positions of the zones can be flexibly changed according to the requirements of an actual application scene, so that the pointing precision of a wave beam is regulated and controlled, and meanwhile, the achievable complexity of metasurface control hardware is reduced. According to the invention, on the premise of keeping the specified beam regulation and control precision, the complexity of a metasurface control architecture and the memory occupied space of coding can be obviously reduced, and the application development of the low-cost and high-performance reconfigurable metasurface is promoted.

Description

Technical Field

[0001] The present invention belongs to the field of metasurface unit design, metasurface array design and mathematical optimization, and in particular relates to a metasurface control architecture design method. Background Art

[0002] Electromagnetic metasurfaces can manipulate the amplitude, phase, frequency, and polarization of electromagnetic waves. They are easy to manufacture, have low profiles, and have low losses. They are playing a huge role in the fields of beam deflection, electromagnetic stealth, holographic imaging, and wireless communications. However, as the scale of programmable metasurfaces continues to expand, their control configuration becomes increasingly complex, which poses significant challenges to practical applications. In order to improve the communication speed and coverage in free space while maintaining low hardware complexity, it is particularly important to propose new modulation technologies to support advanced wireless communication applications. Traditional programmable metasurfaces usually have two hardware control configurations: one is a row or column controlled metasurface, in which the feed voltage of each column unit is the same. This control architecture is simple and easy to design and deploy. However, it can only regulate electromagnetic waves in one dimension, which greatly limits the application of metasurfaces in practical environments. The other is a unit-independently controlled metasurface, in which the working state of each unit in the array can be independently controlled. This control architecture can complete any encoding scheme of the array, thereby realizing any beam steering of the metasurface in free space. However, this control architecture requires a separate control line for each unit, so the hardware complexity is high, and it increases greatly with the increase of the array size. In addition, in many scenarios, ultra-high beam steering accuracy is not required, and this control architecture will cause some waste of resources. Therefore, the above-mentioned methods all have their own defects, and it is difficult to obtain the beam steering accuracy according to the actual scenario requirements while minimizing the complexity of the hardware control architecture. Summary of the invention

[0003] The purpose of the present invention is to provide a method for designing a metasurface control architecture to solve the defects of the existing control architecture methods.

[0004] To solve the above technical problems, the specific technical solution of the present invention includes the following three steps:

[0005] Step 1: A basic cross-control architecture is proposed to simplify the complexity of metasurface hardware control while maintaining the accuracy of metasurface spatial beam steering. This architecture encodes the high and low control voltages of the row and column units of the metasurface array to obtain the encoding matrix of the row and column control voltages, and then obtains the unit working state of the metasurface array by multiplying the row and column voltage encoding matrices. Different control voltage encoding matrices will obtain different array unit state arrangements, thereby realizing different beam steering phenomena.

[0006] Step 2: Based on the basic cross-control architecture, the basic cross-control architecture is deployed in different regions on the metasurface to realize a multi-region cross-control architecture. The number of partitions and the size of the regions will affect the accuracy of the metasurface beam steering and the complexity of the control hardware implementation. The array unit arrangement coding of the partitioned cross-control architecture metasurface mainly depends on the array coding acquisition method established in step 1.

[0007] Step 3: In order to quickly obtain the row and column control voltage coding of the partitioned cross-control architecture metasurface under the specified signal beam control direction, a genetic optimization algorithm is used to optimize the selection of the control voltage high and low coding matrices that can achieve the target signal beam control.

[0008] Furthermore, step 1 specifically includes the following steps: a basic cross control architecture metasurface unit is proposed, specifically, a basic cross control architecture metasurface unit array, the upper part of the same row unit is connected to the positive terminal of the unit PIN diode, and the lower part of the same column unit is connected to the negative terminal of the unit PIN diode through the metal aperture. By providing high voltage or low voltage to these two parts, the working state of the unit PIN diode is controlled. At this time, each unit diode in the array has four voltage combinations. When the row voltage of the unit is high voltage and the column voltage is low voltage, the unit diode is in the on state. Under the other three voltage combinations, the diode is in the off state. Here, by determining the high and low voltage states of all rows and columns of the array, the working state of the diode in the metasurface array can be determined. For an array containing M×N metasurface units, a vector V containing M elements and a vector H containing N elements are used to represent the control voltages of rows and columns, respectively, where V i =1 and V i = 0 (i = 0, 1, ..., M) represent the high and low voltages of the i-th row respectively; similarly, H j =0 and H j =1 (j=0, 1, ..., N) represents the high and low voltages of the jth row respectively. According to the coding matrix of row and column control voltages, the electromagnetic response of the metasurface array unit can be characterized as:

[0009] C=V T ·H, (2)

[0010] Where C represents the electromagnetic response state matrix of the metasurface array unit. The matrix element C (m,n) (m=1,2,…,M and n=1,2,…,N) represents the working state of the PIN diode located in the mth row and the nth column, C (m,n) =0 and C (m,n) =1 indicates that the diode is in the off state and the on state respectively. The two working states of the diode correspond to the two opposite electromagnetic phase responses of the metasurface unit.

[0011] Furthermore, step 2 specifically includes the following steps: based on the basic row-column control architecture, a partitioned row-column control architecture is implemented; assuming that the number of partition items is K, that is, a K-zone cross-control hypersurface, using vector V 1 ,V 2 ,…,V K and H 1 ,H 2 ,…,H K Represent the row and column control high and low voltage coding of K regions respectively. Through the product operation of these two sets of vectors, the electromagnetic response state matrix of the cross-controlled metasurface array unit in K regions can be obtained as:

[0012]

[0013] Furthermore, step 3 specifically includes the following steps: the optimal choice is row-column control high and low voltage coding, and a genetic algorithm is used to solve this optimization problem; assuming is the main beam deflection angle of the signal beam, then the phase distribution of the corresponding deflection angle of the metasurface unit in the corresponding array can be expressed as:

[0014]

[0015] where Φ(m,n) is the phase of the m-th row and n-th column element in the array, (x i ,y i ) is the position of the unit in the Cartesian coordinate system.

[0016] Next, define a vector X = [V 1 ,V 2 ,…,V K ,H 1 ,H 2 ,…,H K ], which contains the codes for controlling high and low voltages of all partition rows and columns. At this time, relying on the method for acquiring the electromagnetic response state matrix of the metasurface array unit established in step 2, the reflection phase coding distribution of the metasurface array can be obtained as πC KPCM , which is a function of vector X. Assume that the deflection angle of the array main beam is Then the optimization target can be set as the array phase distribution Φ of the metasurface under the beam pointing angle, and the optimization of the array row and column control high and low voltage coding matrix can be defined as the following objective function:

[0017]

[0018] Among them U 1 represents the objective function evaluated at a given value of X, ||·|| F represents the Ferrobenius norm of the given matrix. At this time, the optimization problem can be expressed as:

[0019]

[0020] Where X* represents the optimal solution of X. By completing this optimization, it is possible to quickly obtain the row and column control voltage encoding of the partitioned cross-control architecture metasurface in the specified signal beam control direction.

[0021] The present invention also provides a metasurface, which adopts the above-mentioned metasurface control architecture design method to realize hardware control.

[0022] The metasurface control architecture design method of the present invention has the following advantages:

[0023] 1. The present invention creates a framework for rapidly designing metasurface units, which includes a basic cross-control architecture, a partitioned cross-control architecture, and a row-column high- and low-voltage coding optimization algorithm.

[0024] 2. The basic cross-control architecture applies high and low voltages to the row units and column units of the metasurface array respectively, and obtains the unit electromagnetic response state matrix of the array through the product of the row and column voltage coding vectors; broadens the spatial beamforming capability of the metasurface array.

[0025] 3. Based on the basic cross-control architecture, the partitioned cross-control architecture is independently deployed in multiple areas, and the unit electromagnetic response state matrix of the entire metasurface array is obtained through matrix operations; the phase distribution degree of freedom of the metasurface array is increased.

[0026] 4. The row and column high and low voltage coding optimization algorithm takes the array phase distribution corresponding to the target main beam pointing angle as the optimization target, optimizes the selection of row and column control voltage high and low coding, and uses genetic algorithms to quickly obtain the optimal solution.

[0027] 5. The method of the present invention is simple, and subsequent full-wave simulation and experimental tests have proved the effectiveness of the method, which has practical engineering significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the operation of a four-zone cross-control architecture metasurface according to an implementation example of the present invention.

[0029] Figure 2 This is the working mechanism of the cross-control architecture metasurface unit of the implementation case of the present invention; (a) gives the basic cross-control architecture metasurface structure diagram, and (b) gives the working state of the metasurface unit PIN diode and the row and column control high and low voltage coding.

[0030] Figure 3This is a method for characterizing the state of a metasurface array unit in a basic cross-control architecture for an implementation example of the present invention; (a) is a row-column control high and low voltage coding vector product operation, and (b) gives the operation result and the unit electromagnetic response state encoding of the metasurface array.

[0031] Figure 4 This is a method for characterizing the state of a metasurface array unit in a partitioned cross-control architecture of an implementation example of the present invention; (a) is a product operation of high and low voltage coding vectors for row and column control of different zones, and (b) gives the operation results of different zones and the final electromagnetic response state coding of the metasurface array unit.

[0032] Figure 5 Schematic diagram of achievable spatial main beam coverage of the metasurface array under different partitioned cross-control architectures of the implementation cases of the present invention.

[0033] Figure 6 This is a structural diagram of a 1-bit phase-controlled cross-control architecture metasurface unit in an implementation example of the present invention.

[0034] Figure 7 The electromagnetic response simulation results of a 1-bit phase-controlled cross-control architecture metasurface unit in different states of an implementation case of the present invention; (a) gives the reflection amplitude diagram of the unit, and (b) gives the reflection phase diagram of the unit.

[0035] Figure 8 The experimental results of beam scanning on the E-plane and H-plane of the four-zone cross-control architecture metasurface of the implementation case of the present invention; (a) is the E-plane beam scanning result diagram, and (b) is the H-plane beam scanning result diagram.

[0036] Fig. 9 The diagram is a comparison of beam scanning results of a four-zone cross-control architecture metasurface in actual space of an implementation case of the present invention; (a) is a calculation result diagram of an independent control architecture metasurface and a four-zone cross-control architecture metasurface when the beam pointing angle is (45°, 20°); (b) is a comparison diagram of simulation and experimental results of a four-zone cross-control architecture metasurface when the beam pointing angle is (45°, 20°). DETAILED DESCRIPTION

[0037] In order to better understand the purpose, structure and function of the present invention, a method for designing a super surface control architecture of the present invention is further described in detail below in conjunction with the accompanying drawings.

[0038] Step 1: Propose a basic cross-control architecture metasurface

[0039] A basic cross control architecture metasurface cell array, where the upper part of the same row of cells is connected to the positive terminal of the cell PIN diode, and the lower part of the same column of cells is connected to the negative terminal of the cell PIN diode through a metal aperture. By providing high voltage or low voltage to these two parts, the working state of the cell PIN diode is controlled, such as Figure 2 (a) is shown. At this time, each unit diode in the array has four voltage combinations. When the row voltage of the unit is high and the column voltage is low, the unit diode is in the on state. Under the other three voltage combinations, the diode is in the off state, such as Figure 2 (b) Here, by determining the high and low states of the control voltages of all rows and columns of the array, the working state of the diodes in the metasurface array can be determined. For an array containing M×N metasurface units, a vector V containing M elements and a vector H containing N elements are used to represent the control voltages of the rows and columns, respectively, where V i =1 and V i = 0 (i = 0, 1, ..., M) represent the high and low voltages of the i-th row respectively; similarly, H j =0 and H j =1 (j=0,1,…,N) represent the high and low voltages of the jth row, respectively. Figure 2 (b) According to the coding matrix of row and column control voltages, the electromagnetic response of the metasurface array unit can be characterized as:

[0040] C=V T ·H, (7)

[0041] Where C represents the electromagnetic response state matrix of the metasurface array unit. The matrix element C (m,n) (m=1,2,…,M and n=1,2,…,N) represents the working state of the PIN diode located in the mth row and the nth column, C (m,n) =0 and C (m,n) =1 indicates that the diode is in the off and on states respectively. The two working states of the diode correspond to the two opposite electromagnetic phase responses of the metasurface unit. Assuming that the row and column control voltages are encoded as V = [010101], H = [110011], the corresponding array encoding calculation process is as follows: Figure 3 As shown in (a), the electromagnetic response distribution of the metasurface array unit generated under the row and column control voltage coding is shown in Figure 3 (b) as shown.

[0042] Step 2: Build a partitioned cross-control architecture metasurface

[0043] Based on the basic cross control architecture, a partitioned row-column control architecture is proposed to independently implement the basic cross control architecture hypersurface in each area; assuming that the number of partition items is K, that is, the K-area cross control hypersurface, with vector V1 ,V 2 ,…,V K and H 1 ,H 2 ,…,H K Represent the row and column control high and low voltage coding of K regions respectively. Through the product operation of these two sets of vectors, the electromagnetic response state matrix of the cross-controlled metasurface array unit in K regions can be obtained as:

[0044]

[0045] Assuming a three-zone cross-control architecture metasurface, the row and column cross-control high and low voltage codes of each zone are: V 1 =

[011] ,V 2 =

[110] ,V 3 =

[101] ,H 1 =

[111] ,H 2 =

[001] , H 3 =[101011], the corresponding matrix coding calculation process is as follows Figure 4 As shown in (a), the electromagnetic response distribution of the metasurface array unit generated under the row and column control voltage coding is shown in Figure 4 (b) When the metasurface array scale is 8×8, under the cross-control architecture of each partition, the spatial main beam pointing angle coverage of the metasurface is as follows: Figure 5 shown.

[0046] Step 3: Row and column control high and low voltage coding optimization algorithm

[0047] The optimal choice is the row-column control high and low voltage coding, and the genetic algorithm is used to solve this optimization problem; assuming is the main beam deflection angle of the signal beam, then the phase distribution of the corresponding deflection angle of the metasurface unit in the corresponding array can be expressed as:

[0048]

[0049] where Φ(m,n) is the phase of the m-th row and n-th column element in the array, (x i ,y i ) is the position of the unit in the Cartesian coordinate system.

[0050] Next, define a vector X = [V 1 ,V 2 ,…,V K ,H 1 ,H 2 ,…,H K], which contains the codes for controlling high and low voltages of all partition rows and columns. At this time, relying on the method for acquiring the electromagnetic response state matrix of the metasurface array unit established in step 2, the reflection phase coding distribution of the metasurface array can be obtained as πC KPCM , which is a function of vector X. Assume that the deflection angle of the array main beam is Then the optimization target can be set as the array phase distribution Φ of the metasurface under the beam pointing angle, and the optimization of the array row and column control high and low voltage coding matrix can be defined as the following objective function:

[0051]

[0052] Among them U 1 represents the objective function evaluated at a given value of X, ||·|| F represents the Ferrobenius norm of the given matrix. At this time, the optimization problem can be expressed as:

[0053]

[0054] Where X * The optimal solution of X is expressed as X. By completing this optimization, it is possible to quickly obtain the row and column control voltage encoding of the partitioned cross control architecture metasurface in the specified signal beam control direction.

[0055] In order to quickly obtain the optimized control voltage encoding under the target beam control direction, the classic genetic algorithm is used for optimization. Genetic algorithm is an optimization algorithm based on the principles of natural selection and genetics. It is a type of evolutionary algorithm used for optimization and search of complex problems. Genetic algorithm gradually approaches the optimal solution in the solution space by simulating the selection, crossover, mutation and other processes in biological evolution. Combined with the above-mentioned optimization problem, the actual operation mainly includes the following steps: 1. Initialization: Use binary strings to represent the high and low voltages of row and column control, that is, the X value, and randomly generate a certain number of individuals as the initial population. 2. Fitness evaluation: According to the above objective function, the fitness of each individual is evaluated to characterize the quality of each solution. The higher the fitness value, that is, the smaller the objective function value, the greater the possibility that the individual will be retained and passed on. 3. Selection: Select the parent individual according to the fitness value to generate the next generation of individuals. Commonly used selection methods are roulette selection and tournament selection. 4. Crossover: Randomly select two individuals from the parent generation and generate new offspring through gene crossover. The crossover operation can simulate the genetic behavior of organisms, and methods such as single-point crossover, two-point crossover, and uniform crossover can be used. 5. Mutation: Under a certain probability, randomly change some gene values ​​of individuals to increase the diversity of the population and avoid falling into a local optimal solution. For example, change the voltage of a column or row of the row and column control voltage from high to low or from low to high. 6. Replacement: Replace the individuals of the current population with the generated offspring to form a new generation of population, and perform iterative optimization. 7. Termination condition check: End the algorithm according to the termination conditions specified in the design. For example, the expected optimal solution is reached, the number of iterations reaches the upper limit, or the fitness change is too small. According to the above steps, the row and column control voltage coding optimization of the array under the target beam is performed to obtain the optimal row and column control voltage distribution.

[0056] Here is a specific implementation case:

[0057] A 1-bit phase-controlled four-zone cross-control architecture metasurface is designed to work in the China Mobile communication frequency band. The unit structure of the cross-control architecture metasurface is as follows: Figure 6 As shown. After forming an array, the top-layer patches in the same row unit are connected to each other, one end of which is connected to the row control circuit, and the other end is connected to the positive electrode of the PIN diode; the bottom-layer feed lines in the same column unit are connected to each other, one end of which is connected to the negative electrode of the PIN diode through the feed column, and the other end is connected to the column control circuit. By adjusting the level of row and column control voltages, the phase state switching of the basic cross-control architecture metasurface array can be achieved. The electromagnetic amplitude phase response of this unit is shown in Figure 7 shown.

[0058] In order to increase the spatial beam pointing coverage of the metasurface, a four-zone cross-control architecture metasurface is realized based on the designed basic cross-control architecture metasurface unit, such as Figure 1As shown. By optimizing the selection of the rows and columns of the metasurface to control the high and low voltage coding, the directional beam deflection of the metasurface in space is realized. In order to verify the characteristics of the designed four-zone cross control architecture metasurface, the beam scanning performance of the metasurface on the E and H surfaces is actually processed and tested. Figure 8 As shown in the figure, the results are basically consistent with the target design, which fully demonstrates the effectiveness of the proposed control architecture method. In addition, the far-field patterns of the four-zone cross-control architecture metasurface and the unit independent control architecture metasurface at the same beam pointing angle are compared. Fig. 9 As shown in (a), the two results are not much different in the main beam angle pointing, which shows that the four-zone cross-control architecture metasurface has a higher spatial beamforming accuracy. Fig. 9 (b) shows the comparison between the simulation and test results of the far-field pattern of the metasurface at a specified beam pointing angle. There is a certain error between the actual test results and the simulation results, which may be due to certain errors in the actual test environment and the plate processing. In general, the results successfully verify the effectiveness of the proposed control architecture method.

[0059] In summary, the metasurface unit optimization design method of the present invention is a very fast and effective method. The effectiveness of the optimization method has been strongly demonstrated from full-wave simulation and physical testing, and it has great practical significance for the research on the rapid design of metasurface units.

[0060] It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

Claims

1. A method for designing a metasurface control architecture, characterized in that: The steps include: Establish a basic cross control architecture metasurface unit array, which includes M×N metasurface units, and the units in the same row and the same column are connected to the positive terminal and negative terminal of the unit PIN diode respectively. By controlling the high and low voltages of each column and each row of the metasurface array, the working state of the unit PIN diode is controlled; The basic cross control architecture metasurface unit array is divided into K regions, and vectors V1, V2, …, V K and H1,H2,…,H K The rows and columns representing K regions control high and low voltage coding respectively; Multiply the high and low voltage coding matrices controlled by rows and columns to obtain the unit electromagnetic response state matrix C of the metasurface array KPCM , and then the reflection phase coding distribution of the metasurface array is obtained as πC KPCM , which is a vector X=[V1,V2,…,V K ,H1,H2,…,H K ]; Construct the following objective function: where U1 represents the objective function evaluated at a given value of X, ||·|| F represents the Ferrobenius norm of the given matrix, Φ represents the array phase distribution of the metasurface under the target beam pointing angle; By solving the optimization problem: Get the row and column control voltage encoding of the partition cross control architecture metasurface in the specified signal beam steering direction, where X * It is represented as the optimal solution of X.

2. A method for designing a metasurface control architecture according to claim 1, characterized in that: A genetic algorithm is used to solve the optimization problem.

3. A metasurface, characterized in that: The hardware control is realized by adopting the metasurface control architecture design method described in any one of claims 1 or 2.

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