Metasurface near-field unit response difference calibration method and device

Abstract

This invention provides a method and apparatus for calibrating the response differences of near-field units on a metasurface. The method includes: generating control signals based on the modulation period and position of the metasurface units; obtaining harmonic distributions by Fourier series decomposition of the control signals of each metasurface unit, and obtaining a standard harmonic distribution matrix based on the harmonic distributions of all metasurface units; after the receiving module receives the signal radiated by the metasurface units, performing a fast Fourier transform on the digital signal sampled by the digital module to obtain harmonic components; calculating the propagation response using a spherical wave model based on the position of the receiving module and the positions of each metasurface unit; obtaining the radiation response of each metasurface unit to the feed signal based on the standard harmonic distribution matrix, harmonic components, and propagation response, and calibrating the differences between the radiation responses of the metasurface units. This invention achieves measurement and calibration of inter-unit differences using periodic-time modulation.

Description

Technical Field

[0001] This invention relates to the field of wireless communication technology, and in particular to a method and apparatus for calibrating the response differences of near-field cells on a metasurface (RIS). Background Technology

[0002] Unlike far-field communication, when wireless communication occurs in the near-field region, the angle of arrival / angle of departure of all antenna elements cannot be approximately equal. This requires measuring the response of the user signal to each element in order to concentrate the radiated energy to the target area, i.e., beam focusing.

[0003] Metasurfaces are a novel type of artificial electromagnetically tunable surface. Each metasurface unit can be controlled individually. Compared to traditional antenna arrays, they are less complex and consume less energy, and are easier to deploy, making them an important technology for next-generation wireless communication. However, due to differences in manufacturing processes and the materials themselves, there are certain differences in the electromagnetic responses of metasurface units. Therefore, it is necessary to calibrate these differences in unit response to achieve precise control. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention provides a method and apparatus for calibrating the response difference of metasurface near-field units.

[0005] This invention provides a method for calibrating the response difference of near-field units on a metasurface, comprising:

[0006] Based on the modulation period and position of the metasurface unit, a control signal for the metasurface unit within the modulation period is generated;

[0007] The control signals of each metasurface unit are decomposed using Fourier series to obtain the harmonic distribution of each metasurface unit. The standard harmonic distribution matrix is ​​then obtained based on the harmonic distribution of all metasurface units.

[0008] After the receiving module receives the signal radiated by the metasurface unit, the digital signal sampled by the digital module in the receiving module is subjected to a fast Fourier transform to obtain the harmonic components.

[0009] The propagation response from each metasurface unit to the receiving module is calculated using a spherical wave model based on the position of the receiving module and the position of each metasurface unit.

[0010] Based on the standard harmonic distribution matrix, harmonic components, and propagation response, the radiation response of each metasurface unit to the feed signal is obtained, and the differences between the radiation responses of the metasurface units are calibrated.

[0011] According to the present invention, a method for calibrating the response difference of a metasurface near-field unit is provided, which generates a control signal of the metasurface unit within the modulation period based on the modulation period and position of the metasurface unit using the following formula:

[0012] ;

[0013] in, Let T be the control signal for the metasurface element in row m and column n at time t. p The modulation period is M, and M and N are the total number of rows and columns of the metasurface units, respectively.

[0014] According to the present invention, a method for calibrating the response difference of near-field elements of a metasurface is provided, which obtains the harmonic distribution of each metasurface element by performing Fourier series decomposition on the control signal of each metasurface element using the following formula:

[0015] ;

[0016] in, The qth harmonic of the control signal for the metasurface unit in the m-th row and n-th column;

[0017] The formula for the standard harmonic distribution matrix A is: , where Q is the harmonic order, and 2Q≥MN.

[0018] According to the present invention, a method for calibrating the response difference of near-field elements of a metasurface is provided. The propagation response of each metasurface element to the receiving module is calculated using a spherical wave model based on the position of the receiving module and the position of each metasurface element, according to the following formula:

[0019] ;

[0020] in, Let r be the propagation response from the metasurface unit in row m and column n to the receiving module. m,n Let be the distance from the metasurface unit in the m-th row and n-th column to the receiving module. is the propagation constant.

[0021] According to the present invention, a method for calibrating the response difference of near-field elements of a metasurface is provided, which obtains the radiation response of each metasurface element to the feed signal based on the standard harmonic distribution matrix, harmonic components, and propagation response using the following formula:

[0022] ;

[0023] Where g is the radiation response of the metasurface element to the feed signal, A is the standard harmonic distribution matrix, and h is the propagation response of all metasurface elements. , represents the harmonic components from -Q to +Q, {}+ denotes finding the pseudo-inverse, and diag denotes constructing a diagonal matrix based on the vector.

[0024] According to the present invention, a method for calibrating the difference in near-field element response of a metasurface further includes, after calibrating the difference in radiation response between the metasurface elements:

[0025] Based on the target position of the near-field beam focusing of the metasurface unit and the position of each metasurface unit, calculate the propagation distance from each metasurface unit to the target position;

[0026] The signals radiated by each metasurface unit are weighted and summed to form the maximum energy superposition at the target location, resulting in the strongest signal power.

[0027] According to the metasurface near-field element response difference calibration method provided by the present invention, after calibrating the differences in the radiation responses of the metasurface elements, the ideal radiation response of each metasurface element satisfies:

[0028] ;

[0029] Among them, g mn Let be the ideal radiation response of the metasurface element in the m-th row and n-th column.

[0030] According to the present invention, a method for calibrating the response difference of near-field elements of a metasurface is provided, wherein the signal formula of the metasurface element radiation is:

[0031] ;

[0032] Where s is the total signal radiated by the metasurface at spatial position r and time t, r is the spatial position vector representing the coordinates of the observation point, t is the time variable, w is the angular frequency, and E is the power or amplitude factor of the feed signal.

[0033] The present invention also provides a metasurface near-field unit response difference calibration device, comprising:

[0034] The generation module is used to generate a control signal for the metasurface unit within the modulation period based on the modulation period and position of the metasurface unit;

[0035] The acquisition module is used to obtain the harmonic distribution of each metasurface unit by Fourier series decomposition of the control signal of each metasurface unit, and to obtain the standard harmonic distribution matrix based on the harmonic distribution of all metasurface units.

[0036] The transformation module is used to perform a fast Fourier transform on the digital signal sampled by the digital module in the receiving module after the receiving module receives the signal radiated by the metasurface unit to obtain the harmonic components.

[0037] The calculation module is used to calculate the propagation response from each metasurface unit to the receiving module based on the position of the receiving module and the position of each metasurface unit using a spherical wave model.

[0038] The calibration module is used to obtain the radiation response of each metasurface unit to the feed signal based on the standard harmonic distribution matrix, harmonic components and propagation response, and to calibrate the differences between the radiation responses of the metasurface units.

[0039] The present invention also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the metasurface near-field unit response difference calibration method as described above.

[0040] The present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the metasurface near-field unit response difference calibration method as described above.

[0041] The present invention also provides a computer program product, including a computer program that, when executed by a processor, implements the metasurface near-field unit response difference calibration method as described above.

[0042] The metasurface near-field unit response difference calibration method and apparatus provided by this invention have the following beneficial effects:

[0043] 1. This invention takes into account the inconsistency of the radiation response of metasurface units and uses a periodic time modulation method to measure and calibrate the differences between units, overcoming the impact of inconsistency errors introduced by production and processing on practical applications. Moreover, it is simple and quick to operate and does not introduce additional hardware.

[0044] 2. This invention introduces a near-field spherical wave model on the basis of traditional beamforming, taking into account the metasurface radiation in the near-field range. After completing the near-field radiation calibration of the unit, the near-field beam focusing effect is improved, which has important reference value for actual scenarios.

[0045] 3. This invention has no special requirements for the system and is applicable to reflective and transmissive metasurface systems. Moreover, it can be combined with existing time modulation timing and metasurface spatial coding to further optimize the effect. For different situations, only the controller software program needs to be adjusted, without changing the hardware. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0047] Figure 1 This is a schematic flowchart of the metasurface near-field unit response difference calibration method provided by the present invention;

[0048] Figure 2 This is a schematic diagram of a scenario for the metasurface near-field unit response difference calibration method provided by the present invention;

[0049] Figure 3 This is a schematic diagram of the receiver harmonic distribution of the metasurface unit according to the periodic timing switching state in the metasurface near-field unit response difference calibration method provided by the present invention;

[0050] Figure 4 This is a schematic diagram comparing the response amplitude and phase difference of the metasurface unit before and after calibration in the metasurface near-field unit response difference calibration method provided by the present invention;

[0051] Figure 5 This is a schematic diagram of the metasurface spatial encoding state in the metasurface near-field unit response difference calibration method provided by the present invention;

[0052] Figure 6(a) is a schematic diagram of the absolute amplitude of the energy distribution of the near-field beam focusing signal in the metasurface near-field unit response difference calibration method provided by the present invention;

[0053] Figure 6(b) is a schematic diagram of the normalized amplitude of the energy distribution of the near-field beam focusing signal of the metasurface in the metasurface near-field unit response difference calibration method provided by the present invention;

[0054] Figure 7 This is a schematic diagram of the metasurface near-field unit response difference calibration device provided by the present invention. Detailed Implementation

[0055] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0056] The following is combined with Figure 1 A method for calibrating near-field element response differences on a metasurface, as described in this invention, includes:

[0057] Step 101: Generate a control signal for the metasurface unit within the modulation period based on the modulation period and position of the metasurface unit;

[0058] Step 102: The control signal of each metasurface unit is decomposed by Fourier series to obtain the harmonic distribution of each metasurface unit, and the standard harmonic distribution matrix is ​​obtained based on the harmonic distribution of all metasurface units.

[0059] Step 103: After the receiving module receives the signal radiated by the metasurface unit, the digital signal sampled by the digital module in the receiving module is subjected to fast Fourier transform to obtain the harmonic components.

[0060] Step 104: Using a spherical wave model, calculate the propagation response from each metasurface unit to the receiving module based on the position of the receiving module and the position of each metasurface unit;

[0061] Step 105: Based on the standard harmonic distribution matrix, harmonic components, and propagation response, obtain the radiation response of each metasurface unit to the feed signal, and calibrate the differences between the radiation responses of the metasurface units.

[0062] like Figure 2 As shown, the metasurface near-field unit calibration and beam focusing system in this embodiment includes:

[0063] Transmitting module: includes a feed antenna, a controller, and a reflective metasurface array. The controller generates state signals for the metasurface elements and changes the phase shift of the elements to the incident feed signal through control lines. The reflective metasurface transmits the signal to the receiver.

[0064] The receiving module includes analog and digital modules. The analog module receives, down-converts, and filters the received signal, while the digital module samples and processes the signal to obtain the desired information. The analog module includes a receiving antenna, a low-noise amplifier, a mixer, and filters; the digital module includes a sampler and a digital signal processing module.

[0065] Both the feed antenna and the receiving antenna are located in the near field of the metasurface, and there is no significant electromagnetic interference between the transmitting and receiving ends.

[0066] The metasurface comprises M×N periodically arranged tunable structural units, which can be reflective, transmissive, or a reflective / transmissive adjustable structure.

[0067] The receiver in the analog module of the receiving module has the same local crystal oscillator signal as the transmitter module. The controller in the transmitter module and the digital signal processing in the receiver module are performed by a computer, which controls the system by connecting to the transceiver.

[0068] This embodiment includes two parts: near-field unit calibration and near-field beam focusing, both of which are based on metasurfaces. Time modulation is used to measure and calibrate the near-field response of each metasurface unit and to achieve near-field beam focusing.

[0069] A feed antenna located in the near-field range of the metasurface transmits radio frequency signals to the metasurface. Each element of the metasurface changes its state sequentially according to a certain timing sequence. A receiving antenna located in the near-field range of the metasurface receives the signals reflected / transmitted by the metasurface.

[0070] The receiving module amplifies, downconverts, and filters the signal to obtain the baseband signal. The digital module samples the signal to obtain a digital signal for easy processing. The digital signal is then subjected to a fast Fourier transform to obtain the harmonic components.

[0071] The propagation response from the metasurface to the receiver is obtained by calculating the amplitude and phase changes of each element of the metasurface to the receiver based on the position of the receiving antenna. A spherical wave model is used to consider the influence of distance.

[0072] The response of the metasurface unit to the feed signal is obtained by comparing the harmonic distribution of the received signal with the standard harmonic distribution. This result can be used for calibration, thereby achieving precise control.

[0073] This embodiment considers the inconsistency of the radiation response of metasurface units and applies a periodic time modulation method to measure and calibrate the differences between units; a near-field spherical wave model is introduced to consider the metasurface radiation in the near-field range.

[0074] Based on the above embodiments, this embodiment generates the control signal of the metasurface unit within the modulation period according to the modulation period and position of the metasurface unit using the following formula:

[0075] ;

[0076] in, Let T be the control signal for the metasurface element in row m and column n at time t. p The modulation period is M, and M and N are the total number of rows and columns of the metasurface units, respectively.

[0077] Based on the above embodiments, in this embodiment, the control signals of each metasurface unit are decomposed using Fourier series to obtain the harmonic distribution of each metasurface unit:

[0078] ;

[0079] in, The qth harmonic of the control signal for the metasurface unit in the m-th row and n-th column;

[0080] The formula for the standard harmonic distribution matrix A is: , where Q is the harmonic order, and 2Q≥MN.

[0081] Based on the above embodiments, this embodiment uses the spherical wave model to calculate the propagation response from each metasurface unit to the receiving module according to the position of the receiving module and the position of each metasurface unit, using the following formula:

[0082] ;

[0083] in, Let r be the propagation response from the metasurface unit in row m and column n to the receiving module. m,n Let be the distance from the metasurface unit in the m-th row and n-th column to the receiving module. is the propagation constant.

[0084] The response of the entire metasurface can be written as:

[0085] ;

[0086] Based on the above embodiments, this embodiment obtains the radiation response of each metasurface unit to the feed signal using the following formula, according to the standard harmonic distribution matrix, harmonic components, and propagation response:

[0087] ;

[0088] Where g is the radiation response of the metasurface element to the feed signal, A is the standard harmonic distribution matrix, and h is the propagation response of all metasurface elements. , where represents the harmonic components from -Q to +Q, and each element is a complex exponent.

[0089] This embodiment can obtain the radiation response from the feed to the metasurface, including the attenuation during propagation and the amplitude and phase changes introduced by the metasurface. This result can be used for calibration, thereby achieving precise control.

[0090] Based on the above embodiments, this embodiment, after calibrating the differences in the radiation responses of the metasurface units, further includes:

[0091] Based on the target position of the near-field beam focusing of the metasurface unit and the position of each metasurface unit, calculate the propagation distance from each metasurface unit to the target position;

[0092] The signals radiated by each metasurface unit are weighted and summed to form the maximum energy superposition at the target location, resulting in the strongest signal power.

[0093] Near-field beam focusing methods include the following steps:

[0094] Step 1: Measure and calibrate the difference between the feed source and the metasurface unit according to the near-field unit calibration method, so that the radiation signal from each metasurface unit to the receiver can be directly analyzed. The response of the metasurface unit to the feed source signal is... .

[0095] Step 2: Calculate the propagation path based on the target position and the metasurface element positions. Let the target position coordinates be (x0, y0, z0), and the metasurface element position coordinates be (x0, y0, z0). m,n , y m,n , z m,n Then the propagation distance is:

[0096] ;

[0097] Step 3: By performing wavefront compensation on the spherical wave, the radiation signals of each element are weighted and summed to form a maximum energy superposition at the target focal point, resulting in the strongest signal power. Based on the calibration values ​​and the required compensation values, the ideal amplitude and phase response of each metasurface element is calculated, such that for any m, n, the following holds:

[0098] ;

[0099] Among them, g mn Let be the ideal radiation response of the metasurface element in the m-th row and n-th column. The calibration value refers to the actual radiation response of each metasurface element to the feed signal, measured and calculated using the metasurface near-field element response difference calibration method proposed in this application. The compensation value refers to the phase (and amplitude) correction calculated based on the spherical wave propagation difference between the target position and the position of each metasurface element after calibration to achieve near-field beam focusing.

[0100] Based on the characteristics of the metasurface unit in different states, the quantized unit states are obtained, and the signal emitted by the metasurface can be written as:

[0101] ;

[0102] Where s is the total signal radiated by the metasurface at spatial position r and time t, r is the spatial position vector representing the coordinates of the observation point, t is the time variable, w is the angular frequency, and E is the power or amplitude factor of the feed signal.

[0103] Compared to far-field beamforming, the near-field beam focusing method involves the superposition of amplitude and phase differences in the radiated signals of different elements, thus requiring measurement and calibration of the differences in element responses.

[0104] Both near-field element calibration and beam focusing methods are analyzed within the radiation near-field (or Snell's region) of the metasurface, meaning the distance from the metasurface to the transmitter / receiver satisfies... , where D is the metasurface size and λ is the wavelength corresponding to the operating frequency.

[0105] For example, the transmitter's metasurface is a reflective 1-bit phase-modulated metasurface with a size of 16×16, an operating frequency of 4.5 GHz, and a unit spacing of half a wavelength. The feed uses a horn antenna to transmit radio frequency signals. Assume the amplitude and phase response differences between the metasurface units range from [-3, 3] dB to [-10°, 10°], generated by a random function. The receiving antenna is located in the near field of the metasurface, with coordinates (0.5m, 0, 2m) relative to the center of the metasurface array.

[0106] The state of each metasurface unit is controlled by a controller. Assuming the time modulation frequency of the unit control signal is 1 MHz, i.e., the modulation period is 1 μs, the expression for the control signal of the unit in the m-th row and n-th column within one period is:

[0107] ;

[0108] It should be noted that the above-described metasurface unit modulation method and modulation function are only one example. Various modulation methods and functions that meet different functional requirements can be applied according to different application needs and optimization objectives. According to the control signal, the 256 units of the metasurface switch scattering states sequentially by row and column, with the scattering signals of the same unit differing in phase by 180° between the two states.

[0109] With a signal-to-noise ratio of 20dB, the harmonic distribution of the received signal after Fast Fourier Transform is shown in the attached figure. Figure 3 As shown, the fundamental signal is the highest, but since the DC component of the signal is real and carries little information, we start from the ±1st harmonic and take ±128th harmonics to obtain a set of harmonic complex vectors. .

[0110] According to the metasurface control signal expression U m,n (t) The harmonic distribution of the emitted signal in each unit cell of the metasurface is obtained, and Fourier series decomposition yields:

[0111] ,in ;

[0112] Construct a standard harmonic distribution matrix using the results .

[0113] Based on the positions of the metasurface elements and the receiving elements, the transmission response is calculated as follows:

[0114] ,in ;

[0115] The measured values ​​of the near-field response differences of the metasurface units based on the harmonics of the received signal are... , where {}+ denotes finding the pseudo-inverse, and diag denotes constructing a diagonal matrix based on the vector and comparing the amplitude and phase of g' with g. (Appendix) Figure 4 The setpoints and estimates of 256 metasurface elements are shown. The near-field element calibration method can reduce the amplitude difference from ±3dB to within ±0.5dB and the phase difference to within ±1°. The element response can be measured and calibrated, making subsequent analysis more accurate.

[0116] The near-field unit calibration method can improve the accuracy of the near-field response by changing the position of the receiving antenna and taking multiple measurements. When the position of the receiving end is determined, the time modulation period can be changed to complete multiple measurements.

[0117] After completing the near-field element calibration, the feed signal needs to be concentrated to the receiving area through the metasurface. The coordinates of the receiving antenna relative to the center of the metasurface array are (0.5m, 0, 2m), and the radiation power of the feed antenna is fixed.

[0118] Propagation distance from the metasurface element to the receiving antenna:

[0119] ;

[0120] The propagation phase difference between element (m1,n1) and element (m2,n2) is:

[0121] ;

[0122] The propagation phase difference is analyzed by treating the phase change of the signal propagating in the induced near-field of the metasurface unit as the same value. Taking the metasurface unit in the first row and first column as the reference, the phase difference value vector is obtained:

[0123] ;

[0124] For ease of analysis, we consider directly determining the metasurface phase modulation state based on the phase of the near-field response and the propagation phase of the metasurface unit, i.e.:

[0125] ;

[0126] The metasurface state code obtained from the above setting parameters is as follows: Figure 5 As shown, the elements in the two states are represented by black and white respectively. The radiation energy distribution of the metasurface on the y=0 plane is shown in Figure 6(a) and Figure 6(b). The energy intensity is higher near the target region, which can achieve near-field beam focusing.

[0127] Near-field beamforming methods can be combined with existing beamforming methods to reduce sidelobes or radiation in undesirable directions. The effectiveness of near-field beamforming methods will be improved for digital metasurfaces that can be simultaneously amplitude- and phase-modulated.

[0128] The metasurface near-field element response difference calibration device provided by the present invention is described below. The metasurface near-field element response difference calibration device described below can be referred to in correspondence with the metasurface near-field element response difference calibration method described above.

[0129] like Figure 7 As shown, the device includes a generation module 701, an acquisition module 702, a transformation module 703, a calculation module 704, and a calibration module 705.

[0130] The generation module 701 is used to generate a control signal for the metasurface unit within the modulation period based on the modulation period and position of the metasurface unit;

[0131] The acquisition module 702 is used to obtain the harmonic distribution of each metasurface unit by Fourier series decomposition of the control signal of each metasurface unit, and to obtain the standard harmonic distribution matrix based on the harmonic distribution of all metasurface units.

[0132] The transformation module 703 is used to perform a fast Fourier transform on the digital signal sampled by the digital module in the receiving module after the receiving module receives the signal radiated by the metasurface unit to obtain the harmonic components.

[0133] The calculation module 704 is used to calculate the propagation response from each metasurface unit to the receiving module based on the position of the receiving module and the position of each metasurface unit using a spherical wave model.

[0134] The calibration module 705 is used to obtain the radiation response of each metasurface unit to the feed signal based on the standard harmonic distribution matrix, harmonic components and propagation response, and to calibrate the differences between the radiation responses of the metasurface units.

[0135] This embodiment considers the inconsistency of the radiation response of metasurface units and applies a periodic time modulation method to measure and calibrate the differences between units; a near-field spherical wave model is introduced to consider the metasurface radiation in the near-field range.

[0136] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for calibrating the difference in near-field unit response of a metasurface, characterized in that, include: Based on the modulation period and position of the metasurface unit, a control signal for the metasurface unit within the modulation period is generated; The control signals of each metasurface unit are decomposed by Fourier series to obtain the harmonic distribution of each metasurface unit. The standard harmonic distribution matrix is ​​obtained based on the harmonic distribution of all metasurface units. After the receiving module receives the signal radiated by the metasurface unit, the digital signal sampled by the digital module in the receiving module is subjected to a fast Fourier transform to obtain the harmonic components. The propagation response from each metasurface unit to the receiving module is calculated using a spherical wave model based on the position of the receiving module and the position of each metasurface unit. Based on the standard harmonic distribution matrix, harmonic components, and propagation response, the radiation response of each metasurface unit to the feed signal is obtained, and the differences between the radiation responses of the metasurface units are calibrated.

2. The metasurface near-field unit response difference calibration method according to claim 1, characterized in that, The control signal for the metasurface unit within the modulation period is generated using the following formula, based on the modulation period and position of the metasurface unit: ； in, Let T be the control signal for the metasurface element in row m and column n at time t. p The modulation period is M, and M and N are the total number of rows and columns of the metasurface units, respectively.

3. The metasurface near-field unit response difference calibration method according to claim 2, characterized in that, The harmonic distribution of each metasurface element is obtained by performing Fourier series decomposition on the control signal of each metasurface element using the following formula: ； in, The qth harmonic of the control signal for the metasurface unit in the m-th row and n-th column; The formula for the standard harmonic distribution matrix A is: Where Q is the harmonic order, 2Q≥MN, C is the set of complex numbers, and j is the imaginary number. Let T be the control signal for the metasurface element in row m and column n at time t. p The modulation period.

4. The metasurface near-field unit response difference calibration method according to claim 2, characterized in that, The propagation response from each metasurface unit to the receiving module is calculated using the spherical wave model based on the positions of the receiving module and each metasurface unit, according to the following formula: ； in, Let r be the propagation response from the metasurface unit in row m and column n to the receiving module. m,n Let be the distance from the metasurface unit in the m-th row and n-th column to the receiving module. Let j be the propagation constant, and j be an imaginary number.

5. The metasurface near-field unit response difference calibration method according to claim 1, characterized in that, The radiation response of each metasurface element to the feed signal is obtained using the following formula, based on the standard harmonic distribution matrix, harmonic components, and propagation response: ； Where g is the radiation response of the metasurface element to the feed signal, A is the standard harmonic distribution matrix, and h is the propagation response of all metasurface elements. , represents the harmonic components from -Q to +Q, {}+ denotes finding the pseudo-inverse, and diag denotes constructing a diagonal matrix based on the vector.

6. The metasurface near-field unit response difference calibration method according to claim 1, characterized in that, After calibrating the differences in the radiative responses of the metasurface units, the method further includes: Based on the target position of the near-field beam focusing of the metasurface unit and the position of each metasurface unit, calculate the propagation distance from each metasurface unit to the target position; The signals radiated by each metasurface unit are weighted and summed to form the maximum energy superposition at the target location, resulting in the strongest signal power.

7. The metasurface near-field unit response difference calibration method according to claim 4, characterized in that, After calibrating the differences in the radiation responses of the metasurface units, the ideal radiation response of each metasurface unit satisfies: ； Among them, g mn Let be the ideal radiative response of the metasurface element in the m-th row and n-th column. Let be the tunable reflection or transmission coefficient of the metasurface element in the m-th row and n-th column, where j is an imaginary number and r is an imaginary number. m,n Let be the distance from the metasurface unit in the m-th row and n-th column to the receiving module. is the propagation constant.

8. The metasurface near-field unit response difference calibration method according to claim 7, characterized in that, The formula for the signal emitted by metasurface unit radiation is: ； Where s is the total signal radiated by the metasurface at spatial position r and time t, r is the spatial position vector representing the coordinates of the observation point, t is the time variable, w is the angular frequency, E is the power or amplitude factor of the feed signal, M and N are the total number of rows and columns of the metasurface cells, respectively, and g mn Let be the ideal radiative response of the metasurface element in the m-th row and n-th column. Let be the tunable reflection or transmission coefficient of the metasurface element in the m-th row and n-th column, where j is an imaginary number and r is an imaginary number. m,n Let be the distance from the metasurface unit in the m-th row and n-th column to the receiving module. is the propagation constant.

9. A metasurface near-field unit response difference calibration device, characterized in that, include: The generation module is used to generate a control signal for the metasurface unit within the modulation period based on the modulation period and position of the metasurface unit; The acquisition module is used to obtain the harmonic distribution of each metasurface unit by Fourier series decomposition of the control signal of each metasurface unit, and to obtain the standard harmonic distribution matrix based on the harmonic distribution of all metasurface units. The transformation module is used to perform a fast Fourier transform on the digital signal sampled by the digital module in the receiving module after the receiving module receives the signal radiated by the metasurface unit to obtain the harmonic components. The calculation module is used to calculate the propagation response from each metasurface unit to the receiving module based on the position of the receiving module and the position of each metasurface unit using a spherical wave model. The calibration module is used to obtain the radiation response of each metasurface unit to the feed signal based on the standard harmonic distribution matrix, harmonic components and propagation response, and to calibrate the differences between the radiation responses of the metasurface units.

10. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the metasurface near-field unit response difference calibration method as described in any one of claims 1 to 8.

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