A near-field correction method for massive millimeter-wave MIMO antenna arrays

Abstract

The embodiments of the present application relate to the technical field of MIMO antenna arrays, and in particular to a near-field correction method for a large-scale millimeter-wave MIMO antenna array, including: modeling the spatial positions of the MIMO antenna array and a metal cylinder as a correction cooperation target, determining the total transmission distance between the transceiver antenna pair, and solving the minimum value of the total transmission distance based on the BFGS convex optimization algorithm; modeling the echo signal, and deriving the expression of the correction coefficient of the delay deviation and the expression of the correction coefficient of the amplitude deviation and the phase deviation based on the model of the echo signal and the minimum value of the total transmission distance; collecting the echo data of the metal cylinder and preprocessing it, determining the correction coefficient of the delay deviation and the correction coefficient of the amplitude deviation and the phase deviation; collecting the echo data of the imaging target, and correcting the echo data of the imaging target in the order of the transceiver antenna pair based on the determined correction coefficient. This method reduces the correction cost and improves the correction effect.

Description

Technical Field

[0001] Embodiments of the present application relate to the technical field of MIMO antenna arrays, and in particular to a near-field correction method for a large-scale millimeter-wave MIMO antenna array. Background Art

[0002] The development of integrated circuit technology and radio frequency technology has created conditions for the manufacture of large-scale millimeter-wave MIMO (Multiple Input Multiple Output) antenna arrays. Large-scale millimeter-wave MIMO antenna arrays are widely used, including medical diagnosis, non-destructive testing, the Internet of Things, indoor personnel detection, communications, and radar imaging. MIMO antenna arrays use relatively few antennas to form a large sparse antenna array to obtain a large antenna aperture. In near-field imaging, the large bandwidth brought by the millimeter-wave frequency band is conducive to high resolution in the distance dimension, and the large antenna aperture is conducive to high resolution in the horizontal and vertical directions. The advantages of radar imaging are very obvious. It can work all day and all weather, while optical imaging is limited by light and weather. In addition, millimeter waves have a certain degree of penetration into clothing and cardboard, which optical cameras do not have.

[0003] The massive millimeter wave MIMO antenna array consists of multiple parts, including direct digital synthesizers, power amplifiers, power dividers, and signal transmission cables. These devices will have certain system errors, which are ultimately reflected in the delay, amplitude, and phase of the echo. If these deviations are not corrected, they will affect the system performance, which is reflected in the radar imaging as image defocus. Therefore, it is very necessary to correct these deviations.

[0004] There are many methods for correcting the deviation between antennas. The most common methods are to use a horn antenna and to collect the echo of a cooperative target. Kong et al. proposed to use a horn antenna to correct the RF antenna, and to collect the signal radiated by the horn antenna through the receiving antenna to calculate the deviation of the antenna itself. Sherif et al. proposed to use a metal sphere as a correction cooperative target. According to geometric optics, the reflection point of the electromagnetic wave radiated by the transmitting antenna on the sphere is calculated, and the propagation distance of the electromagnetic wave between the transmitting and receiving antennas and the target is calculated. The deviation between the transmitting and receiving channels is derived based on this parameter. Georg et al. proposed to use a metal plate as a correction cooperative target, regard the reflection of the metal plate as a mirror reflection, and use the method of geometric optics to calculate and compensate the propagation distance of the RF signal, and calculate the phase correction data. Pan Feng et al. used a metal cylinder as a correction cooperative target, and used the Newton iteration method to calculate the propagation distance of the RF signal from the transmitting and receiving array element to the cylinder, and then obtained the target peak of the spectrum through Fourier transform, and obtained the amplitude deviation and phase deviation between channels based on the target peak.

[0005] However, the correction method based on the horn antenna is expensive because the signal generator that generates high carrier frequency and large bandwidth is very expensive, and this method has high requirements for the positioning accuracy of the horn antenna during correction. The metal ball is used as a correction cooperation target. The radar cross-section (RCS) of the ball is small and the echo is weak. In actual operation, the metal ball needs to be installed with an auxiliary structure to ensure that the metal ball is easy to move and accurately positioned. The metal plate is used as a correction cooperation target. Its size should be comparable to that of the antenna array. The RCS of the metal plate is large, there is a strong multipath in the echo, and because of gravity, the metal plate is prone to physical bending. For metal balls, metal cylinders and metal plates of similar sizes, the RCS of the metal cylinder is between the metal ball and the metal plate. Pan Feng et al. used the metal cylinder as a correction cooperation target and used the Newton iteration method to calculate the distance between the transmitting and receiving array elements. When the antenna scale is large, the timeliness is not high, and this method does not include the delay deviation between antenna channels. Summary of the invention

[0006] The embodiment of the present application proposes a near-field correction method for a large-scale millimeter-wave MIMO antenna array, which uses a metal cylinder as a correction cooperation target. No auxiliary structure is required. The metal cylinder only needs to be placed vertically in front of the center of the antenna array. The construction cost is low, and the BFGS algorithm is used to calculate the propagation distance of the radio frequency signal between the MIMO antenna array and the metal cylinder, which improves the calculation efficiency and ultimately greatly improves the deviation correction effect.

[0007] In the first aspect, an embodiment of the present application proposes a near-field correction method for a large-scale millimeter-wave MIMO antenna array, comprising the following steps: modeling the spatial positions of the MIMO antenna array and a metal cylinder as a correction cooperation target, determining the total transmission distance of the FMCW (Frequency Modulation Continuous Wave) emitted by the mth transmitting antenna and received by the nth receiving antenna after being reflected by the metal cylinder, and solving the minimum value of the total transmission distance based on the BFGS convex optimization algorithm; wherein the metal cylinder is placed directly in front of the center of the MIMO antenna array, and the MIMO antenna array consists of M transmitting antennas and N receiving antennas, M and N are both integers greater than 1, m∈M, n∈N; modeling the echo signal of the FMCW emitted by the mth transmitting antenna and received by the nth receiving antenna after being reflected by the metal cylinder, and deriving the delay deviation, amplitude deviation and phase deviation between the transmitting and receiving antenna pairs based on the model of the modeled echo signal and the minimum value of the total transmission distance. The expression of the correction coefficient of the time delay deviation and the expression of the correction coefficient of the amplitude deviation and the phase deviation are derived; the MIMO antenna array is started, and when the MIMO antenna array reaches thermal equilibrium, the echo data of the metal cylinder is collected and preprocessed, and the correction coefficient of the time delay deviation and the correction coefficient of the amplitude deviation and the phase deviation are combined to determine the correction coefficient of the time delay deviation and the correction coefficient of the amplitude deviation and the phase deviation; the echo data of the imaging target is collected, and based on the determined correction coefficient of the time delay deviation and the correction coefficient of the amplitude deviation and the phase deviation, the echo data of the imaging target is corrected in the order of the transmitting and receiving antenna pairs.

[0008] Compared with metal balls and metal plates, metal cylinders are the best choice for correcting cooperative targets. Metal cylinders not only have a greater RCS than metal balls, but are also less likely to produce strong multipath effects. They are very convenient to locate, install and carry. No auxiliary structure is required. The metal cylinder only needs to be placed vertically in front of the center of the antenna array, and the construction cost is very low. Before correction, the spatial position of the MIMO antenna array and the metal cylinder is modeled first, the total transmission distance of the FMCW emitted by the mth transmitting antenna after being reflected by the metal cylinder and received by the nth receiving antenna is determined, and the minimum value of the total transmission distance is solved based on the BFGS convex optimization algorithm. The BFGS convex optimization algorithm eliminates the complex calculation of the Hessian matrix and matrix inversion in the Newton method, and has very high computational efficiency. Subsequently, the echo signal of the FMCW emitted by the mth transmitting antenna after being reflected by the metal cylinder and received by the nth receiving antenna is modeled, and the expressions of the delay deviation, amplitude deviation and phase deviation are derived, and then the expressions of the correction coefficients of the delay deviation, amplitude deviation and phase deviation are derived. When performing correction, the echo data of the metal cylinder is collected after the MIMO antenna array reaches thermal equilibrium, which can avoid the adverse effect of temperature on the correction. Finally, the correction coefficients of the delay deviation and the amplitude deviation and phase deviation are determined based on the derived expression, so as to correct the echo data of the imaging target, greatly improving the deviation correction speed, correction efficiency and correction effect.

[0009] In the second aspect, an embodiment of the present application proposes a near-field correction system for a large-scale millimeter-wave MIMO antenna array, the system comprising: a MIMO antenna array, a metal cylinder, a spatial position modeling module, a correction modeling module, an acquisition execution module and a correction execution module, the metal cylinder is placed directly in front of the center of the MIMO antenna array, the MIMO antenna array is composed of M transmitting antennas and N receiving antennas, M and N are both integers greater than 1; the spatial position modeling module is used to model the spatial position of the MIMO antenna array and the metal cylinder as the correction cooperation target, determine the total transmission distance of the FMCW emitted by the mth transmitting antenna after being reflected by the metal cylinder and received by the nth receiving antenna, and solve the minimum value of the total transmission distance based on the BFGS convex optimization algorithm, m∈M, n∈N; the correction modeling module is used to model the FMCW emitted by the mth transmitting antenna after being reflected by the metal cylinder and received by the nth receiving antenna The echo signal is modeled, and based on the model of the echo signal obtained by modeling and the minimum value of the total transmission distance, the expressions of the delay deviation, amplitude deviation and phase deviation between the transmitting and receiving antenna pairs are derived, and then the expression of the correction coefficient of the delay deviation and the expression of the correction coefficient of the amplitude deviation and the phase deviation are derived; the acquisition execution module is used to start the MIMO antenna array, and when the MIMO antenna array reaches thermal equilibrium, the echo data of the metal cylinder is collected and preprocessed, and the correction coefficient of the delay deviation and the correction coefficient of the amplitude deviation and the phase deviation are combined to determine the correction coefficient of the delay deviation and the correction coefficient of the amplitude deviation and the phase deviation; the acquisition execution module is also used to collect the echo data of the imaging target; the correction execution module is used to correct the echo data of the imaging target in the order of the transmitting and receiving antenna pairs based on the determined correction coefficient of the delay deviation and the correction coefficient of the amplitude deviation and the phase deviation.

[0010] In a third aspect, an embodiment of the present application proposes an electronic device, comprising: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute a near-field correction method for a large-scale millimeter-wave MIMO antenna array as described in the first aspect above.

[0011] In a fourth aspect, an embodiment of the present application proposes a computer-readable storage medium storing a computer program, which, when executed by a processor, implements a near-field correction method for a large-scale millimeter-wave MIMO antenna array as described in the first aspect above.

[0012] It can be understood that the beneficial effects of the second to fourth aspects mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the related technologies, the drawings required for use in the embodiments of the present application or the related technical descriptions will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0014] Figure 1 is a flowchart of a near-field correction method for a massive millimeter-wave MIMO antenna array provided in one embodiment of the present application;

[0015] Figure 2 is a schematic diagram of the arrangement of a single sub-array antenna in a MIMO antenna array provided in an embodiment of the present application;

[0016] Figure 3 is a schematic diagram of the spatial positions of four sub-array antennas and metal cylinders provided in an embodiment of the present application;

[0017] Figure 4 is a schematic diagram of a Cartesian coordinate system provided in one embodiment of the present application;

[0018] Figure 5 is a flowchart of a BFGS convex optimization algorithm provided in one embodiment of the present application;

[0019] Figure 6 is a structural schematic diagram of a near-field correction system for a massive millimeter-wave MIMO antenna array provided in another embodiment of the present application;

[0020] Figure 7 is a schematic diagram of a propagation path of a radio frequency signal between a transceiver antenna and a target provided in another embodiment of the present application;

[0021] Figure 8 is a schematic diagram of the positions of four simulated sub-arrays and scattered targets provided in another embodiment of the present application;

[0022] Fig. 9 is an imaging result diagram of an uncorrected scattered point target provided in another embodiment of the present application;

[0023] Fig.10 is an imaging result diagram of a corrected scattered target provided in another embodiment of the present application;

[0024] Fig.11 It is a structural schematic diagram of an electronic device provided in another embodiment of the present application. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the embodiments of the present application will be described in detail below in conjunction with the accompanying drawings. In the various embodiments of the present application, many technical details are proposed in order to make the reader better understand the present application. However, even without these technical details and various changes and modifications based on the following embodiments, the technical scheme claimed in the present application can also be implemented. The division of the following embodiments is only for the convenience of description, and the specific implementation mode of the present application should not constitute any limitation. The various embodiments can be combined with each other and referenced to each other under the premise of no contradiction.

[0026] An embodiment of the present application proposes a near-field correction method for a large-scale millimeter-wave MIMO antenna array, which is applied to an electronic device, wherein the electronic device can be a terminal or a server. In this embodiment and the following embodiments, the electronic device is described using a server as an example. The implementation details of the near-field correction method for a large-scale millimeter-wave MIMO antenna array proposed in this embodiment are specifically described below. The following content is only the implementation details provided for ease of understanding and is not necessary for the implementation of this solution.

[0027] The specific process of the near-field calibration method for a massive millimeter-wave MIMO antenna array proposed in this embodiment can be as follows: Figure 1 As shown, including:

[0028] Step 101, modeling the spatial position of the MIMO antenna array and the metal cylinder as the correction cooperation target, determining the total transmission distance of the FMCW emitted by the mth transmitting antenna and received by the nth receiving antenna after being reflected by the metal cylinder, and solving the minimum value of the total transmission distance based on the BFGS convex optimization algorithm.

[0029] In the specific implementation, the server first needs to model the spatial position of the MIMO antenna array and the metal cylinder as the correction cooperation target. The metal cylinder is placed in front of the center of the MIMO antenna array. The MIMO antenna array consists of M transmitting antennas and N receiving antennas, where M and N are both integers greater than 1. The server determines the total transmission distance of the FMCW emitted by the mth transmitting antenna after being reflected by the metal cylinder and received by the nth receiving antenna through modeling, and solves the minimum value of the total transmission distance based on the BFGS convex optimization algorithm. Where m∈M, n∈N.

[0030] In one example, the diameter and height of the metal cylinder are much larger than the wavelength of the FMCW corresponding to the MIMO antenna array. The diameter and height of the metal cylinder are determined based on the frequency band, antenna pattern, size and portability of the FMCW corresponding to the MIMO antenna array. The surface of the metal cylinder satisfies mirror reflection, and the FMCW emitted by all transmitting antennas of the MIMO antenna array can be reflected back to the receiving antenna at one time. Mirror reflection makes the process of calculating the propagation path of electromagnetic waves simpler.

[0031] There are many arrangements of antenna arrays. Here we choose a sub-array antenna arrangement as follows: Figure 2 The upper and lower rows are transmitting antennas, and the left and right columns are receiving antennas. There are 64 transmitting antennas in each row and 64 receiving antennas in each column. The distance between adjacent antennas is , is the wavelength of the millimeter wave RF signal, where the frequency of the RF signal is Four subarrays are used for calibration and calibration result analysis. The four subarrays have 512 transmit antennas and 512 receive antennas, for a total of 262,144 transmit and receive antenna pairs. The distance between the centers of the two subarrays is The spatial position diagram of the four sub-arrays and the metal cylinder is shown in Figure 3 The positions of the antenna subarrays can be determined using Figure 4 The Cartesian coordinate system shown in FIG. 1 shows that the origin of the Cartesian coordinate system is the center of the antenna array. In the Cartesian coordinate system, the position of the mth transmitting antenna is , the position of the nth receiving antenna is The distance between the axis of the metal cylinder and the antenna array is , the height of the metal cylinder is 0.6m, which can cover the height of four sub-arrays, and the radius of the metal cylinder is The points on the surface of the metal cylinder are expressed in the cylindrical coordinate system where the metal cylinder is located. In the Cartesian coordinate system, the positive direction of the x-axis is expressed in the cylindrical coordinate system. , the negative direction of the x-axis indicates Because the reflection point of the RF signal is only on the cylindrical surface of the metal cylinder, it is only necessary to express the coordinates of the points on the cylindrical surface. The points on the cylindrical surface in the cylindrical coordinate system are .

[0032] In an example, the total transmission distance of the FMCW signal transmitted by the mth transmitting antenna and received by the nth receiving antenna after being reflected by the metal cylinder is determined by the following formula:

[0033] ;

[0034] ;

[0035] ;

[0036] in, It represents the total transmission distance of the FMCW emitted by the mth transmitting antenna and received by the nth receiving antenna after being reflected by the metal cylinder. represents the distance from the mth transmitting antenna to the reflection point on the metal cylindrical surface, Indicates the distance from the nth receiving antenna to the reflection point on the metal cylindrical surface, represents a point on the surface of a metal cylinder, represents the spatial position of the mth transmitting antenna, Indicates the spatial position of the nth receiving antenna.

[0037] According to Fermat's principle, the distance between two points is the shortest. For example, the position of the transmitting and receiving antennas is fixed, and the point on the cylindrical surface is the independent variable, then is the propagation distance of electromagnetic waves, Corresponding is the reflection point of the RF signal corresponding to the mth transmitting antenna and the nth receiving antenna on the cylindrical surface. is a convex function, so we solve A convex optimization method may be used. In this embodiment, the BFGS convex optimization algorithm is selected to solve the minimum value of the total transmission distance.

[0038] In an example, the flow of the BFGS convex optimization algorithm can be as follows Figure 5 As shown, a point on the surface of the metal cylinder The cylindrical coordinates are expressed as , is the radius of the metal cylinder, and To cause The changing independent variable, , Indicates the number of iterations, the upper right corner represents the transposition operation, then the iterative formula for solving the minimum value of the total transmission distance based on the BFGS convex optimization algorithm is expressed as:

[0039] ;

[0040] ;

[0041] ;

[0042] in, Indicates the step size, which can also be set to 1 for simplicity. express exist The descending direction at point express exist The scale matrix at the point, express exist The gradient at a point;

[0043] The iterative formula is expressed as:

[0044] ;

[0045] ;

[0046] ;

[0047] in, , is the 2nd-order identity matrix.

[0048] Step 102, modeling the echo signal of the FMCW emitted by the mth transmitting antenna and received by the nth receiving antenna after being reflected by the metal cylinder, deriving the expressions of the delay deviation, amplitude deviation and phase deviation between the transmitting and receiving antenna pairs based on the model of the echo signal obtained by modeling and the minimum value of the total transmission distance, and then deriving the expression of the correction coefficient of the delay deviation and the expression of the correction coefficient of the amplitude deviation and the phase deviation.

[0049] In the specific implementation, after solving the minimum value of the total transmission distance, the server needs to model the echo signal of the FMCW emitted by the mth transmitting antenna and reflected by the metal cylinder and received by the nth receiving antenna. Based on the model of the echo signal obtained by modeling and the minimum value of the total transmission distance, the expressions of the delay deviation, amplitude deviation and phase deviation between the transmitting and receiving antenna pairs are derived, and then the expression of the correction coefficient of the delay deviation and the expression of the correction coefficient of the amplitude deviation and phase deviation are derived.

[0050] In one example, the modulation mode of the MIMO antenna array is set to FMCW, and the RF signal form of FMCW is expressed by the formula:

[0051] ;

[0052] in, represents the period of the sweep signal, represents the rectangular function, hour, ,otherwise, , represents the starting frequency, Indicates the frequency modulation slope.

[0053] like Figure 4As shown, represents the signal transmitted by the mth transmitting antenna, It represents the signal reflected by the target back to the nth receiving antenna. The echo signal of the FMCW emitted by the mth transmitting antenna and reflected by the metal cylinder and received by the nth receiving antenna is modeled. The model of the echo signal obtained by modeling is expressed by the formula:

[0054] ;

[0055] in, Indicates the target range, It represents the delay caused by the FMCW signal being transmitted from the mth transmitting antenna and reflected by the metal cylinder and then received by the nth receiving antenna. and They represent the phase deviation and amplitude deviation between the mth transmitting antenna and the nth receiving antenna, respectively. represents the model of the echo signal obtained by modeling, , represents the time delay caused by spatial position, Represents the time delay caused by system errors.

[0056] neglect In , and then remove the integral sign, Updated to:

[0057] ;

[0058] ;

[0059] ;

[0060] Determined based on the minimum value of the total transmission distance The value of , is the minimum value of the total transmission distance, is the speed of light;

[0061] based on The value of The value of and Conjugation Multiply them together and you get , ;

[0062] right Perform Fourier transform and get :

[0063] ;

[0064] in, represents the symplectic function;

[0065] based on The relative frequency spectrum peak shift of The corresponding compensation term is :

[0066] ;

[0067] Will and Multiply and then perform Fourier transform, and we get :

[0068] ;

[0069] Will Substitution In the equation, we get the phase term with amplitude for:

[0070] ;

[0071] based on Derived ;

[0072] based on Derived , represents the complex phase angle function;

[0073] Will , and Expand to all transmit and receive antenna pairs, and get the expression of the delay deviation between the transmit and receive antenna pairs , the expression of amplitude deviation The expression of phase deviation is ;

[0074] Will and Expanding to all transmit and receive antenna pairs, we get and , The expression for the correction factor of the delay deviation is based on and Derived , , for The echo amplitude value of any transmitting and receiving antenna pair in That is, the expression of the correction coefficient of amplitude deviation and phase deviation.

[0075] Step 103, start the MIMO antenna array. When the MIMO antenna array reaches thermal equilibrium, collect the echo data of the metal cylinder and perform preprocessing. Combine the expression of the correction coefficient of the delay deviation and the expression of the correction coefficient of the amplitude deviation and the phase deviation to determine the correction coefficient of the delay deviation and the correction coefficient of the amplitude deviation and the phase deviation.

[0076] In the specific implementation, after the server completes the modeling stage, it can enter the correction stage. The server starts the MIMO antenna array. When the MIMO antenna array reaches thermal equilibrium, the echo data of the metal cylinder is collected and preprocessed. The correction coefficient of the delay deviation and the correction coefficient of the amplitude deviation and phase deviation are combined to determine the correction coefficient of the delay deviation and the correction coefficient of the amplitude deviation and phase deviation.

[0077] The electronic components and circuit parameters in the MIMO antenna array will change with temperature. This change will make it impossible for the obtained correction coefficient to completely compensate for the deviation. Therefore, the echo of the cooperative target and the echo of the imaging target should be collected and corrected after the MIMO antenna array reaches thermal equilibrium.

[0078] In one example, when the server collects and preprocesses the echo data of a metal cylinder, it needs to collect the echo data of the metal cylinder and the background data when the MIMO antenna array is working, and then perform background cancellation based on the echo data of the metal cylinder and the background data to obtain the echo data after background cancellation. Finally, the echo data after background cancellation is filtered through a bandpass filter to retain the signal within the target range, and the Kaiser window is added to the filtered echo signal to obtain the echo data of the preprocessed metal cylinder. Background cancellation can effectively eliminate the coupling signal between antennas and the interference signal in the environment, the bandpass filter can retain the signal within the target range, which is conducive to the extraction of the target signal, and the addition of the Kaiser window can further reduce the side lobes and improve the signal-to-noise ratio.

[0079] Step 104 , collecting echo data of the imaging target, and correcting the echo data of the imaging target according to the order of the transmitting and receiving antenna pairs based on the determined correction coefficient of the delay deviation and the correction coefficients of the amplitude deviation and the phase deviation.

[0080] In a specific implementation, after the server determines the correction coefficient of the delay deviation, as well as the correction coefficients of the amplitude deviation and the phase deviation, it can collect the echo data of the imaging target, and based on the determined correction coefficient of the delay deviation, as well as the correction coefficients of the amplitude deviation and the phase deviation, correct the echo data of the imaging target in the order of the transmitting and receiving antenna pairs.

[0081] In one example, the server multiplies the echo data of the imaging target by the phase term in the correction coefficient of the delay deviation and the inverse of the correction coefficients of the amplitude deviation and the phase deviation in the order of the transmitting and receiving antenna pairs to correct the delay deviation, amplitude deviation and phase deviation in the echo data of the imaging target.

[0082] In an example, for a MIMO antenna array in a non-FMCW modulation mode, the server may calculate a corresponding correction coefficient for compensation based on the calculated delay deviation, amplitude deviation, and phase deviation.

[0083] In this embodiment, compared with metal balls and metal plates, metal cylinders are the best choice for correcting cooperative targets. Metal cylinders not only have a greater RCS than metal balls, but are also less likely to produce strong multipath effects. They are very convenient to position, install and carry. No auxiliary structure is required. The metal cylinder only needs to be placed vertically in front of the center of the antenna array, and the construction cost is very low. Before correction, the spatial position of the MIMO antenna array and the metal cylinder is modeled, the total transmission distance of the FMCW emitted by the mth transmitting antenna after being reflected by the metal cylinder and received by the nth receiving antenna is determined, and the minimum value of the total transmission distance is solved based on the BFGS convex optimization algorithm. The BFGS convex optimization algorithm eliminates the complex calculation of the Hessian matrix and matrix inversion in the Newton method, and has very high computational efficiency. Subsequently, the echo signal of the FMCW emitted by the mth transmitting antenna after being reflected by the metal cylinder and received by the nth receiving antenna is modeled, and the expressions of the delay deviation, amplitude deviation and phase deviation are derived, and then the expression of the correction coefficient of the delay deviation, as well as the expression of the correction coefficient of the amplitude deviation and the phase deviation are derived. When performing correction, the echo data of the metal cylinder is collected after the MIMO antenna array reaches thermal equilibrium, which can avoid the adverse effect of temperature on the correction. Finally, the correction coefficients of the delay deviation and the amplitude deviation and phase deviation are determined based on the derived expression, so as to correct the echo data of the imaging target, greatly improving the deviation correction speed, correction efficiency and correction effect.

[0084] Another embodiment of the present application proposes a near-field correction system for a large-scale millimeter-wave MIMO antenna array. The implementation details of the near-field correction system for a large-scale millimeter-wave MIMO antenna array proposed in this embodiment are described in detail below. The following content is only the implementation details provided for the convenience of understanding and is not necessary for the implementation of this example.

[0085] Figure 6It is a structural schematic diagram of a near-field correction system for a large-scale millimeter-wave MIMO antenna array proposed in this embodiment, the system comprising: a MIMO antenna array 201, a metal cylinder 202, a spatial position modeling module 203, a correction modeling module 204, an acquisition execution module 205 and a correction execution module 206, the metal cylinder 202 is placed directly in front of the center of the MIMO antenna array 201, the MIMO antenna array 201 consists of M transmitting antennas and N receiving antennas, and M and N are both integers greater than 1.

[0086] The spatial position modeling module 203 is used to model the spatial positions of the MIMO antenna array 201 and the metal cylinder 202 as the correction cooperation target, determine the total transmission distance of the FMCW emitted by the mth transmitting antenna and received by the nth receiving antenna after being reflected by the metal cylinder 202, and solve the minimum value of the total transmission distance based on the BFGS convex optimization algorithm, m∈M, n∈N.

[0087] The correction modeling module 204 is used to model the echo signal of the FMCW emitted by the mth transmitting antenna and received by the nth receiving antenna after being reflected by the metal cylinder 202. Based on the model of the echo signal obtained by modeling and the minimum value of the total transmission distance, the expressions of the delay deviation, amplitude deviation and phase deviation between the transmitting and receiving antenna pairs are derived, and then the expression of the correction coefficient of the delay deviation and the expression of the correction coefficient of the amplitude deviation and the phase deviation are derived.

[0088] The acquisition execution module 205 is used to start the MIMO antenna array 201. When the MIMO antenna array 201 reaches thermal equilibrium, the echo data of the metal cylinder 202 is collected and preprocessed, and the correction coefficient of the delay deviation and the correction coefficient of the amplitude deviation and the phase deviation are combined to determine the correction coefficient of the delay deviation and the correction coefficient of the amplitude deviation and the phase deviation.

[0089] The acquisition execution module 205 is also used to acquire echo data of the imaging target 301 .

[0090] The correction execution module 206 is used to correct the echo data of the imaging target according to the order of the transmitting and receiving antenna pairs based on the determined correction coefficient of the delay deviation and the correction coefficients of the amplitude deviation and the phase deviation.

[0091] It is not difficult to find that this embodiment is a system embodiment corresponding to the above method embodiment, and this embodiment can be implemented in conjunction with the above method embodiment. The relevant technical details and technical effects mentioned in the above embodiments are still valid in this embodiment, and in order to reduce repetition, they are not repeated here. Accordingly, the relevant technical details mentioned in this embodiment can also be applied in the above embodiments.

[0092] It is worth mentioning that all modules involved in this embodiment are logic modules. In practical applications, a logic unit can be a physical unit, a part of a physical unit, or a combination of multiple physical units. In addition, in order to highlight the innovative part of this application, this embodiment does not introduce units that are not closely related to solving the technical problems proposed by this application, but this does not mean that there are no other units in this embodiment.

[0093] In another embodiment, in order to verify the superiority of the correction method proposed in this application, the correction method proposed in this application is simulated as follows. Figure 3 The metal cylinder shown is used as the correction cooperation target of the four sub-arrays. The diameter of the metal cylinder is 12 cm, and the closest distance between the cylinder surface and the plane where the antenna array surface is located is 75 cm. The propagation distance of the RF signal between the transceiver antenna and the target is calculated as follows: Figure 7 First, simulate the echo of the MIMO antenna array to the metal cylinder, add a fixed deviation with Gaussian noise to the delay and amplitude of the echo signal of each receiving channel, and add The random deviation of the sweep time is 8us, the ADC sampling rate is 20Msps, and the bandwidth is 4GHz. Secondly, the correction coefficient of the MIMO antenna array is obtained according to the correction method proposed in this application and the metal cylinder echo data. The positions of the simulated four subarrays and scattered targets can be as follows Figure 8 As shown in the figure, the same fixed deviation of time delay and amplitude as the metal cylinder echo is added to the echo, and the phase deviation is also a phase random deviation consistent with the metal cylinder echo. These deviations are the properties of the system and can be considered fixed each time data is collected. The obtained correction coefficient is used to correct the scattered target echo data. Finally, the scattered target echo data before and after correction are imaged by the back-projection algorithm, and the following is obtained: Fig. 9 The imaging results of the uncorrected scattered target shown in Fig.10 The imaging result of the corrected scattered target is shown in FIG. By comparing the imaging results before and after correction, the effectiveness of the correction method proposed in the present application can be verified.

[0094] Another embodiment of the present application provides an electronic device, the structure of which is as follows: Fig.11 As shown, it includes: at least one processor 401; and a memory 402 that is communicatively connected to the at least one processor 401; wherein the memory 402 stores instructions that can be executed by the at least one processor 401, and the instructions can be executed by the at least one processor 401 so that the at least one processor 401 can execute a near-field correction method for a large-scale millimeter-wave MIMO antenna array described in the above-mentioned method embodiments.

[0095] Among them, the memory and the processor are connected in a bus manner, and the bus may include any number of interconnected buses and bridges, and the bus connects various circuits of one or more processors and memories together. The bus can also connect various other circuits such as peripheral devices, voltage regulators, and power management circuits, which are well known in the art and will not be further described in this article. The bus interface is responsible for providing an interface between the bus and the transceiver. The transceiver can be one component or multiple components, such as multiple receivers and transmitters, providing a unit for communicating with various other devices on a transmission medium. The data processed by the processor is transmitted on a wireless medium through an antenna, and further, the antenna also receives data and transmits the data to the processor.

[0096] The processor is responsible for managing the bus and general processing, and can also provide various functions, including timing, peripheral interfaces, voltage regulation, power management, and other control functions. Memory can be used to store data used by the processor when performing operations.

[0097] Another embodiment of the present application proposes a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, it can implement a near-field correction method for a large-scale millimeter-wave MIMO antenna array as described in the above method embodiments.

[0098] That is, those skilled in the art can understand that all or part of the steps in the above-mentioned embodiment method can be completed by instructing the relevant hardware through a program, and the program is stored in a storage medium, including a number of instructions to enable a device (which can be a single-chip microcomputer, chip, etc.) or a processor to execute all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, ROM (Read-Only Memory), RAM (Random Access Memory), disk or optical disk and other media that can store program codes.

[0099] Those skilled in the art will appreciate that the above embodiments are specific embodiments for implementing the present application, and in actual applications, various changes may be made thereto in form and detail without departing from the spirit and scope of the present application.

Claims

1. A near-field calibration method for a massive millimeter-wave MIMO antenna array, characterized in that: include: The spatial positions of the MIMO antenna array and the metal cylinder as the correction cooperation target are modeled, the total transmission distance of the FMCW emitted by the mth transmitting antenna and received by the nth receiving antenna after being reflected by the metal cylinder is determined, and the minimum value of the total transmission distance is solved based on the BFGS convex optimization algorithm; wherein the metal cylinder is placed in front of the center of the MIMO antenna array, and the MIMO antenna array consists of M transmitting antennas and N receiving antennas, M and N are both integers greater than 1, m∈M, n∈N; The FMCW emitted by the mth transmitting antenna is reflected by the metal cylinder and then received by the nth receiving antenna. The model of the echo signal obtained by modeling is expressed by the formula: ； in, Indicates the target range, represents the period of the sweep signal, represents the rectangular function, It represents the delay caused by the FMCW signal being transmitted from the mth transmitting antenna and reflected by the metal cylinder and then received by the nth receiving antenna. represents the starting frequency, represents the frequency modulation slope, and They represent the phase deviation and amplitude deviation between the mth transmitting antenna and the nth receiving antenna, respectively. represents the model of the echo signal obtained by modeling, , represents the time delay caused by spatial position, represents the time delay caused by system error; neglect In , and then remove the integral sign, Updated to: ； ； ； Determined based on the minimum value of the total transmission distance The value of , is the minimum value of the total transmission distance, is the speed of light; based on The value of The value of and Conjugation Multiply them together and you get , ; right Perform Fourier transform and get : ； in, represents the symplectic function; based on The relative frequency spectrum peak shift of The corresponding compensation term is : ； Will and Multiply and then perform Fourier transform, and we get : ； Will Substitution In the equation, we get the phase term with amplitude for: ； based on Derived ; based on Derived , represents the complex phase angle function; Will , and Expanded to all transmit and receive antenna pairs, the expression of the delay deviation between the transmit and receive antenna pairs is obtained , the expression of amplitude deviation The expression of phase deviation is ; Will and Expanding to all transmit and receive antenna pairs, we get and , The expression for the correction factor of the delay deviation is based on and Derived , , for The echo amplitude value of any transmitting and receiving antenna pair in That is, the expression of the correction coefficient of amplitude deviation and phase deviation; The MIMO antenna array is started, and when the MIMO antenna array reaches thermal equilibrium, the echo data of the metal cylinder is collected and preprocessed, and the correction coefficient of the delay deviation and the correction coefficient of the amplitude deviation and the phase deviation are determined by combining the expression of the correction coefficient of the delay deviation and the expression of the correction coefficient of the amplitude deviation and the phase deviation; The echo data of the imaging target is collected, and based on the determined correction coefficient of the delay deviation and the correction coefficients of the amplitude deviation and the phase deviation, the echo data of the imaging target is corrected in the order of the transmitting and receiving antenna pairs.

2. The near-field calibration method for a massive millimeter-wave MIMO antenna array according to claim 1, characterized in that: The diameter and height of the metal cylinder are much larger than the wavelength of the FMCW corresponding to the MIMO antenna array. The diameter and height of the metal cylinder are determined based on the frequency band, antenna radiation pattern, size and portability of the FMCW corresponding to the MIMO antenna array. The surface of the metal cylinder satisfies mirror reflection, and the FMCW emitted by all transmitting antennas of the MIMO antenna array can be reflected back to the receiving antenna at one time.

3. The near-field calibration method for a massive millimeter-wave MIMO antenna array according to claim 1, characterized in that: The total transmission distance of the FMCW emitted by the mth transmitting antenna and received by the nth receiving antenna after being reflected by the metal cylinder is determined by the following formula: ； ； ； in, It represents the total transmission distance of the FMCW emitted by the mth transmitting antenna and received by the nth receiving antenna after being reflected by the metal cylinder. represents the distance from the mth transmitting antenna to the reflection point on the metal cylindrical surface, Indicates the distance from the nth receiving antenna to the reflection point on the metal cylindrical surface, represents a point on the surface of a metal cylinder, represents the spatial position of the mth transmitting antenna, Indicates the spatial position of the nth receiving antenna.

4. The near-field calibration method for a massive millimeter-wave MIMO antenna array according to claim 3, characterized in that: A point on the surface of a metal cylinder The cylindrical coordinates are expressed as , is the radius of the metal cylinder, and To cause Changing independent variables; make , Indicates the number of iterations, the upper right corner represents the transposition operation, then the iterative formula for solving the minimum value of the total transmission distance based on the BFGS convex optimization algorithm is expressed as: ； ； ； in, represents the step length, express exist The descending direction at point express exist The scale matrix at the point, express exist The gradient at a point; The iterative formula is expressed as: ； ； ； in, , is the 2nd-order identity matrix.

5. A near-field calibration method for a massive millimeter-wave MIMO antenna array according to any one of claims 1 to 4, characterized in that: Collect echo data of metal cylinders and perform preprocessing, including: Collect echo data of metal cylinders and background data when the MIMO antenna array is working; Perform background cancellation based on the echo data and background data of the metal cylinder to obtain echo data after background cancellation; The echo data after background cancellation is passed through a bandpass filter to retain the signal within the target range, and a Kaiser window is added to the filtered echo signal to obtain the echo data of the preprocessed metal cylinder.

6. A near-field calibration method for a massive millimeter-wave MIMO antenna array according to any one of claims 1 to 4, characterized in that: Based on the determined correction coefficients of the delay deviation and the correction coefficients of the amplitude deviation and the phase deviation, the echo data of the imaging target is corrected in the order of the transmitting and receiving antenna pairs, specifically: The echo data of the imaging target is multiplied by the phase term in the correction coefficient of the delay deviation and the reciprocal of the correction coefficient of the amplitude deviation and the phase deviation in the order of the transmitting and receiving antenna pairs to correct the delay deviation, amplitude deviation and phase deviation in the echo data of the imaging target.

7. A near-field correction system for a massive millimeter-wave MIMO antenna array, characterized in that: include: MIMO antenna array, metal cylinder, spatial position modeling module, correction modeling module, acquisition execution module and correction execution module, the metal cylinder is placed in front of the center of the MIMO antenna array, the MIMO antenna array is composed of M transmitting antennas and N receiving antennas, and M and N are both integers greater than 1; The spatial position modeling module is used to model the spatial position of the MIMO antenna array and the metal cylinder as the correction cooperation target, determine the total transmission distance of the FMCW emitted by the mth transmitting antenna after being reflected by the metal cylinder and received by the nth receiving antenna, and solve the minimum value of the total transmission distance based on the BFGS convex optimization algorithm, m∈M, n∈N; The correction modeling module is used to model the echo signal of the FMCW emitted by the mth transmitting antenna and received by the nth receiving antenna after being reflected by the metal cylinder. The model of the echo signal obtained by modeling is expressed by the formula: ； in, Indicates the target range, represents the period of the sweep signal, represents the rectangular function, It represents the delay caused by the FMCW signal being transmitted from the mth transmitting antenna and reflected by the metal cylinder and then received by the nth receiving antenna. represents the starting frequency, represents the frequency modulation slope, and They represent the phase deviation and amplitude deviation between the mth transmitting antenna and the nth receiving antenna, respectively. represents the model of the echo signal obtained by modeling, , represents the time delay caused by spatial position, represents the time delay caused by system error; neglect In , and then remove the integral sign, Updated to: ； ； ； Determined based on the minimum value of the total transmission distance The value of , is the minimum value of the total transmission distance, is the speed of light; based on The value of The value of and Conjugation Multiply them together and you get , ; right Perform Fourier transform and get : ； in, represents the symplectic function; based on The relative frequency spectrum peak shift of The corresponding compensation term is : ； Will and Multiply and then perform Fourier transform, and we get : ； Will Substitution In the equation, we get the phase term with amplitude for: ； based on Derived ; based on Derived , represents the complex phase angle function; Will , and Expanded to all transmit and receive antenna pairs, the expression of the delay deviation between the transmit and receive antenna pairs is obtained , the expression of amplitude deviation The expression of phase deviation is ; Will and Expanding to all transmit and receive antenna pairs, we get and , The expression for the correction factor of the delay deviation is based on and Derived , , for The echo amplitude value of any transmitting and receiving antenna pair in That is, the expression of the correction coefficient of amplitude deviation and phase deviation; The acquisition execution module is used to start the MIMO antenna array. When the MIMO antenna array reaches thermal equilibrium, the echo data of the metal cylinder is collected and preprocessed, and the correction coefficient of the delay deviation and the correction coefficient of the amplitude deviation and the phase deviation are combined to determine the correction coefficient of the delay deviation and the correction coefficient of the amplitude deviation and the phase deviation; The acquisition execution module is also used to acquire echo data of the imaging target; The correction execution module is used to correct the echo data of the imaging target according to the order of the transmitting and receiving antenna pairs based on the determined correction coefficient of the delay deviation and the correction coefficients of the amplitude deviation and the phase deviation.

8. An electronic device, characterized in that: include: at least one processor; and, a memory communicatively coupled to the at least one processor; In which, the memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute a near-field correction method for a large-scale millimeter-wave MIMO antenna array as described in any one of claims 1 to 6.

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