Method and apparatus for evaluating antenna array calibration coefficients, and storage medium

Abstract

The application discloses an antenna array calibration coefficient evaluation method and device and a storage medium, wherein the method comprises the following steps: emitting a test signal to an angle reflection radar in a darkroom, determining the position coordinates of the angle reflection in a Cartesian coordinate system with the geometric center of the radar as the origin at each test angle, obtaining the echo signal fed back by the angle reflection to form an original echo data matrix, and obtaining a wave path phase difference matrix corresponding to multiple channels according to the position information of the antenna; compensating the original echo data matrix according to the wave path phase difference matrix and the antenna array calibration coefficient; obtaining an angle spectrum based on the compensated echo data matrix, and then evaluating the antenna array calibration coefficient. The technical scheme provided by the application can solve the technical problem that the array calibration coefficient generated by the near-field method in the darkroom in the prior art may have errors, the present scheme can evaluate the array calibration coefficient of the MIMO radar under the near-field condition, and the accuracy of the array calibration coefficient is ensured.

Description

Technical Field

[0001] This invention relates to the field of radar technology, and in particular to a method, apparatus, and storage medium for evaluating antenna array calibration coefficients. Background Technology

[0002] MIMO (Multiple Input Multiple Output) radar has the ability to transmit multiple orthogonal signals simultaneously. By matching and separating the signals at the receiver, a very large virtual aperture can be obtained, which can greatly improve the target angular resolution.

[0003] While proper wiring matching can minimize phase offset between the MIMO radar chip and the antenna's PCB (Printed Circuit Board), this phase offset cannot be completely eliminated through wiring. Furthermore, due to packaging and internal chip variations, a fixed phase difference inevitably exists between the received signals, and this fixed phase difference varies across different antenna boards. Therefore, the array antenna needs to be calibrated before using the MIMO radar.

[0004] Calibration coefficients need to be pre-generated in an anechoic chamber using a near-field equivalent method, or directly generated outdoors using a far-field method. Because outdoor testing is easily affected by weather and other factors, in the mass production of MIMO radars, a near-field equivalent method is generally used to generate calibration coefficients to improve production efficiency. After the calibration coefficients are generated, their effectiveness needs to be verified to ensure the angle measurement performance of the MIMO radar. In existing technologies, because the anechoic chamber environment does not meet the far-field conditions, angle measurement cannot be performed directly, thus presenting a technical problem where calibration coefficients generated using the near-field method may contain errors. Summary of the Invention

[0005] This invention provides a method, apparatus, and storage medium for evaluating antenna array calibration coefficients, aiming to effectively solve the technical problem that calibration coefficients generated in an anechoic chamber using a near-field method may have errors. This solution can evaluate the array calibration coefficients of MIMO radar under near-field conditions, ensuring the accuracy of the array calibration coefficients.

[0006] According to one aspect of the present invention, an evaluation method for antenna array calibration coefficients is provided for a MIMO radar, the MIMO radar comprising a plurality of transmitting antennas and a plurality of receiving antennas, the plurality of transmitting antennas and the plurality of receiving antennas constituting a plurality of channels, the method comprising:

[0007] The turntable carrying the radar in the anechoic chamber is driven to rotate stepwise in a preset manner and transmit radar test signals to the angular reflection at a preset position in the anechoic chamber at each test angle. For each test angle, the position coordinates of the angular reflection in the Cartesian coordinate system with the geometric center of the radar as the origin are determined, and the echo signal fed back by the angular reflection in response to the radar test signal is obtained.

[0008] Based on the echo signal, the echo data of the multiple channels at each test angle are obtained to form the original echo data matrix;

[0009] The path phase difference of the multiple channels at each test angle is obtained based on the position information of the multiple transmitting antennas and the multiple receiving antennas in the Cartesian coordinate system, so as to form a path phase difference matrix;

[0010] The original echo data matrix is ​​compensated based on the path phase difference matrix and the antenna array calibration coefficient to be evaluated to obtain the compensated echo data matrix.

[0011] The angular spectrum is obtained based on the compensated echo data matrix, and the calibration coefficients of the antenna array to be evaluated are evaluated based on the angular spectrum.

[0012] Further, the step of obtaining the path phase difference of the multiple channels at each test angle based on the position information of the multiple transmitting antennas and the multiple receiving antennas in the Cartesian coordinate system, in order to form a path phase difference matrix, includes:

[0013] For each channel at each test angle, a first distance phase difference is obtained based on the position coordinates of the transmitting antenna corresponding to the channel and the position coordinates of the angular reflection. A second distance phase difference is obtained based on the position coordinates of the receiving antenna corresponding to the channel and the position coordinates of the angular reflection. The path phase difference corresponding to the channel is obtained based on the first distance phase difference and the second distance phase difference.

[0014] The path phase difference matrix is ​​formed based on the path phase difference of all channels, wherein the path phase difference of each channel constitutes the element at the corresponding position in the path phase difference matrix.

[0015] Further, the step of compensating the original echo data matrix based on the path phase difference matrix and the antenna array calibration coefficients to be evaluated to obtain the compensated echo data matrix includes:

[0016] The compensated echo data matrix is ​​obtained according to the following formula:

[0017] S nm =D mn *conj(TRmn )*repmat(C n ,M,1),

[0018] Among them, S nm D represents the compensated echo data matrix. mn Represents the original echo data matrix, TR mn C represents the path phase difference matrix. n The function conj(TR) represents the calibration coefficient of the antenna array to be evaluated, M represents the number of angular reversals, and the function is... mn ) indicates that for TR mn Perform the conjugate operation, function repmat(C n M,1) represents C n Repeat M times to form a corresponding M×N dimension matrix, where N represents the number of the plurality of channels.

[0019] Further, the step of obtaining the angular spectrum based on the compensated echo data matrix and evaluating the calibration coefficients of the antenna array to be evaluated based on the angular spectrum includes:

[0020] The angular spectrum is obtained by performing a fast Fourier transform on the compensated echo data matrix.

[0021] The calibration coefficients of the antenna array to be evaluated are assessed based on the angular spectrum peak value, angular accuracy, and angular signal-to-noise ratio, respectively.

[0022] Furthermore, the evaluation of the calibration coefficients of the antenna array to be evaluated based on the angular spectrum peak value, angular accuracy, and angular signal-to-noise ratio respectively includes:

[0023] Obtain the maximum signal amplitude corresponding to the maximum peak value in the angular spectrum;

[0024] Calculate the difference between the signal amplitude of each spectral peak in the angular spectrum and the maximum signal amplitude;

[0025] The number of spectral peaks corresponding to the difference being greater than a preset amplitude threshold is obtained. If the number of spectral peaks is greater than a preset number threshold, the antenna array calibration coefficient to be evaluated is determined to be an unusable antenna array calibration coefficient.

[0026] Furthermore, the evaluation of the antenna array calibration coefficients to be evaluated based on the angular spectrum peak value, angular accuracy, and angular signal-to-noise ratio respectively also includes:

[0027] Based on the angular spectrum, the angle value corresponding to each channel at each test angle is obtained. If any angle value is greater than a preset angle threshold, the antenna array calibration coefficient is determined to be an unusable antenna array calibration coefficient.

[0028] Furthermore, the evaluation of the antenna array calibration coefficients to be evaluated based on the angular spectrum peak value, angular accuracy, and angular signal-to-noise ratio respectively also includes:

[0029] The mean signal amplitude of the angular spectrum is obtained, and the angular signal-to-noise ratio is obtained based on the maximum signal amplitude and the mean signal amplitude. If the angular signal-to-noise ratio is less than a preset signal-to-noise ratio threshold, the antenna array calibration coefficient is determined to be an unusable antenna array calibration coefficient.

[0030] Furthermore, the stepwise rotation of the turntable carrying the radar in the anechoic chamber, which drives the turntable to rotate in a preset manner and emits radar test signals at a preset position in the anechoic chamber at each test angle, includes:

[0031] The turntable is driven to rotate in steps within the field of view of the radar, wherein each rotation step is 0.5°.

[0032] According to another aspect of the present invention, the present invention also provides an evaluation apparatus for antenna array calibration coefficients for a MIMO radar, the MIMO radar including a plurality of transmitting antennas and a plurality of receiving antennas, wherein the plurality of transmitting antennas and the plurality of receiving antennas constitute a plurality of channels, the apparatus comprising:

[0033] The drive and echo signal acquisition unit is used to drive the turntable carrying the radar in the anechoic chamber to rotate stepwise in a preset manner and transmit radar test signals to the angular reflection at a preset position in the anechoic chamber at each test angle, and for each test angle, determine the position coordinates of the angular reflection in the Cartesian coordinate system with the geometric center of the radar as the origin, and acquire the echo signal fed back by the angular reflection in response to the radar test signal.

[0034] The raw echo data matrix determination unit is used to obtain the echo data of the multiple channels at each test angle based on the echo signal, so as to form the raw echo data matrix.

[0035] The path phase difference matrix determination unit is used to obtain the path phase difference of the multiple channels at each test angle based on the position information of the multiple transmitting antennas and the multiple receiving antennas in the Cartesian coordinate system, so as to form a path phase difference matrix;

[0036] The compensation unit is used to compensate the original echo data matrix according to the path phase difference matrix and the antenna array calibration coefficient to be evaluated, so as to obtain the compensated echo data matrix.

[0037] An evaluation unit is used to obtain an angular spectrum based on the compensated echo data matrix and to evaluate the calibration coefficients of the antenna array to be evaluated based on the angular spectrum.

[0038] According to another aspect of the invention, the invention also provides a storage medium storing a plurality of instructions adapted to be loaded by a processor to perform an evaluation method for any of the antenna array calibration coefficients as described above.

[0039] Through one or more embodiments of the above embodiments of the present invention, at least the following technical effects can be achieved:

[0040] In the technical solution disclosed in this invention, echo signals of all channels under different test angles are obtained to obtain the corresponding original echo data matrix. Then, the path phase difference generated between the transmitting antenna, receiving antenna and the angular reflection in the radar anechoic chamber is calculated. The original echo data matrix is ​​then compensated according to the path phase difference matrix and the antenna array calibration coefficient to be evaluated to obtain the compensated echo data matrix. Finally, the corresponding angular spectrum is obtained, and the antenna array calibration coefficient is evaluated according to the angular spectrum related information.

[0041] The usable antenna array calibration coefficients determined after evaluation can simultaneously ensure that multiple performance indicators of the angular spectrum meet the measurement requirements. Specifically, the usable antenna array calibration coefficients guarantee a small spectral peak error, high angular accuracy, and a large signal-to-noise ratio in the measurement results. By evaluating the antenna array calibration coefficients, the detection accuracy of the radar can be significantly improved, ensuring high-precision radar measurements.

[0042] In addition, when mass-producing radar products, the technical solution of this application enables the evaluation of calibration coefficients in a near-field manner within an anechoic chamber, avoiding the need to test the angle measurement performance of each radar (i.e. whether the calibration coefficients are correct) outdoors, simplifying the testing method and significantly improving production efficiency. Attached Figure Description

[0043] The technical solution and other beneficial effects of the present invention will become apparent from the following detailed description of specific embodiments of the invention, in conjunction with the accompanying drawings.

[0044] Figure 1 A flowchart illustrating the steps of an antenna array calibration coefficient evaluation method provided in an embodiment of the present invention;

[0045] Figure 2 A schematic diagram of a radar testing anechoic chamber provided for an embodiment of the present invention;

[0046] Figure 3 This is a schematic diagram of an echo signal processing flow provided in an embodiment of the present invention;

[0047] Figure 4 A schematic diagram of the angular inverse coordinates provided in an embodiment of the present invention;

[0048] Figure 5 This is a schematic diagram of an antenna array calibration coefficient evaluation device provided in an embodiment of the present invention. Detailed Implementation

[0049] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0050] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the term "and / or" in this document is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Furthermore, the character " / " in this document, unless otherwise specified, generally indicates that the preceding and following related objects have an "or" relationship.

[0051] In radar systems, the principle of radar target detection is based on the time difference between the transmitted and received pulses and the propagation speed of electromagnetic waves (speed of light) to obtain the precise distance between the radar and the target. The principle of target angular position measurement utilizes the antenna's directivity; when the antenna beam is aligned with the target, the echo signal is strongest. Based on the direction of the antenna beam when the received echo is strongest, the target's direction can be determined. The principle of velocity measurement is based on the Doppler effect caused by the relative motion between the radar and the target. The frequency of the target echo received by the radar differs from the radar's transmitted frequency; the difference between the two is called the Doppler frequency. One of the main pieces of information that can be extracted from the Doppler frequency is the rate of change of distance between the radar and the target, which in turn determines the target's velocity. In summary, information such as the target's velocity, direction of motion, and distance can be obtained.

[0052] MIMO (Multiple-Input Multiple-Output) radar technology refers to the use of multiple transmit and receive antennas at both the transmitting and receiving ends, enabling signal transmission across multiple channels and thus improving communication quality. It makes full use of space resources, achieving multiple transmissions and receptions through multiple antennas, and can significantly increase system channel capacity without increasing spectrum resources or antenna transmission power.

[0053] In a MIMO radar system, the antenna includes multiple transmitting antennas and multiple receiving antennas, where each transmitting antenna and each receiving antenna corresponds to a channel. One transmitting antenna corresponds to multiple receiving antennas, and correspondingly, the one transmitting antenna and the multiple receiving antennas form a channel array.

[0054] Before using MIMO radar, the array antenna needs to be calibrated. Setting up a far-field testing environment requires extremely long distances, making direct far-field testing in a fully anechoic chamber unsuitable. Furthermore, finding an outdoor testing base is difficult, and its use is limited by weather conditions. Due to time and cost constraints in far-field antenna testing, near-field equivalent generation is generally used to improve production efficiency.

[0055] Generally, an antenna near-field measurement system is an automated measurement system controlled by a central computer, performing antenna near-field scanning, data acquisition, test data processing, and test result display and output. Near-field measurements are typically conducted in an anechoic chamber. An anechoic chamber is also known as a radio anechoic chamber, microwave anechoic chamber, or non-reflection chamber. The primary function of an anechoic chamber is to prevent interference from external electromagnetic waves, ensuring that measurement activities are unaffected by the external electromagnetic environment and preventing test signals from radiating outwards and creating interference sources that pollute the electromagnetic environment and interfere with other electronic equipment. On the one hand, testing in an anechoic chamber ensures confidentiality and avoids external electromagnetic interference, resulting in stable and reliable operation. On the other hand, performing tests in the indoor testing environment of an anechoic chamber allows for 24 / 7 operation, unaffected by environmental factors.

[0056] In a radar anechoic chamber testing environment, corner reflectors are required. Corner reflectors, also known as radar reflectors, are radar wave reflectors made of metal sheets in different specifications according to different applications. When radar electromagnetic waves scan a corner reflection, the electromagnetic waves are refracted and amplified at the metal corner, generating a strong echo signal. Correspondingly, a strong echo target appears on the radar receiving system.

[0057] After generating the calibration coefficients, their effectiveness needs to be verified to ensure the angle measurement performance of the MIMO radar. In existing technologies, because anechoic chamber scenarios do not meet far-field conditions, angle measurement cannot be directly performed, leading to potential errors in calibration coefficients generated using near-field methods. This solution can evaluate the array calibration coefficients of the MIMO radar under near-field conditions, ensuring their accuracy.

[0058] According to one aspect of the present invention, an evaluation method for antenna array calibration coefficients is provided for a MIMO radar, the MIMO radar comprising multiple transmitting antennas and multiple receiving antennas, the multiple transmitting antennas and the multiple receiving antennas constituting multiple channels. Figure 1The diagram shows a flowchart of the evaluation method for antenna array calibration coefficients provided in an embodiment of the present invention. The method includes:

[0059] Step 101: Drive the turntable carrying the radar in the anechoic chamber to rotate stepwise in a preset manner and transmit the radar test signal to the corner reflection at a preset position in the anechoic chamber at each test angle. For each test angle, determine the position coordinates of the corner reflection in the Cartesian coordinate system with the geometric center of the radar as the origin at that test angle, and obtain the echo signal fed back by the corner reflection to the radar test signal.

[0060] Step 102: Obtain the echo data of the multiple channels at each test angle based on the echo signal to form the original echo data matrix;

[0061] Step 103: Based on the position information of the plurality of transmitting antennas and the plurality of receiving antennas in the Cartesian coordinate system, obtain the path phase difference corresponding to each test angle of the plurality of channels, so as to form a path phase difference matrix;

[0062] Step 104: Compensate the original echo data matrix according to the path phase difference matrix and the antenna array calibration coefficient to be evaluated to obtain the compensated echo data matrix;

[0063] Step 105: Obtain the angular spectrum based on the compensated echo data matrix, and evaluate the calibration coefficients of the antenna array to be evaluated based on the angular spectrum.

[0064] For example, Figure 2 This is a schematic diagram of a radar testing anechoic chamber provided in an embodiment of the present invention. Inside the anechoic chamber, the radar, corner reflector, and turntable are arranged... Figure 2 The radar is arranged as shown. It is mounted on a turntable and rotates with the turntable. The radar's measurement angle changes as it rotates to different positions. The reflector is positioned at a preset location, with a distance R between the radar and the reflector.

[0065] The following is a detailed description of steps 101 to 105 above.

[0066] In step 101 above, the turntable carrying the radar in the anechoic chamber is driven to rotate stepwise in a preset manner and transmit radar test signals to the angular reflection at a preset position in the anechoic chamber at each test angle. For each test angle, the position coordinates of the angular reflection in the Cartesian coordinate system with the geometric center of the radar as the origin are determined, and the echo signal fed back by the angular reflection in response to the radar test signal is obtained.

[0067] For example, Figure 2In the anechoic chamber shown, the radar is mounted on a turntable. The turntable rotates in a step-by-step manner according to a preset pattern, that is, it stops and rotates again within a certain range of rotation angles, repeating this cycle. Each pause of the turntable corresponds to a test angle. At that test angle, the radar transmits a radar test signal to the corner and receives the echo signal reflected back from the corner.

[0068] Meanwhile, at each test angle, the positions of the transmitting antenna, the receiving antenna, and the relative positions of the angular reflection all change. To obtain the phase difference caused by different distances, a three-dimensional Cartesian coordinate system needs to be established, where the origin is the geometric center of the radar. Then, at each test angle, the position coordinates of the angular reflection in the Cartesian coordinate system are obtained for subsequent phase difference calculations.

[0069] In step 102 above, echo data of the multiple channels at each test angle are obtained based on the echo signal to form an original echo data matrix.

[0070] For example, in a MIMO radar system, the antenna includes multiple transmit antennas and multiple receive antennas, wherein each transmit antenna and each receive antenna corresponds to a channel, and there is a corresponding channel array. For instance, assuming the radar has 6 transmit antennas and 8 receive antennas, there are 48 channels. Accordingly, for each transmitted radar test signal, the 48-channel array corresponds to 48 echo signals.

[0071] Figure 3 This is a schematic diagram of an echo signal processing flow provided by an embodiment of the present invention. At each test angle, the echo signal reflected back by the angle is acquired, and signal processing is performed on the echo signal, such as... Figure 3 As shown, signal processing is performed on N data points from antenna 1 to antenna N, including a two-dimensional Fast Fourier Transform (FFT). Then, constant false alarm rate (CFAR) detection is applied to filter out background clutter to obtain echo data. Specifically, this includes the angle-reflected range Doppler index. Based on the range Doppler index, the data of strong detection points of each receiving channel are extracted from the two-dimensional FFT matrix to form the original echo data matrix.

[0072] Based on the angular reflection distance Doppler index detected by CFAR, the echo data of each receiving channel is extracted from the two-dimensional FFT matrix. Specifically, the original echo data matrix can be constructed according to the following formula:

[0073]

[0074] Among them, D mnThe original echo data matrix is ​​represented by m = (1,2,...,M), where M represents the maximum number of times the turntable rotates, and n = (1,2,...N), where N represents the number of virtual antenna arrays for the MIMO radar.

[0075] In step 103 above, the path phase difference of the multiple channels at each test angle is obtained based on the position information of the multiple transmitting antennas and the multiple receiving antennas in the Cartesian coordinate system, so as to form a path phase difference matrix.

[0076] For example, radar target detection requires calculating the phase difference of the echo signal. In this invention, in order to evaluate the antenna array calibration coefficient, the path phase difference needs to be obtained at each test angle based on the distance information between the transmitting antenna and the angular reflector, as well as the distance information between the angular reflector and the receiving antenna. Then, the path phase difference obtained from all test angles is used to obtain the path phase difference matrix.

[0077] In step 104 above, the original echo data matrix is ​​compensated according to the path phase difference matrix and the antenna array calibration coefficient to be evaluated to obtain the compensated echo data matrix.

[0078] For example, the antenna array calibration coefficient is calculated based on the echo signal when the radar is tested in the near field at the factory. Because there is a gap between the transmitting antenna and the receiving antenna, there is an error phase difference between the echo signals received by each channel at the same detection point. In order to eliminate this error phase difference, the antenna array calibration coefficient is calculated based on the echo signal.

[0079] The path phase difference matrix is ​​the phase difference generated by the transmission distance of each channel calculated based on the position of the transmitting antenna, the position of the receiving antenna, and the angular inversion position in this invention.

[0080] Based on the path phase difference matrix and the calibration coefficients of the antenna array to be evaluated, phase compensation is performed on the original echo data matrix to obtain the compensated echo data matrix.

[0081] In step 105 above, the angular spectrum is obtained based on the compensated echo data matrix, and the calibration coefficient of the antenna array to be evaluated is evaluated based on the angular spectrum.

[0082] For example, a Fast Fourier Transform (FFT) is performed on the echo data matrix corresponding to all channels under all test angles to obtain the angular spectrum for each corresponding angle. By analyzing the angular spectrum, the angle value can be obtained. By analyzing the data from three dimensions—the number of peaks in the angular spectrum (SPN), the angle accuracy (AA), and the angle signal-to-noise ratio (SNR)—when all preset requirements are met, the antenna array calibration coefficients are determined to be usable antenna array calibration coefficients.

[0083] Further, the step of obtaining the path phase difference of the multiple channels at each test angle based on the position information of the multiple transmitting antennas and the multiple receiving antennas in the Cartesian coordinate system, in order to form a path phase difference matrix, includes:

[0084] For each channel at each test angle, a first distance phase difference is obtained based on the position coordinates of the transmitting antenna corresponding to the channel and the position coordinates of the angular reflection. A second distance phase difference is obtained based on the position coordinates of the receiving antenna corresponding to the channel and the position coordinates of the angular reflection. The path phase difference corresponding to the channel is obtained based on the first distance phase difference and the second distance phase difference.

[0085] The path phase difference matrix is ​​formed based on the path phase difference of all channels, wherein the path phase difference of each channel constitutes the element at the corresponding position in the path phase difference matrix.

[0086] For example, Figure 4 This is a schematic diagram of the angular reflection coordinates provided in an embodiment of the present invention, wherein the coordinate system is a Cartesian coordinate system established with the geometric center of the radar structure as the origin, and the spatial geometric relationship between the radar and the angular reflection is as follows. Figure 4 As shown, the position coordinates of the angular reflection can be expressed as:

[0087] C m =(R m cos(φ m sin(θ) m ),R m cos(φ m cos(θ) m ),R m sin(φ m )),

[0088] Among them, R m The distance between the radar and the angular reflector at the current test angle; when the test angle is different, R... m There are slight changes, φ m Let θ be the vertical elevation angle between the radar and the angular reflector. m This is the azimuth angle between the radar and the angular reflector in the horizontal direction.

[0089] The position coordinates of the radar transmitting antenna can be represented as:

[0090] T m =[T1,T2,...,T Nt Among them, T k =(x,y,z)(k=1,2,...N) t ), N t It refers to the number of transmitting antennas.

[0091] The position coordinates of the radar receiving antenna can be expressed as:

[0092] R m =[R1,R2,...,R Nr R k =(x,y,z)(k=1,2,...N) r ), N r This refers to the number of receiving antennas.

[0093] After determining the position coordinates of the transmitting antenna, receiving antenna, and angular reflection, for each channel at each test angle, the first distance phase difference and the second distance phase difference are obtained. Based on the first distance phase difference and the second distance phase difference, the path phase difference corresponding to that channel is obtained.

[0094] Specifically, since the distance between the radar and the angular reflector does not meet the far-field condition, the plane wave assumption is not made for the echo signal of the angular reflector; instead, the path phase difference of the angular reflector is generated directly in a near-field manner. The generation process of the path phase difference is explained below using transmitting antenna T1 and receiving antenna R1.

[0095] The distance between the position coordinates T1 of the transmitting antenna corresponding to the channel and the position coordinates of the angular reversal can be expressed as: R_C m T1 = sqrt(T1 - C) m Accordingly, the first distance phase difference is: T phase =e i2πRct / λ .

[0096] Similarly, the distance between the position coordinates R1 and the angular reversal position coordinates of the receiving antenna corresponding to the channel can be expressed as: R_C xyz R1 = sqrt(R1 - C) xyz Correspondingly, the second distance phase difference is: R phase =e i2πRcr / λ .

[0097] Based on the first distance phase difference and the second distance phase difference, the path phase difference corresponding to this channel is obtained. That is, the phase of the signal transmitted by the transmitting antenna T1, after angular reflection, returns to the receiving antenna R1 is: T1R 1phase =e i2πRct / λ e i2 πRcr / λ .

[0098] Similarly, the path phase difference of other antennas at various angles on the turntable can be derived. The path phase difference matrix is ​​formed based on the path phase differences of all channels, where the path phase difference of each channel constitutes the element at the corresponding position in the path phase difference matrix. The path phase difference matrix is ​​specifically shown in the following formula:

[0099]

[0100] Where m = (1,2,...,M), M is the number of times the turntable rotates, and n = (1,2,...N), N is the number of virtual antenna arrays for the MIMO radar.

[0101] Further, the step of compensating the original echo data matrix based on the path phase difference matrix and the antenna array calibration coefficients to be evaluated to obtain the compensated echo data matrix includes:

[0102] The compensated echo data matrix is ​​obtained according to the following formula:

[0103] S nm =D mn *conj(TR mn )*repmat(C n ,M,1),

[0104] Among them, S nm D represents the compensated echo data matrix. mn Represents the original echo data matrix, TR mn C represents the path phase difference matrix. n The function conj(TR) represents the calibration coefficient of the antenna array to be evaluated, M represents the number of angular reversals, and the function is... mn ) indicates that for TR mn Perform the conjugate operation, function repmat(C n M,1) represents C n Repeat M times to form a corresponding M×N dimension matrix, where N represents the number of the plurality of channels.

[0105] For example, the raw echo data matrix D from each angle radar channel is collected. ij Compensation for path phase difference TR caused by path length mn The phase difference C between the various arrays of the radar itself n =(c1,c2,...,c n (i.e., calibration coefficients), where n = (1, 2, ... N), and N is the number of virtual antenna arrays for the MIMO radar.

[0106] Further, the step of obtaining the angular spectrum based on the compensated echo data matrix and evaluating the calibration coefficients of the antenna array to be evaluated based on the angular spectrum includes:

[0107] The angular spectrum is obtained by performing a fast Fourier transform on the compensated echo data matrix.

[0108] The calibration coefficients of the antenna array to be evaluated are assessed based on the angular spectrum peak value, angular accuracy, and angular signal-to-noise ratio, respectively.

[0109] For example, signal processing such as Fast Fourier Transform is performed on the compensated echo data matrix to obtain the angular spectrum A. m For each angular spectrum A m Performing a modulus operation yields the amplitude spectrum, i.e., the peak value V of the angular spectrum. m This represents the signal strength. All the angular spectral peaks together form the angular spectral peak diagram, based on angular spectrum A. m The location of the peak value of the angular spectrum can determine relevant information about the target.

[0110] Then, based on the angular spectral peak V of the angular spectrum respectively m The angular accuracy (AA) and angular signal-to-noise ratio (SNR) are used to evaluate the antenna array calibration coefficients to be evaluated. When all preset requirements are met, the antenna array calibration coefficients are determined to be usable antenna array calibration coefficients.

[0111] Furthermore, the evaluation of the calibration coefficients of the antenna array to be evaluated based on the angular spectrum peak value, angular accuracy, and angular signal-to-noise ratio respectively includes:

[0112] Obtain the maximum signal amplitude corresponding to the maximum peak value in the angular spectrum;

[0113] Calculate the difference between the signal amplitude of each spectral peak in the angular spectrum and the maximum signal amplitude;

[0114] The number of spectral peaks corresponding to differences greater than a preset amplitude threshold is obtained. If the number of spectral peaks is greater than a preset number threshold, the antenna array calibration coefficient to be evaluated is determined to be an unusable antenna array calibration coefficient.

[0115] For example, in the angular spectrum peak plot, when the antenna array calibration coefficient is relatively accurate, there is only one maximum peak in the plot. Therefore, the maximum peak can be used as a reference standard. If one or more spectral peaks with large amplitudes appear, it may indicate that the antenna array calibration coefficient is unusable.

[0116] For example, using a 3dB drop in the maximum peak value in the angular spectrum as a reference value, the number of spectral peaks greater than this reference value (denoted as SPN) is determined. If SPN is greater than 1, the angular spectrum quality is considered poor, and the array calibration coefficients are unusable in this case.

[0117] The difference in amplitude between each spectral peak and the maximum peak value can also be calculated, and the usability of the antenna array calibration coefficients can be determined based on this difference.

[0118] Furthermore, the evaluation of the antenna array calibration coefficients to be evaluated based on the angular spectrum peak value, angular accuracy, and angular signal-to-noise ratio respectively also includes:

[0119] Based on the angular spectrum, the angle value corresponding to each channel at each test angle is obtained. If any angle value is greater than a preset angle threshold, the antenna array calibration coefficient is determined to be an unusable antenna array calibration coefficient.

[0120] For example, due to the compensated echo data matrix S mn The path and phase differences caused by the wave path have been compensated for, as well as the inherent phase difference of the radar array (i.e., the antenna array calibration coefficient). Therefore, the measurement results at each angle should all be 0, i.e., the angle value V. i The deviation from 0° should be very small.

[0121] Based on the angular spectrum, the angle value corresponding to each channel at each test angle is obtained, and it is compared with a preset angle threshold to determine whether the antenna array calibration coefficient is usable. For example, in practical applications, through batch testing of radar, the angle accuracy AA value is generally less than 0.5°. In all channels at all test angles, if the angle value of one wave position is greater than 0.5°, the antenna array calibration coefficient is considered unusable.

[0122] Furthermore, the evaluation of the antenna array calibration coefficients to be evaluated based on the angular spectrum peak value, angular accuracy, and angular signal-to-noise ratio respectively also includes:

[0123] The mean signal amplitude of the angular spectrum is obtained, and the angular signal-to-noise ratio is obtained based on the maximum signal amplitude and the mean signal amplitude. If the angular signal-to-noise ratio is less than a preset signal-to-noise ratio threshold, the antenna array calibration coefficient is determined to be an unusable antenna array calibration coefficient.

[0124] For example, the angular signal-to-noise ratio (SNR) is defined as the angular spectrum A. m Main peak and A m The logarithm of the ratio of the means is shown in the following formula:

[0125] SNR = 20log 10 (A h / mean(A i )),

[0126] Where A h Indicates main peak A m The main peak, mean(A) m ) is used to calculate the mean of the angular spectrum.

[0127] For example, assuming the signal-to-noise ratio (SNR) threshold is 12dB, the calibration coefficient is considered unusable when the SNR is less than 12dB.

[0128] Furthermore, the stepwise rotation of the turntable carrying the radar in the anechoic chamber, which drives the turntable to rotate in a preset manner and emits radar test signals at a preset position in the anechoic chamber at each test angle, includes:

[0129] The turntable is driven to rotate in steps within the field of view of the radar, wherein each rotation step is 0.5°.

[0130] For example, the turntable rotates once every 0.5°, and the rotation range can be set to ±30°. Therefore, in this example, the total rotation angle is 60°, and with each 0.5° rotation, it can rotate a total of 120 times. In practical applications, this can be adjusted according to the radar's field of view (FOV), but this invention does not limit this adjustment.

[0131] Through one or more embodiments of the above embodiments of the present invention, at least the following technical effects can be achieved:

[0132] In the technical solution disclosed in this invention, echo signals of all channels under different test angles are obtained to obtain the corresponding original echo data matrix. Then, the path phase difference generated between the transmitting antenna, receiving antenna and the angular reflection in the radar anechoic chamber is calculated. The original echo data matrix is ​​then compensated according to the path phase difference matrix and the antenna array calibration coefficient to be evaluated to obtain the compensated echo data matrix. Finally, the corresponding angular spectrum is obtained, and the antenna array calibration coefficient is evaluated according to the angular spectrum related information.

[0133] The usable antenna array calibration coefficients determined after evaluation can simultaneously ensure that multiple performance indicators of the angular spectrum meet the measurement requirements. Specifically, the usable antenna array calibration coefficients guarantee a small spectral peak error, high angular accuracy, and a large signal-to-noise ratio in the measurement results. By evaluating the antenna array calibration coefficients, the detection accuracy of the radar can be significantly improved, ensuring high-precision radar measurements.

[0134] In addition, when mass-producing radar products, the technical solution of this application enables the evaluation of calibration coefficients in a near-field manner within an anechoic chamber, avoiding the need to test the angle measurement performance of each radar (i.e. whether the calibration coefficients are correct) outdoors, simplifying the testing method and significantly improving production efficiency.

[0135] According to another aspect of the present invention, based on the same inventive concept as the method for evaluating antenna array calibration coefficients in an embodiment of the present invention, the present invention also provides an antenna array calibration coefficient evaluation apparatus for a MIMO radar, the MIMO radar including multiple transmitting antennas and multiple receiving antennas, wherein multiple channels are formed between the multiple transmitting antennas and the multiple receiving antennas. Please refer to [reference needed]. Figure 5 The device includes:

[0136] The drive and echo signal acquisition unit 201 is used to drive the turntable carrying the radar in the anechoic chamber to rotate stepwise in a preset manner and transmit radar test signals to the angular reflection at a preset position in the anechoic chamber at each test angle, and for each test angle, determine the position coordinates of the angular reflection in the Cartesian coordinate system with the geometric center of the radar as the origin, and acquire the echo signal fed back by the angular reflection in response to the radar test signal.

[0137] The raw echo data matrix determination unit 202 is used to obtain the echo data of the multiple channels at each test angle based on the echo signal, so as to form a raw echo data matrix;

[0138] The path phase difference matrix determination unit 203 is used to obtain the path phase difference of the multiple channels at each test angle based on the position information of the multiple transmitting antennas and the multiple receiving antennas in the Cartesian coordinate system, so as to form a path phase difference matrix.

[0139] The compensation unit 204 is used to compensate the original echo data matrix according to the path phase difference matrix and the antenna array calibration coefficient to be evaluated, so as to obtain the compensated echo data matrix.

[0140] Evaluation unit 205 is used to obtain the angular spectrum based on the compensated echo data matrix and evaluate the calibration coefficient of the antenna array to be evaluated according to the angular spectrum.

[0141] Furthermore, the path phase difference matrix determination unit 203 is also used for:

[0142] For each channel at each test angle, a first distance phase difference is obtained based on the position coordinates of the transmitting antenna corresponding to the channel and the position coordinates of the angular reflection. A second distance phase difference is obtained based on the position coordinates of the receiving antenna corresponding to the channel and the position coordinates of the angular reflection. The path phase difference corresponding to the channel is obtained based on the first distance phase difference and the second distance phase difference.

[0143] The path phase difference matrix is ​​formed based on the path phase difference of all channels, wherein the path phase difference of each channel constitutes the element at the corresponding position in the path phase difference matrix.

[0144] Furthermore, the compensation unit 204 is also used for:

[0145] The compensated echo data matrix is ​​obtained according to the following formula:

[0146] S nm =D mn *conj(TR mn )*repmat(C n ,M,1),

[0147] Among them, S nm D represents the compensated echo data matrix. mn Represents the original echo data matrix, TR mn C represents the path phase difference matrix. n The function conj(TR) represents the calibration coefficient of the antenna array to be evaluated, M represents the number of angular reversals, and the function is... mn ) indicates that for TR mn Perform the conjugate operation, function repmat(C n M,1) represents C n Repeat M times to form a corresponding M×N dimension matrix, where N represents the number of the plurality of channels.

[0148] Furthermore, the evaluation unit 205 is also used for:

[0149] The angular spectrum is obtained by performing a fast Fourier transform on the compensated echo data matrix.

[0150] The calibration coefficients of the antenna array to be evaluated are assessed based on the angular spectrum peak value, angular accuracy, and angular signal-to-noise ratio, respectively.

[0151] Furthermore, the evaluation unit 205 is also used for:

[0152] Obtain the maximum signal amplitude corresponding to the maximum peak value in the angular spectrum;

[0153] Calculate the difference between the signal amplitude of each spectral peak in the angular spectrum and the maximum signal amplitude;

[0154] The number of spectral peaks corresponding to differences greater than a preset amplitude threshold is obtained. If the number of spectral peaks is greater than a preset number threshold, the antenna array calibration coefficient to be evaluated is determined to be an unusable antenna array calibration coefficient.

[0155] Furthermore, the evaluation unit 205 is also used for:

[0156] Based on the angular spectrum, the angle value corresponding to each channel at each test angle is obtained. If any angle value is greater than a preset angle threshold, the antenna array calibration coefficient is determined to be an unusable antenna array calibration coefficient.

[0157] Furthermore, the evaluation unit 205 is also used for:

[0158] The mean signal amplitude of the angular spectrum is obtained, and the angular signal-to-noise ratio is obtained based on the maximum signal amplitude and the mean signal amplitude. If the angular signal-to-noise ratio is less than a preset signal-to-noise ratio threshold, the antenna array calibration coefficient is determined to be an unusable antenna array calibration coefficient.

[0159] Furthermore, the driving and echo signal acquisition unit 201 is also used for:

[0160] The turntable is driven to rotate in steps within the field of view of the radar, wherein each rotation step is 0.5°.

[0161] Other aspects and implementation details of the antenna array calibration coefficient evaluation device are the same as or similar to the antenna array calibration coefficient evaluation method described above, and will not be repeated here.

[0162] According to another aspect of the invention, the invention also provides a storage medium storing a plurality of instructions adapted to be loaded by a processor to perform an evaluation method for any of the antenna array calibration coefficients as described above.

[0163] In summary, although the present invention has been disclosed above with reference to preferred embodiments, the above preferred embodiments are not intended to limit the present invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the scope defined in the claims.

Claims

1. A method for evaluating antenna array calibration coefficients, used in a MIMO radar, the MIMO radar comprising multiple transmitting antennas and multiple receiving antennas, the multiple transmitting antennas and the multiple receiving antennas constituting multiple channels, characterized in that, The method includes: The turntable carrying the radar in the anechoic chamber is driven to rotate stepwise in a preset manner and transmit radar test signals to the angular reflection at a preset position in the anechoic chamber at each test angle. For each test angle, the position coordinates of the angular reflection in the Cartesian coordinate system with the geometric center of the radar as the origin are determined, and the echo signal fed back by the angular reflection in response to the radar test signal is obtained. Based on the echo signal, the echo data of the multiple channels at each test angle are obtained to form the original echo data matrix; The path phase difference of the multiple channels at each test angle is obtained based on the position information of the multiple transmitting antennas and the multiple receiving antennas in the Cartesian coordinate system, so as to form a path phase difference matrix; The original echo data matrix is ​​compensated based on the path phase difference matrix and the antenna array calibration coefficient to be evaluated to obtain the compensated echo data matrix. The angular spectrum is obtained based on the compensated echo data matrix, and the calibration coefficients of the antenna array to be evaluated are evaluated based on the angular spectrum. The step of obtaining the path phase difference of the multiple channels at each test angle based on the position information of the multiple transmitting antennas and the multiple receiving antennas in the Cartesian coordinate system, in order to form a path phase difference matrix, includes: For each channel at each test angle, a first distance phase difference is obtained based on the position coordinates of the transmitting antenna corresponding to the channel and the position coordinates of the angular reflection. A second distance phase difference is obtained based on the position coordinates of the receiving antenna corresponding to the channel and the position coordinates of the angular reflection. The path phase difference corresponding to the channel is obtained based on the first distance phase difference and the second distance phase difference. The path phase difference matrix is ​​formed based on the path phase difference of all channels, wherein the path phase difference of each channel constitutes the element at the corresponding position in the path phase difference matrix.

2. The method as described in claim 1, characterized in that, The step of compensating the original echo data matrix based on the path phase difference matrix and the antenna array calibration coefficients to be evaluated to obtain the compensated echo data matrix includes: The compensated echo data matrix is ​​obtained according to the following formula: S nm =D mn *conj （ TR mn ） *repmat （ C n ,M,1 ） ， in, S nm This represents the compensated echo data matrix. D mn This represents the original echo data matrix. TR mn This represents the path phase difference matrix. C n This represents the calibration coefficient of the antenna array to be evaluated. M The function represents the number of times the angle reverses. conj ( TR mn ) indicates to TR mn Perform the conjugate operation, function repmat ( C n ,M,1 ) indicates that C n repeat M to form a corresponding M × N A matrix of dimension, where, N This indicates the number of the multiple channels.

3. The method as described in claim 2, characterized in that, The step of obtaining the angular spectrum based on the compensated echo data matrix and evaluating the calibration coefficients of the antenna array to be evaluated based on the angular spectrum includes: The angular spectrum is obtained by performing a fast Fourier transform on the compensated echo data matrix. The calibration coefficients of the antenna array to be evaluated are assessed based on the angular spectrum peak value, angular accuracy, and angular signal-to-noise ratio, respectively.

4. The method as described in claim 3, characterized in that, The evaluation of the calibration coefficients of the antenna array to be evaluated based on the angular spectrum peak value, angular accuracy, and angular signal-to-noise ratio includes: Obtain the maximum signal amplitude corresponding to the maximum peak value in the angular spectrum; Calculate the difference between the signal amplitude of each spectral peak in the angular spectrum and the maximum signal amplitude; The number of spectral peaks corresponding to the difference being greater than a preset amplitude threshold is obtained. If the number of spectral peaks is greater than a preset number threshold, the antenna array calibration coefficient to be evaluated is determined to be an unusable antenna array calibration coefficient.

5. The method as described in claim 4, characterized in that, The evaluation of the calibration coefficients of the antenna array to be evaluated based on the angular spectrum peak value, angular accuracy, and angular signal-to-noise ratio respectively also includes: Based on the angular spectrum, the angle value corresponding to each channel at each test angle is obtained. If any of the angle values ​​is greater than a preset angle threshold, the antenna array calibration coefficient is determined to be an unusable antenna array calibration coefficient.

6. The method as described in claim 5, characterized in that, The evaluation of the calibration coefficients of the antenna array to be evaluated based on the angular spectrum peak value, angular accuracy, and angular signal-to-noise ratio respectively also includes: The mean signal amplitude of the angular spectrum is obtained, and the angular signal-to-noise ratio is obtained based on the maximum signal amplitude and the mean signal amplitude. If the angular signal-to-noise ratio is less than a preset signal-to-noise ratio threshold, the antenna array calibration coefficient is determined to be an unusable antenna array calibration coefficient.

7. The method as described in claim 1, characterized in that, The process of driving the turntable carrying the radar in the anechoic chamber to rotate in a stepwise manner and emitting radar test signals at a predetermined position in the anechoic chamber at each test angle includes: The turntable is driven to rotate in steps within the field of view of the radar, wherein each rotation step is 0.5°.

8. An evaluation device for antenna array calibration coefficients, used in a MIMO radar, the MIMO radar comprising multiple transmitting antennas and multiple receiving antennas, wherein the multiple transmitting antennas and the multiple receiving antennas constitute multiple channels, characterized in that, The device includes: The drive and echo signal acquisition unit is used to drive the turntable carrying the radar in the anechoic chamber to rotate stepwise in a preset manner and transmit radar test signals to the angular reflection at a preset position in the anechoic chamber at each test angle, and for each test angle, determine the position coordinates of the angular reflection in the Cartesian coordinate system with the geometric center of the radar as the origin, and acquire the echo signal fed back by the angular reflection in response to the radar test signal. The raw echo data matrix determination unit is used to obtain the echo data of the multiple channels at each test angle based on the echo signal, so as to form the raw echo data matrix. A path phase difference matrix determination unit is used to obtain the path phase difference of the multiple channels at each test angle based on the position information of the multiple transmitting antennas and the multiple receiving antennas in the Cartesian coordinate system, so as to form a path phase difference matrix, including: For each channel at each test angle, a first distance phase difference is obtained based on the position coordinates of the transmitting antenna corresponding to the channel and the position coordinates of the angular reflection. A second distance phase difference is obtained based on the position coordinates of the receiving antenna corresponding to the channel and the position coordinates of the angular reflection. The path phase difference corresponding to the channel is obtained based on the first distance phase difference and the second distance phase difference. The path phase difference matrix is ​​formed based on the path phase difference of all channels, wherein the path phase difference of each channel constitutes the element at the corresponding position in the path phase difference matrix. The compensation unit is used to compensate the original echo data matrix according to the path phase difference matrix and the antenna array calibration coefficient to be evaluated, so as to obtain the compensated echo data matrix. An evaluation unit is used to obtain an angular spectrum based on the compensated echo data matrix and to evaluate the calibration coefficients of the antenna array to be evaluated based on the angular spectrum.

9. A storage medium, characterized in that, The storage medium stores a plurality of instructions adapted for loading by a processor to execute the method for evaluating antenna array calibration coefficients as described in any one of claims 1 to 7.

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