CN-121978646-A - Vortex electromagnetic wave azimuth angle high-resolution estimation method

CN121978646ACN 121978646 ACN121978646 ACN 121978646ACN-121978646-A

Abstract

The invention discloses a vortex electromagnetic wave azimuth angle high-resolution estimation method, which remarkably improves azimuth estimation precision under the condition of low signal-to-noise ratio through a characteristic value correction strategy. A Uniform Circular Array (UCA) geometric model based on MIMO is established, vortex electromagnetic waves carrying orbital angular momentum are used as information carriers, and a receiving signal matrix is constructed through modal domain sampling. Aiming at the problem that the performance of the traditional MUSIC algorithm is reduced under the conditions of a coherent signal source and a low signal-to-noise ratio, a method for carrying out weighted correction on noise subspace characteristic values is innovatively provided, and the construction of a spatial spectrum function is improved by optimizing the noise characteristic value utilization rate. Compared with the traditional MUSIC and FFT methods, the method has more excellent target azimuth estimation performance.

Inventors

GONG YANYUN
LIU ZE
HAN CHUANG
SUN WENBIN
CHEN LILI
LIU HAOCHEN
Gou Yuewen
WANG LING

Assignees

西北工业大学

Dates

Publication Date: 20260505
Application Date: 20251225

Claims (5)

1. A vortex electromagnetic wave azimuth angle high-resolution estimation method is characterized by comprising the following steps of: step 1, establishing a vortex electromagnetic wave target azimuth angle estimation geometric model based on MIMO; n identical isotropic array elements form a uniform circular array as a transmitting antenna, and the radius of the UCA is First, the Azimuth angle of each array element is Circumferentially located at A noodle; Establishing a spherical coordinate system by taking the central point of the UCA as the origin, and the distance Pitch angle for the length of the line between origin and target Connecting line and connecting line for origin and target Included angle, azimuth angle of axial half shaft From the UCA origin to the target The shaft is rotated anticlockwise by the axle shaft, and the target position is ; And 2, adopting a linear frequency modulation signal as a transmitting signal, wherein the linear frequency modulation signal fed by all transmitting array elements is as follows: (1) In the middle of As a function of the time variable, For the duration of the pulse(s), For the frequency modulation rate of the chirp signal, As the center frequency of the signal, As a matrix function, namely: (2) To generate OAM mode value as Is added with phase shift to each array element of the circular array in turn Vortex electromagnetic wave target detection irradiates a target to be observed by traversing vortex electromagnetic waves of different modes; The single element transmit signal is: (3) the UCA transmits a pulse signal as follows: (4) Step 3, any one detection point Where the transmitted signal The writing is as follows: (5) Wherein the method comprises the steps of , , C represents the propagation speed of electromagnetic waves; satisfies the condition Thus, it is (6) When (when) When sufficiently large, the pair of formula (6) Expressed as an integral: (7) Wherein the method comprises the steps of , Is the first The order of the first class of bessel functions, Wave number of the signal; step 4, all antennas on UCA are used to receive the echo scattered by the target, the first Multiplying the signals received by the antennas The total echo signal is expressed as: (8) Wherein the method comprises the steps of , Radar cross section RCS representing a target; Assuming coexistence of Each target is approximately a point target, and each target point position is recorded as The corresponding RCS is noted as The total echo is then expressed as: (9) Wherein the method comprises the steps of ; When the condition is satisfied And is also provided with When the Bessel function is approximately transformed as follows: (10) The square is obtained: (11) neglecting the high-frequency oscillation term, the method is simplified as follows: (12) Phase term of echo signal Compensating, the compensated echo signal is represented by an approximate deformation of equation (12): (13) Assume that Is that The sampling rate under the domain is based on the Nyquist sampling theory to ensure that the estimate is not aliased , The requirements are satisfied: (14) Wherein, the Is that The maximum frequency of the domain is set to be, Is that Maximum angular frequency of domain, thus ; Consider Real-time echo signals calibrated in OAM modes and for vortex echo signals Domain sampling, and constructing a receiving signal matrix after echo amplitude normalization as follows: (15) Wherein the method comprises the steps of For the steering vector matrix of the receiving matrix, In order to modify the echo signal vector, Indicating the modified first The source signal of the individual target is selected, Is received as Gaussian white noise, and (16) (17) Wherein, the The symbols represent a matrix conjugate transpose; Covariance operation is carried out on the received signal matrix to obtain a covariance matrix The method comprises the following steps: (18) Wherein, the Representing the mathematical expectation that the data will be, , Representing the covariance matrix of the target source signal, For the power of the noise in the environment, Is that A unit matrix; According to the smoothing theory, the mode domain Dividing the samples into A plurality of mixed sub-sample blocks, each sub-sample block comprising Samples of then In order to realize the full rank of the covariance matrix of the echo signals, the number of samples in the sub-sample block should satisfy the following condition At this time, orthogonality between the signal system space and the noise subspace is ensured; the covariance matrix of the echo signal after the space smoothing decorrelation process is as follows: (19) Wherein, the Is the first Individual sub-sample blocks Is a covariance matrix of (a); For covariance matrix And (3) performing characteristic decomposition to obtain: (20) Wherein, the As a value of the characteristic(s), Is the corresponding feature vector; sorting the feature values from large to small to obtain: Front (front) Individual components Rear (back) Individual components Covariance matrix Can be decomposed into: (21) Wherein the method comprises the steps of And Respectively a signal subspace and a noise subspace; The algorithm azimuth search formula of the MUSIC algorithm is as follows: (22) taking into account the denominator of the spatial spectral function Independent of the noise characteristic value, the method for weighting the corresponding noise characteristic vector by using the corrected noise characteristic value is as follows: (23) Wherein the method comprises the steps of , In order to correct the characteristic value after the correction, Is a correction value; On the premise that the information theory criterion can accurately estimate the number of the information sources, the ratio of the maximum value to the minimum value of the noise characteristic value is not more than 2, namely: (24) Bringing formula (23) into formula (24) gives formula (25): (25) further, the minimum is obtained A value; the improved noise subspace is written as: (26) Wherein, the Is the eigenvector of the original noise subspace, Is the corrected noise characteristic value, and then is obtained : (27) The final new spatial spectrum function is: (28) Wherein, the ; And searching spectrum peaks aiming at the new space spectrum function to obtain an azimuth angle estimation result of the target.
2. An electronic device comprising a processor and a memory, the memory for storing a computer program, the processor for executing the computer program stored in the memory to cause the electronic device to perform the method of claim 1.
3. A computer readable storage medium, on which a computer program is stored, which computer program, when being executed by a processor, implements the method according to claim 1.
4. A chip comprising a processor for calling and running a computer program from a memory, causing a device on which the chip is mounted to perform the method of claim 1.
5. A computer program product comprising a computer storage medium storing a computer program comprising instructions executable by at least one processor, the instructions when executed by the at least one processor implementing the method of claim 1.

Description

Vortex electromagnetic wave azimuth angle high-resolution estimation method Technical Field The invention belongs to the technical field of radars, and particularly relates to a vortex electromagnetic wave azimuth angle high-resolution estimation method. Background Based on the propagation characteristics of electromagnetic waves, the radar can work in all weather, all day time and long distance conditions, and can acquire the scattering information of targets on the electromagnetic waves in various complex environments, so that target reconstruction detection, identification and tracking can be performed. The traditional radar detection method depends on the antenna observation angle in azimuth, wherein the azimuth resolution of the real aperture radar is related to the real aperture size, and huge real aperture cannot be obtained in practical application, the synthetic aperture radar needs to perform azimuth resolution through Doppler information of a target formed by the relative motion of the antenna and the target, the resolution quality is easily influenced by a platform track, and the method has certain limitation. The electromagnetic wave is used as the carrier of information, the traditional modulation mode is mainly carried out in the time domain, the frequency domain and the polarization domain, and the approximation of far-field plane waves is mainly utilized. Orbital Angular Momentum (OAM) brings new degrees of freedom of modulation to electromagnetic waves, and electromagnetic waves carrying orbital angular momentum, the wave fronts of which exhibit a helical characteristic, are called vortex electromagnetic waves. The generation of vortex electromagnetic waves, wireless communication, radar imaging, and the like have led to extensive studies by many scholars. When the radiation field of the vortex electromagnetic wave irradiates the target, the echo signal received by the radar contains the information of the azimuth angle of the target. Therefore, when vortex electromagnetic waves are used for carrying out target azimuth resolution, the target azimuth information can be obtained from the echo signals by means of signal processing without relative movement between the radar and the target. Scholars apply vortex electromagnetic waves to the field of radar imaging, indicating the ability of vortex electromagnetic waves to have azimuthal resolution for radar targets. Then, a learner applies the MUSIC algorithm to radar imaging, and high resolution of radar target azimuth angles is realized under the condition of a small number of OAM modes. However, when the signal-to-noise ratio is small, the azimuth resolution accuracy of the target is low. Disclosure of Invention In order to overcome the defects of the prior art, the invention provides the vortex electromagnetic wave azimuth angle high-resolution estimation method, and the azimuth estimation precision under the condition of low signal-to-noise ratio is obviously improved through a characteristic value correction strategy. A Uniform Circular Array (UCA) geometric model based on MIMO is established, vortex electromagnetic waves carrying orbital angular momentum are used as information carriers, and a receiving signal matrix is constructed through modal domain sampling. Aiming at the problem that the performance of the traditional MUSIC algorithm is reduced under the conditions of a coherent signal source and a low signal-to-noise ratio, a method for carrying out weighted correction on noise subspace characteristic values is innovatively provided, and the construction of a spatial spectrum function is improved by optimizing the noise characteristic value utilization rate. Compared with the traditional MUSIC and FFT methods, the method has more excellent target azimuth estimation performance. The technical scheme adopted for solving the technical problems is as follows: step 1, establishing a vortex electromagnetic wave target azimuth angle estimation geometric model based on MIMO; n identical isotropic array elements form a uniform circular array as a transmitting antenna, and the radius of the UCA is First, theAzimuth angle of each array element isCircumferentially located atA noodle; Establishing a spherical coordinate system by taking the central point of the UCA as the origin, and the distance Pitch angle for the length of the line between origin and targetConnecting line and connecting line for origin and targetIncluded angle, azimuth angle of axial half shaftFrom the UCA origin to the targetThe shaft is rotated anticlockwise by the axle shaft, and the target position is; And 2, adopting a linear frequency modulation signal as a transmitting signal, wherein the linear frequency modulation signal fed by all transmitting array elements is as follows: (1) In the middle of As a function of the time variable,For the duration of the pulse(s),For the frequency modulation rate of the chirp signal,As the center frequency of the signal,As a matrix fu