Beam tracking method and system based on orthogonal double-frequency uniform linear array

Abstract

The invention discloses a beam tracking method and system based on an orthogonal dual-frequency uniform linear array, and the method comprises the steps: initializing base station parameters and kinematics parameters, the kinematics parameters comprise a speed vector and a position vector of a target, and the base station comprises an orthogonal dual-frequency linear antenna array; performing two-dimensional projection on the kinematics parameters to calculate echo signals reflected by a target and received by the base station; performing matrix modeling on the echo signals received by the base station in each coherent processing interval to obtain an echo signal multi-dimensional matrix; and iteratively solving the echo signal multi-dimensional matrix of each coherent processing interval to obtain a target speed predicted value and a target position predicted value. According to the invention, different carrier frequencies are allocated to the two linear sub-arrays, so that same-frequency interference between signals is avoided. Through projection transformation, the perception precision of the target motion state is improved, and the joint estimation capability of the multi-dimensional velocity component of the moving target is enhanced, so that the overall performance of the system is improved.

Description

Technical Field

[0001] The present invention belongs to the field of wireless communication, and particularly relates to a beam tracking method and system based on an orthogonal dual-frequency uniform linear array. Background Art

[0002] In recent years, due to the increasingly obvious trend of using large-aperture antennas and high-frequency signals for wireless communication, the near-field region has become a new research hotspot in the field of wireless communication. With the increase of the array aperture and carrier frequency, the range of the near-field region continues to expand, and the exploration of communication and sensing in the near-field region of the antenna array has attracted great interest. In order to characterize the unique near-field effect, various near-field channel models have been proposed. In near-field sensing, the propagation of spherical waves depends on the polar coordinates of angle and distance. Therefore, the sensing signal exhibits good structural characteristics, but the dual dependence of the near-field channel on direction and distance also poses challenges to obtaining accurate channel state information.

[0003] The current near-field wireless communication sensing system mainly faces the following problems: First, in the spatial dimension, existing systems are mostly limited to the beam control strategy in the two-dimensional plane and fail to effectively utilize the three-dimensional space channel characteristics; second, in the dynamic characteristic dimension, existing schemes are constructed based on the assumption of a static user scenario, and the preset beam codebook is difficult to adapt to the time-varying channel response caused by the high-speed movement of the terminal; third, in the environmental perception dimension, traditional methods rely on simplified channel models and lack the ability to perceive dynamic interferences such as multipath time-variation and obstacle occlusion in complex propagation environments in real time.

[0004] In summary, the traditional beamforming method and speed prediction method have limitations, are difficult to meet the performance requirements, and are easily affected by signal attenuation or multipath effects. Therefore, both the acquisition accuracy and prediction accuracy are relatively low. Summary of the Invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a beam tracking method and system based on an orthogonal dual-frequency uniform linear array. The technical problems to be solved by the present invention are realized through the following technical solutions: A beam tracking method based on an orthogonal dual-frequency uniform linear array, comprising: Initializing base station parameters and kinematic parameters, wherein the kinematic parameters include the velocity vector and position vector of the target, and the base station includes an orthogonal dual-frequency linear antenna array; Performing two-dimensional projection on the kinematic parameters to calculate the echo signal received by the base station reflected by the target; Performing matrix modeling on the echo signals received by the base station within each coherent processing interval to obtain an echo signal multi-dimensional matrix; Iteratively solve the multi-dimensional matrix of the echo signal for each coherent processing interval to obtain the predicted target velocity value and the predicted target position value.

[0006] In a specific embodiment, the orthogonal dual-frequency linear antenna array is two sets of antenna structures placed crosswise, each set of the antenna structures includes at least 256 antennas, and the distance between two adjacent antennas is λ / 2.

[0007] In a specific embodiment, performing two-dimensional projection on the kinematic parameters to calculate the echo signal received by the base station from the target reflection includes: Performing dimensionality reduction processing on the three-dimensional space to construct a two-dimensional projection plane; Based on the two-dimensional projection plane, obtaining a projection signal after the baseband echo signal received at the m-th antenna is reflected by the moving target; Introducing Doppler frequency shift to optimize the projection signal to obtain the echo signal received by the base station from the target reflection.

[0008] In a specific embodiment, the projection signal is: , , , , , , , , where, represents the channel gain, represents the number of antennas placed crosswise in each group, n represents the time index, T s represents the duration of each index, represents the time-varying propagation distance from the m-th antenna to the target, represents the time-varying propagation distance from the i-th antenna to the target, and respectively represent the radial velocity and the transverse velocity, respectively represent the projections of the radial velocity and the transverse velocity along the line connecting the m-th antenna and the target on ULA_x, represents and the sum velocity of, r, θ, and φ respectively represent the distance, azimuth angle, and elevation angle of the moving target relative to the base station center, represents the distance from the m-th antenna to the central antenna, represents the projection of the distance from the target user to the m-th antenna on the xoy plane, and z represents the height at which the moving target is located. represents the projection of the distance from the target user to the base station center on the xoy plane. represents the distance between the target user and the base station. represents the signal transmitted by the m-th antenna, and λ represents the signal wavelength. represents complex Gaussian noise.

[0009] In a specific embodiment, the echo signal reflected by the target is: , where represents the channel gain parameter. represents the array response matrix. represents the Doppler frequency shift matrix. represents the signal transmitted by the antenna array. represents the noise vector.

[0010] In a specific embodiment, the echo signal multi-dimensional matrix is: , where represents the channel gain parameter. represents the echo signal received by the base station when the time index ranges from 1 to N. is the maximum time index. represents the position vector. represents the velocity vector. , represents the Khatri-Rao product of the array response and velocity Doppler compensation. represents the noise matrix.

[0011] In a specific embodiment, iteratively solving the echo signal multi-dimensional matrix for each coherent processing interval to obtain the target velocity prediction value and the target position prediction value includes: Converting the solution of the echo signal multi-dimensional matrix into the objective function of a maximization optimization problem. Using the quasi-Newton method to iteratively calculate the gradient expression of the objective function with respect to the velocity vector v to obtain the target velocity prediction value. Calculating the target position prediction value based on the target velocity prediction value.

[0012] In a specific embodiment, the objective function is: , , , Among them, the expression is the objective function to be maximized, which is obtained by expanding the two-norm. Among them, represents the product of and the transmitted signal. represents the Khatri-Rao product of the array response and the velocity Doppler compensation at the n-th time index. represents the echo signal reflected by the target. The superscript H represents the conjugate transpose of the matrix, Re{} represents taking the real part, and tr represents the trace of the matrix. represents the Doppler frequency shift compensation vector. represents the transpose of; The gradient expression is: , where , … respectively represent the velocities on the projections of the corresponding 1-M antennas. … represents the 1-M entries of the Doppler frequency shift compensation vector . represents the velocity components in each direction. .

[0013] In a specific embodiment, the formula for calculating the predicted target position according to the predicted target velocity value is: , where , , respectively represent the predicted position parameters of the target in cylindrical coordinates. , , respectively represent the corresponding , , velocity components. The superscripts t and t + 1 respectively represent the current time and the next time.

[0014] The present invention also provides a beam tracking system based on an orthogonal dual-frequency uniform linear array, including: An initialization module for initializing the base station parameters and kinematic parameters, where the kinematic parameters include the velocity vector and position vector of the target, and the base station includes an orthogonal dual-frequency linear antenna array; An echo signal calculation module for two-dimensionally projecting the kinematic parameters to calculate the echo signal received by the base station from the target reflection; A multi-dimensional matrix modeling module, which is used to perform matrix modeling on the echo signals received by the base station within each coherent processing interval to obtain a multi-dimensional matrix of echo signals; An iterative calculation module, which is used to iteratively solve the multi-dimensional matrix of echo signals for each coherent processing interval to obtain a predicted value of the target speed and a predicted value of the target position.

[0015] Advantages of the present invention: In the beam tracking method based on an orthogonal dual-frequency uniform linear array of the present invention, by using a uniform linear array with an orthogonal layout on the horizontal x-axis and the vertical z-axis, different carrier frequencies are assigned to the two linear sub-arrays to avoid co-frequency interference between signals. In addition, by means of projection transformation, the high-dimensional parameter estimation problem is transformed into a low-dimensional subspace optimization problem, realizing the joint perception and position prediction of multi-dimensional velocity components, thereby improving the perception accuracy of the target motion state, enhancing the joint estimation ability of multi-dimensional velocity components of a moving target, being able to capture the motion information of the target more comprehensively, and thus providing richer data support for subsequent beamforming and communication optimization, improving the overall performance of the system, especially the coping ability in a dynamic environment.

[0016] The present invention will be further described in detail below with reference to the drawings and embodiments. Description of the Drawings

[0017] Figure 1 is a schematic flowchart of a beam tracking method based on an orthogonal dual-frequency uniform linear array provided by an embodiment of the present invention; Figure 2 is a schematic model diagram of a beam tracking system based on an orthogonal dual-frequency uniform linear array provided by an embodiment of the present invention; Figure 3 is a block diagram of a beam tracking system module based on an orthogonal dual-frequency uniform linear array provided by an embodiment of the present invention. Detailed Embodiments

[0018] The present invention will be further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0019] Embodiment 1 Please refer to Figure 1 , Figure 1 which is a schematic flowchart of a beam tracking method based on an orthogonal dual-frequency uniform linear array provided by an embodiment of the present invention, and includes: S1. Initialize the base station parameters and kinematic parameters, where the kinematic parameters include the velocity vector and position vector of the target, and the base station includes an orthogonal dual-frequency linear antenna array; It should be noted that the base station in this embodiment can implement full-duplex operation using the time-division duplex (TDD) system. The isolation between the transmitting and receiving links is achieved through a circulator. The orthogonal dual-frequency linear antenna array is composed of two groups of M-element ULAs, which are placed crosswise. The horizontal ULA is arranged along the x-axis, and the vertical ULA is arranged along the z-axis. The center of the array is located at the origin of the coordinate system, and the two groups of ULAs are respectively configured with different carrier frequencies. The sensing target is a moving point source, which will generate velocity components in three directions in the three-dimensional near-field region.

[0020] During specific deployment, the element spacing of the base station is, for example, half a wavelength , the bandwidth of the system is denoted as B, and the corresponding symbol period is Ts = 1 / B. In a specific CPI, let r, θ, and φ respectively represent the distance, azimuth angle, and elevation angle of the moving target relative to the center of the ULA. The velocity components are divided using the cylindrical coordinate system, and v r , v θ and v z respectively represent the radial velocity, azimuth angular velocity, and normal velocity of the target relative to the center of the ULA. The target kinematic parameters are described as follows: Velocity vector: , Position vector: .

[0021] S2. Project the kinematic parameters into two dimensions to calculate the echo signal received by the base station from the target reflection; To better illustrate the dimensionality reduction process of the transmitted signal and the received echo signal, please refer to Figure 2 , Figure 2 which is a schematic diagram of a model based on an orthogonal dual-frequency uniform linear array provided by an embodiment of the present invention.

[0022] S21. Perform dimensionality reduction processing on the three-dimensional space to construct a two-dimensional projection plane; First, it is divided into the following two plane dimensions: Construct an xoy plane sensing subsystem, and project the target motion parameters onto this two-dimensional plane for analysis. Consider the velocity components on this plane, namely v r and v θ , which are sensed by the ULA (ULA_x) placed along the x-axis; Construct a plane sensing subsystem formed by the z-axis and the User, and consider the velocity component on this plane, namely v z , which is sensed by the ULA (ULA_x) placed along the x-axis.

[0023] Taking the xoy plane as an example for analysis, the polar axis projected onto this plane is denoted as r xy , and the signal transmitted by the horizontal antenna array in the nth time slot on this plane is as follows and satisfies the constraint , represents the transmit power.

[0024] (1) S22. Based on the two-dimensional projection plane, obtain a projection signal after the baseband echo signal received at the m-th antenna is reflected by a moving target; The projection signal after the baseband echo signal received at the m-th antenna is reflected by a moving target is expressed as follows: (2) (3) (4) (5) (6) (7) (8) Among them, represents the channel gain, represents the number of antennas placed crosswise in each group, n represents the time index, T s represents the duration of each index, represents the time-varying propagation distance from the m-th antenna to the target, represents the time-varying propagation distance from the i-th antenna to the target, and respectively represent the radial velocity and the transverse velocity,, respectively represent the projections of the radial velocity and the transverse velocity along the line connecting the m-th antenna and the target in ULA_x, represents and the sum velocity of, r, θ and φ respectively represent the distance, azimuth angle and elevation angle of the moving target relative to the base station center, represents the distance from the m-th antenna to the central antenna, represents the projection of the distance from the target user to the m-th antenna on the xoy plane, z represents the height where the moving target is located, represents the projection of the distance from the target user to the base station center on the xoy plane, represents the distance between the target user and the base station, represents the signal transmitted by the -th antenna, λ represents the signal wavelength, represents complex Gaussian noise.

[0025] S23. Introduce Doppler frequency shift to optimize the projection signal to obtain the echo signal received by the base station after being reflected by the target.

[0026] Since the frequency and wavelength of electromagnetic waves change when the wave source and the receiver are in relative motion, this embodiment takes into account this change difference, i.e., the Doppler frequency shift, so that introducing the Doppler frequency shift vector can more accurately sense the speed change. , so the echo signal reflected by the target received by the base station is: , where represents the channel gain parameter, represents the array response matrix, represents the Doppler frequency shift matrix, represents the signal transmitted by the antenna array, represents the noise vector.

[0027] S3. Model the echo signals received by the base station within each coherent processing interval into a multi-dimensional matrix of echo signals; Model the echo signals received by the base station within each coherent processing interval into matrix form, then , where, represents the channel gain parameter, represents the echo signals received by the base station when the time index ranges from 1 to N, is the maximum time index, represents the position vector, represents the velocity vector, , represents the Khatri-Rao product of the array response and velocity Doppler compensation, represents the noise matrix.

[0028] S4. Iteratively solve the multi-dimensional matrix of echo signals for each coherent processing interval to obtain the predicted target velocity value and the predicted target position value.

[0029] Specifically, it includes: S41. Transform the solution of the multi-dimensional matrix of echo signals into the objective function of a maximization optimization problem; Specifically, based on the maximum likelihood estimation criterion, transform the estimation problem of velocity v into the following unconstrained optimization problem P1: (9) (10) Expand the solution problem of the second norm in formula (9) into the form of a trace, then the above minimization optimization problem can be transformed into a maximization optimization problem P2: (11) The objective function is (12) S42. Use the quasi - Newton method to iteratively calculate the gradient expression of the objective function with respect to the velocity vector v to obtain the predicted target velocity value; Specifically, the quasi - Newton method (L - BFGS) is used for iterative optimization. By approximating the Hessian matrix, direct calculation of the second - order derivative is avoided, significantly reducing the computational complexity while ensuring the convergence accuracy.

[0030] When specifically implemented, it is necessary to calculate the gradient expression of the objective function with respect to the velocity vector v, and its expanded form is as follows: (13) (14) (15) (16) Among them, the expression is the objective function that needs to be maximized, which is obtained by expanding the two - norm. Among them, represents the product of and the transmitted signal represents the Khatri - Rao product of the array response and velocity Doppler compensation at the n - th time index, represents the echo signal reflected by the target. The superscript H represents the conjugate transpose of the matrix, Re{} represents taking the real part, and tr represents the trace of the matrix, represents the Doppler frequency shift compensation vector, represents the transpose of , … respectively represent the velocities on the 1 - M antenna projections, … represents the 1 - M - th entry of the Doppler frequency shift compensation vector , represents the velocity components in each direction, .

[0031] S43. Calculate the predicted target position value according to the predicted target velocity value.

[0032] Specifically, based on the accurate estimation of the target velocity, the predicted target position value of the target user at each CPI can be calculated through the following formula.

[0033] (17) Among them, , , respectively represent the predicted position parameters of the target in cylindrical coordinates, , , respectively represent the corresponding , , speed components. The superscripts t and t + 1 represent the current moment and the next moment respectively.

[0034] This embodiment conducts a simulation test in an actual application scenario. Specifically, it simulates the logistics transportation of an unmanned aerial vehicle (UAV) in an indoor warehouse, and the flight trajectory presents a complete process of vertical takeoff and acceleration from the ground, uniform horizontal flight during the cruise stage, and decelerated descent to the target point.

[0035] In this scenario, the base station is equipped with two sets of linear antenna arrays with M = 256 antennas and an antenna spacing of λ / 2, which are placed crosswise. The carrier frequencies are set to 28 GHz and 30 GHz respectively. The system bandwidth B is set to 100 KHz, and the corresponding symbol duration Ts = 1×10 -6 , the number of symbols transmitted within each CPI is N = 200, and the noise power N0 and the transmitted signal power Pt are set to thermal noise -174 dBm and 10 dBm respectively. In addition, it is also compared with a single ULA antenna array structure. When using a single ULA array structure, the speed perception in a three-dimensional scenario fluctuates greatly, and there will be a large deviation as the distance between the base station and the user increases. The dual-frequency cross antenna structure of this embodiment not only expands the near-field perception range, but also the error between the speed perception and the true value can be controlled within the -3 order of magnitude, can accurately track the real-time state of the UAV, and greatly improves the perception accuracy.

[0036] In summary, the beam tracking method based on an orthogonal dual-frequency uniform linear array of the present invention uses uniformly linear arrays on the horizontal x-axis and vertical z-axis with an orthogonal layout, assigns different carrier frequencies to the two linear sub-arrays, and avoids co-frequency interference between signals. In addition, by means of projection transformation, the high-dimensional parameter estimation problem is transformed into a low-dimensional subspace optimization problem, realizing the joint perception and position prediction of multi-dimensional speed components, thereby improving the perception accuracy of the target motion state, enhancing the joint estimation ability of multi-dimensional speed components of a moving target, being able to capture the motion information of the target more comprehensively, and thus providing richer data support for subsequent beamforming and communication optimization, improving the overall performance of the system, especially the response ability in a dynamic environment.

[0037] Please refer to Figure 3 , Figure 3 which is a block diagram of a beam tracking system module based on an orthogonal dual-frequency uniform linear array provided by an embodiment of the present invention, including: An initialization module for initializing base station parameters and kinematic parameters, where the kinematic parameters include the velocity vector and position vector of the target, and the base station includes an orthogonal dual-frequency linear antenna array; An echo signal calculation module for performing two-dimensional projection on the kinematic parameters to calculate the echo signal received by the base station from the reflection of the target; A multi-dimensional matrix modeling module for performing matrix modeling on the echo signals received by the base station within each coherent processing interval to obtain an echo signal multi-dimensional matrix; An iterative calculation module for iteratively solving the echo signal multi-dimensional matrix of each coherent processing interval to obtain a target velocity prediction value and a target position prediction value.

[0038] The above content is a further detailed description of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention pertains, without departing from the concept of the present invention, several simple deductions or substitutions can be made, and all should be regarded as belonging to the protection scope of the present invention.

Claims

1. A beam tracking method based on an orthogonal dual-frequency uniform linear array, characterized in that Including: Initializing base station parameters and kinematic parameters, where the kinematic parameters include the velocity vector and position vector of the target, and the base station includes an orthogonal dual-frequency linear antenna array; Performing two-dimensional projection on the kinematic parameters to calculate the echo signal received by the base station reflected by the target; Performing matrix modeling on the echo signals received by the base station within each coherent processing interval to obtain a multi-dimensional matrix of echo signals; Iteratively solving the multi-dimensional matrix of echo signals for each coherent processing interval to obtain the predicted target velocity value and the predicted target position value.

2. The beam tracking method based on an orthogonal dual-frequency uniform linear array according to claim 1, wherein The orthogonal dual-frequency linear antenna array is a structure of two sets of cross-placed antennas, and each set of the antenna structures includes at least 256 antennas, and the distance between adjacent two antennas is λ / 2.

3. The beam tracking method based on an orthogonal dual-frequency uniform linear array according to claim 1, characterized in that Performing two-dimensional projection on the kinematic parameters to calculate the echo signal received by the base station reflected by the target, including: Performing dimensionality reduction processing on the three-dimensional space to construct a two-dimensional projection plane; Based on the two-dimensional projection plane, obtaining a projection signal after the baseband echo signal received at the m-th antenna is reflected by the moving target; Introducing Doppler frequency shift to optimize the projection signal to obtain the echo signal received by the base station reflected by the target.

4. The beam tracking method based on an orthogonal dual-frequency uniform linear array according to claim 3, wherein The projection signal is: ， ， ， ， ， ， ， ， Among them, represents the channel gain, represents the number of antennas placed crosswise in each group, n represents the time index, and T s represents the duration of each index, represents the time-varying propagation distance from the m-th antenna to the target, represents the time-varying propagation distance from the i-th antenna to the target, and represent the radial velocity and the transverse velocity respectively, and represent the projections of the radial velocity and the transverse velocity along the line connecting the m-th antenna of ULA_x and the target respectively, represents and the sum velocity of, r, θ and φ represent the distance, azimuth angle and elevation angle of the moving target relative to the base station center respectively, represents the distance from the m-th antenna to the central antenna, represents the projection on the xoy plane of the distance from the target user to the m-th antenna, z represents the height where the moving target is located, represents the projection on the xoy plane of the distance from the target user to the base station center, represents the distance between the target user and the base station, represents the signal transmitted by the m-th antenna, λ represents the signal wavelength, represents complex Gaussian noise.

5. The beam tracking method based on an orthogonal dual-frequency uniform linear array according to claim 4, wherein The echo signal reflected by the target is: , where represents the channel gain parameter, represents the array response matrix, represents the Doppler shift matrix, represents the signal transmitted by the antenna array, represents the noise vector.

6. The beam tracking method based on an orthogonal dual-frequency uniform linear array according to claim 1, wherein The multi-dimensional matrix of echo signals is: ， Among them, represents the channel gain parameter, represents the echo signals received by the base station when the time index ranges from 1 to N, is the maximum time index, represents the position vector, represents the velocity vector, , represents the Khatri-Rao product of the array response and velocity Doppler compensation, represents the noise matrix.

7. The beam tracking method based on an orthogonal dual-frequency uniform linear array according to claim 1, wherein Iteratively solving the multi-dimensional matrix of echo signals for each coherent processing interval to obtain the predicted target velocity value and the predicted target position value, including: Converting the solution of the multi-dimensional matrix of echo signals into the objective function of a maximization optimization problem; Using the quasi-Newton method to iteratively calculate the gradient expression of the objective function with respect to the velocity vector v to obtain the predicted target velocity value; Calculating the predicted target position value according to the predicted target velocity value.

8. The beam tracking method based on an orthogonal dual-frequency uniform linear array according to claim 7, wherein The objective function is: ， ， ， Among them, the expression is the objective function to be maximized, which is derived from expanding the two-norm. Among them, represents the product with the transmitted signal . represents the Khatri-Rao product of the array response and velocity Doppler compensation at the n-th time index, represents the echo signal reflected by the target. The superscript H represents the conjugate transpose of the matrix, Re{} represents taking the real part, and tr represents the trace of the matrix, represents the Doppler frequency shift compensation vector, represents the transpose of; The gradient expression is: ， Among them, , … respectively represent the velocities on the corresponding 1-M antenna projections, … represent the 1-Mth entries of the Doppler frequency shift compensation vector and represent the velocity components in each direction, .

9. The beam tracking method based on an orthogonal dual-frequency uniform linear array according to claim 7, characterized in that The formula for calculating the predicted target position value according to the predicted target velocity value is: ， Among them, , , respectively represent the predicted position parameters of the target in cylindrical coordinates, , , respectively represent the corresponding , , velocity components, and the superscripts t and t + 1 represent the current moment and the next moment respectively.

10. A beam tracking system based on an orthogonal dual-frequency uniform linear array, characterized in that, Including: An initialization module, configured to initialize base station parameters and kinematic parameters, where the kinematic parameters include the velocity vector and position vector of the target, and the base station includes an orthogonal dual-frequency linear antenna array; An echo signal calculation module, configured to perform two-dimensional projection on the kinematic parameters to calculate the echo signal received by the base station reflected by the target; A multi-dimensional matrix modeling module, configured to perform matrix modeling on the echo signals received by the base station within each coherent processing interval to obtain a multi-dimensional matrix of echo signals; An iterative calculation module, configured to iteratively solve the multi-dimensional matrix of echo signals for each coherent processing interval to obtain the predicted target velocity value and the predicted target position value.

Images