Beam forming and sea surface arrival angle estimation system and method based on intelligent reflecting surface

Abstract

The invention discloses a beam forming and sea surface arrival angle estimation system and method based on an intelligent reflecting surface. The system comprises an active intelligent reflecting surface deployed on the sea surface, an airborne array antenna arranged on a flight platform and an airborne base station. The airborne array antenna is used for receiving a radio frequency signal from a sea surface signal source and sending the radio frequency signal to the airborne base station; the airborne base station performs down-conversion processing on the radio frequency signal to separate an analog baseband signal, and performs dynamic beam forming processing based on the analog baseband signal; in the dynamic beam forming processing, firstly, digital baseband signals are generated through sampling, and part of the digital baseband signals are subjected to azimuth resolving, geometric analysis and AIRS beam forming within the direction finding duration to obtain a phase shift matrix and a gain matrix of the active intelligent reflecting surface for dynamic beam forming of the active intelligent reflecting surface; other digital baseband signals obtain azimuth information of a sea surface signal source under the view angle of the airborne base station based on power statistics so as to realize DOA (Direction of Arrival) estimation.

Description

Technical Field

[0001] This invention belongs to the field of radar detection technology, specifically relating to a beamforming and sea surface angle of arrival estimation system and method based on intelligent reflector, used to accurately estimate the angle of arrival of distant sea surface signal sources when the sea surface multipath effect is significant. Background Technology

[0002] The sustained and rapid development of the marine economy has placed higher demands on the performance of marine communication technologies. Similar to terrestrial communication systems, various traditional and innovative applications in marine communication systems require high-quality communication connections and strong sensing capabilities, and angle of arrival (DOA) estimation plays a crucial role in wireless communication systems and source localization. The sea surface environment is often affected by factors such as wind, waves, fish activity, and tides, resulting in varying degrees of roughness (waves). The complex multipath effects introduced by these waves significantly impact the estimation accuracy of sea surface DOA systems. Simultaneously, the increasing demands for real-time performance and accuracy in sea surface DOA estimation pose a significant challenge to the estimation performance of sea surface DOA systems.

[0003] Current sea surface DOA estimation techniques are typically based on array antennas, and commonly used algorithms are generally as follows: MUSIC (Multiple Signal Classification) technology: The core of MUSIC lies in constructing a spatial spectrum function using the orthogonality between the noise subspace and the signal direction vector. It then determines the direction of arrival (DOA) of the signal source by searching for spectral peaks in the spatial spectrum. The algorithm first collects received data from an array antenna and calculates the sample covariance matrix. Then, it performs eigenvalue decomposition on the sample covariance matrix, distinguishing it into a signal subspace and a noise subspace. Based on these constructed subspaces, a corresponding noise spatial spectrum function is constructed, and finally, the corresponding DOA estimate is obtained through spectral peak search. However, in environments with multipath propagation, such as rough sea surfaces, the direct wave and the reflected wave from the rough sea surface are highly coherent. This strong coherence results in a difference between the rank of the signal covariance matrix and the rank of the incoherent signal source, leading to signal subspace diffusion. Since the MUSIC algorithm requires signal sources to be incoherent, the diffusion of the signal subspace can cause spectral peak splitting, shifting, or complete disappearance in the estimated spatial spectrum, ultimately resulting in a serious deviation in the DOA estimation result. Furthermore, the dynamic changes in ocean waves further exacerbate the coherence of the signal. Therefore, the performance of traditional MUSIC algorithms degrades significantly when faced with rough sea environments.

[0004] Spatial smoothing technology: The core principle of spatial smoothing is to divide a uniform linear array containing N elements into K overlapping continuous subarrays. Then, the sample covariance matrix of the received signal in each subarray is calculated, and the covariance matrices of all K subarrays are averaged to obtain a full-rank or near-full-rank overall covariance matrix. The reconstructed matrix is ​​then used as input to algorithms based on subspace decomposition, such as MUSIC or Capon, to obtain the DOA estimation result. This technique effectively destroys the correlation between highly coherent multipath signals through subarray averaging, thereby restoring the decomposability of the covariance matrix and improving the DOA estimation accuracy in highly coherent multipath environments. However, spatial smoothing techniques still face significant limitations when dealing with complex multipath effects caused by rough sea surfaces. First, the decoherence capability of this technique mainly depends on the number of subarrays, K. Increasing K can improve the decoherence effect, but it will also reduce the effective physical aperture of the subarrays, leading to a decrease in DOA resolution. Second, the dynamic wave motion causes multipath signals to exhibit non-ideal partial coherence characteristics, and the processing effect of spatial smoothing is significantly weakened under this condition. Finally, the sea surface reflection path changes rapidly with the dynamic fluctuations of the waves, which makes it difficult for the reconstructed smooth covariance matrix to converge stably, causing significant fluctuations in the DOA estimation results and reducing the algorithm's environmental adaptability and DOA estimation accuracy.

[0005] Compressed sensing technology: DOA estimation based on compressed sensing models DOA estimation as a sparse signal recovery problem. Its core principle lies in constructing an overcomplete azimuth dictionary matrix Φ, representing the array-received signal as a sparse vector S, where the non-zero elements of the sparse vector S correspond to the true DOA of the signal source. By solving a constraint optimization problem, the sparse angular distribution can be directly recovered from the received signal. Compressed sensing has significant advantages in multipath environments at sea: highly coherent direct waves and sea-reflected waves can be represented in the dictionary as several neighboring angular components. The sparse recovery algorithm can simultaneously estimate the propagation paths of multipath signals, thus avoiding the model collapse problem caused by coherence in traditional subspace algorithms. However, this technology still has certain drawbacks in practical engineering applications: First, the dynamic sea surface causes the reflected signal to spread in the angular domain, which cannot be accurately represented by the preset discrete dictionary grid, leading to increased sparse recovery errors; second, time-varying multipath effects require the dictionary to be updated in real time to match dynamic reflection paths, which significantly increases the solution complexity; in addition, under strong sea clutter background noise, sparsity constraints may suppress the estimation of weak reflection path components. While the impact of the sea surface can be partially mitigated through dynamic dictionary construction or off-grid correction techniques, such improvements will further increase the computational burden on base stations and consume a large amount of computing resources. Summary of the Invention

[0006] The purpose of this invention is to provide a beamforming and sea surface angle of arrival estimation system and method based on intelligent reflective surfaces, which solves the problems of performance degradation and unsatisfactory estimation accuracy of existing technologies when facing rough sea surface environments.

[0007] To achieve the above objectives, the present invention employs the following technical solution: A beamforming and sea surface angle-of-arrival estimation system based on a smart reflector includes an active smart reflector deployed on the sea surface, an airborne array antenna mounted on a flight platform, and an airborne base station, wherein: The airborne array antenna is used to receive radio frequency signals from signal sources on the sea surface and transmit them to the airborne base station; The airborne base station performs down-conversion processing on the radio frequency signal to separate the analog baseband signal, and then performs dynamic beamforming processing based on the analog baseband signal. In the dynamic beamforming processing, a digital baseband signal is first generated through sampling. During the direction finding duration, a portion of the digital baseband signal is used for azimuth calculation and geometric analysis. AIRS Beamforming is used to obtain the phase shift matrix and gain matrix of the active smart reflector, which are then used for dynamic beamforming of the active smart reflector. The remaining digital baseband signals are used to obtain the azimuth information of the sea surface signal source from the airborne base station's perspective based on power statistics. DOA estimate.

[0008] Furthermore, the airborne base station includes a down-conversion processing board, a dynamic beamforming processing board, and AIRS Communication radio frequency link board and Beidou positioning module; among which: The downconversion processing board includes a low-noise amplifier, multiple analog filters, and an analog downconverter connected in sequence; the dynamic beamforming processing board includes... AD The module consists of a sampling module, a channel correction module, and an arbitration module; one output of the punching module is sequentially connected to the signal orientation calculation module and the geometric analysis module. AIRS The beamforming module; another output is connected in sequence to the power statistics module and the coordinate system transformation module; the Beidou positioning module is connected to the geometric analysis module and the coordinate system transformation module.

[0009] Furthermore, the radio frequency signal captured by the airborne array antenna is sent to the low-noise amplifier after reaching the downconverter processing board to amplify the signal amplitude. The amplified signal is then sent to multiple analog filters for bandpass filtering to obtain the analog intermediate frequency signal. The analog intermediate frequency signal is then sent to the analog downconverter to mix the local oscillator signal with the analog intermediate frequency signal and filter it to separate the high-frequency carrier and the analog baseband signal.

[0010] Furthermore, the downconverter processing board at each moment t The internal system will perform a total analysis of the radio frequency signals received by the airborne array antenna. PThe processed analog baseband signal is then sent to the dynamic beamforming processing board. AD Sampling module at each time t Internal total processing of analog baseband signals P Each sample is processed by a down-converter to obtain a digital intermediate frequency (IF) signal. The IF signal obtained from each sample is then corrected by a channel correction module. t The first time on the machine terminal p The digital baseband signal is measured; then, the arbitration module determines whether the current digital baseband signal flows to the signal orientation calculation module or the power statistics module; when p When the number is odd, the digital baseband signal is determined by the arbitration module to be sent to the signal orientation calculation module; otherwise, it is sent to the power statistics module.

[0011] Furthermore, when the determination is made to be a direction signal azimuth calculation module, the digital baseband signal will be sent to the azimuth calculation module based on... MUSIC Algorithm pair t The digital baseband signal at time =0 is used to determine the angle of arrival. DOA Estimate the azimuth information from the airborne perspective; then, the azimuth information is sent to the geometric analysis module, which, based on the data from the airborne base station... AIRS The real-time latitude and longitude coordinates of the active intelligent reflector received by the communication RF link board are analyzed and calculated together with the real-time latitude and longitude coordinates of the flight platform measured by the BeiDou positioning module in the airborne base station to obtain... AIRS The azimuth information of the sea surface signal source and the azimuth information of the flight platform, viewed from the perspective, are transmitted to... AIRS Beamforming module, AIRS The beamforming module calculates based on the two sets of azimuth information. AIRS The phase shift matrix and gain matrix are obtained, and the two matrices are passed through... AIRS The communication RF link board returns to the active smart reflector on the sea surface, enabling dynamic beamforming of the active smart reflector; after completing one dynamic beamforming cycle, the airborne base station obtains the second... p Scan results at each azimuth angle; Complete the first P During the measurement, the power statistics module plots the digital baseband signal corresponding to each azimuth angle into a success rate curve and performs peak finding processing. It then outputs the azimuth information of the sea surface signal source corresponding to the peak value from the perspective of the active intelligent reflector to the coordinate transformation module. The coordinate transformation module outputs the received true azimuth information as the azimuth information of the sea surface signal source from the perspective of the airborne base station, thus obtaining accurate... DOA Estimation results.

[0012] Furthermore, the active intelligent reflective surface includes a main control board, a reflective unit driver board, andAIRS Communication radio frequency link board, Beidou positioning module and uniform area array reflector; AIRS The communication RF link board is used to receive the phase shift matrix and gain matrix sent by the airborne base station. According to the phase shift matrix and gain matrix, the main control board sequentially changes the phase shift and reflection gain of each reflection unit in the uniform area array reflection array through the reflection unit drive board, thereby performing dynamic beamforming; the Beidou positioning module is used to provide latitude and longitude coordinate information to the main control board.

[0013] Beamforming and sea surface angle of arrival estimation methods based on smart reflectors include: The sea surface signal source radiates radio frequency signals to the surrounding area through an omnidirectional antenna. After passing through a direct channel, the radio frequency signals reach the airborne array antenna, which then sends the received radio frequency signals to the downconversion processing board for extraction of analog baseband signals. Airborne base stations perform dynamic beamforming processing on analog baseband signals: first, digital baseband signals are generated through sampling; then, during the direction finding duration, a portion of the digital baseband signal is processed based on azimuth calculation and geometric analysis. AIRS Beamforming is used to obtain the phase shift matrix and gain matrix of the active smart reflector, which are then used for dynamic beamforming of the active smart reflector; the remaining digital baseband signals are used to obtain the azimuth information of the sea surface signal source based on power statistics.

[0014] Furthermore, AIRS The beamforming module's processing steps include: AIRS The beamforming module constructs the first beam based on the received azimuth information. p In this measurement AIRS Far-field function of reflected signal With the target far-field function And establish the optimization problem:

[0015]

[0016] Where exp is the natural exponential function. j The imaginary unit; For the uniform area reflective array, the first m OK n The number of reflection units in the column at the first p The phase shift introduced in the digital baseband signal of the second measurement; the uniform array of the active smart reflector has a total of M OK N List of reflective units; d y and d xThe longitudinal center-to-center distance and the transverse center-to-center distance of each reflective unit; The wavelength of the radio frequency signal emitted by the sea surface signal source is given; the normal vector of the uniform area array reflection array is taken as... X Axis construction AIRS Local coordinate system For the local incident azimuth and incident elevation angles in the local coordinate system; These are the launch azimuth and launch elevation angles; For a uniform area reflective array, the reflecting element is at the first... p Phase shift introduced into the digital baseband signal of the second measurement; These are the azimuth and phase shift parameters; The target far-field function is constructed as follows:

[0017] Optimization problem:

[0018] in Active intelligent reflective surface AIRS Maximum signal gain, , These represent the phase shift matrix and the gain matrix, respectively.

[0019] Furthermore, the optimization problem is solved using a genetic algorithm, including: First, construct a structure with a size of... Individual:

[0020] The gene range is , , for AIRS No. m OK n The gain coefficient and phase shift coefficient of each reflective unit in the column; To minimize the optimization problem, a fitness function is designed. as follows:

[0021] Individual selection is conducted in the form of a tournament. Individuals are continuously randomly selected from the population, their fitness is calculated, and the two individuals with the highest fitness are retained as parents. Simulated binary crossover is then performed to obtain offspring genes until the population size is restored. Subsequently, Gaussian perturbations are added to the gain coefficients and phase coefficients of the offspring genes to act as mutations, and constraints are applied to complete one round of iteration. Once the preset number of rounds or the fitness function value converges to the preset threshold, the optimal solution can be obtained, thus yielding the phase shift matrix and gain matrix that satisfy the constraints.

[0022] Furthermore, when the receiver counter of the power statistics module reaches... T At that time, the power statistics module will perform superposition analysis according to the following formula:

[0023] in For target power ， For a moment t Inner p During the measurement process AIRS Incident azimuth in local coordinate system The power of the digital baseband signal received at the corresponding power statistics module; where, , The duration of the direction finding behavior; P For a moment t Total number of measurements of radio frequency signals by the onboard base station; The preset azimuth scanning parameters are used; the power statistics module calculates... corresponding This allows us to obtain the true azimuth information of the sea surface signal source and output the true azimuth information to the coordinate system transformation module.

[0024] A terminal device includes a processor, a memory, and a computer program stored in the memory; when the processor executes the computer program, it implements the beamforming and sea surface angle of arrival estimation method based on a smart reflector.

[0025] A computer-readable storage medium storing a computer program; when executed by a processor, the computer program implements the beamforming and sea surface angle of arrival estimation method based on a smart reflector.

[0026] Compared with the prior art, the present invention has the following technical features: This invention is based on the study of the time-varying characteristics of multipath channels on the sea surface. By deploying AIRS on the sea surface and dynamically adjusting its reflection phase and reflection gain, and by using an airborne base station to superimpose the signal power at different times and azimuth angles at the AIRS to obtain a power curve, a precise DOA azimuth angle result can be obtained. The overall structure is scientific and reasonable, easy to install, low in manufacturing cost, and environmentally friendly, making it easy to popularize and promote its use. Attached Figure Description

[0027] Figure 1 This is a system model diagram of the present invention; Figure 2 This is a schematic diagram of the system structure of the present invention; Figure 3 This is a flowchart of the genetic algorithm; Figure 4 This is a comparison diagram (azimuth plane) of the main lobe of the reflected wave at different times in an embodiment of the present invention; Figure 5 These are thermal images of the optimized reflected beams of AIRS at different times in this embodiment of the invention. Figure 6 These are IRS phase matrix diagrams at different times in embodiments of the present invention; Figure 7 This is a comparison chart of the root mean square error (RMSE) of DOA estimation results of different algorithms under different SNR conditions in the embodiments of the present invention. Detailed Implementation

[0028] This invention provides a beamforming and sea surface angle of arrival estimation system and method based on intelligent reflectors. It makes full use of the time-varying characteristics of sea surface multipath channels and achieves high-precision DOA estimation of sea surface signal sources in rough sea surface environments through genetic algorithms and power superposition processing, while accurately obtaining robust processing results.

[0029] See Figure 1 and Figure 2 The system of the present invention includes an airborne array antenna, an airborne base station, and an active intelligent reflector (AIRS); the airborne base station and the airborne array antenna are deployed together on a flight platform, and the active intelligent reflector (AIRS) is deployed on the sea surface; wherein the flight platform can be, for example, a helicopter, a drone, etc., with a flight altitude of 0~500m.

[0030] 1. Sea surface signal source.

[0031] The antenna used for the direction finding target (sea surface signal source) in this invention system is an omnidirectional antenna or other antenna without directional radiation function. The sea surface signal source radiates radio frequency signals to the surrounding area through the omnidirectional antenna, and the radio frequency signals reach the airborne array antenna after passing through the direct-path channel.

[0032] A direct channel exists between the signal source and the airborne base station. However, after the active intelligent reflector (AIRS) performs beamforming, the signal source signal is reflected and amplified in the AIRS. Therefore, the signal reaching the airborne base station is mainly the AIRS reflected signal, and the original signal from the signal source to the base station through the direct channel is negligible. Thus, the signal processed is also the AIRS reflected signal.

[0033] 2. Airborne array antenna.

[0034] The airborne array antenna is a high-performance active electronically scanned phased array (AESA). AESA The airborne array antenna receives radio frequency signals from a signal source on the sea surface and sends them to the downconversion processing board in the airborne base station for extraction of analog baseband signals.

[0035] 3. Airborne base station.

[0036] Airborne base stations include downconversion processing boards, dynamic beamforming processing boards, AIRS The communication RF link board and BeiDou positioning module; the downconversion processing board includes a low-noise amplifier, multiple analog filters, and an analog downconverter; the dynamic beamforming processing board includes... AD Sampling module, channel correction module, signal orientation calculation module, geometric analysis module AIRS Beamforming module, arbitration module, power statistics module, and coordinate system transformation module.

[0037] The radio frequency signal captured by the airborne array antenna is sent to a low-noise amplifier after reaching the down-converter processing board to amplify the signal amplitude. The amplified signal is then sent to multiple analog filters for bandpass filtering to obtain the analog intermediate frequency (IF) signal near the airborne array antenna frequency. Subsequently, the analog IF signal is sent to an analog down-converter, where the local oscillator signal and the analog IF signal are mixed and filtered to separate the high-frequency carrier and the analog baseband signal, so that the dynamic beamforming processing board can process the signal. AD The sampling module performs sampling processing.

[0038] Downconverter processing board at each moment t The internal system will perform a total analysis of the radio frequency signals received by the airborne array antenna. P The second measurement process, followed by the transmission of the resulting analog baseband signal to the dynamic beamforming processing board: AD Sampling module at each time t Internal total processing of analog baseband signals P Each sample is processed by a down-converter to obtain a digital intermediate frequency (IF) signal. The IF signal obtained from each sample is then corrected by a channel correction module. t The first time on the machine terminal p The received signal in this measurement is the digital baseband signal; subsequently, the arbitration module determines whether the current digital baseband signal flows to the signal orientation calculation module or the power statistics module; when p When the number is odd, the digital baseband signal is determined by the arbitration module to be sent to the signal orientation calculation module; otherwise, it is sent to the power statistics module. When the signal is determined to be flowing into the azimuth calculation module, the digital baseband signal will be sent to the azimuth calculation module based on... MUSIC Algorithm pair t The digital baseband signal at time =0 is used to determine the angle of arrival. DOA Estimate the azimuth information from the airborne perspective; then, the azimuth information is sent to the geometric analysis module, which, based on the data from the airborne base station... AIRS The communication radio frequency link board received AIRSThe real-time latitude and longitude coordinates of the flight platform are analyzed and calculated together with the real-time latitude and longitude coordinates of the flight platform measured by the BeiDou positioning module in the airborne base station to obtain... AIRS The azimuth information of the sea surface signal source and the azimuth information of the flight platform, viewed from the perspective, are transmitted to... AIRS Beamforming module, AIRS The beamforming module calculates based on the two sets of azimuth information. AIRS The phase shift matrix and gain matrix are obtained, and the two matrices are passed through... AIRS The communication RF link board returns the signal to the active smart reflector on the sea surface, enabling dynamic beamforming of the active smart reflector. After completing one dynamic beamforming cycle, the airborne base station obtains the scanning results. At this point, the arbitration module will decide on the next digital baseband signal, which is... t Time of the first p The +1 input digital baseband signal is sent to the power statistics module; the power statistics module locally stores the received signal level and corresponding angle information of this digital baseband signal; subsequently, the arbitration module will... t within p The +2 input digital baseband signals are then sent to the signal orientation calculation module, and this process is repeated until completion. t within P Second measurement.

[0039] In the last P During the measurement, the arbitration module transmits the digital baseband signal to the power statistics module. The power statistics module plots the success rate curves of the digital baseband signal corresponding to each azimuth angle, performs peak finding processing, and outputs the azimuth angle information of the sea surface signal source from the perspective of the active intelligent reflector corresponding to the peak value to the coordinate transformation module. The coordinate transformation module outputs the received true azimuth angle information as the azimuth information of the sea surface signal source from the perspective of the airborne base station, thus obtaining accurate azimuth information. DOA Estimation results.

[0040] 3. Active intelligent reflective surface ( AIRS ).

[0041] The active intelligent reflector includes a main control board, a reflector unit driver board, AIRS Communication radio frequency link board, Beidou positioning module and possess M OK N A uniform surface reflective array of column reflective units.

[0042] AIRS The communication RF link board is used to receive the phase shift matrix and gain matrix sent by the airborne base station. According to the phase shift matrix and gain matrix, the main control board sequentially changes the phase shift and reflection gain of each reflection unit in the uniform area array reflection array through the reflection unit drive board, thereby performing dynamic beamforming; the Beidou positioning module is used to provide latitude and longitude coordinate information to the main control board.

[0043] Both the single active intelligent reflector and the single sea surface signal source are deployed on the sea surface. The array normal vector of the uniform surface reflector array continuously points to the midpoint of the line connecting the sea surface signal source and the flight platform. The projection of the angle between the sea surface signal source, the active intelligent reflector, and the flight platform on the sea surface is less than 180°, and it is recommended not to exceed 150°.

[0044] Based on the above technical solutions, the present invention further provides a beamforming and sea surface angle of arrival estimation method based on a smart reflector, comprising the following steps: Step 1: The sea surface signal source radiates radio frequency signals to the surrounding area through an omnidirectional antenna. After passing through the direct-path channel, the radio frequency signals reach the airborne array antenna. The airborne array antenna sends the received radio frequency signals to the downconversion processing board for extraction of analog baseband signals.

[0045] Step 2: After the RF signal reaches the downconverter processing board, it is sent to a low-noise amplifier to amplify the signal amplitude. The amplified signal is then sent to multiple analog filters for bandpass filtering to obtain the analog intermediate frequency (IF) signal near the airborne array antenna frequency. Subsequently, the analog IF signal is sent to the analog downconverter, where the local oscillator signal and the analog IF signal are mixed and filtered to separate the high-frequency carrier and the analog baseband signal, so that the dynamic beamforming processing board can... AD The sampling module performs sampling processing.

[0046] Downconverter processing board at each moment t The internal system will perform a total analysis of the radio frequency signals received by the airborne array antenna. P The second processing step involves sending the resulting analog baseband signal to the dynamic beamforming processing board. AD Sampling module at each time t Internal total processing of analog baseband signals P Each sample is processed by a down-converter to obtain a digital intermediate frequency (IF) signal. The IF signal obtained from each sample is then corrected by a channel correction module. t The first time on the machine terminal p The received signal in this measurement is also the digital baseband signal. Its composition is as follows:

[0047] In the formula For the first p Additive white Gaussian noise during the measurement process; the uniform array of the active smart reflective surface has a total of M OK N List a reflection unit, For the uniform area reflective array, the first m OK n The number of reflection units in the column at the firstp The phase shift introduced into the digital baseband signal in this measurement For the first p During the second measurement, each reflecting unit... p The gain generated by the digital baseband signal in this measurement M OK N Column gain matrix; e It is a natural constant. j The imaginary unit, for t Within a certain time p During the measurement process, the sea surface signal source reaches the uniform surface reflection array via the sea surface channel. m OK n The radio frequency signal at the reflective unit of the column is composed as follows:

[0048] in and These are the sea surface signal source and the first r The incident azimuth and incident elevation angles of the scattering points at the active smart reflector surface R The number of scattering points; for t Within a certain time p Radio frequency signals emitted by the sea surface signal source during this measurement process d y and d x The longitudinal center-to-center spacing and the transverse center-to-center spacing of each reflective unit are given. The wavelength of the radio frequency signal emitted by the sea surface signal source. For the uniform area reflective array, the first m OK n The reflection unit of the column in t Within a certain time p Additive white Gaussian noise in the measurement.

[0049] Step 3, t =0 time p =During the first measurement, the active smart reflector did not perform beamforming-related operations because the airborne base station did not perform beamforming-related operations. AIRS Gain matrix With phase shift matrix All were random; apart from that, in the remaining measurement process AIRS Gain matrix With phase shift matrix All are provided by the airborne base station; the channel correction module performs signal correction on the digital intermediate frequency signal to obtain the signal. t Time onboard terminal p The digital baseband signal measured ,whenp When the number is odd, the digital baseband signal is determined by the arbitration module to be used for sea surface orientation. The signal is then transmitted to the signal azimuth calculation module, which is based on... MUSIC Algorithm pair t digital baseband signal at time conduct DOA The system estimates the azimuth information of the sea surface signal source from the airborne perspective. Simultaneously, to achieve the scanning function, the signal azimuth calculation module calculates the azimuth angle based on a preset azimuth scanning parameter range. by For step length in MUSIC A fixed offset is superimposed on the azimuth information estimated by the algorithm; if used for sea surface orientation, the fixed offset is... .

[0050] Step 4: The azimuth information estimated by the signal azimuth calculation module is sent to the geometric analysis module. The geometric analysis module then calculates the azimuth information based on the information from the airborne base station. AIRS The communication radio frequency link board received AIRS The real-time latitude and longitude coordinates of the flight platform are analyzed and calculated together with the real-time latitude and longitude coordinates of the flight platform measured by the BeiDou positioning module in the airborne base station to obtain... AIRS The location information of the sea surface signal source and the location information of the flight platform from the perspective of [the above]. t Time of the first p The incident azimuth angle of the active intelligent reflector during this measurement process Pitch angle and reflection azimuth Pitch angle These two pieces of location information were transmitted to AIRS The beamforming module calculates based on two sets of azimuth information. AIRS phase shift matrix and gain matrix .

[0051] Step 5, AIRS The beamforming module constructs the first beam based on the received azimuth information. p In this measurement dB as a unit AIRS Far-field function of reflected signal With the target far-field function And establish the optimization problem:

[0052]

[0053] Where exp is the natural exponential function, and the normal vector of the uniform area reflection array is... X Axis construction AIRS Local coordinate system Here are the local incident azimuth and incident elevation angles in the local coordinate system; correspondingly, These are the launch azimuth and launch elevation angles; For a uniform area reflective array, the reflecting element is at the first... p Phase shift introduced into the digital baseband signal of the second measurement; far-field function Perform normalization; These are the azimuth and phase shift parameters.

[0054] Similarly, construct the target far-field function:

[0055] Optimization problem:

[0056] in Active intelligent reflective surface AIRS Maximum signal gain ( dB ), Refers to the phase shift matrix and gain matrix This is a problem of minimizing the input variables.

[0057] Step 6, due to the optimization problem constructed in step 5 P Since the surface is not convex, a genetic algorithm is used for optimization to obtain the desired solution. AIRS The phase shift matrix and gain matrix; AIRS The beamforming module transmits the calculated phase shift matrix and reflection gain matrix to the airborne base station. AIRS The communication RF link board returns data to the active smart reflector via a dedicated wireless link. AIRS of AIRS Communication radio frequency link board. For example... Figure 3 As shown, the optimization process of the genetic algorithm is as follows: First, construct a structure with a size of... Individual:

[0058] The gene range is , , for AIRS No. m OK n The gain coefficient and phase shift coefficient of each reflective unit in the column.

[0059] To minimize Design fitness function for Negative numbers:

[0060] The genetic algorithm uses a tournament format for individual selection, continuously randomly drawing individuals from the population, calculating their fitness, and retaining the two individuals with the highest fitness as parents for simulated binary crossover. SBX Obtain offspring genes until the population size recovers:

[0061] in and That is, the two selected parent individuals. The hybridization rate determines the amount of gene hybridization; subsequently, the gain coefficient and phase coefficient in the genes of the offspring individuals are summed and averaged. and The Gaussian perturbation is treated as a mutation, and then constraints are applied to complete one round; the constraint application is as described above. Once the preset number of rounds is completed or the fitness function value converges to the preset threshold, the optimal solution can be obtained. The gain coefficient and phase coefficient contained in the individual of the optimal solution constitute the phase shift matrix and gain matrix that satisfy the constraints.

[0062] Step 7, AIRS The beamforming module transmits the calculated phase shift matrix and gain matrix information to the airborne base station. AIRS Communication RF link board transmits to active smart reflector AIRS On AIRS Communication radio frequency link board.

[0063] Step 8, Active Smart Reflector AIRS The main control board will receive the phase shift matrix and gain matrix information and sequentially change the phase shift and reflection gain of each reflection unit in the uniform area array reflection array through the reflection unit drive board.

[0064] Step 9, because the signal strength of the original direct channel is relatively lower than that of the active smart reflector... AIRS The enhanced signal after reflection is negligible, therefore the airborne array antenna in the first... p During the +1 measurement process, the main receiver will be... AIRS The reflected radio frequency signal; the arbitration module on the airborne base station will determine based on... p Whether the number is odd or even, the decision will send the digital baseband signal to the signal location calculation module or the power statistics module.

[0065] Step 10, the airborne base station passes through t Repeat steps 1 through 9 continuously. P The entire direction finding process lasted for [number] times. T ;when t = TAt that time, the signal orientation calculation module and the power statistics module each received T * P / 2nd digital baseband signal, which also means obtaining 0~ T Within a certain time period P Group AIRS Local coordinate system Inner For each local incident azimuth at intervals The strength of the digital baseband signal; when the receiver counter of the power statistics module reaches... T At that time, the power statistics module will perform superposition analysis according to the following formula:

[0066] in For target power ， For a moment t Inner p During the measurement process AIRS Incident azimuth in local coordinate system The power of the digital baseband signal received at the corresponding power statistics module; the power statistics module calculates the power of the digital baseband signal. corresponding This allows the acquisition of the azimuth information of the sea surface signal source, and the output of the true azimuth information to the coordinate system transformation module.

[0067] Step 11: The coordinate system transformation module calculates the precise azimuth information estimation result of the sea surface signal source from the airborne perspective based on the real-time latitude and longitude data of the airborne base station obtained by the Beidou positioning module and the azimuth information of the sea surface signal source sent by the power statistics module.

[0068] Example: Figure 4 It shows different moments, AIRS -Airborne base station connection AIRS A cross-sectional view of the main lobe of the reflected beam, and Figure 5 Fully displayed AIRS Thermal maps of the reflected beams from different perspectives. Both images demonstrate the superior dynamic tracking characteristics of the system of this invention. The red main lobe region effectively locks onto the flying object, reflecting the incident signal from the sea surface signal source onto the flying object. Figure 6 Showing different moments AIRS The phase matrix diagram was used to verify the rationality of the optimization results. Figure 7 For different SNR Different algorithms under different conditions DOA Root mean square error of the estimation results ( RMSE (Comparison chart. As can be seen from the chart, the system proposed in this invention...) DOA Estimated performance compared to traditional methods relying solely on airborne array antennasDOA The estimation algorithm shows a significant performance improvement. With... SNR With the improvement of [something], the number of scattering points on the sea surface decreases. DOA Accuracy has been significantly improved, with a signal-to-noise ratio greater than 20. dB hour DOA The estimated results RMSE It's already close to the lower boundary of Crame-Roll.

[0069] In summary, this invention fully utilizes the time-varying characteristics of multipath channels on the sea surface, and achieves high-precision detection of sea surface signal sources in rough sea environments through genetic algorithms and power superposition processing. DOA It can estimate and at the same time accurately obtain robust processing results.

[0070] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A beamforming and sea surface angle of arrival estimation system based on a smart reflector, characterized in that, This includes active smart reflectors deployed on the sea surface, airborne array antennas mounted on flight platforms, and airborne base stations, among which: The airborne array antenna is used to receive radio frequency signals from signal sources on the sea surface and transmit them to the airborne base station; The airborne base station performs down-conversion processing on the radio frequency signal to separate the analog baseband signal, and then performs dynamic beamforming processing based on the analog baseband signal. In the dynamic beamforming processing, a digital baseband signal is first generated through sampling. During the direction finding duration, a portion of the digital baseband signal is used for azimuth calculation and geometric analysis. AIRS Beamforming is used to obtain the phase shift matrix and gain matrix of the active smart reflector, which are then used for dynamic beamforming of the active smart reflector. The remaining digital baseband signals are used to obtain the azimuth information of the sea surface signal source from the airborne base station's perspective based on power statistics. DOA estimate.

2. The beamforming and sea surface angle of arrival estimation system based on intelligent reflector surface according to claim 1, characterized in that, Airborne base stations include downconversion processing boards, dynamic beamforming processing boards, AIRS Communication radio frequency link board and Beidou positioning module; among which: The downconversion processing board includes a low-noise amplifier, multiple analog filters, and an analog downconverter connected in sequence; the dynamic beamforming processing board includes... AD The module consists of a sampling module, a channel correction module, and an arbitration module; one output of the punching module is sequentially connected to the signal orientation calculation module and the geometric analysis module. AIRS The beamforming module; another output is connected in sequence to the power statistics module and the coordinate system transformation module; the Beidou positioning module is connected to the geometric analysis module and the coordinate system transformation module.

3. The beamforming and sea surface angle of arrival estimation system based on intelligent reflector surface according to claim 1, characterized in that, After the radio frequency signal captured by the airborne array antenna reaches the downconverter processing board, it is sent to the low noise amplifier to amplify the signal amplitude. The amplified signal is then sent to multiple analog filters for bandpass filtering to obtain the analog intermediate frequency signal. The analog intermediate frequency signal is fed into the analog downconverter, where the local oscillator signal and the analog intermediate frequency signal are mixed and filtered to separate the high-frequency carrier and the analog baseband signal.

4. The beamforming and sea surface angle of arrival estimation system based on intelligent reflector surface according to claim 1, characterized in that, Downconverter processing board at each moment t The internal system will perform a total analysis of the radio frequency signals received by the airborne array antenna. P The processed analog baseband signal is then sent to the dynamic beamforming processing board. AD Sampling module at each time t Internal total processing of analog baseband signals P Each sample is processed by a down-converter to obtain a digital intermediate frequency (IF) signal. The IF signal obtained from each sample is then corrected by a channel correction module. t The first time on the machine terminal p The digital baseband signal measured in this test; The arbitration module then determines whether the current digital baseband signal is flowing to the signal orientation calculation module or the power statistics module. when p When the number is odd, the digital baseband signal is determined by the arbitration module to be sent to the signal orientation calculation module; otherwise, it is sent to the power statistics module.

5. The beamforming and sea surface angle of arrival estimation system based on intelligent reflector surface according to claim 1, characterized in that, When the signal is determined to be flowing into the azimuth calculation module, the digital baseband signal will be sent to the azimuth calculation module based on... MUSIC Algorithm pair t The digital baseband signal at time =0 is used to determine the angle of arrival. DOA Estimate and obtain azimuth information from the airborne perspective; Subsequently, the azimuth information is sent to the geometric analysis module, which then analyzes it based on the information from the airborne base station. AIRS The real-time latitude and longitude coordinates of the active intelligent reflector received by the communication RF link board are analyzed and calculated together with the real-time latitude and longitude coordinates of the flight platform measured by the BeiDou positioning module in the airborne base station to obtain... AIRS The azimuth information of the sea surface signal source and the azimuth information of the flight platform, viewed from the perspective, are transmitted to... AIRS Beamforming module, AIRS The beamforming module calculates based on the two sets of azimuth information. AIRS The phase shift matrix and gain matrix are obtained, and the two matrices are passed through... AIRS The communication radio frequency link board returns to the active smart reflector on the sea surface, realizing dynamic beamforming of the active smart reflector; After completing one dynamic beamforming cycle, the airborne base station obtains the first... p Scan results at each azimuth angle; Complete the first P During the measurement, the power statistics module plots the digital baseband signal corresponding to each azimuth angle into a success rate curve and performs peak finding processing. It then outputs the azimuth information of the sea surface signal source corresponding to the peak value from the perspective of the active intelligent reflector to the coordinate transformation module. The coordinate transformation module outputs the received true azimuth information as the azimuth information of the sea surface signal source from the perspective of the airborne base station, thus obtaining accurate... DOA Estimation results.

6. The beamforming and sea surface angle of arrival estimation system based on intelligent reflector surface according to claim 1, characterized in that, The active intelligent reflector includes a main control board, a reflector unit driver board, AIRS Communication radio frequency link board, Beidou positioning module and uniform area array reflector; AIRS The communication RF link board is used to receive the phase shift matrix and gain matrix sent by the airborne base station. According to the phase shift matrix and gain matrix, the main control board sequentially changes the phase shift and reflection gain of each reflection unit in the uniform area array reflection array through the reflection unit drive board, thereby performing dynamic beamforming. The BeiDou positioning module is used to provide latitude and longitude coordinate information to the main control board.

7. A method for beamforming and sea surface angle of arrival estimation based on intelligent reflectors, characterized in that, include: The sea surface signal source radiates radio frequency signals to the surrounding area through an omnidirectional antenna. After passing through a direct channel, the radio frequency signals reach the airborne array antenna, which then sends the received radio frequency signals to the downconversion processing board for extraction of analog baseband signals. Airborne base stations perform dynamic beamforming processing on analog baseband signals: first, digital baseband signals are generated through sampling; then, during the direction finding duration, a portion of the digital baseband signal is processed based on azimuth calculation and geometric analysis. AIRS Beamforming is used to obtain the phase shift matrix and gain matrix of the active smart reflector, which are then used for dynamic beamforming of the active smart reflector. The remaining digital baseband signals are used to obtain the azimuth information of the sea surface signal source based on power statistics.

8. The beamforming and sea surface angle of arrival estimation method based on intelligent reflector surface according to claim 7, characterized in that, AIRS The beamforming module's processing steps include: AIRS The beamforming module constructs the first beam based on the received azimuth information. p In this measurement AIRS Far-field function of reflected signal With the target far-field function And establish the optimization problem: Where exp is the natural exponential function. j The imaginary unit; For the uniform area reflective array, the first m OK n The number of reflection units in the column at the first p The phase shift introduced in the digital baseband signal of the second measurement; the uniform array of the active smart reflector has a total of M OK N List of reflective units; d y and d x The longitudinal center-to-center distance and the transverse center-to-center distance of each reflective unit; The wavelength of the radio frequency signal emitted by the sea surface signal source is given; the normal vector of the uniform area array reflection array is taken as... X Axis construction AIRS Local coordinate system For the local incident azimuth and incident elevation angles in the local coordinate system; These are the launch azimuth and launch elevation angles; For a uniform area reflective array, the reflecting element is at the first... p Phase shift introduced into the digital baseband signal of the second measurement; These are the azimuth and phase shift parameters; The target far-field function is constructed as follows: Optimization problem: in Active intelligent reflective surface AIRS Maximum signal gain, , These represent the phase shift matrix and the gain matrix, respectively.

9. The beamforming and sea surface angle of arrival estimation method based on intelligent reflector surface according to claim 7, characterized in that, Solving the optimization problem using a genetic algorithm includes: First, construct a structure with a size of... Individual: The gene range is , , for AIRS No. m OK n The gain coefficient and phase shift coefficient of each reflective unit in the column; To minimize the optimization problem, a fitness function is designed. as follows: Individual selection is conducted in the form of a tournament. Individuals are continuously randomly selected from the population, their fitness is calculated, and the two individuals with the highest fitness are retained as parents. Simulated binary crossover is then performed to obtain offspring genes until the population size is restored. Subsequently, Gaussian perturbations are added to the gain coefficients and phase coefficients of the offspring genes to act as mutations, and constraints are applied to complete one round of iteration. Once the preset number of rounds or the fitness function value converges to the preset threshold, the optimal solution can be obtained, thus yielding the phase shift matrix and gain matrix that satisfy the constraints.

10. The beamforming and sea surface angle of arrival estimation method based on intelligent reflector surface according to claim 7, characterized in that, When the power statistics module's receiver counter reaches T At that time, the power statistics module will perform superposition analysis according to the following formula: in For target power ， For a moment t Inner p During the measurement process AIRS Incident azimuth in local coordinate system The power of the digital baseband signal received at the corresponding power statistics module; where, , The duration of the direction finding behavior; P For a moment t Total number of measurements of radio frequency signals by the onboard base station; The preset azimuth scanning parameters are used; the power statistics module calculates... corresponding This allows us to obtain the true azimuth information of the sea surface signal source and output the true azimuth information to the coordinate system transformation module.

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