A method and system for processing collision signals of satellite-borne AIS based on array antenna

Abstract

A method and system for processing collision signals in spaceborne AIS based on an array antenna is disclosed. The method involves acquiring data sequences received by the array antenna, performing channel equalization, and then forming a fixed-direction beam data sequence. Each data sequence is then subjected to FFT transformation to obtain frequency domain data sequences, from which quantity estimates, elevation angle estimates, and azimuth angle estimates θ are calculated. An enhanced beam data sequence is obtained by using an optimal weight matrix W to enhance the received signal at the estimated azimuth angle, while suppressing received signals from other directions. The fixed-direction beam data sequence is demodulated to obtain a first set of AIS message data, and the enhanced beam data sequence is demodulated to obtain a second set of AIS message data. The final AIS message information is obtained based on the two sets of AIS message data. This invention reduces the number of sampling points required to estimate the signal direction, determines signal arrival based on a synchronization sequence, and reduces system coordination complexity.

Description

Technical Field

[0001] This invention belongs to the field of satellite communication technology, and specifically relates to a method and system for processing collision signals of onboard AIS based on an array antenna. Background Technology

[0002] The global shipping industry is developing rapidly, and the AIS system provides effective protection for the safe navigation of ships. At present, the main sources of AIS information for ships worldwide are AIS shore station systems and AIS satellite systems. The near-shore area cannot be covered due to the limited range of AIS shore stations. Satellite AIS systems have a large antenna coverage area, but AIS signal collisions are serious, and the demodulation efficiency in near-shore areas is seriously reduced. The commonly used methods to improve the demodulation performance of collision signals of satellite AIS are: (1) Research new collision signal demodulation algorithms to improve the AIS signal acquisition and demodulation efficiency under poor signal-to-noise conditions (signal collision conditions). At present, the space for improving efficiency through algorithm optimization alone is relatively limited. (2) Use array antennas to reduce the number of ships covered within a single beam range through spatial multi-beam method, thereby reducing the probability of AIS signal collision. This method has good practicality after verification. (3) Research collision signal feature extraction methods to achieve collision signal stripping through feature extraction and remodulation. Summary of the Invention

[0003] This invention proposes a method and system for processing spaceborne AIS collision signals based on an array antenna, which solves the problems of severe AIS signal collisions and high noise in received AIS signals.

[0004] This invention proposes a spaceborne AIS collision signal processing method based on an array antenna, comprising:

[0005] S1. Sample the intermediate frequency signals received by each array antenna to obtain the corresponding data sequences;

[0006] S2. Perform channel equalization processing on each data sequence to ensure that the gain, phase, and zero values ​​of each data sequence meet the consistency requirements.

[0007] S3. After channel equalization processing, each data sequence is demodulated using a fixed beam to form a fixed pointing beam data sequence.

[0008] S4. Perform FFT transform on each data sequence after channel equalization to obtain each frequency domain data sequence. Determine whether the amplitude of the non-AIS frequency band signal in each frequency domain data sequence exceeds a threshold. If it does not exceed the threshold, it is determined that there is no noise interference, and the frequency domain data sequence is directly estimated. If noise interference is determined, the amplitude of the corresponding non-AIS frequency band signal is set to zero, and then IFFT transform is performed to obtain the denoised frequency domain data sequence. Then, the frequency domain data sequence is estimated. The frequency domain data sequence estimation includes: calculating the quantity estimate and elevation angle estimate of each received signal based on the frequency domain data sequence. And the corresponding azimuth estimate θ, and the elevation estimate The corresponding azimuth angle estimate θ is used as the direction of arrival estimate of the corresponding received signal;

[0009] S5. The maximum signal-to-interference ratio beamforming method is used to calculate the optimal weight matrix W for directional beamforming. The optimal weight matrix W is then used to process the received signal from the direction of travel estimated in step S4 to obtain the enhanced beam data sequence.

[0010] S6. Demodulate the fixed pointing beam data sequence to obtain the first group of AIS message data, and demodulate the enhanced beam data sequence to obtain the second group of AIS message data;

[0011] S7. Obtain the final AIS message information based on the first group of AIS message data and the second group of AIS message data.

[0012] Furthermore, in S2, the channel equalization process performed on each data sequence to ensure that the gain, phase, and zero values ​​of each data sequence meet the consistency requirements further includes:

[0013] (1) Assume that the channel gain responses corresponding to each data sequence are A1-A1, A2, A3, A4, A5, A6, A7, A8, A9, A1 ... N Then for sampled data A i Multiply by A1 / A N Adjust the amplitude, where A i ∈[A1,A N ], where i is the receiving data channel number, i = 1, ..., N, and N is the total number of receiving data channels;

[0014] (2) Assume that the channel phase response corresponding to each data sequence is θ1-θ N Then for the sampled data θ i Multiply by e -j(θN-θ1) To perform phase adjustment, θ i ∈[θ1,θ N ;

[0015] (3) Assume that the zero-value responses of the channels corresponding to each data sequence are V1-V. N Then, the adjustment is made by zeroing the data in the i-th channel;

[0016] Where i is the receiving data channel number, i = 1, ..., N, and N is the total number of receiving data channels.

[0017] Furthermore, in S4, the estimated quantity and elevation angle of each received signal are calculated based on the frequency domain data sequences. And the azimuth estimate θ, and the elevation estimate The corresponding azimuth angle estimate θ is used as the direction of arrival estimate of the received signal, specifically including:

[0018] Computational spatial spectrum U is the steering vector for the incoming received signals of N channels. n For the noise subspace, scan the spatial spectrum. Obtain the pitch angle And the corresponding azimuth angle θ scan results: N-1 is used as the estimated number of received signals for each channel, where N is the total number of received data channels. The first N-1 signals from the scanning results are selected as the elevation angle estimates. The corresponding azimuth angle estimate θ is then used as the direction estimate of the received signal.

[0019] Furthermore, in S5, the process of processing the estimated received signal from the direction of arrival to obtain the enhanced beam data sequence specifically includes:

[0020] The estimated azimuth angle θ is obtained by using the optimal weight matrix W. d The received signal is filtered to obtain the output power P of the received signal at the corresponding elevation angle.

[0021] According to P=W H R, and Obtain the azimuth angle θ d and the beam steering vector a(θ) corresponding to the pitch angle direction. d ), using a(θ) d Multiplying the received data sequence corresponding to the estimated incoming direction value yields the enhanced beam data sequence; where W is the optimal weight matrix, W H Let W be the conjugate of R, and R be the correlation matrix of each received signal; the correlation matrix of each received signal Where r(i) are the received data sequences of channels 1 to N, and i is the received data channel number, i = 1, ..., N.

[0022] Furthermore, in S7, the removal of duplicate AIS message data specifically includes: comparing the first group of AIS message data and the second group of AIS message data; if the two groups of AIS message data are the same, then only one group of AIS message data is retained; if the two groups of AIS message data are different, then both the first group of AIS message data and the second group of AIS message data are retained.

[0023] This invention also proposes a spaceborne AIS collision signal processing system based on an array antenna, comprising: a signal sampling module, a channel equalization module, a digital beamforming module, a noise and signal feature estimation module, a phase compensation processing module, an AIS message demodulation module, and an AIS message deduplication module;

[0024] The signal sampling module samples the intermediate frequency signals received by each array antenna to obtain the corresponding data sequences and sends them to the channel equalization module.

[0025] The channel equalization module performs channel equalization on each data sequence to ensure that the gain, phase, and zero values ​​of each data sequence meet the consistency requirements, and then sends the data to the digital beamforming module and the noise and signal feature estimation module.

[0026] The digital beamforming module performs fixed beam demodulation on each data sequence to form a fixed-pointing beam data sequence, and sends it to the AIS message demodulation module.

[0027] The noise and signal feature estimation module performs FFT transformation on each data sequence to obtain each frequency domain data sequence. It then determines whether the amplitude of the non-AIS frequency band signal in each frequency domain data sequence exceeds a threshold. If it does not exceed the threshold, there is no noise interference, and the frequency domain data sequence is directly estimated. If noise interference exists, the amplitude of the corresponding non-AIS frequency band signal is set to zero, and then IFFT transformation is performed to obtain the denoised frequency domain data sequences. The frequency domain data sequence estimation process includes: calculating the quantity estimate and elevation angle estimate of each received signal based on the data sequences. And the corresponding azimuth estimate θ, and the elevation estimate The corresponding azimuth angle estimate θ is used as the direction estimate of the received signal and sent to the phase compensation processing module.

[0028] The phase compensation processing module uses the maximum signal-to-interference ratio beamforming method to calculate the optimal weight matrix W for directional beamforming. The optimal weight matrix W is used to process the received signal from the direction of origin estimated by the noise and signal feature estimation module to obtain the enhanced beam data sequence, which is then sent to the AIS message demodulation module.

[0029] The AIS message demodulation module demodulates the fixed beam data sequence to obtain the first set of AIS message data, demodulates the enhanced beam data sequence to obtain the second set of AIS message data, and sends the two sets of AIS message data to the AIS message deduplication module.

[0030] The AIS message deduplication module obtains the final AIS message information based on the first set of AIS message data and the second set of AIS message data.

[0031] Furthermore, the channel equalization module performs channel equalization on each data sequence to ensure that the gain, phase, and zero values ​​of each data sequence meet consistency requirements, further including:

[0032] (1) Assume that the channel gain responses corresponding to each data sequence are A1-A1, A2, A3, A4, A5, A6, A7, A8, A9, A1 ... N Then for sampled data A i Multiply by A1 / A N Adjust the amplitude, where A i ∈[A1,A N ];

[0033] (2) Assume that the channel phase response corresponding to each data sequence is θ1-θ N Then for the sampled data θ i Multiply by e -j(θN-θ1) To perform phase adjustment, θ i ∈[θ1,θ N ];

[0034] (3) Assume that the zero-value responses of the channels corresponding to each data sequence are V1-V. N Then, the adjustment is made by zeroing the data in the i-th channel;

[0035] Where i is the receiving signal channel number, i = 1, ..., N, and N is the total number of receiving signal channels.

[0036] Furthermore, the noise and signal feature estimation module calculates the quantity estimate and elevation angle estimate of each received signal based on the frequency domain data sequences. And the azimuth estimate θ, and the elevation estimate The corresponding azimuth angle estimate θ is used as the direction of arrival estimate of the received signal, specifically including:

[0037] Computational spatial spectrum U is the steering vector for the incoming received signals of N channels. n For the noise subspace, scan the spatial spectrum. Obtain the pitch angle And the corresponding azimuth angle θ scan results: N-1 is used as the estimated number of received signals for each channel, where N is the total number of received data channels. The first N-1 signals from the scanning results are selected as the elevation angle estimates. The corresponding azimuth angle estimate θ is then used as the direction estimate of the received signal.

[0038] Furthermore, the phase compensation processing module processes the estimated received signal from the direction of arrival to obtain an enhanced beam data sequence, specifically including:

[0039] The estimated azimuth angle θ is obtained by using the optimal weight matrix W. d The received signal is filtered to obtain the output power P of the received signal at the corresponding elevation angle.

[0040] According to P=W H R, and Obtain the azimuth angle θ d and the beam steering vector a(θ) corresponding to the pitch angle direction. d ), using a(θ) d Multiplying the received data sequence corresponding to the estimated incoming direction value yields the enhanced beam data sequence; where W is the optimal weight matrix, W H Let W be the conjugate of R, and R be the correlation matrix of each received signal; the correlation matrix of each received signal Where r(i) are the received data sequences of channels 1 to N, and i is the received data channel number, i = 1, ..., N.

[0041] Furthermore, the AIS message deduplication module removes duplicate AIS message data by: comparing the first group of AIS message data and the second group of AIS message data. If the two groups of AIS message data are the same, only one group of AIS message data is retained. If the two groups of AIS message data are different, both the first group of AIS message data and the second group of AIS message data are retained.

[0042] This invention can improve the performance of satellite AIS receiving systems based on array antennas. It adopts a receiving signal processing method that combines noise equalization, the number of received signals, and the direction of arrival estimation. By using noise equalization, the number of sampling points required to estimate the signal direction of arrival through the MUSIC algorithm is reduced, enabling signal arrival determination based on the synchronization sequence and reducing the complexity of system coordination. Attached Figure Description

[0043] Figure 1 This is a block diagram of a spaceborne AIS collision signal processing system based on an array antenna according to the present invention;

[0044] Figure 2 This is a block diagram of a noise and signal feature estimation submodule in a spaceborne AIS collision signal processing system based on an array antenna according to the present invention. Detailed Implementation

[0045] This invention provides a method and system for processing spaceborne AIS collision signals based on an array antenna. The processing method can be implemented by a corresponding processing system using hardware and software. The system includes the following modules: an antenna array, a radio frequency channel, a baseband processing module, and a power supply. The antenna array receives AIS signals, the radio frequency channel amplifies, filters, and controls the frequency conversion of AIS signals, and the baseband processing module includes submodules for signal sampling, digital beamforming, channel equalization, noise and signal feature estimation, phase compensation processing, directional beam processing, and signal demodulation. The signal sampling module implements digital sampling of the input intermediate frequency signals for each RF channel; the digital beamforming module is used for forming multiple fixed beams; the channel equalization module implements gain equalization and noise balancing for each channel, and can adjust the channel equalizer parameters based on the calculation results of the noise and signal characteristic estimation module; the noise and signal characteristic estimation module estimates the noise characteristics from the sampled data, calculates the number of signals, the direction of arrival, power, and start time of each signal, and determines the demodulation reference channel for each signal; the directional signal enhancement processing implements gain enhancement beamforming in the specified direction based on the direction of arrival of each signal, thus supplementing the function of the beamforming module; the signal demodulation module implements buffering, demodulation, and deduplication control of the input AIS signal.

[0046] Please refer to Figure 1 , Figure 1 This is a block diagram of the spaceborne AIS collision signal processing system based on an array antenna according to the present invention. The system configuration in this embodiment is as follows:

[0047] The system comprises the following modules: antenna array, radio frequency channel, power supply, and baseband processing module. Among them:

[0048] Module 10 is an antenna array used to receive AIS signals.

[0049] Module 20 is the radio frequency channel, used to complete AIS signal amplification, filtering, and frequency conversion control.

[0050] Module 30 is the power supply, used to receive external power and provide the secondary voltage required by the entire system.

[0051] Module 40 is the baseband processing module, which includes a signal sampling submodule, a channel equalization submodule, an equalization adjustment submodule, a digital beamforming submodule, a frame header positioning submodule, a noise and signal feature estimation submodule, a phase compensation processing submodule, a directional beam processing submodule, and a signal demodulation submodule.

[0052] Submodule 401 is a signal sampling submodule, used to implement digital sampling of the input intermediate frequency signal of each RF channel.

[0053] Submodule 402 is a channel equalization submodule, used to achieve channel gain equalization, noise equalization and other processing. The channel equalizer parameters can be adjusted according to the calculation results of the noise and signal characteristic estimation module.

[0054] Submodule 403 is the equalization adjustment submodule, which is used to adjust the channel equalization characteristics.

[0055] Submodule 404 is a digital beamforming submodule used to form multiple fixed beams.

[0056] Submodule 405 is a frame header positioning submodule, used to implement the signal search function.

[0057] Submodule 406 is a noise and signal characteristic estimation submodule, used to estimate noise characteristics from sampled data, calculate the number of signals, the direction of arrival, power, and start time of each signal, and determine the demodulation reference channel for each signal.

[0058] Submodule 407 is a phase compensation processing submodule used for channel equalization with feedback adjustment switch.

[0059] Submodule 409 is a directional beam processing submodule, used to achieve gain enhancement beamforming in a specified direction based on each signal, thus supplementing the function of the beamforming module.

[0060] Submodule 410 is a signal demodulation submodule, used to implement input AIS signal buffering, demodulation, and deduplication control.

[0061] To improve the performance of satellite AIS receiving systems based on array antennas, this invention proposes a collision signal processing method that combines noise equalization, collision signal arrival time estimation, collision signal quantity, and direction estimation. Noise equalization reduces the number of sampling points required to estimate the signal direction using the MUSIC algorithm, making it consistent with the time slice for signal arrival determination and arrival time estimation based on synchronization sequences.

[0062] Please refer to Figure 2 , Figure 2 The flowchart of a spaceborne AIS collision signal processing method based on an array antenna includes the following steps:

[0063] Before implementing signal sampling and data processing, the satellite layout of the AIS antennas should be determined, the field of view of each AIS antenna on the ground should be determined, and the beamforming coefficients of each multi-beam on the ground should be calculated based on the field of view of each antenna on the ground.

[0064] Step 101, Signal Sampling: Acquire the received signals from each array antenna, sample the intermediate frequency signals received by each array antenna to obtain the corresponding data sequences, and acquire the sampled sequences X1, X2, ..., X1 of each antenna received signal in a parallel sampling manner. NHere, N represents the number of antenna array elements and serves as the number of each receiving channel; its value ranges from natural numbers. The intermediate frequency signals received by each array antenna are synchronized and sampled at a sampling rate no less than 10 times the AIS message data rate, with a sampling pulse width no less than 12 bits.

[0065] Step 102, Channel Equalization: Perform channel equalization processing on the sampled data of each channel, adjust the gain, phase and zero value of each channel to meet the consistency requirements, and improve the accuracy of subsequent signal search and direction estimation caused by the satellite noise-related characteristics introduced by each channel.

[0066] Adjusting the gain, phase, and zero values ​​of each data stream to meet consistency requirements, further including:

[0067] (1) Assume that the channel gain responses corresponding to each data sequence are A1-A1, A2, A3, A4, A5, A6, A7, A8, A9, A1 ... N Then A N Using A1 as the baseline, the sampled data A i Multiply by A1 / A N Amplitude adjustments are made to achieve consistent response amplitude across all channels, reducing errors in subsequent array processing. After adjustment, the consistent response error across all channels is less than 1 dB; where A i ∈[A1,A N ], where i is the receiving data channel number, i = 1, ..., N, and N is the number of antenna array elements and is used as the total number of receiving data channels, with a value range of natural numbers.

[0068] (2) Assume that the channel phase response corresponding to each data sequence is θ1-θ N , then θ N Using θ1 as a reference, for the sampled data θ i Multiply by e -j(θN-θ1) Perform phase adjustment, θ i ∈[θ1,θ N The meanings of i and N are the same as above. This achieves phase consistency adjustment of each channel response to reduce the error of subsequent array processing. After adjustment, the amplitude consistency response error of each channel is less than 5°.

[0069] (3) Assume that the zero-value responses of the channels corresponding to each data sequence are V1-V. N Then, the adjustment is made by zeroing the data of the i-th channel, specifically by subtracting V from the zero-value response corresponding to channel i. N This ensures that the zero value of the sampled data is zeroed, and that the residual zero value error of each channel after zeroing is less than the last 3 significant bits of the AD sampled data. Here, N is the channel number, and its value range is a natural number.

[0070] Step 103, Digital beamforming: After channel equalization processing, each data sequence is demodulated using a fixed beam demodulation scheme to form a fixed beam, and the AIS signal within the corresponding beam is demodulated to obtain a fixed pointing beam data sequence.

[0071] Step 104, Noise and Signal Feature Estimation: Perform FFT transformation on each data sequence to obtain each frequency domain data sequence. Determine whether the amplitude of the non-AIS frequency band signal in each transformed frequency domain data sequence exceeds a threshold. If it does not exceed the threshold, there is no noise interference, and the frequency domain data sequence is directly estimated. If it exceeds the threshold, there is noise interference, so the amplitude of the corresponding non-AIS frequency band signal is set to zero, and then IFFT transformation is performed to obtain the denoised frequency domain data sequences. Then, the frequency domain data sequences are estimated. The frequency domain data sequence estimation includes: calculating the quantity estimate and elevation angle estimate of each received signal based on the data sequences. And the corresponding azimuth estimate θ, and the elevation estimate The corresponding azimuth angle estimate θ represents the elevation and azimuth angle matrix of the one-dimensional signal, which serves as the estimated direction of arrival for the corresponding received signal.

[0072] Specifically, the MUSIC algorithm is used to calculate the estimated number of received signals and the estimated elevation angle for each channel. And the estimated azimuth angle θ:

[0073] Constructing the spatial spectrum

[0074] in U is the steering vector for the incoming received signals of N channels. n This is the noise subspace, and the superscript "H" indicates the conjugate symbol.

[0075] In practice, the length of the r(i) sequence is no less than 24 bits of duration data. Scanning the two-dimensional spatial spectrum. The local maximum value of the slope of adjacent scan points greater than 2 is determined as the effective signal direction angle, and each signal (signal S1~S2) is obtained. N Pitch angle And azimuth angle θ: That is, pitch angle estimate The azimuth angle estimate θ corresponds to the azimuth angle estimate. The total number of received data channels is subtracted by 1 to obtain the estimated number of received signals, i.e., N-1 is used as the estimated number of received signals for each channel, where N is the total number of received data channels. Then, the first N-1 signals from the effective azimuth angles are selected as the elevation angle estimate. The corresponding azimuth angle estimate θ is then used as the direction of arrival estimate of the received signal. These are the objects to be processed, where N is the number of antenna array elements and the total number of received data channels.

[0076] In practice, during the signal non-crossing phase, the signal quantity is estimated to be 1; during the signal crossing phase, the signal quantity is estimated to be 2.

[0077] Step 105: Phase compensation processing. The optimal weight matrix W for directional beamforming is calculated using the maximum signal-to-interference ratio (SIR) beamforming method. The received signal at the estimated azimuth angle is then processed to obtain the enhanced beam data sequence. The specific implementation method is as follows:

[0078] Using the optimal weight matrix W and the correlation matrix R of each received signal to determine the azimuth angle θ d and corresponding pitch angle The received signal is filtered to obtain the output power P of the received signal.

[0079] According to P=W H R, and Obtain the azimuth angle θ d and corresponding pitch angle Beam steering vector a(θ) from the direction of arrival d ), using a(θ) d Multiplying the received data sequence corresponding to the incoming direction estimate by W yields the enhanced beam data sequence; where W is the optimal weight matrix. H Let W be the conjugate of W, and R be the correlation matrix of each received signal. (Correlation matrix of each received signal) Where r(i) are the received data sequences of channels 1 to N, and i is the received data channel number, i = 1, ..., N.

[0080] Preferably, received signals from other directions can also be suppressed.

[0081] Step 106, AIS message demodulation. The fixed-beam data sequence is demodulated to obtain the first set of AIS message data, and the enhanced-beam data sequence is demodulated to obtain the second set of AIS message data. Specifically, the Viterbi demodulation algorithm is used to reduce the signal-to-noise ratio requirements of demodulation.

[0082] Step 107: AIS packet deduplication. Compare the first group of AIS packet data with the second group of AIS packet data. If the two groups of AIS packet data are the same, remove the duplicate AIS packet data. For example, if the two groups of AIS packet data are the same, remove the second group of AIS packet data and keep the first group of AIS packet data. If the two groups of AIS packet data are different, keep both the first and second groups of AIS packet data. This yields the final AIS packet information. In specific implementation, a timestamp + packet information method is used to remove duplicate AIS packets from each part of the demodulation.

[0083] This invention also proposes a spaceborne AIS collision signal processing system based on an array antenna, the signal processing system being based on... Figure 1 The hardware system architecture shown includes: a signal sampling module, a channel equalization module, a digital beamforming module, a noise and signal feature estimation module, a phase compensation processing module, an AIS message demodulation module, and an AIS message deduplication module.

[0084] The signal sampling module acquires the received signals from each array antenna, samples the intermediate frequency (IF) signals received by each array antenna to obtain the corresponding data sequences. The IF signals received by each array antenna are synchronized, sampled, and sent to the channel equalization module. The sampling rate is no less than 10 times the AIS message data rate, and the sampling pulse width is no less than 12 bits.

[0085] The channel equalization module performs channel equalization on each data sequence to ensure that the gain, phase, and zero values ​​of each data sequence meet the consistency requirements, and then sends the data to the digital beamforming module and the noise and signal feature estimation module; specifically including:

[0086] (1) Let the channel gain responses corresponding to each data sequence be A1-A1, respectively. N Then A N Using A1 as the baseline, the sampled data A i Multiply by A1 / A N After amplitude adjustment, the amplitude consistency response error of each channel is less than 1dB, where A i ∈[A1,A N ], where i is the receiving signal channel number, i = 1, ..., N, and N is the total number of receiving signal channels, the same below.

[0087] (2) Let the channel phase response corresponding to each data sequence be θ1-θ N , then θ N Using θ1 as a reference, for the sampled data θ i Multiply by e -j(θN-θ1) Perform phase adjustment, θ i ∈[θ1,θ N After adjustment, the amplitude consistency response error of each channel is less than 5°.

[0088] (3) Let the zero-value responses of each data sequence be V1-V1, V2, V3, V4, V5, V6, V7, V8, V9, V1, V1, V2, V3, V4, V5 ... N Then, the adjustment is made by zeroing the data of the i-th channel, specifically by subtracting V from the zero-value response corresponding to channel i. N To ensure that the zero value of the sampled data is zeroed, where N is the channel number and the value range is a natural number, the residual zero value error of each channel after zero value adjustment is less than the last 3 significant bits of the AD sampled data.

[0089] The digital beamforming module uses fixed beam demodulation to process each data sequence to form a fixed-point, fixed-beam data sequence.

[0090] The noise and signal feature estimation module performs FFT transform on each data sequence to obtain the frequency domain data sequence. It then determines whether the amplitude of the non-AIS frequency band signal in each frequency domain data sequence exceeds a threshold. If the amplitude does not exceed the threshold, there is no noise interference, and the frequency domain data sequence is directly estimated. Otherwise, noise interference exists, so the amplitude of the corresponding non-AIS frequency band signal is set to zero, and then IFFT transforms it to obtain the denoised frequency domain data sequence. The frequency domain data sequence estimation process includes calculating the quantity estimate and elevation angle estimate of each received signal based on the frequency domain data sequence. And the azimuth estimate θ, and the elevation estimate The corresponding azimuth angle estimate θ is used as the direction estimate of the received signal and sent to the phase compensation processing module.

[0091] The MUSIC algorithm is used to calculate the estimated number of received signals and the estimated elevation angle of each signal. And the estimated azimuth angle θ,

[0092] Scan the spatial spectrum Spatial spectrum

[0093] in, U is the incoming signal steering vector for N channels, where N is the number of antenna array elements and the number of receiving signal channels. n For the noise subspace, scan the spatial spectrum. Obtain the pitch angle And the corresponding azimuth angle θ scan results: N-1 is used as the estimated number of received signals for each channel, where N is the total number of received data channels. The first N-1 signals are selected as the estimated elevation angle. The corresponding azimuth angle estimate θ is then used as the direction estimate of the received signal, which is then used as the object to be processed.

[0094] The phase compensation processing module uses the maximum signal-to-interference ratio (SIR) beamforming method to calculate the optimal weight matrix W for directional beamforming. It then uses this optimal weight matrix W to process the received signal at the estimated azimuth angle to obtain an enhanced beam data sequence; specifically, this includes:

[0095] The estimated azimuth angle θ is obtained by using the optimal weight matrix W. d and corresponding pitch angle The received signal is filtered to obtain the output power P of the received signal.

[0096] P = W H R, and

[0097] The azimuth angle θ of the approach direction is obtained from the above formula. d and the beam steering vector a(θ) corresponding to the pitch angle direction. d ), forming a directional beam; W is the optimal weight matrix, W H Let W be the conjugate of the signal vectors, R be the spatial correlation matrix of the received signal vectors, and the correlation matrix of each received signal be... Where r(i) are the received data sequences of channels 1 to N, and i is the received data channel number, i = 1, ..., N.

[0098] The AIS message demodulation module demodulates the fixed beam data sequence to obtain the first set of AIS message data, and demodulates the enhanced beam data sequence to obtain the second set of AIS message data.

[0099] The AIS message deduplication module obtains the final AIS message information based on the first set of AIS message data and the second set of AIS message data. Specifically, this includes:

[0100] Compare the first set of AIS message data and the second set of AIS message data. If the two sets of AIS message data are the same, only one set of AIS message data is retained. If the two sets of AIS message data are different, both the first set of AIS message data and the second set of AIS message data are retained.

[0101] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A method for processing collision signals in spaceborne AIS based on an array antenna, characterized in that, include: S1. Sample the intermediate frequency signals received by each array antenna to obtain the corresponding data sequences; S2. Perform channel equalization processing on each data sequence to ensure that the gain, phase, and zero values ​​of each data sequence meet the consistency requirements. S3. After channel equalization processing, each data sequence is demodulated using a fixed beam to form a fixed pointing beam data sequence. S4. Perform FFT transformation on each data sequence after channel equalization to obtain each frequency domain data sequence. Determine whether the amplitude of the non-AIS frequency band signal of each frequency domain data sequence exceeds the judgment threshold. If it does not exceed the judgment threshold, it is determined that there is no noise interference, and the frequency domain data sequence is directly estimated. If noise interference is detected, the amplitude of the corresponding non-AIS frequency band signal is set to zero, and then the denoised frequency domain data sequence is obtained by IFFT transformation. Then, the frequency domain data sequence is estimated. The frequency domain data sequence estimation process includes: calculating the quantity estimate and elevation angle estimate of each received signal based on the frequency domain data sequences. And the corresponding azimuth estimate θ, and the elevation estimate The corresponding azimuth angle estimate θ is used as the direction of arrival estimate of the corresponding received signal; S5. The maximum signal-to-interference ratio beamforming method is used to calculate the optimal weight matrix W for directional beamforming. The optimal weight matrix W is then used to process the received signal from the direction of travel estimated in step S4 to obtain the enhanced beam data sequence. S6. Demodulate the fixed pointing beam data sequence to obtain the first group of AIS message data, and demodulate the enhanced beam data sequence to obtain the second group of AIS message data; S7. Obtain the final AIS message information based on the first group of AIS message data and the second group of AIS message data.

2. The method according to claim 1, characterized in that, In S2, the channel equalization process performed on each data sequence to ensure that the gain, phase, and zero values ​​of each data sequence meet the consistency requirements further includes: (1) Assume that the channel gain responses corresponding to each data sequence are A1-A1, A2, A3, A4, A5, A6, A7, A8, A9, A1 ... N Then for sampled data A i Multiply by A1 / A N Adjust the amplitude, where A i ∈[A1,A N ]; (2) Assume that the channel phase response corresponding to each data sequence is θ1-θ N Then for the sampled data θ i Multiply by e -j(θN-θ1) To perform phase adjustment, θ i ∈[θ1,θ N ]; (3) Assume that the zero-value responses of the channels corresponding to each data sequence are V1-V. N Then, the adjustment is made by zeroing the data in the i-th channel; Where i is the receiving data channel number, i = 1, ..., N, and N is the total number of receiving data channels.

3. The method according to claim 2, characterized in that, In S4, the estimated quantity and elevation angle of each received signal are calculated based on the frequency domain data sequences of each channel. And the azimuth estimate θ, and the elevation estimate The corresponding azimuth angle estimate θ is used as the direction of arrival estimate of the received signal, specifically including: Computational spatial spectrum Let N be the incoming signal steering vectors for the N channels. for conjugate, U n For the noise subspace, scan the spatial spectrum. Obtain the pitch angle And the corresponding azimuth angle θ scan results: N-1 is used as the estimated number of received signals for each channel, where N is the total number of received data channels. The first N-1 signals from the scanning results are selected as the elevation angle estimates. The corresponding azimuth angle estimate θ is then used as the direction estimate of the received signal.

4. The method according to claim 3, characterized in that In S5, the process of processing the estimated received signal from the direction of arrival to obtain the enhanced beam data sequence specifically includes: Using the optimal weight matrix W to adjust the azimuth angle θ d The received signal is filtered to obtain the output power P of the received signal at the corresponding elevation angle. According to P=W H R and Obtain the azimuth angle θ d and the beam steering vector a(θ) corresponding to the pitch angle direction. d ), using a(θ) d Multiplying the received data sequence corresponding to the estimated incoming direction value yields the enhanced beam data sequence; where W is the optimal weight matrix, W H Let W be the conjugate of R, and R be the correlation matrix of each received signal; the correlation matrix of each received signal Where r(i) are the received data sequences of channels 1 to N, and i is the received data channel number, i = 1, ..., N.

5. The method according to claim 4, characterized in that, In S7, obtaining the final AIS message information based on the first set of AIS message data and the second set of AIS message data specifically includes: Compare the first set of AIS message data and the second set of AIS message data. If the two sets of AIS message data are the same, only one set of AIS message data is retained. If the two sets of AIS message data are different, both the first set of AIS message data and the second set of AIS message data are retained.

6. A spaceborne AIS collision signal processing system based on an array antenna, characterized in that, include: Signal sampling module, channel equalization module, digital beamforming module, noise and signal feature estimation module, phase compensation processing module, AIS message demodulation module, and AIS message deduplication module; The signal sampling module samples the intermediate frequency signals received by each array antenna to obtain the corresponding data sequences and sends them to the channel equalization module. The channel equalization module performs channel equalization on each data sequence to ensure that the gain, phase, and zero values ​​of each data sequence meet the consistency requirements, and then sends the data to the digital beamforming module and the noise and signal feature estimation module. The digital beamforming module performs fixed beam demodulation on each data sequence to form a fixed-pointing beam data sequence, and sends it to the AIS message demodulation module. The noise and signal feature estimation module performs FFT transformation on each data sequence to obtain each frequency domain data sequence, and determines whether the amplitude of the non-AIS frequency band signal of each frequency domain data sequence exceeds the judgment threshold. If it does not exceed the judgment threshold, there is no noise interference, and the frequency domain data sequence is directly estimated. If there is noise interference, the amplitude of the corresponding non-AIS frequency band signal is set to zero, and then the denoised frequency domain data sequence is obtained by IFFT transformation. Then, the frequency domain data sequence is estimated. The frequency domain data sequence estimation process includes: calculating the quantity estimate and elevation angle estimate of each received signal based on the frequency domain data sequences. And the corresponding azimuth estimate θ, and the elevation estimate The corresponding azimuth angle estimate θ is used as the direction estimate of the received signal and sent to the phase compensation processing module. The phase compensation processing module uses the maximum signal-to-interference ratio beamforming method to calculate the optimal weight matrix W for directional beamforming. The optimal weight matrix W is then used to process the received signal from the direction of travel estimated by the noise and signal feature estimation module to obtain the enhanced beam data sequence, which is then sent to the AIS message demodulation module. The AIS message demodulation module demodulates the fixed pointing beam data sequence to obtain a first set of AIS message data, demodulates the enhanced beam data sequence to obtain a second set of AIS message data, and sends the two sets of AIS message data to the AIS message deduplication module. The AIS message deduplication module obtains the final AIS message information based on the first set of AIS message data and the second set of AIS message data.

7. The system according to claim 6, characterized in that, The channel equalization module performs channel equalization on each data sequence to ensure that the gain, phase, and zero values ​​of each data sequence meet the consistency requirements, and further includes: (1) Assume that the channel gain responses corresponding to each data sequence are A1-A1, A2, A3, A4, A5, A6, A7, A8, A9, A1 ... N Then for sampled data A i Multiply by A1 / A N Adjust the amplitude, where A i ∈[A1,A N ]; (2) Assume that the channel phase response corresponding to each data sequence is θ1-θ N Then for the sampled data θ i Multiply by e -j(θN-θ1) To perform phase adjustment, θ i ∈[θ1,θ N ]; (3) Assume that the zero-value responses of the channels corresponding to each data sequence are V1-V. N Then, the adjustment is made by zeroing the data in the i-th channel; Where i is the receiving signal channel number, i = 1, ..., N, and N is the total number of receiving signal channels.

8. The system according to claim 7, characterized in that, The noise and signal feature estimation module calculates the quantity estimate and elevation angle estimate of each received signal based on the frequency domain data sequences. And the azimuth estimate θ, and the elevation estimate The corresponding azimuth angle estimate θ is used as the direction of arrival estimate of the received signal, specifically including: Computational spatial spectrum Let N be the incoming signal steering vectors for the N channels. for conjugate, U n For the noise subspace, scan the spatial spectrum. Obtain the pitch angle And the corresponding azimuth angle θ scan results: N-1 is used as the estimated number of received signals for each channel, where N is the total number of received data channels. The first N-1 signals from the scanning results are selected as the elevation angle estimates. The corresponding azimuth angle estimate θ is then used as the direction estimate of the received signal.

9. The system according to claim 8, characterized in that, The phase compensation processing module processes the estimated received signal from the incoming direction to obtain an enhanced beam data sequence, specifically including: The estimated azimuth angle θ is obtained by using the optimal weight matrix W. d The received signal is filtered to obtain the output power P of the received signal at the corresponding elevation angle. According to P=W H R, and Obtain the azimuth angle θ d and the beam steering vector a(θ) corresponding to the pitch angle direction. d ), using a(θ) d Multiplying the received data sequence corresponding to the estimated incoming direction value yields the enhanced beam data sequence; where W is the optimal weight matrix, W H Let W be the conjugate of R, and R be the correlation matrix of each received signal; the correlation matrix of each received signal Where r(i) are the received data sequences of channels 1 to N, and i is the received data channel number, i = 1, ..., N.

10. The system according to claim 9, characterized in that, The AIS message deduplication module removes duplicate AIS message data specifically including: Compare the first set of AIS message data and the second set of AIS message data. If the two sets of AIS message data are the same, only one set of AIS message data is retained. If the two sets of AIS message data are different, both the first set of AIS message data and the second set of AIS message data are retained.

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