Search

In the field of multistatic remote detection for underwater target, as a time-variant and multi-path channel interfered by environmental noise, complex underwater acoustic environment limits the spatial share of channel and poses a great challenge against spatial-division-multiplexing (SDM) in multistatic detection. In this paper, a kind of method of spatial-division-multiplexing(SDM) based on vector adaptive time-reversal technique is proposed. By use of time-reversal technique, multi-path structure of channel is efficiently restrained; Meanwhile, with adaptive filtering applied, time-variant characteristic of channel is effectively suppressed. Moreover, with single vector hydrophone, spatial focus of target echoes and noise interference suppression is accomplished by spatial filtering. Finally, excellent results are performed in SDM of multistatic detection, supported by the experimental simulation.

The detecting performance of active sonar have been affected by the weak targets scattering and serious noise background. If artificial reducing the threshold to get high detecting capability, the false alarm probability will be very high. Therefore, this paper propose a weak target detecting method based on multistatic information fusion. After getting more information about the target from different positions and extracting the target feature vectors to make a fusion, a better recogniting performance will be present. The target scattering centers are extracted by CLEAN technique, which could avoid extracting the false scattering centers, and adapt in low signal to noise ratio (SNR). The neural network classifier is used to make a fusion and recognize the target. Simulation results show that this method has better target identification performance and low false alarm probability, demonstrating the target features fusion has high value for active sonar detecting in the future.

In the field of multistatic remote detection for underwater target, as a time-variant and multi-path channel interfered by environmental noise, underwater acoustic environment limits the spatial share of channel and poses a great challenge against spatial-division-multiplexing(SDM) in multistatic detection. In this paper, a kind of method of spatial-division-multiplexing(SDM) in time-variant channel based on vector adaptive time-reversal technique is proposed. By using time-reversal technique, multi-path structure of channel is efficiently restrained ; Applied adaptive filtering, time-variant characteristic of channel is effectively suppressed; With single vector hydrophone, spatial focus of target echoes and noise interference suppression is accomplished by spatial filtering. Finally, excellent results are performed in spatial-division-multiplexing(SDM) of multistatic detection, supported by the experimental simulation.

A kind of underwater communication receiver combined with Vector Time-Reversal algorithm and multichannel decision feedback equalizer (VTR-MDFE) is studied, which can address the problem of inter-symbol interference and waveform distortion, resulting from time-varying multipath channel. Impacts of environmental noise can be suppressed by use of vector sensor’s combined directivity and Corresponding vector signal processing technology. Meanwhile, error rate is reduced while system capacity is enhanced by time-reversal algorithm’s anti-multipath ability. The performance of VTR-MDFE are proved by simulated results in the communication channel provided by a ray-based acoustic model, for different ocean conditions and source-receiver geometries.

Depending on species-specific characteristics of echolocation and recognition,dolphin could travel in groups without collision, and they could also prey and defend mutually. As a multi-harmonics, frequency-modulated signal, the variety of whistles revealed the rich group identification and location information of free-ranging Indo-Pacific humpback dolphins (Sousa chinensis). This paper introduces the features of whistle on the basis of Joint time-frequency distribution, dealing with recording data collected in the area of Guangxi and Zhanjiang seacoast, in China. Then the ability of individual identification is discussed from the correlation of whistles, we will get the knowledge of dolphins how to cognize the communication information in the complex environment. The transmission loss function will be depicted using the BELLHOP at last. By extracting the acoustical features, the modeling of whistle signal is implemented based on the Sinusoids Model (Buck, 2000). Specifically, the validity of mathematical ...

Strong direct path interference suppression is one of the problems to be solved in AUVs' cluster system which has the advantages of concealment, precision, anti-jamming capability and function distance. In order to estimate the target direction，3 methods of beamforming，including covariance matrix taper(CMT) condition，null-constrained condition and second-order cone programing(SOCP) constraint condition, are used to restrain direct path interference suppression separately in this paper. Comparing the 3 methods with simulation, SOCP gives the weights taking main lobe response, sidelobe level, depth, and width of zeros into consideration; null-constrained condition has a smaller amount of calculate and better anti-interference ability. But when the array disturbance exists, all the methods' performances are not good. Then, an improved algorithm is proposed to improve the tolerance of array disturbances.