Zhang Qunfei

Study on the long-distance target apperception techniques for underwater vehicles

Abstract The limited physical size for autonomous underwater vehicles (AUV) or unmanned underwater vehicles (UUV) makes it difficult to acquire enough space gain for localizing long-distance targets. A new technique about long-distance target apperception with passive synthetic aperture array for underwater vehicles is presented. First, a synthetic aperture-processing algorithm based on the FFT transform in the beam space (BSSAP) is introduced. Then, the study on the flank array passive long-distance apperception techniques in the frequency scope of 11–18 kHz is implemented from the view of improving array gains, detection probability and augmenting detected range under a certain sea environment. The results show that the BSSAP algorithm can extend the aperture effectively and improve detection probability. Because of the augment of the transmission loss, the detected range has the trend of decline with the increase of frequency under the same target source level. The synthesized array could improve the space gain by nearly 7 dB and SNR is increased by about 5 dB. The detected range is enhanced to nearly 2 km under the condition of 108–118 dB of the target source level for AUV system in measurement interval of nearly 1 s.

An embedded signal transmitter for UAC based on H-bridge class-D power amplifier

The signal transmitter for underwater acoustic communication (UAC) is a core component of underwater acoustic equipment. To satisfy the demand of underwater acoustic transmitter for small size and high source level, an embedded power amplifier based on H-bridge topology and an independent matching network are designed and implemented. The integrative performance is tested by water pool experiment, and the feasibility and advancement are verified. The test result shows that the prototype can reach the aim of 184.25dB to 187.19dB emission source level and 19% of average total electro-acoustic conversion efficiency within the frequency range of 8~16kHz, which can meet the needs of shipboard and embedded request at 180 × 120 × 70 (mm)3 volume.

Optimal sensor-target geometries analysis for Angle-of-arrival localization

The target position accuracy suffers from the bad relative sensor-target geometries for Angle-of-arrival localization techniques. To reduce the impact, the optimal sensor-target geometries in the 2D plane are investigated based on maximizing the determinant of the Fisher information matrix. To solve the optimal problem, the conditions that the local optimal solutions should satisfy are studied by discussing the first derivative and Hessian matrix. For two sensors with arbitrary distance to the target, it is shown that the optimal geometry is obtained if the two bearing lines are mutually perpendicular. The optimal geometry is studied for more than two sensors with the equal distance. Simulation results illustrate the effectiveness of the proposed the optimal relative sensor-target geometries.

Sparse sample matrix inversion with diagonal loading for reverberation suppression

The main problem of active sonar detection is that the reverberation has spatial and temporal two-dimensional coupling characteristic which is similar to clutters in airborne radar. This paper presents a sparse sample matrix inversion with diagonal loading (SSMI-DL) for reverberation suppression in active sonar. The proposed method transfers Pulse Doppler radar STAP processing techniques into active sonar application, which utilizes the inverse reverberation covariance matrix to obtain adaptive weights and avoids singular reverberation covariance matrix with diagonal loading due to limited available received data. Simulation results are provided to verify that the SSMI-DL is more effective for improving slowly moving target detection for CW pulse than the conventional methods.