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ABSTRACT: Based on the fact that the transfer function vector between a source receiver array and the dominant scatterer of boundary
reverberation at a range can be obtained from the corresponding reverberations scattered from this range cell, a reverberation
nulling concept using time reversal processing has been proposed. However, current reverberation nulling methods have certain
limitations when applied into practice, which would null boundary reverberation and target echo simultaneously. As a solution,
a passive reverberation nulling and echo enhancement method at low frequency using waveguide invariance is proposed in this
paper. In this method, the reverberation subspace for the target range cell is not obtained directly from the return signals
scattered by the target range cell but from the return signals scattered by a range cell located before the target using waveguide
invariance, so as to suppress the reverberation embodied in the target echo by passive reverberation nulling. Besides, a range-dependent
optimal weighting vector rather than conventional projector matrix is deduced to null the reverberation component meanwhile
maximizing the target echo, thereby enhancing the echo-to-reverberation ratio furthest. Numerical simulations in typical range-independent
shallow water environment demonstrate the efficacy and the improved performance of the proposed method for echo-to-reverberation
enhancement.
Keywordsreverberation nulling–echo-to-reverberation enhancement–waveguide invariance–time reversal
Chinese Science Bulletin 04/2012; 56(2):142-150. · 1.32 Impact Factor
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Proceedings of the IEEE International Conference on Wireless Communications, Networking and Information Security, WCNIS 2010, 25-27 June 2010, Beijing, China; 01/2010
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ABSTRACT: A priori knowledge of noise information at array sensors is necessary in the optimization procedure with aim of improving passive broadband detection performance of array. When several noise sources are present and/or an analytical expression of the noise transfer function is not available, the sensor noise needs to be measured in the optimization which is very demanding when an array with large number of sensors is considered. To avoid the tedious work of noise measurement, a new numerical method is developed in this paper. In this method, several noise sources in near field are assigned and the noise responses at the array sensors are calculated via the boundary element method and the result is applied to optimize passive broadband detection performance of array through the adjustment of array shading weights. A sphere array and a cylinder array were taken as examples and water-tank experiment shows the effectiveness of the proposed method. By using this method, the detection performance of a sensor array can be predicted before it is physically built and tested in under practical condition.
Industrial Electronics and Applications, 2009. ICIEA 2009. 4th IEEE Conference on; 06/2009
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ABSTRACT: A passive sonar target can be regarded as a sounder from the viewpoint of sonar operators. The impulse response of the sounder in the cepstrum domain, which shows physical features of targets, can be obtained from the radiated-noise of targets using LPC cepstrum and Mel cepstrum. A set of cepstrum-domain features is extracted based on the above two cepstrums of the impulse response. The neural network target classifier was designed using cepstrum-domain features. The classification experiments were carried out for three different kinds of targets based on practical data. The experimental results show that the feature extraction method based on two cepstrums are useful.
Bioinformatics and Biomedical Engineering, 2008. ICBBE 2008. The 2nd International Conference on; 06/2008
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ABSTRACT: The acoustic diffraction of array supporting structure will result in the large difference of the amplitude and phase response of each hydrophone, which leads to the distortion of beampattern. A method for obtaining the array manifold of arbitrary geometry acoustic array is proposed in this paper. We measured the array response vector in many directions with a fixed angular step in anechoic water tank. The array response vectors were smoothed to eliminate the measurement system error. Using these smoothed array response vectors, the robust beampattern of arbitrary geometry array is obtained via beam synthesis method. A 16 element volumetric acoustic array was constructed and tested in an anechoic water tank. Robust low sidelobe beampatterns based on the measured manifold were formed, and then the beamouputs were used to apply to beamspace high resolution DOA estimation methods. The experimental results show that our method can suppress noise and interferences outside the beam coverage regions, and get high resolution DOA estimation results. When the array geometry has some distortion, the weighting vectors of beamforming can still work well to form good beampatterns, and then get accurate DOA estimation results. This verifies the effectiveness of our proposed method.
The Journal of the Acoustical Society of America 06/2008; 123(5):3336. · 1.55 Impact Factor
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ABSTRACT: Different from the generally adopted criteria of minimizing the sidelobe level and maximizing the array gain in the weighting design of a sonar array, an approach was proposed recently to optimize the shading weights with the aim of maximizing the deflection coefficient in the square-law detector, which in essence suppresses the self-noise by including the noise information at array sensors in the optimization procedure. When several noise sources are present andor an analytical expression of the noise transfer function is not available, the sensor noise needs to be measured in forming the sensor noise response cross correlation matrix required in the optimization which is very demanding when an array with large number of sensors is considered. To avoid the tedious work of noise measurement, a numerical method is developed in this paper. In this method, the main self-noise sources are assigned with different positions and strengths and the noise field at the array sensors is calculated via either the finite element method or the boundary element method. Tank experiment validated the effectiveness of this method. By using this method, the detection performance of a sensor array can be predicted before it is physically built and tested in under practical conditions.
The Journal of the Acoustical Society of America 06/2008; 123(5):3952. · 1.55 Impact Factor
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ABSTRACT: Blind beamforming algorithms have the ability to recover the desired signals from array outputs without any prior knowledge of the array geometry. After blind separation of the signals, the DOAs can be estimated for each source individually. In this paper, the performance of the multistage constant modulus (CM) array, one of the most striking blind beamforming algorithms, for the source DOA estimation was analyzed via water tank experiments, and was compared to that of other DOA estimation algorithms including the 'non-blind' and the 'blind' algorithms. Results of water tank experiments showed that the multistage CM array can not only blindly recover the independent signal, but also correctly estimate the DOAs. The angle separating ability of the CM array was beyond the Rayleigh resolution limit.
Computational Advances in Multi-Sensor Adaptive Processing, 2007. CAMPSAP 2007. 2nd IEEE International Workshop on; 01/2008
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ABSTRACT: All beamspace DOA (direction of arrival) estimation algorithms are based on the beam outputs and the beamformers play an important role in providing high quality beam output data for further processing. In this paper, robust Capon beamformer (RCB) combined with null-broadening technique is applied to the element outputs. It can effectively suppress the fast-moving strong interferers outside the beam coverage region and overcome the distortion in beampattern due to array steering vector errors. Performance of beamspace MUSIC using null broadened robust beamformers against fast moving interferer is studied via computer simulation for uniform linear array. The simulation results show that the proposed scheme has good spatial resolution and improved detection probability of weak stationary signals
Antennas and Propagation Society International Symposium 2006, IEEE; 08/2006
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ABSTRACT: An effective method was proposed to simultaneously estimate the Directions-of-Arrival (DOAs) and the sensor positions of a bended towed line array during a turn, which is called the array shape self-calibration problem. Firstly, the incident independent signals were blindly separated from the output of the multistage Constant Modulus (CM) array without any information of the towed array shape. The steering vectors corresponding to the signals were reconstructed at the same time. Then, based on the information contained in the estimated steering vectors, the towed array shape self-calibration problem could be described as a nonlinear constrained optimization problem and solved by the Genetic Algorithm. The effectiveness of the proposed method was illustrated by numerical examples.
Oceans 2005 - Europe; 07/2005
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ABSTRACT: The design of FIR digital filter based on minimum mean square error criterion can be implemented via adaptive approach. An iterative algorithm is proposed in this paper to enhance the effectiveness of adaptive FIR digital filter design through adaptively obtaining optimum cost functions. This modified approach results in the best values of the cost function to reach a best fit between the FIR digital filter response and the design requirements. The adaptive design approach is used to get the weights of FIR filters in time domain broadband beamformers. An example of broadband beamforming for a 12-element arc array is illustrated to show the effectiveness of the iterative algorithm proposed in this paper.
TENCON 2004. 2004 IEEE Region 10 Conference; 12/2004
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ABSTRACT: A new method is proposed to detect the number of signals and estimate their directions-of-arrival (DOAs) in the multipath channels. Based on the coherency among signals, multiple independent sources resulted from multipaths are automatically divided into several independent groups from the multistage constant modulus array with power signal detector, and the spatial signature corresponding to each group is estimated. Then the problem for combined detection and estimation is transformed into solving for the coherent signals from each spatial signature and finally handled by utilizing the invariance property of noise subspace. The proposed method not only can deal with the situation where there are more incident signals than sensors in the array, but also is applicable to arbitrary array geometry. Effectiveness of the method is demonstrated by computer simulations and water tank experiments
OCEANS '04. MTTS/IEEE TECHNO-OCEAN '04; 12/2004
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ABSTRACT: In this paper, a new method is presented to design low-sidelobe wideband constant beamwidth beamformers (WCBB) in time domain, which alleviates the effect caused by array mismatch errors by applying the measured array models into the design procedure. A combination of FIR filters and digital delay lines is used in the beamformer structure to reduce the order of FIR filters. In FIR filter design, the semi-definite programming is utilized which is able to constrain both the mainlobe shapes and the sidelobe levels within the whole design frequency band. Results from lake experiments with a practical sonar system verified the effectiveness of the proposed method.
OCEANS '04. MTTS/IEEE TECHNO-OCEAN '04; 12/2004
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ABSTRACT: All beamspace DOA estimation algorithms are based on the beam outputs and the beamformers play an important role in providing high quality beam output data for further processing. We use -broadened MVDR beamformers to apply to the element outputs. The broadened can reject the interfering sources not only from a specific direction but from a specific spatial region as well. Performance of beamspace MUSIC using broadened beamformers is studied via computer simulation for uniform linear array. The simulation results show that the proposed scheme has good spatial resolution than conventional beamspace DOA estimation algorithms.
OCEANS '04. MTTS/IEEE TECHNO-OCEAN '04; 12/2004
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ABSTRACT: To overcome the azimuth sampling constraints imposed in synthetic aperture sonar (SAS), many SAS systems employ a single transmitter and multiple-receiver configuration, which can be regarded as a system containing many bistatic transmit-receive pairs. In traditional reconstruction, the multiple receiver system data is often preprocessed into an equivalent single receiver (monostatic) data by using the phase center approximation (PCA) and along track interpolation, and then followed by standard image reconstruction algorithms. But a blurring will occur at the edge of the target area as the length of the receiver array increases. In this paper, a novel approach is proposed to overcome the blurring problem caused by PCA based on the bistatic model. In this method, an image is firstly reconstructed with the data of each hydrophone independently, and then all the images are coherently added to give the high quality imagery. Simulation results show the feasibility and availability by applying this algorithm
OCEANS '04. MTTS/IEEE TECHNO-OCEAN '04; 12/2004
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ABSTRACT: An effective method is proposed for "half blindly" recovering coherent signals impinging on a uniform linear array (ULA) and estimating their directions of arrival (DOAs). The generalized steering vector is blindly estimated from the CM array, where the steering vectors to all coherent signals are reconstructed directly by using the property of subarray shift-invariance. When used as the array weighting, the-steering vectors will provide recovered signals in corresponding beams. DOAs can be estimated from the angular spectrum subsequently. Results from the computer simulations and the real data analysis are in good agreement with theoretical analysis. Our method not only can resolve closely spaced coherent signals, but also is shown to be more robust to system errors compared to some other DOA estimation algorithms.
OCEANS 2003. Proceedings; 10/2003
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ABSTRACT: In this paper, a new method for obtaining the array manifold in sensor array beampattern design and optimization is proposed. The basic idea behind the proposed method is replacing the theoretical obtained or experimentally measured array manifold by the calculated one, which is obtained by calculating the sound field at each element positions in the array. The acoustical boundary element method is used to calculate the sound field and the array manifold is obtained by accumulating the values at all sensor in all interested directions. By doing so, the effects of the array supporting structure or baffle can be included so as to yield a result which is more approaching the practical situation, and at the same time, avoids the tedious work of practical measurements. A conformal array with 27 sensors was designed and built and analyzed by the proposed method. The calculated sensor directivity by the proposed method has a similar tendency with that measured in an anechoic water-tank, and the design requirements of beampatterns which use the optimized weighting coefficient obtained from the array manifold calculated by the proposed method are well met in practical system. The simulation results have verified the effectiveness and feasibility of the proposed method.
