This paper concerns the problem of array shape estimation from clutter (ASEC) for a towed active sonar array. Although heading sensors can provide towed-array shape information, they are sometimes not sufficiently ava...
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ISBN:
(纸本)0780375513
This paper concerns the problem of array shape estimation from clutter (ASEC) for a towed active sonar array. Although heading sensors can provide towed-array shape information, they are sometimes not sufficiently available or accurate to facilitate beamforming with low sidelobe levels necessary for detection of low-Doppler targets, especially in the presence of severe bottom reverberation. We propose a maximum likelihood array shape calibration technique that exploits the azimuth-Doppler frequency relationship of the clutter by fitting the reverberation snapshots from a single sonar ping to the low rank space-time clutter subspace.
Standard high resolution arrayprocessing techniques are based on simultaneous sampling of the whole multiple sensorarray and, hence, require that the number of receivers should be equal to the number of receiving an...
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ISBN:
(纸本)0780375513
Standard high resolution arrayprocessing techniques are based on simultaneous sampling of the whole multiple sensorarray and, hence, require that the number of receivers should be equal to the number of receiving antennas. A switch antenna array FMCW radar system is introduced as a promising substitute for the multiple-channel array due to its lower cost and a simpler front-end circuitry. New high-resolution signalprocessing algorithms for the system composed of a single transmitter, m receiving antennas, and a single receiving channel are based on the new nonstationary version of the Capon beamforming. Simulation demonstrates that the new algorithms yield very good performance in terms of both estimation accuracy and multiple-target resolution. These algorithms give better estimation than the MUSIC algorithm even for the case of slow moving targets.
Ultrasonic inspection methods are commonly used in the nondestructive evaluation of welds to detect flaws in the weld region. An important characteristic of ultrasonic inspection is the ability to identify the type of...
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ISBN:
(纸本)0780375513
Ultrasonic inspection methods are commonly used in the nondestructive evaluation of welds to detect flaws in the weld region. An important characteristic of ultrasonic inspection is the ability to identify the type of discontinuity that gives rise to a particular signal. Standard techniques rely on differences in individual A-scans to classify the signals. This paper proposes an ultrasonic signal classification technique based on the information in a group of signals. The approach is based on a 2-dimensional transform and principal component analysis, for generating a reduced dimensional feature vector for classification. Results of applying the technique to data obtained from the inspection of welds are presented.
In sensor networks, where power and bandwidth are at a premium, there is a clear need to use compression to limit the amount of information exchanged by the sensors. In this paper we study the signal compression probl...
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ISBN:
(纸本)0780375513
In sensor networks, where power and bandwidth are at a premium, there is a clear need to use compression to limit the amount of information exchanged by the sensors. In this paper we study the signal compression problem in situations where signals are being processed for the purpose of source localization. In these scenarios compression should be optimized for the accuracy of source localization, rather than to provide a reproduction of the signals with some desired fidelity. We show how this leads to novel design techniques that have clear advantages over standard quantizer design approaches.
In this primarily tutorial paper, a perspective on the development of Adaptive Data Orthogonalization (ADO) for spatial sensorarray sampled data vectors is presented. The development of ADO methods is traced from a g...
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ISBN:
(纸本)0780375513
In this primarily tutorial paper, a perspective on the development of Adaptive Data Orthogonalization (ADO) for spatial sensorarray sampled data vectors is presented. The development of ADO methods is traced from a generalization of the split array, cross-correlation arrival angle tracker for a single source, plane wave arrival to multiple coherent arrivals. Development is followed through to the more recent maximization of the ratio of two quadratic forms that expresses beamformer array gain. Specifically, the reduced complexity implementation of a signal model error robust Minimum Variance Distortionless Response (MVDR) Adaptive Beamformer (ABF) is described. This robust beamformer is a simple, explicit linear blend (combination) of the inherently robust shaded time delay-and-sum Conventional Beamformer (CBF) and the Enhanced Minimum Variance (EMV) Dominant Mode Rejection (DMR) ABF. This ABF construction places an easily implemented upper bound on the signal suppression caused by signal model mismatch and allows a trade-off between spatial resolution and Main Lobe signal Maintenance (MLM). Several methods for robust DMR ABF are compared.
It is known that the design of antenna array configuration is an important issue to the antenna array applications. In this paper, we present a method to design antenna array configurations for space-time adaptive pro...
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ISBN:
(纸本)0780375513
It is known that the design of antenna array configuration is an important issue to the antenna array applications. In this paper, we present a method to design antenna array configurations for space-time adaptive processing (STAP) applied to mobile communication systems. We first derive an upper bound of the residual error power of STAP systems under the minimum mean square error (MMSE) criterion. Then, the relationship between the bound and the space-time channel auto- and cross-correlation functions is established. According to this relationship, an objective function under perfect Monte Carlo sampling is proposed, based on which the array configuration that optimizes the performance is thus obtained. Numerical simulation results under a given statistical signa environment show the effectiveness of the proposed design method.
Microphone arrays provide new opportunities for noise reduction and speech enhancement. This paper presents a novel decomposition of the estimation problems for short-time spectral amplitude (STSA), log STSA, and phas...
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ISBN:
(纸本)0780375513
Microphone arrays provide new opportunities for noise reduction and speech enhancement. This paper presents a novel decomposition of the estimation problems for short-time spectral amplitude (STSA), log STSA, and phase in the Bayesian estimation framework. The decomposition is based on the notion of sufficient statistics for the microphone array case. It nicely generalizes the well-known single-channel Ephraim-Malah estimators [4, 5] to the microphone array case. We also compare noise reduction obtained in the single channel with the two- and four-channel cases on real data.
This paper proposes a novel wideband structure for arraysignalprocessing. A new wideband model is formed where the observations are linear functions of the source amplitudes, but nonlinear in the direction of arriva...
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ISBN:
(纸本)0780375513
This paper proposes a novel wideband structure for arraysignalprocessing. A new wideband model is formed where the observations are linear functions of the source amplitudes, but nonlinear in the direction of arrival (DOA) parameters. The method lends itself well to a Bayesian approach for jointly estimating the model order and the DOAs through a reversible jump Markov chain Monte Carlo (MCMC) procedure. The source amplitudes are estimated through a maximum a posteriori (MAP) procedure. The DOA estimation performance of the proposed method is compared with the theoretical Cramer-Rao lower bound (CRLB) for this problem. Simulation results demonstrate the effectiveness and robustness of the method.
We introduce Spatial processing: Optimized and Constrained (SPOC) as a new front-end display processing method that operates on arraysensor data as an alternative to conventional or adaptive beamforming. The output o...
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ISBN:
(纸本)0780375513
We introduce Spatial processing: Optimized and Constrained (SPOC) as a new front-end display processing method that operates on arraysensor data as an alternative to conventional or adaptive beamforming. The output of our approach is computed on a single-snapshot basis so that no stationarity assumptions are required. We use a maximum a posteriori approach to develop a constrained optimization solution. A parametric representation provides the framework for the presented solution. Some degrees of freedom are fixed by the constraint, and the rest remain free to optimize the cost function. We develop an iterative solution in terms of the free parameters. This method provides significantly improved resolution over conventional beamforming. Two simulated cases demonstrate algorithm performance.
One of the important problems in ocean acoustics is to localize an underwater wideband sound source from the array hydrophone data. Among the algorithms developed, estimation of source parameters via maximum likelihoo...
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