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sensor array and multichannel signal processing workshop

作者： Jian Li Guoqing Liu Nanzhi Jiang P. Stoica Department of Electrical and Computer Engineering University of Florida Gainesville FL USA

We study the clutter and jamming suppression and moving target detection and feature extraction for airborne phased array radar. For the low range resolution (LRR) case, we use a vector autoregressive (VAR) filtering technique for clutter suppression and compare it to the displaced phase center antenna (DPCA) processing technique in the presence of various system errors. For the high range resolution (HRR) case, we first show how to use the VAR filter to suppress the ground clutter. We divide the HRR range profiles into LRR segments to avoid the range migration problems that occur in the HRR radar data. Since each LRR segment contains a sequence of HRR range bins, no loss of resolution occurs due to the division. We then propose new algorithms for moving target detection and super resolution feature extraction. Numerical results are provided to demonstrate the effectiveness of the proposed algorithms.

关键词： Phased arrays Airborne radar Radar clutter Jamming Object detection Feature extraction Reactive power Radar antennas Filtering Filters

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The time-reversal technique re-interpreted: subspace-based signal processing for multi-static target location

The time-reversal technique re-interpreted: subspace-based s...

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sensor array and multichannel signal processing workshop

作者： H. Lev-Ari A.J. Devancy Department of Electrical and Computer Engineering Northeastern University Boston MA USA Northeastern University Boston MA US

The time-reversal field processing technique for active remote sensing is re-interpreted in the conceptual framework of subspace-based signal processing. Though both of these subjects have a long and extensive history, we believe that our work is the first to relate these two rather different signal processing approaches. The concept at the heart of both approaches is the multi-static frequency response matrix (FRM) of the active antenna array. It is a function of array/scatterer geometry (via a suitable Green function) and of the scatterers' reflection coefficients. The time-reversal technique locates the most reflective target by determining the largest singular value of the FRM and the corresponding (right) singular vector. Consequently, it performs well only when the scatterers are "well-resolved," i.e., when the Green function vectors used in forming the FRM are approximately orthogonal to each other. In contrast, we show that subspace-based signal processing can be successfully used even when the targets are not "well-resolved." Moreover, the performance of our subspace-based schemes can be further enhanced by using wideband signals and combining FRM information from multiple frequencies. The coupling of time-reversal field processing with subspace methods leads to a powerful approach for locating targets under arbitrary wave-propagation conditions (both near-field and far-field), including arbitrary non-homogeneous media and arbitrary geometries.

关键词： Scattering array signal processing Geometry Green function signal processing Remote sensing History Heart Frequency response Antenna arrays

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Passive range estimation and range rate detection

Passive range estimation and range rate detection

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sensor array and multichannel signal processing workshop

作者： R. Jeffers B. Breed B. Gallemore Digital Syst. Resource Inc. Fairfax VA USA Breed and Harvel Associates Austin TX USA Digital Systems Resources Inc. Fairfax VA USA

The problem of interest is a rapidly closing object (e.g. a torpedo) emitting broadband and narrowband acoustic signatures. A high negative range rate is indicative of a torpedo threat, and good range-bearing estimates provide good target localization. A linear, towed hydrophone array is used as a receiver, and in many cases the received signals will display high signal-to-noise ratio. It is desirable to detect at ranges greater than the near field range of the array. High-resolution range-bearing estimators have been developed using narrowband signatures and broadband signatures. The range difference to the target across an array causes target signals to display a wave-front curvature. Range estimation is based on wave-front curvature determination using a matched-filtering post beamformer approach. First a target is selected for range estimation in which a subset of beams is chosen for sector inverse beamforming. Curvature pattern replicas over range and bearing are computed and used in a Capon form beamformer. Simulations and experiments with in-water data compare the algorithm performance to a derived benchmark. In addition, a cepstrum-based range rate indicator was demonstrated using experimental data displaying multipath propagation (Lloyd mirror).

关键词： Acoustic signal detection Narrowband Displays Acoustic emission Sonar equipment signal to noise ratio Acoustic beams array signal processing Computational modeling Mirrors

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Early experimental results for a large-aperture microphone-array system

Early experimental results for a large-aperture microphone-a...

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sensor array and multichannel signal processing workshop

作者： H.F. Silverman W.R. Patterson J.M. Sachar Brown University Providence RI USA

Microphone arrays offer a potential solution to the important problem of obtaining high-quality sound pick-up from remote acoustic sources. Most reported results for microphone array technology have been theoretical, proposed algorithms with predicted performance, or based on ideal or near-ideal simulations of microphone-array systems and room environments. Previous work that is based on real data has usually been for a small number of microphones. In this paper, for the first time, measured results for a large number of microphones, 256, in a large-aperture, real-time, all DSP system are reported. The array system is mounted in a moderate-sized (8M/spl times/8M) room with a significant reverberation time. While listeners to the locationing/tracking/beamforming system claim to hear near-close-talking microphone performance when the system acquires a talker, our measured results of the real-time system indicate that a true 9 dB separation of a source from other sources in the room has been achieved and that reverberant effects have been significantly reduced. This level of isolation is maintained at all locations throughout the room. In addition to reporting these early performance measures, this paper discusses the nuances of the real-time algorithms, the latency in such systems, and introduces some of the issues of making real-time, real-room measurements.

关键词： Microphone arrays Real time systems Acoustic arrays Prediction algorithms Predictive models Time measurement Digital signal processing Reverberation array signal processing Delay

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Approximate maximum likelihood DOA estimation in multiplicative noise environments

Approximate maximum likelihood DOA estimation in multiplicat...

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sensor array and multichannel signal processing workshop

作者： O. Besson F. Vincent P. Stoica A.B. Gershman Department of Avionics and Systems ENSICA Toulouse France Department of Electrical and Computer Engineering McMaster University Hamilton Canada

We consider the problem of localizing a source by means of a uniform linear array of sensors when the received signal is corrupted by multiplicative noise. Since the exact maximum likelihood (ML) estimator is computationally intensive, two approximate solutions are proposed, originating from the analysis of the high and low signal to noise ratio (SNR) cases, respectively. First, starting with the no additive noise case, a very simple approximate ML (AML/sub 1/) estimator is derived. A theoretical expression for its asymptotic variance in the presence of additive noise is derived. It shows that the AML/sub 1/ estimator has a performance close to the Cramer-Rao bound (CRB) for moderate to high SNR. Next, the low SNR case is considered and the corresponding AML2 solution is derived. It is shown that the approximate ML criterion can be concentrated with respect to (w.r.t.) both the multiplicative and additive noise powers, leaving out a 2-D minimization problem instead of a 4-D problem required by the exact ML. Numerical results illustrate the performance of the estimators and confirm the validity of the theoretical analysis.

关键词： Maximum likelihood estimation Direction of arrival estimation Working environment noise sensor arrays signal to noise ratio Scattering Integrated circuit noise Integrated circuit modeling Additive noise Parameter estimation

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Subband STAP processing, the fifth generation

Subband STAP processing, the fifth generation

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sensor array and multichannel signal processing workshop

作者： A.O. Steinhardt N.B. Pulsone DARPA Tactical Technology Office Arlington VA USA MIT Lincoln Laboratories Lexington MA USA

Adaptive array processing has moved through several stages of evolution. First there was spatial only adaptation, using gradient based algorithms. Second was true space-time adaptivity using time-taps on multiple channels. Third came more rapid convergence, using sample matrix inversion strategies. Fourth came dimensionally large system solutions, which focused on the need for reduced DOF such as beamspace, eigenspace, MUSIC, ESPRIT, BASS-ALE, etc. This paper argues that we are on the threshold of the fifth generation of STAP; mainly STAB in the subband domain. Subband STAP, is an elegant and computationally efficient solution to the need for increasing bandwidth in radar and sonar processing as well as mobile communications. We begin by motivating the need for wider bandwidths, from a SAR imaging perspective. Next, we show that the computational burden of wideband STAP is untenable for existing and emerging military requirements. Having motivated a compelling need we then propose subband STAP as a solution, motivated from an active sensor perspective. We describe subband STAP as an extension of the familiar STAP 3D datacube (range, angle, Doppler) to a 40 hypercube (subband range, angle, subband Doppler, subband frequency). Subbanding allows us to overcome challenging wideband effects such as Doppler-frequency coupling, high-resolution range migration, target self-nulling, channel decorrelation, and dispersion. We describe the challenges of subband STAP interference rejection and subband recombination with artifacts.

关键词： Military computing Bandwidth Wideband array signal processing Multiple signal classification Radar imaging Sonar Mobile communication Radar polarimetry Hypercubes

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Multi-rate adaptive beamforming (MRABF)

Multi-rate adaptive beamforming (MRABF)

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sensor array and multichannel signal processing workshop

作者： H. Cox ORINCON Corporation Arlington VA USA

An important trend in underwater acoustics is the use of large arrays with many elements and small resolution cells in an effort to detect weak signals. Frequently, the background noise is dominated by multiple moving surface ships that act like discrete interferers. These interferers may move through many spatial resolution cells in the time required to obtain sufficient "snapshots" for covariance matrix estimation. The non-stationarity of the background limits the performance of adaptive algorithms. Reduced degree-of-freedom approaches that can track and rapidly null interferers before they move too far are of great interest. The paper presents a new class of algorithms in which a low-rank, dynamically changing interference sub-space is estimated and tracked using a short-term average. An orthogonal projection is then applied to the data to null components in the interference sub-space. A second stage of adaptive beamforming that uses a longer averaging time is then applied to the projected data. Unlike most sub-space approaches that work for strong signals, there is no requirement that the signal be contained in the interference sub-space. It is shown how multiple interferers moving rapidly across beams can be tracked and nulled to reveal the presence of a weak target not visible with conventional, adaptive, or usual sub-space methods. The effectiveness of multi-rate adaptive beamforming is illustrated by examples. It is shown that moving interferers are effectively nulled to allow detection of weak signals when other methods including MVDR, conventional, and signal subspace fail.

关键词： array signal processing Interference Spatial resolution signal detection Underwater acoustics signal resolution Acoustic signal detection Underwater tracking Background noise Marine vehicles

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Beamforming, Doppler compensation, and differential space-time coding

Beamforming, Doppler compensation, and differential space-ti...

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sensor array and multichannel signal processing workshop

作者： M.A. Ingram Kuo-Hui Li A. van Nguyen T. Pratt School of Electrical and Computer Engineering Georgia Institute of Technology Atlanta GA USA Information Technology and Telecommunication Laboratory Georgia Tech Research Institute Georgia Institute of Technology Atlanta GA USA

We consider the design of two beams, formed at the base station, that will serve as the two channels for differential space-time block coding in a high-mobility outdoor scenario. The mobile is assumed to have one omnidirectional antenna. In one approach, we consider selecting assuming no interference, the two most powerful beams produced by an RF beamformer. In the other approach, we make a compromise between power and Doppler spectrum partitioning. One channel is a beam that points directly at the mobile. The other beam is the difference of left and right beams, symmetric about the mobile. These left and right beams are Doppler compensated prior to forming their difference. Using computer simulation, we find that selecting beams based on power is more effective than selecting beams based on Doppler partitioning. We also find that using the two most powerful beams formed from eight antenna elements yields 7 dB and 8 dB SNR improvements, at 1.9 GHz and 5.8 GHz, respectively, relative to spatial diversity with two omnidirectional antennas.

关键词： array signal processing Diversity reception Block codes Downlink Space technology Base stations Mobile antennas Azimuth Chebyshev approximation Design engineering

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Distributed source localization with multiple sensor arrays and frequency-selective spatial coherence

IEEE Signal Processing Workshop on Statistical Signal and Ar...

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ieee signal processing workshop on Statistical signal and array processing, SSAP 2000年 419-423页

作者： Kozick, Richard J. Sadler, Brian M. Bucknell Univ Lewisburg United States

Multiple sensor arrays distributed over a planar region provide the means for highly accurate localization of the (x, y) position of a source. In some applications, such as microphone arrays receiving aeroacoustic signals from ground vehicles, random fluctuations in the air lead to frequency-selective coherence of the signals that arrive at widely separated arrays. We present a performance analysis for localization of a wideband source using multiple sensor arrays. The wavefronts are modeled with perfect spatial coherence over individual arrays and with frequency-selective coherence between distinct arrays. The sensor signals are modeled as wideband Gaussian random processes, and we study the Cramer-Rao bound (CRB) on source localization accuracy for varying levels of signal coherence and for processing schemes with different levels of complexity. We show that significant improvements in source localization accuracy are possible when partial signal coherence from array to array is exploited. Further, we show that a distributed processing scheme involving bearing estimation at the individual arrays and time-delay estimation between pairs of sensors performs nearly as well as the optimum scheme that jointly processes the signals from all sensors. Results based on measured aeroacoustic data are included to illustrate frequency-selective signal coherence at distributed arrays.

关键词： sensor data fusion

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Joint channel estimation and detection for interference cancellation in multi-channel systems

Joint channel estimation and detection for interference canc...

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ieee workshop on Statistical signal and array processing

作者： C. Martin B. Ottersten Department of Signals Sensors & Systems Royal Institute of Technology Stockholm Sweden

Interference from other users and interference due to multipath propagation limit the capacity of wireless communication networks. As the number of users and the demand for new services in the networks increases, co-channel interference will be a limiting factor. This paper proposes an iterative structured multichannel receiver algorithm that jointly estimates the communication channels and desired data while canceling interference. A general way of adding training redundancy to a data frame is also introduced. From simulations the proposed method is shown to achieve low bit error rates also in the presence of strong interference. These simulations also show that by distributing the training information in a data burst elaborately further improvements in performance are achievable.

关键词： Channel estimation Interference cancellation Intersymbol interference Radio transmitters Intelligent networks Wireless sensor networks Iterative algorithms Antenna arrays Receiving antennas Transmitting antennas

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