We consider iterative electromagnetic imaging of metallic targets hidden behind dielectric walls using sparse regularization. As in the equivalent-source method, we assume that the targets can be approximated by a set...
详细信息
ISBN:
(纸本)9781467310710
We consider iterative electromagnetic imaging of metallic targets hidden behind dielectric walls using sparse regularization. As in the equivalent-source method, we assume that the targets can be approximated by a set of filament currents whose locations are unknown. By using the iterative procedure, we reveal additional filament currents thus enlarging the target image. In order to take into account the mutual interaction between the current sources, and yet obtain the model amenable to signalprocessing, we combine the method of moments and the ray tracing.
This work studies a new beamformer for non-periodic sparse bidimensional ultrasonic array transducer. It is based on a weighting factor based on signals phase dispersion to enhance the image points where the phase coh...
详细信息
ISBN:
(纸本)9781467310710
This work studies a new beamformer for non-periodic sparse bidimensional ultrasonic array transducer. It is based on a weighting factor based on signals phase dispersion to enhance the image points where the phase coherence between the received signals is high. A method to measure the phase dispersion based on Fourier analysis and its integration in the beamformer are presented. Its performance is evaluated using a non-periodic 2D sparse array based on Fermat spiral with 96 elements and a diameter of 60 lambda. Compared with conventional Delay-And-Sum beamformer the proposed solution reduces the aperture lateral resolution and improves its dynamic range, achieving up to 50dB of contrast in the image and less 1 degrees in lateral resolution.
In space-time adaptive processing (STAP) applications, temporally stationary clutter results in a Toeplitz-block clutter covariance matrix. In the reduced-order parametric matched filter STAP technique, this covarianc...
详细信息
ISBN:
(纸本)9781424422401
In space-time adaptive processing (STAP) applications, temporally stationary clutter results in a Toeplitz-block clutter covariance matrix. In the reduced-order parametric matched filter STAP technique, this covariance matrix is reconstructed from a small number of estimated parameters, resulting in a much more efficient use of training samples. This paper explores a computationally advantageous "relaxed" maximum entropy (Burg) reconstruction technique which does not restore a strict Toeplitz-block structure, but does preserve the Burg spectrum. Performance of the reconstructed covariance matrix model as a STAP filter is evaluated using the DARPA KASSPER dataset and compared with "proper" Toeplitz-block reconstruction.
The Bayesian mixture of factor analyzers (BMFA), which achieves joint clustering and dimensionality reduction, is with an appealing feature of automatic hyper-parameter learning. In addition to its great success in va...
详细信息
ISBN:
(数字)9781728119465
ISBN:
(纸本)9781728119465
The Bayesian mixture of factor analyzers (BMFA), which achieves joint clustering and dimensionality reduction, is with an appealing feature of automatic hyper-parameter learning. In addition to its great success in various unsupervised learning tasks, it exemplifies how the Bayesian statistics can be leveraged to achieve automatic hyper-parameter learning, which is an open problem of modern simultaneous (deep) dimensionality reduction and clustering. Due to the importance of the BMFA, in this paper, its mechanism is carefully investigated, and a robust variant of the BMFA that can mitigate potential outliers is further proposed. Numerical studies are presented to show the remarkable performance of the proposed algorithm in terms of accuracy and robustness.
We propose a MUSIC based array imaging method for ultrasonic non-destructive testing (NDT) applications. We take the mode conversion phenomenon into account and develop a MUSIC-based imaging technique which exploits t...
详细信息
ISBN:
(纸本)9781467310710
We propose a MUSIC based array imaging method for ultrasonic non-destructive testing (NDT) applications. We take the mode conversion phenomenon into account and develop a MUSIC-based imaging technique which exploits the additional information that is present in all propagating modes to the advantage of the imaging process-a problem not previously addressed in the context of NDT applications. Both the numerical simulations as well as data validation show that our proposed approach performs better than the traditional MUSIC based and delay-and-sum (DAS) based imaging algorithms in terms of root mean square error (RMSE) and also provides higher resolution and better side lobe suppression capabilities.
Following a geometric paradigm, the estimation of a Toeplitz structured covariance matrix is considered. The estimator minimizes the distance from the Sample Covariance Matrix (SCM) while complying with some specific ...
详细信息
ISBN:
(纸本)9781728119465
Following a geometric paradigm, the estimation of a Toeplitz structured covariance matrix is considered. The estimator minimizes the distance from the Sample Covariance Matrix (SCM) while complying with some specific constraints modeling the covariance structure. The resulting constrained optimization problem is solved globally resorting to the Dykstra' projection framework. Each step of the procedure involves the solution of two convex sub-problems, whose minimizers are available in closed form. Simulation results related to typical radar environments highlight the effectiveness of the devised method.
In this paper, we investigate the joint multiple-input multiple-output (MIMO) radar and communications system convergence problem and develop a joint radar-communications performance bound using the concept of estimat...
详细信息
ISBN:
(纸本)9781538647523
In this paper, we investigate the joint multiple-input multiple-output (MIMO) radar and communications system convergence problem and develop a joint radar-communications performance bound using the concept of estimation rate for radar system and data information rate for communications system. At the radar receiver, we propose a Successive Interference Cancellation (SIC) strategy to estimate radar parameters and decode communications signal simultaneously. While, at the MIMO communications transmitter, we propose a spectrum sharing scheme and show that the optimal communications performance can be achieved through a spectral and spatial waterfilling algorithm. In the end, we show that the Multiple-Access (MAC) performance bound outperforms the result from the spectrally isolated MIMO radar-communications system.
This work is concerned with direction-of-arrival (DOA) estimation of narrowband signals from multiple targets using a planar antenna array. We illustrate the shortcomings of Maximum Likelihood (ML), Maximum a Posterio...
详细信息
ISBN:
(纸本)9781479914814
This work is concerned with direction-of-arrival (DOA) estimation of narrowband signals from multiple targets using a planar antenna array. We illustrate the shortcomings of Maximum Likelihood (ML), Maximum a Posteriori (MAP), and Minimum Mean Squared Error (MMSE) estimation, issues that can be attributed to the symmetry in the likelihood function that must exist when there is no information about labeling of targets. We proffer the recently introduced concept of Minimum Mean OSPA (MMOSPA) estimation that is based on the optimal sub-pattern assignment (OSPA) metric for sets and hence inherently incorporates symmetric likelihood functions.
We consider a decentralized detection problem in a power-constrained wireless sensor networks (WSNs), in which a number of sensor nodes collaborate to detect the presence of a deterministic vector signal. The signal t...
详细信息
ISBN:
(纸本)9781467310710
We consider a decentralized detection problem in a power-constrained wireless sensor networks (WSNs), in which a number of sensor nodes collaborate to detect the presence of a deterministic vector signal. The signal to be detected is assumed known a priori. Each sensor conducts a local linear processing to convert its observations into one or multiple messages. The messages are conveyed to the fusion center (FC) by an uncoded amplify-and-forward scheme, where a global decision is made. Given a total network transmit power constraint, we investigate the optimal linear processing strategy for each sensor. Our study finds that the optimal linear precoder has the form of a matched filter. Depending on the channel characteristics, one or multiple versions of the filtered/compressed message should be reported to the FC.
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...
详细信息
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.
暂无评论