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Target localization accuracy gain in MIMO radarbased systems
 1279 of Theoretical and Applied Information Technology 31 st January 2013. Vol. 47 No.3 © 2005  2013 JATIT & LLS. All rights reserved . ISSN: 19928645 www.jatit.org EISSN
, 2010
"... Abstract—This paper presents an analysis of target localization accuracy, attainable by the use of multipleinput multipleoutput (MIMO) radar systems, configured with multiple transmit and receive sensors, widely distributed over an area. The Cramer–Rao lower bound (CRLB) for target localization ac ..."
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Abstract—This paper presents an analysis of target localization accuracy, attainable by the use of multipleinput multipleoutput (MIMO) radar systems, configured with multiple transmit and receive sensors, widely distributed over an area. The Cramer–Rao lower bound (CRLB) for target localization accuracy is developed for both coherent and noncoherent processing. Coherent processing requires a common phase reference for all transmit and receive sensors. The CRLB is shown to be inversely proportional to the signal effective bandwidth in the noncoherent case, but is approximately inversely proportional to the carrier frequency in the coherent case. We further prove that optimization over the sensors ’ positions lowers the CRLB by a factor equal to the product of the number of transmitting and receiving sensors. The best linear unbiased estimator (BLUE) is derived for the MIMO target localization problem. The BLUE’s utility is in providing a closedform localization estimate that facilitates the analysis of the relations between sensors locations, target location, and localization accuracy. Geometric dilution of precision (GDOP) contours are used to map the relative performance accuracy for a given layout of radars over a given geographic area. Index Terms—Adaptive array, Cramer–Rao bound, multipleinput multipleoutput (MIMO) radar, spatial processing, target localization.
PhasedMIMO Radar: A Tradeoff Between 1 PhasedArray and MIMO Radars
, 908
"... We propose a new technique for multipleinput multipleoutput (MIMO) radar with colocated antennas which we call phasedMIMO radar. The new technique enjoys the advantages of MIMO radar without sacrificing the main advantage of phasedarray radar which is the coherent processing gain at the transmit ..."
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Cited by 26 (9 self)
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We propose a new technique for multipleinput multipleoutput (MIMO) radar with colocated antennas which we call phasedMIMO radar. The new technique enjoys the advantages of MIMO radar without sacrificing the main advantage of phasedarray radar which is the coherent processing gain at the transmitting side. The essence of the proposed technique is to partition the transmitting array into a number of subarrays that are allowed to overlap. Then, each subarray is used to coherently transmit a waveform which is orthogonal to the waveforms transmitted by other subarrays. Coherent processing gain can be achieved by designing a weight vector for each subarray to form a beam towards a certain direction in space. Moreover, the subarrays are combined jointly to form a MIMO radar resulting in higher resolution capabilities. The substantial improvements offered by the proposed phasedMIMO radar technique as compared to previous techniques are demonstrated analytically and by simulations through analysis of the corresponding beampatterns and achievable output signaltonoiseplusinterference ratios. Both analytical and simulation results validate the effectiveness of the proposed phasedMIMO radar. Index Terms MIMO radar, phasedarray radar, coherent processing gain, transmit/receive beamforming.
Transmit/receive beamforming for MIMO radar with colocated antennas
 Proc. IEEE Intl. Conf. Acoust., Speech, and Signal Proc
, 2009
"... We propose a new technique for multipleinput multipleoutput (MIMO) radar with colocated antennas. The essence of the proposed technique is to partition the transmitting array into a number of subarrays that are allowed to overlap. Each subarray is used to coherently transmit a waveformwhich is or ..."
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Cited by 13 (5 self)
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We propose a new technique for multipleinput multipleoutput (MIMO) radar with colocated antennas. The essence of the proposed technique is to partition the transmitting array into a number of subarrays that are allowed to overlap. Each subarray is used to coherently transmit a waveformwhich is orthogonal to the waveforms transmitted by other subarrays. Coherent processing gain can be achieved by designing a weight vector for each subarray to form a beam towards a certain direction in space. Moreover, the subarrays are combined jointly to form a MIMO radar resulting in higher resolution capabilities. Simulation results show the substantial improvements offered by the proposed technique as compared to previous techniques that validate its effectiveness. Index Terms — MIMO radar, phasedarray radar, adaptive arrays, adaptive beamforming. 1.
Source enumeration via MDL criterion based on linear shrinkage estimation of noise subspace covariance matrix
 IEEE Trans. Signal Process. 2013
"... Abstract—Numerous methodologies have been investigated for source enumeration in samplestarving environments. For those having their root in the framework of random matrix theory, the involved distribution of the sample eigenvalues is required. Instead of relying on the eigenvalue distribution, thi ..."
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Cited by 7 (4 self)
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Abstract—Numerous methodologies have been investigated for source enumeration in samplestarving environments. For those having their root in the framework of random matrix theory, the involved distribution of the sample eigenvalues is required. Instead of relying on the eigenvalue distribution, this work devises a linear shrinkage based minimum description length (LSMDL) criterion by utilizing the identity covariance matrix structure of noise subspace components. With linear shrinkage and Gaussian assumption of the observations, an accurate estimator for the covariance matrix of the noise subspace components is derived. The eigenvalues obtained from the estimator turn out to be a linear function of the corresponding sample eigenvalues, enabling the LSMDL criterion to accurately detect the source number without incurring significantly additional computational load. Furthermore, the strong consistency of the LSMDL criterion for and is proved, where and are the antenna number and snapshot number, respectively. Simulation results are included for illustrating the effectiveness of the proposed criterion. Index Terms—Linear shrinkage, minimum description length, sample covariance matrix, source enumeration. I.
Optimal Joint Target Detection and Parameter Estimation By MIMO Radar
, 908
"... We consider multipleinput multipleoutput (MIMO) radar systems with widelyspaced antennas. Such antenna configuration facilitates capturing the inherent diversity gain due to independent signal dispersion by the target scatterers. We consider a new MIMO radar framework for detecting a target that ..."
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Cited by 6 (3 self)
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We consider multipleinput multipleoutput (MIMO) radar systems with widelyspaced antennas. Such antenna configuration facilitates capturing the inherent diversity gain due to independent signal dispersion by the target scatterers. We consider a new MIMO radar framework for detecting a target that lies in an unknown location. This is in contrast with conventional MIMO radars which break the space into small cells and aim at detecting the presence of a target in a specified cell. We treat this problem through offering a novel composite hypothesis testing framework for target detection when (i) one or more parameters of the target are unknown and we are interested in estimating them, and (ii) only a finite number of observations are available. The test offered optimizes a metric which accounts for both detection and estimation accuracies. In this paper as the parameter of interest we focus on the vector of timedelays that the waveforms undergo from being emitted by the transmit antennas until being observed by the receive antennas. The analytical and empirical results establish that for the proposed joint target detection and timedelay estimation framework, MIMO radars exhibit significant gains over phasedarray radars for extended targets which consist of multiple independent scatterers. For point targets modeled as single scatterers, however, the detection/estimation accuracies of MIMO and phasedarray radars for this specific setup (joint target detection and timedelay estimation) are comparable. 1
Waveform Preconditioning for Clutter Rejection in Multipath for Sparse Distributed Apertures
"... The idea of preconditioning transmit waveforms for optimal clutter rejection in radar imaging is presented. Waveform preconditioning involves determining a map on the space of transmit waveforms, and then applying this map to the waveforms before transmission. The work applies to systems with an arb ..."
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Cited by 3 (3 self)
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The idea of preconditioning transmit waveforms for optimal clutter rejection in radar imaging is presented. Waveform preconditioning involves determining a map on the space of transmit waveforms, and then applying this map to the waveforms before transmission. The work applies to systems with an arbitrary number of transmitand receiveantenna elements, and makes no assumptions about the elements being colocated. Waveform preconditioning for clutter rejection achieves efficient use of power and computational resources by distributing power properly over a frequency band and by eliminating clutter filtering in receive processing.
1 Conditional and Unconditional CramérRao Bounds for NearField Source Localization
"... Nearfield source localization problem by a passive antenna array makes the assumption that the timevarying sources are located near the antenna. In this context, the farfield assumption (i.e. planar wavefront) is, of course, no longer valid and one has to consider a more complicated model paramet ..."
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Nearfield source localization problem by a passive antenna array makes the assumption that the timevarying sources are located near the antenna. In this context, the farfield assumption (i.e. planar wavefront) is, of course, no longer valid and one has to consider a more complicated model parameterized by the bearing (as in the farfield case) and by the distance, named range, between the source and a reference coordinate system. One can find a plethora of estimation schemes in the literature, but their ultimate performance in terms of Mean Square Error (MSE) have not been fully investigated. To characterize these performance, the CramérRao Bound (CRB) is a popular mathematical tool in signal processing. The main cause for this is that the MSE of several highresolution direction of arrival algorithms are known to achieve the CRB under quite general/weak conditions. In this correspondence, we derive and analyze the socalled conditional and unconditional CRBs for a single timevarying nearfield source. In each case, we obtain non matrix closedform expressions. Our approach has two advantages: (i) due to the fact that one has to inverse the Fisher information matrix, the computational cost for a large number of snapshots (in the case of the conditional CRB) and/or for a large number of sensors (in the case of the unconditional CRB), of a matrixbased CRB can be high while our approach is low and (ii) some useful information can be deduced from the behavior of the bound. In particular, an explicit relationship between the conditional and the unconditional CRBs is provided and one shows that closer is the source from the array and/or higher is the signal carrier frequency, better is the range estimation.
SPARSE FREQUENCY WAVEFORM DESIGN FOR MIMO RADAR
"... Abstract—Multipleinput multipleoutput (MIMO) radar has superior performance to conventional one. It has been introduced to almost every application field of conventional radar in recent years. In practical application, MIMO radar also faces the problem of congested spectrum assignment, which makes ..."
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Abstract—Multipleinput multipleoutput (MIMO) radar has superior performance to conventional one. It has been introduced to almost every application field of conventional radar in recent years. In practical application, MIMO radar also faces the problem of congested spectrum assignment, which makes it not possible to have a continuous clear band with large bandwidth. Sparse frequency waveform that contains several individual clear bands is a desirable solution to this problem. In this paper, we propose a method to design sparse frequency waveform set with low sidelobes in autocorrelations and crosscorrelations by optimizing an objective function constructed based on Power Spectrum Density requirement and sidelobe performances of waveform set. Thus, besides the property of approximate orthogonality, the designed waveforms obtain the ability of avoiding spectrum interference to/from other users. The waveform is phasecoded and thereby has constant modulus. The effectiveness of the proposed method is illustrated by numerical studies. Practical implementation issues such as quantization effect and Doppler effect are also discussed. 1.
Directionofarrival estimation for coherent signals without knowledge of source number
 2014) 3267–3273.Trans. Signal Process
, 1995
"... Abstract — A new method for directionofarrival (DOA) estimation of coherent signals is devised in this paper. The coherency of sources is decorrelated by employing an existing algorithm in which each row of the sample covariance matrix can be used to form a full rank Toeplitz matrix. Based on the ..."
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Cited by 2 (1 self)
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Abstract — A new method for directionofarrival (DOA) estimation of coherent signals is devised in this paper. The coherency of sources is decorrelated by employing an existing algorithm in which each row of the sample covariance matrix can be used to form a full rank Toeplitz matrix. Based on the joint diagonalization structure of the full set of Toeplitz matrices constructed from the rows, a new cost function that does not require a priori information of the source number is designed. A new spatial spectrum is then obtained where the DOAs are estimated via a 1D search. Numerical examples are provided to demonstrate effectiveness of the proposed approach. Index Terms — Directionofarrival (DOA) estimation, coherent signals, joint diagonalization, Toeplitz matrix. I.
Finite Sample Size Optimality of GLR Tests
, 903
"... In binary hypothesis testing, when the hypotheses are composite or the corresponding data pdfs contain unknown parameters, one can use the well known generalized likelihood ratio test (GLRT) to reach a decision. This test has the very desirable characteristic of performing simultaneous detection and ..."
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In binary hypothesis testing, when the hypotheses are composite or the corresponding data pdfs contain unknown parameters, one can use the well known generalized likelihood ratio test (GLRT) to reach a decision. This test has the very desirable characteristic of performing simultaneous detection and estimation in the case of parameterized pdfs or combined detection and isolation in the case of composite hypotheses. Although GLRT is known for many years and has been the decision tool in numerous applications, only asymptotic optimality results are currently available to support it. In this work a novel, finite sample size, detection/estimation formulation for the problem of hypothesis testing with unknown parameters and a corresponding detection/isolation setup for the case of composite hypotheses, is introduced. The resulting optimum scheme has a GLRTlike form which is closely related to the criterion one adopts for the parameter estimation or isolation part. When this criterion is selected in a very specific way we recover the well known GLRT of the literature while interesting novel tests are obtained with alternative criteria. The mathematical derivations are surprisingly simple considering they solve a problem that has been open for more than half a century.