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  • 1.
    Andersson, Sören
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Asymptotic Analysis of Subspace Methods for Beamspace Direction-of-Arrival Estimation using Large Arrays1992Report (Other academic)
    Abstract [en]

    Asymptotic analysis methods for performance prediction of so-called subspace directionof -arrival estimation methods has been developed earlier, assuming that a large-enough number of array measurements, or snapshots, is collected. This paper also addresses the problem of making performance predictions, but for beamspace-based subspace methods. The novel approach in this paper assumes the number of array elements to be large, while the number of snapshots is arbitrary. The perturbation effect, due to additive sensor noise, on a certain subspace is used for establishing the asymptotic behavior of direction-of-arrival estimates. The asymptotic estimation errors for the estimators resulting from Signal Subspace Fitting methods, such as WSF, and Noise Subspace Fitting (NSF) methods, such as MUSIC and a multi-dimensional counterpart to WSF, are shown to be asymptotically unbiased and normally distributed. Provided that the array response vectors become orthogonal when the number of array elements increases, the NSF methods are shown to give consistent estimates even in the case of fully coherent emitter signals, and the WSF method is shown to be consistent for coherent emitter signals even without this assumption. Comparisons with results for Maximum-Likelihood methods yield conditions for guaranteeing efficiency of the methods. Some simulation examples are also included.

  • 2.
    Andersson, Sören
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Beamspace Transformation Matrix Design using Numerical Optimization1992Report (Other academic)
    Abstract [en]

    This paper addresses the problem of designing a data-dimension reducing transformation matrix, to be used for beamspace direction-of-arrival (DOA) estimation. The design of the transformation matrix is based on numerical optimization techniques. The criteria to be satisfied is to retain as much as possible of the achievable, optimal estimation accuracy using the non-reduced data-sizes, while also taking into account the sidelobe levels of the beampattern. Comparisons of estimation accuracy and sensitivity to out-of-sector emitters for the design methods considered herein are carried out by means of simulation examples, using the WSF-method for the DOA-estimation. In order to reduce the number of parameters to be optimized, a parametrization of the transformation matrix is made, that utilizes the properties of Householder-reflections.

  • 3.
    Andersson, Sören
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    On Optimal Dimension Reduction for Sensor Array Signal Processing1991Report (Other academic)
    Abstract [en]

    The computational complexity for direction-of-arrival estimation using sensor arrays increases very rapidly with the number of sensors in the array. One way to lower the amount of computations is to employ some kind of reduction of the data dimension. This is usually accomplished by employing linear transformations for mapping full dimension data into a lower dimensional space. Different approaches for selecting these transformations have been proposed. In this paper, a transformation matrix is derived that makes it possible to theoretically attain the full-dimension Cramér-Rao bound also in the reduced space. A bound on the dimension of the reduced data set is given, above which it is always possible to obtain the same accuracy for the estimates of the source localizations, using the lower-dimension data, as that achievable by using the full dimension data. Furthermore, a method is devised for designing the transformation matrix. Numerical examples, using this design method, are presented, where the achievable performance of the (optimal) Weighted Subspace Fitting method with full dimension data is compared to the performance obtained with reduced dimension data. The problem of estimating parameters of sinusoidal signals from noisy data is also addressed by a direct application of the results derived herein.

  • 4.
    Andersson, Sören
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    On Two-Stage Schemes for Beamspace Direction-of-Arrival Estimation1992Report (Other academic)
    Abstract [en]

    This paper addresses performance analysis of two-stage methods for direction-of-arrival (DOA) estimation. By first finding crude initial DOA-estimates, the idea is to use these estimates for designing a transformation matrix as the first step. Then this matrix is employed for mapping the data to the lower-dimensional beamspace. Different ways for obtaining the first-stage DOA-estimates are discussed and various trade-offs that have to be considered are pointed out. The beamspace version of the Weighted Subspace Fitting (WSF) method is used for obtaining the final DOA estimates. An approximate performance bound is stated that assumes the first-stage DOA-estimates to be close to the true DOAs. For comparing the performance of some different ways to obtain the first-stage DOA-estimate, some numerical examples are included.

  • 5.
    Andersson, Sören
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Optimal Dimension Reduction for Sensor Array Signal Processing1991Report (Other academic)
    Abstract [en]

    The computational complexity for direction-of-arrival estimation using sensor arrays increases very rapidly with the number of sensors in the array. One way to lower the amount of computations is to employ some kind of reduction of the data dimension. This is usually accomplished by employing linear transformations for mapping full-dimension data into a lower-dimensional space. In the present work, a transformation matrix is derived, that makes it possible to attain the full-dimension Cramer-Rao bound also in the reduced space. A bound on the dimension of the reduced data set is given, above which it is always possible to obtain the same accuracy for the lower-dimension estimates of the source localizations as that achievable by using the full-dimension data. Furthermore, a method is devised for designing the transformation matrix.

  • 6.
    Andersson, Sören
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Reduced Dimension Beam-Space Transformation Design using Optimization1990Report (Other academic)
  • 7.
    Andersson, Sören
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Millnert, Mille
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Viberg, Mats
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Wahlberg, Bo
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    A Study of Adaptive Arrays for Mobile Communication Systems1991In: Proceedings of the 1991 International Conference on Acoustics, Speech and Signal Processing, 1991, p. 3289-3292Conference paper (Refereed)
    Abstract [en]

    The application of adaptive antenna techniques to increase the channel capacity in mobile radio communication is discussed. Directional sensitivity is obtained by using an antenna array at the base station, possibly both in receiving and transmitting mode. A scheme for separating several signals at the same frequency is proposed. The method is based on high-resolution direction finding following by optimal combination of the antenna outputs. Comparisons to a method based on reference signals are made. Computer simulations are carried out to test the applicability of the technique to scattering scenarios that typically arise in urban areas. The proposed scheme is found to have great potential in rejecting cochannel interference, albeit at the expense of high computational requirements.

  • 8.
    Andersson, Sören
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Millnert, Mille
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Viberg, Mats
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Wahlberg, Bo
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    A Study of Adaptive Arrays for Mobile Communication Systems1990Report (Other academic)
    Abstract [en]

    The application of adaptive antenna techniques to increase the channel capacity in mobile radio communication is discussed. Directional sensitivity is obtained by using an antenna array at the base station, possibly both in receiving and transmitting mode. A scheme for separating several signals at the same frequency is proposed. The method is based on high-resolution direction finding following by optimal combination of the antenna outputs. Comparisons to a method based on reference signals are made. Computer simulations are carried out to test the applicability of the technique to scattering scenarios that typically arise in urban areas. The proposed scheme is found to have great potential in rejecting cochannel interference, albeit at the expense of high computational requirements.

  • 9.
    Andersson, Sören
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Millnert, Mille
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Viberg, Mats
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Wahlberg, Bo
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    An Adaptive Array for Mobile Communication Systems1991In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 40, no 1, p. 230-236Article in journal (Refereed)
    Abstract [en]

    The use of adaptive antenna techniques to increase the channel capacity is discussed. Directional sensitivity is obtained by using an antenna array at the base station, possibly both in receiving and transmitting mode. A scheme for separating several signals at the same frequency is proposed. The method is based on high-resolution direction-finding followed by optimal combination of the antenna outputs. Comparison with a method based on reference signals is made. Computer simulations are carried out to test the applicability of the technique to scattering scenarios that typically arise in urban areas. The proposed scheme is found to have great potential in rejecting cochannel interference, albeit at the expense of high computational requirements.

  • 10.
    Andersson, Sören
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Nehorai, Arye
    Yale University, USA.
    Analysis of a polarized seismic wave model1994Report (Other academic)
    Abstract [en]

    We present a model for polarized seismic waves where the data are collected by three-component geophone receivers. The model is based on two parameters describing the polarization properties of the waveforms. These parameters are the ellipticity and the orientation angle of the polarization ellipse. The model describes longitudinal waveforms (P-waves) as well as elliptically polarized waves. For the latter waves the direction-of-propagation of the waveform is in the plane spanned by the ellipse's major and minor axes; Rayleigh waves are treated as a special case. We analyze the identifiability of the models and derive the Cramer-Rao and mean-square-angular-error (MSAE) bounds involving one or two three-component geophones.

  • 11.
    Andersson, Sören
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Nehorai, Arye
    Yale University, USA.
    Optimal Dimension Reduction for Array Processing: Generalized1993Report (Other academic)
    Abstract [en]

    This correspondence extends previously reported work [1, 2] on the problem, or rather possibility, of achieving optimality of beamspace (BS) array processing, where use is made of dimensionally reduced data vectors. The optimality here is with respect to the best possible element space (ESP) parameter estimation accuracy, i.e., the Cramér-Rao bound.

  • 12.
    Andersson, Sören
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Nehorai, Arye
    Yale University, USA.
    Some Comparisons of Cramer-Rao Bounds for Vector Sensors and Scalar Sensor Arrays for Array Processing1993Report (Other academic)
    Abstract [en]

    The effect from polarization of emitted wave fronts on the parameter estimation accuracy for an array composed only of sensors sensitive to just one polarization direction has not been addressed in the literature this far. Antennas with such characteristics are, e.g., dipole (or scalar) antennas. A vector sensor, on the other hand, is a sensor whose output data consists of, for the electromagnetic case, the complete electric and magnetic fields at the sensor. This paper examines some of the effects on the Cram'er-Rao Bound for the elevation and/or azimuth angles to a single source emitting a polarized (electromagnetic) waveform. Since only one vector sensor is needed for estimation of both azimuth and elevation, it would be of interest to compare the lower parameter estimation error bound resulting from the vector sensor data model to the "ordinary" one, i.e. the data model used for scalar arrays. Such comparisons, both analytically and numerically, are herein made for an acoustic data model, as well as for an electromagnetic measurement model, for some simple scenarios and array configurations.

  • 13.
    Andersson, Sören
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Stoica, Petre
    Polytechnic Institute of Bucharest, Romania.
    Viberg, Mats
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Nehorai, Arye
    Yale University, USA.
    Eigenvector Matrix-Beamformers in Array Processing1994Report (Other academic)
1 - 13 of 13
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