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Radar, Sonar and Navigation, IEE Proceedings -

Issue 4 • Date 5 Aug. 2005

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Displaying Results 1 - 9 of 9
  • Nonuniform linear antenna arrays minimising Cramer-Rao bounds for joint estimation of single source range and direction of arrival

    Page(s): 225 - 231
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (232 KB)  

    Different antenna placements in nonuniform linear arrays for the joint estimation of the range and direction-of-arrival (DOA) of one source are considered. It is shown that the Cramer-Rao bound (CRB) for the range and DOA estimates can be expressed as a function of the angles at which the source sees the antennas. This new formulation of the CRB easily reveals the geometrical properties that the array should have in order to minimise the CRB. Based on the new representation of the CRB, a result found in the literature (which was concerned with the special case of a number of antennas that is divisible by four) is generalised to include the case of an arbitrary number of antennas. Furthermore, it is shown that symmetric arrays are close to uniformly optimal for different DOAs when the range is much larger than the aperture of the arrays. View full abstract»

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  • Interference subspace approximation based adaptive beamforming in the presence of a desired signal

    Page(s): 232 - 238
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (243 KB)  

    A novel subspace-based adaptive beamforming method is proposed which is very efficient in computation and can be applied to arrays of arbitrary geometry. In the proposed method, an approximate basis of the interference subspace is obtained from a matrix in which the desired signal component has been removed using the information on its direction. The matrix is updated recursively with data samples and so there is no need for the estimation of the array covariance matrix. A simple direction correction scheme is readily incorporated into the beamformer, so that it is robust to errors in both the look direction and the detected number of the incident signals. The theoretical analysis and simulation results demonstrate the effectiveness of the simple beamforming method. View full abstract»

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  • Modified gain extended Kalman filter with application to bearings-only passive manoeuvring target tracking

    Page(s): 239 - 244
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (213 KB)  

    The feasibility of Song and Speyer's modified gain extended Kalman filter using bearings-only measurements is explored for underwater applications. A much simpler version of the modified function introduced by Galkowski and Islam is considered for the development of this algorithm. This algorithm estimates target motion parameters and detects target manoeuvre, using zero mean chi-square distributed random sequence residuals, in sliding window format. During the period of target manoeuvring, the covariance of the process noise is increased sufficiently in such a way that the disturbance in the solution is less. When a target manoeuvre is completed, the covariance of process noise is lowered. The performance of this algorithm is evaluated in Monte Carlo simulation and results are shown for various typical geometries. View full abstract»

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  • Reflectivity tuning in multi-layer phase-switched active radar absorbers

    Page(s): 245 - 247
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (117 KB)  

    An 'array' polynomial approach is used to predict the positions of the reflectivity s for an ideal phase-switched screen (PSS) having many active layers. Several layer-switching schemes are examined and it is found that the resulting position diagrams exhibit bifurcation behaviour similar to that found in many dynamical systems. The chaotic state is never achieved, however, since the ideal PSS is a linear system. View full abstract»

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  • RCS reduction of spiral patch antenna using a PSS boundary

    Page(s): 248 - 252
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (308 KB)  

    The use of a phase-switched screen (PSS) boundary to control the radar cross-section (RCS) of a spiral patch antenna is investigated. A theoretical analysis based on a transmission line analogue is used to examine the concept and to provide basic design criteria. The design of an experimental system that includes a novel dual polarised active PSS boundary is described. Measured results are presented, which show that the demonstrator system provides active RCS control between 11 GHz and 13 GHz. View full abstract»

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  • Contrast maximisation based technique for 2-D ISAR autofocusing

    Page(s): 253 - 262
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (999 KB)  

    An image contrast based algorithm for 2-D ISAR image autofocusing is proposed. The problem of ISAR image autofocusing is formulated analytically by defining geometry and dynamics of the radar-target system and by assuming a mathematical model for the received signal. The image focusing is then achieved by estimating the model parameters through the maximisation of the image contrast. The problem of the maximum search is solved numerically by means of an iterative search method. An algorithm able to produce an accurate initial guess is also developed by using the radon transform. The good accuracy of the initial guess guarantees the convergence of the optimisation problem solution to the global maximum. The performance of the proposed autofocusing technique is tested by comparing it to the point prominent processing (PPP) algorithm, the phase gradient algorithm (PGA) and the image entropy based technique (IEBT), through the use of real data. Results confirm the effectiveness of the proposed algorithm. View full abstract»

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  • Mosaicing of acoustic camera images

    Page(s): 263 - 270
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (692 KB)  

    An algorithm for image registration and mosaicing on underwater sonar image sequences characterised by a high noise level, inhomogeneous illumination and low frame rate is presented. Imaging geometry of acoustic cameras is significantly different from that of pinhole cameras. For a planar surface viewed through a pinhole camera undergoing translational and rotational motion, registration can be obtained via a projective transformation. For an acoustic camera, it is shown that, under the same conditions, an affine transformation is a good approximation. A novel image fusion method, which maximises the signal-to-noise ratio of the mosaic image is proposed. The full procedure includes illumination correction, feature based transformation estimation, and image fusion for mosaicing. View full abstract»

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  • Position domain filtering and range domain filtering for carrier-smoothed-code DGNSS: an analytical comparison

    Page(s): 271 - 276
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (136 KB)  

    Carrier-smoothed-code filters for differential Global Navigation Satellite System (GNSS) positioning can be partitioned into two groups: position domain filters and range domain filters. In carrier-smoothed-code filtering, noise terms of incremental carrier phase act as equivalent propagation noise. The equivalent propagation noises in carrier-smoothed-code filtering are temporally correlated and bounded in time, unlike white Gaussian noises in Kalman filtering. Thus, it seems that carrier-smoothed-code filtering does not inherit all the characteristics of classical Kalman filtering. To demonstrate that position domain filtering is better than range domain filtering a rigorous analysis is performed. View full abstract»

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  • Fast FFT based GPS satellite acquisition methods

    Page(s): 277 - 286
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (925 KB)  

    A Global Positioning System (GPS) receiver uses satellite signals to determine position, velocity, and timing information. Measurements are obtained by synchronising the locally generated signal in the receiver with the signals received. A synchronisation procedure called acquisition adjusts the code phases of the incoming signal and the locally generated pseudo-random replica sequence of the corresponding satellite to a small timing offset and finds the residual frequency modulation after carrier wipe-off. New fast techniques for acquiring signals indoors in conditions that require a significant number of computations are presented. In this work many arithmetic operations are shared when exploring different search options by using fast Fourier transform (FFT) and a technique based on the frequency domain replica shifting. It is shown that FFT can be used for the joint processing of multiple (code-phase/frequency) search options in both dimensions at once. With a slight degradation in performance, the algorithm has a modified version that implements the technique using two-dimensional FFT. Several possible processing schemes are presented. Moreover, the presented shifting replica approach in the frequency domain can significantly reduce computational complexity by jointly acquiring different satellites. View full abstract»

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Aims & Scope

IEE Proceedings Radar, Sonar and Navigation covers the theory and practice of systems involving the processing of signals for radar, radio location, radio navigation and surveillance purposes.

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