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Radar, Sonar and Navigation, IEE Proceedings -

Issue 1 • Date Feb 2001

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Displaying Results 1 - 7 of 7
  • Communication structure planning for multisensor detection systems

    Page(s): 2 - 8
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (552 KB)  

    The authors address the problem of communication structure planning in multisensor detection systems under communication constraints and also under a generalised cost formulation. The communication constraint is specified in terms of the amount of communication allowed in the system, while the generalised cost functions measure the efficiency of communication used. System optimisation algorithms are developed for both criteria. Examples for both Bayesian and Neyman-Pearson formulations are presented for illustration. A variety of scenarios are considered to study their effect on system performance View full abstract»

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  • Extraction of moving ground targets by a bistatic ultra-wideband SAR

    Page(s): 35 - 40
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (488 KB)  

    The use of a bistatic antenna configuration for ground moving target indication in an ultra-wideband and widebeam synthetic aperture radar system is discussed. To suppress the strong clutter signal the radar channels have a strict requirement on equality. In a bistatic system they are not equal, and the author investigates how to compensate for the bistatic configuration. Bistatic effects on clutter scattering cannot be compensated, and an attempt is therefore made to estimate the bistatic scattering influence of the ground moving target indication. The bistatic to monostatic synthetic aperture inversion in a wide antenna beam is derived in both the time and the frequency domain. The mismatch between the radar channels will cause clutter leakage. The pulse compressed impulse response leakage is determined both for the time and frequency domains View full abstract»

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  • Contextual information in SAR target detection

    Page(s): 41 - 47
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (932 KB)  

    Established target detection schemes make a statistical decision as to whether the value of a test pixel is more likely to have arisen due to the presence of a target or of clutter. Subject to prior probabilities for the occurrence of targets or clutter. However, such schemes do not take into account the contextual information which is available. For example, it will be known that military vehicles may be more likely to be located in fields close to hedges and woodland edges to provide cover and will often travel in groups. It is demonstrated how such contextual information may be incorporated into a SAR target detection scheme, while maintaining the statistical rigour of established techniques. A theoretical framework is developed in which the prior probability for the presence of a target is modified by the contextual influences via conditional dependencies. The resulting detection scheme is applied to simulated SAR images to obtain target detection rates for various combinations of contextual information. An improvement in performance of about 13% is observed when the context is fully exploited View full abstract»

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  • Efficient algorithm for localising 3-D narrowband multiple sources

    Page(s): 23 - 26
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (316 KB)  

    The authors propose an efficient 3-D source localisation algorithm using three uniform linear subarrays. The proposed algorithm replaces the 3-D search required in conventional 3-D MUSIC with three 1D searches, and thus reduces the computational burden. An estimate of the 1-D incident angle obtained from a subarray under the far field assumption satisfies the nonlinear algebraic equation of the true source bearing angle, elevation angle, and range. The proposed algorithm estimates source location by solving three algebraic equations obtained from three subarrays. When comparing 3-D MUSIC spectra of the estimated source locations, the proposed algorithm is able to solve the pairing problem in localisation of multiple sources View full abstract»

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  • Pseudo-linear estimator for bearings-only passive target tracking

    Page(s): 16 - 22
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (424 KB)  

    The pseudo-linear extended Kalman tracking filter previously developed for passive target tracking using bearings-only measurements required the use of a null target state vector as an initial estimate to obtain convergence for all types of scenarios. The pseudo-linear estimator is projected in such a way that it does not require any initial estimate at all and at the same time offers all the features of the extended Kalman filter based pseudo-linear filter; namely sequential processing, flexibility to adopt the variance of each measurement, etc. The algorithm is tested in Monte Carlo simulations and its results are presented for two typical scenarios at various noise levels View full abstract»

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  • Comparative study of five LMS-based adaptive time delay estimators

    Page(s): 9 - 15
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (584 KB)  

    A number of adaptive algorithms have been proposed to model the delay between signals received at two spatially separated sensors using an FIR filter. Among them, there are the LMSTDE, CTDE, ETDE, SETDE and ETDGE, which are computationally efficient because of the LMS implementation. These five methods are compared in terms of estimation accuracy and computational complexity. It is proved that the LMSTDE and ETDGE attain performance for sufficiently long filter lengths, although the ETDE and SETDE perform similarly to the ETDGE at high signal-to-noise ratio (SNR) and low SNR, respectively. The CTDE involves minimum computational load but it is the worst estimator in the presence of noise. In addition, optimum realisations of the LMSTDE as well as the ETDE and its variants are derived and their delay variances are compared with the Cramer-Rao lower bound. Simulation results show that ETDGE outperforms the other four methods for a wide range of filter lengths at different SNRs View full abstract»

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  • Tomographic imaging of isolated ground surfaces using radio ground waves and conjugate gradient methods

    Page(s): 27 - 34
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (904 KB)  

    The ground surface of the Earth is usually mapped using microwave radar, and in particular synthetic aperture radar. A different technique is presented for the imaging of isolated ground surfaces, which may range from the order of a metre to a few kilometres in diameter, using radiowaves generated from antennas on the ground surface of the Earth. The technique is first formulated using groundwave propagation theory to solve the forward electromagnetic scattering problem of the isolated surface. Conjugate gradient methods are then used to solve the inverse problem to obtain the normalised surface impedance distribution in an iterative manner, with the establishment of a cost function of the measured and scattered fields around the surface. Numerical simulations at 0.5 MHz of two ground features, namely dry ground and dry-wet mixed ground surfaces confined within a diameter of 500 m and surrounded by seawater, show that the distributions of both real and imaginary parts of the normalised surface impedance can be well reconstructed using the technique. It is also shown that the Polak-Ribiere-Polyak conjugate gradient method gives a faster rate of convergence than the Fletcher-Reeves method. The simulation at 300 MHz of dry ground with a buried metallic object confined within a diameter of 50 cm shows that the metallic object and its position can be identified from the images of normalised surface impedance distribution. The study demonstrates a new technique for the tomographic imaging of isolated ground surfaces which may be useful in ground surface mapping, remote sensing and monitoring, and detection of buried metallic objects 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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