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Radar, Sonar and Navigation, IEE Proceedings -

Issue 6 • Date Dec 1996

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Displaying Results 1 - 8 of 8
  • Reconstruction of the spatial distribution of radar reflectivity of precipitation through linear-inversion techniques

    Publication Year: 1996 , Page(s): 375 - 382
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (784 KB)  

    The authors present a method aiming to remove the smoothing effect due to the antenna beamwidth in the reconstruction of the rain reflectivity based on radar measurements. The function to be reconstructed is the spatial distribution Z(x,y,h) of the radar reflectivity Z of the precipitation, which is shown to be related by a Fredholm integral equation to the power received by the radar. This integral equation is transformed into a set of linear equations and subsequently solved through a constrained-linear-inversion technique. The method is then applied to the cases of both stratiform and convective rain, leading to an improved estimation of the reflectivity-peak location and intensity, and of the overall reflectivity profile View full abstract»

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  • Simultaneous mean and texture edge detection in SAR clutter

    Publication Year: 1996 , Page(s): 391 - 399
    Cited by:  Papers (8)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1408 KB)  

    The authors consider simultaneous edge detection of synthetic aperture radar (SAR) images in terms of both the local mean value and a texture parameter related to the depth of modulation. They assume that SAR clutter has K-distributed statistics which can be completely characterised by the mean and order parameter of the distribution. Approximate distributions, based on matching a gamma distribution to the K-distributed amplitude or intensity, are derived. Analytic maximum likelihood tests for the presence of an edge are then derived. Two criteria for optimisation are considered: maximising the total probability of detecting an edge within a window; and maximising the accuracy with which the edge position can be determined. The authors consider each test separately and also investigate a two-stage test which approximately optimises both measures. They indicate the effect of different prior knowledge on the ability to detect edges and also demonstrate the limitations imposed by the approximations made View full abstract»

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  • Fractional lower-order statistics-based ambiguity functions for differential delay Doppler estimation

    Publication Year: 1996 , Page(s): 358 - 365
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (716 KB)  

    The problem of estimation of differential-delay Doppler in an environment in which the signal of interest is embedded in highly impulsive interference is addressed. A signal model is formulated with wide applications in radar, sonar, communications and biomedicine and the construction of a new ambiguity function is proposed which is based on the recently-developed concepts of fractional, lower-order statistics and is, therefore, resistant to the presence of severe outliers in the observed time series. The performance of the proposed differential-delay Doppler estimators is theoretically analysed, verified via Monte Carlo simulation, and compared to the performance of traditional, second-order statistics-based estimators View full abstract»

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  • High resolution processing of hybrid strip-map/spotlight mode SAR

    Publication Year: 1996 , Page(s): 366 - 374
    Cited by:  Papers (35)  |  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1320 KB)  

    Synthetic aperture radars have traditionally operated in either the spotlight mode, in which the coverage is limited, or in the strip-map mode, in which the resolution is limited. It is shown that, by steering the radar antenna about a point further away from the radar than the centre of the area being imaged, illumination times between that of strip-map and spotlight mode are achieved, thus resulting in different combinations of resolutions and spot sizes than is the case for traditional spotlight mode. The theory underlying this mode is derived from first principles, and it is shown that strip-map and spotlight modes are limiting cases. A wavenumber domain processing technique is presented that correctly compensates for range curvature and its equivalence to range Doppler processing described mathematically. This technique results in focused images and is applied to both simulated and real data. The advantages of this mode are a reduced data rate at high resolution, the use of a higher gain antenna, and achieving high resolution over an area larger than that possible in the spotlight mode. This technique may be applied to both space and airborne radar where a combination of high resolution and wide area coverage is important View full abstract»

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  • Accurate approximation to the optimum parameter estimate for K-distributed clutter

    Publication Year: 1996 , Page(s): 383 - 390
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (864 KB)  

    The authors analyse the suboptimal performance of simple texture measures for estimating the order parameter of K-distributed radar clutter. A noncommittal neural net has been applied to the parameter estimation task and it shows that improved error estimates are obtained when multiple moments are used to characterise the texture. A new estimator is proposed which combines the mean normalised log intensity and the amplitude contrast moments of the imaged data to provide a more accurate measure of the texture information, which results in lower errors in the parameter estimates. The relative weighting in which the two moments are combined determines the error performance of the estimator. Using a constant weight value, an estimator has been derived which gives close to maximum likelihood performance on the estimates over a wide range of the parameter values which are of interest. Thus it is shown that the use of multiple moments in a texture measure produces a closer approximation to the optimum parameter estimate for a K-distributed process View full abstract»

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  • IEE Proceedings Radar, Sonar and Navigation vol. 143, 1996 Author Index

    Publication Year: 1996 , Page(s): 401 - 404
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (356 KB)  

    First Page of the Article
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  • Manifold of a planar array and its effects on the accuracy of direction-finding systems

    Publication Year: 1996 , Page(s): 349 - 357
    Cited by:  Papers (10)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (744 KB)  

    The authors are concerned with the accuracy of azimuth and elevation estimates provided by a planar array of sensors and its relation to the array manifold differential geometry. The paper builds on previously published results regarding the influence of the manifold differential geometry on the detection and resolution capabilities of linear arrays. The manifold of a planar array is introduced in terms of two families of constant-azimuth and constant-elevation curves, and their differential geometry is analysed as a function of the array configuration. Circular approximation is subsequently employed to derive novel expressions for the Cramer-Rao lower bound on azimuth and elevation estimates in terms of the arc lengths and first curvatures of the respective constant-parameter manifold curves. The scenarios considered include the cases of a single emitter as well as that of two closely spaced uncorrelated emitters of arbitrary powers. The results obtained are demonstrated for the cases of two practical array configurations View full abstract»

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  • Unitary Hessenberg and state-space model based methods for the harmonic retrieval problem

    Publication Year: 1996 , Page(s): 346 - 348
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (272 KB)  

    The connections between two families of methods for the harmonic retrieval problem are explored: the unitary Hessenberg methods and the state-space model based methods. It is shown that in a noise-free situation, the unitary Hessenberg methods can be understood as one particular case of a very popular high resolution algorithm, the Toeplitz approximation method (TAM) of S.Y. Kung (1981) 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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