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Radar, Sonar and Navigation, IEE Proceedings -

Issue 2 • Date Apr 2004

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Displaying Results 1 - 8 of 8
  • Pattern recognition of multiple signals from ground penetrating radar for metal and plastic objects

    Page(s): 91 - 99
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1551 KB)  

    The author describes methods for pattern recognition of multiple time signals of embedded targets in water or soil. The received time signals are investigated using characteristic features of metal and plastic pipes in water for better detection of plastic and for soil with noisy signals. The classification of time signals is done by statistical signal parameters, ARMAX, Prony modelling, a new difference vector method of the model transfer function H(z) in the coefficient vector feature space, principal component analysis (PCA), and the classification (more than the estimation or identification) of radar targets via complex frequencies (CNR - complex natural resonances) of these multiple time signals. View full abstract»

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  • Non-cooperative target recognition in the frequency domain

    Page(s): 77 - 84
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1379 KB)  

    Non-cooperative target recognition is investigated in the frequency domain using measured in-flight aircraft data. It is found that the frequency domain target signatures are distinct for different aircraft types and at different aspects. As a result, target identification in the frequency domain is just as viable as using conventional high-range resolution profiles in the range domain. In addition, there are many advantages of working in the frequency domain; many of the problems encountered in the range domain can be avoided. This leads to a much simpler task in performing target recognition. View full abstract»

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  • Adaptive anti-interference technique using subarrays in HF surface wave radar

    Page(s): 100 - 104
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1533 KB)  

    To improve the capability of high frequency (HF) surface wave radar to suppress interference, an adaptive anti-interference technique was evaluated by using subarrays in OSMAR2000 (Ocean State Monitor and Analysis Radar, manufactured in 2000). The authors propose a scheme to suppress the external HF radio strong interference based on OSMAR2000 radar without increasing any auxiliary facilities, and some radar experiments were carried out by using a monopole as the main antenna and the other three vertical monopoles as auxiliary antennas. The results of a preliminary study of an adaptive system with subarrays for the suppression of strong interference are presented. The results of the study show that the technique worked well against the observed interference. View full abstract»

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  • Reconstruction of textured seafloors from side-scan sonar images

    Page(s): 114 - 126
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1911 KB)  

    The seafloor is subject to attention and exploitation in many branches of science and technology. The acquisition of seabed information using AUVs equipped with a visual system composed of cameras and sonars is becoming more common. However, although most of these sensors, such as side-scan sonar, can generate a 2-D representation of the seafloor, 3-D information, which is crucial for environmental and geological studies, is only provided by a few sensors and often only at very low resolution. A linear shape-from-shading approach is presented, which is novel in the context of side-scan sonar images. This technique aims to recover the 3-D shape of textured seabeds from side-scan sonar images. For comparison purposes, an existing propagation shape from shading approach is also considered. Results showed that both techniques yield good results in terms of similarity and accuracy, although the linear shape-from-shading technique presented superior results when noise was present in the images, a condition which is very common with side-scan sonar images. View full abstract»

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  • Approach to object classification using dispersive scattering centres

    Page(s): 85 - 90
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1530 KB)  

    The dispersive scattering centre (DSC) model characterises high-frequency backscatter from radar objects as a finite sum of localised scattering geometries distributed in range. These geometries, along with their locations, can be conveniently used as features in a one-dimensional automatic object recognition algorithm. The DSC model's type and range parameters correspond to geometry and distance features according to the geometric theory of diffraction (GTD). To demonstrate the viability of feature extraction based on the DSC model's range and type parameters, a typical object classification experiment was performed. The experimental data contained direct range radar measurements of four model fighter aircraft of similar size and shape at 0° elevation and 0°-30° azimuth. After implementing DSC model feature extraction on these data, a fully-connected two-layer neural net obtained over 98% classification accuracy. In addition, DSC model feature extraction gave an approximately 85% reduction in the number of required features when compared to the numerous range bin magnitudes used in template matching techniques. View full abstract»

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  • Bounding the angular scale factor error for adaptive arrays

    Page(s): 71 - 75
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1582 KB)  

    When compared with a conventional gimballed antenna a phased-array antenna conveys some important advantages to a tracking radar system, including inertialess beam-steering and the ability to modify the beam pattern to suppress interference. For successful tracking of a radar target the linearity of the antenna angular response must be carefully controlled. The effect of array calibration errors on the linearity of the response of an adaptive phased-array antenna is considered. Through analysis of the maximum likelihood estimate (MLE) of target angle, a lower bound is derived on the variance of the angular scale factor error achievable when tracking a target with an adaptive phased-array antenna in the presence of residual calibration errors and interference. It is shown that while the presence of a sidelobe interferer has little impact on the achievable variance, a strong mainbeam interferer can result in a very significant degradation. View full abstract»

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  • Simultaneous localisation of multiple emitters

    Page(s): 65 - 70
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1330 KB)  

    Exploiting several arrays of sensors enables simultaneous detection of a number of emitters. Fusion of the respective array data yields lines containing possible positions as a function of the frequency. Identifying multiple intersections eventually leads to unambiguous localisation of the sources. The usual unwanted ghost detections do not appear in this approach. Simulations are performed to demonstrate the feasibility of the formalism. View full abstract»

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  • Limitations of nonlinear chaotic dynamics in predicting sea clutter returns

    Page(s): 105 - 113
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2095 KB)  

    The ability to describe sea clutter returns via nonlinear, and more specifically chaotic, dynamics is examined. It is shown that the commonly used chaotic invariant measures of correlation dimension and Lyapunov exponent are incapable of uniquely identifying chaotic processes, and produce similar results for measured sea clutter returns and simulated stochastic processes. The potential existence of an underlying chaotic texture masked by stochastic overlying speckle is examined but found to be inconsistent with the measured properties of the sea clutter data. Finally, the performance of three linear and nonlinear predictors is tested against high-resolution measured sea clutter data but no improvement is found to exist for the nonlinear predictor tested with respect to linear prediction performance. 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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