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Radar, Sonar and Navigation, IEE Proceedings -

Issue 2 • Date Apr 1998

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Displaying Results 1 - 8 of 8
  • Improved azimuthal resolution of forward looking SAR by sophisticated antenna illumination function design

    Page(s): 128 - 134
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (744 KB)  

    In comparison to side looking synthetic aperture radar (SAR), in a forward looking SAR it is much more difficult to achieve high angular resolution. The reason for this resolution problem is that terrain points situated symmetrically about the flight path have the same Doppler history, and the gradient of the Doppler frequency is small in the flight direction. A promising way to improve the resolution consists in using minimum variance unbiased (MVU) estimation in the receiver. Unfortunately, MVU estimation leads to undesirable noise enhancement. It is shown that an appropriate method to determine the achievable angular resolution consists in studying this noise enhancement. To minimise the noise enhancement and thus maximise the angular resolution, the author proposes antennas with specific aperture illumination functions. These illumination functions result in radiation patterns which are spread in the angular domain and are simultaneously fine-structured. Quantitative results concerning the noise enhancement and the angular resolution are presented and discussed View full abstract»

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  • Modal morphing on meteorological radar data for rainfall pattern analysis

    Page(s): 123 - 127
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (520 KB)  

    The authors present the application of a modal morphing technique to meteorological data obtained from radar. The procedure, based on the recently introduced modal matching method for shape analysis and description, allows efficient exploitation of the information about detected rainfall patterns and their evolution. After some considerations about the use of the modal matching method for meteorological data handling, the authors offer a simple method for the analysis of rainfall movements in a case study of a hurricane which occurred in Florida View full abstract»

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  • Analysis of a frequency estimator for a class of laser signals with time-varying amplitude

    Page(s): 109 - 118
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (796 KB)  

    The authors address the problem of estimating a particle's velocity in the vicinity of an aircraft by means of a laser velocimeter. A model for the signal generated by a particle of air passing through a probe volume consisting of equidistant bright and dark fringes is given. From this model, a frequency estimator based on the phase of the correlation sequence of the signal is proposed. A theoretical analysis of the frequency estimator is presented. In particular, a formula for the variance of the estimate is derived under the assumption of small estimation errors. Numerical examples confirm the validity of the analysis. It is reported that this estimator, although simpler than the maximum likelihood approach, comes close to the Cramer-Rao bound. Finally, the effectiveness of the proposed algorithm is demonstrated on real data View full abstract»

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  • Properties of estimability criteria for target motion analysis

    Page(s): 92 - 99
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (708 KB)  

    A significant amount of study has been devoted to the observability analysis for passive target motion analysis. A unified presentation of observability and estimability is provided. Using a common formalism, explicit results are thus obtained View full abstract»

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  • How narrow is narrowband?

    Page(s): 85 - 91
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (624 KB)  

    The “narrowband” assumption is often made in the analysis of array signal processing algorithms. The author provides a definition for the notion of narrowband, and the derivation of an expression which is useful in determining if a particular scenario qualifies as narrowband. The expression derived correctly predicts where the narrowband assumption fails for some super-resolution algorithms, the Cramer-Rao bound on angle estimation and the signal-to-interference plus noise performance of adaptive beamformers View full abstract»

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  • Intratropospheric range delay for two refractivity models

    Page(s): 119 - 122
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (272 KB)  

    Closed form expressions for range delay are derived the dual-quartic refractivity model developed by H. Hopfield in 1969. Graphical results are presented as functions of source-to-target slant range and elevation angle for three typical refractivity profiles. Asymptotic, or transtropospheric values of range delay at 0° and 90° elevation angles, are compared for the dual-quartic and more conventional exponential refractivity models. Relating the parameters of the two models via this comparison leads to the demonstration that both models yield results within a few per cent of each other at all the target slant ranges and elevation angles which were investigated View full abstract»

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  • Lineshape analysis of breaking-wave Doppler spectra

    Page(s): 135 - 139
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (516 KB)  

    Based on analyses of spectral densities of microwave backscatter from ocean waves, it has previously been observed that the Doppler spectra could be decomposed into different components, with Bragg scatterers represented by Gaussian lineshapes and faster-than-Bragg scatterers represented by Lorentzian and/or Voigtian lineshapes. It has been conjectured that the faster-than-Bragg scatterers are due to scattering from breaking waves, and established that the scattering mechanisms are non-Bragg in nature. In order to test the conjecture regarding the decomposition of spectral lineshapes which represent meaningful scattering processes, experiments have now been conducted at a wave tank facility. The lineshapes of breaking-wave Doppler spectra are analysed. It is found that for mechanically-generated breaking waves in the absence of wind, the co-polarised (HH and VV) spectra have predominantly Voigtian or Lorentzian shape and that the cross-polarised (VH and HV) spectra have exclusively Voigtian shape View full abstract»

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  • Data compression, data fusion and Kalman filtering in wavelet packet sub-bands of a multisensor tracking system

    Page(s): 100 - 108
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (832 KB)  

    In a multisensor target tracking system in which centralised Kalman filtering is employed, the amount of data to be transmitted from the sensors to the central processor demands a huge communication cost. In addition, the amount of data received by the central processor further imposes an enormous computational load on the Kalman filter. The authors propose the use of wavelet packet decomposition on the observed data vectors so that the insignificant sub-band components may be suppressed transmitted resulting in the communication cost. Furthermore, optimum fusion is applied to the sub-band components before the data vectors are reconstructed. Two tracking schemes, tracking by reconstructed compressed data (TRCD) and tracking by compressed sub-band data (TSCD), are proposed. In TRCD, Kalman filtering is applied to the reconstructed data vector, whereas in TCSD, Kalman filtering is only applied to the components in the dominant sub-band of the decomposition. Simulation results show that, in terms of communications and/or computation economy, these two schemes offer attractive alternatives without over-sacrificing 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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