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Radar, Sonar and Navigation, IEE Proceedings -

Issue 6 • Date Dec 1998

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Displaying Results 1 - 10 of 10
  • Basic functional requirements and results for an MSSR on-site evaluator based on RF target injection

    Page(s): 361 - 366
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (416 KB)  

    Modern quality control in radar systems is based on the input of known signals into the radar chain. These signals are used in a remote air traffic control centre to determine the current parameters of the radar system. In this framework, the paper describes the functional requirements of a monopulse secondary surveillance radar (MSSR) evaluator based on RF target injection. In particular, those aspects concerning the reply generation function are described. The azimuth of the emulated plot can be affected by different error sources which are not due to the radar extractor but are related to the generation and injection process. Errors in the amplitude and phase of Σ and Δ result in azimuth errors and must be kept to a minimum. Synchronisation with the turn of the antenna will also lead to unavoidable azimuth errors. These error sources are studied, and three different data analyses carried out on real radar are also presented View full abstract»

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  • Time-varying complex spectral analysis via recursive APES

    Page(s): 354 - 360
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (808 KB)  

    APES (amplitude and phase estimation) is an adaptive FIR filtering approach introduced previously for complex spectral estimation. For stationary signals, APES can yield more accurate spectral estimates than the widely used Capon and FFT estimators. The authors present a recursive APES algorithm for time-varying spectral analysis, which is compositionally efficient and only involves FFT and simple matrix operations. The recursive APES algorithm is applied to ISAR (inverse synthetic aperture radar) imaging and feature extraction of targets with complex manoeuvring motion. Both numerical and experimental examples are provided to demonstrate the performance of the proposed method View full abstract»

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  • Fuzzy logic approach to manoeuvring target tracking

    Page(s): 337 - 341
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (416 KB)  

    The authors describe an extension to the interacting multiple model (IMM) algorithm using a fuzzy logic framework. Each Kalman filter is considered to be locally valid, applicable over a region of the target acceleration space defined by the filter conditioning value. The validity of each Kalman filter is determined using fuzzy sets and an estimate of the target acceleration. With suitable choice of the fuzzy set overlap, only a subset of models close to the acceleration estimate need be evaluated. Simulation results are included for a typical manoeuvring target scenario which illustrate the effect of different forms of fuzzy sets. These confirm that the approach compares favourably with IMM in terms of both estimation accuracy and computational load View full abstract»

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  • Performance analysis of ETDGE-an efficient and unbiased TDOA estimator

    Page(s): 325 - 330
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (504 KB)  

    A computationally efficient estimator is proposed which can provide instantaneous delay measurement for many practical applications such as radar, sonar and geolocation via satellites. It consists of an adaptive FIR filter to model the time difference of arrival (TDOA) between the received signals from two sensors and a variable gain to adapt to the changing signal-to-noise ratio environment. The TDOA is obtained directly on a sample-by-sample basis and no interpolation is necessary. The proposed algorithm gives an unbiased delay estimate, and its performance for both stationary and nonstationary conditions is evaluated rigorously, It is also proved that the least-squares realisation of the estimator attains the Cramer-Rao lower bound View full abstract»

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  • Improved multiple targets angle tracking algorithm using the joint probabilistic data association filter

    Page(s): 331 - 336
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (448 KB)  

    The joint probabilistic data association filter is used for angle tracking of multiple moving targets. To improve the performance, in terms of data association, this filter uses power measurements, in addition to angle measurements. These measurements are provided by the MUSIC algorithm. The tracking performance of the algorithm is assessed by Monte Carlo simulations using different trajectories View full abstract»

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  • Effects of nonzero bandwidth on direction of arrival estimators in array signal processing

    Page(s): 317 - 324
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (592 KB)  

    The authors consider the impact of a small but nonzero bandwidth on narrowband direction-of-arrival (DOA) estimation using an array of sensors. They derive expressions for the DOA error for three commonly used array processing algorithms: MUSIC, ESPRIT and weighted subspace fitting (WSF). The error expressions are found by a perturbation analysis of these algorithms for small relative bandwidths of the sources. The perturbation-based error predictions are compared to the exact deviation for some special cases of interest View full abstract»

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  • Numerical comparison of techniques for estimating Doppler velocity time series from coherent sea surface scattering measurements

    Page(s): 367 - 373
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (544 KB)  

    A number of techniques for estimating the Doppler velocity time series from coherent sea surface scattering measurements are compared by observing their behaviour with computer simulated signals. These techniques include the finite difference instantaneous frequency estimator, the covariance moment estimation technique, tracking the peak of the short-time Fourier transform and tracking the peak of the cross Wigner-Ville time-frequency distribution. This comparison is achieved by examining the ability of each technique to track the instantaneous frequency of a unity amplitude, sinusoidal frequency law, complex exponential signal embedded in white Gaussian noise. The response of the estimators to various signal conditions, including low signal-to-noise ratios, high Doppler frequency excursions and high modulation frequencies, is investigated. Using the results, consideration is given to the suitability of each technique for estimating the magnitude, phase and power spectrum of the Doppler velocity time series. These are fundamental quantities required for studying sea scattering mechanisms and remotely sensing oceanographic properties View full abstract»

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  • Doppler-sensitive active sonar pulse designs for reverberation processing

    Page(s): 347 - 353
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (592 KB)  

    The performance of active sonars operating in shallow water is often limited by the reverberation level (Waite, 1998). If a target is moving relative to the reverberating scatterers, it may be possible to isolate its Doppler-scaled echo from the zero-Doppler reverberation provided that the Doppler shift is greater than the bandwidth of the transmitted pulse. In practice, this generally implies the use of narrowband long-duration continuous-wave (CW) pulses. The major disadvantages of this method are the poor range resolution of such pulses leading to poor reverberation processing with low Doppler targets. To detect slowly moving or stationary targets, linear period modulation (LPM) chirps are often used in preference. Several new classes of pulse design have been proposed which theoretically provide superior reverberation processing to CW pulses by virtue of their comb-like spectra. The paper reviews the theory behind Newhall trains, sinusoidal frequency modulated pulses and geometric comb waveforms, comparing their theoretical reverberation processing gains against CW and LPM pulses using the Q-function. Experimental results from low-frequency active sonar sea trials are also presented to verify theoretical predictions View full abstract»

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  • Minimum variance monopulse technique for an adaptive phased array radar

    Page(s): 374 - 380
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (544 KB)  

    Monopulse techniques allow the direction of arrival of a target to be estimated to better than a beamwidth accuracy from a single time sample of data. If adaptive beamforming is employed the sum and difference beams are distorted and the usual monopulse formulas produce errors. These errors are greatest in main beam jamming scenarios. A number of papers have been written on monopulse correction schemes which account for the distortion produced through adaptive beamforming, to produce an improved estimate of the target direction. However in the previous work, estimated noise has not been considered in detail. A new minimum variance adaptive monopulse (MVAM) scheme is developed which gives the unbiased target direction estimate least prone to the effects of noise. The advantages of MVAM over existing monopulse approaches are demonstrated using simulation data for targets set in severe clutter and mainbeam jamming environments View full abstract»

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  • Failure detection approach applying to GPS autonomous integrity monitoring

    Page(s): 342 - 346
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (352 KB)  

    There has been a growing interest within the potential user community in applying GPS to a variety of high-precision navigation problems such as aircraft nonprecision approach, river and harbour navigation, real-time or kinematic surveying, etc. In view of more and more GPS applications, the reliability of GPS is at issue. This promotes the need for several proposed receiver autonomous integrity monitoring (RAIM), GPS integrity channel (GIG), and wide area augmentation system (WAAS) schemes. The authors propose an approach for autonomous GPS satellite failure detection. The method exploits total least squares (TLS) optimisation to achieve fault detection. The traditional least squares approach fails to address the change in the data matrix associated with GPS satellite constellation. This drawback is shown to be remedied by the total least squares method. The proposed method can further be extended to account for failure isolation in which failed GPS satellites are identified and hence excluded in positioning 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.

Full Aims & Scope