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Radar, Sonar and Navigation, IEE Proceedings -

Issue 4 • Date Aug 1995

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Displaying Results 1 - 10 of 10
  • Detailed inherent bias analysis in ground referenced aircraft height monitoring

    Publication Year: 1995 , Page(s): 195 - 198
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (268 KB)  

    The authors present the results of an in-depth investigation of the systematic error resulting in aircraft geometric height computations derived by a height monitoring unit consisting of one typical secondary surveillance radar (SSR) and one omnidirectional radar. The systematic error is inherently generated by the nonlinear equation employed to calculate the height from the noisy distance and bearing measurements. Such inherent bias errors are expected in the output of almost every nonlinear system that processes noisy inputs. The inherent bias evaluation is based on a power series expansion which theoretically includes infinite number of terms but in practice has to be truncated at some order. The adequacy of the accuracy achieved with lower order terms is investigated in relation to various geometric factors and noise magnitude combinations View full abstract»

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  • Predicted performance of a symmetric-pair direction finding system in low signal-to-noise environments

    Publication Year: 1995 , Page(s): 199 - 205
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (512 KB)  

    The detection probability of an antenna pair of a symmetric-pair direction finding (DF) system in the presence of Gaussian noise is investigated. The question of system sensitivity as a function of the signal's angle of arrival is addressed. Expressions for false-alarm rate and probability of detection of a single symmetric-pair for different widths of the intermediate zone, a symmetric-pair specific parameter, are derived. It is shown that the width of the intermediate zones hardly affects the peak sensitivity but has an effect on the probability of detection for certain angles of arrival. A technique that yields hardly changing detection probability of the DF system for constant threshold and varying signal and noise levels is discussed View full abstract»

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  • Control of the spectra of DS-SS split signals by interleaving

    Publication Year: 1995 , Page(s): 206 - 210
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (380 KB)  

    Direct-sequence spread-spectrum transmissions are increasingly employed in terrestrial radio-location systems to minimise interference with narrowband communications services in shared bands. Further flexibility in band planning is afforded by a scheme to generate from the high-rate sequence an integral number of lower-rate, narrow-bandwidth, `split-signal' sequences which are transmitted in available gaps in the spectrum. The paper shows that the bandwidth and power density of the transmission may be further controlled by overlapping or interleaving the spectra of the split signals without unacceptable degradation of positioning performance due to their mutual interference View full abstract»

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  • ICA-based technique for radiating sources estimation: application to airport surveillance [and reply]

    Publication Year: 1995
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (84 KB)  

    Newcombe comments on a paper by Chaumette et al. (IEE Proc. F. Radar Signal Process. vol.140, no.6, p.395-401, 1993) about air traffic control. A reply is given by Comon and Chaumette View full abstract»

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  • 2-D multitarget angle tracking algorithm using sensor array

    Publication Year: 1995 , Page(s): 158 - 161
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (208 KB)  

    The authors extend the algorithm proposed by Sastry et al. (1991) from one-dimensional (1-D) to two-dimensional (2-D) scenerios for tracking both azimuth and elevation angles of moving targets using an array of sensors. The angle tracking is initiated by using the MUSIC algorithm and is then achieved through successive minimisation of a cost function. The analytic expressions for the gradient vector of the cost function are derived. The advantage of this algorithm is that the angle estimates are automatically correctly associated with the previous estimates and thus the data association problem does not arise. Computer simulations are provided to illustrate the performances of the algorithm in 2-D angular space View full abstract»

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  • Pulse arrival time estimation based on pulse sample ratios

    Publication Year: 1995 , Page(s): 153 - 157
    Cited by:  Papers (7)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (292 KB)  

    Standard methods of determining the time of arrival (ToA) of an unknown pulse are adaptive thresholding (ATH) and double differentiation (DD). The former first finds the amplitude of the pulse, and uses a fraction, say 1/2, of the amplitude as a threshold (TH). The ToA estimate is the time when the leading edge of the pulse exceeds TH. In DD, the ToA estimate is the time at which the maximum slope of the leading edge occurs. In ATH, there is the requirement of storing measurements, until slightly past the pulse center, and of a peak detection. Due to differentiation, DD is unreliable at even moderate noise situations. By using the ratio of pulse samples as a detection statistic, the ratio thresholding (RTH) scheme requires only a constant TH. Simplicity in implementation is its main advantage over ATH. Its theoretical variance is derived and corroborated by simulation. The performance of RTH is superior to DD and close to ATH View full abstract»

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  • Estimating the correlation properties of k-distributed SAR clutter

    Publication Year: 1995 , Page(s): 167 - 178
    Cited by:  Papers (11)  |  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (860 KB)  

    The authors extend previous analysis of the texture properties of k-distributed SAR clutter by including spatial correlation properties. Throughout they compare operating in the intensity domain with using its logarithm or square root (amplitude). Initially they derive the variance of the correlation coefficients in the three domains, assuming a negative exponential texture autocorrelation function (ACF), and demonstrate the advantage of both the log and amplitude domains over the intensity. In addition it is shown that a normalised estimator yields a further reduction in the variance. Finally, the results are combined in a derivation of the errors in the correlation length obtained by fitting the correlation coefficients to an assumed exponential autocorrelation function View full abstract»

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  • Calculating the K-distribution by saddlepoint integration

    Publication Year: 1995 , Page(s): 162 - 166
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (248 KB)  

    An important probability distribution for modelling non-Gaussian phenomenon is the K-distribution. Because of its widespread use in radar and underwater acoustics, a method for calculating the distribution is required which is both easy and efficient. The paper presents a method for calculating the K-distribution, in particular the K-Bessel function, using saddlepoint integration. The paper provides a detailed truncation-error analysis of the technique, and an implementation in MATLAB View full abstract»

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  • Doppler ambiguity resolution using staggered PRF with a new chirp sweep-rate estimation algorithm

    Publication Year: 1995 , Page(s): 191 - 194
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (268 KB)  

    The use of a quadratic staggered pulse-repetition-frequency (PRF) law in a surveillance radar, transposes unambiguous Doppler frequency estimation to a chirp sweep-rate estimation problem. An algorithm is proposed which achieves this estimation task efficiently. The method relies on a nonlinear recurrent equation which permits the construction of a pseudo forward-backward prediction matrix. The sweep rate is then estimated using the classical minimum-norm method and the new Doppler ambiguity domain is fixed by a sampling parameter. Performances are finally derived by computer simulations View full abstract»

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  • Performance of adaptive optimal Doppler processors in heterogeneous clutter

    Publication Year: 1995 , Page(s): 179 - 190
    Cited by:  Papers (7)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (740 KB)  

    The performance of adaptive Hsiao-optimal clutter-suppression filters operating in spatially varying clutter backgrounds is investigated. The case of practical adaptive estimation of the covariance matrix, and limiting cases where the estimate of the covariance matrix tends to the mean clutter covariance matrix, are considered. Three classes of nonhomogeneous clutter are studied: the amplitude and spectral width in each range bin are drawn from spatially invariant independent gamma distributed parent populations; clutter edges, in which the range profiles of the amplitude and/or spectrum exhibit a step change; and homogeneous clutter in which some range bins are corrupted by point-clutter sources or extraneous targets with significantly different amplitude and spectral characteristics. The use of prefilter MTI is investigated as a means of reducing losses in improvement factor (IF) in some classes of clutter nonhomogeneity. It is shown that adaptive filters suffer significant reductions in IF in nonhomogeneous clutter environments. These losses are generally greater than the benefit afforded by ideal adaptive processors over other conventional Doppler processors. The mean IF loss is an optimistic performance measure in adaptive Doppler processors 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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