Your browser does not support JavaScript!
http://iet.metastore.ingenta.com
1887
banner image
image of Volume 1, Issue 3
Online ISSN 1751-8792 Print ISSN 1751-8784

IET Radar, Sonar & Navigation

Volume 1, Issue 3, June 2007

Volumes & issues:

Volume 1, Issue 3

June 2007

Show / Hide details

    • Estimating the ballistic coefficient of a re-entry vehicle
      • Author(s): P. Dodin ; P. Minvielle ; J.P. Le Cadre
      • Source: IET Radar, Sonar & Navigation, Volume 1, Issue 3, p. 173 –183
      • DOI:  10.1049/iet-rsn:20060064
      • Type: Article
      • + Show details - Hide details
      • p. 173 –183 (11)
        Theoretical bounds for estimating the ballistic coefficient of a ballistic object during the re-entry phase have been addressed. One essential characteristic of the vehicle trajectory is its deceleration when it reaches dense atmospheric layers. The intensity of the phenomenon is proportional to a scalar, called the ballistic coefficient. This leads to an highly nonlinear time-varying dynamic. To understand the dimensioning parameters for estimating the ballistic coefficient, accurate approximations of the Fisher information matrix are developed. The main result is a closed-form expression of a lower bound for the variance of the ballistic coefficient estimate.
        Add to favourites
        Export citations
      Non-parametric techniques for the estimation of spatial spectra in non-stationary environments
      • Author(s): P.R. White
      • Source: IET Radar, Sonar & Navigation, Volume 1, Issue 3, p. 184 –190
      • DOI:  10.1049/iet-rsn:20050073
      • Type: Article
      • + Show details - Hide details
      • p. 184 –190 (7)
        A novel approach to the problem of estimating a spatial spectrum in a non-stationary environment has been presented. The approach adopted relies on the same principle as that which underpins the Wigner distribution. The proposed methodology results in the construction of a new sufficient statistic that can be used in conjunction with a variety of existing array-processing techniques. The resulting schemes are shown to be robust to source motions. Some of the limitations of this approach have been discussed and how they can be overcome is demonstrated.
        Add to favourites
        Export citations
      Image frequency suppression in frequency-scanned direction-of-arrival estimation systems
      • Author(s): W. Wasylkiwskyj ; I. Kopriva ; M. Doroslovački
      • Source: IET Radar, Sonar & Navigation, Volume 1, Issue 3, p. 191 –197
      • DOI:  10.1049/iet-rsn:20050078
      • Type: Article
      • + Show details - Hide details
      • p. 191 –197 (7)
        A novel signal processing approach to the problem of image frequency suppression in wide-band frequency-scanned radio frequency (RF) receiving arrays that employ digital signal processing (DSP) techniques to estimate the direction of arrival (DOA) of incoming radiation has been presented. The conventional approach to image rejection in RF receivers is to employ a front-end RF tuner before downconversion to the intermediate frequency. As DOA processing employs a separate receiver channel for each array element, an RF tuner would be needed behind each element. Clearly for scanned systems at microwave frequencies, this is not a viable option where the tuners would generally have to be implemented in RF hardware. The need for RF tuners can be eliminated by downconversion down to baseband and employing I&Q mixers, which provide an intrinsic image rejection capability. Unfortunately, such a solution requires two analog-to-digital (A/D) converters per array element. An alternative approach is to use image rejection mixers in which case only one A/D converter per array element is needed. The approach also requires only one A/D per array element but achieves the image rejection through a DSP implementation. As a result, use of relatively expensive image rejection mixers is avoided without sacrificing performance. Experimental results are presented that validate the theoretical predictions.
        Add to favourites
        Export citations
      Subcanceller: adaptive generalised sidelobe canceller with optimum subband decomposition
      • Author(s): W.-S. Yang ; W.-H. Fang ; C.-Y. Lin
      • Source: IET Radar, Sonar & Navigation, Volume 1, Issue 3, p. 198 –206
      • DOI:  10.1049/iet-rsn:20050095
      • Type: Article
      • + Show details - Hide details
      • p. 198 –206 (9)
        This paper presents a subband beamformer with the generalised sidelobe canceller (GSC) as the underlying structure. This new beamformer, referred to as the subcanceller, determines the statistically optimum filter bank succeeding the blocking matrix of the GSC based on the minimum mean-square error criterion. As a consequence, the signals passing through the lower branch of the GSC are decomposed into more appropriate subband components by such filter banks according to the input data statistics to enhance the interference suppression capability. The determination of the filter bank coefficients, however, calls for computationally demanding nonlinear optimisation. To alleviate the computational overhead, an iterative procedure is also proposed, which solves the Rayleigh quotient in each iteration. Furthermore, a detailed performance analysis of the proposed beamformer is conducted, which includes the development expression of the output signal to interference-plus-noise ratio and its implications, and the analysis of the convergence characteristic. Furnished simulations show that the new scheme yields superior interference suppression performance with a faster convergence rate compared with previous studies.
        Add to favourites
        Export citations
      Joint estimation of Doppler centroid and rate for SAR with large range migration
      • Author(s): M. Yu ; J. Xu ; Y.-N. Peng ; X. Wang
      • Source: IET Radar, Sonar & Navigation, Volume 1, Issue 3, p. 207 –212
      • DOI:  10.1049/iet-rsn:20060065
      • Type: Article
      • + Show details - Hide details
      • p. 207 –212 (6)
        For synthetic aperture radar (SAR) with large range migration, the estimation accuracy of Doppler rate may be poor without range migration correction (RMC), while inversely the correct RMC needs the accurate knowledge of Doppler parameters. By exploiting the statistical property of SAR range-Doppler domain signal, a novel Doppler parameter estimation method is proposed to solve the above dilemma. Free of a priori knowledge of platform motion including antenna beam pointing direction and flying velocity, the proposed method can realise pulse repetition frequency-ambiguity resolving, clutter-locking and auto-focusing both accurately and jointly. It is also robust to scene contrast. Experimental results based on real RADARSAT data are provided to demonstrate the effectiveness of the proposed method.
        Add to favourites
        Export citations
      Optimum relative speed discretisation for detection of moving objects in wide band SAR
      • Author(s): M.I. Pettersson
      • Source: IET Radar, Sonar & Navigation, Volume 1, Issue 3, p. 213 –220
      • DOI:  10.1049/iet-rsn:20060082
      • Type: Article
      • + Show details - Hide details
      • p. 213 –220 (8)
        Here, Ground moving target indication (GMTI) using synthetic aperture radar (SAR) is considered. SAR GMTI requires that relative speed between the target and the SAR platform is included in the detection algorithm. A separation between the true relative speed and the relative speed used in the SAR process will cause unfocused targets, and decrease detectability. Blind hypotheses of relative speeds are used in the detection phase of moving targets in SAR. The step size between the hypotheses (or discretisation step) in relative speed involves a trade off between the number of hypotheses to test and detectability. A large number of tests will increase detectability but will also increase computation load and vice versa. The relevance of relative speed increases as the azimuth integration time gets larger. Long integration time is associated with low signature moving target detection in strong clutter environments, or for SAR GMTI at low frequencies. The optimum discretisation of normalised relative speed for moving target detection has been determined. The optimum discretisation is derived from the moving target impulse response. Use of optimum discretisation reduces the computation burden in SAR GMTI and secures the detectability.
        Add to favourites
        Export citations
      MCMC methods for tracking two closely spaced targets using monopulse radar channel signals
      • Author(s): A. Isaac ; P. Willett ; Y. Bar-Shalom
      • Source: IET Radar, Sonar & Navigation, Volume 1, Issue 3, p. 221 –229
      • DOI:  10.1049/iet-rsn:20060117
      • Type: Article
      • + Show details - Hide details
      • p. 221 –229 (9)
        Four techniques to successfully track two closely spaced and unresolved targets using monopulse radar measurements have been discussed, the quality of such tracking being a determinant of successful detection of target spawn. The paper explores statistical estimation techniques based on the maximum likelihood criterion and Gibbs sampling, and addresses concerns about the accuracy of the measurements delivered thereby. In particular, the Gibbs approach can deliver joint measurements (and the associated covariances) from both targets, and it is therefore natural to consider a joint filter. The ideas are compared, and among the various strategies discussed, a particle filter that operates directly on the monopulse measurements seems to be the best.
        Add to favourites
        Export citations
      Polarimetric angular smoothing algorithm for an electromagnetic vector-sensor array
      • Author(s): Y. Xu  and  Z. Liu
      • Source: IET Radar, Sonar & Navigation, Volume 1, Issue 3, p. 230 –240
      • DOI:  10.1049/iet-rsn:20050108
      • Type: Article
      • + Show details - Hide details
      • p. 230 –240 (11)
        The polarimetric angular smoothing (PAS) technique for coherent direction-of-arrival (DOA) estimation and adaptive beamforming is explored and enriched by taking into account the cross-correlations among the smoothed subarrays and using non-uniform weights. The PAS using annihilating weights is shown to be free of signal cancellation [which occurs in the conventional spatial smoothing (SS) technique for uncorrelated sources] while effectively suppressing coloured noise with unknown Toeplitz covariance matrix, but may be incompetent for DOA estimation. The PAS technique is still shown to be more attractive than the SS scheme in a very difficult situation that the direct signals and the reflecting signals are of very close DOAs. The penalised Toeplitz-block-Toeplitz scheme is further suggested for more thorough source decorrelation with an L-shaped electromagnetic vector-sensor array to gain improved interference suppression. The analytical expression for the mean-squared error of DOA estimates obtained from the weight-PAS pre-processed root-multiple signal classification is derived and analysed. A hybrid DOA estimator incorporating PAS and integrating some existing techniques is also described. Numerical results are finally given.
        Add to favourites
        Export citations
      Intelligent tracking algorithm for manoeuvering target using Kalman filter with fuzzy gain
      • Author(s): S.Y. Noh ; J.B. Park ; Y.H. Joo
      • Source: IET Radar, Sonar & Navigation, Volume 1, Issue 3, p. 241 –247
      • DOI:  10.1049/iet-rsn:20060030
      • Type: Article
      • + Show details - Hide details
      • p. 241 –247 (7)
        An intelligent filter with fuzzy gain is proposed, which calculates a manoeuver input into the time-varying variance of the overall process noise and compensates an estimation error by using a fuzzy gain. The proposed technique not necessary to predesign the acceleration levels according to the target manoeuver properities. The manoeuver input is esitmated using the difference between the non-manoeuvering filter and the manoeuvering one. To compensate the estimation error, the fuzzy gain is used to describe the relationship between the filter residual and its variation. A fuzzy system is utilised for an universal approximator. It is optimised by using a genetic algorithm. A computer simulations show that the effectiveness of the proposed method is compared with multiple filters.
        Add to favourites
        Export citations
      Comment: Multi-range-resolution radar using sideband spectrum energy
      Reply: Multi-range-resolution radar using sideband spectrum

Most viewed content for this Journal

Article
content/journals/iet-rsn
Journal
5
Loading

Most cited content for this Journal

Print this page
This is a required field
Please enter a valid email address