Online ISSN
1751-8792
Print ISSN
1751-8784
IET Radar, Sonar & Navigation
Volume 6, Issue 6, July 2012
Volumes & issues:
Volume 6, Issue 6
July 2012
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- Author(s): R. Voles
- Source: IET Radar, Sonar & Navigation, Volume 6, Issue 6, p. 413 –416
- DOI: 10.1049/iet-rsn.2011.0254
- Type: Article
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The first modern bistatic radar system, Klein Heidelberg (KH), was developed by the Germans during World War II to exploit the transmissions from the British Chain Home (CH) radars and achieved detection ranges against Allied bombers well behind CH. The small backlobe of the system would also have unavoidably detected German aircraft flying behind KH. After estimating the front–back ratio of the antenna, the detection ranges of these German aircraft were derived, showing that they would have been detected out many tens of kilometres and have been incorrectly plotted as Allied aircraft flying well over South East England. While this study is essentially historical in nature, it is based on data in intelligence reports that were declassified only recently and illustrates the need for designers of such systems to anticipate all unwanted modes of operation. - Author(s): L. Zou ; J. Lasenby ; Z. He
- Source: IET Radar, Sonar & Navigation, Volume 6, Issue 6, p. 417 –424
- DOI: 10.1049/iet-rsn.2011.0293
- Type: Article
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A simple and general design procedure is presented for the polarisation diversity of arbitrary conformal arrays; this procedure is based on the mathematical framework of geometric algebra and can be solved optimally using convex optimisation. Aside from being simpler and more direct than other derivations in the literature, this derivation is also entirely general in that it expresses the transformations in terms of rotors in geometric algebra which can easily be formulated for any arbitrary conformal array geometry. Convex optimisation has a number of advantages; solvers are widespread and freely available, the process generally requires a small number of iterations and a wide variety of constraints can be readily incorporated. The study outlines a two-step approach for addressing polarisation diversity in arbitrary conformal arrays: first, the authors obtain the array polarisation patterns using geometric algebra and secondly use a convex optimisation approach to find the optimal weights for the polarisation diversity problem. The versatility of this approach is illustrated via simulations of a 7×10 cylindrical conformal array. - Author(s): F. Liu ; F. Zhao ; W. Yu ; L. Shi ; R. Wang
- Source: IET Radar, Sonar & Navigation, Volume 6, Issue 6, p. 425 –431
- DOI: 10.1049/iet-rsn.2011.0139
- Type: Article
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A novel technique is presented for the ship detection and ship speed estimation based on the azimuth scanning mode of synthetic aperture radar. The improved Doppler beam sharpening imaging algorithm is used to produce a sequence of individual sub-images of ships in the same scan region from different aspect angles with a high revisit rate. These sub-images have an inherent property that they are formed at different discretely delayed times. The azimuth resolutions of the sub-images formed in different scan angles are discussed. The cross-correlation function of two specific sub-images, which have the same azimuth resolution, is then produced. The radar cross-section of ships is higher than the surrounding sea clutter, so that their sub-images possess a higher degree of coherence than the uncorrelated random images of the surrounding sea surface. Moreover, the speed vector of moving ships can be estimated based on the shift of the correlation peak. The processing results show the effectiveness of the algorithms. - Author(s): P. Rocca ; L. Poli ; L. Manica ; A. Massa
- Source: IET Radar, Sonar & Navigation, Volume 6, Issue 6, p. 432 –442
- DOI: 10.1049/iet-rsn.2012.0005
- Type: Article
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The synthesis of time-modulated planar arrays for the design of monopulse antennas is addressed. The sum beam is generated through an optimal set of static excitations and the difference beam is yielded by aggregating the array elements into sub-arrays suitably modulated in time by means of a set of radio-frequency (RF) switches. Towards this aim, an analytically based iterative deterministic approach is proposed for the joint definition of the sub-array configuration and the pulse sequence controlling the RF switches to reproduce an optimal difference pattern at the working frequency, whereas minimising the power losses in the harmonic radiation caused by the on-off switch commutations. A set of representative numerical results is reported and discussed to illustrate the effectiveness and the numerical efficiency of the proposed approach. - Author(s): C.-L. Chang
- Source: IET Radar, Sonar & Navigation, Volume 6, Issue 6, p. 443 –457
- DOI: 10.1049/iet-rsn.2011.0151
- Type: Article
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This study proposes a multiplexing scheme capable of adaptively responding to various forms of interference. The scheme comprises a signal detector, decision logic and interference mitigation modules. Following the detection and characterisation of interference, decision logic is used to select a specific interference mitigation module to effectively nullify or remove that form of interference. This study conducted simulations of continuous wave interference and spoofing signals. The experimental results demonstrate the ability of the proposed scheme to effectively detect and mitigate interference, particularly in the presence of multiple types of interference. Comparisons and analysis of relevant anti-jamming techniques are also presented. - Author(s): C. Ouyang ; H. Ji ; C. Li
- Source: IET Radar, Sonar & Navigation, Volume 6, Issue 6, p. 458 –464
- DOI: 10.1049/iet-rsn.2011.0377
- Type: Article
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The cardinality-balanced multi-target multi-Bernoulli (CBMeMBer) filter is a promising algorithm for multi-target tracking. However, there exists a problem that when the legacy tracks cardinality is big enough, the effect of measurement innovation will be negligible, even if the measurement is close to the target state prediction. Such a problem is shown analytically in this study, and then an improved MeMBer filter has been proposed, which balances the posterior cardinality by modifying the legacy rather than the measurement-updated tracks parameters. The sequential Monte Carlo (SMC) implementation of the proposed algorithm is developed and its performance has been verified by simulation experiments. - Author(s): R. Jiang ; D. Zhu ; M. Shen ; Z. Zhu
- Source: IET Radar, Sonar & Navigation, Volume 6, Issue 6, p. 465 –471
- DOI: 10.1049/iet-rsn.2011.0312
- Type: Article
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An eigenvector method for maximum-likelihood estimation (MLE) of phase error has better algorithmic performance than phase gradient autofocus (PGA), which is implemented by the simultaneous processing of multiple-pulse vectors of the range-compressed data. However, this method requires eigendecomposition of the sample covariance matrix, which is a computationally expensive task and also limits the real-time application. In order to overcome such difficulty, this study proposes a novel autofocus algorithm using the projection approximation subspace tracking (PAST) approach. With this methodology, the computational cost can be reduced effectively to the level of PGA via avoiding the procedures of covariance matrix estimation and eigendecomposition. Monte Carlo tests and real synthetic aperture radar (SAR) data validate that although undergoing performance loss compare with the original multiple-pulse MLE algorithm, the new approach outperforms the mostly used PGA. - Author(s): Y. Liu ; Y. Kai Deng ; R. Wang ; O. Loffeld ; X. Wang
- Source: IET Radar, Sonar & Navigation, Volume 6, Issue 6, p. 472 –482
- DOI: 10.1049/iet-rsn.2011.0276
- Type: Article
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Bistatic frequency-modulated continuous wave (FMCW) synthetic aperture radar (SAR) mounts the radar transmitter and receiver on separate platforms, which offers considerable capabilities, reliability and flexibility in designing FMCW SAR missions. Moreover, the spatial separation achieves better isolation between transmission and reception channels compared with the monostatic FMCW SAR where the two separate dedicated antennas are fixed on one platform. In this study, a bistatic FMCW SAR signal model is proposed to formulate the bistatic slant range history in bistatic FMCW configuration. Based on the preceding model, an approach is presented to deal with the double-square-root (DSR) term, and thus an accurate FMCW bistatic point target reference spectrum (BPTRS) is derived. Besides accurately addressing the signal characteristics of bistatic FMCW SAR, the proposed spectrum also significantly simplifies the signal processing of bistatic FMCW SAR, which will really push the applications of bistatic FMCW SAR in remote sensing fields. Furthermore, based on the proposed BPTRS, an extended inverse chirp-Z transform (EICZT) algorithm is proposed to process the bistatic FMCW SAR data by introducing a perturbation function to deal with the range-variance of second- and third-order range–azimuth coupling terms. Two simulation experiments are carried out to verify the accuracy of this novel formulation and highlight the performance of the proposed focusing approach. - Author(s): C. Hao ; J. Yang ; X. Ma ; C. Hou ; D. Orlando
- Source: IET Radar, Sonar & Navigation, Volume 6, Issue 6, p. 483 –493
- DOI: 10.1049/iet-rsn.2011.0234
- Type: Article
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This study deals with the problem of detecting distributed targets in the presence of homogeneous and partially homogeneous Gaussian disturbance with unknown covariance matrix. The proposed detectors improve the adaptive beamformer orthogonal rejection test (ABORT) idea to address detection of distributed targets, which makes it possible to decide whether some observations contain a useful target or a signal belonging to the orthogonal complement of the useful subspace. At the design stage, the authors resort to either the plain generalised likelihood ratio test (GLRT) or ad hoc design procedures. Remarkably, the considered criteria lead to receivers ensuring the constant false alarm rate (CFAR) property with respect to the unknown quantities. Moreover, authors’ derivations show that the ad hoc detector for a partially homogeneous environment coincides with the generalised adaptive subspace detector. The performance assessment conducted by Monte Carlo simulation has confirmed the effectiveness of the newly proposed detection algorithms. - Author(s): D. Flores-Tapia ; C.M. Alabaster ; S. Pistorius
- Source: IET Radar, Sonar & Navigation, Volume 6, Issue 6, p. 494 –506
- DOI: 10.1049/iet-rsn.2011.0097
- Type: Article
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During the last decade, radar imaging has been used in near-field scenarios where a cylindrical scan geometry is required to properly illuminate the scan region, such as breast microwave radar imaging and microwave wood inspection. Nevertheless, current cylindrical near-field radar image formation algorithms are not fast enough to provide the throughput required by these novel applications. A real-time wavefront reconstruction approach for the formation of three-dimensional cylindrical near-field radar images is proposed in this study. This technique parallelises the mapping procedures during the reconstruction process in order to increase its computational efficiency. To further reduce the execution time of the proposed approach, it was implemented in a general purpose graphic processing unit in order to take advantage of the computing capabilities of this platform. The proposed method yielded accurate results when applied to simulated and experimental data sets and yielded speed improvements of two orders of magnitude compared to conventional cylindrical near-field radar reconstruction approaches.
False detections in Klein Heidelberg
Polarisation diversity of conformal arrays based on geometric algebra via convex optimisation
Ship detection and speed estimation based on azimuth scanning mode of synthetic aperture radar
Synthesis of monopulse time-modulated planar arrays with controlled sideband radiation
Multiplexing scheme for anti-jamming global navigation satellite system receivers
Improved multi-target multi-Bernoulli filter
Synthetic aperture radar autofocus based on projection approximation subspace tracking
Model and signal processing of bistatic frequency-modulated continuous wave synthetic aperture radar
Adaptive detection of distributed targets with orthogonal rejection
Real-time reconstruction of three-dimensional cylindrical near-field radar images using a single instruction multiple data interpolation approach
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- Author(s): T.G. Leighton and A. Balleri
- Source: IET Radar, Sonar & Navigation, Volume 6, Issue 6, p. 507 –509
- DOI: 10.1049/iet-rsn.2012.0146
- Type: Article
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- Author(s): G.H. Chua ; P.R. White ; T.G. Leighton
- Source: IET Radar, Sonar & Navigation, Volume 6, Issue 6, p. 510 –515
- DOI: 10.1049/iet-rsn.2011.0199
- Type: Article
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Dolphins are known to outperform man-made sonar in detecting and classifying targets in a shallow water environment where the returned signal is dominated by clutter in the vicinity of targets. During target interrogation, some species (such as the Atlantic bottlenose dolphin, Tursiops truncatus) emit trains of clicks. Each click can be modelled as consisting of two distinct down-chirping components over differing frequency bands. This study proposes a processing scheme called biased pulse summation sonar (BiaPSS) by which such trains can be interpreted to enhance target detection and reduce clutter in bubbly water, provided that the animal changes the amplitude of the clicks within the click train. A theoretical study is carried out using two dolphin-like clicks of different amplitude to determine the efficacy of such a pulse train in target discrimination in a bubble-filled environment. By adding and subtracting the responses from the two similar pulses, which are identical except that one has twice the amplitude of the other, the linear backscatter contribution from the target (e.g. a fish) can be discriminated from the non-linear backscattered reverberation (e.g. bubbles). For the bubble population used, the detection rate of the linear target using the pulse pair is showed to outperform the ‘standard sonar’ processing. - Author(s): F. Schillebeeckx ; D. Vanderelst ; J. Reijniers ; H. Peremans
- Source: IET Radar, Sonar & Navigation, Volume 6, Issue 6, p. 516 –525
- DOI: 10.1049/iet-rsn.2011.0069
- Type: Article
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This study aims to provide a better understanding of how bat bio-sonar operates so that the authors can apply this improved understanding to the design of simple in-air sonar systems based on the same operational principles. It focuses on the effect of component and configuration choices on the generated binaural spectral cues. Configurations composed of conventional receivers are evaluated for varying reflection strengths and compared to a system with artificial pinnae receivers. Localisation performance is quantified by an information-theoretic performance criterion expressing the mutual information carried by a binaural spectrum on the corresponding three-dimensional reflector location. Results show that the narrow beamwidth of conventional transducers limits the localisation information carried by the generated binaural spectra. The more complex spatial sensitivity patterns of organic pinna forms such as that of the Phyllostomus discolor bat species are shown to provide additional spectral cues that greatly improve localisation information transfer. The authors have found that the varying acoustic axis in the head-related transfer function of the pinna has a positive effect, but that the higher peripheral sensitivity around the varying acoustic axis is the driving force behind the artificial pinna's superior localisation performance. - Author(s): Q.-W. Li ; G.-Y. Huo ; H. Li ; G.-C. Ma ; A.-Y. Shi
- Source: IET Radar, Sonar & Navigation, Volume 6, Issue 6, p. 526 –535
- DOI: 10.1049/iet-rsn.2011.0193
- Type: Article
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For synthetic aperture radar (SAR) images, traditional edge detection methods can hardly extract the complete and true edges since they are sensitive to noise. In this study, the authors propose an edge detection method based on bionic vision in non-subsampled contourlet transform (NSCT) domain for SAR images, which makes use of the characteristics of NSCT (e.g. multiscale, multidirection edge expression and outstanding edge location) and the mechanisms of strengthening and positioning the image edge by fixational eye movements. First, source images are decomposed in the NSCT domain. The minimum mean squared error (MMSE) filter in the NSCT domain is adopted to reduce speckle noise of SAR images. Movement, difference and competition are applied on each subband to obtain original multiscale and multidirection subband edges. Lipschitz regularity and non-maximum suppression are also adopted to effectively remove noise points. Finally, hysteresis thresholding with adaptive thresholds is introduced to avoid streaking and trial-and-error, and multiscale edge fusion is used to reduce the false alarm rate. Edge extraction results of simulated and real SAR images demonstrate that the proposed method is better than other edge detection methods based on Canny operator, ratio of averages (ROA) operator, ratio of exponentially weighted averages (ROEWA) operator, wavelet modulus maximum and curvelet. - Author(s): A. Balleri ; H.D. Griffiths ; C.J. Baker ; K. Woodbridge ; M.W. Holderied
- Source: IET Radar, Sonar & Navigation, Volume 6, Issue 6, p. 536 –544
- DOI: 10.1049/iet-rsn.2011.0259
- Type: Article
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Automatic target classification under all conditions is a key challenge for modern radar and sonar systems. Echolocating nectar feeding bats are able to detect and select flowers of bat-pollinated plants even in highly cluttered environments. It is thought that these flowers have evolved to ease classification by bats, and that their echo-acoustic signatures contain critical information that aids the bat in choosing the most suitable flowers. In investigating the features of these flowers that aid the bats search for nectar, the strategy underpinning the task of classification of static targets by bats may be understood and this may additionally offer lessons for radar and sonar systems. Here, we analyse a real set of data containing high range resolution profiles of unpollinated corollas of Cobaea scandens, which is a flower of the type that is pollinated by bats. These were collected by transmitting a synthetic wideband linear chirp with an acoustic radar capable of very high range resolution. Classification performance of a k-NN classifier and a Naïve Bayesian classifier is assessed using information available in both the time and frequency domains. This facilitates quantification of the differences in these echoes because of the flower wilting process and lack of physical parts. - Author(s): D.C. Finfer ; P.R. White ; G.H. Chua ; T.G. Leighton
- Source: IET Radar, Sonar & Navigation, Volume 6, Issue 6, p. 545 –555
- DOI: 10.1049/iet-rsn.2011.0348
- Type: Article
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This study investigates the extent of the possible correlation between small odontocetes that predominantly inhabit littoral waters, and those which have been associated with the detection of echolocation clicks that consist of multiple pulses. The echolocation clicks discussed are primarily characterised as short, high frequency (>100 kHz) and narrow band. There are many sources that report clicks that contain multiple pulses and there is more than one structure associated with such pulses. A review of the literature provides a list of odontocetes which have been associated with such sounds and the structure of those reported clicks. The competing hypotheses regarding the origins of such multiple pulses in recordings are discussed. Regardless of the mechanism by which multiple pulse clicks occur, there are potential competitive advantages which may arise from them, and these are highlighted. - Author(s): J.A. Simmons and J.E. Gaudette
- Source: IET Radar, Sonar & Navigation, Volume 6, Issue 6, p. 556 –565
- DOI: 10.1049/iet-rsn.2012.0009
- Type: Article
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Big brown bats emit brief frequency-modulated (FM) biosonar signals in the 20–100 kHz frequency band. They use a unique delay-based processing method to focus target images and defocus clutter. Broadcasts and echoes are received by the ears and encoded as spectrogram-like representations by parallel auditory band-pass filters. Neural responses to successive frequencies in broadcasts travel along parallel neuronal delay-lines to serve as a template for comparison with similar responses to incoming echoes. Coincidence comparisons between responses to broadcasts and echoes are used to form images of echo delay. Interference between multiple reflections from the target introduces nulls at selected frequencies and activates a second, cepstrum-like process for estimating the time separation of the reflections. For lowpass echoes from clutter, the global weakening of higher frequencies defocuses the images of clutter and allows focused target images to emerge from the background. Temporal misalignment of neuronal responses to low-amplitude frequencies leads to a novel computational solution to the clutter problem in sonar. The wider biomimetic lesson is to implement totally parallel computations using only 1-bit timing comparisons, and not to emulate these computations in conventional digital signal processing with cumbersome digital arithmetic operating on multiple-bit bytes. - Author(s): W.W.L. Au and S.W. Martin
- Source: IET Radar, Sonar & Navigation, Volume 6, Issue 6, p. 566 –575
- DOI: 10.1049/iet-rsn.2011.0194
- Type: Article
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Dolphins have been found to have an excellent sonar system that is able to detect and recognise targets in noisy and highly reverberant environments. However, their ‘equipment’ has only mediocre characteristics from a technological sonar perspective. How dolphins perform the biosonar task so well is addressed in this manuscript. Echolocating dolphins have the capability to make fine discrimination of target properties such as wall thickness difference of water-filled cylinders and material differences in metallic plates, and to discriminate and recognise species of fish food. The high temporal resolution of the biosonar signals along with the high dynamic range of its auditory system are critical factors for target discrimination. An experiment in metallic plate composition discrimination suggests that dolphins attended to echoes 20–30 dB below the maximum level. Some of the properties of the dolphin sonar system are fairly mediocre, yet the total performance of the system is often outstanding. When compared to some technological sonar, the energy content of the dolphin sonar signal is not very high, the transmission and receiving beamwidths are fairly large, and the auditory filters are not very narrow. Yet the dolphin sonar has demonstrated excellent capabilities in spite of some mediocre features of its ‘hardware.’
Editorial: Biologically-inspired radar and sonar systems
Use of clicks resembling those of the Atlantic bottlenose dolphin (Tursiops truncatus) to improve target discrimination in bubbly water with biased pulse summation sonar
Evaluating three-dimensional localisation information generated by bio-inspired in-air sonar
Bionic vision-based synthetic aperture radar image edge detection method in non-subsampled contourlet transform domain
Analysis of acoustic echoes from a bat-pollinated plant species: insight into strategies for radar and sonar target classification
Review of the occurrence of multiple pulse echolocation clicks in recordings from small odontocetes
Biosonar echo processing by frequency-modulated bats
Why dolphin biosonar performs so well in spite of mediocre ‘equipment’
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