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Radar, Sonar & Navigation, IET

Issue 5 • Date October 2007

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Displaying Results 1 - 8 of 8
  • Degrading effects of the lower atmosphere on long-range airborne synthetic aperture radar imaging

    Publication Year: 2007 , Page(s): 329 - 339
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (863 KB)  

    The imaging performance of airborne synthetic aperture radar (SAR) systems has advanced to the point that the effects of clear-air refractive index perturbations cannot be ignored. Operating at long ranges, and low grazing angles, in particular, require propagation geometries through regions of the lower atmosphere that may cause noticeable and, sometimes, severe degradation of the images. The range of image anomalies that can be attributed to the atmospheric boundary layer (ABL) is illustrated, the pertinent characteristics of the ABL is discussed, a first-order SAR imaging model that incorporates the refractive index perturbations associated with the ABL is developed and the magnitude of the image anomalies resulting from measured refractive index perturbations is estimated. The model predictions correlate well with the observed image anomalies and measured properties of the ABL. On the basis of theory and measurements, it is expected that the degrading effect of clear-air atmospheric refractive index perturbations is much more common than previously thought and may be a limiting factor for long-range SAR imaging performance. View full abstract»

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  • Deinterleaving of radar signals and PRF identification algorithms

    Publication Year: 2007 , Page(s): 340 - 347
    Cited by:  Papers (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (547 KB)  

    Electronic warfare (EW) receivers are passive receivers which receive emissions from other platforms, and do certain analysis on these emissions. Some EW receivers receive radar pulses, measure the parameter of each pulse received and group the pulses that belongs to the same emitter together to determine the radar parameters for each emitter. These parameters are then compared with values stored for known radar types, to identify the emitter type. Two parts are focused, emitters deinterleaving and PRF-type identification. The deinterleaving is done through parameters clustering. Two parameters are selected for clustering direction of arrival and radio frequency. A self-organising neural network called Fuzzy ART is proposed for clustering. This algorithm has a very good clustering quality and can run in real-time applications.The PRF-type identification is done through time-of-arrival (TOA) analysis. Three previously presented algorithms are combined in new scheme to do the TOA analysis (or PRF-type identification). These algorithms are difference TOA histogram, TOA folding histogram and sequence search algorithm. The complete proposed system has been tested using three different tests. These tests are simple PRI test, jittered PRI test and staggered PRI test. The proposed system identifies up to 90 simple emitters, 20 jittered emitters and 20 staggered emitters. In all tests, the data were simulated and generated using software. View full abstract»

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  • Integration of synthetic aperture radar image segmentation method using Markov random field on region adjacency graph

    Publication Year: 2007 , Page(s): 348 - 353
    Cited by:  Papers (12)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (640 KB)  

    A novel approach to obtain precise segmentation of synthetic aperture radar (SAR) images using Markov random field model on region adjacency graph (MRF-RAG) is presented. First, to form a RAG, the watershed algorithm is employed to obtain an initially over-segmented image. Then, a novel MRF is defined over the RAG instead of pixels so that the erroneous segmentation caused by speckle in SAR images can be avoided and the number of configurations for the combinatorial optimisation can be reduced. Finally, a modification method based on Gibbs sampler is proposed to correct edge errors, brought by the over-segmented algorithm, in the segmentations obtained by MRF-RAG. The experimental results both on simulated and real SAR images show that the proposed method can reduce the computational complexity greatly as well as increase the segmentation precision. View full abstract»

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  • Rigid data association for shallow water surveys

    Publication Year: 2007 , Page(s): 354 - 361
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (744 KB)  

    An automatic procedure for target data association is presented here. The procedure is particularly appropriate for shallow water applications, where navigation errors are limited and where sufficient overlap is present between successively surveyed areas. The proposed method includes a performance check that can be used to confirm that solutions are meaningful and also to produce a time-bounded implementation suitable for real-time operation. Main applications for the procedure include change detection and navigation enhancements (for example, by concurrent mapping and localisation/simultaneous localisation and mapping procedures). Results are presented for different survey platforms. View full abstract»

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  • Design and evaluation of a low-cost multistatic netted radar system

    Publication Year: 2007 , Page(s): 362 - 368
    Cited by:  Papers (14)  |  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (502 KB)  

    This paper reports on the design and initial evaluation of a low-cost multistatic radar system that exploits digital components. The system is based on a commercial-off-the-shelf and open architecture approach, using a direct digital synthesiser, a field programmable gate array and a digital signal processor as core components. Instrument function testing, calibration and the results of the initial field tests are reported. Some of the first multistatic experimental results are reported and demonstrate a number of aspects of the performance of such a configuration. The advantages and limitations of a low-cost digital radar design are discussed and further system development possibilities outlined. This system will enable the collection of a wide range of novel multistatic data and has the potential to demonstrate a number of new radar applications. View full abstract»

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  • Analytic performance prediction of feature-aided global nearest neighbour algorithm in dense target scenarios

    Publication Year: 2007 , Page(s): 369 - 376
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (230 KB)  

    An analytic performance prediction method for the feature-aided global nearest neighbour tracking algorithm in multi-target tracking (MTT) scenarios is proposed. The approach serves as an alternative to the costly Monte Carlo simulation method. In MTT, evaluation of interference among multiple targets remains a crucial issue on tracking performance study. This issue is investigated in dense target scenarios with feature information and unrestrictive motion. Analytic expressions are developed for tracking performance in terms of the probability of correct association and estimation accuracy. Feature information of targets is incorporated in the formulation which provides us an insight on how the tracking performance is impacted by features. In the derivations, a series of simplification assumptions are made and the results are not intended to be used directly in practical tracking applications. The major contribution of the paper is to provide a theoretical exploration and a methodology for analytic performance prediction of MTT. View full abstract»

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  • Statistical prediction of monopulse angle measurement

    Publication Year: 2007 , Page(s): 377 - 387
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (224 KB)  

    The statistical prediction of monopulse angle measurement where the amplitude fluctuation law of the signal source is unknown and multiple observations are available is presented. The mean and the variance of the monopulse ratio have been derived for the general case where the signal source is embedded in spatially coloured Gaussian noise and the receiver sum-channel is possibly completed by a detection step. This result completes the statistical prediction of a Swerling target and provides a powerful method to compute the mean and variance of the monopulse ratio conditioned by the detection test, whatever the amplitude fluctuation law of the signal source. View full abstract»

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  • Adaptive neuro-fuzzy module for inertial navigation system/global positioning system integration utilising position and velocity updates with real-time cross-validation

    Publication Year: 2007 , Page(s): 388 - 396
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (919 KB)  

    Recently, methods based on artificial intelligence (AI) have been suggested to provide reliable positioning information for different land vehicle navigation applications. The majority of these applications utilise both the global positioning system (GPS) and the inertial navigation system (INS). These AI modules were trained to mimic the latest vehicle dynamics so that, in case of GPS outages, the system relies on INS and the recently updated AI module to provide the vehicle position. Several neural networks and neuro-fuzzy techniques were implemented in real-time in a de-centralised fashion and provided acceptable accuracy for short GPS outages. It was reported that these methods provided poor positioning accuracy during relatively long GPS outages. In order to prevail over this limitation, this study optimises the Al-based INS/GPS integration schemes utilising adaptive neuro-fuzzy inference system with performing, in real-time, both GPS position and velocity updates. In addition, a holdout cross validation method during the update procedure was utilised in order to ensure generalisation of the model. The proposed system is tested using differential GPS and both navigational and tactical grades INS field test data obtained from a land vehicle experiment. The results showed that the effectiveness of the proposed system over both the existing Al-based and the conventional INS/GPS integration techniques, especially during long GPS outages. This method may have one limitation related to the unusual significant changes of the vehicle dynamics between the update and the prediction stages of operation which may influence the overall positioning accuracy. View full abstract»

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Aims & Scope

IET Radar, Sonar & Navigation covers the theory and practice of systems involving the processing of signals for radar, radiolocation, radionavigation and surveillance purposes.

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