1,721,105 research outputs found
Rotation motion estimation for high resolution ISAR and hybrid SAR/ISAR target imaging
No full textThe problem of very high resolution Inverse Synthetic Aperture Radar (ISAR) imaging of moving targets is considered. In particular, the focus of the paper is on the estimation of those parameters concerning the target rotation motion, needed to correctly focus and scale the target images. To this aim, two new estimation techniques are proposed based respectively on the Maximum Likelihood and Constrast Optimisation criteria. Both cases of constant and variable rotation rate are considered. A complete theoretical performance analysis and examples of application to very high resolution live ISAR data are provided showing the effectiveness of the proposed approach. © 2008 IEEE
Multiband coherent radar detection against compound-Gaussian clutter
No full textA Multiband GLRT-LQ (Generalized Likelihood Ratio Test-Linear Quadratic), MBGLRT-LQ, detector is derived for the coherent radar target detection against a compound-Gaussian clutter background. This scheme is an extension to the multiband case of the Asymptotically Optimum Detector (AOD) [1], also derived under the name of GLRT-LQ in [2], The proposed multiband version of the algorithm shows two main advantages with respect to the original single-band algorithm 1) For the. adaptive implementation, it requires a much smaller area of homogeneous clutter echoes to estimate the covariance matrix of the interference; 2) it provides an optimum processing of the radar echoes when the radar operates in frequency agility, as electronic counter-countermeasure (ECCM) strategy, A closed form performance analysis is provided for the MBGLRT-LQ detector, which is used to compare it with the single-band version. An application to live recorded data is also presented to validate the obtained results
Exploiting the polarimetric information for the coherent adaptive detection against compound-Gaussian clutter
No full textPeebles, U
Slope-based frame selection and scaling technique for ship ISAR imaging
No full textThe authors address the problem of optimum imaging time selection and angular motion estimation for ship ISAR or hybrid SAR/ISAR imaging. The aim is to select proper imaging times and to estimate ship angular motion in order to obtain high-quality top view or side view scaled images of the ship, suitable for processing by classification/identification procedures. For this purpose, a new technique is proposed, able to select the time instants better suited for top or side view image formation and to estimate the rotation motion for image scaling. The technique is based on a novel model of the phase/Doppler frequency of the generic ship scatterer and operates entirely in the range-Doppler image domain (as obtained via Fourier transform) by using the slopes of some extracted linear features, thus without requiring coherent processing. The performance of the complete ISAR technique is analysed in depth; the results of the application of the proposed technique to both simulated and live ISAR data prove the effectiveness of the proposed approach
Exploitation of the COSMO-SkyMed SAR system for GMTI applications
No full textThe focus of this paper is on the exploitation of COSMO-SkyMed spotlight SAR images for Ground Moving Target Indication (GMTI). To this purpose, a two-step processing chain is proposed: the first step performs stationary clutter removal, whereas the second step performs moving targets detection. Both the steps are based on the use of a bank of focusing filters, each one matched to a different relative speed between the radar antenna and the target, here implemented as Chirp Scaling Algorithms in order to keep low the computational burden. The performance of the proposed technique is investigated by applying it to COSMO-SkyMed Single Look Complex spotlight SAR images and compared to theoretical performance: the analysis shows the effectiveness of the proposed technique in suppressing the stationary clutter and providing a high gain in signal to background power ratio, thus allowing subclutter visibility despite the single-channel nature of COSMO-SkyMed data. Moreover, the information provided by the bank is used to estimate the target motion and, by using a knowledge-based approach, relocate in along-track direction the detected movers. The shown results prove the feasibility of a GMTI mode for the COSMO-SkyMed SAR system and more in general for single-channel spaceborne systems
Pattern control for adaptive antenna processing with overlapped sub-arrays
No full textThis paper deals with the optimization of adaptive techniques operating with partially overlapped sub-arrays. Three new adaptive schemes are introduced that properly cancel jamming signals when present, but give exactly the desired quiescent pattern in the absence of jammers. These schemes solve the problem of the antenna pattern control under adaptive operation even for the case of overlapped sub-arrays
Quiescent pattern control in adaptive antenna processing at sub-array level
No full textThis paper deals with the optimization of adaptive techniques operating with partially overlapped sub-arrays. A new adaptive scheme is introduced, that properly cancels jamming signals when present, but gives exactly the desired quiescent pattern in the absence of jammers. The proposed scheme is shown to work properly in both cases of linear and planar arrays for both sum and delta patterns; moreover, the performance analysis shows that the pattern control capability is achieved at the expenses of little detection losses when compared to the performance of the optimum filter
Multi-frame data fusion techniques for ATR of ship targets from multiple ISAR images
No full textThis paper deals with the topic of Automatic Target Recognition (ATR) of Non Cooperative Targets. Specifically the focus is on the ATR of ships from multiple ISAR images. An investigation on different techniques for the fusion of the information provided by multiple image frames is presented. The techniques exploit the principles of multi-feature based ATR and apply them to the case of availability of several images. The recognition process makes use of a wire-frame models library which undergoes a step of candidate models selection before feeding the target model declaration step. Both cases of centralized and decentralized data fusion techniques are considered. The performance of the proposed techniques is investigated in depth by means of simulated data. Moreover the paper provides a comparison of the results of the proposed techniques when applied to live ISAR images of ship targets. © 2009 EuMA
Polarimetric detectors of extended targets for ship detection in SAR images
No full textThis paper deals with polarimetric detection of ships in SAR images of medium/high resolution (about meters). The aim is to develop detection techniques able to exploit the polarimetric information in order to improve the detection capability of ships or generally man-made targets modelled as extended targets (i.e. occupying multiple pixels). Both a decentralized and a centralized approach are considered for the fusion of the polarimetric information and their performance are characterized
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