1,721,647 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
Cinema bella presenza offresi
No full textStudio della figura registica di Giorgio Pastina, a cavallo tra cinema d'epoca fascista e neorealismo, letteratura e teatro, tra contraddizioni e atteggiamenti di pungente e rivelatore conservatorism
Application of track-before-detect techniques in GNSS-based passive radar for maritime surveillance
No full textGNSS-based passive radar has been recently proved able to enable moving target detection in maritime surveillance applications. The main restriction lies in the low Equivalent Isotropic Radiated Power (EIRP) level of navigation satellites. Extending the integration times with proper target motion compensation has been shown to be a viable solution to improve ship detectability, but this involves computational complexity and increasing sensitivity to motion model mismatches. In this work, we consider the application of a Track-Before-Detect (TBD) method to considerably increase the integration time (and therefore the detection capability) at the same time keeping the computational complexity affordable by practical systems. Dynamic programming TBD algorithms have been specialized for the considered framework and tested against experimental dataset. The obtained results show the effectiveness of this approach to improve the detection capability of the system despite the restricted power budget
Multistatic passive ISAR based on geostationary satellites for coastal surveillance
No full textThe paper proposes a Passive Multistatic ISAR mode (PM-ISAR) for coastal surveillance based on the exploitation of multiple transmitting satellites and a single receiver (with multiple receiving channels). A proper processing technique able to focus the single bistatic images of the ship target of interest, to align them to the same reference plane and to properly combine them is introduced. The use of multiple transmitters allows a proper integration of the information concerning the different scattering centers of the target when observed by different bistatic pairs. Thus the resulting multistatic ISAR image could be very useful for ATR (Automatic Target Recognition) purposes. © 2013 IEEE
A parasitic array receiver for ISAR imaging of ship targets using a coastal radar
No full textThe detection and identification of ship targets navigating in coastal areas are essential in order to prevent maritime accidents and to take countermeasures against illegal activities. Usually, coastal radar systems are employed for the detection of vessels, whereas noncooperative ship targets as well as ships not equipped with AIS transponders can be identified by means of dedicated active radar imaging system by means of ISAR processing. In this work, we define a parasitic array receiver for ISAR imaging purposes based on the signal transmitted by an opportunistic coastal radar over its successive scans. In order to obtain the proper cross-range resolution, the physical aperture provided by the array is combined with the synthetic aperture provided by the target motion. By properly designing the array of passive devices, the system is able to correctly observe the signal reflected from the ships over successive scans of the coastal radar. Specifically, the upper bounded interelement spacing provides a correct angular sampling accordingly to the Nyquist theorem and the lower bounded number of elements of the array ensures the continuity of the observation during multiple scans. An ad hoc focusing technique has been then proposed to provide the ISAR images of the ships. Simulated analysis proved the effectiveness of the proposed system to provide top-view images of ship targets suitable for ATR procedures
Multi-feature based automatic recognition of ship targets in ISAR
No full textThis paper deals with the problem of non-cooperative target recognition. Specifically, the aim is the automatic recognition of ship targets from inverse synthetic aperture radar (ISAR) images. For this purpose a new two-step multi-feature based technique is proposed; this technique uses a number of features extracted from the ship radar image and matches these features with those extracted from the images obtained by properly projecting the target models of the classification library. Both cases of a priori known or unknown ship aspect angles are considered: the knowledge of the ship aspect (as available from tracking data) allows the selection of the candidate models on the basis of the matching between the ship and the model length, thus resulting in a performance improvement. Moreover, both single- and multi-frame-based processing techniques are proposed in order to assess the performance improvement achievable when an increasing number of ISAR images are involved in the decision; the fusion strategy adopted for the exploitation of the information from the multiple images is also described. The performance of the overall proposed technique is deeply investigated against simulated data. Results of its application to a set of live ISAR images of a ship target are also provided showing the effectiveness of the proposed approach
Multi-grazing ISAR for side-view imaging with improved cross-range resolution
No full textThe use of multiple radar systems, carried by a set of air platforms flying in formation, is demonstrated to be able to provide side-view ISAR images of pitching and rolling targets with increased cross-range resolution. The multi-grazing ISAR technique is devised for two different cases: (i) multistatic case with a single platform carrying an active radar and the remaining equipped with receiving only devices, (ii) MIMO case with each platform carrying an active radar. The needed focusing technique is presented with the results obtained against simulated ISAR data; the performance analysis shows that the proposed technique is able to provide an increase of the cross-range resolution up to the number of radar systems in the multistatic case or even higher in the MIMO case. The multi-grazing ISAR is especially suitable for the application to ship target imaging in the presence of low sea state giving rise to side-views of poor quality when imaged with conventional ISAR. © 2011 IEEE
Distributed ISAR focusing for targets undergoing 3D motion
No full textThe issue of focusing ISAR images with improved cross-range resolution of targets undergoing 3D motion observed by multiple radar systems is here addressed. Both multi-aspect and multi-grazing acquisition geometries are here considered. The Distributed Point Spread Function is devised with two possible approaches: (i) ID Multi-Aspect/Multi-Grazing and (ii) 3D approach, when the distributed processing is matched to the vertical/horizontal or to the effective component of the rotation motion respectively. The needed focusing technique is presented with the results obtained against simulated data; performance analysis shows that, despite some spatially variant degradation experienced with respect to ideal case (i.e. acquisition geometry completely matched to the motion characteristics) ISAR images of quality considerably higher than in the conventional single sensor case can be obtained
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
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