The aim of this work is to propose a method for detection and parameter estimation of nonlinear FM signals, mono- or multicomponent, embedded in white Gaussian noise. The proposed approach consists in mapping the signal into the time-frequency plane hy a time-frequency distribution with reassignment, and then in applying a pattern recognition technique, like the Hough transform, to the time-frequency representation to recognize specific shapes. The advantages of this method over the conventional maximum likelihood estimator are 1) a simpler implementation, because it reduces the dimension of the search space and 2) a consistent attenuation of the interference terms between different components of a signal or between signal and noise

TopOwl ® is an original concept of binocular Helmet Mounted Sight and Display system (HMSD) for helicopters, where two Image Intensifier Tubes (IIT) are integrated on the headgear and optically coupled to the clear visor placed in front of the pilot's eyes. Thales recently developed a new version of its TopOwl ® 's Display Module with the objective to have an HMSD capable to achieve all kind of missions up to the darkest night levels. The main enhancements are the redesign of the optical combination, the use of new optical materials and of latest generation of optical design tools. Two flyable prototypes of this new design were manufactured. A performance assessment has been conducted, showing a significant improvement of the night vision performances, reaching performances equivalent to those of last issued NVGs. These evaluations are being completed by different flight test evaluations.

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3)We propose in this paper a formulation for the matchedfilter (MF) based on frame of wavelets. We precisely compare the performance of the time-domain MF to that of this wavelet-based MF, with respects to the level of redundancy of the sampling of the time-scale plane, or equivalently, of the frame. The main result is that the redundancy of the discrete wavelet transform, instead of improving the detection performance, iatroduces false alarms which degrades this performance in the sense of the Neyman-Pearson criterion. /iT e ( t ) s*(t -T ) dt 1. MOTIVATION = In the framework of time-frequency analysis, some authors gave an equivalent formulation of the matched filter in the time-frequency plane using unitary distributions ([KBB85], [Fla86]). It is also possible, thanks to the unitarity of the continuous wavelet transform, to rewrite it in the time-scale plane :where * denotes the complex conjugate and Cq a constant involved in the inversion formula of the wavelet transform. The motivation for such an expression is that it offers a nice framework to study the robustness of the matched-filter with respect to deviation of the received signal from the reference. This will be part of a forthcoming work.Whereas the Whittaker-Shannon sampling theorem provides conditions for exact equality between continuPatrice Abry CNRS URA 1325 ENS Lyon -Laboratoire de Physique 46, allke d'Italie 69 364 Lyon Cedex 07 France Tkl : (33) 72 72 84 93 E-mail : pabry@physique.ens-1yon.fr. ous and discrete summations for the time-domain MF, a discrete suimnation over the time-scale plane would only provide us with an approximation of the continuous one :