N. de Beaucoudrey
University of Nantes
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Featured researches published by N. de Beaucoudrey.
european radar conference | 2007
Janic Chauveau; N. de Beaucoudrey; Joseph Saillard
In resonance domain, the radar scattering response of any object can be modelled by natural poles of resonance with the formalism of the singularity expansion method. The mapping of these poles in the complex plane gives useful information for the discrimination of a radar target, as its general shape, its characteristic dimension and its constitution. However, the full frequency band corresponding to the resonance domain of a radar target is not always available, thus it is often necessary to look for a compromise. In this paper, we propose to show that it is possible to extract resonance poles one-by-one in tuning a reduced frequency band to the frequency of each wanted pole. This avoids the use of ultra wide band (UWB) data and allows to extract at least some dominant poles of resonance in available narrow frequency bands.
european radar conference | 2005
Janic Chauveau; N. de Beaucoudrey; Joseph Saillard
In resonance domain, the radar scattering response can be modeled by natural poles of resonance, with the formalism of the singularity expansion method. The mapping of poles gives useful information for the discrimination of radar targets. In this paper, we show that a reduced number of poles is sufficient to characterize an object. Furthermore, we propose a procedure for selecting poles actually contributing to the scattering response. Results are presented for different canonical targets
ieee antennas and propagation society international symposium | 2010
Janic Chauveau; N. de Beaucoudrey
The stealthiness is intended to produce a very weak radar return in usual radar frequency bands. But, this can be countered with lower frequencies studies. These lower frequency bands correspond to the Rayleigh region and the resonance region for object dimensions respectively small and of the same order compared to electromagnetic wavelengths. Contrary to high frequency imaging, low frequency methods cannot provide high resolution but they give information on the overall dimension and the approximate shape of the target. A low frequency method, proposed by Young [1] and known as the ramp response technique, permits to generate a three dimensional (3D) image of the target shape from its ramp response signatures. The ramp response of a target is directly related to the profile function of the target, namely its transverse cross-sectional area along the line-of-sight. Usual 3D image generation uses “approximate limiting surfaces” [1], supposed to enclose the unknown target, and gives an estimate of the target shape by iteratively fitting some geometrical parameters. However, this algorithm can be used only for convex and single objects. That is why we have proposed a new algorithm permitting to reconstruct objects with arbitrary shape, as well as separated objects [2]. In this paper, we determine the limit of separation provided by this new imaging algorithm, using the example of two perfectly electric conducting (PEC) spheres.
2nd International Workshop on New Computational Methods for Inverse Problems (NCMIP'2012) | 2012
Yanhua Wen; N. de Beaucoudrey; Joseph Saillard; Janic Chauveau; Philippe Pouliguen
Low frequency Radar imaging can be used to reconstruct the global shape of targets using the ramp response technique, which only needs no more than 3 observing angles. We have developed a new algorithm permitting to generate promising shapes of targets for mutually orthogonal directions, but giving distorted results otherwise. To solve this ill-posed inverse problem, we use the level set method, which iteratively deforms the shape of the target under a velocity field, and we analyze the property of the desirable velocity. Numerical results obtained by this method in arbitrary directions are given as well.
ieee antennas and propagation society international symposium | 2006
Janic Chauveau; N. de Beaucoudrey; Joseph Saillard
This paper proposes to characterize the resonance behavior of targets with the quality factor, defined by comparison with resonant circuits. Results are presented exhibiting the advantage of using this Q parameter
3rd International Workshop on New Computational Methods for Inverse Problems (NCMIP 2013) | 2013
Yanhua Wen; N. de Beaucoudrey; J. Chauveau; Philippe Pouliguen
The profile function of an object is defined as its transverse cross-sectional area versus distance along the observing direction and it is used by the ramp response technique to identify radar targets. Existing reconstruction algorithms have good performance with profile functions from 3 mutually orthogonal directions, while they give distorted results otherwise. To solve this inverse problem, we use the level set method, which iteratively deforms the shape of the target under a velocity field. An appropriate velocity is used and satisfactory reconstructed 3D images are presented for arbitrary directions.
international geoscience and remote sensing symposium | 2012
Nicolas Pinel; Christophe Bourlier; Bertrand Chapron; N. de Beaucoudrey; Antoine Ghaleb; René Garello
In this paper, for moderate winds, the statistics of the field backscattered from sea surfaces are studied by simulation, by using a numerical model. It is observed that the field phase and amplitude are close to a uniform distribution and a Rayleigh distribution, respectively. However, reducing the radar resolution limit induces a departure from the Rayleigh distribution. This departure depends on several parameters: it gets stronger when the wind speed increases or the incidence angle decreases.
ieee antennas and propagation society international symposium | 2008
Janic Chauveau; N. de Beaucoudrey; Joseph Saillard
Since the development of radar systems, extensive researches have been conducted on the detection and the identification of radar targets. In military context, these targets are often stealthy to assure their security. This can be provided by using composite materials, absorbing electromagnetic waves in usual radar frequency bands. Consequently, studies are involved in lower frequencies. These frequency bands correspond to the resonance region for object dimensions of the same order as electromagnetic wavelengths. Therefore, the fluctuation of the energy scattered by the target is significant and resonance phenomena clearly appear in this region. In this paper, we propose to show, with the example of a perfectly conducting (PC) rectangular cavity, how resonances of a target depend on its dimensions and that these resonances have two origins: external resonances corresponding to creeping waves on the surface of the target and internal resonances corresponding to possible cavity waves. Internal resonances are usually stronger than external resonances, then we propose to use internal resonance parameters of air-intakes for the identification of aircrafts.
european microwave conference | 2010
Janic Chauveau; N. de Beaucoudrey
european microwave conference | 2007
Janic Chauveau; N. de Beaucoudrey; Joseph Saillard