International audienceIn this paper, the accuracy of the singularity expansion method (SEM) used for antenna characterization is investigated. A well-known limitation of the SEM is that pole extraction is very sensitive to noise. A comparison between two main methods of pole extraction is presented. The matrix pencil (MP) method and the Cauchy's method are used to extract poles from the radiated fields of a dipole antenna and two bowtie antennas. Results are presented for simulated fields, and the robustness to a white Gaussian noise is also analyzed. We show that the MP method allows working with lower SNR than Cauchy's method and is more accurate for field reconstruction

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In the resonance region, the radar scattering response of any object can be modelled by natural poles with the formalism of the singularity expansion method. These natural poles are resonance parameters which provide useful information for the discrimination of radar targets as their general shape, characteristic dimensions and constitution. In the case of an open radar target, high-Q internal resonances and low-Q external resonances occur respectively inside the target and on its surface. Because internal resonances have a higher Q, they may have a higher total energy and can thus be used for target identification. In this paper, we choose to study the resonance behavior of a perfectly conducting rectangular cavity with a rectangular aperture. With this simple example, we intend to show how to distinguish between the two origins of these resonances: external resonances corresponding to traveling waves on the surface of the target and internal resonances corresponding to cavity waves. Indeed, this can be applied to characterize aircrafts, whose apertures (such as inlets, open ducts, airintakes, cavities etc.) contribute significantly to the overall radar cross section.

International audienceThis paper presents a new approach to extract the physical poles of antennas. The Singularity Expansion Method (SEM) allows modelling the antenna backscattering using poles which are theoretically independent of the wave incident angle, making them useful for antenna identification. Nevertheless, only the physical poles respect this property while the spurious poles change for each incident angle. Indeed, we call physical the poles linked to the antenna itself and spurious the poles linked to anything but the antenna (excitation, noise…). The goal of this paper is to highlight the method to define the optimal time windowing applied on the antenna backscattering in order to obtain the physical poles of the antenna. The approach is based on the Window Decreasing Technique and the Window Increasing Technique. The SEM is applied on the backscattered field measured in the boresight direction of three antennas: a narrowband patch antenna, a wideband helix antenna and a UWB antenna. By using these poles to reconstruct the field backscattered in several directions, we show that the poles extracted from one direction with this new approach are relevant to reconstruct the backscattered field for any other directions. Moreover, we show that these poles can be extracted directly from these other directions