Apparent Radar Cross Section of a Large Target Illuminated by a Surface Wave Above the Sea

Abstract

Abstract-Classical assesssment of the received power by a radar leads to a decorrelation of many relevant phenomena (i.e. propagation, backscattering), which may introduce modelling errors notably in the presence of large target with respect to the wavelength. To overcome this limitation, a new hybrid approach is proposed. It combines a method of propagation calculation (the parabolic wave equation) with a method of scattering calculation (the EFIE solved by a method of moment approach) and an application of the reciprocity principle (the power coupling factor). Each method constituting the hybrid approach is described; the example of a large cargo is chosen and its apparent RCS is evaluated above the sea at low frequency. The results are discussed, studying the influence of the different parts of the boat on the apparent RCS. † Also with UPS-AD2M-IGEEP, 118 route de Narbonne,

Ultra Wide Band RCS Optimization of Multilayerd Cylindrical Structures for Arbitrarily Polarized Incident Plane Waves

“…The frequency spectrum for RCS is divided into three regions [1,2]: (1) Low frequency or Rayleigh region, where the object dimensions are much smaller than the wavelengths, which is attributed by its own approximation leading to the RCS being proportional to the fourth power of frequency; (2) High frequency region (or visible light), where the object dimensions are much larger than the wavelengths and high frequency techniques are successfully used for the computation of RCS, such as geometric optics (GO), physical optics (PO), geometrical theory of diffraction (GTD), uniform theory of diffraction (UTD), etc; (3) The middle frequency region or resonance region, where the object dimensions are comparable with the wavelengths and the common low frequency and high frequency approximations are not applicable. Several methods are developed for the computation of reflection coefficient and RCS of various structures [3][4][5][6]. Computation of radar cross-section in the middle frequency range requires the application of full-wave numerical techniques, such as MoM, FDTD, TLM, FEM, etc.…”

Forward Radar Propagation Over Oil Slicks on Sea Surfaces Using the Ament Model With Shadowing Effect

“…11, but for a frequency f = 300 MHz. Let us note that following [4][5][6], the results of the approximate methods are in excellent agreement with exact numerical methods. Indeed, the Ament model is valid for R a,r < 1.25 [9], and here, for x 2 = 2 km, h 2 ∈ [0; 180] m, which implies that R a,r ∈ [0.031; 0.402], and for x 2 = 5 km, h 2 ∈ [0; 450] m, which implies that R a,r ∈ [0.012; 0.383].…”

“…withp h,11 (ζ; θ i ) given by equation (6). Then, for an uncorrelated Gaussian process, and by considering the Smith formulation,Ȃ r is given byȂ…”

“…Thus, the Ament model [5], which is a fast and simple model that describes the forward (i.e., in the specular direction) radar propagation over rough surfaces, can be used for such a configuration. Here, based on the Parabolic Wave Equation [6][7][8], it is applied to the forward propagation over sea surfaces for coastal radar configuration. This model, which is based on a ray approach, uses the Rayleigh parameter to describe the scattering from the rough interface for grazing incidence in a simple way.…”

Ship detection and tracking using multi-frequency HFSWR

“…This tracking robustness is achieved by avoiding target fading due to echo nulls from frequency and azimuthal variations in ship radar-cross-section (RCS) that occur using a single radar frequency [7].…”