Scattering predictions are very useful in many research and industrial fields, such as :

  • Radar Cross Section (RCS) prediction of targets (aircrafts, helicopter, …)
  • Doppler signature of moving objects (cars, bikes, drones, wind turbines)
  • Fields strength in a given region with obstacles (communications, radar detection, …)

In this research topic, we are particularly interested in the study of the scattering mechanisms occuring when an EM wave interacts with objets which have the following characteristics :

  • Electrically large (hundreds of wavelengths)
  • Smoothly curved
  • In motion (rotationnal and other)

Those characteristics do not allow us to use classic full-wave methods – such as the Method of Moments (MoM) – to evaluate the scattering effects. Indeed, classical MoM requires to store solve a linear system of size NxN (N being the number of sampling points, typically 10 per wavelength), which usually does not fit into the memory of a standard computer.

One way to reduce the complexity of the problem consists in the direct evaluation of the currents on the object surface using the Physical Optics (PO) approximation. For objects which are smoothly curved and have a radius of curvature which is large in terms of wavelength, the PO approximation removes the object and introduces equivalent currents as defined on the figure below.

Physical optics approximation

In terms of RCS, this method gives good results in the back-scattering region around the specular point as well as in the foward-scattering region (θ = π) but is quite innacurate for other bistatic angles ranging from π/2 to 3π/2.

Current work is focused on a modification of the PO method when one is interested in evaluating the fields in the forward-scattering region. The proposed method shows promising preliminary results in 2 dimensions. In parallel, an extension to the 3D case is ongoing.