Physical optics approximation from the modified EFIE and MFIE integral equations
Résumé
The computation of the scattered field from an object and its Radar Cross Section (RCS) can be a very time
consuming task and may also require a high memory. Indeed, as the problem’s size scales with the number of
edges NEdge of the object, the need of fast and memory-efficient algorithm arose to solve high frequency problems.
Thus, to overcome this issue, approximations can be introduced in order to reduce the computing time. In high
frequency, a possible candidate can be the Physical Optics (PO), and can be obtained from the principal value (PV)
of the Magnetic Field Integral Equation (MFIE). That way, the mesh can be coarser, which reduces the number of
unknowns NEdge and thus both decrease the memory requirement and the computation time.
However, the MFIE is known to be inaccurate with some geometries, particularly when edge diffraction occurs,
and can only be used for closed surfaces. At the contrary, EFIE is more accurate but its main problems come
from its ill-conditioned matrix. The purpose of this paper is to construct the PO approximation from the EFIE,
hoping that the resulting sparse impedance matrix predicts better results than those obtained from the PV of the
MFIE.
This new method was then tested on different geometries and its results were compared to other methods, such
as the EFIE, the MFIE, and the classical PO. Similarly to PO, we also used shadowing on this new method, and
results were compared to the ones obtained with the methods previously cited, with and without shadowing.