This thesis dissertation deals with the computation of the Radar Cross Section (RCS) of complex-shaped open-ended cavities whose dimensions are large compared to the wavelength. Many methods have been developed for such a calculation and IPO (Iterative Physical Optics) has been chosen for its interesting trade-off between the accuracy and the computation time. It is an asymptotic method based on an iterative resolution of the electromagnetic fields integral equations by Physical Optics. The thesis works aim at improving IPO, in terms of both accuracy and computation time.The first original contribution of the thesis concerns a detailed study of the shadowing phenomenon, which has a significant impact on the accuracy. The method, called physical shadowing, has been developed, based on fields integral equations applied to coupled objects, and the shadow radiation of Physical Optics. The method has been tested and compared to classical approaches for open surfaces and open-ended cavities.The second original contribution concerns the acceleration of IPO, based on a technique of matrix compression. First, IPO has been written into a matrix formulation, which allows to apply the ACA (Adaptive Cross Approximation) algorithm, and its recompressed version R-ACA, to compress the interactions matrices of IPO. Moreover, the computation time has been reduced by applying the S-IPO, consisting in separating the cavity in sub-sections where IPO is applied. The simulations has shown a reduction of the computation time and the memory requirements.
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