In this letter, the problem of electromagnetic scattering by a shallow elliptical-shaped cavity in a perfect electric conductor plane is considered. We propose an efficient modal approach based on the region-matching technique that can calculate scattered fields without the use of the Mathieu functions. By enforcing boundary conditions at a semicircular auxiliary border, a system of linear equations is constructed. The results obtained by this method are compared with those provided by the method of moment. Finally, the effect of the shape of the cavity on the scattering signature is investigated.
