Simple formula for the RCS of a finite hollow circular cylinder

A plain and simple, yet accurate, formula is obtained to calculate the backscattered radar cross-section (RCS) of a perfectly conducting, finite, hollow, circular cylinder with a closed termination. The reradiated field from the cavity region is evaluated via the Kirchhoff approximation and the reciprocity theorem. The scattering from the exterior surface is approximated by the geometrical theory of diffraction (GTD), in conjunction with the equivalent current (EC) concept. The solution neglects the multiple scattering between the open and closed ends of the cavity and can be easily applied to the electromagnetic scattering from a very large cavity.