Electromagnetic scattering from ducts with irregular edges. I. Circular case

A formulation is developed for electromagnetic scattering from finite circular ducts terminated with irregular edges. The analysis is based on the solution of the electric field integral equation using an entire-domain Galerkin expansion for both the axial and the circumferential variation of the currents, defined in terms of an edge-slope-dependent vector field that provides simplifying symmetry properties for the method-of-moments system matrix. Comparisons are made with edge-slope-independent formulations. The analysis is general and applicable for cases in which the functional variation of the edge irregularities is specified by either a deterministic or a random process. Circumferential modal decoupling occurs when the irregularities are specified by a stationary stochastic process having a periodic correlation function. Numerical results are given for edge irregularities governed by a Gaussian random process and are compared for various limiting cases with results for right circular cylindrical ducts