On the acceleration of the coupled-integral-equations technique and its application to multistub E-plane discontinuities

A technique to accelerate the numerical solution of scattering from multiple waveguide discontinuities by the Coupled-Integral-Equations Technique (CIET) is presented. The sums appearing in the numerical solution of the integral equations are computed at an initial frequency point and then used to accelerate the analysis at subsequent frequency points. Only few, typically 2 to 3, terms are needed to reach convergence for all structures investigated. Basis functions which include the edge conditions are used to guarantee numerical efficiency. A special routine to take advantage of the sparsity of the matrix relating the expansion coefficients to the incident excitation is also used. The method is applied to determine the scattering from rectangular waveguide E-plane discontinuities as well as multistub E-plane structures. Results from this work are compared to measurement and to those from the Mode-Matching Technique (MMT) to demonstrate its superiority.