Computer-aided design of in-line resonator filters with multiple elliptical apertures

A CAD procedure for a new type of in-line resonator filters with multiple elliptical-apertures irises is presented. The proposed design procedure, based on the concept of automated CAD of coupled resonator filters, considerably simplifies filter design since, with this approach, the choice of the initial geometrical dimensions is not critical. To increase the computational efficiency, at first optimization is carried out by using multivariate surrogate models derived from full wave analysis; final dimensions are then directly obtained by a rigorous full-wave optimization of the entire structure. Two examples of filters with two transmission zeros at lower and upper stop-band are presented in order to illustrate the approach.