Computer-aided design models for millimeter-wave suspended-substrate microstrip line

Abstract

An equivalent circuit model was derived for the series gap discontinuity in shielded suspended-substrate transmission line. Numerical values of the circuit parameters were computed for various sets of line dimensions, over a range of operating frequencies. The shielded suspended-substrate line is a transmission medium useful for radar and microwave circuits in the Ka band frequency range, 30 - 40 GHz. In order to utilize this transmission medium in the construction of microwave circuits and filters, it is necessary to have valid circuit models for typical discontinuous change in width. These discontinuity characteristics may be deduced on the basis of a calculation of their scattering coefficients for propagating waves in the medium. The approach chosen in this thesis, however, is that of placing the selected discontinuity in an open-ended strip resonator in the transmission medium. An appropriate circuit model is adopted for the given discontinuity, and its circuit elements are then deduced on the basis of the perturbation of the resonance frequency of the strip resonator which is induced by the mode. The boundary-value problem associated with the microstrip resonator structure has been approached in a rigorous manner based on a full-wave analysis which utilizes a process of solving the electromagnetic (EM) boundary value problem with inclusion of all the field components.