Field distribution and dispersion characteristics of fundamental and higher-order modes in miniature hybrid MIC (MHMIC) considering finite conductor thickness and conductivity

A hybrid-mode analysis of coplanar transmission lines on a 10-mil alumina substrate with lossy back metallization is presented. A self-consistent approach is used with the method of lines to determine the propagation constant, losses, and field distribution, considering finite metallization thickness and conductor losses. Results for the fundamental and first two higher-order modes are given. It was found that the thin substrate allows higher-order modes to propagate at frequencies lower than 30 GHz. Under the influence of conductor losses, the field distribution for the fundamental mode becomes hybrid even at lower frequencies and at very low frequencies (<1 GHz), there is a negative slope of the propagation constant versus frequency. The method presented is general and can be used in the analysis of miniature hybrid microwave integrated circuits and monolithic microwave integrated circuits, and can include semiconductor losses.<>