Rigorous analysis of 3-D planar circuit discontinuities using the space-spectral domain approach (SSDA)

The space-spectral domain approach (SSDA) has been developed to determine scattering parameters for arbitrarily shaped multilayered planar MIC/MMIC discontinuities. Although the basic framework was introduced previously, only resonant frequencies of planar circuit discontinuities could be calculated. The SSDA presented is not only significantly extended, but also introduces the concept of self-consistent hybrid boundary conditions to replace the modal source concept in the feed line. A general error function is derived to provide a direct assessment of the discretization accuracy. The convergence behavior of this method is investigated, and current standing-wave profiles along microstrip throughlines with matched, open, and short-circuited conditions are given. S-parameters for several microstrip discontinuities with abrupt and smooth transition are obtained to demonstrate the flexibility of the approach