Efficient spectral domain analysis of generalized multistrip lines in stratified media including thin, anisotropic, and lossy substrates

The full-wave analysis of multiconductor microstrip lines used in electooptic modulators (EOMs), MMICs, or high-speed VLSI applications is addressed. An arbitrary number of coupled coplanar strips are embedded in a stratified medium involving iso/anisotropic dielectric and/or semiconductor layers. The numerical aspects of the computation of the propagation constants using spectral domain analysis (SDA) are stressed. An efficient scheme is used to accurately compute attenuation and propagation constants and current distributions with reasonable CPU times. Convergence problems due to the existence of very thin layers adjacent to the metallized interface have been explicitly considered. An algorithm for computing the modal characteristic impedances regardless of the number and nature of substrate layers is provided. A reciprocity related definition of modal impedances is used to ensure the symmetry of the multiport scattering matrix associated with the structure