Enhanced fullwave approach for accurate parameter computation of multilayer microwave couplers including anisotropic substrates

In this paper, a hybrid-mode method is presented for an efficient propagation parameter computation of a large variety of shielded coupled planar circuits. Conductor strips are assumed to be embedded in a multilayered isotropic and/or anisotropic medium. The proposed technique is based on extension of the spectral domain approach and provides accurate expressions for computing the dyadic Green´s functions. Furthermore, the effect of anisotropy is investigated. Some particular multilayered structures are analyzed, which could be applied to the design of directional couplers and filters. Numerical results are discussed and compared with the published data.