Enhancing performances of multilayered directional couplers on anisotropic substrates

In this paper, we present an efficient variational technique for the analysis of the characteristics of multilayered directional couplers fabricated on anisotropic substrates on a quasi-static approach. Numerical results are presented for coupler designs in multilayered configurations. The variation of its characteristic parameters with crystal axis offsets is also reported. It is shown that high directivity can be achieved by making use of the substrate anisotropy in conjunction with a top cover to equalize even and odd-mode phase velocities.