Coupled Microstrips on Double Anisotropic Layers (Short Papers)

A variational expression is presented for the mode capacitances of coupled microstrip lines with double anisotropic layered substrates. It is shown that the even-and odd-mode phase velocities can be made equal when a sapphire layer is deposited on a boron nitride substrate. High coupler directivity can be achieved with appropriate values of both layers' thicknesses.