Scattering parameters of arbitrarily oriented slot-coupled microstrip lines

The reciprocity method is extended to analyse arbitrarily oriented slot-coupled microstrip lines. The case of uniaxially anisotropic dielectric substrates is considered. The exact Green functions for these anisotropic substrates are used to solve for the unknown slot electric field, from which scattering parameters of a four-port network for this structure are obtained by using the reciprocity theorem. Comparison of numerical results for parallel microstrip lines with other available measured and computed data shows good agreement. It is found that for arbitrarily oriented microstrip lines, by varying slot inclination the angle coupling level can be widely controlled, and there exists maximum coupling for a certain value of slot inclination angle. Effects of other parameters such as slot length and dielectric anisotropy are also investigated