Hybrid finite-element-modal-expansion method for matched magic T-junction

This paper presents a hybrid finite-element-modal-expansion (FE-ME) method for the rigorous analysis and design of a matched magic T-junction. The electromagnetic fields in the standard waveguide port arms are expanded into the summation of their modal functions. The junction region involving tuning irregularities is discretized by the finite-element method. These two methods are then combined to enforce the boundary condition that tangential electric and magnetic field components must be continuous along the port surfaces. This hybrid technique is computationally efficient and can analyze the standard magic T-junction with tuning elements. Numerical results for a standard magic T agree well with available data in the literature and the measured results for a matched magic T-junction are presented.