Analysis of Millimeter Wave Y-Junction Microstrip Circulator

FEM (finite element method) based on the weak form of Helmholtz equation is first here employed to deal with the inhomogeneous structure, shielded Y-junction microstrip circulator at millimeter-wave band. The scattering parameters of the circulator are computed in two steps. As a first step, the field distribution in the shielded microstrip is calculated in the two-dimensional (2-D) FEM. In second step, the three-dimensional (3-D) Vector-FEM is used to model the inhomogeneous structure of the circulator, and FEM field are matched with the field of microstrip at the 3 interfaces. So a sparse matrix equation is obtained, and it is solved with the SSOR-BICG algorithm. Numerical results of the circulator are presented and compared when the ferrite disk radius changed. Also, the electric field distribution in the ferrite disk is depicted to show the circulating process.