Numerical analysis of the radiation properties of ferrite patch antennas

Patch antennas on ferrite substrates are attractive because they offer greater agility in controlling the radiation characteristics of the antenna. Their inherent anisotropy and non-reciprocal properties, permit variable frequency tuning, and antenna polarization diversity. External biasing of the ferrite substrate also allows for beam steering, pattern shape control, and radar cross section control, by forcing the ferrite into a cut-off state. To provide for greater flexibility in modeling the ferrite substrate and the substrate cavity, we perform an analysis of the ferrite patch using the Finite Element-Boundary Integral (FE-BI) method. As usual, the substrate housed within the cavity is modeled by the Finite Element Method (FEM) using an edge-based formulation. Consequently, multiple substrate (and superstrate) layers can be handled easily including lateral material inhomogeneities within each layer. Although we have already implemented rectangular brick elements, we employ tetrahedral elements because of their ability to model various geometries. In our formulation, the FE mesh is truncated at the surface of the cavity using the rigorous BI method. Thus, the proposed FE-BI implementation is equally rigorous to the traditional MoM (employing the substrate Green´s function) and allows modeling of finite and inhomogeneous substrates.