Patch antennas on ferromagnetic substrates

Patch antennas on ferrite substrates allow for pattern control, frequency s hifting, and scattering reduction, This is achieved by external magnetic he ld biasing coupled,vith the inherent magnetization of the ferrite substrate . Measurements and analytical studies based on the method of moments (MoM) have verified these attractive properties of ferrite substrates. However, v erification of the analysis is difficult and, furthermore, previous models have relied on uniform biasing across the substrate, In this paper, we pres ent a hybrid finite element-boundary integral (FE-BI) method, which permits modeling of the true nonuniform bias fields within the substrate for a mor e accurate prediction of the ferrite patch performance. After validation of the proposed simulation and a demonstration of the inherent properties of the ferrite patch, it is shown that nonuniform biasing is responsible for a dditional frequency shifts. We also identify the poor condition of the resu lting matrix systems and relate this situation to the predictable occurrenc e of nonpropagating substrate modes, A more robust iterative solver with pr econditioning is, therefore, proposed and applied to handle these situation s.