Modeling and simulation of a partially-magnetized ferrite LTCC circulator

This paper compares three simulators (Matlab, Ansys HFSS and CST Studio) in modeling a partially magnetized ferrite LTCC circulator. It demonstrates the limitation of Ansys HFSS in manually creating permeability tensor and the flexibility of CST Studio in defining partially magnetized ferrite materials. A mathematical model is firstly introduced in Matlab to realize the theoretical analyses. Then a 3D circulator is drawn in HFSS and the partially magnetized ferrite is simulated by reducing its magnetization saturation Ms and entering the corresponding internal Hi bias. The simulation shows that the circulator's frequency tunability cannot be predicted in HFSS, and only when the internal magnetization M is close to its saturation Ms, the S-parameters in HFSS have the same accuracy as these in CST Studio. Finally, a full tensor material model is described in CST Studio, and after implementing the partially magnetized ferrite tensor equations in the ‘History List’, the simulation shows the circulator's frequency tunability to agreement with measurements.