Design of X band multilayer chip microstrip ferrite circulator

The microwave circulator is expected to be integrated with low temperature co-fired ceramics (LTCC) technique by multilayer chip structure design. In this paper, the X band microstrip ferrite circulator is designed with the three-dimensional electromagnetic simulation method. The whole substrate consists of gyrotropic stack layers, which provides different saturation magnetization. The results show that the stack number and saturation magnetization of the stack layers exhibit considerable effect on the return loss and reverse isolation for the circulator. It suggests to be correlated with the input equivalent circuit parameters for the circulator, which are affected by the interface and varied saturation magnetization of the stack layers in multilayer chip structure. High return loss, high reverse isolation and low insertion loss can be obtained with the optimized design. However, it is found that the bandwidth of the circulator is unaffected by the stack number and saturation magnetization of the stack layers, which is difficult to be improved with the optimized design.