Ferrite Isolator Design with Low Intermodulation Distortion under High Power Condition

Based on the analysis of the nonlinearity of ferrite material under high power condition, this paper proposes some effective measures to reduce the nonlinearity and the intermodulation distortion of the system. These measures include selecting appropriate materials, correctly designing inner conductor and using of heat conductive body in the external of resistance. In order to deduce the size of the isolator, this paper adopts two sections of striplines to match. A method to evaluate the intermodulation distortion of a ferrite element by the two-tone method is proposed in which a test fixture operating at frequencies around 2 GHz was designed and the corresponding IMD results are presented. It is concluded that, to a certain extent, the methods mentioned above lead to a reduction in IMD in ferrite isolator as well as an increase in power handling capability.