20GHz band active circulator utilizing fin-line

This paper treats an active circulator operating at frequency region of 17GHz to 21.5GHz. Proposed active circulator is composed of three amplifiers which consist of FETs mounted at fin-line circuits in rectangular waveguides, and three waveguide-type directional couplers using a dielectric block and taper structures at the side walls of each directional coupler. The feature of this circulator is no requirement of ferrite materials. As a measurement result of the trial circulator, about 40dB isolations and 0.1dB forward insertion losses can be obtained with the frequency range of 17.0 to 21.5 GHz. Amplifiers used in this research are available for 10 to 20dBm input power.