Tunable active three-way circulator using tunable transistor feedback network

Abstract

An active three-way circulator is proposed to have the tunable property by the tunable transistor feedback network (TTFN). This tunable design shows its tunable frequency range from 1.15 to 1.85 GHz (bandwidth of 47%) with the isolation >20 dB, the insertion losses of around 3.5 dB and return losses better than 10 dB at each port at the tuned frequency. This tunable property is controlled by the varactor diodes added at the input and output of the FET in TTFNs.