A New MIC 4-port Circulator

Based on the well known microstrip-slot-coupler [1, 2] an interesting nonreciprocal extention is proposed. It is shown that a 4-port circulator can be obtained if an additional ferrite substrate is underlayed on the slot side (Fig.1a,b). The S-parameters of this new device are derived and the electrical properties are discussed. First experiments verify the correctness of the theory.