Nonreciprocal Mode Converting Waveguide and Circulator

In this work, a class of antisymmetrically biased ferrite-loaded substrate integrated waveguides (SIWs) is studied in detail along with the definition of three main regions of operation. With focus on one of those newly defined regions, a nonreciprocal mode waveguide (NRMW) is introduced for the first time and its related design procedure is explained and illustrated. Furthermore, a fundamental approach is proposed and devised for developing a fully integrated structure called nonreciprocal mode-converting waveguide (NRMCW). This ferrite-based device is capable of effectively converting TE
₁₀
mode into TE
₂₀
mode only in one direction, thereby suggesting that the original mode be preserved in the reverse direction. In other words, the mode conversion, in this case, is unidirectional, which has never been reported so far. To substantiate the usefulness of the proposed structure and physical mechanism, a class of circulators is designed, fabricated, and demonstrated on the basis of the introduced NRMCW, thus validating the formulated theory of NRMCW in this work and providing an application example of such devices. Both theoretical and experimental results are presented in support of the claims made in this work regarding the proposed circuit concept and its related foundation work.