Enhancement of Phase-Shifting Nonreciprocity in Microstrip-Line-Based Metamaterials by Using a Combination of Their Curvatures and Asymmetrical Insertion of Stubs

摘要

A new approach to enhance the phase-shifting nonreciprocity of microstrip-line-based metamaterials with normally magnetized ferrite substrates is proposed, by using a combination of curvature of the lines and asymmetric insertion of stubs. In the analytical approach, the nonreciprocity is approximately formulated by introducing asymmetric surface admittance on the side walls at the strip edges, showing that a linear combination of two factors due to the line curvature and the difference of asymmetric admittances contributes to geometrical asymmetry of the wave-guiding structures. Numerical simulation and measurement results verify predictions from the analytical approach. It is demonstrated that a combination of larger curvature of the metamaterial lines and hybrid insertion of inductive and capacitive stubs on the inner and outer sides, respectively, provides significant enhancement of the nonreciprocity compared to the single side insertion of stubs.