Electronic Control of Structural Asymmetry for Tunable Nonreciprocal Phase Shift in CRLH Transmission Lines

Electronic control of structural asymmetry using varactor diodes is proposed for tunable nonreciprocal phase shift in composite right-/left-handed (CRLH) transmission lines constructed on a perpendicularly magnetized ferrite substrate. The CRLH line with varactor diodes inserted was designed, a prototype of the line was fabricated, and the transmission characteristics were measured. The experimental results validate that the nonreciprocal phase shift observed at a Dirac point in the dispersion diagram is continuously and electronically controllable by varying the asymmetry of the line while the operating frequency is kept fixed.