Symmetric coupled composite right-/left-handed transmission line with dual-mode balanced filter characteristics

In this paper, a symmetric coupled composite right-/left-handed transmission line (CRLH-TL) with dual-mode balanced filter characteristics is proposed. Unlike the other symmetric structures, this configuration has the ability to operate under both common- and differential-mode excitation. This ability is achieved by providing a physical short circuit by means of ground vias at the center of each unit-cell along the symmetry plane of the structure. In this study, we implemented a dual-mode balanced filter on the basis of the fact that CRLH unit-cells can be operated under both common- and differential-mode excitation. To validate this ability, a five-cell four port symmetric coupled CRLH-TL is simulated, fabricated, and its performance is measured. The obtained results are in good agreement with the simulation results under both common- and differential-mode excitation.