A generalized negative-refractive-index transmission-line (NRI-TL) metamaterial for dual-band and quad-band applications

A generalized negative-refractive-index transmission-line (NRI-TL) metamaterial is proposed with two left-handed (backward) and two right-handed (forward) passbands. A condition for closing the corresponding two stopbands between these alternating left-handed and right-handed bands is derived. Moreover, possible applications are identified, including quad-band microwave passive components (e.g., couplers, dividers) and dual-band or quad-band filters. The proposed topology is physically realizable using embedded passives in a host TL (e.g., mtcrostrip).