Physical implementation of a generalized NRI-TL medium for quad-band applications

A form of generalized negative-refractive-index transmission-line (NRI-TL) is presented. This NRI-TL features four controllable passbands, two of which are left-handed (backward) and two of which are right-handed (forward). The topology and method of operation of the line are discussed. Simulated results for a single section with open stopbands and closed stopbands are shown. Moreover, a fabricated NRI-TL unit cell in microstrip technology that features closed stopbands is shown (i.e. with two points at which beta = 0). The transmission parameters of the fabricated unit cell compare favourably with simulated results. A NRI-TL with four controllable passbands would be useful in a number of quad-band applications.