Miniaturized microwave components and antennas using negative-refractive-index transmission-line (NRI-TL) metamaterials

Negative-refractive-index transmission-line (NRI-TL) metamaterials comprise transmission lines loaded periodically with series capacitors and shunt inductors, such that the phase flow and power flow are contra-directional on the lines. These NRI-TL media exhibit properties that can be utilized for miniaturizing microwave components and antennas. In this mainly review paper, a compact antenna, power divider and branch-line coupler are presented to demonstrate the miniaturization techniques enabled by NRI-TLs. Furthermore, a generalized NRI-TL is described that exhibits two left-handed and two right-handed bands. This can be exploited for realizing compact dual-band and quad-band RF/microwave components. This generalized NRI-TL can be designed to exhibit two distinct frequencies where the corresponding propagation constants vanish.