Dispersion characteristics of metamaterial slow-wave coupled lines

A novel coupled line structure based on two inter-wound right-handed metamaterial transmission lines is investigated. The basic approach is to compress, twist, and fragment (CTF) metal strips or discs periodically in a multi-layer structure to form a four port structure that carries the feature of a large slow-wave factor with a band selection capability. Dispersion characteristics of both odd and even modes are investigated with emphasis on phase equalization and impedance design. A specific metamaterial couple-lines structure is designed, fabricated and tested as an example. The measured results of the slow-wave factor and line impedance are in good agreement with those of simulated results. Potential applications of the proposed coupled line structure are also discussed.