Composite Right / Left Handed (CRLH) based devices for microwave applications

Metamaterials (MMs) became a very actual topic in the present research interest field, due to their unusual but interesting characteristics, not encountered in nature (Veselago, 1968) (Engheta & Ziolkowski, 2005). A way to obtain media having MM characteristics is to develop circuits which, under certain conditions, model the MMs properties. Using different lattice structures or periodic repetition of unit cells, different types of two-dimensional MMs have been suggested (Sievenpiper et.al., 1999; Caloz & Itoh, 2003). A particular class of MMs consists of artificial LH (L eft-Hand) transmission lines, which may be obtained using series capacitors and parallel connected inductors. With this approach and using SMDs (surface mounted devices), circuits such as branch couplers (Lin et al., 2003) and ring couplers (Okabe et al., 2004) operating up to a few GHz, have been reported. The main advantage of these circuits compared to the classical ones is the dual frequency response for any two frequency ratio.