Left-handed structures for microwave applications

In this paper, dispersion/attenuation diagrams are investigated for purely left-handed (PLH) and for composite right/left handed (CRLH) transmission lines. The magnitude and phase of the S parameters of these structures are analyzed in a broadband (1-7 GHz) range. The investigations on microstrip CRLH lines demonstrate the presence of the left-handed range, the stop-band (only for the unbalanced lines) and the right-handed range. By edge-coupling two such CRLH lines, devices with new properties, different from conventional microstrip devices were obtained. Symmetric and asymmetric 0 dB backward couplers working in the stop-band of the CRLH line were achieved. Very short 3 dB couplers (with only 2 or 3 unit cells) were also investigated.