Unusual propagation characteristics in CRLH structures

A purely LH material (V.G. Veselago, Soviet Physics Uspekhi. vol. 10, no. 4, pp. 509-514. 1968) cannot exist physically because it would violate Einstein's relativity: in such a hypothetical material, the group velocity would be unbounded and would become larger than the speed of light at high frequencies. In fact, natural right-handed (RH) series-L/shunt-C parasitics are always present and become dominant at high frequencies, limiting group velocity to that associated with the RH contributions only. Therefore a practical LH material is in effect a composite right/left-handed material (CRLH), already described in previous publications (C. Caloz and I. Itoh, IEEE Trans. Antennas Propagat.; A. Sanada et al, IEEE Microwave Wireless Comp. Lett.), and applied to several novel components and antennas. However, unique CRLH effects never occurring in conventional periodic structures, such as non-zero group velocity associated with infinite wavelength and guided wavelength increasing with frequency in the LH frequency range have never been analyzed in detail thus far. This is the object of the present contribution, where these effects are demonstrated for the different cases of homogeneous, ideal-lumped and real physical CRLH TLs. For simplicity, the discussion is restricted to lossless TLs without loss of generality.