Numerical analysis of impulse regime phenomena in linear and non-linear metamaterial transmission lines

This paper examines pulse propagation along linear and non linear composite right/left handed transmission lines (CRLH TLs). An analytical time-domain Green's functions approach is employed in the linear case. Pulse spreading in time, due to the dispersive features of the line, and tunable pulse group velocity are demonstrated and validated using Agilent ADS. The formulation is further extended to analyze non-linear CRLH TLs (loaded with shunt varactors), using an iterative scheme. This type of lines combines dispersion and nonlinearity phenomena, which may provide optical-inspired applications at microwaves. A microstrip prototype of a nonlinear CRLH TL has been fabricated and tested, and a unit-cell circuital model is proposed. The variation of the varactor's DC bias is employed to electrically control the band-gap which occurs at the CRLH transition frequency. Finally, harmonic generation is experimentally demonstrated showing good agreement with the proposed theory.