Direct observation of negative phase velocity and positive group velocity in time domain for composite right/left-handed transmission lines

We use the time-domain method to directly determine the negative phase velocity and positive group velocity in the composite right/left-handed transmission line (CRLH TL). Within the frequency region of a left-handed passband, the position and time behavior of a Gaussian modulated wave form with a frequency of 1 GHz is investigated, and it shows that the phase velocity and group velocity are reversed along the CRLH TL. The experimental results of the time-domain method are compared with the results derived from the dispersion relation obtained using the frequency-domain method. The experimental results of both the time-domain and frequency-domain method agree well with theoretical values. (c) 2006 American Institute of Physics.