A planar miniaturized left-handed (LH) metamaterial in C band is designed with broad bandwidth and low loss while the size of the unit cell is small and the structure is simple. In addition, the center of the frequency band where the LH metamaterial is applicable is tunable within the range of 4 to 20 GHz. A semi-infinite slab made of the planar LH metamaterial is simulated and the phase velocity is respectively extracted from the transmission and reflection data at normal incidence and the phase of wave front, results show the LH metamaterials studied exhibit backward wave (BW) properties in the frequency range of interest.