In this paper, we propose a novel tunable left-handed metamaterial (LHM), the capacitor-loaded short wire pairs (CL-SWPs). It is composed of a pair of short wires connected through a variable capacitor. This LHM is
single-sided, and it exhibits not only tunable negative permeability, but also a wide band negative permittivity. It is pointed out with theoretical analysis that its left-handed performance is related to the mutual coupling
coefficient. A tunable dual-band LHM is also proposed by simply adding a double slits split ring resonator to this LHM. The simulated results indicate that the closer the two LH bands are, the better performance the CLSWP related left-handed band is, hence identifying our theoretical analysis. The proposed structure is geometrically simple, low-cost and easy for fabrication, and it can be used as a basic particle in the design of tunable multi-band LHMs.