Metamaterial exhibiting left-handed properties over multiple frequency bands

We present experimental measurements at microwave frequencies of a double band left-handed metamaterial. The sample of metamaterial is composed of an extended version of the S-shaped resonators that exhibit simultaneously a negative permittivity and a negative permeability response at comparable frequencies. The experimental results clearly show that there exist two frequency bands where the refraction index is negative. The double left-handed passbands are due to the multiple capacitances and inductances induced in the structure, which can be further tuned to realize a metamaterial with multiple (more than two) left-handed frequency bands.