A quad-band bandpass filter using negative-refractive-index transmission-line (NRI-TL) metamaterials

In this paper, we present a design for a quad-band filter that is based entirely on NRI-TL metamaterial unit cells and exhibits narrow passbands with good selectivity. The multiple passbands of these cells are exploited to provide the overall characteristics of the device. The cells are printed in microstrip, resulting in a low-profile planar device. The device can also be designed as a tri-band or dual-band filter without changing its topology.