Metamaterial filters with attenuation poles in the pass band for ultra wide band applications

In this work, a composite right/left handed (CRLH) transmission line implemented by means of complementary split rings resonators (CSRRS) and interdigital capacitors is designed to provide a transmission band useful for ultra wide band (UWB) applications, i.e., in the interval 3.1-10.6 GHz. This huge bandwidth is obtained by balancing the line, namely by merging the left handed (LH) and right handed (RH) bands typical of these structures. The result is a single and broad transmission band, which exhibits a sharp cut-off at the lower edge due to the presence of a transmission zero. In these UWB band pass filters, an attenuation pole within the band may be of interest for the elimination of possible interfering signals. It is demonstrated that such attenuation poles can be introduced by adding properly designed spiral resonators (SRs) at both sides of the host line on the top layer of the design. The fabricated device is small (area A = 0.66 cm2) and exhibits reasonable performance. This work contributes to demonstrate the potentiality of transmission line metamaterials for the design of microwave components in planar technology. © 2007 Wiley Periodicals, Inc.