New Left Handed Microstrip Lines with Complementary Split Rings Resonators (CSRRs) Etched in the Signal Strip

In this work, left handed (LH) microstrip lines with complementary split rings resonators (CSRRs) and series capacitive gaps, both etched in the upper metal level (signal strip), are presented for the first time. Contrarily to previous implementations of CSRR-based LH or negative permittivity microstrip lines, where the CSRRs were etched in the ground plane, the bottom metal is not printed in the proposed structures. This is of interest in many practical applications, where the substrate lies in a metallic holder. Moreover, no vias are required in these implementations since the shunt positive reactance needed to generate the LH band is provided by the CSRRs. It will be shown in the paper that to accurately describe the proposed structures in the region of interest, additional elements in the lumped element circuit (as compared to previous models) must be introduced. Advantages and drawbacks of this new implementation of the resonant-type approach of metamaterial transmission lines (as compared to previous ones) are pointed out, and an illustrative example is given.