Guided-Wave Propagation Characteristics of Fully-Integrated Coplanar-Waveguide Metamaterials with Distributed Loading

Jing GAO  Lei ZHU  Keren LI  

Publication
IEICE TRANSACTIONS on Electronics   Vol.E91-C   No.1   pp.34-40
Publication Date: 2008/01/01
Online ISSN: 1745-1353
DOI: 10.1093/ietele/e91-c.1.34
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Recent Progress in Electromagnetic Theory and Its Application)
Category: Artificial and Nolinear Materials
Keyword: 
transmission line metamaterials,  coplanar-waveguide,  periodic structure,  guided-wave,  left-handed and right-handed passbands,  

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Summary: 
Transmission line metamaterials on coplanar waveguide with series-capacitive and shunt-inductive distributed loading in periodical intervals are characterized using our developed fullwave self-calibrated method of moments. Firstly, the two effective per-unit-length transmission parameters, i.e., complex propagation constant and characteristic impedance, are numerically extracted. The results provide a straightforward insight into the forward- and backward-wave propagation characteristics in several distinctive bands, including the left- and right-handed stopbands and passbands. In particular, it is demonstrated that in the whole left-handed passband, the propagation constant has purely negative phase constant while the characteristic impedance has only positive real quantity. Next, varied left- and right-handed passbands are studied in terms of lower/higher cut-off frequencies based on ideal equivalent circuit model and practical distributed CPW elements, respectively. Of particular importance, the left-handed and right-handed passbands find to be able to be directly connected with a seamless bandgap under the condition that normalized inductance and capacitance of loaded CPW inductive and capacitive elements become exactly the same with each other. Finally, the 9-cell metamaterial circuits on CPW with actual 50 Ω feed lines are designed and implemented for experimental validation on the derived per-unit-length parameters.