A controllable bandwidth filter using varactor-loaded metamaterial-inspired transmission lines

This letter presents a tunable bandwidth bandpass filter based on varactor-loaded metamaterial coplanar waveguide (CPW) lines. The CPW lines are based on series gaps and split-ring resonators. The varactors are reverse-biased semiconductor diodes connected between both sides of each series gap. This configuration, directly inspired from the so-called metamaterial technology, takes advantage of the high dispersion of the loaded transmission line. Therefore, strong permittivity and permeability responses induced by means of the resonators are obtained. A single varactor-loaded transmission line is first analyzed. Then, a third-order tunable filter with fractional bandwidth tuning range from 5.8% to 21.5% is experimentally assessed. The proposed filters can be used in several practical applications such as multichannel wireless and satellite communication systems, where reconfigurable devices are often required.
This work was supported in part by the Centre National d'Etudes Spatiales (CNES), the Ministerio de Ciencia e Innovacion, Spanish Government under Research Project TEC2010-21520-C04, and the Autonomous Government of Castilla-La Mancha under Research Projects PPII10-0027-1277 and TC20112325.