METAMATERIAL SUBSTRATES feature dielectric behavior that can be altered by the application of a voltage. In order to understand how such materials might be used in the design of a band-reject filter, Zachary Thomas and a group of fellow researchers at the Massachusetts Institute of Technology (MIT) in Cambridge, MA experimented with left-handed metamaterials (LHMs) to enhance the performance of a stopband filter created by the addition of open-circuit shunt stubs to microstrip lines. The stubs were selected for a quarter wavelength at the design frequency of 6 GHz.
Measurements showed the the performance of a stopband filter on metamaterial was a marked improvement compared to a similar design realized on standard dielectric substrate material as well as compared to a form of hybrid dielectric-based filter on metamaterials. See "Enhanced Microstrip Stopband Filter Using A Metamaterial Substrate," Microwave and Optical Technology Letters, August 2006, Vol. 48, No 8, p. 1522.