Resonant crystal band gap metamaterials in the microwave regime and their exotic amplification of evanescent waves

The authors realize resonant crystal band gap metamaterials (CBMs) using circuit structures in the microwave regime, which behave quite differently from the conventional photonic band gap structures. They show that a periodic array of series inductor and shunt capacitor is equivalent to a CBM similar to a magnetic plasma at higher frequency band, and a periodic array of series capacitor and shunt inductor behaves like a CBM similar to an electric plasma at lower frequency band. The equivalent medium parameters have been derived in both cases, which show the existence of conjugate loss in imaginary parts. When two such structures are cascaded together, the authors demonstrate that evanescent waves are amplified and transmitted in a very narrow frequency band under the antimatching condition. Such a feature can be used to design extremely narrow band filters. Theoretical predictions, circuit simulations, and experimental results are presented to validate their conclusions. (c) 2007 American Institute of Physics.