Compact negative-epsilon stop-band structures based on double-layer chiral inclusions

Here the authors propose to use electrically excited compact chiral resonators in microstrip configurations for realisation of weakly-radiating stop-band transmission lines. The fundamental resonant mode of these resonators can be excited by both electric and magnetic fields applied parallel to the spiral axis. The authors propose to use a racemic arrangement of an equal amount of left- and right-handed chiral particles between the ground plane and the signal strip and orient the particles so that they are excited by the electric field of the microstrip line. The advantage of this configuration (in addition to strong coupling and weak radiation from excited particles) is that the ground plane can be preserved from being etched (continuous ground structure). The other advantage is that the size of negative permittivity lines loaded with chiral particles can be made very small compared to previous implementations based on complementary split-ring resonators. The circuit models with properly extracted parameters accurately describe the behaviour of both negative permittivity and double-negative lines loaded with electrically coupled resonators. This parameter extraction technique is based on the comparison between the simulated (or measured) transmission and reflection characteristics of the host line loaded with such resonators and those obtained from its lumped-element equivalent circuit model.