Resonance mode splitting in split-ring resonator arrays used in the microwave invisibility cloak

This paper describes the resonance splitting phenomena in fragments of the microwave cloak metamaterial composed of split-ring resonators. Splitting of elementary resonances was observed within the bands exceeding 1 GHz that could obstruct spatial distribution of the effective parameters in the cloak prescribed by the transformation optics relations. At some split frequencies, however, groups of resonators demonstrated coherent responses, which could be possibly used for supporting the cloak performance.