Band-Pass Filtering by Below-Cut-off Waveguides Loaded with Split-Ring Resonators: Relevance to Lefthandedness

Electromagnetic (EM) response of broadside coupled split-ring resonators (BC-SRRs) in standard waveguides is found to be affected by additional resonance-like field enhancement in the gaps between the resonators and the waveguide. This resonance-like response defines the dominant peak of EM transmission below cut-off. FDTD simulations of experiments used to demonstrate subwavelength pass-band in waveguides loaded by a chain of BC-SRRs show that the net magnetic moment of the resonators is equal to zero in this band. Therefore, the response of the BC-SRRs cannot be characterized by effective negative permeability, and, hence, the subwavelength transmission can not be attributed to the double negativity of the medium.