Study on the resonance properties of combinations of different split ring resonator cells

We combine different split ring resonator (SRR) unit cells along three axes respectively and study the electromagnetic behaviors of combinations numerically, with the purpose of broadening the frequency band of negative permeability. When combining SRRs in z-direction, the wave propagation direction, it is found that the bandwidth of negative permeability is broadened by 0.22 GHz. The same bandwidth expansion effects, however, are not observed along the other two axes. In addition, it is feasible to obtain two isolated frequency bands with negative permeability by combining SRRs along three axes.