Nested U-ring resonators: a novel multi-band metamaterial design in microwave region

In this study, a novel metamaterial topology, called M-band nested U-ring resonator (M-NURR), is proposed to provide multiple band operation with an electrically small and geometrically simple unit cell design. The M-NURR unit cell has M-nested and unconnected U-shaped metal rings printed on a dielectric substrate where each ring is primarily associated with a distinct LC type resonance frequency where L and C stand for inductance and capacitance, respectively. Therefore this M-NURR topology has the novel property that each of these resonance frequencies can be controlled almost independently by adjusting the arm length of the associated U-ring. In this study, three different M-NURR structures (for M=1, 2, 3) are designed, fabricated and characterised both numerically and experimentally with very good agreement. The suggested sub-wavelength M-NURR metamaterial topology is anticipated to be useful in the design of miniaturised multi-band mobile communication devices as it makes the fine tuning of operation frequencies possible by a simple parametric adjustment.