Analysis of bandwidth for metamaterial-based zeroth-order resonant antennas

Recently, there has been intense research on metamaterial-based transmission lines (or RLH-TL). The resonant RLH-TL´s have also been analyzed and applied for zeroth-order resonant (ZOR) antennas in with a good deal of their promising features such as resonance with a very small size. The return loss bandwidths of ZOR antennas reported in these papers and others are narrow (typically less than 10%). The bandwidth has been reported to be the key limiting factor of ZOR antennas. In this paper, the works in are refined through modeling of radiation effects using simple circuit parameters and very convenient design formulas are provided based on them. Besides, we analyze the bandwidth of the ZOR antennas based on the Q-factor considering effects of coupling elements.