Electrically Small Resonant Planar Antennas: Optimizing the quality factor and bandwidth

The fundamental limitation (lower bound) on the quality factor (Q) of an electrically small antenna that fully occupies a spherical volume is defined by the well-known Chu limit. More recently, the subject of lower bounds for small antennas of arbitrarily shaped volumes has been given considerable attention in the literature. Gustafsson et al. were the first to present lower bounds for the Q of antennas of arbitrary volume. More significantly, they presented details on the optimum aspect ratios for minimizing the Q of electrically small antennas that fully occupy cylindrical volumes and planar areas. In previous works, we have described several electrically small-wire antenna designs that fully occupy spherical and cylindrical volumes and that are impedance matched and efficient and exhibit Qs that most closely approach the Chu limit and the Gustafsson limit, respectively.