Progress in the design and realization of an electrically small Huygens source

In this paper, we describe our progress to date in the design and realization of an electrically small Huygens source. We begin discussing work by Yaghjian that predicts the maximum directivity achievable with single and dual Huygens sources. Here, we attempt to realize the Huygens source utilizing electrically small electric and magnetic dipoles. Using straight-wire dipole and circular-loop elements, we demonstrate that the directivities predicted by Yaghjian can be achieved with the single and dual Huygens sources. Next, we attempt to realize the Huygens source using recently described, more practical electrically small electric and magnetic dipoles. In free space, these antennas are impedance matched to 50 Ohms and exhibit a quality factor (Q) that approaches the lower bound (the Chu limit). When used in the realization of a Huygens source, these antennas no longer exhibit matched impedances nor low Q's. The limitations that arise in realizing the Huygens source are discussed.