The electrically small dipole-loop pair revisited

The properties of single and double dipole-loop pair antennas have been the topic of some discussion in the past several years. In (Grimes et al., 2000), Grimes et al studied these antennas and claimed they exhibit a Q 20 times lower than the theoretical lower bound on Q (the fundamental Chu-limit). It was also claimed that in certain instances, these antennas could exhibit a Q equal to zero. In (Hansen, 2001), Hansen discussed the properties of these antennas, emphasizing that the zero Q antenna does not exist. Hansen also discussed the practical issues associated with inter-antenna coupling and feeding the double dipole-loop pair. In (Hwon, 2005), Kwon studied equal TM and TE mode dipole moments and concluded that the minimum radiation Q (the fundamental Chu-limit) can be obtained only when the TM and TE modes are the equal. Here, we will revisit these conclusions and provide an analysis of these antennas that includes discussion of the antenna´s radiation patterns, polarization, impedance, quality factor (Q), and dipole-loop coupling. It is evident that the use of these antennas in their simplest form is impractical.