Efficiency Optimization for Electrically Small Antennas

In this paper, a study of the impact of miniaturization strategies on radiation efficiency for electrically very small antennas is proposed. Four differential-fed antennas are designed and simulated and then compared at two electrical sizes of ka=0.14 and ka=0.27, with several shapes and with or without a dielectric core material. The excited spherical wave modes of the proposed antennas are $T E_{10}$ and $T M_{10}: T E_{20}$, and the proposed antennas include capacitive loading, material loading, and folding linearly and spirally. It is shown that some miniaturization strategies are more efficient than others, depending on the electrical size of the antenna.