Harold Wheeler, in his classic 1947 papers (Wheeler, 1947a, 1947b), created the field of electrically small antennas (ESA), although, as shown in the history (Appendix A), the early antennas were all electrically small. This field has long been important for frequencies below roughly 1 GHz, where a half-wavelength is about 6 in. These electrically small antennas have characteristics in common that limit performance: low radiation resistance, high reactance, low efficiency, narrow bandwidth, and increased loss in the matching network. Most of these limitations are shared by two other classes of antennas: superdirective antennas and superconducting antennas.
The original intent was to update Electrically Small, Superdirective, and Superconducting Antennas with a second edition. Sufficient material became available to broaden the scope of that book; the result is this book with a new title. This book provides mathematical foundations for important topics including ENG shells, ESA with or cores, including lossy cores, and focused/subwavelength imaging.
Chapter 1 contains detailed electromagnetic derivations of Chu and Thal formulations, formulas for when or cores are used, ...