A Low Q Electrically Small Magnetic (TE Mode) Dipole

Abstract

Electrically small antennas can be made to exhibit omnidirectional, dipole-like radiation patterns when operating in the transverse magnetic (electric dipole) mode, the transverse electric (magnetic dipole) mode or some combination of transverse magnetic (TM) and transverse electric (TE) mode radiation. When designing electrically small antennas whose performance properties closely approach theoretical limits, engineers generally focus on the design of electric dipoles or TM mode radiators. These radiators can be designed to exhibit low voltage standing wave ratio (VSWR), high radiation efficiency, and a low quality factor. TM mode radiators also have the advantage of a straightforward transition from the dipole to the monopole configuration for use over metallic ground planes or surfaces. Following our previous work in the design of small electric dipoles, we present the design of a new, electrically small magnetic dipole or TE mode radiator. This new design is shown to exhibit low VSWR, high radiation efficiency, and a low quality factor. We show that the quality factor of the magnetic dipole radiator approaches the lower bound (the Chu-limit) to within a ratio consistent with recent limits presented by Thal.