A Novel Electrically Small Spherical Wire Antenna With Almost Isotropic Radiation Pattern

Two new electrically small spherical antennas are presented in this letter. The antennas have perpendicular arms to reduce radiation cancellation. While having low resonant frequency and high radiation efficiency, the radiation patterns of the antennas are almost isotropic. The proposed folded spherical wire antenna (SWA) shows approximately 50-Omega radiation resistance which eliminates the need for using a matching circuit for antenna feeding. Moreover, the proposed folded SWA is fabricated to verify simulation results. An attempt has been made to approach the fundamental limitations of small antennas for better characteristics while keeping the size as small as possible.