Design of an Electrically Small 3-D Antenna with Quasi-Isotropic Radiation Pattern

An electrically small three-dimensional (3-D) antenna is proposed to generate a quasi-isotropic radiation pattern. The proposed antenna consists of a single layer conductor with bilateral symmetrical structure before being wrapped in a cylindrical foam. An H-shaped inductive coupling element is used to feed the antenna to obtain a magnetic dipole and a pair of short electric dipoles after the antenna is wrapped in a cylindrical foam. Therefore, by combining orthogonal complementary dipoles with the same radiation intensity and quadrature phase difference, a quasi-isotropic radiation pattern can be obtained. As a proof of this design, a 3-D antenna structure operating at 2.45 GHz is designed, fabricated and measured. It has been shown that the gain variation of the proposed electrically small antenna (ka = 0.48) in total space is 2.72 dB in simulation and 3.53 dB in measurement.