A miniaturized HF coil antenna with reconfigurable patterns by magnetic ferrite loading

A simple and compact pattern-reconfigurable coil antenna with magnetic ferrite loading for high frequency (HF) applications is presented in this paper. The antenna consists of two cross-shaped magnetic core, four segments of coil, and two feeding sources. The proposed antenna operates at 28 MHz with the reflection coefficient (S11) reaching a value of -18 dB. By manipulating the amplitude of the feeding voltage, the antenna radiation pattern can be switched to four radiation states. Two of the radiation states exhibit unidirectional radiation, oriented at ±90° in the horizontal plane, respectively. The remaining two states demonstrate omnidirectional radiation in the horizontal and vertical plane, respectively.