Excitation of metal casing using bent and folded dipole antenna with three conductors

Abstract

The antennas installed in mobile devices are small and low-profile compared to wavelength at the operating frequency. In general, low-profile horizontal elements and short monopole antennas have low radiation resistance. Low radiation resistance requires matching circuit between 50 Ω feed line and decreases radiation efficiency. By using the characteristic mode, excitation of the ground plane to improve the radiation resistance has been investigated. This paper proposes the structure with the modified folded dipole antenna, which is placed close to the metal casing. The surface current on the casing is excited by modified folded dipole antenna and contributes to the radiation.