Radiation Efficiency Improvement of U-shaped Slot Antennas on Metal Casings Using Characteristic Mode Analysis

When conventional inverted-F or -L antennas are installed on a metal casing, the performance of such antennas is degraded due to their proximity to the metal casing. This paper presents the characteristic mode analysis of the metal casing. The radiation efficiency can be improved when the current distribution excited by U-shaped slot elements approaches that of the ideal characteristic mode.