Optimal placement of PCB-integrated diversity elements in a compact tunable handset antenna

This paper investigates the optimal placement of diversity elements integrated on the printed circuit board (PCB) of a compact mobile terminal. The main antenna of the terminal is based on a capacitive coupling element (CCE) which is frequency reconfigurable through an adaptive impedance tuning circuit. Characteristic mode analysis is used to find optimal locations for two PCB-integrated diversity elements. The goal is to place the diversity antennas on the PCB in such a way that the mutual coupling between the antenna ports is minimized within the frequency bands. It is found out that those capacitive fed diversity elements at maxima of the PCB current distribution yield favorable performance in terms of electromagnetic (EM) isolation between the antennas. The concept is verified with EM simulated examples in two E-UTRA operation bands 2 and 7 (1.9GHz and 2.6GHz).