In this paper, the impact of decoupler type has been analysed on the performance of planar inverted-F antenna (PIFA)-based multiple-input multiple-output (MIMO) antenna. A T-type and a loop-type decoupler have been employed for the isolation of the MIMO antennas, and the performances of the two cases have been compared. The decouplers have been selected based on their different coupling mechanisms with the dominant ground mode. The antennas have been designed for the ground configuration of a USB dongle operating at 2.45 GHz band. Characteristic mode analysis of the ground plane has been carried out, and the MIMO systems have been analysed based on the coupling among the antenna, decoupler and the dominant characteristic mode of the ground plane. It has been observed that the coupling between the decoupler and the ground mode significantly affects the radiation efficiency as well as the diversity performance of the MIMO antenna.
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