Decoupling networks (DNs) have frequently been used to obtain high isolation performance between coupled antennas in multiple-input multiple-output (MIMO) systems due to their advantage of spatial efficiency, which is particularly important for mobile devices. However, conventional DNs suffer from narrowband limitations. In this paper, a broadband decoupling technique is proposed that broadens the isolation bandwidth using a parallel resonant point. A 1.95 GHz MIMO antenna system with 460 MHz of bandwidth (fractional bandwidth, FBW = 23.6%) is designed and measured using the scattering parameters. The isolation is found to be better than -15 dB, while the reflection coefficient is better than -6 dB. Furthermore, the antenna efficiency and envelope correlation coefficient (ECC) are evaluated in a reverberation chamber.
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