Compactly Placed High-Isolated Antenna Pair With Independent Control of Decoupling Amplitude and Phase

We propose a compactly placed high-isolated antenna pair through the decoupling of the transmission line (TL) for the application of mobile terminals. Especially, the TL, loaded with a decoupling branch and a phase shift circuit, is employed to create two transmission paths, where the coupling powers through such two paths are capable of being counteracted perfectly. By adjusting the decoupling branch and the phase shift circuit, the decoupling amplitude and phase could be controlled independently, thus realizing a very high isolation of such antenna pair. Both measured and simulated results show that the isolation of the antenna pair, with compact distance from 1/
$40 \lambda _{0} $
to 1/
$8 \lambda _{0} $
, is better than 25 dB in Wi-Fi 2.4G/Bluetooth band with a peak value of over than 40 dB. Furthermore, the decoupling technique is extended to multi-element and dual-band operations. Our proposed design, with independent control of decoupling amplitude and phase, should provide promising values for the application of multiple-input multiple-output (MIMO) and diversity systems.