Feeding-line-based decoupling patch antennas

Mutual coupling among multiple antennas has been a problem needed to be tackled in multiple-input-multiple-output (MIMO) systems. A decoupling method based on short decoupling feeding lines (DFLs) for MIMO patch antennas is proposed. The decoupling method utilises the feeding transmission line to create a new coupling path between the closely placed patch antennas. By adjusting the intensity and phase of the introduced new coupling, the original coupling can be cancelled out. The proposed method can realise both E- and H-plane decoupling. A 1 × 2 H-plane MIMO patch antenna array is first presented to explain the decoupling mechanism. Then, two practical examples of 2 × 2 and 4 × 4 MIMO patch antenna arrays are designed, fabricated and measured. The results indicate that the port isolation can be apparently improved from 15 to 38 dB for H-plane coupling and from 19 to 35 dB for E-plane coupling at the centre frequency of 3.5 GHz. Moreover, the proposed method is promising to be applied in arrays with other antenna type by adjusting the position and size of short DFLs.