Compact MIMO antenna with embedded decoupling network

In this paper, a compact multiple-input-multiple-output (MIMO) antenna with embedded network is presented. The MIMO antenna consists of two symmetric monopoles with edge-to-edge separation of only 0.01 λ at 3.5 GHz. To enhance the isolation, a decoupling network is designed and embedded between the two antennas, which does not increase the footprint of the antenna system. It is observed that the coupling current is trapped by the network and cannot be transmitted to the adjacent antenna. In the way, |S
₁₁
| ≤-10dB and |S
₂₁
| ≤-20dB are achieved over the band from 3.4 GHz-3.6 GHz. Compared with the antennas without decoupling, the isolation is improved from around 6 dB to more than 40 dB. Additionally, the envelope correlation coefficient (ECC) of proposed antennas is reduced to smaller than 0.03 and the total efficiency is increased by over 10%. The measured results are in good agreement with the theoretical and simulated ones.