A novel compact wideband MIMO system with four elements for LTE-A mobile terminals

In this paper, a compact wideband Multiple Input Multiple Output (MIMO) antenna system operating at 3.5 GHz (band 22) for LTE-A mobile terminals is presented. The MIMO antenna design with a small size equal to 66.89 × 39.57 × 0.8mm
³
consists of L-shaped printed monopole radiating elements separated by almost 0.1λ for each two adjacent antennas. To mitigate the mutual coupling effect, a new decoupling structure based on two Squared Split Ring Resonators (SSRRs) as a band stop filter is used between elements. By suitable arrangement and design, the proposed MIMO structure covers a very wide −10dB return loss bandwidth equal to 350MHz, 380MHz, 440MHz and 410MHz for the first, second, third and fourth antenna respectively. A minimum capacity loss of (0.47bits/s/Hz) and an improvement of 17.84% for the radiation efficiency are also demonstrated. The performances of the 4 × 4 MIMO system are further investigated in terms of S-parameters and Envelope Correlation Coefficient (ECC). The results indicate that the proposed approach has good characteristics of diversity and can be embedded in LTE-A mobile terminals thanks to its small size while covering the band-22 3.5 GHz (3510–3590, 3410–3490).