Multiple-input and multiple-output (MIMO) is currently regarded as a key technology for long term evolution (LTE), but a critical effect is mutual coupling (S21) due to space constraint in miniaturized design. A compact-size antenna with low mutual coupling will be an ideal choice for better system performance. This paper describes the design of a small-size (48 × 48 mm2) MIMO antenna system with low mutual coupling for LTE 800 MHz applications. The antenna system comprises two FR-4 substrate layers; one printed with two meander line antennas (MLAs) and the other printed with reactive impedance surface (RIS) and defected ground structure (DGS). The properties of the antenna, such as S-Parameters, excited surface current distribution, far-field radiation pattern and diversity performance characteristics, were studied. The results indicated that MLAs rendered compactness to the system. Introduction of air gap (AG) between the two substrates, DGS and periodic square patches of RIS resulted in 452 MHz bandwidth and mutual coupling of -41.18 dB between antenna elements. The performance of the proposed design compared with other reported geometry has been demonstrated. Parameters including bandwidth, ratio of antenna area/improvement in S21, antenna efficiency and the envelope correlation coefficient were compared. Considering the results, the present system appears to be comparatively more efficient.
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