Dual-Layer EBG-Based Miniaturized Multi-Element Antenna for MIMO Systems

A dual-layer electromagnetic band-gap (EBG) mushroom structure is proposed in this paper. Based on the concept of slow-wave propagation, this structure can reduce the size of multi-element microstrip patch antennas (MPAs) by 61%. While the mushroom inner layer aids in the antenna miniaturization, the more compact upper layer acts as a band-stop filter further reducing the mutual coupling between the miniaturized patch antenna elements, which is otherwise not possible for a single-layer EBG structure. Various 2- and 4-element miniaturized MPAs are proposed for 2.5-GHz band applications, with antenna elements closely spaced at 0.5λ and low mutual coupling levels in the range of -28 dB to -50 dB. Furthermore, the achievable multiple-input-multiple-output (MIMO) channel capacities of these miniaturized multi-antennas are analyzed using the Kronecker channel model and tested in various propagation scenarios like the anechoic chamber, reverberation chamber and indoor. It is observed that the miniaturized MPAs can provide significant gains in MIMO capacity in all the signal scattering environments and are close to the theoretical limit of i.i.d. Rayleigh fading.