Analysis of compact suspended MIMO antennas

Studies have shown that the MIMO systems perform well in rich multi-path environments when the correlation between the branch signals transmitted by the individual antenna elements is low [1]. This correlation is determined by antenna array configurations in terms of mutual coupling between the elements as well as the channels where transmitted branch signals propagate. The inter-element mutual coupling is primarily determined by the spacing between antenna elements, as well as radiation patterns and polarization of the elements. The methods to reduce the inter-element mutual coupling can be categorized into the optimization of array configuration, the application of modified ground planes, the usage of optimized impedance matching networks [2, 3], or any combination of the techniques mentioned above. The antennas with optimized configurations can reduce the inter-element mutual coupling, which enhance the performance of MIMO systems with reduced probability of fading and increased capacity due to the multi-path signals [4]. However, it should be noted that the analysis of MIMO systems are complicated since its performance in terms of reliability and capacity is determined by many factors such as the antennas, channel, and signal processing. This paper presents the analysis and optimization of compact suspended plate antennas for multiple-input-multiple-output (MIMO) wireless local area network (WLAN) applications. A performance metric using the two- and three-dimensional patterns of the envelope correlation coefficients are proposed to evaluate the diversity performance of antennas in MIMO systems. Following this, a compact three-element suspended plate antenna array with a bent ground plane is presented for WLAN MIMO applications. The diversity performance of the design is experimentally and numerically analyzed.