Performance Evaluation of a Four-Element Antenna Array with Selection Circuits for Adaptive MIMO Systems

Reconfigurable antenna arrays increase the flexibility of adaptive MIMO systems. At present, most designs have adopted antenna arrays with reconfigurable elements. However, antenna selection is also an effective method, which has not been fully investigated. In this paper, the potential benefits of a four-element antenna array with selection circuits in the UMTS band (1920-2170 MHz) are explored. The array has eight pin-diodes embedded in the feeding network to select any sub-set of elements. For evaluation, an adaptive MIMO system was set up and a measurement campaign was taken in an indoor multi-path environment. The measurements were performed over a 300 MHz bandwidth centered at 2.05 GHz, covering the UMTS band. The results show that different channel conditions prefer different antenna array configurations. Therefore, in varying channel conditions the antenna array can support antenna selection algorithms to select the best sub-set of elements to increase channel capacity.