Since the onset of the explosive growth in demand for wireless communications during the 1990s, researchers are giving increasing attention to the use of adaptive antenna systems (AASs) technology to overcome practical challenges in providing the service. The main benefit of the technology lies in its ability to exploit the spatial domain, on top of the temporal and frequency domains, to improve on transceiver performance. This thesis presents a unified study on two classes of preprocessing techniques for uniform circular arrays (UCAs). UCAs are of interest because of their natural ability to...