Uniform circular arrays for smart antennas

As the growing demand for mobile communications constantly increases, the need for better coverage, improved capacity, and higher transmission quality rises. Thus, a more efficient use of the radio spectrum is required. Small antenna systems are capable of efficiently utilizing the radio spectrum and, thus, hold a promise for an effective solution to the present wireless systems´ problems, while also achieving reliable and robust high-speed high-data-rate transmission. Although numerous studies for smart antennas have already been conducted using rectilinear arrays, including mostly uniform linear arrays (ULAs) and uniform rectangular arrays (URAs), not as much effort has been devoted to other configurations. In this paper, the performance of smart antennas with uniform circular arrays (UCAs) is examined. A profound justification for this selection is the symmetry possessed by uniform circular arrays. This property provides uniform circular arrays with a major advantage: the ability to scan a beam azimuthally through 360° with little change in either the beamwidth or the sidelobe level. With the use of uniform circular arrays, the two main issues related to smart antennas - estimation of the direction of arrival from incoming signals and bearnforming - are both examined.