Adaptive array performance in the presence of spatially spreaded interference signals

The adaptive array antenna is becoming an important element of mobile communications for both suppressing co-channel interference signals and avoiding multipath fading, in order to increase the communication capacity and improve the communication quality. There are many reflecting and scattering waves in the actual land mobile communication environment, and they have some spatial spreading, or a spatial angle profile. To obtain sufficient suppression of the undesired signals, an adaptive array needs a degree-of-freedom (DOF) greater than the number of undesired signals. However, it is not sufficient for a single DOF to suppress an undesired signal with spatial spreading. The performance of an LMS adaptive array in the presence of spatially spreaded undesired signals is analyzed. It is made clear that the output SINR degrades as the spatial spread of the undesired signal increases. The relationship between the output SINR and the spread angle, the spatial signal correlation coefficient, is investigated.