Interference Rejection Degradation in Function of the DOA in a Beamforming System

This paper analyzes the interference rejection degradation in a narrowband beamforming system formed by a Uniform Linear Array (ULA), as a function of the Direction of Arrival (DOA) of the desired signal. To calculate the beamforming weights, the Recursive Least Squares (RLS) algorithm was used. For each DOA of the desired signal, the Signal to Noise plus Interference Ratio (SINR) is estimated. When the DOA of the desired signal is near to the sector edge, the SINR is significantly degraded because of less effectiveness in the interference mitigation algorithm. A quantitative estimation of this degradation is provided in this work. Some possible solutions to cope with this situation are discussed, and also some design criteria are provided.