Interference nulling in direct-sequence spread-spectrum systems using a main-beam reference in the delay space

The authors discuss an interference nulling technique that transforms the output vector of a linear antenna array to a vector made of independent beams in the delay space. The signal of interest (SOI) is located in the center of a main beam in the delay space and is used as a reference in two steepest-descent feedback algorithms to null interference appearing on the remaining beams. When direct-sequence spread-spectrum is incorporated in the model, it is found that the SOI only affects nulling when the spreading code is not synchronized and the signal is spatially misaligned with the main beam of the antenna array