An improved eigenvector beamformer

Most techniques for computing beamformer tap weights do so by maximizing the overall signal-to-noise ratio at the system output, where noise includes both thermal noise and directional interference. This is the optimal solution if the two noise sources count equally. However, there do exist scenarios where directional interference is more harmful to system performance. For this reason, the authors introduced a new beam-former based on eigenvector techniques[1] which is able to exactly null interference even when thermal noise is present. Unfortunately, however, the new method can also cause signal cancellation, depending on the geometry of the interference. This cancellation can be reduced by introducing additional eigenvectors in the tap weight solution. We develop a criterion for choosing these additional vectors which allows the user to set the maximum tolerable signal cancellation. Given this signal cancellation constraint, the directional interference power is minimized. Simulation results are presented which demonstrate the modified eigenvector beamformer. We also comment on the extension of the method to wide-band signals.