Methods to combine deterministic nulling and adaptive nulling

摘要

Antenna array processing techniques such as steering, tapering and nulling are commonly applied in practical radar. Antenna steering points the beam to the desired target direction. Tapering can be applied to control the sidelobes of the antenna beam to cope with clutter. In addition, nulling can be applied to cope with interference and/or clutter. Deterministic nulling is used when the directions are known and adaptive nulling is used when the interference directions are not known but can be derived from the measured data. This paper provides a review on the methods for deterministic nulling and adaptive nulling and then introduces techniques for combining them. Specifically, deterministic nulls can be imposed on the desired signal vector in the adaptive processing, or they can be imposed by modifying the adaptive beamforming weight vector, or they can be incorporated as part of the constraint set in the adaptive processing. The weights for the three methods can all be expressed in terms of the quiescent tapered beamforming weight, the covariance matrix and the null space of the desired antenna response to the null region. The adapted patterns are generated to show the efficacies of these techniques. Furthermore, 2 implementation schemes are derived from the constrained method.