Optimum array processing is an optimum multichannel filtering problem. The objective of array processing is to enhance the reception (or detection) of a desired signal that may be either random or deterministic in a signal environment containing numerous interference signals. The desired signal may also contain one or several uncertain parameters (e.g., spatial location, signal energy, phase) that it may be advantageous to estimate. Optimum array processing techniques are broadly classified as processing appropriate for ideal propagation conditions and processing appropriate for perturbed propagation conditions. Ideal propagation implies an ideal nonrandom, nondispersive medium where the desired signal is a plane (or spherical) wave and the receiving sensors are distortionless. In this case the optimum processor is said to be matched to a plane wave signal. Any performance degradation resulting from deviation of the actual operating conditions from the assumed ideal conditions is minimized by the use of complementary methods, such as the introduction of constraints. When operating under the aforementioned ideal conditions, vector weighting of the input data succeeds in matching the desired signal.