Techniques are considered for processing the outputs of a sensor array that is observingJdistinct signal sources. Three types of wideband signals are discussed: unknown, stochastic, and parameterized. Narrowband signals are a special case. Four types of random errors are discussed: additive sensor noise, sensor gain errors, sensor time-delay errors, and "beam-pointing' errors. It is concluded that the so-called decoupled-beam data processor is a very promising technique, which can be implemented by passing the output ofJindividual "beams" through aJ-input,J-output linear system. When sensor gain-delay and beam-pointing errors are not present, the decoupled-beam data processor provides "infinite sidelobe rejection."