Abstract: A spread spectrum signal detection system comprising two spatially separated receivers, a correlator, such as a time integrating correlator employing acousto-optic cells, which is connected to the outputs from the two receivers to produce a signal representative of the cross correlation function of the two spread spectrum signals, a filter arranged to transmit only the central portion of the cross correlation function and a signal processor to produce the cross spectral density and thereby determine the presence of the spread spectrum signal. The direction of arrival of the spread spectrum signal can be determined by measurement of the angle of the phase slope of the cross spectral density. The acousto-optic cells can be Bragg cells.