| 摘要 |
<p>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. The output signal from one of the receivers can be applied to a first Bragg cell arranged to point modulate light from a laser light source, the output then being transmitted through a beam expander to a second Bragg cell to which the output signal from the second receiver can be applied, the output from the second Bragg cell then being detected by a photo-detector array. The output from the second Bragg cell can be spatially filtered by providing adjustable imaging optics arranged such that only light corresponding to the central portion of the cross correlation function is transmitted. The processor can be arranged to demodulate the signals to produce data corresponding to the central portion of the cross correlation function and to Fourier transform the data to produce the cross spectral density.</p> |
