Combined beam forming and cross correlation of broadband signals from a multidimensional array using coherent optics.

A coherent optical system design is proposed for simultaneously heterodyning, correlating, and beam forming on a large number of input channels. Techniques are described with application to two- as well as one-dimensional arrays. To accommodate the former, one direction in the optical aperture must serve both as a time and space dimension. The particular technique proposed resolves the apparent ambiguity. The method uses the phase of the correlation amplitude, after heterodyning, to effect the beam forming operation. Although the full theoretical correlation processing gain against background noise is not realized, very substantial gains and fine time and angle resolutions can be achieved. Because of its inherent physical simplicity, particularly as contrasted with electronic methods of similar capacity, the coherent optical correlator-beam former has significant advantages for many applications.