Bispectral magnitude and phase recovery using a wide bandwidth acousto-optical processor

摘要

A hybrid optical/digital processor has been developed that computes both the magnitude and phase of the bispectrum for wide bandwidth RF signals. The overall optical architecture is that of a modified Mach-Zehnder interferometer which contains three acousto-optic modulators and appropriate transforming lenses. The intensity distribution in the output plane of the interferometer contains an interference term which represents the real part of the bispectrum multiplied by a spatial carrier (the interference fringes). To isolate the bispectrum information, the output image is digitized and digitally filtered. The imaginary part of the bispectrum is obtained by Hilbert transforming the real part, and the bispectrum magnitude and phase are then computed. We demonstrate the performance of the processor with three different test signal sets where the signals have a bandwidth of either 6 MHz or 12 MHz. The test results illustrate the successful recovery of magnitude and phase information for the bispectrum of quadratically related signals.