Abstract

The raster-scanning of a 1-D signal in a TV format is shown to be equivalent to a 2-D delay line. A 1-D Fourier transform along the rows directly yields the time-sampled cross-ambiguity functions of a multicomponent input signal with the row aperture. The quadratic detection of this output is a simultaneous computation of the cross-Wigner representations between the input signal components, smoothed with the Wigner distribution of the row aperture. Using an optically addressed light valve to perform this quadratic detection, another horizontal 1-D Fourier transform yields vertically the time history of the mutual covariances of the input components. This enables a selective filtering of stationary vs nonstationary signals, using a vertical 1-D Fourier transform. To compute the ambiguity functions, the second light valve can be addressed as above, or it can be used to perform the coherent product of two successive rastered inputs (one being optically reversed). Then a 2-D Fourier transform yields the ambiguity functions (symmetrical) in both cases, but with exchanged axes and resolutions. As a conclusion, the classical folded spectrum analysis is reviewed to consider the general case of signals having a time-varying frequency.

© 1985 Optical Society of America