Optical Signal Processing.

Abstract

Abstract : We studied optical processing techniques to detect and track frequency hopped radio signals in a dense electromagnetic environment by using cross-spectrum of two signals obtained from antenna elements spaced by one-half an RF wavelength. We decimate the array by retaining only every Mth element and scan the cross-spectrum past the decimated array. We therefore reduce the circuit complexity, but suffer some loss in system performance because we require more photodetector bandwidth to accommodate the scanning action. An extension of the decimated array concept is to decimate the reference waveform in the heterodyne spectrum analyzer. In this case, we generate only 64 optical probes in the Fourier domain instead of the 2048 that are normally required. The advantage is that all of the optical power in the reference beam can be concentrated into the reduced number of optical probes, thereby offsetting some of the intrinsic loss in performance experienced by the cross-spectrum analyzer. (JHD)