Development of a real-time spectral synthesizer

Under contract with AFCRL a study of real-time Fourier transform techniques suitable for use in rapid-scan Fourier spectroscopy and Hadamard spectroscopy was initiated. The primary purpose of the study was to develop a method to greatly improve the real-time transforms of only a small spectral window of the total potential spectrum. Thus, the fast Fourier transform was not suitable. This led to further development of the discrete Fourier transform. Several methods were studied and the CORDIC technique was chosen as most suitable. A real-time spectral synthesizer, along with the associated software, was then developed which performs three main functions: (a) time samples are digitized and recorded for future analysis, (b) real time discrete Fourier transforms or Hadamard transforms are taken and (c) the resulting spectra are displayed on a CRT tube at the conclusion of each scan. The synthesizer was designed to interface with an airborne rapid scan far infrared interferometer.