SPECTRAL WINDOW OF THE ACOUSTOOPTIC FOLDED SPECTRUM ANALYZER

I derive here the spectral window of the acousto-optic folded spectrum analyzer proposed by [K. Wagner and D. Psaltis, Proc. Soc. Photo-Opt. Instrum. Eng. 564,209-223(1985)]. This window function turns out to be quite informative. It clarifies important characteristics that distinguish this system from the more conventional digital spectrum analyzers, and it clarifies the relationships between various system design parameters and helps guide their selection. The spectral window of one specific implementation of a finer-resolution version of this analyzer (the super-fine-resolution variant suggested in the above reference) is also determined. Analysis shows that for certain narrow-frequency ranges this window has two main lobes separated by a large number of super-fine frequency-resolution bins. This characteristic makes it unacceptable in many applications.