A Fast Digital Spectral Analyzer

This paper describes a processor that is being used for radar and multichannel sonar spectral analysis of band-limited input signals. Its design is based on a shift-register implementation of a fast Fourier transform algorithm coupled with a single flow-through arithmetic unit. In less than 12 ms, 4096 complex input data samples can be transformed, making it one of the faster systems in operation. Speed is obtained by using an organization that performs the rapid data reordering required for executing the algorithm. A postprocessing unit is used to increase quality of estimation of line spectra in statistically random short-term spectra. The unit can be used either as an integrator or first-order recursive filter. It is implemented in a floating-point format to maintain dynamic range. Hardware is kept to a minimum by establishing minimum and maximum ratios of the two signals required in the recursive filter computation.