A digital equivalent of an analog spectrum analyzer

Analyzers with a single-stage filter and a two-stage filter corresponding to skirts on the line shape with -6 and -12 dB/octave roll-off, respectively, are developed. The digital filters can automatically reduce the size of the frequency increments (i.e., reduce the slew rate) to follow steep features in the power spectral density. This materially improves the acceptance of the resulting spectrum plots and saves time relative to the case of constant increments. The digital filters are realized using ARIMA models. As with the analog spectrum analyzer, one can cascade filters to realize sharp skirts on the resonance line width and, hence, it can separate near sidebands