The effects of digitization on nonstationary stochastic signals with applications to pulsar signal baseband recording

The process of digitizing a stochastic signal introduces systematic distort ions into the resulting digitized data. Further processing of these data ma y result in the appearance of unwanted artifacts, especially when the input signal was generated by a nonstationary stochastic process. In this paper the magnitude of these distortions are calculated analytically and the resu lts are applied to a specific example found in pulsar signal processing. A pulsar signal is an excellent example of a nonstationary stochastic process . When analyzing pulsar data, the effects of interstellar medium (ISM) disp ersion must be removed by digitally filtering the received signal. The dist ortions introduced through the digitization process cause unwanted artifact s to appear in the final "dedispersed" signal. These artifacts are demonstr ated using actual a-bit (4-level) digitized data of the pulsar PSR B0833-45 (Vela). Techniques are introduced that simultaneously minimize these artif acts and maximize the signal-to-noise ratio of the digitized data. The dist ortion analysis and artifact removal techniques described in this paper hol d for an arbitrary number of input digitization thresholds (i.e., number of bits). Also presented are tables of the optimum digitizer thresholds for b oth uniform and nonuniform input threshold digitizers.