Realistic Approach to Description of Signals at Output of A/D Converters

Abstract

It is common knowledge that no signals having the form of a sequence of weighted Dirac deltas, as they are currently modelled so, are present, in reality, at the output of analog-to-digital converters (ADC). No such signals are available in the otherwise large variety of physical signals. This has been illustrated in many works and shown by means of measurements. However, it is highly intriguing that the same papers (with the exception of this article) consider it necessary to model the signals at the output of ADC via sequences of Dirac deltas because only such an approach allows to describe the aliasing effect occurring in the spectra of these signals. But due to this incorrect description such an approach is obviously incomprehensible to everyone. In accepting this, however, it has been overlooked that this does not have to be the case at all. The effect of aliasing in the spectrum of a sampled signal may be explained by modeling this signal as a weighted step function. Moreover, such an approach offers also a quantitatively more accurate result for this spectrum than the one obtained using the current method. All that is illustrated in this paper that focuses on this specific theme.