Avoiding Misconceptions about the Nyquist Criterion
Sampling theory represents one of the fundamentals in Digital Signal Processing and is treated as a separate chapter by almost every textbook on the market. Despite this large coverage, most of the literature emphasizes the basic low-pass sampling concept based on the Nyquist theorem. The general assumption is that the signal has frequencies components from dc to some upper value fa. However, for signals which do not extend to dc, the minimum required sampling rate is a function of the bandwidth of the signal as well as its position in the frequency spectrum. This technique is often called undersampling, harmonic sampling, band-pass sampling or Super-Nyquist sampling. In this paper we are going to examine both aspects with more, in depth analysis of the band-pass sampling technique and its applications.