Discrete Time-Frequency Analysis and Sampling

Summary

The reconstruction formula for windowed Fourier transforms is highly redundant since it uses all the notes gω,t to recover the signal and these notes are linearly dependent. In this chapter we prove a reconstruction formula using only a discrete subset of notes. Although still redundant, this reconstruction is much more efficient and can be approximated numerically by ignoring notes with very large time or frequency parameters. The present reconstruction is a generalization of the well-known Shannon sampling theorem, which underlies digital recording technology. We discuss its advantages over the latter, including the possibility of cutting the frequency spectrum of a signal into a number of "subbands" and processing these subbands in parallel.